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Sample records for schist

  1. Geochemistry of Schists of Northwest Obudu Plateau, Southeastern ...

    African Journals Online (AJOL)

    Precambrian, highly foliated, fine – medium grained schists, which comprise migmatitic schist (MS), quartz mica schist (QMS), biotite mica schist (BMS) and hornblende biotite schist (HBS) constitute important lithological unit in Northwest Obudu Plateau. The schists are associated with gneisses, amphibolites and ...

  2. Petrology and Geochemistry of Calc-Silicate Schists and Calc ...

    African Journals Online (AJOL)

    Chemically the calc-silicate schists are characterized by relatively high CaO, MgO, Cr, Ni, Sr, La, Ce and Nd contents compared with the mica schist regionally associated with the marble as well as the Post-Archean Australian Shale (PAAS). Relative to the ultramafic schist the calc-silicate schists are characterized by higher ...

  3. Gravity inferred subsurface structure of Gadwal Schist belt, Andhra ...

    Indian Academy of Sciences (India)

    Detailed gravity data collected across the Gadwal schist belt in the state of Andhra Pradesh show an 8.4 mgal residual gravity anomaly associated with meta-sediments/volcanics of the linear NNW-SSE trending schist belt that shows metamorphism from green schist to amphibolite facies. This schist belt is flanked on either ...

  4. The Alta schist, North Norway: unique rock with unique history

    Science.gov (United States)

    Heldal, Tom; Aasly, Kari; Meyer, Gurli

    2015-04-01

    Near the small town of Alta, northernmost Norway, are more than thousand small and large schist quarries, some of them dating back to the 1850's. It was the need for roofing material on a local church and a hospital that triggered the production. Since then, the Alta schist has been widely applied in Norway and abroad, known for its quality for roofing material and hard floor covering. The quality lies in the processes behind the formation of the schist. Emplacement of thrust nappes during the Caledonian mountain chain formation in the Silurian caused deformation and metamorphism of the rocks. The Alta schist is situated in one such nappe sheet, where arkosic sandstone where flattened and transformed into mylonite. This made fine mica layers along which the rock can be split, rythmically spaced and separated by quartz-dominated bands. The production of the Alta schist is still characterized by old craft traditions, reflecting a rich history and culture around the schist production.

  5. Amphiboles from the garnet glaucophane schists in the Bizan area, Sambagawa metamorphic belt, eastern Shikoku, Japan

    OpenAIRE

    Kabir, Md. Fazle; Takasu, Akira

    2015-01-01

    The Sambagawa metamorphic belt in the Bizan area consists mainly of pelitic schists, basic schists, and siliceous schists, along with minor garnet glaucophane schists. Garnet glaucophane schists consist mainly of garnet and amphibole (glaucophane, ferroglaucophane, barroisite, katophorite and taramite), with minor amounts of epidote, phengite, paragonite, chlorite, albite, titanite, and quartz. Clinopyroxene (jadeite-omphacite), chloritoid, rutile, ilmenite, calcite, K-feldspar, zircon occur ...

  6. PETROLOGY AND GEOCHEMISTRY OF CALC-SILICATE SCHISTS ...

    African Journals Online (AJOL)

    DR OKONKOWO

    2012-02-29

    Feb 29, 2012 ... Calc-silicate diffusion zones between marble and pelitic schist. Journal of. Petrology, 16, 314-346. Turner, D. C., 1983. Upper Proterozoic Schist Belts in the Nigerian sector of the Pan-African province of West Africa. Precambrian Research, 21, 55-. 79. Van de Kamp, P. C., 1968. Geochemistry and origin of.

  7. 'Indicator'carbonaceous phyllite/graphitic schist in the Archean ...

    Indian Academy of Sciences (India)

    Carbonaceous rocks in the form of graphitic schist and carbonaceous phyllite are the major host rocks of the gold mineralization in Kundarkocha gold deposit of the Precambrian Singhbhum orogenic belt in eastern India. The detection of organic carbon, essentially in the carbonaceous phyllite and graphitized schist within ...

  8. Geochemistry of semipelitic schist of Isanlu area, south west Nigeria ...

    African Journals Online (AJOL)

    Field and geochemical studies carried out on the semipelitic quartz-mica schist of Isanlu area, SW Nigeria have been used to speculate on the geodynamic activity prevalent in the Egbe-Isanlu palaeobasin at the time its sediment was deposited. Basement rock exposures in the Egbe-Isanlu schist belt are dominated by ...

  9. Rare Earth Element Geochemistry And Protoliths Of Schists In ...

    African Journals Online (AJOL)

    The Nigerian schist belts constitute the most important lithologic units necessary for the unravelling of the geochemical and geodynamic evolution of the basement complex. The schists have however undergone extensive alterations owing to weathering and metamorphism. REE abundance and distribution patterns of ...

  10. REE Geochemistry of ore zones in the Archean auriferous schist ...

    Indian Academy of Sciences (India)

    . The eastern Dharwar Craton of southern India includes at least three ∼2700Ma supracrustal belts (schist belts) which have mesothermal, quartz-carbonate vein gold mineralization emplaced within the sheared metabasalts. In the Hutti and ...

  11. Metamorphic Evolution of Garnet-bearing Epidote-Barroisite Schist from the Meratus Complex in South Kalimantan, Indonesia

    OpenAIRE

    Nugroho Imam Setiawan; Yasuhito Osanai; Nobuhiko Nakano; Tatsuro Adachi; Amril Asy’ari

    2015-01-01

    DOI:10.17014/ijog.2.3.139-156This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote schist, muscovite schist, and serpentinite, were investigated in detail its petrological and mineralogical characteristi...

  12. carbonaceous phyllite/graphitic schist in the Archean Kundarkocha ...

    Indian Academy of Sciences (India)

    mafic rocks and meta volcano-sedimentary units. (Saha 1994; Mahadevan 2002). The gold mineral- ization occurs within the Archean Badampahar–. Gorumahisani schist belt (ca. 3.12소0.01 Ga; Ghose. 1996) representing the Iron Ore Group. The litho- logical sequence associated with gold mineral- ization in and around ...

  13. Reconnaissance geochemical study of a part of Igarra Schist Belt ...

    African Journals Online (AJOL)

    Geochemical exploration of Orle district within the Igarra schist belt in southwestern Nigeria was carried out using reconnaissance stream-sediment survey. A total of 56 samples were collected and chemically analysed for 22 trace elements including Au, Ag, As, Pb, Zn, Cu, Co, Mo, Hg, Sb, Tl, Sc, Cr, Ni, La, W, V, U, Th, ...

  14. Structural appraisal of the Gadag schist belt from gravity investigations

    Indian Academy of Sciences (India)

    : the high density Gadag schist belt is characterized by a gravity high and occurs in two discontinuous segments — the main N-S trending segment, and its thinner NW-SE trending extension, the two separated by a NE-SW trending deep ...

  15. Geochemistry of Gold Deposits in Anka Schist Belt, Northwestern ...

    African Journals Online (AJOL)

    Gold quartz veins have been identified associated with the rock formations of the Anka Schist Belt forming eight gold deposits that include Kuba I, Kuba II, Doka, Dumi I, Dumi II, Zurzurfa I, Zurzurfa II, Jameson and Kwali. The present study involves the use of major and trace elements to characterize some of the features that ...

  16. Polyphase deformation and garnet growth in politic schists of Sausar ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 116; Issue 5. Polyphase deformation and garnet growth in politic schists of Sausar Group in Ramtek area, Maharashtra, India: A study of porphyroblast–matrix relationship. A Chattopadhyay N Ghosh. Volume 116 Issue 5 October 2007 pp 423-432 ...

  17. Geochemistry of Gold Deposits in Anka Schist Belt, Northwestern ...

    African Journals Online (AJOL)

    HP USER

    ABSTRACT. Gold quartz veins have been identified associated with the rock formations of the Anka Schist Belt forming eight gold deposits that include Kuba I, Kuba II, Doka, Dumi I, Dumi II, Zurzurfa I, Zurzurfa II, Jameson and Kwali. The present study involves the use of major and trace elements to characterize some of the.

  18. Polyphase deformation and garnet growth in pelitic schists of Sausar ...

    Indian Academy of Sciences (India)

    Polyphase deformation and metamorphism of pelitic schists of Chorbaoli Formation of Sausar. Group in and around Ramtek area, Nagpur district, Maharashtra, India has led to the development of garnet and staurolite porphyroblasts in a predominantly quartz–mica matrix. Microstructural study of oriented thin sections of ...

  19. Uraniferous schists of the Alsacian side of Vosges mountains; Les schistes uraniferes du versant Alsacien des Vosges Moyennes

    Energy Technology Data Exchange (ETDEWEB)

    Grimbert, A.; Carlier, A. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    Since the discover of uraniferous schists in 1951 in the Ribeauville region (Haut-Rhin), the atomic energy commission has been interested in low content uranium deposits. It originated in France a new interest in uranium sedimentary deposit which were, until now, of a less interest than deposits in crystalline vein-stone. A general description of the oriental versant of Vosges mountains is given and a petrographical and tectonic study is described as well as the mineralization and radioactivity of the region. It studied in particular the uranium deposits near the Schaentzel summit. An historic of the local research is given as well as a study of the borings. A description of the different rock formations, which have been found on the site, is given: sandstone, schists, arkoses, granites. A comparison of the Schaentzel uraniferous schists with other known uraniferous schists is made. finally, interpretations of the study and origin of the uraniferous mineralization in Schaentzel sedimentary deposits are discussed. (M.P.)

  20. Gravity inferred subsurface structure of Gadwal schist belt, Andhra ...

    Indian Academy of Sciences (India)

    The results indicate a synformal structure having a width of 1.8 km at the surface, tapering at a depth of about 2.6 km with a positive density contrast of 0.15 gm/cc with respect to the surrounding peninsular gneissic complex. 1. Introduction. Detailed geophysical appraisal of the northern schist belts of the Dharwar craton, (i.e. ...

  1. Geochemistry of amphibolites from the Kolar Schist Belt

    Science.gov (United States)

    Balakrishnan, S.; Hanson, G. N.; Rajamani, V.

    1988-01-01

    How the Nd isotope data suggest that the amphibolites from the schist belt were derived from long-term depleted mantle sources at about 2.7 Ga is described. Trace element and Pb isotope data from the amphibolites also suggest that the sources for the amphibolites on the western and eastern sides of the narrow schist belt were derived from different sources. The Pb data from one outcrop of the central tholeiitic amphibolites lies on a 2.7 Ga isochron with a low model. The other amphibolites (W komatiitic, E komatiitic, and E tholeiitic) do not define isochrons, but suggest that they were derived from sources with distinct histories of U/Pb. There is some suggestion that the E komatiitic amphibolites may have been contaminated by fluids carrying Pb from a long-term, high U/Pb source, such as the old granitic crust on the west side of the schist belt. This is consistent with published galena Pb isotope data from the ore lodes within the belt, which also show a history of long-term U/Pb enrichment.

  2. Eucisia schist a natural stone from Northern Portugal

    Science.gov (United States)

    Aires, Silvia; Carvalho, Cristina; Noronha, Fernando

    2013-04-01

    The aim of this work was to study the "Xisto" (Portuguese word for "schist", lato sensum) as geological resource of Trás-os-Montes and Alto Douro (TMAD) region, by its economic and social impact. The main outcome of this contribution is to improve the knowledge about mineralogy, fabric, chemistry and technology of the "Eucisia schist", belonging to "Douro Group"- Variscan basement. in order to promote its exploitation and use as a natural stone. The Trás-os-Montes and Alto Douro (TMAD) region is located in the NW sector of the Hesperian Massif of the Variscan Chain. The studied site is geologically located in Central Iberian Zone (CIZ) corresponding to an Autochthonous terrain during Variscan orogeny, [1, 2 and 3]. The Variscan basement was structured by three sucessive phases of Variscan deformation: D1, D2 and D3. In CIZ only D1 and D3 are represented. The metamorphic evolution of the NW of Hesperian Massif is characterized by a syn-D2 regional orogenic metamorphism of Barrovian type which changed to high temperature and low pressure between D2 and D3 phases. "Eucisia schist" is a stone with very fine grain, gray colour with a brownish to greenish patine, a well-marked foliation, generally parallel to the stratification and a metamorphism of low grade (greenschist facies). "Eucisia schist" under petrographic and geochemical studies corresponds to a phyllite with chlorite. The content of major elements, particularly Al2O3 and trace elements such as V, discriminate the relative abundance of pelitic component on the rock. Higher values of Al2O3 (19.66%) and V (105ppm) correspond to a significant involvement of a clay matrix. The physical and mechanical tests as compressive strength (CS), flexural strength (FS), apparent density (AD), open porosity (OP), water absorption (WA), abrasion resistance (AR) and resistance to ageing by thermal shock (RTS) were determinant to define the suitable applications of studied phyllite. The results concerning the studied stone are

  3. Preliminary results of the investigation of the central galician schist area (prov. of Orense and Pontevedra, NW Spain)

    NARCIS (Netherlands)

    Meerbeke, van G.L.E.; Hilgen, J.D.; Floor, P.

    1973-01-01

    Probably Lower Paleozoic quartzo-pelitic schists with bands of feldspathic schists, white and black quartzites, graphite schists and amphibolites have been folded twice. Hercynian regional metamorphism led to porphyroblastic growth of chlorite, albite, biotite, garnet, staurolite mainly between F1

  4. Properties of Schist Extracted in the City of Denizli Surroundings as Construction Material

    OpenAIRE

    Saffet Yağız

    2011-01-01

    There are various type of building stone extracted at stone quarries in the city of Denizli surroundings. Travertine, limestone and schist quarries are the most common in the area. Schist that is one of the units of Menderes massive is the main natural stone sources in Çal, Bekilli and Baklan Triangle in the northeast of the City. The aim of this study is to investigate the usability of schist stone as building stone quarried in the area. To obtain the aim, geological investigations were cond...

  5. Early Paleozoic blueschist from the schist of Skookum Gulch, eastern Klamath Mountains, northern California

    Energy Technology Data Exchange (ETDEWEB)

    Cotkin, S.J. (Univ. of Arkansas, Fayetteville (United States)); Cotkin, M.L. (Univ. of Wisconsin, Madison (United States)); Armstrong, R.L. (Univ. of British Columbia, Vancouver (Canada))

    1992-05-01

    Late Ordovician blueschist from the schist of Skookum Gulch, eastern Klamath Mountains, California, is the oldest known blueschist in California and one of the oldest in North America. Lawsonite-bearing glaucophane schist occurs as lenses intimately interlayered with chlorite schist, quartz-albite schist, and dolomite marble. Detailed investigation of a portion of the Skookum Gulch schist demonstrates that these rock types share a common deformational and metamorphic history. The first deformation occurred during blueschist metamorphism and produced similar-style isoclinal folds and an axial-planar foliation. During subsequent deformations, parallel-style open to tight folds and local kink bands deformed foliation but produced no recognizable recrystallization. A phengite Rb-Sr date of 447 {plus minus} 9 Ma (Late Ordovician) is statistically indistinguishable from previously published K-Ar dates and is interpreted as the time of blueschist-facies metamorphism. Mineral separates from one rock yield a date of 353 {plus minus} 18 Ma, suggesting resetting during a Devonian to Early Mississippian thermal event. The schist of Skookum Gulch is a critical component of the Middle Ordovician to Early Silurian Callahan event, which included volcanism, plutonism, metamorphism, deformation, and sedimentation and occurred in response to collisional tectonics. Paleontological and provenance information indicate that the Callahan event occurred relatively close to the North American continental margin. In this regard, features produced by the Callahan event record the earliest period of Phanerozoic plate convergence recognized within the US Cordillera.

  6. Properties of Schist Extracted in the City of Denizli Surroundings as Construction Material

    Directory of Open Access Journals (Sweden)

    Saffet Yağız

    2011-03-01

    Full Text Available There are various type of building stone extracted at stone quarries in the city of Denizli surroundings. Travertine, limestone and schist quarries are the most common in the area. Schist that is one of the units of Menderes massive is the main natural stone sources in Çal, Bekilli and Baklan Triangle in the northeast of the City. The aim of this study is to investigate the usability of schist stone as building stone quarried in the area. To obtain the aim, geological investigations were conducted in the field and representative samples were collected from the quarries. On the samples, petrograpical, mineralogical (XRD, chemical (XRF analysis and geomechanical test (i.e., uniaxial compressive strength, Schmidt hardness, water absorption by weight, effective porosity, fullness ratio, flexural strength, sonic wave velocity, modulus of elasticity, natural and saturated unit weight were conducted and the usability of schist stone as building stone have been studied by evaluating obtained findings. Analysis and relevant tests were conducted in accordance with international standards and procedures. Concluding remark is that quarried schist stone in the area are acceptably good as building stone to be used for both interior and exterior of construction building and outdoors as coverage material.

  7. Handling of quarry waste from schist production at Oppdal, Norway

    Science.gov (United States)

    Willy Danielsen, Svein; Alnæs, Lisbeth; Azrague, Kamal; Suleng, Jon

    2017-04-01

    Handling of quarry waste from schist production at Oppdal, Norway Svein Willy Danielsen1), Lisbeth Alnæs2), Kamal Azrague2), Jon Suleng3) 1) Geomaterials Consultant, Trondheim Norway, 2) SINTEF, Trondheim, Norway, 3) AF Gruppen AS, Oppdal, Norway A significant amount of aggregate research in Norway has been focused on the recovery and use of surplus sizes from hard rock aggregate quarries. The use of sand sized quarry waste (QW) from crushing/processing has been motivated by the rapid depletion of traditional sand/gravel resources, increasing land-use conflicts, and the need to minimise QW deposits which for some quarries are becoming a critical factor for economy as well as for environmental reasons. With an annual aggregate production of 77 million tons, out of which approximately 83 % comes from hard rock, the annual volume of size strict requirements to the finished products, both regarding processing and the character of the parent rock. The need to deposit large amounts of QW is a serious setback for the quarry economy. Within a limited time horizon the volumes of QW can threaten the further exploitation by merely choking the quarry. On the opposite side - any process that can convert the QW into sellable products will give a tremendous added value for the producer. Besides, the area in question is about to drain out its available aggregate resources, having to rely on long-transported sand and gravel. This has consequences not only for the economy, but also for the environment since heavy lorry transport will not be sustainable. An on-going project is now looking into converting the QW into quality aggregate both for road construction and concrete. Novel crusher technology and processing strategy is being applied and adapted, and the finished products will be tested in laboratories to establish the relevant application parameters and obtainable quality. By producing coarse aggregates for primarily road purpose, it is estimated that the QW can be reduced

  8. Rb- Sr isochron dating of granitoids from the Kazaure schist belt ...

    African Journals Online (AJOL)

    The results of Rb-Sr isochron dating of granites from the crystalline basement complex of Kazaure Schist Belt are presented in this paper. Whole rock Rb-Sr radiometric age determination of five samples of a syntectonic coarse-grained porphyritic granite define a 4-point whole-rock Rb-Sr isochron (MSWD=1.2) ...

  9. TL/OSL properties of natural schist for archaeological dating and retrospective dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Afouxenidis, D.; Stefanaki, E.C.; Polymeris, G.S. [Archaeometry Laboratory, Cultural and Educational Technology Institute/R.C. ' Athena' , Tsimiski 58, Xanthi 67100 (Greece); Physics Department, Aristotle University of Thessaloniki, University campus, Thessaloniki GR-54124 (Greece); Sakalis, A. [Archaeometry Laboratory, Cultural and Educational Technology Institute/R.C. ' Athena' , Tsimiski 58, Xanthi 67100 (Greece); Tsirliganis, N.C. [Archaeometry Laboratory, Cultural and Educational Technology Institute/R.C. ' Athena' , Tsimiski 58, Xanthi 67100 (Greece)], E-mail: tnestor@ceti.gr; Kitis, G. [Physics Department, Aristotle University of Thessaloniki, University campus, Thessaloniki GR-54124 (Greece)

    2007-09-21

    Schist, a metamorphic rock composed largely of quartz and muscovite, has been used as a building stone through the centuries in many parts of the world. In ancient Greece, it was used in buildings and monuments (Knossos, Karthaia, etc). Basic TL and OSL properties of schist are studied in the present work to evaluate its potential use in archaeological dating and retrospective dosimetry. In particular, the optical stability, as well as the linearity of the TL and OSL signal were investigated for samples of natural schist obtained from a roofing slate. The results indicate that both signals are rapidly bleached when the sample is exposed to sunlight. An exposure of 1 min reduces the TL signal by 93%, the IRSL signal by 99% and the post-IR BSL signal by 90%. The dose response was found to be linear for a radiation dose at least up to 75 Gy for the TL and the IR OSL signal and at least up to 25 Gy for the post-IR BSL signal.

  10. New evidence for polyphase metamorphism of glaucophane schist and eclogite exotic blocks in the Franciscan Complex, California and Oregon

    Science.gov (United States)

    Moore, Diane E.; Blake, M.C.

    1989-01-01

    The early metamorphic history of high-grade exotic blocks in the Franciscan Complex may be more complicated than previously supposed. The different assemblages of high-grade glaucophane schists, eclogite, amphibolite and hornblende schist are commonly considered to have formed at the same time from essentially unmetamorphosed oceanic crust. However, new textural and mineralogical data presented here suggest that high-grade glaucophane schist and eclogite have replaced an earlier epidote-amphibolite facies assemblage that is identical to the primary assemblages in many of the hornblende-rich blocks. At least some of the hornblende-rich blocks may therefore be well-preserved remnants of the earlier metamorphism. Comparison of the mineral assemblages and element partititioning in the mixed-assemblage blocks suggests that the glaucophane schist and eclogite metamorphism took place at slightly lower temperatures but at the same or higher pressures than the earlier, hornblende-forming stage. -Authors

  11. Metamorphic Evolution of Garnet-bearing Epidote-Barroisite Schist from the Meratus Complex in South Kalimantan, Indonesia

    Directory of Open Access Journals (Sweden)

    Nugroho Imam Setiawan

    2015-09-01

    Full Text Available DOI:10.17014/ijog.2.3.139-156This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote schist, muscovite schist, and serpentinite, were investigated in detail its petrological and mineralogical characteristics by using polarization microscope and electron probe micro analyzer (EPMA. Furthermore, the pressure-temperature path of garnet-bearing epidote-barroisite schist was estimated by using mineral parageneses, reaction textures, and mineral chemistries to assess the metamorphic history. The primary stage of this rock might be represented by the assemblage of glaucophane + epidote + titanite ± paragonite. The assemblage yields 1.7 - 1.0 GPa in assumed temperature of 300 - 550 °C, which is interpreted as maximum pressure limit of prograde stage. The peak P-T condition estimated on the basis of the equilibrium of garnet rim, barroisite, phengite, epidote, and quartz, yields 547 - 690 °C and 1.1 - 1.5 GPa on the albite epidote amphibolite-facies that correspond to the depth of 38 - 50 km. The retrograde stage was presented by changing mineral compositions of amphiboles from the Si-rich barroisite to the actinolite, which lies near 0.5 GPa at 350 °C. It could be concluded that metamorphic rocks from the Meratus Complex experienced low-temperature and high-pressure conditions (blueschist-facies prior to the peak metamorphism of the epidote amphibolite-facies. The subduction environments in Meratus Complex during Cretaceous should be responsible for this metamorphic condition.

  12. A regional gradient in the composition of metamorphic fluids in pelitic schist, Pecos Baldy, New Mexico

    Science.gov (United States)

    Grambling, Jeffrey A.

    1986-06-01

    Two metamorphic isograds cut across graphitic schist near Pecos Baldy, New Mexico. The southern isograd marks the first coexistence of staurolite with biotite, whereas the northern isograd marks the first coexistence of andalusite with biotite. The isograds do not record changes in temperature or pressure. Instead, they record a regional gradient in the composition of the metamorphic fluid phase. Ortega Quartzite, which contains primary hematite, lies immediately north of the graphitic schist. Mineral compositions within the schist change gradually toward the quartzite, reflecting gradients inμ _{{text{O}}_{text{2}} } andμ _{{text{H}}_{text{2}} {text{O}}}. The chemical potential gradients, locally as high as 72 cal/m inμ _{{text{O}}_{text{2}} } and 9 cal/m inμ _{{text{H}}_{text{2}} {text{O}}}, controlled the positions of the two mapped isograds. The staurolite-biotite isograd records whereX_{{text{H}}_{text{2}} {text{O}}} fell below 0.80, atf_{{text{O}}_{text{2}} } near 10-23 bars; the andalusite-biotite isograd records whereX_{{text{H}}_{text{2}} {text{O}}} fell below 0.25, atf_{{text{O}}_{text{2}} } near 10-22 bars. Dehydration and oxidation were coupled by graphite-fluid equilibrium. The chemical potential gradients apparently formed during metamorphism, as graphite in schist reacted with hematite in quartzite. Local oxidation of graphite formed CO2 which triggered dehydration reactions along the schistquartzite contact. This process created a C-O-H fluid which infiltrated into overlying rocks. Upward infiltration, local fluid-rock equilibration and additional infiltration proceeded until the composition of the infiltrating fluid evolved to that in equilibrium with the infiltrated rock. This point occurs very close to the staurolite-biotite isograd. Pelitic rocks structurally above this isograd show no petrographic evidence of infiltration, even though calculations indicate that volumetric fluid/rock ratios may have exceeded 15 and thin, rare calc

  13. Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway.

    Science.gov (United States)

    Kirkland, Christopher L; MacGabhann, Breandán A; Kirkland, Brian L; Daly, J Stephen

    2016-01-01

    The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later.

  14. Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway.

    Directory of Open Access Journals (Sweden)

    Christopher L Kirkland

    Full Text Available The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later.

  15. Zirconology of garnet-glaucophane schists of the Maksyutov complex (Southern Urals)

    Science.gov (United States)

    Krasnobaev, A. A.; Valizer, P. M.; Anfilogov, V. N.; Busharina, S. V.

    2015-04-01

    The studies of zircons from garnet-glaucophane schists of the Maksyutov complex (Novotashlinskii area) have shown that their substrate was constituted of magmatic gabbroids of Neoproterozoic age (670 Ma). The long-term evolution of zircons encompassed the interval from the Neoproterozoic until the Carboniferous (673.1 ± 5.4, 592.6 ± 9.4, 517.0 ± 7.4, 444.9 ± 4.7, and 323.0 ± 8.8 Ma) and proceeded within a common geochemical area including the stages of inversed development with changes in the zircon compositions, involving the processes of crushing and dissolution. Unit II of the complex contains metamagmatic rocks, which points to the participation of a wider variety of rocks of different compositions and ages in the Maksyutov complex.

  16. Rheological property of mafic schist and geological interpretation to the subduction dynamics

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    Okazaki, K.; Hirth, G.

    2013-12-01

    To understand the spatial and temporal distribution of deformation (e.g., underplating and exhumation of metamorphic rocks) and earthquakes in subduction zones, it is important to constrain the rheological properties of metamorphic rocks (i.e., altered oceanic crust and sediments), and how they evolve during metamorphic reactions following hydration, carbonation and dehydration of the down-going slab. Metamorphism of oceanic crust has stimulated hypotheses on the relationship between intra-slab earthquakes and slab-wedge coupling along plate boundaries in subduction zone. While it is well known that metamorphisms have important effects on material circulation and arc volcanisms at subduction system, it remains unclear how the formation of metamorphic minerals followed by fluid release on the subduction dynamics influences rheology. Past experimental studies on mafic metamorphic rocks were mostly concentrated on phase equilibrium of mineral, thus there are very few reports on the mechanical data for these metamorphic rocks. We conducted triaxial deformation experiments on a mafic greenschist using Griggs-type solid pressure-medium apparatus installed in Brown University. Mafic schist (chlorite - amphibole - epidote - albite schist) containing calcite and quartz veins from Sambagawa metamorphic belt (Japan), which is metamorphosed at the condition of nearly the corner of mantle wedge in hot subduction (1 GPa of pressure and 520C of temperature), was used as experimental samples for typical metamorphic rocks composing oceanic crust in warm subduction zones. Constant strain rete experiments and strain rate step experiment were conducted at 1.0 GPa of confining pressure, 400 ~ 500C of temperature and 10-5 ~ 5×10-7 1/s of strain rate. At stable conditions of samples (1 GPa of confining pressure and 400 and 500C of temperature), differential stresses were higher than 1 GPa. Microstructure of recovered samples showed backing and several localized shear zones. Although

  17. Modelling metamorphism in the Hoosac Schist, Western Massachusetts: new approaches to a New England problem

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    Bidgood, Anna; Waters, Dave; Gardiner, Nick

    2015-04-01

    Along the western margin of the metamorphic Appalachians in New England, Taconic (Ordovician) tectonism and metamorphism are overprinted towards the east by Acadian (Devonian) structures and metamorphism. The Hoosac Schist, a probable correlate of the well-known Gassetts Schist of Vermont, lies in the region of overprinting. It forms a narrow N-S-trending tectonically-bound zone crossing several Barrovian mineral-assemblage zones from garnet to kyanite grade. Highly aluminous units containing cm-sized garnets (Cheney & Brady, 1992) are noted for the occurrence of textural unconformities within the garnets, separating inclusion-rich cores from inclusion-poor rims. Matrix domains contain both paragonite and muscovite. Muscovite is present in at least two compositionally distinct generations, with broad later laths cutting across a microfolded earlier fabric. Rutile is restricted to inclusions in garnet, whereas the matrix Ti- phase is ilmenite. These features suggest a polymetamorphic history, potentially recording the superimposition of Acadian metamorphism on Taconic, but it has not yet proved possible to demonstrate the presence of two metamorphic cycles. This study aims to test and employ the new and revised activity models recently developed for metapelites in the full system MnNCKFMASHTO (White et al, 2014), for use with the Holland & Powell data-set 6. Features that can now be more explicitly modelled include garnet zonation in relation to its inclusion suites and microstructural features, the occurrence, texture and distribution of Ti-bearing accessory minerals, and the assemblages and compositional trends in white micas. Preliminary modelling, correlated with microstructural observation, indicates (1) some confirmation of the concern expressed by White et al (2014) that the stability of margarite-bearing assemblages may be somewhat overestimated, (2) that apart from this, the early growth history of garnet is consistent with its suite of trapped inclusions

  18. Litho-structural analysis of eastern part of Ilesha schist belt, Southwestern Nigeria

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    Fagbohun, Babatunde Joseph; Adeoti, Blessing; Aladejana, Olabanji Odunayo

    2017-09-01

    The Ilesha schist belt is an excellent example of high strain shear belt within basement complex of southwestern Nigeria which is part of the larger West African Shield. The Ilesha schist belt is characterised by metasediment-metavolcanic, migmatite-gneiss and older granite rocks and the occurrence of a Shear zone which has been traced to and correlated with the central Hoggar Neoproterozoic shear zone as part of the Trans-Saharan Belt. Although the area is interesting in terms of geologic-tectonic setting, however, detailed geological assessment and structural interpretation of features in this area is lacking due accessibility problem. For these reasons we applied principal component analysis (PCA) and band ratio (BR) techniques on Landsat 8 OLI data for lithological discrimination while for structural interpretation, filtering techniques of edge enhancement and edge detection was applied on digital elevation model (DEM) acquired by shuttle radar topographic mission (SRTM) sensor. The PCA outperform BR for discrimination between quartzite and granite which are the most exposed rock units in the area. For structural interpretation, DEM was used to generate shaded relief model and edge maps which enable detailed structural interpretation. Geologic fieldwork was further conducted to validate structures and units identified from image processing. Based image interpretation, three deformation events were identified. The first event (D1) which is majorly a ductile deformation produced foliations and folds whose axial planes trend in NNE-SSW. The second event (D2) resulted in reactivation and rotation of the D1 structures particularly the folds in the NE-SW. The third event (D3) produced a transgressive deformation starting with the ductile deformation resulting in the development of sigmoidal structures oriented in NE-SW to E-W direction and the brittle deformation occurring at later stages producing fractures oriented in the E-W to NE-SW directions. These results have

  19. Kinematics of post-orogenic extension and exhumation of the Taku Schist, NE Peninsular Malaysia

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    Md Ali, M. A.; Willingshofer, E.; Matenco, L.; Francois, T.; Daanen, T. P.; Ng, T. F.; Taib, N. I.; Shuib, M. K.

    2016-09-01

    Recent studies imply that the formation and evolution of many SE Asian basins was driven by extensional detachments or systems of low-angle normal faults that created significant crustal exhumation in their footwalls. In this context, the architecture of the Triassic Indosinian orogen presently exposed in Peninsular Malaysia is compatible with significant extension post-dating the orogenic event. In this study we performed a kinematic analysis based on fieldwork and microstructural observations in the Taku Schist, Kemahang granite and the surrounding Gua Musang sediments of northern Peninsular Malaysia in order to shed light on processes related to the build-up and subsequent demise of the Indosinian orogen. The first three phases of deformation were related to an overall period of E-W oriented contraction and burial metamorphism. These phases of deformation are characterized by isoclinal folding with flat lying axial plane cleavages (D1), asymmetrical folding, top-to-the-W-SW shearing (D2) and upright folding (D3). All are in general agreement with observations of the previously inferred Permo-Triassic Indosinian orogeny. During these times, the Taku Schist, a sequence of Paleozoic clastic sediments with mafic intercalations was metamorphosed to amphibolite facies. These rocks are most likely equivalent to the ones exposed in the Bentong-Raub suture zone. Structural relations suggest that the Triassic Kemahang pluton is syn-kinematic, which provides important constraints for the timing of these contractional events. We demonstrate that the overall shortening was followed by a hitherto undescribed extension in NW-SE direction resulting in the formation of a large-scale detachment, the Taku detachment, in northern Peninsular Malaysia. Extension probably reactivated the former subduction plane as a detachment and exhumed previously buried and metamorphosed rocks of similar lithological composition to the neighboring Bentong-Raub suture zone. Such a mechanism is

  20. Late Cretaceous extension and exhumation of the Stong Complex and Taku Schist, NE Peninsular Malaysia

    Science.gov (United States)

    François, Thomas; Afiq Md, Muhammad; Matenco, Liviu; Willingshofer, Ernst; Fatt Ng, Tham; Iskandar Taib, N.; Kamal Shuib, Mustaffa

    2017-04-01

    Dismembering large continental areas by post-orogenic extension requires favourable geodynamic conditions and frequently occurs along pre-existing suture zones or nappe contacts as exemplified by the Stong Complex and Taku Schist of northern Peninsular Malaysia. For this particular case we have employed a field and microstructural kinematic study combined with low temperature thermo-chronology to analyse the tectonic and exhumation history. The results show that the late Palaeozoic - Triassic Indosinian orogeny created successive phases of burial related metamorphism, shearing and contractional deformation. This orogenic structure was then dismembered during a Cretaceous thermal event that culminated in the formation of a large scale late Santonian - early Maastrichtian extensional detachment, genetically associated with crustal melting, the emplacement of syn-kinematic plutons and widespread migmatisation. The emplacement of these magmatic rocks led to an array of simultaneously formed structures that document deformation conditions over a wide temperature range, represented by amphibolite-facies mylonites and more brittle structures, such as cataclastic zones and normal faults that formed during exhumation in the footwall of the detachment. The formation of this detachment and a first phase of Late Cretaceous cooling was followed by renewed Eocene - Oligocene exhumation evidenced from our apatite fission track ages. We infer that an initial Cretaceous thermal anomaly was responsible for the formation of an extensional gneiss dome associated with simple shear and normal fault rotation. These Cretaceous processes played a critical role in the establishment of the presently observed crustal structure of Peninsular Malaysia.

  1. Detection of near-surface horizontal anisotropy in a weathered metamorphic schist at Llano Uplift (Texas) by transient electromagnetic induction

    Science.gov (United States)

    Collins, Jamie L.; Everett, Mark E.; Johnson, Brann

    2006-10-01

    The use of transient controlled-source electromagnetic prospecting to detect buried, steeply dipping foliation in metamorphic rocks is illustrated with data acquired over the Precambrian Packsaddle schist in the Llano Uplift of central Texas. The azimuthal variation of the transient voltage at a given transmitter-receiver separation about a fixed central point is consistent with the forward model response of a homogeneous halfspace exhibiting horizontal electrical anisotropy. The loop-loop exploration configuration is ideally suited to probe horizontal anisotropy. A quantitative match of the forward response to the observed data produces reasonable electrical conductivity values and coefficient of anisotropy for resistive, crystalline geological materials. The most conductive direction consistently lies within a few degrees of the geologically mapped foliation strike direction. The electrical anisotropy is strongest below the near-surface weathered layer, within the more competent bedrock. The agent responsible for generating the anistropy cannot be definitively determined, because it is likely to be a combination of geological factors, such as weathering, compositional banding and microcracking, all of which enhance electrical conductivity parallel to the plane of foliation. The transient electromagnetics is supplemented by DC resistivity and seismic surveys. The elastic anisotropy is evident in the near-surface weathered layer, but it may not persist very deep into the underlying competent schist. The exposure of foliated schist at the surface is not sufficient to rule out a possible role for systematically aligned macrofracture sets as a secondary cause of the observed anisotropy.

  2. Lithologies, structure and basement-cover relationships in the schist belt of the Dom Feliciano Belt in Uruguay

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    Henri Masquelin

    Full Text Available ABSTRACT: This work is the result of a multiyear effort to use field geology to describe lithologies, to establish contact relationships and to create a sketch of the tectonic evolution of the Meso- to Neoproterozoic metasedimentary successions within the Schist Belt of the Dom Feliciano Belt. This low-grade metamorphic cover rests on the high-grade metamorphic basement of the La China and Las Tetas complexes. This basement is Archean-Paleoproterozoic in age. The Schist Belt is overlapped unconformably by the Barriga Negra formation. The Lavalleja complex and the Barriga Negra formation both deformed together during the D2 deformation event (~ 570 -540 Ma, but the Barriga Negra only partially recorded the D2 transpressive event, whereas the Lavalleja complex was affected by both the D1 tangential event and the D2 event. Event D1 would have developed a fold nappe with vergence to the south. This hypothesis is supported by different structures: (i recumbent and upright folds oriented E-W, (ii subhorizontal mylonitic foliation in marbles (calc-schists, (iii stretching lineations plunging towards the SW in metaconglomerates of the Las Tetas Complex, and (iv a reworking of the subhorizontal foliation parallel to the Sarandí del Yí strike-slip shear zone.

  3. Comparison of the high-pressure schist belts of New Caledonia and Sanbagawa, Japan

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    Brothers, R. N.; Yokoyama, K.

    1982-06-01

    The high-pressure schist terranes of New Caledonia and Sanbagawa were developed along the oceanic sides of sialic forelands by tectonic burial metamorphism. The parent rocks were chemically similar, as volcanic-sedimentary trough or trench sequences, and metamorphic temperatures in both belts were 250° to 600° C. From phase equilibria curves, total pressures were higher for New Caledonia (6 15 kb) than for Sanbagawa (5 11 kb) and the estimated thermal gradients were 7 10° C/km and 15° C/km respectively. PT paths identify the higher pressure in New Caledonia ( P differences 2 kb at 300° C and 4 kb at 550° C) with consequent contrast in progressive regional metamorphic zonation for pelites in the two areas: lawsonite-epidote-omphacite (New Caledonia) and chlorite-garnet-biotite (Sanbagawa). In New Caledonia the Na-amphibole is dominantly glaucophane and Na-pyroxenes associated with quartz are Jadeite (Jd95 100) and omphacite; in Sanbagawa the amphibole is crossite or riebeckite and the pyroxene is omphacite (Jd50). For both areas, garnet rims show increase in pyrope content with advancing grade, but Sanbagawa garnets are richer in almandine. Progressive assemblages within the two belts can be equated by such reactions as: New Caledonia Sanbagawa glaucophane+paragonite+H2O⇌albite+chlorite+quartz glaucophane+epidote+H2O⇌albite+chlorite+actinolite and the lower pressure Japanese associations appear as retrogressive phases in the New Caledonia epidote and omphacite zones. The contrasts in PT gradient, regional zonation and mineralogy are believed due to differences in the tectonic control of metamorphic burial: for New Caledonia, rapid obduction of an upper sialic plate over an inert oceanic plate and sedimentary trough; and for Sanbagawa, slower subduction of trench sediments beneath a relatively immobile upper plate.

  4. K-Ar ages of muscovite from greenstone in the Ino formation and schists blocks associated with the Kurosegawa tectonic zone near Kochi city, central Shikoku

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    Ueda, Y. (Tohoku Univ., Sendai (Japan). Faculty of Science); Nakajima, T.; Matsuoka, K.; Maruyama, S.

    1980-07-01

    The Kurosegawa tectonic zone is a serpentinite melange zone in which occur various kinds of tectonic blocks. This report is on the ages of muscovites from the weakly metamorphosed greenstone (so-called semischist) and schist block among the members of the Kurosegawa tectonic zone. The former suffered glaucophane schist facies to pumpellyite-actinolite facies metamorphism. Muscovites coexisting with high-pressure minerals gave 352 - 394 m.y. They indicate so-called semischists are neither metamorphosed at the time of formation of the Kurosegawa tectonic zone, nor by the Sanbagawa metamorphism, but are another distinct metamorphic event older than Middle Carboniferous. This is the oldest radiometric ages among glaucophane schists in Japan. Muscovites from the schists xenolith of albite-epidote amphibolite facies grade, were dated to be 317 and 327 m.y. by K-Ar method. Hornblende and barroisite are sometimes replaced by actinolite or riebeckite along their cleavages or irregular cracks. Muscovite is also deformed showing kink-band folding and is chloritized parallel to the cleavage or along the irregular cracks. Therefore, the value 317 and 327 m.y. may not show the time of albite-epidote amphibolite facies metamorphism, but needless to say, the K-Ar ages are older than those of the Sanbagawa schists.

  5. Petrography, Mineral Chemistry and Geothermobarometry of Andalusite- Bearing Schists North of Azna (Northern Sanandaj-Sirjan Zone, Iran

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    Karim Abdollahi Silabi

    2016-07-01

    Full Text Available Introduction The area studied is located north of Azna (Lorestan Province in a small portion of the Sanandaj – Sirjan structural zone (Mohajjel et al., 2003.This area is part of the Zagros orogenic belt, formed by the opening and closure of Neotethyan ocean. From NE to SW, it consists of three parallel tectonic regions: the Orumieh-Dokhtar magmatic belt, the Sanandaj-Sirjan structural zone and the Zagros thrust-fold belt (Ghasemi and Talbot, 2005. The Sanandaj-Sirjan structural zone is a metamorphic belt composed mostly of greenschist, amphibolite and eclogite facies rocks. The development of the zonetook placeduring the opening of the Tethys ocean and its subsequent closing during the Cretaceous and earlyTertiary convergence of the Afro-Arabian and Eurasian plates (Mohajjel and Fergusson, 2000. The second stage of metamorphism and deformation of the zone, designated D2, is the most important, resulting from the opening and closure of the Neotethyan ocean and the collision of the Arabian plate with the southwestern part of central Iran in the Late Cretaceous to Tertiary (Laramideorogenic phase (Ghasemi and Talbot, 2005; Aghanabati, 2004; Mohajjel et al., 2003; Mohajjel and Fergusson, 2000; Alavi, 1994. In the Sanandaj-Sirjanzone, which includes the Azna area, Cretaceous granitic intrusions into the schists were followed byfolding and faulting. The intrusions produced contact metamorphism, and have lens-shaped outlines, trendingNW-SE. Consequently, the Azna area has a varied petrologic assemblage with polyphase metamorphism and deformation, including schists, metabasites and mylonitic granites. The phases include: 1. Deformation D1, and dynamothermal metamorphism (M1,a result of the subduction of Neotethysoceanic crust beneath the Iranian plate in the Late Jurassic. 2.Deformation D2, and thermal metamorphism (M2,a result of Paleocene continental collision and 3. Deformation D3, and dynamic metamorphism (M3. This deformation is a progressive

  6. Structural observations and U-Pb mineral ages from igneous rocks at the Archaean-Palaeoproterozoic boundary in the Salahmi Schist Belt, central Finland: constraints on tectonic evolution

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    Pietikäinen, K.

    1999-06-01

    Full Text Available The study area in Vieremä, central Finland, contains part of Archaean-Palaeoproterozoic boundary. In the east, the area comprises Archaean gneiss and the Salahmi Schist Belt. The rocks of the schist belt are turbiditic metagreywackes, with well-preserved depositional structures, occurring as Proterozoic wedge-shaped blocks, and staurolite schists, the latter representing higher-strained and metamorphosed equivalents of the metagreywackes. In the west of the area there is an Archaean gneiss block, containing strongly elongated structures, and deformed Svecofennian supracrustal rocks, which are cut by deformed granitoids. These are juxtaposed with the schist belt. The boundaries of these tectonometamorphic blocks are narrow, highly strained mylonites and thrust zones. The metamorphic grade of the supracrustal rocks increases from east to west, the increase being stepwise across the mylonitic block boundaries. The rocks are more deformed from east to west with younger structures overprinting. In the staurolite schists of the Salahmi Schist Belt, the most prominent structure is a lineation (L2 that overprints the bedding and axial plane foliation. In Sorronmäki quarry, at the western boundary of the schist belt, this Palaeoproterozoic lineation dominates all the structures in tonalite gneiss, which gives a U-Pb age of 2731±6 Ma. Southeast of the quarry, at the same boundary, the Salahmi schists have been overturned towards the northeast, suggesting that the Archaean gneiss at Sorronmäki has been thrust towards the northeast over these rocks. In the western part of the study area, the Leppikangas granodiorite that intrudes the Svecofennian supracrustal rocks gives a U-Pb age of 1891+6 Ma. In the granodiorite, a strong lineation formed by the intersection of two foliations, which maybe L2 is associated with thrusting towards the northeast. The monazite age of the Archaean Sorronmäki gneiss is 1817+3 Ma, and the titanite age of the Svecofennian

  7. Petrology and geochemistry of meta-ultramafic rocks in the Paleozoic Granjeno Schist, northeastern Mexico: Remnants of Pangaea ocean floor

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    Torres-Sánchez Sonia Alejandra

    2017-08-01

    Full Text Available The Granjeno Schist is a meta-volcanosedimentary upper Paleozoic complex in northeastern Mexico. We suggest different tectonic settings for metamorphism of its serpentinite and talc-bearing rocks based on petrographic and geochemical compositions. According to the REE ratios (LaN/YbN = 0.51 –20.0 and LaN/SmN = 0.72–9.1 and the enrichment in the highly incompatible elements Cs (0.1 ppm, U (2.8 ppm, and Zr (60 ppm as well as depletion in Ba (1 – 15 ppm, Sr (1 –184 ppm, Pb (0.1 –14 ppm, and Ce (0.1 –1.9 ppm the rocks have mid-ocean ridge and subduction zones characteristics. The serpentinite contains Al-chromite, ferrian chromite and magnetite. The Al-chromite is characterized by Cr# of 0.48 to 0.55 suggesting a MORB origin, and Cr# of 0.93 to 1.00 for the ferrian chromite indicates a prograde metamorphism. We propose at least two serpentinization stages of lithospheric mantle for the ultramafic rock of the Granjeno Schist, (1 a first in an ocean-floor environment at sub-greenschist to greenschist facies conditions and (2 later a serpentinization phase related to the progressive replacement of spinel by ferrian chromite and magnetite at greenschist to low amphibolite facies conditions during regional metamorphism. The second serpentinization phase took place in an active continental margin during the Pennsylvanian. We propose that the origin of the ultramafic rocks is related to an obduction and accretional event at the western margin of Pangea.

  8. Petrology and geochemistry of meta-ultramafic rocks in the Paleozoic Granjeno Schist, northeastern Mexico: Remnants of Pangaea ocean floor

    Science.gov (United States)

    Torres-Sánchez, Sonia Alejandra; Augustsson, Carita; Jenchen, Uwe; Rafael Barboza-Gudiño, J.; Alemán Gallardo, Eduardo; Ramírez Fernández, Juan Alonso; Torres-Sánchez, Darío; Abratis, Michael

    2017-08-01

    The Granjeno Schist is a meta-volcanosedimentary upper Paleozoic complex in northeastern Mexico. We suggest different tectonic settings for metamorphism of its serpentinite and talc-bearing rocks based on petrographic and geochemical compositions. According to the REE ratios (LaN/YbN = 0.51 -20.0 and LaN/SmN = 0.72-9.1) and the enrichment in the highly incompatible elements Cs (0.1 ppm), U (2.8 ppm), and Zr (60 ppm) as well as depletion in Ba (1 - 15 ppm), Sr (1 -184 ppm), Pb (0.1 -14 ppm), and Ce (0.1 -1.9 ppm) the rocks have mid-ocean ridge and subduction zones characteristics. The serpentinite contains Al-chromite, ferrian chromite and magnetite. The Al-chromite is characterized by Cr# of 0.48 to 0.55 suggesting a MORB origin, and Cr# of 0.93 to 1.00 for the ferrian chromite indicates a prograde metamorphism. We propose at least two serpentinization stages of lithospheric mantle for the ultramafic rock of the Granjeno Schist, (1) a first in an ocean-floor environment at sub-greenschist to greenschist facies conditions and (2) later a serpentinization phase related to the progressive replacement of spinel by ferrian chromite and magnetite at greenschist to low amphibolite facies conditions during regional metamorphism. The second serpentinization phase took place in an active continental margin during the Pennsylvanian. We propose that the origin of the ultramafic rocks is related to an obduction and accretional event at the western margin of Pangea.

  9. Ediacaran ( 620 Ma) high grade regional metamorphism in the northern Arabian Nubian Shield: U/Th-Pb monazite ages of the Elat schist

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    Elisha, Bar; Katzir, Yaron; Kylander-Clark, Andrew

    2017-04-01

    Ediacaran times witnessed a hemisphere-scale orogenesis forming the extensive Pan-African mountain ranges and resulting in the final assembly of Gondwana supercontinent. The Elat metamorphic basement (S Israel) located at the northernmost tip of a major Pan-African orogenic suture, the Arabian Nubian Shield (ANS), comprises amphibolite facies schists and gneisses and was most likely shaped by this major continental collision. However the timing, number and duration of metamorphic events in Elat and elsewhere in the ANS are non-conclusive and a major emphasis was given to pre-Ediacaran island-arc related tectonics. This is mostly because U-Pb dating of zircon, widely used in Elat and elsewhere, is very successful in constraining the ages of the igneous and sedimentary protoliths, but is 'blind' to metamorphism at grades lower than granulite. Here U/Th-Pb dating of monazite, a precise chronometer of metamorphic mineral growth, is systematically applied to the Elat schist and unveils the tectono-metamorphic evolution of the Elat basement. Previous U-Pb dating of detrital zircon has shown that the sedimentary protoliths of the Elat schist are the oldest basement components (≥800 Ma), and detailed structural observations of the schists portrayed a complex deformation history including four successive phases (Shimron, 1972). The earliest three phases were defined as ductile and penetrative, but some of the available geochronological data apparently contradict field relations. In-situ analysis of metamorphic monazites by LASS (Laser Ablation Split Stream) involves simultaneous measurement of U/Th-Pb isotope ratios and REE contents in a single 10 μm sized grain or domain, thus allowing determining the age of specific texture and metamorphic assemblage. Monazite dating of the Elat schist yielded two concordant age clusters at 712±6 and 613±5 Ma. The corresponding REE patterns of the dated monazite grains indicate that porphyroblast growth, either garnet or staurolite

  10. Steatite and schist as contenders for the Global Heritage Stone Resource due to their importance in Brazil's natural stone built heritage

    Science.gov (United States)

    Gilberto Costa, Antônio

    2013-04-01

    In Brazil, European natural stones, such as marble and limestone, were used as building material at historically important buildings and monuments, mainly in coastal cities, as well as in contemporary urban centers. However, in the country's central region, these Italian and Portuguese marbles and limestones were scarcely used. Instead, they were substituted for soapstone and several types of schist. As of 1755, the former was employed because of the ease with which it can be worked, essentially in the sculptural art and in the production of ornamental elements. Characterized by the presence of talc, steatite can feature other minerals such as serpentine, chlorite, carbonate, amphiboles, oxides like hematite and magnetite, and sulfites like pyrite, all in broadly variable amounts, which can result in modification of its technological properties (Volumetric Weight, Porosity, Water Absorption, Uniaxial Compression, Abrasion Resistance, Thermal Expansion etc.). In such rocks, talc content will be a decisive factor in their coloration. The higher its talc content is the clearer and softer the stone type will be, which ends up being known as talc stone. In such cases, the rock can display different hues of green, blue and gray. When compared to other rocks, texture patterns containing talc crystals, chlorite and carbonate contribute to low absorption and porosity for steatites. Schists were equally used at historical buildings in the Brazilian inland, especially in constructions in Minas Gerais towns, both in the production of structural elements such as bases, corners, pillars and foundations and in the creation of ornaments. Featuring different compositions, such rocks - which almost always occur interlayered with other ones such as quartzite - display coloration ranging from hues of gray to green to blue. They can be quartz-sericite-albite-chlorite schists featuring great or no amounts of carbonate, magnetite, epidote and tourmaline, sometimes with garnet, such as in

  11. Omphacite-bearing calcite marble and associated coesite-bearing pelitic schist from the meta-ophiolitic belt of Chinese western Tianshan

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    Lü, Zeng; Bucher, Kurt; Zhang, Lifei

    2013-10-01

    In the meta-ophiolitic belt of Chinese western Tianshan, marble (5-50 cm thick) is found interlayered with pelitic schist. The marble is mainly composed of calcite (>90% in volume) and accessory phases include omphacite, quartz, dolomite, albite, phengite, clinozoisite and titanite with or without rutile core. This is the first omphacite (Jd35-50) reported from marble of Chinese western Tianshan. It mainly occurs in the calcite matrix, rarely as inclusion in albite. The presence of omphacite suggests that the layered marble was subjected to eclogite-facies metamorphism, consistent with the occurrence of high-Si phengite (Si a.p.f.u. up to 3.7) and aragonite relic in albite. The associated pelitic schist consists of quartz, white mica (phengite + paragonite), garnet, albite, amphibole (barroisite ± glaucophane) and rutile/titanite, as well as minor amounts of dolomite, tourmaline and graphite. Coesite is optically recognized within porphyroblastic pelitic garnet and is further confirmed via Raman spectroscopy. Thermodynamic models support the UHP metamorphism of calcite marble, similar to the associated pelitic schist. Shared UHP-LT history of calcareous and pelitic rocks in Chinese western Tianshan suggests that the supracrustal carbon-rich sediments have been carried to depths of >90 km during fast subduction and thus are potential sources for carbon recycled into arc crust.

  12. CHEMICAL AND GEOCHEMICAL CHARACTERISTICS OF THE ČEMERNICA ANTIMONITE DEPOSIT IN THE MID-BOSNIAN SCHIST MOUNTAINS

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    Ivan Jurković

    1999-12-01

    Full Text Available The Čemernica Sb-Zn-Hg-W quartz vein system is situated in Lower Palaeozoic metasediments formed under 3-5 kbars and 350° to 450 °C, intruded by Upper Palaeozoic rhyolites. K-Ar dating indicated three metamorphic phases. The first, 343 Ma old affected phyllite rocks, the second 120-90 Ma metamorphosed rhyolites and the third one, 46 to 37 Ma caused formation of ottrelite schist, host rocks of ore deposit. The Čemernica vein (NW-SE, 1,5 km long, and over 350 m deep, on average 0,67 m thick, is faulted in four separated parts: »Southern vein«: »Erbstollcn vein«; »Main vein* and »NW-vein«. Structures of the veins are massive, banded, rarely brecciated. Par-agenesis: quartz I (50-95% of ore mass as the main gangue mineral; antimonite I, II, sphalerite I, II. cinnabar as the main ore minerals; subordinate are chalcedony, siderite, ferberite, jamesonite.berthierite, boulangerile, plagionite, arsenopyrite, scarce arc pyrite I, II, marcasite, pyrrhotite, barite, chalcopyrite I, II, tetrahedrite and enargite, whereas accessories are galena, quartz II, realgar, gold and mineral »X«. Chemical analysis of 177 ore samples taken from old Saxon and Austrian mining works gave 4.33% Zn, 2,22% Sb and 137 gr/t Ag. Fifteen samples gave trace to 0.1% Hg and eight samples trace to 0.l gr/t Au. Untouched part ol the »Main vein« gave5.9(1% Zn, 8.93%Sb and 126 g/t Ag. Remnant ore gave 2.60-3.28% Zn, 0.69-0.73% Sb and 161 to 190 gr/t Ag. Entire proved, probable and posssible ore reserves (306.000 t have 5.9% Zn, 4.0% Sb and 114 gr/t Ag. The 34 S of antimonite is +2.6 ‰ and of sphalerite +3.7‰ indi¬cating juvenile origin of sulphur, Fluid inclusion study of quartz iden-tified three types of fluids: Variscan NaCI-KCI-H2O type related to the Late Palaeozoic granite (rhyolite megmatism, post-Variscan NaCl-CaCl2 + MgCl2-H2O type formed by admixing of hot saline connate waters originated from the Late Permian evaporite complex and meta

  13. A km-scale "triaxial experiment" reveals the extreme mechanical weakness and anisotropy of mica-schists (Grandes Rousses Massif, France)

    Science.gov (United States)

    Bolognesi, Francesca; Bistacchi, Andrea

    2018-02-01

    The development of Andersonian faults is predicted, according to theory and experiments, for brittle/frictional deformation occurring in a homogeneous medium. In contrast, in an anisotropic medium it is possible to observe fault nucleation and propagation that is non-Andersonian in geometry and kinematics. Here, we consider post-metamorphic brittle/frictional deformation in the mechanically anisotropic mylonitic mica-schists of the Grandes Rousse Massif (France). The role of the mylonitic foliation (and of any other source of mechanical anisotropy) in brittle/frictional deformation is a function of orientation and friction angle. According to the relative orientation of principal stress axes and foliation, a foliation characterized by a certain coefficient of friction will be utilized or not for the nucleation and propagation of brittle/frictional fractures and faults. If the foliation is not utilized, the rock behaves as if it was isotropic, and Andersonian geometry and kinematics can be observed. If the foliation is utilized, the deviatoric stress magnitude is buffered and Andersonian faults/fractures cannot develop. In a narrow transition regime, both Andersonian and non-Andersonian structures can be observed. We apply stress inversion and slip tendency analysis to determine the critical angle for failure of the metamorphic foliation of the Grandes Rousses schists, defined as the limit angle between the foliation and principal stress axes for which the foliation was brittlely reactivated. This approach allows defining the ratio of the coefficient of internal friction for failure along the mylonitic foliation to the isotropic coefficient of friction. Thus, the study area can be seen as a km-scale triaxial experiment that allows measuring the degree of mechanical anisotropy of the mylonitic mica-schists. In this way, we infer a coefficient of friction μweak = 0.14 for brittle-frictional failure of the foliation, or 20 % of the isotropic coefficient of internal

  14. Deformation fabrics of blueschist facies phengite-rich, epidote-glaucophane schists from Ring Mountain, California and implications for seismic anisotropy in subduction zone

    Science.gov (United States)

    Jung, H.; HA, Y.; Raymond, L. A.

    2016-12-01

    In many subduction zones, strong seismic anisotropy is observed. A part of the seismic anisotropy can be attributed to the subducting oceanic crust, which is transformed to blueschist facies rocks under high-pressure, high-temperature conditions. Because glaucophane, epidote, and phengite constituting the glaucophane schists are very anisotropic elastically, seismic anisotropy in the oceanic crust in hot subduction zones can be attributed to the lattice preferred orientation (LPO) of these minerals. We studied deformation fabrics and seismic properties of phengite-rich, epidote-glaucophane schists from the Franciscan Complex of Ring Mountain, California. The blueschist samples are mainly composed of glaucophane, epidote, and phengite, with minor garnet, titanite, and chlorite. Some samples contain abundant phengite (up to 40 %). We determined LPOs of minerals using SEM/EBSD and calculated seismic anisotropy of minerals and whole rocks. LPOs of glaucophane have [001] axes aligned subparallel to lineation, and both (110) poles and [100] axes subnormal to foliation. Epidote [001] axes are aligned subnormal to foliation, with both (110) and (010) poles subparallel to lineation. LPOs of phengite are characterized by maxima of [001] axes subnormal to foliation, and both (110) and (010) poles and [100] axes aligned in a girdle subparallel to foliation. Phengite showed much stronger seismic anisotropy (AVP = 42%, max.AVS = 37%) than glaucophane or epidote. Glaucophane schist with abundant phengite showed much stronger seismic anisotropy (AVP = 30%, max.AVS = 23%) than epidote-glaucophane schist without phengite (AVP = 13%, max.AVS = 9%). Therefore, phengite clearly can significantly affect seismic anisotropy of whole rocks. When the subduction angle of phengite-rich blueschist facies rocks is considered for a 2-D corner flow model, the polarization direction of fast S-waves for vertically propagating S-waves changed to a nearly trench-parallel direction for the subduction

  15. Experimental Investigation of Biotite-Rich Schist Reacting with B-Bearing Fluids at Upper Crustal Conditions and Correlated Tourmaline Formation

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    Andrea Orlando

    2017-08-01

    Full Text Available Fluid–rock interaction experiments between a biotite-rich schist (from Mt. Calamita Formation, Elba Island, Italy and B-bearing aqueous fluids were carried out at 500–600 °C and 100–130 MPa. The experiments have been carried out in order to reproduce the reaction, which would have produced tourmalinisation of the biotite schist, supposedly by circulation of magmatic fluids issued from leucogranitic dykes. The reacting fluids were either NaCl-free or NaCl-bearing (20 wt % aqueous solutions, with variable concentration of H3BO3 (0.01–3.2 M. The experimental results show that tourmaline (belonging to the alkali group crystallise under high-temperature and upper crustal conditions (500–600 °C, 100–130 MPa when H3BO3 concentration in the system is greater than 1.6 M. The composition of tourmaline is either dravitic (Mg-rich or schorlitic (Fe-rich, depending if an NaCl-bearing or NaCl-free aqueous solution is used. In the first case, a significant amount of Fe released from biotite dissolution remains in the Cl-rich solution resulting from the experiment. By contrast, when pure water is used, Na/K exchange in feldspars makes Na available for tourmaline crystallisation. The high concentration of Fe in the residual fluid has an important metallogenic implication because it indicates that the interaction between the saline B-rich fluid of magmatic derivation and biotite-rich schists, besides producing tourmalinisation, is capable of mobilising significant amounts of Fe. This process could have produced, in part or totally, the Fe deposits located close to the quartz–tourmaline veins and metasomatic bodies of the Mt. Calamita Formation. Moreover, the super-hot reservoir that likely occurs in the deepest part of the Larderello–Travale geothermal field would also be the site of an extensive reaction between the B-rich fluid and biotite-bearing rocks producing tourmaline. Thus, tourmaline occurrence can be a useful guide during deep

  16. Electrical properties of schist and mylonite from the South Island, New Zealand: Exploring the source of the Southern Alps Anomalous Conductor

    Science.gov (United States)

    Kluge, Katherine; Toy, Virginia; Ohneiser, Chrisitan; Lockner, David

    2017-04-01

    The Southern Alps Electrical Conductor (SAC), identified from magnetotelluric surveys of the South Island Geophysical Transect (SIGHT) in the South Island, New Zealand, has high electrical conductivity relative to surrounding lithology (0.1 to 1 S/m between 5 and 25 km depth). This phenomenon is spatially coincident with shear zones of the Alpine Fault transform boundary and a region of anomalously low seismic velocity. It has been suggested these geophysical anomalies indicate dynamically linked fluids or graphite networks at depth, but this is unconfirmed. The convergent component of deformation within the Southern Alps orogen exhumes the lower crust. Because of this, we have been able to examine the relationship between electric properties, porosities, and mineral arrangement of hanging wall rock samples across metamorphic and strain gradients approaching the Alpine Fault. These allow us to constrain the roc properties which yield the source of the Southern Alps Electrical Conductor. We measured the electrical properties of 7 hand samples at the USGS Rock Physics Lab in Menlo Park, California. Complex resistivity of samples under confining pressure was measured up to 200 MPa, with a saturating brine of 0.1 M KCl. Laboratory measurements were then converted to complex conductivity. Mylonite conductivities were also averaged at each confining pressure and extrapolated to Alpine Fault conditions at depth (using fluid conductivity, geothermal gradient and effective confining pressure) to find projected in situ values between 0 and 9.4 km depth. Porosity ranges from 1.2 to 5.4% for hanging wall metamorphic schists and 1.0 to 1.9% for Alpine Fault Zone mylonites. Schist porosity substantially decreases with increasing proximity to the Alpine Fault, but mylonite porosity exhibits no systematic trend. Conductivity at 5 MPa effective confining pressure and 20 Hz ranges from 9.70x10-5 to 2.23x10-3 S/m for schists and 1.48x10-3 to 4.33x10-3 S/m for mylonites. Schist

  17. Tectonomagmatic setting and provenance of the Santa Marta Schists, northern Colombia: Insights on the growth and approach of Cretaceous Caribbean oceanic terranes to the South American continent

    Science.gov (United States)

    Cardona, A.; Valencia, V.; Bustamante, C.; García-Casco, A.; Ojeda, G.; Ruiz, J.; Saldarriaga, M.; Weber, M.

    2010-10-01

    Metamorphosed volcano-sedimentary rocks accreted to the northern South American continental margin are major vestiges of the Caribbean oceanic plate evolution and its interactions with the continent. Selected whole rock geochemistry, Nd-Sr isotopes and detrital zircon geochronology were obtained in metabasic and metasedimentary rocks from the Santa Marta and San Lorenzo Schists in northernmost Colombia. Trace element patterns are characterized by primitive island arc and MORB signatures. Similarly initial 87Sr/ 86Sr-ɛ Nd isotopic relations correlate with oceanic arcs and MORB reservoirs, suggesting that the protoliths were formed within a back-arc setting or at the transition between the inta-oceanic arc and the Caribbean oceanic crust. Trace element trends from associated metasedimentary rocks show that the provenance was controlled by a volcanic arc and a sialic continental domain, whereas detrital U/Pb zircons from the Santa Marta Schists and adjacent southeastern metamorphic units show Late Cretaceous and older Mesozoic, Late Paleozoic and Mesoproterozoic sources. Comparison with continental inland basins suggests that this arc-basin is allocthonous to its current position, and was still active by ca. 82 Ma. The geological features are comparable to other arc remnants found in northeastern Colombia and the Netherland Antilles. The geochemical and U/Pb detrital signatures from the metasedimentary rocks suggest that this tectonic domain was already in proximity to the continental margin, in a configuration similar to the modern Antilles or the Kermadec arc in the Pacific. The older continental detritus were derived from the ongoing Andean uplift feeding the intra-oceanic tectonic environment. Cross-cutting relations with granitoids and metamorphic ages suggest that metamorphism was completed by ca. 65 Ma.

  18. SIMS U-Pb, Sm-Nd isotope and geochemical study of an arkosite-amphibolite suite, Peräpohja Schist Belt: evidence for ca. 1.98 Ga A-type felsic magmatism in northern Finland

    Directory of Open Access Journals (Sweden)

    Eero Hanski

    2005-01-01

    Full Text Available In the northern and north-eastern part of the Peräpohja Schist Belt, northern Finland, an extensive supracrustal rock unit has been identified which is composed of alternating amphibolitic and arkositic components. The amphibolites form layers whose thickness varies from one millimeter to some tens of meters, being most often a few tens of centimeters. They represent mafic tuff beds deposited concurrently with more abundant arkositic rocks. Most of the arkosites have a modal and major and trace element compositionsimilar to that of A2-type granites. For example, they exhibit high LREE/HREE, negative Eu anomalies, and flat HREE and are moderately enriched in Nb, Zr, and Y. The genesis of the arkosites is enigmatic as they show features supporting either a volcaniclastic or an epiclastic origin. In the latter case, they were derived via erosion of a source dominated by A2-type granitic rocks. Previous conventional ID-TIMS and new SIMS U-Pb dating of zircons from two arkosite samples and one mica schist sample, all three picked from the northern part of the schist belt, indicate that these rocks contain a single population of zircons with an age of ca. 1975 Ma suggesting that they are among the youngest supracrustal rocks in the schist belt. In contrast, one mica schist sample from the western part of the belt revealed only the presence of Archean zircons. The samples do not differ markedly in terms of their Nd isotopecomposition as they all have a moderately negative εNd(1900 Ma. Regardless of the genesis of the arkosites, their isotopic and geochemical data suggest a previously unknown occurrence of extensive A-type felsic magmatism at ca. 1.98 Ga, contemporaneously withsome continental flood basalts. However, concrete evidence for this felsic A-type magmatism in the form of ca. 1.98 Ga felsic plutonic rocks is virtually absent in the presently exposed Fennoscandian Shield.

  19. The Schistes à Blocs Fm: the ultimate member of the Annot Sandstones in the Southern Alps (France); slope gullies or canyon system?

    Science.gov (United States)

    Rubino, Jean-Loup; Mercier, Louison; Daghdevirenian, Laurent; Migeon, Sébastien; Bousquet, Romain; Broucke, Olivier; Raisson, Francois; Joseph, Philippe; Deschamp, Remi; Imbert, Patrice

    2017-04-01

    Described since a long time, the Schistes à Blocs Fm is the ultimate member of the famous tertiary Grès d'Annot Sandstones in southern alpine foredeep basin in SE France. It mainly consists of shales, silty shales, debris flows, olistoliths and a subordinate amount of sandstones. Since their introduction, and because of their location down to major thrust sheet, they have been considered as a tectono-sedimentary unit linked to the nappe's emplacement and refer as an olistostrome, (Kerckove 1964-1969). However they are separated from the underlying Annot Sandstones by a major erosional surface which deeply cuts, up to 500m, into the sandy turbidites; this surface definitively predates the infill and the nappe emplacement. This is supported by the fact that imbricates affect the upper part of the Schistes and also because of the age; the Schistes à Blocs being Upper Eocene to Lower Oligocene whilst the nappe is latest Oligocene to Lower Miocene. A detailed analysis of the erosional surface in la Bonette area reveals a complex geometry which shows obvious similarities with these observed either on submarine canyons or in slope dissected by gullies as shown by numerous seabeams or 3D seismic images. The infill is quite complex, no basal lag have been observed, however bioturbations suggest occurrence of by pass. Most commonly the lower part of the infill is made of muddy or silty sediments. In some areas, decametric to pluri hectometric olistoliths are interbedded within these deposits. Debris flows are also common with a muddy matrix and finally isolated turbidite channels including the same material than in the Annot Sandstones occur. The reworked material into the debris flows and in the olistoliths suggests that it doesn't only derived from canyon flanks (sandstones) but includes elements belonging to older tethyan series such as Triassic and Liassic carbonates which must be exposed on the sea floor on local highs in the more internal part of the Alps but much

  20. Efeito do uso do xisto em características químicas do solo e nutrição do tomateiro Effect of the use of schist on chemical characteristics of soil and on tomato nutrition

    Directory of Open Access Journals (Sweden)

    Hamilton Seron Pereira

    2004-06-01

    Full Text Available Um dos principais problemas ambientais que ocorre com o processo de exploração do xisto é a produção de quantidades maciças de xisto retortado de alta alcalinidade. Este resíduo, depositado em larga escala, libera elementos tóxicos no ambiente, poluindo o solo, a água de superfície e até o ar atmosférico. Avaliou-se o efeito do xisto nas características químicas do solo e na nutrição do tomateiro em dois experimentos conduzidos em Argissolos Vermelho Amarelo, em ambiente protegido. Foram aplicadas e incorporadas ao solo as doses de 0; 3; 6; 9 e 12 t ha-1 de xisto. O delineamento utilizado foi em blocos ao acaso com quatro repetições. A adição de xisto promoveu aumento significativo nos teores de enxofre e silício no solo e nas folhas do tomateiro. Não foram verificadas alterações no valor do pH do solo nem nos teores de cátions trocáveis, mas, observou-se aumento na disponibilidade de fósforo. Não se verificou dano ao ambiente, por contaminações químicas de metais pesados, nem diminuição na produtividade do tomate em função da aplicação dos tratamentos. O xisto se mostrou apto para ser usado na agricultura, nas doses utilizadas.Among the main environmental problems due to the use of schist is a massive production of highly alkaline schist processing waste. This residue, when deposited in great amounts liberates toxic elements in the atmosphere, polluting the soil, the surface water and the atmospheric air. The effect of the use of schist in agriculture was evaluated on the soil chemical attributes and tomato crop nutrition. Two experiments were performed on Typic Eutrustults under greenhouse conditions. Schist rates of 0; 3; 6; 9 and 12 t ha-1 were applied and incorporated in the soil. A randomized block design with four replications was used. Schist use promoted a significant sulfur and silicon content increase in the soil as well as in the tomato leaves; no soil pH alteration was verified neither the

  1. U-Pb (SHRIMP) and Sm-Nd geochronology of basaltic green schists of the Aracuai orogen: implications for the age of the Macaubas group; Geocronologia U-Pb (SHRIMP) e Sm-Nd de xistos verdes basalticos do orogeno Aracuai: implicacoes para a idade do grupo Macaubas

    Energy Technology Data Exchange (ETDEWEB)

    Babinski, Marly [Universidade de Sao Paulo, SP (Brazil). Inst. de Geociencias. Centro de Pesquisas Geocronologicas]. E-mail: babinski@usp.br; Gradim, Rafael Jaude; Alkmim, Fernando Flecha de [Universidade Federal de Ouro Preto, MG (Brazil). Escola de Minas. Dept. de Geologia]. E-mails: rafaelgradim@gmail.com; alkmim@degeo.ufop.br; Pedrosa-Soares, Antonio Carlos; Noce, Carlos Mauricio [Minas Gerais Univ., Belo Horizonte (Brazil). Inst. de Geociencias; Liu, Dunyi [Chinese Academy of Geological Sciences, Beijing (China). Beijing SHRIMP Lab.

    2005-12-15

    The age and stratigraphic position of the basaltic green schists of the Rio Preto valley, located in the western part of the Aracuai Belt (ca. 60 km north of Diamantina, Minas Gerais) were a matter of controversy in the geologic literature, because several authors correlated them to the Neo proterozoic Macaubas Group but others to the lower Espinhaco Supergroup (ca. 1.7 Ga). However, detailed studies demonstrate that these green schists represent an interplay of submarine basaltic volcanism, volcanoclastic sedimentation and fire fountaining, and that they belong to the Chapada Acaua Formation of the Macaubas Group (Gradim et al., 2005). Geochemical studies indicate that the green schist protoliths evolved in a continental intra plate environment. Zircon crystals were separated from a green schist sample and analyzed by the U-Pb SHRIMP method. A Sm-Nd whole-rock isotopic analysis was obtained from the same sample. The Sm- Nd model age of ca. 1.52 Ga suggests that the green schist protoliths are younger than the magmatism of the Espinhaco rift. Most analyzed zircon crystals show features of detrital grains. The older ages indicate zircon grains inherited from the Archean- Paleoproterozoic basement and from magmatic rocks of the Espinhaco rift. The younger U-Pb values constrain the maximum age of the green schist protoliths at ca. 1,16 Ga. (author)

  2. Construction of horizontal mining facilities through schist`s massive

    OpenAIRE

    Doneva, Nikolinka; Hadzi-Nikolova, Marija; Mirakovski, Dejan; Mijalkovski, Stojance

    2013-01-01

    This paper presents cost analysis for horizontal mining facilities through schist’s massive. Two variables, headings cross section and rock-quality designation (RQD) were considered. Based on a real data analyses we were able to define two parameters functional relation between costs and cross-section. Examples and clasifications are elaborated in details.

  3. Structural control on gold mineralization in the Satulinmäki and Riukka prospects, Häme Schist Belt, southern Finland

    Directory of Open Access Journals (Sweden)

    Kerstin Saalmann

    2007-01-01

    Full Text Available The Satulinmäki and Riukka prospects located in the Häme Schist Belt in southern Finland are dominated by mafic and intermediate to felsic metavolcanic rocks of the Forssa Group formed in a continental arc setting. This magmatic belt formed some 1890–1880 Ma ago and has been deformed during the Svecofennian orogeny. The dominant penetrative foliation is represented by Sn+1, which is axial planar to cm- to dm-scale iscolinal Fn+1 folds and thus parallel to the layering Sn. Associated ductile shearing might reflect early thrusting. Dn+2 post-dating peak metamorphism is characterized by small-scale to regional-scale refolding of Fn+1 folds around ~SW-NE fold axes. This phase is transitional to development of SW-NE to WSW-ENE and NW-SE striking shear zones and faults formed due to dextral transpressionduring Dn+3 at retrograde conditions crossing the brittle-ductile transition. Many mineralized quartz veins have formed during this event. Later faults and quartz veins and reactivation of pre-existing structures during Dn+4 indicate rotation of the stress field to ~NESWoriented compression. A clear ~SW-NE trend of sulphide mineralization and elevated gold contents and the spatial association to Dn+3 quartz veins, shear zones and faults suggest a strong structural control, typical of orogenic gold deposits, and that mineralization took place during Dn+3. The controlling structures, (i WSW-ENE to SW-NE shear zones and faults and (ii NW-SE oriented fault, are second and third order structures to major regional-scale shear zones. The fault zones and their intersection points impart a directional permeability so that the mineralising fluids were channelled along dilatant zones. Approximately (WNW-(ESE trending faults being (reactivated as extensional faults or dilatant shear planes during Dn+3 transpression with WNW-ESE to NW-SE oriented compression direction could have acted as conduits for fluids during upward flow from deeper crustal level. Future

  4. Alterações de atributos químicos do solo e do crescimento de plantas de milho pela aplicação de xisto Changes in soil chemical attributes and corn growth due to schist application

    Directory of Open Access Journals (Sweden)

    Lucia H. G. Chaves

    2006-03-01

    Full Text Available Este trabalho foi o ponto-chave para se avaliar os efeitos de resíduo xisto retortado nos atributos químicos do solo e no crescimento vegetativo do milho em um experimento conduzido em Neossolo Regolítico Ta Eutrófico, em casa de vegetação. O delineamento experimental foi inteiramente casualizado, com três repetições, sendo cinco os tratamentos com xisto retortado (0, 3, 6, 9 e 12 t ha-1. O xisto foi incorporado ao solo em cada unidade experimental, que se compunha de vasos com 2 dm³ de solo, as quais permaneceram incubadas durante 10 dias. Após este período, semeou-se o milho e, depois de 60 dias, foram avaliados: a altura da planta, o diâmetro do caule e a matéria verde e seca das plantas. Amostras de solo das unidades experimentais coletadas antes e depois do plantio do milho foram submetidas às análises químicas. A adição de xisto retortado promoveu aumento significativo na soma de bases trocáveis e nos teores de enxofre e silício no solo, porém não houve aumento nos valores do pH do solo. O crescimento vegetativo das plantas de milho não foi influenciado pelas quantidades utilizadas de xisto retortado.The objective of this work was to evaluate the effects of schist processing waste on soil chemical attributes and on vegetative growth of corn. The experiment was conducted in Regosol Eutrophic under greenhouse conditions. The treatments consisted of five rates of schist processing waste (0, 3, 6, 9 and 12 t ha-1 in a completely randomized experimental design with three replications. The schist was incorporated in the soil in each experimental unit, constituted by pots with 2 dm³ of soil, which remained incubated during 10 days. After this period the corn was sown and after 60 days the plant height, the stem diameter and the fresh and dry matter of the shoots were evaluated. Soil samples were taken from each experimental unit before and after sowing for chemical analysis. Application of schist promoted a significant

  5. Tratamentos térmicos do calxisto para uso como camada de cobertura no cultivo de Agaricus brasiliensis Thermal treatments on lime schist casing layer for Agaricus brasiliensis cultivation

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    Nelson Barros Colauto

    2010-07-01

    Full Text Available A escolha da camada de cobertura é uma das mais importantes etapas do cultivo de Agaricus brasiliensis. Apesar dessa importância, poucos estudos relatam o uso de diferentes tratamentos térmicos para o controle da microbiota em camadas de cobertura alternativas. Assim, o objetivo deste trabalho foi avaliar o efeito da pasteurização e da autoclavagem do material alternativo calxisto para utilização como camada de cobertura no cultivo de A. brasiliensis. O fungo foi inicialmente crescido em grãos de trigo e transferido para meio de cultivo previamente compostado. Após a completa colonização, a camada de cobertura (calxisto pasteurizada ou autoclavada foi adicionada. Avaliaram-se a eficiência biológica, o número e a biomassa de cogumelos produzidos e o fluxo de produção. Concluiu-se que a camada de cobertura com calxisto autoclavado reduzem o tempo de produção, a eficiência biológica e o número e a biomassa de cogumelos cultivados. Entretanto, a camada de cobertura com o calxisto pasteurizado é a mais eficiente para o cultivo de A. brasiliensis.Casing layer choice is one of the most important phases on Agaricus brasiliensis cultivation. Besides the importance of it few studies report the use of different heat treatments to control the microbiota in alternative casing layers. Thus, the objective of this work was to evaluate the effect of pasteurized or autoclaved lime schist as an alternative casing layer on A. brasiliensis cultivation. The fungus was previously grown on wheat grains and transferred to a substratum previously composted. After substratum mycelium colonization a pasteurized or autoclaved lime schist casing layer was added on. It was evaluated the biological efficiency, the number and mass of produced mushroom and the production flush along cultivation. It was concluded that autoclaved lime schist casing layer decreases period of production, biological efficiency, number and mass of cultivated mushrooms. However

  6. Oil Shale and Its Relation to Petroleum and Other Fuels (Summary Les schistes à l'huile et leurs relation avec le pétrole et les autres combustibles (résumé

    Directory of Open Access Journals (Sweden)

    Billo S. M.

    2006-10-01

    Full Text Available World oil reserves in oil shales (1. 2 to 2 trillion barrels are at least 4 times as large as proven crude oil petroleum reserves (310 billion barrels. Petroleum is produced from oil shale by pyrolysis (destructive distillation by hecit. Coal can also be converted ta synthetic petroleum products by direct hydrogenation and by the modified Fischer-Tropsch process. Rising cost of oil exploration and production and increasing efficiency of synthetizing processes indicate that synthetic fuels may increase the supply of natural liquid fuels in the foreseeable future. The term kerogen is often used to comprise all the organic matter contained in sediments and may be of two kinds: 1 coalylike kerogen, and 2 sapropellic kerogen - oil shale type. It is believed that both kerogen and petroleum were formed from hypothetical ancestor - protopetroleum. They are found together in sedimenfs and their C13C12 ratios are similar. The largest producer of oil shale ore China, the USSR and Sweden. The USA is technologically prepared to begin production of synthetized fuels through varying economic condition. Richness and size of deposits, cost of mining, cost of retorting, character of products, and location of deposit in relation to plant and market, determine the economic value of a given deposit. Les réserves mondiales de schistes à huile (1,2 à 2 x 10. 12 barils sont au moins quatre fois supérieures aux réserves prouvées de pétrole brut (310 x 10. 9 barils. On extrait le pétrole des schistes par pyrolyse (distillation destructive thermique. Le charbon peut aussi être transformé en hydrocarbures par hydrogénation et par le procédé Fischer-Tropsch modifié. L'augmentation des coûts de l'exploration et de la production du pétrole et amélioration de l'efficacité des procédés synthétiques montrent que les produits synthétiques vont jouer un rôle croissant dans l'approvisionnement en combustibles liquides au cours des années à venir. Le terme k

  7. Phase equilibrium, geothermobarometric and xenotime age dating constraints on the Alpine metamorphism recorded in chloritoid schists from the southern part of the Tisia Mega-Unit (Slavonian Mts., NE Croatia)

    Science.gov (United States)

    Balen, Dražen; Horváth, Péter; Finger, Fritz; Starijaš, Biljana

    2013-06-01

    The chloritoid schists from the Slavonian Mts., which are attributed to the basal part of Devonian to Permian "Hercynian Semimetamorphic Complex," represent a very rare lithology, not only in the Tisia Mega-Unit outcrops in Croatia, but also in the wider area. The investigated outcrop in the Kutjevačka Rijeka transect (Mt. Papuk) encompasses chloritoid-bearing metapelitic and metapsammitic lithologies. Both contain K-white mica, chlorite, chloritoid (10-15 vol.%), quartz and minor K-feldspar, plagioclase (albite), opaque minerals and pyrophyllite, together with accessory zircon, rutile, xenotime. The Th-U-Pb age dating on xenotime grains within the K-white mica + chlorite + quartz matrix and on inclusions found inside the chloritoids gave an average age 120 ± 36 Ma. Peak metamorphic conditions during the Alpine chloritoid-forming event reached 3.5-4 kbar and 340-380 °C, based on phengite barometry, chlorite-chloritoid thermometry and intersection of chlorite and chloritoid isopleths in the KFMASH quantitative phase diagram. The post-tectonic character of lath- and rosette-shaped chloritoids with respect to two foliations in the rock, together with the older age of 219 ± 81 Ma obtained on Yb-rich xenotime core domain(s), implies a possible existence of older low-grade metamorphic phase(s). The chemistry of the chloritoid schists bears the signature of upper continental crustal felsic rocks as potential protoliths, probably the felsic rocks of the nearby Papuk Complex of Slavonian Mts. The evidence presented here for the chloritoid-bearing low-grade metamorphic rocks from the Slavonian Mountains clearly show that the prograde Alpine metamorphic event had a more significant influence on the evolution of the southern part of Tisia Mega-Unit than previously considered.

  8. Future Recovery of Energy and Mineral Values from Organic-Rich Shales (Summary L'avenir de la production d'énergie et de la valeur minérale des schistes riches en matière organique (résumé

    Directory of Open Access Journals (Sweden)

    Park W. C.

    2006-10-01

    Full Text Available Oil shale deposits vary significantly in their geological nature and can represent enormous reserves of low grades ores for various minerals such as alumina, sodium carbonates, molybdenum, nickel, vanadium, and uranium. The treatment of these rocks for mineral values can be economically attractive when coupled with the production of synthetic oil. Mutually shared costs for extractinq the mineral values can be favorably affected by utilizing by-products from the oil shale retorting. These can include the residual char for a carbonaceous reductant or fuel, C02 for acidification, or lime and soda ash for caustic. Conversely, an inappropriate choice of oil shale retorting conditions can substantially lower subsequent recovery of mineral values from the spent shale. The proceeding considerations will be discussed for several oil shale deposits including: 1. The Green River formation in the mid-western United States which is not only oil rich but also represents a nearly inexhaustible domestic supply of alumina and sodium carbonates and 2. The block shale of Julia Creek, Queensland, Australia, the Devonian Chattanooga shale in the United States, the Cambrian Kulm shale in Sweden, the Permian Lodeve shale in southern France, and the Paleozoic shales from Korea and USSR for energy and metal values such as molybdenum, nickel, vanadium, and uranium. La nature géologique des dépôts de schistes à huile est très variée ; ces schistes peuvent représenter des réserves énormes de minerais à faible teneur de métaux tels que l'aluminium, le molybdène, le nickel, le vanadium, l'uranium, sans oublier le carbonate de sodium. Le traitement de ces roches pour leur valeur minérale peut être attractif économiquement s'il est associé à la production d'huile synthétique. La répartition des coûts d'extraction des métaux peut être favorablement affectée en utilisant les sous-produits du traitement des schistes à huile. Ceci peut comprendre le goudron

  9. Glaucophane schists from california and new caledonia

    Science.gov (United States)

    Coleman, R.G.

    1967-01-01

    In California and New Caledonia, metamorphism of eugeosynclinal rocks has produced blueschist facies in limited areas. The outcrop pattern and structure suggest that the shape of the zone of blueschist metamorphism is elongate parallel to major tectonic trends. Juxtaposition of large ultramafic bodies, subparallel to the blueschist belts, indicates a close tectonic relationship between metamorphism and the tectonic emplacement of the ultramafic masses. Initial emplacement of ultramafics along the depressed axis of the eugeosyncline may have produced deformation related to blueschist metamorphism. Mineral assemblages developed in blueschist facies are characterized by having formed under conditions where pressure is predominant over temperature. That pressure is relatively high requires extremely low thermal gradients combined with a rheology that would allow development of tectonic overpressures. ?? 1967.

  10. Provenance And Tectonomagmatic Setting Of The Santa Marta Schists, Northern Colombia Caribbean Region: Insights On The Styles Of Growth And Approach Of Caribbean Intra- Oceanic Domains To The Continental Margin

    Science.gov (United States)

    Cardona, A.; Jaramillo, C.; Ojeda, G.; Ruiz, J.; Valencia, V.; Weber, M.

    2007-12-01

    The life cycle of an intra-oceanic terranemincludes different phases and styles of magmatic growth, accretion with other terranes and translation before reaching a continental margin. In order to unveil the nature of these phases in crystalline rocks from northern Colombia, U/Pb LA-MC-ICP-MS detrital geochronology and whole rock geochemical data were obtained from stacks of intercalated metavolcanic-sedimentary rocks of the Santa Marta Schists in the Sierra Nevada de Santa Marta. Immobile elements whole rock geochemistry from greenschist to amphibolite facies units are characterized by low to moderate LREE/HREE, variable Th enrichment and weakly negative Nb and Ti anomalies, which are similar to island arc and MORB signatures. The intercalated metasedimentary rocks show a REE pattern similar to the PAAS and high Zr/Sc vs Th/Sc ratios, which suggest a felsic and highly diferentiated upper crust sources for the protoliths. Detrital zircons from three different units were obtained, The maximum depositional age for the northwestern unit is limited to the late Cretaceous, with a major peak of 83 Ma. Variable input of older crustal sources with Jurassic (153 Ma), Permo-Triassic (250-290 Ma), Cambrian to Late Neoproterozoic (520-560 Ma) and Middle Mesoproterozic (1000-1500 Ma) ages which are clearly recognized in older units of the Sierra Nevada de Santa Marta massif and the northern South American basement are also recorded. This type of volcano-sedimentary record within an intra-oceanic arc bears strong similarities with the modern Lesser-Antilles and the Tonga-Kermadec arcs, where continentally derived sediments can be transported houndred of kilometers to the fore-arc, back-arc or the accretionary prism of the active intra-oceanic arc. This record also suggests that this arc has an intra-Americas position, near to its final accretionary stop. Although the metamorphic overprint has obliterated the stratigraphic relations, apparent variations of the LREE/HREE in the

  11. Production, nutritional status and chemical properties of soils with addition of cattle manure, reactive natural phosphate and biotite schist in Massai cultivar Produção, estado nutricional e propriedades químicas do solo com aplicação de esterco bovino, fosfato natural reativo e biotita xisto na cultivar Massai

    Directory of Open Access Journals (Sweden)

    Adônis Moreira

    2010-09-01

    Full Text Available The objective of this work was to evaluate the effects of cattle manure, reactive natural phosphate and biotite schist on the soil fertility, yield and nutritional status of Megathyrsus spp. cv. Massai. The experiment was conducted under field conditions, in a dystrophic Red Yellow Latosol (Oxisol. It was used a randomized block experimental design with the following treatments: three natural reactive rock phosphate from Algeria (Djebel-Onk doses (0, 100 and 200 kg ha-1 of P2O5, three biotite schist doses (0, 150 and 300 kg ha-1 of K2O and three cattle manure doses (0, 20 and 40 t ha-1. The application of natural phosphate increased dry matter yield, however, application of cattle manure and biotite schist did not influence this variable. Foliar levels of nitrogen, potassium and magnesium (cattle manure, phosphorous and boron (natural rock phosphate and potassium (biotite schist were influenced by the applied fertilizer doses. Only the levels of phosphorous in the soil and in the plant and levels of magnesium and boron in the plant show interaction with dry matter yield of Massai cultivar.Objetivou-se avaliar os efeitos de esterco bovino, fosfato natural reativo e biotita xisto sobre a fertilidade do solo, a produção e o estado nutricional de Megathyrsus spp. cv. Massai. O experimento foi realizado em condições de campo, em Latossolo Vermelho Amarelo distrófico (Oxisol. O delineamento experimental utilizado foi o de blocos casualizados, com os seguintes tratamentos: três doses de fosfato natural reativo da Argélia, Djebel-Onk (0, 100 e 200 kg ha-1 de P2O5, três doses de biotita xisto (0, 150 e 300 kg ha-1 de K2O e três doses de esterco bovino (0, 20 e 40 t ha-1. A aplicação de fosfato natural aumentou a produção de matéria seca, enquanto as aplicações de esterco bovino e a biotita xisto não influenciaram esta variável. Os teores de nitrogênio, potássio e magnésio (esterco bovino, fósforo e boro (fosfato natural e pot

  12. Mise en évidence de Provinces géochimiques dans les schistes bitumeux du Toarcien de l'est du bassin de Paris Geocheminical Provinces Revealed in Toarcien Oil Shales in the Eastern Paris Basin. Analysis of the Soluble Organic Fraction

    Directory of Open Access Journals (Sweden)

    Huc A. Y.

    2006-11-01

    Full Text Available L'étude de la matière organique soluble dans le chloroforme des schistes du Toarcien de la partie orientale du bassin de Paris met en évidence l'existence d'une province géochimique nord et d'une province géochimique sud dont la frontière commune se trouve dans la région de Fécocourt. La province septentrionale se caractérise par une influence du domaine continental (massif des Ardennes au niveau de l'apport organique. Alors que la province méridionale se révèle exempt d'apport terrestre. Ces résultats sont en accord avec les indications sédimentologiques fournies par la littérature et apportent une dimension géochimique à la paléogéographie de ce bassin. An anaalysis of soluble organic motter in the chloroform from Toarcian shales from the eastern part of the Paris Basin reveals the existence of a northern geochemical province and a southern geochemical province whose commun boundary lies in the Fecocourt region. The northern province is characterized by the influence of the continental domain (Ardennes range with regard to organic influx, whereas no terrestrial influx is found in the southern province. These findings agree with the sedimentological indications supplied by the literature and add a geochemical dimension to the paleogeography of this basin.

  13. geochemistry of schists of northwest obudu plateau, southeastern ...

    African Journals Online (AJOL)

    REV YOUNG EZENWA OBIOHA

    Evidence of Paleo-Proterozoic (Ca. 1769Ma) component in the Basement Complex of. Southeastern Nigeria. J. Min. Geol. 33: 81- 88. Ekwueme, B. N. and Onyeagocha, A. C., 1986. Geochemistry of metasedimentary rocks of. Uwet area, Oban Massif, Southeastern Nigeria. Geol. Rundsch. 75, 411 – 420. Ephraim, B. E. ...

  14. U-Pb GEOCHRONOLOGY OF METASEDIMENTARY SCHISTS IN ...

    African Journals Online (AJOL)

    PROF EKWUEME

    Out of 131 analyses 117 yielded useful geochronological data. 67 of these gave 90-110% ... These first-ever geochronological data from rocks of Akwanga area are further evidence of the polycyclic nature of the Nigerian basement. ... composed of feldspar and quartz whilst the dark band shows parallel alignment of biotite.

  15. REE Geochemistry of ore zones in the Archean auriferous schist ...

    Indian Academy of Sciences (India)

    R. Narasimhan, Krishtel eMaging Solutions

    for gold deposits. Cameron (1988) attributed the. Archean lode gold mineralization to the granuliti- zation process which occurred during the principal period of crustal thickening and .... mineralization (Kolar Gold Fields) a massive, fine- grained, tholeiitic .... for the complete recovery of REEs were done by mixing pure metal ...

  16. Structural appraisal of the Gadag schist belt from gravity investigations

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    SE major faults. Quantitative evaluation from forward modeling/inversion of five profiles in the region, assuming a density contrast of 0.29gm/cc of the anomalous schistose body with the gneissic host rocks indicated a synclinal structure plunging ...

  17. Application des fluides supercritiques à la production d'hydrocarbures. Exploitation des gisements par récupération assistée et applications diverses : pétrole, sables, schistes, charbons Application of Supercritical Fluids to Hydrocarbon Production. Enhanced Oi Recovery and Miscellaneous Applications: Oil, Tar Sands, Shales, Coals

    Directory of Open Access Journals (Sweden)

    Behar E.

    2006-11-01

    Full Text Available Le taux moyen de récupération par drainage naturel des gisements pétroliers atteint à peine 30 %. La récupération assistée désigne l'ensemble des procédés d'exploitation qui permettent d'accroître très sensiblement ce taux. Parmi ces procédés, l'injection de fluides supercritiques joue un rôle prometteur. Les principaux fluides actuellement utilisés sont : le méthane (ou plus généralement les gaz hydrocarbures dits pauvres , l'azote et enfin le gaz carbonique. Les domaines d'application et les mécanismes thermodynamiques mis en jeu sont brièvement exposés, les sources de fluides supercritiques disponibles au voisinage des gisements pétroliers sont rapidement répertoriées et certains problèmes d'exploitation évoqués. Outre leur application en récupération assistée, les fluides supercritiques sont également impliqués dans des procédés de raffinage et d'extraction divers. C'est le procédé de désasphaltage de fractions pétrolières lourdes qui, en 1956, a fait l'objet de la première application industrielle exploitant les fortes variations du pouvoir solvant d'un fluide au voisinage de son point critique. Ce procédé connaît, depuis une dizaine d'années, un regain d'intérêt du fait de l'économie d'énergie qu'il permet de réaliser. D'autre part, les schistes bitumineux, les sables asphaltiques et les charbons, sources d'hydrocarbures considérables pour l'avenir, constituent des domaines d'applications potentielles originales des fluides supercritiques. Les procédés spécifiques, pour la plupart en cours de développement au stade pilote, sont passés en revue. The average recovery by natural drainage from oil fields is barely 30%. Enhanced recovery includes all production processes which appreciably increase this rate. Among such processes, supercritical fluid flooding is quite promising. The main fluids now used are methane (or, more generally, so-called leangaseous hydrocarbons, nitrogen and carbon

  18. Earth Sciences Geochemistry of slates and semi-pelitic schists from ...

    African Journals Online (AJOL)

    Global Journal of Pure and Applied Sciences. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 7, No 2 (2001) >. Log in or Register to get access to full text downloads.

  19. Relationships between basin architecture, basin closure, and occurrence of sulphide-bearing schists

    DEFF Research Database (Denmark)

    Kalliomäki, Henrik; Torvela, Taija; Moreau, Julien

    2014-01-01

    We present field observations from the Palaeoproterozoic volcano-sedimentary Tampere palaeobasin, where the primary structures have been exceptionally well preserved. We use the observations to construct a new tectonic model for the southeastern margin of the Tampere basin during its inversion...... and subsequent closure. The observed volcano-sedimentary and structural features suggest a change in the local structural style from thick-skinned inversion to thin-skinned thrusting, in order to accommodate the crustal shortening during basin closure. Furthermore, it is suggested that there is a genetic...

  20. The real shale gases scandal; Le vrai scandale des gaz de schiste

    Energy Technology Data Exchange (ETDEWEB)

    Jobert, Marine; Veillerette, Francois

    2011-08-28

    Shale and oil gases are in the center of a national debate in France. They are accused of being responsible of aquifers and ground pollution, of air poisoning, of earthquake triggering and so on. Opponents to shale gas exploitation have won the first round but the potential beneficiaries, the industrialists and politics, have not given up. This book unravels the existing connections between the administration, industrial and political powers and demonstrates why the shale gases exploitation projects are not abandoned despite their proven harmful impact on the environment. (J.S.)

  1. Compositional variations in the Mesoarchean chromites of the Nuggihalli schist belt, Western Dharwar Craton (India)

    DEFF Research Database (Denmark)

    Mukherjee, Ria; Mondal, Sisir Kanti; Rosing, Minik Thorleif

    2010-01-01

    .01-0.38; Cr-ratio = 0.02-0.99) and in silicate-rich chromitite (Mg-ratio = 0.06-0.48; Cr-ratio = 0.60-0.99). In the massive chromitites, the sub-solidus re-equilibration for chromite is less or absent. However, the re-equilibration is prominent in the co-existing interstitial and included olivine (Fo(96...... has been used to compute the nature of the parental melt. The parental melt calculations indicate derivation from a high-Mg komatiitic basalt that is similar to the composition of the komatiitic rocks reported from the greenstone sequences of the Western Dharwar Craton. Tectonic discrimination...

  2. Shale gas, a hazardous exploitation; Gaz de schiste, une exploitation a risque

    Energy Technology Data Exchange (ETDEWEB)

    Maincent, G.

    2011-04-15

    In march 2010 three authorizations to search for shale gases were delivered in France in the regions of Montelimar, Nant and Villeneuve-de-Berg. A general public outcry has led the government to freeze the projects till a complete assessment of the impact on the environment is made. The fears of the public are based on the feedback experience in the Usa where some underground waters were polluted. The source of pollution is twofold: first the additives used in the injected fluids (methanol as an anti-microbic agent, hydrochloric acid to dissolve natural cements or glycol ethylene as a deposit inhibitor) and secondly metal particles of copper, zinc or lead trapped in the clay layers and released by the injection of the fluids. It appears also that the injection of high pressure fluids near a crack can induce earth tremors by reactivating the crack. (A.C.)

  3. Retrograde mineral and fluid evolution in high-pressure metapelites (Schistes Lustres unit, Western Alps).

    NARCIS (Netherlands)

    Agard, Ph.; Goffe, B.; Touret, J.L.R.; Vidal, O.

    2000-01-01

    Fluid inclusions have been analysed in successive generations of syn-metamorphic segregations within low-grade, high-pressure, low-temperature (HP-LT) metapelites from the Western Alps. Fluid composition was then compared to mass transfer deduced from outcrop-scale retrograde mineral reactions. Two

  4. On the evolution of the Kazaure Schist Belt of NW Nigeria: a re ...

    African Journals Online (AJOL)

    Global Journal of Geological Sciences. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 8, No 2 (2010) >. Log in or Register to get access to full text downloads.

  5. Study on Change of Pipes Formed in the Upper Part of a Collapse in a Crystalline Schist Area and Response of Pipe Flow to Rain

    OpenAIRE

    平松, 晋也; 前川, 美紀子; 小山内, 信智; Shinya, HIRAMATSU; Mikiko, MAEKAWA; Nobutomo, Osanai; 高知大学農学部; 国土交通名四国山地砂防工事事務所; Faculty of Agriculture, Kochi University; Shikoku Mountainous Region Sabo Work Office, Ministry of Land, Infrastructure and Transport:(Present office)Tosa National Road Office, Ministry of Land, Infrastructure and Transport

    2002-01-01

    Pipes formed by a small animal-activity, root decay and underground erosion exist frequently in the upper part of rain-induced collapse sites. These pipes affect significantly on water discharge and occurrences of hillside landslides in a watershed. Many hillside landslides occurred at Nishiiyayama village in Tokushima Prefecture, on June 29 th, 1999, due to heavy rainfall. In the upper part of C torrent of Tobinosu-valley, hillside landslides occurred, and several pipes appeared. Investigati...

  6. On the role of Yttrium during plurifacial Hercynian metamorphism as expressed in the Northern part of the Central galician schist Area (NW Spain)

    NARCIS (Netherlands)

    Hilgen, J.D.

    1981-01-01

    Recent investigations of the distribution of trace elements in metamorphic index minerals of metapelites have revealed, that the plurifacial character of the Hercynian metamorphism in this area is confirmed by the distribution of Yttrium in Hercynian garnets of the metamorphic series.

  7. Tectonic imprints within a granite exposed near Srinagar, Rajasthan ...

    Indian Academy of Sciences (India)

    that the metasedimentary rock package of DFB in the study area comprises a basal polymictic conglomerate overlain successively by calc-silicate gneiss, pelitic schist of diverse mineralogies (biotite schist, garnet schist, and staurolite schist, form- ing a partial Barrovian sequence of metamor- phism), quartz-biotite schist and ...

  8. Recuperation of the organic matter from oil shales with phenol in subcritical conditions; Recuperation a l'autoclave de la matiere organique de schistes bitumineux marocains par le phenol en conditions sub-critiques

    Energy Technology Data Exchange (ETDEWEB)

    Abourriche, A.; Oumam, M.; Hannache, H. [Faculte des Sciences Ben M' sik, Lab. des Materiaux Thermostructuraux, Casablanca (Morocco); Pailler, R.; Naslain, R. [Bordeaux-1 Univ., Lab. des Composites Thermostructuraux, UMR 5801 CNRS-CEA-Snecma, 33 - Pessac (France); Birot, M.; Pillot, J.P. [Bordeaux-1 Univ., Lab. de Chimie Organique et Organometallique, UMR 5802 CNRS, 33 - Pessac (France)

    2005-02-01

    Phenol was used for the recovery of the organic matter from Tarfaya's oil shales in subcritical conditions. The analyses carried out on the recovered oils revealed that phenol had a significant role on the increase of the yield of recuperation, amount of maltenes, aromatic compounds and the reduction of the amount of sulphur in oils. (author)

  9. Elaboration and characterization of a new adsorbent material from Moroccan oil shale; Elaboration et caracterisation d'un nouveau materiau adsorbant a partir des schistes bitumineux du Maroc

    Energy Technology Data Exchange (ETDEWEB)

    Oumam, M.; Abourriche, A.; Adil, A.; Hannache, H. [Faculte des Sciences Ben M' Sik, Lab. des Materiaux Themostructuraux, Casablanca (Morocco); Pailler, R.; Naslain, R. [Bordeaux-1 Univ., Lab. des Composites Thermostructuraux, 33 - Talence (France); Birot, M.; Pillot, J.P. [Bordeaux-1 Univ., Lab. de Chimie Organique et Organometalliques, 33 - Talence (France)

    2003-08-01

    This work describes the elaboration method of a new adsorbent material from Moroccan oil shale. The manufacturing of this material was carried out by thermal treatment of carbonate-free oil shale originating from the Tarfaya deposit. The effect of temperature and activation time on the adsorption parameters of the material was studied using methylene blue and bichromate ions as pollutants. The results show that the optimum conditions which provide the best adsorbent properties are T = 250 deg C and t = 1 hour. (authors)

  10. Amadi et al (22)

    African Journals Online (AJOL)

    DELL

    granite. The static water level measurement revealed a westward groundwater flow direction which also coincides with the regional structural trend of the area. .... Climate and vegetation. The study area is characterized by two distinct ... schist, garnet-rich bands and carbonaceous schists). The abrupt changes in the schist.

  11. New adsorbents prepared by phosphoric acid activation of Moroccan oil shales: Influence of the experimental conditions on the properties of the adsorbents; Nouveaux adsorbants prepares par activation chimique des schistes bitumineux marocains par l'acide phosphorique: influence des conditions experimentales sur les proprietes des adsorbants

    Energy Technology Data Exchange (ETDEWEB)

    Khouya, E.H.; Fakhi, S. [Faculte des Sciences Ben M' sik, Lab. de Radiochimie, Casablanca (Morocco); Khouya, E.H.; Ichcho, S.; Legrouri, K.; Hannache, H. [Faculte des Sciences Ben M' sik, Lab. des Materiaux ThermoStructuraux, Casablanca (Morocco); Nourredine, A. [Universite Louis Pasteur, Institut de Recherche Subatomique, UMR 7500 CNRS-IN2P3, 67 - Strasbourg (France); Pailler, R.; Naslain, R. [Bordeaux-1 Univ., Lab. des Composites Thermostructuraux, UMR 5801 CNRS-CEA-SNECMA, 33 - Pessac (France)

    2006-09-15

    New adsorbents were prepared from Moroccan oil shale of Tarfaya (layer R3) by chemical activation with phosphoric acid. The objective was to investigate different factors that control the activation process, in order to determine the optimum conditions of preparation. The examined factors were holding time in the oven, pre-processing and atmosphere (N{sub 2}/air). The impact of the different factors was investigated by determining the yield of adsorbent and the maximum capacity of adsorption for methylene blue. Due to the existence of numerous factors, a two-level factorial design was used to find the most influential factors and their mutual interactions. The results of this study yielded the following classification of the factors: atmosphere, pre-processing, activation temperature and holding time in the oven. The best properties were found for a particular combination of the chosen parameters: temperature and activation time equal to 250 C and 2 hours, respectively, in air. The adsorption capacity for methylene blue and specific surface area (SBET) of this adsorbent were 500 mg/g and 600 m{sup 2}/g, respectively. Furthermore, in these conditions the adsorbent developed important surface functions. (authors)

  12. Application des fluides supercritiques à la production d'hydrocarbures. Exploitation des gisements par récupération assistée et applications diverses : pétrole, sables, schistes, charbons Application of Supercritical Fluids to Hydrocarbon Production. Enhanced Oi Recovery and Miscellaneous Applications: Oil, Tar Sands, Shales, Coals

    OpenAIRE

    Behar E.; Mikitenko P.

    2006-01-01

    Le taux moyen de récupération par drainage naturel des gisements pétroliers atteint à peine 30 %. La récupération assistée désigne l'ensemble des procédés d'exploitation qui permettent d'accroître très sensiblement ce taux. Parmi ces procédés, l'injection de fluides supercritiques joue un rôle prometteur. Les principaux fluides actuellement utilisés sont : le méthane (ou plus généralement les gaz hydrocarbures dits pauvres ), l'azote et enfin le gaz carbonique. Les domaines d'application et l...

  13. 1362-IJBCS-Article-Bernard Adiaffi

    African Journals Online (AJOL)

    hp

    La conjugaison des trois méthodes d'analyse des schistes permet d'obtenir des résultats semi quantitatifs très fiables pour mener à bien cette étude d'interaction eau-schiste. Hydrochimie. Le matériel hydrochimique se limite aux éléments chimiques des eaux souterraines échantillonnées dans les schistes. Il s'agit des.

  14. 西彼杵半島長崎変成岩類の岩石学的研究 : とくに緑色岩複合岩体と反応促進型延性変形について

    OpenAIRE

    西山, 忠男; Tadao, NISHIYAMA; 九州大学理学部地質学教室; Department of Geology, Faculty of Science, Kyushu University

    1989-01-01

    The Nagasaki metamorphic rocks in the Nishisonogi Peninsula, western Kyushu, mainly consists of crystalline schists with small amounts of serpentinite and the greenrock complexes, which have a character of serpentine melange. The crystalline schists belong to the epidote-glaucophane subfacies, characterized by the common presence of glaucophane + hematite + rutile in graphite-free psammitic schists and by minor occurrence of epidote + glaucophane in metabasites. The greenrock complexs are thi...

  15. THE STRUCTURAL FRAMEWORK UNDERLYING THE ...

    African Journals Online (AJOL)

    The structural framework underlying the metamorphic aspect of the various rocks in Kazaure schist belt (KZSB) was studied. The KZSB consists of metasediments and metavolcanics that are bounded by Older Granites and gneisses. Detailed structural analysis of the Kazaure schist belt revealed the occurrence of structures ...

  16. IJS v10 n1.cdr

    African Journals Online (AJOL)

    De Don

    constitutes one of the Neo-Proterozoic schist belts However, Adekoya (1996) has suggested that the in the Nigerian basement complex, which contain both sedimentary progenitors of the Nigerian schist belts, alluvial and primary gold deposits. These deposits which host both alluvial and primary gold deposits have been ...

  17. rights reserved Geophysical Identification of Hydrothermally Altered ...

    African Journals Online (AJOL)

    ADOWIE PERE

    The Schist Belts comprise low grade, meta-sediment-dominated belts which are best developed in the western half of. Nigeria. These belts are considered to be Upper. Proterozoic supracrustal rocks which have been infolded into the migmatite-gneiss-quartzite complex. Most metallogenetic features of the Schist belts are.

  18. Pseudotachylyte and associated fault rocks at Alabameta area ...

    African Journals Online (AJOL)

    This paper reports the occurrence of pseudotachylytes and associated fault rocks along Ifewara fault at Alabameta within the Ife-Ilesha Schist Belt, Southwestern Nigeria. The fault separates the schist belt into two lithostratigraphic units: a western unit composed mainly of mafic to ultramafic rocks and metapelites and an ...

  19. Earth Sciences The geochemistry, tectonic setting and origin of the ...

    African Journals Online (AJOL)

    A massive melanocratic amphibolite, (MMA) occurs in Ilesha schist belt within a series of muscovite schists and amphibolite gneiss. Though metamorphosed, MMA shows no obvious textural deformation. Actinolite, tremolite, hornblende and boitite constitute the major minerals in MMA. Minor minerals in MMA include calcite, ...

  20. Groundwater resources assessment of part of Ilesa, Southwestern ...

    African Journals Online (AJOL)

    An integrated geophysical survey involving the electromagnetic (EM) and direct current resistivity methods was carried out in part of Ilesha, Osun State, underlain by schists, quartzite and quartz schist complex, with a view to assessing the groundwater potential. The EM survey was conducted along eighteen (18) EM profiles ...

  1. Information report brought in according to article 145 of the rule by the mission of information on shale gas and oil on the behalf of Sustainable Development and Land Planning Commission; Rapport d'information depose en application de l'article 145 du reglement par la mission d'information sur les gaz et huile de schiste au nom de la Commission du Developpement Durable et de l'Amenagement du Territoire

    Energy Technology Data Exchange (ETDEWEB)

    Gonnot, F.M.; Martin, Ph.

    2011-07-01

    The first part of this report gives an overview of technical definitions, of economic aspects and of the international situation: presentation of non conventional hydrocarbons, of exploitation techniques (horizontal drilling, hydraulic fracturing), strategic impact of these new resources in Northern America, in the World, in the European Union and in France. The second part describes the frightening American example, the impact of this exploitation on land (new pits are always to be drilled, large surfaces are concerned, unceasing road traffic), the risks associated with the use of chemical additives, and the problem of protection of water resources (consumption of huge quantities of water, risks of water contamination, the issue of used waters), and of atmospheric release (greenhouse gas emissions). The third part outlines the current imperfections of the French mining code, its weaknesses and its necessary reform

  2. Extensional reactivation of the Chocolate Mountains subduction thrust in the Gavilan Hills of southeastern California

    Science.gov (United States)

    Oyarzabal, F.R.; Jacobson, C.E.; Haxel, G.B.

    1997-01-01

    The NE vergent Chocolate Mountains fault of south-eastern California has been interpreted as either a subduction thrust responsible for burial and prograde metamorphism of the ensimatic Orocopia Schist or as a normal fault involved in the exhumation of the schist. Our detailed structural analysis in the Gavilan Hills area provides new evidence to confirm the latter view. A zone of deformation is present at the top of the Orocopia Schist in which lineations are parallel to those in the upper plate of the Chocolate Mountains fault but oblique to ones at relatively deep levels in the schist. Both the Orocopia Schist and upper plate contain several generations of shear zones that show a transition from crystalloblastic through mylonitic to cataclastic textures. These structures formed during retrograde metamorphism and are considered to record the exhumation of the Orocopia Schist during early Tertiary time as a result of subduction return flow. The Gatuna fault, which places low-grade, supracrustal metasediments of the Winterhaven Formation above the gneisses of the upper plate, also seems to have been active at this time. Final unroofing of the Orocopia Schist occurred during early to middle Miocene regional extension and may have involved a second phase of movement on the Gatuna fault. Formation of the Chocolate Mountains fault during exhumation indicates that its top-to-the-NE sense of movement provides no constraint on the polarity of the Orocopia Schist subduction zone. This weakens the case for a previous model involving SW dipping subduction, while providing support for the view that the Orocopia Schist is a correlative of the Franciscan Complex.

  3. Stratigraphic and structural implications of conodont and detrital zircon U-Pb ages from metamorphic rocks of the Coldfoot terrane, Brooks Range, Alaska

    Science.gov (United States)

    Moore, T.E.; Aleinikoff, J.N.; Harris, A.G.

    1997-01-01

    New paleontologic and isotopic data from the Emma Creek and Marion Creek schists of the Coldfoot terrane, Arctic Alaska superterrane, central Brooks Range, suggest Devonian and possibly younger ages of deposition for their sedimentary protoliths. Conodonts from marble of the Emma Creek schist, intruded by a roughly 392 Ma orthogneiss, are late Lochkovian (early Early Devonian, between about 408 and 396 Ma) and Silurian to Devonian at two other locations. Spherical to oblong detrital zircons from quartz-mica schist of the overlying Marion Creek schist yield mostly discordant U-Pb data suggestive of provenance ages of 3.0, 2.0-1.8, and 1.5-1.4 Ga; however, several euhedral grains of zircon from Marion Creek quartz-mica schist have concordant U-Pb ages from 370 to 360 Ma. The Marion Creek schist in our study area therefore is at least 26 m.y. younger than the Emma Creek schist. The age data imply that the protolith of the Emma Creek schist is age correlative with Devonian carbonate rocks in the Hammond and North Slope terranes, whereas the Marion Creek schist is age correlative with Upper Devonian and Lower Mississippian clastic sedimentary rocks of the Endicott Group in the Endicott Mountains terrane and shale and carbonate units in the De Long Mountains and Sheenjek River terranes. Consequently, tectonic models restoring the entire Coldfoot terrane beneath partly or wholly coeval rocks of the Hammond, Endicott Mountains, De Long Mountains, and Sheenjek River terranes of the Arctic Alaska superterrane require revision. Alternative reconstructions, including restoration of the Coldfoot terrane inboard of the Endicott Mountains terrane or outboard of the De Long Mountains and Sheenjek River terranes are plausible but require either larger amounts of shortening than previously suggested or indicate problematic facies relations. copyright. Published in 1997 by the American Geophysical Union.

  4. Plate tectonics 2.5 billion years ago: evidence at kolar, South India.

    Science.gov (United States)

    Krogstad, E J; Balakrishnan, S; Mukhopadhyay, D K; Rajamani, V; Hanson, G N

    1989-03-10

    The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accrted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics sugesting that their volcanic protoliths were derived from dint mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on Earth by 2500 Ma.

  5. Plate tectonics 2.5 billion years ago - Evidence at Kolar, south India

    Science.gov (United States)

    Krogstad, E. J.; Hanson, G. N.; Balakrishnan, S.; Rajamani, V.; Mukhopadhyay, D. K.

    1989-01-01

    The Archean Kolar Schist Belt, south India, is a suture zone where two gneiss terranes and at least two amphibolite terranes with distinct histories were accreted. Amphibolites from the eastern and western sides of the schist belt have distinct incompatible element and isotopic characteristics suggesting that their volcanic protoliths were derived from different mantle sources. The amphibolite and gneiss terranes were juxtaposed by horizontal compression and shearing between 2530 and 2420 million years ago (Ma) along a zone marked by the Kolar Schist Belt. This history of accretion of discrete crustal terranes resembles those of Phanerozoic convergent margins and thus suggests that plate tectonics operated on earth by 2500 Ma.

  6. Analysis of mechanical behavior of soft rocks and stability control in deep tunnels

    Directory of Open Access Journals (Sweden)

    Hui Zhou

    2014-06-01

    Full Text Available Due to the weakness in mechanical properties of chlorite schist and the high in situ stress in Jinping II hydropower station, the rock mass surrounding the diversion tunnels located in chlorite schist was observed with extremely large deformations. This may significantly increase the risk of tunnel instability during excavation. In order to assess the stability of the diversion tunnels laboratory tests were carried out in association with the petrophysical properties, mechanical behaviors and water-weakening properties of chlorite schist. The continuous deformation of surrounding rock mass, the destruction of the support structure and a large-scale collapse induced by the weak chlorite schist and high in situ stress were analyzed. The distributions of compressive deformation in the excavation zone with large deformations were also studied. In this regard, two reinforcement schemes for the excavation of diversion tunnel bottom section were proposed accordingly. This study could offer theoretical basis for deep tunnel construction in similar geological conditions.

  7. Browse Title Index

    African Journals Online (AJOL)

    supported sorbents, Details. P Shallsuku, TO Aina ... Vol 38, No 1 (2002), Late Pan-African tectonics and origin of gold mineralization and rare-metal pegmatities in the Kushaka schist belt, northwestern Nigeria, Details. I GARBA.

  8. LA-ICP-MS U-Pb detrital zircon study and structural observations of the Cycladic Blueschist Unit on Heraklia Island (Cyclades, Greece)

    Science.gov (United States)

    Laskari, Sofia; Soukis, Konstantinos; Lozios, Stylianos; Stockli, Daniel

    2017-04-01

    At the central and southern part of the Attic-Cycladic complex (Aegean Sea, Greece) significant exposures of the Cycladic Basement Unit orthogneisses and meta-sediments are observed. These are mainly cropping out in Paros, Naxos and Ios islands and to a much lesser extend in Sikinos Island and they comprise Variscan (granitic) orthogneisses and late Paleozoic metasediments. In this paper we present evidence of a hitherto not identified possible outcrop of the Cycladic Basement in Heraklia Island (central Cyclades). The small Heraklia Island, situated at the center of the Attic-Cycladic core complex in the Aegean, between the islands of Naxos and Ios, consists of rocks that are attributed to the Cycladic Blueschist Unit. The tectonostratigraphy of Heraklia Island includes: a) a lowermost schist sequence with interbedded lenses of felsic orthogneisses whose primary relationship is obliterated by later subduction and exhumation related shearing b) A 200m thick variegated marble sequence with sparse calk-schist intercalations, which is isoclinally folded together with 100m thick overlying quartz-mica and calc-schists schists. All rocks comprise a penetrative foliation formed by greenschist facies mineral assemblages but in the uppermost schists relics of the Eocene HP event are found in the form of glaucophane inclusions within albite porphyroblasts. A mylonitic planar fabric with a cataclastic overprint is observed at the base of the marble sequence and the roof of the underlying schists and orthogneisses. It is accompanied by a N-S stretching lineation, subparallel to isoclinal folding in all scales. Numerous kinematic indicators reveal a top-to-N sense of shear thus linking the Heraklia rocks kinematically with the crustal extensional detachment systems of both Naxos and Ios islands. LA-ICP-MS U-Pb detrital zircon study of schists and gneisses is used in order to identify provenance and to elucidate the tectonostratigrachic relationship between the lower and upper

  9. The first data on paleomagnetism of Palaeoproterozoic rocks of the Serpovidny structure (the Kola region, northeastern Baltic Shield

    Directory of Open Access Journals (Sweden)

    Matyushkin A. V.

    2016-03-01

    Full Text Available The orientation of natural magnetization vector components in amphibolites and amphibole schists (magnetite up to 10 % coincides with that of the modern magnetic field vector. Different orientations have been discovered only in quartzitic gneiss (magnetite ≤ 2 % and regressively changed chlorite-amphibole schist. The palaeopole position determined for these rocks corresponds on the apparent pole wander path to ages of 1.95 Ga and ~1.80 Ga, respectively

  10. short communications oviparity in two south african sxinxs of the ...

    African Journals Online (AJOL)

    bam owl roosts and pellet collection sites are listed below. South West A/rica. 1. 25 km east of Windhoek. 22°32'S/17°16'E. Roost in a cave in mica schist. 30 April 1972. 2. Valencia Ranch, Friedenthal district. 23°IO'S/. 16°25'E. Roost in a cave in mica schist. 23. May 1973. 3. Gamsberg. 23°15'S/16°24'E. Roost in a deser-.

  11. Study on mineralization at Jian copper deposit, Fars province, using petrographical and geochemical data

    Directory of Open Access Journals (Sweden)

    Mohamad Ali Rajabzade

    2013-04-01

    Full Text Available Jian Cu deposit is hosted by Surian volcano-sedimentary complex of Permo-Triassic age on the eastern edge of the Sanandaj-Sirjan metamorphic zone at a distance of 195 km from Shiraz, southwestern Iran. The complex consists mainly of metabasalt, chlorite-quartz schist, chlorite-muscovite schist, mica schist and graphite schist. Pyrite is the most important sulfide and chalcopyrite is the major Cu-bearing mineral occurring as disseminated grains and veinlets in host chlorite-quartz schist and chlorite-muscovite schist. Chondrite-normalized REE pattern of metabasalt with La/LuN=2/9 indicates mantle tholeiitic basalt as the source of metamorphosed igneous rocks. Geochemical data on the metabasalts, especially the content of immobile elements (e.g., Ti and High Field Strength Elements (HFSE (e.g., Zr، Nb and Y, show low degree of partial melting for parental magma with E-MORB affinity. Chloritic, silicification and minor sericitic assemblages are the main alteration types associated with the Jian Cu deposit. The Y/Ho ratio of Cu ores varies from 29.9 to 32.5, indicating the important role of sea water in the mineralizing system. Petrographical and geochemical data indicate that the Jian Cu deposit was formed as volcano-sedimentary hosted massive sulfide. The Ishikawa alteration index (AI in association with chlorite-carbonate-pyrite index (CCP is useful for the geochemical exploration of Cu deposits in the study area.

  12. Early history and reactivation of the rand thrust, southern California

    Science.gov (United States)

    Postlethwaite, Clay E.; Jacobson, Carl E.

    The Rand thrust of the Rand Mountains in the northwestern Mojave Desert separates an upper plate of quartz monzonite and quartzofeldspathic to amphibolitic gneiss from a lower plate of metagraywacke and mafic schist (Rand Schist). The Rand thrust is considered part of the regionally extensive Vincent/Chocolate Mountain thrust system, which is commonly believed to represent a Late Cretaceous subduction zone. The initial direction of dip and sense of movement along the Vincent/Chocolate Mountain thrust are controversial. Microfabrics of mylonites and quartzites from the Rand Mountains were analyzed in an attempt to determine transport direction for this region, but the results are ambiguous. In addition, the southwestern portion of the Rand thrust was found to have been reactivated as a low-angle normal fault after subduction. Reactivation might have occurred shortly after subduction, in which case it could account for the preservation of high-pressure mineral assemblages in the Rand Schist, or it could be related to mid-Tertiary extension in the western United States. In either event, the reactivation might be responsible for the complicated nature of the microfabrics. The Rand Schist exhibits an inverted metamorphic zonation. Isograds in the schist are not significantly truncated by the reactivated segment of the Rand thrust. This indicates that other segments of the Vincent/Chocolate Mountain thrust should be re-evaluated for the possibility of late movement, even if they show an apparently undisturbed inverted metamorphic zonation.

  13. Geochemical and zircon U-Pb dating analysis of metamagmatic rocks from the Yuli belt in Taiwan

    Science.gov (United States)

    Hung, Chia-Chia

    2016-04-01

    The Tananao Schist Complex of the oldest rocks in Taiwan is exposed at the eastern limb of Backbone Range. Based on the lithologic and metamorphic characteristics, the complex can be divided into the Tailuko and Yuli belts. The Tailuko belt consists of marble, gneiss, and subordinate scattered metabasite; the Yuli belt is composed of greenschist, serpentinite, meta-tuff, meta-gabbro, metabasite, and glaucophane-schist blocks which enclosed by spotted schist of the host rocks. The metamorphic belts were inferred as a Mesozoic mélange. It's still controversial due to the difficulty of analyzing metamorphic rocks. In this study, we focus on the zircon U-Pb dating, geochemistry, and petrographic analysis of spotted schist, metabasite, meta-gabbro, and meta-tuff in order to constrain the formation and crystallization ages and interpret its tectonic setting. Based on zircon U-Pb dating, the host rocks of spotted schist and the exotic blocks of meta-tuff, meta-gabbro (the peak age of 14.4, 15.8, and 16.7 Ma), and metabasite occurred at Miocene. Geochemical characteristics for metabasite and meta-gabbro blocks show Ta-Nd-Ti depletion and LREE depletion in spidergram occurring volcanic arc and N-MORB type affinities, respectively. Results as above mentioned, we suggest that the metamagmatic rocks in the Yuli belt occur within a mélange during the Eurasia continental margin subduction at the Middle-Late Miocene.

  14. Sur l'origine par altération du substratum schisteux de la minéralisation chlorurée des eaux d'une nappe côtière sous climat semi-aride (Chtouka-Massa, Maroc)

    Science.gov (United States)

    Krimissa, Samira; Michelot, Jean-Luc; Bouchaou, Lhoussaine; Mudry, Jacques; Hsissou, Youssef

    2004-11-01

    The origin of chloride ions in groundwater from the Chtouka-Massa plain (Morocco) was studied by using chemical and isotopic analyses of water, and petrographic and chemical analyses of rocks. It appears that the schist formation, which forms the basement of the studied aquifer, is the main source of the high Cl - concentrations in groundwater. In these schists, chloride is, for a part, probably contained in biotites, and is released into groundwater through the weathering of these minerals. However, the exceptionally high chloride contents of these schists are difficult to explain if one does not assume that they also contain evaporitic-type minerals. To cite this article: S. Krimissa et al., C. R. Geoscience 336 (2004).

  15. Stratigraphy, tectonics and detrital zircon U-Pb (LA-ICP-MS) geochronology of the Rio Preto Belt and northern Paramirim corridor, NE, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Alcantara, Davi da Costa Bezerra Gobira de; Uhlein, Alexandre; Caxito, Fabricio de Andrade; Pedrosa-Soares, Antonio Carlos, E-mail: davibgobira@hotmail.com, E-mail: auhlein@gmail.com, E-mail: facaxito@yahoo.com.br, E-mail: pedrosasoares@gmail.com [Universidade Federal de Minas Gerais (CPMTC/UFMG), Belo Horizonte, MG (Brazil). Instituto de Geociencias. Centro de Pesquisa Professor Manoel Teixeira da Costa; Dussin, Ivo, E-mail: ivodusin@yahoo.com.br [Universidade Estadual do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Faculdade de Geologia

    2017-04-15

    Two important Proterozoic metasedimentary sequences, the Rio Preto and Santo Onofre Groups, crop out along the northwestern margin of the Sao Francisco craton and in northern Paramirim corridor, respectively. The Rio Preto Group, involved in the eponymous fold-thrust belt along the northwestern cratonic boundary, comprises the Formosa (garnet schist, quartz schist, quartzite, chlorite-sericite schist and ferriferrous quartz schist) and Canabravinha (quartzite, micaceous quartzite, metarhytmite, phylite, schist and metaturbidite) formations. The Santo Onofre Group occurs exclusively in the Paramirim corridor, and is composed of quartzite and minor carbonaceous or Mn-rich phylite. These units record sedimentation in shallow to deep-water marine settings related to rift basins, and were deformed and metamorphosed under green schist facies conditions during the Brasiliano orogeny. Here we present 427 new detrital zircon U-Pb ages, which constrain the maximum depositional ages of ca. 971 Ma for the Santo Onofre Group, ca. 912 Ma for the Canabravinha Formation, and ca. 65 Ma for the Formosa Formation of the Rio Preto Group. Our data suggests that the Santo Onofre and the Rio Preto Groups accumulated in two distinct basin settings. The latter, composed mostly of sandy rocks, would represent a relatively stable, shallow-marine shelf environment. The Rio Preto Group, with metadiamictite, quartzite, pelitic and rhythmitic rocks, represents a shallow to deep marine environment influenced by gravity flows. Both groups were probably deposited in the Late Tonian, and are potential correlatives of the lower (pre-glacial) units of the Macaubas Group of the Aracuai belt. (author)

  16. Zoned amphibole in an eclogite from the Hida Marginal belt in the Hakuba district, Nagano Prefecture, Japan

    OpenAIRE

    Takasu, Akira; Sakurai, Tsuyoshi; Kashiwabara, Y.; Minamide, Sachiyo

    2003-01-01

    A cobble-sized clast of eclogite was recently found in gravels in the bed of the Matsukawa River at Wadano in Hakuba village,Nagano Prefecture.The cobble was probably derived from an area in the Hida Marginal belt,which consists of high-pressure type schists and closely associated serpentinites,and also includes blocks of garnet glaucophane schist and garnet-epidote-glaucophane schist. The eclogite cobble consists mainly of garnet,omphacite,epidote and amphibole,along with small amounts of qu...

  17. Influence of Parent Material and Topography on some Soil ...

    African Journals Online (AJOL)

    Differences among topographic positions reflected soil properties that are typically associated with bio and geochemical processes (weathering and leaching). Parent material × topography interaction was significant (p<0.05) for Fe. With respect to chemical soil fertility, soils developed on banded gneiss and quartzite schist ...

  18. Geochemistry and petrogenesis of Proterozoic granitic rocks from ...

    Indian Academy of Sciences (India)

    of occurrence of Bathani volcano-sedimentary sequences (BVS), northeast to our study area in juxtaposition to the Munger–Rajgir metasedimen- tary fold belt also adds emphasis to this study. (Ahmad and Wanjari 2009; Saikia et al. 2014). This volcano-sedimentary sequence comprised of garnet- mica schist, banded iron ...

  19. Global Journal of Geological Sciences - Vol 2, No 1 (2004)

    African Journals Online (AJOL)

    PETROCHEMISTRY, Pb ISOTOPE SYSTEMATICS, AND GEOTECTONIC SETTING OF THE GRANITE GNEISSES IN ILESHA SCHIST BELT, ... SP AND VES RESPONSES OVER PB-ZN AND ASSOCIATED SULPHIDES MINERALIZED ZONE OF IZZI AREA, NIGERIA · EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD ...

  20. Page 1 Studies on Archaean Dharwar Tectonic Province 433 ...

    Indian Academy of Sciences (India)

    1988 Archaean stromatolites from Chitradurga schist belt, Dharwar craton, South India; Precamb. Res. 43 239-250. Srinivasan R, Subba Rao DV, Pantulu G V C, Sivaraman TV, Balaram V and Gopalan K 1990 Negative europium anomalies and Rb-Sr reset ages of Archaean detrital metasediments of the low-grade.

  1. Abhilash S Assimilation of Doppler weather radar observations in a ...

    Indian Academy of Sciences (India)

    ern continental margin of the East European Plat- form, tracers of a single heterogeneous lithospheric mantle source. 469. Chattopadhyay A. Polyphase deformation and garnet growth in pelitic schists of Sausar Group in Ramtek area, Maha- rashtra, India: A study of porphyroblast-matrix relationship. 423. Chodankar A R.

  2. Erecting Gas Storage Facilities and Oil Centers

    Science.gov (United States)

    1975-01-21

    standard metal, reenforced concrete, or stone storage tanks; while high-viscosity dark pro- ducts ( bitumens , residual oils and tar oils) are stored in...sedimentary (dense limestones, dolomites, gypsum, chalk, aleurites, argillites, etc.), metamorphic (clay schists and slates, quartzite, siliceous

  3. Journal of Mining and Geology - Vol 38, No 1 (2002)

    African Journals Online (AJOL)

    Late Pan-African tectonics and origin of gold mineralization and rare-metal pegmatities in the Kushaka schist belt, northwestern Nigeria · EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. I GARBA, 1-12. http://dx.doi.org/10.4314/jmg.v38i1.18768 ...

  4. Author Details

    African Journals Online (AJOL)

    Abubakar, YI. Vol 14 (2009): 13 and 14, 2008-2009 - Articles Geochemistry of Gold Deposits in Anka Schist Belt, Northwestern, Nigeria Abstract PDF. ISSN: 1119-0221. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and ...

  5. Author Details

    African Journals Online (AJOL)

    Danbatta, UA. Vol 14 (2009): 13 and 14, 2008-2009 - Articles Geochemistry of Gold Deposits in Anka Schist Belt, Northwestern, Nigeria Abstract PDF. ISSN: 1119-0221. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and ...

  6. 56th Annual Meeting

    Indian Academy of Sciences (India)

    1991-01-01

    Jan 1, 1991 ... The skill of the architects and artisans in chiselling soft stones like. Khondalites, Fluorite-Schists and other such building materials is outstanding and carving, ..... human being, he loved people and the people in turn loved him. A fine work culture and harmony in team-work was hallmark of his leadership.

  7. Records of near-isothermal decompression and clockwise P-T history from the Paleoproterozoic Mahakoshal Belt, Central Indian Tectonic Zone: Constraints from pseudosection modelling and monazite geochronology

    Science.gov (United States)

    Deshmukh, Tanzil; Naraga, Prabhakar; Bhattacharya, Abhijit; Kaliappan, Madhavan

    2017-04-01

    The Mahakoshal Belt (MB) is regarded as the oldest subunit along the northern collar of the Central Indian Tectonic Zone (CITZ) arguably representing the zone of accretion between the North India Block and the South India Block. The following study focuses on deciphering the structural and metamorphic P-T-t history of the schists/phyllites from the eastern part of the belt, and provides insights into the Paleoproterozoic tectonic development in the CITZ. The schists comprise phengite, quartz, andalusite, biotite, muscovite and margarite, and are associated with veins of rare andalusite + corundum + quartz assemblage. The field relations combined with deformation microtextures in the MB schists suggests three episodes of metamorphism, M1, M2 and M3, corresponding with D1, D2 and D3 deformation events respectively. Inclusion trails (S1) of phengite + biotite + quartz ± chlorite in syn/post-S2 andalusite porphyroblasts constrain the M1 metamorphic event in pelitic schists. The application of pseudosection modelling estimated peak metamorphic conditions at ˜8 kbar and 520 ˚ C. Near isothermal decompression (Australia) and the Trans North China Orogen. Therefore, these global correlations possibly corroborate new configurations on the assembly and fragmentation of Columbia Supercontinent, but await further studies and robust age determinations in the various parts of CITZ.

  8. Anasagar gneiss: A folded granitoid pluton in the Phanerozoic South ...

    Indian Academy of Sciences (India)

    The Anasagar gneiss was emplaced as a concordant sheet like body along the contact of quartzite and pelitic/semipelitic schist horizons in the northern part of the South Delhi Fold Belt. It is typically a granite gneiss containing megacrysts of K-feldspar set in a recrystallised foliated matrix. The megacrysts are in general ...

  9. PROCESS TEST WORK FOR THE RECOVERY OF TANTALITE ...

    African Journals Online (AJOL)

    The Nassarawa Pegmatoids which intrude gneisses, schists and metabasites occur in the northeastern part of half – degree sheet 209. The study aims at elevating the knowledge of economic potentials of Ta – Nb mineralization in the area and enhancing the recovery and extraction percentage of the Ta – Nb concentrates ...

  10. 77 FR 25736 - Notice of Intent To Repatriate Cultural Items: Northwest Museum of Arts & Culture, Spokane, WA...

    Science.gov (United States)

    2012-05-01

    ... pendant, 18 rolled copper beads, 6 dentalium, 1 piece of cordage, 1 long jadeite celt, and 1 chipped flint..., 1 jadeite chip, 1 jadeite celt, 46 bone implements, 3 stone pipes, 4 projectile points, 9 schist... spear point, 1 antler, 1 antler horn implement, 2 chalcedony drill or graver, 1 stone chip, 1 stone...

  11. 75 FR 58424 - Notice of Intent to Repatriate Cultural Items: Northwest Museum of Arts & Culture, Spokane, WA

    Science.gov (United States)

    2010-09-24

    ... rolled copper beads, 6 dentalium, 1 piece of cordage, 1 long jadeite celt and 1 chipped flint fragment... celt, 44 bone implements, 3 stone pipes, 3 projectile points, 3 schist scrapers, 1 mussel shell, 1... and shell pendants, 1 spear point, 1 carved stone pipe, 1 jadeite celt, 1 jadeite adze, 2 bone...

  12. Informe preliminar sobre los estudios de la petrografia del extremo occidental de Galicia

    NARCIS (Netherlands)

    Woensdregt, C.F.

    1967-01-01

    The extreme western part of Galicia around Cape Finisterre and Cape Toriñana, consists of pre-migmatic metamorphic rocks, partly migmatised, intruded by syn- and posttectonic granites. The pre-migmatic rocks are of sedimentary origin (biotite schists or gneisses) and of probable igneous origin

  13. Stratigraphie et structure de Trás-os-Montes oriental (Portugal)

    NARCIS (Netherlands)

    Ribeiro, Antonio; Almeida Rebelo, Jose

    1967-01-01

    Rocks in the eastern part of the province of Trás-os-Montes, N. Portugal belong to five units: 1: a complex of pre-Ordovician schists and greywackes; 2: Ordovician and Silurian sediments; 3: a low-grade metamorphic scries of Silurian age; 4: two complexes of probably Precambrian, predominantly meso-

  14. Mineralogy And Raw Material Characterization Of Esie Stone ...

    African Journals Online (AJOL)

    Electronprobe mineral data of samples of Esie statues is presented as a possible tool for provenance studies. Most of the samples contain talc, chlorite, cummingtonite and rarely tremolite. Other talc-bearing schists are prevalent in the Esie area. However talc-cummingtonite rocks, similar to the raw materials used for the ...

  15. Forms of iron in soils on basement complex rocks of Kaduna state in ...

    African Journals Online (AJOL)

    The forms of iron extracted by different methods were studied in soils developed on four basement complex rocks within Northern Guinea Savanna of Nigeria namely: migmatite gneisses, older granite, quartzites and mica schists. The study shows that forms of iron generally decreased in the order of total elemental iron ...

  16. Evidences of inclined transpression at the contact between ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 125; Issue 5. Evidences of inclined transpression at the contact between Vinjamuru group and Udayagiri group of Nellore Schist Belt, Andhra Pradesh, India. Sankha Das Devasheesh Shukla S K Mitra. Volume 125 Issue 5 July 2016 pp 1007-1020 ...

  17. Geochemistry of crystalline basement rocks SW Ugep, Nigeria ...

    African Journals Online (AJOL)

    Geochemical data on low-grade metasedimentary phyllites and schists of SW Ugep show that they were derived from predominantly pelitic parent rocks. They form a supracrustal cover on an orthogneiss of granitic composition. The metasediments are enriched in Si02, Al203 and Zr but improverished in Ni. Intrusion of ...

  18. Lithostratigraphic contact – a significant site for hydrogeological ...

    Indian Academy of Sciences (India)

    The domain-wise study reveals higher fracture-frequencies adjacent to the lithostratigraphic ..... Modal values of fracture-frequencies for (a) quartz biotite granite gneiss, (b) mica schist for domains having no ... Variation in frequencies of fractures with its distance from lithocontact in single lithological domain: (a) quartz.

  19. Petrochemistry And Tectonic Setting Of Metabasic Rocks Of Isanlu ...

    African Journals Online (AJOL)

    Trace elements including Nb, Y and Rb are low in abundance while Sr and Ba show marked enrichment reflecting the abundance of modal plagioclase. Refractory elements including Ni, Co, ... Keywords: Petrochemistry, Tectonic setting, Amphibolite, Ensialic basin, Egbe-Isanlu schist belt. Global Journal of Geological ...

  20. K-Ar ages of low-grade metapelites from the Ryoke belt, the Iwakuni district, Yamaguchi Prefecture, Japan

    National Research Council Canada - National Science Library

    Owada, Masaaki; Midorikawa, Takahiro; Imaoka, Teruyoshi

    2014-01-01

    .... In this paper, we report on a method of sample preparation for, and results of, K-Ar dating. Samples obtained from a slate and a pelitic schist were collected for K-Ar dating from the low-grade parts of the Ryoke belt...

  1. Are phenolic compounds released from the Mediterranean shrub Cistus albidus responsible for changes in N cycling in siliceous and calcareous soils?

    Science.gov (United States)

    Eva Castells; Josep Peñuelas; David W. Valentine

    2004-01-01

    We studied the effects of Cistus albidus leaf leachates on nitrogen-cycling processes in two siliceous soils (granite and schist) and one calcareous soil. We compared those effects with gross N-transformation rates in soils sampled underneath Cistus. Our results show that although phenolic compounds leached from green foliage...

  2. Uranium anomaly evaluation in groundwaters: a hydrogeochemieal

    NARCIS (Netherlands)

    Dekkers, M.J.; Vriend, S.P.; Weijden, C.H. van der; Gaans, P.F.M. van

    1989-01-01

    The hydrogeochemistry of the Nisa region, central Portugal, an area of known U mineralization, was studied. The geology of the region comprises an S-type high-level granite intrusion with vein-type U-mineralization, its contact-metamorphic aureole developed in a schist host rock

  3. 83 - 92_Maniyunda

    African Journals Online (AJOL)

    USER

    weathered (Van Wambeke, 1962; Yakubu and. Ojanuga, 2009). From Si/C ratio, weathering intensity significantly increased in order of soils on mica schist. (MS) < older granite (OG) < quartzite (QZ) < migmatite gneiss (MG). Table 1: Range and means of selected physical and chemical properties of soils of the studied areas ...

  4. Untitled

    Indian Academy of Sciences (India)

    samples from a normal population, 528. The mineralogy and chemical composition of gar- nets from the schist-complex of Nellore, 148. An optical method of determining the relative co- agulating powers of electrolytes, 193. Reaction between nitric acid and tin in presence of catalysts, I, 115. See Wali and Katti. Dispersion of ...

  5. Untitled

    Indian Academy of Sciences (India)

    economic deposits of gold in steep shear zones. Most of the schist belts include greywackes (with economic deposits of manganese in the Sandur belt), polymict conglomerates (with clasts of banded ferru- ginous chert, metabasalt and granite: Some of the boulders of granite in the conglomerates in the Kolar belt are up to ...

  6. Rootless calc-silicate folds in granite: An implication towards syn to ...

    Indian Academy of Sciences (India)

    36

    Northern extremity of Godhra granite is. 10 marked by the contact with the Lunavada Group of rocks. The field evidence for granite and. 11 related pegmatites intruding foliation in schists of Kadana Formation, Lunavada Group,. 12 indicates that the intrusion continued even after D3 deformation of the Lunavada region. 13.

  7. Utility of pollution indices in assessment of soil quality around ...

    African Journals Online (AJOL)

    The quality of soil in the vicinity of Madaka mining sites were investigated in this study using Environmental Pollution Indices. Geological mapping of the study area indicated that the area was dominated by schist and granite. The static water level measurement revealed a westward groundwater flow direction which also ...

  8. Mineral chemistry of tourmaline from Mashak Pahar, South Purulia ...

    Indian Academy of Sciences (India)

    The area of investigation at and around Mashak Pahar, Bankura district, West Bengal, India comprises a number of rock types namely: granite gneiss, migmatized quartz tourmaline gneiss, quartz pebbleconglomerate, ferruginous quartzite, quartz tourmaline veins (as veins) and graphite schists. Interestingly, the study area ...

  9. Author Details

    African Journals Online (AJOL)

    ADEYEMI, GO. Vol 38, No 1 (2002) - Articles Geotechnical properties of lateritic soil developed over quartz schist in Ishara area, south western Nigeria Details · Vol 44, No 1 (2008) - Articles Comparative study of the influence of cement and lime stabilization on geotechnical properties of lateritic soil derived from pegmatite ...

  10. Structural mapping of Chikotra River basin in the Deccan Volcanic ...

    Indian Academy of Sciences (India)

    Qualitative interpretation of these products help identify the distribution of magnetic sources, viz., the Deccan basalts, dolerite intrusives and older greenstone and schist belts in the subsurface. Present study suggests that the Chikotra basin is composed of three structural units; a NE–SW unit superposed on deeper NW–SE ...

  11. Aquifer characteristics and groundwater recharge pattern in a typical ...

    African Journals Online (AJOL)

    EJIRO

    Physoigraphy, geology and hydrogeology. The study area is the Federal College of Education, Osiele,. Abeokuta, Southwestern, Nigeria. The area falls under the Base- ment Complex area of Ogun State, Southwestern Nigeria (Figure. 1). The basement rocks comprise of folded gneiss, schist, quartzite, older granite, and ...

  12. Geology and environmental impact of artisanal gold mining around ...

    African Journals Online (AJOL)

    Geology and effect of artisanal gold mining was investigated in Kataeregi and environ, North-central Nigeria with the aim of determining its host rock and assessing the impact of such activity on the surrounding. Geological field mapping show the area comprise of the Migmatite-Gneiss complex, Schist, Granite and ...

  13. Geology of the Pan-African basement Complex in Ube-Wulko area ...

    African Journals Online (AJOL)

    The Ube-Wulko area of southeast Akwanga falls within the Pan-African remobilized Basement Complex of northcentral Nigeria. It consists of intensely multi-deformed high grade polymetamorphic basement rocks, predominantly composed of migmatitic gneisses and schists and subordinate quartzites, marbles, and ...

  14. Tectonic Plates of China

    Science.gov (United States)

    1977-04-01

    crusts from the middle Chilien range towards the Alashan block. Melanges and glaucophane schists, as well as pairs of metamorphic zones, are found along...8217 . S. .. .. 4. esoztc dld2 main dpost•7l - ..LA -22- formation, which contains glaucophane and represents a low temperature-high pressure metamorphic

  15. Continental Scientific Drilling Program.

    Science.gov (United States)

    1979-01-01

    assemblage associated with a Jurassic subduction zone. In this formation, ophiolites, cherts, pillow basalts, glaucophane schists, graywacke, and melanges...RESOURCES 121 follow clear-cut safeguards to avoid any degradation of the geyser and hot spring systems. Any such drilling must also be totally

  16. Magnetic surveying as an aid to geological mapping: a case study ...

    African Journals Online (AJOL)

    The derivative maps showed that the area is clearly divided into three main magnetic (and pseudogravity) anomaly zones, demarcated by five contact locations (C1 to C5), which had close associations with the main lithologies of grey (or banded) gneiss, granite-gneiss and mica schist. The contact C1 indicated that the ...

  17. Journal of Mining and Geology - Vol 40, No 1 (2004)

    African Journals Online (AJOL)

    Industrial assessment of the residual clay bodies over gneisses and schists of Yaounde area, southern Cameroon · EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. AA Elueze, NL Ekengele, AT Bolarinwa, 9-15. http://dx.doi.org/10.4314/jmg.v40i1.18804 ...

  18. Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

    Science.gov (United States)

    Rye, R.O.; Schuiling, R.D.; Rye, D.M.; Jansen, J.B.H.

    1976-01-01

    At Naxos, Greece, a migmatite dome is surrounded by schists and marbles of decreasing metamorphic grade. Sillimanite, kyanite, biotite, chlorite, and glaucophane zones are recognized at successively greater distances from the migmatite dome. Quartz-muscovite and quartz-biotite oxygen isotope and mineralogie temperatures range from 350 to 700??C. The metamorphic complex can be divided into multiple schist-rich (including migmatites) and marblerich zones. The ??18O values of silicate minerals in migmatite and schist units and quartz segregations in the schist-rich zones decrease with increase in metamorphic grades. The calculated ??18OH2O values of the metamorphic fluids in the schist-rich zones decrease from about 15??? in the lower grades to an average of about 8.5??? in the migmatite. The ??D values of OH-minerals (muscovite, biotite, chlorite, and glaucophane) in the schist-rich zones also decrease with increase in grade. The calculated ??DH2O values for the metamorphic fluid decrease from -5??? in the glaucophane zone to an average of about -70??? in the migmatite. The ??D values of water in fluid inclusions in quartz segregations in the higher grade rocks are consistent with this trend. The??18O values of silicate minerals and quartz segregations in marble-rich zones are usually very large and were controlled by exchange with the adjacent marbles. The ??D values of the OH minerals in some marble-rich zones may reflect the value of water contained in the rocks prior to metamorphism. Detailed data on 20 marble units show systematic variations of ??18O values which depend upon metamorphic grade. Below the 540??C isograd very steep ??18O gradients at the margins and large ??18O values in the interior of the marbles indicate that oxygen isotope exchange with the adjacent schist units was usually limited to the margins of the marbles with more exchange occurring in the stratigraphic bottom than in the top margins. Above the 540??C isograd lower ??18O values occur in

  19. Mantle peridotite in newly discovered far-inland subduction complex, southwest Arizona: Initial report

    Science.gov (United States)

    Haxel, Gordon B.; Jacobson, Carl E.; Wittke, James H.

    2015-01-01

    The latest Cretaceous to early Palaeogene Orocopia Schist and related units are generally considered a low-angle subduction complex that underlies much of southern California and Arizona. A recently discovered exposure of Orocopia Schist at Cemetery Ridge west of Phoenix, Arizona, lies exceptionally far inland from the continental margin. Unexpectedly, this body of Orocopia Schist contains numerous blocks, as large as ~300 m, of variably serpentinized mantle peridotite. These are unique; elsewhere in the Orocopia and related schists, peridotite is rare and completely serpentinized. Peridotite and metaperidotite at Cemetery Ridge are of three principal types: (1) serpentinite and tremolite serpentinite, derived from dunite; (2) partially serpentinized harzburgite and olivine orthopyroxenite (collectively, harzburgite); and (3) granoblastic or schistose metasomatic rocks, derived from serpentinite, made largely of actinolite, calcic plagioclase, hercynite, and chlorite. In the serpentinite, paucity of relict olivine, relatively abundant magnetite (5%), and elevated Fe3+/Fe indicate advanced serpentinization. Harzburgite contains abundant orthopyroxene, only slightly serpentinized, and minor to moderate (1–15%) relict olivine. Mantle tectonite fabric is locally preserved. Several petrographic and geochemical characteristics of the peridotite at Cemetery Ridge are ambiguously similar to either abyssal or mantle-wedge (suprasubduction) peridotites and serpentinites. Least ambiguous are orthopyroxene compositions. Orthopyroxene is distinctively depleted in Al2O3, Cr2O3, and CaO, indicating mantle-wedge affinities. Initial interpretation of field and petrologic data suggests that the peridotite blocks in the Orocopia Schist subduction complex at Cemetery Ridge may be derived from the leading corner or edge of a mantle wedge, presumably in (pre-San Andreas fault) southwest California. However, derivation from a subducting plate is not precluded.

  20. Stream nitrate variations explained by ground water head fluctuations in a pyrite-bearing aquifer.

    Science.gov (United States)

    Grimaldi, C; Viaud, V; Massa, F; Carteaux, L; Derosch, S; Regeard, A; Fauvel, Y; Gilliet, N; Rouault, F

    2004-01-01

    In the context of agricultural nitrogen excesses in northwestern France, pyrite-bearing weathered schist aquifers represent important hydrological compartments due to their capacity to eliminate nitrate (NO3-). Under oxygen-free conditions, nitrate is reduced simultaneously with the oxidation of pyrite leading to the release of sulfate (SO4/2-). The aim of the present study is to identify the hydrological conditions under which the weathered schist ground water influences the stream water chemistry, leading to a decrease in NO3- concentration. We measured the ground water head on a small catchment over weathered schist, near the bank and under the streambed, and analyzed the chemical composition of the ground water as well as the stream water on both seasonal and storm-event timescales. Using SO4/2- as a tracer of the weathered schist ground water, we showed that ground water inflow caused a decrease of NO3- concentration in the stream during the autumn as well as during storm events in spring and summer. In summer, the NO3- concentration was controlled by the sources of the stream, and in winter by the shallow ground water inflow. The effect of the weathered schist ground water on the NO3- depletion remained relatively limited in time. This effect persisted into late autumn as long as the NO3(-) -rich shallow ground water did not feed the stream. The duration and intensity of the effect would be extended by decreasing the shallow ground water inflow, which depends on climate as well as the presence of landscape features such as hedges and buffer zones.

  1. Fabric and elastic properties of antigorite, mica and amphibole-rich rocks and implications for the tectonic interpretation of seismic anisotropy

    Science.gov (United States)

    Shao, Tongbin

    C. Comparisons of laboratory velocities measured at high pressure with CPO data measured using EBSD techniques demonstrate that seismic anisotropy in high temperature serpentinites, which is essentially controlled by the antigorite c-axis fabric, is independent on the operating slip system but strongly dependent on the regime and magnitude of finite strain experienced by the rock. Extrapolation of experimental data with both pressure and temperature suggests that Vp anisotropy decreases but shear-wave splitting (DeltaVs) and V p/Vs increase with increasing pressure in either cold or hot subduction zones. For a cold, steeply subducting slab, antigorite is most likely deformed by nearly coaxial flattening or trench-parallel movement, forming trench-parallel seismic anisotropy. For a hot, shallowly subducting slab, however, antigorite is most likely deformed by simple shear or transpression. Trench-normal seismic anisotropy can be observed when the subducting dip angle is smaller than 30°. The geophysical characteristics of the Tibetan Plateau, such as strong heterogeneity in V p, Vs and attenuation, shear-wave splitting and electric conductivity, may be explained by the presence of strongly deformed serpentinites in lithospheric shear zones reactivated along former suture zones between amalgamated blocks, hydrated zones of subducting lithospheric mantle, and the crust-mantle boundary if the temperature is below 700 °C in the region of interest. Chapter 3 provides a detailed calibration on the magnitude and symmetry of seismic anisotropy for 132 schists to constrain their departures from transverse isotropy (TI) that is usually assumed in the interpretation of seismic data. The average bulk Vp anisotropy at 600 MPa for chlorite schists, mica schists, phyllites, sillimanite-mica schists, and amphibole schists examined is 12.0%, 12.8%, 12.8%, 17.0%, and 12.9%, respectively. Most of the schists show Vp anisotropy in the foliation plane which averages 2.4% for phyllites, 3.3% for

  2. Unlocking the biogeochemical black box: What drives microbial response to climate forcing in semi-arid soils?

    Science.gov (United States)

    Moravec, B. G.; McLain, J. E.; Lohse, K. A.

    2009-12-01

    Microbial mediated cycling of carbon (C) and nitrogen (N) and their loss from soils are closely linked to soil moisture and temperature. Yet, it is unclear how microbial communities will respond to climatic forcing (namely increased inter-annual precipitation variability and severe drought) and to what extent parent material controls these responses. We used Real Time Polymerase Chain Reaction (RT-PCR) and C utilization assays to determine the relative abundance and diversity of microbial populations during pre-, mid- and post-monsoon time intervals at four sites along a steep elevation gradient (temperature and precipitation range of >10°C and >50 cm, respectively) in the Santa Catalina Mountains, AZ. Contrasting parent materials (schist and granite) were paired at elevations. RT-PCR results showed large increases of bacterial and fungal biomarkers at high elevations with the onset of precipitation (pre- to mid- monsoon conditions) (as much as 824%). In contrast, bacteria biomarkers did not change at low elevation granite site as a result of the onset of precipitation whereas fungal biomarkers increased by 177% at this site. Both bacteria and fungal biomarkers increased substantially at low elevation schist sites with the onset of precipitation. Finally, C utilization assays indicated that high elevation sites had a relatively high diversity of C utilization compared to low elevation soils. We hypothesize that increased bacterial and fungal abundance in low elevation schist-derived soils relative to granite soils after the onset of monsoon rains may be a function of soil texture, with higher clay content in schist soils leading to higher soil moisture availability. Alternatively, differences in microbial responses may be due to higher C availability in schist soils compared to granite soils. Higher C utilization diversity as well as similar bacteria and fungal biomarker responses found at high elevation sites (both granite and schist soils) in response to

  3. Unraveling an antique subduction process from metamorphic basement around Medellín city, Central Cordillera of Colombian Andes

    Science.gov (United States)

    Bustamante, Andres; Juliani, Caetano

    2011-10-01

    In the surroundings of Caldas and El Retiro cities (Colombia) metamorphic rocks derived from basic and pelitic protoliths comprise the Caldas amphibole schist and the Ancón schist respectively. Subordinated metamorphosed granite bodies (La Miel gneiss) are associated to these units, and The El Retiro amphibolites, migmatites and granulites crops out eastwards of these units, separated by shear zones. The Caldas amphibole schist and the Ancón schist protoliths could have been formed in a distal marine reduced environment and amalgamated to the South American continent in an apparent Triassic subduction event. The El Retiro rocks are akin to a continental basement and possible include impure metasediments of continental margin, whose metamorphism originated granulite facies rocks and migmatites as a result of the anatexis of quartz-feldspathic rocks. The metamorphism was accompanied by intense deformation, which has juxtaposed both migmatites and granulite blocks. Afterward, heat and fluid circulation associated with the emplacement of minor igneous intrusions resulted in intense fluid-rock interaction, variations in the grain size of the minerals and, especially, intense retrograde metamorphic re-equilibrium. Thermobarometric estimations for the Caldas amphibole schist indicate metamorphism in the Barrovian amphibolite facies. The metamorphic path is counter-clockwise, but retrograde evolution could not be precisely defined. The pressures of the metamorphism in these rocks range from 6.3 to 13.5 kbar, with narrow temperature ranging from 550 to 630 °C. For the Ancón schist metapelites the P- T path is also counter-clockwise, with a temperature increase evidenced by the occurrence of sillimanite and the cooling by later kyanite. The progressive metamorphism event occurred at pressures of 7.6-7.2 kbar and temperatures of 645-635 °C for one sample and temperature between 500 and 600 °C under constant pressure of 6 kbar. The temperature estimated for these rocks

  4. Contrasting P- T- t paths from the basement of the Tisia Unit (Slavonian Mts., NE Croatia): Application of quantitative phase diagrams and monazite age dating

    Science.gov (United States)

    Horváth, Péter; Balen, Dražen; Finger, Fritz; Tomljenović, Bruno; Krenn, Erwin

    2010-06-01

    Medium-grade mica schists and intercalated paragneisses and amphibolites from the basement of the Tisia Unit, Slavonian Mountains., northeastern Croatia, contain complexly zoned garnets. At the Kutjevo locality, mica schists are characterised by garnets with Mn-rich cores and Ca-rich rims. Mn decreases steadily from core to rim and Ca increases abruptly. This is in contrast to the paragneisses and amphibolites which contain garnets with smoothly decreasing Ca from core to rim. Quantitative phase diagrams and garnet composition isopleths calculated from bulk rock analyses reveal that the Ca-poor garnet cores in the mica schists formed during an earlier event at 584-592 °C and 6.4-7.8 kbar. Ca-rich rims formed at conditions of 600-660 °C and 11-12 kbar — calculated using garnet isopleths and mineral thermobarometry. The paragneiss and amphibolite provide similar P- T information for the later peak event (ca. 650 °C, 10-12 kbar) but do not preserve a record of the earlier, lower P- T event and modelling shows that garnet was not stable at these conditions. Contrary to previous studies on this outcrop and rock type, no staurolite was observed and quantitative phase diagrams contoured for H 2O mode isopleths indicate that the rock did not cross staurolite-bearing fields during the retrograde P- T path. Mica schists from the Krndija locality contain zoned polyphase garnets. Phase diagram calculations reveal that Ca-rich garnet cores formed between 520 and 630 °C and 7-8 kbar. Rims have a lower Ca content and formed at considerably reduced pressures together with andalusite and staurolite at ca 530-570 °C and 3-4 kbar. Since both localities were traditionally considered to be part of the same tectono-metamorphic unit, evidence presented here clearly shows that this cannot be the case. EMP monazite ages are Variscan (350 Ma) in the Krndija mica schists and around pre- or early Variscan (440 Ma) in the Kutjevo mica schists. We therefore propose a more complex

  5. Is the Vincent fault in southern California the Laramide subduction zone megathrust?

    Science.gov (United States)

    Xia, H.; Platt, J. P.

    2016-12-01

    The Vincent fault (VF) in the San Gabriel Mountains, southern California separates a Meso-Proterozoic gneiss complex and Mesozoic granitoid rocks in the upper plate from the ocean-affiliated Late Cretaceous Pelona schist in the lower plate, and it has been widely interpreted as the original Laramide subduction megathrust. A 500 to 1000 m thick mylonite zone, consisting of a low-stress (LS) section at the bottom, a high-stress (HS) section at the top, and a weakly deformed section in between, is developed above the VF. Our kinematic, thermobarometric and geochronological analysis of the mylonite zone indicates that the VF is a normal fault. Shear sense indicators including asymmetric porphyroblasts, quartz new grain fabric, mineral fish, and quartz CPO from the HS and the LS sections exhibit a top-to-SE sense of shear on the SW-dipping mylonitic foliation, which is contrary to what one would expect for the Laramide subduction megathrust. A few samples from the LS section were overprinted by HS microstructure, implying that the LS mylonites predate the HS mylonites. TitaniQ thermometer and Si-in-muscovite barometer show that the P-T conditions are 389 ± 6 °C, 5 kbar for the LS mylonites and 329 ± 6 °C, 2.4 kbar for HS mylonites. Considering the temporal sequence of HS and LS mylonites, they are likely to be formed during exhumation. A comparison with the lower plate leads to the same conclusion. The top 80-100 m of the Pelona schist underneath the VF is folded and also mylonitized, forming the Narrows synform and S3 simultaneously. Our previous study found that S3 of the Pelona schist has a top-to-SE sense of shear and similar P-T conditions as the LS mylonite in the upper plate, so S3 of the Pelona schist is likely to be formed together with the LS mylonites in the upper plate. While mylonitization of Pelona schist (S3) overprinted both the subduction-related S1 fabric and the return-flow-related S2 fabric, it is reasonable to argue that the mylonite zone above

  6. Early Cretaceous wedge extrusion in the Indo-Burma Range accretionary complex: implications for the Mesozoic subduction of Neotethys in SE Asia

    Science.gov (United States)

    Zhang, Ji'en; Xiao, Wenjiao; Windley, Brian F.; Cai, Fulong; Sein, Kyaing; Naing, Soe

    2017-06-01

    The Indo-Burma Range (IBR) of Myanmar, the eastern extension of the Yarlung-Tsangpo Neotethyan belt of Tibet in China, contains mélanges with serpentinite, greenschist facies basalt, chert, sericite schist, silty slate and unmetamorphosed Triassic sandstone, mudstone and siltstone interbedded with chert in the east, and farther north high-pressure blueschist and eclogite blocks in the Naga Hills mélange. Our detailed mapping of the Mindat and Magwe sections in the middle IBR revealed a major 18 km antiformal isocline in a mélange in which greenschist facies rocks in the core decrease in grade eastwards and westwards symmetrically `outwards' to lower grade sericite schist and silty slate, and at the margins to unmetamorphosed sediments, and these metamorphic rocks are structurally repeated in small-scale imbricated thrust stacks. In the Mindat section the lower western boundary of the isoclinal mélange is a thrust on which the metamorphic rocks have been transported over unmetamorphosed sediments of the Triassic Pane Chaung Group, and the upper eastern boundary is a normal fault. These relations demonstrate that the IBR metamorphic rocks were exhumed by wedge extrusion in a subduction-generated accretionary complex. Along strike to the north in the Naga Hills is a comparable isoclinal mélange in which central eclogite lenses are succeeded `outwards' by layers of glaucophane schist and glaucophanite, and to lower grade greenschist facies sericite schist and slate towards the margins. In the Natchaung area (from west to east) unmetamorphosed Triassic sediments overlie quartzites, sericite schists, actinolite schists and meta-volcanic amphibolites derived from MORB-type basalt, which are in fault contact with peridotite. Olivine in the peridotite has undulatory extinction suggesting deformation at 600-700 °C, similar to the peak temperature of the amphibolite; these relations suggest generation in a metamorphic sole. The amphibolites have U/Pb zircon ages of 119

  7. P, M and G tectonites: a classification based on origin of mineral preferred orientations

    Science.gov (United States)

    Shelley, David

    The mechanisms responsible for mineral preferred orientations can be used as the basis for a classification of tectonites. P tectonites develop mineral preferred orientations by plastic deformation, M tectonites by mechanical reorientation of inequidimensional grains and G tectonites by various growth processes. Intermediate tectonite types can be defined with the aid of a triangular diagram. Examples discussed include marble and quartzite ( P-types), slates ( M- or MG-types), certain hornblende or feldspar-rich schists ( G-types), granite-derived gneisses and mylonites ( PM-types), and common schists ( MG- or PMG-types). The classification is designed to promote a holistic approach to fabric studies. In addition, the PMG triangle provides a framework for tracking the sequential fabric development of tectonites.

  8. Tunnel support design by comparison of empirical and finite element analysis of the Nahakki tunnel in mohmand agency, pakistan

    Science.gov (United States)

    Riaz, Asif; Jamil, Syed Muhammad; Asif, Muhammad; Akhtar, Kamran

    2016-03-01

    The paper analyses the geological conditions of study area, rock mass strength parameters with suitable support structure propositions for the under construction Nahakki tunnel in Mohmand Agency. Geology of study area varies from mica schist to graphitic marble/phyllite to schist. The tunnel ground is classified and divided by the empisical classification systems like Rock mass rating (RMR), Q system (Q), and Geological strength index (GSI). Tunnel support measures are selected based on RMR and Q classification systems. Computer based finite element analysis (FEM) has given yet another dimension to design approach. FEM software Phase2 version 7.017 is used to calculate and compare deformations and stress concentrations around the tunnel, analyze interaction of support systems with excavated rock masses and verify and check the validity of empirically determined excavation and support systems.

  9. Tunnel support design by comparison of empirical and finite element analysis of the Nahakki tunnel in mohmand agency, pakistan

    Directory of Open Access Journals (Sweden)

    Riaz Asif

    2016-03-01

    Full Text Available The paper analyses the geological conditions of study area, rock mass strength parameters with suitable support structure propositions for the under construction Nahakki tunnel in Mohmand Agency. Geology of study area varies from mica schist to graphitic marble/phyllite to schist. The tunnel ground is classified and divided by the empisical classification systems like Rock mass rating (RMR, Q system (Q, and Geological strength index (GSI. Tunnel support measures are selected based on RMR and Q classification systems. Computer based finite element analysis (FEM has given yet another dimension to design approach. FEM software Phase2 version 7.017 is used to calculate and compare deformations and stress concentrations around the tunnel, analyze interaction of support systems with excavated rock masses and verify and check the validity of empirically determined excavation and support systems.

  10. Le métamorphisme Tardi-Crétacé à Éocène des zones internes de la chaîne Indo-Birmane (Myanmar occidental) : implications géodynamiquesLate Cretaceous to Eocene metamorphism of the internal zone of the Indo-Burma range (western Myanmar): geodynamic implications

    Science.gov (United States)

    Socquet, Anne; Goffé, Bruno; Pubellier, Manuel; Rangin, Claude

    Metamorphic study on Triassic schists in the internal zone of the Indo-Burma range, essentially based on chlorite-mica equilibrium in metapelites, allows a P- T path to be quantified. During the prograde metamorphism, the geothermic gradient evolves from that of a 'normal' crust (30 °C km -1) to that of a thickened crust (18 °C km -1). The peak conditions are around 8 kbar and 450 °C. This thickening (25-30 km) is probably made in a wedge set up between the Late Cretaceous and the Eocene, in front of the obduction. The obtained cold retrograde path requires a mechanism allowing thermal re-equilibration, implying slow exhumation. It occurred along a shear zone that put into contact the micaschists of the core with the Triassic schists of the roof. To cite this article: A. Socquet et al., C. R. Geoscience 334 (2002) 573-580.

  11. Réservoirs fluides et transferts en contexte d'exhumation orogénique : implications sur la position structurale des minéralisations Cu-Pb-Zn-Fe-Ag dans la région Lavrion-Eubée (Grèce)

    OpenAIRE

    Scheffer, Christophe

    2016-01-01

    This thesis is focused on the Attico-Cycladic orogenic wedge formed during the Alpine orogeny. From a multi-method and multi-scale approach using structural geology, petrography, mineral thermobarometry, element and isotope geochemistry, and PVTX data of associated fluid inclusions, this study deciphers the relationships between fluid circulation, fluid-rock interactions and mobilisation-transport-deposits of metals. Marbles and schists from the Evia Island and the Lavrion peninsula testify t...

  12. Characterizing Optical Properties of Disturbed Surface Signatures

    Science.gov (United States)

    2013-01-01

    thermal properties. These properties include the particle size distribution and shapes of the grains that compose the soil as well as the roughness...of the surface to include the number and shape of rock shards and soil aggregates. Sometimes there are changes in the larger scale topography, the...location, also had significant clasts of schist and other metamorphic rocks, which added mica grains to the soil. There was little organic plant

  13. SUGARLOAF ROADLESS AREA, CALIFORNIA.

    Science.gov (United States)

    Powell, Robert E.; Campbell, Harry W.

    1984-01-01

    On the basis of geologic, geochemical, and geophysical investigations and a survey of mines, quarries, and prospects the Sugarloaf Roadless Area, California, has little promise for the occurrence of metallic mineral or energy resources. Units of carbonate rock and graphitic schist have demonstrated resources of magnesian marble and graphite. Sand, gravel, and construction stone other than carbonate rock are present in the roadless area, but similar or better quality materials are abundant and more accessible outside the area.

  14. Environmental Assessment for Implementation of 2005 Base Realignment and Closure Commission Recommendations at Eielson Air Force Base, Alaska

    Science.gov (United States)

    2007-08-01

    to the northeast of the base are composed of Precambrian and Paleozoic-age schists, micaceous Eielson AFB Realignment and Closure Actions EA...identify and assess environmental health and safety risks to children, coordinate research priorities on children’s health, and ensure that their...Development Council 2006). Additional economic factors contributing to the Fairbanks economy include mining, education and research , tourism, and

  15. Dicty_cDB: SHE533 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available soma japonicum cDNA, mRNA sequence. 56 0.001 1 CV682907 |CV682907.1 service43_H06_sjs2-16-2B11-T3 SJS Schist...osoma japonicum cDNA, mRNA sequence. 56 0.001 1 CV682854 |CV682854.1 service30_G09_sjs2-14-10C09-T3 SJS Schi

  16. Identifying Seismogenic Deposits in Cascadia Inland Lake Sediments: A Natural Experiment Recorded in the Sedimentary Records at Squaw Lakes, Oregon, USA

    Science.gov (United States)

    Morey, A. E.; Gavin, D. G.; Goldfinger, C.; Nelson, A. R.

    2013-12-01

    A natural experiment began after a landslide dammed Squaw Creek located ~100 km from the Oregon coast at the Oregon/California border (42.035804°N, 123.021973°W) separating the drainages at the confluence of Squaw and Slickear Creeks, resulting in the formation of Upper (Little) Squaw Lake and Lower (Big) Squaw Lake. Upper Squaw Lake is the smaller of the two lakes (7.2 ha) with a large drainage (40 sq km) and the sediments contain a 2000-y record of disturbance events. The thickest (~5 cm to ~35 cm) of the disturbance deposits correlate in timing and frequency as compared to the onshore/offshore record of seismogenic turbidites suggesting they were possibly triggered by strong shaking from great earthquakes. Both the drainage and the lake itself are situated within the Condrey Mountain Schist Terrane which consists of black graphitic quartz-mica schist ('blackschist'), with considerable amounts of chlorite-actinolite schist ('greenschist'), and is prone to failures. In contrast, Lower Squaw Lake is a larger, long lake (18.6 ha) with a small drainage (19 sq km). Lower Squaw Lake is also surrounded by the Condrey Mountain Schist, but approximately 95% of the drainage is located in the Western Hayfork Terrane, composed primarily of metavolcaniclastic andesitic agglomerate and tuff which is much more resistant to erosion and failure. These differences in geologic setting allow for the identification of deposits formed internally to the lake at Lower Squaw Lake, which can then be compared to the record from Upper Squaw Lake where the frequency of disturbance event deposits is much higher than reasonably expected from earthquakes. Because disturbance event deposits in Pacific Northwest lakes have been typically attributed to post-fire erosion or extreme hydrologic events, we take advantage of these differences in setting to differentiate between seismogenic and aseismic deposits in Cascadia lake sediments.

  17. 2567-IJBCS-Article-Amani Michel Kouassi

    African Journals Online (AJOL)

    hp

    est qu'on y trouve à la fois des roches issues de l'orogenèse libérienne et des orogenèses les plus récentes (Burkinienne et Eburnéenne). Les formations rencontrées dans le domaine. Sassandra-Cavally (SASCA) sont les schistes, les micaschistes, les arkoses, les quartzites, les tufs métamorphiques, les metarhyolites, les.

  18. Lu/Hf dating of garnet constrains timing of metamorphism and deformation, Prince Rupert Area, British Columbia

    Science.gov (United States)

    Wolf, D. E.; Andronicos, C. L.; Vervoort, J. D.; Mansfield, M.

    2008-12-01

    We present new Lu-Hf garnet ages that constrain the timing of deformation and metamorphism in the Western Metamorphic Belt (WMB), near Prince Rupert, British Columbia. We examined four samples of grt- bearing schist collected within the aureole to the Ecstall Pluton in the WMB. Garnets were separated from these rocks and dated using the Lu-Hf method at Washington State University. We determined geologically meaningful ages from three of these samples. The tectonic history of the Prince Rupert area is marked by phases of transpressive deformation, which included the development of crustal scale strike-slip shear zones and thrust slices with inverted metamorphic gradients. The Grenville Channel shear zone (GCSZ) is a crustal-scale sinistral-slip shear zone over 300 km long that strikes NW with a steep dip and shallow lineation. The GCSZ cuts through the WMB, a ductile fold and thrust belt composed of gneiss and schist with an inverted metamorphic sequence. Index minerals range from: chl and chd-grade units at the bottom of the sequence, str-bearing rocks in the middle, and ky-grt schist and local migmatites at the top of the thrust stack. The WMB was deformed and intruded by the Ecstall Pluton after the inverted metamorphic sequence had formed. The Ecstall is an epi-bearing hbl-qtz diorite emplaced between 91 and 93.5±1 Ma (Butler et al., 2001). Sample G-16A from Kumeleon Inlet (W of the Ecstall pluton) is a schist containing grt+biot+musc+qtz+epi+amph+sil, with small (date garnet growth during metamorphism and deformation in the Prince Rupert area, and show that development of the inverted metamorphic sequence predated emplacement of the Ecstall pluton by 10 to 15 Ma. The data further indicate that left lateral strike slip shearing occurred between 107 and 102 Ma, at the same time much of the North American Cordillera was undergoing major contractional deformation.

  19. Groundwater potential evaluation using electrical resistivity method ...

    African Journals Online (AJOL)

    ... anisotropy of between 1.18 and 1.88. This weathered to a mixture of clay and sand with low to medium groundwater yield; Mica-schist with aquifer resistivity in the range of 16 – 40m and coefficient of anisotropy of between 1.3 and 2.3. This weathered into more of clay because of its high ferromagnetic mineral content and ...

  20. 岡山県大佐地域の三郡変成帯中の藍閃石とフェロ藍閃石

    OpenAIRE

    Watanabe, Teruo

    1984-01-01

    The Sangun metamorphic terrane, which is situated in the inner side of southwest Japan, is one of the glaucophanitic metamorphic terranes of high-pressure intermediate type in late Paleozoic−early Mesozoic. It is characterized by widespread occurrences of pumpellyite-bearing assemblages and sodic amphibole-bearing assemblages in mafic schists. Sodic amphibole in the Sangun terrane is mainly crossite− magnesioriebeckite with b = Z (Hashimoto, 1968a & b; Nishimura, 1971; Okamura et al., 1975; K...

  1. Southern California Coastal Processes Annotated Bibliography.

    Science.gov (United States)

    1985-12-01

    A report describing the program which is to restore and enhance a degraded wetland on the San Diego coast. Program is to be included in the local...42 DESCRIPTION " Describes the occurrence of cobbles and boulders of glaucophane schist and rock grains in sedimentary rocks in Southern California...San Juan Creek and Trabuco Creek, Facility Nos. LO and L02, Aggradation/ Degradation Study CITATION : Orange County Environmental Management Agency

  2. Geology of the USSR (Chapter IV).

    Science.gov (United States)

    1979-10-05

    exi.tence and subsequent degradation of th= icp shield, whica covered 6atire archipelago as a whole, we them re lat- to Pleistocene. Th, visible thickness...greenschist formation, and by crystalline schists with stdIrolite, chloritoid and glaucophane which now outcrop in North Taimyr and in the southern part of... degradation of glaciaticn brought in the specific stage to gradual melting away of the edges of plateau of islands and shaping of terraces on their slopes in

  3. Dicty_cDB: VFE106 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available 38 1.8 2 AL612339 |AL612339.1 T3 end of clone 003AF09 of library SmBAC1 from strain Puerto-Rican of Schistos.... 36 2.1 4 AL616943 |AL616943.1 T3 end of clone 016AB06 of library SmBAC1 from strain Puerto-Rican of Schist

  4. Microbial Reduction of Structural Fe3+ in Nontronite by a Thermophilic Bacterium and its Role in Promoting the Smectite to Illite Reaction

    Science.gov (United States)

    2007-01-01

    5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Gengxin Zhang, Hailiang Dong, JinWook Kim, D.D. Eberl 5d. PROJECT NUMBER 5e. TASK...granulile facies containing schist, gneiss, and amphibolite from Uley Graphite Mine near Port Lincoln in South Australia (Keeling et al. 2000). Bulk...when the anaerobic culture tubes were opened inside a glove box, apparently because the gas composition of headspace in the tribes was different from

  5. New geochemical and geochronological data constraining metamorphism of the Tavşanlı Zone, NW Turkey

    Science.gov (United States)

    Aydın, Halil Can; Özdamar, Şenel

    2016-04-01

    The Tavşanlı Zone is a high-grade metamorphic belt, representing subduction and exhumation between the Sakarya Zone and the Afyon-Bolkardaǧ Zone in Western Anatolia. The Sivrihisar area of the Tavşanlı Zone comprises Paleozoic metamorphic rocks including sedimentary and magmatic origanated; Eocene granites; Neogene sedimentary rocks and alluvium. Metasedimantary rocks are composed of marble, schist and quartzite. Metamagmatics are gneiss and metabazites. This study presents new and precise, whole-rock chemistry; phengite-40Ar/39Ar age data from this area to constrain the high pressure (HP)-low temperature (LT) metamorphism of the Tavşanlı Zone. 40Ar/39Ar dating of two phengite samples from schists gave plateau ages between 82,5 ± 0,14 and 83,29 ± 0,22 Ma, which are interpreted as the metamorphic age of these schists, and as the age of metamorphism affected the Tavşanlı Zone. Also these ages constrain the timing of the closure of the Neo-Tethys.

  6. Mineral chemistry of garnet in pegmatite and metamorphic rocks in the Hamedan area

    Directory of Open Access Journals (Sweden)

    Ahmad Ahmadi Khalaji

    2015-10-01

    Full Text Available Introduction The area of this study is located near Hamadan within the Sanandaj - Sirjan tectonic zone. In the Hamadan area, consisting mainly of Mesozoic plutonic and metamorphic rocks, aplites and pegmatites locally contain garnets.(Baharifar et al., 2004, Amidi and Majidi, 1977; Torkian, 1995. Garnet-bearing schists and hornfelses in the area are products of regional metamorphism shown by slate and phyllite (Baharifar, 2004. In this investigation the distribution of elements in garnet in different rock type was studied to determine their mineral types and conditions of formation. Garnet samples from igneous and metamorphic rocks were analyzed by electron microprobe (EMPA, the results of which are presented in this article. Materials and methods Thirty-five samples were selected for thin section preparation and twenty thin-polished sections were prepared for mineralogical and microprobe analysis. Thin sections of garnet-bearing igneous (pegmatite and metamorphic rocks (schist and hornfels were studied by polarizing microscope. Chemical analysis was performed on the garnets (38 points using a Caimeca SX100 electron microprobe at an acceleration voltage of 15 kV and electric current of 15 nA in the Mineral Processing Research Center, Iran. Separation of iron (II and Fe (III was calculated by Droop’s method (1987 and the structural formulas of the garnets were calculated using 24 oxygens to determine the relative proportions of the end-members using the mineral spreadsheet software of Preston and Still (2001. Results Based on the analyses, almandine (Fe - Al garnet and spessartine (Mn - Al garnet are the principal types of the (Kamari metamorphic and (Abaro pegmatitic garnets, that belong to the well-known pyralspite garnet group. Chemical zoning patterns of the garnets in the metamorphic rocks (schists differ from those in the igneous rocks (pegmatite, showing different compositions from core to rim. Petrographic evidence such as: co

  7. Age of the emerald mineralization from the Itabira-Nova Era District, Minas Gerais, Brazil, based on LA-ICP-MS geochronology of cogenetic titanite

    Directory of Open Access Journals (Sweden)

    Hanna Jordt-Evangelista

    Full Text Available ABSTRACT: In the Itabira-Nova Era Emerald District, southeast Brazil, gemological emerald is extracted from underground mines found in schist-type deposits at the contact zone of the Archean Metavolcanosedimentary Sequence of the Guanhães Complex and Paleoproterozoic anorogenic granites of the Borrachudos Suite. Schist-type deposits are commonly generated by reactions enhanced by deformation and heat during regional metamorphism. The age of the mineralization in the region has been a matter of debate for decades: Ages ranging from the Archean to the Neoproterozoic are mentioned in the literature. In the mineralized zone from the Piteiras mine fluorine-aluminum-bearing titanite is found in metamafic rocks. The fluorine content was probably derived from the Borrachudos granites and pegmatites like the beryllium for emerald, thus both minerals could have been generated during the same event. U-Pb titanite geochronology via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS was performed on a thin section of a phlogopite-plagioclase-hornblende schist from the Piteiras mine. The determined age of 576 ± 7 Ma is also the probable age for emerald generation during the Brasiliano cycle, which was the only tectonometamorphic event postdating the intrusion of the granites. This event provided heat and fluids necessary for reactions between the Be- and the Cr-bearing rocks, thus enabling the formation of emeralds.

  8. Metamorphism in the Potomac composite terrane, Virginia-Maryland

    Energy Technology Data Exchange (ETDEWEB)

    Drake, A.A. Jr.

    1985-01-01

    Metamorphic rocks in the Potomac Valley occur in three allochthon-precursory melange pairs unconformably overlain by the Popes Head Formation which is at greenschist facies of metamorphism. The highest motif, the Piney Branch Complex and Yorkshire Formation are also in the greenschist facies. The middle motif, consists of the Peters Creek Schist and the Sykesville Formation. Quartzose schists and metagraywacke of the Peters Creek contain serpentinite debris and have had a complex metamorphic history: Barrovian prograde to amphibolite facies (with sillimanite), a localized retrograde event producing chlorite phyllonite, and a later greenschist prograde event. The Sykeville is at biotite +/- garnet grade and contains deformed olistoliths of Peters Creek, including phyllonite, at various grades. The lower motif consists of the Annandale Group (pelitic schists and metasandstone) and Indian Run Formation. The Annandale has experienced two greenschist metamorphisms. The Indian Run is at biotite +/- garnet grade and contains previously metamorphosed and deformed olistoliths of Annandale. The allochthons have had different histories, but after stacking they were metamorphosed with their melanges and the Popes Head to biotite grade. The Popes Head has experienced three phases of folding, the earliest synkinematic with Occoquan emplacement. These fold phases are superposed on earlier structures in the older rocks and are probably of Late Cambrian age (Penobscotian). Earlier deformation is probably of Late Proterozoic age (Cadomian). Neither of these deformations is recognized in North American rocks.

  9. U-Pb detrital zircon geochronology from the basement of the Central Qilian Terrane: implications for tectonic evolution of northeastern Tibetan Plateau

    Science.gov (United States)

    Liu, Changfeng; Wu, Chen; Zhou, Zhiguang; Yan, Zhu; Jiang, Tian; Song, Zhijie; Liu, Wencan; Yang, Xin; Zhang, Hongyuan

    2017-08-01

    The Tuolai Group dominates the Central Qilian Terrane, and there are different opinions on the age and tectonic attribute of the Tuolai Group. Based on large-scale geologic mapping and zircon dating, the Tuolai Group is divided into four parts: metamorphic supracrustal rocks, Neoproterozoic acid intrusive rocks, early-middle Ordovician acid intrusive rocks and middle Ordovician basic intrusive rocks. The metamorphic supracrustal rocks are the redefined Tuolai complex-group and include gneiss and schist assemblage by faulting contact. Zircon U-Pb LA-MC-ICP-MS dating was conducted on these samples of gneiss and migmatite from the gneiss assemblage, quartzite, two-mica schist and slate from the schist assemblage. The five detrital samples possess similar age spectra; have detrital zircon U-Pb main peak ages of 1.7 Ga with youngest U-Pb ages of 1150 Ma. They are intruded by Neoproterozoic acid intrusive rocks. Therefore, the Tuolai Group belonging to late Mesoproterozoic and early Neoproterozoic. With this caveat in mind, we believe that U-Pb detrital zircon dating, together with the geologic constraints obtained from this study and early work in the neighboring regions. We suggest that the formation age of the entire crystalline basement rocks of metasedimentary sequence from the Central Qilian Terrane should be constrained between the Late Mesoproterozoic and the Late Neoproterozoic, but not the previous Paleoproterozoic. The basement of the Central Qilian Terrane contains the typical Grenville ages, which indicates the Centre Qilian Terrane have been experienced the Grenville orogeny event.

  10. Mapeamento geológico do Pegmatito Alto do Tibiri: aspectos estruturais e mineralógicos

    Directory of Open Access Journals (Sweden)

    Paulo Jedean da Silva Araújo

    2017-05-01

    Full Text Available The Alto Tibiri is a pegmatite body located in the southern region of the Rio Grande do Norte, in Parelhas city, geologically inserted in the Borborema Pegmatite Province and occur intruding the mica schists of the Seridó Formation. Currently, both mica and feldspar are commercially exploited in this pegmatite body. In the field missions, 39 outcrops were described, in each one the main texture and mineralogical aspects of the outcropping rock were described. The geological mapping has allowed us to distinguish two types of schists, based on content and size of the mineral phases. There is a garnet rich schists and other with a relevant cordierite content. The studied region shows narrow pegmatite dykes, composed of quartz, feldspar, muscovite and/or biotite and black tourmaline, these dikes were classified as homogeneous. It’s possible to observe in Alto Tibiri a well- defined mineral zoning, as follows: i border area, marked by the abundance of muscovite; ii Zone II, composed of quartz, feldspar and mica, in which the main mineral resources occur (tantalite, spodumene, apatite, etc. and iii quartz pockets. The observed mineral zoning is similar to that described as mixed traditional pegmatite bodies.

  11. Low-angle normal faults in the south-central Brooks Range fold and thrust belt, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalk, R.R.; Oldow, J.S.

    1988-05-01

    A north-south structural transect through the south-central Brooks Range, Alaska, exposes three lithologically distinct, fault-bounded packages of rock, all regionally metamorphosed during the Late Jurassic to Early Cretaceous contractional deformation that formed much of the Brooks Range fold and thrust belt. These are, from south to north and structurally highest to lowest, (1) the prehnite-pumpellyite facies ophiolitic rocks of the Angayucham terrane, (2) the low-grade metasedimentary rocks of the Rosie Creek allochthon, and (3) pumpellyite-actinolite to glaucophane-epidote facies metamorphic rocks of the schist belt. The presence of rocks metamorphosed and deformed at shallow levels of the fold and thrust belt (the Angayucham terrane and Rosie Creek allochthon) lying structurally above rocks representing the deepest exposed levels of the fold and thrust belt (the schist belt) indicates that the imbricate stack is disrupted by south-dipping, low-angle normal faults along the southern margin of the Brooks Range. The authors propose that normal faults developed in response to the uplift of the schist belt and the overlying metasedimentary and ophiolitic allochthons by north-directed thrusting in the late Early Cretaceous. Thrusting resulting in the oversteepening of the imbricate stack, causing compensatory normal faulting along the southern flank of the ramp structure. Normal faults may have provided at least local structural control of the locus of Albian and younger sedimentation in the Koyukuk basin. 34 references.

  12. Seismically Derived Gondwana and Proterozoic Sediments East of Cuddapah Basin, South Indian Shield and Its Possible Geotectonic Implications

    Science.gov (United States)

    Chandrakala, K.; Pandey, O. P.; Sai, V. V. Sesha; Vasanthi, A.; Kumar, K. Satish

    2017-07-01

    The study area situated east of the intracratonic Proterozoic Cuddapah basin, that covers Nellore Schist belt, Ongole domain of the Eastern Ghats Belt and adjacent East Coast Terrain, forms a geodynamically important segment of the Dharwar craton. This region came into focus due to proposition that during Paleoproterozoic to Mesoproterozoic era, it underwent persistent oceanic subduction, continent-continent collision and multi-stage accretional growth. In view of this, we have reprocessed in detail the deep seismic sounding data over this region and integrated the obtained results with other geophysical studies to decipher the deep subsurface crustal structure underneath. The derived shallow seismic section across this region showed the presence of a thin layer ( 250 m) of Gondwana sediments with a distinct velocity of 4.20 km/s and a lateral dimension of about 40 km around Vinjamuru region of the Nellore Schist Belt. Another important finding has been the depiction of 5.3 and 5.5 km/s velocity sediments (comparable to upper and lower Cuddapah sediments) between Nellore Schist Belt and the east coast, indicating the possible presence of an additional Proterozoic sedimentary terrain (named here as East Coast Sedimentary Basin), overlying the concealed Archean crystalline basement. The presence of this sedimentary terrain, which is separated from the Cuddapah basin by an exhumed horst-like feature, situated below Nellore Schist Belt, would indicate Proterozoic sedimentation in a much larger area during Columbia and Rodinia supercontinental assembly periods than hitherto known. Importantly, no seismic trace of the Eastern Ghats Belt has been found between Nellore Schist Belt and the east coast. It appears that during the Gondwana period, entire eastern segment of the east Dharwar craton has been persistently rifting, uplifting and eroding together with other Gondwana grabens in India, thereby leaving behind only a thin veneer of Gondwana sediments at many places. In

  13. Reconnaissance geology of the Sabkhat Muraysis quadrangle, Kingdom of Saudi Arabia

    Science.gov (United States)

    Overstreet, William C.; Whitlow, Jesse William; Ankayr, Abdullah O.

    1972-01-01

    The Sabkhat Muraysis quadrangle .covers an area of 2843 sq km in the central part of the Kingdom of Saudi Arabia. In the northwestern quarter of the area Precambrian rocks are exposed. They are overlain toward the .south and east by sedimentary formations of Permian and younger age. Four main units of Precambrian .rocks were identified in this area. From oldest to youngest they are: hornblende-biotite granite gneiss; amphibolite and rhyolite of the Halaban Group; graywacke and chlorite-sericite schist of the Bi'r Khountina Group; and biotite-hornblende granite, The hornblende-biotite granite gneiss unit and the biotite-hornblende granite .unit are both poorly exposed and largely covered by veneers of sand, Owing to these factors the boundaries between the granitic, rocks are obscure, Much of what is shown as hornblende-biotite granite gneiss may actually be biotite-hornblende granite. The Halaban Group is represented by an older amphibolite unit called the Umm Mushraha Formation and by a younger rhyolite unit., called the Wadi al Jifr Formation. Layered and msslve components in the Umm Mushraha Formation represent metamorphosed .andesite and graywacke, ,and metamorphosed diorite., gabbro, and pyroxenite. The Wadi al Jifr Formation consists of virtually unmetamorphosed to strongly sheared and metamorphosed rhyolite, rhyolite porphyry, and rhyolite tuff which at many places has been metamorphosed to quartz-sericite schist and biotite-muscovite schist. These schists retain porphyroclasts of blue quartz which also form conspicuous phenocrysts in the unsheared rhyolite. Locally, the sheared rhyolite ha s been hydrothermally altered resulting in the formation of quartz-chlorite-ankerite veins and a sparse impregnation of pyrite. The Bi'r Khountina Group consists of a unit of graywacke and argillite with interbedded andesite that is metamorphosed to chlorite-sericite schist near the contacts of intrusive biottte-hornblende granite. This .unit is-called the Abu Sawarir

  14. Structural and rheological evolution of the Laramide subduction channel in southern California

    Science.gov (United States)

    Xia, Haoran; Platt, John P.

    2017-03-01

    The Pelona Schist in the San Gabriel Mountains, southern California, formed in the Laramide subduction channel, exhibits multiple phases of deformation/metamorphism and provides valuable insights into the rheological properties of the subduction channel. Petrological and microstructural analysis indicates that the Pelona Schist has undergone three major deformational/metamorphic events. Subduction of volcanic and sedimentary protoliths during D1 was recorded by aligned mineral inclusions in albite and epidote porphyroblasts. Metamorphic temperature and pressure at the end of subduction yielded by Raman spectroscopy of carbonaceous material and phengite barometry were 519 ± 20 °C and 10.5 ± 0.4 kbar, respectively. During D1 the dominant deformation mechanism was quartz pressure solution, and the estimated shear stress at the end of D1 was less than 10 MPa. D2, the first stage exhumation of the Pelona Schist along the upper section of the subduction channel during return flow, was recorded by retrogressive metamorphism, isoclinal folding, and a pervasive schistosity that wraps around earlier porphyroblasts. Metagreywacke was deformed mainly by quartz pressure solution and metachert was deformed dominantly by dislocation creep during D2. The shear stress in metagreywacke was less than 10 MPa and that in metachert was between 8.3 + 2.7/- 1.5 and 12.9 + .9/- 2.3 MPa, resulting in a strain rate of 1.4 × 10-13 to 5.5 × 10-13 s-1. A topography driven model is proposed as the main driving force of D2 exhumation. D3 records normal-sense movement on the Vincent Fault, which separates the schist from overlying arc and continental basement. This resulted in the second stage of exhumation, creating a major synform and associated mylonitic fabric in the upper section of the Pelona Schist. Conditions at the beginning of D3 were 390 ± 13 °C and 5.8 ± 0.8 kbar given by the TitaniQ thermometer and phengite geobarometer. The deformation was dominated by quartz dislocation

  15. U-Pb dating of minerals in alteration halos of Superior Province massive sulfide deposits: syngenesis versus metamorphism

    Science.gov (United States)

    Davis, D. W.; Schandl, E. S.; Wasteneys, H. A.

    1994-02-01

    U-Pb geochronology of igneous zircon from rhyolitic host rocks to the Archean Kidd Creek, Geco and Winston Lake massive sulfide deposits, in the Superior Province of Ontario, shows that volcanism, which accompanied mineralization, occupied a narrow time span (2717±2 Ma, 2720±2 Ma and 2723±2 Ma, respectively). Precise ages of hydrothermal monazite, allanite and rutile from alteration zones surrounding the above deposits indicate that these minerals crystallized 40 70 million years after volcanism. Monazite from Kidd Creek mine is 2659±3 Ma old, in agreement with spatially associated 2664±25 Ma old rutile. Monazite from a biotite schist at Geoco mine gives a similar age of 2661±1 Ma. However, monazite from a sericite schist, which hosts the ore at Geco mine, is 2675±2 Ma old. Abraded large monazite grains from three units in the Winston Lake deposit are coeval with biotite crystallization and record an age of 2677±2 Ma, approximately the same as monazite in the sericite schist at Geco. Data points from allanite fractions from both the Winston Lake and Geco deposits fall on a Pb-Pb isochron that gives an age of 2672±5 Ma. Rutile from Winston Lake gives a younger age of 2651±6/-2 Ma and may date retrograde alteration of biotite to chlorite. The ca. 2676 Ma age of monazite from Winston Lake and in the sericite schist at Geco mine probably dates a regional metamorphic event that affected most of the southern Superior Province. The ca. 2660 Ma old monazite in the biotite schist at Geco mine and in the chlorite-sericite alteration at Kidd Creek may date later K-metasomatism caused by metamorphically derived fluids that were focussed along old fault structures. Such fluids were also responsible for local sulfide remobilization. Monazite and rutile are spatially associated with chlorite and sericite alterations at Kidd Creek. Their young ages indicate that these originally syngenetic mineral assemblages may have been significantly affected by regional metamorphism

  16. Preliminary results of spectral induced polarization measurements, Wadi Bidah District, Kingdom of Saudi Arabia

    Science.gov (United States)

    Smith, Bruce D.; Tippens, C.L.; Flanigan, V.J.; Sadek, Hamdy

    1983-01-01

    Laboratory spectral induced polarization (SIP) measurements on 29 carbonaceous schist samples from the Wadi Bidah district show that most are associated with very long polarization decays or, equivalently, large time constants. In contrast, measurements on two massive sulfide samples indicate shorter polarization decays or smaller time constants. This difference in time constants for the polarization process results in two differences in the phase spectra in the frequency range of from 0.06 to 1Hz. First, phase values of carbonaceous rocks generally decrease as a function of increasing frequency. Second, phase values of massive sulfide-bearing rocks increase as a function of increasing frequency. These results from laboratory measurements agree well with those from other reported SIP measurements on graphites and massive sulfides from the Canadian Shield. Four SIP lines, measured by using a 50-m dipole-dipole array, were surveyed at the Rabathan 4 prospect to test how well the results of laboratory sample measurements can be applied to larger scale field measurements. Along one line, located entirely over carbonaceous schists, the phase values decreased as a function of increasing frequency. Along a second line, located over both massive sulfides and carbonaceous schists as defined by drilling, the phase values measured over carbonaceous schists decreased as a function of increasing frequency, whereas those measured over massive sulfides increased. In addition, parts of two lines were surveyed down the axes of the massive sulfide and carbonaceous units. The phase values along these lines showed similar differences between the carbonaceous schists and massive sulfides. To date, the SIP survey and the SIP laboratory measurements have produced the only geophysical data that indicate an electrical difference between the massive sulfide-bearing rocks and the surrounding carbonaceous rocks in the Wadi Bidah district. However, additional sample and field measurements in

  17. 13C-isotopic fingerprint of Pinus pinaster Ait. and Pinus sylvestris L. wood related to the quality of standing tree mass in forests from NW Spain.

    Science.gov (United States)

    Fernandez, Irene; González-Prieto, Serafin J; Cabaneiro, Ana

    2005-01-01

    Pine forest plantations of Pinus pinaster Ait. and P. sylvestris L. located in Galicia, NW Spain, were selected to study the 13C/12C-isotopic fingerprint in wood core samples in order to find possible relationships between the delta(13)C at natural abundance levels and the quality of the standing tree mass. For each pine species, 24 forests growing on acidic soils were studied: half developed over granite and half over schists. Two dominant trees from each plot, corresponding to all possible combinations of forest stands with high or low site index and with adults or young trees, were drilled at the basal part of trunks using a Pressler drill to obtain tree ring samples. The C-isotopic compositions of the litter and the soil organic matter from different soil depths were also determined and statistically significant correlations between these values and the 13C content of the wood were observed. Despite internal variations due to the influence of site index, tree age and parent material, the isotopic fingerprint of P. pinaster wood (mean value delta13C=-26.2+/-0.8 per thousand) significantly differed (P<0.001) from that of P. sylvestris (mean value delta13C=-24.6+/-0.7 per thousand). Relationships between the quality of the stand and the C-isotopic composition of the wood were observed, high quality stands having trees more 13C-depleted than low quality ones. A high correlation between wood delta13C and site index values for P. pinaster stands (r=-0.667, P<0.001) was found, this correlation being even clearer when only P. pinaster growing over schists (r=-0.833, P<0.001) are considered. Again, the correlation between the site index and the wood delta13C of young P. pinaster trees is higher when plots over granite or schists are separately considered. A similar fact occurs for adult P. sylvestris trees from schists stands, high quality specimens being 13C-depleted compared with low quality ones. On the other hand, 13C natural abundance of wood from P. sylvestris

  18. MULTIDISCIPLINARY APPROACH TO STUDY MIGMATITES: ORIGIN AND TECTONIC HISTORY OF THE NASON RIDGE MIGMATITIC GNEISS, WENATCHEE BLOCK, CASCADES CRYSTALLINE CORE, WA, USA

    Directory of Open Access Journals (Sweden)

    Stowell Harold H.

    2008-12-01

    Full Text Available The Nason Ridge Migmatitic Gneiss of the Cascades Core is a migmatitic unit comprising concordant pelitic schist and gneiss, amphibolite, and tonalite gneiss, and cross cutting tonalite, quartz-rich granitoid, and pegmatite. There are several generations of 'igneous' lithologies (leucosomes = tonalite, quartz-rich granitoid, and pegmatite some of which are concordant; others clearly crosscut the strongly deformed host rocks. The host rocks are interpreted to be Chiwaukum Schist with metasedimentary (pelitic schist and some gneiss and metavolcanic(amphibolites origins. Metamorphic fabric in the Nason Ridge Migmatitic Gneiss is characterized by preferred orientation of platy minerals (continuous schistosity, compositional layering, mineral lineations (elongate grains and grain aggregates, and non-coaxial deformational features (asymmetric augen, grain offsets,rotated porphyroblasts, etc.. Compositional layering is characterized by quartz-plagioclase lenses and patches (mm to cm scale and by large variations in biotite content. This composite fabric is faulted and folded by mesoscopic structures. The most strongly foliated leucosomes (gneissic tonalites are generally concordant with the regional trend of foliation, while weakly foliated leucosomes (tonalites and pegmatite veins crosscut host rock and tonalite gneisses. Thin melanosome layers (biotiteand amphibole schist are developed locally around quartz - plagioclase lenses and patches. Metamorphism in the Nason Ridge Migmatitic Gneiss and the nearby Chiwaukum Schist likely peaked after intrusion of the Mt. Stuart Batholith ca. 91-94 Ma. Peak temperatures and pressures for the Nason Ridge Migmatitic Gneiss in the Wenatchee Ridge and Pacific Crest areas were 650 - 720 °C and 6 - 9 kbar with a pressure increase of £ 2.0 kbar during metamorphism. Thermodynamic modeling indicates that hydrous partial melting would begin at ca. 660 °C and is relatively pressure independent. Field

  19. Reaction-induced grain boundary cracking and anisotropic fluid flow during prograde devolatilization reactions within subduction zones

    Science.gov (United States)

    Okamoto, Atsushi; Shimizu, Hiroyuki; Fukuda, Jun-ichi; Muto, Jun; Okudaira, Takamoto

    2017-09-01

    Devolatilization reactions during prograde metamorphism are a key control on the fluid distribution within subduction zones. Garnets in Mn-rich quartz schist within the Sanbagawa metamorphic belt of Japan are characterized by skeletal structures containing abundant quartz inclusions. Each quartz inclusion was angular-shaped, and showed random crystallographic orientations, suggesting that these quartz inclusions were trapped via grain boundary cracking during garnet growth. Such skeletal garnet within the quartz schist formed related to decarbonation reactions with a positive total volume change (Δ V t > 0), whereas the euhedral garnet within the pelitic schists formed as a result of dehydration reaction with negative Δ V t values. Coupled hydrological-chemical-mechanical processes during metamorphic devolatilization reactions were investigated by a distinct element method (DEM) numerical simulation on a foliated rock that contained reactive minerals and non-reactive matrix minerals. Negative Δ V t reactions cause a decrease in fluid pressure and do not produce fractures within the matrix. In contrast, a fluid pressure increase by positive Δ V t reactions results in hydrofracturing of the matrix. This fracturing preferentially occurs along grain boundaries and causes episodic fluid pulses associated with the development of the fracture network. The precipitation of garnet within grain boundary fractures could explain the formation of the skeletal garnet. Our DEM model also suggests a strong influence of reaction-induced fracturing on anisotropic fluid flow, meaning that dominant fluid flow directions could easily change in response to changes in stress configuration and the magnitude of differential stress during prograde metamorphism within a subduction zone.

  20. Variscan tectonics in Dodecanese, Kalymnos island, Greece

    Science.gov (United States)

    Chatziioannou, Eleftheria; Grasemann, Bernhard; Schneider, David; Hubmann, Bernhard; Soukis, Konstantinos

    2015-04-01

    Kalymnos island is located in the Dodecanese, southeastern Aegean Sea, and geologically appears to be part of the external Hellenides. Pre-Alpidic basement rocks on the Dodecanese islands have been suggested to record compelling similarities with the basement rocks in Eastern Crete with respect to their lithologies and pre-Alpidic metamorphic evolution. The lithotectonic units experienced greenschist to amphibolite facies conditions during the Variscan orogeny. Whereas the rocks in Eastern Crete reveal Alpine high-pressure overprint, the Variscan basement units in the Dodecanese record no or low-grade Alpine metamorphism. A field study of basement rocks below Mesozoic limestones and dolomites in the NW part of Kalymnos near Emporios uncovered a complex history of metamorphism, folding and faulting. Three different tectonic units can be discriminated from top to bottom: a) a quartz-mica schist, b) a white-grey, fossiliferous coarse grained marble and c) a fine-grained fossiliferous blue-grey marble. In the marbles macrofossils such as brachiopods, ammonoid cephalopods (Goniatids?) and crinoids suggest a Middle-Upper Devonian deposition age (Givetian- Frasnian). Structural mapping the area resolved a dominant W-E shortening event, resulting in an overall inverted metamorphic gradient. The lowermost blue-grey marble unit is folded into large-scale upright folds, which are truncated by top-to-east overthrusting of the white-grey marble unit. Whereas deformation mechanisms in the blue-grey marble unit are dominated by dissolution-precipitation creep, the white-grey marble suffered intense crystal plastic deformation with localized high-strain mylonitic shear zones. The uppermost quartz-mica schist unit is separated from the lower units by a cataclastic phyllonitic shear zone. 40Ar/39Ar geochronological dating on white micas from the quartz-mica schists yielded cooling ages between 240 and 334 Ma indicative of Variscan cooling. Our data suggest that this part of the

  1. Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State; Geologia e geocronologia da Ilha de Cardoso, sudeste do Estado de Sao Paulo

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Werner

    1998-07-01

    This aim of work is the geological and geochronological study of rocks cropping out on Cardoso Island, on the southeastern coast of Sao Paulo States, close to be boundary with Parana State. The Island with an area of about 151 km{sup 2} is a protected area administered by the Forest Institute of Environment Secretariat of the State of Sao Paulo. It is mountanious, with a peak at 814 m, and is covered by dense Mata Atlantica vegetation. The terrains which compose the island are mainly an igneous complex with light grey leucocratic, inequigranular, medium - to coarse-grained syenites. The predominant Tres Irmaos Syenite (STI), composed of pyroxene, hornblende, and perthitic to mesoperthitic microcline, has a magmatic flow structures, and is cut by the Cambriu alkali-feldspar Granites (GC), which is pinkish grey, leucocratic and medium-grained. Geochemical analysis of STI and GC demonstrate their meta luminous alkaline nature and late-orogenic to an orogenic character. The geochronological results suggest that the bodies were formed between 620 and 570 My according to the U-Pb method in zircons, with cooling between 597 and 531 My (K-Ar in amphiboles). Whole rock Sm-Nd analysis yield T{sub DM} ages in the Meso and Paleoproterozoic (1.200 - 2.200 My). belt of low grade meta sedimentary rocks occurs in the northern part of the island. Quartz schist, quartz-mica schist and mica-quartz schist, often containing andaluzite and cordierite, predominate. The geochemical and geochronological data suggest that the sources of the metasediments were andesites of continental arc whose protolities separated from the mantle during the Paleoproterozoic, between 1.800 and 2.200 My. These metasediments probably continue on the continent in the Taquari region and extend southwards in narrow strips between the granitoids of the Paranagua Domain. Although quaternary deposits are expressive, they were not studied in details since they were not the objectives of this study. (author)

  2. The Characteristics and triggering Factors of the October 2013 Obudu International Tourist Centre catastrophic Landslide South-East Nigeria

    Science.gov (United States)

    Fukuoka, Hiroshi; Igwe, Ogbonnaya

    2015-04-01

    The October 2013 catastrophic landslides at the Obudu international tourist zone south-east Nigeria destroyed resources worth several millions of dollars and trapped international tourist who were later rescued by a helicopter. Intense rainfall caused several slope failures on the steep slopes of the hills. These landslides occurred after several days of heavy rain (> 600 mm) and were the first reported slope failures in this region. The failures were on a predominantly metamorphic terrain and only on slopes adjacent to the main road. They occurred as slides, not debris flow, but produced a wide range of casualties. The failures were of residual materials (about 1 m thick) obtained from weathering of schist. One of the landslides involved the movement of about 70,000 m3 debris for 8.6 m with depth of slip surface of 6 m. Another, which produced the most fatality initiated on a slope greater than 40o and displaced about 77, 000 m3. It had a runout length of 60 m, width of 98 m, depth to slip surface of 8 m and depositional area of about 2,500 m2. Had the opposite slope bounding the other side of the road not hindered the movement of debris, the runout distance could have been larger. The research found that all the landslides occurred on slope-portions composed of schist rather than gneiss or granite. Slip surfaces developed within the regolith and the shear zone was characterized by the presence of silty materials supported by clayey matrix. Field observations indicated that the failures generally developed as localized translational slides within the semi-consolidated, cohesive soil units (with high plasticity and low strength) within the upper to middle weathered zone of the schist. The increase in pore pressure arising from elevated water table during rainfall created instability by weakening the shear strength along the failure plane. However, differences in permeability favored the formation of perched water table which eventually triggered sliding.

  3. Mayer Kangri metamorphic complexes in Central Qiangtang (Tibet, western China): implications for the Triassic-early Jurassic tectonics associated with the Paleo-Tethys Ocean

    Science.gov (United States)

    Wang, Yixuan; Liang, Xiao; Wang, Genhou; Yuan, Guoli; Bons, Paul D.

    2017-09-01

    The Mesozoic orogeny in Central Qiangtang Metamorphic Belt, northern Tibet, provides important insights into the geological evolution of the Paleo-Tethys Ocean. However, the Triassic-early Jurassic tectonics, particularly those associated with the continental collisionstage, remains poorly constrained. Here we present results from geological mapping, structural analysis, P-T data, and Ar-Ar geochronology of the Mayer Kangri metamorphic complex. Our data reveal an E-W-trending, 2 km wide dome-like structure associated with four successive tectonic events during the Middle Triassic and Early Jurassic. Field observations indicate that amphibolite and phengite schist complexes in this complex are separated from the overlying lower greenschist mélange by normal faulting with an evident dextral shearing component. Open antiform-like S2 foliation of the footwall phengite schist truncates the approximately north-dipping structures of the overlying mélange. Microtextures and mineral chemistry of amphibole reveal three stages of growth: Geothermobarometric estimates yield temperatures and pressures of 524 °C and 0.88 GPa for pargasite cores, 386 °C and 0.34 GPa for actinolite mantles, and 404 °C and 0.76 GPa for winchite rims. Peak blueschist metamorphism in the phengite schist occurred at 0.7-1.1 GPa and 400 °C. Our Ar-Ar dating of amphibole reveals rim-ward decreasing in age bands, including 242.4-241.2 Ma, ≥202.6-196.8, and 192.9-189.8 Ma. The results provide evidence for four distinct phases of Mesozoic tectonic evolution in Central Qiangtang: (1) northward oceanic subduction beneath North Qiangtang ( 244-220 Ma); (2) syn-collisional slab-break off (223-202 Ma); (3) early collisional extension driven by buoyant extrusion flow from depth ( 202.6-197 Ma); and (4) post-collision contraction and reburial (195.6-188.7 Ma).

  4. P-T evolution of metasedimentary rocks of the Santa Filomena Complex, Riacho do Pontal Orogen, Borborema Province (NE Brazil): Geothermobarometry and metamorphic modelling

    Science.gov (United States)

    Santos, Felipe H.; Amaral, Wagner S.; Luvizotto, George L.; Martins de Sousa, Daniel F.

    2018-03-01

    We present in this paper petrologic data and discuss the pressure-temperature (P-T) metamorphic history of the neoproterozoic metasedimentary rocks of the Santa Filomena Complex, Riacho do Pontal Orogen, which is inserted in the southern portion of the Borborema Province (Northeast Brazil). Therefore, the data provide constraints on metamorphic evolution during Neoproterozoic Brasiliano Orogeny in Northeast Brazil. The rocks studied are aluminous schists and paragneisses. Silver-gray and red pelitic schists are intensely deformed, biotite-muscovite rich, contain centimeter-sized garnet, staurolite and kyanite porphyroblasts, and subordinately plagioclase and quartz. Paragneisses are from light gray to dark gray colored, medium to coarse-grained and display a well-spaced foliated matrix of biotite, and kyanite and garnet porphyroblasts. Locally, the schists and paragneisses are migmatized. Pressure-temperature modelling based on thermobarometric calculations indicate that metamorphism reached 643 °C with pressures estimated in 12 kbar. Pre-peak and post-peak metamorphic conditions are constrained by mineralogical and textural relationships: garnet inclusion-rich and inclusion-free (possible of higher T) are documented and the inclusion-rich core probably indicates a Sn-1 foliation that was transposed by Sn. The pre-peak stage most probably occurred close to 500 °C and 8 kbar, in upper greenschist to lower amphibolite facies metamorphism along kyanite stability field. We also propose that post-peak stage was associated with isothermal decompression along a possible path of tectonic exhumation in conditions of 600 °C and 7 kbar. To further evaluate the equilibrium condition, pressure-temperature pseudosections were calculated for the metasedimentary rocks. Thus, the estimated metamorphic peak took place in the upper amphibolite facies. A suggested clockwise pressure-temperature path is compatible with the regional tectonic setting of continent-continent collision

  5. Fluid Inclusion Characteristics of Domaniç (Kütahya) Porphyry Cu-Mo Mineralization

    Science.gov (United States)

    Sendir, H.; Sarıiz, K.; Bozkaya, G.

    2012-04-01

    The study area is located at 30 km northwest of Domaniç (Kütahya) and covers on approximately 250 square kilometers. The Devonian (Paleozoic) schists which are composed of gneiss, mica schist and chlorite schist is the oldest unit of the study area. This units are overlain unconformably by the Permian Allıkaya Marbles. Eocene granodioritic intrusives cut other rock series and located as a batholite. Magmatic units present porphyric and holocrystalline textures. Granodioritic intrusions are represented by tonalite, tonalite porphyr, granodiorite, granodiorite porphyr, granite, diorite, diorite porphyries. Potassic, phyllitic and prophyllitic hydrothermal alteration zones are determined in host rocks and wallrocks. Mineralizations are observed as disseminated, and stockwork types within the granodioritic rocks. Ore minerals are pyrotine, pyrite, chalcopyrite, molybdenite, rutile, bornite, sphalerite, marcasite and limonite. Geochemically, it is of sub-alkaline affinity, belongs to the high-K, calc-alkaline series and displays features of typical I-type affinity. They show enrichment in large-ion lithophile elements (LIL) and depletion Nb and Ti indicating a subduction zone related magmatic signature for their origin. Fluid inclusion assemblages (FIAs) were measured from quartz using a Linkam THMS-600 heating/cooling stage. The inclusions contain two-phase aqueous fluids (L+V) at room temperature. All fluid inclusions belong to the H2O- NaCl-CaCl2 system. Fluid inclusion microthermometry in the ore deposits suggest two main hydrothermal fluids, with modal homogenization temperatures and salinities (wt. % equivalent NaCl): (a) between 380.2o 140.7oC and ~22.3 - 13.1 %, (b) 75.2o -128.7oC and between ~10.8 - 9.2 %, respectively.

  6. Tectonic and regional metamorphic implications of the discovery of Middle Ordovician conodonts in cover rocks east of the Green Mountain massif, Vermont

    Science.gov (United States)

    Ratcliffe, N.M.; Harris, A.G.; Walsh, G.J.

    1999-01-01

    Middle Ordovician (late Arenigian - early Caradocian) conodonts were recovered from a dolostone lens in carbonaceous schist 30 m below the base of the Pinney Hollow Formation in the Eastern Cover sequence near West Bridgewater, Vermont. These are the first reported fossils from the metamorphic cover sequence rocks east of the Green Mountain, Berkshire, and Housatonic massifs of western New England. The conodonts are recrystallized, coated with graphitic matter, thermally altered to a color alteration index (CAI) of at least 5, and tectonically deformed. The faunule is nearly monospecific, consisting of abundant Periodon aculeatus Hadding? and rare Protopanderodus. The preponderance of Periodon and the absence of warm, shallow-water species characteristic of the North American Midcontinent Conodont Province suggest a slope or basin depositional setting. The conodont-bearing carbonaceous schist is traceable 3 km southeast to the Plymouth area, where it had been designated the uppermost member of the Plymouth Formation, previously regarded as Early Cambrian in age. The age and structural position of the carbonaceous schist above dolostones of the Plymouth Formation but below the Pinney Hollow Formation (upper Proterozoic and Lower Cambrian?) suggest that this unit may be correlative or time transgressive with the Ira Formation, which underlies the Taconic allochthons in the Vermont Valley. Such a correlation supports the concept of placing the western limit of the root zone of the Taconic allochthons beneath the Pinney Hollow Formation. An approximate absolute age assignment for the conodont-bearing rock is between 470 and 454 Ma. This suggests that dynamothermal metamorphism during the Taconian orogeny on the east flank of the Green Mountains was younger than early Caradocian, which is in accord with the middle Caradocian age of the Ira Formation west of the Green Mountain massif.

  7. Pulverization Texturein Fault Damage Zones: A result of Implosion Damage or Dynamic Compressive Stresses?

    Science.gov (United States)

    Rockwell, T. K.; Girty, G.; Whearty, J.; Mitchell, T. M.

    2015-12-01

    Micro-brecciation, or pulverization, is recognized as a fundamental component of the architecture and damage products of many large faults, although the precise mechanisms to produce this damage are debated, with both compressive and tensile mechanisms proposed. We characterized several sites along the San Jacinto fault, southern California, where the total depth of exhumation for the life history of the fault can be determined, to study the confining stresses required for pulverization. In basement rock near Anza, where exhumation is less than 100 m, granitic dikes injected into schist of the Burnt Valley Complex are pulverized out to several meters from the fault core, whereas the schist is brecciated at the macro-scale and contains narrow centimeter-thick seams of black cataclasite. Similar relationships are observed in Horse Canyon, which is exhumed about 400 m below a regional Tertiary erosion surface, where granitic dikes emplaced into schist are pulverized out to distances of several tens of meters from the fault core. These observations imply that very low confining stress is required for micro-brecciation in granitic rock. Unconsolidated sandstones (alluvial fan deposits) along the SJF in Rock House Canyon are undeformed where the deposits are exhumed by about 70 m, but show incipient pulverization (high-density, sub-grain cracking) at 120 m depth of exhumation. Cracks oriented perpendicular to the fault formed in individual quartz and feldspar grains out to a few meters from the fault core. These observations suggest that the confining stress required for onset of pulverization in unconsolidated deposits is on the order of 2-2.5 MPa. As the tensile strength of quartz is an order of magnitude higher than these confining stresses, the most likely mechanism that is producing this damage is dynamic compressive stresses during passage of the rupture front.

  8. K-Ar ages of the rocks of two kinds existed in the Kamuikotan metamorphic rocks located in the Horokanai district, Hokkaido

    Energy Technology Data Exchange (ETDEWEB)

    Imaizumi, M. (Chiba Univ. (Japan). Faculty of Science); Ueda, Y.

    1981-03-01

    In the Fransiscan metamorphic rocks known as the typical high-pressure type metamorphic belts, existence of the blocks of high grade metamorphic rocks of older age in the widely distributed low grade ones of younger age is commonly noticed. This feature has been explained as a phenomenon that the blocks had been tectonically mixed with the surroundings - so-called tectonic blocks - based on the absolute age determination of the component minerals. The Kamuikotan tectonic belt is a melange zone in which occur various kinds of metamorphic rocks of high-pressure and low-pressure types. The high-pressure Kamuikotan metamorphic rocks can be classified into two kinds based upon the modes of occurrence and mineral paragenesis. One is the low grade metamorphic rocks of greenschist and glaucophane schist and the other, the high grade metamorphic rocks of epidote glaucophane schist and epidote amphibolite. The high grade metamorphic rocks always occur as isolated blocks in the low grade metamorphics and associated serpentinite. The report discusses the age of muscovites separated from the two types of high-pressure Kamuikotan metamorphic rocks in the Horokanai district, central Hokkaido. The muscovites separated from the low grade metamorphics of the district give the age of 72 - 116 m.y., while those separated from the high grade metamorphics give the age of 132 - 145 m.y. These ages seem to agree with the idea that the blocks of high grade metamorphics (epidote glaucophane schist and epidote amphibolite) would be the ''tectonic blocks'' - namely the fragments tectonically mixed into the low grade metamorphics of younger age.

  9. Management of city aquifers from anthropogenic activities: Example of the Windhoek aquifer, Namibia

    Science.gov (United States)

    Mapani, Benjamin S.; Schreiber, Ute

    As the city of Windhoek is growing rapidly, it has become increasingly obvious that dangers to the underlying groundwater aquifer have become imminent, and need addressing immediately. Water infiltration and the transportation of contaminants from anthropogenic activities through soils into the bedrock and hence the aquifer involve soil maturity, chemical and microbial processes and the climate of a particular area. The thin immature soil horizon (circa 5-20 cm) over the Windhoek schist implies that most areas of the city are built directly on bedrock, making the aquifer vulnerable. Anthropogenic activities from the use of pesticides for weed control, oil spills, toxic chemical spills, dumping of undesired substances by residents and high fertilizer application rates for lawns can lead to the contamination of groundwater. The result of our study show that the soil composition in Windhoek lacks mature clay minerals and is enriched in micas, quartz and albite. Some areas in the northern and southern industrial areas show contamination in heavy metals Pb, Zn, Cu and Ni. To the west of the city, close to the textile factory, soils are contaminated with ammonium compounds. The hydrochemistry of these pesticides and fertilizers can cause severe pollution to the groundwater if the practice is not carefully monitored. In addition, the rapid expansion of uncontrolled settlements without proper sanitation and reticulation has made the problems much more difficult. The geology of the city of Windhoek consists of the Kuiseb Schist, locally known as the “Windhoek Schist” and amphibolites. The Kuiseb schist possesses pervasive cleavage that renders the underlying lithology to be permeable to percolating water and fluids from the surface into the aquifer. The fissility and fracture density of the schist imply that leakage of surface waters, phenols, septic tank spills and industrial contaminants may reach the aquifer in unusually high rainfall years. Organic fuels and oils

  10. Structural control and (remobilization of the extinct Haveri Au-Cu deposit, southern Finland

    Directory of Open Access Journals (Sweden)

    Nironen, M.

    1994-06-01

    Full Text Available The extinct Haveri Au-Cu deposit is located within mafic metalavas and mafic/ intermediate banded rocks of the Haveri Formation, in the western part of the Paleoproterozoic Tampere Schist Belt. The sulfide-bearing banded rocks display a large E-W trending fold structure in magnetic and electromagnetic maps. Field evidence suggest that the Au-Cu deposit is in a F1/F2 fold interferrence pattern in the western core of the large fold. The ore-forming elements concentrated into the F1 fold closure during D1 deformation. Sulfide-bearing fractures subparallel to S2 spaced cleavage indicate slight remobilization during D2.

  11. Natural radionuclides in ground water in western Spain

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, F.; Lozano, J.C.; Gomez, J.M.G. (Salamanca Univ. (Spain). Lab. de Radioactividad Ambiental)

    1992-01-01

    A survey of natural radioactivity in drinking water was carried out in a granitic area in western Spain covering the so-called greywacke-schist complex. This region is known to be rich in uranium ores, such that natural radionuclides should be expected in the groundwater. During 1988, 345 water samples were collected from the water supplies of 115 different villages. These samples were analysed for gross alpha U, Th and Ra. The average concentrations of radionuclides were found to be 5-30 times higher in groundwater from bedrock than in groundwater from soil. The results indicate that Ra makes the highest contribution to the effective dose equivalent. (author).

  12. Oils

    Energy Technology Data Exchange (ETDEWEB)

    Cobbett, G.T.B.

    1907-07-08

    Crude petroleum having a density of 850 to 900 is purified with sulfuric acid, decanted, mixed with benzine or petrol, and again treated with sulfuric acid and decanted. The remaining acid and coloring-matter are removed by washing with water, or treating with oxalic acid, zinc carbonate, lead carbonate, calcium carbonate, or oxide of zinc. The product is used as a fuel for internal-combustion engines. Specifications No. 28,104, A.D. 1906, and No. 12,606, A.D. 1907, are referred to. According to the Provisional Specification, the process is applicable to shale or schist oil.

  13. Catchment and in-stream influences on iron-deposit chemistry, algal-bacterial biomass and invertebrate richness in upland streams, Northern Ireland.

    Science.gov (United States)

    Macintosh, Katrina Ann; Griffiths, David

    2013-04-01

    The density and composition of upland stream bed iron-deposits is affected by physical, chemical and biological processes. The basic chemical processes producing ochre deposits are well known. Mobilisation of iron and manganese is influenced by bedrock weathering, the presence of acidic and/or reducing conditions and the concentration of dissolved organic carbon. Ferromanganese-depositing bacteria are significant biogenic agents and can cause/enhance the deposition of metals in streams as (hydr)oxides. Metal concentrations from stream waters in two geological blocks in Northern Ireland were compared to determine the contributions of catchment characteristics and in-stream conditions. One block is composed of metamorphosed schist and unconsolidated glacial drift, with peat or peaty podzol (mainly humic) soils, while the other block consists of tertiary basalt with brown earth and gley soils. Water samples were collected from 52 stream sites and analysed for iron, manganese and aluminium as well as a range of other chemical determinands known to affect metal solubility. Stone deposit material was analysed for metal concentrations, organic matter content and epilithic algae, chlorophyll a concentration. Invertebrates were collected by area-standardised kick samples and animals identified to family and numbers counted. Higher conductivities and concentrations of bicarbonate, alkalinity, calcium and magnesium occurred on basalt than on schist. Despite higher iron and manganese oxide concentrations in basalt-derived non-humic soils, stream water concentrations were much lower and stone deposit concentrations only one third of those occurring on schist overlain by humic soils. Peat-generated acidity and the limited acid neutralising capacity of base-poor metamorphosed schist has resulted in elevated concentrations of metals and ochre deposit in surface waters. Algal biomass was determined by catchment level factors whereas in-stream conditions affected bacterial biomass

  14. Dicty_cDB: SSA778 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available . 76 4e-14 2 AI067312 |AI067312.1 EST208990 Schistosoma mansoni, Phil LoVerde/Joe...ence. 54 7e-05 2 AI067329 |AI067329.1 EST209007 Schistosoma mansoni, Phil LoVerde/Joe Merrick Schistosoma ma...sequence. 54 8e-05 2 AI067953 |AI067953.1 EST209642 Schistosoma mansoni, Phil LoVerde/Joe Merrick Schistosom...067936 |AI067936.1 EST209624 Schistosoma mansoni, Phil LoVerde/Joe Merrick Schist

  15. Gold deposits in the western sector of the Central Spanish System; Depositos auriferos del sector occidental del sistema Central espanol

    Energy Technology Data Exchange (ETDEWEB)

    Barrios, S.; Florido, P.; Reguilon, R.

    2010-07-01

    The gold deposits in the western sector of the Central Spanish System can be grouped in: (1) gold quartz veins type (El Chivote, La Pedrera), (2) paleoplacers: gold nuggets in tertiary alluvial deposits (Las Cavenes, Sierro de Coria), (3) quaternary placers (Rio Erjas), (4) gold nuggets in a regolith developed on the Schist and Graywacke Complex (CEG) (Casillas de Coria). The morphological study of gold nuggets will provide physical, chemical, bacteriological and climatic characteristics. Mining works are located on these deposits from roman time to the present day. (Author)

  16. Precambrian crustal evolution and Cretaceous–Palaeogene faulting in West Greenland: The Nordre Strømfjord shear zone and the Arfersiorfik quartz diorite in Arfersiorfik, the Nagssugtoqidian orogen, West Greenland

    Directory of Open Access Journals (Sweden)

    Stensgaard, Bo Møller

    2006-12-01

    Full Text Available The Nordre Strømfjord shear zone in the fjord Arfersiorfik, central West Greenland, consists of alternating panels of supracrustal rocks and orthogneisses which together form a vertical zone up to 7 km wide with sinistral transcurrent, ductile deformation, which occurred under middle amphibolite facies conditions. The pelitic and metavolcanic schists and paragneisses are all highly deformed, while the orthogneisses appear more variably deformed, with increasing deformation evident towards the supracrustal units. The c. 1.92 Ga Arfersiorfik quartz diorite is traceable for a distance of at least 35 km from the Inland Ice towards the west-south-west. Towards its northern contact with an intensely deformed schist unit it shows a similar pattern of increasing strain, which is accompanied by chemical and mineralogical changes. The metasomatic changes associated with the shear zone deformation are superimposed on a wide range of original chemical compositions, which reflect magmatic olivine and/or pyroxene as well as hornblende fractionation trends. The chemistry of the Arfersiorfik quartz diorite suite as a whole is comparable to that of Phanerozoic plutonic and volcanic rocks of calc-alkaline affinity.

  17. Identifying the Transition Zone Between East and West Dharwar Craton by Seismic Imaging

    Science.gov (United States)

    Ashish; Parvez, Imtiyaz A.

    2018-01-01

    The data from 12 temporary broadband seismic stations operated across east-west corridor in Dharwar region of Indian Peninsula along with ten other seismic stations operated by CSIR National Geophysical Research Institute (NGRI) in the region have been analysed that provide high-resolution image of southern Dharwar crust. Crust along the corridor is imaged by receiver function H-k stacking, common conversion point stacking using data from 22 sites in combination with joint inversion modeling of receiver functions and Rayleigh wave group velocity dispersion curves. The velocity image reveals thinner crust (36-38 km) except one site (coinciding with Cuddapah basin on the surface) in East Dharwar Craton (EDC), while crust beneath the West Dharwar Craton (WDC) is thicker (46-50 km). This study also observed a transition zone between EDC and WDC starting west of Closepet granite to the east of Chitradurga Schist Belt (CSB), which shows diffused Moho with a thickness of 40-44 km. Chitradurga Schist Belt is identified as the contact between Mesoarchean (WDC) and Neoarchean (EDC) crustal blocks. The lowermost part of the crust (V_s > 4.0) is thin (2-6 km) beneath EDC, intermediate (6-8 km) beneath transition zone and thicker (14-30 km) beneath WDC across the profile.

  18. A reinterpretation of the metamorphic Yuli belt: Evidence for a middle-late Miocene accretionary prism in eastern Taiwan

    Science.gov (United States)

    Chen, Wen-Shan; Chung, Sun-Lin; Chou, Hsien-Yuan; Zugeerbai, Zul; Shao, Wen-Yu; Lee, Yuan-Hsi

    2017-02-01

    The Yuli metamorphic belt has been the topic of petrological and geochronological studies for over 40 years and has been interpreted as a Cretaceous mélange. Our study utilizes zircon U-Pb dating of schist and exotic blueschist blocks in the Yuli belt. These new ages indicate that these metamorphic rocks are actually middle Miocene in age and may represent the deeper structural levels of an accretionary prism. Several distinctive detrital zircon U-Pb age populations are recognized from 14 siliceous schists of mélange-hosted rocks that are similar in age population to the Cretaceous, Eocene-Oligocene, and Miocene strata of Taiwan. The wide range of ages is interpreted as a product mixing of various sedimentary strata prior to metamorphism. Three blueschists of a volcanic-arc protolith enclosed within the host rocks yield crystallization ages of 15.4 ± 0.4, 15.5 ± 0.3, and 16.0 ± 0.2 Ma based on zircon U-Pb dating. In consideration of the new data regarding the Cretaceous-Miocene host rocks and the middle Miocene exotic blueschist blocks, it strongly suggests that the Yuli belt formed at deeper levels of an accretionary wedge during subduction of South China Sea oceanic crust at the middle-late Miocene. Subsequently, the rapid uplift of the metamorphic belt was probably related to doubly vergent wedge extrusion due to the Pliocene arc-continent collision.

  19. The provenance and internal structure of the Cycladic Blueschist Unit revealed by detrital zircon geochronology, Western Cyclades, Greece

    Science.gov (United States)

    Seman, S.; Stockli, D. F.; Soukis, K.

    2017-07-01

    This study presents detrital zircon U-Pb analyses of 23 samples of the Cycladic Blueschist Unit (CBU) from Kea, Kythnos, and Serifos islands, as well as the Lavrion Peninsula of SE Attica. The maximum depositional ages (MDA) and age distributions of detrital zircon U-Pb dates are used to correlate metasediments between the islands considered herein and infer their provenance. Two distinct detrital zircon U-Pb age distributions are found in CBU metasediments: "Proterozoic," comprised of >40% Neoproterozoic zircons with Triassic-Early Jurassic maximum depositional ages and "Paleozoic," containing >30% Paleozoic zircons and yielding Late Jurassic-Cretaceous MDAs. Proterozoic affinity metasediments are rift margin deposits derived from the northern Gondwanan margin. Paleozoic metasediments are flysch sediments most probably sourced from the Internal Hellenides. This metamorphosed flysch forms a distinct marker horizon found in a similar structural position in Lavrion, Kythnos, and Serifos. Based on lithologic correlation, sediment provenance, and MDA estimates, the CBU of Kythnos is correlative to the Lavrion Schists of Attica. On the islands of Serifos and Kythnos and within the Lavrion Schists only young-on-old relationships exist between rocks based on MDA estimates.

  20. Phosphates du Protérozoïque supérieur dans la chaîne des Dahomeyides ( circa 600 Ma) de la région de Bassar (Nord-Togo, Afrique de l'Ouest

    Science.gov (United States)

    Blot, Alain; Affaton, Pascal; Seddoh, Komlanvi F.; Aregba, Ankoun P.; Godonou, Senyo K.; Lenoir, Francois; Drouet, Jean-Jacques; Simpara, NkouéTh.; Magat, Philippe

    The phosphate deposit of Bassar is located in the Dahomeyide orogenic belt within the schist group of the Atacora structural unit. This schist group is regarded as the tectonic and metamorphic equivalent of the Late Precambrian Oti supergroup of the Volta basin. The phosphatic rocks are interbedded horizons (<30 m thick each). They generally consist of apatite pellets (both fairly pure and recrystallized individuals being present) within an essentially phosphatic matrix. The P205 content of these sedimentary primary phosphates is high (35-41.5%). Reserves are estimated in several hundreds of thousands of metric tons per metre of depth. This phosphate deposit can be counted among the phosphate prospects (Meckrou, Aloub Djouana, Arly and Pagala) or deposits (Tapoa and Kodjari) known within the Volta basin and, more rarely, within the external units of the Dahomeyide orogenic belt. Together with the Aloub Djouana and Pagala prospects, the Bassar deposit might present an interesting extension within the frontal units of the Dahomeyide orogenic belt representing a high economic asset.

  1. Hydrogeochemical characterization of a shallow groundwater system in the weathered basement aquifer of Ilesha area, southwestern Nigeria

    Directory of Open Access Journals (Sweden)

    M. N. Tijani

    2014-09-01

    Full Text Available Hydrogeochemical characterization of a weathered basement aquifer in Ilesha area, southwest Nigeria, was carried out with respect to geogenic and anthropogenic influences on the shallow groundwater system. Physico-chemical parameters revealed a pH of 6.4–8.4 and EC of 22–825 μs/cm in the urban areas compared to a pH of 7.3–10.5 and relatively higher EC of 126–1027 μs/cm in the peri-urban area. The concentrations of major cations (Ca, Na, K, Mg in the urban areas revealed relatively lower average concentrations of 28.4, 16.7, 8.4 and 5.0 mg/L, respectively, compared to 82.5, 33.4, 19.3 and 12.4 mg/L, respectively, for the peri-urban areas. The low concentrations of major cations in the urban areas can be attributed to low mineral dissolution of quartzite and muscovite quartz-schist bedrocks compared to the weathered granitic, amphibolite and biotite schist in the peri-urban areas. Hydrochemical characterization revealed two main water types; namely Ca-Mg-(Na-HCO3 mostly in the urban areas suggesting CO2-charged infiltrating recharge rainwater, and Ca-Na-(K-SO4-Cl type in the peri-urban areas as products of water–rock interactions.

  2. Mapping rock forming minerals at Boundary Canyon, Death Valey National Park, California, using aerial SEBASS thermal infrared hyperspectral image data

    Science.gov (United States)

    Aslett, Zan; Taranik, James V.; Riley, Dean N.

    2018-02-01

    Aerial spatially enhanced broadband array spectrograph system (SEBASS) long-wave infrared (LWIR) hyperspectral image data were used to map the distribution of rock-forming minerals indicative of sedimentary and meta-sedimentary lithologies around Boundary Canyon, Death Valley, California, USA. Collection of data over the Boundary Canyon detachment fault (BCDF) facilitated measurement of numerous lithologies representing a contact between the relatively unmetamorphosed Grapevine Mountains allochthon and the metamorphosed core complex of the Funeral Mountains autochthon. These included quartz-rich sandstone, quartzite, conglomerate, and alluvium; muscovite-rich schist, siltstone, and slate; and carbonate-rich dolomite, limestone, and marble, ranging in age from late Precambrian to Quaternary. Hyperspectral data were reduced in dimensionality and processed to statistically identify and map unique emissivity spectra endmembers. Some minerals (e.g., quartz and muscovite) dominate multiple lithologies, resulting in a limited ability to differentiate them. Abrupt variations in image data emissivity amongst pelitic schists corresponded to amphibolite; these rocks represent gradation from greenschist- to amphibolite-metamorphic facies lithologies. Although the full potential of LWIR hyperspectral image data may not be fully utilized within this study area due to lack of measurable spectral distinction between rocks of similar bulk mineralogy, the high spectral resolution of the image data was useful in characterizing silicate- and carbonate-based sedimentary and meta-sedimentary rocks in proximity to fault contacts, as well as for interpreting some mineral mixtures.

  3. Geochemical characteristics and conditions of formation of the Chah-Bazargan peraluminous granitic patches, ShahrBabak, Iran

    Science.gov (United States)

    Fazlnia, Abdolnaser

    2017-10-01

    Xenoliths of garnet-biotite-kyanite schist from the Qori metamorphic complex (southern part of the Sanandaj-Sirjan zone, northeast Neyriz, Zagros orogen in Iran) in the 173.0±1.6 Ma Chah-Bazargan leuco-quartz diorite intrusion were studied. This intrusion caused these schist xenoliths to be metamorphosed to the pyroxene hornfels facies (approximately 4.5±1.0 kbar and 760±35 °C), converting them to diatexite migmatite as a result of partial melting of the xenoliths. These melts are granites in composition. Melt volumes of 20 to 30 vol. % were calculated for small patches of the peraluminous granites. It is possible that anatectic melting affected only the leucosome, such that melting was more than 20 to 30 vol. %. It is possible that a large amount of melt was not extracted due to balanced in situ crystallization, the adhesion force between melt and crystal (restite), and high viscosity of the leucosome. The Chah-Bazargan peraluminous granites are depleted in trace elements such as REEs, HFSE (Ti, Zr, Ta, Nb, Th, U, Hf, Y), Ba, Pb, and Sr. These elements are largely insensitive to source enrichment, but sensitive to the amounts of main and accessory minerals. These elements were hosted by minerals such as garnet, biotite, muscovite, K-feldspar, plagioclase, ilmenite, apatite, monazite, and zircon in the source (diatexitic migmatitic xenoliths).

  4. Contribution to the geology of the Niari basin: sedimentology and metallogeny of the mining region; Contribution a la geologie du Bassin du Niari sedimentologie et metallogenie de la region miniere

    Energy Technology Data Exchange (ETDEWEB)

    Bigotte, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1956-01-15

    This thesis is divided in two parts: a detailed petrographical and stratigraphical study of the upper layers of calcareous schist in Congo which lead to some sedimentological considerations, and a metallogenic study of the ores of Niari basin which lead to a theoretical description of the metallogeny in Congo. In the first part, after a brief description of the methods used, a petrographical survey of the rocks of the upper layers of calcareous schist of the Boko-Congo area is given as well as sedimentological conclusions and stratigraphical data. The studies and conclusions related to this limited area are extended to a region scale. A structural study and precised descriptions of this region lead to an attempt of tectonic explanation. In the second part, an inventory and description of known mineralisation points in the Niari basin are given and in particular the detailed descriptions of four deposits: La Grande-Mine, M'Passa, Diangala and Djenguile. The interpretations and conclusions are based on the study of the general characters of the mineralisation in Niari basin and its comparison with the mineralisation in Katanga (now Shaba region) and North Rhodesia (now Zambia). (M.P.)

  5. Nonlinear creep damage constitutive model for soft rocks

    Science.gov (United States)

    Liu, H. Z.; Xie, H. Q.; He, J. D.; Xiao, M. L.; Zhuo, L.

    2017-02-01

    In some existing nonlinear creep damage models, it may be less rigorous to directly introduce a damage variable into the creep equation when the damage variable of the viscous component is a function of time or strain. In this paper, we adopt the Kachanov creep damage rate and introduce a damage variable into a rheological differential constitutive equation to derive an analytical integral solution for the creep damage equation of the Bingham model. We also propose a new nonlinear viscous component which reflects nonlinear properties related to the axial stress of soft rock in the steady-state creep stage. Furthermore, we build an improved Nishihara model by using this new component in series with the correctional Nishihara damage model that describes the accelerating creep, and deduce the rheological constitutive relation of the improved model. Based on superposition principle, we obtain the damage creep equation for conditions of both uniaxial and triaxial compression stress, and study the method for determining the model parameters. Finally, this paper presents the laboratory test results performed on mica-quartz schist in parallel with, or vertical to the schistosity direction, and applies the improved Nishihara model to the parameter identification of mica-quartz schist. Using a comparative analysis with test data, results show that the improved model has a superior ability to reflect the creep properties of soft rock in the decelerating creep stage, the steady-state creep stage, and particularly within the accelerating creep stage, in comparison with the traditional Nishihara model.

  6. Characterization of gold mineralization in Garin Hawal area, Kebbi State, NW Nigeria, using remote sensing

    Directory of Open Access Journals (Sweden)

    Talaat M. Ramadan

    2010-12-01

    Full Text Available Garin Hawal area, Kebbi State, NW Nigeria is part of the Neoproterozoic to Early Phanerozoic terrane separating the west African and Congo Cratons. Three main gold-bearing shear zones were detected in the study area from the processed Landsat ETM+ images and extensive ground investigation. Field and petrographical studies indicate that the Neoproterozoic rocks are represented by a highly folded and faulted belt constituted of hornblende, muscovite and graphite schist. They are intruded by granondiorites and late to post granitic dykes. Extensive alteration zones were identified using high resolution QuickBird image along Garin Hawal shear zone. The alteration zones and associated quartz veins are generally concordant with the main NE–SW regional structural trend and are dipping to the NW. Geochemical studies indicate that the gold content reaches 8 g/t in the alteration zones, while it reaches up to 35 g/t in the quartz veins. Mineralogical studies indicate that the alterations are strongly potassium-enriched. Pyrophyllite, kaolinite, illite, gypsum and quartz also occur. The main ore minerals are gold, chalcopyrite, arsenopyrite, pyrite, galena and iron oxides. This study indicates that the alteration zones and the associated quartz veins in the muscovite schist are promising and need more detailed exploration for Au and Ag mineralization to evaluate their potential.

  7. Chemical and boron isotopic composition of tourmaline from the Mariinsky emerald deposit, Central Urals, Russia

    Science.gov (United States)

    Baksheev, Ivan A.; Trumbull, Robert B.; Popov, Mikhail P.; Erokhin, Yuri V.; Kudryavtseva, Olesya E.; Yapaskurt, Vasily O.; Khiller, Vera V.; Vovna, Galina M.; Kiselev, Vladimir I.

    2017-07-01

    Tourmaline is abundant at the Mariinsky schist-hosted emerald deposit in the Central Urals, Russia, both in emerald-bearing phlogopite veins (type 1) and later, emerald-free pockets, lenses, and veinlets cutting the phlogopite veins (type 2). The Ca content in tourmaline is influenced by the host rocks (ultramafic and mafic rocks), associated minerals, and minerals crystallized before tourmaline (amphibole, fluorite, margarite). The Na concentration in tourmaline depends on the presence or absence of paragonite, and the association with micas also strongly influences the contents of Li, Zn, Ni, and Co in tourmaline. Type 1 tourmalines associated with phlogopite are relatively depleted in these elements, whereas type 2 tourmalines associated with margarite or paragonite are enriched. Some differences in isomorphic substitutions along with the trace element composition (Zn, V, Sr, Co, REE) may have value in exploration of emerald-bearing and emerald-free veins in schist-hosted emerald deposits. The δ11B values in tourmaline of all types fall in a narrow total range from -11.3 to -8.4‰. These values, combined with a mineralization temperature of 420-360 °C, yield an estimated δ11B fluid composition of -7.4 to -6.8‰ suggesting a mixed source of boron, likely dominated from the granitic rocks surrounding the emerald belt. The narrow range of B-isotope compositions in tourmaline from throughout the Mariinsky deposit suggests a well-mixed hydrothermal system.

  8. Geological Features of Iron Formations and Associate Rock in Bulunkuole Group, West Kunlun, Xinjiang, China

    Science.gov (United States)

    Huang, Chaoyang; Wang, He; Ren, Guangli; Wu, Wenying

    2017-05-01

    West Kunlun is located at northwest part of the Tibetan plateau, and it’s divided into North Kunlun terrane, South Kunlun terrane and Tianshuihai terrane. Bulunkuole Group is located in Tianshuihai terrane, and Taaxi, Yelike, Laobing, Zankan, Mokaer and Jiertiekegou iron deposit was found in this terrane. Those iron deposits are set to the important iron ore mineralization belt of Xinjiang and even China. By investigation the geological features, ore distributions, and mineralization characters; and analyze the electron microprobe of magnetite and pyrite, stable isotope of pyrite, magnetite and anhydrite to discussion the tectonic setting and its genesis analysis iron ore deposit in Blunkuole Group, and establish the metallogenic model in this area. By contrastive analyzing of Taaxi, Yelike Zankan-Mokar iron ore deposits in Bulunkuole Group, it was found that all the iron ore deposit share the similar sedimentary environment. Those deposits have 3 ∼ 4 ore bodies, each get a meter to dozens of meters in width, extend to thousands of meters. The wall rocks are biotite quartz schist and plagioclase amphibole schist, and the two rocks interbed usually. It should be distinguish in the stratigraphic correlation of Bulunkuole Group for the influenced by the magma intrusion, such as granite and felsite porphyry.

  9. Eluvial gold placer formation on actively rising mountain ranges, Central Otago, New Zealand

    Science.gov (United States)

    Craw, D.; Youngson, J. H.

    1993-05-01

    Eluvial gold deposits in Central Otago, New Zealand, have formed and are still forming on the flanks of actively rising antiformal mountain ranges. These gold deposits are derived mainly by erosion and concentration of fine-grained ( soil and sequences (up to 60 m thick) of poorly sorted immature schist gravels. The gravel sequences consist mainly of matrix-supported mass flow deposits and channellised proximal fan deposits, intercalated on a 1-10 m scale. Gold is concentrated in coarse lag gravels (up to 40 cm clasts) at channel bases. Topographic slopes on the rising ranges show an evolutionary trend in space and time, from gentle weakly dissected surfaces, through slightly degraded but convex slopes, to deeply incised convex streams. Eluvial gold occurs sporadically on the gentle slopes, but the most efficient concentration processes occurred where steeper convex slopes yielded an apron of fan sediments. Gold concentration at these sites resulted from selective and localized removal ("winnowing") of most schist debris, leaving coarse lag gravels and gold. The combination of authigenic grain size increase and residual concentration ensures that the eluvial deposits retain coarse-grained gold, and that only fine-grained gold is released to the alluvial systems downstream.

  10. Provenance and depositional age of metavolcano-sedimentary sequences of the Santa Terezinha de Goias, based on Sm-Nd and U-Pb zircon single grain; Proveniencia e idade deposicional de sequencias metavulcano-sedimentares da regiao de Santa Terezinha de Goias, baseada em dados isotopicos Sm-Nd e U-Pb em monocristal de zircao

    Energy Technology Data Exchange (ETDEWEB)

    Dantas, Ellton Luiz; Jost, Hardy; Fuck, Reinhardt A.; Brod, Jose Afonso; Pimentel, Marcio Martins; Meneses, Paulo Roberto [Brasilia Univ., DF (Brazil). Inst. de Geociencias]. E-mail: elton@unb.br

    2001-09-01

    Supracrustal rocks of the Santa Terezinha de Goias region, Central Brazil, presumably represent a southern extension of the Mara Rosa magmatic arc tectonically juxtaposed to Archean terrains and consist of a meta volcanic unit and a meta sedimentary unit. The aim of the paper is to present and discuss the first U-Pb and Sm-Nd data of rocks belonging to both units of that region. U-Pb data of zircons from a felsic meta volcanic rock inter layered with chlorite-rich schists (metandesites?) yield a concordant age of of 660 My, while the Sm-Nd model age of a variety of chlorite-schists indicate a juvenile age between 1.1 and 1.3 Ga. These data indicate that the meta volcanic rocks are Neo proterozoic in age and may be correlated with rocks of the Mara Rosa magmatic arc. On the other hand, the prevailing provenance of rocks belonging to the meta sedimentary unit indicate a Paleoproterozoic, or older, source. Thus, the deposition of both units are explained by means of the erosion of source-areas of variable age. (author)

  11. Relations of zoned pegmatites to other pegmatites, granite, and metamorphic rocks in the southern Black Hills, South Dakota

    Science.gov (United States)

    Norton, J.J.; Redden, J.A.

    1990-01-01

    The pegmatite field and the Harney Peak Granite of the southern Black Hills, South Dakota, form an igneous system that progresses from slightly biotitic muscovite granite through layered pegmatitic granite, with alternating sodic and potassic rocks, to simple plagioclase-quartz-perthite pegmatites, and on to zoned pegmatites. Most of the country rocks are Lower Proterozoic mica schists. At 1700 Ga, intrusion of the Harney Peak Granite created a large dome in these rocks, a thermal aureole with a staurolite, a first sillimanite isograd, and a small area of metamorphism above the second sillimanite isograd. The zoned pegmatites have a strong tendency to occur in clusters, and the types of pegmatites are different in different clusters. A less obvious tendency is a regional zonation in which rare-mineral pegmatites become more abundant and muscovite pegmatites less abundant toward the outskirts of the region. The composition of the granite indicates that its magma originated by partial melting of metasedimentary mica schists similar to those at the present surface. The pegmatitic nature of most of the granite probably reflects exsolution of an aqueous phase. -from Authors

  12. Identifying the Transition Zone Between East and West Dharwar Craton by Seismic Imaging

    Science.gov (United States)

    Ashish; Parvez, Imtiyaz A.

    2017-09-01

    The data from 12 temporary broadband seismic stations operated across east-west corridor in Dharwar region of Indian Peninsula along with ten other seismic stations operated by CSIR National Geophysical Research Institute (NGRI) in the region have been analysed that provide high-resolution image of southern Dharwar crust. Crust along the corridor is imaged by receiver function H-k stacking, common conversion point stacking using data from 22 sites in combination with joint inversion modeling of receiver functions and Rayleigh wave group velocity dispersion curves. The velocity image reveals thinner crust (36-38 km) except one site (coinciding with Cuddapah basin on the surface) in East Dharwar Craton (EDC), while crust beneath the West Dharwar Craton (WDC) is thicker (46-50 km). This study also observed a transition zone between EDC and WDC starting west of Closepet granite to the east of Chitradurga Schist Belt (CSB), which shows diffused Moho with a thickness of 40-44 km. Chitradurga Schist Belt is identified as the contact between Mesoarchean (WDC) and Neoarchean (EDC) crustal blocks. The lowermost part of the crust (V_s > 4.0 ) is thin (2-6 km) beneath EDC, intermediate (6-8 km) beneath transition zone and thicker (14-30 km) beneath WDC across the profile.

  13. Stripping in hot mix asphalt produced by aggregates from construction and demolition waste.

    Science.gov (United States)

    Pérez, I; Pasandín, A R; Gallego, J

    2012-01-01

    This paper analyses the effect of water on the durability of hot asphalt mixtures made with recycled aggregates from construction and demolition debris. Indirect tensile stress tests were carried out to evaluate stripping behaviour. The mixtures tested were fabricated with 0, 20, 40 and 60% recycled aggregates. Two types of natural aggregates were used: schist and calcite dolomite. An increase in the percentage of recycled aggregates was found to produce a decrease in the tensile stress ratio of the hot asphalt mixtures. To study this phenomenon, two and three factor analyses of variance (ANOVA) were performed with indirect tensile stress being used as the dependent variable. The factors studied were the percentage of recycled aggregates (0, 20, 40 and 60%), the moisture state (dry, wet) and the type of natural aggregate (schist, calcite). On the basis of the ANOVA results, it was found that the most important factor affecting resistance was the moisture state (dry, wet) of the specimens. The percentage of recycled aggregate also affected indirect tensile stress, especially in the dry state. The type of natural aggregate did not have a significant effect on indirect tensile stress. The hot asphalt mixture specimens made with different percentages of recycled aggregates from construction and demolition debris and of natural quarry aggregates showed poor stripping behaviour. This stripping behaviour can be related to both the poor adhesion of the recycled aggregates and the high absorption of the mortar of cement adhered to them.

  14. Microwave Acid Extraction to Analyze K and Mg Reserves in the Clay Fraction of Soils

    Directory of Open Access Journals (Sweden)

    Araína Hulmann Batista

    Full Text Available ABSTRACT: Extraction of K and Mg with boiling 1 mol L-1 HNO3 in an open system for predicting K and Mg uptake by plants is a method of low reproducibility. The aim of this study was to compare the extraction capacity of different acid methods relative to hydrofluoric acid extraction for K and Mg. A further objective was to develop a chemical extraction method using a closed system (microwave for nonexchangeable and structural forms of these nutrients in order to replace the traditional method of extraction with boiling HNO3 on a hot plate (open system. The EPA 3051A method can be used to estimate the total content of K in the clay fraction of soils developed from carbonate and phyllite/mica schist rocks. In the clay fraction of soils developed from basalt, recoveries of K by the EPA 3051A (pseudo-total method were higher than for the EPA 3052 (total hydrofluoric extraction method. The relative abundance of K and Mg for soils in carbonate rocks, phyllite/mica schist, granite/gneiss, and basalt determined by aqua regia digestion is unreliable. The method using 1 mol L-1 HNO3 in an closed system (microwave showed potential for replacing the classical method of extraction of nonexchangeable forms of K (boiling 1 mol L-1 HNO3 in an open system - hot plate and reduced the loss of Si by volatilization.

  15. High-pressure metamorphism in the Chinshuichi area, Yuli belt, eastern Taiwan

    Science.gov (United States)

    Keyser, William; Tsai, Chin-Ho; Iizuka, Yoshiyuki; Oberhänsli, Roland; Ernst, W. G.

    2016-12-01

    Tectonic blocks and slabs of mafic-ultramafic rocks are distributed discontinuously in the Yuli metamorphic belt of Taiwan. The blocks include rare omphacite metagabbros and garnet-epidote blueschists in the Wanjung and Juisui (Tamayen) areas, respectively. Such high-pressure (HP) mineral assemblages have been attributed to a mid-Miocene subduction event. However, the surrounding psammitic, pelitic and chloritic schists are the dominant greenschist-facies lithologies of the Yuli belt. In the Chinshuichi area, tectonic blocks are enclosed in garnet-bearing metapelites, suggesting elevated pressures. In this area, we recently discovered meta-plagiogranite containing the assemblage glaucophane + omphacite (XJd up to 0.39) + rutile + quartz, indicating P-T conditions near 13 kbar/550 °C. New equilibrium phase modeling of a garnet-paragonite mica schist and compositional isopleths for peak assemblage minerals garnet and phengite (Si = 3.33-3.37 pfu) indicate metamorphic conditions of 15.5-17 kbar/530-550 °C. These P-T estimates are higher than previously reported in the Yuli belt and suggest that both tectonic blocks and host metapelites underwent HP metamorphism. The juxtaposition of tectonic blocks and metapelites apparently occurred during the formation of a subduction-accretionary complex, followed by exhumation facilitated by a collisional event. These new findings imply that HP metamorphism was not limited to tectonic blocks, and instead played a significant role attending orogenesis in eastern Taiwan.

  16. Seismic properties and mineral crystallographic preferred orientations from EBSD data: Results from a crustal-scale detachment system, Aegean region

    Science.gov (United States)

    Cossette, Élise; Schneider, David; Audet, Pascal; Grasemann, Bernhard; Habler, Gerlinde

    2015-05-01

    The crystallographic preferred orientations (CPOs) were measured on a suite of samples representative of different structural depths along the West Cycladic Detachment System, Greece. Electron backscatter diffraction (EBSD) analyses were conducted on calcitic and mica schists, impure quartzites, and a blueschist, and the average seismic properties of the rocks were calculated with the Voigt-Reuss-Hill average of the single minerals' elastic stiffness tensor. The calcitic and quartzitic rocks have P- and S-wave velocity anisotropies (AVp, AVs) averaging 8.1% and 7.1%, respectively. The anisotropy increases with depth represented by the blueschist, with AVp averaging 20.3% and AVs averaging 14.5%, due to the content of aligned glaucophane and mica, which strongly control the seismic properties of the rocks. Localised anisotropies of very high magnitudes are caused by the presence of mica schists as they possess the strongest anisotropies, with values of ~ 25% for AVp and AVs. The direction of the fast and slow P-wave velocities occurs parallel and perpendicular to the foliation, respectively, for most samples. The fast propagation has the same NE-SW orientation as the lithospheric stretching direction experienced in the Cyclades since the Late Oligocene. The maximum shear wave anisotropy is subhorizontal, similarly concordant with mineral alignment that developed during extension in the Aegean. Radial anisotropy in the Aegean mid-crust is strongly favoured to azimuthal anisotropy by our results.

  17. Organic geochemical characteristics of the Paleocene-Eocene oil shales in the Nallihan Region, Ankara, Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Sari, Ali [Ankara University, Faculty of Engineering, Department of Geological Engineering, 06100, Tandogan, Ankara (Turkey); Aliyev, Saday Azadoglu [Ankara University, Science and Technology Research and Application Center, 06100, Tandogan, Ankara (Turkey)

    2006-08-15

    Units of Paleozoic, Mesozoic and Cenozoic age are exposed in the study area which extends along the Sakarya River by the Sarycakaya town of Eskibehir at west and Nallyhan district of Ankara at East. Paleozoic is represented with metamorphites consisting of glaucophane schist, muscovite schist and marble alternations and granites cutting them. The Mesozoic composing of Jurassic-Cretaceous Sogukcam limestones at the northern part of the area is in tectonic contact with other units. The Tertiary is characterized by the Paleocene-Eocene Kizilcay Group which consists of the Beykoy, Camalan and Lacin Formations. The Camalan Formation is composed of sandstone, limestone, oil shale and locally coal bands. In the area, as a result of intense tectonic activity by the late Eocene, sedimentary sequence that compacted within the Paleozoic metamorphic rocks were folded and fractured. The Paleocene-Eocene shales have adequate organic material content to form potential source rocks. In order to determine hydrocarbon potential of the unit, various organic geochemical analysis techniques were performed. According to pyrolysis results (TOC, S{sub 1} and S{sub 2}), the Paleocene-Eocene shales are perfect source rocks for oil. On the basis of Rock-Eval pyrolysis analyses, kerogens are Type I and Type II kerogens. Spore Color Index and T{sub max} evaluations indicate that maturity of the unit is between diagenesis and early mature oil zone and at the beginning of the oil-producing stage. Organic facies of the Paleocene-Eocene shales are A, AB and B. (author)

  18. Blueschist-facies metamorphism related to regional thrust faulting

    Science.gov (United States)

    Blake, M.C.; Irwin, W.P.; Coleman, R.G.

    1969-01-01

    Rocks of the blueschist (glaucophane schist) facies occur throughout the world in narrow tectonic belts associated with ultramafic rocks. In the Coast Range province of California, blueschist rocks are devloped in the eugeosynclinal Franciscan Formation of Late Mesozoic age. The blueschist rocks form a narrow belt for more than 800 km along the eastern margin of this province and commonly are separated from rocks of an overlying thrust plate by serpentinite. Increasing metamorphism upward toward the thrust fault is indicated mineralogically by a transition from pumpellyite to lawsonite and texturally by a transition from metagraywacke to schist. The blueschist metamorphism probably occurred during thrusting in a zone of anomalously high water pressure in the lower plate along the sole of the thrust fault. This tectonic mode of origin for blueschist differs from the generally accepted hypothesis involving extreme depth of burial. Other belts of blueschist-facies rocks, including the Sanbagawa belt of Japan, the marginal synclinal belt of New Zealand, and the blueschist-ultramafic belts of Venezuela, Kamchatka, Ural mountains, and New Caledonia have similar geologic relations and might be explained in the same manner. ?? 1969.

  19. Late Cretaceous-Early Tertiary paleomagnetism of Aruba and Bonaire (Netherlands Leeward Antilles)

    Science.gov (United States)

    Stearns, Carola; Mauk, Frederick J.; van der Voo, Rob

    1982-02-01

    For a paleomagnetic study of the Upper Cretaceous of the Netherlands Leeward Antilles, we have analyzed 187 oriented samples from the complex norite-tonalite batholith and the diabase-schist-tuff formation on Aruba and 44 oriented samples from various igneous units of the Washikemba Formation on Bonaire. Both alternating field and thermal demagnetization procedures were used to demagnetize the samples. Most of the cores yielded univectorial Zijderveld diagrams above 10-20 mT or 400° C. Virtual geomagnetic poles calculated from site means were then compared with equivalently aged poles for cratonic South America and other Caribbean sites. The Washikemba Formation of Bonaire and the diabase-schist-tuff formation of Aruba yield poles that are similar to those of Guajira (Colombia) and the Caribbean Mountains of northern Venezuela, whereas they are rotated approximately 90° with respect to the pole for stable South America. The batholith on Aruba yields a pole which is rotated clockwise over approximately 20° with respect to the South American pole. Thus, our data strongly support the hypothesis that Aruba and Bonaire have been rotated clockwise by as much as 90° since the Late Cretaceous. In addition, paleolatitudes calculated from the inclinations of the paleomagnetic vectors suggest that there was a northward drift with respect to South America of perhaps as much as 10° of the islands during the rotation, although this can hardly be called a statistically significant amount.

  20. Phytocenological and edaphic characteristics of sessile oak forests on Miroč Mt in northeastern Serbia

    Directory of Open Access Journals (Sweden)

    Cvjetićanin Rade

    2013-01-01

    Full Text Available This research was carried out in natural stands of sessile oak (Quercus petraea agg. Ehrendorfer 1967 on Miroč mountain. Three comunities were investigated: Pure sessile oak forest (Quercetum montanum Čer. et Jov. 1953. s.l., sessile oak-common hornbeam forest (Querco-Carpinetum moesiacum Rud. 1949. s.l. and sessile oak-balkan beech forest (Querco-Fagetum Gliš. 1971. Pure sessile oak forests are found on the following soils: dystric ranker and acid cambic soil on sandstone, dystric ranker and acid cambisols on phyllite, and acid cambic soil on schists. Sessile oak-hornbeam forests grow on sandstone, granite and schists. Sessile oak-beech forests are found on acid cambisol on phyllite and sandstone conglomerate. Various ecological conditions (exposition, slope, altitude, soil types and bedrock on Mt Miroč caused the occurence of diverse sessile oak forest communities, while different states of these forest stands resulted from the implementation of management measures. [Projekat Ministarstva nauke Republike Srbije, br. 37008: Održivo gazdovanje ukupnim potencijalima šuma u Republici Srbiji

  1. Chester County ground-water atlas, Chester County, Pennsylvania

    Science.gov (United States)

    Ludlow, Russell A.; Loper, Connie A.

    2004-01-01

    Chester County encompasses 760 square miles in southeastern Pennsylvania. Groundwater- quality studies have been conducted in the county over several decades to address specific hydrologic issues. This report compiles and describes water-quality data collected during studies conducted mostly after 1990 and summarizes the data in a county-wide perspective. In this report, water-quality constituents are described in regard to what they are, why the constituents are important, and where constituent concentrations vary relative to geology or land use. Water-quality constituents are grouped into logical units to aid presentation: water-quality constituents measured in the field (pH, alkalinity, specific conductance, and dissolved oxygen), common ions, metals, radionuclides, bacteria, nutrients, pesticides, and volatile organic compounds.Waterquality constituents measured in the field, common ions (except chloride), metals, and radionuclides are discussed relative to geology. Bacteria, nutrients, pesticides, and volatile organic compounds are discussed relative to land use. If the U.S. Environmental Protection Agency (USEPA) or Chester County Health Department has drinkingwater standards for a constituent, the standards are included. Tables and maps are included to assist Chester County residents in understanding the water-quality constituents and their distribution in the county. Ground water in Chester County generally is of good quality and is mostly acidic except in the carbonate rocks and serpentinite, where it is neutral to strongly basic. Calcium carbonate and magnesium carbonate are major constituents of these rocks. Both compounds have high solubility, and, as such, both are major contributors to elevated pH, alkalinity, specific conductance, and the common ions. Elevated pH and alkalinity in carbonate rocks and serpentinite can indicate a potential for scaling in water heaters and household plumbing. Low pH and low alkalinity in the schist, quartzite, and

  2. Tectono-metamorphic evolution of the upper plate of the Eo-Alpine nappe-stack: constraints from the Oberhof Window (Carinthia, Austria)

    Science.gov (United States)

    Hollinetz, Marianne Sophie; Huet, Benjamin; Iglseder, Christoph; Rantitsch, Gerd; Grasemann, Berhard

    2017-04-01

    The Upper Austro-Alpine Unit in the Eastern Alps corresponds to a nappe-stack that formed during the Eo-Alpine Cretaceous event. It is dominated by crystalline rocks that show Variscan, Permo-Triassic, Eo-Alpine and Neo-Alpine metamorphic imprints. Understanding the tectono-metamorphic evolution of the Eo-Alpine nappe-stack is therefore hampered by a complex polyphase history. Most published studies focused on the subducted lower plate that contains the eclogite-bearing nappes (Koralpe-Wölz nappe system) but the upper plate (Ötztal-Bundschuh nappe system and Drauzug-Gurktal nappe system) is less understood. Our contribution focuses on the tectono-metamorphic evolution of the Bundschuh nappe (Oberhof Window, Carinthia, Austria). This nappe contains metasediments intruded by granites of Ordovician age. Characteristically, these rocks underwent Variscan amphibolite-facies. They were later covered by Carboniferous to Mesozoic sediments and, all together, overprinted by greenschist to amphibolite-facies metamorphism in the upper plate of the Eo-Alpine wedge. During this event, the Bundschuh nappe was overthrusted by the nappes of the Drauzug-Gurktal nappe system. The core of the window is occupied by the middle-grained "Oberhof orthogneiss". LA-ICP-MS U/Pb zircon dating yielded a late Ordovician age for its protolith. The orthogneiss is overlain by the transgressive Carboniferous metasediments comprising meta-conglomerate, graphite schist and quartzite. The Bundschuh nappe is overthrusted by garnet-micaschist, amphibolite, hornblende-garbenschist, calc-micaschist, quarzite and graphitic schist interpreted as parts of the basal Drauzug-Gurktal nappe system. Deformation is characterized by isoclinal folds with an E-W/SE-NW trending fold-axes and top-to-the-East/South-East shearing. This kinematics is related to normal faulting in the upper part of the Eo-Alpine orogenic wedge. The graphite schist contains an assemblage of isolated round garnet and abundant chloritoid in

  3. Mid-Late Triassic metamorphic event for Changhai meta-sedimentary rocks from the SE Jiao-Liao-Ji Belt, North China Craton: Evidence from monazite U-Th-Pb and muscovite Ar-Ar dating

    Science.gov (United States)

    Liu, Fulai; Wang, Fang; Liou, J. G.; Meng, En; Liu, Jianhui; Yang, Hong; Xiao, Lingling; Cai, Jia; Shi, Jianrong

    2014-11-01

    The precise constraints on the timing of metamorphism of the Changhai metamorphic complex is of great importance considering the prolonged controversial issue of the north margin and the extension of the Sulu-Dabie HP-UHP Belt. While the monazite U-Th-Pb and muscovite 40Ar/39Ar techniques are widely accepted as two of the most powerful dating tools for revealing the thermal histories of medium-low grade metamorphic rocks and precisely constraining the timing of metamorphism. The Changhai metamorphic complex at the SE Jiao-Liao-Ji Belt, North China Craton consists of a variety of pelitic schist and Grt-Ky-bearing paragneiss, and minor quartzite and marble. Analyses of mineral inclusions and back-scattered electric (BSE) images of monazites, combined with LA-ICP-MS U-Th-Pb ages for monazites and 40Ar/39Ar ages for muscovites, provide evidence of the origin and metamorphic age of the Changhai metamorphic complex. Monazites separates from various Grt-Mus schists and Grt-Ky-St-Mus paragneisses exhibit homogeneous BSE images from cores to rims, and contain inclusion assemblages of Grt + Mus + Qtz ± Ctd ± Ky in schist, and Grt + Ky + St + Mus + Pl + Kfs + Qtz inclusions in paragneiss. These inclusion assemblages are very similar to matrix minerals of host rocks, indicating they are metamorphic rather than inherited or detrital in origin. LA-ICP-MS U-Th-Pb dating reveals that monazites of schist and paragneiss have consistent 206Pb/238U ages ranging from 228.1 ± 3.8 to 218.2 ± 3.7 Ma. In contrast, muscovites from various schists show slightly older 40Ar/39Ar plateau ages of 236.1 ± 1.5 to 230.2 ± 1.2 Ma. These geochronological and petrological data conclude that the pelitic sediments have experienced a metamorphic event at the Mid-Late Triassic (236.1-218.2 Ma) rather than the Paleoproterozoic (1950-1850 Ma), commonly regarded as the Precambrian basement for the Jiao-Liao-Ji Belt. Hence, the Changhai metamorphic complex should be considered as a discrete

  4. Structural evolution of the La Paya pluton (Sierra de Cachi, NW Argentina): insights from the study of its magnetic fabric

    Science.gov (United States)

    Aranguren, Aitor; Hongn, Fernando; María Tubía, José; Vegas, Néstor

    2017-04-01

    The La Paya granite is a pluton elongated in a northerly direction that spreads over 10 km2 in the Sierra de Cachi (Eastern Cordillera of Salta, Andean belt, NW Argentina). This pluton intrudes into high-temperature and low-pressure migmatites and schists. The metamorphic evolution of the country rocks and the emplacement of the La Paya pluton took place in an extensional tectonic setting during Ordovician times (Hongn et al., 2014). Subsequently, a compressional tectonic event led to the formation of large E-verging folds with a penetrative axial planar foliation. Due to the folding event, the current metamorphic zonation is inverted and the metamorphic degree rises towards the west. The granite is concordant with the metamorphic zonation and with the country rocks foliation. Schists with biotite and andalucite (low to medium metamorphic grade) crop out in the eastern border of the pluton and schists with cordierite (high grade) in the western border. The pluton is characterized by the coexistence of magmatic and solid-state structures. The deformation is localized in shear bands concentrated in the pluton roof. Wide sectors of the pluton core preserve medium- to coarse-grained equigranular textures of magmatic origin on which we have collected samples from 28 sites in order to perform an AMS study. Susceptibility values are very low, with k ranging between 19 and 67 x 10-6 SI. The obtained anisotropy values are in agreement with the magmatic character of the analysed samples (Pj between 1,03-1,07). The magnetic foliations are concordant with the contacts of the pluton. They show northwards trends and dips to the west that are steeper close to the eastern pluton border. Magnetic lineations are concentrated in two main maxima that define a great circle parallel to the pluton elongation. The parallelism between the magnetic fabrics from areas with magmatic structures and the structures observed in domains with solid-state deformation points to a syn

  5. Minimum age of the Neoproterozoic Seven Hundred Acre Island Formation and the tectonic setting of the Islesboro Formation, Islesboro block, Maine

    Science.gov (United States)

    Stewart, D.B.; Tucker, R.D.; Ayuso, R.A.; Lux, D.R.

    2001-01-01

    Two platformal stratigraphic sequences occur on Islesboro, Penobscot Bay, Maine. The older Seven Hundred Acre Island Formation is at least 200 m thick, its base is not exposed, and it makes up fault-bounded blocks of siliceous colour-banded dolomitic marble, muscovite-rich quartzite, coarse-grained splendent muscovite-garnet-staurolite-andalusite schist, and calcareous metapelite, with minor garnet amphibolite and amphibolite. It was initially metamorphosed to lower amphibolite facies and was later to lower greenschist facies. The lower amphibolite facies metamorphism is Neoproterozoic (670 to 650 Ma) as inferred from the 40Ar/39Ar high temperature release spectra of hornblende separates. A U-Pb zircon age of 646.7 ?? 2.7 Ma obtained for a pegmatite that intruded deformed rocks is taken to be the minimum age of the Formation. The platformal Islesboro Formation probably unconformably overlies the Seven Hundred Acre Island Formation. It is primarily turbiditic pelite with many beds of quartzite, impure dolomitic marble, some conglomerate, and a few feldsparrich volcaniclastic beds and is thought to be either Neoproterozoic or Cambrian. It was metamorphosed only to lower greenschist facies, possibly in the same event that retrograded the Seven Hundred Acre Island Formation. Geochemical interpretations of minor and trace element analyses of six amphibolite and four schist samples from the Seven Hundred Acre Island Formation show that the protoliths of the amphibolite samples were intermediate between tholeiitic and within-plate type basaltic flows or dikes that intruded attenuated continental crust, or were eroded from these basalts. Four amphibolite and three schist samples analyzed for Pb isotopes were found to be enriched in radiogenic Pb. The Pb isotopic compositions are similar to those in peri-Gondwanan basement rocks from Atlantic Canada. The peri-Gondwanan Islesboro block was placed against the peri-Gondwanan Middle and Late Cambrian Ellsworth terrane on the

  6. Tectonic origin and deformation process of the Mayer Kangri medium-high pressure metamorphic dome in Central Qiangtang of Tibet

    Science.gov (United States)

    Wang, Y.; Liang, X.

    2016-12-01

    The metamorphic characteristics, deformation process, geochronology of the medium-high pressure metamorphic rocks in blueschist bearing Central Qiangtang Metamorphic belt (CQMB) of Tibet were less well constrained. It is, however, commonly assumed that these rock slices in the margin also contain important implications on the evolution of the entire metamorphic belt. The well-exposed Mayer Kangri medium-high pressure metamorphic dome in north flank of the CQMB provides an unique opportunity to investigate the outer part of the CQMB, which could facilitate the study on the subduction-exhumation-post orogenic scenarios of the Triassic accretionary orogeny in Central Qiangtang. Field structural analyses indicate the Mayer Kangri metamorphic dome are bounded by low-angle normal faults (LANF) within the hanging wall of low-green schist facies mélange. It majorly consists of epidote-amphibolites, quartz-phengite schist, epidote-albite schist. The outcrop and micro structural observations of footwall metamorphic rocks show an open anticline with multiple foliation replacement, which largely differentiate themselves from the dextral strike-slip shearing of the hanging wall. Well-zoned amphiboles were found within the epidote-amphibolite after micro-structural observations and electron probe microanalyses (EPMA), which indicate that the amphibole zonation demonstrates a Hastingsite core, a Ferro-actinolite mantle and a Ferro-winchite rim in most cases. The mean temperature and pressure estimates of the zoned amphibolites change from 544 °, 0.98Gpa in the core, to 426°, 0.34Gpa in the mantle, and to ca.364° and 0.70 GPa in the rim. The detailed analyses on the stepwise-heating Ar-Ar results of the zoned amphiboles provide good constrains on the episodic deformation process of the CQMB. For Hast-cores, we obtained near plateau ages of 242.4-241.2 Ma, indicating the onset of the oceanic subduction is earlier than the Anisian stage of Middle Triassic. The subsequent

  7. Geology and preliminary hydrogeologic characterization of the cell-house site, Berlin, New Hampshire, 2003-04

    Science.gov (United States)

    Degnan, James R.; Clark, Stewart F.; Harte, Philip T.; Mack, Thomas J.

    2005-01-01

    At the cell-house site, thin, generally less than 20-foot thick overburden, consisting of till and demolition materials, overlies fractured crystalline bedrock. Bedrock at the site consists of gneiss with thin discontinuous lenses of chlorite schist and discontinuous tabular pegmatite. Two distinct fracture domains, with principal trends to the west and northwest, and to the north, overlap near the site. The cell-house site shows principal trends common to both domains. Gneiss is the most abundant rock at the site. Steeply dipping fractures within the gneiss terminate on subhorizontal contacts with pegmatite and on moderately dipping contacts with chlorite schist. Steeply northwest-dipping en Echelon fracture zones, parallel joint zones, and silicified brittle faults show consistent strikes to the northeast. Gently east-dipping to subhorizontal fractures, sub-parallel to gneissosity, strike northeast. The impermeable cap, barrier wall, and bedrock surface topography affect ground-water flow in the overburden. There is relatively little ground-water flow in the overburden in the capped area and a poor hydraulic connection between the overburden and the underlying bedrock over most of the site. The overburden beneath the cap may receive inflow through or beneath the barrier wall, or by flow through vertical fractures in the underlying bedrock beneath the barrier wall. The bedrock aquifer near the river is well connected to the river and head difference in the bedrock across the site are large (greater than 13 ft). Horizontal hydraulic conductivities of 0.2 to 20 ft/d were estimated for the bedrock. Individual fractures or fracture zones likely have hydraulic conductivities greater than the bulk rock. Subhorizontal fractures occur at pegmatite contacts or along chlorite schist lenses and may serve as ground-water conduits to the steeply dipping fractures in gneiss. The effective hydraulic conductivity across the site is likely to be in the low range of the estimated

  8. Is localised dehydration and vein generation the tremor-generating mechanism in subduction zones?

    Science.gov (United States)

    Fagereng, Ake; Meneghini, Francesca; Diener, Johann; Harris, Chris

    2017-04-01

    The phenomena of tectonic, non-volcanic, tremor was first discovered at the down-dip end of the seismogenic zone in Japan early this millennium. Now this low amplitude, low frequency, noise-like seismic signal has been observed at and/or below the deep limit of interseismic coupling along most well-instrumented subduction thrust interfaces. Data and models from these examples suggest a link between tremor and areas of elevated fluid pressure, or at least fluid presence. Tremor locations appear to also correlate with margin-specific locations of metamorphic fluid release, determined by composition and thermal structure. We therefore hypothesise that: (i) tremor on the deep subduction thrust interface is related to localised fluid release; and (ii) accretionary complex rocks exhumed from appropriate pressure - temperature conditions should include a record of this process, and allow a test for the hypothesis. Hydrothermal veins are a record of mineral precipitation at non-equilibrium conditions, commonly caused by fracture, fluid influx, and precipitation of dissolved minerals from this fluid. Quartz veins are ubiquitous in several accretionary complexes, including the Chrystalls Beach Complex, New Zealand, and the Kuiseb Schist of the Namibian Damara Belt. In both locations, representing temperatures of deformation of tremor. In the Chrystalls Beach Complex, quartz δ18O values range from 14.1 ‰ to 17.0 ‰ (n = 18), whereas in the Kuiseb schist, values range from 9.4 ‰ to 17.9 ‰ (n = 30). In the latter, values less than 14.0‰ are associated with long-lived shear zones. Excluding the lower values in the Kuiseb schist, the δ18O values are consistent with metamorphic fluids in near equilibrium with the host rocks. We thus infer that the veins that developed on the prograde path formed at a small range of temperatures from a local fluid source. This interpretation is consistent with the veins forming in response to a spatially localised metamorphic fluid

  9. Paleoproterozoic structural evolution of rocks exposed in the underground science and engineering laboratory, Lead SD, USA

    Science.gov (United States)

    Terry, M. P.; Redden, J. A.

    2008-12-01

    The lab provides a unique 3-dimensional view of the crustal structure of the Precambrian core of the Black Hills that lies along the margin of the Wyoming Craton. The Paleoproterozoic structural evolution of these rocks controls the distribution of lithologies and rock fabric and thus the rheologic properties in the lab. These properties have potential to influence later formed structures such as fractures and a range of experiments from in the areas hydrology to rock mechanics. The rock at the lab is composed of metamorphosed volcanic and sedimentary rocks that include, from oldest to youngest, the Yates unit, Poorman Formation, Homestake Formation and Ellison Formation. The Yates unit is a hornblende- plagioclase schist. The Poorman Formation is a sericite-biotite carbonate-bearing phyllite. The Homestake Formation is a grunerite-siderite schist with interbedded chlorite or biotite phyllite. The Ellison Formation is a sericite-biotite phyllite or schist with interbedded impure quartzite (biotite-quartzschist). Compilation of available structural data and analysis indicate a complex evolution of folds and fabrics between 1780 and 1715 Ma. The lab is located on a late upright SE-plunging anticlinorium which is interpreted to deform the earliest folds (NE trending?). The earliest phase resulted in repetition is Homestake Formation and associated units. Overprinting during later deformation events caused tightening and local dismemberment of these early folds that led to the previous interpretation that multiple iron formations existed in the lab. The second phase of folding shallow to moderate upright SE-plunging folds and associated northwest striking, steeply dipping foliation. The third phase of folding overprints the previous phase to varying degrees and produced four structural domains that are recognized by changes in the orientation of structural fabrics. The third phase of folding is best developed in the western part of the lab and is represented by steeply

  10. Sedimentology of latero-frontal moraines and fans on the west coast of South Island, New Zealand

    Science.gov (United States)

    Evans, David J. A.; Shulmeister, James; Hyatt, Olivia

    2010-12-01

    Exposures through the LGM latero-frontal moraine loops at sites along the west coast of South Island, New Zealand reveal a depositional environment that was dominated by the progradation of steep fronted, debris flow-fed fans, manifest in crudely stratified to massive diamictons, arranged in sub-horizontal to steeply dipping clinoforms and containing discontinuous bodies of variably sorted, stratified sediment (LFA 1). The fans were constructed by debris-covered glaciers advancing over outwash plains, as recorded by well stratified and horizontally bedded gravels, sands and diamicts (LFA 0). The ice-contact slopes of the fans are offlapped by retreat phase deposits in the form of glacilacustrine depo-centres (LFA 2), which record the existence of moraine-dammed lakes. Interdigitation of lake rhythmites and subaerial to subaqueous sediment gravity flow deposits documents intense debris-flow activity on unstable moraine/fan surfaces. Glacier readvances in all catchments are documented by glacitectonic disturbance and localized hydrofracturing of LFA 2, followed by the emplacement of schist-dominated debris flow-fed fans (LFA 3) inside and over the top of the earlier latero-frontal moraine/fan loops. Contorted and disturbed bedding in LFA 3 reflects its partial deposition in supraglacial positions. Clast lithologies in LFAs 1 and 3 reveal that two distinct transport pathways operated during moraine construction, with an early period of latero-frontal fan construction involving mixed lithologies and a later period of ice-contact/supraglacial fan construction dominated by schist lithologies from the mountains. These two periods of deposition were separated by a period of moraine abandonment and paraglacial reworking of ice-contact slopes to produce LFA 2. The occurrence of LFA 3 at all sites indicates that the glacier readvance phase responsible for its deposition was not localized or glacier-specific, and involved the transfer of large volumes of schist, possibly due

  11. Geologic Map of the Kings Mountain and Grover Quadrangles, Cleveland and Gaston Counties, North Carolina, and Cherokee and York Counties, South Carolina

    Science.gov (United States)

    Horton, J. Wright

    2008-01-01

    This geologic map of the Kings Mountain and Grover 7.5-min quadrangles, N.C.-S.C., straddles a regional geological boundary between the Inner Piedmont and Carolina terranes. The Kings Mountain sequence (informal name) on the western flank of the Carolina terrane in this area includes the Neoproterozoic Battleground and Blacksburg Formations. The Battleground Formation has a lower part consisting of metavolcanic rocks and interlayered schist and an upper part consisting of quartz-sericite phyllite and schist interlayered with quartz-pebble metaconglomerate, aluminous quartzite, micaceous quartzite, manganiferous rock, and metavolcanic rocks. The Blacks-burg Formation consists of phyllitic metasiltstone interlayered with thinner units of marble, laminated micaceous quartzite, hornblende gneiss, and amphibolite. Layered metamorphic rocks of the Inner Piedmont terrane include muscovite-biotite gneiss, muscovite schist, and amphibolite. The Kings Mountain sequence has been intruded by metatonalite and metatrondhjemite (Neoproterozoic), metagabbro and metadiorite (Paleozoic?), and the High Shoals Granite (Pennsylvanian). Layered metamorphic rocks of the Inner Piedmont in this area have been intruded by the Toluca Granite (Ordovician?), the Cherryville Granite and associated pegmatite (Mississippian), and spodumene pegmatite (Mississippian). Diabase dikes (early Jurassic) are locally present throughout the area. Ductile fault zones of regional scale include the Kings Mountain and Kings Creek shear zones. In this area, the Kings Mountain shear zone forms the boundary between the Inner Piedmont and Carolina terranes, and the Kings Creek shear zone separates the Battleground Formation from the Blacksburg Formation. Structural styles change across the Kings Mountain shear zone from steeply dipping layers, foliations, and folds on the southeast to gently and moderately dipping layers, foliations, and recumbent folds on the northwest. Mineral assemblages in the Kings Mountain

  12. Orebody geometry, fluid and metal sources of the Omitiomire Cu deposit in the Ekuja Dome of the Damara Belt in Namibia

    Science.gov (United States)

    Kitt, Shawn; Kisters, Alexander; Vennemann, Torsten; Steven, Nick

    2017-04-01

    The Omitiomire Cu deposit (resource of 137 Mt at 0.54% Cu) in the Ekuja Dome of the Damara Belt in Namibia is hosted by an anastomosing, low-angle Pan-African (ca. 520 Ma) shear zone system developed around an older (ca. 1100-1060 Ma), late Mesoproterozoic intrusive breccia between a suite of mafic rocks (originally lava flows) and later tonalitic gneisses. High-grade ore shoots preferentially formed along contacts between tectonically interleaved biotite-epidote-quartz-chalcocite schists and felsic gneisses, and are directly related to an increase in the number and cumulative thickness of thin, contact-parallel mineralized shear zones. Alteration and mineralization are associated with elevated concentrations of K2O, Cr, Rb, S, and Cu and a loss of Na2O, CaO, and MgO. Oxygen isotope fractionation for quartz-biotite, quartz-feldspar, and quartz-amphibole mineral pairs support equilibrium temperatures of between 500 and 650 °C during the fluid/rock interaction. Mineral separates from amphibole-biotite gneisses and mineralized schists have similar ranges in δ18O values of about 1.2 to 2 ‰ relative to VSMOW. Coexisting minerals are arranged in an order of increasing δ18O values from biotite, to epidote, amphibole, and quartz, suggesting that the Omitiomire Shear Zone was a rock-dominated system. Similarly, H-isotope results for mineral separates from biotite-epidote schists and amphibole gneisses do not show any reversals for D/H fractionations, with δD values of between -48 and -82 ‰, typical of metamorphic-magmatic rocks. The homogeneous and low δ34S values (-6.1 to -4.7 ‰ CDT) are compatible with a local redistribution of sulfur from magmatic rocks and interaction with sulfur derived from metamorphic fluids of metasedimentary origin. The relatively low fluid/rock ratios and elevated Cu values (>1500 ppm) from unaltered amphibolite point to a local redistribution of an earlier (late Mesoproterozoic) Keweenaw-type Cu mineralization into later Pan

  13. Triassic High-P Metamorphism of the central Qiangtang terrane, Tibet; constraints using mineral equilibria modelling and 40Ar/39Ar geochronology

    Science.gov (United States)

    Rajkumar, A.; Hui, L.; Clarke, G. L.; Aitchison, J. C.; Forster, M. A.

    2014-12-01

    The SE-trending Qiangtang metamorphic belt (QMB) stretches more than 500 km through the Qiangtang terrane in central Tibet and comprises tectonically disrupted blueschist and eclogite in lower-grade garnet-phengite-bearing schist and quartzite. These rocks record the closure of a paleo-Tethyan Triassic ocean that formerly separated Cathaysian and Gondwana components of Asia, now forming the northern and southern Qiangtang blocks. Eclogite is extensively recrystallized to high-P amphibolite and greenschist facies assemblages, formed during water ingression that accompanied terrane uplift. P-T pseudosections constructed in Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O-TiO2-O (NCKMASHTO) in the context of petrography and mineral chemistry provides the ability to recover a dynamic PT history for the eclogite facies assemblages. Prograde (S1) assemblages for the Gemu Co eclogite are predicted to have formed at P≈21.5 kbars and T≈505°C and involved garnet, glaucophane, omphacite, rutile, lawsonite and chlorite, based on garnet composition and inferred pseudomorphs after lawsonite. Peak (S2) assemblages of garnet, barroisite, omphacite, rutile, epidote and quartz reflect P≈15 kbars and T≈570°C. Based on textural relations, post-peak stages can be divided into epidote-amphibolite and greenschist facies. The geothermal gradient for the prograde S1 assemblage and the peak S2 assemblage is 7.1 and 11.5°C/km respectively.40Ar/39Ar geochronology of phengitic mica using step heating in recrystallized eclogite components and surrounding garnet-mica schist components both yield maximum ages ranging 230-220 Ma. The congruency in ages of the deeply subducted high-pressure eclogites to the surrounding garnet phengite schists indicate they were the most probable source of fluids to extensively recrystallize most of the high-pressure eclogite components in the high-pressure belt. The P-T history of the high-P rocks of the QMB records the deep subduction of paleo-Tethyan oceanic crust to

  14. Identification of metalliferous ecotypes of Cistus ladanifer L. using RAPD markers

    Energy Technology Data Exchange (ETDEWEB)

    Quintela-Sabaris, C.; Fraga, M.I. [Dept. of Botany, Univ. of Santiago de Compostela (Spain); Kidd, P.S. [Dept. of Soil Science and Chemical Agronomy, Univ. of Santiago de Compostela (Spain)

    2005-04-01

    The genetic diversity of Cistus ladanifer ssp. ladanifer (Cistaceae) growing on ultramafic and non-ultramafic (basic and schists) soils in the NE of Portugal was studied in order to identify molecular markers that could distinguish the metal-tolerant ecotypes of this species. Random Amplified Polymorphic DNA (RAPD) markers were used in order to estimate genetic variation and differences between populations. The RAPD dataset was analysed by means of a cluster analysis and an analysis of molecular variance (AMOVA). Our results indicate a significant partitioning of molecular variance between ultramafic and non-ultramafic populations of Cistus ladanifer, although the highest percentage of this variance was found at the intra-population level. Mantel's test showed no relationship between inter-population genetic and geographic distances. A series of RAPD bands that could be related to heavy metal tolerance were observed. The identification of such markers will enable the use of Cistus ladanifer in phytoremediation procedures. (orig.)

  15. Identification of metalliferous ecotypes of Cistus ladanifer L. using RAPD markers.

    Science.gov (United States)

    Quintela-Sabarís, Celestino; Kidd, Petra S; Fraga, María Isabel

    2005-01-01

    The genetic diversity of Cistus ladanifer ssp. ladanifer (Cistaceae) growing on ultramafic and non-ultramafic (basic and schists) soils in the NE of Portugal was studied in order to identify molecular markers that could distinguish the metal-tolerant ecotypes of this species. Random Amplified Polymorphic DNA (RAPD) markers were used in order to estimate genetic variation and differences between populations. The RAPD dataset was analysed by means of a cluster analysis and an analysis of molecular variance (AMOVA). Our results indicate a significant partitioning of molecular variance between ultramafic and non-ultramafic populations of Cistus ladanifer, although the highest percentage of this variance was found at the intra-population level. Mantel's test showed no relationship between inter-population genetic and geographic distances. A series of RAPD bands that could be related to heavy metal tolerance were observed. The identification of such markers will enable the use of Cistus ladanifer in phytoremediation procedures.

  16. Politique énergétique 2030 du Québec : l’étonnante absence d'une stratégie de transport soutenable

    OpenAIRE

    Feurtey, Évariste; Boudreault, Louis-Étienne; Bourque, Gilles; Breton, Simon-Philippe; Reid, Réal; Saucier, Carol; Saulnier, Bernard; Sauvé, Lucie

    2017-01-01

    Suite à un texte paru dans le Soleil le 7 avril 2016 intitulé « L’avenir contraint de l’énergie éolienne au Québec » (Saucier et al., 2016), huit chercheurs du Collectif scientifique sur la question du gaz de schiste, se questionnent sur l'ambition et les orientations stratégiques de la Politique énergétique du Québec (PEQ) 2030 en matière de transport. Les auteurs partent du constat que le Québec prévoit d'importants surplus d'électricité renouvelable (8,3 TWh par an jusqu'en 2023) et que ce...

  17. Coeval brittle and ductile structures associated with extreme deformation partitioning in a multilayer sequence

    Science.gov (United States)

    Druguet, Elena; Alsop, G. Ian; Carreras, Jordi

    2009-05-01

    An investigation on the effects of a strong rheological contrast in the deformation of layered anisotropic rocks is presented. The study focuses on the geometric and kinematic analysis of complex structures developed within and adjacent to a thin marble-metapsammite multilayer unit from the Cap de Creus tectonometamorphic belt (NE Spain). Zones of high ductile strain localise in the marble layers, which exhibit complex folds, whereas metapsammites show mostly brittle (boudinage) structures. These structures strongly contrast with coeval retrogressive discrete shear zones developed in the surrounding migmatitic schists. The extreme strain partitioning is due to the rheological contrast between different lithological layers. In addition, the specific orientation of this multilayer unit induces a reversal of local kinematics with regard to bulk kinematics. Consequently, caution should be exercised when interpreting regional tectonics in highly partitioned domains associated with rheological heterogeneities.

  18. Land Snail Fauna of “Porţile de Fier” (“Iron Gates” Nature Park (Banat, Romania

    Directory of Open Access Journals (Sweden)

    Gheoca Voichiţa

    2014-12-01

    Full Text Available The paper presents an analysis of terrestrial mollusc fauna of the “Iron Gates” Nature Park. Various types of habitats (e.g. forests, rocks, riparian areas and substrates (e.g. limestone, conglomerate, crystalline schist were analyzed. A total of 45 species of terrestrial gastropods were identified in 17 sampling points, four of which are mentioned for the first time in the area. Six other species cited in the literature were not found. Limestone substrate allows the development of large populations of terrestrial gastropods, but the specific diversity is larger when it is associated with a forest habitat. The current legal and illegal exploitation of limestone threatens the mollusc communities associated with this type of habitat. The subsequent erosion process and the low mobility of these animals make their colonization of habitats difficult.

  19. Characterizing multiple sources and interaction in the critical zone through Sr-isotope tracing of surface and groundwater

    Science.gov (United States)

    Negrel, Philippe; Pauwels, Hélène

    2017-04-01

    The Critical Zone (CZ) is the lithosphere-atmosphere boundary where complex physical, chemical and biological processes occurs and control the transfer and storage of water and chemical elements. This is the place where life-sustaining resources are, where nutrients are being released from the rocks. Because it is the place where we are living, this is a fragile zone, a critical zone as a perturbed natural ecosystem. Water resources in hard-rocks commonly involve different hydrogeological compartments such as overlying sediments, weathered rock, the weathered-fissured zone, and fractured bedrock. Streams, lakes and wetlands that drain such environments can drain groundwater, recharge groundwater, or do both. Groundwater resources in many countries are increasingly threatened by growing demand, wasteful use, and contamination. Surface water and shallow groundwater are particularly vulnerable to pollution, while deeper resources are more protected from contamination. Here, we first report on Sr isotope data as well as major ions, from shallow and deep groundwater in several granite and schist areas over France with intensive agriculture covering large parts of these catchments. In three granite and Brioverian 'schist' areas of the Armorican Massif, the range in Sr contents in groundwater from different catchments agrees with previous work on groundwater sampled from granites in France. The Sr content is well correlated with Mg and both are partly related to agricultural practices and water rock interaction. The relationship between Sr- isotope and Mg/Sr ratios allow defining the different end-members, mainly rain, agricultural practice and water-rock interaction. The data from the Armorican Massif and other surface and groundwater for catchment draining silicate bedrocks (300-450Ma) like the Hérault, Seine, Moselle, Garonne, Morvan, Margeride, Cantal, Pyrénées and Vosges are scattered between at least three geochemical signatures. These include fertilizer and

  20. The State of stress in the Sanford Underground Research Facility (SURF) in Lead South Dakota

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Moo Y. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-10-01

    As a part of the U.S. Department of Energy (DOE) SubTER (Subsurface Technology and Engineering Research, Development and Demonstration) initiative, University of Wisconsin- Madison, Sandia National Laboratories, and Lawrence Berkeley National Laboratory conducted the Permeability (k) and Induced Seismicity Management for Energy Technologies (kISMET) project. The objectives of the project are to define the in situ status of stress in the Sanford Underground Research Facility (SURF) in Lead, South Dakota and to establish the relations between in situ stress and induced fracture through hydraulically stimulating the fracture. (SURF) in Lead, South Dakota. In situ tests are conducted in a 7.6 cm diameter and 100 long vertical borehole located in the 4850 Level West Access Drift near Davies Campus of SURF (Figure 1). The borehole is located in the zone of Precambrian Metamorphic Schist.

  1. Lithological 3D grid model of the Vuonos area built by using geostatistical simulation honoring the 3D fault model and structural trends of the Outokumpu association rocks in Eastern Finland

    Science.gov (United States)

    Laine, Eevaliisa

    2015-04-01

    The Outokumpu mining district - a metallogenic province about 100 km long x 60 km wide - hosts a Palaeoproterozoic sulfide deposit characterized by an unusual lithological association. It is located in the North Karelia Schist Belt , which was thrust on the late Archaean gneissic-granitoid basement of the Karelian craton during the early stages of the Svecofennian Orogeny between 1.92 and 1.87 Ga (Koistinen 1981). Two major tectono-stratigraphic units can be distinguished, a lower, parautochthonous 'Lower Kaleva' unit and an upper, allochthonous 'upper Kaleva' unit or 'Outokumpu allochthon'. The latter consists of tightly-folded deep marine turbiditic mica schists and metagraywackes containing intercalations of black schist, and the Outo¬kumpu assemblage, which comprises ca. 1950 Ma old, serpentinized peridotites surrounded by carbonate-calc-silicate ('skarn')-quartz rocks. The ore body is enclosed in the Outokumpu assemblage, which is thought to be part of a disrupted and incomplete ophiolite complex (Vuollo & Piirainen 1989) that can be traced to the Kainuu schist belt further north where the well-preserved Jormua ophiolite is ex¬posed (Kontinen 1987, Peltonen & Kontinen 2004). Outokumpu can be divided into blocks divided by faults and shear zones (Saalmann and Laine, 2014). The aim of this study was to make a 3D lithological model of a small part of the Outokumpu association rocks in the Vuonos area honoring the 3D fault model built by Saalmann and Laine (2014). The Vuonos study area is also a part of the Outokumpu mining camp area (Aatos et al. 2013, 2014). Fault and shear structures was used in geostatistical gridding and simulation of the lithologies. Several possible realizations of the structural grids, conforming the main lithological trends were built. Accordingly, it was possible to build a 3D structural grid containing information of the distribution of the possible lithologies and an estimation the associated uncertainties. References: Aatos, S

  2. Geological mapping and analysis in determining resource recitivity limestone rocks in the village of Mersip and surrounding areas, district Limun, Sorolangun Regency, Jambi Province

    Science.gov (United States)

    Dona, Obie Mario; Ibrahim, Eddy; Susilo, Budhi Kuswan

    2017-11-01

    The research objective is to describe potential, to analyze the quality and quantity of limestone, and to know the limit distribution of rocks based on the value of resistivity, the pattern of distribution of rocks by drilling, the influence mineral growing on rock against resistivity values, the model deposition of limestone based on the value resistivity of rock and drilling, and the comparison between the interpretation resistivity values based on petrographic studies by drilling. Geologic Formations study area consists of assays consisting of altered sandstone, phyllite, slate, siltstone, grewake, and inset limestone. Local quartz sandstone, schist, genealogy, which is Member of Mersip Stylists Formation, consists of limestone that formed in shallow seas. Stylists Formation consists of slate, shale, siltstone and sandstone. This research methodology is quantitative using experimental observation by survey. This type of research methodology by its nature is descriptive analysis.

  3. Syn- to post-orogenic exhumation of metamorphic nappes: Structure and thermobarometry of the western Attic-Cycladic metamorphic complex (Lavrion, Greece)

    Science.gov (United States)

    Scheffer, Christophe; Vanderhaeghe, Olivier; Lanari, Pierre; Tarantola, Alexandre; Ponthus, Léandre; Photiades, Adonis; France, Lydéric

    2016-05-01

    The Lavrion peninsula is located along the western boundary of the Attic-Cycladic metamorphic complex in the internal zone of the Hellenic orogenic belt. The nappe stack is well exposed and made, from top to bottom, of (i) a non-metamorphic upper unit composed of an ophiolitic melange, (ii) a middle unit mainly composed of the Lavrion schists in blueschist facies, (iii) and a basal unit mainly composed of the Kamariza schists affected by pervasive retrogression of the blueschist facies metamorphism in greenschist facies. The middle unit is characterized by a relatively steep-dipping foliation associated with isoclinal folds of weakly organized axial orientation. This foliation is transposed into a shallow-dipping foliation bearing a N-S trending lineation. The degree of transposition increases with structural depth and is particularly marked at the transition from the middle to the basal unit across a low-angle mylonitic to cataclastic detachment. The blueschist facies foliation of the Lavrion schists (middle unit) is underlined by high pressure phengite intergrown with chlorite. The Kamariza schists (basal unit) contains relics of the blueschist mineral paragenesis but is dominated by intermediate pressure phengite also intergrown with chlorite and locally with biotite. Electron probe micro-analyzer chemical mapping combined with inverse thermodynamic modeling (local multi-equilibrium) reveals distinct pressure-temperature conditions of crystallization of phengite and chlorite assemblages as a function of their structural, microstructural and microtextural positions. The middle unit is characterized by two metamorphic conditions grading from high pressure (M1, 9-13 kbar) to lower pressure (M2, 6-9 kbar) at a constant temperature of ca. 315 °C. The basal unit has preserved a first set of HP/LT conditions (M1-2, 8-11 kbar, 300 °C) partially to totally transposed-retrogressed into a lower pressure mineral assemblage (M3, 5-8.5 kbar) associated with a slight but

  4. Origin of emerald deposits of Brazil

    Science.gov (United States)

    Giuliani, G.; Silva, L. J. H. D.; Couto, P.

    1990-01-01

    Precambrian emerald deposits of Brazil are found in a typical geologic setting with Archean basement and supracrustal, ultramafic, granitoid and rocks. Volcano-sedimentary series occur as imbricated structures or as bodies affected by complex folding and deformation. Emerald mineralization belongs to the classic biotite-schist deposit, which formed by the reaction of pegmatitic veins within ultrabasic rocks. At the same time, pegmatite-free emerald deposits linked to ductile shear zones are also known. Emerald formation is attributed to infiltrational metasomatic processes provoking a K-metasomatism of the ultrabasic rocks and also a desilication of the pegmatites. A new classification based on the geological setting, structural features, and ore paragenesis is proposed.

  5. Graphite Black shale of Vendas de Ceira, Coimbra, Portugal

    Science.gov (United States)

    Quinta-Ferreira, Mário; Silva, Daniela; Coelho, Nuno; Gomes, Ruben; Santos, Ana; Piedade, Aldina

    2017-04-01

    The graphite black shale of Vendas de Ceira located in south of Coimbra (Portugal), caused serious instability problems in recent road excavation slopes. The problems increased with the rain, transforming shales into a dark mud that acquires a metallic hue when dried. The black shales are attributed to the Devonian or eventually, to the Silurian. At the base of the slope is observed graphite black shale and on the topbrown schist. Samples were collected during the slope excavation works. Undisturbed and less altered materials were selected. Further, sampling was made difficult as the graphite shale was covered by a thick layer of reinforced concrete, which was used to stabilize the excavated surfaces. The mineralogy is mainly constituted by quartz, muscovite, ilite, ilmenite and feldspar without the presence of expansive minerals. The organic matter content is 0.3 to 0.4%. The durability evaluated by the Slake Durability Test varies from very low (Id2 of 6% for sample A) to high (98% for sample C). The grain size distribution of the shale particles, was determined after disaggregation with water, which allowed verifying that sample A has 37% of fines (5% of clay and 32% of silt) and 63% of sand, while sample C has only 14% of fines (2% clay and 12% silt) and 86% sand, showing that the decrease in particle size contributes to reduce durability. The unconfined linear expansion confirms the higher expandability (13.4%) for sample A, reducing to 12.1% for sample B and 10.5% for sample C. Due the shale material degradated with water, mercury porosimetry was used. While the dry weight of the three samples does not change significantly, around 26 kN/m3, the porosity is much higher in sample A with 7.9% of pores, reducing to 1.4% in sample C. The pores size vary between 0.06 to 0.26 microns, does not seem to have any significant influence in the shale behaviour. In order to have a comparison term, a porosity test was carried out on the low weatherable brown shale, which is

  6. Human impact on Karst: the example of Lusaka (Zambia.

    Directory of Open Access Journals (Sweden)

    De Waele Jo

    2003-01-01

    Full Text Available Lusaka, the capital of Zambia with over 2,000,000 inhabitants, is built on an extensive plateau composed mainly of schists and dolomitic marbles, constituting a very important aquifer that provides the city with almost half of its drinking water needs. Recent demographic growth, leading to uncontrolled urban expansion, and mismanagement of the water resource and of urban waste has lead, in the past 20 years, to an overexploitation of the aquifer and to a generalised water quality depletion, putting in serious danger the future social and economical development of the capital. This third world city has, for these reasons, become a terrifying example of human impact on a vulnerable karst environment, and if no measures will be taken in the very near future, quality of life in the city will be at serious risk.

  7. Surface Luminescence Dating Of 'Dragon Houses' And Armena Gate At Styra (Euboea, Greece)

    Science.gov (United States)

    Liritzis, I.; Polymeris, G. S.; Zacharias, N.

    The Optical Stimulated Luminescence (OSL) surface dating employing the singlealiquot regenerative (SAR) technique on quartz was applied to some small enigmatic buildings made of large marble schist slabs in a skillful corbelling technique, and a fortified megalithic gate, at Styra, Kapsala, Laka Palli and Kastro Armena in southern Euboea. The function and origins of the structures have created a puzzle that has fed the imagination and lead to various interpretations by many scholars. No archaeological excavations or methods of dating have been available for the megalithic-like structures. The dates reported suggest the earliest construction to have taken place during the Classical period. Re-use of these structures has occurred during Hellenistic and Roman times (the latter associated with the large scale quarrying of marbles), as well as, in Medieval times (found in agreement with the historical literature) and the contemporary period (as reported by shepherds). In all cases the datable slabs were rather reset as repairs.

  8. A modified failure criterion for transversely isotropic rocks

    Directory of Open Access Journals (Sweden)

    Omid Saeidi

    2014-03-01

    Full Text Available A modified failure criterion is proposed to determine the strength of transversely isotropic rocks. Mechanical properties of some metamorphic and sedimentary rocks including gneiss, slate, marble, schist, shale, sandstone and limestone, which show transversely isotropic behavior, were taken into consideration. Afterward, introduced triaxial rock strength criterion was modified for transversely isotropic rocks. Through modification process an index was obtained that can be considered as a strength reduction parameter due to rock strength anisotropy. Comparison of the parameter with previous anisotropy indexes in literature showed reasonable results for the studied rock samples. The modified criterion was compared to modified Hoek-Brown and Ramamurthy criteria for different transversely isotropic rocks. It can be concluded that the modified failure criterion proposed in this study can be used for predicting the strength of transversely isotropic rocks.

  9. BAKOVIĆI THE BIGEST GOLD DEPOSIT OF BOSNIA AND HERZEGOVINA

    Directory of Open Access Journals (Sweden)

    Ivan Jurković

    1995-12-01

    Full Text Available Tectonic setting, para genesis, structure and texture of ores, sulphide sulphur isotopic composition allign the Bakovići veiny deposit in the group of polymetallic, postmagmatic hydrothermal deposits in the Mid-Bosnian Schist Mountains area. Crude ore is rich in gold (15 g/t. Main ore mineral is gold-bearing pyrite; quartz and siderite are the main gangue minerals Accessories are: tetrahedrite, arsenopyrite, chalcopyrjte, stibnite, galena, barite, gypsum. Production between 1895-1938 gave 2.24 t of gold and 7.47 t of silver. The Bakovići deposit was the biggesl producer of gold in Bosnia and Herzegovina. The deposit is relaled to the Late Variscan rhyolite magmatism.

  10. Evaluation of radon occurrence in groundwater from 16 geologic units in Pennsylvania, 1986–2015, with application to potential radon exposure from groundwater and indoor air

    Science.gov (United States)

    Gross, Eliza L.

    2017-05-11

    Results from 1,041 groundwater samples collected during 1986‒2015 from 16 geologic units in Pennsylvania, associated with 25 or more groundwater samples with concentrations of radon-222, were evaluated in an effort to identify variations in radon-222 activities or concentrations and to classify potential radon-222 exposure from groundwater and indoor air. Radon-222 is hereafter referred to as “radon.” Radon concentrations in groundwater greater than or equal to the proposed U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) for public-water supply systems of 300 picocuries per liter (pCi/L) were present in about 87 percent of the water samples, whereas concentrations greater than or equal to the proposed alternative MCL (AMCL) for public water-supply systems of 4,000 pCi/L were present in 14 percent. The highest radon concentrations were measured in groundwater from the schists, gneisses, and quartzites of the Piedmont Physiographic Province.In this study, conducted by the U.S. Geological Survey in cooperation with the Pennsylvania Department of Health and the Pennsylvania Department of Environmental Protection, groundwater samples were aggregated among 16 geologic units in Pennsylvania to identify units with high median radon concentrations in groundwater. Graphical plots and statistical tests were used to determine variations in radon concentrations in groundwater and indoor air. Median radon concentrations in groundwater samples and median radon concentrations in indoor air samples within the 16 geologic units were classified according to proposed and recommended regulatory limits to explore potential radon exposure from groundwater and indoor air. All of the geologic units, except for the Allegheny (Pa) and Glenshaw (Pcg) Formations in the Appalachian Plateaus Physiographic Province, had median radon concentrations greater than the proposed EPA MCL of 300 pCi/L, and the Peters Creek Schist (Xpc), which is in the Piedmont

  11. Integrated analysis of the geophysical, morphological and geological information of the Northeastern compartment of Roraima State, Brazil; Analise integrada de informacoes geofisicas, morfologicas e geologicas da porcao Centro-Nordeste do Estado de Roraima

    Energy Technology Data Exchange (ETDEWEB)

    Silva Carvalho, Joao da; Araujo, Rutenio Luiz Castro de [Amazonas Univ., Manaus, AM (Brazil)

    1995-12-31

    The studied area is located in the central portion of the Northeastern Compartment of Roraima State, in Brazil. It is characterized by typical flat geomorphology with residual topographic features related to the Cauarane Moca and Murupu Hills, probably controlled by structures formed during former tectonic events. It is comprised by gneissic and granitic terranes of the Urariquera metamorphic suite, as well as by quartzites, amphibolite, piroxenites, and schists of the Cauarane group (lower proterozoic). So part of the Sururiu group (medium proterozoic), riodalites, dacites, and riolites are also presented. Additionally, milonites and cataclases associated with the K`Mudku tectonothermal event (upper proterozoic) occur in the area together with basic dikes of the Apoteri suite (mesozoic), as well as sands and clays of the Boa Vista Formation and of the recent deposits unit (tertiary and quaternary ages). Available geophysical data provide valuable information for a better understanding of the structures and lithological behavior of the studied area. 8 refs., 3 figs

  12. A geophysical survey on the archaeological site of Mugardos (NW Iberian peninsula)

    Science.gov (United States)

    Matias, M. Senos; Almeida, F.

    1992-08-01

    Archaeological indications near Mugardos (Ferrol, NW Spain) suggest the existence of a Roman settlement. In fact, in the area were found pavements, walls with north-south and east-west orientations and some structures that endured heating. These remains are covered by soil, more than 1 m thick, and lie over schists. In order to determine the archaeological potential of the area and to delimit future excavations a geophysical survey, consisting of a joint resistivity and magnetic survey, was planned and carried out. The square array of electrodes was used and the data are discussed as apparent square array resistivity maps and azimuthal inhomogeneity ratio ( AIR) maps. The magnetic survey included total field measurements using sensor heights of 0.30 and 2.30 m above the ground, so that a magnetic gradient could be computed. A combined interpretation of both resistivity and magnetic data is discussed. Later excavations have confirmed the geophysical interpretation.

  13. General geology, alteration, and iron deposits in the Palaeoproterozoic Misi region, northern Finland

    Directory of Open Access Journals (Sweden)

    Tero Niiranen

    2003-01-01

    Full Text Available The Paleoproterozoic Misi region forms the northeastern part of the Peräpohja Schist Belt in northern Finland. The area comprises mafic volcanic and sedimentary rocks, differentiated gabbros, and late-orogenic granitoids. Three geochemically different mafic volcanic units were recognised: LREE-depleted amygdaloidal lavas, slightly LREE-enriched lavas, and mafic tuffs that have a flat REE pattern. Sedimentary rocks include arkosites, mica gneisses, dolomitic marbles, quartzites, tuffites, mica schists, calc-silicate rocks and graphite-bearing schists. Two types of gabbros wereidentified: one with a LREE-enriched pattern and another with flat REE pattern. The age of the former is according to Perttunen and Vaasjoki (2001 2117±4 Ma, whereas there is no age determination for the latter. The granitoid intrusions belong to the ca. 1800 Malate-orogenic group of the Central Lapland Granitoid Complex. The geochemistry and the stable isotope data on mafic lavas and dolomitic marbles show similarities with the mafic volcanic rocks and marbles of the lower part of the Kivalo group in the western part of Peräpohja Schist Belt. Peak metamorphic conditions in the region vary from upper-greenschist to upper-amphibolite facies. Three major stages of deformation were distinguished: N-S compressional D1 with ductile deformation, NE-SW compressional D2 with ductile to brittle-ductile deformation, and E-W compressional D3 with brittle deformation. Several magnetite occurrences are known in the region and four of those have been mined for iron. The ores are mainly composed of magnetite with minor haematite, pyrite, chalcopyrite and bornite. Besides iron, the ores contain small amounts of P, S and V aswell as trace amounts of Cu, Co, Te and Au. The magnetite bodies are hosted by skarnoids within the ca. 2220–2120 Ma dolomitic marble-quartzite sequence, and highly differentiated, intensely albitised, LREE-enriched gabbro. Multistage and -type alteration is

  14. Trébas

    OpenAIRE

    Prat, Henri

    2013-01-01

    Date de l'opération : 1990 (SU) Inventeur(s) : Prat Henri A l’occasion d’un terrassement ponctuel exécuté à proximité d’une maison d’habitation, une structure linéaire creuse, difficilement interprétable (tranchée, fossé de drainage) a été dégagée sur plus de 5 m de long, d’une largeur de 0,60 m et une profondeur de plus de 2 m. Elle était comblée, dans sa partie supérieure, par un apport de terre végétale qui surmontait une forte épaisseur d’argile, de dallettes de schiste et de grès, mêlés...

  15. Abrupt spatial and geochemical changes in lamprophyre magmatism related to Gondwana fragmentation prior, during and after opening of the Tasman Sea

    DEFF Research Database (Denmark)

    van der Meer, Quinten; Storey, Michael; Scott, James

    2016-01-01

    the Alpine Schist at 72–68 Ma indicates a period of possible reactivation of this proto Alpine Fault before it served as a zone of weakness during the opening of the oceanic Emerald Basin (at ~45 Ma) and eventually the formation of the present-day plate boundary (~25 Ma–recent)....... in different areas. The oldest magmatism, 102–100 Ma, is concentrated in the South Westland region that represents the furthest inboard portion of New Zealand in a Gondwana setting. A later pulse of magmatism from ~92 Ma to ~84 Ma, concentrated in North Westland, ended when the first oceanic crust formed...... represent the oldest Western Province representatives of alkaline magmatism in the greater New Zealand region that peaked in activity during the Cenozoic and has remained active up to the present day. Cretaceous alkaline dikes were emplaced parallel to predicted normal faults associated with dextral shear...

  16. Biological support media influence the bacterial biofouling community in reverse osmosis water reclamation demonstration plants.

    Science.gov (United States)

    Ferrera, Isabel; Mas, Jordi; Taberna, Elisenda; Sanz, Joan; Sánchez, Olga

    2015-01-01

    The diversity of the bacterial community developed in different stages of two reverse osmosis (RO) water reclamation demonstration plants designed in a wastewater treatment plant (WWTP) in Tarragona (Spain) was characterized by applying 454-pyrosequencing of the 16S rRNA gene. The plants were fed by secondary treated effluent to a conventional pretreatment train prior to the two-pass RO system. Plants differed in the material used in the filtration process, which was sand in one demonstration plant and Scandinavian schists in the second plant. The results showed the presence of a highly diverse and complex community in the biofilms, mainly composed of members of the Betaproteobacteria and Bacteroidetes in all stages, with the presence of some typical wastewater bacteria, suggesting a feed water origin. Community similarities analyses revealed that samples clustered according to filter type, highlighting the critical influence of the biological supporting medium in biofilm community structure.

  17. Evolution of crystalline target rocks and impactites in the chesapeake bay impact structure, ICDP-USGS eyreville B core

    Science.gov (United States)

    Horton, J. Wright; Kunk, M.J.; Belkin, H.E.; Aleinikoff, J.N.; Jackson, J.C.; Chou, I.-Ming

    2009-01-01

    The 1766-m-deep Eyreville B core from the late Eocene Chesapeake Bay impact structure includes, in ascending order, a lower basement-derived section of schist and pegmatitic granite with impact breccia dikes, polymict impact breccias, and cataclas tic gneiss blocks overlain by suevites and clast-rich impact melt rocks, sand with an amphibolite block and lithic boulders, and a 275-m-thick granite slab overlain by crater-fill sediments and postimpact strata. Graphite-rich cataclasite marks a detachment fault atop the lower basement-derived section. Overlying impactites consist mainly of basement-derived clasts and impact melt particles, and coastalplain sediment clasts are underrepresented. Shocked quartz is common, and coesite and reidite are confirmed by Raman spectra. Silicate glasses have textures indicating immiscible melts at quench, and they are partly altered to smectite. Chrome spinel, baddeleyite, and corundum in silicate glass indicate high-temperature crystallization under silica undersaturation. Clast-rich impact melt rocks contain ??- cristobalite and monoclinic tridymite. The impactites record an upward transition from slumped ground surge to melt-rich fallback from the ejecta plume. Basement-derived rocks include amphibolite-facies schists, greenschist(?)-facies quartz-feldspar gneiss blocks and subgreenschist-facies shale and siltstone clasts in polymict impact breccias, the amphibolite block, and the granite slab. The granite slab, underlying sand, and amphibolite block represent rock avalanches from inward collapse of unshocked bedrock around the transient crater rim. Gneissic and massive granites in the slab yield U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon dates of 615 ?? 7 Ma and 254 ?? 3 Ma, respectively. Postimpact heating was 7lt;~350 ??C in the lower basementderived section based on undisturbed 40Ar/ 39Ar plateau ages of muscovite and sand above the suevite based on 40Ar/39Ar age spectra of detrital microcline. ?? 2009 The

  18. Natural radioactivity in stream sediments of Oltet River, Romania

    Science.gov (United States)

    Ion, Adriana

    2017-04-01

    The concentration of naturally occurring radionuclides (U-238, Th-232 and K-40) in stream sediments of the Oltet River was measured in order to establish the primary sources of radionuclides, the transport pathways and the geochemical factors favouring their mobilisation and concentration in the existing geological context. The Oltet River has a length of 185 Km and crosses the southern central part of the country, being the right tributary of the Olt River. The range in elevation of the watercourse varies between 1963 m in the springs area (Parîng Mountains) and 200 m at the confluence with the Olt River, whereas the relief of the Oltet Basin has a varied character, manifested by the presence of diverse forms of relief, starting with major mountainous heights and ending with low-lying plains regions. In cross section from North to South, the Olteț River cuts metamorphic rocks (schist, gneisses, quartzite, marble, mica-schist's), magmatic rocks (granite and granitoid massifs - intruded by veins of microgranite, aplite, pegmatite and lamprophyre) and limestone, followed by deposits composed of clays, marls, sands and gravels, that are characterized by the presence of lignite seams. 44 stream sediment samples were collected in summer of 2016 from sampling points distributed along the river with an equidistance of about 4 - 5 km. The activity concentrations of the U-238, Th-232 and K-40 were measured by gamma ray spectrometry using HPGe detector (ORTEC) with 26% relative efficiency in multilayer shielding. The reference materials used were IAEA - RGK-1 and IAEA - 314. Analysis was performed on the geochemical process the amounts of thorium and potassium released are modest, leaching of uranium being the dominant feature (uranyl ion). The downstream lignite seams are the secondary geochemical barriers in accumulation of uranium; the radiometric data obtained for stream sediments emphasize this enrichment.

  19. Trace-element geochemistry of metabasaltic rocks from the Yukon-Tanana Upland and implications for the origin of tectonic assemblages in east-central Alaska

    Science.gov (United States)

    Dusel-Bacon, C.; Cooper, K.M.

    1999-01-01

    We present major- and trace- element geochemical data for 27 amphibolites and six greenstones from three structural packages in the Yukon-Tanana Upland of east-central Alaska: the Lake George assemblage (LG) of Devono-Mississippian augen gneiss, quartz-mica schist, quartzite, and amphibolite; the Taylor Mountain assemblage (TM) of mafic schist and gneiss, marble, quartzite, and metachert; and the Seventymile terrane of greenstone, serpentinized peridotite, and Mississippian to Late Triassic metasedimentary rocks. Most LG amphibolites have relatively high Nb, TiO2, Zr, and light rare earth element contents, indicative of an alkalic to tholeiitic, within-plate basalt origin. The within-plate affinities of the LG amphibolites suggest that their basaltic parent magmas developed in an extensional setting and support a correlation of these metamorphosed continental-margin rocks with less metamorphosed counterparts across the Tintina fault in the Selwyn Basin of the Canadian Cordillera. TM amphibolites have a tholeiitic or calc-alkalic composition, low normalized abundances of Nb and Ta relative to Th and La, and Ti/V values of ocean-floor basalt origin. Y-La-Nb proportions in both TM and Seventymile metabasalts indicate the proximity of the arc and marginal basin to continental crust. The arc geochemistry of TM amphibolites is consistent with a model in which the TM assemblage includes arc rocks generated above a west-dipping subduction zone outboard of the North American continental margin in mid-Paleozoic through Triassic time. The ocean-floor or within-plate basalt geochemistry of the Seventymile greenstones supports the correlation of the Seventymile terrane with the Slide Mountain terrane in Canada and the hypothesis that these oceanic rocks originated in a basin between the continental margin and an arc to the west.

  20. Fluid-controlled grain boundary migration and switch in slip systems in a high strain, high temperature contact aureole, California, USA

    Science.gov (United States)

    Morgan, Sven S.; Nabelek, Peter I.; Student, James; Sadorski, Joseph F.

    2016-04-01

    Within the highly strained aureole surrounding the Eureka Valley-Joshua Flat-Beer Creek (EJB) composite pluton of eastern California, an inversion in microstructures and crystallographic preferred orientations (CPOs) exists with distance from the contact. An inner aureole ( slip in quartz. Within the outer aureole (250 m to 1500 m from the contact), quartzites are interbedded with pelitic schist and are completely recrystallized and microstructures are indicative of extensive GBM. CPOs are indicative of prism [c] slip. Oxygen isotope ratios in the inner aureole are only slightly shifted from their original values. Oxygen isotopes from the outer aureole are shifted more, which is consistent with equilibration with locally derived fluids. We suggest that recrystallization in the outer aureole was aided by pore water, water derived from fluid inclusions, and water generated by prograde reactions in the schists. The pore fluids in the inner aureole were also probably initially water-rich. However, during prograde reactions in the intervening calc-silicate rocks, and perhaps more importantly, between calcite cement and quartz in the quartzites, the pore fluid composition in the inner aureole changed to become dominated by CO2, which acted as a non-wetting phase and decreased the fugacity of water slowing grain boundary mobility. Low water fugacity also suppressed the activity of prism [c] slip. Therefore, we propose that dry conditions or a grain boundary fluid with a significant non-wetting component (CO2) can result in apparent temperatures of deformation that are more than 100 °C lower than the real temperatures of deformation.

  1. Host-rock controlled epigenetic, hydrothermal metasomatic origin of the Bayan Obo REEFe-Nb ore deposit, Inner Mongolia, P.R.C.

    Science.gov (United States)

    Chao, E.C.T.; Back, J.M.; Minkin, J.A.; Yinchen, R.

    1992-01-01

    Bayan Obo, a complex rare earth element (REE)FeNb ore deposit, located in Inner Mongolia, P.R.C. is the world's largest known REE deposit. The deposit is chiefly in a marble unit (H8), but extends into an overlying unit of black shale, slate and schist unit (H9), both of which are in the upper part of the Middle Proterozoic Bayan Obo Group. Based on sedimentary structures, the presence of detrital quartz and algal fossil remains, and the 16-km long geographic extent, the H8 marble is a sedimentary deposit, and not a carbonatite of magmatic origin, as proposed by some previous investigators. The unit was weakly regionally metamorphosed (most probably the lower part of the green schist facies) into marble and quartzite prior to mineralization. Tectonically, the deposit is located on the northern flank of the Sino-Korean craton. Many hypotheses have been proposed for the origin of the Bayan Obo deposit; the studies reported here support an epigenetic, hydrothermal, metasomatic origin. Such an origin is supported by field and laboratory textural evidence; 232Th/208Pb internal isochron mineral ages of selected monazite and bastnaesite samples; 40Ar/39Ar incremental heating minimum mineral ages of selected alkali amphiboles; chemical compositions of different generations of both REE ore minerals and alkali amphiboles; and evidence of host-rock influence on the various types of Bayan Obo ores. The internal isochron ages of the REE minerals indicate Caledonian ages for various episodes of REE and Fe mineralization. No evidence was found to indicate a genetic relation between the extensive biotite granitic rocks of Hercynian age in the mine region and the Bayan Obo are deposit, as suggested by previous workers. ?? 1992.

  2. Metamorphic Rock-Hosted Orogenic Gold Deposit Type as a Source of Langkowala Placer Gold, Bombana, Southeast Sulawesi

    Directory of Open Access Journals (Sweden)

    Arifudin Idrus

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v6i1.114In 2008, placer gold was discovered in Langkowala area (Bombana Regency, Southeast Sulawesi, Indonesia, and more than 60,000 traditional gold miners in the early 2009 have been operating by digging vertical pits and panning active stream sediments. The grade of placer gold ranges from 50 to 140 g/t. Local geological framework indicates that the placer gold is not related to volcanic rock-related hydrothermal gold deposit, e.g. epithermal, skarn or porphyry. This paper describes a preliminary study on possible primary deposit type as a source of the Langkowala (Bombana secondary placer gold. A field study indicates that the Langkowala (Bombana placer/paleoplacer gold is possibly related to gold-bearing quartz veins/veinlets hosted by metamorphic rocks particularly mica schist and metasediments in the area. These quartz veins/veinlets are currently recognized in metamorphic rocks at Wumbubangka Mountains, a northern flank of Rumbia Mountain Range. Sheared, segmented quartz veins/veinlets are of 2 cm to 2 m in width and contain gold in a grade varying between 2 and 61 g/t. At least, there are two generations of the quartz veins. The first generation of quartz vein is parallel to foliation of mica schist and metasediments with general orientation of N 300oE/60o; the second quartz vein generation crosscut the first quartz vein and the foliation of the wallrock. The first quartz veins are mostly sheared/deformed, brecciated, and occasionally sigmoidal, whereas the second quartz veins are relatively massive. The similar quartz veins/veinlets types are also probably present in Mendoke Mountain Range, in the northern side of Langkowala area. This primary gold deposit is called as ‘orogenic gold type’. The orogenic gold deposit could be a new target of gold exploration in Indonesia in the future.

  3. P-T and structural constraints of lawsonite and epidote blueschists from Liberty Creek and Seldovia: Tectonic implications for early stages of subduction along the southern Alaska convergent margin

    Science.gov (United States)

    López-Carmona, Alicia; Kusky, Timothy M.; Santosh, M.; Abati, Jacobo

    2011-01-01

    The southern Alaska convergent margin contains several small belts of sedimentary and volcanic rocks metamorphosed to blueschist facies, located along the Border Ranges fault on the contact between the Wrangellia and Chugach terranes. These belts are significant in that they are the most inboard, and thus probably contain the oldest record of Triassic-Jurassic northward-directed subduction beneath Wrangellia. The Liberty Creek HP-LT schist belt is the oldest and the innermost section of the Chugach terrane. Within this belt lawsonite blueschists contains an initial high-pressure assemblage formed by lawsonite + phengite + chlorite + sphene + albite ± apatite ± carbonates and quartz. Epidote blueschists are composed of sodic, sodic-calcic and calcic amphiboles + epidote + phengite + chlorite + albite + sphene ± carbonates and quartz. P-T pseudosections computed from four representative samples constrain maximum pressures at 16 kbar and 250-280 °C for the Lawsonite-bearing blueschists, and 15 kbar and 400-500 °C for the epidote-bearing blueschists, suggesting a initial subduction stage of 50-55 km depth. The growth of late albite porphyroblasts in all samples suggests a dramatic decompression from ca. 9 kbar to 5 kbar. The Liberty Creek schists can be correlated with the Seldovia blueschist belt on the Kenai Peninsula. Metamorphism in both terranes took place in the Early Jurassic (191-192 Ma), recording an early stage of subduction beneath Wrangellia. In the nearby terranes of the same margin, the age of metamorphism records an early stage of subduction at 230 Ma. Based on this difference in age, a maximum of 40 Ma were necessary to subduct the protoliths of the Seldovia and Liberty Creek blueschists to depths of circa 50-55 km, suggesting a minimum vertical component of subduction of 1.2-1.5 cm/year.

  4. Rapid cooling and exhumation as a consequence of extension and crustal thinning: Inferences from the Late Miocene to Pliocene Palu Metamorphic Complex, Sulawesi, Indonesia

    Science.gov (United States)

    Hennig, Juliane; Hall, Robert; Forster, Margaret A.; Kohn, Barry P.; Lister, Gordon S.

    2017-08-01

    Metamorphic complexes forming high mountains of 1.5-2 km in Western Sulawesi were previously considered to be Mesozoic or older basement of Gondwana crust. However, many of the metamorphic rocks are much younger than previously thought. Some have Eocene sedimentary protoliths. New geothermobarometric and geochronological data from metamorphic rocks of the Palu Metamorphic Complex (PMC) and associated granitoids provide information on the timing and mechanisms of Neogene metamorphism and contemporaneous rapid exhumation. The metamorphic rocks are strongly deformed and some were partially melted to form migmatites. Schists contain relict andalusite, cordierite, staurolite and Mn-rich garnet which are wrapped by a pervasive fabric. 40Ar/39Ar dating of biotite, white mica and amphibole from strongly deformed, mylonitic schists and recrystallised amphibolites reveals cooling occurred in the Early Pliocene (c. 5.3-4.8 Ma) in the northern part and during the Late Pliocene (c. 3.1-2.7 Ma) in the southern part of the PMC. U-Pb, 40Ar/39Ar and (U-Th)/He analyses of various minerals from PMC metamorphic and S-type magmatic rocks give very similar mid to Late Pliocene ages, indicating very fast cooling and rapid exhumation, and show the high speed at which tectonic processes, including magmatism, exhumation, and reworking into a sediment, must have occurred. The high rates could be unique to this area but we suggest they record the true speed of metamorphic complex exhumation in a very young orogenic belt. Rates in older orogens appear lower because they are averages measured over longer periods of time. Contemporaneous magmatism and deformation are interpreted as a consequence of decompressional melting due to extension and thinning of the crust, promoted by possible detachment faults and normal faulting at the major NW-trending Palu-Koro and Tambarana Faults. In contrast, I-type magmatic rocks, separated from the PMC by the Palu-Koro Fault, were exhumed from upper crustal

  5. Characterization and nutrient release from silicate rocks and influence on chemical changes in soil

    Directory of Open Access Journals (Sweden)

    Douglas Ramos Guelfi Silva

    2012-06-01

    Full Text Available The expansion of Brazilian agriculture has led to a heavy dependence on imported fertilizers to ensure the supply of the growing food demand. This fact has contributed to a growing interest in alternative nutrient sources, such as ground silicate rocks. It is necessary, however, to know the potential of nutrient release and changes these materials can cause in soils. The purpose of this study was to characterize six silicate rocks and evaluate their effects on the chemical properties of treated soil, assessed by chemical extractants after greenhouse incubation. The experimental design consisted of completely randomized plots, in a 3 x 6 factorial scheme, with four replications. The factors were potassium levels (0-control: without silicate rock application; 200; 400; 600 kg ha-1 of K2O, supplied as six silicate rock types (breccia, biotite schist, ultramafic rock, phlogopite schist and two types of mining waste. The chemical, physical and mineralogical properties of the alternative rock fertilizers were characterized. Treatments were applied to a dystrophic Red-Yellow Oxisol (Ferralsol, which was incubated for 100 days, at 70 % (w/w moisture in 3.7 kg/pots. The soil was evaluated for pH; calcium and magnesium were extracted with KCl 1 mol L-1; potassium, phosphorus and sodium by Mehlich 1; nickel, copper and zinc with DTPA; and the saturation of the cation exchange capacity was calculated for aluminum, calcium, magnesium, potassium, and sodium, and overall base saturation. The alternative fertilizers affected soil chemical properties. Ultramafic rock and Chapada mining byproduct (CMB were the silicate rocks that most influenced soil pH, while the mining byproduct (MB led to high K levels. Zinc availability was highest in the treatments with mining byproduct and Cu in soil fertilized with Chapada and mining byproduct.

  6. New views on 40Ar/39Ar dating of high pressure rock exhumation: an example from Oman

    Science.gov (United States)

    Warren, C. J.; Sherlock, S.; Kelley, S. P.

    2008-12-01

    40Ar/39Ar dating has long been considered an unreliable method for determining cooling ages of high pressure terranes as a result of the common (though not ubiquitous) presence of excess argon. New advances in analytical techniques now allow 40Ar/39Ar spots and traverses to be measured within different zones of individual mica grains, thereby creating the possibility of measuring intra-grain age changes in order to determine spatial and temporal variations of excess argon in the micas. We will present phengite single grain fusion and intra-grain UV laser 40Ar/39Ar data from a variety of rocks of different composition and metamorphic grade from Saih Hatat, NE Oman. This high pressure terrane, subducted and exhumed during the Late Cretaceous obduction of the Semail Ophiolite Complex, provides ideal material for testing and refining models of subduction-exhumation mechanisms. Single-grain 40Ar/39Ar fusion data from the highest grade phengites fall into two distinct groups. Chemically growth-zoned phengites from the mafic eclogites and surrounding calcareous and quartz schists yield a spread of ages from 80-120 Ma within individual samples, equal to the complete range of previously reported bulk 40Ar/39Ar (mainly step-heating) ages. By comparison, chemically homogeneous phengites from the interlayered eclogite-facies pelitic schists yield a single age population, with mean ages of ca. 80 Ma, similar to the previously reported 79 Ma U-Pb zircon age. The difference between the 40Ar/39Ar cooling age and the U-Pb crystallisation age indicates either remarkably rapid cooling or the presence of some excess argon. However the tight grouping of ages suggests that the excess argon is distributed similarly in each grain. The combination of these data with zircon U-Pb ages and phengite major- element chemistry, allow us to begin quantifying the behaviour of argon in high pressure phengites, and potentially determine better constrained timescales for orogenic cycling.

  7. A preserved early Ediacaran magmatic arc at the northernmost portion of the Transversal Zone central subprovince of the Borborema Province, Northeastern South America

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    Benjamim Bley de Brito Neves

    Full Text Available ABSTRACT: Magmatic arcs are an essential part of crust-forming events in planet Earth evolution. The aim of this work was to describe an early Ediacaran magmatic arc (ca. 635-580 Ma exposed in the northernmost portion of the Transversal Zone, central subprovince of Borborema Province, northeast Brazil. Our research took advantage of several syntheses by different authors, including theses and dissertations, carried out on magmatic rocks of the study area for the last 30 years. The ca. 750 km long and up to 140 km wide arc, trending ENE-WSW, is preserved to the south of the Patos Lineament, between 35º15' and 42º30'W and 7º15' and 8ºS. About 90 different stocks and batholiths of I-type granitic rocks were mapped along this orogenic zone, preferentially intruding low-grade schists of the Cryogenian-Ediacaran Piancó-Alto Brígida (SPAB belt. Three igneous supersuites are recognized: a epidote-bearing granodiorites and tonalites ("Conceição" type; b high-K calc-alkaline granites ("Itaporanga" type; c biotite granodiorites of trondhjemite affinity ("Serrita" type. A fourth group of peralkalic and shoshonitic rocks occurs to the south of the previous ones, reflecting special tectonic conditions. NNE-SSW trending Paleoproterozoic fold belts, surrounding Archean nuclei, characterize the continental part of the northern lower plate. The oceanic fraction of this lower plate was recycled by subduction and scarce remnants of which may be seen either within the enclosing low-grade schists or as xenoliths within the arc intrusions. The upper continental plate presents WSW-ENE structural trends and is composed of Neoproterozoic fold belts and Paleoproterozoic reworked basement inliers. Available data bear clear evidence of an Ediacaran magmatic arc built at the northern portion of the Transversal Zone in the Borborema Province, northeast Brazil.

  8. Silicon sources for rice crop

    Directory of Open Access Journals (Sweden)

    Pereira Hamilton Seron

    2004-01-01

    Full Text Available Although silicon is not an essential nutrient, its application is beneficial for plant growth and development. To evaluate silicon sources in relation to agronomic efficiency and economic viability in rice crops (Oryza sativa L., a greenhouse experiment was conducted, Quartzipsamment soil, in a completely randomized experimental design (n = 4. Treatments were 12 silicon sources and a control. Silicon was applied at the rate of 125 kg Si ha-1. Data were compared to a standard response curve for Si using the standard source Wollastonite at rates of 0, 125, 250, 375, and 500 kg Si ha-1. All treatments received CaCO3 and MgCO3 to balance pH, Ca and Mg. One hundred and fifty days after sowing, evaluations on dry matter yield in the above-ground part of plants, grain yield, and Si contents in the soil and plant tissues were performed. Wollastonite had linear response, increasing silicon in the soil and plants with increasing application rates. Differences between silicon sources in relation to Si uptake were observed. Phosphate slag provided the highest Si uptake, followed by Wollastonite and electric furnace silicates which however, did not show differed among themselves. The highest Si accumulation in grain was observed for stainless steel, which significantly differed from the control, silicate clay, Wollastonite, and AF2 (blast furnace of the company 2 slag. Silicate clay showed the lowest Si accumulation in grain and did not differ from the control, AF2 slag, AF1 slag, schist ash, schist, and LD4 (furnace steel type LD of the company 4 slag.

  9. Late Paleozoic accretionary complexes on the Gondwana margin of southern Chile: Evidence from the Chonos Archipelago

    Science.gov (United States)

    Davidson, John; Mpodozis, Constantino; Godoy, Estanislao; Hervé, Francisco; Pankhurst, Robert; Brook, Maureen

    The late Paleozoic "basement" rocks that crop out along the Pacific side of the Chonos Archipelago (44°-46°S) can be divided into two north-south trending belts: (1) an eastern belt formed of submarine fan-turbidites and subordinate pelagic cherts, each containing well-preserved primary sedimentary structures, and (2) a western belt, mainly formed by strongly foliated mica schists and greenschists. Trace element contents in the cherts and greenschists indicate rocks of oceanic affinity. The structures present within the eastern rock suite are principally subiso-clinal folds (with tectonic imbrication) and locally developed zones of broken formation. The transition from these rocks into the foliated schists appears to be related to a progressive increase in metamorphism and strain associated with the development of westward verging recumbent folds and a flat-lying crenulation cleavage. It is inferred that these structures developed during the construction of a Late Carboniferous-Early Permian accretionary prism (about 260 Ma Rb-Sr ages), although sedimentation may have taken place throughout the upper Paleozoic. Rb-Sr whole-rock isochrons giving Late Jurassic to Early Cretaceous ages for some localities may indicate much later development of S2 structures. Alternatively, they may represent isotopic resetting by hydrothermal effects during the emplacement of transgressive Early Cretaceous granites, one of which gives a new Rb-Sr isochron age of 125±2Ma. This overall scenario seems to be consistent with that reported in the slightly older coastal metamorphic basement north of 34°S and equivalent or younger complexes farther south in the Madre de Dios Archipelago.

  10. Pressure-temperature evolution of Neoproterozoic metamorphism in the Welayati Formation (Kabul Block), Afghanistan

    Science.gov (United States)

    Collett, Stephen; Faryad, Shah Wali

    2015-11-01

    The Welayati Formation, consisting of alternating layers of mica-schist and quartzite with lenses of amphibolite, unconformably overlies the Neoarchean Sherdarwaza Formation of the Kabul Block that underwent Paleoproterozoic granulite-facies and Neoproterozoic amphibolite-facies metamorphic events. To analyze metamorphic history of the Welayati Formation and its relations to the underlying Sherdarwaza Formation, petrographic study and pressure-temperature (P-T) pseudosection modeling were applied to staurolite- and kyanite-bearing mica-schists, which crop out to the south of Kabul City. Prograde metamorphism, identified by inclusion trails and chemical zonation in garnet from the micaschists indicates that the rocks underwent burial from around 6.2 kbar at 525 °C to maximum pressure conditions of around 9.5 kbar at temperatures of around 650 °C. Decompression from peak pressures under isothermal or moderate heating conditions are indicated by formation of biotite and plagioclase porphyroblasts which cross-cut and overgrow the dominant foliation. The lack of sillimanite and/or andalusite suggests that cooling and further decompression occurred in the kyanite stability field. The results of this study indicate a single amphibolite-facies metamorphism that based on P-T conditions and age dating correlates well with the Neoproterozoic metamorphism in the underlying Sherdarwaza Formation. The rocks lack any paragenetic evidence for a preceding granulite-facies overprint or subsequent Paleozoic metamorphism. Owing to the position of the Kabul Block, within the India-Eurasia collision zone, partial replacement of the amphibolite-facies minerals in the micaschist could, in addition to retrogression of the Neoproterozoic metamorphism, relate to deformation associated with the Alpine orogeny.

  11. Neoproterozoic extension in the greater dharwar craton: A reevaluation of the "betsimisaraka suture" in madagascar

    Science.gov (United States)

    Tucker, R.D.; Roig, J.-Y.; Delor, C.; Amlin, Y.; Goncalves, P.; Rabarimanana, M.H.; Ralison, A.V.; Belcher, R.W.

    2011-01-01

    The Precambrian shield of Madagascar is reevaluated with recently compiled geological data and new U-Pb sensitive high-resolution ion microprobe (SHRIMP) geochronology. Two Archean domains are recognized: the eastern Antongil-Masora domain and the central Antananarivo domain, the latter with distinctive belts of metamafic gneiss and schist (Tsaratanana Complex). In the eastern domain, the period of early crust formation is extended to the Paleo-Mesoarchean (3.32-3.15 Ga) and a supracrustal sequence (Fenerivo Group), deposited at 3.18 Ga and metamorphosed at 2.55 Ga, is identified. In the central domain, a Neoarchean period of high-grade metamorphism and anatexis that affected both felsic (Betsiboka Suite) and mafic gneisses (Tsaratanana Complex) is documented. We propose, therefore, that the Antananarivo domain was amalgamated within the Greater Dharwar Craton (India + Madagascar) by a Neoarchean accretion event (2.55-2.48 Ga), involving emplacement of juvenile igneous rocks, high-grade metamorphism, and the juxtaposition of disparate belts of mafic gneiss and schist (metagreenstones). The concept of the "Betsimisaraka suture" is dispelled and the zone is redefined as a domain of Neoproterozoic metasedimentary (Manampotsy Group) and metaigneous rocks (Itsindro-Imorona Suite) formed during a period of continental extension and intrusive igneous activity between 840 and 760 Ma. Younger orogenic convergence (560-520 Ma) resulted in east-directed overthrusting throughout south Madagascar and steepening with local inversion of the domain in central Madagascar. Along part of its length, the Manampotsy Group covers the boundary between the eastern and central Archean domains and is overprinted by the Angavo-Ifanadiana high-strain zone that served as a zone of crustal weakness throughout Cretaceous to Recent times.

  12. Ore Mineralogy Features of Hayriye and Arapdede Mineralizations in (Inegol-Bursa) Area

    Science.gov (United States)

    Sendir, Hüseyin; Kocatürk, Hüseyin; Cesur, Duru; Toygar, Özlem

    2016-04-01

    Western Anatolia (Turkey) experienced widespread Cenozoic magmatism after the collision between the Sakarya and Anatolide-Tauride continental blocks in the pre-middle Eocene. The widespread magmatic activity in NW Anatolia postdates this continental collisional event in the region. The following magmatic episode during the Oligocene and Early Miocene is known to have produced the widespread granitic plutons. Many skarn mineralization associated with plutons formed in the region (such as Hayriye and Arapdede Mineralizations). The Paleozoic aged Devlez Metabasite is the oldest unit of the study area. This unit includes amphibolite, glaucophane-lawsonite schist, muscovite schists. The unit has widely spread in area. This units are overlain unconformably by the Geyiktepe Marbles. Paleocene aged Domaniç granitoidic intrusives cut other rock series and located as a batholite. Magmatic units present porphyric and holocrystalline textures. Granitoidic intrusions are represented by tonalite, tonalite porphyr, granodiorite, granodiorite porphyr, granite, diorite, diorite porphyries. The Domaniç granitoid intruded in to the metamorphides during Paleocene and caused formations of skarn zones and related Cu-Pb-Zn mineralizations along the contacts. Mineralizations are known in the locations named as Arapdede and Hayriye. The mineralizations occur along the metamorphites - plutonics contact, in the pockets and fractures extending towards marble. The thickness of the mineralized bodies can reach up to 1 -2 m. Primary minerals are galenite, magnetite, pyrite, chalcopyrite and sphalerite at Hayriye mineralizations and sphalerite, galenite, chalcopyrite and pyrite minerals at the Arapdede mineralizations. This study supported by ESOGU BAP (201115031) Keywords: Ore mineralogy, mineralization, Cu-Pb-Zn deposits, Inegöl (Bursa).

  13. Root development during soil genesis: effects of root-root interactions, mycorrhizae, and substrate

    Science.gov (United States)

    Salinas, A.; Zaharescu, D. G.

    2015-12-01

    A major driver of soil formation is the colonization and transformation of rock by plants and associated microbiota. In turn, substrate chemical composition can also influence the capacity for plant colonization and development. In order to better define these relationships, a mesocosm study was set up to analyze the effect mycorrhizal fungi, plant density and rock have on root development, and to determine the effect of root morphology on weathering and soil formation. We hypothesized that plant-plant and plant-fungi interactions have a stronger influence on root architecture and rock weathering than the substrate composition alone. Buffalo grass (Bouteloua dactyloides) was grown in a controlled environment in columns filled with either granular granite, schist, rhyolite or basalt. Each substrate was given two different treatments, including grass-microbes and grass-microbes-mycorrhizae and incubated for 120, 240, and 480 days. Columns were then extracted and analyzed for root morphology, fine fraction, and pore water major element content. Preliminary results showed that plants produced more biomass in rhyolite, followed by schist, basalt, and granite, indicating that substrate composition is an important driver of root development. In support of our hypothesis, mycorrhizae was a strong driver of root development by stimulating length growth, biomass production, and branching. However, average root length and branching also appeared to decrease in response to high plant density, though this trend was only present among roots with mycorrhizal fungi. Interestingly, fine fraction production was negatively correlated with average root thickness and volume. There is also slight evidence indicating that fine fraction production is more related to substrate composition than root morphology, though this data needs to be further analyzed. Our hope is that the results of this study can one day be applied to agricultural research in order to promote the production of crops

  14. Fissured Rocks and Water Reservoirs in Eastern Thessaly Mountain Range, Greece (Olympus, Ossa, Maurovouni and Pelion): The Role of Tectonic Deformation

    Science.gov (United States)

    Papanikolaou, I.; Migiros, G.; Stamatis, G.; Yoxas, G.

    2009-04-01

    The storage capacity of fractured hard rocks is lower than porous media and karst formations, though they can yield groundwater of sufficiently good quality for drinking purposes and may host important water resources, even if they are often of low permeability. In particular, for countries like Greece, where water needs for the local population and the tourist industry are excessive and waterfall limited, these reservoirs are of strategic importance. The mountain Range in Eastern Thessaly comprises an extensive nappe of metamorphic rocks, consisting of schists, gneisses, involving partly some ophiolithic rocks and marble intercalations. The thickness of the nappe exceeds 600 m in Ossa, whereas in the area of Pelion is estimated up to 3.000 m. This nappe rests on top of the Autochthonous Olympus- Ossa unit, which forms a massive Mesozoic carbonate sequence. Extensive fieldwork data supported by the analysis of the physical and chemical properties of a large number of springs and combined by the study of the geological structure both local and regional, resulted in important outcomes regarding the fissured rocks permeability, water flow and springs distribution. Schists are characterized by heterogeneity regarding their permeability features. They are divided into hard-rocks where quartz, epidote and amphiboles prevail, displaying higher permeability and soft-rocks where clay minerals prevail, exhibiting low permeability features, because the presence of clay blocks the fissures and prevent any infiltration process. The marbles are of high permeability, but are of limited extent. A few springs are located in marbles, but the vast majority of the springs are associated to the hard-rock schists, are scattered and characterized by high seasonal discharges. In the area of Ossa in particular, the most important reservoirs exist at the bordering zones of the metamorphic and the post-alpine formations due to the enrichment of the sedimentary post-alpine formations. In the

  15. Lulak Abad Iron Occurrence, Northwest of Zanjan: Metamorphosed and Deformed Volcano-Sedimentary Type of Mineralization in Central Iran

    Directory of Open Access Journals (Sweden)

    Mehri Karami

    2016-07-01

    Full Text Available Keywords: Iron mineralization, hydrothermal vein, alteration, Lulak Abad, Zanjan, Central Iran Introduction The Lulak Abad iron occurrence is located in the northwestern part of the Central Iran, 55 km west of Zanjan. Mineralization at the Lulak Abad area was originally identified by Zamin Gostar Company (2007, during a geophysical exploration. The present paper provides an overview of the geological framework, the mineralization characteristics, and the results of a geochemical study of the Lulak Abad iron occurrence with an application to the ore genesis. Identification of these characteristics can be used as a model for exploration of this type of iron mineralization in the Central Iran and elsewhere. Materials and methods Detailed field work was carried out at different scales (give scales in parentheses in the Lulak Abad area. About 16 polished thin and thin sections from host rocks and mineralized and altered zones were studied by conventional petrographic and mineralogical methods at the Department of Geology, University of Zanjan. In addition, a total of 7 samples from ore zones at the Lulak Abad occurrence were analyzed by ICP-OES for minor and trace elements and REE compositions at Geological Survey of Iran, Tehran, Iran. Result Rock units exposed in the Lulak Abad area consist of schists and metavolcanic units the Kahar Formation; Lotfi, 2001 that were intruded by granite and microdiorite bodies. The schist units consist of chlorite-biotite-muscovite schist and muscovite schist that show granolepidoblastic texture with foliation-parallel disseminated magnetite. The metavolcanic units consist of metadacite, rhyolitic metatuff and meta-andesite with porphyritic textures. They are marked by dominant mylonitic foliation surrounding feldspar and quartz porphyroclasts. Alkali feldspar and quartz are the principal minerals of the granite. The intrusion is characterized by intense deformation features and is highly mylonitized. Based on field

  16. Thermal evolution and exhumation of deep-level batholithic exposures, southernmost Sierra Nevada, California

    Science.gov (United States)

    Saleeby, J.; Farley, K.A.; Kistler, R.W.; Fleck, R.J.

    2007-01-01

    The Tehachapi complex lies at the southern end of the Sierra Nevada batholith adjacent to the Neogene-Quaternary Garlock fault. The complex is composed principally of high-pressure (8-10 kbar) Cretaceous batholithic rocks, and it represents the deepest exposed levels of a continuous oblique crustal section through the southern Sierra Nevada batholith. Over the southern ???100 km of this section, structural/petrologic continuity and geochronological data indicate that ???35 km of felsic to intermediate-composition crust was generated by copious arc magmatism primarily between 105 and 99 Ma. In the Tehachapi complex, these batholithic rocks intrude and are bounded to the west by similar-composition gneissic-textured high-pressure batholithic rocks emplaced at ca. 115-110 Ma. This lower crustal complex is bounded below by a regional thrust system, which in Late Cretaceous time tectonically eroded the underlying mantle lithosphere, and in series displaced and underplated the Rand Schist subduction assemblage by low-angle slip from the outboard Franciscan trench. Geophysical and mantle xenolith studies indicate that the remnants of this shallow subduction thrust descend northward through the crust and into the mantle, leaving the mantle lithosphere intact beneath the greater Sierra Nevada batholith. This north-dipping regional structure records an inflection in the Farallon plate, which was segmented into a shallow subduc-tion trajectory to the south and a normal steeper trajectory to the north. We combine new and published data from a broad spectrum of thermochronom-eters that together form a coherent data array constraining the thermal evolution of the complex. Integration of these data with published thermobarometric and petro-genetic data also constrains the tectonically driven decompression and exhumation history of the complex. The timing of arc magmatic construction of the complex, as denoted above, is resolved by a large body of U/Pb zircon ages. High

  17. Mineralogical variation of skarn ore from the Tellerhäuser deposit, Pöhla, Germany

    Science.gov (United States)

    Simons, Bethany; Andersen, Jens Christian; Rollinson, Gavyn; Armstrong, Robin; Dolgopolova, Alla; Seltmann, Reimar; Stanley, Chris; Roscher, Marco

    2017-04-01

    The polymetallic Zn-Fe-Sn-Cu-In skarns at Pöhla Tellerhäuser in the western Erzgebirge represent some of the largest unexploited occurrences of Sn and In in Europe. The skarns developed in schists and gneisses at the margin of the Schwarzenberg Gneiss cupola and the Eibenstock granites. The flat-lying skarn layers display extreme mineralogical variability with alternating units of pyroxene, sphalerite, magnetite, amphibole and calc-silicate skarns with hanging wall schist and feeder stockwork. The polymetallic skarn ores represent a complex challenge for mineral processing, with fine-grained, locked target minerals and partitioning of target metals into silicates (e.g. Sn in malayaite). Optical microscopy, QEMSCAN® and electron-probe microanalysis have been used to determine the mineralogical variability of the skarn types with the aim to determine the deportment of the target metals to guide mineral processing test work. The composition of the skarns is extremely variable reflecting the complex mineralogy and indicating substantial variability associated with replacement reactions through the protolith(s). Cassiterite (SnO2) is the dominant Sn-bearing mineral in all the skarn types. However, the skarns also carry malayaite (CaSnO[SiO4], up to 0.03 vol%), which locally dominates over cassiterite. Cassiterite is intergrown with Fe-amphibole, grossular garnet, fluorite and magnetite. The cassiterite is unaltered, but some grains have rare iron oxide rims and inclusions. Malayaite shows a similar association to cassiterite and is intergrown as clusters of grains with silicate gangue, particularly Fe amphibole and grossular garnet and remains unaltered with no inclusions. Zinc is exclusively hosted in sphalerite and varies from 0.02 wt.% in the hanging wall schist to 36.5 wt.% in the sphalerite skarn. The high Zn values are accompanied by high values of Cd (locally in excess of 1000 ppm) and In (up to 180 ppm). Sphalerite grains are locally up to 4 mm, subhedral

  18. The composition of Alpine marine sediments (Bündnerschiefer Formation, W Alps) and the mobility of their chemical components during orogenic metamorphism

    Science.gov (United States)

    Garofalo, Paolo S.

    2012-01-01

    The Bündnerschiefer of the Swiss-Italian Alps is a large sedimentary complex deposited on the Piemonte-Liguria and Valais oceans and associated continental margins from the upper Jurassic to Eocene. It is made of a large variety of sequences associated or not with an ophiolitic basement. The Bündnerschiefer makes an accretionary prism that developed syn-tectonically from the onset of alpine subduction, and it records orogenic metamorphism following episodes of HP metamorphism. The Bündnerschiefer shares important similarities with the Otago schists of New Zealand and with the Wepawaug schists of Connecticut, both of which form accretionary prisms and have an orogenic metamorphic imprint. With the aim of testing the hypothesis of mobility of chemical components as a function of metamorphic grade, in this work I present fifty-five bulk chemical analyses of various lithological facies of the Bündnerschiefer collected along the well-studied field gradient of the Lepontine dome of Central Switzerland, in the Prättigau half window of East Switzerland, and in the Tsaté Nappe of Valle d'Aosta (Italy). The dataset includes the concentration of major components, large ion lithophile elements (Rb, Sr, Ba, Cs), high field strength elements (Zr, Ti, Nb, Th, U, Ta, Hf), fluid-mobile light elements (B, Li), volatiles (CO 2, S), REEs, and Y, V, Cr, Co, Sn, Pb, Cu, Zn, Tl, Sb, Be, and Au. These data are compared against the compositions of the global marine sediment reservoir, typical crustal reservoirs, and against the previously measured compositions of Otago and Wepawaug schists. Results reveal that, irrespective of their metamorphic evolution, the bulk chemical compositions of orogenic metasediments are characterized by mostly constant compositional ratios ( e.g., K 2O/Al 2O 3, Ba/Al 2O 3, Sr/CaO, etc.), whose values in most cases are undistinguishable from those of actual marine sediments and other crustal reservoirs. For these rocks, only volatile concentrations

  19. Reconnaissance Geologic Map of the Hayfork 15' Quadrangle, Trinity County, California

    Science.gov (United States)

    Irwin, William P.

    2010-01-01

    The Hayfork 15' quadrangle is located just west of the Weaverville 15' quadrangle in the southern part of the Klamath Mountains geologic province of northern California. It spans parts of six generally north-northwest-trending tectonostratigraphic terranes that are, from east to west, the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, Western Hayfork, and Rattlesnake Creek terranes. Remnants of a once-widespread postaccretionary overlap assemblage, the Cretaceous Great Valley sequence, crop out at three localities in the southern part of the Hayfork quadrangle. The Tertiary fluvial and lacustrine Weaverville Formation occupies a large, shallow, east-northeast-trending graben in the south half of the quadrangle. The small area of Eastern Klamath terrane is part of the Oregon Mountain outlier, which is more widely exposed to the east in the Weaverville 15' quadrangle. It was originally mapped as a thrust plate of Bragdon(?) Formation, but it is now thought by some to be part of an outlier of Yreka terrane that has been dislocated 60 km southward by the La Grange Fault. The Central Metamorphic terrane, which forms the footwall of the La Grange Fault, was formed by the eastward subduction of oceanic crustal basalt (the Salmon Hornblende Schist) and its overlying siliceous sediments with interbedded limestone (the Abrams Mica Schist) beneath the Eastern Klamath terrane. Rb-Sr analysis of the Abrams Mica Schist indicates a Middle Devonian metamorphic age of approximately 380 Ma, which probably represents the age of subduction. The North Fork terrane, which is faulted against the western boundary of the Central Metamorphic terrane, consists of the Permian(?) North Fork ophiolite and overlying broken formation and melange of Permian to Early Jurassic (Pliensbachian) marine metasedimentary and metavolcanic rocks. The ophiolite, which crops out along the western border of the terrane, is thrust westward over the Eastern Hayfork terrane. The Eastern

  20. Geologic Map of the Weaverville 15' Quadrangle, Trinity County, California

    Science.gov (United States)

    Irwin, William P.

    2009-01-01

    The Weaverville 15' quadrangle spans parts of five generally north-northwest-trending accreted terranes. From east to west, these are the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, and Western Hayfork terranes. The Eastern Klamath terrane was thrust westward over the Central Metamorphic terrane during early Paleozoic (Devonian?) time and, in Early Cretaceous time (approx. 136 Ma), was intruded along its length by the massive Shasta Bally batholith. Remnants of overlap assemblages of the Early Cretaceous (Hauterivian) Great Valley sequence and the Tertiary Weaverville Formation cover nearly 10 percent of the quadrangle. The base of the Eastern Klamath terrane in the Weaverville quadrangle is a peridotite-gabbro complex that probably is correlative to the Trinity ophiolite (Ordovician), which is widely exposed farther north beyond the quadrangle. In the northeast part of the Weaverville quadrangle, the peridotite-gabbro complex is overlain by the Devonian Copley Greenstone and the Mississippian Bragdon Formation. Where these formations were intruded by the Shasta Bally batholith, they formed an aureole of gneissic and other metamorphic rocks around the batholith. Westward thrusting of the Eastern Klamath terrane over an adjacent body of mafic volcanic and overlying quartzose sedimentary rocks during Devonian time formed the Salmon Hornblende Schist and the Abrams Mica Schist of the Central Metamorphic terrane. Substantial beds of limestone in the quartzose sedimentary unit, generally found near the underlying volcanic rock, are too metamorphosed for fossils to have survived. Rb-Sr analysis of the Abrams Mica Schist indicates a metamorphic age of approx. 380 Ma. West of Weavervillle, the Oregon Mountain outlier of the Eastern Klamath terrane consists mainly of Bragdon Formation(?) and is largely separated from the underlying Central Metamorphic terrane by serpentinized peridotite that may be a remnant of the Trinity ophiolite. The North Fork

  1. Microtectonic-assisted P-T determination on low-grade Alpine metamorphic rocks from the "Tisia Mega-Unit" of the Slavonian Mountains in Croatia

    Science.gov (United States)

    Balen, Dražen; Lihter, Iva; Massonne, Hans-Joachim

    2016-04-01

    The internal structure of the Tisia (Tisza) Mega-Unit in the Alpine-Carpathian-Dinaridic orogenic system encompasses large Alpine nappe systems brought to its present-day position by complex regional-scale movements. The Slavonian Mountains are part of the Bihor nappe system which is below the Codru and above the Mecsek nappe systems. The low-grade metamorphic schist unit of the Slavonian Mountains includes numerous rocks which were previously related to Precambrian and/or Lower Paleozoic orogeneses. However, recent studies (e.g. Balen, 2014, European Geosciences Union General Assembly, EGU 2014-6122) show that the metapelites of this unit should be attributed to the Alpine orogeny and the poorly known P-T conditions, which they experienced, should be refined. Although metapelites can be sensitive to changes of metamorphic conditions and, therefore, be suitable for the P-T estimation of metamorphic event(s), the extraction of mineral assemblages, being in equilibrium, and associated microtectonic data for particular low-grade metamorphic rocks is not straightforward. On the contrary, due to lack of suitable minerals and complex mictotectonic features, one can be faced with a severe problem concerning (dis)equilibrium. To avoid this, the observation scale in the research was set to the sub-mm level taking into account microtectonic positions of minerals. The investigated samples from the Slavonian Mountains are fine-grained schists consisting of chlorite (15-30 vol. %), white mica (15-25 vol. %), quartz (10-25 vol. %), feldspars (albite 10-15 vol. %; some K-feldspar), biotite (<5 vol. %), opaques (<5 vol. %), and accessory minerals (zircon, monazite, xenotime, apatite, chalcopyrite, pyrite, barite, parisite-(Ce), rutile). The schists show complex microtectonic fabric including well-developed foliations, pervasive folding, crenulation and cleavage. Foliations are defined by the preferred orientation of phyllosilicates and thin quartz and feldspar ribbons. Chlorite

  2. Sanford Underground Research Facility - The United State's Deep Underground Research Facility

    Science.gov (United States)

    Vardiman, D.

    2012-12-01

    The 2.5 km deep Sanford Underground Research Facility (SURF) is managed by the South Dakota Science and Technology Authority (SDSTA) at the former Homestake Mine site in Lead, South Dakota. The US Department of Energy currently supports the development of the facility using a phased approach for underground deployment of experiments as they obtain an advanced design stage. The geology of the Sanford Laboratory site has been studied during the 125 years of operations at the Homestake Mine and more recently as part of the preliminary geotechnical site investigations for the NSF's Deep Underground Science and Engineering Laboratory project. The overall geology at DUSEL is a well-defined stratigraphic sequence of schist and phyllites. The three major Proterozoic units encountered in the underground consist of interbedded schist, metasediments, and amphibolite schist which are crosscut by Tertiary rhyolite dikes. Preliminary geotechnical site investigations included drift mapping, borehole drilling, borehole televiewing, in-situ stress analysis, laboratory analysis of core, mapping and laser scanning of new excavations, modeling and analysis of all geotechnical information. The investigation was focused upon the determination if the proposed site rock mass could support the world's largest (66 meter diameter) deep underground excavation. While the DUSEL project has subsequently been significantly modified, these data are still available to provide a baseline of the ground conditions which may be judiciously extrapolated throughout the entire Proterozoic rock assemblage for future excavations. Recommendations for facility instrumentation and monitoring were included in the preliminary design of the DUSEL project design and include; single and multiple point extensometers, tape extensometers and convergence measurements (pins), load cells and pressure cells, smart cables, inclinometers/Tiltmeters, Piezometers, thermistors, seismographs and accelerometers, scanners (laser

  3. Structure, petrology and U-Pb zircon age of Mesoproterozoic nepheline syenites from the Rengali Province, eastern India: Implications for their petrogenesis and geodynamic evolution

    Science.gov (United States)

    Sheikh, Janisar M.; Champati, Anil K.; Patel, Suresh C.; Prabhakar, Naraga; Gerdes, Axel

    2017-04-01

    Three Mesoproterozoic nepheline syenite intrusions, namely Chhatabar, Lodhajhari and Baradangua intrusions, have been concordantly emplaced within a polydeformed and amphibolite facies metamorphosed sedimentary sequence (quartzites and mica schists) in the Rengali Province, eastern India. The metasedimentary sequence and the nepheline syenite intrusions both record three phases of folding (F1, F2 and F3). The penetrative fabric in quartzites is a schistosity (S1SS), while that in mica schists is a crenulation cleavage (S2SS), which has transposed to S1SS. The nepheline syenite intrusions exhibit magmatic to solid state deformation structures and microstructures. Magmatic layering in the rocks is commonly transposed by a prominent schistosity (S1NN). Fold geometries and deformation fabrics of the metasedimentary sequence and the nepheline syenites indicate that the latter were emplaced syntectonically during F1 folding of the metasedimentary sequence. The dominant rock type in the intrusions is nepheline syenite, while nepheline monzosyenite and nepheline monzodiorite occur in subordinate amounts in the form of centimeter to metre scale layers. Essential felsic minerals in the rocks are microcline (Or88-92Ab8-12) and nepheline, while sodic plagioclase (Ab88-96An4-12Or0.3-1.4) is additionally present in nepheline monzosyenite and nepheline monzodiorite. End member compositions of nephelines (Ne77-80Ks17-20Qtz1.6-3.6An0.5-2.6) fall below the 500oC isotherm in the nepheline-kalsilite-quartz projection from anorthite which indicates low temperature re-equilibration of the mineral after magmatic crystallization. Common mafic minerals in the rocks include biotite and amphibole, the latter being taramite in nepheline syenite, and hastingsite in nepheline monzosyenite and nepheline monzodiorite. Melt-present deformation microstructures which indicate syntectonic emplacement of the intrusions include late magmatic grains of nearly pure albite (Ab98-99An0.8-1.5Or0.2-0.6) and

  4. Aplicações de fertilizantes foliares na nutrição e na produção do pimentão e do tomateiro Foliar fertilizer applications on nutrition and yield of sweet pepper and tomato

    Directory of Open Access Journals (Sweden)

    Hamilton S. Pereira

    2002-12-01

    Full Text Available Avaliou-se a eficiência de fertilizantes foliares, contendo Ca e B, na nutrição e produção do pimentão cv. Mayata e do tomate cv. Carmem, cultivados em estufas. O delineamento experimental foi de blocos ao acaso com seis tratamentos, três e quatro repetições, respectivamente, para o tomateiro e pimentão. Os tratamentos foram a água de retortagem de xisto (100; 78; 3,0; 12,5; 3,0; 12,5; 4,0 e 0,2 g.L-1 de N, K, S, Ca, Mg, B, Mn e Mo, respectivamente a 0,1; 0,25; 0,5 e 1%; os sais ácido bórico (170 g.kg-1 de B a 0,15% mais cloreto de cálcio a 0,15% e o quelato de cálcio (200 g.kg-1 de Ca a 0,1% e boro orgânico (10 g.kg-1 de B a 0,15%. A aplicação de água de retortagem de xisto a 0,5% via foliar aumentou em 27,4% a produção de frutos de pimentão e os teores foliares de Mg e S em relação à aplicação desse fertilizante a 0,1%. Para o tomateiro, as pulverizações com água de retortagem de xisto a 0,5 e 1% elevaram em 60,5 e 93,8% a produção de frutos em comparação à menor dose desse fertilizante. Os maiores teores de B nas folhas de pimentão e de tomate foram obtidos com as aplicações de sais e resultaram em sintomas visuais de toxicidade de B no início do desenvolvimento das culturas.The efficiency of foliar fertilizers was evaluated on nutrition and yield of sweet pepper cv. Mayata and tomato cv. Carmem, cultivated in plastic greenhouse. For the two experiments the experimental design consisted of randomized blocks with three and four replications for tomato and sweet pepper, respectively, and six treatments (schist retortage water 0.1; 0.25; 0.5 and 1%; boric acid 0.15% plus clorate calcium 0.15% and quelate Ca 0.1% plus organic B 0.15%. The foliar application of schist retortage water 0.5% increased 27.4% the sweet pepper fruit yield and foliar concentrations of Mg and S compared to this fertilizer 0.1%. For tomato, the application of schist retortage water 0.5 and 1% increased 60.5 and 93.8% the fruit yield

  5. Tectonic evolution of the western boundary of the Attico-Cycladic complex (Lavrio, Greece)

    Science.gov (United States)

    Scheffer, Christophe; Vanderhaeghe, Olivier; Tarantola, Alexandre; Lanari, Pierre; Ponthus, Leandre; France, Lyderic; Photiades, Adonis

    2015-04-01

    The Lavrio peninsula, South East of Athens, is located along the western boundary of the Attic-Cycladic Metamorphic Complex in the internal zone of the Hellenic orogenic belt, at the intersection between thrusts and detachments. It is thus a perfect target to decipher the tectonic evolution of an orogenic wedge from tectonic accretion to gravitational collapse. The nappe stack is overlain by a non-metamorphic limestone and is made, from top to bottom by (i) an ophiolitic melange, (ii) the Lavrio tectonic unit dominated by schists and displaying mineral paragenesis typical of blueschist facies, (iii) the Kamariza tectonic unit dominated by marbles and affected by pervasive greenschist facies metamorphism. The Lavrio and Kamariza tectonic units are juxtaposed by a low-angle mylonitic to cataclastic detachement. A more detailed investigation of the relationships between mineral paragenesis and microstructures indicates that the transition from the Lavrio to the Kamariza tectonic units, across the low-angle detachment, is marked by progressive transposition of the blueschist facies fabric coeval with retrogression under greenschist facies conditions. Indeed, the Kamariza unit is characterized by a relatively steep foliation associated with isoclinal folds of weakly organized axial orientation that is partially to totally transposed into a shallow dipping foliation bearing a N-S trending lineation. The degree of transposition increases from top to bottom and is particularly marked at the transition from the Lavrio to the Kamariza unit across the low-angle detachement. The blueschist facies foliation of the Lavrio schists is underlined by glaucophane and HP phengite intergrown with chlorite crystals. The Kamariza tectonic unit is dominated by LP phengite intergrown with chlorite but contains relics of the blueschist mineral paragenesis. Detailed microprobe mapping of the composition of the phengite and chlorite crystals reveal distinct variations of the PT conditions

  6. Recurrent metalliferous fluid flow, Khetri Copper Belt, northern Rajasthan, NW India

    Science.gov (United States)

    Stein, Holly J.; Pandit, Manoj K.; Hannah, Judith L.; Torsvik, Trond H.

    2013-04-01

    Proterozoic copper deposits in deformed sedimentary rocks present a challenging geologic environment for unraveling ore history. Typically, copper ores are broadly but not strictly stratabound and show deformed, less deformed and undeformed generations. A common observation is a late oxidation episode, unrelated to modern weathering, which affects primary sulfides. Thus, formation of Proterozoic copper deposits may span intervals of time within larger orogenic histories, with ores episodically upgraded or even downgraded by multiple generations of introduced fluids moving at regional scales. U-Pb dating of standard minerals (monazite, titanite, zircon) in Proterozoic copper belts is challenging as the isotope systematics may respond unfavorably to post-depositional ingress of fluids. Re-Os dating, on the other hand, can be used to target specific generations of sulfide minerals, thereby directly dating fluid-flow events that move metals. Application of Re-Os dating in multiply-deformed Proterozoic terranes is not without challenge, however, especially when a record of oxidation is clearly visible in the ore-forming history. Utmost care in sampling within a well-defined paragenesis and regional geologic setting is essential. Sulfide mineralization is well known from the Archean-Proterozoic Aravalli-Delhi fold belt in NW India. The northern Delhi fold belt contains the rich Khetri Cu belt, which is hosted in the Ajabgarh Group (quartz-biotite schists, retrograde chlorite-garnet-magnetite-hematite schists, banded amphibolite-quartzites, graphitic schists, calc-silicate units) within the Middle Proterozoic Delhi Supergroup. Recent U-Pb dating of key units in the southern Aravalli-Delhi fold belt reveals a complex history of Neoproterozoic magmatism (1 Ga and 850-750 Ma) along the western side. The northern Delhi fold belt, in contrast, has far fewer radiometric ages other than 1.8 to 1.7 Ga ages for basement granitoids. We provide some of the first geochronology for

  7. Primeras evidencias de arte mueble paleolítico en el sur de Portugal

    Directory of Open Access Journals (Sweden)

    Simón Vallejo, María D.

    2012-06-01

    Full Text Available This paper presents the first evidence for Palaeolithic portable art in Southern Portugal. This include two plaques, dated between 20,500 and 19,500 BP from Solutrean levels from the site of Vale Boi, Western Algarve (Portugal. One of the pieces is a small engraved schist plaque (14,6 × 8,1 mm with abstract lines on one side. The other artefact is an 8 × 5 cm schist plaque. One side is an oxide natural deposit, used to produce dye; the other side has three aurochs and a probable cervid. Stilistic information and the engraving sequence indicate probably production by a single artist. The stylistic characteristics are in full agreement withi those from late Gravettian and early Solutrean art known from Valencia, Andalucia (Spain and the Côa valley (Portugal, thus confirming the absolute AMS dates from the Vale Boi Levels.

    En este trabajo presentamos la primera evidencia de arte mueble paleolítico en el sur de Portugal: dos plaquetas de pizarra procedentes de niveles solutrenses del yacimiento de Vale Boi, zona occidental del Algarve (Portugal. La primera de las piezas es una pequeña placa (14,6 × 8,1 mm que presenta sobre una de sus caras un ideomorfo grabado. La segunda (8 × 5 cm cuenta con una superficie ocupada por óxido de hierro natural de color amarillento, tiene claros indicios de extracción de mineral para producir colorantes. En la superficie opuesta han sido grabados tres uros y una posible cierva. El estilo y secuencia de los grabados apuntan a un solo artista. Las características estilísticas de los zoomorfos concuerdan bien con los rasgos comunes del arte del ciclo Gravetiense final y Solutrense antiguo del País Valenciano, Andalucía y Valle de Côa (Portugal. Esta afinidad sintoniza asimismo con las fechas AMS de los niveles solutrenses de Vale Boi, datados entre ca. 20.500 y 19.500 BP.

  8. Occurrence and Mineralogical Characteristics of Tremolite Asbestos Occurred in Boryeong area, Chungnam, South Korea

    Science.gov (United States)

    Yoon, K.; Hwang, J.; Oh, J.; Lee, H.

    2009-12-01

    Abandoned tremolite mines, which had been exploited for several decades since 1930, are distributed in Boryeong, Chungnam. It is known that tremolite asbestos is approximately 100 times more harmful than chrysotile asbestos. Recently, it become a regional social problem because lung disease (mesothelioma and lung cancer) suspect patients are largely found among the residents of the mining area. Therefore, Korean government making every endeavor to remove asbestos risk in the area. However, there is insufficiency geological and mineralogical studies for tremolite asbestos. In the present study, the occurrence and mineralogical characteristics of tremolite asbestos were studied using polarization microscope, XRD, XRF, EPMA, SEM and TEM. Mica-schist of precambrian metasedimentary rock, which is widely distributed in the area, is the host rock of tremolite deposits. The rocks are largely disturbed by faults and folds, and shows sudden changes in strike and slope of strata. Tremolite ore bodies, which show relatively light colored, mainly occur as stratiform or veinlet and some occurs in brecciated rock fragments. Tremolite is a major asbestos mineral, and chrysotile, talc, mica, chlorite and quartz occurs as associated minerals. Considerable amount of ore containing pure tremolite is found, and ores having mineral assemblages of tremolite+talc, tremolite+quartz and chrysotile+talc also occurs. From optical microscope observations, most tremolites are asbestos from that meets to the criterion (length > 5 μm, diameter 3:1) defined by the international organization (WHO, ILO), but non-asbestos form tremolites are also included. Most asbestos form tremolites have the size range of 1.0-2.0 μm width and 5-10 μm length. The length can be shorten with crushing experiments, but the width remains unchanged. Non-asbestos form hardly change to asbestos form by mechanical crushing. From comprehensive studies for geological occurrence and mineral assemblage, it is considered that

  9. Cretaceous crust beneath SW Borneo: U-Pb dating of zircons from metamorphic and granitic rocks

    Science.gov (United States)

    Davies, L.; Hall, R.; Armstrong, R.

    2012-12-01

    Metamorphic basement rocks from SW Borneo are undated but have been suggested to be Palaeozoic. This study shows they record low pressure 'Buchan-type' metamorphism and U-Pb SHRIMP dating of zircons indicates a mid-Cretaceous (volcaniclastic) protolith. SW Borneo is the southeast promontory of Sundaland, the continental core of SE Asia. It has no sedimentary cover and the exposed basement has been widely assumed to be a crustal fragment from the Indochina-China margin. Metamorphic rocks of the Pinoh Group in Kalimantan (Indonesian Borneo) are intruded by granitoid rocks of Jurassic-Cretaceous age, based on K-Ar dating, suggesting emplacement mainly between 130 and 80 Ma. The Pinoh metamorphic rocks have been described as a suite of pelitic schists, slates, phyllites, and hornfelses, and have not been dated, although they have been correlated with rocks elsewhere in Borneo of supposed Palaeozoic age. Pelitic schists contain biotite, chlorite, cordierite, andalusite, quartz, plagioclase and in some cases high-Mn almandine-rich garnet. Many have a shear fabric associated with biotite and fibrolite intergrowth. Contact metamorphism due to intrusion of the granitoid rocks produced hornfelses with abundant andalusite and cordierite porphyroblasts. Granitoids range from alkali-granite to tonalite and contain abundant hornblende and biotite, with rare white mica. Zircons from granitoid rocks exhibit sector- and concentric- zoning; some have xenocrystic cores mantled by magmatic zircon. There are four important age populations at c. 112, 98, 84 and 84 Ma broadly confirming earlier dating studies. There is a single granite body with a Jurassic age (186 ± 2.3 Ma). Zircons from pelitic metamorphic rocks are typically euhedral, with no evidence of rounding or resorbing of grains; a few preserve volcanic textures. They record older ages than those from igneous rocks; U-Pb ages are Cretaceous with a major population between 134 and 110 Ma. A single sample contains Proterozoic

  10. The Sierra de Calalaste in Northwestern Argentina, a counterpart of the peri-Gondwanan Ellsworth Terrane in the northern Appalachians?

    Science.gov (United States)

    Escayola, M. P.; van Staal, C. R.; Davis, W. J.; Rogers, N.

    2009-05-01

    The Ellsworth terrane, coastal Maine, is one of a number of fault-bounded blocks that occur along the eastern margin of Ganderia, a peri-Gondwanan terrane that underlies the bulk of the central part of the northern Appalachians. The Ellsworth block is considered part of the Ganderia microcontinent based on its geological history during the Early Paleozoic lithological characteristics and abundance of Early Cambrian detrital zircon. U-Pb zircon geochronology of rhyolitic schists indicates that both the Ellsworth schists (508 ± 0.8 Ma) and overlying Castine volcanics (503 ± 2.5 Ma) are middle Cambrian in age. The rhyolitic tuffs are interlayered with lava flows of enriched MORB affinity. The ɛ Nd (500) is depleted + 5.8 to +7.5, and Pb isotopic composition is unradiogenic to relatively enriched. Serpentinezed ultramafic sheets and massive sulfide deposits are present. The geologic, geochemical and isotopic characteristics of the bimodal volcanic sequences led recent workers to interpret the Ellsworth terrane as the remnants of a proto-oceanic rift system. The occidental sector of Puna in NW Argentina contains Cambrian to Ordovician magmatic associations distributed in two belts, the Occidental Eruptive Belt and the Oriental Eruptive Belt. Bimodal, basalts and rhyolites of the Occidental eruptive belt correspond to subalkaline, tholeiitic, low-K sequences developed in a suprasubduction zone environment. The Sierra de Calaste Ranges of the Occidental Eruptive Belt comprise a sequence of metaquarzites, rhyolitic flows and tuffs, mafic gabbroic rocks and some serpentinezed ultramafic sheets. Small massive sulfide deposits are locally also present. U-Pb zircon ages on rhyolites are Upper Cambrian (495 ± 3Ma). Their ɛ Nd values are +4 to+7. Pb isotopic compositions are unradiogenic. The rocks are interpreted to belong to a rift setting similar to that proposed for the Ellsworth terrane, which is nearly coeval in age. Recent reconnaissance fieldwork highlight strong

  11. Uranium (-nickel-cobalt-molybdenum) mineralization along the Singhbhum copper belt, India, and the problem of ore genesis

    Science.gov (United States)

    Sarkar, S. C.

    1982-08-01

    Uranium mineralization is present at many places along the 200 km long Singhbhum copper belt, but the mineralization is relatively concentrated at the central part of it. The belt is characterized by many shear zone features, such as mylonites, phyllonites, and L-S type of structures and of course, copious metasomatism. Country rocks are basic schists, metapelites, quartzose rocks and albite schist/gneiss (‘Soda Granite’). Orebodies are sheet-like, conformable with the pervasive planar structures in the host rocks. No pronounced ‘wall rock alteration’ accompanied the mineralization. Grade of the ore is low (crystal structure. Additionally, nickel, cobalt and molybdenum are present at Jaduguda-Bhatin in the form of millerite, gersdorffite, melonite, nickel-bearing pyrite, molybdenite etc. Dominance of uraninite over pitchblende and the larger cell-edge of uraninite, development of hematite-bearing quartz and Na-oligoclase at places in the ore zone, association of uranium mineralization with Ni-Co-Mo(-S-As) mineralization at Jaduguda-Bhatin and continuation of the orebodies to considerable depths, suggest that the uranium mineralization along the Singhbhum belt belongs to moderate to high temperature ‘vein type’. The age obtained by Pb207/Pb206 ratio and the concordia method suggest that the uranium mineralization in Singhbhum took place 1500 1600 Ma ago and this age is not far different from the age of formation of uranium-vein deposits in many other Precambrian shields of the world. The following two mechanisms of the formation of the deposits are discussed: 1) uranium precipitated in the Dhanjori basal sediments was mobilized during deformation and metamorphism into ore deposits, 2) the hydrodynamic system that leached out copper from the metabasic rocks to form the copper deposits at an earlier stage, could, in one of the oxidised pulses leach out uranium from the basal sediments and precipitate it in the favourable situations. Subsequent small

  12. Cenozoic Extension of the Southern Menderes Massif along the Kayabuku Shear Zone, Western Anatolia Extended Terrane, Turkey

    Science.gov (United States)

    Diniz, E.; Cemen, I.; Catlos, E. J.; Konak, N.; Goncuoglu, C. M.; Kohn, M. J.; Baker, C.; Hancer, M.

    2006-12-01

    Four major low angle extensional shear zones are located in the Menderes massif of the Western Anatolia Extended Terrane in western Turkey. The shear zones are, from north to south, Simav, Alasehir, Buyuk Menderes and Kayabuku (Selimiye) shear zones. We have conducted a detailed field oriented study to determine the role of the Kayabuku (Selimiye) shear zone in the Cenozoic extensional evolution of the Menderes massif. The south-dipping Kayabuku (Selimiye) shear zone of the southern Menderes massif contains well- developed mesoscopic and microscopic shear sense indicators, and separates orthogneiss and augengneiss in its footwall from schist and marble rock units in its hanging wall. Within the shear zone, the average attitude of the foliation planes between the towns of Milas and Yatagan is measured as N86W/50°S. The shear zone shows two ductile sense of shearing; 1) top to the north and 2) top to the south which overprinted the former one. Many thin sections also show top to the south brittle shear sense indicators overprinting the ductile shear sense indicators. The trend of the ductile shear sense indicators, such as stretching lineations, range from N10E to N30E indicating that they are parallel to the shear sense indicators measured along the Simav shear zone of the northern and, Alasehir and Buyuk Menderes shear zones of the central Menderes massif. This suggests to us that the Cenozoic extension which was initiated in Oligocene by the processes of Orogenic Collapse effected the Kayabuku (Selimiye) shear zone. The hanging wall of the Kayabuku shear zone is also locally brittely deformed by a south-dipping normal fault zone, discontinuously exposed between the schist and marble units. The fault zone suggests that the hanging wall of the shear zone has been brittely deformed during the extensional exhumation of the southern Menderes massif. Our field observations and microtectonic studies suggest that the rocks within the Kayabuku (Selimiye) shear zone gained

  13. Geochemical evolution of a high arsenic, alkaline pit-lake in the Mother Lode Gold District, California

    Science.gov (United States)

    Savage, Kaye S.; Ashley, Roger P.; Bird, Dennis K.

    2009-01-01

    The Harvard orebody at the Jamestown gold mine, located along the Melones fault zone in the southern Mother Lode gold district, California, was mined in an open-pit operation from 1987 to 1994. Dewatering during mining produced a hydrologic cone of depression; recovery toward the premining ground-water configuration produced a monomictic pit lake with alkaline Ca-Mg-HCO3-SO4–type pit water, concentrations of As up to 1,200 μg/L, and total dissolved solids (TDS) up to 2,000 mg/L. In this study, pit-wall rocks were mapped and chemically analyzed to provide a context for evaluating observed variability in the composition of the pit-lake waters in relationship to seasonal weather patterns. An integrated hydrogeochemical model of pit-lake evolution based on observations of pit-lake volume, water composition (samples collected between 1998–2000, 2004), and processes occurring on pit walls was developed in three stages using the computer code PHREEQC. Stage 1 takes account of seasonally variable water fluxes from precipitation, evaporation, springs, and ground water, as well as lake stratification and mixing processes. Stage 2 adds CO2fluxes and wall-rock interactions, and stage 3 assesses the predictive capability of the model.Two major geologic units in fault contact comprise the pit walls. The hanging wall is composed of interlayered slate, metavolcanic and metavolcaniclastic rocks, and schists; the footwall rocks are chlorite-actinolite and talc-tremolite schists generated by metasomatism of greenschist-facies mafic and ultramafic igneous rocks. Alteration in the ore zone provides evidence for mineralizing fluids that introduced CO2, S, and K2O, and redistributed SiO2. Arsenian pyrite associated with the alteration weathers to produce goethite and jarosite on pit walls and in joints, as well as copiapite and hexahydrite efflorescences that accumulate on wall-rock faces during dry California summers. All of these pyrite weathering products incorporate arsenic at

  14. Revised nomenclature and stratigraphic relationships of the Fredericksburg Complex and Quantico Formation of the Virginia Piedmont

    Science.gov (United States)

    Pavlides, Louis

    1980-01-01

    The Fredericksburg Complex, in part a migmatitic terrane in northeast Virginia, is subdivided on the basis of lithology, as well as aeromagnetic and aeroradiometric data, into two metamorphic suites. These suites are separated by the northeast-trending Spotsylvania lineament, a rectilinear geophysical feature that is probably the trace of an old fault zone. East of the lineament, the Po River Metamorphic Suite, of Proterozoic Z and (or) early Paleozoic age, consists dominantly of biotite gneiss, generally augen gneiss, and lesser amounts of hornblende gneiss and mica schist. West of the Spotsylvania lineament is the Ta River Metamorphic Suite, composed mostly of amphibolite and amphibole gneiss. However, to the southwest, along its strike belt, the Ta River contains abundant biotite gneiss and mica schist. Both the Ta River and Po River contain abundant foliated granitoid and pegmatoid bodies as concordant tabular masses and as crosscutting dikes; these rocks are considered part of the Ta River and Po River Metamorphic Suites. The amphibolitic Holly Corner Gneiss is interpreted to be a western allochthonous equivalent of the Ta River. Both the Ta River and Holly Corner are considered to be coeval, eastern, distal facies of the Lower Cambrian(?) Chopawamsic Formation. The Paleozoic Falls Run Granite Gneiss intrudes the Ta River Metamorphic Suite and the Holly Corner Gneiss; locally the Falls Run is interpreted to have been transported westward with the Holly Corner after intrusion. The Quantico Formation, in the core of the Quantico-Columbia synclinorium, rests with angular unconformity along its northwest and southeast limbs, respectively, on the Chopawamsic Formation and the Ta River Metamorphic Suite. The Quantico Formation is assigned the same Late Ordovician age and similar stratigraphic position as the Arvonia Slate of the Arvonia syncline. The youngest rocks of the area are the granitoid and pegmatoid bodies of the Falmouth Intrusive Suite. They consist of

  15. Mapping Post-Fire Vegetation Recovery at Different Lithologies of Taygetos mt (greece) with Multi-Temporal Remote Sensing Data

    Science.gov (United States)

    Vassilakis, Emmanuel; Mallinis, George; Christopoulou, Anastasia; Farangitakis, Georgios-Pavlos; Papanikolaou, Ioannis; Arianoutsou, Margarita

    2017-04-01

    Mt Taygetos (2407m), located at southern Peloponnese (Greece) suffered a large fire during the summer of 2007. The fire burned approximately 45% of the area covered by the endemic Greek fir (Abies cephalonica) and Black Pine (Pinus nigra) forest ecosystems. The aim of the current study is to examine the potential differences on post-fire vegetation recovery imposed by the lithology as well as the geomorphology of the given area over sites of the same climatic and landscape conditions (elevation, aspect, slope etc.). The main lithologies consist of carbonate, permeable, not easily erodible formations (limestones and marbles) and clastic, impermeable (schists, slate and flysch) erodible ones. A time-series of high spatial resolution satellite images were interpreted, analyzed and compared in order to detect changes in vegetation coverage which could prioritize areas of interest for fieldwork campaigns. The remote sensing datasets were acquired before (Ikonos-2), a few months after (Quickbird-2) and some years after (Worldview-3) the 2007 fire. High resolution Digital Elevation Model was used for the ortho-rectification and co-registration of the remote sensing data, but also for the extraction of the mountainous landscape characteristics. The multi-temporal image dataset was analyzed through GEographic-Object Based Image Analysis (GEOBIA). Objects corresponding to different vegetation types through time were identified through spectral and textural features. The classification results were combined with basic layers such as lithological outcrops, pre-fire vegetation, landscape morphology etc., supplementing a spatial geodatabase used for classifying burnt areas with varying post-fire plant community recovery. We validated the results of the classification during fieldwork and found that at a local scale, where the landscape features are quite similar, the bedrock type proves to be an important factor for vegetation recovery, as it clearly defines the soil generation

  16. Chapter L: U.S. Industrial Garnet

    Science.gov (United States)

    Evans, James G.; Moyle, Phillip R.

    2006-01-01

    The United States presently consumes about 16 percent of global production of industrial garnet for use in abrasive airblasting, abrasive coatings, filtration media, waterjet cutting, and grinding. As of 2005, domestic garnet production has decreased from a high of 74,000 t in 1998, and imports have increased to the extent that as much as 60 percent of the garnet used in the United States in 2003 was imported, mainly from India, China, and Australia; Canada joined the list of suppliers in 2005. The principal type of garnet used is almandite (almandine), because of its specific gravity and hardness; andradite is also extensively used, although it is not as hard or dense as almandite. Most industrial-grade garnet is obtained from gneiss, amphibolite, schist, skarn, and igneous rocks and from alluvium derived from weathering and erosion of these rocks. Garnet mines and occurrences are located in 21 States, but the only presently active (2006) mines are in northern Idaho (garnet placers; one mine), southeastern Montana (garnet placers; one mine), and eastern New York (unweathered bedrock; two mines). In Idaho, garnet is mined from Tertiary and (or) Quaternary sedimentary deposits adjacent to garnetiferous metapelites that are correlated with the Wallace Formation of the Proterozoic Belt Supergroup. In New York, garnet is mined from crystalline rocks of the Adirondack Mountains that are part of the Proterozoic Grenville province, and from the southern Taconic Range that is part of the northern Appalachian Mountains. In Montana, sources of garnet in placers include amphibolite, mica schist, and gneiss of Archean age and younger granite. Two mines that were active in the recent past in southwestern Montana produced garnet from gold dredge tailings and saprolite. In this report, we review the history of garnet mining and production and describe some garnet occurrences in most of the Eastern States along the Appalachian Mountains and in some of the Western States where

  17. Geology, lithogeochemistry and paleotectonic setting of the host sequence to the Kangasjärvi Zn-Cu deposit, central Finland: implications for volcanogenic massive sulphide exploration in the Vihanti-Pyhäsalmi district

    Directory of Open Access Journals (Sweden)

    Michael D. Roberts

    2004-01-01

    Full Text Available The Kangasjärvi Zn-Cu deposit is a highly deformed and metamorphosed Paleoproterozoic volcanogenic massive sulphide (VMS deposit located in the Vihanti-Pyhäsalmi base metal mining district of central Finland. The host sequence to the deposit, referred to as the Inner Volcanic Sequence (IVS, is comprised of a bimodal suite of metavolcanic rocks and a regionally extensive tonalite-trondhjemite gneiss (sub-volcanic intrusions?. A separate and perhaps younger sequence of mafic volcanic rocks, with irregular intervals of undifferentiated intermediate to felsic schists and metalimestones, referred to as the Outer Volcanic Sequence (OVS, are separated from the IVS sequence by intervals of metagreywacke and U-P-bearing graphitic schists. A stratigraphic scheme for rocks within the IVS is proposed based on outcrop observations, locally preserved volcanic textures, aspects of seafloor-related hydrothermal alteration and lithogeochemistry. In this scheme, rare andesites form the lowermostvolcanic stratigraphy and are overlain by typical island-arc basalts that were erupted in a subaqueous setting. Tonalite-trondhjemite subvolcanic intrusions were locally emplaced within andesites and coeval rhyolites were extruded on the basaltic substrate. The extrusion of rhyolites, including high-silica rhyolites, was coeval with regional-scale, pre-metamorphic seafloor hydrothermal alteration and local sulphide mineralization. Extensively altered rhyolites envelope massive sulphides and are underlain by altered basalts. The latter rocks are now characterized by a variety of low-variance metamorphic mineral assemblages (e.g. orthoamphibole-cordierite rocks and define a domain of intense pre-metamorphic chlorite ± sericite alteration in the stratigraphic footwall of the deposit. The altered nature of these rocks is attributed to reaction with seawater-related hydrothermal fluids within a zone of upflow at or near the seafloor. The fundamental controls on convective

  18. 3D inclusion trail geometry determination within individual porphyroblasts using reflected light optical microscopy of oriented blocks

    Science.gov (United States)

    Munro, Mark; Bowden, Douglas; Ord, Alison; Hobbs, Bruce

    2015-04-01

    It is vital to interpret porphyroblast microstructures accurately relative to both one another and to external matrix structures when using them to reconstruct the tectono-metamorphic evolution of orogenic terranes. Mis-interpretation may have profound implications for either the deformation component or the inferred metamorphic reactions resulting in erroneous Pressure-Temperature-time-Deformation (P-T-t-D) trajectories. A number of well-established approaches have been devised for measuring porphyroblast inclusion trails including pitch and strike measurement, 'FitPitch' best-fit plane assignment, and the radial asymmetry method. A long-standing limitation of these methods is that they generally permit only a single measurement to be extracted from each individual porphyroblast, and therefore provide mean 3D orientation data for an entire population. Alternatively, High-Resolution X-ray Computed Tomography (HRXCT) facilitates the imaging of 3D internal geometries within individuals. However, at present significant operating costs render it unviable for routine application to large numbers of samples required for extracting meaningful tectonic interpretations. Here, a new method is presented for the determination of 3D geometries within porphyroblasts using reflected light examination of polished schist material. Reflected light microscopy yields good quality representation of inclusion trails preserved within porphyroblasts. Sectioning oriented samples into small, oriented blocks allows multiple intersections through porphyroblasts (generally >5mm) to be measured via mechanical stage and amalgamated to reconstruct the plane in 3D. The method represents an accessible alternative to HRXCT, which is applicable to any porphyroblastic phase of adequate size to permit at least two intersections. The technique is demonstrated on garnets from the Mesoproterozoic Mount Barren Group, southern Albany-Fraser orogen of S. W. Australia. Porphyroblasts within a structural

  19. Geochemistry of the Shuksan greenschists and blueschists, North Cascades, Washington: Variably fractionated and altered metabasalts of oceanic affinity

    Science.gov (United States)

    Dungan, M. A.; Vance, J. A.; Blanchard, D. P.

    1983-06-01

    The Shuksan schist comprises a structurally coherent, metabasaltic member of the Easton Formation, the uppermost allochthon (Shuksan thrust plate) in the thrust system of the western North Cascades of Washington State. Late Jurassic metamorphism at moderately high P/T produced interlayering of actinolite-bearing greenschist assemblages with blue amphibole-bearing rocks. Major and trace element analyses of twelve greenschist and blueschist samples have been used to establish similarities between the basaltic protolith and moderately to strongly fractionated Type I MORB, to distinguish the effects of seafloor alteration superimposed on the primary igneous chemistry, and to evaluate the origin and nature of the chemical controls which produced the two mineral assemblages. The twelve analyzed samples exhibit moderate to strong LREE depletion, and characteristically low concentrations of other non-labile trace elements such as Nb, Th and Hf. The highly to moderately incompatible elements Ti, P, Nb, Zr, Hf, Y, Sc, and the REE vary by factors of 1.5 to 3.5 within the suite in a systematic pattern, increasing smoothly with increasing total iron. The relative enrichments of these elements are inversely proportional to bulk partition coefficients estimated for fractionation of basaltic magmas. The magnitude of the negative europium anomaly increases with overall incompatible element enrichment. These variations are consistent with the production of a wide spectrum of compositions by different degrees of low pressure fractionation of similar Type I MORB parent magmas. The concentrations of Sr, Rb, Na, and K vary irregularly and do not correlate with the non-labile trace elements. K and Rb are substantially elevated over typical MORB values in most samples and exhibit a consistently lower ratio (K/Rb=400 vs 1000) than fresh MORB. Concentrations of these four elements are believed to have been modified by low temperature seafloor alteration (pre-metamorphic) characterized by

  20. Evaluation of environmental impacts in the mining of solid fossil fuels; Avaliacao de impactos ambientais na mineracao de combustiveis fosseis solidos

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Gilda Carneiro

    1989-07-01

    This study evaluates the environmental problems caused by the mining works of coal, peat and oil schists; also it evaluates the kind of treatment used by the mining companies against water, air and ground pollution, as well as the necessary control according to the mine activities and the affected environment. the studied areas are situated at brasilian states of Santa Catarina (Criciuma, Urussanga and Sideropolis), Rio Grande do Sul (Charqueada, Bage, Cachoeira do Sul, Butia and Arroio dos Ratos), Parana (Figueira and Sao Mateus do Sul), and Sao Paulo (Iguape and Sao Jose dos Campos). This study was done through a direct inquiry, by sending questionnaire to fifteen coal mining companies, three of peat ones and one of oil schists one. besides it was done a compilation of federal and state laws concerning to the environment and on the rights and duties of the mining companies. The information brought up in this way were compiled into a data bank, which allowed and sample surveys of environmental condition in the different industries and further it enabled a comparison between the real facts and the bibliography suggestions about adequate monitoring of the air, waters and ground, during mining activities. this analysis showed that the environment problems, created by the three former kind of mining works, are under control through projects of environment restoring and monitoring in phase of implantation and that these projects are restricted to that less expensive and easier to construct (holding back in pools or reservoirs, pouring in pits and aspersion). It was not notices a significant monitoring of parameters considered to be critical to the environment (metals, cyanides, sulphide and general bacteria). Almost all the companies have not yet exact data about the efficiency of each kind of environmental treatment because it is new ones and are just in follow-up and consequently they have not yet parameters to change the adequate the steps of the treatment, because

  1. Contrasting distributions of groundwater arsenic and uranium in the western Hetao basin, Inner Mongolia: Implication for origins and fate controls

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Huaming, E-mail: hmguo@cugb.edu.cn [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083 (China); School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Jia, Yongfeng [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Wanty, Richard B. [U.S. Geological Survey, MS 964d Denver Federal Center, Denver, CO 80225 (United States); Jiang, Yuxiao; Zhao, Weiguang [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Xiu, Wei [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083 (China); School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Shen, Jiaxing [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Li, Yuan [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083 (China); School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Cao, Yongsheng [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Wu, Yang [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083 (China); Zhang, Di [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); Wei, Chao [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083 (China); The National Institute of Metrology, Beijing 100013 (China); Zhang, Yilong; Cao, Wengeng [Institute of Hydrogeology and Environmental Geology, China Academy of Geological Sciences, Shijiazhuang, Hebei, 050061 (China); and others

    2016-01-15

    Although As concentrations have been investigated in shallow groundwater from the Hetao basin, China, less is known about U and As distributions in deep groundwater, which would help to better understand their origins and fate controls. Two hundred and ninety-nine groundwater samples, 122 sediment samples, and 14 rock samples were taken from the northwest portion of the Hetao basin, and analyzed for geochemical parameters. Results showed contrasting distributions of groundwater U and As, with high U and low As concentrations in the alluvial fans along the basin margins, and low U and high As concentrations downgradient in the flat plain. The probable sources of both As and U in groundwater were ultimately traced to the bedrocks in the local mountains (the Langshan Mountains). Chemical weathering of U-bearing rocks (schist, phyllite, and carbonate veins) released and mobilized U as UO{sub 2}(CO{sub 3}){sub 2}{sup 2−} and UO{sub 2}(CO{sub 3}){sub 3}{sup 4−} species in the alluvial fans under oxic conditions and suboxic conditions where reductions of Mn and NO{sub 3}{sup −} were favorable (OSO), resulting in high groundwater U concentrations. Conversely, the recent weathering of As-bearing rocks (schist, phyllite, and sulfides) led to the formation of As-bearing Fe(III) (hydr)oxides in sediments, resulting in low groundwater As concentrations. Arsenic mobilization and U immobilization occurred in suboxic conditions where reduction of Fe(III) oxides was favorable and reducing conditions (SOR). Reduction of As-bearing Fe(III) (hydr)oxides, which were formed during palaeo-weathering and transported and deposited as Quaternary aquifer sediments, was believed to release As into groundwater. Reduction of U(VI) to U(IV) would lead to the formation of uraninite, and therefore remove U from groundwater. We conclude that the contrasting distributions of groundwater As and U present a challenge to ensuring safe drinking water in analogous areas, especially with high

  2. Application of Finite Element Method of Numerical Modelling to Understand Toe Buckling Deformation in the Southern Alps of New Zealand.

    Science.gov (United States)

    Ridl, Romy; Bell, David; Villeneuve, Marlene

    2017-04-01

    models were used to model the anisotropic nature of the schist rock mass, and a sequential unloading method was adopted to simulate valley evolution. Far-field tectonics were incorporated into the model by comparing topographically induced gravitational stresses with in situ field stress measurements. The results of sensitivity analyses demonstrate that the dominant parameters governing toe buckling deformation in the Cromwell Gorge are a function of the anisotropy of the schist (foliation orientation and stiffness), and the intersection of the two induced stress fields near the base of the slopes.

  3. Jurassic-Paleogene intraoceanic magmatic evolution of the Ankara Mélange, north-central Anatolia, Turkey

    Science.gov (United States)

    Sarifakioglu, E.; Dilek, Y.; Sevin, M.

    2014-02-01

    Oceanic rocks in the Ankara Mélange along the Izmir-Ankara-Erzincan suture zone (IAESZ) in north-central Anatolia include locally coherent ophiolite complexes (∼ 179 Ma and ∼ 80 Ma), seamount or oceanic plateau volcanic units with pelagic and reefal limestones (96.6 ± 1.8 Ma), metamorphic rocks with ages of 256.9 ± 8.0 Ma, 187.4 ± 3.7 Ma, 158.4 ± 4.2 Ma, and 83.5 ± 1.2 Ma indicating northern Tethys during the late Paleozoic through Cretaceous, and subalkaline to alkaline volcanic and plutonic rocks of an island arc origin (∼ 67-63 Ma). All but the arc rocks occur in a shale-graywacke and/or serpentinite matrix, and are deformed by south-vergent thrust faults and folds that developed in the middle to late Eocene due to continental collisions in the region. Ophiolitic volcanic rocks have mid-ocean ridge (MORB) and island arc tholeiite (IAT) affinities showing moderate to significant large ion lithophile elements (LILE) enrichment and depletion in Nb, Hf, Ti, Y and Yb, which indicate the influence of subduction-derived fluids in their melt evolution. Seamount/oceanic plateau basalts show ocean island basalt (OIB) affinities. The arc-related volcanic rocks, lamprophyric dikes and syenodioritic plutons exhibit high-K shoshonitic to medium- to high-K calc-alkaline compositions with strong enrichment in LILE, rare earth elements (REE) and Pb, and initial ɛNd values between +1.3 and +1.7. Subalkaline arc volcanic units occur in the northern part of the mélange, whereas the younger alkaline volcanic rocks and intrusions (lamprophyre dikes and syenodioritic plutons) in the southern part. The late Permian, Early to Late Jurassic, and Late Cretaceous amphibole-epidote schist, epidote-actinolite, epidote-chlorite and epidote-glaucophane schists represent the metamorphic units formed in a subduction channel in the northern Neotethys. The Middle to Upper Triassic neritic limestones spatially associated with the seamount volcanic rocks indicate that the northern

  4. Prograde high- to ultrahigh-pressure metamorphism and exhumation of oceanic sediments at Lago di Cignana, Zermatt-Saas Zone, western Alps

    Science.gov (United States)

    Reinecke, T.

    1998-03-01

    Pelagic metasediments and MORB-type metabasalts of the former Tethyan oceanic crust at Cignana, Valtournanche, Italy, experienced UHP metamorphism and subsequent exhumation during the Early to Late Tertiary. Maximum PT conditions attained during UHP metamorphism were 600-630 °C, 2.7-2.9 GPa, which resulted in the formation of coesite-glaucophane-eclogites in the basaltic layer and of garnet-dolomite-aragonite-lawsonite-coesite-phengite-bearing calc-schists and garnet-phengite-coesite-schists with variable amounts of epidote, talc, dolomite, Na-pyroxene and Na-amphibole in the overlying metasediments. During subduction the rocks followed a prograde HP/UHP path which in correspondance with the Jurassic age of the Tethyan crust reflects the thermal influence of relatively old and cold lithosphere and of low to moderate shear heating. Inflections on the prograde metamorphic path may correspond to thermal effects that arise from a decrease in shear heating due to brittle-plastic transition in the quartz-aragonite-dominated rocks, induced convection in the asthenospheric mantle wedge and/or heat consumption by endothermic reactions over a restricted PT segment during subduction. After detachment from the downgoing slab some 50-70 Ma before present, the Cignana crustal slice was first exhumed to ca. 60 km and concomitantly cooled to ca. 550 °C, tracing back the UHP/HP prograde path displaced by 50-80 °C to higher temperatures. Exhumation at this stage is likely to have occurred in the Benioff zone, while the subduction of cool lithosphere was going on. Subsequently, the rocks were near-isothermally exhumed to ca. 30 km, followed by concomitant decompression and cooling to surface conditions (at glaucophane eclogites, the HP/UHP assemblages of the metasediments have been largely obliterated during exhumation. Relics from which the metamorphic evolution of the rocks during prograde HP metamorphism and the UHP stage can be retrieved are restricted to rigid low

  5. Middle Ordovician subduction of continental crust in the Scandinavian Caledonides - an example from Tjeliken, Seve Nappe Complex, Sweden

    Science.gov (United States)

    Fassmer, Kathrin; Andersson, Barbro; Klonowska, Iwona; Walczak, Katarzyna; Froitzheim, Nikolaus; Majka, Jarosław; Fonseca, Raul

    2017-04-01

    The Seve Nappe Complex (SNC) in the Scandinavian Caledonides represents the distal part of the margin of Baltica, which was subducted to depth of UHP metamorphism during the Caledonian orogeny. In contrast to the ages determined for the Western Gneiss Complex in Western Norway (ca. 420 - 400 Ma) which is interpreted to represent the subducted Baltican basement , the ages in the SNC and related nappes are overall older (ca. 500-430 Ma), with a general trend of higher ages in the North (Norrbotten) than in the South (Jämtland). As the previously published ages in the SNC are quite diverging it is difficult to reconstruct the tectonometamorphic history of this unit. Therefore exact dating with different methods is necessary to get a better constraint on the exact timing of subduction. We present new age determinations on an eclogite and a garnet-phengite schist from Tjeliken in northern Jämtland, Sweden. There the SNC can be divided into three tectonic units, an Eastern, Middle and Western belt. The locality of Mt. Tjeliken is situated in the Eastern Belt. Thermodynamic modelling of the eclogite yielded a pressure of 25-26 kbar at 650-700 °C (Majka et al. 2014). Previous dating produced diverging ages of 460±4 Ma (Sm-Nd mineral isochrones, Brueckner & Van Roermund 2007) and 446±1 Ma (U-Pb zircon dating, Root & Corfu 2012). In this study metamorphic rims of zircons from the garnet-phengite schist were dated using secondary ion mass spectrometry (SIMS) and yielded a concordia age of 458.9 ± 2.5 Ma. Lu-Hf garnet-whole rock dating yielded 458.5 ± 1.1 Ma for the eclogite. Garnet in the eclogite shows a prograde major-element zoning and a concentration of Lu in the cores, indicating that this age is related to garnet growth during pressure increase, i.e. subduction. The identical ages from both rock types confirm subduction of the outer margin of Baltica during the Middle Ordovician in a fast subduction-exhumation cycle. The fact that Sm-Nd and Lu-Hf dating yielded

  6. Contrasting distributions of groundwater arsenic and uranium in the western Hetao basin, Inner Mongolia: Implication for origins and fate controls

    Science.gov (United States)

    Guo, Huaming; Jia, Yongfeng; Wanty, Richard B.; Jiang, Yuxiao; Zhao, Weiguang; Xiu, Wei; Shen, Jiaxing; Li, Yuan; Cao, Yongsheng; Wu, Yang; Zhang, Di; Wei, Chao; Zhang, Yilong; Cao, Wengeng; Foster, Andrea L.

    2016-01-01

    Although As concentrations have been investigated in shallow groundwater from the Hetao basin, China, less is known about U and As distributions in deep groundwater, which would help to better understand their origins and fate controls. Two hundred and ninety-nine groundwater samples, 122 sediment samples, and 14 rock samples were taken from the northwest portion of the Hetao basin, and analyzed for geochemical parameters. Results showed contrasting distributions of groundwater U and As, with high U and low As concentrations in the alluvial fans along the basin margins, and low U and high As concentrations downgradient in the flat plain. The probable sources of both As and U in groundwater were ultimately traced to the bedrocks in the local mountains (the Langshan Mountains). Chemical weathering of U-bearing rocks (schist, phyllite, and carbonate veins) released and mobilized U as UO2(CO3)22 − and UO2(CO3)34 − species in the alluvial fans under oxic conditions and suboxic conditions where reductions of Mn and NO3− were favorable (OSO), resulting in high groundwater U concentrations. Conversely, the recent weathering of As-bearing rocks (schist, phyllite, and sulfides) led to the formation of As-bearing Fe(III) (hydr)oxides in sediments, resulting in low groundwater As concentrations. Arsenic mobilization and U immobilization occurred in suboxic conditions where reduction of Fe(III) oxides was favorable and reducing conditions (SOR). Reduction of As-bearing Fe(III) (hydr)oxides, which were formed during palaeo-weathering and transported and deposited as Quaternary aquifer sediments, was believed to release As into groundwater. Reduction of U(VI) to U(IV) would lead to the formation of uraninite, and therefore remove U from groundwater. We conclude that the contrasting distributions of groundwater As and U present a challenge to ensuring safe drinking water in analogous areas, especially with high background values of U and As.

  7. Oxygen, carbon and sulphur isotope studies in the Keban Pb-Zn deposits, eastern Turkey: An approach on the origin of hydrothermal fluids

    Science.gov (United States)

    Kalender, Leyla

    2011-03-01

    Pb-Zn deposits are widespread and common in various parts of the Taurus Belt. Most of the deposits are of pyrometasomatic and hydrothermal origin. The Keban Pb-Zn deposits are located along the intrusive contact between the Paleozoic - Lower Triassic Keban Metamorphic Formation and the syenite porphyry of the Upper Cretaceous Keban igneous rocks. Various studies have already been carried out; using fluid inclusion studies on fluorite, calcite and quartz on the pyrite-chalcopyrite bearing Keban ore deposits. This study focuses on the interpretation of stable isotope compositions in connexion with fluid inclusion data. Sulphur isotope values (δ 34S) of pyrite are within the range of -0.59 to +0.17‰ V-CDT ( n = 10). Thus, the source of sulphur is considered to be magmatic, as evidenced by associated igneous rocks and δ 34S values around zero"0". Oxygen isotope values δ 18O of quartz vary between +10.5 and +19.9‰ (SMOW). However, δ 18O and δ 13C values of calcite related to re-crystallized limestone (Keban Metamorphic Formation) reach up to +27.3‰ (SMOW) and +1.6‰ (PDB), respectively. The δ 34S, δ 13C and δ 18O values demonstrate that skarn-type Pb-Zn deposits formed within syeno-monzonitic rocks and calc-schist contacts could have developed at low temperatures, by mixing metamorphic and meteoric waters in the final stages of magmatism.

  8. Raman micro-spectroscopy on diamond, graphite and other carbon polymorphs from the ultrahigh-pressure metamorphic Kimi Complex of the Rhodope Metamorphic Province, NE Greece

    Science.gov (United States)

    Perraki, Maria; Proyer, Alexander; Mposkos, Evripidis; Kaindl, Reinhard; Hoinkes, Georg

    2006-01-01

    Raman micro-spectroscopy was applied on carbon inclusions in garnet porphyroblasts from kyanite-biotite-garnet schists of the Rhodope Metamorphic Province (RMP), NE Greece. Diamond and cuboids of poorly to highly ordered graphite were identified either as single phase inclusions or as polyphase inclusions along with CO 2 and/or carbonates (calcite/magnesian calcite). Questionable Raman bands that may be assigned to other C-phases (?nanodiamond/?lonsdaleite/?a different C-polymorph) have been observed. The presence of diamond confirms beyond any doubt the ultrahigh-pressure (UHP) metamorphism reported by Mposkos and Kostopoulos [1] [E. Mposkos, D. Kostopoulos, Diamond, former coesite and supersilisic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established, Earth Planet. Sci. Lett. 192 (2001) 497-506] in the RMP. Cuboid graphite showing variable degree of disordering most probably formed after diamond. The possible involvement of CO 2 and or C-O-H fluids in the formation of diamond is discussed.

  9. Mineralogy, geochemistry and origin of Zafarabad iron deposit based on REE and trace elements of magnetite

    Directory of Open Access Journals (Sweden)

    Mehrdad Barati

    2013-10-01

    Full Text Available Zafarabad iron deposit is located northwest of Divandareh, in the northern margin of Sanandaj-Sirjan plutonic-metamorphic zone. The deposit is in lentoid to tubular shape, within a shear zone and occrrued in host rocks of calc-schist and limestone. Magnetite with massive, cataclastic and replacement textures are the main phases, while pyrite and other sulfide minerals are found. Major and trace elements are measured by ICP-MS and ICP-AES methods. Based on some ratios of trace elements in the ore samples and (Ti+V vs. Cal+Al+Mn and Ti+V vs. Ni/(Cr+Mn diagrams which are used for classification of iron deposit types, Zafarabad iron deposit fall in the range of skarn deposits. Spider diagrams show a steady decline from LREE to HREE elements with Eu (mean value of 0.06 ppm and Ce (mean value of 0.94 ppm negative anomalies. Comparing the distribution patterns of REE for the Zafarabad magnetites with those of various types of iron deposits shows that the REE pattern for Zafarabad is similar to these deposits. Analysis of calculated parameters for REE shows that the hydrothermal fluids responsible for mineralization are mainly of magmatic origin through fractionation and crystallization processes of a deep iron rich fluid phase and its emplacement within the carbonate rocks, forming iron skarn.

  10. In situ radiation measurement and estimation of U/Th ratio to reflect on the uranium bearing potential zone in metamorphic rocks of Mahendragarh district, Haryana

    Science.gov (United States)

    Somani, O. P.; Sunil Kumar, T. S.; Kukreti, B. M.; Bhaumik, B. K.; Gorikhan, R. A.

    2009-06-01

    Gross gamma radiation survey was carried out using Nal(Tl) scintillator based portable gamma ray spectrometer (PGRS) around areas of Gaonri, Dholera, Pachnota and Meghot in Mahendragarh district, Haryana. Geologically the area forms part of north Delhi fold belt comprising calc-silicate, quartz biotite schist, impure marble, quartzite and pegmatite rocks. Equivalent uranium (eU3O8) concentration in ppm was estimated in situ on a regular grid pattern of 500 m (E-W) × 1000 m (N-S) and grab samples were collected at grid locations for analyzing in the laboratory for estimating the contents of eU3Os Raeq, ThO2 and %K. A comparison with the laboratory analysed grab samples for eU308 data and in situ radiation measurements shows a good match of the two sets of data. The in situ measurements indicate higher concentration of eU3O8 in Chapra Bibipur in northeastern most corners, Maghot area in central part, Gaonri in western part and Pachnota in southwestern part of the study area. As index to uranium favorability, U(Raeq)-Th contour map (prepared using Surfer software with Krieging interpolation method for this grid size) based on the data on grab samples was generated which show three major clusters of relatively high U-Th ratio. The blocks delineated are enriched in sodic mineral albite which support albite hosted uranium mineralization potential in metamorphic rocks in Haryana.

  11. Geology of northwestern Mindoro and its offshore islands: Implications for terrane accretion in west Central Philippines

    Science.gov (United States)

    Canto, A. P. B.; Padrones, J. T.; Concepcion, R. A. B.; Perez, A. D. C.; Tamayo, R. A.; Dimalanta, C. B.; Faustino-Eslava, D. V.; Queaño, K. L.; Yumul, G. P.

    2012-11-01

    In over four decades, terrane studies of Mindoro Island have evolved from one terrane- to three terrane-models. Recent mapping of northwestern Mindoro and the islands of Lubang and Ambil roughly agrees with a 1990 suggestion that the island is composed of two terranes: the Central Range and the San Jose Platform. However, in contrast to this older model, our study, which takes into consideration the petrochemical and paleontological characteristics of the units, subdivides Northwest Mindoro into the Amnay Ophiolite and the Halcon Metamorphic terranes. Southwest-verging thrust faults parallel to the currently active Manila Trench demarcate the younger Amnay Ophiolite from the latter. Components of the older Mangyan Ophiolitic Complex, formerly thought to represent a terrane distinct from the metamorphic body, are now suggested to occur as disrupted bodies enclosed within the schists of the Halcon Metamorphics. The timing of incorporation of these megaclast materials and the regional metamorphism that occurred is constrained by the deposition of the sedimentary sequences of the Late Eocene Lasala Formation. Petrochemical studies of these younger sedimentary units reveal their continent-derived character. Therefore, accretion of the Cretaceous Mangyan Ophiolitic Complex marks the collision between the Cretaceous oceanic lithosphere and mainland Asia that is considered to be the protolith of the Halcon Metamorphics. A subsequent collision occurred which led to the amalgamation of the Amnay Ophiolite suite to the metamorphosed terrane.

  12. San Ignacio (La Tembladera) geothermal site, Departamento de Francisco Morazan, Honduras, Central America: Geological field report

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, M.J.; Eppler, D.; Heiken, G.; Flores, W.; Ramos, N.; Ritchie, A.

    1987-06-01

    The San Ignacio (La Tembladera) geothermal site is located on the north side of the Siria Valley, Departamento de Francisco Morazan, near the village of Barrosa. Hot springs are located along a northwest-trending fault scarp at the edge of the valley and along north-trending faults that cross the scarp. The rocks in the area are primarily Paleozoic metamorphic rocks, overlain by patches of Tertiary Padre Miguel Group tuffs and alluvial deposits. Movement probably occurred along several faults during latest Tertiary and possibly early Quaternary times. Four spring areas were mapped. Area 1, the largest, is associated with a sinter mound and consists of 40 spring groups. About half of the springs, aligned along a north-south trend, are boiling. Area 2 is a small sinter mound with several seeps. Area 3 consists of a group of hot and boiling springs aligned along a north-trending fault. The springs rise through fractured schists and a thin cover of alluvium. Area 4 is located at the intersection of several faults and includes one of the largest boiling springs in the area.

  13. Review of potential host rocks for radioactive waste disposal in the southeast United States-Southern Piedmont subregion

    Energy Technology Data Exchange (ETDEWEB)

    1980-10-01

    A literature study was conducted on the geology of the Southern Piedmont province in the states of Maryland, Virginia, North Carolina, South Carolina, and Georgia. The purpose was to identify geologic areas potentially suitable for containment of a repository for the long-term isolation of solidified radioactive waste. The crystalline rocks of the Southern Piedmont province range in age from Precambrian to Paleozoic, and are predominantly slates, phyllites, argillites, schists, metavolcanics, gneisses, gabbros, and granites. These rock units were classified as either favorable, potentially favorable, or unfavorable as potential study areas based on an evaluation of the geologic, hydrologic, and geotechnical characteristics. No socio-economic factors were considered. Rocks subjected to multiple periods of deformation and metamorphism, or described as highly fractured, or of limited areal extent were generally ranked as unfavorable. Potentially favorable rocks are primarily the high-grade metamorphic gneisses and granites. Sixteen areas were classified as being favorable for additional study. These areas are primarily large igneous granite plutons as follows: the Petersburg granite in Virginia; the Rolesville-Castallia, Churchland, and Landis plutons in North Carolina; the Liberty Hill, Winnsboro, and Ogden plutons in South Carolina; and the Siloam, Elberton, and six unnamed granite plutons in Georgia.

  14. SHRIMP zircon U-Pb ages and tectonic implications of igneous events in the Ereendavaa metamorphic terrane in NE Mongolia

    Science.gov (United States)

    Miao, Laicheng; Zhang, Fochin; Baatar, Munkhtsengel; Zhu, Mingshuai; Anaad, Chimedtseren

    2017-08-01

    The Ereendavaa metamorphic terrane in NE Mongolia has long been considered as a Pre-Altaid block or a Precambrian cratonic terrane with a Paleoproterozoic basement overlain by Neoproterozoic-Cambrian rocks, but the idea has not been supported by any isotopic dating. Sensitive high resolution ion microprobe (SHRIMP) zircon U-Pb dating on gneisses, amphibolite and schists (mylonites) of the Ereendavaa terrane suggests that the terrane mainly formed during Early Paleozoic (495-464 Ma) and Late Paleozoic-Early Mesozoic (295-172 Ma). A minor amount of Precambrian rocks might have been involved in the formation of the protoliths of these rocks, as shown by Precambrian inherited zircons (1796-794 Ma). The new age data also suggest that the Ereendavaa terrane experienced at least two periods of magmatism: (1) Early Paleozoic (495-464 Ma) and (2) Late Paleozoic-Early Mesozoic (295-172 Ma), which are probably produced by the subduction of the Paleo Asian Ocean in the south and the subduction of the Mongol-Okhotsk Ocean in the north, respectively. The mylonitized granite (172 Ma) and undeformed pegmatite (163 Ma) are interpreted to be syn- and post-kinematic products. The new age data constrain the closure of the Mongol-Okhotsk Ocean at mid-Jurassic.

  15. Technical viability of self-compacting concretes with by-products from crushed coarse aggregate production

    Directory of Open Access Journals (Sweden)

    Edgar Bacarji

    Full Text Available Abstract The main objective of this work is to present the technical viability of Self Compacting Concretes (SCC containing by-products from crushed coarse aggregate production. For this purpose, a vast characterization of these by-products was made; six mixtures of SCC were produced using two different aggregates: granite and mica schist. The binder/dry aggregate (b/agg ratio by mass was 1:3. The following properties were analyzed: compressive strength, direct tensile strength, flexural tensile strength and splitting tensile strength. Granite presented the best mechanical performance. The replacement of natural sand by granite sand generated concretes with the same level of compressive strength and caused an increase in tensile strength values. The incorporation of silica fume into concrete with granite produced an increase of 17% in compressive strength. So, the use of these by-product materials can provide a technically feasible solution that is also consistent with the aims of sustainable development and preservation of the environment.

  16. Magnetic susceptibility measurements in Yellowstone National Park, USA; Beikoku Yellowstone kokuritsu koen ni okeru genchi jikaritsu sokutei

    Energy Technology Data Exchange (ETDEWEB)

    Okuma, S. [Geological Survey of Japan, Tsukuba (Japan)

    1997-05-27

    For the purpose of interpreting data of the aeromagnetic anomalies in Yellowstone National Park in the U.S.A., in-situ magnetization intensity measurements have been carried out in 1994 and 1995 on geological outcrops of rocks in that area. Comparisons and discussions were given on the measurement results, and existing rock magnetic data and aeromagnetic anomaly data available for the area. Outside the Yellowstone caldera, part of granitic gneisses among the Precambrian granitic gneisses and crystalline schists distributed to the north has an abnormally high magnetization intensity of 1 {times} 10 {sup -2} SI. This could be a powerful anomaly source for the high magnetic anomaly in this area. Paleogene volcanic rocks distributed widely in the eastern part of the park also have magnetization intensity as high as 1 {times} 10 {sup -2} SI or higher, which are also thought a powerful anomaly source in this area. Part of Pleistocene basalts which are exposed partially in the western part of the park has also very high magnetization intensity at 1 {times} 10 {sup -2} SI or higher. This suggests correlation with the magnetic anomaly in the east-west direction distributed in this area. Quaternary rhyolites are more magnetic than Quaternary welded tuffs, which should give greater effects to the magnetic anomaly. 10 refs., 5 figs.

  17. Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis

    Science.gov (United States)

    Zaharescu, Dragos G.; Burghelea, Carmen I.; Dontsova, Katerina; Presler, Jennifer K.; Maier, Raina M.; Huxman, Travis; Domanik, Kenneth J.; Hunt, Edward A.; Amistadi, Mary K.; Gaddis, Emily E.; Palacios-Menendez, Maria A.; Vaquera-Ibarra, Maria O.; Chorover, Jon

    2017-02-01

    The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plant-microbes-mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake.

  18. Structural evidence for northeastward movement on the Chocolate Mountains Thrust, southeasternmost California

    Science.gov (United States)

    Dillon, J.T.; Haxel, G.B.; Tosdal, R.M.

    1990-01-01

    The Late Cretaceous Chocolate Mountains Thrust of southeastern California and southwestern Arizona places a block of Proterozoic and Mesozoic continental crust over the late Mesozoic continental margin oceanic sedimentary and volcanic rocks of the Orocopia Schist. The Chocolate Mountains Thrust is interpreted as a thrust (burial, subduction) fault rather than a low-angle normal fault. An important parameter required to understand the tectonic significance of the Chocolate Mountains and related thrusts is their sense of movement. The only sense of movement consistent with collective asymmetry of the thrust zone folds is top to the northeast. Asymmetric microstructures studied at several localities also indicate top to the northeast movement. Paleomagnetic data suggest that the original sense of thrusting, prior to Neogene vertical axis tectonic rotation related to the San Andreas fault system, was northward. Movement of the upper plate of the chocolate Mountains thrust evidently was continentward. Continentward thrusting suggests a tectonic scenario in which an insular or peninsular microcontinental fragment collided with mainland southern California. -from Authors

  19. Frequency-size distribution of competent lenses in a block-in-matrix mélange: Imposed length scales of brittle deformation?

    Science.gov (United States)

    Fagereng, Å.

    2011-05-01

    This study explores the frequency-size distribution of competent lenses (phacoids) in the Chrystalls Beach Complex, a mélange shear zone within the Otago Schist accretion-collision assemblage, New Zealand. The distribution of phacoids within a cleaved, pelitic matrix follows a power law distribution with exponent 1.18 discontinuous deformation, D = 1.4 ± 0.2. It is suggested that D ≫ 1.4 indicates dominant continuous deformation, whereas D ≪ 1.4 is indicative of localized deformation on shear discontinuities. In this mélange, D therefore appears a function of dominant deformation style. Actively deforming mélange shear zones likely exhibit a range of seismic styles and earthquake magnitudes at length scales limited by lithological layering and shear zone thickness. A hypothesis is suggested where strongly coupled shear zone segments may be distinguished by a high volume fraction of competent material (low D), while aseismically creeping regions are characterized by a high proportion of incompetent rock (high D). As the b value in the Gutenberg-Richter frequency-magnitude relationship also tends to be high in coupled and low in creeping fault segments, it may be that D is analogous to b, and the b value is also related to the ratio of incompetent/competent material and dominant fault zone deformation style.

  20. Deformation mechanisms in the frontal Lesser Himalayan Duplex in Sikkim Himalaya, India

    Science.gov (United States)

    Matin, Abdul; Mazumdar, Sweety

    2009-08-01

    Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to the complex nature of the deformed rocks and their genesis. Crustal deformation in the Himalayan thrust belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at depths controlled mainly by regional strain-rate and geothermal gradient. However, material property, grain-size and their progressive changes during deformation are also important controlling factors. We present evidence of EF deformation from Gondwana rocks developed during the emplacement of one of the frontal horses (Jorthang horse) in the Lesser Himalayan Duplex (LHD) structure associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the Rangit window near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand meso-structures from an undeformed protolith to cataclasite suggesting that it was emplaced under elastico-frictional conditions. Meso- to micro-scale shear fractures are seen developed in Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates are deformed by cataclastic flow suggesting that material property and grain-size have played an important role in the deformation of the Jorthang horse. In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation structures. This suggests that the Jorthang horse was emplaced under shallower crustal conditions than the antiformally folded Ramgarh thrust sheet even though the Ramgarh sheet presently overlies the Jorthang horse.

  1. Garnet-Amphibolites Mineralogy and thermobarometry in Aliabad-Damagh (south of Hamedan, Sanandaj-Sirjan Zone

    Directory of Open Access Journals (Sweden)

    Ali Akbar Baharifar

    2017-11-01

    Full Text Available The garnet-amphibolites in Aliabad-Damagh area, occurs as layers and are enveloped by staurolite-schist. They composed predominantly of garnet, hornblende, feldspar (± muscovite and quartz with titanite, epidote, ilmenite and graphite as accessory minerals. The euhedral garnet porphyroblasts mainly composed of almandine and grossular components, with normal compositional zoning. The hornblende crystals as prophyroblast or in the matrix, are magnesio- and ferro-hornblende (amphibole core to tchermakitic-hornbelende (amphibole rim in composition. Muscovites, if present, with minor phengite and paragonite components, are foliated forming minerals. Feldspars vary from pure K-feldspar to sanidine composition in the vicinity of hornblendes and oligoclase in matrix. Epidotes as pure clinozoisite to epidote, form small crystals inside hornblende or in the matrix. Using different thermobarometry methods, T and P estimated as 600-620 (± 25 °C and 5-6 (± 1 kbar, respectively. Calculated P-T-t path, considering core and rim composition of hornblendes, is in accordance with low-pressure (at the beginning of metamorphism to medium-pressure type (at the end. Considering P-T-t path, metamorphism could occur during Neo-Tethys subduction and collision process in the Mesozoic time

  2. Geologic Map of the Warm Spring Canyon Area, Death Valley National Park, Inyo County, California, With a Discussion of the Regional Significance of the Stratigraphy and Structure

    Science.gov (United States)

    Wrucke, Chester T.; Stone, Paul; Stevens, Calvin H.

    2007-01-01

    Warm Spring Canyon is located in the southeastern part of the Panamint Range in east-central California, 54 km south of Death Valley National Park headquarters at Furnace Creek Ranch. For the relatively small size of the area mapped (57 km2), an unusual variety of Proterozoic and Phanerozoic rocks is present. The outcrop distribution of these rocks largely resulted from movement on the east-west-striking, south-directed Butte Valley Thrust Fault of Jurassic age. The upper plate of the thrust fault comprises a basement of Paleoproterozoic schist and gneiss overlain by a thick sequence of Mesoproterozoic and Neoproterozoic rocks, the latter of which includes diamictite generally considered to be of glacial origin. The lower plate is composed of Devonian to Permian marine formations overlain by Jurassic volcanic and sedimentary rocks. Late Jurassic or Early Cretaceous plutons intrude rocks of the area, and one pluton intrudes the Butte Valley Thrust Fault. Low-angle detachment faults of presumed Tertiary age underlie large masses of Neoproterozoic dolomite in parts of the area. Movement on these faults predated emplacement of middle Miocene volcanic rocks in deep, east-striking paleovalleys. Excellent exposures of all the rocks and structural features in the area result from sparse vegetation in the dry desert climate and from deep erosion along Warm Spring Canyon and its tributaries.

  3. Geology and industrial mineral resources of the Macon-Gordon Kaolin District, Georgia

    Science.gov (United States)

    Buie, Bennett Frank; Hetrick, J.H.; Patterson, S.H.; Neeley, C.L.

    1979-01-01

    The Macon-Gordon kaolin district is about 80 miles (130 km) southeast of Atlanta, Georgia. It extends across the boundary between, and includes parts of, the Piedmont and Atlantic Coastal Plain physiographic provinces. The rocks in the Piedmont are mainly intensely folded sericite schist and granite gneiss containing irregular masses of amphibolite and feldspathic biotite gneiss and scattered igneous intrusive rocks. Most of the crystalline rocks are thought to be of Paleozoic age, but some of the intrusive rocks may be younger. The crystalline rocks are cut by a major unconformity and are overlain by sedimentary formations ranging in age from Cretaceous to Miocene. The valuable kaolin deposits occur in the Cretaceous beds, undivided, and in the Huber Formation which is of Paleocene to middle Eocene age. The resources of kaolin in the district are estimated in millions of metric tons as follows: reserves, 100; subeconomic resources, 700 to 900; undiscovered resources, probably 700 to 1,000. In addition to kaolin, the leading mineral commodity mined in the district, crushed stone and sand are now being produced, and fuller's earth and a minor amount of limestone were formerly produced. The crushed stone is quarried from igneous rocks in the Piedmont province. The sand is washed from the Cretaceous beds, undivided. The fuller's earth was mined from the Twiggs Clay Member of the Barnwell Formation, and limestone was dug from the Tivola Limestone.

  4. Structural analysis of sheath folds in the Sylacauga Marble Group, Talladega slate belt, southern Appalachians

    Science.gov (United States)

    Mies, J.W.

    1993-01-01

    Remnant blocks of marble from the Moretti-Harrah dimension-stone quarry provide excellent exposure of meter-scale sheath folds. Tubular structures with elliptical cross-sections (4 ???Ryz ??? 5) are the most common expression of the folds. The tubes are elongate subparallel to stretching lineation and are defined by centimeter-scale layers of schist. Eccentrically nested elliptical patterns and opposing asymmetry of folds ('S' and 'Z') are consistent with the sheath-fold interpretation. Sheath folds are locally numerous in the Moretti-Harrah quarry but are not widely distributed in the Sylacauga Marble Group; reconnaissance in neighboring quarries provided no additional observations. The presence of sheath folds in part of the Talladega slate belt indicates a local history of plastic, non-coaxial deformation. Such a history of deformation is substantiated by petrographic study of an extracted hinge from the Moretti-Harrah quarry. The sheath folds are modeled as due to passive amplification of initial structures during simple shear, using both analytic geometry and graphic simulation. As indicated by these models, relatively large shear strains (y ??? 9) and longitudinal initial structures are required. The shear strain presumably relates to NW-directed displacement of overlying crystalline rocks during late Paleozoic orogeny. ?? 1993.

  5. Tipologías de cuarzo como indicadores de la procedencia en areniscas: excepciones al método de Basu et al. (1975

    Directory of Open Access Journals (Sweden)

    Arribas, J.

    1988-12-01

    Full Text Available In this study we have analized the content of the different detrital quartz types (Basu et al., 1975 in recent sands derived from single source areas (granitic, gneissic and slate-schists lithologies in the Sistema Central. Following the methodology of Basu et al (1975, for sand provenance interpretation, we have observed Ibat, in these deposits, the content of monocrystaline quartz types is not useful to discriminate plutonic and high rank metamorphic sources. However, we can confirm the validity of the policrystaline types content to distinguish sands of low rank metamorphic parentage.En el presente trabajo se analiza el contenido de las distintas tipologías de cuarzo, definidas por Basu et al. (1975 para análisis de procedencia, en depósitos arenosos actuales, generados a partir de macizos del Sistema Central con distintas litologías (granitos, gneises, pizarras-esquistos. Aplicando la metodología de dichos autores se observa que, para los depósitos estudiados, pierde validez para discriminar áreas de procedencia plutónica y metamórfica de alto grado en función del contenido en las tipologías monocristalinas. No obstante, se corrobora la utilidad del contenido en las tipologías policristalinas para diferenciar áreas metamórficas de bajo grado.

  6. Review of Biohydrometallurgical Metals Extraction from Polymetallic Mineral Resources

    Directory of Open Access Journals (Sweden)

    Helen R. Watling

    2014-12-01

    Full Text Available This review has as its underlying premise the need to become proficient in delivering a suite of element or metal products from polymetallic ores to avoid the predicted exhaustion of key metals in demand in technological societies. Many technologies, proven or still to be developed, will assist in meeting the demands of the next generation for trace and rare metals, potentially including the broader application of biohydrometallurgy for the extraction of multiple metals from low-grade and complex ores. Developed biotechnologies that could be applied are briefly reviewed and some of the difficulties to be overcome highlighted. Examples of the bioleaching of polymetallic mineral resources using different combinations of those technologies are described for polymetallic sulfide concentrates, low-grade sulfide and oxidised ores. Three areas for further research are: (i the development of sophisticated continuous vat bioreactors with additional controls; (ii in situ and in stope bioleaching and the need to solve problems associated with microbial activity in that scenario; and (iii the exploitation of sulfur-oxidising microorganisms that, under specific anaerobic leaching conditions, reduce and solubilise refractory iron(III or manganese(IV compounds containing multiple elements. Finally, with the successful applications of stirred tank bioleaching to a polymetallic tailings dump and heap bioleaching to a polymetallic black schist ore, there is no reason why those proven technologies should not be more widely applied.

  7. Tectonic burial, thrust emplacement, and extensional exhumation of the Cabot nappe in the Appalachian hinterland of Cape Breton Island, Canada

    Science.gov (United States)

    Lynch, Gregory

    1996-02-01

    Silurian imbricate thrusting, Early Devonian high-grade metamorphic nappe emplacement, and Devonian-Carboniferous extensional denudation characterize deformation in the Appalachian hinterland of Cape Breton Island. Compressional deformation following Early Silurian arc volcanism features imbrication of Cambrian-Precambrian basement rocks of Gondwana derivation with Ordovician-Silurian cover sequences across thick zones of mylonite during south directed transport. High grade metamorphism and gneissic rocks of late Silurian age in the region indicate that significant tectonic burial and crustal thickening occurred as a result of the thrusting. Partial denudation of the high grade assemblages occurred during Early Devonian thrust emplacement of the Cabot nappe toward the northwest, along the Highlands Shear Zone. The nappe is characterized by an amphibolitic gneiss and high-grade schist complex defining a large folded klippe above Silurian units. Kyanite is widespread within the nappe, and a distinctive feature of the thrust sheet is the dynamothermal metamorphism of cooler greenschist-grade footwall rocks producing inverted isograds; staurolite is regionally distributed and occurs in pelitic units in the immediate footwall of the Highlands Shear Zone forming a discontinuous halo around the klippe. Greenschist-grade footwall rocks are exposed in structural windows as a result of folding and faulting. Shear sense indicators along the margins of the Cabot nappe have been rotated into their present positions due to superposed folding, providing apparent movement directions for the nappe. Complete exhumation to surface occurred during Late Devonian extension along the low-angle Margaree Shear Zone.

  8. Concentrations and distributions of Al, Fe, Ba and Zn in soils of Pre-Littoral Range, Sector Sentmenat (Catalonia, Spain).

    Science.gov (United States)

    Tume, Pedro; Bech, Jaume; Longan, Lluis; Roca, Nuria; Reverter, Ferrán; Sanchez, Pedro

    2013-04-01

    The Pre-Littoral Range is one of the six morphological units of the Barcelona province parallel to the coast, formed to the SW of the Lobregat fault by conglomerates, sandstones, and limestones. This Mesozoic-Paleogene range covers Paleozoic sediments with outcrops showing mainly Silurian schists and also granites. The main soils are Alfisols, Inceptisols and Entisols. Concentrations and distributions of five elements - Al, Fe, Ba and Zn - in 28 Sentmenat soil profiles (117 soil samples) were investigated. Background data ranges were estimated with the box plot [median ±2 median absolute deviation (MAD)] procedure as follows: Al: 6115 - 13731 mg kg-1, Fe: 7322 - 15106 mg kg-1, Ba: 17.6 - 90.8 mg kg-1 and Zn: 16.3 - 40.7 mg kg-1. Median concentrations of Ba and Zn are lower than the concentration in other European countries. Al concentrations were correlated with clay content, and Ba and Zn were negative correlated with CaCO3. Element distributions in soils reflected parent materials and pedogenic factor determining variation between and within soil profiles. Generally, metal contents decreased in the order of Alfisols> Entisols > Inceptisols and A > B >C horizons.

  9. Glacial landforms and relicts in the high mountains of Taiwan

    Science.gov (United States)

    Chu, H.-T.

    2009-04-01

    Glacial landforms and relicts in the high mountains of Taiwan Hao-tsu Chu Central Geological Survey, MOEA, Taiwan ROC Glacial landforms and relicts are well preserved in the high mountains of Taiwan although substantial orographic precipitation, periglacial, earthquakes, and surface erosion processes have been active ever since the retreat of the last glaciations. Variations of glacial landforms and relicts in the northern, central, and southern areas of Taiwan are attributed mainly to differences in lithology. Cirque glaciers and rectilinear trough valleys are distinctive glacial landforms in the Hseuhshan (3884m) and the Nanhutashan (3742m) area, respectively, in north-central Taiwan. Both of these areas are composed of hard and durable thick layers of meta-sandstone, meta-conglomerate, and quartzite with minor slate. Diagnostic glacial landform and glacial erosional features of streamlined bodies and striated moraines are widely distributed in the high ground above 3300m of the Hohuanshan (3416m) area and the Shangyang Shan (3496m) - Sanchar Shan (3602m) area, respectively in north-central and southern Taiwan. These two areas are mainly composed of weaker rocks of slate, schist with minor meta-sandstones. Whereas in central Taiwan, in the Mount Yushan (3952m) area, limited glacial landforms of polished and striated bedrock surface was found. The preservation of geomorphic surfaces with glacial erosional forms is highly favorable near or at the top of drainage divide where the effect of stream headward erosion, mass wasting, and surface creeping are not obvious.

  10. Petrogenesis of the granitic Donkerhuk batholith in the Damara Belt of Namibia: protracted, syntectonic, short-range, crustal magma transfer

    Science.gov (United States)

    Clemens, J. D.; Buick, I. S.; Kisters, A. F. M.; Frei, D.

    2017-07-01

    The areally extensive (>5000 km2), syn-tectonic, ca. 520 Ma, mainly S-type Donkerhuk batholith was constructed through injection of thousands of mainly sheet-like magma pulses over 20-25 Myr. It intruded schists of the Southern Zone accretionary prism in the Damara Belt of Namibia. Each magma pulse had at least partly crystallised prior to the arrival of the following batch. However, much of the batholith may have remained partially molten for long periods, close to the H2O-saturated granite solidus. The batholith shows extreme variation in chemistry, while having limited mineralogical variation, and seems to be the world's most heterogeneous granitic mass. The Nd model ages of 2 Ga suggest that Eburnean rocks of the former magmatic arc, structurally overlain by the accretionary wedge, are the most probable magma sources. Crustal melting was initiated by mantle heat flux, probably introduced by thermal diffusion rather than magma advection. The granitic magmas were transferred from source to sink, with minimal intermediate storage; the whole process having occurred in the middle crust, resulting in feeble crustal differentiation despite the huge volume of silicic magma generated. Source heterogeneity controlled variation in the magmas and neither mixing nor fractionation was prominent. However, due to the transpressional emplacement régime, local filter pressing formed highly silicic liquids, as well as felsic cumulate rocks. The case of the Donkerhuk batholith demonstrates that emplacement-level tectonics can significantly influence compositional evolution of very large syn-tectonic magma bodies.

  11. Darwin as a geologist in Africa – dispelling the myths and unravelling a confused knot

    Directory of Open Access Journals (Sweden)

    Sharad Master

    2012-09-01

    Full Text Available Two myths persist concerning the role played by Charles Darwin as a geologist in Africa during his epic voyage around the world (1831–1836. The first myth is that Darwin was a completely self-taught geologist, with no formal training. The second myth is that it was Darwin who finally solved the problem of the granite–schist contact at the famous Sea Point coastal exposures in Cape Town, after deliberately setting out to prove his predecessors wrong. These myths are challenged by the now ample evidence that Darwin had excellent help in his geological education from the likes of Robert Jameson, John Henslow and Adam Sedgwick. The story of Darwin and his predecessors at the Sea Point granite contact has become confused, and even conflated, with previous descriptions by Basil Hall (1813 and Clark Abel (1818. Here, the historical record is unravelled and set straight, and it is shown from the evidence of his notebooks that Darwin was quite unaware of the outcrops in Cape Town. His erudite account of the contact was a result of the 8 years spent in writing and correspondence after his return to England and not because of his brilliant insights on the outcrop, as the myth would have it. While there has been little to indicate Darwin’s landfalls in Africa, a new plaque now explains the geology of the Sea Point Contact, and includes a drawing of Darwin’s ship, the Beagle, and quotes from his work.

  12. Consideration on stability of slope in the designated landslide-threatened area using residual strength; Zanryu kyodo wo mochiita jisuberi shiteichinai no shamen no anteisei no kento

    Energy Technology Data Exchange (ETDEWEB)

    Yatabe, R.; Yagi, N.; Yokota, K. [Ehime University, Ehime (Japan). Faculty of Engineering; Matsumura, S. [Kiso-Jiban Consultants Co. Ltd., Tokyo (Japan)

    1997-06-01

    This paper reports an example of the discussion on landslide preventive construction associated with construction of an expressway which passes through the designated landslide-threatened area in Ehime Prefecture. The subject area is located in Umehara area in Nakayama Town of Iyo County in Ehime Prefecture. Its geology consists as the basic rock of green schist belonging to the Minamigawa metamorphic rocks of Palaeozoic and Mesozoic eras. In order to discuss stability of the subject area, a shear test was carried out on soil of the assumed slide surface. The test consisted of a tri-axial test of compaction non-drainage type and a ring shear test. Residual strength of the soil is a shear strength in a condition in which particles are oriented along the slide surface. If the discussion on stability of the landslide-threatened area by using the residual strength determines the area stable, there would be no risk of sliding. The stability was calculated by using the least strength constant among those derived from the ring shear test and such data as the highest ground water level taken during the observation period. As a result, the derived safety factor was found 1.42 even in the smallest figure, largely exceeding 1.0. Thus, this area was determined having no risk of landslide whatever. 5 refs., 7 figs., 3 tabs.

  13. Magnetic prospecting in Kaibuki-yama ancient tomb; Kaibukiyama kofun ni okeru zenjiryoku sokutei

    Energy Technology Data Exchange (ETDEWEB)

    Nishitani, T. [Akita University, Akita (Japan). Mining College

    1996-10-01

    Kaibuki-yama ancient tomb located in Kumeda, Kishiwada City, Osaka has a square shape in the front and an orbicular shape in the rear, which was considered to be made in the 4th century. This ancient tomb has a total length about 135 m, a diameter of orbicular shape in the rear about 82 m, and a height about 9 m, which is a symbolical existence of the Kumeda ancient tombs. Stone chamber and stone casket made of Sanbagawa crystalline schist or rhyolitic-andesitic tuff are expected in this tomb. Magnetic prospecting in this study is accompanied with this survey. A differential type proton magnetometer was used for the measurements, which were conducted using meshes with 1 m edges. A pair of distinct positive and negative magnetic anomalies were observed in the center of orbicular shape in the rear. This coincides with a location of main body buried, which is archaeologically estimated. The magnetic anomaly might be caused by the article buried in the tomb, such as ironware, based on the measurement of magnetic intensity. From the calculated values of magnetic anomaly using a model, the buried article with magnetic anomaly was considered to have a size with length of 1 m, width of 0.1 m, and height of 0.2m. The negative magnetic anomaly could not be explained only by this. It is necessary to consider the other reasons. 8 refs., 8 figs.

  14. Reaction progress during mylonitization of basaltic dikes along the Särv thrust, Swedish Caledonides

    Science.gov (United States)

    Gilotti, Jane A.

    1989-01-01

    The mylonite zone at the base of the Särv thrust sheet, Swedish Caledonides, contains diabase dikes which record intense deformation and syntectonic greenschist facies metamorphism. An angular shear strain of γ≈100 is calculated for a single dike which can be followed for 50 m in the mylonite zone and abundant centimeter thick greenschist layers imply shear strains in excess of 1000. This extraordinary amount of deformation is comparable to the largest strains attained during experimental superplastic deformation of metals and alloys and, by analogy, suggests that dike deformation was macroscopically superplastic. The progress of five syntectonic reactions was measured as a function of increasing strain for the continuously exposed dike in order to assess the contribution of reactionenhanced ductility and fluid-rock interactions to strain localization along the thrust. Reaction progress calculations suggest that the breakdown of amphibole to form weaker phyllosilicates (which are added to the incompetent matrix fraction) is the important strain softening mechanism below γ≈100. The ultimate tectonite is a stable biotite-epidote schist comprised of a uniformly fine grain size (K-metasomatism above γ≈40 also support diffusional flow. Diffusion-accomodated grain boundary sliding is thought to be the dominant micromechanism once the stable biotite-epidote tectonite forms.

  15. Microbial abundance in the deep subsurface of the Chesapeake Bay impact crater: Relationship to lithology and impact processes

    Science.gov (United States)

    Cockell, Charles S.; Gronstal, Aaron L.; Voytek, Mary A.; Kirshtein, Julie D.; Finster, Kai; Sanford, Ward E.; Glamoclija, Mihaela; Gohn, Gregroy S.; Powars, David S.; Horton, J. Wright

    2009-01-01

    Asteroid and comet impact events are known to cause profound disruption to surface ecosystems. The aseptic collection of samples throughout a 1.76-km-deep set of cores recovered from the deep subsurface of the Chesapeake Bay impact structure has allowed the study of the subsurface biosphere in a region disrupted by an impactor. Microbiological enumerations suggest the presence of three major microbiological zones. The upper zone (127–867 m) is characterized by a logarithmic decline in microbial abundance from the surface through the postimpact section of Miocene to Upper Eocene marine sediments and across the transition into the upper layers of the impact tsunami resurge sediments and sediment megablocks. In the middle zone (867–1397 m) microbial abundances are below detection. This zone is predominantly quartz sand, primarily composed of boulders and blocks, and it may have been mostly sterilized by the thermal pulse delivered during impact. No samples were collected from the large granite block (1096–1371 m). The lowest zone (below 1397 m) of increasing microbial abundance coincides with a region of heavily impact-fractured, hydraulically conductive suevite and fractured schist. These zones correspond to lithologies influenced by impact processes. Our results yield insights into the influence of impacts on the deep subsurface biosphere.

  16. The influence of tectonical structures on the stability rock massif in the area of the magnesite deposit Jelšava of the Dúbrava massif

    Directory of Open Access Journals (Sweden)

    Sasvári Tibor

    2002-12-01

    Full Text Available Magnesite deposits Dúbrava and Miková are located in Carboniferous formations between Brádno and Ochtiná (Dúbrava massif. Carboniferous magnesites are, according to the lithostratigraphic division of Early Paleozoic complexes of Gemericum by Bajaník et al. (1983, situated in the Dobšiná Group, more precisely in the upper part of the Ochtiná Formation, in the environment of black schists with intercalation of metabasalts and their pyroclastics. In the lower parts of the formation are small-pebble conglomerates and polymict sandstones. Carbonatic bodies of the Dúbrava massif has the directional length, 4 500 m, course NE-SW, inclination 55-60o to SE and maximal thickness 600 m. A calculation in 1967 indicated above 500 millions kt of reserves whish after a modification of conditional parameters was reduced to its three fifths. Reserves excluded during the second calculation had a higher content of Fe2O3 causing the lowering of fireproof products quality.In the text the structural and stability conditions in the area of the Dúbrava deposit and the Miková deposit of the Dúbrava massif are analysed.

  17. Vertical displacement during late-collisional escape tectonics (Brasiliano Orogeny) in the Ribeira Belt, São Paulo State, Brazil

    Science.gov (United States)

    Hackspacher, P. C.; Godoy, A. M.

    1999-07-01

    During the Brasiliano-Pan-African Orogeny, West Gondwana formed by collisional processes around the São Francisco-Congo Craton. The Ribeira belt, in southeastern Brazil, resulted from northwestward collision (650-600 Ma), followed by large-scale northeast-southwest dextral strike-slip shear movements related to late-collisional escape tectonics ( ca 600 Ma). In São Paulo State, three groups, also interpreted as terranes, are recognised in the Ribeira Belt, the Embu, Itapira and São Roque Groups. The Embu and Itapira Groups are formed of sillimanite-gneisses, schists and migmatites intruded by Neoproterozoic calc-alkaline granitoids, all thrusted northwestward. The São Roque Group is composed of metasediments and metavolcanics in greenschist-facies. Its deformation indicates a transpressional regime associated with tectonic escape. Sub-alkaline granites were emplaced in shallow levels during this regime. Microstructural studies along the Itu, Moreiras and Taxaquara Shear Zones demonstrate the coexistence of horizontal and vertical displacement components during the transpressional regime. The vertical component is regarded as responsible for the lateral juxtaposition of different crustal levels.

  18. Geochronology and crustal evolution of the deposit area Cu-Au Gameleira, Carajas mineral province, Para state, Brazil; Geocronologia e evolucao crustal da area do deposito de Cu-Au Gameleira, provincia mineral de Carajas (Para), Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Galarza, Marco Antonio; Macambira, Moacir Jose Buenano [Para Univ. (UFPA), Belem (Brazil). Centro de Geociencias. Lab. de Geologia Isotopica (Para-Iso)

    2002-12-15

    The Gameleira Cu-Au deposit is hosted by rocks of the Igarape Pojuca Group, Itacaiunas Supergroup, Carajas Mineral Province, southeastern Amazonian Craton. This group is represented mainly by mafic metavolcanic rocks (MVN), amphibolite, biotite schist, banded iron formation and/or hydrothermalite and cut by intrusive mafic rocks (IMR) as well as by deformed Itacaiunas granites of Archean age (2.56 Ga) and Pojuca and Gameleira granites of Proterozoic age (1.87 and 1.58 Ga). Zircon crystals from a saprolite (2615 {+-} 10 Ma and 2683 {+-} 7 Ma) and from an IMR sample (2705 {+-} 2 Ma) are coeval with those from gabbros of the neighboring Aguas Claras deposit. Pb-Pb dating of whole rock samples and chalcopyrite from the MVR indicated ages of 2245 {+-} 29 Ma and 2419 {+-} 12 Ma, respectively, while leached chalcopyrite yielded ages of 2217 {+-} 19 Ma and 2180 {+-} 84 Ma. These ages are interpreted as due to partial resetting provoked by the Proterozoic granitic intrusions or by tectonic reactivation along the Carajas and Cinzento strike slip systems or alternatively, as due to total resetting provoked by the last one. The T{sub DM} ages between 3.12 and 3.33 Ga for the MVR and IMR, and the initial epsilon{sub Nd} (t) values of -0.89 to -3.26 suggest continental contribution from older crustal material and possibly magma generation in a continental rift or active continental margin environment. (author)

  19. Soil microbial biomass under pine forests in the north-western Spain: influence of stand age, site index and parent material

    Energy Technology Data Exchange (ETDEWEB)

    Mahia, J.; Perez-Ventura, L.; Cabaneiro, A.; Diaz-Ravina, M.

    2006-07-01

    The effects of stand age, site index and parent material on soil biochemical properties related to biomass (extractable C, microbial C and metabolic quotient) were examined in the 0-15 cm mineral soil layers of Pinus pinaster and Pinus sylvestris stand from NW Spain. Two productivity levels (low and high site index), two ages (young and old) and two parent soil materials (granite and acid schists) were considered. The data indicated that there were differences in microbial parameters in soils under different species. In general in P. pinaster forest higher values of biochemical parameters expressed on organic C basis, were observed in the stands of high site index as compared with the low ones; in contrast, in P. sylvestris no differences among stand site index were detected. In both species different results were also observed depending on parent material and a significant effect of stand age was detected for extractable C and microbial C in P. pinaster forest developed over granite. The data seem to indicate that measured parameters may have the potential to be used as indicators of the effect of forest management on soil organic matter quality. (Author) 25 refs.

  20. Supracrustal suite of the Precambrian crystalline crust in the Ghor Province of Central Afghanistan

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    Gediminas Motuza

    2017-01-01

    Full Text Available The Proterozoic pre-Ediacaran metamorphic basement of the southern Tajik (North Afghanistan continental block and the adjacent Band-e-Bayan zone is exposed in the Ghor Province of Central Afghanistan. It is predominantly composed of the EW-striking supracrustal succession consisting of interbedded felsic schists and gneisses (metapsammites, amphibolites (metabasalts, calcite and dolomite marbles. The metamorphic facies changes from greenschist in the Band-e-Bayan zone to amphibolite facies in the Tajik block. The supracrustal rocks of the Band-e-Bayan zone and Tajik block possess common features suggesting that the former represents a tectonized part of the latter. The geochemical characteristics of metapsammites indicate derivation of the clastic material from a continental arc and, partly from a passive continental margin, whereas the composition of metabasalts suggests their possible formation in a continental rift basin. The tectonic setting of supracrustal unit could be interpreted as a back-arc type basin. We presume that the Tajik microcontinent split off the Gondwana supercontinent along an ancient rift zone during the late Paleozoic.

  1. Réflexions sur la notion de réserves énergétiques The Concept of Energy Reserves

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    Boy De la Tour X.

    2006-11-01

    Full Text Available L'étude qui est présentée ici rassemble les estimations les plus récentes relatives aux réserves énergétiques. Les combustibles nucléaires, les combustibles solides, les sables et schistes bitumineux sont tour à tour passés en revue et l'importance de leurs réserves est, pour chacun d'entre eux, comparée aux besoins présents et prévisibles. Les hydrocarbures font l'objet d'une analyse plus détaillée au cours de laquelle les principales estimations sont examinées. L'étude du ratio Réserves/Production courante conduit à s'interroger sur la signification des estimations de réserves et sur l'emploi qui doit être fait de cette notion. This article gathers the most recent estimates with regard ta energy reserves. Nuclear fuels, solid fuels, tar sands and oil sables are token up one by one, and the amount of reserves for each is comparéd with present and foreseeable needs. Hydrocarbons make up the subject of a more detailed analysis during which the leading estimates are examined. An analysis of the ratio between Reserves and present production raises questions as to the significance of estimates of reserves and the use that should be made of this concept.

  2. Equilibration conditions of eclogite lenses from Isla Margarita, Venezuela: Implications for the tectonic evolution of the metasedimentary Juan Griego Group

    Science.gov (United States)

    Bocchio, R.; De Capitani, L.; Liborio, G.; Maresch, W. V.; Mottana, A.

    1996-02-01

    The constituent primary and secondary minerals in a suite of fifteen samples of eclogite, amphibole-eclogite and garnet-amphibolite, scattered as boudins and pods in metapelitic schists and gneisses on Isla Margarita, Venezuela, have been analysed by electron microprobe to augment existing bulk-rock chemical data. The large sample population available allows spurious effects of stoichiometric Fe 3+ calculation procedures and bulk-rock influence to be recognised and eliminated. All samples belong to one population with a relatively homogeneous character. The equilibration temperatures are derived from {Fe 2+}/{Mg} fractionation between garnet and clinopyroxene and range from 525-650 °C. Jadeite contents of clinopyroxene and the persistence of minor stable albite constrain pressures to between 13 and 19 kbar. Combined with new evidence for high-pressure metamorphism in the enclosing metapelites and with existing data on an eclogitic metabasic unit exposed in north-eastern Isla Margarita (La Rinconada Group), these data show convincingly that the Margarita crustal block is and has been a relatively coherent unit ever since the entire complex suffered high-pressure metamorphism in Late Mesozoic times.

  3. Methods to ensure the quality of excavated soil material from geogenically metalliferous sites

    Science.gov (United States)

    Liebhard, Peter; Sager, Manfred

    2017-04-01

    Soils at geogenically metalliferous sites might exceed heavy metal threshold levels with respect to agricultural use, apart from anthropogenic contamination sources. As a fundamental substrate for green plants and green plant production, soil is not easily renewable, its formation needs long time (e.g. 500 years for 20 mm). In Austria, about 10ha of soil get sealed every day, resulting in complete loss of its biological functions. Excavated soil material has been classified as waste from a legal point of view, which made 33 mill. tons resp. 48% of total waste in Austria in 2010. Recycling of excavated soil material for agricultural use will be an important task to reduce future waste and to enlarge agricultural substrate volumes, but methods to ensure proper qualities are needed to improve regulations. Within this investigation, the transfer of various metals from geogenically metalliferous soils to various crop plants will be investigated, and correlated with various simple soil test methods. Four excavated soil materials from the metalliferous schist zone within the Austrian province of Styria (Kraubath/Mur, Übelbach) and a low-metal reference sample have been taken as substrates to grow raygrass (lolium multiflorum) as a green cover, salad (Lactuca sativa) as a vegetable food item, oats (Avena sativa), maize (Zea mais) and stinging nettle (Urtica dioica) as a hyperaccumulating species. Results and recommendations will be presented.

  4. Behaviour of the Sm-Nd and Rb-Sr systems of the mafic-ultramafic layered sequence from Ribeirao dos Motas (Archaean), meridional craton Sao Francisco: evidences of mantle source enrichment and isotopic fractionation; Comportamento dos sistemas Sm-Nd e Rb-Sr da sequencia acamadada mafico-ultramafico Ribeirao dos Motas (Arqueano), craton Sao Francisco Meridional: evidencias de enriquecimento mantelico e fracionamento isotopico

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Mauricio Antonio; Carvalho Junior, Irneu Mendes de; Oliveira, Arildo Henrique de [Ouro Preto Univ., (UFOP), MG (Brazil). Dept. de Geologia]. E-mail: mauricio@degeo.ufop.br; Teixeira, Wilson [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica; Pimentel, Marcio Martins [Brasilia Univ., DF (Brazil). Inst. de Geociencias. Lab. de Geocronologia

    2004-10-15

    The Ribeirao dos Motas layered sequence (SARM) crops out in the southern part of the Sao Francisco Craton, Brazil. This sequence comprises phaneritic meta ultramafic and metamafic rocks, which, although slightly deformed and metamorphosed, retain primary igneous layers. Porphyritic rocks with idiomorphic pyroxene crystals and heteradcumulate and adcumulate textures are also present. Eighteen isotopic analyses were performed in the SARM, comprising rocks with primary (relict) textures, as well as rocks in amphibolite facies and retro-metamorphosed to green-schist facies. Seven samples yield a Sm/Nd isochron age of 2.79 +- 0.30 Ga (MSWD=1.2 e epsilon {sub Ndt}=+0.48), constraining the accretion time of the SARM rocks. The positive epsilon {sub Ndt} value coupled with the Rb/Sr evidence is consistent with mantle source relatively enriched in Nd and Sr isotopes. Nevertheless, some SARM samples display isotopic fractionation and disturbance, which can be ascribed to the following processes or their combinations: a) mobilization of the incompatible elements due to regional high grade metamorphism; b) isotopic changes during upper amphibolite facies overprint; c) isotopic resetting by low-grade fluids associated to the Claudio Shear zone, which is located nearby the SARM. (author)

  5. Araxa Group in the type-area: A fragment of Neoproterozoic oceanic crust in the Brasilia Fold Belt; Grupo Araxa em sua area tipo: um fragmento de crosta oceanica Neoproterozoica na faixa de dobramentos Brasilia

    Energy Technology Data Exchange (ETDEWEB)

    Seer, Hildor Jose [Centro Federal de Educacao Tecnologica de Araxa, (CEFET), MG (Brazil); Brod, Jose Affonso; Fuck, Reinhardt Adolfo; Pimentel, Marcio Martins; Boaventura, Geraldo Resende; Dardenne, Marcel Auguste [Brasilia Univ., DF (Brazil). Inst. de Geociencias

    2001-09-01

    This study reviews the geological characteristics and puts forward a new evolution model for the Araxa Group in its type-area, the southern segment of the Neo proterozoic Brasilia Belt, Minas Gerais, Brazil. The Araxa Group is confined within a thrust sheet belonging to a syn formal regional fold, the Araxa Syn form, overlying two other thrust sheets made of the Ibia and Canastra Groups. The Araxa Group is described as a tectono stratigraphic terrane in the sense of Howell (1993). It comprises an igneous mafic sequence, with fine and coarse grained amphibolites, associated with pelitic meta sedimentary rocks, and subordinate psanmites. All rocks were metamorphosed to amphibolite facies at ca. 630 Ma ago and were intruded by collisional granites. The amphibolites represent original basaltic and gabbroic rocks, with minor ultramafic (serpentinite/ amphibole-talc schist). The basalts are similar to high Fe O tholeiites, with REE signatures that resemble E-MORB and {epsilon}{sub Nd(T)} =+ 1.1. The meta sedimentary rocks are interpreted as the result of a marine deep-water sedimentation. They have Sm-Nd model ages of 1,9 Ga, and {epsilon}{sub Nd(T)} = -10.21. The amphibolites and metasediments could represent a fragment of back-arc oceanic crust. The data presented here differ significantly from the original definition of Barbosa et al. (1970) who describe the Araxa Group as a pelitic/psanmitic sequence and the collisional granites as a basement complex. (author)

  6. STRATIGRAPHIC FEATURES OF NEOGENE DEPOSITS OF DİLEKÇİ (WEST OF KONYA AREA

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    A. Müjdat ÖZKAN

    1999-03-01

    Full Text Available The basement of the investigated area is Silurian-Cretaceous aged basement rocks. The basement rocks consists of phillite, schist, quartzite, limestone, dolomite, spilite, diorite, gabbro, diabase and serpentinite. This basement is overlined unconformably by Upper Miocene-Lower Pliocene aged Sille formation, Yalıtepe formation, Ulumuhsine formation, Küçükmuhsine formation, Lower Pliocene aged Yürükler formation and Upper Pliocene-Quaternary aged Topraklı formation. Sille formation consists of red conglomerate, sandstone and mudstone, deposited in alluvial fan and braided stream environments. Yalıtepe formation contains cream, brown stromatolitic limestone formed in a shallow lake environment. Ulumuhsine formation is made by cream, limestone, clayey limestone, clayey limestone-mudstone alternation, mudstone, marl, dolomite, nodules and bands of chert-bearing, fossils-bearing limestone deposited in a shallow and open lake environment. Küçükmuhsine formation formed in a shallow and open lake environment consists of tuffite. Yürükler formation overlies conformably and unconformably in local Ulumuhsine and Küçükmuhsine formations, and contains conglomerate, and caliche nodulled mudstone deposited in alluvial fan and braided Stream environments. All these lithologies is overlined unconformably by Upper Pliocene-Quaternary aged Topraklı formation. Topraklı formation consists of conglomerate deposited in alluvial fan and braided stream environments. Neogene basin in the region have characteristics of an intra-mountain basin, time to time controlled by tectonics.

  7. Control of rock joint parameters on deformation of tunnel opening

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    Suman Panthee

    2016-08-01

    Full Text Available Tunneling in complex rock mass conditions is a challenging task, especially in the Himalayan terrain, where a number of unpredicted conditions are reported. Rock joint parameters such as persistence, spacing and shear strength are the factors which significantly modify the working environments in the vicinity of the openings. Therefore, a detailed tunnel stability assessment is critically important based on the field data collection on the excavated tunnel's face. In this context, intact as well as rock mass strength and deformation modulus is obtained from laboratory tests for each rock type encountered in the study area. Finite element method (FEM is used for stability analysis purpose by parametrically varying rock joint persistence, spacing and shear strength parameters, until the condition of overbreak is reached. Another case of marginally stable condition is also obtained based on the same parameters. The results show that stability of tunnels is highly influenced by these parameters and the size of overbreak is controlled by joint persistence and spacing. Garnetiferous schist and slate characterized using high persistence show the development of large plastic zones but small block size, depending upon joint spacing; whereas low persistence, low spacing and low shear strength in marble and quartzite create rock block fall condition.

  8. Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis.

    Science.gov (United States)

    Zaharescu, Dragos G; Burghelea, Carmen I; Dontsova, Katerina; Presler, Jennifer K; Maier, Raina M; Huxman, Travis; Domanik, Kenneth J; Hunt, Edward A; Amistadi, Mary K; Gaddis, Emily E; Palacios-Menendez, Maria A; Vaquera-Ibarra, Maria O; Chorover, Jon

    2017-02-23

    The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plant-microbes-mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake.

  9. Estimation of soft sediment thickness in Kuala Lumpur based on microtremor observation data

    Science.gov (United States)

    Chiew, Chang Chyau; Cheah, Yi Ben; Tan, Chin Guan; Lau, Tze Liang

    2017-10-01

    Seismic site effect is one of the major concerns in earthquake engineering. Soft ground tends to amplify the seismic wave in surficial geological layers. The determination of soft ground thickness on the surface layers of the earth is an important input for seismic hazard assessment. This paper presents an easy and convenient approach to estimate the soft sediment thickness at the site using microtremor observation technique. A total number of 133 survey points were conducted in selected sites around Kuala Lumpur area using a microtremor measuring instrument, but only 103 survey points contributed to the seismic microzonation and sediment thickness plots. The bedrock of Kuala Lumpur area is formed by Kenny Hill Formation, limestone, granite, and the Hawthornden Schist; however, the thickness of surface soft ground formed by alluvial deposits, mine tailings, and residual soils remains unknown. Hence, the predominant frequency of the ground in each site was determined based on Nakamura method. A total number of 14 sites with known depth to bedrock from the supply of geotechnical reports in the study area were determined. An empirical correlation was developed to relate the ground predominant frequency and soft ground thickness. This correlation may contribute to local soil underlying the subsurface of Kuala Lumpur area. The finding provides an important relationship for engineers to estimate the soft ground thickness in Kuala Lumpur area based on the dynamic characteristics of the ground measured from microtremor observation.

  10. Resource investigation of low- and moderate-temperature geothermal areas in San Bernardino, California. Part of the third year report, 1980-81, of the US Department of Energy-California State-Coupled Program for Reservoir Assessment and Confirmation

    Energy Technology Data Exchange (ETDEWEB)

    Youngs, L.G.; Bezore, S.P.; Chapman, R.H.; Chase, G.W.

    1981-08-01

    Ninety-seven geothermal wells and springs were identified and plotted on a compiled geologic map of the 40-square-mile study area. These wells and springs were concentrated in three distinguishable resource areas: Arrowhead Hot Springs; South San Bernardino; and Harlem Hot Springs - in each of which detailed geophysical, geochemical, and geological surveys were conducted. The Arrowhead Hot Springs geothermal area lies just north of the City of San Bernardino in the San Bernardino Mountains astride a shear zone (offshoot of the San Andreas fault) in pre-Cambrian gneiss and schist. The Harlem Hot Springs geothermal area, on the east side of the City, and the south San Bernardino geothermal area, on the south side, have geothermal reservoirs in Quaternary alluvial material which overlies a moderately deep sedimentary basin bound on the southwest by the San Jacinto fault (a ground water barrier). Geothermometry calculations suggest that the Arrowhead Hot Springs geothermal area, with a maximum reservoir temperature of 142/sup 0/C, may have the highest maximum reservoir temperature of the three geothermal areas. The maximum temperature recorded by CDMG in the south San Bernardino geothermal area was 56/sup 0/C from an artesian well, while the maximum temperature recorded in the Harlem Hot Springs geothermal area was 49.5/sup 0/C at 174 meters (570 feet) in an abandoned water well. The geophysical and geological surveys delineated fault traces in association with all three of the designated geothermal areas.

  11. The surge tank of the Kops II HPP. Design, technical concept and construction; Das hochdruckseitige Wasserschloss des Kopswerks II. Bauliche Planung, Konzeption und technische Ausfuehrung

    Energy Technology Data Exchange (ETDEWEB)

    Wegeler, Gerd; Gerstner, Reinhold [Vorarlberger Illwerke AG, Schruns (Austria)

    2010-01-15

    The Hydropower Plant (HPP) Kops II (Western Austria), arranged as a parallel plant to the existing HPP-Kops I, utilizes the existing reservoir Kops as upper reservoir, and the balancing reservoir Rifa, as lower reservoir. Due to the very fast regulation time of the three hydropower production units, the headrace system containing a penstock, a surge tank and a high head pressure tunnel, is exposed to high dynamic loads. The surge tank with an inclined shaft and a upper and lower chamber is facing different ground water tables, separated by layers of mica schist. Due to the geological and hydrogeological conditions and to the internal pressure conditions, a special surge tank geometry and different types of lining were applied. According to the low internal pressure, the upper chamber was lined with a contact grouted non reinforced cast in situ concrete shell. In the surge tank's inclined shaft a pre-stressed and predominantly non reinforced concrete lining was installed. And in the lower chamber, caused by different structural engineering reasons, both, a steal lining and a concrete lining, pre-stressed by grouting, was applied. (orig.)

  12. Effect of the spatial distribution of physical aquifer properties on modelled water table depth and stream discharge in a headwater catchment

    Directory of Open Access Journals (Sweden)

    C. Gascuel-Odoux

    2010-07-01

    Full Text Available Water table depth and its dynamics on hillslopes are often poorly predicted despite they control both water transit time within the catchment and solute fluxes at the catchment outlet. This paper analyses how relaxing the assumption of lateral homogeneity of physical properties can improve simulations of water table depth and dynamics. Four different spatial models relating hydraulic conductivity to topography have been tested: a simple linear relationship, a linear relationship with two different topographic indexes, two Ks domains with a transitional area. The Hill-Vi model has been modified to test these hypotheses. The studied catchment (Kervidy-Naizin, Western France is underlain by schist crystalline bedrock. A shallow and perennial groundwater highly reactive to rainfall events mainly develops in the weathered saprolite layer. The results indicate that (1 discharge and the water table in the riparian zone are similarly predicted by the four models, (2 distinguishing two Ks domains constitutes the best model and slightly improves prediction of the water table upslope, and (3 including spatial variations in the other parameters such as porosity or rate of hydraulic conductivity decrease with depth does not improve the results. These results underline the necessity of better investigations of upslope areas in hillslope hydrology.

  13. Three-dimensional grain fabric measurements using high-resolution X-ray computed tomography

    Science.gov (United States)

    Ketcham, Richard A.

    2005-07-01

    High-resolution X-ray computed tomography (HRXCT) provides detailed imagery of the interiors of rocks up to hand-sample size, non-destructively and in three dimensions. New tools described here allow these data to be used for analysis of grain fabrics. Two separate sets of measurement techniques have been developed. The first concentrates on quantifying individual crystals (phenocrysts, porphyroblasts) or other discrete objects or void spaces within a sample. Quantifiable properties include location, size, shape, orientation, and contact relationships with adjacent objects. The second set of techniques performs a more general fabric analysis on any distinguishable component in a sample. A fabric tensor can be computed based on a number of metrics, including the star volume distribution (SVD), star length distribution (SLD), and mean intercept length (MIL) methods. The fabric tensors provide principal component directions and magnitudes, which in turn provide a measure of degree of anisotropy and shape indices. Because the SVD and SLD measure only the material of interest, whereas the MIL is also influenced by spatial distribution, results can be divergent for sparse phases. Also introduced is a three-dimensional rose diagram that can be viewed interactively and inspected to reveal further details about non-orthogonal directional components. These techniques are demonstrated through analysis of a garnet-kyanite schist from Mica Dam, British Columbia.

  14. POLARIMETRIC SIGNATURES IDENTIFICATION FOR DIFFERENT FEATURES IN RADARSAT-2 POLSAR IMAGE: A CASE STUDY OF HALAYIB AREA, EGYPT

    Directory of Open Access Journals (Sweden)

    A. H. Nasr

    2016-06-01

    Full Text Available In fully polarized SAR (PolSAR data the returned signal from a target contains all polarizations. More information about this target may be inferred with respect to single-polarization. Distinct polarization separates targets due to its different backscattering responses. A Radarsat-2 PolSAR image acquired on December 2013 of part of Halayib area (Egypt was used in this study. Polarimetric signatures for various features (Wadi deposits, Tonalite, Chlorite schist, and Radar penetrated areas were derived and identified. Their Co-polarized and Cross-polarized signatures were generated, based on the calculation of the backscattered power at various ellipticity and orientation angles. Graphical 3D-representation of these features was provided and more details of their physical information are depicted according to their different polarization bases. The results illustrate that polarimetric signatures, obtained due to factors like surface roughness, dielectric constant and feature orientation, can be an effective representation for analyzing various features. The shape of the signature is significant and can also indicate the scattering mechanisms dominating the features response.

  15. The provenance of selected heavy metals in soils near power plant of Hamedan: A pedological approach

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    Sh. Nosratipoor

    2014-11-01

    Full Text Available To determine the origin of heavy metals, the effects of parent materials, soil genesis, and human activities on the content and distribution of selected metals in soils near Mofateh Martyr powerhouse, Hamedan, were assessed. Six types of parent materials including shale, schist, limestone, alluvial plain, alluvial terraces and fan deposits were identified and soil genesis were studied. Total content of Cd, Cu, Mn, Ni, Zn, Pb, Fe were determined in soil horizons and parent materials. Concentration of the metals in four different chemical phases, including acetic acid extractable, reducible, oxidizable and residual fractions, was determined with four-step sequential extraction procedure. Soil development is limited in the studied region so that the discrepancy between solum and parent material in terms of heavy metal content is not great in general. Calcareous soils and limestone have the lowest amount of copper, manganese, nickel, zinc, lead and iron. Independent of soil types and parent materials, most of the heavy metals, except Mn, were present in the residual fraction. The concentration of Mn in all profiles is highest in reducible fraction. Low degree of soil development and the prevalent presence of metals in residual fraction show the influential role of parent materials in controlling metal concentration and distribution; pedogenic processes have minor effects. The role of human activities is limited for most of the selected metals; however, the tangible presence of Pb and, in some cases, Cd in acetic acid extractable fraction, reflects the impact of human activities on the concentrations of these two metals.

  16. An Early Cretaceous garnet pressure-temperature path recording synconvergent burial and exhumation from the hinterland of the Sevier orogenic belt, Albion Mountains, Idaho

    Science.gov (United States)

    Kelly, Eric D.; Hoisch, Thomas D.; Wells, Michael L.; Vervoort, Jeffrey D.; Beyene, Mengesha A.

    2015-08-01

    Rocks may undergo complex pressure-temperature ( P- T) histories during orogenesis in response to alternating episodes of synconvergent burial and exhumation. In this study, chemical zoning in garnets combined with textural and chemical evidence from the schist of Willow Creek in the Albion Mountains of south-central Idaho (USA), reveals a complex P- T path during the early stages of Sevier orogenesis. The distribution of quartz inclusions combined with internal resorption features establishes a hiatus in garnet growth. Chemical zoning was simulated using a G-minimization approach to yield a P- T path consisting of three distinct pressure changes during increasing temperature, defining an "N" shape. Lu-Hf isochron ages from multiple garnet fractions and whole-rock analyses in two samples are 132.1 ± 2.4 and 138.7 ± 3.5 Ma. The samples were collected from the hanging wall of the Basin-Elba thrust fault and yielded results similar to those previously obtained from the footwall. This leads to several conclusions: (1) Both the hanging wall and footwall experienced the same metamorphic event, (2) the paths document a previously unrecognized crustal thickening and synorogenic extension cycle that fills an important time gap in the shortening history of the Sevier retroarc, suggesting progressive eastward growth of the orogen rather than a two-stage history, and (3) episodes of extensional exhumation during protracted convergent orogenesis are increasingly well recognized and highlight the dynamic behavior of orogenic belts.

  17. The Sabzevar blueschists of the North-Central Iranian micro-continent as remnants of the Neotethys-related oceanic crust subduction

    Science.gov (United States)

    Omrani, Hadi; Moazzen, Mohssen; Oberhänsli, Roland; Altenberger, Uwe; Lange, Manuela

    2013-07-01

    The Sabzevar ophiolites mark the Neotethys suture in east-north-central Iran. The Sabzevar metamorphic rocks, as part of the Cretaceous Sabzevar ophiolitic complex, consist of blueschist, amphibolite and greenschist. The Sabzevar blueschists contain sodic amphibole, epidote, phengite, calcite ± omphacite ± quartz. The epidote amphibolite is composed of sodic-calcic amphibole, epidote, albite, phengite, quartz ± omphacite, ilmenite and titanite. The greenschist contains chlorite, plagioclase and pyrite, as main minerals. Thermobarometry of a blueschist yields a pressure of 13-15.5 kbar at temperatures of 420-500 °C. Peak metamorphic temperature/depth ratios were low (~12 °C/km), consistent with metamorphism in a subduction zone. The presence of epidote in the blueschist shows that the rocks were metamorphosed entirely within the epidote stability field. Amphibole schist samples experienced pressures of 5-7 kbar and temperatures between 450 and 550 °C. The presence of chlorite, actinolite, biotite and titanite indicate greenschist facies metamorphism. Chlorite, albite and biotite replacing garnet or glaucophane suggests temperatures of >300 °C for greenschist facies. The formation of high-pressure metamorphic rocks is related to north-east-dipping subduction of the Neotethys oceanic crust and subsequent closure during lower Eocene between the Central Iranian Micro-continent and Eurasia (North Iran).

  18. The radiolarian evidence for the accretion of the Fu-saki Formation with the inferred oceanic plate stratigraphy: A case of weakly-metamorphosed accretionary complex in Ishigaki Jima, southern Ryukyu Arc, Japan

    Science.gov (United States)

    Nakae, Satoshi

    2013-09-01

    The island of Ishigaki Jima, located in the western part of the southern Ryukyu Arc, Japan, is underlain by a basement comprising the Tumuru and Fu-saki formations. The former is a pelitic glaucophane schist with a metamorphic age of 220-190 Ma, and the latter is a weakly metamorphosed accretionary complex, composed mainly of chert, mudstone and sandstone with minor amounts of limestone and mafic rocks. The Fu-saki Formation was weakly metamorphosed at ∼140 Ma. Latest Carboniferous-Early Jurassic microfossils have been obtained from the limestones, cherts and siliceous mudstones of this formation, but no fossils have been collected from the phyllitic mudstones. The radiolarian fauna of the phyllitic mudstones described herein indicates a late Pliensbachian-early Toarcian (Early Jurassic) age. This result, when combined with existing data, enables the reconstruction of an oceanic plate stratigraphy, showing a succession of (in ascending order) Upper Carboniferous-Triassic cherts, Sinemurian-lower Pliensbachian siliceous mudstones and upper Pliensbachian-lower Toarcian phyllitic mudstones and sandstones. The radiolarians from the phyllitic mudstones are important in constraining the timing of the accretion of the Fu-saki Formation to the base of the Tumuru Formation.

  19. A weakening mechanism for intermediate-depth seismicity? Detailed petrographic and microtextural observations from blueschist facies pseudotachylytes, Cape Corse, Corsica

    Science.gov (United States)

    Deseta, N.; Andersen, T. B.; Ashwal, L. D.

    2014-01-01

    Gabbro- and peridotite-hosted pseudotachylytes from the Alpine Schistes Lustres Unit in Corsica, previously determined to have formed at blueschist to lawsonite-eclogite facies conditions, have been causally linked to the generation of intermediate-depth earthquakes, which occur at depths of 50-300 km. Detailed petrographic and microtextural analyses of these pseudotachylytes suggest that their initiation may be controlled by a thermally-activated shear runaway process that is controlled by rheology rather than mineralogy. This is documented by sheared out, prolate, kinked and twinned wallrock clasts that have been peeled off and entrained into the pseudotachylyte vein as sigmoid survivor clasts. The presence of metastable high temperature crystallisation products in the pseudotachylyte, such as hoppers and dendrites of olivine, enstatite and diopside (peridotite) and Al-rich omphacite and Fe-rich anorthite in metagabbro, are suggestive of a short-lived high-temperature event resulting from thermal instability. These high temperature mineral assemblages are overprinted by ones indicating a return to ambient conditions of lower temperatures, but still high pressures: glaucophane, albite and epidote in metagabbro and clinochlore; and fine-grained granoblastic olivine, enstatite and diopside in peridotite. The observations from this detailed study of natural samples suggest that intermediate-depth seismicity may be generated by a thermal runaway process.

  20. Thermobarometric and fluid expulsion history of subduction zones

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, W.G. (Univ. of California, Los Angeles (United States))

    1990-06-10

    Phanerozoic, unmetamorphosed, weathered, and altered lithotectonic complexes subjected to subduction exhibit the prograde metamorphic facies sequence: zeolite {r arrow} prehnite-pumpellyite {r arrow} glaucophane schist {r arrow} eclogite. Parageneses reflect relatively high-P trajectories, accompanied by semicontinuous devolatilization. The thermal evolution of convergent plate junctions results in early production of high-rank blueschists, high-P amphibolites, and eclogites at depth. Inclusion studies suggest that two-phase immiscible volatiles are evolved in turn during progressive metamorphism of the subducted sections. Expulsion of pore fluids and transitions from weathered and altered supracrustal rocks to zeolite facies assemblages release far more fluid than the better understood higher-grade transformations. Many blueschist parageneses (e.g., Western Alps) have been partially overprinted by later greenschist and/or epidote-amphibolite facies assemblages. Less common blueschist terranes (e.g., Franciscan belt of western California) preserve metamorphic aragonite and other high-P minerals, and lack a low-pressure overprint; physical conditions during retrogression approximately retraced the prograde path or, for early formed high-grade blocks, reflect somewhat higher pressures and lower temperatures. The ease with which volatiles are expelled from a subduction complex and migrate upward along the plate junction zone is roughly proportional to the sandstone/shale ratio: low-permeability mudstones tend to maintain P{sub fluid} values approaching lithostatic, lose strength, and deform chaotically (forming melange belts), whereas permeable sandstone-rich sections retain structural/stratigraphic coherence and fail brittlely (forming coherent terranes).

  1. Tectonic superposition of the Kurosegawa Terrane upon the Sanbagawa metamorphic belt in eastern Shikoku, southwest Japan; K-Ar ages of weakly metamorphosed rocks in northeastern Kamikatsu town, Tokushima Prefecture

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Hisashi; Isozaki, Yukio (Yamaguchi Univ. (Japan). Faculty of Science); Itaya, Tetsumaru

    1990-02-01

    Weakly metamorphosed pre-Cenozoic accretionary complex in the northern part of the Chichibu Belt in Kamikatsu Town, eastern Shikoku, consists of two distinct geologic units; the Northern Unit and Southern Unit. The Northern Unit is composed mainly of phyllitic pelites and basic tuff with allochthonous blocks of chert and limestone, and possesses mineral paragenesis of the glaucophane schist facies. The Southern Unit is composed mainly of phyllitic pelites with allochthonous blocks of sandstone, limestone, massive green rocks, and chert, and possesses mineral paragenesis of the pumpellyite-actinolite facies. The Southern Unit tectonically overlies the Northern Univ by the south-dipping Jiganji Fault. K-Ar ages were dated for the recrystallized white micas from 11 samples of pelites and basic tuff in the Northern Unit, and from 6 samples of pelites in the Southern Unit. The K-Ar ages of the samples from the Northern Unit range in 129-112 Ma, and those from the Southern Unit in 225-194 Ma. In terms of metamorphic ages, the Northern Unit and Southern Unit are referred to the constituents of the Sanbagawa Metamorphic Belt, and to those of the Kurosegawa Terrane, respectively. Thus, tectonic superposition of these two units in the study area suggests that the Kurosegawa Terrane occurs in a higher structural position over the Sanbagawa Metamorphic Belt in eastern Shikoku. (author).

  2. Oxygen and hydrogen isotope compositions of eclogites and associated rocks from the Eastern Sesia zone (Western Alps, Italy)

    Science.gov (United States)

    Desmons, J.; O'Neil, J.R.

    1978-01-01

    Oxygen and hydrogen isotope analyses have been made of mineral separates from eclogites, glaucophanites and glaucophane schists from the eastern Sesia zone (Italian Western Alps). Regularities in (1) hydrogen isotope compositions, (2) order of 18O enrichment among coexisting minerals, and (3) ?? 18O (quartz-rutile) and ?? 18O (quartz-phengite) imply attainment of a high degree of isotopic equilibrium. However, some scattering of ??18O values of individual minerals indicates that the eclogitic assemblage did not form in the presence of a thoroughly pervasive fluid. Minerals from an eclogitic lens enclosed in marble have ??18O values distinctly different from those measured in the other rocks. The ??18O values are high in comparison with other type C eclogites of the world, and it is proposed that the fluid present during the high pressure metamorphism has to a large extent been inherited from the precursor rocks of amphibolite facies. An average formation temperature of 540 ?? C is inferred from the oxygen isotope fractionations between quartz and rutile and between quartz and white mica. This temperature is in accordance with petrologic considerations and implies subduction of the precursor rocks into the upper mantle to achieve the high pressures required. ?? 1978 Springer-Verlag.

  3. Geology of the Lake Pillsbury area, northern coast ranges, California

    Energy Technology Data Exchange (ETDEWEB)

    Etter, S.D.

    1979-01-01

    Rock units in the Lake Pillsbury area are Franciscan Complex and non-Franciscan (Great Valley Sequence-type) strata and surficial deposits. Franciscan units include relatively coherent sequences, broken-formations, and malanges comprising chiefly graywackes and mudstone, with variable abundances of both native and exotic blocks. Non-Franciscan units comprise generally mildly deformed coherent sequences of graywacke, shale, conglomerate, and limestone. A larger portion of the Lake Pillsbury area is underlain by non-Franciscan lithologies than had been indicated by previous mapping. Franciscan strata range in age from Mid-Jurassic or older to Late Cretaceous (Cenomanian .); non-Franciscan strata range from Jurassic (Tithonian) to Middle Tertiary. The distributions of metamorphic minerals in graywackes (chiefly lawsonite, aragonite, jadeitic pyroxene, glaucophane, pumpellyite, and laumontite) indicate that most Franciscan rocks have undergone high pressure - low temperature blue-schist metamorphism, and that non-Franciscan rocks have undergone lower pressure, zeolite metamorphism. Franciscan rocks are, on average, more dense than non-Franciscan rocks. Franciscan graywackes contain virtually no detrital K-feldspar; K-feldspar content of non-Franciscan sandstones increases with decreasing age and inferred depth of burial. Overall, compositions and physical properties of Lake Pillsbury non-Franciscan sandstones are similar to those of sandstones of the same age from Great Valley Sequence strata.

  4. Petrology and U-Pb zircon dating of coesite-bearing metapelite from the Kebuerte Valley, western Tianshan, China

    Science.gov (United States)

    Yang, Xin; Zhang, Lifei; Tian, Zuolin; Bader, Thomas

    2013-07-01

    This paper deals with the petrology and U-Pb dating of coesite-bearing garnet-phengite schist from the Kebuerte Valley, Chinese western Tianshan. It mainly consists of porphyroblastic garnet, phengite, quartz and chlorite with minor amounts of paragonite, albite, zoisite and chloritoid. The well preserved coesite inclusions (˜100 μm) in garnet are encircled by a narrow rim of quartz. They were identified by optical microscopy and confirmed by Raman spectroscopy. Using the computer program THERMOCALC, the peak metamorphic conditions of 29 kbar and 565 °C were obtained via garnet isopleth geothermobarometry. The predicted UHP peak mineral assemblage comprises garnet + jadeite + lawsonite + carpholite + coesite + phengite. The metapelite records prograde quartz-eclogite-facies metamorphism, UHP coesite-eclogite-facies peak metamorphism, and a late greenschist-facies overprint. Phase equilibrium modeling predicts that garnet mainly grew in the mineral assemblages garnet + jadeite + lawsonite + chloritoid + glaucophane + quartz + phengite and garnet + jadeite + lawsonite + carpholite + glaucophane + quartz + phengite. SHRIMP U-Pb zircon dating of the coesite-bearing metapelite yielded the peak metamorphic age 320.4 ± 3.7 Ma. For the first time, age data of coesite-bearing UHP metapelite from the Chinese western Tianshan are presented in this paper. They are in accord with published ages obtained from eclogite from other localities in the Chinese western Tianshan and the Kyrgyz South Tianshan and therefore prove a widespread occurrence of UHP metamorphism.

  5. Baikal rift basement: structure and tectonic evolution

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, A.I.; Mazukabzov, A.M.; Sklyarov, E.V.; Vasiljev, E.P. (AN SSSR, Irkutsk (Russian Federation). Sibirskij Ehnergeticheskij Inst.)

    1994-06-30

    The Baikal rift zone in East Siberia has, due to its very long history, starting in the Early Precambrian and continuing into the Cenozoic, an heterogeneous structure. Two major structural elements are distinguished: the Siberian craton and the Sayan-Baikal fold system, which is part of the Central Asian Fold Belt. Within the craton, the following units are recognized: the Early Precambrian metamorphic rocks of the basement, the Vendian-Paleozoic sedimentary cover with superimposed Paleozoic and Mesozoic basins and a reworked margin which is transitional between the craton and the fold belt. The Sayan-Baikal fold system comprises the Barguzin, Tuva-Mongolian and Dzhida terranes. The Barguzin and Tuva-Mongolian terranes are composite, consisting of separate Early Precambrian massifs, volcanic-sedimentary and carbonate Phanerozoic terranes, impregnated by granites. They are thus super-terranes. The oldest units are ophiolites, dated around 1.1 - 1.3 Gy in the Barguzin terrane and 0.9 - 1.1 Gy in the Tuva-Mongolian terrane. They associate with complexes of immature island-arc accretionary wedges of mainly terrigenous or terrigeno-volcanic composition with occasional slices of ophiolite and glaucophane schists. (authors). 68 refs., 12 figs., 2 tabs.

  6. The thermodynamic regime of metamorphism in the ancient subduction zones

    Science.gov (United States)

    Perchuk, L. L.; Aranovich, L. Ya.

    1981-02-01

    Based on mineralogical themometry and baroraetry and computation of mineral reactions modelling metamorphic sequence, a geotherm for metamorphic belts of the subduction zones has been deduced. Relatively low PT-values (3 kbar/200° C) correspond to zeolite and prehnite-pumpellyite metasediments and at higher pressures and temperatures (10 kbar/400 °C) lawsonite-glaucophane assemblages become unstable. The PT-curve achieves maximum at 11 kbar and 470° C to drop down to normal geotherm (Perchuk 1977). High concentration of H2O in the metamorphic fluid has been revealed, the difference between Pf1 and P_{{text{H}}_{text{2}} {text{O}}} being less than 2 kbar. Consideration has also been given to specific thermodynamic regime of zeolite and prehnite-pumpellyite zones of the younger island arcs, where lawsoniteglaucophane zones are absent. Here the geotherm has been found to rise from 0.2kbar/120° C up to 4 kbar/350° C and P_{{text{H}}_{text{2}} {text{O}}}-regime similar to that of glaucophane schists formations.

  7. Fine-grained clay fraction (,0.2 {mu}m): An interesting tool to approach the present thermal and permeability state in active geothermal systems

    Energy Technology Data Exchange (ETDEWEB)

    Patrier, P.; Papapanagiotou, P.; Beaufort, D.; Traineau, H.; Bril, H.

    1992-01-01

    We have investigated by X-ray diffraction the very fine grained secondary minerals (< 0.2 {micro}m) developed in geothermal systems, in relation with their present thermal and permeability state. Because the smallest particles are the most reactive part of a rock, they are the youngest mineral phases of the geothermal fields. This study has been performed on two active geothermal fields: Milos field, Greece (130 < T < 320 C) and Chipilapa field, Salvador (90 < T < 215 C). In the Milos field, the mineralogical composition of the < 0.2 {micro}m clay fraction observed in the reservoir strongly differs from the overlying altered metamorphic schists in the presence of abundant quantities of saponite and talc/saponite interstratified minerals at unusually high temperature. These phases are considered to be kinetically control-led ''metastable'' minerals which rapidly evolve towards actinolite and talc for present temperatures higher than 300 C. Their occurrence is a good indicator of discharge in highly permeable zones. In the geothermal field of Chipilapa, the mineralogical composition of the < 0.2 {micro}m clay fractions fairly agrees with the temperatures presently measured in the wells, whereas several discrepancies may be pointed out from the compositions of coarser clay fractions (< 5 {micro}m) which contain minerals inherited from higher temperature stages. Permeable zones may be evidenced from an increase of expandable components in the interstratified minerals and a decrease of the coherent domain of the unexpandable clay particles (chlorite).

  8. Assessment of WorldView-3 Data for Lithological Mapping

    Directory of Open Access Journals (Sweden)

    Bei Ye

    2017-11-01

    Full Text Available The WorldView-3 (WV-3 satellite is a new sensor with high spectral resolution, which equips eight multispectral bands in the visible and near-infrared (VNIR and additional eight bands in the shortwave infrared (SWIR. In order to meet the requirements of large-scale geological mapping, this paper assessed WV-3 data for lithological mapping in comparison with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER and Operational Land Imager (OLI/Landsat-8 data. The study area is located in the Pobei area of the Xinjiang Uygur Autonomous Region, where bedrock outcrops are widely distributed. The whole experiment was divided into six steps: data pre-processing, visual interpretation of various lithological units, samples procedure, lithological mapping by a support vector machine algorithm (SVM, accuracy evaluation, and assessment. The results showed that the classification accuracy of WV-3 data was 87%, which kept 17% higher than that of ASTER data, 14% higher than that of OLI/Landsat-8 data, indicated that WV-3 data contained more diagnostic absorption features mainly thanks to its SWIR bands, and benefited by its high spatial resolution, as well. However, it also confirmed that there were some considerable flaws, such as the confusing identification of biotite-quartz schist. Overall, the WV-3 data is still the most promising data for geological applications currently.

  9. Factors Controlling the Metal Levels in Headwater Stream Draining an Agroforestry Catchment (Galicia, NW Spain)

    Science.gov (United States)

    Palleiro, Laura; Rodríguez-Blanco, M. Luz; Mercedes Taboada-Castro, M.; Taboada-Castro, M. Teresa

    2016-10-01

    Concentrations of Al, Fe, Mn, Cu and Zn (dissolved and particulate), suspended sediment, dissolved organic carbon, and pH and discharge were determined during a 3-year period in a stream water of an agroforestry catchment in Galicia (NW Spain). The objective of this study is to investigate the role of these variables in the control of dissolved and particulate concentrations of each metal in the stream water. The soils in the catchment are developed on metamorphic schist. Stream water samples were collected at the catchment outlet every 15 days and more frequently with increased stream flows. Metal concentrations were measured by ICP- MS. Pearson correlation coefficients were calculated to examine the possible associations between metals and the four variables under consideration. Stepwise multiple regressions were applied to determine which predictor variables have the strongest influences on controlling concentrations of each metal in the stream. The results showed that metal concentrations were relatively low (Fe > Al > Mn > Zn > Cu), but particulate metals were predominant over those dissolved. Stepwise multiple regression analysis revealed that the most important variable to explain dissolved concentrations for Al, Fe and Cu was the dissolved organic carbon, whereas the suspended sediment was for dissolved Zn and the discharge was for dissolved Mn. The suspended sediment was also a good predictor of particulate metal levels.

  10. Heavy metal sedimentary record in a Galician Ria (NW Spain): background values and recent contamination.

    Science.gov (United States)

    Cobelo-García, Antonio; Prego, Ricardo

    2003-10-01

    Two long sediment cores were sampled at the Ferrol Ria (Galicia, NW Spain) and the heavy metal (Co, Cr, Cu, Fe, Ni, Pb and Zn) concentrations measured in order to (i) state accurate background values providing baseline relationships with respect to a reference element and (ii) to investigate the recent metal contamination trends. Background values were found to agree well with the world average values for granite/schists-genisses rocks. However, Cu, Co, Pb and Zn were found to be lower than those previously reported as background values for the Galician Rias. Results emphasize the importance of using baseline relationships with respect to a normalizing element in order to reduce the scattering of data and to allow an accurate statement of background values. The distribution of metals in the cores showed an evident enrichment in the surface layers belonging to the industrial era. Normalized enrichment factors (NEF) for copper and zinc are in the order of 3-5 (certain/severe contamination) in the surface sediments, decreasing with depth. Lead contamination has decreased in the recent years from NEF of 3-7 down to a NEF of 2 (i.e. moderate contamination), probably due to the introduction of unleaded gasolines. Chromium, cobalt and nickel NEFs were always in the <1-2 range indicating null/low contamination by these metals.

  11. Geology and Mineral Resources of the Northern Part of the North Cascades National Park, Washington

    Science.gov (United States)

    Staatz, Mortimer Hay; Tabor, Rowland W.; Weis, Paul L.; Robertson, Jacques F.; Van Noy, Ronald M.; Pattee, Eldon C.

    1972-01-01

    The northern part of the North Cascades National Park in northern Washington is north of the Skagit River between Mount Shuksan on the West and Ross Lake on the east. The area occupies approximately 500 square miles of steep mountains and thickly forested valleys centered on the precipitous Picket Range. Old metamorphic rocks and young volcanic and sedimentary rocks are intruded by large masses of granitic rocks that together form a diverse, complicated, but well-exposed geologic section. The granitic rocks are the most abundant in the area; they intrude most of the other rocks, and they separate one suite of rocks in the eastern part of the area from a second suite in the western part. In the eastern part of the area, the oldest rocks are the Custer Gneiss of McTaggart and Thompson, a thick sequence of biotite and hornblende gneisses and schists. We have divided these rocks into three generalized units: light-colored gneiss, banded gneiss, and amphibole-rich gneiss. To the northeast of these rocks lies a metagabbro. This rock type is complex and is made up of several types of gabbro, diorite, amphibolite, ultramafic rocks, and quartz diorite that crop out along the Ross Lake fault zone. To the northeast of these rocks and also along the Ross Lake fault zone is the phyllite and schist of Ross Lake. These rocks are the highly sheared and metamorphosed equivalents of the plagioclase arkose and argillite sequence of Jurassic and Cretaceous age that is so widespread on the east side of Ross Lake. The Cretaceous Hozomeen Group of Cairnes lies along Ross Lake northeast of the phyllite and schist and consists mainly of slightly metamorphosed greenstones with subordinate chert and phyllite. The phyllite in this unit is similar to that in the underlying phyllite and schist of Ross Lake with which it appears to be interbedded. The youngest rocks in the eastern part of the area are the Skagit Volcanics a thick sequence of welded tuff-breccia with some flows and air-laid tuffs

  12. Geology of quadrangles H-12, H-13, and parts of I-12 and I-13, (zone III) in northeastern Santander Department, Colombia

    Science.gov (United States)

    Ward, Dwight Edward; Goldsmith, Richard; Cruz, Jaime B.; Restrepo, Hernan A.

    1974-01-01

    A program of geologic mapping and mineral investigation in Colombia was undertaken cooperatively by the Colombian Instituto Nacional de Investigaciones Geologico-Mineras (formerly known as the Inventario Minero Nacional), and the U. S. Geological Survey; by the Government of Colombia and the Agency for International Development, U. S. Department of State. The purpose was to study, and evaluate mineral resources (excluding of petroleum, coal, emeralds, and alluvial gold) of four selected areas, designated Zones I to IV, that total about 70,000 km2. The work in Zone III, in the Cordillera Oriental, was done from 1965 to 1968. The northeast trend of the Cordillera Oriental of Colombia swings abruptly to north-northwest in the area of this report, and divides around the southern end of the Maracaibo Basin. This section of the Cordillera Oriental is referred to as the Santander Massif. Radiometric age determinations indicate that the oldest rocks of the Santander massif are Precambrian and include high-grade gneiss, schist, and migmatite of the Bucaramanga Formation. These rocks were probably part of the Precambrian Guayana Shield. Low- to medium-grade metamorphic rocks of late Precambrian to Ordovician age .include phyllite, schist, metasiltstone, metasandstone, and marble of the Silgara Formation, a geosynclinal series of considerable extent in the Cordillera Oriental and possibly the Cordillera de Merida of Venezuela. Orthogneiss ranging from granite to tonalite is widely distributed in the high- and medium-grade metamorphic rocks of the central core of the massif and probably represents rocks of two ages, Precambrian and Ordovician to Early Devonian. Younger orthogneiss and the Silgara are overlain by Middle Devonian beds of the Floresta Formation which show a generally low but varying degree of metamorphism. Phyllite and argillite are common, and infrequent marble and other calcareous beds are fossiliferous. Except for recrystallization in limestones of !the

  13. Documenting Mica Microstructures in Mylonites of the Cossato-Mergozzo-Brissago Line, Northern Italy

    Science.gov (United States)

    Aslin, Joe; Mariani, Elisabetta; Wheeler, John

    2016-04-01

    The rheology of the Earth's crust is ultimately a function of the properties of its constituent minerals. Nowhere are the results of applied tectonic stresses within the Earth's crust more evident than along large scale fault zones and shear zones where strains become focussed producing localised deformation and displacement. These dynamic tectonic discontinuities are often dominated by fault rocks and mylonites that contain an abundance of phyllosilicates (such as micas) whose inherent weakness, relative to other silicate phases (Mariani et al. 2006), acts to concentrate deformation along these narrow regions. Experimental studies show that even in rocks where the concentration of weak phases, such as micas, is low, their effect on the strength and fabric of the rock is significant due to processes such as strain-induced interconnectivity (Holyoke & Tullis 2006). Once this interconnectivity has been established, very high strains can be accommodated within very narrow regions, termed shear bands or micro-shear zones. In this study, a combination of optical and scanning electron microscope (SEM) based techniques including electron backscatter diffraction (EBSD) have been used to observe and document features that are indicative of such processes within samples collected from the Cossato-Mergozzo-Brissago (CMB) shear zone in North Western Italy. This tectonic discontinuity is interpreted to be of Permian age and separates the metapelitic schists of the Kinzigite formation of the lower crustal Ivrea-Verbano zone from the mid-crustal schists and amphibolites of the Serie dei Laghi. Despite its present vertical attitude, the CMB line is believed to have formed as a gently inclined, mid-crustal shear zone during the early stages of post-Hercynian crustal stretching (Rutter et al. 2007). This has produced mylonites composed predominantly of quartz, feldspar and abundant phyllosilicates which serve as perfect natural examples on which to study the distribution of micas

  14. Geochemical, microtextural and petrological studies of the Samba prospect in the Zambian Copperbelt basement: a metamorphosed Palaeoproterozoic porphyry Cu deposit.

    Science.gov (United States)

    Master, Sharad; Mirrander Ndhlovu, N.

    2015-04-01

    Ever since Wakefield (1978, IMM Trans., B87, 43-52) described a porphyry-type meta-morphosed Cu prospect, the ca 50 Mt, 0.5% Cu Samba deposit (12.717°S, 27.833°E), hosted by porphyry-associated quartz-sericite-biotite schists in northern Zambia, there has been controversy about its origin and significance. This is because it is situated in the basement to the world's largest stratabound sediment-hosted copper province, the Central African Copperbelt, which is hosted by rocks of the Neoproterozoic Katanga Supergroup. Mineralization in the pre-Katangan basement has long played a prominent role in ore genetic models, with some authors suggesting that basement Cu mineralization may have been recycled into the Katangan basin through erosion and redeposition, while others have suggested that the circulation of fluids through Cu-rich basement may have leached out the metals which are found concentrated in the Katangan orebodies. On the basis of ca 490-460 Ma Ar-Ar ages, Hitzman et al. (2012, Sillitoe Vol., SEG Spec. Publ., 16, 487-514) suggested that Samba represents late-stage impregnation of copper mineralization into the basement, and that it was one of the youngest copper deposits known in the Central African Copperbelt. If the Samba deposit really is that young, then it would have post-dated regional deformation and metamorphism (560-510 Ma), and it ought to be undeformed and unmetamorphosed. The Samba mineralization consists of chalcopyrite and bornite, occurring as disseminations, stringers and veinlets, found in a zone >1 km along strike, in steeply-dipping lenses up to 10m thick and >150m deep. Our new major and trace element XRF geochemical data (14 samples) show that the host rocks are mainly calc-alkaline metadacites. Cu is correlated with Ag (Cu/Ag ~10,000:1) with no Au or Mo. Our study focused on the microtextures and petrology of the Samba ores. We confirm that there is alteration of similar style to that accompanying classical porphyry Cu mineralization

  15. Petrochronological investigations to unravel the tectono-metamorphic history of Alpine subduction (Briançonnais, Queyras, Western Alps)

    Science.gov (United States)

    Lanari, Pierre

    2015-04-01

    The study of the tectonic and metamorphic history of the Alpine metamorphic belt involving oceanic and continental subduction processes requires knowledge of detailed Pressure-Temperature-time-deformation (P-T-t-ɛ) paths recorded by different tectono-metamorphic units across the belt. This task is particularly challenging in low-grade rocks, e.g. metapelites, (a) for thermobarometry, and (b) for geochronology. Metapelites at greenschist facies metamorphic conditions show a narrow spectrum of metamorphic minerals, notably quartz, chlorite and K-white mica, in addition to commonly detrital relics inherited from previous metamorphic rocks. To obtain reliable P-T estimates, a multi-method approach is required, which usefully combines Raman study of Carbonaceous Material (RSCM), chemical analysis in standardized X-ray maps, and multi-equilibrium inverse thermodynamic modelling of chlorite and white mica. In order to be able to link each assemblage to a specific metamorphic stage and determine the time scales and rates of metamorphism, it is critical to use in situ dating techniques. In this study, high-resolution geochronology was conducted including single-grain 40Ar/39Ar dating (step heating), where possible in combination with U-Th-Pb age-dating of allanite by LA-ICP-MS analysis. In the French western Alps, the Briançonnais zone is a remnant of the continental subduction wedge, while the Liguro-Piedmontais zone is a fossil oceanic subduction wedge. Metapelites from these two complexes were investigated to constrain the individual P-T-t paths recorded in each tectonic slice. This study focussed on deciphering four tectono-metamorphic units in the Briançonnais zone: (B1) The Internal basement; (B2) the Lower and (B3) Upper Zone Houillère; (B4) the Mesozoic Nappe Stack. These continental units recorded green-schist Alpine metamorphic conditions. In the Liguro-Piedmontais zone, five tectono-metamorphic units are identified: (LP1) the Péouvou; (LP2) Saint-Véran; (LP

  16. Deformation of the Songshugou ophiolite in the Qinling orogen

    Science.gov (United States)

    Sun, Shengsi; Dong, Yunpeng

    2017-04-01

    The Qinling orogen, middle part of the China Central Orogenic Belt, is well documented that was constructed by multiple convergences and subsequent collisions between the North China and South China Blocks mainly based on geochemistry and geochronology of ophiolites, magmatic rocks as well as sedimentary reconstruction. However, this model is lack of constraints from deformation of subduction/collision. The Songshugou ophiolite outcropped to the north of the Shangdan suture zone represents fragments of oceanic crust and upper mantle. Previous works have revealed that the ophiolite was formed at an ocean ridge and then emplaced in the northern Qinling belt. Hence, deformation of the ophiolite would provide constraints for the rifting and subduction processes. The ophiolite consists chiefly of metamorphosed mafic and ultramafic rocks. The ultramafic rocks contain coarse dunite, dunitic mylonite and harzburgite, with minor diopsidite veins. The mafic rocks are mainly amphibolite, garnet amphibolite and amphibole schist, which are considered to be eclogite facies and retrograde metamorphosed oceanic crust. Amphibole grains in the mafic rocks exhibit a strong shape-preferred orientation parallel to the foliation, which is also parallel to the lithologic contacts between mafic and ultramafic rocks. Electron backscattered diffraction (EBSD) analyses show strong olivine crystallographic preferred orientations (CPO) in dunite including A-, B-, and C-types formed by (010)[100], (010)[001] and (100)[001] dislocation slip systems, respectively. A-type CPO suggests high temperature plastic deformation in the upper mantle. In comparison, B-type may be restricted to regions with significantly high water content and high differential stress, and C-type may also be formed in wet condition with lower differential stress. Additionally, the dunite evolved into amphibolite facies metamorphism with mineral assemblages of olivine + talc + anthophyllite. Assuming a pressure of 1.5 GPa

  17. Landslide hazard and forest fires - the relevance of geology for landslide type and development

    Science.gov (United States)

    Fernandez-Steeger, Tomas M.; Wiatr, Thomas; Papanikolaou, Ioannis; Reicherter, Klaus

    2010-05-01

    the additional weight of the saturated soils change substantially the limit equilibrium. In general the findings show that the changed environmental conditions due to the fires drastically increased the landslide activity in the area at least locally. In Attica, the affected areas are mostly located in Mesozoic metamorphic units build up from schist and marbles. As the fires stopped only two months before our site visit, the landslide effects are not that explicit and were just beginning to develop. Furthermore, due to the different geology and morphology the areas are not known as typical landslide areas. In the schist areas besides the development of rills and gullies, at several localities shallow soil slip with some 10 m extension could be observed. Anyhow the processes were limited to the weathered cover of the rocks which are much more permeable. On the other hand, in the marble areas only local erosion in the thin soil cover and first activation of debris could be observed. Anyhow, heavy precipitation events lead already to flooding. The results show that the type and extend of landslides which develop after a fire incident are also controlled by geological features like rock types or permeability. Moreover, in an appropriate landslide environment even very large landslides might develop after a forest fires. Moriondo, M. et al. 2006. Potential impact of climate change on fire risk in the Mediterranean area. Climate Res. 31, 85-95. Shakesby, R.A. & Doerr, S.H. 2006. Wildfire as a hydrological and geomorphological agent. Earth Sci. Rev. 74, 269- 307. Swanson, F.J., 1981. Fire and geomorphic processes. in: Mooney et al. (Eds.), Fire Regime and Ecosystem Properties, USDA For. Serv. Gen. Tech. Rep. WO-26, 401-421.

  18. Age of granites of Wrangel Island metamorphic complex

    Science.gov (United States)

    Luchitskaya, Marina; Sergeev, Sergey; Sokolov, Sergey; Tuchkova, Marianna

    2014-05-01

    Within huge arctic shelf of Eastern-Siberian and Chukchi seas the metamorphic basement (Wrangel complex, Berri Formation) is exposed only on the Wrangel Island. There are different points of views on the age of metamorphic rocks of Wrangel complex (Berri Formation): (1) Neoproterozoic (Kameneva, 1970; Ageev, 1979; Kos'ko et al., 1993, 2003), (2) Devonian (Til'man et al., 1964, 1970; Ganelin, 1989). Metamorphic basement is represented by stratified complex, composed of dislocated metavolcanic, metavolcaniclastic and metasedimentary rocks (schists, metasandstones, metaconglomerated) with single lenses and layers of carbonate rocks (Wrangel Island…, 2003). Among basement rocks in the central part of Wrangel Island there are felsic intrusive bodies. They form small tabular bodies from tens centimeters to 70-80 meters in thickness, rarely dikes and small stocks (up to 20 x 30 m) and are composed of granite-porphyres, rarely muscovite porphyr-like granites and granosyenites (Wrangel Island…, 2003). The age of intrusions allow to determine the age of basement formation. Earlier the age of intrusions was determined by different methods and correlated to the boundary between Neoproterozoic and Paleozoic: K-Ar 570-603 Ma, Pb-Pb 590±50 Ma (S.M. Pavlov, Institute of Precambrian Geology and Geochronology, USSR Academy of Sciences), Rb-Sr 475±31 Ma (I.M.Vasil'eva, Institute of Precambrian Geology and Geochronology, USSR Academy of Sciences), U-Pb 609, 633, 677 Ma (Geological Survey of Canada) (Wrangel Island…, 2003; Kos'ko et al., 1993; Cecile et al., 1991). In the lower part of metamorphic rocks of Wrangel complex there are conformable tabular bodies of gneissosed and foliated granitoides. The latter are meramorphosed and transformed in biotite-muscovite-feldspar-quartz-sericite and muscovite-feldspar-quartz-sericite gneisses and schists, where relics of primary minerals (quartz, plagioclase, potassium feldspar, rarely biotite and muscovite) and equigranular granitic

  19. Influence of graphite and serpentine minerals along landslide failure surfaces

    Science.gov (United States)

    Alberti, Stefano; Battista Crosta, Giovanni; Wang, Gonghui; Dattola, Giuseppe; Bertolo, Davide

    2017-04-01

    simulate the formation of the shear zone and the post-failure mobility of high-speed landslides, monitoring pore-pressure generation, and mobilized shear resistance together with shear displacement. Reference List: Ambrosi, C., & Crosta, G. B. (2006). Large sackung along major tectonic features in the Central Italian Alps. Engineering Geology, 83(1), 183-200. Craw, D. (2002). Geochemistry of late metamorphic hydrothermal alteration and graphitisation of host rock, Macraes gold mine, Otago Schist, New Zealand. Chemical Geology, 191(4), 257-275. Nakamura, Y., Oohashi, K., Toyoshima, T., Satish-Kumar, M., & Akai, J. (2015). Strain-induced amorphization of graphite in fault zones of the Hidaka metamorphic belt, Hokkaido, Japan. Journal of Structural Geology, 72, 142-161. Sassa K, Fukuoka H, Wang FW (1997) Mechanism and risk assessment of landslide- triggered-debris flows: lesson from the 1996.12.6 Otari debris flow disaster, Nagano, Japan. In: Cruden DM, Fell R (eds) Landslide risk assessment, proceedings of the international workshop on landslide risk assessment. Honolulu, 19-21 February, pp 347-356 Zulauf, G., Kleinschmidt, G., & Oncken, O. (1990). Brittle deformation and graphitic cataclasites in the pilot research well KTB-VB (Oberpfalz, FRG). Geological Society, London, Special Publications, 54(1), 97-103. Yamasaki, S., Chigira, M., & Petley, D. N. (2016). The role of graphite layers in gravitational deformation of pelitic schist. Engineering Geology, 208, 29-38.

  20. Selected fluvial monazite deposits in the southeastern United States

    Science.gov (United States)

    Overstreet, William C.; White, A.M.; Theobald, P.K.; Caldwell, D.W.

    1971-01-01

    Farther southwest in Georgia, around Griffin and Zebullon, along streams tributary to the Flint River in the monazite belt the flood plains are generally small and discontinuous, and only about 1 percent of the sediment is gravel. The area between Griffin, Zebullon, and the Flint River is underlain by biotite schist and biotite gneiss into which biotite granite has been intruded. Only along one stream, Flat Creek, which drains monazite-bearing granite near Zetella, Ga., are the tenors in monazite even moderately high, but a combination of thick, clayey overburden and discontinuous flood plains make the stream unsuitable for placer mining. Elsewhere in the Flint River area the heavy-mineral concentrates contain less than 1 percent monazite. The southwesternmost area in which reconnaissance of the monazite belt was conducted includes a groups of southwest-flowing tributaries to the Chattahoochee River north of Pine Mountain and near La Grange, Ga. A combination of three characteristics of the alluvium make the area unfavorable for mining: (1) the upper half of the sedimentary sequence is clay and silt, (2) there is scant gravel, and (3) much of the sand is fine grained. Monazite is associated with the Snelson Granite, schists, and gneisses north of the Towaliga fault, but even in this area the tenor of most riffle sediments is only 0.1 to 0.5 pound of monazite per cubic yard, and the average tenor of the alluvium is about 0.2 pound per cubic Yard. Rocks south of the Towaliga fault contain scant monazite. The monazite-bearing area in the drainage basin of the Chattahoochee River has no monazite placers. Evidence from the areas on the Flint and Chattahoochee Rivers shows that streams in western Georgia are a much poorer source of monazite than streams farther to the northeast in Georgia, South Carolina, and North Carolina. Also, the northeastern part of the belt in the drainage basins of the Yadkin and Dan Rivers is a poorer source for monazite than the area between

  1. Palaeoproterozoic prograde metasomatic-metamorphic overprint zones in Archaean tonalitic gneisses, eastern Finland

    Directory of Open Access Journals (Sweden)

    Pajunen, M.

    1999-06-01

    Full Text Available Several occurrences of coarse-grained kyanite rocks are exposed in the Archaean area of eastern Finland in zones trending predominantly northwest-southeast that crosscut all the Archaean structures and, locally, the Palaeoproterozoic metadiabase dykes, too. Their metamorphic history illustrates vividly Palaeoproterozoic reactivation of the Archaean craton. The early-stage kyanite rocks were formed within the framework of ductile shearing or by penetrative metasomatism in zones of mobile brecciation. Static-state coarse-grained mineral growth during the ongoing fluid activity covered the early foliated fabrics, and metasomatic zoning developed. The early-stage metasomatism was characterized by Si, Ca and alkali leaching. The late-stage structures are dilatational semi-brittle faults and fractures with unstrained, coarse-grained fabrics often formed by metasomatic reactions displaying Mg enrichment along grain boundaries. Metamorphism proceeded from the low-T early-stage Chl-Ms-Qtz, Ky/And-St, eventually leading to the high-T late-stage Crd-Sil assemblages. The thermal peak, at 600-620°C/4-5 kbar, of the process is dated to 1852+2 Ma (U-Pb on xenotime. Al-silicate growth successions in different locations record small variations in the Palaeoproterozoic clockwise P-T paths. Pressure decreased by c. 1 kbar between the early and late stage, i.e. some exhumation had occurred. Fluid composition also changed during the progression, from saline H2O to CO2, rich. Weak retrograde features of high-T phases indicate a rapid cooling stage and termination of fluid activity. The early-stage Ky-St assemblages resemble those described from nearby Palaeoproterozoic metasediments in the Kainuu and North Karelia Schist Belts, where the metamorphic peak was achieved late with respect to Palaeoproterozoic structures. The static Ky-St metamorphism in kyanite rocks was generated by fluid-induced leaching processes at elevated T during the post-orogenic stage after

  2. Close or not so close? Provenance studies of megalithic monuments from Alentejo (Portugal)

    Science.gov (United States)

    Boaventura, R.; Moita, P.

    2012-04-01

    There has been a significant amount of studies about megalithic tombs conducted in the Alentejo region. However the geological provenance of monoliths used in the construction of those tombs usually was not a priority among researchers with rare exceptions (Dehn, Kalb and Vortisch, 1991; Boaventura, 2000). Recent studies of dolmens (Oliveira, 1997 and 2006; Gonçalves, 2003) refer only to a brief characterization of rocks, such as "granite or schist slabs", highlighting certain types if the geological stratum is identical or not to the stone blocks. On the other hand, when the type of raw material appears to be similar with the bedrock, it is common and empirically assumed its local provenance. With the aim of testing and expand the knowledge about the provenance of the slabs used in the construction of megalithic tombs, several lithic samples from dolmen slabs and outcrops in their surroundings were collected for analysis and comparison. The samples were characterized by petrographic studies in thin section as well with a geochemical analyses performed by XRF that gives major elements as well some trace elements. The dolmens tested for this project are located roughly between the northeast to west of the town of Monforte (Upper region of Alentejo, Portugal) and are named, from south to north, as Serrinha, Rabuje group (1 to 5), Geodésico de Besteiros 3 and Velho. The field work and petrographic studies revealed that the slabs are constituted mainly by several types of granitoids (gnaissic, red, white, tonalitic), amphibolites and mottled schist shale. The comparison of chemical analyses between slabs and selected outcrops revealed that the provenances are in most of the cases from the nearby geological stratum. In fact, major elements (e.g. MgO, SiO2, CaO) as well trace elements (e.g. Sr, Y, Zr, Nb) compositions are similar on slab samples and in rocks from the outcrops. If in terms of major elements a similarity was already expectable, or easier to obtain, the

  3. Structure of a shear zone at the base of the seismogenic zone, Norumbega fault system, Maine; Potential for comparison with upper-crustal fault structure

    Science.gov (United States)

    Price, N. A.; Johnson, S. E.; Gerbi, C. C.; Koons, P. O.

    2011-12-01

    Studies of large strike-slip faults provide a detailed picture of the upper crustal structure of a seismogenic fault system (e.g. Chester et al., 1993; Ben-Zion and Sammis, 2003; Wibberley et al., 2008). Few studies have provided that same degree of detail for such faults at greater depths. Because of this, it is not well understood how the structure of the fault at the surface correlates with the structure of a fault with depth, particularly across the frictional-to-viscous transition. Our study of the Sandhill Corner shear zone (SCSZ) within the Norumbega fault system (a long-lived, subvertical, seismogenic fault system in Maine, USA) focuses on this depth level and provides an informative view of across and along strike variations within a shear zone from the base of the seismogenic zone. We suggest that the structure of this shear zone correlates with the structure of modern strike slip faults like the San Andreas. The SCSZ is a 300-500m wide shear zone exhumed from depths of ~10-15km that preserves mutually-overprinting pseudotachylyte and mylonite. Using over 100 samples from 6 transects, we considered the spatial variation in (1) quartz fabric intensity, grain size, and CPO data; (2) the prevalence of mineral-filled fractures and shattered porphyroclasts; and (3) the amount of pseudotachylyte (deformed and undeformed). We find a focused shear zone core (1-7m) that contains ultramylonite and phyllonite nearly devoid of porphyroclasts and rich in deformed pseudotachylyte with the finest sizes of quartz new grains. This core region is comparable to the focused core region of upper crustal faults rich in foliated gauge where most of the slip is thought to occur. The core of the SCSZ is surrounded by a wider zone of quartzofeldspathic mylonite and protomylonite, mylonitized calc-silicates, and sheared schist (~100-500m). There is an increased incidence of shattered porphyroclasts and deformed pseudotachylyte in these rocks with proximity to the fault core but

  4. Mechanical study of the Chartreuse Fold-and-Thrust Belt: relationships between fluids overpressure and decollement within the Toarcian source-rock

    Science.gov (United States)

    Berthelon, Josselin; Sassi, William; Burov, Evgueni

    2016-04-01

    Many source-rocks are shale and constitute potential detachment levels in Fold-and-Thrust Belts (FTB): the toarcian Schistes-Cartons in the French Chartreuse FTB for example. Their mechanical properties can change during their burial and thermal maturation, as for example when large amount of hydrocarbon fluids are generated. A structural reconstruction of the Chartreuse FTB geo-history places the Toarcian Formation as the major decollement horizon. In this work, a mechanical analysis integrating the fluids overpressuring development is proposed to discuss on the validity of the structural interpretation. At first, an analogue of the Chartreuse Toarcian Fm, the albanian Posidonia Schist, is documented as it can provide insights on its initial properties and composition of its kerogen content. Laboratory characterisation documents the vertical evolution of the mineralogical, geochemical and mechanical parameters of this potential decollement layer. These physical parameters (i.e. Total Organic Carbon (TOC), porosity/permeability relationship, friction coefficient) are used to address overpressure buildup in the frontal part of the Chartreuse FTB with TEMISFlow Arctem Basin modelling approach (Faille et al, 2014) and the structural emplacement of the Chartreuse thrust units using the FLAMAR thermo-mechanical model (Burov et al, 2014). The hydro-mechanical modeling results highlight the calendar, distribution and magnitude of the overpressure that developed within the source-rock in the footwall of a simple fault-bend fold structure localized in the frontal part of the Chartreuse FTB. Several key geological conditions are required to create an overpressure able to fracture the shale-rocks and induce a significant change in the rheological behaviour: high TOC, low permeability, favourable structural evolution. These models highlight the importance of modeling the impact of a diffuse natural hydraulic fracturing to explain fluids propagation toward the foreland within

  5. Structural geology and sedimentology of the Sermat Quartzites, Strandja Massif, NW Turkey

    Science.gov (United States)

    Yazıcı, Müge; Natal'in, Boris A.

    2015-04-01

    The Strandja Massif, NW Turkey, is the eastern continuation of the Rhodope Massif in Bulgaria. The massif is generally correlated with the Hercynian orogenic belt that was later modified by the Cimmerian orogeny. The basement of the massif is composed by various kinds of gneisses and schists, which are intruded by the metagranites. In the studied area, the Cambrian K-feldspar metagranites are unconformably overlain by metaclastics, where both units have fault contacts with volcano-sedimentary rocks. The metagranite intrusions yield Carboniferous U-Pb zircon ages (Natal'in et al., 2012a). All of them constitute the basement of the Strandja Massif. Cambrian age of metagranites and their subduction related nature as well as the subduction related nature of the Carboniferous igneous rocks suggest a prolong evolution of the Strandja Massif (Natal'in et al., 2012a). The Cambrian metagranites are unconformably overlain by a metasedimetary cover unit, which is known in the literature as the Şermat Quartzite of presumably Permo-Triassic age (Çağlayan and Yurtsever, 1998). In the studied region, detrital zircons extracted from quartzites show that their depositional age is not younger than the Ordovician (Natal'in et al., 2012a). The basement of the Strandja Massif is subjected to the epidote-amphibolite-greenschist facies of metamorphism and high strain deformation in the late Jurassic - early Cretaceous times. The Şermat Quartzite forms a transgressive sequence, which starts with metaconglomerates, metasandstones and grades up to quartz-sericite schists. The thickness of bedding changes from thin to medium with parallel bedding planes, containing lens-shaped bodies of massive quartzites. The late Jurassic - early Cretaceous foliation (S1) is generally parallel to the primary bedding plane. Foliations and lineations consistently dip to the northeast and kinematic indicators suggest a tectonic transport in the same direction. High strain in the Şermat Quartzite

  6. The Formation of a Retroarc Fold-Thrust Belt by the Closure and Inversion of a Back-Arc Basin; Patagonian-Fuegian Fold-Thrust Belt, Chile

    Science.gov (United States)

    Betka, P.; Klepeis, K. A.; Mosher, S.

    2012-12-01

    The Late Cretaceous closure and inversion of the Late Jurassic Rocas Verdes back-arc basin (RVB) defines the onset of the Andean orogeny and the development of the Patagonian retroarc fold-thrust belt (FTB) between 50°-54.5° S. Back-arc extension in the RVB led to the generation of new oceanic crust that was coeval with the deposition of syn-rift silicic volcanoclastic rocks on the continental margin. A > 500 m thick succession of mudstone and distal turbidite deposits accumulated in the RVB (post-rift). New maps and line-balanced cross-sections from three transects across the FTB show a transition through time from thin-to thick-skinned structural styles that is controlled by the inherited stratigraphic architecture and structure of the RVB. The closure of the RVB and development of the FTB occurred in two stages. During the initial stage, mafic schist, gabbro, basalt, and hemipelagic mudstone of the RVB floor were imbricated and thrust onto the continental margin resulting in the formation of the Magallanes foreland basin and underthrusting of the continental crust to depths of ~ 35 km. Displacement from the obduction of the RVB was transferred along two decollement levels into the FTB by ~85 Ma. Each decollement level formed at a rheological boundary within the syn- and post-rift stratigraphy. The lower decollement formed in quartz-chlorite schist (basement) > 1 km beneath the top-basement contact with relatively strong syn-rift volcanoclastic deposits. The lower decollement is defined by a ~1 km thick ductile shear zone. C-S fabrics, C-C' shear bands and prominent SW plunging quartz stretching lineations that occur within the shear zone indicate a top-NE transport direction. Isoclinal recumbent F2 folds and inclined tight F3 folds refold the S1/L1 surface. The decollement cuts up-section through the syn-rift volcanoclastic deposits to join a structurally higher decollement that formed within weak, post-rift mudstone and turbidite deposits on the continental

  7. Gold grade distribution within an epithermal quartz vein system, Kestanelik, NW Turkey: implications for gold exploration

    Science.gov (United States)

    Gulyuz, Nilay; Shipton, Zoe; Gulyuz, Erhan; Lord, Richard; Kaymakci, Nuretdin; Kuscu, İlkay

    2017-04-01

    Vein-hosted gold deposits contribute a large part to the global gold production. Discovery of these deposits mainly include drilling of hundreds of holes, collecting thousands of soil and rock samples and some geophysical surveys which are expensive and time consuming. Understanding the structures hosting the veins and the variations in gold concentrations within the veins is crucial to constrain a more economic exploration program. The main aim of this study is to investigate the gold grade distribution in the mineralized quartz veins of a well exposed epithermal gold deposit hosted by Paleozoic schist and Eocene quartz-feldspar-hornblende porphyry in Lapseki, NW Turkey. We have constructed 3D architecture of the vein surfaces by mapping their outcrop geometries using a highly sensitive Trimble GPS, collecting detailed field data, well-logs and geochemistry data from 396 drill holes (255 diamond cut and 141 reverse circulation holes). Modelling was performed in MOVE Structural Modelling and Analysis software granted by Midland Valley's Academic Software Initiative, and GIS application softwares Global Mapper and Esri-ArcGIS. We envisaged that while fluid entering the conduit ascents, a sudden thickness increase in the conduit would lead to a drop in the fluid pressure causing boiling (the most dominant gold precipitation mechanism) and associated gold precipitation. Regression analysis was performed between the orthogonal thickness values and gold grades of each vein, and statistical analyses were performed to see if the gold is concentrated at specific structural positions along dip. Gold grades in the alteration zones were compared to those in the adjacent veins to understand the degree of mineralization in alteration zones. A possible correlation was also examined between the host rock type and the gold grades in the veins. These studies indicated that gold grades are elevated in the adjacent alteration zones where high gold grades exist in the veins. Schist

  8. Diffusivity database (DDB) for major rocks. Database for the second progress report

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Haruo

    1999-10-01

    De data for 6 elements have been reported for basalt, andesite and schist. For sedimentary rock (argillaceous/tuffaceous rock), totally, 54 De data for 8 elements have been reported for mudstone, politic schist and tuff, and for sedimentary rock (psammitic rock/sandy stone), 11 De data for 1 element have been reported for siliceous sedimentary rock. As is clear, much De data are found in granitic rocks. Whilst, De data for psammitic rocks are short comparing to those for the other kinds of rocks. Correlativities have been approximately found between De values and rock porosities for all kinds of the rocks, but significant porosity dependencies have not been found for Da values. In addition, correlations between various parameters such as that between formation factors and rock porosities, that between geometric factors and rock porosities, that between De values and ionic charge, that between De values and Do values, and that between De values and element, were also discussed. (author)

  9. Large-scale recumbent isoclinal folds in the footwall of the West Cycladic Detachment System (Greece)

    Science.gov (United States)

    Rice, A. Hugh N.; Grasemann, Bernhard

    2017-04-01

    The Pindos Zone in the Cyclades underwent Eocene high-pressure metamorphism and syn-orogenic exhumation, overprinted by Miocene low-angled extension. Although this represents a combination of likely high-strain-events, structural evidence of large-scale folding is rare. Here potential examples of such folding on Kea and Kythnos, in the Western Cyclades, are evaluated. These islands lie within the Cycladic Blueschist Nappe (lower nappe) of the Pindos Zone and in the footwall of the top-to-SSW West Cycladic Detachment System (WCDS). On Kea, no lithostratigraphy can be established in the 450 m thick greenschist facies mixed sedimentary-volcanoclastic-marble mylonite/phyllonite succession. On the east side of the island, lensoid marble layers frequently bifurcate, which might be reflecting early, sheared-out isoclinal folding, although no evidence of folded compositional layering has been found in potential fold-hinge zones and the bifurcation points are not arranged in a way suggestive of a fold axes parallel to the NNE-SSW oriented stretching lineation. However, at two localities, medium-scale recumbent isoclinal folding has been mapped, with NNE-SSW fold-axes exposed for up to 250 m and amplitudes of up to 170 m. On Kythnos, stretching lineations in greenschist facies rocks show a rotation from ENE-WSW in the north to NNE-SSW in the south, taken to represent a reorientation of the Eocene exhumation strain during block rotation coincident with top-to-SSW movement of the WCDS. The distribution of the three marble units that crop out in central/southern Kythnos suggest large-scale, likely isoclinal folding occurred. (1) Petroussa Lithodeme - a blue-grey calcite (BGC) marble with quartz-calcite-white-mica (QCWM) schists, forming a continuous outcrop around the island, thinning from >16m in the SE to cropping out above the Flabouria Lithodeme south of Aghios Dimitrios, directly below the WCDS; (3) Mavrianou Lithodeme - mylonitic QCWM schists with lenses of BGC mylonites

  10. Sedimentary uranium deposits in France and French Union; Les gisements uraniferes dans les formations sedimentaires en France et dans l'Union francaise

    Energy Technology Data Exchange (ETDEWEB)

    Kervella, F. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1958-07-01

    The author gives the actual state of our knowledge on uranium deposits found in recent years. Till now in precambrian formations only one important deposit has been found, at Mounana (Gabon) in a series of conglomeratic sandstones belonging to the 'Francevillien'. The observed mineralization is of the uranium-vanadium type. To the carboniferous formations corresponds in France a series of deposits, among which the most important ones are located at Saint-Hippolyte. Uranium as carburans, organic-bound complexes, is contained in lacustrine schists of Westphalian or lower Stephanian formations. A number of occurrences are also known in permo-triassic formations, particularly in the Vanoise Alps, in the Maritime Alps and in the Herault, where important occurrences have recently been found not far from Lodeve. The cretaceous and tertiary systems contain uranium deposits in phosphate rocks (Morocco, Senegal, Togo, Middle-Congo). Two sedimentary oligocene deposits are known in France. Lastly, the Vinaninkarena deposit in Madagascar, known for a long time, is the only important one reported in the quaternary series. (author) [French] L'auteur fait le point des connaissances acquises sur les gisements decouverts dans les formations sedimentaires en France et dans l'Union francaise au cours des dernieres annees. Les gisements sont classes selon l'age de la formation dans laquelle on les observe. Les terrains precambriens n'ont pour l'instant fourni qu'un seul gisement notable; situe a Mouana (Gabon). C'est en decembre 1956 que cet important gisement fut decouvert dans une serie de gres conglomeratiques appartenant au Francevillien. La mineralisation observee est du type vanadium-uranium. Au carbonifere correspond en France metropolitaine une serie de gisements d'interet variable. Les plus importants sont ceux de Saint-Hippolyte (Haut-Rhin) ou l'uranium est contenu dans des schistes lacustres du Westphalien ou du

  11. Geologic map of the Dusar area, Herat Province, Afghanistan; Modified from the 1973 original map compilations of V.I. Tarasenko and others

    Science.gov (United States)

    Tucker, Robert D.; Stettner, Will R.; Masonic, Linda M.; Bogdanow, Anya K.

    2017-10-24

    The geologic maps and cross sections presented in this report are redrafted and modified versions of the Geologic map and map of useful minerals of the Dusar area (scale 1:50,000) and Geologic sketch map of the Dusar and Namak-sory ore occurrences (scale 1:10,000), located in the Herat Province, Afghanistan. The original maps and cross sections are contained in unpublished Soviet report no. 0290 (Tarasenko and others, 1973) prepared in cooperation with the Ministry of Mines and Industries of the Royal Government of Afghanistan, in Kabul during 1973 under contract no. 50728. The redrafted maps and cross sections (modified from Tarasenko and others, 1973) illustrate the geological structure and mineral occurrences of the Dusar copper-gold-silver-lead-zinc prospect area of western Afghanistan, located within the Dusar-Shaida copper and tin area of interest (AOI), Herat Province, Afghanistan.Mineralization in the Dusar area is hosted within Early Jurassic to Early Cretaceous stratified volcanic and sedimentary rocks associated with numerous diabase and gabbro-diabase intrusive bodies and is generally near a major northeast-trending system of faults and quartz veins. Host rocks consist of quartz keratophyre and quartz-feldspar porphyry, with layers of schist, phyllite, and quartz-chlorite and chlorite-sericite slate; and limestone and shale, with schist and carbonate-chlorite and chlorite slate. Known mineralization includes an extensive quartz vein system, shown on the map as the “northern occurrence,” as well as the Dusar and Namak-sory gossan zones, interpreted to have formed from remnant pyrite mineralization. The veins of the northern occurrence and their altered host rocks are known to contain anomalous to economic concentrations of precious and base metals, with concentrations locally in excess of 2 parts per million gold, 100 parts per million silver, 5 percent copper, and 1 percent lead. These veins occur in swarms, and are hosted along structures that are

  12. Jurassic–Paleogene intraoceanic magmatic evolution of the Ankara Mélange, north-central Anatolia, Turkey

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    E. Sarifakioglu

    2014-02-01

    Full Text Available Oceanic rocks in the Ankara Mélange along the Izmir–Ankara–Erzincan suture zone (IAESZ in north-central Anatolia include locally coherent ophiolite complexes (~ 179 Ma and ~ 80 Ma, seamount or oceanic plateau volcanic units with pelagic and reefal limestones (96.6 ± 1.8 Ma, metamorphic rocks with ages of 256.9 ± 8.0 Ma, 187.4 ± 3.7 Ma, 158.4 ± 4.2 Ma, and 83.5 ± 1.2 Ma indicating northern Tethys during the late Paleozoic through Cretaceous, and subalkaline to alkaline volcanic and plutonic rocks of an island arc origin (~ 67–63 Ma. All but the arc rocks occur in a shale–graywacke and/or serpentinite matrix, and are deformed by south-vergent thrust faults and folds that developed in the middle to late Eocene due to continental collisions in the region. Ophiolitic volcanic rocks have mid-ocean ridge (MORB and island arc tholeiite (IAT affinities showing moderate to significant large ion lithophile elements (LILE enrichment and depletion in Nb, Hf, Ti, Y and Yb, which indicate the influence of subduction-derived fluids in their melt evolution. Seamount/oceanic plateau basalts show ocean island basalt (OIB affinities. The arc-related volcanic rocks, lamprophyric dikes and syenodioritic plutons exhibit high-K shoshonitic to medium- to high-K calc-alkaline compositions with strong enrichment in LILE, rare earth elements (REE and Pb, and initial εNd values between +1.3 and +1.7. Subalkaline arc volcanic units occur in the northern part of the mélange, whereas the younger alkaline volcanic rocks and intrusions (lamprophyre dikes and syenodioritic plutons in the southern part. The late Permian, Early to Late Jurassic, and Late Cretaceous amphibole-epidote schist, epidote-actinolite, epidote-chlorite and epidote-glaucophane schists represent the metamorphic units formed in a subduction channel in the northern Neotethys. The Middle to Upper Triassic neritic limestones spatially associated with the

  13. The High-Pressure Cataclasites from SW Tianshan, China: An Implication for the Mechanisms of Intermediate-Depth earthquakes

    Science.gov (United States)

    Xia, Y.; Zhang, L.

    2012-12-01

    Intermediate-depth earthquakes have been observed in several presently active subduction zones worldwide, at the depth of 70 to 300 km. It is considered to be closely related to metamorphic dehydration reactions in the subducting slabs. However, there are not enough field evidences in previous studies to support this hypothesis. Two types of cataclasites which are possibly related to metamorphic dehydration reactions have been discovered and collected from the high to ultra-high pressure (HP-UHP) metamorphic belt in southwestern Tianshan, China, which is generally recognized as a typical oceanic cold subduction zone. Based on the mineralogy of fragments in the cataclasites, they are classified into blueschist cataclasites and eclogite cataclasites. There are few detail studies of blueschist cataclasites and eclogite cataclasites in oceanic subduction zone worldwide, especially of blueschist cataclasites in previous studies. This study is aimed to understand the relationship between metamorphic dehydration reactions and seismicity in the subducting slab through the field evidence. For the blueschist cataclasites, the blueschist fragments are cemented by eclogite facies matrix. The matrix is basically veins formed in the original fractures of the cataclasites. The blueschist fragments are composed of approximately 75% glaucophane, 20% epidote/zoisite and minor amount of garnet, while the matrix contains about 20% garnet, 5% omphacite, 45% actinolite (mostly altered from omphacite), 25% epidote/zoisite with some minor minerals. The petrographic observations and mineral chemical analysis indicate that the cataclasites formed during the transition from blueschist to ecologite. In the eclogite-facies cataclasites, the eclogite-facies fragments are cemented by matrix of garnet-mica schists and later carbonate fluids. The mineral assemblage of eclogite fragments is dominated by more than 90% omphacite, with rutile, sphene and garnet as accessory mineral. The matrix that

  14. Malenco Serpentine: proposed as a candidate for "Global Heritage Stone Resource" designation

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    Primavori, Piero

    2017-04-01

    The Malenco Serpentine (Serpentine of Val Malenco) is the commercial name of a meta-peridotitic geological formation, Jurassic-Lower Cretaceous in age, entirely restricted to the borders of the valley of the same name (Malenco Valley), and geographically located in Sondrio Province, Lombardy Region, North Italy. Geologically speaking, it is part of an ophiolithic suture zone situated at the contact of the Austroalpine and Penninic nappes of the Alps (Rhaetian sector); petrographically, it is the result of a polymetamorphic (both regional and contact) and polytectonic history, with the development of a paragenesis of antigorite + chrysotile + chlorite + magnetite + diopside + olivine + titanolivine ± chromite ± pyrite ± brucite, and other iron and copper sulphurs. Malenco Serpentine extends over an area of approximately 170 km2, with a thickness ranging from 1 to 2 km. Lithological and mineralogical features allow the recognition of three distinct lythotypes: 1) a strongly foliated Serpentine - called Serpentine-schist of Val Malenco, with a regular and penetrative schistosity, which makes it possible to split the rock into very fine sheets ("pioda"); 2) a massive Serpentine, with no remarkable foliation, called with different commercial names (Green Vittoria, Green Mare, Green Torre S. Maria etc.); 3) A Clorithic schist (Val Malenco Ollare Stone), in turn subdivisible into two main types, depending on the predominance of Chlorite or Talc, and well known for their thermal behaviour and historical utilization for the production of stoves and cooking pots. The stone is quarried and processed since Middle Ages, and used in building and urban décor since 1800. Particularly, the splittable Serpentine has totally characterized - and still characterizes - the typology of the roofs and the urban style of the Malenco Valley architecture. "Pioda" is the name given to the roofing elements; initially used only for the local building, they were processed and transported out

  15. Tracing the contribution of debris flow-dominated channels to gravel-bed torrential river channel: implementing pit-tags in the upper Guil River (French Alps)

    Science.gov (United States)

    Arnaud-Fassetta, Gilles; Lissak, Candide; Fort, Monique; Bétard, François; Carlier, Benoit; Cossart, Etienne; Madelin, Malika; Viel, Vincent; Charnay, Bérengère; Bletterie, Xavier

    2014-05-01

    In the upper, wider reaches of Alpine valleys, shaping of active channels is usually subject to rapid change. It mostly depends upon hydro-climatic variability, runoff concentration and sediment supply, and may result in alternating sequences of fluvial and debris-flow pulses, as recorded in alluvial fans and terraces. Our study, carried in the frame of SAMCO (ANR) project, focuses on the upper Guil River Valley (Queyras, Southern French Alps) cut into the slaty shale "schistes lustrés". Steep, lower order drains carry a contrasted solid discharge, including predominantly sandy-loam particles mixed with gravels and boulders (sandstone schists, ophiolites). Abundant sediment supply by frost shattering, snow avalanche and landslides is then reworked during snowmelt or summer storm runoff events, and may result in catastrophic, very destructive floods along the main channel, as shown by historical records. Following the RI-30 year 2000 flood, our investigations included sediment budgets, i.e. balance of erosion and deposition, and the mapping of the source, transport and storage of various sediments (talus, colluvium, torrential fans, terraces). To better assess sediment fluxes and sediment delivery into the main channel network, we implemented tracers (pit-tags) in selected sub-catchments, significantly contributing to the sediment yield of the valley bottoms during the floods and/or avalanches: Maloqueste, Combe Morel, Bouchouse and Peyronnelle catchments. The first three are direct tributaries of the Guil River whereas the Peyronnelle is a left bank tributary of the Peynin River, which joins the Guil River via an alluvial cone with high human and material stakes. The Maloqueste and the Combe Morel are two tributaries facing each other in the Guil valley, representing a double lateral constraint for the road during flood events of the Guil River. After pit-tag initialisation in laboratory, we set them up along the four tributaries: Maloqueste (20 pit-tags), Combe

  16. Polymetamorphic evolution of the granulite-facies Paleoproterozoic basement of the Kabul Block, Afghanistan

    Science.gov (United States)

    Collett, Stephen; Faryad, Shah Wali; Mosazai, Amir Mohammad

    2015-08-01

    The Kabul Block is an elongate crustal fragment which cuts across the Afghan Central Blocks, adjoining the Indian and Eurasian continents. Bounded by major strike slip faults and ophiolitic material thrust onto either side, the block contains a strongly metamorphosed basement consisting of some of the only quantifiably Proterozoic rocks south of the Herat-Panjshir Suture Zone. The basement rocks crop-out extensively in the vicinity of Kabul City and consist predominantly of migmatites, gneisses, schists and small amounts of higher-grade granulite-facies rocks. Granulite-facies assemblages were identified in felsic and mafic siliceous rocks as well as impure carbonates. Granulite-facies conditions are recorded by the presence of orthopyroxene overgrowing biotite in felsic rocks; by orthopyroxene overgrowing amphibole in mafic rocks and by the presence of olivine and clinohumite in the marbles. The granulite-facies assemblages are overprinted by a younger amphibolite-facies event that is characterized by the growth of garnet at the expense of the granulite-facies phases. Pressure-temperature (P-T) conditions for the granulite-facies event of around 850 °C and up to 7 kbar were calculated through conventional thermobarometry and phase equilibria modeling. The younger, amphibolite-facies event shows moderately higher pressures of up to 8.5 kbar at around 600 °C. This metamorphism likely corresponds to the dominant metamorphic event within the basement of the Kabul Block. The results of this work are combined with the litho-stratigraphic relations and recent geochronological dating to analyze envisaged Paleoproterozoic and Neoproterozoic metamorphic events in the Kabul Block.

  17. Site response investigation at the seismological station Ostrava-Krásné Pole (OKC

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    Jana Rušajová

    2007-10-01

    Full Text Available Seismic waves generated by earthquakes, quarry blasts, ocean waves and various technological sources cause vibrations that spread through underlying strata into the broad vicinity of these sources. The aim of our experiments was to identify and characterize possible sources of seismic noise generated primarily by technical sources in the Ostrava-Karviná urban agglomeration, which is part of north-eastern Moravia (Czech Republic. The solution of this issue was initiated upon the demand for new knowledge of particle velocity amplitudes and spectral content of disturbing effects, using a newly developed data acquisition method and a system of digitized data processing. A detailed investigation of the influence of different seismogeological conditions at the two sites of observation was performed. While the seismic cellar (OKC A: φ = 49.8375o N, λ = 18.1472o E and h = +272 m is underlain by glaciofluvial sediments (clay loams, sands and gravels, the thickness of which is approximately up to 22 m, the underlying beds in the nearby experimental gallery (OKC B: φ = 49.8353o N, λ = 18.1423o E, and h = +250 m are represented by compact Culm-facies schists (Lower Carboniferous. The thickness of these Culm-facies that represent the underlying bed of the coal-bearing Upper Carboniferous (Namurian A is about 1,200 m. The experimental gallery is situated at a distance of approximately 450 m from the original seismic cellar and about 22 m below its bottom. Different physical-mechanical properties of sub-surface layers at both sites result in different values of acoustic impedance, which naturally influences the particle velocity values, while the shape of calculated amplitude spectra displays a noticeable similarity. On the basis of experimental measurements, some results related to particle velocities and corresponding amplitude spectra of seismic noise are briefly discussed.

  18. Geochemistry of amphibolites and related graphitic gneisses from the Suchý and Malá Magura Mountains (central Western Carpathians – evidence for relics of the Variscan ophiolite complex

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    Ivan Peter

    2015-10-01

    Full Text Available Three small bodies of amphibolites and associated graphitic gneisses from the Suchý and Malá Magura Mountains (Tatric Megaunit, central Western Carpathians have been studied by petrographic and geochemical methods. Isolated, fault-bounded bodies first hundreds of meters in size are located in the complex of the Early Paleozoic paragneisses and migmatites intruded by the Lower Carboniferous granitoid rocks. Amphibolites (locally actinolite schists were formed from effusive basalts, dolerites or isotropic gabbros hydrothermally altered and veined before the regional metamorphic transformation. Distribution of the trace elements relatively immobile during the metamorphic alteration (HFSE, REE, Cr, V, Sc is similar to E-MORB type in the Malá Magura Mountain or to N-MORB/E-MORB types in the Suchý Mountain. Graphitic gneisses to metacherts are rich in silica (up to 88 wt. % and Ctot, poor in other major element contents and display negative Ce-anomaly, enrichment in HREE, V, Cr and U. They were probably originally deposited as non-carbonate and silica-rich deep-sea sediments in anoxic conditions. The oceanic provenance of amphibolites and related graphitic gneisses clearly indicates their oceanic crust affinity and identity with the uppermost part of the ophiolite sequence. Ophiolite bodies from the Suchý and Malá Magura Mountains are supposed to be relic fault blocks identical with the Upper Devonian Pernek Group which represents a Variscan ophiolite nappe preserved to large extent in the Malé Karpaty Mountains located in the Tatric Megaunit further to the southwest. All these ophiolite relics are vestiges of the original ophiolite suture created by oceanic closure in the Lower Carboniferous.

  19. Geochemistry of amphibolites and related graphitic gneisses from the Suchý and Malá Magura Mountains (central Western Carpathians) - evidence for relics of the Variscan ophiolite complex

    Science.gov (United States)

    Ivan, Peter; Méres, Štefan

    2015-10-01

    Three small bodies of amphibolites and associated graphitic gneisses from the Suchý and Malá Magura Mountains (Tatric Megaunit, central Western Carpathians) have been studied by petrographic and geochemical methods. Isolated, fault-bounded bodies first hundreds of meters in size are located in the complex of the Early Paleozoic paragneisses and migmatites intruded by the Lower Carboniferous granitoid rocks. Amphibolites (locally actinolite schists) were formed from effusive basalts, dolerites or isotropic gabbros hydrothermally altered and veined before the regional metamorphic transformation. Distribution of the trace elements relatively immobile during the metamorphic alteration (HFSE, REE, Cr, V, Sc) is similar to E-MORB type in the Malá Magura Mountain or to N-MORB/E-MORB types in the Suchý Mountain. Graphitic gneisses to metacherts are rich in silica (up to 88 wt. %) and Ctot, poor in other major element contents and display negative Ce-anomaly, enrichment in HREE, V, Cr and U. They were probably originally deposited as non-carbonate and silica-rich deep-sea sediments in anoxic conditions. The oceanic provenance of amphibolites and related graphitic gneisses clearly indicates their oceanic crust affinity and identity with the uppermost part of the ophiolite sequence. Ophiolite bodies from the Suchý and Malá Magura Mountains are supposed to be relic fault blocks identical with the Upper Devonian Pernek Group which represents a Variscan ophiolite nappe preserved to large extent in the Malé Karpaty Mountains located in the Tatric Megaunit further to the southwest. All these ophiolite relics are vestiges of the original ophiolite suture created by oceanic closure in the Lower Carboniferous.

  20. The Benedikt hydrothermal system (north-eastern Slovenia)

    Science.gov (United States)

    Kralj, Peter; Eichinger, Lorenz; Kralj, Polona

    2009-10-01

    Deep welling in the Benedikt area has proven the existence of recently active hydrothermal system in pre-Tertiary basement composed of banded gneiss, marble and schist originating from a regionally metamorphosed sequence of clastic sediments. Two aquifers with very high fracture porosity were tapped—at depths between 1,485-1,530 and 1,848-1,857 m, where the welling stopped owing to a technical failure. The water temperature exceeds 90°C, while the yield of 100 l/s is limited only by the well performances. The Na-HCO3 dominated water is classified as a CO2-rich healing mineral water suitable for drinking, bottling and balneology. The free degassing gas is almost pure CO2 (99.9 %) and its δ13C composition indicates volcanic origin. The tapped water is relatively old, probably of Pleistocene age at least, and the planned exploitation must consider reinjection in order to protect this valuable natural resource from overexploitation. This recent hydrothermal system is characterised by dominating vertical circulation of waters and is superimposed on older, already inactive hydrothermal system(s), recognised by veins of either metal sulphides and quartz, or calcite. These vein minerals precipitated from hydrothermal fluids migrating from a deeper source towards the ancient surface through a fracture system, which is now self-sealed already. The distribution of metal sulphides indicates that the source might have been a deep-seated Neogene pluton genetically related to the tonalites and quartz diorites that outcrop in the Pohorje Mountains, or a subvolcanic-level volcanic body related to the Neogene volcanic activity in the Graz Basin.

  1. Earth mortars and earth-lime renders

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    Maria Fernandes

    2008-01-01

    Full Text Available Earth surface coatings play a decorative architectural role, apart from their function as wall protection. In Portuguese vernacular architecture, earth mortars were usually applied on stone masonry, while earth renders and plasters were used on indoors surface coatings. Limestone exists only in certain areas of the country and consequently lime was not easily available everywhere, especially on granite and schist regions where stone masonry was a current building technique. In the central west coast of Portugal, the lime slaking procedure entailed slaking the quicklime mixed with earth (sandy soil, in a pit; the resulting mixture would then be combined in a mortar or plaster. This was also the procedure for manufactured adobes stabilized with lime. Adobe buildings with earth-lime renderings and plasters were also traditional in the same region, using lime putty and lime wash for final coat and decoration. Classic decoration on earth architecture from the 18th-19th century was in many countries a consequence of the François Cointeraux (1740-1830 manuals - Les Cahiers d'Architecture Rurale" (1793 - a French guide for earth architecture and building construction. This manual arrived to Portugal in the beginning of XIX century, but was never translated to Portuguese. References about decoration for earth houses were explained on this manual, as well as procedures about earth-lime renders and ornamentation of earth walls; in fact, these procedures are exactly the same as the ones used in adobe buildings in this Portuguese region. The specific purpose of the present paper is to show some cases of earth mortars, renders and plasters on stone buildings in Portugal and to explain the methods of producing earth-lime renders, and also to show some examples of rendering and coating with earth-lime in Portuguese adobe vernacular architecture.

  2. A phytogeochemical study of the Trás-os-Montes region (NE Portugal): possible species for plant-based soil remediation technologies.

    Science.gov (United States)

    Díez Lázaro, J; Kidd, P S; Monterroso Martínez, C

    2006-02-01

    Phytoremediation techniques are now considered to be promising alternatives to conventional techniques for the remediation of diffused or moderately contaminated soils. Despite their growing acceptance relatively few plant species have been studied for phytoremediation purposes. Further geobotanical surveys and plant screenings are necessary since these could lead to the identification of additional species with potential value for such applications. Serpentine areas could prove valuable sources of such plants. In this study heavy metal accumulation was determined in the flora associated with ultramafic and non-ultramafic soils of the Trás-os-Montes region of NE Portugal. Study sites were selected to represent a wide range of soil-forming rocks (serpentinized (S), ultrabasic (UB), basic (B) and acid (migmatite, M and schists, SC) rocks) and plant metal accumulation was related to soil metal bioavailability. Nine plant species (representing 7 families) were sampled including the Ni hyperaccumulator Alyssum serpyllifolium subsp. lusitanicum. The greatest metal accumulation, transport (leaf[metal]:root[metal]) and bioaccumulation (leaf[metal]/soil[metal]) was found in four of the non metal-hyperaccumulating species: Cistus ladanifer, Lavandula stoechas, Plantago subulata subsp. radicata and Thymus mastichina. Metal accumulation depended on both the plant species and the edaphic conditions at its provenance. While P. subulata is of less interest due to its low biomass the remaining three species could be of use in phytoremediation technologies such as phytoextraction, and particularly in soils contaminated with Cr, Mn and Zn. These three species are also of economic interest due to their oil and fragrance producing biomass.

  3. Friction and stress coupling on the subduction interfaces

    Science.gov (United States)

    Tan, E.; Lavier, L.; van Avendonk, H.

    2011-12-01

    At a subduction zone, the down-going oceanic plate slides underneath the overriding plate. The frictional resistance to the relative motion between the plates generates great earthquakes along the subduction interface, which can cause tremendous damage in the civil life and property. There is a strong incentive to understand the frictional strength of the subduction interface. One fundamental question of mechanics of subuction is the degree of coupling between the plates, which is linked to the size of earthquakes. It has been noted that the trench-parallel (along-strike) gravity variation correlates positively with the trench-parallel topography anomaly and negatively with the activity of great earthquake (Song and Simons, 2003). Regions with a negative trench-parallel gravity anomaly are more likely to have great earthquakes. The interpretation of such correlation is that strong coupling along subduction interface will drag down the for-arc region of the overriding plate, which generates the gravity and topography anomalies, and could store more strain energy to be released during a great earthquake. We developed a 2D numerical thermo-mechanical code for modeling subduction. The numerical method is based on an explicit finite element method similar to the Fast Lagrangian Analysis of Continua (FLAC) technique. The constitutive law is visco-elasti-plastic with strain weakening. The cohesion and friction angle are reduced with increasing plastic strain after yielding. To track different petrologic phases, Lagrangian particles are distributed in the domain. Basalt-eclogite, sediment-schist and peridotite-serpentinite phase changes are included in the model. Our numerical models show that the degree of coupling negatively correlates with the coefficient of friction. In the low friction case, the subduction interface has very shallow dipping angle, which helps to elastically couple the downing plate with the overriding plate. The topography and gravity anomalies of the

  4. Lead and neodymium isotopic results from metabasalts of the Haveri Formation, southern Finland: evidence for Palaeoproterozoic enriched mantle

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    Vaasjoki, M.

    1999-06-01

    Full Text Available Tholeiitic metabasalts and coexisting sulphides have been analysed for their Pb and Nd isotopic compositions from the Proterozoic Haveri Formation, which forms the basal unit of the Tampere Schist Belt in southern Finland. Ten whole rock samples analysed for Pb isotopes form a sublinear array which yields rather uncertain age estimates in the 1900-2000 Ma range and lies on the 207Pb/204Pb vs. 206Pb/204Pb diagram well below the average global lead evolution curve. The initial lead isotopic composition inferred from the whole rock data and measured on chalcopyrite is the least radiogenic obtained from the Svecofennian domain, and precludes involvement of old upper crustal material in basalt genesis. This together with the geochemical composition and initial eNd (1900 of +0.5±0.6 suggest that the Haveri mafic metavolcanic rocks were not derived from convective MORB-type mantle. The source was rather a mantle, which had been enriched in LREE for a considerable time period. Some chalcopyrite trace leads plot close to the whole rock array while others lie above it. This is interpreted as indicating two distinct mineralisation processes. The primary and major process involved lead which was cogenetic with the basalts, while the second mineralising fluid introduced radiogenic (high 207Pb upper crustal lead scavenged from the adjacent sedimentary rocks. The least radiogenic leads at Haveri and in the Outokumpu ophiolite complex some 300 km NE are similar and the two occurrences can be coeval. The preservation of original mantle material at Haveri may be interpreted as suggesting that continental crust had formed in the Tampere area 1900-2000 Ma ago.

  5. Petrography and mineral chemistry of carbonatites and mica-rich rocks from the Araxá complex (Alto Paranaíba Province, Brazil

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    TRAVERSA GIANBOSCO

    2001-01-01

    Full Text Available The Araxá complex (16 km² comprises carbonatites forming a central core and a complex network of concentric and radial dykes as well as small veins; additionally, it includes mica-rich rocks, phoscorites and lamprophyres. Fenites also occur and are represented by Proterozoic quartzites and schists of the Araxá Group. The petrographic study of 130 borehole samples indicates that the complex is basically made up by two rock-types, carbonatites and mica-rich rocks, and subordinately by a third unit of hybrid composition. Carbonatites range chemically in composition, the most abundant type being magnesiocarbonatites. Dolomite and calcite correspond to the chief constituents, but other carbonate phases, including the Ce-group RE minerals, are also recognized. Phosphates and oxides are widespread accessories whereas silicate minerals consist of olivine, clinopyroxene, mica and amphibole. Mica-rich rocks are represented by abundant glimmeritic rocks and scarce cumulitic phlogopite-, olivine- and diopside-bearing pyroxenites. Hybrid rocks mainly contain phlogopite and tetraferriphlogopite as cumulus and intercumulus phases, respectively; carbonate minerals may also be found. Chemical data indicate that the carbonatites are strongly enriched in REE and have lower contents of Nb, Zr, V, Cr, Ni and Rb compared to the mica-rich rocks. The higher K, Nb and Zr contents of the latter rocks are believed to be related to metasomatic processes (glimmeritization of the pyroxenites. Similar REE patterns for carbonatites and mica-rich rocks seem to suggest that they are related to a single parental magma, possibly of ijolitic composition. Steep LREE/HREE fractionation and high sigmaREE content of some carbonatite samples would be explained by hydrothermal and supergenic processes.

  6. A field-guide to the geology of Kythnos, Western Cyclades, Greece

    Science.gov (United States)

    Rice, A. Hugh N.; Grasemann, Bernhard

    2017-04-01

    This poster advertises a new field-guide to the island of Kythnos, within the Western Cyclades: kmz files of the outcrop descriptions etc. can be downloaded from the QR-code. Kythnos comprises schists and marbles of the Cycladic Blueschist Nappe in the footwall of the Miocene West Cycladic Detachment System, with a small outcrop of the hanging wall (Pelagonian Zone) in the southwest of the island. Stretching lineations change from ENE-WSW in the north to NNE-SSW in the south, reflecting a reorientation of Eocene exhumation strains towards the West Cycladic Detachment System extension direction; overall, finite strains increase towards the south and west. The guide is divided into six day-long excursions, with a total of 63 stops; for several excursions more outcrops than can be reasonably visited in one day are given, allowing some choice in the outcrops seen. However, the island is so small (20 x 11 km) that almost any selection of outcrops can be included in a day, since most lie beside or close to a road and require little walking. Descriptions of six outcrops as seen from the local ferries are also given. The guide documents both the dominant and unusual lithologies on the island as well as the major structural features of the island. In particular; deformation associated with the emplacement of the Pelagonian Zone hanging wall along the West Cycladic Detachment System; the development of an intermediate-scale low-angled detachment linking higher-angled Riedel fractures (Ag. Ioannis Detachment); the pervasive thinning and down-faulting of the rocks to the west, with contemporary ductile deformation in blue-grey marble and brittle deformation in quartz-rich layers within the blue-grey marble; and the possibility that a very large-scale recumbent isoclinal fold forms the island.

  7. Detrital zircon U-Pb and Hf isotopic data for meta-sedimentary rocks from the Heilongjiang Complex, northeastern China and tectonic implications

    Science.gov (United States)

    Zhu, Chloe Yanlin; Zhao, Guochun; Sun, Min; Han, Yigui; Liu, Qian; Eizenhöfer, Paul R.; Zhang, Xiaoran; Hou, Wenzhu

    2017-06-01

    The Heilongjiang Complex is a blueschist facies metamorphic belt located within the Zhangguangcailing Orogen between the Jiamusi and Songliao blocks in Northeast China. This complex has been regarded as an accretionary belt related to the subduction of an intervening oceanic domain between the two blocks. However, the timing of ocean closure and final amalgamation has not been well constrained, with different models arguing for a period of 210-180 Ma or sometime after 140 Ma. This work reports in-situ detrital zircon U-Pb and Hf isotopic analyses of meta-sedimentary rocks from the Heilongjiang Complex. Detrital zircons from seven meta-sedimentary rocks samples yield U-Pb ages spanning from 1690 to 167 Ma, with main populations matching those of multi-phase magmatism in the Jiamusi and Songliao blocks. Several Precambrian age groups (600 Ma, 700 Ma, 900 Ma, 960 Ma, 1200 Ma, and 1300 Ma) are consistent with the inherited zircons from the mafic rocks in the Heilongjiang Complex. A comparison with compiled data of magmatic rocks suggests that the two blocks may have been connected to each other during Permian time. Detrital zircon dating of all siliciclastic rocks yielded the youngest age component of 170 Ma, suggesting that the latest deposition of the mica schists happened at some time after 170 Ma. We propose that the Jiamusi and Songliao blocks once existed as a single block around Late Permian, which underwent a rifting event in the Permian to form a rifting basin that was subsequently evolved into an oceanic domain (Heilongjiang Ocean). The closure of the Heilongjiang Ocean occurred after 170 Ma.

  8. Interpretation of shallow crustal structure of the Imperial Valley, California, from seismic reflection profiles

    Energy Technology Data Exchange (ETDEWEB)

    Severson, L.K.

    1987-05-01

    Eight seismic reflection profiles (285 km total length) from the Imperial Valley, California, were provided to CALCRUST for reprocessing and interpretation. Two profiles were located along the western margin of the valley, five profiles were situated along the eastern margin and one traversed the deepest portion of the basin. These data reveal that the central basin contains a wedge of highly faulted sediments that thins to the east. Most of the faulting is strike-slip but there is evidence for block rotations on the scale of 5 to 10 kilometers within the Brawley Seismic Zone. These lines provide insight into the nature of the east and west edges of the Imperial Valley. The basement at the northwestern margin of the valley, to the north of the Superstition Hills, has been normal-faulted and blocks of basement material have ''calved'' into the trough. A blanket of sediments has been deposited on this margin. To the south of the Superstition Hills and Superstition Mountain, the top of the basement is a detachment surface that dips gently into the basin. This margin is also covered by a thick sequence sediments. The basement of the eastern margin consists of metamorphic rocks of the upper plate of the Chocolate Mountain Thrust system underlain by the Orocopia Schist. These rocks dip to the southeast and extend westward to the Sand Hills Fault but do not appear to cross it. Thus, the Sand Hills Fault is interpreted to be the southern extension of the San Andreas Fault. North of the Sand Hills Fault the East Highline Canal seismicity lineament is associated with a strike-slip fault and is probably linked to the Sand Hills Fault. Six geothermal areas crossed by these lines, in agreement with previous studies of geothermal reservoirs, are associated with ''faded'' zones, Bouguer gravity and heat flow maxima, and with higher seismic velocities than surrounding terranes.

  9. Olivine-antigorite orientation relationships: Microstructures, phase boundary misorientations and the effect of cracks in the seismic properties of serpentinites

    Science.gov (United States)

    Morales, Luiz F. G.; Mainprice, David; Kern, Hartmut

    2018-01-01

    Antigorite-bearing rocks are thought to contribute significantly to the seismic properties in the mantle wedge of subduction zones. Here we present a detailed study of the microstructures and seismic properties in a sample of antigorite-olivine schist previously studied by Kern et al. (1997, 2015). We have measured crystallographic orientations and calculated the seismic properties in three orthogonal thin sections. Microstructures indicate that deformation is localized in the bands with high antigorite fractions, resulting in strong crystallographic preferred orientations (CPOs) with point maxima of poles to (100) parallel to lineation and poles to (001) to the foliation normal. Olivine CPO suggests deformation under high temperature and low stress, with a [100] fiber texture. The CPO strength varies with grain size, but is strong even in fine-grained antigorite, and larger grains tend to display higher internal misorientation. Orientation relationships between olivine and antigorite are evident in phase boundary misorientation analysis, (100)ol||(001)atg being more frequent than [001]ol||[010]atg. Two new orientation relationships between olivine and antigorite have been documented. Seismic velocities decrease while anisotropy increases with increasing antigorite modal content. Antigorite grain shape has a weak effect on seismic velocities, but it is important on anisotropy. Comparison between CPO-derived seismic velocities using Voigt, Reuss, Hill averages and geometric mean only showed good agreement in 1/3 of experimental velocities. If the crack porosity of 1.63% measured experimentally at 600 MPa was used in the self-consistent model with two crack orientations with planes normal to Z and Y, good match with all experimental velocities was achieved. The self-consistent model implies important crack porosity in the foliation plane at 600 MPa that reduces Vp normal to the foliation by 0.3 km/s.

  10. Geologic map of the Fraser 7.5-minute quadrangle, Grand County, Colorado

    Science.gov (United States)

    Shroba, Ralph R.; Bryant, Bruce; Kellogg, Karl S.; Theobald, Paul K.; Brandt, Theodore R.

    2010-01-01

    The geologic map of the Fraser quadrangle, Grand County, Colo., portrays the geology along the western boundary of the Front Range and the eastern part of the Fraser basin near the towns of Fraser and Winter Park. The oldest rocks in the quadrangle include gneiss, schist, and plutonic rocks of Paleoproterozoic age that are intruded by younger plutonic rocks of Mesoproterozoic age. These basement rocks are exposed along the southern, eastern, and northern margins of the quadrangle. Fluvial claystone, mudstone, and sandstone of the Upper Jurassic Morrison Formation, and fluvial sandstone and conglomeratic sandstone of the Lower Cretaceous Dakota Group, overlie Proterozoic rocks in a small area near the southwest corner of the quadrangle. Oligocene rhyolite tuff is preserved in deep paleovalleys cut into Proterozoic rocks near the southeast corner of the quadrangle. Generally, weakly consolidated siltstone and minor unconsolidated sediments of the upper Oligocene to upper Miocene Troublesome Formation are preserved in the post-Laramide Fraser basin. Massive bedding and abundant silt suggest that loess or loess-rich alluvium is a major component of the siltstone in the Troublesome Formation. A small unnamed fault about one kilometer northeast of the town of Winter Park has the youngest known displacement in the quadrangle, displacing beds of the Troublesome Formation. Surficial deposits of Pleistocene and Holocene age are widespread in the Fraser quadrangle, particularly in major valleys and on slopes underlain by the Troublesome Formation. Deposits include glacial outwash and alluvium of non-glacial origin; mass-movement deposits transported by creep, debris flow, landsliding, and rockfall; pediment deposits; tills deposited during the Pinedale and Bull Lake glaciations; and sparse diamictons that may be pre-Bull Lake till or debris-flow deposits. Some of the oldest surficial deposits may be as old as Pliocene.

  11. Stratigraphy and Mesozoic-Cenozoic tectonic history of northern Sierra Los Ajos and adjacent areas, Sonora, Mexico

    Science.gov (United States)

    Page, William R.; Gray, Floyd; Iriondo, Alexander; Miggins, Daniel; Blodgett, Robert B.; Maldonado, Florian; Miller, Robert J.

    2010-04-01

    Geologic mapping in the northern Sierra Los Ajos reveals new stratigraphic and structural data relevant to deciphering the Mesozoic-Cenozoic tectonic evolution of the range. The northern Sierra Los Ajos is cored by Proterozoic, Cambrian, Devonian, Mississippian, and Pennsylvanian strata, equivalent respectively to the Pinal Schist, Bolsa Quartzite and Abrigo Limestone, Martin Formation, Escabrosa Limestone, and Horquilla Limestone. The Proterozoic-Paleozoic sequence is mantled by Upper Cretaceous rocks partly equivalent to the Fort Crittenden and Salero Formations in Arizona, and the Cabullona Group in Sonora, Mexico. Absence of the Upper Jurassic-Lower Cretaceous Bisbee Group below the Upper Cretaceous rocks and above the Proterozoic-Paleozoic rocks indicates that the Sierra Los Ajos was part of the Cananea high, a topographic highland during the Late Jurassic and Early Cretaceous. Deposition of Upper Cretaceous rocks directly on Paleozoic and Proterozoic rocks indicates that the Sierra Los Ajos area had subsided as part of the Laramide Cabullona basin during Late Cretaceous time. Basal beds of the Upper Cretaceous sequence are clast-supported conglomerate composed locally of basement (Paleozoic) clasts. The conglomerate represents erosion of Paleozoic basement in the Sierra Los Ajos area coincident with development of the Cabullona basin. The present-day Sierra Los Ajos reaches elevations of greater than 2600 m, and was uplifted during Tertiary basin-and-range extension. Upper Cretaceous rocks are exposed at higher elevations in the northern Sierra Los Ajos and represent an uplifted part of the inverted Cabullona basin. Tertiary uplift of the Sierra Los Ajos was largely accommodated by vertical movement along the north-to-northwest-striking Sierra Los Ajos fault zone flanking the west side of the range. This fault zone structurally controls the configuration of the headwaters of the San Pedro River basin, an important bi-national water resource in the US

  12. Reactivation of normal faults as high-angle reverse faults due to low frictional strength: Experimental data from the Moonlight Fault Zone, New Zealand

    Science.gov (United States)

    Smith, S. A. F.; Tesei, T.; Scott, J. M.; Collettini, C.

    2017-12-01

    Large normal faults are frequently reactivated as high-angle reverse faults during basin inversion. Elevated fluid pressure is commonly invoked to explain high-angle reverse slip. Analogue and numerical modeling have demonstrated that frictional weakening may also promote high-angle reverse slip, but there are currently no frictional strength measurements available for fault rocks collected from large high-angle reverse faults. To test the hypothesis that frictional weakening could facilitate high-angle reverse slip, we performed single- and double-direct friction experiments on fault rocks collected from the Moonlight Fault Zone in New Zealand, a basin-bounding normal fault zone that was reactivated as a high-angle reverse fault (present-day dip angle 60°-75°). The fault core is exposed in quartzofeldspathic schists exhumed from c. 4-8 km depth and contains a <20 m thick sequence of breccias, cataclasites and foliated cataclasites that are enriched in chlorite and muscovite. Friction experiments on water-saturated, intact samples of foliated cataclasite at room temperature and normal stresses up to 75 MPa yielded friction coefficients of 0.19<μ < 0.25. On the assumption of horizontal maximum compressive stress, reactivation analysis indicates that a friction coefficient of <0.25 will permit slip on high-angle reverse faults at hydrostatic (or even sub-hydrostatic) fluid pressures. Since foliated and phyllosilicate-rich fault rocks are common in large reactivated fault zones at basement depths, long-term frictional weakening is likely to act in concert with episodic build-ups of fluid pressure to promote high-angle reverse slip during basin inversion.

  13. Estimation of groundwater flow directions and the tensor of hydraulic conductivity in crystalline massif rocks using information from surface structural geology and mining exploration boreholes

    Science.gov (United States)

    Florez, C.; Romero, M. A.; Ramirez, M. I.; Monsalve, G.

    2013-05-01

    In the elaboration of a hydrogeological conceptual model in regions of mining exploration where there is significant presence of crystalline massif rocks., the influence of physical and geometrical properties of rock discontinuities must be evaluated. We present the results of a structural analysis of rock discontinuities in a region of the Central Cordillera of Colombia (The upper and middle Bermellon Basin) in order to establish its hydrogeological characteristics for the improvement of the conceptual hydrogeological model for the region. The geology of the study area consists of schists with quartz and mica and porphyritic rocks, in a region of high slopes with a nearly 10 m thick weathered layer. The main objective of this research is to infer the preferential flow directions of groundwater and to estimate the tensor of potential hydraulic conductivity by using surface information and avoiding the use of wells and packer tests. The first step of our methodology is an analysis of drainage directions to detect patterns of structural controls in the run-off; after a field campaign of structural data recollection, where we compile information of strike, dip, continuity, spacing, roughness, aperture and frequency, we built equal area hydro-structural polar diagrams that indicate the potential directions for groundwater flow. These results are confronted with records of Rock Quality Designation (RQD) that have been systematically taken from several mining exploration boreholes in the area of study. By using all this information we estimate the potential tensor of hydraulic conductivity from a cubic law, obtaining the three principal directions with conductivities of the order of 10-5 and 10-6 m/s; the more conductive joint family has a NE strike with a nearly vertical dip.

  14. Geologic columns for the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure: Impactites and crystalline rocks, 1766 to 1096 m depth

    Science.gov (United States)

    Horton, J. Wright; Gibson, R.L.; Reimold, W.U.; Wittmann, A.; Gohn, G.S.; Edwards, L.E.

    2009-01-01

    The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville drill cores from the Chesapeake Bay impact structure provide one of the most complete geologic sections ever obtained from an impact structure. This paper presents a series of geologic columns and descriptive lithologic information for the lower impactite and crystalline-rock sections in the cores. The lowermost cored section (1766-1551 m depth) is a complex assemblage of mica schists that commonly contain graphite and fibrolitic sillimanite, intrusive granite pegmatites that grade into coarse granite, and local zones of mylonitic deformation. This basement-derived section is variably overprinted by brittle cataclastic fabrics and locally cut by dikes of polymict impact breccia, including several suevite dikes. An overlying succession of suevites and lithic impact breccias (1551-1397 m) includes a lower section dominated by polymict lithic impact breccia with blocks (up to 17 m) and boulders of cataclastic gneiss and an upper section (above 1474 m) of suevites and clast-rich impact melt rocks. The uppermost suevite is overlain by 26 m (1397-1371 m) of gravelly quartz sand that contains an amphibolite block and boulders of cataclasite and suevite. Above the sand, a 275-m-thick allochthonous granite slab (1371-1096 m) includes gneissic biotite granite, fine- and medium-to-coarse-grained biotite granites, and red altered granite near the base. The granite slab is overlain by more gravelly sand, and both are attributed to debris-avalanche and/or rockslide deposition that slightly preceded or accompanied seawater-resurge into the collapsing transient crater. ?? 2009 The Geological Society of America.

  15. Detrital zircon age patterns from turbidites of the Balagne and Piedmont nappes of Alpine Corsica (France): Evidence for an European margin source

    Science.gov (United States)

    Lin, Wei; Rossi, Philippe; Faure, Michel; Li, Xian-Hua; Ji, Wenbin; Chu, Yang

    2018-01-01

    At the front of metamorphic Cenozoic Alpine nappe of Schistes Lustrés, Western Alpine Corsica (France) exposes non- to very low grade metamorphic nappes, such as the Piedmont nappes, Upper nappes, and the Balagne nappe. The provenance of the Balagne nappe remains still opened: an origin close to the Corsican continental margin; or an origin far East from the Corsican margin toward the "Apenninic" oceanic domain. This would constrain that the Balagne ophiolite be derived from the opposite OCT (Ocean - Continent transition), close to a microcontinent located to the East of the Mesozoic Corsican margin. A systematic U-Pb dating of 586 detrital zircon grains collected from the turbidites in the Balagne and Piedmont nappes has been performed to constrain the source of sediments. The zircon grains yield U-Pb age spectra ranging from Neoarchean to Late Paleozoic with age peaks at 2600 Ma, 2080 Ma, 1830 Ma, 910 Ma, 600 Ma, 560 Ma, 450 Ma, 330 Ma and 280 Ma with different continental model ages (TDM2) from 3.5 Ga to 1.0 Ga. The variety of composition of the Corsican batholith, unique in its present Mediterranean environment, and in spite of Alpine transcurrent movements, provide a key to analyze the detrital zircon age distribution patterns of sedimentary rocks. These new results i) confirm the lack of any Cretaceous zircon that validates absence of a magmatic arc of this age, at least in the surroundings of the turbiditic formations from the Balagne and the Piedmont nappes; ii) fully support an European provenance of detritus of the Balagne nappe, iii) put forward evidence that no ophiolitic zircon was contained neither in the Cretaceous nor in the Eocene turbidites samples, and iv) question both the deposition of the Piedmont Narbinco flysch within the ocean continent transition and its possible relationships with the Late Cretaceous Pyrenean basins.

  16. Reactive Fluid Flow and Applications to Diagenesis, Mineral Deposits, and Crustal Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Rye, Danny M.; Bolton, Edward W.

    2002-11-04

    The objective is to initiate new: modeling of coupled fluid flow and chemical reactions of geologic environments; experimental and theoretical studies of water-rock reactions; collection and interpretation of stable isotopic and geochemical field data at many spatial scales of systems involving fluid flow and reaction in environments ranging from soils to metamorphic rocks. Theoretical modeling of coupled fluid flow and chemical reactions, involving kinetics, has been employed to understand the differences between equilibrium, steady-state, and non-steady-state behavior of the chemical evolution of open fluid-rock systems. The numerical codes developed in this project treat multi-component, finite-rate reactions combined with advective and dispersive transport in multi-dimensions. The codes incorporate heat, mass, and isotopic transfer in both porous and fractured media. Experimental work has obtained the kinetic rate laws of pertinent silicate-water reactions and the rates of Sr release during chemical weathering. Ab-initio quantum mechanical techniques have been applied to obtain the kinetics and mechanisms of silicate surface reactions and isotopic exchange between water and dissolved species. Geochemical field-based studies were carried out on the Wepawaug metamorphic schist, on the Irish base-metal sediment-hosted ore system, in the Dalradian metamorphic complex in Scotland, and on weathering in the Columbia River flood basalts. The geochemical and isotopic field data, and the experimental and theoretical rate data, were used as constraints on the numerical models and to determine the length and time scales relevant to each of the field areas.

  17. Crop residue effects on Ca, Mg, K and Na concentrations and loads in runoff water

    Science.gov (United States)

    Miras-Avalos, J. M.; Sande-Fouz, P.; Bertol, I.; Paz-Gonzalez, A.

    2009-04-01

    Soil organic matter constitutes and important source of macro and micronutrients for plants and microorganisms while improving some physical and chemical properties of the soil. In Galicia (NW Spain), cultivated soils developed on schists from the Ordenes series show a relatively high susceptibility to surface degradation, which tends to be increased when soil organic content decreases. Therefore, management systems providing a high protection to the soil and increasing its organic matter content should also improve its quality. However, tillage practices may reduce the organic matter content in soil surface horizons, causing crust formation. Degraded soil surface conditions favor surface runoff, thus enhancing nutrient losses. This study examined the effect of applying crop residues to the soil surface on main nutrient (Ca, Mg, K and Na) losses by runoff from a tilled soil with a relatively low organic matter content. Runoff and sediment yield were made over 1 m2 plots using a rainfall simulator with constant 65 mmh-1 intensity. Four successive rainfall applications were performed, the first three ones 25 mm each and the last one 65 mm. Added corn straw varied between 0 and 4 tha-1 in the five studied treatments. Total and dissolved concentrations of the studied elements showed a trend to decrease due to the effect of corn straw on soil losses. After 140 mm cumulative rainfall, total nutrient losses were as follows: Ca from 12.32 to 28.94 mg L-1, Mg from 20.81 to 148.90 mg L-1, K from 14.20 to 35.17 mg L-1 and Na from 14.99 to 23.41 mg L-1. The relative contribution of the dissolved fraction to the total nutrient content loss was highly variable, being up to 90% in the case of Na. The obtained results confirmed that corn residues applied to a degraded soil, with low structural stability, prevented macronutrient losses.

  18. La faja cataclástica del borde oriental del Sistema de FamatIna, ArgentIna

    Directory of Open Access Journals (Sweden)

    Indri, D. A.

    1992-12-01

    Full Text Available The cataclastic rocks autcrops are located at the northwestern Pampean Ranges and have a N-S direction. They are limiting the Famatina system to the eastern and carne along the Puna.They have been recognized protomylonites, mylonite gneiss and mylonite schists which may be formed under 10 or 15 km of deep and 275-350° C temperatures of source.The main dominant structure have NNW direction and dips to the eastern. There can be seen compressive movements related to western blocks displacements.During de Ocloyica distrophic phase (Upper Ordovician-Lower Silurian may be formed these cataclastic rocks, related to the Antofalla Craton collision.En las Sierras Pampeanas Noroccidentales del noroeste argentino se desarrolla una faja cataclástica de rumbo submeridional, en rocas del basamento ígneo-metamórfico pertenecientes al Paleozoico Inferior. Esta estructura coincide con el límite oriental del Sistema de Famatina y su porción septentrional se extiende dentro de la provincia morfoestructural de la Puna.En el área estudiada se reconocen protomilonitas, gneises y esquistos miloníticos, los que, en base a sus características texturales, se habrían formado a profundidades de 10 a 15 km y a temperaturas de 275-350° C.El plano principal de cizalla tiene rumbo NNW e inclina hacia el este y sobre el mismo se distinguen movimientos compresivos con desplazamientos relativos de bloques hacia el oeste.La faja de cataclasitas se habría originado durante la Fase Diastrófica Oclóyica (Ordovícico Superior-Silúrico Inferior relacionada con la colisión del Cratón de Antofalla.

  19. Delineation of faults, fractures, foliation, and ground-water-flow zones in fractured-rock, on the southern part of Manhattan, New York, through use of advanced borehole-geophysical techniques

    Science.gov (United States)

    Stumm, Frederick; Chu, Anthony; Monti, Jack

    2004-01-01

    Advanced borehole-geophysical techniques were used to assess the geohydrology of crystalline bedrock in 20 boreholes on the southern part of Manhattan Island, N.Y., in preparation for construction of a third water tunnel for New York City. The borehole-logging techniques included natural gamma, single-point resistance, short-normal resistivity, mechanical and acoustic caliper, magnetic susceptibility, borehole-fluid temperature and resistivity, borehole-fluid specific conductance, dissolved oxygen, pH, redox, heatpulse flowmeter (at selected boreholes), borehole deviation, acoustic and optical televiewer, and borehole radar (at selected boreholes). Hydraulic head and specific-capacity test data were collected from 29 boreholes. The boreholes penetrated gneiss, schist, and other crystalline bedrock that has an overall southwest to northwest-dipping foliation. Most of the fractures penetrated are nearly horizontal or have moderate- to high-angle northwest or eastward dip azimuths. Foliation dip within the potential tunnel-construction zone is northwestward and southeastward in the proposed North Water-Tunnel, northwestward to southwestward in the proposed Midtown Water-Tunnel, and northwestward to westward dipping in the proposed South Water-Tunnel. Fracture population dip azimuths are variable. Heat-pulse flowmeter logs obtained under pumping and nonpumping (ambient) conditions, together with other geophysical logs, indicate transmissive fracture zones in each borehole. The 60-megahertz directional borehole-radar logs delineated the location and orientation of several radar reflectors that did not intersect the projection of the borehole.Fracture indexes range from 0.12 to 0.93 fractures per foot of borehole. Analysis of specific-capacity tests from each borehole indicated that transmissivity ranges from 2 to 459 feet squared per day; the highest transmissivity is at the Midtown Water-Tunnel borehole (E35ST-D).

  20. Platinum-group mineralization at the margin of the Skaergaard intrusion, East Greenland

    Science.gov (United States)

    Andersen, Jens C. Ø.; Rollinson, Gavyn K.; McDonald, Iain; Tegner, Christian; Lesher, Charles E.

    2017-08-01

    Two occurrences of platinum-group elements (PGEs) along the northern margin of the Skaergaard intrusion include a sulfide-bearing gabbro with slightly less than 1 ppm PGE + Au and a clinopyroxene-actinolite-plagioclase-biotite-ilmenite schist with 16 vol% sulfide and 1.8 ppm PGE + Au. Both have assemblages of pyrrhotite, pentlandite, and chalcopyrite typical for orthomagmatic sulfides. Matching platinum-group mineral assemblages with sperrylite (PtAs2), kotulskite (Pd(Bi,Te)1-2), froodite (PdBi2), michenerite (PdBiTe), and electrum (Au,Ag) suggest a common origin. Petrological and geochemical similarities suggest that the occurrences are related to the Skaergaard intrusion. The Marginal Border Series locally displays Ni depletion consistent with sulfide fractionation, and the PGE fractionation trends of the occurrences are systematically enriched by 10-50 times over the chilled margin. The PGE can be explained by sulfide-silicate immiscibility in the Skaergaard magma with R factors of 110-220. Nickel depletion in olivine suggests that the process occurred within the host cumulate, and the low R factors require little sulfide mobility. The sulfide assemblages are different to the chalcopyrite-bornite-digenite assemblage found in the Skaergaard Layered Series and Platinova Reef. These differences can be explained by the early formation of sulfide melt, while magmatic differentiation or sulfur loss caused the unusual sulfide assemblage within the Layered Series. The PGEs indicate that the sulfides formed from the Skaergaard magma. The sulfides and PGEs could not have formed from the nearby Watkins Fjord wehrlite intrusion, which is nearly barren in sulfide. We suggest that silicate-sulfide immiscibility led to PGE concentration where the Skaergaard magma became contaminated with material from the Archean basement.

  1. Ultrasound-assisted extraction for total sulphur measurement in mine tailings

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Adnan Hossain, E-mail: ad_li2@yahoo.com [Department of Civil and Environmental Engineering, University of Western Ontario (Canada); Shang, Julie Q.; Alam, Raquibul [Department of Civil and Environmental Engineering, University of Western Ontario (Canada)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer We develop a total sulphur measuring procedure of mine tailings. Black-Right-Pointing-Pointer Ultrasound is used in the sample pre-treatment process. Black-Right-Pointing-Pointer Full factorial design is applied to identify the best level of effecting factors. - Abstract: A sample preparation method for percentage recovery of total sulphur (%S) in reactive mine tailings based on ultrasound-assisted digestion (USAD) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) was developed. The influence of various methodological factors was screened by employing a two-level and three-factor (2{sup 3}) full factorial design and using KZK-1, a sericite schist certified reference material (CRM), to find the optimal combination of studied factors and %S. Factors such as the sonication time, temperature and acid combination were studied, with the best result identified as 20 min of sonication, 80 Degree-Sign C temperature and 1 ml of HNO{sub 3}:1 ml of HCl, which can achieve 100% recovery for the selected CRM. Subsequently a fraction of the 2{sup 3} full factorial design was applied to mine tailings. The percentage relative standard deviation (%RSD) for the ultrasound method is less than 3.0% for CRM and less than 6% for the mine tailings. The investigated method was verified by X-ray diffraction analysis. The USAD method compared favorably with existing methods such as hot plate assisted digestion method, X-ray fluorescence and LECO Trade-Mark-Sign -CNS method.

  2. New isotopic age data constrain the depositional age and accretionary history of the Neoproterozoic-Ordovician Mona Complex (Anglesey-Lleyn, Wales)

    Science.gov (United States)

    Asanuma, Hisashi; Fujisaki, Wataru; Sato, Tomohiko; Sakata, Shuhei; Sawaki, Yusuke; Aoki, Kazumasa; Okada, Yoshihiro; Maruyama, Shigenori; Hirata, Takafumi; Itaya, Tetsumaru; Windley, Brian F.

    2017-06-01

    The Mona Complex in Anglesey-Lleyn, Wales formed by Avalonian subduction and accretion from the latest Neoproterozoic to early Paleozoic. It comprises an ophiolite, high-pressure metamorphic rocks, volcaniclastic sediments and mélanges. However, understanding of the tectonic evolution has been held back by the paucity of age constraints, thus only a major geochronological study will be sufficient to decipher the subduction, accretion and exhumation history of this significant Avalonian orogen. We conducted U-Pb dating of detrital zircons in the Monian Supergroup in order to constrain the maximum depositional ages, and undertook K-Ar dating of phengites and U-Pb dating of detrital zircons in the Blueschist unit, the Central Shear Zone (CSZ), and the New Harbour Group to estimate the timing and duration of the metamorphic events, and to constrain the minimum depositional ages of the Gwna Group. Our geochronological data give minimum (K-Ar) depositional ages of 578-530 Ma on phengites and maximum (U-Pb zircon) depositional ages of 878-550 Ma, which indicates that the sediments in the structurally uppermost Gwna Group were deposited earlier than those in the middle New Harbour Group (maximum depositional ages of 548-515 Ma, this study) and earlier than in the lowermost South Stack Group (maximum depositional ages of 569-522 Ma, this study). Phengite-rich schists in the Blueschist unit and the CSZ show indistinct K-Ar ages ranging from ca. 578 to 530 Ma. However, the K-Ar age of the New Harbour Group is ca. 474 Ma, which we interpret to reflect a later metamorphic event. In a larger perspective, our new ages are broadly contemporaneous with the calc-alkaline continental arc magmatism in NW Wales and Central England that formed by successive eastward subduction from ca.711 to 474 Ma.

  3. Reconstructing the Mid-Tertiary Southwestern North America Cordilleran Crust: Crustal Anisotropy

    Science.gov (United States)

    Porter, R. C.; Zandt, G.; McQuarrie, N.; Gilbert, H. J.; Hacker, B. R.

    2009-12-01

    The deployment of EarthScope USArray stations provides researchers with unprecedented quantities and coverage of publicly available seismic data that can be combined with other techniques to better understand the tectonic evolution of western North America. We utilize the receiver function method to map the crustal thickness and investigate the occurrence and orientation of lower crustal anisotropy for the southwestern U.S. Using the tectonic reconstruction of McQuarrie and Wernicke (2005), we then reconstruct the location and orientation of the anisotropy back to 36 Ma. We have completed the reconstruction for central and southern California, and found a dominant SW-NE oriented trend that we interpret as a fossilized fabric within underplated schists created from top-to-southwest sense of shear that existed along the length of coastal California during pre-transform, early-Tertiary subduction. Initial results from the Basin and Range show a generally consistent E-W anisotropy trend within the northern and central Basin and Range, orthogonal to modern faulting and mountain ranges. Within this area there is a correlation of generally stronger crustal anisotropy and thinner crust in the eastern Basin and Range. In the southern Basin and Range we observe more scatter in our anisotropy results, with a majority of stations exhibiting either a SW-NE or NNW-SSE orientation. Despite the variability in results, most anisotropy orientations appear to be orthogonal to nearby mountain ranges. These observations suggest that Tertiary extension in the Basin and Range is producing a lower crustal zone of anisotropy throughout the province. We are currently working to expand on these results by integrating elasticity tensors calculated from electron-backscatter diffraction measurements of samples of lower crustal rocks from the southwestern U.S.

  4. Chemical and mineralogical data and processing methods management system prototype with application to study of the North Caucasus Blybsky Metamorphic Complexes metamorphism PT-condition

    Science.gov (United States)

    Ivanov, Stanislav; Kamzolkin, Vladimir; Konilov, Aleksandr; Aleshin, Igor

    2014-05-01

    There are many various methods of assessing the conditions of rocks formation based on determining the composition of the constituent minerals. Our objective was to create a universal tool for processing mineral's chemical analysis results and solving geothermobarometry problems by creating a database of existing sensors and providing a user-friendly standard interface. Similar computer assisted tools are based upon large collection of sensors (geothermometers and geobarometers) are known, for example, the project TPF (Konilov A.N., 1999) - text-based sensor collection tool written in PASCAL. The application contained more than 350 different sensors and has been used widely in petrochemical studies (see A.N. Konilov , A.A. Grafchikov, V.I. Fonarev 2010 for review). Our prototype uses the TPF project concept and is designed with modern application development techniques, which allows better flexibility. Main components of the designed system are 3 connected datasets: sensors collection (geothermometers, geobarometers, oxygen geobarometers, etc.), petrochemical data and modeling results. All data is maintained by special management and visualization tools and resides in sql database. System utilities allow user to import and export data in various file formats, edit records and plot graphs. Sensors database contains up to date collections of known methods. New sensors may be added by user. Measured database should be filled in by researcher. User friendly interface allows access to all available data and sensors, automates routine work, reduces the risk of common user mistakes and simplifies information exchange between research groups. We use prototype to evaluate peak pressure during the formation of garnet-amphibolite apoeclogites, gneisses and schists Blybsky metamorphic complex of the Front Range of the Northern Caucasus. In particular, our estimation of formation pressure range (18 ± 4 kbar) agrees on independent research results. The reported study was

  5. Upper crustal structure of the North Anatolian Fault Zone from ambient seismic noise Rayleigh and Love wave tomography

    Science.gov (United States)

    Taylor, George; Rost, Sebastian; Houseman, Gregory; Hillers, Gregor

    2017-04-01

    By utilising short period surface waves present in the noise field, we can construct images of shallow structure in the Earth's upper crust: a region that is usually poorly resolved in earthquake tomography. Here, we use data from a dense seismic array (Dense Array for Northern Anatolia - DANA) deployed across the North Anatolian Fault Zone (NAFZ) in the region of the 1999 magnitude 7.6 Izmit earthquake in western Turkey. The NAFZ is a major strike-slip system that extends ˜1200 km across northern Turkey and continues to pose a high level of seismic hazard, in particular to the mega-city of Istanbul. We obtain maps of group velocity variation using surface wave tomography applied to short period (1- 6 s) Rayleigh and Love waves to construct high-resolution images of the upper 5 km of a 70 km x 35 km region centred on the eastern end of the fault segment that ruptured in the 1999 Izmit earthquake. The average Rayleigh wave group velocities in the region vary between 1.8 km/s at 1.5 s period, to 2.2 km/s at 6 s period. The NAFZ bifurcates into northern and southern strands in this region; both are active but only the northern strand moved in the 1999 event. The signatures of both the northern and southern branches of the NAFZ are clearly associated with strong gradients in surface wave group velocity. To the north of the NAFZ, we observe low Rayleigh wave group velocities ( 1.2 km/s) associated with the unconsolidated sediments of the Adapazari basin, and blocks of weathered terrigenous clastic sediments. To the south of the northern branch of the NAFZ, we detect high velocities ( 2.5 km/s) associated with a shallow crystalline basement, in particular a block of metamorphosed schists and marbles that bound the northern branch of the NAFZ.

  6. Geology, petrology, U-Pb (SHRIMP) geochronology of the Morrinhos granite - Paragua terrane, SW Amazonian craton: implications for the magmatic evolution of the San Ignacio orogeny

    Energy Technology Data Exchange (ETDEWEB)

    Franca, Ohana; Ruiz, Amarildo Salina; Sousa, Maria Zelia Aguiar de, E-mail: ohana.geo@gmail.com, E-mail: asruiz@gmail.com, E-mail: mzaguiar@terra.com.br [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Instituto de Ciencias Exatas e da Terra. Dept. de Geologia Geral; Batata, Maria Elisa Froes, E-mail: elisabatata@bol.com.br [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Grupo de Pesquisa em Evolucao Crustal e Tectonica; Lafon, Jean-Michel [Universidade Federal do Para (GEOCIAM/UFPA), Belem, PR (Brazil). Inst. Nacional de Cencia e Tecnologia de Geociencias da Amazonia

    2014-09-15

    Morrinhos granite is a batholith body that is slightly elongated in the NNW direction and approximately 1,140 km{sup 2} long; it is located in the municipality of Vila Bela da Santissima Trindade of the state of Mato Grosso, Brazil, in the Paragua Terrane, Rondonian-San Ignacio Province, in the SW portion of the Amazonian Craton. This intrusion displays a compositional variation from tonalite to monzogranite, has a medium to coarse inequigranular texture and is locally porphyritic; biotite is the predominant mafic in one of the facies, and hornblende is predominant in the other, with both metamorphosed into the green schist facies. The studied rocks characterize an intermediate to acidic sequence that was formed by a subalkaline magmatism; the series is alkali-calcic to metaluminous to slightly peraluminous, and the rocks evolved through fractioned crystallization mechanisms. The structural data show two deformation phases represented by penetrative foliation (S{sub 1}) and open folds (D{sub 2}), and both phases were most likely related to the San Ignacio Orogeny. The geochronological (U-Pb SHRIMP) and isotopic (Sm-Nd) investigations of these rocks indicated a crystallization age of 1350±12Ma, T{sub DM} of approximately 1.77 Ga and εNd{sub (1.35}) with a negative value of -2.57, suggesting that their generation was related to a partial melting process of a Paleoproterozoic (Statherian) continental crust. The results herein indicate that the Morrinhos granite was generated in a continental magmatic arc in a late- to post-orogenic stage of the San Ignacio Orogeny, and it can be recognized as belonging to the Pensamiento Intrusive Suite. (author)

  7. Long-term impact of reduced tillage on water and pesticide flow in a drained context.

    Science.gov (United States)

    Dairon, R; Dutertre, A; Tournebize, J; Marks-Perreau, J; Carluer, N

    2017-03-01

    Influence of more than 20 years (1988-2010) of reduced tillage (RT) practices on water and pesticide balances and dynamics is analyzed and compared to results from a conventional tillage plot (CT). The field study soils are described as silty clay stagnic luvisol, developed on a low permeable schist layer. A drainage network was set up according to French criteria (0.9 m deep, 10 m space) to avoid soil winter waterlogging. Climate is temperate oceanic and drainage generally occurs from November to March. Data were analyzed at yearly, weekly (pesticides) and hourly (water) time steps. Over the long term, cumulated drainage decreases significantly on RT (3999 mm) compared to CT (5100 mm). This differentiation becomes significant from 1999, 10 years after plowing was stopped. Strikingly, hourly drainage peak flows are higher under RT, especially during the second period (2000-2010), associated with low or no base flow. These results suggest a strong influence of the macropore network under RT practice. In particular, drainage peaks are higher at the beginning of the drainage season (mid-October to December). Consistently, pesticides applied in late autumn, which are the most quantified on this site, are often significantly more exported under RT. For atrazine, applied in spring, fluxes are linked to cumulative flow and are de facto higher under CT. For others pesticides, losses appear to be heterogeneous, with generally low or null export rates for spring application. Generally speaking, higher concentrations are measured on RT plot and explain observed exportation rate differences. Finally, there is no clear evidence of correlation between pesticide losses and long-term impacts of RT on hydrodynamics, pointing the importance of studying the short-term effect of tillage on water and especially solute flow.

  8. The copper spoil heap Knappenberg, Austria, as a model for metal habitats – Vegetation, substrate and contamination

    Energy Technology Data Exchange (ETDEWEB)

    Adlassnig, Wolfram; Weiss, Yasmin S. [University of Vienna, Core Facility Cell Imaging and Ultrastructure Research, Althanstraße 14, A-1090 Vienna (Austria); Sassmann, Stefan [University of Vienna, Core Facility Cell Imaging and Ultrastructure Research, Althanstraße 14, A-1090 Vienna (Austria); University of Exeter, College of Life and Environmental Sciences, Biosciences, Stocker Road, Exeter EX4 4QD (United Kingdom); Steinhauser, Georg [Leibniz University Hannover, Institute of Radioecology and Radiation Protection, Herrenhäuser Straße 2, D30419 Hannover (Germany); Hofhansl, Florian [University of Vienna, Department of Microbiology and Ecosystem Science, Althanstraße 14, A-1090 Vienna (Austria); Instituto Nacional de Pesquisas da Amazônia, Coordenação de Dinâmica Ambiental, Manaus (Brazil); Baumann, Nils [Helmholtz-Zentrum Dresden-Rossendorf, Division of Biogeochemistry, Bautzner Landstraße 400, D-01328 Dresden (Germany); Lichtscheidl, Irene K. [University of Vienna, Core Facility Cell Imaging and Ultrastructure Research, Althanstraße 14, A-1090 Vienna (Austria); Lang, Ingeborg, E-mail: ingeborg.lang@univie.ac.at [University of Vienna, Core Facility Cell Imaging and Ultrastructure Research, Althanstraße 14, A-1090 Vienna (Austria)

    2016-09-01

    Historic mining in the Eastern Alps has left us with a legacy of numerous spoil heaps hosting specific, metal tolerant vegetation. Such habitats are characterized by elevated concentrations of toxic elements but also by high irradiation, a poorly developed substrate or extreme pH of the soil. This study investigates the distribution of vascular plants, mosses and lichens on a copper spoil heap on the ore bearing Knappenberg formed by Prebichl Layers and Werfener Schist in Lower Austria. It serves as a model for discriminating between various ecological traits and their effects on vegetation. Five distinct clusters were distinguished: (1) The bare, metal rich Central Spoil Heap was only colonised by highly resistant specialists. (2) The Northern and (3) Southern Peripheries contained less copper; the contrasting vegetation was best explained by the different microclimate. (4) A forest over acidic bedrock hosted a vegetation overlapping with the periphery of the spoil heap. (5) A forest over calcareous bedrock was similar to the spoil heap with regard to pH and humus content but hosted a vegetation differing strongly to all other habitats. Among the multiple toxic elements at the spoil heap, only Cu seems to exert a crucial influence on the vegetation pattern. Besides metal concentrations, irradiation, humidity, humus, pH and grain size distribution are important for the establishment of a metal tolerant vegetation. The difference between the species poor Northern and the diverse Southern Periphery can be explained by the microclimate rather than by the substrate. All plant species penetrating from the forest into the periphery of the spoil heap originate from the acidic but not from the calcareous bedrock. - Highlights: • Strong impact on plant diversity by isolation and extreme abiotic conditions • Both, microclimate and substrate explain species distribution. • Increased cellular metal tolerance of plants from the Central Spoil Heap • Among toxic elements

  9. Revisions to the stratigraphic nomenclature of the Abiquiu Formation, Abiquiu and contiguous areas, north-central New Mexico

    Science.gov (United States)

    Maldonado, Florian; Kelley, Shari A.

    2009-01-01

    Stratigraphic studies and geologic mapping on the Abiquiu 7.5-min quadrangle have led to revision of the stratigraphic nomenclature for the Oligocene to Miocene Abiquiu Formation in north-central New Mexico. The Abiquiu Formation had previously been defined to include informal upper, middle (Pedernal chert member), and lower members. The basement-derived conglomeratic lower member in the northern Jemez Mountains and Abiquiu embayment is here redefined. We propose removing the "lower member" from the Abiquiu Formation because provenance of these coarse sediments is dramatically different than the volcaniclastic strata of the "upper member." Furthermore, we propose that the term "lower member of the Abiquiu Formation" be replaced with an existing unit name, the Ritito Conglomerate of Barker (1958), and that the name Abiquiu Formation be restricted to the volcaniclastic succession. The lower part of the Ritito Conglomerate in Arroyo del Cobre on the Abiquiu quadrangle is 47 m (155 ft) thick and is composed of arkosic conglomeratic beds interbedded with arkosic sands and siltstones. Clasts include, in descending order of abundance, Proterozoic quartzite, granite, metavolcanic rocks, quartz, schist, and gneiss and a trace of Mesozoic sandstone and Paleozoic chert. Clasts are predominantly of pebble and cobble size but range from granule to boulder size. Paleocurrent data collected in the Arroyo del Cobre area indicate that the Ritito Conglomerate was deposited by a south-flowing river system during the Oligocene, eroding Laramide highlands such as the Tusas Mountains to the northeast, which contain predominantly Proterozoic rocks. This depositional setting has also been suggested by previous workers. The middle member or Pedernal chert member is present both at the top of the Ritito Conglomerate and as lenses within the lower part of the Abiquiu Formation. This post-depositional diagenetic chert remains an informal unit called the Pedernal chert.

  10. Production flush of Agaricus blazei on Brazilian casing layers

    Directory of Open Access Journals (Sweden)

    Nelson Barros Colauto

    2011-06-01

    Full Text Available This study aimed to verify the biological efficiency and production flushes of Agaricus blazei strains on different casing layers during 90 cultivation days. Four casing layers were used: mixture of subsoil and charcoal (VCS, lime schist (LSC, São Paulo peat (SPP and Santa Catarina peat (SCP; and two genetically distant A. blazei strains. The fungus was grown in composted substratum and, after total colonization, a pasteurized casing layer was added over the substratum, and fructification was induced. Mushrooms were picked up daily when the basidiocarp veil was stretched, but before the lamella were exposed. The biological efficiency (BE was determined by the fresh basidiocarp mass divided by the substratum dry mass, expressed in percentage. The production flushes were also determined over time production. The BE and production flushes during 90 days were affected by the strains as well as by the casing layers. The ABL26 and LSC produced the best BE of 60.4%. Although VCS is the most used casing layer in Brazil, it is inferior to other casing layers, for all strains, throughout cultivation time. The strain, not the casing layer, is responsible for eventual variations of the average mushroom mass. In average, circa 50% of the mushroom production occurs around the first month, 30% in the second month, and 20% in third month. The casing layer water management depends on the casing layer type and the strain. Production flush responds better to water reposition, mainly with ABL26, and better porosity to LSC and SCP casing layers.

  11. Igneous activity, metamorphism, and deformation in the Mount Rogers area of SW Virginia and NW North Carolina: A geologic record of Precambrian tectonic evolution of the southern Blue Ridge Province

    Science.gov (United States)

    Tollo, Richard P.; Aleinikoff, John N.; Mundil, Roland; Southworth, C. Scott; Cosca, Michael A.; Rankin, Douglas W.; Rubin, Allison E.; Kentner, Adrienne; Parendo, Christopher A.; Ray, Molly S.

    2012-01-01

    Mesoproterozoic basement in the vicinity of Mount Rogers is characterized by considerable lithologic variability, including major map units composed of gneiss, amphibolite, migmatite, meta-quartz monzodiorite and various types of granitoid. SHRIMP U-Pb geochronology and field mapping indicate that basement units define four types of occurrences, including (1) xenoliths of ca. 1.33 to ≥1.18 Ga age, (2) an early magmatic suite including meta-granitoids of ca. 1185–1140 Ma age that enclose or locally intrude the xenoliths, (3) metasedimentary rocks represented by layered granofels and biotite schist whose protoliths were likely deposited on the older meta-granitoids, and (4) a late magmatic suite composed of younger, ca. 1075–1030 Ma intrusive rocks of variable chemical composition that intruded the older rocks. The magmatic protolith of granofels constituting part of a layered, map-scale xenolith crystallized at ca. 1327 Ma, indicating that the lithology represents the oldest, intact crust presently recognized in the southern Appalachians. SHRIMP U-Pb data indicate that periods of regional Mesoproterozoic metamorphism occurred at 1170–1140 and 1070–1020 Ma. The near synchroneity in timing of regional metamorphism and magmatism suggests that magmas were emplaced into crust that was likely at near-solidus temperatures and that melts might have contributed to the regional heat budget. Much of the area is cut by numerous, generally east- to northeast-striking Paleozoic fault zones characterized by variable degrees of ductile deformation and recrystallization. These high-strain fault zones dismember the terrane, resulting in juxtaposition of units and transformation of basement lithologies to quartz- and mica-rich tectonites with protomylonitic and mylonitic textures. Mineral assemblages developed within such zones indicate that deformation and recrystallization likely occurred at greenschist-facies conditions at ca. 340 Ma.

  12. The Belgian coal tips: geomorphic and pedogenetic research with community service and educational aspects

    Science.gov (United States)

    Nyssen, Jan; Vermeersch, Dominiek; Diependaele, Stijn; van Ranst, Eric; Derycke, Anja; Corexenos, Pavlos; Palmers, Jo; Poesen, Jean

    2010-05-01

    Coal tips are composed of various materials, essentially sterile rock but also waste such as mine wood, scrap metal as well as scoria from surface facilities. Rocks composing Belgian coal tips belong to the Westfalian and Namurian (approx. 320 Ma) and include psammites, schists and coal residues. Currently, these coal tips are increasingly regarded as socio-cultural heritage. Worldwide, several studies have focused on the factors controlling the magnitude of geomorphic processes, such as nature of slope material, vegetation type and cover, the role of self-ignition and combustion, time and slope gradient. In the international literature, research gaps concern particular processes, such as causes and consequences of the widespread tree toppling and root throw, rock fragment movement at the surface, or gully control by check dams. Especially spatially distributed erosion rates by the various processes active on coal tips, neither sediment budgets seem ever to have been established. The same holds for regional (subcontinental) variability in slope processes on coal tips. The many Belgian coal tips that have not been levelled provide a unique opportunity for geomorphological and pedogenetical studies, which have so far demonstrated the existence of: - correlations between the intensity of observed geomorphic processes and a broad range of bio-physical explanatory factors; - strong and reciprocal influences between the vegetation of coal tips and the morphology of the colonised slopes; - absence of strong relations between gully activity and slope angle, resulting from the narrow range of slope gradients on coal tips; - possibilities to locate landslide risk zones through combined use of Digital Elevation Models and thermographic imagery; - presence of neoformed minerals on burning/burned coal tips, which impact the soil forming processes as well as soil quality.

  13. Physicochemical conditions of skarn formation in contact of the Alvand batholith with the meta-calcareous rocks, Hamedan, western Iran

    Directory of Open Access Journals (Sweden)

    Adel Saki

    2012-04-01

    Full Text Available The Cheshin meta-calcareous rocks (Permo Triassic in southeast Hamedan outcrop in association with a variety of pelitic schists and hornfels rocks. The intrusion of the Alvand Batholith (Jurassic age into pelitic and calcareous host rocks has produced metamorphic rocks in the Hamedan area (Cheshin village. On the basis of the dominance of calcite/dolomite, silicate and ore minerals, the calcareous rocks can be divided into two groups: a marbles and calc-silicates; b skarn rocks. The ore bodies occur in a contact zone between sillimanite-hornfels and calc-silicate rocks and formed the skarn rocks. Based on mineralogy, skarn rocks in the studied area consist mainly of diopside, garnet, tremolite, vesuvianite, epidote and ore minerals (magnetite and hematite. The skarnification processes occurred at two stages: (1 prograde metamorphism; and (2 retrograde metamorphism. The first stage involved prograde metasomatism and anhydrous minerals such as garnet and pyroxene formed. Second stage of retrograde skarn development is also recognized. In addition to Fe, Si and Mg, substantial amounts of Fe, along with volatile components were added to the skarn system. Consequently, considerable amounts of hydrous minerals, oxides and carbonates replaced the anhydrous minerals in the host rocks and hydrous minerals such as epidote+chlorite+amphibole formed. Using multiple equilibria by THERMOCALC® program, temperature (~630 ºC, pressure (~4 kbar, and fluid composition (XCO2 as low as 0.17 have been calculated for the formation of the calc-silicate rocks. Skarn mineralogy shows good agreement with these calculations.

  14. 40-years of fires in a touristic area from South of Spain.

    Science.gov (United States)

    Martínez-Murillo, Juan F.; Aranda-Gómez, Francisco; Damián Ruiz-Sinoga, José

    2014-05-01

    Costa del Sol in the Province of Malaga is one of the major touristic region in Spain. Its develop started in the 1960s of the XXth century at the same time as other regions in Mediterranean Europe. Since then, this area has become a holiday touristic centre for different countries and regions from Europe (United Kingdom, Escandinavia, Germany, Netherlands, Russia, etc.). Likewise, Costa del Sol has been characterised by a constant grow of the residence tourism rendering in an extreme increment of urban areas, especially in those municipalities located in the coast. This expansión of urban áreas was carried out against rural and natural vegetated areas. The region is characterised by very montanious topography, predominant impermeable rocks (shales, schists and peridotites) and abundant rainfalls from October to May, especially, in the western area (where a climatic gradient is observed from humid to dry conditions). All of these features, joined a very spread and intense occupation by urban, infrastructures and touristic land uses, renders in a very high vulnerability to fires and their consequences. As fire removes vegetation cover and accelerate water erosion, local relief and climatic conditions induce to extreme high risk of soil loss and floodings. During the last 40 years, in the study area, the number of fires increased as weell as the affected area, following the similar trend for the rest of Spain and other Mediterranean countries. This situation increases the exposition to fire risk for more than one-million of people, which become at least two-millions during the summer months when fire conditions are expected.

  15. Transdomes: Emplacement of Migmatite Domes in Oblique Tectonic Settings

    Science.gov (United States)

    Teyssier, C. P.; Rey, P. F.; Whitney, D. L.; Mondy, L. S.; Roger, F.

    2014-12-01

    Many migmatite domes are emplaced within wrench corridors in which a combination of strike-slip and extensional detachment zones (pull-apart, extensional relay, or transfer zones) focus deep-crust exhumation. The Montagne Noire dome (France, Variscan Massif Central) exemplifies wrench-related dome formation and displays the following structural, metamorphic, and geochronologic characteristics of a 'transdome': the dome is elongate in the direction of extension; foliation outlines a double dome separated by a high-strain zone; lineation is shallowly plunging with a fairly uniform trend that parallels the strike of the high-strain zone; subdomes contain recumbent structures overprinted by upright folds that affected upward by flat shear zones associated with detachment tectonics; domes display a large syn-deformation metamorphic gradient from core (upper amphibolite facies migmatite) to margin (down to greenschist facies mylonite); some rocks in the dome core experienced isothermal decompression revealed by disequilibrium reaction textures, particularly in mafic rocks (including eclogite); and results of U-Pb geochrononology indicate a narrow range of metamorphic crystallization from core to mantling schist spanning ~10 Myr. 3D numerical modeling of transdomes show that the dome solicits a larger source region of partially molten lower crust compared to 2D models; this flowing crust creates a double-dome architecture as in 2D models but there are differences in the predicted thermal history and flow paths. In a transtension setting, flow lines converge at depth (radial-centripetal flow) toward the zone of extension and diverge at shallow levels in a more uniform direction that is imposed by upper crust motion and deformation. This evolution produces a characteristic pattern of strain history, progressive fabric overprint, and P-T paths that are comparable to observed dome rocks.

  16. Zircon dating and mineralogy of the Mokong Pan-African magmatic epidote-bearing granite (North Cameroon)

    Science.gov (United States)

    Tchameni, R.; Sun, F.; Dawaï, D.; Danra, G.; Tékoum, L.; Nomo Negue, E.; Vanderhaeghe, O.; Nzolang, C.; Dagwaï, Nguihdama

    2016-09-01

    We present the mineralogy and age of the magmatic epidote-bearing granite composing most of the Mokong pluton, in the Central Africa orogenic belt (North Cameroon). This pluton intrudes Neoproterozoic (~830 to 700 Ma) low- to high-grade schists and gneisses (Poli-Maroua group), and is crosscut or interleaved with bodies of biotite granite of various sizes. The pluton is weakly deformed in its interior, but solid-state deformation increases toward its margins marked by narrow mylonitic bands trending NNE-SSW. The magmatic epidote granitic rocks are classified as quartz monzodiorite, granodiorite, monzogranite, and syenogranite. They are medium- to coarse-grained and composed of K-feldspar + plagioclase + biotite + amphibole + epidote + magnetite + titanite + zircon + apatite. In these granites, the pistacite component [atomic Fe+3/(Fe3+ + Al)] in epidote ranges from 16 to 29 %. High oxygen fugacity (log ƒO2 - 14 to -11) and the preservation of epidote suggest that the magma was oxidized. Al-in hornblende barometry and hornblende-plagioclase thermometry indicate hornblende crystallization between 0.53 and 0.78 GPa at a temperature ranging from 633 to 779 °C. Zircon saturation thermometry gives temperature estimates ranging from 504 to 916 °C, the latter being obtained on samples containing inherited zircons. U/Pb geochronology by LA-ICP-MS on zircon grains characterized by magmatic zoning yields a concordia age of 668 ± 11 Ma (2 σ). The Mokong granite is the only known occurrence magmatic epidote in Cameroon, and is an important milestone for the comparison of the Central Africa orogenic belt with the Brasiliano Fold Belt, where such granites are much more abundant.

  17. Advanced Seismic Imaging Techniques Characterize the Alpine Fault at Whataroa (New Zealand)

    Science.gov (United States)

    Lay, V.; Buske, S.; Lukács, A.; Gorman, A. R.; Bannister, S. C.

    2015-12-01

    The plate-bounding Alpine Fault in New Zealand is a large transpressive continental fault zone that is late in its earthquake cycle. The Deep Fault Drilling Project (DFDP) aims to deliver insight into the geological structure of this fault zone and its evolution by drilling and sampling the Alpine Fault at depth. We have acquired and processed reflection seismic data to image the subsurface around the drill site. The resulting velocity models and seismic images of the upper 5 km show complex subsurface structures around the Alpine Fault zone. The most prominent feature is a strong reflector at depths of 1.2-2.2 km with a dip of ~40° to the southeast below the DFDP-2 borehole, which we assume to be the main trace of the Alpine Fault. The reflector exhibits varying lateral reflectivity along its extent. Additionally, subparallel reflectors are imaged that we interpret as secondary branches of the main fault zone. The derived P-wave velocity models reveal a 400-600 m thick sedimentary layer with velocities of ~2.3 km/s above a schist basement with velocities of 4.5-5.5 km/s. A pronounced low-velocity layer with velocities of approximately 3.5 km/s can be observed within the basement at 0.8-2 km depth. Small-scale low-velocity anomalies appear at the top of the basement and can be correlated to the fault zone. The results provide a reliable basis for a seismic site characterization at the DFDP-2 drill site that can be used for further structural and geological investigations of the architecture of the Alpine Fault in this area.

  18. Assisted bioremediation tests on three natural soils contaminated with benzene

    Directory of Open Access Journals (Sweden)

    Maria Manuela Carvalho

    2015-07-01

    Full Text Available Bioremediation is an attractive and useful method of remediation of soils contaminated with petroleum hydrocarbons because it is simple to maintain, applicable in large areas, is economic and enables an effective destruction of the contaminant. Usually, the autochthone microorganisms have no ability to degrade these compounds, and otherwise, the contaminated sites have inappropriate environmental conditions for microorganism’s development. These problems can be overcome by assisted bioremediation (bioaugmentation and/or biostimulation. In this study the assisted bioremediation capacity on the rehabilitation of three natural sub-soils (granite, limestone and schist contaminated with benzene was evaluated. Two different types of assisted bioremediation were used: without and with ventilation (bioventing. The bioaugmentation was held by inoculating the soil with a consortium of microorganisms collected from the protection area of crude oil storage tanks in a refinery. In unventilated trials, biostimulation was accomplished by the addition of a nutrient mineral media, while in bioventing oxygen was also added. The tests were carried out at controlled temperature of 25 ºC in stainless steel columns where the moist soil contaminated with benzene (200 mg per kg of soil occupied about 40% of the column’s volume. The processes were daily monitored in discontinued mode. Benzene concentration in the gas phase was quantified by gas chromatography (GC-FID, oxygen and carbon dioxide concentrations were monitored by respirometry. The results revealed that the three contaminated soils were remediated using both technologies, nevertheless, the bioventing showed faster rates. With this work it was proved that respirometric analysis is an appropriate instrument for monitoring the biological activity.

  19. Late Neogene deformation of the Chocolate Mountains Anticlinorium: Implications for deposition of the Bouse Formation and early evolution of the Lower Colorado River

    Science.gov (United States)

    Beard, Sue; Haxel, Gordon B.; Dorsey, Rebecca J.; McDougall, Kristin A.; Jacobsen, Carl E.

    2016-01-01

    Deformation related to late Neogene dextral shear can explain a shift from an estuarine to lacustrine depositional environment in the southern Bouse Formation north of Yuma, Arizona. We infer that late Neogene deformation in the Chocolate Mountain Anticlinorium (CMA) created a barrier that blocked an estuary inlet, and that pre-existing and possibly active structures subsequently controlled the local course of the lower Colorado River. Structural patterns summarized below suggest that the CMA absorbed transpressional strain caused by left-stepping segments of dextral faults of the San Andreas fault system and/or the eastern California shear zone and Gulf of California shear zone. For this hypothesis to be correct, about 200-250 m of post-6 Ma, pre- ~5.3 Ma uplift along the CMA crest would be required to cut off a marine inlet. The 220-km-long CMA, cored by the early Paleogene Orocopia Schist subduction complex, extends from the Orocopia Mountains (Calif.) southeastward through the Chocolate Mountains (parallel to the southern San Andreas fault). Where Highway 78 crosses the Chocolate Mountains (Fig. 1), the CMA turns eastward through the Black Mountain-Picacho area (Calif.) and Trigo Mountains (Ariz.) into southwest Arizona. It separates southernmost Bouse Formation outcrops of the Blythe basin from subsurface Bouse outcrops to the south in the Yuma area. South of Blythe basin the CMA is transected by the lower Colorado River along a circuitous path. Here we focus on the geology of an area between the central Chocolate Mountains and the Yuma Proving Grounds in Arizona. Specific landmarks include the southeast Chocolate Mountains, Midway Mountains, Peter Kane Mountain, Black Mountain, Picacho Peak, and Gavilan Hills. For simplicity, we refer to this as the eastern Chocolate Mountains.

  20. Drilling into an active mofette: pilot-hole study of the impact of CO2-rich mantle-derived fluids on the geo–bio interaction in the western Eger Rift (Czech Republic

    Directory of Open Access Journals (Sweden)

    R. Bussert

    2017-11-01

    Full Text Available Microbial life in the continental deep biosphere is closely linked to geodynamic processes, yet this interaction is poorly studied. The Cheb Basin in the western Eger Rift (Czech Republic is an ideal place for such a study because it displays almost permanent seismic activity along active faults with earthquake swarms up to ML 4.5 and intense degassing of mantle-derived CO2 in conduits that show up at the surface in form of mofettes. We hypothesize that microbial life is significantly accelerated in active fault zones and in CO2 conduits, due to increased fluid and substrate flow. To test this hypothesis, pilot hole HJB-1 was drilled in spring 2016 at the major mofette of the Hartoušov mofette field, after extensive pre-drill surveys to optimize the well location. After drilling through a thin caprock-like structure at 78.5 m, a CO2 blowout occurred indicating a CO2 reservoir in the underlying sandy clay. A pumping test revealed the presence of mineral water dominated by Na+, Ca2+, HCO3−, SO42− (Na-Ca-HCO3-SO4 type having a temperature of 18.6 °C and a conductivity of 6760 µS cm−1. The high content of sulfate (1470 mg L−1 is typical of Carlsbad Spa mineral waters. The hole penetrated about 90 m of Cenozoic sediments and reached a final depth of 108.50 m in Palaeozoic schists. Core recovery was about 85 %. The cored sediments are mudstones with minor carbonates, sandstones and lignite coals that were deposited in a lacustrine environment. Deformation structures and alteration features are abundant in the core. Ongoing studies will show if they result from the flow of CO2-rich fluids or not.

  1. Drilling into an active mofette: pilot-hole study of the impact of CO2-rich mantle-derived fluids on the geo-bio interaction in the western Eger Rift (Czech Republic)

    Science.gov (United States)

    Bussert, Robert; Kämpf, Horst; Flechsig, Christina; Hesse, Katja; Nickschick, Tobias; Liu, Qi; Umlauft, Josefine; Vylita, Tomáš; Wagner, Dirk; Wonik, Thomas; Estrella Flores, Hortencia; Alawi, Mashal

    2017-11-01

    Microbial life in the continental deep biosphere is closely linked to geodynamic processes, yet this interaction is poorly studied. The Cheb Basin in the western Eger Rift (Czech Republic) is an ideal place for such a study because it displays almost permanent seismic activity along active faults with earthquake swarms up to ML 4.5 and intense degassing of mantle-derived CO2 in conduits that show up at the surface in form of mofettes. We hypothesize that microbial life is significantly accelerated in active fault zones and in CO2 conduits, due to increased fluid and substrate flow. To test this hypothesis, pilot hole HJB-1 was drilled in spring 2016 at the major mofette of the Hartoušov mofette field, after extensive pre-drill surveys to optimize the well location. After drilling through a thin caprock-like structure at 78.5 m, a CO2 blowout occurred indicating a CO2 reservoir in the underlying sandy clay. A pumping test revealed the presence of mineral water dominated by Na+, Ca2+, HCO3-, SO42- (Na-Ca-HCO3-SO4 type) having a temperature of 18.6 °C and a conductivity of 6760 µS cm-1. The high content of sulfate (1470 mg L-1) is typical of Carlsbad Spa mineral waters. The hole penetrated about 90 m of Cenozoic sediments and reached a final depth of 108.50 m in Palaeozoic schists. Core recovery was about 85 %. The cored sediments are mudstones with minor carbonates, sandstones and lignite coals that were deposited in a lacustrine environment. Deformation structures and alteration features are abundant in the core. Ongoing studies will show if they result from the flow of CO2-rich fluids or not.

  2. P-T-time evolution of the Mejillones Metamorphic Complex: Insights into Late Triassic to Early Jurassic orogenic processes in northern Chile

    Science.gov (United States)

    Calderón, M.; Massonne, H.-J.; Hervé, F.; Theye, T.

    2017-10-01

    Better constrained pressure-temperature (P-T) histories of metamorphic complexes along the Andean continental margin are important for understanding the late Paleozoic and Mesozoic tectonic evolution of the southwestern margin of Gondwana. The Mejillones Metamorphic Complex of the northern Chilean Coastal Cordillera is composed of two tectonic units, the Morro Mejillones and Morro Jorgiño blocks. These units are bound by the NW-trending Caleta Herradura fault and show distinctly metamorphic ages and thermal evolution. The Morro Mejillones block was metamorphosed at low pressure conditions (andalusite-sillimanite series) during the intrusion of tonalitic plutons at ca. 208 Ma, as indicated by available geochronological data. In contrast, the Morro Jorgiño block comprises amphibolite-facies schists, gneisses and foliated metabasites with characteristic garnet-bearing mineral assemblages. For garnet-bearing pelitic gneisses, a clockwise P-T path has been determined from pseudosection modelling in the MnNCKFMASHTO system. The proposed evolution is characterized by a pressure increase from 7.5 to 8.5 kbar at increasing temperatures from 585 to 615 °C. Decompression to 6 kbar followed, accompanied by heating to 630-640 °C. Electron microprobe Th-U-Pb in-situ dating of high-Y monazite grains yielded a weighted average age of ca. 190 ± 4 Ma, which is interpreted as the age of tectonic burial of metamorphic rocks of the Morro Jorgiño tectonic unit. We infer that the block was buried to 25 km depth through contractional deformation of the continental edge in a subduction zone, likely linked to the docking of the Mejillonia terrane. Rapid exhumation followed and the ensuing juxtaposition of both tectonic units was controlled by Jurassic transtensional activity of the Atacama Fault System.

  3. Burkholderia susongensis sp. nov., a mineral-weathering bacterium isolated from weathered rock surface.

    Science.gov (United States)

    Gu, Jia-Yu; Zang, Sheng-Gang; Sheng, Xia-Fang; He, Lin-Yan; Huang, Zhi; Wang, Qi

    2015-03-01

    A novel type of mineral-weathering bacterium was isolated from the weathered surface of rock (mica schist) collected from Susong (Anhui, China). Cells of strain L226(T) were Gram-stain-negative. The strain grew optimally at 30 °C, with 1 % (w/v) NaCl and at pH 7.0 in trypticase soy broth. On the basis of 16S rRNA gene phylogeny, strain L226(T) was shown to belong to the genus Burkholderia and the closest phylogenetic relatives were Burkholderia sprentiae WSM5005(T) (98.3 %), Burkholderia acidipaludis NBRC 101816(T) (98.2 %), Burkholderia tuberum STM678(T) (97.2 %) and Burkholderia diazotrophica JPY461(T) (97.1 %). The DNA G+C content was 63.5 mol% and the respiratory quinone was Q-8. The major fatty acids were C16 : 0, C17 : 0 cyclo and C19 : 0 cyclo ω8c. The polar lipid profile of strain L226(T) consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, unknown lipids and unidentified aminophospholipids. Based on the low level of DNA-DNA relatedness (ranging from 25.8 % to 34.4 %) to the tested type strains of species of the genus Burkholderia and unique phenotypic characteristics, it is suggested that strain L226(T) represents a novel species of the genus Burkholderia, for which the name Burkholderia susongensis sp. nov., is proposed. The type strain is L226(T) ( = CCTCC AB2014142(T) = JCM 30231(T)). © 2015 IUMS.

  4. Behaviour of radionuclides during microbially-induced mining of nickel at Talvivaara, Eastern Finland.

    Science.gov (United States)

    Tuovinen, Hanna; Pohjolainen, Esa; Lempinen, Janne; Vesterbacka, Daniela; Read, David; Solatie, Dina; Lehto, Jukka

    2016-01-01

    The Talvivaara mine in Eastern Finland utilizes microbe-induced heap leaching to recover nickel and other valuable metals (Zn, Cu, Co) from a black schist ore. In addition to the target metals, the ore contains uranium at a concentration of 17 mg/kg, incorporated as uraninite (UO2). Uranium oxidizes from the U(IV) to U(VI) state during leaching and dissolves as the uranyl ion (UO2(2+)) in the acidic pregnant leach solution. Mobilisation of uranium has caused sufficient concern that plans have been developed for uranium recovery. The aim of this study is to generate new data leading to a better understanding of the fate of its radiotoxic daughter nuclides, primarily (226)Ra, (210)Pb and (210)Po, in the mining process. It is shown that uranium daughters mostly remain in the heaps during the leaching process and are associated with secondary minerals, including jarosite, goethite and gypsum. Thorium and progeny ((232)Th plus (228)Th, (228)Ra) are also mainly retained. High sulphate concentrations in the acidic solutions limit the solubility of radium by incorporation in the crystal lattices of precipitated secondary sulphates. Electron probe microanalysis shows that goethite in the heaps is uraniferous, resulting from the adsorption of U(VI). After recovery of target metals, the pregnant leach solution is neutralized to further remove metal contaminants and the resulting slurries stored in a bunded tailings pond. The activity concentrations of thorium, radium, lead and polonium isotopes are generally low in the pond owing to prior retention by secondary minerals in the heaps. However, (238)U activity concentrations range up to 3375 Bq/kg, which exceeds the permitted value (1000 Bq/kg) for natural radionuclides of the (238)U series. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Geology of the South Yolla Bolly area, northern California, and its techtonic implications

    Energy Technology Data Exchange (ETDEWEB)

    Worrall, D.M.

    1979-01-01

    The South Yolla Bolly area contains the mutual boundary of three tectonic provinces: the Franciscan trench-wedge complex, the Great Valley forearc basin sequence, and the Klamath Mountains igneous and metamorphic complex. Within the Franciscan complex, several distinct units are distinguished by rock type, textural grade, metamorphic grade, style of deformation, and fabric. Grain distortion, recrystallization, metamorphic grade, and intensity of folding increase eastwardly in increments across faults. Hence, the most highly metamorphosed unit, the South Fork Mountain Schist, is also the easternmost and structurally the highest. Lithologic and structural data collected in this area, as well as regional age relationships, indicate that these faults originated as underthrust faults which in at least two instances were localized at or near the sediment/ocean crust contact. Later, while subduction continued to the west in the continually accreting trench, the lithic slabs bounded by these faults were partly extruded out of the upper part of the trench wedge. Subsequent to their upward emplacement, these metasedimentary rocks with their boundary faults were bent in such a fashion that today the structural grain changes from north-south where these Franciscan rocks are juxtaposed against the Great Valley sequence, to west-northwest where they are faulted against rocks of the Klamath Mountains. This bending occurred as the Klamath Mountains moved westward relative to the trench wedge in Late Cretaceous time, an event which is recorded in the South Yolla Bolly and adjacent areas by several northwest trending left lateral strike-slip faults. These faults cut only superjacent Klamath and Great Valley rocks, and do not transect the Franciscan trench wedge, which was largely buttressed against the advancing Klamath mass. (JMT)

  6. Electrical Conductance Map for the Kachchh Rift Basin: Constraint on Tectonic Evolution and Seismotectonic Implications

    Science.gov (United States)

    Subba Rao, P. B. V.; Arora, B. R.; Singh, A. K.

    2014-09-01

    Geomagnetic field variations recorded by an array of magnetometers spread across the Kachchh Rift basin are reduced to a set of induction arrows as a diagnostic of lateral electrical conductivity variations. A non-uniform thin-sheet electrical conductance model is developed to account for the salient induction patterns. It indicates that the imaged conductivity anomalies can be related to the sediment-filled structural lows in between the fault bounded uplifts. It is suggested that sagging structural lows preserved the marine sediments deposited during the Mesozoic sea transgression and later developed into first order embayment basins for the deposition of sediments in association with Late Eocene transgression. Depth integrated electrical conductance helped in mapping two depo-centres: along the ENE-WSW trending Banni half-Graben bounded by the Kachchh Main fault on the south and, second, along the Vinjan depression formed in response to the subsidence between the Vigodi fault and westward extension of the Katrol Hill fault together with the westward bending of the Median High. Presence of metamorphosed graphite schist clasts in shale dominated Mesozoic sequence and/or thin films of carbon resulting from the thermal influence of Deccan activity on Carbonate-rich formations can account for the high electrical conductivity anomalies seen in the depo-centres of thick Mesozoic and Tertiary sediments. Additionally two high conductivity zones are imaged encompassing a block defined by the 2001 Bhuj earthquake and its aftershocks. In agreement with gravity, magnetic and seismic velocity signatures, aqueous fluids released by recrystallizing magmatic bodies intruded in association with Deccan trap activity account for mapped high conductivity zones. High fluid pressure in such a fractured domain, surrounding the intruded magmatic plugs, perturb the regional stress concentrations to produce frequent and low magnitude aftershocks in the shallow section of the epicentral

  7. Porites corals as recorders of mining and environmental impacts: Misima Island, Papua New Guinea

    Science.gov (United States)

    Fallon, Stewart J.; White , Jamie C.; McCulloch, Malcolm T.

    2002-01-01

    In 1989 open-cut gold mining commenced on Misima Island in Papua New Guinea (PNG). Open-cut mining by its nature causes a significant increase in sedimentation via the exposure of soils to the erosive forces of rain and runoff. This increased sedimentation affected the nearby fringing coral reef to varying degrees, ranging from coral mortality (smothering) to relatively minor short-term impacts. The sediment associated with the mining operation consists of weathered quartz feldspar, greenstone, and schist. These rocks have distinct chemical characteristics (rare earth element patterns and high abundances of manganese, zinc, and lead) and are entering the near-shore environment in considerably higher than normal concentrations. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), we analyzed eight colonies (two from high sedimentation, two transitional, two minor, and two unaffected control sites) for Y, La, Ce, Mn, Zn, and Pb. All sites show low steady background levels prior to the commencement of mining in 1988. Subsequently, all sites apart from the control show dramatic increases of Y, La, and Ce associated with the increased sedimentation as well as rapid decreases following the cessation of mining. The elements Zn and Pb exhibit a different behavior, increasing in concentration after 1989 when ore processing began and one year after initial mining operations. Elevated levels of Zn and Pb in corals has continued well after the cessation of mining, indicating ongoing transport into the reef of these metals via sulfate-rich waters. Rare earth element (REE) abundance patterns measured in two corals show significant differences compared to Coral Sea seawater. The corals display enrichments in the light and middle REEs while the heavy REEs are depleted relative to the seawater pattern. This suggests that the nearshore seawater REE pattern is dominated by island sedimentation. Trace element abundances of Misima Island corals clearly record

  8. The Early Mesozoic volcanic arc of western North America in northeastern Mexico

    Science.gov (United States)

    Barboza-Gudiño, José Rafael; Orozco-Esquivel, María Teresa; Gómez-Anguiano, Martín; Zavala-Monsiváis, Aurora

    2008-02-01

    Volcanic successions underlying clastic and carbonate marine rocks of the Oxfordian-Kimmeridgian Zuloaga Group in northeastern Mexico have been attributed to magmatic arcs of Permo-Triassic and Early Jurassic ages. This work provides stratigraphic, petrographic geochronological, and geochemical data to characterize pre-Oxfordian volcanic rocks outcropping in seven localities in northeastern Mexico. Field observations show that the volcanic units overlie Paleozoic metamorphic rocks (Granjeno schist) or Triassic marine strata (Zacatecas Formation) and intrude Triassic redbeds or are partly interbedded with Lower Jurassic redbeds (Huizachal Group). The volcanic rocks include rhyolitic and rhyodacitic domes and dikes, basaltic to andesitic lava flows and breccias, and andesitic to rhyolitic pyroclastic rocks, including breccias, lapilli, and ashflow tuffs that range from welded to unwelded. Lower-Middle Jurassic ages (U/Pb in zircon) have been reported from only two studied localities (Huizachal Valley, Sierra de Catorce), and other reported ages (Ar/Ar and K-Ar in whole-rock or feldspar) are often reset. This work reports a new U/Pb age in zircon that confirms a Lower Jurassic (193 Ma) age for volcanic rocks exposed in the Aramberri area. The major and trace element contents of samples from the seven localities are typical of calc-alkaline, subduction-related rocks. The new geochronological and geochemical data, coupled with the lithological features and stratigraphic positions, indicate volcanic rocks are part of a continental arc, similar to that represented by the Lower-Middle Jurassic Nazas Formation of Durango and northern Zacatecas. On that basis, the studied volcanic sequences are assigned to the Early Jurassic volcanic arc of western North America.

  9. Actual geomorphological processes on hillslope viticulture from Axarquía in the Montes de Málaga (Spain).

    Science.gov (United States)

    Rodrigo Comino, Jesús; María Senciales González, José; Seeger, Manuel; Damián Ruiz Sinoga, José; Ries, Johannes B.

    2015-04-01

    Hillslope viticulture is one of the agricultural activities affecting the eco-geomorphological system. Specifically, in the vineyards of the Axarquía on the Montes de Málaga (Spain), where the popular Moscatel and Pedro Ximénez grapes are produced, several problems of degradation of the chemical and physical properties of the soils have been reported by several authors, but not real quantifications of sediment losses. Soils have developed mainly on Palaeozoic schists and slates with different degrees of metamorphism, but also include marbles, limestone, quartz and gneiss. On steep slopes (36-76%), surface rock fragment cover (45 to 75%) and occasional generation of rills and gullies characterize the principal geomorphological processes. Degradation processes are due to two causes: i) the concentrated heavy rainfall events during a few hours within no more than 30 days per year; ii) soil tillage of the vine-workers, removing vegetation cover under and around the vines. Anyhow, farmers take measures against soil erosion, such as building rills to canalize the surface flow (called 'sangrías') and small walls of stones ('albarradas') to reduce soil loss. Actual soil degradation as a consequence of intensive agricultural activities starting with Muslim ages (s. VIII-XV). The objective of this work is to show the geomorphological processes during summer, autumn and winter (2014-2015) on experimental plots along a hillslope in the south of Spain (Almáchar, Málaga). Six sediment traps (50 liters) with their respective collectors (60 liters) were installed in three different points along a hillslope exposed to south-west. After each rainfall, all sediments were collected and analyzed to calculate soil losses (g), surface flow (l) and the sediment concentration (g l-1). Furthermore, a meteorological station (rainfall, temperature, wind and air humidity) was installed close to the plot. Final results show elevated soil loss and surface flow rates with different

  10. Geology of Telford and the Coalbrookdale Coalfield: memoir for parts of 1:50000 geological sheets 152 and 153 (England and Wales): 1:25000 sheet SJ60 with parts of 61, 70, 71

    Energy Technology Data Exchange (ETDEWEB)

    Hamblin, R.J.O.; Coppack, B.C. [British Geological Survey, Keyworth (United Kingdom)

    1995-11-01

    The district described in this United Kingdom geological memoir is dominated by Telford new town, and the Coalbrookdale Coalfield, and extends from Sheinton, in the valley of the River Severn in the south-west, to Lilleshall in the north-east. The solid rocks at outcrop include some of the oldest in Britain, including the Uriconian volcanic rocks, the Rushton Schists and the Primrose Hill metamorphic rocks, all of Precambrian age. The youngest solid strata preserved are sandstones and conglomerates of the Sherwood Sandstone Group, formed in near-desert conditions during the Triassic period. A wide range of rocks of Cambrian, Ordovician and Silurian ages adds variety to this fascinating microcosm of British geology, but it is the Carboniferous-age Coal Measures of the Coalbrookdale Coalfield which form the immediate substratum of most of the new town. The rocks are heavily faulted and this adds complexity to the planning both of mineral extraction and of land reclamation. The whole of the district was glaciated during the last ice age and glacial deposits still cover most of its surface, also occupying a series of buried valleys cut by meltwater beneath the retreating icesheet. The memoir concentrates largely on the Coal Measures because of the problems induced by earlier generations of underground and opencast mining. The area was chosen for new town development because of its high proportion of derelict land, a legacy of the industrial revolution which was founded on the mineral wealth of the coalfield. Old mine workings have to be stabilised for development, and coal is still worked opencast. Both the glacial deposits and hard rocks are worked for aggregates, and the Sherwood Sandstone Group and Bridgnorth Sandstone provide a valuable aquifer in the north-west of the district. 155 refs., 52 figs., 4 tabs.

  11. Integrated stratigraphy and geochemistry of the Early Jurassic Posidonienschiefer from the Lower Saxony Basin, NW Germany

    Science.gov (United States)

    Celestino, Ricardo; Ruhl, Micha; Dickson, Alexander J.; Jenkyns, Hugh C.; Idiz, Erdem; Huggett, Jennifer; Mattioli, Emanuela; Minisini, Daniel; Weijers, Johan; Tegelaar, Erik; Hesselbo, Stephen P.

    2017-04-01

    The Posidonienschiefer (Early Jurassic, 183 Ma) is the expression of the Toarcian Oceanic Anoxic Event (T-OAE) in Germany and Northern Switzerland and comparable to its correlative units in the UK (Jet Rock) and France (Schistes Carton) is composed of organic-rich, laminated clayey and calcareous mudstone. The carbon isotope record is marked by the occurrence of an up to 7 ‰ negative excursion, both in bulk carbonate and organic carbon, thought to have been caused by a large release of methane (from gas hydrates, thermal metamorphic processes and/or volcanogenic sources). The sedimentology, biostratigraphy, organic geochemistry, astrochronology, and isotope chemostratigraphy of the Posidonienschiefer have been largely described in the literature, but most of the studies have focused on the regions of Southern Germany and Northern Switzerland with less information available from Northern Germany due to a lack of outcropping sections. Here we complement the existing datasets from NW Europe with an integrated study performed on cores from the Lower Saxony Basin, Northern Germany, an area that is still poorly correlated with the better known southern German localities. In particular, we present new results from high-resolution carbon-isotope stratigraphy, biostratigraphy and hand-held XRF analysis combined with quantitative mineralogy and organic geochemistry. Further advances in understanding are likely to come from taking a broader palaeogeographic overview of the development of the T-OAE through the whole of the Toarcian Stage, including consideration of sea-level and palaeoclimatic cycles that both pre-date and post-date the core negative carbon-isotope excursion. The new observations from Northern Germany indicate substantial differences in the expression of the T-OAE (duration of maximum organic carbon enrichment/development of hiatuses) compared to other locations from the Laurasian Seaway of NW Europe, contributing to a detailed understanding of the

  12. Rapid crustal exhumation and mantle-melt extraction: Where has the crust gone?

    Science.gov (United States)

    Alvarez-Valero, A. M.; Jagoutz, O.; Manthei, C.

    2012-04-01

    The emplacement of the Beni Bousera and Ronda ultramafic massifs of the Betico-Rifean belt (N Morocco-S Spain) has been discussed for several decades. These massifs are among the largest exposures of mantle rocks on Earth's surface, which obviously confers a special interest for mantle research in Earth Sciences. We present an integrated study of mantle and the surrounding crustal material of Beni Bousera in order to understand the interplay between melt percolation and emplacement of the ultramafic rocks and their relationships to the surrounding crust. Here we focus specifically on detailed petrological studies coupled with phase diagram modeling to elucidate the tectono-metamorphic history of the surrounding granulites. We then compare and relate these results to our understanding of the evolution of the Beni Bousera mantle rocks. The orogenic lherzolite of the ultramafic massif is surrounded by mostly metapelitic high-grade granulites (with local mylonitic layers) that are rimmed in turn by a successive sequence of lower metamorphic grade, from gneisses (with minor migmatites) to schists. The northern part of the massif offers exceptional exposures of a continuous lithospheric section from the ultramafics, via the Moho to the whole granulite packet by showing within the latter the preservation of two pressure events at fairly constant HT of c. 750 °C. A prograde higher-pressure episode (> 12 kbar) is characterized by equilibrium micro-domains with Grt+Bt+Ky+Rt followed by a lower-pressure (c. 5kbar) symplectic assemblage of Crd+Spl. This reveals a dramatic decompression event registered within less than 2 kms of crustal thickness. These results together with structures, numerical modelling and geochronology will extend the knowledge of the mechanisms of mantle emplacement in particular and global tectonics in general.

  13. Geotechnical Study of the OAN/SPM

    Science.gov (United States)

    Sánchez, B.; Castellanos, V.; Castilla, J. E.; Grijalva, J.; Díaz v., G.; Porres, R.; Garay, F.; Zamarripa, V.

    2003-09-01

    The geotechnical characterization of the San Pedro Mártir (SPM), Baja California site was carried out in 2000 by the Gerencia de Estudios de Ingeniería Civil of the Comisión Federal de Electricidad (GEIC/CFE). The principal aim of the series of geological and geotechnical studies was to characterize the subsoil performance at one of the possible construction sites of a new telescope, which may also provide an idea of the characteristics of other locations at the Observatorio Astronómico Nacional in San Pedro Mártir (OAN/SPM) Sierra summit. The full report of the GEIC/CFE geotechnical study of the SPM site includes results from the topographic, geological and geophysical surveys carried out. In the present paper a review of the geotechnical study is presented and some of the important results are summarized. The study shows that the subsoil can be classified in three principal horizons or layers (A, B and C). The A-horizon consists of decompressed rock of depth 1.3 to 3.0 m, which has to be removed for the foundations. Layer B consists of fractured rock with an RQD (rock quality designation) between 65%-80%, a thickness of 10-12 m, and a high load bearing capacity. This implies that the required depth excavations for the foundation footings ranges from 2 to 3 m, where an adequate dynamic modulus of elasticity can be reached. Horizon C from 13 to 22 m, the maximum depth explored, consists of rock (gray schist) of massive nature with some granite intrusions that appears slightly fractured, with an RQD above 90%. For the electric grounding instalation the best place is layer B due to its lower resistivity.

  14. Características petrográficas y geoquímicas de la Tonalita La Ovejería, borde oriental de la Sierra del Aconquija, Tafí del Valle, Tucumán: integración con la Granodiorita El Infiernillo

    Directory of Open Access Journals (Sweden)

    Castro, Antonio

    2011-12-01

    Full Text Available The La Ovejería Tonalite is a N-S elo ngated body that crops out on the eastern side of the Sierra del Aconquija, west of of Tafi del Valle, Tucumán Province, Argentina. It is located just south of thelarger, and probably genetically related, El Infiernillo Granodiorite. The studied pluton has a zoning determined by different grain sizes and mineralogies: the northern outcrops are medium-grained and composed of plagioclase, quartz scarce microcline, and biotite and pistacite (± tourmaline as major accessories; the southern part of the intrusive is fine grained and composed of plagioclase, quartz scarce microcline, and biotite and sphene as accessory minerals. Two meter thick granitic dikes cross-cut the tonalites. The tonalite is calc-alkaline and peraluminous, with an ASI between 1.10 and 1.48. It intrudes metamorphic basement rocks composed of low grade schists that are characterized by an increase in static metamorphism, by syntectonic intrusions and by the intensity of flow folds.The emplacement of the La Ovejería Tonalite probably occurred during the Lower Paleozoic and was structurally controlled by the Tafi Megafracture, like the other intrusive bodies of the area. The El Infiernillo intrusive is composed of a two-mica (± tourmaline equigranular granodiorite main facies and a biotite and epidote bearing (without primary muscovite tonalitic border facies. According to field relations and petrographic, geochemical and structural data, the La Ovejería Tonalite may correspond to the northern border facies of the El Infiernillo intrusive.

  15. Structural geometry and gravity constraints on the Palos Verdes and Cabrillo faults

    Science.gov (United States)

    Cengelcik, Yeliz

    The thesis presents and evaluates five new gravity constrained structural cross-sections about the Palos Verdes and Cabrillo faults of southern California. They both have been active since the Miocene, however the Palos Verdes fault zone is considered to be a greater seismic hazard. Using geologic, gravity and seismic data we present new interpretations about the geometry of the Palos Verdes and Cabrillo faults. In the San Pedro and Los Angeles Harbor region approximately125 new gravity data were collected with a Worden gravimeter and new structural cross-sections were constructed by using data of our gravity surveying. The collected data displays a Simple Bouguer gravity anomaly high near the Cabrillo fault and northwards toward the Palos Verdes fault there is an approximately 30 mGal decrease. The Palos Verdes fault itself is characterized by an inflection in the gravity data and a relatively flat zone immediately to the north. This shelf in the gravity data is important because the highly productive Wilmington Oil Field is located in this area and it is likely a product of the particular geometry in the region. The Palos Verdes fault also forms the edge of the larger Los Angeles Basin. Our basic interpretation is that the Palos Verdes and Cabrillo faults are primarily strike slip faults. However, a horst-like block between the two faults has been uplifted and horizontally shortened. Our main interpretation is that Catalina Schist basement uplift and subsequent basin fill to the north is responsible for the large negative gravity anomalies associated with the Palos Verdes fault.

  16. Upper-crustal structure of the inner Continental Borderland near Long Beach, California

    Science.gov (United States)

    Baher, S.; Fuis, G.; Sliter, R.; Normark, W.R.

    2005-01-01

    A new P-wave velocity/structural model for the inner Continental Borderland (ICB) region was developed for the area near Long Beach, California. It combines controlled-source seismic reflection and refraction data collected during the 1994 Los Angeles Region Seismic Experiment (LARSE), multichannel seismic reflection data collected by the U.S. Geological Survey (1998-2000), and nearshore borehole stratigraphy. Based on lateral velocity contrasts and stratigraphic variation determined from borehole data, we are able to locate major faults such as the Cabrillo, Palos Verdes, THUMS-Huntington Beach, and Newport Inglewood fault zones, along with minor faults such as the slope fault, Avalon knoll, and several other yet unnamed faults. Catalog seismicity (1975-2002) plotted on our preferred velocity/structural model shows recent seismicity is located on 16 out of our 24 faults, providing evidence for continuing concern with respect to the existing seismic-hazard estimates. Forward modeling of P-wave arrival times on the LARSE line 1 resulted in a four-layer model that better resolves the stratigraphy and geologic structures of the ICB and also provides tighter constraints on the upper-crustal velocity structure than previous modeling of the LARSE data. There is a correlation between the structural horizons identified in the reflection data with the velocity interfaces determined from forward modeling of refraction data. The strongest correlation is between the base of velocity layer 1 of the refraction model and the base of the planar sediment beneath the shelf and slope determined by the reflection model. Layers 2 and 3 of the velocity model loosely correlate with the diffractive crust layer, locally interpreted as Catalina Schist.

  17. Volatile (Li, B, F and Cl) mobility during amphibole breakdown in subduction zones

    Science.gov (United States)

    Debret, Baptiste; Koga, Kenneth T.; Cattani, Fanny; Nicollet, Christian; Van den Bleeken, Greg; Schwartz, Stephane

    2016-02-01

    Amphiboles are ubiquitous minerals in the altered oceanic crust. During subduction, their breakdown is governed by continuous reactions up to eclogitic facies conditions. Amphiboles thus contribute to slab-derived fluid throughout prograde metamorphism and continuously record information about volatile exchanges occurring between the slab and the mantle wedge. However, the fate of volatile elements and especially halogens, such as F and Cl, in amphibole during subduction is poorly constrained. We studied metagabbros from three different localities in the Western Alps: the Chenaillet ophiolite, the Queyras Schistes Lustrés and the Monviso meta-ophiolitic complexes. These samples record different metamorphic conditions, from greenschist to eclogite facies, and have interacted with different lithologies (e.g. sedimentary rocks, serpentinites) from their formation at mid-oceanic ridge, up to their devolatilization during subduction. In the oceanic crust, the initial halogen budget is mostly stored in magmatic amphibole (F = 300-7000 ppm; Cl = 20-1200 ppm) or in amphibole corona (F = 100-7000 ppm; Cl = 80-2000 ppm) and titanite (F = 200-1500 ppm; Cl glaucophane at the expense of magmatic and amphibole coronas. This episode is accompanied with a decrease of halogen concentrations in amphiboles (glaucophane (up to 600 ppm) whereas halogen concentrations are unaffected. At eclogite facies conditions, metagabbros display low halogens concentrations (< 20 ppm of F and < 100 ppm of Cl) relative to altered oceanic crust (F = 40-650 ppm; Cl = 40-1400 ppm) suggesting that these elements are continuously released by fluids during the first 30-80 km of subduction whatever the tectonic environment (e.g. slab, plate interface) and the considered fluid/rock interactions.

  18. Gold-quartz vein deposition in an uplifted blueschist terrane, Seward Peninsula, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Read, J.J.

    1985-01-01

    The Big Hurrah mine, located on the Seward Peninsula, Alaska, consists of gold-quartz-carbonate veins which cut sheared carbonaceous metasedimentary and metavolcanic rocks. The rocks underwent regional syn-kinematic blueschist facies metamorphism in the Jurassic. Glaucophane in metabasite and mafic and pelitic schists has been reported from the central Seward Peninsula. Chlorite+/-epidote+/-albite+/-paragonite pseudomorphs after lawsonite and glaucophane have also been reported. The replacement of these blueschist facies minerals probably occurred during uplift and retrogradation of the terrane. The veins at Big Hurrah range from early, concordant metamorphic quartz lenses to discordant tension veins to discontinuous quartz-Au lodes which occur in sheared zones cross-cutting the foliation. The veins are thought to have formed during the late stages of shearing and uplift. Fluid inclusions in the veins are similar to those found in metamorphic rocks in that they are small, most are secondary, and may contain CO/sub 2/ and CH/sub 4/. The is evidence for CO/sub 2/-CH/sub 4//H/sub 2/O liquid immiscibility. Pressure estimates of 0.8 kbar were calculated from coexisting CO/sub 2/-CH/sub 4/ and aqueous inclusions. Pressure corrected homogenization temperatures for quartz deposition are in the range 300-400/sup 0/C. Hence, the veins were deposited at lower pressures and temperatures than those of the blueschist facies event. It is thought that the veins at Big Hurrah were formed during uplift by a fluid phase derived by metamorphic dehydration and channeled into conduits depositing quartz, carbonate and gold.

  19. The compositions of minerals within high pressure tectonic blocks from Horse Mountain, Northern California

    Energy Technology Data Exchange (ETDEWEB)

    Gilliam, C.E. (Mount Holyoke College, South Hadley, MA (United States). Geology Dept.)

    1993-03-01

    High pressure metamorphic blocks occur within serpentinite between the South Fork Mountain Schist and the Coast Range Fault, Humboldt Co., Northern California. Samples from three of these blocks were studied by petrographic techniques and quantitatively analyzed using the energy dispersive spectrometer on out scanning electron microscope. The mineral assemblages for three samples are as follows: WC86-7-3 contains omphacite (jd53, di36, hd11), pumpellyite, and relic igneous clinopyroxene. WC86-9-3 contains titanite, epidote chlorite, pumpellyite, and relic clinopyroxene. WC86-18-3 contains garnet, lawsonite, glaucophane, albite, chlorite, pumpellyite, minor quartz, and relic clinopyroxene. All samples contain relic clinopyroxene that, in the case of SC86-7-3, acts as a nucleus for omphacite growth. When present in cross cutting veins, omphacite has both radiating fibrous and blocky textures. Some epidote, titanite, clinopyroxene and pumpellyite were too fine to identify optically as well, but occur in the ground mass. Large grains of euhedral glaucophane, (Na[sub 2.0] Ca[sub .2])(Mg[sub 1.3] Fe[sub 2.0] Al[sub 1.7])Si[sub 8.0] O[sub 22] (OH)[sub 2], and garnet, (alm 33, pyO, sp30, gr37), containing relic ( ) clinopyroxene, glaucophane, and albite inclusions, were present in WC86-18-3. The high SiO[sub 2] and low TiO[sub 2] relative to Al[sub 2]O[sub 3] in relic clinopyroxene indicates a non-alkaline tholeiitic protolith. Omphacite compositions correspond to the type IV blueschist typical of the Franciscan Complex and constrain the pressures of metamorphism to be approximately 9 kb while lawsonite in WC86-18-3 implies a temperature below 450C. These observations indicate that the blocks are derived from subducted material that underwent metamorphism in a low temperature, high pressure setting. The process of their exhumation remains a mystery.

  20. Tectonic blocks at Horse Mountain, N. California: A unique occurrence of mafic blueschists in serpentinite along the South Fork fault adjacent to the Klamath Mountains

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, S.R. (Mount Holyoke Coll., Hadley, MA (United States). Geology Dept.); Aalto, K.R. (Humboldt State Univ., Arcata, CA (United States). Geology Dept.); Abitz, R.J. (IT Corp., Albuquerque, NM (United States)); Gilliam, C.E. (Mount Holyoke Coll., Hadley, MA (United States). Geology Dept.)

    1993-04-01

    High-pressure metamorphic blocks within serpentine occur between the South Mtn Schist, Jsfm, (Pickett Peak terrane) of the Franciscan Complex and rocks of the Western Jurassic belt of the Klamaths in the Willow Creek Quadrangle. These rounded to ellipsoidal tectonic blocks range from 1--50 meters and have foliated chlorite [+-] actinolite rinds which presumably resulted from interaction between the mafic blocks and host serpentinite. Metamorphic assemblages within the blocks include lawsonite + glaucophane + chlorite + pumpellyite + albite and subsets of the above with omphacite [+-] quartz [+-] phengite [+-] epidote [+-] aragonite. Relic igneous augite is common, sometimes with omphacite or glaucophane overgrowths. Veins of pumpellyite or fibrous to granular omphacite are rare and epidote + albite [+-] calcite veins are common. Whole-r