WorldWideScience

Sample records for schists

  1. 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 ...

  2. 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

    From qualitative analysis of the gravity data, several tectonic features are ... major types of schist belts are identified in the ... Dharwar craton; Gadag schist belt; gravity method; inversion. ..... the Research Associateship of Dr D Himabindu.

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

    African Journals Online (AJOL)

    PROF EKWUEME

    The geology of Akwnaga area of northcentral Nigeria is dominated by schists, metaigneous gneisses and weakly to non- foliated granites. The Schist shows grades up to the sillimanite zone of the Barrovian type regional metamorphism and occurs as xenoliths in other rocks of the area. The zircons separated from a sample ...

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

    Indian Academy of Sciences (India)

    residual gravity profile data were interpreted using 2-D prism models. The results ... Geological and geophysical layout map of the Gadwal schist belt area, Andhra Pradesh (after Ananda Murty and ... Observed gravity (Bouguer) values, regional, residual and inferred gravity models along traverse I of the Gadwal schist.

  5. 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 ...

  6. Environmental problems caused by bituminous schist and possible solutions

    International Nuclear Information System (INIS)

    Elmas, N.; Aykul, H.; Erarslan, K.; Ediz, I.G.

    1998-01-01

    Schist, as a disposal of mine, has harmful effects on environment. however, several manners can be utilized to prevent the environmental destruction as well as an economical benefit is gained. In this study, environmental problems caused by bituminous schist and other disposals have been investigated on a specific lignite coal mine where schist is disposed as waste material. Pollution and damage on land and in water sources around the coal district and the villages have been observed, recorded and several solutions to environmental problems have been proposed. Discussed proposals will not only solve the environmental pollution problem but also provide waste management facility. Industrial structure of the district enables such a disposal to be used as an economical raw material. Besides, general effects of the coal mine and the power plant nearby have been discussed from environmental point of view, too. 7 refs

  7. 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 ...

  8. 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 ...

  9. 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.

  10. 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.)

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

    African Journals Online (AJOL)

    DR OKONKOWO

    2012-02-29

    silicate reaction bands have higher contents of CaO and Sr and lower concentrations of K2O, Rb, Ni, and Ba relative to the calc-silicate schists; and relatively higher SiO2, TiO2, Al2O3, Fe2O3, MgO, Na2O, K2O and P2O5 and lower ...

  12. Market Segmentation: An Application to the Schist Village Tourism Destinations

    Directory of Open Access Journals (Sweden)

    Manuel Martinho

    2017-01-01

    Full Text Available Purpose – The Schist Village network is a sustainable development project in Portugal’s Pinhal Interior region that includes 27 villages located in the central inland area of the country. Overall, this study sets out evidence about the motivations, interests, behaviors, and images of visitors/tourists (tourism consumers regarding the Schist Villages in the area. Design/Methodology/Approach – The sample of individuals interviewed includes a total of 223 individuals (59 international and 164 national tourists, all of whom personally answered the questionnaire. Findings and implications – Through analysis of the survey results obtained, it is possible to chart a profile of Schist Village visitors/tourists, ascertain their preferences and the key attributes associated with the image of this tourist destination and, based on these, put forward strongly focused orientations and guidelines to help develop future marketing plans for this territory. Limitations – One limitation stems from how the data was gathered and analyzed constitutes but a mere “moment” in a fairly vast and dynamic universe given that the questionnaires were completed across a defined and fairly brief period of time. The fact that the questionnaires were handed out by network partners effectively excluded from the study all those tourism consumers who travel and visit the territory without any direct recourse to the services of the aforementioned partners. Originality – This study presents an easy and clear way to segment the market that could be used by several stakeholders in order to improve their targeting activities.

  13. Relationships between basin architecture, basin closure, and occurrence of sulphide-bearing schists: an example from Tampere Schist Belt, Finland

    DEFF Research Database (Denmark)

    Kalliomäki, Henrik; Torvela, Taija; Moreau, Julien

    , therefore, offers an excellent opportunity to examine the volcano-sedimentary evolution of an ancient marginal basin, and the mechanics of and strain distribution during its subsequent closure. The aim of this study is to investigate the structural development and the architecture of a part of the TSB...... in more detail, including the relationships between the volcano-sedimentary sequences, the tectonic structures, and the sulphide-bearing schist horizons. Important insights are gained into understanding the mechanisms of the basin closure and the localisation of the sulphide mineralisation within......, in order to accommodate the crustal shortening during basin closure. Furthermore, it is suggested that there is a genetic relationship between the interpreted palaeothrusts and the sulphide-bearing schist horizons in the study area: early, gently dipping thrusts acted as both channels and traps...

  14. Surprising discovery of high-grade pelitic schist on Cavalli Seamount, offshore Northland

    International Nuclear Information System (INIS)

    Mortimer, N.; Walker, N.H.; Herzer, R.H.; Calvert, A.; Seward, D.

    1999-01-01

    Serendipity waits in the world's unexplored places. In March 1999, GNS's ONSIDE expedition to the South Fiji Basin made two dredge hauls on Cavalli seamount expecting to recover Miocene oceanic volcanic rocks. Instead dredge DIA recored 1 kg of 10 cm slickensided and chloritised schist pieces and dredge DIB, which was 1.1 km distant, 100 kg of well-foliated biotite schist, mainly in the form of two large subangular boulders. The presence of calsilicate bands initially suggested a correlation with Buller or Takaka Terranes, but whole rock chemical composition of the schist is more consistent with Murihiku, Waipapa or Pahau Terranes. U-Pb TIMS gheochronometry of individual detrital zircons indicates a maximum 170Ma depositional age for the schist protolith, thus clearly ruling out a Buller or Takaka correlation. Rb-Sr whole rock data suggest a young (Cenozoic?) metamorphic age. (author)

  15. 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 market, the economic - and also environmental - potential will be considerable. Understanding the geological conditions and petrographic properties of the rock is vital. This is a quartz-feldspar rich metamorphic rock - a meta-arkose - containing rhythmically distributed planar lamina (less than 2 mm thick) or scattered occurrence of mica, separated by layers composed predominately of quartz and feldspar. The rock can be split along the lamina to slabs varying from 0.5 cm to more than 10 cm in thickness, and the microstructure can be characterized as being granoblastic to gneissic. . This makes it possible by well designed crushing process and careful selection of the in-going rock particles, to obtain well shaped aggregates up to at least 20 mm. The on-going project will also study the total cost situation depending on the QW utilisation, discuss the environmental and sustainability issues with a societal perspective, and also consider the market opportunities.

  16. Sulphur isotopes in a metamorphogenic gold deposit, Macraes mine, Otago Schist, New Zealand

    International Nuclear Information System (INIS)

    Craw, D.; Hall, A.J.; Fallick, A.E.; Boyce, A.J.

    1995-01-01

    The Macraes gold quartz vein deposit, New Zealand, is located in a shear zone cutting greenschist facies metasediments of the Otago Schist. The deposit has been interpreted as being metamorphogenic in origin as there is no evidence for coeval magmatic activity in the Otago Schist orogen. The immediate host rock at the Macraes deposit is pyritic (δ 34 S = -2.7 to -1.3 per mil ) and locally weakly graphitic schist, a rare rock type in the Otago Schist. Sulphur isotope analyses of pyrite and arsenopyrite extracts from auriferous veins and wall-rock schist provide a similar narrow range in δ 34 S values, from -3.0 to -1.0 per mil (n=9). The lack of isotopically depleted sulphur, the narrow range in values, and the replacement sulphide textures help discount a primary bacteriogenic origin for host-rock sulphide. Sulphide in both veins and wall rock is of hydrothermal origin. Sulphides in metasediments and metavolcanics elsewhere in the Otago Schist have δ 34 S in the narrow range -6 to +6 per mil. The sulphur isotope data are consistent with origin of hydrothermal sulphur within the metamorphic pile but provide no constraint on specific rock types which contributed the sulphur to the hydrothermal fluid. The study demonstrates that sulphur isotopic signatures near zero per mil can arise without any direct magmatic input into the mineralisation process. (author). 34 refs., 2 figs., 1 tab

  17. Geochemical and mineralogical controls on mine tailings rehabilitation and vegetation, Otago Schist, New Zealand

    International Nuclear Information System (INIS)

    Craw, D.; Rufaut, C.

    2017-01-01

    Large areas (square kilometre scale) of mine tailings have been deposited from placer gold mines in Central Otago, and are being deposited at Macraes orogenic gold mine in east Otago. Establishment of vegetation on these tailings involves at least some provision of plant nutrients from the rock. Phosphorus is the principal limiting nutrient, as the c. 1000 mg/kg P in accessory apatite, most abundant in micaceous schist, is only sparingly bioavailable on timescales of weeks to months. Nitrogen is an important limiting nutrient but schist, especially micaceous schist, typically contains 500-1000 mg/kg N, and this nitrogen is readily leachable with water on timescales of weeks to months. Arsenic uptake from tailings by pasture species is significant (< 90 mg/kg dry weight), but elevated As in tailings substrates (c. 1500 mg/kg) does not adversely affect plant health. Capping of tailings with variably oxidised schist is the most effective way of facilitating revegetation, and some addition of phosphatic fertiliser is desirable but other nutrients, including nitrogen, are adequately bioavailable in a schist cap and underlying tailings. (author).

  18. Contribution to physico-chemical study of Timahdit bituminous schists (Morocco): Organic matters and metalloporphyrins

    International Nuclear Information System (INIS)

    Saoiabi, A.

    1982-01-01

    The Timahdit bituminous schists have been analysed by different methods. The experimental results obtained using these methods concern the behaviour of the schists and the Kerogen facing the pyrolysis, as well as the separation of the hydrocarbons and the metalloporphyrins. For this purpose the techniques used are: 'Rock Eval' pyrolysis, thermogravimetric analysis and electron paramagnetic resonance (E.P.R.) for the raw rock and the Kerogen; infrared (I.R.), gas chromatography and E.P.R. for the extracted organic matters; E.P.R., I.R., nuclear magnetic resonance (N.M.R.), ultraviolet (U.V.) and mass spectrometry for the metalloporphyrins identification and characterization. The analysis of these schists has shown that: We can extract per solvent only 1% of organic matters, ferric oxide hasn't any effect neither on the pyrolysis nor on the organic matters extraction and that the Kerogen of these schists are relatively rich in hydrocarbonic compounds. The gas chromatography reveal the presence of alkanes with odd number of carbons and isoprenoids. All these criteria indicate an immature, little developped organic matter which having probably a marine origin but possessing a good oil potential. It has also been observed that a part of Iron, Nickel and Vanadium in the schists are incorporated into the organic matters. Nickel and Vanadium are into macrocycles which are porphyrins. A method for extracting and separating these porphyrins has been developped. 43 figs., 21 tabs., 58 refs. (author)

  19. Method for obtaining a varnish with a base of mineral oil obtained by distillation of bituminous schists

    Energy Technology Data Exchange (ETDEWEB)

    Marchionni, A

    1945-07-24

    A method for obtaining a varnish is described characterized by the fact that the following ingredients are being used; mineral oil from the distillation of bituminous schists in the proportions already cited in the description, diluted with benzene or turpentine, with admixture of coloring matter. Varnish with a base of mineral oil from the distillation of bituminous schists is obtained.

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

    African Journals Online (AJOL)

    Global Journal of Geological Sciences ... Abstract. All previous models of evolution of the Kazaure Schist Belt (KZSB) invoked a simple ensialic mechanism in the context of Pan-African deformation which led to the formation of a marginal back-arc basin floored by continental materials that accepted sediments. The closure ...

  1. on the evolution of the kazaure schist belt of nw nigeria

    African Journals Online (AJOL)

    Admin

    2007-05-25

    May 25, 2007 ... ensialic processes, and an evaluation of previous data suggested in previous works is consistent with the new .... Ma ago, led to the formation of a marginal back-arc ..... Turner, D.C., 1983: Upper Proterozoic schist belts in the.

  2. 208-240 M.Y. old jadeite-glaucophane schists in the Kurosegawa tectonic zone near Kochi city, Shikoku

    International Nuclear Information System (INIS)

    Maruyama, Shigenori; Ueda, Yoshio; Banno, Shohei.

    1978-01-01

    A new member of the Kurosegawa tectonic zone was found in the serpentinite near Kochi city. They are high P and low T schists derived from basalt and chert. Three metamorphic events can be deciphered in the high-pressure schists, based upon the texture and mineral paragenesis: first, low P metamorphism at intermediate- to high-grade, second, high P and low T metamorphism of the jadeite-glaucophane facies and the third, retrograde crystallization of the second stage high P schists within the stability field of lawsonit + pumpellyite + glaucophane. Further, the formation of analcime replacing jadeite took place. The second and third metamorphism can be distinguished on pyroxene mineralogy that jadeite + quartz was stable in the second, but albite + quartz + aegirinejadeite in the third stage of metamorphism. Not all of the high P and low T schists had suffered low P metamorphism before they were metamorphosed by the high P one. Some basaltic rocks directly changed to high P and low T schists. Two muscovites in the schists give K-Ar ages of 208 - 240 m.y., and a relic igneous biotite, being partly replaced by chlorite, gives 225 m.y. of K-Ar age. These values are different not only from those of the Sanbagawa schists, but also from the other members of the Kurosegawa zone. (author)

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

    International Nuclear Information System (INIS)

    Afouxenidis, D.; Stefanaki, E.C.; Polymeris, G.S.; Sakalis, A.; Tsirliganis, N.C.; Kitis, G.

    2007-01-01

    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

  4. 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.

  5. Postcrystalline deformation of the Pelona Schist bordering Leona Valley, southern California

    Science.gov (United States)

    Evans, James George

    1978-01-01

    Detailed structural investigations in part of the Leona Valley segment of the San Andreas fault zone, 5-16 km west of Palm dale, focused on the postcrystalline deformation of the block of Mesozoic(?) Pelona Schist underlying Portal and Ritter Ridges. The early fabric of the schist is modified and in places obliterated by cataclasis along shear zones near the San Andreas fault and the Hitchbrook fault, a major west-striking branch of the San Andreas fault system. Anastomosing shear foliations, fabric elements of the postcrystalline deformation, intersect at small angles to one another and are generally vertical or steeply dipping to the north-northeast; they are subparallel to the Hitchbrook fault. Many of these shear foliations are nearly parallel to the compositional layering and schistosity, which commonly dip at moderately steep angles to the northwest. Folds in the shear foliation, commonly intrafolial, generally plunge at moderately steep angles to the north-northeast or are nearly vertical. Other folds, various in form, have axes parallel to the intersections of the early schistosity and the shear foliations and plunge in many other directions. Faults, roughly similar in orientation to the shear foliations, have orientations subparallel to large-scale structures and structural features in the Leona Valley area and in southern California: the San Andreas fault zone in Leona Valley, the Hitchbrook fault, the Garlock fault zone, steep northward-striking faults, the San Andreas fault zone north and south of the Transverse Ranges, and the generally northwest-dipping early compositional layering of the schist. Slickensides on some of the minor faults indicate that the latest movements on the steep faults are predominantly strike slip with indications of less common episodes of predominantly dip slip. The low-angle faults have oblique slip with a large dip component.

  6. New P-T and U-Pb constraints on Alpine Schist metamorphism in south Westland, New Zealand

    International Nuclear Information System (INIS)

    Scott, J.M.; Auer, A.; Muhling, J.R.; Czertowicz, T.A.; Cooper, A.F.; Billia, M.A.; Kennedy, A.K.

    2015-01-01

    Metamorphic mineral compositions of a staurolite-bearing greyschist from the middle reaches of the Moeraki River valley in south Westland reveal peak equilibration at c. 558±50 degrees C and c. 6.1±1.2 kbar. Two c. 83 Ma U-Pb monazite age populations from the cores of monazite-apatite-allanite-epidote corona structures in mylonitised schists from near Fox Glacier confirm that Alpine Schist metamorphism occurred during the Late Cretaceous. The published spread in Late Cretaceous metamorphic ages indicates that metamorphism was diachronous or was a protracted event. Further dating is required to pin down the cryptic transition into the Jurassic-Early Cretaceous metamorphosed Otago Schist, but the Alpine Schist must extend at least 11 km east of the Alpine Fault in south Westland and overprint the suture between the Pounamu and Rakaia terranes. The P-T-t results imply that the Late Cretaceous crust represented by portions of the Alpine Schist was probably of similar thickness to that beneath the Southern Alps today, but with dehydration and partial melting occurring near the base. The crust under Westland and Otago may be dry and therefore strong. (author).

  7. Preferred orientation of phyllosilicates: Comparison of fault gouge, shale and schist

    International Nuclear Information System (INIS)

    Wenk, Hans-Rudolf; Kanitpanyacharoen, Waruntorn; Voltolini, Marco

    2010-01-01

    Samples of fault gouge from the San Andreas Fault drill hole (SAFOD), a shale from the North Sea sedimentary basin and schists from metamorphic rocks in the Alps have been analyzed with high energy synchrotron X-rays to determine preferred orientation of mica and clay minerals. The method relies on obtaining 2D diffraction images which are then processed with the crystallographic Rietveld method, implemented in the software MAUD, allowing for deconvolution of phases and extraction of their orientation distributions. It is possible to distinguish between detrital illite/muscovite and authigenic illite/smectite, kaolinite and chlorite, and muscovite and biotite, with strongly overlapping peaks in the diffraction pattern. The results demonstrate that phyllosilicates show large texture variations in various environments, where different mechanisms produce the rock microfabrics: fault gouge fabrics are quite weak and asymmetric with maxima for (001) in the range of 1.5-2.5 multiples of random distribution (m.r.d.). This is attributed to heterogeneous deformation with randomization, as well as dissolution-precipitation reactions. Shale fabrics have maxima ranging from 3 to 9 m.r.d. and this is due to sedimentation and compaction. The strongest fabrics were observed in metamorphic schists (10-14 m.r.d.) and developed by deformation as well as recrystallization in a stress field. In the analyzed samples, fabrics of co-existing quartz are weak. All phyllosilicate textures can be explained by orientation of (001) platelets, with no additional constraints on a-axes.

  8. Correlations between ultrasonic pulse wave velocities and rock properties of quartz-mica schist

    Directory of Open Access Journals (Sweden)

    Bharti Chawre

    2018-06-01

    Full Text Available Physico-mechanical properties are critically important parameters for rocks. This study aims to examine some of the rock properties of quartz-mica schist (QMS rocks in a cost-effective manner by establishing correlations between non-destructive and destructive tests. Using simple regression analysis, good correlations were obtained between the pulse wave velocities and the properties of QMS rocks. The results were further improved by using multiple regression analysis as compared to those obtained by the simple linear regression analysis. The results were also compared to the ones obtained by other empirical equations available. The general equations encompassing all types of rocks did not give reliable results of rock properties and showed large relative errors, ranging from 23% to 1146%. It is suggested that empirical correlations must be investigated separately for different types of rocks. The general empirical equations should not be used for the design and planning purposes before they are verified at least on one rock sample from the project site, as they may contain large unacceptable errors. Keywords: Pulse wave velocity, Physico-mechanical properties, Quartz-mica schist (QMS rocks, Non-destructive methods, Static elastic constants, Dynamic elastic constants

  9. 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.

  10. Paleoseismology of the Denali fault system at the Schist Creek site, central Alaska

    Science.gov (United States)

    Personius, Stephen F.; Crone, Anthony J.; Burns, Patricia A.C.; Rozell, Ned

    2016-01-06

    Two hand-dug trenches at the Schist Creek site on the Denali fault system in central Alaska exposed evidence of four surface-rupturing earthquakes on the basis of upward terminations of fault strands and at least one buried, scarp-derived colluvial wedge. Limited radiocarbon ages provide some constraints on times of the ruptures. The youngest rupture (PE1) likely occurred about 200–400 years ago, the penultimate rupture (PE2) is younger than 1,200 years old, the third event back (PE3) occurred between 1,200 and 2,700 years ago, and the oldest rupture (PE4) occurred more than 2,700 and less than 17,000 years ago. Evidence for a possible additional rupture (PE4?) is equivocal and probably is related to earthquake PE4. On the basis of a nearby measured slip rate of 9.4 ± 1.6 millimeters per year and the long interevent times between our documented ruptures, we believe that our paleoseismic record at this site is incomplete. We suspect one undocumented earthquake between PE1 and PE2 and one or perhaps two more earthquakes between PE2 and PE3. We found stratigraphic evidence in the trenches for only four or possibly five (PE4?) earthquakes, but the addition of two or three inferred earthquakes yields a record of eight possible surface ruptures at the Schist Creek site. Our interpretation of the paleoseismic history at the site is consistent with recurrence intervals of several hundred years on this section of the Denali fault system.

  11. Structural and metamorphic evolution of the Orocopia Schist and related rocks, southern California: Evidence for late movement on the Orocopia fault

    Science.gov (United States)

    Jacobson, Carl E.; Dawson, M. Robert

    1995-08-01

    The Pelona, Orocopia, and Rand Schists (POR schists) of southern California and southwesternmost Arizona are late Mesozoic or early Tertiary subduction complexes that underlie Precambrian to Mesozoic continental basement along the low-angle Vincent-Chocolate Mountains (VCM) fault system. The VCM faults are often considered to be remnants of the original subduction zone, but recent work indicates that many have undergone substantial postsubduction reactivation. In the Orocopia Mountains, for example, the Orocopia Schist exhibits an exceptionally complex structural and metamorphic history due to multiple periods of movement along the Orocopia fault. Structures in the schist include isoclinal folds with axial-planar schistosity, open-to-tight folds that fold schistosity, penetrative stretching lineations, and crenulation lineations, all of which show a nearly 360° range in trend. Folds and lineations that trend approximately NE-SW occur throughout the schist and are thought to be part of an early phase of deformation related to subduction. Folds of this orientation show no consistent vergence. Folds and lineations that trend approximately NW-SE are concentrated near the Orocopia fault and are interpreted to have formed during exhumation of the schist. The NW-SE trending folds, and shear indicators in late-stage mylonite at the top of the schist, consistently verge NE. The exhumation event culminated in emplacement of the schist against brittlely deformed upper plate. Exhumation of the Orocopia Schist was accompanied by retrograde replacement of garnet, biotite, epidote, and calcic amphibole by chlorite, calcite, and sericite. Matrix amphibole has a lower Na/Al ratio than amphibole inclusions in albite, consistent with a late-stage decrease in pressure. As NE vergence in the Orocopia Mountains is associated with exhumation of the schist, the NE movement along other segments of the VCM fault may also be late and therefore have no bearing on the facing direction of the

  12. 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.

  13. A probabilistic model for the persistence of early planar fabrics in polydeformed pelitic schists

    Science.gov (United States)

    Ferguson, C.C.

    1984-01-01

    Although early planar fabrics are commonly preserved within microlithons in low-grade pelites, in higher-grade (amphibolite facies) pelitic schists fabric regeneration often appears complete. Evidence for early fabrics may be preserved within porphyroblasts but, within the matrix, later deformation often appears to totally obliterate or reorient earlier fabrics. However, examination of several hundred Dalradian pelites from Connemara, western Ireland, reveals that preservation of early fabrics is by no means uncommon; relict matrix domains, although volumetrically insignificant, are remarkably persistent even when inferred later strains are very large and fabric regeneration appears, at first sight, complete. Deterministic plasticity theories are ill-suited to the analysis of such an inhomogeneous material response, and a probabilistic model is proposed instead. It assumes that ductile polycrystal deformation is controlled by elementary flow units which can be activated once their associated stress barrier is overcome. Bulk flow propensity is related to the proportion of simultaneous activations, and a measure of this is derived from the probabilistic interaction between a stress-barrier spectrum and an internal stress spectrum (the latter determined by the external loading and the details of internal stress transfer). The spectra are modelled as Gaussian distributions although the treatment is very general and could be adapted for other distributions. Using the time rate of change of activation probability it is predicted that, initially, fabric development will be rapid but will then slow down dramatically even though stress increases at a constant rate. This highly non-linear response suggests that early fabrics persist because they comprise unfavourable distributions of stress-barriers which remain unregenerated at the time bulk stress is stabilized by steady-state flow. Relict domains will, however, bear the highest stress and are potential upper

  14. Field tracer test for denitrification in a pyrite-bearing schist aquifer

    International Nuclear Information System (INIS)

    Pauwels, H.; Kloppmann, W.; Foucher, J.-C.; Martelat, A.; Fritsche, V.

    1998-01-01

    A small-scale artificial tracer test performed on a schist aquifer in Brittany has helped clarify mechanisms and kinetics of in situ autotrophic denitrification. NO 3 was injected as a pulse simultaneously with a conservative tracer - Br - . During the test, which lasted 210 h, 73% of the injected Br - was recovered, as against only 47% of the NO 3 . The 26% difference in the recovery of the two injected species is interpreted as being the result of denitrification, in part due to the direct oxidation of pyrite present in the solid aquifer according to the reaction: 5FeS 2 +14NO 3 - +4H + approaches7N 2 +10SO 4 2- +5Fe 2+ +2H 2 O, and in part due to subsequent iron oxidation according to the reaction: NO 3 - +5Fe 2+ +6H + approaches1/2N 2 +5Fe 3+ +3H 2 O. Despite the potential increase in SO 4 and Fe resulting from denitrification through pyrite oxidation, the concentrations of these elements in the groundwater remain moderate due to the precipitation of minerals such as jarosite and/or natroalunite. Tracer transfer takes place in a heterogeneous medium which, according to the breakthrough curves, can be simplified to a dual-porosity aquifer comprising a high-permeability (fractures or large fissures) medium of low porosity from which only minor denitrification of circulating NO 3 -bearing water was observed and a low-permeability (small fissures) medium of high porosity which induces a higher denitrification rate in the circulating NO 3 -bearing water. The kinetics of the denitrification reaction are high compared with results obtained for other environments and can be described by a first-order model with a half life of 7.9 days for the low-porosity medium and only 2.1 days for the high-porosity medium. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  15. The origin of copiapite from chlorite pyritic schist (Wiesciszowice, Lower Silesia, Poland) in the light of Moessbauer analysis

    Energy Technology Data Exchange (ETDEWEB)

    Adamczyk, Z., E-mail: zdzislaw.adamczyk@polsl.pl [Silesian University of Technology, Institute of Applied Geology (Poland); Komraus, J. L., E-mail: komraus@us.edu.pl [University of Silesia, Institute of Physics (Poland)

    2008-01-15

    This work presents the results of the analysis of copiapite, formed from weathering and oxidation of pyrite in pyritic schist from Wiesciszowice, Lower Silesia (Poland). The pure phase of copiapite was found in secondary minerals after pyrite and identified by optical microscopy, XRD and Moessbauer spectroscopy. In the analyzed copiapite major cations appear to be Fe{sup 2+} and Fe{sup 3+}. Some Fe{sup 3+} is substituted by other cations, mainly Al{sup 3+}. Al{sup 3+} probably comes from leaching of chlorite from which hydrated sulphates of iron, mainly szomolnokite, form followed by hydrated sulphates fibroferrite, which is replaced by copiapite.

  16. 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

  17. 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

  18. 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.

  19. 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.

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

    Science.gov (United States)

    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

  1. 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

  2. Petrologic significance of Fe-rich staurolite in pelitic schists of the Silgará Formation, Santander Massif

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    Carlos Alberto Ríos

    2016-01-01

    Full Text Available Medium grade metapelites of the Silgará Formation at the Santander Massif (Colombian Andes have been affected by a medium-pressure/high-temperature Barrovian type of metamorphism, developing a sequence of metamorphic zones (biotite, garnet, staurolite and sillimanite. These rocks record a complex tectonometamorphic evolution and reaction history. Metapelitic rocks from the staurolite zone are typically foliated, medium- to coarse-grained, pelitic to semipelitic schists that contain the mineral assemblage biotite + garnet + staurolite ± kyanite; all contain muscovite + quartz + plagioclase with minor K-feldspar, tourmaline, apatite, zircon, epidote, calcite, and Fe–Ti oxides. Field and microscopic evidences reveal that Fe-rich staurolite in pelitic schists is involved in several chemical reactions, which explains its formation and transformation to other minerals, which are very important to elucidate the reaction history of the Silgará Formation metapelites.   Significado Petrológico de Estaurolita Rica en Fe en Esquistos Pelíticos de la Formación Silgará, Macizo de Santander   Resumen Medium grade metapelites of the Silgará Formation en el Macizo de Santander (Andes Colombianos han sido afectadas por un metamorfismo de tipo Barroviense, el cual se ha producido en condiciones de media presión y alta temperatura, desarrollando una secuencia de zonas metamórficas (biotita, granate, estaurolita y silimanita. Estas rocas registran una evolución tectono-metamórfico e historia reacción compleja. Las metapelitas de la zona de la estaurolita están representadas por esquistos pelíticos a semipelíticos de grano medio a grueso típicamente foliados que contienen la paragénesis mineral biotita + granate + estaurolita ± cianita; todos contienen moscovita + cuarzo + plagioclasa con menor feldespato potásico, turmalina, apatito, zircón, epidota, calcita, y óxidos de Fe-Ti. Evidencias de campo y microscópicas revelan que la estaurolita

  3. Duration of convergence at the Pacific-Gondwana plate margin: insights from accessory phase petrochronology of the Alpine Schist, New Zealand

    Science.gov (United States)

    Briggs, S. I.; Cottle, J. M.; Smit, M. A.; Arnush, N. F.

    2016-12-01

    The timing, duration and along-strike synchroneity of metamorphism and anataxis in the Alpine Schist of New Zealand is a matter of considerable debate. Our preliminary data indicate that metamorphism resulting in garnet growth occurred from 97 - 75 Ma, and anatectic melting occurred from 80 - 51 Ma. These events are contemporaneous with rifting of Zealandia from East Gondwana, and Tasman Sea spreading from 83 - 52 Ma. An important implication of these results is that Late Cretaceous convergence along the Zealandia segment of the Pacific-Gondwana plate margin may have persisted much later than previously thought, and that convergence and extension occurred coevally in adjacent areas. This poses the question: for how long did convergence continue along the Pacific-Gondwana plate margin during East Gondwana breakup? To fully decipher the multiple stages of the complex metamorphic history recorded in the Alpine Schist, we combine Lu-Hf garnet geochronology with U-Th/Pb and REE analyses of zircon and monazite. We use the newly developed `single-shot laser ablation split stream' (SS-LASS) analysis method to obtain depth profiles through 5-10 µm metamorphic zircon overgrowths at 100 nm depth resolution to constrain both the timing and petrological context of discrete metamorphic zircon (re-)crystallization events recorded in the Alpine Schist. We also employ high spatial resolution LASS analysis to target rare 5 - 20 µm monazite in thin section to augment garnet and zircon data. Our multi-accessory phase petrochronology approach is capable of resolving discrete short-duration thermal events, strengthening the geological interpretation of `mean' Lu-Hf garnet ages and discerning between an episodic versus a prolonged history of metamorphism. In addition, comparison with geochronology from anatectic pegmatites clarifies the temporal relationship between metamorphism and melting in the Alpine Schist, while providing direct constraints on the timing and duration of

  4. 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

  5. STUDY ON THE DEW POINT TEMPERATURE IN AREAS COVERED BY COLLUVIAL MESOVOID SHALLOW SUBSTRATUM (CRYSTALLINE SCHISTS SCREE IN THE LEAOTA MOUNTAINS, 2014

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    Magdalin Leonard Dorobăţ

    2015-12-01

    Full Text Available This paper present and discussed the results of the monitoring of the dew point values, recorded in October and November 2014, in an ecological station in the Leaota Mountains. In this station, two polls were located in areas covered by colluvial mesovoid shallow substratum (MSS formed by epi- and mesometamorphic crystalline schists. In the ecological stations we located in the Leaota Mountains, almost always we found condensation on the walls of the polls tubes placed at different depths. Most often in spring or autumn or in other cold days, the dew point is more revealing regarding the recording actual amount of moisture in the air, than the relative humidity indicator. This work is part of a larger project that seeks correlations between ecological factors (humidity, temperature and dew point registered in various types of screes (limestone and crystalline schists and some zoocenotic components (invertebrates. This research aim to know the importance of mesovoid shallow substratum for invertebrates or small vertebrates fauna and represents a premiere for Leaota Mountains, not only regarding the continuous monitoring of some ecologic factors of these types of ecosystems (MSS, rarely researched even at global level, and also regarding the inventory of the invertebrate fauna in scree for these mountains.

  6. Age and provenance of mica-schist pebbles from the Eocene conglomerates of the Tylicz and Krynica Zone (Magura Nappe, Outer Flysch Carpathians)

    Science.gov (United States)

    Oszczypko, Nestor; Salata, Dorota; Konečný, Patrik

    2016-06-01

    During the Łate Cretaceous to Palaeogene, the Magura Basin was supplied by clastic material from source areas situated on the northern and southern margins of the basin, which do not outcrop on the surface at present. The northern source area is traditionally connected with the Silesian Ridge, whereas the position of the southern one is still under discussion. A source area situated SE of the Magura Basin supplied the Eocene pebbly para-conglomerates containing partly exotic material. The studied clastic material contains fragments of crystalline rocks, and frequent clasts of Mesozoic to Palaeogene deep and shallow-water limestones. Numerous mica schists, scarce volcanites and granitoids as well as gneisses, quartzites and cataclasites were found in the group of crystalline exotic pebbles. Monazite ages of "exotic" mica-schist pebbles from the Tylicz, Zarzecze and Piwniczna-Mniszek sections document the Variscan 310±10 Ma age of metamorphic processes. The provenance of these exotic rocks could be connected with a remote source area located SE of the Magura Basin, which could be the NW part of the Dacia Mega Unit. The idea is strongly supported by palaeotransport directions from the SE, the absence of material derived from the Pieniny Klippen Belt, the presence of shallow water limestones, typical facies of the Median Dacides belt and metamorphic age distribution proved by monazite dating.

  7. K-Ar and Ar-Ar dating of the Palaeozoic metamorphic complex from the Mid-Bosnian Schist Mts., Central Dinarides, Bosnia and Hercegovina

    International Nuclear Information System (INIS)

    Pamic, J.; Balogh, K.; Hrvatovic, H.; Balen, D.; Palinkas, L.; Jurkovic, I.

    2004-01-01

    K-Ar and Ar-Ar whole rock and mineral ages are presented for 25 samples of metamorphic rocks from the Mid-Bosnian Schist Mts., representing one of the largest allochthonous Palaeozoic terranes incorporated within the Internal Dinarides. Four main age groups can be distinguished: 1) Variscan (∼ 343 Ma), 2) post-Variscan (288-238 Ma), 3) Early Cretaceous (mainly 121-92 Ma), and 4) Eocene (59--35 Ma) ages. Apart from this, an Oligocene (31 Ma) age was obtained on Alpine vein hyalophane. The radiometric dating indicates a polyphase metamorphic evolution of the Palaeozoic formations and suggests a pre-Carboniferous age of the volcano-sedimentary protoliths, an Early Carboniferous age of Variscan metamorphism and deformation, post-Variscan volcanism, an Early Cretaceous metamorphic overprint related to out-of-sequence thrusting of the Palaeozoic complex, and an Eocene and Oligocene metamorphic overprint related to the main Alpine compressional deformation and subsequent strike-slip faulting, and uplift of the metamorphic core. Accordingly, the Mid-Bosnian Schist Mts. can be correlated in its multistage geodynamic evolution with some Palaeozoic tectonostratigraphic units from the Austroalpine domain in the Eastern Alps. (author)

  8. 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

  9. Seismic velocity anisotropy of phyllosilicate-rich rocks: characteristics inferred from experimental and crack-model studies of biotite-rich schist

    Science.gov (United States)

    Nishizawa, O.; Kanagawa, K.

    2010-07-01

    Seismic velocity anisotropy of biotite schist (30 per cent-mode biotite) was measured under confining pressures up to 150 MPa. The rock shows weak orthotropy which was altered from transverse isotropy (TI) generated by biotite-preferred orientation. The orthotropy was caused by microfolding in the rock. The velocity increase under confining pressure indicates that most crack planes are aligned parallel to the cleavage planes (silicate sheet) of the oriented biotite minerals. The anisotropy of the rock is basically TI due to both the aligned biotite minerals and cracks, which have a common symmetry axis. We found that other sheet silicate-rich rocks have a similar anisotropy with the biotite schist, in which the TI-type anisotropy is characterized by the slow P- and S-wave velocities along the symmetry axis. This is caused by the preferred orientation of sheet silicate minerals and the extremely slow P- and S-wave velocities along the axis perpendicular to the silicate sheet compared to the directions along the silicate sheet. When rock contains a large percentage of highly oriented sheet silicates, the fast and slow shear waves exchange their polarities at some off-symmetry axis directions, indicating that the qS-wave (quasi-S wave) velocity exceeds the SH-wave velocity. The phase velocity distribution of qS wave shows an asymmetry with respect to the angle from the symmetry axis, which is characterized by a bulge in this distribution located near the symmetric axis. This is inherent to most sheet silicate minerals. When crack density of aligned cracks increases, the P-wave velocity along the symmetry axis decreases considerably. The qS-wave phase velocity in the off-axis directions also decreases, in accordance with the decrease of the P velocity along the symmetry axis. The asymmetry of the qS-wave phase velocity distribution increases as the P-wave velocity decreases along the symmetry axis. This relationship can be well understood by means of Berryman

  10. Climatic impact on isovolumetric weathering of a coarse-grained schist in the northern Piedmont Province of the central Atlantic states

    Science.gov (United States)

    Cleaves, E.T.

    1993-01-01

    The possible impact of periglacial climates on the rate of chemical weathering of a coarse-grained plagioclase-muscovite-quartz schist has been determined for a small watershed near Baltimore, Maryland. The isovolumetric chemical weathering model formulated from the geochemical mass balance study of the watershed shows that the weathering front advances at a velocity of 9.1 m/m.y., if the modern environmental parameters remain the same back through time. However, recent surficial geological mapping demonstrates that periglacial climates have impacted the area. Such an impact significantly affects two key chemical weathering parameters, the concentration of CO2 in the soil and groundwater moving past the weathering front. Depending upon the assumptions used in the model, the rate of saprolitization varies from 2.2 to 5.3 m/m.y. The possible impact of periglacial processes suggested by the chemical weathering rates indicates a need to reconsider theories of landscape evolution as they apply to the northern Piedmont Province of the mid-Atlantic states. I suggest that from the Late Miocene to the present that the major rivers have become incised in their present locations; this incision has enhanced groundwater circulation and chemical weathering such that crystalline rocks beneath interfluvial areas remain mantled by saprolite; and the saprolite mantle has been partially stripped as periglacial conditions alternate with humid-temperate conditions. ?? 1993.

  11. The role of strength anisotropy in the development of deep-seated gravitational slope deformation features in schist at Roys Peak, South Island, New Zealand

    Science.gov (United States)

    Brideau, M.

    2013-12-01

    This study looked at the interaction between the rock strength anisotropy and discontinuity orientations on the development of well-expressed deep-seated gravitational slope deformation (DSGSD) features around Roys Peak. The project area is located near the town of Wanaka in the Otago region of New Zealand's South Island. The Roys Peak area has well defined geomorphological features (antislope scarps and split ridges) typically associated with DSGSD over a distance extending almost 4.5 km along the Lake Wanaka Valley. The summit corresponds with the intersection of two prominent ridges running approximately north-south and east-west and has an elevation of 1580 metres above sea level with a local relief of 1250 m. The bedrock geology at Roys Peak consists of Late Paleozoic to Mid Mesozoic pelitic schist having a granitic protolith. The study area has been glaciated several times during the Quaternary Period. Glaciers have strongly influenced the landscape by rounding the spurs in the valley bottom and steepening the lower parts of mountains. Roys Peak is located approximately 75km south from the Alpine Fault (boundary between the Pacific and Australian plates) and as such the project area is not particularly seismically active with only 52 earthquakes with a magnitude greater than 4 within a 50km radius of the project area listed in the New Zealand Historical Earthquake Database. Engineering geological mapping at Roys Peak identified three discontinuity sets and a pervasive schistose fabric in a dip-slope position with the main valley orientation. The rock mass quality was described in the field using the Geological Strength Index (GSI). The observed rock mass quality at Roys Peak had a GSI range between 30-45. This corresponds to a blocky/disturbed/seamy structure with fair quality discontinuity surfaces. The intact rock strength of the schist rock was evaluated using field estimates, Schmidt hammer rebound values, and point load tests. The three methods overlap

  12. Recovery of uranium from liquors from shale attack by ion exchange; Recuperation de l'uranium des liqueurs d'attaque des schistes par echange d'ions

    Energy Technology Data Exchange (ETDEWEB)

    Parly, B; Pottier, P

    1959-04-01

    This report deals with the recovery of the uranium from a lot of shale mined at Schaentzel with an U content of 285 ppm. Recovery is realized by alkaline attack with a solution of 25 g/l Na{sub 2}CO{sub 3} at 75 C followed by absorption of the dissolved uranium by an anionic Amberlite resin, IRA 410. Final recovery is done by elution with a solution of M NaNO{sub 3}. These treatment tests determine the capacity of the resin in the case of the above solutions, verify the effects of recycling on this capacity, and finally, provide figures on the consumption of reactive and efficiency of attack and uranium recovery. (author) [French] Il s'agit de la recuperation, de l'uranium d'un lot de schiste- de Schaentzel (puits AO) dont la teneur en U est de 285 ppm. Cette recuperation consiste en une attaque alcaline par une solution de CO{sub 3}Na{sub 2} a 25 g/l et a 75 deg C. L'attaque est suivie de l'adsorption de l'uranium solubilise, sur resine anionique Amberlite IRA 410. On recupere finalement l'uranium par elution a l'aide d'une solution de NO{sub 3}Na M. Cet essai de traitement permit de determiner la capacite de la resine dans le cas de ces solutions, de verifier l'effet du recyclage sur la capacite et enfin de chiffrer la consommation en reactifs ainsi que les rendements d'attaque et de recuperation de l'uranium. (auteur)

  13. 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)

  14. 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

  15. 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

    Directory of Open Access Journals (Sweden)

    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

  16. Application of alkaline leaching to the extraction of uranium from shale of the Vosges; Application de la lixiviation alcaline a l'extraction de l'uranium du schiste des Vosges

    Energy Technology Data Exchange (ETDEWEB)

    Mouret, P; Pottier, P; Le Bris, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Soudan, P [Centre d' Etude de Lalumine, Compagnie Pechiney (France)

    1958-07-01

    Description of chemical treatment of Vosges shales to obtain uranium by alkaline leaching. Mineralogy aspects of ore, physical and chemical conditions of leaching, solid/liquid separation, uranium recovery by either ion exchange process or electrolytic precipitation. (author)Fren. [French] Description du traitement chimique des schistes des Vosges pour extraire l'uranium en milieu alcalin. L'aspect mineralogique, les conditions physiques et chimiques de la lixiviation, la separation solide/liquide et la recuperation de l'uranium soit par echangeurs d'ions, soit par precipitation electrolytique y sont exposes. (auteur)

  17. 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

  18. Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P-T paths and timing of metamorphism of deep-seated garnet-mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

    Science.gov (United States)

    Hyppolito, T.; García-Casco, A.; Juliani, C.; Meira, V. T.; Hall, C.

    2014-10-01

    In this study, the Paleozoic albite-epidote-amphibolite occurring as meter-sized intercalations within garnet-mica schist at Punta Sirena beach (Pichilemu region, central Chile) is characterized for the first time. These rocks constitute an unusual exposure of subduction-related rocks within the Paleozoic Coastal Accretionary Complex of central Chile. Whereas high pressure (HP) greenschist and cofacial metasediments are the predominant rocks forming the regional metamorphic basement, the garnet-mica schist and amphibolite yield higher P-T conditions (albite-epidote amphibolite facies) and an older metamorphic age. Combining detailed mineral chemistry and textural information, P-T calculations and Ar-Ar ages, including previously published material from the Paleozoic Accretionary Complex of central Chile, we show that the garnet-mica schist and associated amphibolite (locally retrograded to greenschist) are vestiges of the earliest subducted material now forming exotic bodies within the younger HP units of the paleo-accretionary wedge. These rocks are interpreted as having been formed during the onset of subduction at the southwestern margin of Gondwana. However, we show that the garnet-mica schist formed at a slightly greater depth (ca. 40 km) than the amphibolite (ca. 30 km) along the same hot-subduction gradient developed during the onset of subduction. Both lithotypes reached their peak-P conditions at ca. 335-330 Ma and underwent near-isobaric cooling followed by cooling and decompression (i.e., counterclockwise P-T paths). The forced return flow of the garnet-mica schist from the subduction channel started at ca. 320 Ma and triggered the exhumation of fragments of shallower accreted oceanic crust (amphibolite). Cores of phengite (garnet-mica schist) and amphibole (amphibolite) grains have similar chemical compositions in both the S1 and S2 domains, indicating rotation of these grains during the transposition of the burial-related (prograde peak-T) foliation S1

  19. 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

  20. The uranium bearing shale ore-body at St-Hippolyte (Haut-Rhin). An example of research with statistical methods; Le gisement des schistes uraniferes de St-Hippolyte (Haut-Rhin). Exemple d'etude par calculs statistiques

    Energy Technology Data Exchange (ETDEWEB)

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

    1958-07-01

    The uranium bearing shale ore-body at St-Hippolyte was mainly proved by drillings, the results of which were studied through statistical methods. The author gives an account of his conclusions regarding the distribution of mineralization, its origin and, the estimate of reserves. The uranium mineralization is irregularly distributed in shales. On a vertical line, levels could be singled out: they are similar, as far as lithology is concerned, but each of them is characterized by a grade-population, according to a lognormal distribution. Horizontally, a connection is noted between grades and the overlying barren sandstone bed. These considerations, as well as a statistical study of U/Ra ratio, induced the author to consider that the mineralization of the richest level has an hydrothermal origin. It is only through an uranium diffusion from that level that the others are mineralized. The uranium which is contained in poorest beds has a syn-genetic origin. Furthermore, statistical methods bring us to an evaluation of reserves. In such a case, the evaluation is equivalent to the ore obtained by common arithmetical methods. Moreover, we are able to state precisely the upper and lower limits where a true tonnage or a true grade could be given with a definite value of statistical certainty. Then the author has been able to study the separation of reserves in grade-groups and to foresee the effect of sorting in connection with the lower possible grade and with extraction units (wagons, lorries, etc...), on which the sorting will be done. To conclude, the author indicates the value of both classical and statistical methods. These two techniques are completing each other and they solve different problems. (author) [French] Le gisement des schistes uraniferes de St-Hippolyte a ete reconnu essentiellement par sondages, dont les resultats ont ete etudies par les methodes du calcul statistique. L'auteur expose les conclusions auxquelles il a ete amene et qui concernent: la

  1. 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.

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

    Indian Academy of Sciences (India)

    metamorphism, minerals that do not participate in the metamorphic ... (internal schistosity – Si) and the matrix foliation .... region along the longer edges of the garnet con- firms that ..... Sarkar S N, Trivedi J R and Gopalan K 1986 Rb-Sr whole.

  3. carbonaceous phyllite/graphitic schist in the Archean Kundarkocha

    Indian Academy of Sciences (India)

    rocks of noble metals (Meyers et al. 1990). Such complexes host gold deposits in North–East. Russia (Natalka, Mayskoe ..... carbonic phases using Laser Raman Spectrometry ... Graphite was formed by the reaction between CH4 and CO2.

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

    African Journals Online (AJOL)

    This enrichment – depletion signature is probably a consequence of the movement of metamorphic remobilised fluids along these shear zones during the Pan-African or earlier events. A further geochemical characterisation of the rock indicates that its protolith was an immature sub-greywacke to greywacke-type sediment ...

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

    Indian Academy of Sciences (India)

    R. Narasimhan, Krishtel eMaging Solutions

    the fluids could be of higher temperature origin. The initial Nd ... of mantle CO2 along shear zones in the lower crust led to the ..... tors such as permeability and composition of pro- ...... Shenberger D M and Barnes H L 1989 Solubility of gold in ...

  6. 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

  7. Metaultramafic schists and dismembered ophiolites of the Ashe Metamorphic Suite of northwestern North Carolina, USA

    Science.gov (United States)

    Raymond, Loren A.; Merschat, Arthur J.; Vance, R. Kelly

    2016-01-01

    Metaultramafic rocks (MUR) in the Ashe Metamorphic Suite (AMS) of northwestern North Carolina include quartz ± feldspar-bearing QF-amphibolites and quartz-deficient, locally talc-, chlorite-, and/or Mg-amphibole-bearing TC-amphibolites. Some workers divide TC-amphibolites into Todd and Edmonds types, based on mineral and geochemical differences, and we provisionally add a third type – olivine ± pyroxene-rich, Rich Mountain-type rocks. Regionally, MUR bodies range from equant, Rich Mountain- to highly elongate, Todd-TC-amphibolite-type bodies. The MURs exhibit three to five mineral associations containing assemblages with olivine, anthophyllitic amphibole, Mg-hornblende, Mg-actinolite, cummingtonite, and serpentine representing decreasing eclogite to greenschist facies grades of metamorphism over time. MUR protoliths are difficult to determine. Southwestern MUR bodies have remnant olivine ± pyroxene-rich assemblages representing ultrabasic-basic, dunite-peridotite-pyroxenite protoliths. Northeastern TC-amphibolite MURs contain hornblende and actinolitic amphiboles plus chlorites – aluminous and calcic assemblages suggesting to some that metasomatism of basic, QF-amphibolites yields all TC-amphibolites. Yet MgO-CaO-Al2O3 and trace element chemistries of many TC-amphibolites resemble compositions of plagioclase peridotites. We show that a few AMS TC-amphibolites had basaltic/gabbroic protoliths, while presenting arguments opposing application of the metasomatic hypothesis to all TC-amphibolites. We establish that MUR bodies are petrologically heterolithic and that TC-amphibolites are in contact with many rock types; that those with high Cr, Ni, and Mg have olivine- or pyroxene-dominated protoliths; that most exhibit three or more metamorphic mineral associations; and that contacts thought to be metasomatic are structural. Clearly, different MUR bodies have different chemistries representing various protoliths, and have different mineral assemblages, reflecting both chemical composition and metamorphic history. Spot sampling of heterolithic MUR bodies does not reveal MUR body character or history or allow ‘type’ designations. We recommend that the subdivision of MUR bodies into ‘types’ be abandoned and that the metasomatic hypothesis be carefully applied. AMS MURs and associated metamafic rocks likely represent fragments of dismembered ophiolites from various ophiolite types.

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

    NARCIS (Netherlands)

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

    2016-01-01

    Abstract 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

  9. 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

    in silicate-rich chromitite (similar to 50% modal chromite) and serpentinite (similar to 2% modal chromite) throughout the entire ultramafic sequence. However, the primary composition of chromite is preserved in the massive chromitites (similar to 60-75% modal chromite) from the Byrapur and the Bhaktarhalli...

  10. 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

  11. 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...

  12. Uranium in the black schists of Goesan (Ogcheon, Korea): relationships between organic matter and uranium

    International Nuclear Information System (INIS)

    Trichet, J.; Chun-Hyuck, O.

    1990-01-01

    The uranium deposit of Goesan is polyphased: its genesis resulted from sedimentary, diagenetic and metamorphic processes which occurred from late Proterozoic (presumed age of the deposition of the black shales) to late Trias. By its geochemical characters, this deposit resulted from the affinity existing between uranium and organic matter. The latter had a role both through the formation of organo-metallic complexes and as a reducing agent of the metal during the diagenetic evolution. Beside these factors favourable to metal accumulation, the possible development of evaporitic conditions and tectono-metamorphic processes can also have played an important role in the reconcentration of uranium as well as other metals [fr

  13. Shale gas, the flaws of the French prohibition; Gaz de schiste, les failles de l'interdit francais

    Energy Technology Data Exchange (ETDEWEB)

    Khalatbari, A.

    2011-12-15

    While describing the shale gas extraction technique (vertical deep drilling, and then horizontal drilling, hydraulic fracturing or maybe electric arc technique), this article gives an overview of the associated risks: massive use of water, lack of knowledge on the impact of the used chemicals, risk of pollution by methane of the underground water, risk of well tightness defects, risks associated with hydraulic fracturing. The main issues are discussed: the ecological assessment is still uncertain, France is a promising site, but will France resist to this treasure?

  14. Geochemical study of the insoluble organic material (kerogen) in the Oklo uranium ore and the associated Francevillian schists

    International Nuclear Information System (INIS)

    Vandenbroucke, M.; Rouzaud, J.N.; Oberlin, A.

    1978-01-01

    The purpose of this study was to describe the organic material associated with uranium ore and ore transformations undergone by it, in terms of the following problems: (1) In the natural reactor zones, evolution of the organic material in the core and as a function of the distance away from it; (2) Comparison of organic materials from a rich and a poor ore; (3) Intercomparison of organic materials in the dispersed and concentrated state; (4) Comparison of organic materials in the uranium ore zones and in the adjacent non-mineralized Francevillian. The organic material from the reactor core could not be isolated by the normal techniques of treatment with acid. It is found in other cases that the organic material is oxidized in the uranium-bearing sediments and that the nearer to the reaction zone, the greater the oxidation, irrespective of the state of dispersion of the organic material in the rock. The uranium content does not affect this phenomenon, which is attributed to the action of the water raised to a high temperature in the vicinity of the reaction zones. On the basis of the present distribution of organic material and uranium the authors suggest a pattern for the formation of the deposit that would take into account localization of the ore in the sandstones and the part played by organic material in the accumulation process. (author)

  15. 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; 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; Faculty of Agriculture, Kochi University; Shikoku Mountainous Region Sabo Work 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...

  16. The nevado-filábride complex in the western part of Sierra de los Filabres (Betic Internal Zone), structure and lithologic succession

    Energy Technology Data Exchange (ETDEWEB)

    Sanz de Galdeano, C.; López Garrido, A.

    2016-07-01

    In the western part of Sierra de los Filabres (in the Nevado-Filábride Complex, within the Betic Internal Zone) several tectonic units have been described, in varying numbers depending on the author describing them. However, new cartographical data show that the limits of these units pass through the lithological formations without displacing them. Moreover, the rocks belonging to some units that are supposedly situated in a lower tectonic position really belong to higher formations. From bottom to top, these lithological formations are the following: (1) dark schists and quartzites; (2) quartzites, sandstones, sands, lutites, schists, and mica schists; (3) schists; (4) marbles, schists, and mica schists. High-angle reverse faults are associated with the great E-W anticline of Sierra de los Filabres. The existence of sands and apparent lutites visibly interlayered between rocks, such as schists and mica schists with garnets, poses a metamorphic problem that has not as yet been addressed. (Author)

  17. 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, ...

  18. Journal of Earth System Science | Indian Academy of Sciences

    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 ...

  19. Metamorphic history of the Central Pyrenees Part II, Valle de Arán, Sheet 4

    NARCIS (Netherlands)

    Zwart, H.J.

    1963-01-01

    The structural geology and metamorphic petrology of the Bosost area in the Valle de Arán (Central Pyrenees) is discussed. The rocks exposed in this area consist of Cambro-Ordovician mica-schists with numerous granite and pegmatite bodies, phyllites and limestones; Silurian slates and schists and

  20. Geology and associated mineral occurrences of the Araxa Group, Mossamedes Region, Goias, Brazil

    International Nuclear Information System (INIS)

    Simoes, L.S.A.

    1984-01-01

    In the region of Mossamedes, State of Goias, Brazil, the Precambrian metamorphic rocks of the Araxa group were mapped at the scale of 1:25,000, with emphasis on stratigraphic, structural, petrographic and economic aspects. These metamorphites represent a continous stratigraphic sequence which, from bottom to top can be subdivided into five informal lithostratigraphic units: 1) psamitic unit (quartzite, metaconglomerate); 2) psamitic-pelitic unit (quartzite, quartz schist, muscovite schist); 3) lower pelitic - volcanic unit (chlorite - biotite schist, fine grained blastoporphyritic gneiss, amphibolite and calc-schist); 4) upper pelitic - volcanic unit (garnet muscovite schist, biotite schist and gneiss, amphibolite, magnetite muscovite schist); 5) gneissic unit (epidote biotite gneiss, amphibolite). Three types of meta-intrusive rocks were found, besides basic dykes related to Mesozoic magmatism. Four phases of deformation affected the volcano-sedimentary sequence;D 1 , D 2 , D 3 and D 4 , each of them developing distinct deformational features. Barrowian type metamorphism increases progressively from North to South from the biotite zone to the garnet zone (greenschist facies), reaching the staurolite-kyanite zone (amphibolite facies). The magmatism throughout the Group's evolution consists of mafic to felsic volcanic activity, mustly intermediary, as well as three intrusive events. Gold, copper and zinc minerals of economic interest occur within the studied area. The gold mineralizations are related to the pelitic-volcanic sequences. Copper occurs in several rocks from the pelitic-volcanic and gneissic sequences. (Author) [pt

  1. Chromian spinels in highly altered ultramafic rocks from the Sartohay ophiolitic mélange, Xinjiang, NW China

    Science.gov (United States)

    Qiu, Tian; Zhu, Yongfeng

    2018-06-01

    The Sartohay ophiolitic mélange is located in western Junggar (Xinjiang province, NW China), which is a major component of the core part of the Central Asian Orogenic Belt (CAOB). Chromian spinels in serpentinite, talc schist, carbonate-talc schist and listwaenite in Sartohay ophiolitic mélange retain primary compositions with Cr# of 0.39-0.65, Mg# = 0.48-0.67, and Fe3+# evolution of chromian spinels in highly altered ultramafic rocks from the Sartohay ophiolitic mélange. Chromian spinels in serpentinite and talc schist were rimmed by Cr-magnetite, which was dissolved completely during transformation from serpentinite/talc schist to listwaenite. Chromian spinels were then transformed into Fe2+-rich chromite in shear zones, which characterized by high fluid/rock ratios. This Fe2+-rich chromite and/or chromian spinels could then be transformed into Fe3+-rich chromite in oxidizing conditions at shallow levels.

  2. Episodic crustal growth in the Bundelkhand craton of central India ...

    Indian Academy of Sciences (India)

    Hiredya Chauhan

    2018-04-12

    Apr 12, 2018 ... geochemical features indicate formation of the K-granites by anhydrous partial melting of the Paleo- ...... A metamorphic episode from white mica schist is reported ...... monian G 2013 Central/eastern Indian Bundelkhand and.

  3. Preliminary Report for the location of drilling in the Raigon aquifer area

    International Nuclear Information System (INIS)

    Heinzen, W.; Santana, J.; Carrion, R.

    1991-01-01

    This work is about the geological and hydrogeological characteristics of Santa Lucia basin belongs to the Raison Aquifer. The tectonic basin of Santa Lucia is a structural complex constituted by the crystalline basement, gneisses, amphibolite s, mica schists and metamorfites

  4. lineament studies of rocks in omifunfun area, southwestern nigeria

    African Journals Online (AJOL)

    PROF EKWUEME

    Omifunfun area is situated in the southern part of Ife-Ilesa Schist Belt of the basement complex of ... The dominant one strikes in the same direction with the same Ifewara mylonitic foliation. ... fractures (joints and faults), drainage, road network,.

  5. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    ... belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at ... In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation structures. ... Journal of Earth System Science | News.

  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. Recommendations for the Development of a Dust Suppressant Test Operations Procedure (TOP) Performed at the U.S. Army Yuma Proving Ground

    Science.gov (United States)

    2010-02-08

    variety of bedrock types including: igneous ( basalt , granite, and rhyolite), metamorphic (schist and gneiss), and sedimentary rocks of Quaternary...TerraLOC® Standard formulation was applied. Chemical dust suppressant formulations vary widely, to include salts, oils, fiber mixtures and synthetic

  8. ETUDE DE LA DISTRIBUTION DES CATIONS ECHANGEABLES

    African Journals Online (AJOL)

    SEI Joseph

    J. Aouam sous le nom de schistes Mokattam et schistes cloisonnés. c- Le dévonien : Les dépôts du Dévonien inférieur sont constitués d'argilites indiquant une sédimentation calme de plate forme externe, qui va s'enrichir en nodules et calcaire. Cette sédimentation carbonatée va subir une perturbation, puisqu'au Dévonien ...

  9. Numerical analysis of the construction of Odelouca Dam using a Subloading Surface Soil Model

    OpenAIRE

    Brito, A.; Maranha, J. R.; Caldeira, L.

    2014-01-01

    Odelouca dam is an embankment dam, with 76 m height, recently constructed in the south of Portugal. It is zoned with a core consisting of colluvial and residual schist soil, and with soil-rockfill mixtures making up the shells (weathered schist with a significant fraction of coarse sized particles). This paper presents a numerical analysis of Odelouca dam construction. In this analysis the explicit finite difference program FLAC is used. An unconventional elastoplastic soil model, a Subloadin...

  10. Geochemistry of the Puna Austral and Cordillera Oriental basement

    International Nuclear Information System (INIS)

    Becchio, Raul; Lucassen, Friedrich; Franz, Gerhard; Kasemann, Simone

    1998-01-01

    Major and trace elements, rare earths, and 143 Nd/ 147 Nd and, 147 Sm/ 144 Nd isotope ratios have been determined in the Puna Austral and Cordillera Oriental basement. The basement is formed by high temperature amphibolite facies rocks ranulites (750-550 degrees C) and green schists. They are represented by schists, paragneiss, orthogneiss, migmatites, few metabasites, marbles and chalcosilicatic banks. Hypotheses on the formation and evolution of the basement are presented

  11. PIXE analysis of museum soapstone sculptures from Esie, south west Nigeria

    International Nuclear Information System (INIS)

    Olabanji, S.O.; Olarewaju, V.O.; Onabajo, O.

    1989-05-01

    The PIXE technique was employed for the study of Esie museum stone sculptures using 2.55 MeV protons from the 3 MeV tandem accelerator (NEC 3 UDH) in Lund, coupled with the geological and archaeological findings. The aim is to elucidate and decipher the prodigious but rather enigmatic and bewildering stone sculptures. PIXE results show that the composition of the stone sculptures are 40.69% talc-tremolite schist, 30.88% talc-chlorite schist, 15.20% talc-tremolite-anthophyllite schist and 13.24% talc-amphibolite schist. Thus the composition of Esie sculptures are found to be the same with the locally available talc-schists present around Esie. The geological evidence (mineralogical results) corroborated this as there was no textural or mineralogical difference between the talc-bearing country rock (outcrop) in Esie and the museum soapstone samples studied. Consequently, there is a very high probability that the sculptures were carved using the locally available talc-schists. (author). 7 refs, 4 figs, 2 tabs

  12. Listwaenite in the Sartohay ophiolitic mélange (Xinjiang, China): A genetic model based on petrology, U-Pb chronology and trace element geochemistry

    Science.gov (United States)

    Qiu, Tian; Zhu, Yongfeng

    2018-03-01

    Listwaenite lenses in the Sartohay ophiolitic mélange (Xinjiang, China) were formed via reactions between serpentinite and metasomatic fluids. First, serpentinite changed into talc schist via the reaction of serpentine + CO2 → talc + magnesite + H2O. Second, talc schist changed into listwaenite via the reaction of talc + CO2 → magnesite + quartz + H2O. Magnetite was progressively destroyed during transformation from serpentinite to talc schist, and completely consumed in listwaenite. Zircon crystals 30-100 μm long, disseminating in talc schist, undeformed listwaenite and mylonitized listwaenite, coexist with talc, quartz and magnesite, while micron-sized zircon grains (ages (302.9 ± 6.8 Ma, 299.7 ± 5.5 Ma and 296.5 ± 3.5 Ma), and are thought to represent the age of formation of the talc schist and listwaenite. These ages are indistinguishable within errors and suggest a rapid transformation from talc schist to listwaenite. Some zircon rims in samples of the undeformed listwaenite and mylonitized listwaenite give much younger apparent U-Pb ages (280-277 Ma), which could be interpreted as a recrystallization age reflecting late-stage shearing in the Sartohay ophiolitic mélange.

  13. Kyanite from the Deep Freeze Range, Terra Nova Bay, Antarctica

    International Nuclear Information System (INIS)

    Skinner, D.N.B.; Estrada, S.

    2002-01-01

    During GANOVEX VII in 1992, kyanite was discovered in quartz veins on the southwest flank of Mt Levick, in the Deep Freeze Range, Terra Nova Bay, Antarctica. The quartz veins cut an isoclinally (D 1 ) folded sequence of low-grade (Mu-Bt-Crd±And±St) pelitic schist with associated para-amphibolites, calc-silicates, and quartzites (Priestley Formation), which forms the western, steeply dipping to overturned limb of a D 2 , kilometric fold. The schists grade northeastwards into higher grade schists (Kfs-Sil-Crd) of the low-angle upper limb of the D 2 fold, and thus the regional metamorphism postdates the fold. D 3 southeast-verging folds lie on the upper limb. The kyanite crystals (up to 3.5 cm long) occur with paragonitic muscovite and minor plagioclase (An 36 . The quartz veins and saddle reefs are cleaved and boudinaged, but the kyanite shows only mild deformation suggesting late tectonic growth. There is no indication that the host schists entered the stability field of kyanite. The change in P-T conditions that promoted the growth of kyanite appears to have been transient and temporally insufficient to allow the country rocks to react. It is suggested that the action of the nearby Boomerang Thrust bringing older gneiss over the Priestley Formation schists could have generated the D 3 folds and provided the necessary overpressure conditions for the kyanite to grow from the quartz vein fluids. (author). 23 refs., 5 figs., 1 tab

  14. Time constraint based on zircon dating for the Jacareacanga group (Tapajos province, Amazon craton, Brazil)

    International Nuclear Information System (INIS)

    Almeida, M.E.; Ferreira, A.L; Macambira, M.J.B.; Sachett, C.R

    2001-01-01

    During long time the Jacareacanga meta-volcano sedimentary sequence have been interpreted as Archean greenstone belt terrain. However, recent data are indicating younger U-Pb ages about 2.1 Ga. In the Tapajos Province (Amazon Craton), the Cuiu-Cuiu Complex (2.00-2.03 Ga), Creporizao granitoids (1.99-1.96 Ga) and Jacareacanga Group are the oldest rocks. The Jacareancaga Group is composed by quartzmica schists, quartzites, ferruginous quartzite, metachert, and minor talc-tremolite-chlorite schist, actinolite-epidote schist, hornfels, metargilites and metawackes metamorphosed in low to medium-grade conditions. The aim of the present paper is to estabilish the maximum age of Jacareacanga sedimentation and identify probable sources in Espirito Santo region (Espirito Santo muscovite-biotite schist). In this research, similar and new results are obtained by zircon evaporation methodology. This research shows geochronological data about the Espirito Santo muscovite-biotite schist related to Jacareacanga Group (Ferreira et al., 2000) in Tapajos Province (Amazon Craton). The area is located near Amazonas and Para States boundary (Northern Brazil) and the sample was obtained at Espirito Santo (garimpo) small-scale gold mine (06 o 00min.48seg.S,58 o 08min.17seg.W) (au)

  15. 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.

  16. 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).

  17. Geology and petrography of basement in south extreme in Sierra Grande de San Luis, Argentina

    International Nuclear Information System (INIS)

    Morosini, A.; Ortiz Suarez, A.

    2007-01-01

    In the south of the Sierra de San Luis is recognized a basement composed by La Escalerilla and Los Puquios granites, accompanied by schist, mylonite s and mafic-ultramafic rocks. The schists, La Escalerilla granite and the mafic -ultramafic rocks are affected by a regional metamorphism in anphibolites facies, the two first present a N-S foliation di ping to east. The mylonite s correspond to a second event of deformation, distributed in thin belts of NNE-SSO direction and inclination to east, developed in green schist to anphibolites facies. Los Puquios granite represents the more young of the basement rocks and the intrusion was associated with a shear zone. Los Puquios granite forms dikes and small plutons cutting La Escalerilla granite and micas chits in high cortical levels

  18. Metasomatism, Fluid Overpressure and Brecciation at the Slab-Mantle Interface: Insights from the Livingstone Fault, New Zealand

    Science.gov (United States)

    Tarling, M.; Smith, S. A. F.; Scott, J.

    2017-12-01

    Juxtaposition of mantle peridotite and serpentinite against quartzofeldspathic and mafic schists occurs along the shallow slab-mantle interface in some subduction zones. This part of the subduction interface has been invoked as a possible source region of episodic tremor and slow slip, yet geological observations of fault zone structures and chemical reactions pertinent to this region are quite rare. The >1000 km long Livingstone Fault in New Zealand is a superbly exposed fault zone that provides a suitable analogue (both in terms of scale and the rock types involved) for the shallow slab-mantle interface. The fault is characterized by a foliated and highly sheared serpentinite mélange tens to several hundreds of meters wide that separates (partially serpentinised) peridotites from quartzofeldspathic schists. Talc- and tremolite-forming metasomatic reactions occurred along the margins of the mélange and around entrained pods due to mixing of serpentinite with silica- and calcium-rich fluids derived from the adjacent quartzofeldspathic schist. The metasomatic reactions generated significant volumes of water at the melange-schist contact that became trapped between the two relatively impermeable fault zone lithologies. On the schist side of the contact, brittle faulting was promoted by the formation of a laterally-continuous silicified zone up to tens of metres wide. On the melange side, a zone up to tens of metres wide of `crackle-breccias' containing veined stockworks of tremolite indicates periodic increases of pore pressure sufficient to cause hydraulic fracture of serpentinite. The crackle-breccias are multi-generational indicating that this process was episodic. Sr and Nd isotope data and permeability calculations suggest that the episodic brecciation process was critical to the transfer of fluids across the melange. Our observations suggest that fluid-producing metasomatic reactions along the shallow slab-mantle interface may contribute to the tremor signal

  19. 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)

  20. Odelouca Dam Construction: Numerical Analysis

    OpenAIRE

    Brito, A.; Maranha, J. R.; Caldeira, L.

    2012-01-01

    Odelouca dam is an embankment dam, with 76 m height, recently constructed in the south of Portugal. It is zoned with a core consisting of colluvial and residual schist soil and with soil-rockfill mixtures making up the shells (weathered schist with a significant fraction of coarse sized particles). This paper presents a numerical analysis of Odelouca Dam`s construction. The material con-stants of the soil model used are determined from a comprehensive testing programme carried out in the C...

  1. Applications of petrography and electron microprobe analysis to the study of Indian stone sculpture

    International Nuclear Information System (INIS)

    Newman, R.

    1992-01-01

    Examples of research on ancient Indian stone artefacts utilizing petrographic examination coupled with qualitative and quantitative electron beam microprobe analysis of specific minerals are described. Types of artefacts discussed include Gandharan schist sculptures, Pala dynasty phyllite and schist objects from eastern India. Hoysala sculptures from Karnataka state (southern India), and sandstone objects from northern India. In spite of the rich history of stone sculpture in the Indian subcontinent, characterization studies to date have been limited in scope, typically involving unprovenanced artefacts. The examples described point to areas in which more extensive research could produce useful information for the provenancing of artefacts. (author)

  2. The emerald deposits of ultramafic rocks of Capoeirana and Belmont, State of Minas Gerais, Brazil

    International Nuclear Information System (INIS)

    Abreu Machado, G.; Schorscher, H.

    1998-01-01

    The emerald deposits of Capoeirana and Belmont, State of Minas Gerais (MG), Brazil, occur vithin an area comprising a deeply weathered Archean Metavulcano-Sedimentary Sequence (SVS) in tectonic contact with the Borrachudos Metagranitoids (GB) and Fluorite bearing Foliated Metagranitoids (MGF). The SVS is formed by intercalation s of ultramafic schists and amphibolites, basic to intermediate amphibolites, vulcanoclastic, metapelitic and calcsilicate schists and gneisses, banded iron formation and metacherts. The metaultramafic rocks include minor chromitite cumulates and occur at the base of the SVS. When metasomatized in the shear zones adjoining GB and MGF they host emerald mineralizations. (author)

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

    African Journals Online (AJOL)

    Selected physical and chemical properties and nutrient ratios on three landscape positions (interfluve crest, middle slope and foot slope) were examined on soils formed on banded gneiss and quartzite schist parent materials. Parent material significantly (p<0.05) influenced gravel, coarse sand and copper contents in the ...

  4. Metamorphism on Ios and the geological history of the Southern Cyclades, Greece

    NARCIS (Netherlands)

    Maar, P.A. van der

    1981-01-01

    The geology and petrology of the island of los, Greece are outlined in chapter I. The geology is determined by a mantled gneiss dome which forms the basement, on top of which a marble-schist series is emplaced. The various rocks of the island are described petrologically and their mineral

  5. Metamorphism on Ios and the geological history of the Southern Cyclades, Greece

    NARCIS (Netherlands)

    van der Maar, P.A.

    1981-01-01

    The geology and petrology of the island of los, Greece are outlined in chapter I. The geology is determined by a mantled gneiss dome which forms the basement, on top of which a marble-schist series is emplaced. The various rocks of the island are described petrologically and their mineral contents

  6. Geology and geochemistry of palaeoproterozoic low-grade ...

    Indian Academy of Sciences (India)

    these volcanic rocks have been metamorphosed to green-schist facies, some ... is generally consistent with fractionation mechanism, also suggested by a change in colour of the .... lying formations show similar attitude. .... other geochemical parameters and therefore only ..... than one phase would potentially result in such.

  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. K-Ar geochronology of the Survey Pass, Ambler River and Eastern Baird Mountains quadrangles, southwestern Brooks Range, Alaska

    Science.gov (United States)

    Turner, Donald L.; Forbes, R.B.; Mayfield, C.F.

    1978-01-01

    We report 76 previously unpublished K-Ar mineral ages from 47 metamorphic and igneous rocks in the southwestern Brooks Range. The pattern of radiometric ages is complex, reflecting the complex geologic history of this area. Local and regional radiometric evidence suggests that the southern Brooks Range schist belt has, at least in part, undergone a late Precambrian metamorphism and that the parent sedimentary and igneous rocks for the metamorphic rocks dated as late Precambrian are at least this old (Precambrian Z). This schist terrane experienced a major thermal event in mid-Cretaceous time, causing widespread resetting of nearly all K-Ar mica ages. A series of apparent ages intermediate between late Precambrian and mid-Cretaceous are interpreted as indicating varying amounts of partial argon loss from older rocks during the Cretaceous event. The schist belt is characterized by dominant metasediments and subordinate metabasites and metafelsites. Blueschists occur within the schist belt from the Chandalar quadrangle westward to the Baird Mountains quadrangle, but geologic evidence does not support the existence of a fossil subduction zone.

  9. Wynoochee Dam Foundation Report

    Science.gov (United States)

    1988-01-01

    schists and in propylitized andesite volcanic rocks. Tests on chlorite-bearing graywackes (Lumni Island and Robe Quarry, Seattle District) and... propylitized chlorite-bearing andesites (Blue River and Lookout Point Dams, Portland District) have shown these rocks to be durable materials with only minor

  10. 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 ...

  11. Transfer of Metasupracrustal Rocks to Midcrustal Depths in the North Cascades Continental Magmatic Arc, Skagit Gneiss Complex, Washington

    Science.gov (United States)

    Sauer, K. B.; Gordon, S. M.; Miller, R. B.; Vervoort, J. D.; Fisher, C. M.

    2017-12-01

    The metasupracrustal units within the north central Chelan block of the North Cascades Range, Washington, are investigated to determine mechanisms and timescales of supracrustal rock incorporation into the deep crust of continental magmatic arcs. Zircon U-Pb and Hf-isotope analyses were used to characterize the protoliths of metasedimentary and metaigneous rocks from the Skagit Gneiss Complex, metasupracrustal rocks from the Cascade River Schist, and metavolcanic rocks from the Napeequa Schist. Skagit Gneiss Complex metasedimentary rocks have (1) a wide range of zircon U-Pb dates from Proterozoic to latest Cretaceous and (2) a more limited range of dates, from Late Triassic to latest Cretaceous, and a lack of Proterozoic dates. Two samples from the Cascade River Schist are characterized by Late Cretaceous protoliths. Amphibolites from the Napeequa Schist have Late Triassic protoliths. Similarities between the Skagit Gneiss metasediments and accretionary wedge and forearc sediments in northwestern Washington and Southern California indicate that the protolith for these units was likely deposited in a forearc basin and/or accretionary wedge in the Early to Late Cretaceous (circa 134-79 Ma). Sediment was likely underthrust into the active arc by circa 74-65 Ma, as soon as 7 Ma after deposition, and intruded by voluminous magmas. The incorporation of metasupracrustal units aligns with the timing of major arc magmatism in the North Cascades (circa 79-60 Ma) and may indicate a link between the burial of sediments and pluton emplacement.

  12. Skarn and ore formation at Seriphos, Greece as a consequence of granodiorite intrusion

    NARCIS (Netherlands)

    Salemink, J.

    1985-01-01

    On the island of Seriphos, Greece, the shallow intrusion of a granodiorite pluton into a series of previously regionally metamorphosed gneisses, marbles and marble-bearing schists produced a contact metamorphic aureole and extensive deposits of Ca-Fe-Mg skarns and Fe-ores. Structural and

  13. adaptation et selection de varietes performantes de riz pluvi

    African Journals Online (AJOL)

    PROJET SOJA

    Mots- clés : Résistivité, phosphates, filtrage, contours, Sidi Chennane, Maroc. .... Toutes les formations reposent par discordance sur les schistes et les .... L'image de départ I(x,y) n'étant pas une fonction continue mais discrète à cause de la.

  14. determination of origin and channel sediments of o on of origin and ...

    African Journals Online (AJOL)

    user pc

    2017-12-02

    Dec 2, 2017 ... south-western Nigeria, is part of Nigerian complex which belongs to the. Precambrian to Early Paleozoic orogeny, comprises. Precambrian crystalline rocks with associated infold. Schist belts. The South-western Nigeria that hosts the study area (Osi) is gener represented by series of older metasediments a.

  15. Geochemistry of sericite deposits at the base of the Paleoproterozoic ...

    Indian Academy of Sciences (India)

    Paleosols are useful rock types for understanding the .... rock contains blades of kyanite. ... Figure 2. Typical section, illustrating the occurrence of sericite deposits near Barodia quarry. Note that .... (c) Sericite schist of Madar area showing variable grain sizes of mica. ... dards that were analyzed during the same runs as the.

  16. STRUCTURAL EVOLUTION OF THE KILOMBERO

    African Journals Online (AJOL)

    The gneissic layering has a general strike of 020 and dip about 35° towards WNW but occasionally they show varying attitudes due to folding and migmatization (Fig. 3). The biotite gneiss, quartzo-felspathic gneiss and the amphibolitic biotite schist contain pervasive mineral foliation defined by preferred orientation of biotite ...

  17. Author Details

    African Journals Online (AJOL)

    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 in Ago-Iwoye area, southwestern Nigeria

  18. 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 ...

  19. 77 FR 51993 - Western Technical College; Notice of Availability of Environmental Assessment

    Science.gov (United States)

    2012-08-28

    ... project area (Source: Normandeau Associates, Inc., 2002)... Table 6. Sustained and burst swimming speeds... time, followed by a layer of Potsdam sandstone surface rock. The Potsdam sandstone layer of this... layer is Archaean-age basement rock, namely highly metamorphic gneiss, granite, and schists. The basin...

  20. 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 ...

  1. The age of the Takatika Grit, Chatham Islands, New Zealand

    NARCIS (Netherlands)

    Hollis, Christopher J.; Stickley, Catherine E.; Bijl, Peter K.; Schiøler, Poul; Clowes, Christopher D.; Li, Xun; Campbell, Hamish

    2017-01-01

    The oldest Paleogene strata on Chatham Islands, east of New Zealand, are the phosphatized conglomerates and sandstones of the Takatika Grit that crops out on the northeastern coast at Tioriori and unconformably overlies the Chatham Schist. An intact Cretaceous–Paleogene boundary transition is not

  2. Stable isotopic information on calcareous pelitic rocks in the Tizapa volcanogenic massive sulfide deposit area, the United Mexican States

    International Nuclear Information System (INIS)

    Morozumi, Haruhisa; Metsugi, Hideya; Kita, Yoshiyuki; Suzuki, Toru

    1999-01-01

    Tizapa volcanogenic massive sulfide (VMS) deposit is hosted in greenschist facies metamorphic rocks; footwall is green schist of felsic to mafic metavolcanic rocks and hanging wall is graphite schist of metasedimentary pelitic rock. Pb-Pb dating of ore samples indicates 103.4Ma to 156.3Ma for the age of mineralization (JICA/MMAJ, 1991). Hanging wall graphite schist is partially calcareous and overlaid by upper formations consisting of calcareous shake and limestone. δ 13 C(per mille) PDB values were measured for carbonate and organic material in the graphite schist, and δ 18 O(per mille) SMOW values were also measured for same carbonate. Although carbonate and organic material were affected by the metamorphism after mineralization, δ 18 O of carbonate decreases from +22.1 per mille to +17.9 per mille, δ 13 C of carbonate decreases from +0.8 per mille to -4.3 per mille and δ 13 C of organic material decreases from -10.0 per mille to -15.6 per mille with the decrease of vertical distances to ore deposit from 54.20 m to 10.28 m. This phenomenon might indicate the change of sedimentary environment of the reduced condition where the sulfides were precipitated, with the change of temperature. If this assumption is adequate, the method applied in this study is useful for semi-quantitative evaluation to distinguish the favorable condition for the precipitation of sulfides of VMS. (author)

  3. Journal of Mining and Geology - Vol 38, No 2 (2002)

    African Journals Online (AJOL)

    Parageneses, conditions and timing of the metamamorphism of the metapeletic rocks in the Ilesha schist belt, southwestern Nigeria · EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. OA IGE, MI HOLNESS, 71-80. http://dx.doi.org/10.4314/jmg.v38i2.18777 ...

  4. Geochemical trends in the weathered profiles above granite gneiss ...

    African Journals Online (AJOL)

    Geochemical trends in the weathered profiles above granite gneiss and schist of Abeokuta area, southwestern Nigeria. Anthony T Bolarinwa, Anthony A Elueze. Abstract. No Abstract. Journal of Mining and Geology 2005, Vol. 41(1): 19-31. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT ...

  5. OSUN STATE, SOUTHWESTERN NIGERIA.

    African Journals Online (AJOL)

    garnet schists. (b) A volcano-sedimentary western facies composed ... aim of this work to describe the occurrence of pseudotachylite ... In some localities, it occurs in close association with ..... Evidence for late Precambrian plate tectonics in West. , Africa. ... Closure and Continental Collision in the 1 loggar-lforas. Segment ...

  6. Stratigraphy, provenance, and diagenesis of the Cretaceous Horse Range Formation, east Otago, New Zealand

    International Nuclear Information System (INIS)

    Mitchell, M.; Craw, D.; Landis, C.A.; Frew, R.

    2009-01-01

    The Horse Range Formation is a structurally controlled late Early Cretaceous to early Late Cretaceous nonmarine unit in east Otago, South Island, New Zealand, containing immature lithic debris. Clasts are generally rounded, with only minor subangular material. The formation contains clasts derived from two principal basement sources: schist and greywacke. Schist debris is most abundant at the base of the described section, and this material is dominated (>60%) by quartz from the greenschist facies core of the Otago Schist belt. Conglomerates with >70% greywacke clasts constitute most of the upper part of the Horse Range Formation. These greywacke conglomerates have a matrix of sand derived mainly from schist. A 60 m thick wedge of quartz-rich, locally carbonaceous sand occurs interlayered with greywacke conglomerates. The Horse Range Formation rests on sub-greenschist facies semischist, which forms only a small proportion ( 18 O SMOW near +24 permil and δ 13 C PDB near -2 permil, and was partly dissolved and redeposited from the immature basement debris (metamorphic calcite) and partly introduced from overlying Late Cretaceous and Teriary marine sediments by groundwater. (author). 43 refs., 11 figs., 1 tab.

  7. 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 ...

  8. Journal of Earth System Science | Indian Academy of Sciences

    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 ...

  9. 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-

  10. Deformation Mechanisms of Darreh Sary Metapelites, Sanandaj‒Sirjan Zone, Iran

    Science.gov (United States)

    Hemmati, O.; Tabatabaei Manesh, S. M.; Nadimi, A. R.

    2018-03-01

    The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275-375, 375-500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed.

  11. PETROCHEMISTRY, Pb ISOTOPE SYSTEMATICS, AND ...

    African Journals Online (AJOL)

    The petrology, geochemistry, geotectonic setting and common Pb isotope model ages for the granite gneisses in Ilesha schist belt have been studied and presented in this paper. These gneisses, apart from the normal rock-forming silicates, contain apatite, monazite, ilmenite and zircon in trace amounts. The occurrence of ...

  12. Global Journal of Pure and Applied Sciences - Vol 7, No 1 (2001)

    African Journals Online (AJOL)

    Agriculture and Biological Sciences Post-harvest ... The geochemistry, tectonic setting and origin of the massive melanocratic amphibolite in the Ilesha schist belt, Southwestern Nigeria. ... Electrical resistivity soundings to determine subsurface contamination in the vicinity of · EMAIL FULL TEXT EMAIL FULL TEXT

  13. 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 ...

  14. Selection and testing of ballast stones for underground railway tracks

    African Journals Online (AJOL)

    Ballast is broken pieces of hard rocks such as sandstones, schist, etc. approximately 25- 60 mm size, over which the railway tracks are laid. The function of the ballast is to transfer the applied load over a large surface, provide adequate elasticity, prevent creep and hold the sleepers in position. Also under wet conditions, ...

  15. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 110; Issue 2 ... It follows that concentrations of these particle-active elements must have varied in the past with ... REE geochemistry of ore zones in the Archean auriferous schist belts of the eastern ... Estimation of source parameters of Chamoli Earthquake, India.

  16. 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 (Ppinaster stands (r=-0.667, Ppinaster growing over schists (r=-0.833, Ppinaster 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 trees seems to be also strongly influenced by the underlying parent material, young trees from granite stands having a statistically higher 13C-isotopic composition (P<0.05) than young trees from schists stands. Copyright (c) 2005 John Wiley & Sons, Ltd.

  17. Tectonic Evolution of Jabal Tays Ophiolite Complex, Eastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    AlHumidan, Saad; Kassem, Osama; Almutairi, Majed; Al-Faifi, Hussain; Kahal, Ali

    2017-04-01

    Microstructural analysis is important for investigation of tectonic evaluation of Jable Tays area. Furthermore, the Jable Tays ophiolite complex is effected by Al Amar -Idsas fault. The nature of the Al Amar-Idsas fault is a part of the Eastern Arabian Shield, which was subjected to multiple interpretations. Through fieldwork investigation, microscopic examination, and microstructural analysis, we aim to understand the evolution and tectonic setting of the Jable Tays area. Finite-strain data displays that the Abt schist, the metavolcanics and the metagranites are highly to moderately deformed. The axial ratios in the XZ section range from 1.40 to 2.20. The long axes of the finite-strain ellipsoids trend NW- SE and W-E in the Jable Tays area while, their short axes are subvertical to subhorizontal foliations. The strain magnitude does not increase towards the tectonic contacts between the Abt schist and metavolcano-sedimentary. While majority of the obtained data indicate a dominant oblate with minor prolate strain symmetries in the Abt schist, metavolcano-sedimentary and metagranites. The strain data also indicate flattening with some constriction. We assume that the Abt schist and the metavolcano-sedimentry rocks have similar deformation behavior. The finite strain in the studied rocks accumulated during the metamorphism that effected by thrusting activity. Based on these results, we finally concluded that the contact between Abt schist and metavolcano-sedimentary rocks were formed during the progressive thrusting under brittle to semi-ductile deformation conditions by simple shear that also involved a component of vertical shortening, causing subhorizontal foliation in Jable Tays area.

  18. Cation export by overland flow in a recently burnt forest area in north-central Portugal.

    Science.gov (United States)

    Machado, A I; Serpa, D; Ferreira, R V; Rodríguez-Blanco, M L; Pinto, R; Nunes, M I; Cerqueira, M A; Keizer, J J

    2015-08-15

    The current fire regime in the Mediterranean Basin constitutes a serious threat to natural ecosystems because it drastically enhances surface runoff and soil erosion in the affected areas. Besides soil particles themselves, soil cations can be lost by fire-enhanced overland flow, increasing the risk of fertility loss of the typically shallow and nutrient poor Mediterranean soils. Although the importance of cations for land-use sustainability is widely recognized, cation losses by post-fire runoff have received little research attention. The present study aimed to address this research gap by assessing total exports of Na(+), K(+), Ca(2+) and Mg(2+) in a recently burnt forest area in north-central Portugal. These exports were compared for two types of planted forest (eucalypt vs. maritime pine plantations), two types of parent materials (schist vs. granite) and for two spatial scales (micro-plot vs. hill slope). The study sites were a eucalypt plantation on granite (BEG), a eucalypt plantation on schist (BES) and a maritime pine plantation on schist (BPS). Overland flow samples were collected during the first six months after the wildfire. Cation losses differed strikingly between the two forest types on schist, being higher at the eucalypt than pine site. This difference was evident at both spatial scales, and probably due to the extensive cover of a needle cast from the scorched pine crowns. The role of parent material in cation export was less straightforward as it varied with spatial scale. Cation losses were higher for the eucalypt plantation on schist than for that on granite at the micro-plot scale, whereas the reverse was observed at the hill slope scale. Finally, cation yields were higher at the micro-plot than slope scale, in agreement with the general notion of scaling-effect in runoff generation. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Short-term nitrogen losses by overland flow in a recently burnt forest area in north-central Portugal: A study at micro-plot scale.

    Science.gov (United States)

    Ferreira, R V; Serpa, D; Machado, A I; Rodríguez-Blanco, M L; Santos, L F; Taboada-Castro, M T; Cerqueira, M A; Keizer, J J

    2016-12-01

    Over the past decades, wildfires have affected extensive areas of the Mediterranean region with negative impacts on the environment. Most of the studies on fire-affected areas have focused on sediment losses by overland flow, whereas few have addressed post-fire nutrient export. The present study aimed to address this research gap by assessing nitrogen (nitrate and total nitrogen) losses by overland flow in a recently burnt area in north-central Portugal. To this end, three burnt slopes were selected for their contrasting forest types (eucalypt vs. pine) and parent materials (granite vs. schist). The selected study sites were a eucalypt site on granite (BEG), a eucalypt site on schist (BES) and a maritime pine site on schist (BPS). Overland flow samples were collected during the first six months after the wildfire on a 1- to 2-weekly basis, after which this study had to be cancelled due to bench terracing of some of the sites. A peak in total nitrogen concentrations was observed in burnt areas immediately after the first post-fire rainfall event as a response to the erosion of the N-enriched ash layer. After this initial peak, smaller peaks were observed throughout the study period, mainly as a response to overland flow and/or erosion events. Nitrogen export differed strikingly between the two types of forests on schist, being higher at the eucalypt than at the pine site, due to the lack of a protective soil layer. Parent material did not play an important role on nitrogen export by overland flow since no significant differences were found between the eucalypt sites on granite and schist. The present study provides some insight into the differences in post-fire soil fertility losses between forest types and parent materials in the Mediterranean region, which is crucial information for defining post-fire land management measures to reduce soil degradation. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. 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

  1. Geochemistry and mineralogy of the radioactive minerals associated with some pegmatite veins of the Ukma-Nawahatu-Hursi sector, Purulia Dist., W.B., in the precambrian Chhotanagpur gneissic complex

    International Nuclear Information System (INIS)

    Baidya, Tapan Kumar

    2013-01-01

    Some barite-bearing pegmatites in the Ukma-Nawahatu-Hursi sector (23° 25'-26'N, 86° 02'-04'E) of the Purulia dist., West Bengal, have association of radioactive minerals in the form of coarse grained pitchblack lumps and irregular patches. This radioactive belt of about 15 km length running through Ukma, Nawahatu and Hursi areas follows ENE-WSW trending shear zone. The barite-bearing pegmatites occur as lenses or lenticular veins hosted by garnetiferous sillimanite-biotite-quartz-schist or occasionally by migmatite. Near Nawahatu the radioactive barite-pegmatite vein occurs at or near the junction between footwall amphibolite and hangingwall garnetiferous schist. The pegmatite veins have mainly followed the schistosity of the host rock and dip 70°-80° towards south

  2. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Finland

    International Nuclear Information System (INIS)

    1977-11-01

    Finland covers an area of 337,000 skm. One third of the country lies north of the northern polar circle. 31,613 skm are covered by lakes. 71% of the landscape are covered by coniferous -wood. Climatlcal conditions are continental. The topography of the country is gently rolling with highest elevations of 300 m in the northern part. The most interesting geological units for uranium are Karelian, marginal meta-sediments, mainly quarzites and conglomerates but also schists. These schists are intruded by orogenlc plutonic rocks which are 1800-My-old. Potassium granites are common adjacent to the contact of the Pre-karelian basement (2500 My). In addition to these geological environment uranium and thorium minerals have been found in a large carbonatite in northern Finland, which is explored now

  3. Investigation into relations between physical and electrical properties of rocks and concretes

    Science.gov (United States)

    Sertçelik, İbrahim; Kurtuluş, Cengiz; Sertçelik, Fadime; Pekşen, Ertan; Aşçı, Metin

    2018-02-01

    The physical and electrical properties of natural rocks, namely limestone, sandstone, amphibolite, arkose, schist, granite, basalt, and concrete were investigated in order to characterize the relationships between these properties. The measurements were conducted on 96 cylindrical specimens of limestone, sandstone, amphibolite, arkose, schist, granite, basalt, and 14 cubic concrete samples. Strong correlations between ultrasonic pulse velocity (UPV), uniaxial compressive strength (UCS), electrical resistivity, and chargeability were confirmed. High correlation coefficients were observed among the properties, varying between 0.53 and 0.92 for all the rocks and concrete. Test results show the following relations among the corresponding parameters: the UPV increases with the increase in UCS, resistivity decreases with the decrease in chargeability for all rocks and concrete, and the electrical resistivities of rock and concrete decrease with the increase in chargeability.

  4. Are the Vinjamur rocks carbonatites or meta-limestones?

    Energy Technology Data Exchange (ETDEWEB)

    Subbarao, K V; Bhaskar Rao, B [Indian Institute of Technology, Bombay (India). Dept. of Earth Sciences; Le Bas, M J [Univ. of Leicester, Leicester (United Kingdom). Dept. of Geology

    1995-08-01

    New whole-rock rare earth element (REE) data for the metacarbonate rocks inter bedded with schists at Vinjamur in the Nellore schist belt of Andhra Pradesh, show low total REE contents ({sigma}9-128 ppm) that are inconsistent with an igneous carbonatitic origin but which correspond more closely with a sedimentary limestone origin. The REE data of these rocks however, do not give absolute discrimination between marbles of meta-limestone and metacarbonatite origin. Micro-probe analytical data give better discrimination, and the chemical compositions of the calcite, micas, amphibole, plagioclase, apatite, monazite and staurolite in the Vinjamur marbles give strong and consistent evidence of a metamorphosed sedimentary rather than an igneous origin. (author). 35 refs., 7 figs., 9 tabs.

  5. Geochemistry and source of iron-formation from Guanhaes group, Guanhaes district, Minas Gerais, Brazil

    International Nuclear Information System (INIS)

    Sad, J.H.G.; Chiodi Filho, C.; Magalhaes, J.M.M.; Carelos, P.M.

    1990-01-01

    The Guanhaes district is underlain by metavolcano-sedimentary rocks of the Guanhaes Group, emplaced over an older Archean basement and intruded by granitic bodies. The Guanhaes Group is composed of pelitic, mafic and ultramafic schists at the base; silicate and carbonate facies iron-formation, calcarious schists, calcsilicates rocks and quartzites at the median portion and para-gneisses (meta-graywacks) at the top. Geochemistry of iron-formation suggest a hydrothermal affinity comparable to the hydrothermal sediments flanking East Pacific Rise. Paragenetic studies indicates that the rocks were submited to two metamorphic processes: one of regional character (high-amphibolite facies) and one of themal character (pyroxene-hornfels facies). Chemical analysis, as X-ray and optic spectrography, atomic absorption and plasma spectrography are presented. (author)

  6. 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.

  7. The 3.1 Ga Nuggihalli chromite deposits, Western Dhawar craton (India)

    DEFF Research Database (Denmark)

    Mukherjee, Ria; Mondal, Sisir K.; Frei, Robert

    2012-01-01

    The Nuggihalli greenstone belt is part of the older greenstone belts (3.4 - 3.0 Ga) in the Western Dharwar Craton, southern India. This greenstone sequence consists of conformable metavolcanic and metasedimentary supracrustal rock assemblages that belong to the Sargur Group. Sill-like ultramafic......-mafic plutonic bodies are present within these supracrustal rocks (schist rocks) which are in turn enclosed by tonalite-trondhjemite-granodiorite gneiss (TTG). The sill-like ultramafic-mafic rocks are cumulates derived from a high-Mg parental magma that are represented by chromitite-hosted serpentinite...... and tremolite-chlorite-actinolite- schist (altered peridotite), anorthosite, pyroxenite, and gabbro hosting magnetite bands. The first whole-rock Sm-Nd data for the peridotite anorthosite- pyroxenite-gabbro unit has been obtained yielding an age of 3125 ± 120 Ma (MSWD = 1.3) which is similar to reported ages...

  8. Estimation of radiological dose from radon, thoron and their progeny levels in the dwellings of Shivamogga district, Karnataka, India

    International Nuclear Information System (INIS)

    Rangaswamvi, D.R.; Sannappa, J.; Srinivasa, E.

    2018-01-01

    Among all natural radiation exposure to man, inhalation of radon, thoron and their progenies are the major contributor (50 %) to the dose from ionizing radiation received by the general population. Based on the results of epidemiological studies in Europe and North America, the World Health Organization (WHO) has recommended reducing the indoor radon reference level from 200 to 100 Bq.m -3 . In view of this, focus has now been given for simultaneous measurement of radon, thoron and their progeny concentration in indoor air and also to estimate radiological dose in the dwellings of the Shivamogga district. The geology of the Shivamogga district comprises different types of rock formation such as granites, schists, magnetites and gneisses, Meta basalt, laterites, quartz and chlorite schist, Graywacke etc. Present study was concentrating more in granite bed rock regions along with their surrounding regions

  9. Gold, uranium and thorium in zones of greenschist displacement metamorphism

    International Nuclear Information System (INIS)

    Gavrilenko, B.V.; Savitskij, A.V.; Titov, V.V.

    1987-01-01

    Distribution of gold, uranium (bar and mobile) and thorium in 15 zones of greenschist dislocated metamorphism in different structures of the Karelo-Kola region carried out by geologic formations of the Early-Archean-Late-Proterozoic age has been studied. More than 200 samples of well core from 0-200 m depths have been analyzed. The results obtained testify to the increase of gold, uranium and less thorium content in zones of green-schist dislocated metamorphism in comparison with the enclosing rocks 1.4-3.1 times. The variation coefficient of gold, uranium and thorium content in green-schist dislocated tectonites increases 1.5-2.9 times. The correlation coefficient of Au/U mob. pair is +0.69, and Au/U bar pair -+0.87. Essential correlation between concentrations of all three elements in enclosing rocks is absent

  10. Are the Vinjamur rocks carbonatites or meta-limestones?

    International Nuclear Information System (INIS)

    Subbarao, K.V.; Bhaskar Rao, B.; Le Bas, M.J.

    1995-01-01

    New whole-rock rare earth element (REE) data for the metacarbonate rocks inter bedded with schists at Vinjamur in the Nellore schist belt of Andhra Pradesh, show low total REE contents (σ9-128 ppm) that are inconsistent with an igneous carbonatitic origin but which correspond more closely with a sedimentary limestone origin. The REE data of these rocks however, do not give absolute discrimination between marbles of meta-limestone and metacarbonatite origin. Micro-probe analytical data give better discrimination, and the chemical compositions of the calcite, micas, amphibole, plagioclase, apatite, monazite and staurolite in the Vinjamur marbles give strong and consistent evidence of a metamorphosed sedimentary rather than an igneous origin. (author). 35 refs., 7 figs., 9 tabs

  11. A study of secondary fabrics in rocks from the lizard Peninsula and adjacent areas in southwest cornwall, england

    Science.gov (United States)

    Rathore, Jaswant Singh

    1980-09-01

    Magnetic susceptibility anisotropy techniques were applied to samples taken in selected areas of the Lizard Peninsula in order to study secondary fabrics due to: (1) the intrusion of granites into sediments; (2) the compression in the sediments to the north of the Lizard thrust boundary; and (3) the intrusion of serpentine into hornblende schists of the Lizard metamorphic block. The magnetic fabric around the Carnmenellis and Godolphin granite masses shows a strong compressional fabric, tending to suggest that the Devonian sediments were compressed radially as the granites intruded them. The high degree of anisotropy observed at the Lizard boundary falls, with increasing distance from the thrust, systematically down to low values in the Devonian sediments. The distinct changes in the fabric parameters at the north end of Church Cove-Landewednack and the southern end of Cadgwith Cove appear to be the remnant secondary fabrics due to the intrusion of serpentine into hornblende schists.

  12. Petrographic and EMP study of metamorphic rocks from the Variscan basement of Dinarides (Vranica Mountains, Bosnia and Herzegovina)

    Energy Technology Data Exchange (ETDEWEB)

    Hrvanovic, S [Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University, 84215 Bratislava (Slovakia)

    2012-04-25

    The Vranica Mountains are located in the middle part of Bosnia and Herzegovina or in the southeastern part of the Mid - Bosnian schist Mountains (MBSM). The Mid - Bosnian schist Mountains represent one of the largest allochtonous Paleozoic terranes in the Dinarides. This region is characterized by a multistage geodynamic evolution. The presented results concern Variscan metamorphism of the Silur-Devonian protolith formations that occurred mainly during the Early Carboniferous in LT/MP greenschist facies. Petrographical description of metamorphic rocks is completed by EMPA of muscovite, chlorite and chloritoid. The Early Alpine metamorphic overprint is related to the closure of a Tethyan Basin and Early Cretaceous collision of the Adria microplate with the Tissia-Moesia continental Blocks. The Neo-Alpine metamorphic overprint occurred due to the collision of the African and Euroasian Plates. (authors)

  13. Recovering volatile liquids

    Energy Technology Data Exchange (ETDEWEB)

    Bregeat, J H

    1925-07-30

    The products of hydrogenation of alicyclic compounds, such as terpenes, for example, pinene or oil of turpentine, are used as washing liquids for absorbing vapours of volatile liquids from gases, such as natural gases from petroliferous regions, gases from the distillation of coal, lignite, schist, peat, etc. or from the cracking of heavy oils. Other liquids such as tar oils vaseline oils, cresols, etc. may be added.

  14. Precambrian Terranes of African affinities in the southeastern part of Brazil and Uruguay

    International Nuclear Information System (INIS)

    Preciozzi, F.; Basei, M.; Siga Junior, H.; Sato, K.; Kaufuss, G.

    2006-01-01

    The interest in correlating terranes at opposite margins of the South Atlantic Ocean reflects a natural curiosity of both researchers who work in the eastern South-America and who study southwestern Africa. On a large scale scenario the geology of this region is characterized by a central portion composed of Neoproterozoic-Cambrian belts (Dom Feliciano, Kao ko, Damara, Gariep, Saldania) having on each side old gneissic-migmatitic terrains on both continents (Luis Alves, Rio de La Plata, Kalahari and Congo). In South America the Neoproterozoic Dom Feliciano Belt (DFB) predominates in the eastern part of the region and is internally organized according to three different crustal segments characterized, from southeast to northwest, by a Granite belt (deformed I-type medium to high calc-alkaline granites and alkaline granitoid rocks; a Schist belt (volcano-sedimentary rocks metamorphosed from green schist to amphibolite facies and intrusive granitoids), and a Fore land basin (anchimetamorphic sedimentary and volcanic rocks), the latter situated between the Schist belt and the Archean-Paleoproterozoic fore land. Despite discontinuously covered by younger sediments, the NS continuity of these three crustal segments is suggested by similar lithotypes, structural characteristics, ages and isotopic signature, as well as by the gravimetric data. The Major Gercino, Cordilheira, and Sierra Ballena shear zones are part of the major NE-SW lineaments that affect all southern Brazilian and Uruguayan Precambrian terrains. They separate the Dom Feliciano Schist Belt (supra crustal rocks of the Brusque-Porongos and Lavalleja groups), to the West, from the granitoids of the Granite belt, to the East. The shear zones are characterized by a regional NE trend and a resultant oblique direction of movement where ductile-brittle structures predominate

  15. Searching pristine source of two gabbric plutons outcroping in Central Sierras Pampeanas Range, Argentina

    International Nuclear Information System (INIS)

    Daziano, C.; Ayala, R.

    2010-01-01

    This work is about the study of two gabbric plutons outcrop ing throughout Central Sierras Pampeanas range (Cordoba province, Argentina). San Lorenzo hill gabbric plutons is in the Upper proterozoic age whereas Cañada del Puerto belongs to the Early proterozoic.They are stock-type igneous bodies and they are intrusive s in an Upper Precambrian crystalline basement; it is mainly composed by gneisses, migmatites, schistes, marbles, amphibolite s, tact's, serpentinites and related rocks

  16. When did the Penglai orogeny begin on Taiwan?: Geochronological and petrographic constraints on the exhumed mountain belts and foreland-basin sequences

    Science.gov (United States)

    Chen, W. S.; Syu, S. J.; Yeh, J. J.

    2017-12-01

    Foreland basin receives large amounts of synorogenic infill that is eroded from the adjacent exhumed mountain belt, and therefore provides the important information on exhumation evolution. Furthermore, a complete stratigraphic sequence of Taiwan mountain belt consists of five units of Miocene sedimentary rocks (the Western Foothills and the uppermost sequence on the proto-Taiwan mountain belt), Oligocene argillite (the Hsuehshan Range), Eocene quartzite (the Hsuehshan Range), Eocene-Miocene slate and schist (Backbone Range), and Cretaceous schist (Backbone Range) from top to bottom. Based on the progressive unroofing history, the initiation of foreland basin received sedimentary lithic sediments from the uppermost sequence of proto-Taiwan mountain belt, afterwards, and receiving low- to medium-grade metamorphic lithic sediments in ascending order of argillite, quartzite, slate, and schist clasts. Therefore, the sedimentary lithics from mountain belt were deposited which represents the onset of the mountain uplift. In this study, the first appearance of sedimentary lithic sediments occurs in the Hengchun Peninsula at the middle Miocene (ca. 12-10 Ma). Thus, sandstone petrography of the late Miocene formation (10-5.3 Ma) shows a predominantly recycled sedimentary and low-grade metamorphic sources, including sandstone, argillite and quartzite lithic sediments of 10-25% which records erosion to slightly deeper metamorphic terrane on the mountain belt. Based on the results of previous thermogeochronological studies of the Yuli belt, it suggests that the middle Miocene occurred mountain uplift. The occurrence of low-grade metamorphic lithic sediments in the Hengchun Peninsula during late Miocene is coincident with the cooling ages of uplift and denuded Yuli schist belt at the eastern limb of Backbone Range.

  17. Model galena ages from Karnataka and surrounding ages

    Energy Technology Data Exchange (ETDEWEB)

    Venkatasubramanian, V S [Indian Inst. of Science, Bangalore. Dept. of Physics; Radhakrishna, B P [Geological Society of India, Bangalore; Jayaram, S [Department of Mines and Geology, Bangalore

    1977-02-01

    Lead isotope ratios have been measured for selected samples from the Chitradurga and Kolar schist belts, the high-grade gneisses E of Karnataka (in Tamil Nadu) and Agnigundala of Cuddapah. Most of the isotope data approximately fit a single-stage model and yield model age at 3000 m.y., 2500 m.y., 1400 m.y. and 1100 m.y. The relations with other available age data are discussed.

  18. 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.

  19. Metal mobility during metamorphism and formation of orogenic gold deposits: Insights from the Dalradian of Scotland

    OpenAIRE

    Engström, Adam

    2013-01-01

    Orogenic gold deposits occur within metamorphic belts throughout the world and have through time represented the source for over 25% of the world’s gold production. Although orogenic gold deposits are of great economic importance, controversies exist on the subject of fluid and metal sources and there have been few studies of gold´s distribution and mobility outside of large economic deposits. Research made by Pitcairn et al. (2006), on the Mesozoic Otago and Alpine schists of New Zealand, ob...

  20. A new genus and two new species of loaches (Teleostei: Nemacheilidae) from Myanmar

    Czech Academy of Sciences Publication Activity Database

    Bohlen, Jörg; Šlechtová, Vendula

    2011-01-01

    Roč. 22, č. 1 (2011), 1-10 ISSN 0936-9902 R&D Projects: GA ČR GA206/08/0637; GA ČR GA206/05/2556; GA AV ČR IAA600450508 Institutional research plan: CEZ:AV0Z50450515 Keywords : Schist ore callidora * Myanmar Subject RIV: EG - Zoology Impact factor: 0.900, year: 2011

  1. Rubidium-strontium isotoppe study of Muruntan deposit. 1.Ore vien dating by isochrone technique

    International Nuclear Information System (INIS)

    Kostitsyn, Yu.A.

    1993-01-01

    Hydrothermal viens of Muruntau gold-ore deposit (Central Kyzylkum) have been studies by the isochrone technique. The ages obtained for the quartz-tourmaline (257+13 Ma), quartz-arsenopyrite (230.3+-3.5 Ma) and quartz-adularia (219.4+-4.2 Ma) hydrothermal viens reflect the different stages of the deposit evolution: gold-ore and gold-silver one. Strontium isotope analysis reveals that the matter of hydrothermal viens is originated from the surrounding black schists

  2. The distribution, character, and rhenium content of molybdenite in the Aitik Cu-Au-Ag-(Mo) deposit and its southern extension in the northern Norrbotten ore district, northern Sweden.

    OpenAIRE

    Wanhainen, C.; Nigatu, W.; Selby, D.; McLeod, C.; Nordin, R.; Bolin, N-J.

    2014-01-01

    Molybdenite in the Aitik deposit and its southern extension was studied through mineralogical/chemical analysis and laboratory flotation tests. It is demonstrated that molybdenite varies considerably in grain size, ranging from coarse (>20 μm) to very fine (<2 μm) and occurs predominantly as single grains in the groundmass of the rocks, as grain aggregates, and intergrown with chalcopyrite and pyrite. The dominating molybdenite-bearing rocks are the mica schists, the quartz-monzodiori...

  3. Geochronologic constraints of the uplift and metamorphism along the Alpine Fault, South Island, New Zealand

    International Nuclear Information System (INIS)

    Chamberlain, C.P.; Zeitler, P.K.; Cooper, A.F.

    1995-01-01

    Geochronological studies of pegmatites and Alpine Schist exposed east of the Alpine Fault, South Island, New Zealand, reveal a complex history beginning with magmatism and metamorphism at c. 68 m.y. ago and ending with rapid uplift and exhumation in the last 5 m.y. Pegmatites exposed in the Mataketake Range give conventional U-Pb monazite and SHRIMP ion-probe zircon ages of 68 ± 2.6 Ma and 67.9 ± 2.5 Ma, respectively. Inasmuch as petrologic and isotopic data indicate that the Alpine pegmatites are melts derived from the Alpine Schist, the age of the pegmatites suggests that, at least locally, the high-grade metamorphism is considerably younger than previously assumed. We tentatively suggest that metamorphism, in at least some areas of the Alpine Schist, may be associated with Late Cretaceous transtension rather than resulting from the consequences of collision during the Rangitata Orogeny. 40 Ar/ 39 Ar studies of hornblendes from the Alpine Schist, collected from the Haast River to the Franz Josef Glacier area, reveal highly disturbed spectra. Despite this complexity, these analyses define a systematic decrease in ages both across-strike toward the Alpine Fault (Haast River traverse) and northwards along-strike towards Mt Cook. This pattern of decreasing 40 Ar/ 39 Ar hornblende ages is also observed in lower closure temperature systems such as zircon and apatite fission-track ages. We interpret the decrease in ages toward the fault to be the result of deeper exhumation in the immediate vicinity of the Alpine Fault, whereas we interpret the northward younging of fault-proximal samples to be a result of both more recent and possibly more extensive exhumation than occurred in areas to the south. (author). 55 refs., 4 figs., 2 tabs

  4. GEOCHEMISTRY AND MINERALOGICAL EVALUATION OF ...

    African Journals Online (AJOL)

    Dr Osondu

    2011-11-05

    Nov 5, 2011 ... mica-schist. AAS and XRD techniques were employed in the determination of chemical and mineralogical composition of ten .... Sample %. British Standard. Institution (BSI). %. American standard. (ASTM) %. SiO2. Al2O3. Fe2O3. TiO2. CaO. MgO. Na2O. K2O. P2O5. LO I. 46.65. 47.67. 1.02. 1.28. 0.10. 0.02.

  5. Metamorphic brines and no surficial fluids trapped in the detachment footwall of a Metamorphic Core Complex (Nevado-Filábride units, Betics, Spain)

    Science.gov (United States)

    Dyja-Person, Vanessa; Tarantola, Alexandre; Richard, Antonin; Hibsch, Christian; Siebenaller, Luc; Boiron, Marie-Christine; Cathelineau, Michel; Boulvais, Philippe

    2018-03-01

    The ductile-brittle transition zone in extensional regimes can play the role of a hydrogeological barrier. Quartz veins developed within an orthogneiss body located in the detachment footwall of a Metamorphic Core Complex (MCC) in the Nevado-Filábride units (Betics, Spain). The detachment footwall is composed mainly of gneisses, schists and metacarbonates from the Bédar-Macael sub-unit. Schist and metacarbonate bodies show evidence of ductile deformation at the time the gneiss was already undergoing brittle deformation and vein opening during exhumation. The vein system provides the opportunity to investigate the origin, composition and PVTX conditions of the fluids that circulated in the detachment footwall while the footwall units were crossing the ductile-brittle transition. The analysis of fluid inclusions reveals the presence of a single type of fluid: 30-40 mass% NaCl > KCl > CaCl2 > MgCl2 brines, with trace amounts of CO2 and N2 and tens to thousands of ppm of metals such as Fe, Sr, Li, Zn, Ba, Pb and Cu. δDfluid values between -39.8 and -16.7‰ and δ18Ofluid values between 4.4 and 11.7 ± 0.5‰ show that the brines have undergone protracted interaction with the host orthogneissic body. Coupled salinity and Cl/Br ratios (200 to 4400) indicate that the brines originate from dissolution of Triassic metaevaporites by metamorphic fluids variably enriched in Br by interaction with graphitic schists. This study highlights the absence of any record of surficial fluids within the veins, despite the brittle deformation conditions prevailing in this orthogneiss body. The fact that fluids from the detachment footwall were isolated from surficial fluid reservoirs may result from the presence of overlying schists and metacarbonates that continued to be affected by ductile deformation during vein formation in the gneiss, preventing downward circulation of surface-derived fluids.

  6. Na-metasomatism in the uranium fields of Singhbhum Shear zone, India

    International Nuclear Information System (INIS)

    Chaki, Anjan

    2013-01-01

    Singhbhum Shear Zone (SSZ) of eastern India hosts uranium, copper and apatite-magnetite mineralization, which occurs either independently or overlaps in space. SSZ is a nearly 200 km long, 1-5 km wide, intensely techtonized, northward-convex, arcuate mobile belt that separates the Archaean cratonic nucleus to its south from the Proterozoic North Singhbhum Fold Belt on the north. Except Bagjata mines in the eastern sector, majority of the known uranium deposits and mines (e.g. Jaduguda, Bhatin, Narwapahar, Banduhurang and Mohuldih) are situated in the central sector of the shear zone. All the deposits are of low grade (0.05% U 3 O 8 ) and low to medium tonnage. The common rock types of the SSZ are quartz-chlorite schists, quartzsericite schists, quartzite, metaconglomerate, soda granite, quartz-albite bearing schists/gneisses, granophyres and tourmalinite. The mineralization occur as lenticular to tabular bodies, which are (pene-) concordant with dominant planer structures, i.e. foliation parallel with the lithological layering (S 3 II S 0 ). Principal uranium mineral is uraninite with low thorium (UO 2 /ThO 2 =70-150), high lead (PbO =14-15%) and moderate REE contents with minor pitchblende and some secondary minerals near the surface. Many ore minerals, particularly the sulfide phases of Ni, Co, Mo, Cu and Fe are common

  7. Characteristics of a Low-Sulfidation Epithermal Deposit in the River Reef Zone and the Watuputih Hill, the Poboya Gold Prospect, Central Sulawesi, Indonesia: Host Rocks and Hydrothermal Alteration

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    Syafrizal

    2017-07-01

    Full Text Available Systematic exploration has delineated significant gold mineralization in the River Reef Zone and the presence of a siliceous body at Watuputih Hill, which is a Poboya gold prospect in Central Sulawesi, Indonesia. The mineralization is hosted within the Palu Metamorphic Complex. The host rocks consist of granite, biotite gneiss, and biotite schist, which is intercalated by feldspar porphyroblastic biotite schist and amphibolitic schist. The X-ray fluorescence (XRF analysis of the granite and biotite gneiss suggests that the granitic rocks can be characterized as magnesian arc calc-alkaline rocks, with a weakly peraluminous composition. Alteration minerals were analyzed by a combination of petrographic and X-ray diffraction (XRD. In the River Reef Zone, the hydrothermal alteration zones can be sorted by their proximity to the primary fluid conduit and divided into inner, high-T, and low-T propylitic zones. In Watuputih Hill, the hydrothermal alteration can be divided into advanced argillic and argillic zones. The hydrothermal alteration assemblages indicated that the fluid was at a near-neutral pH in the River Reef Zone, whereas the fluid was acidic within Watuputih Hill. Because the hill is relatively distant from the River Reef Zone, the presence of these zones at Watuputih Hill may be indicative of another mineralization system beneath the hill.

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

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    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

  9. Isotopic studies of marbles in the Sanbagawa metamorphic terrain, central Shikoku, Japan

    International Nuclear Information System (INIS)

    Wada, Hideki; Enami, Masaki; Yanagi, Takeru.

    1984-01-01

    Carbon, oxygen and strontium isotopic studies were carried out on marbles occurring in crystalline schists and epidote amphibolites of the Sanbagawa metamorphic terrain, central Shikoku, Japan, in order to estimate metamorphic temperatures and to elucidate their origin. Carbon isotopic fractionation between calcite and graphite shows the metamorphic temperature of 460 deg C at the transitional part between the garnet and albite-biotite zones. Marbles are isotopically classified into two groups. (1) some marbles in epidote amphibolite masses show characteristically negative delta 13 C values and low 87 Sr/ 86 Sr ratios. These marbles are interpreted as have been derived from magmatic or deep-seated carbonates. (2) marbles collected from the crystalline schists and from the marginal part of epidote amphibolite masses, have high 87 Sr/ 86 Sr ratios and delta 13 C values similar to those of typical sedimentary carbonates. They were probably derived from sedimentary carbonates and/or carbonates re-equilibrated with metamorphic fluid segregated from crystalline schists during the Sanbagawa metamorphism. (author)

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

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    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.

  11. Uranium and thorium abundances in some graphite-bearing precambrian rocks of India and implications

    International Nuclear Information System (INIS)

    Pandey, U.K.; Krishnamurthy, P.

    1995-01-01

    Graphite schists from parts of Gujarat in the Aravalli supergroup show maximum contents of uranium (70-95 ppm), hosted mainly in the graphites, whereas such schists from the Tamil Nadu granulite terrain contain distinctly lower amounts of uranium (7-9 ppm). Graphite-bearing hornblende gneiss and calc-granulites from Madurai, Tamil Nadu, contain higher amounts of uranium (12-28 ppm) than the schists, and uranium is mainly hosted by the magnetite and allanite occurring as independent grains with flaky graphite and also as inclusions within quartz. Khondalites from Andhra Pradesh are depleted in uranium (0.9-1.3 ppm) compared to Th (17.5-20.2 ppm). Except for the khondalites, which have high Th/U ratio (13.5-22.4), all the other samples have very low Th/U ratios (0.10-0.80) compared to the crustal average (3-4). Such variations among similar rock types, may in part be related to uranium and thorium abundances inherited from parental rocks, modified later by hydrothermal and/or metasomatic processes. Graphites from such rock types can provide both in situ and migrant reductants for hosting a variety of uranium and other metallic deposits. (author). 12 refs., 1 tab., 1 fig

  12. 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

    2018-03-01

    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.

  13. Laboratory measurements of the seismic velocities and other petrophysical properties of the Outokumpu deep drill core samples, eastern Finland

    Science.gov (United States)

    Elbra, Tiiu; Karlqvist, Ronnie; Lassila, Ilkka; Høgström, Edward; Pesonen, Lauri J.

    2011-01-01

    Petrophysical, in particular seismic velocity, measurements of the Outokumpu deep drill core (depth 2.5 km) have been carried out to characterize the geophysical nature of the Paleoproterozoic crustal section of eastern Finland and to find lithological and geophysical interpretations to the distinct crustal reflectors as observed in seismic surveys. The results show that different lithological units can be identified based on the petrophysical data. The density of the samples remained nearly constant throughout the drilled section. Only diopside-tremolite skarns and black schists exhibit higher densities. The samples are dominated by the paramagnetic behaviour with occasional ferromagnetic signature caused by serpentinitic rocks. Large variations in seismic velocities, both at ambient pressure and under in situ crustal conditions are observed. The porosity of the samples, which is extremely low, is either intrinsic by nature or caused by decompaction related to fracturing during the core retrieval. It is noteworthy that these microfractures have dramatically lowered the VP and VS values. From the measured velocities and density data we have calculated the seismic impedances, Young's modulus and Poisson's ratios for the lithological units of the Outokumpu section and from these data the reflection coefficients for the major lithological boundaries, evident in the surveyed section, were determined. The data show that the strong and distinct reflections visible in wide-angle seismic surveys are caused by interfaces between diopside-tremolite skarn and either serpentinites, mica schist or black schist.

  14. Assessment of role of metamorphic remobilization in genesis of uranium ores from Ralston Buttes area, Colorado

    International Nuclear Information System (INIS)

    Chatterjee, S.K.

    1984-01-01

    The Ralston Buttes mining district, the principal source of commercial uranium in the Front Range since the late 1940s, is located northeast of Golden and southeast of the Front Range mineral belt. Uranium ore occurs in veins emplaced in fault breccia in Precambrian metamorphic rocks. The progenitors of the metamorphic rocks are a possible source for the uranium. Hornblende gneisses of the Idaho Springs Formation is the major rock type in the area, thus its origin is a major consideration in assessing the quantity of uranium that might have been contributed by metamorphic processes. To evaluate this, 41 rock samples (19 hornblende gneisses, 7 biotite gneisses, 5 chlorite gneisses, and 10 metapelites) were analyzed for major elements, and 3 rock samples (16 hornblende gneisses, 8 biotite gneisses, 4 chlorite gneisses, and 5 mica schists) were analyzed for trace metals (Rb, Sc, Zr, V, Ni, Co, Cr, Ba, U, and Th). Four samples of hornblende gneiss and 1 sample of mica schists were also analyzed for rare earth elements. Major elements are rare earth data indicate that the hornblende gneiss was derived from sediments and tholeiitic basalts. Trace element data suggest a volcanic provenance for these sediments. Rare earth patterns and uranium and thorium abundances of metapelites are similar to average North American shales. Low uranium and thorium values and low thorium-uranium ratios in hornblende gneisses and mica schists preclude large-scale uranium remobilization during metamorphism of these source rocks

  15. Short-time phosphorus losses by overland flow in burnt pine and eucalypt plantations in north-central Portugal: A study at micro-plot scale.

    Science.gov (United States)

    Ferreira, R V; Serpa, D; Cerqueira, M A; Keizer, J J

    2016-05-01

    Over the past decades, wildfires have affected vast areas of Mediterranean ecosystems leading to a variety of negative on- and off-site environmental impacts. Research on fire-affected areas has given more attention to sediment losses by fire-enhanced overland flow than to nutrient exports, especially in the Mediterranean region. To address this knowledge gap for post-fire losses of phosphorus (P) by overland flow, a recently burnt forest area in north-central Portugal was selected and instrumented immediately after a wildfire. Three slopes were selected for their contrasting forest types (eucalypt vs. pine) and parent materials (granite vs. schist). The selected study sites were a eucalypt site on granite (BEG), a eucalypt site on schist (BES) and a maritime pine site on schist (BPS). Micro-plots were monitored over a period of six months, i.e. till the construction of terraces for reforestation obliged to the removal of the plots. During this 6-month period, overland flow samples were collected at 1- to 2-weekly intervals, depending on rainfall. Total P and PO4-P losses differed markedly between the two types of forests on schist, being lower at the pine site than at the eucalypt site, probably due to the presence of a protective layer of pine needle cast. Parent material did not play an important role in PO4-P losses by overland flow but it did in TP losses, with significantly lower values at the eucalypt site on granite than that on schist. These differences in TP losses can be attributed to the coarser texture of granite soils, typically promoting infiltration and decreasing runoff. The present findings provided further insights into the spatial and temporal patterns of post-fire soil nutrient losses in fire-prone forest types during the initial stages of the window-of-disturbance, which can be useful for defining post-fire emergency measures to reduce the risk of soil fertility losses. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Structural and petrophysical characterization: from outcrop rock analogue to reservoir model of deep geothermal prospect in Eastern France

    Science.gov (United States)

    Bertrand, Lionel; Géraud, Yves; Diraison, Marc; Damy, Pierre-Clément

    2017-04-01

    The Scientific Interest Group (GIS) GEODENERGIES with the REFLET project aims to develop a geological and reservoir model for fault zones that are the main targets for deep geothermal prospects in the West European Rift system. In this project, several areas are studied with an integrated methodology combining field studies, boreholes and geophysical data acquisition and 3D modelling. In this study, we present the results of reservoir rock analogues characterization of one of these prospects in the Valence Graben (Eastern France). The approach used is a structural and petrophysical characterization of the rocks outcropping at the shoulders of the rift in order to model the buried targeted fault zone. The reservoir rocks are composed of fractured granites, gneiss and schists of the Hercynian basement of the graben. The matrix porosity, permeability, P-waves velocities and thermal conductivities have been characterized on hand samples coming from fault zones at the outcrop. Furthermore, fault organization has been mapped with the aim to identify the characteristic fault orientation, spacing and width. The fractures statistics like the orientation, density, and length have been identified in the damaged zones and unfaulted blocks regarding the regional fault pattern. All theses data have been included in a reservoir model with a double porosity model. The field study shows that the fault pattern in the outcrop area can be classified in different fault orders, with first order scale, larger faults distribution controls the first order structural and lithological organization. Between theses faults, the first order blocks are divided in second and third order faults, smaller structures, with characteristic spacing and width. Third order fault zones in granitic rocks show a significant porosity development in the fault cores until 25 % in the most locally altered material, as the damaged zones develop mostly fractures permeabilities. In the gneiss and schists units, the

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

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    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

  18. Unraveling the Alteration History of Serpentinites and Associated Ultramafic Rocks from the Kampos HPLT Subduction Complex, Syros, Greece

    Science.gov (United States)

    Cooperdock, E. H. G.; Stockli, D. F.

    2016-12-01

    Serpentinization, hydration of peridotite, has a profound effect on fundamental tectonic and petrologic processes such as deformation of the lithosphere, bulk rheology, fluid-mobile element cycling and deep earth carbon cycling. Though numerous studies have investigated the petrology, structure and geochemistry of serpentinites, the absolute chronology of serpentinization remains elusive due to a lack of accessory minerals that can be dated using established geochronological techniques. Magnetite forms as a common secondary mineral in serpentinites from the fluid-induced breakdown reaction of primary peridotite minerals. Magnetite (U-Th)/He chronometry provides the potential to directly date the cooling of exhumed ultramafic bodies and the low-temperature fluid alteration of serpentinites. We present the first application of magnetite (U-Th)/He chronometry to date stages of alteration in ultramafic rocks from the Kampos mélange belt, a high-pressure low-temperature (HP-LT) subduction complex that experienced exhumation in the Miocene on the island of Syros, Greece. Two generations of magnetite are distinguishable by grain size, magnetite trace element geochemistry and (U-Th)/He age. Large magnetite grains (mm) from a chlorite schist and a serpentinite schist have distinct geochemical signatures indicative of formation during blackwall-related fluid alteration and record Mid-Miocene exhumation-related cooling ages, similar to zircon (U-Th)/He ages from northern Syros. Smaller grains (µm) from the serpentinite schist lack blackwall-related fluid signatures and record post-exhumation mineral formation associated with widespread high-angle Pliocene normal faulting. These results reveal evidence for multiple episodes of fluid-rock alteration, which has implications for the cooling history and local geochemical exchanges of this HP-LT terrane. Given the fundamental impact of serpentinizaton on a vast array of tectonic, petrological, and geochemical processes, the

  19. Looking Like Gold: Chlorite and Talc Transformation in the Golden Slip Ware Production (Swat Valley, North-Western Pakistan

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    Lara Maritan

    2018-05-01

    Full Text Available The archaeometric study of the “golden slip” ware (second century BCE—fourth century CE at the site of Barikot (Swat, north-western Pakistan aimed to define its manufacturing technology and provenance of the raw materials used. For this reason, a multianalytical approach consisting of the microscopic, microstructural and mineralogical analysis of both the golden slip and the ceramic paste was adopted. The slip was found to be composed by platy minerals, microchemically identified as talc and chlorite; their intimate association indicated clearly that they derived from a chlorite-talc schist. This rock is geologically available near the site in the “green stones” lenses within the Mingora ophiolites outcropping in the Swat valley. Due to the use of this stone also for the production of stone tools, it cannot be excluded that the chlorite-talc schist used for the golden slip can be derived from manufacturing residues of the Gandharan sculptures. In order to constrain the firing production technology, laboratory replicas were produced using a locally collected clay and coating them with ground chlorite-talc schist. On the basis of the mineralogical association observed in both the slip and the ceramic paste and the thermodynamic stability of the pristine mineral phases, the golden slip pottery underwent firing under oxidising conditions in the temperature interval between 800 °C and 850 °C. The golden and shining looks of the slip were here interpreted as the result of the combined light reflectance of the platy structure of the talc-based coating and the uniform, bright red colour of the oxidized ceramic background.

  20. Ground water geochemistry in the vicinity of the Jabiluka deposits

    International Nuclear Information System (INIS)

    Deutscher, R.L.; Mann, A.W.; Giblin, A.

    1980-01-01

    Seventeen exploration drill holes in the vicinity of the Jabiluka One and Jabiluka Two deposits were logged for Eh-pH and conductivity at 5 metre intervals to depths of up to 195 metres below ground surface. Forty-seven water samples from exploration drill holes, augered holes on the Magela flood plain and from two billabongs in the vicinity of the deposits were collected and analyzed. Analyses for pH and Fe were conducted in the field, and further analyses for major ions Ca 2+ , Mg 2+ , Na + , K + , SO 4 2- , Cl - , HCO 3 - and Si and minorelements Zn, Cd, Pb, Cu and U were conducted in the laboratory. The in situ Eh-pH and conductivity measurements, and analyses for major and minor elements of ground waters suggest that deep-lying chlorite-graphite schists containing the uranium mineralization are well protected from, or do not react rapidly with, ground water under present-day conditions, i.e. the schists of the Cahill Formation are a stable host for uranium mineralization at depth. In the vicinity of the Magela flood plain where the Cahill Formation and the permanent water table are close to the surface, some samples were found to contain high concentrations of sulphate, zinc, lead and iron. These same samples were characterized by low pH's in the pH range 3.0-4.0. The anomalies suggest weathering of sulphides associated with the mineralized Cahill Formation, where the schists are at shallow depths and in an oxidizing environment. The anomalies are not, however, necessarily indicative of zones of uranium enrichment in this formation. (author)

  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. Alteration Mineralogy and Geochemical Characteristics of Porphyry Cu-Mo Mineralization in Domaniç (Kütahya) Area

    Science.gov (United States)

    Sariiz, K.; Sendir, H.

    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. δ18O (quartz) values range from 8,8 to 12,1 ‰. δ18O (biotite) and δD (biotite) values range from 2,6 to 6,1 ‰ and -87 - -125 (SMOW). These values indicate that mixture magmatic-meteoric of hydrothermal solutions origin which are potassic to propylitic zones. δ13C (calcite) values range from 1,9 to 3,3 ‰ (PDB). Calcite values within the marine carbonates in the study area.

  3. Neoproterozoic alkaline magmatism in Ilha do Cardoso, southeastern coast of Sao Paulo State, Brazil

    International Nuclear Information System (INIS)

    Weber, Werner; Basei, Miguel A.S.; Siga Junior, Oswaldo; Sato, Kei

    2001-01-01

    This work focuses on the geology and geochronology of rocks cropping out on Cardoso Island, on the southeastern coast of Sao Paulo State, close to the boundary with Parana State. The island, with an area of about 151 km 2 is a protected area administered by the Forest Institute of the Secretariat for the Environment of the State of Sao Paulo. It is mountainous, with a peak at 814 m, and is covered by dense Atlantic Forest vegetation. The island is made up mainly of an igneous complex with light grey leucocratic, inequigranular, medium to coarse-grained syenites. The Tres Irmaos Syenite (STI), composed of pyroxene, hornblende, and perthitic to mesoperthitic microcline, predominates has magmatic flow structures, and it cut by the pinkish grey, leucocratic medium-grained Cambriu alkali-feldspar granites (GC). Geochemical analysis of STI and GC demonstrate their metaluminous alkaline nature and late orogenic to anorogenic character. The bodies formed between 620 and 570 Ma according to U-Pb dating of zircons and cooled between 597 and 531 Ma (K-Ar in amphiboles). Whole rock Sm-Nd analyses yield Meso- and Paleoproterozoic TDM ages (1,500 - 2,200 Ma). A belt of low-grade metasedimentary rocks occurs in the northern part of the island. Quartz schist, quartz-mica schist and mica-quartz schist, often-containing andalusite and cordierite, predominate. Geochemical and geochronological data suggest that the sources of the metasediments were continental arc andesites of whose protoliths separated from the mantle between 1,800 and 2,200 Ma during the Paleoproterozoic. These metasediments probably continue on the continent in the Taquari region and extend southwards in narrow strips between the granitoids of the Paranagua Domain. (author)

  4. Water-rock-tailings interactions and sources of sulfur and metals in the subtropical mining region of Taxco, Guerrero (southern Mexico): A multi-isotopic approach

    International Nuclear Information System (INIS)

    Talavera Mendoza, Oscar; Ruiz, Joaquin; Díaz Villaseñor, Elvia; Ramírez Guzmán, Alejandro; Cortés, Alejandra; Salgado Souto, Sergio Adrián; Dótor Almazán, Azucena; Rivera Bustos, Reymundo

    2016-01-01

    Multi-isotope (H, O, S, Sr, Pb) systems coupled with conventional (major and trace element) hydrogeochemical analysis were applied to determine the origin of water, to model water-rock-tailings interactions and for source apportionment of sulfur and associated toxic metals in the mining region of Taxco, Guerrero in southern Mexico. Oxygen and H isotopes indicate that meteoric water in the zone is rainwater undergoing varying degrees of isotopic fractionation by atmospheric evaporation whereas Sr isotopes trace the interaction of pristine water from volcanics of the regional recharge zone and subsequently flowing through sandstone and shale to spring points. Leachates form from two distinctive sources (spring water and surface water) having differential interactions with bedrocks prior to entering the tailings. Compared to pristine water, leachates are enriched in sulfate, metals (e.g. Fe, Mn, Pb and Zn) and metalloids (e.g. As). The sulfur isotopic composition of ore-sulfides, leachates, secondary precipitates, regional surface water and hypogenic sulfates is described in terms of a two-component mixing model with shale of Mexcala and limestone of Morelos formations representing the light and heavy end-members, respectively, whereas Sr isotopic composition is bracketed combining three lithogenic (Mexcala/Morelos, Tilzapotla and Taxco Schist) sources. Finally, leachates have a mixture of lead from ore-sulfides and Taxco Schist Formation (Family I) or from ore-sulfides alone (Family II). The application of multiple environmental isotopic techniques is an outstanding tool for elucidating complex interactions of water with bedrocks and tailings and for determining the source of sulfur and toxic metal from mining and other metal polluted environments. - Highlights: • We applied multi-isotope techniques to model water-bedrocks-tailings interaction. • Spring water records fractionation by evaporation and interaction with local rocks. • The sulfur cycle is modeled in

  5. Groundwater recharge in the Kolokani-Nara region in Mali

    International Nuclear Information System (INIS)

    Dincer, T.; Dray, M.; Zuppi, G.M.; Guerre, A.; Tazioli, G.S.; Traore, S.

    1984-01-01

    The area studied is part of the Nara, Kolokani, Banamba and Koulikoro regions and lies between the Mauritanian frontier and Bamako. It is a Sahel zone devoid of active surface hydrography, the annual rainfall varying between 1000 mm in the south and 400 mm in the north. The altitude decreases from 600 m to 250 m from the Mandingues Plateaux to the Nara plain. The Nara area consists of a basin filled with Cambrian schists containing seams of dolomitic limestones and sandstones cemented by limestone. The thickness of the series is thought to be about 300-500 m. The area of the Mandingues Plateaux is composed of Lower Cambrian sandstone-schist formations with a thickness of several hundred metres, covered with a crust of weathering. The two formations have aquifers of the same type - they are discontinuous with predominantly fissure-type permeability. The permeable zones in the Cambrian schist aquifers are more discontinuous than those in the Cambrian sandstones and are less developed in depth. The recharge conditions, on the other hand, are quite good on account of the sand cover which allows rapid infiltration of rain water. The Lower Cambrian aquifer is highly heterogeneous but much less discontinuous. The transfer of groundwater takes place at the level of small local sub-basins over short distances. The hydrogeological and hydrogeochemical data point to the existence of recent recharge and mixing with older water. The groundwater renewal rate indicates, in many cases, limited water reserves. Infiltration is associated, in some cases, with storms of greater intensity and, in other cases, also with small sudden showers. Under natural conditions, the infiltrated water is generally used up by evapotranspiration. Under conditions of exploitation, a fraction of this recharge is recovered either almost directly or indirectly by replacement of the water taken from the fissured zones of the substratum. (author)

  6. 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.

    2018-03-01

    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).

  7. Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the granite megablock and amphibolite megablock of the Eyreville B core, Chesapeake Bay impact structure, USA

    Science.gov (United States)

    Townsend, G.N.; Gibson, R.L.; Horton, J. Wright; Reimold, W.U.; Schmitt, R.T.; Bartosova, K.

    2009-01-01

    The Eyreville B core from the Chesapeake Bay impact structure, Virginia, USA, contains a lower basement-derived section (1551.19 m to 1766.32 m deep) and two megablocks of dominantly (1) amphibolite (1376.38 m to 1389.35 m deep) and (2) granite (1095.74 m to 1371.11 m deep), which are separated by an impactite succession. Metasedimentary rocks (muscovite-quartz-plagioclase-biotite-graphite ?? fibrolite ?? garnet ?? tourmaline ?? pyrite ?? rutile ?? pyrrhotite mica schist, hornblende-plagioclase-epidote-biotite- K-feldspar-quartz-titanite-calcite amphibolite, and vesuvianite-plagioclase- quartz-epidote calc-silicate rock) are dominant in the upper part of the lower basement-derived section, and they are intruded by pegmatitic to coarse-grained granite (K-feldspar-plagioclase-quartz-muscovite ?? biotite ?? garnet) that increases in volume proportion downward. The granite megablock contains both gneissic and weakly or nonfoliated biotite granite varieties (K-feldspar-quartz-plagioclase-biotite ?? muscovite ?? pyrite), with small schist xenoliths consisting of biotite-plagioclase-quartz ?? epidote ?? amphibole. The lower basement-derived section and both megablocks exhibit similar middleto upper-amphibolite-facies metamorphic grades that suggest they might represent parts of a single terrane. However, the mica schists in the lower basement-derived sequence and in the megablock xenoliths show differences in both mineralogy and whole-rock chemistry that suggest a more mafi c source for the xenoliths. Similarly, the mineralogy of the amphibolite in the lower basement-derived section and its association with calc-silicate rock suggest a sedimentary protolith, whereas the bulk-rock and mineral chemistry of the megablock amphibolite indicate an igneous protolith. The lower basement-derived granite also shows bulk chemical and mineralogical differences from the megablock gneissic and biotite granites. ?? 2009 The Geological Society of America.

  8. Petrographic and geochemical comparisons between the lower crystalline basement-derived section and the granite megablock and amphibolite megablock of the Eyreville-B core, Chesapeake Bay impact structure

    Science.gov (United States)

    Townsend, Gabrielle N.; Gibson, Roger L.; Horton, J. Wright; Reimold, Wolf Uwe; Schmitt, Ralf T.; Bartosova, Katerina

    2009-01-01

    The Eyreville B core from the Chesapeake Bay impact structure, Virginia, USA, contains a lower basement-derived section (1551.19 m to 1766.32 m deep) and two megablocks of dominantly (1) amphibolite (1376.38 m to 1389.35 m deep) and (2) granite (1095.74 m to 1371.11 m deep), which are separated by an impactite succession. Metasedimentary rocks (muscovite-quartz-plagioclase-biotite-graphite ± fibrolite ± garnet ± tourmaline ± pyrite ± rutile ± pyrrhotite mica schist, hornblende-plagioclase-epidote-biotite-K-feldspar-quartz-titanite-calcite amphibolite, and vesuvianite-plagioclase-quartz-epidote calc-silicate rock) are dominant in the upper part of the lower basement-derived section, and they are intruded by pegmatitic to coarse-grained granite (K-feldspar-plagioclase-quartz-muscovite ± biotite ± garnet) that increases in volume proportion downward. The granite megablock contains both gneissic and weakly or nonfoliated biotite granite varieties (K-feldspar-quartz-plagioclase-biotite ± muscovite ± pyrite), with small schist xenoliths consisting of biotite-plagioclase-quartz ± epidote ± amphibole. The lower basement-derived section and both megablocks exhibit similar middle- to upper-amphibolite-facies metamorphic grades that suggest they might represent parts of a single terrane. However, the mica schists in the lower basement-derived sequence and in the megablock xenoliths show differences in both mineralogy and whole-rock chemistry that suggest a more mafic source for the xenoliths. Similarly, the mineralogy of the amphibolite in the lower basement-derived section and its association with calc-silicate rock suggest a sedimentary protolith, whereas the bulk-rock and mineral chemistry of the megablock amphibolite indicate an igneous protolith. The lower basement-derived granite also shows bulk chemical and mineralogical differences from the megablock gneissic and biotite granites.

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

    International Nuclear Information System (INIS)

    Imaizumi, Masayuki; Ueda, Yoshio.

    1981-01-01

    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. (author)

  10. Site selection methods for nuclear waste storage in sub-schistic granites

    International Nuclear Information System (INIS)

    Alsac, C.; Chantraine, J.; Chevremont, P.

    1984-02-01

    Intrusive granites in schists, where most of the roof is at a depth of several hundred metres can be regarded as favourable sites for storing radioactive waste since the schistic cover has extremely low permeability. This configuration exists in various parts of France. In this paper the authors describe methods which can be applied to the study of such structures, taking a region in the Armorican Massif as a reference example. The geological evidence here showed an extensive zone with a slight gravimetric anomaly around a few granite outcrops dispersed in the schists. This structure gave reason to believe that a shallow granite mass would be found under the schistic cover, and geological and gravimetric surface studies did indeed prove that this supposition was correct. Apart from the slight gravimetric anomaly, the extent of which has been confirmed and the outlines determined, the transformations (contact metamorphism and hydrothermalism) of the enclosing schists are particularly indicative of the presence of granite. The gravimetric model shows that the thickness of the granite is at least 2.3 km and provides an initial representation of the shape and depth of the roof. These results, together with those of the structural analysis, can be used to demarcate a favourable region for investigations at depth which will make it possible: to monitor the geological structures; to define the geotechnical characteristics of the formations; to analyse and model the hydrogeological behaviour, at present known only from surface studies which do not appear to indicate any circulation of water upwards towards the surface

  11. Tectonic evolution of part of the Southern Metamorphic Belt of the Armorican Massif including the Ile de Groix

    Science.gov (United States)

    Richards, Lawrence Edward

    The Southern Metamorphic Belt (SMB) of the Armorican Massifextends 400km along the south coast of Brittany and into Vendee. It is separated from the Central Armorican Domain by a major, late-Hercynian shear belt, known as the South Armorican Shear Zone. In the area studied, belts of metasedimentary and metavolcanic schist of uncertain age are separated by belts of granitic gneiss; areas of migmatite and Hercynian granite plutons cross-cut these belts. Three distinctive lithologic assemblages have been identified in the schist belts, characteristic of different depositional environments: the Le Pouldu Group, Kerleven and Gouesnach formations probably originated as abyssal black shales deposited on oceanic crust; the St. Laurent Formation and Melgven Schists probably formed as distal greywacke deposits on a deep continental shelf; the Nerly and Beg-Meil formations probably formed in a proximal marine or fluviatile environment. These disparate assemblages were tectonically juxtaposed by overthrusting (obduction) before an amphibolite facies metamorphism and deformation during the Cadomian Orogeny. The Moelan Gneiss, a Lower Ordovician alkali-granite intrusion, postdates M1/D1 and probably formed in a rifting environment at the onset of ocean-floor spreading along an axis south of the present Armorican Massif. The famous blueschists of the Ile de Groix probably formed in a subduction zone on the south side of the ocean and were obducted onto the passive southern margin of the Armorican Massif following closure of the ocean and continental collision. A second phase of regional deformation, producing a cataclastic foliation in the Moelan Gneiss, probably resulted from the collision. Large-scale overthrusting of the southern continent onto the Armorican Massif took place, causing metamorphism with partial melting at depth generating migmatites. A third phase of pervasive deformation may correlate with oroclinal bending of the Ibero-Armorican Arc during the Hercynian

  12. Finite Strain Analysis of the Wadi Fatima Shear Zone in Western Arabia, Saudi Arabia

    Science.gov (United States)

    Kassem, O. M. K.; Hamimi, Z.

    2018-03-01

    Neoproterozoic rocks, Oligocene to Neogene sediments and Tertiary Red Sea rift-related volcanics (Harrat) are three dominant major groups exposed in the Jeddah tectonic terrane in Western Arabia. The basement complex comprises amphibolites, schists, and older and younger granites unconformably overlain by a post-amalgamation volcanosedimentary sequence (Fatima Group) exhibiting post-accretionary thrusting and thrust-related structures. The older granites and/or the amphibolites and schists display mylonitization and shearing in some outcrops, and the observed kinematic indicators indicate dextral monoclinic symmetry along the impressive Wadi Fatima Shear Zone. Finite strain analysis of the mylonitized lithologies is used to interpret the deformation history of the Wadi Fatima Shear Zone. The measured finite strain data demonstrate that the amphibolites, schists, and older granites are mildly to moderately deformed, where XZ (axial ratios in XZ direction) vary from 2.76 to 4.22 and from 2.04 to 3.90 for the Rf/φ and Fry method respectively. The shortening axes ( Z) have subvertical attitude and are associated with subhorizontal foliation. The data show oblate strain ellipsoids in the different rocks in the studied area and indication bulk flattening strain. We assume that the different rock types have similar deformation behavior. In the deformed granite, the strain data are identical in magnitude with those obtained in the Fatima Group volcanosedimentary sequence. Finite strain accumulated without any significant volume change contemporaneously with syn-accretionary transpressive structures. It is concluded that a simple-shear deformation with constant-volume plane strain exists, where displacement is strictly parallel to the shear plane. Furthermore, the contacts between various lithological units in the Wadi Fatima Shear Zone were formed under brittle to semi-ductile deformation conditions.

  13. Anisotropy effect on strengths of metamorphic rocks

    Directory of Open Access Journals (Sweden)

    Ahmet Özbek

    2018-02-01

    Full Text Available This paper aims to study the effect of anisotropy on strengths of several metamorphic rocks of southern (Çine submassif of Menderes metamorphic massif in southwest Turkey. Four different metamorphic rocks including foliated phyllite, schist, gneiss and marble (calcschist were selected and examined. Discontinuity surveys were made along lines for each rock and evaluated with DIPS program. L-type Schmidt hammer was applied in the directions parallel and perpendicular to foliation during the field study. Several hand samples and rock blocks were collected during the field study for measurements of dry and saturated densities, dry and saturated unit weights and porosity, and for petrographic analysis and strength determination in laboratory. L- and N-type Schmidt hammers were applied in the directions perpendicular (anisotropy angle of 0° and parallel (anisotropy angle of 90° to the foliation on selected blocks of phyllite, schist, gneiss and marble (calcschist. The phyllite and schist have higher porosity and lower density values than the other rocks. However, coarse crystalline gneiss and marble (calcschist have higher rebound values and strengths, and they are classified as strong–very strong rocks. Generally, the rebound values in the direction perpendicular to the foliation are slightly higher than that in the direction parallel to foliation. Rebound values of N-type Schmidt hammer are higher than the L-type values except for phyllite. Sometimes, the rebound values of laboratory and field applications gave different results. This may result from variable local conditions such as minerals differentiation, discontinuities, water content, weathering degree and thickness of foliated structure.

  14. The Dom Feliciano belt (Brazil-Uruguay)and its fore land (Rio de la Plata Craton): framework, tectonic evolution and correlations with similar terranes of southwestern Africa

    International Nuclear Information System (INIS)

    Basei, M.; Siga, O.; Masquelin, H.; Harara, O.; Reis Neto, J.; Preciozzi, F.

    2000-01-01

    The Dom Feliciano Belt (DFB) stretches for ca. 1,200 km along southeastern Brazil and eastern Uruguay, with an average width of 150 km. From its northern limit in Santa Catarina to its termination m Uruguay, DFB is internally organized according three crustal segments characterized, from southeast to northwest, by a Granitoid belt (calci-alkaline to alkaline granitoid rocks deformed to different degrees); a Schist belt (volcano-sedimentary rocks metamorphosed from green schist to amphibolite facies), and a Fore land belt (sedimentary and anchimetamorphic volcanic rocks), the latter situated between the Schist belt and the old western terranes. Despite discontinuously covered by younger sediments, the continuity of these three segments is suggested by the similar lithotypes and structural characteristics, as well as by the gravimetric geophysical signature.In this work, DBF is interpreted as the product of successive subduction s and collisions related to the agglutination of different terranes generated or intensely reworked from the Neoproterozoic to the Cambrian, during the Brasiliano and Rio Doce orogenesis, with maximum time starting at 900 Ma (opening of the Adamastor Ocean) and ending at 530 Ma (deformation of the fore land basins) related to the tecto no-magmatic events associated with the formation of the Western Gondwana.Besides the Neoproterozoic DFB and its fore land, the Rio de la Plata Craton and the Luis Alves Microplate, constituted by Paleoproterozoic gneissic-migmatitic rocks, two other tectonic units can be recognized in southeastern Brazil and eastern Uruguay: the Sao Gabriel Block (RS) where Neoproterozoic juvenile material can be characterized in regional scale (in great part associated with an island are), and the Punta del Este Terrane, which presents, in southern Uruguay, an ortho gneiss basement with ages around 1,000 Ma and a meta sedimentary cover (Rocha Group), which can correspond in the South-American portion, to the Namaqua and Gariep

  15. Geology and geochronology of Cardoso Island, in the southeastern coast of Sao Paulo State

    International Nuclear Information System (INIS)

    Weber, Werner

    1998-01-01

    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 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 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)

  16. K-Ar ages of some metamorphic rocks of Oban massif and their implications for the tectonothermal evolution of Southeastern Nigeria

    International Nuclear Information System (INIS)

    Ekwueme, B.N.; Itaya, Tetsumaru; Yabe, Hisatomo

    2000-01-01

    The following K-Ar ages have been obtained on mineral separates from some metamorphic rocks in the Oban massif: amphibolites (592-930 Ma), banded gneisses (492-538 Ma), granodioritic gneiss (502 Ma), schists (514-519 Ma) and charnockite (481 Ma). Comparison of these ages with previous dates obtained by the Rb-Sr whole rock method and the Pb-Pb evaporation technique on single zircon throws light on the cooling history and orogenic events in the Oban massif. The banded gneiss in the Oban massif yields a zircon age of 1932±5 Ma, indicating that it was emplaced during the early Proterozoic (Eburnean orogeny). The K-Ar age of 492-538 Ma suggests that these rocks were metamorphosed during the Pan-African orogeny. This age is similar to the Rb-Sr isochron age of 510±10 Ma earlier suggested to be the age of migmatization in the Oban massif. The amphibolite yielded Rb-Sr isochron ages of 784±31 Ma and 1313±37 Ma. The age of 1313±37 Ma fits into the Kibaran event. The K-Ar hornblende age of 930±37 Ma on the same amphibolite strongly suggests that this amphibolite belongs to an event older than Pan-African (600±150 Ma) and has not been reset perfectly by the Pan-African event. The migmatitic schists in the Oban massif yielded a Rb-Sr isochron age of 527±16 Ma which has been interpreted as the age of its migmatization. One sample of this schist, however, gave a model age of 676±24 Ma. The K-Ar ages for the Oban massif schists (514-519 Ma) are close to the Rb-Sr isochron age of ca. 527 Ma and confirm that a metamorphic event occurred in the area at this time. This was followed by final cooling at 515±10 Ma. Charnockite in the Oban area has yielded a zircon age of 584±20 Ma, which is Pan-African. The age possibly dates the time of formation of the charnockites. The K-Ar age (481 Ma) obtained in this study is approximately 100 Ma younger than the zircon age and possibly dates the subsequent cooling of the charnockite through hornblende blocking temperature. (author)

  17. Gold deposits in the western sector of the Central Spanish System

    International Nuclear Information System (INIS)

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

    2010-01-01

    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)

  18. Natural radionuclides in ground water in western Spain

    International Nuclear Information System (INIS)

    Fernandez, F.; Lozano, J.C.; Gomez, J.M.G.

    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)

  19. 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).

  20. Petrogenetic significance of rare earth element patterns of selected samples of Ingaldhal metavolcanics, Karnatak State, India : Consortium studies no. 1

    Energy Technology Data Exchange (ETDEWEB)

    Murali, A V; Pawaskar, P B; Reddy, G R; Sankar Das, M [Bhabha Atomic Research Centre, Bombay (India). Analytical Chemistry Div.; Subbarao, K V [Indian Inst. of Tech., Bombay, Geology Dept.; Vasudev, V N [Chitradurga Copper Co., Bangalore (India)

    1979-07-01

    Rare earth element contents of metavolcanics of the Ingaldhal area of Chitradurga schist belt in India have been analysed by instrument neutron activation analysis on the coarse fraction (approximately 30 mesh) and radiochemical neutron activation analysis on the fine fraction (-200 mesh). The coarse and fine fractions of the samples were irradiated separately in the CIRUS reactor at a flux of 10/sup 13/n cm/sup -2/ sec/sup -1/ for 24 hours. The counting assembly consisted of a Ge(Li) detector (45 cc; coupled to 1024 channel analyser) and the system resolution was FWHM 2.3 keV at 1332 keV. Results are presented.

  1. 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.

  2. Seismically imaged shallow and deep crustal structure and potential field anomalies across the Eastern Dharwar Craton, south Indian shield: Possible geodynamical implications

    Science.gov (United States)

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

    2018-05-01

    The time-bound crustal evolution and subsequent deformation of the Cuddapah basin, Nellore Schist Belt and Eastern Ghats terrain of Eastern Dharwar Craton, which have undergone sustained geodynamic upheavals since almost 2.0 billion years, remain enigmatic. An attempt is made here to integrate newly available potential field data and other geophysical anomalies with deep seismic structure, to examine the generative mechanism of major crustal features, associated with this sector. Our study indicates that the initial extent of the Cuddapah basin sedimentation may have been much larger, extending by almost 50-60 km west of Tadipatri during Paleoproterozoic period, which subsequently shrank due to massive erosion following thermal uplift, caused by SW Cuddapah mantle plume. Below this region, crust is still quite warm with Moho temperatures exceeding 500 °C. Similarly, Nallamalai Fold Belt rocks, bounded by two major faults and extremely low gravity, may have occupied a large terrain in western Cuddapah basin also, before their abrasion. No geophysical signatures of thrusting are presently seen below this region, and thus it could not be an alien terrain either. In contrast, Nellore Schist Belt is associated with strikingly high positive gravity, possibly caused by a conspicuous horst structure and up dipping mafic crustal layers underneath, that resulted due to India-east Antarctica collision after the cessation of prolonged subduction (1.6-0.95 Ga). Further, the crustal seismic and gravity signatures would confirm presence of a totally distinct geological terrain east of the Cuddapah basin, but the trace of Eastern Ghats Belt is all together missing. Instead, all the geophysical signatures, point out to presence of a Proterozoic sedimentary terrain, east of Nellore Schist Belt. It is likely that the extent of Prorerozoic sedimentation was much larger than thought today. In addition, presence of a seismically detected Gondwana basin over Nellore Schist Belt, apart

  3. Stratigraphic setting and mineralogy of the Arctic volcanogenic massive sulfide prospect, Ambler district, Alaska.

    Science.gov (United States)

    Schmidt, J.M.

    1986-01-01

    The Arctic prospect, south central Brooks Range, is among the 30 largest of 508 volcanic-hosted massive sulphide deposits in the world. The massive sulphide lenses are interlayered with graphitic schist between metamorphosed rhyolite porphyries in Middle Devonian to early Mississippian metamorphosed volcanic, volcaniclastic and sedimentary rocks. Hydrothermal alteration is of three types: chloritic, phyllic s.l., and pyrite-phengite, each type strata-distinctively and respectively below, in, and above the sulphides. Maximum alteration conforms with metal zoning in the sulfides to suggest predominantly northwestward dispersal from a linear vent area in the elongate basin containing the deposit.-G.J.N.

  4. The Petäjäskoski Formation, a new lithostratigraphic unit in the Paleoproterozoic Peräpohja Belt, northern Finland

    Directory of Open Access Journals (Sweden)

    Markus Kyläkoski

    2012-12-01

    Full Text Available This paper gives the first description of a newly-recognized, basin-wide metasedimentary unit in the Paleoproterozoic (~2.4–1.9 Ga Peräpohja Belt, northern Finland. The unit, which is named the Petäjäskoski Formation (PFm after the single location where the rocks are known to be exposed, is situated stratigraphically in the middle part of the Kivalo Group between the quartzites of the>2.22 Ga Palokivalo Formation and the mafic volcanic rocks of the ~2.1 Ga Jouttiaapa Formation.The bulk of the PFm comprises phlogopitic-sericitic and albitic schists with abundant hematite as a diagnostic feature. Quartzite and dolomite interbeds are common. Based on drillcore and geophysical data, the succession is several hundreds of meters thick. The unit has prograde, chiefly lower greenschist facies mineral assemblages and, though being commonly intensely deformed, shows well-preserved sedimentary structures that imply deposition in shallow-water tosubaerial environments. Based on the original lithological features, the Petäjäskoski Formation can be defined as a claystone-siltstone-sandstone-dolostone association. On the geochemical and stratigraphic basis, the albite schists likely represent albitized equivalents of the micaceous claystones and siltstones. They are intercalated with stratabound collapse breccias, up to tens of meters in thickness, with clasts composed mainly of bordering albite schist. A mafic sill intruding the Petäjäskoski Formation yielded a U-Pb zircon age of 2140 ± 11 Ma. The older, c. 2220 Ma, differentiated sills are not known to reach the stratigraphic level of thePetäjäskoski Formation and hence, the depositional age of the PFm sediments can be bracketed between c. 2220 and 2140 Ma. Detrital zircon grains dated from a quartzitic sample from the PFmshow an Archean (c. 2650–3470 Ma provenance.The moderate to high MgO (~6–13 wt.%, K2O (~3–8 wt.% and FeOtot(8–15 wt.% contents, low CaO and Na2O contents, and abundant

  5. Rare earth element patterns in biotite, muscovite and tourmaline minerals

    International Nuclear Information System (INIS)

    Laul, J.C.; Lepel, E.A.

    1986-01-01

    Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10 -4 g/g to 10/sup -10g//sub g/. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization

  6. Geochronological studies on some rocks and minerals from selected areas

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, J N [Department of Atomic Energy, Hyderabad (India). Atomic Minerals Div.

    1979-01-01

    Ages obtained at the Atomic Minerals Division laboratory, Hyderabad on a number of rock and mineAal samples are presented. Rb-Sr mineral ages from Pungurthy (Tamil Nadu), Sarguja (Madhya Pradesh), Hazaribagh (Bihar) and whole rock isochron age of the granitic bodies surrounding the Kolar schist belt are reported. Discordant U-Pb ages obtained on the uraninites from Kulu (H.P.) and its interpretation in terms of episodic loss has been discussed. Further facilities that are being set up for undertaking other isotopic analysis work for various geoscientific investigations are outtined.

  7. A Gravity data along LARSE (Los Angeles Regional Seismic Experiment) Line II, Southern California

    Science.gov (United States)

    Wooley, R.J.; Langenheim, V.E.

    2001-01-01

    The U.S. Geological Survey conducted a detailed gravity study along part of the Los Angeles Regional Seismic Experiment (LARSE) transect across the San Fernando Basin and Transverse Ranges to help characterize the structure underlying this area. 249 gravity measurements were collected along the transect and to augment regional coverage near the profile. An isostatic gravity low of 50-60 mGal reflects the San Fernando-East Ventura basin. Another prominent isostatic gravity with an amplitude of 30 mGal marks the Antelope Valley basin. Gravity highs occur over the Santa Monica Mountains and the Transverse Ranges. The highest isostatic gravity values coincide with outcrops of Pelona schist.

  8. Scheelite distribution a long of amphibolitic belt from greenstone belt Barbacena, Minas Gerais, Brazil

    International Nuclear Information System (INIS)

    Pereira, R.M.; Alexandre, C.A.

    1990-01-01

    In the middle southern portion of the Minas Gerais state a 60 Km long and 12 Km wide tungsten belt was discovered, and related to the amphibolitic rocks of the Barbacena Greenstone. Tungsten, present as scheelite, is associated with amphibolites, amphibole schists and amphibole gneisses, with chemical characteristics indicating an igneous origin. Chemical analyses on pan concentrates by I.C.P. showed high values on lead, tin, yttrium, lanthanum, cerium and zirconium, and average values for zinc and copper. The scheelite mineralization is probably strata bound and has a possible submarine exhalative origin. (author)

  9. Rb/Sr ages of metamorphites of the Herbert Mountains, Shackleton Range, Antarctica

    International Nuclear Information System (INIS)

    Hofmann, J.; Pilot, J.; Schlichting, M.

    1981-01-01

    Results of Rb/Sr-age determinations from six mica schists, sampled in the upper part of the Shackleton metamorphic complex (Herbert Mountains, Shackleton Range, Antarctica) are reported. A three point isochrone gives an age of 470 +- 36 mio. yrs., a two point isochrone an age of 1414 +- 185 mio yrs. The first age marks a thermo-magmatic activation of early paleozoic age, the second one is interpretated as the age of regional metamorphism from the upper parts of the Shackleton metamorphic complex. The results are discussed under consideration of former age determinations. (author)

  10. A mélange of subduction temperatures: Evidence from Zr-in-rutile thermometry for strengthening of the subduction interface

    Science.gov (United States)

    Penniston-Dorland, Sarah C.; Kohn, Matthew J.; Piccoli, Philip M.

    2018-01-01

    The Catalina Schist contains a spectacular, km-scale amphibolite facies mélange zone, thought to be part of a Cretaceous convergent margin plate interface. In this setting, blocks ranging from centimeters up to ≥100 m in diameter are surrounded by finer-grained matrix that is derived from the blocks. Blocks throughout the mélange represent a diversity of protoliths derived from basalts, cherts and other sediments, and hydrated mantle, but all contain assemblages consistent with upper amphibolite-facies conditions, suggesting a relatively restricted range of depths and temperatures over which material within the mélange was metamorphosed. This apparent uniformity of metamorphic grade contrasts with other mélanges, such as the Franciscan Complex, where coexisting rocks with highly variable peak metamorphic grade suggest extensive mixing of materials along the subduction interface. This mixing has been ascribed to flow of material within relatively low viscosity matrix. The Zr content of rutile in samples from across the amphibolite facies mélange of the Catalina Schist was measured to determine peak metamorphic temperatures, identify whether these temperatures were different among blocks, and whether the spatial distribution of temperatures throughout the mélange was systematic or random. Resolvably different Zr contents, between 290 and 720 (±10-40) ppm, are found among the blocks, corresponding to different peak metamorphic temperatures of 650 to 730 (±2-16) °C at an assumed pressure of 1 GPa. These results are broadly consistent with previous thermobarometric estimates. No systematic distribution of temperatures was found, however. Like other mélange zones, material flow within the Catalina Schist mélange was likely chaotic, but appears to have occurred on a more restricted scale compared to some other localities. Progressive metamorphism of mélange matrix is expected to produce rheologically stiffer matrix minerals (such as amphiboles and pyroxenes

  11. Pre-impact tectonothermal evolution of the crystalline basement-derived rocks in the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure

    Science.gov (United States)

    Gibson, R.L.; Townsend, G.N.; Horton, J. Wright; Reimold, W.U.

    2009-01-01

    Pre-impact crystalline rocks of the lowermost 215 m of the Eyreville B drill core from the Chesapeake Bay impact structure consist of a sequence of pelitic mica schists with subsidiary metagraywackes or felsic metavolcanic rocks, amphibolite, and calc-silicate rock that is intruded by muscovite (??biotite, garnet) granite and granite pegmatite. The schists are commonly graphitic and pyritic and locally contain plagioclase porphyroblasts, fi brolitic sillimanite, and garnet that indicate middle- to upper-amphibolite-facies peak metamorphic conditions estimated at ??0.4-0.5 GPa and 600-670 ??C. The schists display an intense, shallowly dipping, S1 composite shear foliation with local micrometer- to decimeter-scale recumbent folds and S-C' shear band structures that formed at high temperatures. Zones of chaotically oriented foliation, resembling breccias but showing no signs of retrogression, are developed locally and are interpreted as shear-disrupted fold hinges. Mineral textural relations in the mica schists indicate that the metamorphic peak was attained during D1. Fabric analysis indicates, however, that subhorizontal shear deformation continued during retrograde cooling, forming mylonite zones in which high-temperature shear fabrics (S-C and S-C') are overprinted by progressively lower- temperature fabrics. Cataclasites and carbonate-cemented breccias in more competent lithologies such as the calc-silicate unit and in the felsic gneiss found as boulders in the overlying impactite succession may refl ect a fi nal pulse of low-temperature cataclastic deformation during D1. These breccias and the shear and mylonitic foliations are cut by smaller, steeply inclined anastomosing fractures with chlorite and calcite infill (interpreted as D2). This D2 event was accompanied by extensive chlorite-sericitecalcite ?? epidote retrogression and appears to predate the impact event. Granite and granite pegmatite veins display local discordance to the S1 foliation, but elsewhere

  12. Method for production of fuel oils and diesel motor oils free of sediments and with unlimited miscibility

    Energy Technology Data Exchange (ETDEWEB)

    1942-01-13

    A method is described for the production of fuel and diesel oils free of sediments and with unlimited miscibility by their recovery from substances poor in hydrogen, such as tars of fossil carbon, from lignite, from peat, from schist oils, from wood, or tar oils of corresponding extracts, poorly hydrogenated carbohydrates and the like, characterized by the fact that these substances are being subjected without mixing with selective solvents to a chemical purification and then immediately subjected to a redistillation and the obtained distillates being cut with hydrogen-rich oils to obtain normal diesel oils.

  13. Uranium distribution in Puerto Galera-San Teodoro, Northern Mindoro, Philippines

    International Nuclear Information System (INIS)

    Santos, G. Jr.; Seguis, J.E.

    1982-09-01

    Geochemical mapping of uranium in stream sediment with the use of delayed neutron activation analysis (DNAA) was conducted in northeastern Mindoro Island. Uranium was determined in stream sediments by means of an automated analysis system utilizing a neutron activation/delayed neutron counting technique. Stream sediments were collected at a density of less than one sample per 2 sq. km. A total of 428 samples were analyzed. The background and threshold uranium values were 2.6 ppm and 4.5 ppm, respectively. Three small anomalous localities were identified in areas underlain by Paleozoic (Carboniferous) Mindoro Metamorphics (undifferentiated schist and marble). Further exploration of these anomalous areas is warranted. (author)

  14. Compared model of formation of AU, SN-W, and TA-NB-Li-SN ore deposits within the tras-os-montes domain of the hercynian orogen (NW Spain). The role of intrusion on the mineralogical and fluid inclusion characteristics.

    OpenAIRE

    Gloaguen , Eric; Cathelineau , M.; Boiron , M.C.; Marignac , C.; Lerouge , Catherine; Fourcade , S.; Branquet , Yannick; Chauvet , Alain; Bouchot , Vincent; Le Goff , Maxime

    2006-01-01

    International audience; The study area is located in the Galicia-Trás-os-Montes Zone (GTMZ zone, Arenas et al. 1986; Farias et al. 1987 Fig. 1) a part of the Iberian hercynian massif. The GTMZ belongs to the internal zone of the Hercynian belt and is composed of a relative autochthonous and parautochthonous units overthrusted by allochthonous complexes. Studied area is located in the Schistose Domain (parautochthonous Marquínez García 1984) which is composed by a monotonous sequence of schist...

  15. Geology, mineralogy, geochemistry and origin of phosphates from Jandia, Cansa Perna, Itacupim (Para) and Pirocaua and Trauira (Maranhao)

    International Nuclear Information System (INIS)

    Costa, M. L. da.

    1980-01-01

    The phosphate occurrences of Northeastern Para and Northwestern Maranhao were formed by strong lateritic weathering of phosphorus-rich Precambrian rocks. The rock formation affected by those processes were phyllites and schists of the Gurupi Group in Cansa Perna and Pirocaua, a complex of felsic to mafic and ultramafic rocks metamorphosed in the greenschist facies in Itacupim and Trauira and probably phosphoritic sandstone in Jandia. The geology, the mineralogy of phosphates, oxides, hydroxides and silicates, the geochemistry of element distribution (aluminium, silicon, iron, calcium, etc) and trace elements distribution (strontium, rubidium, barium, rare earths, zirconium, niobium uranium, thorium, etc) and the phosphates origin are studied. (C.G.C.)

  16. Occurrence of uranium in the itabiritic iron ore of Morro Agudo on the NE border of the iron Quadrangle/Minas Gerais, Brasilien

    International Nuclear Information System (INIS)

    Guba, I.

    1982-01-01

    The precambrian itabirites and hematite ores of the Morro Agudo iron ore mine on the NE border of the Quadrilatero Ferrifero in Minas Gerais/Brazil contain uranium-bearing minerals and rare-earth elements. In association with phosphates they occupy planes of joints, fractures and cleavage in the area of amphibolitic schist which is intercalated in the s 1 -planes of the itabirites and hematite ores. Preliminary analyses of the uranium-bearing minerals were made by energy dispersive X-ray spectrometry and electron microscopy. The results are presented in connection with the lithologic and tectonic features of the Morro Agudo mine. (orig.) [de

  17. Graphite as an indicator of contact influence of Western Keivy alkaline granite intrusion, the Kola Peninsula

    Directory of Open Access Journals (Sweden)

    Fomina E. N.

    2017-03-01

    Full Text Available The results of complex petro-mineragraphic, Raman and isotope- geochemical study of three types of graphite- bearing rocks circulated at different distances from the alkaline granites: (1 kyanite schists of Bolshiye Keivy, sampled at a considerable distance from a contact with alkaline gran ites; (2 sillimanite schists, sampled close to the contact, and (3 silexites, located in the inner part of th e alkaline granite massif Western Keivy have been presented. Five morphogenetic types of graphite have been revealed in the rocks under consideration: fine- grained Gr-1, intergranular Gr-2, nest-shaped Gr-3, vein Gr- 4 and spherulitic Gr-5. Current study demonstrates that these five types of graphite distinctly vary not only i n morphology, but also in temperature of crystallization, as determined by RSCM-Raman geothermometer, and in carbon isotop e composition. The most likely source for the anomalous "light" graphite Gr-1 and Gr-2 [δ 13 C(PDB = −43...−45 ‰] from kyanite schists is a water- methane fluid originating from sedimentary rocks with org anic compounds. The carbon of graphite Gr-5 of the silexites selected at the inner part of alkaline granite massif West ern Keivy, on the contrary, proved to be most "heavy" [δ 13 C(PDB = −8 ‰], which indicates its origin from the lower crustal or mantle carbon dioxide fluid. Thus, carbon extracted into the rocks of Keivy structure from at least two contrasting isotope sources. Graphite Gr-3, that makes up the bulk of graphite of exocontact sil limanite schists, is also isotopically light, but not anomalously [δ 13 C(PDB = −17...−28 ‰]. The crystallization temperature of the gi ven graphite (435−520 ºC, and its structural relationships with other minerals of th e rock evidence of its synmetamorphic origin. The presence of veinlets of isotopically heavy [δ 13 C(PDB = −10 ‰...−11 ‰] high-temperature (570−670 ºC graphite intersecting minerals of the metamorphic paragenesis (i

  18. Electrical properties of Egyptian natural graphite

    International Nuclear Information System (INIS)

    El-Shazly, O.; El-Wahidy, E.F.; Elanany, N.; Saad, N.A.

    1992-06-01

    The electrical properties of Egyptian natural graphite flakes, obtained from the graphite schists of Wadi Bent, Eastern Desert, were measured. The flakes were ground and compressed into pellets. The standard four probe dc method was used to measure the temperature dependence of the electric resistivity from room temperature down to 12 K. The transverse and longitudinal magnetoresistance were measured in the low magnetic field range at temperatures 300 K, 77 K and 12 K. The transverse magnetoresistance data was used to estimate the average mobility, assuming a simple two-band model. (author). 20 refs, 4 figs, 1 tab

  19. Nanodiamond Formation at the Lithogenesis and Low-Stages of Regional Metamorphism

    Science.gov (United States)

    Simakov, S. K.; Melnik, N. N.; Vyalov, V. I.

    2018-02-01

    Samples of gilsonite from Adzharia, anthraxolite and graphite of coal from Taimyr, shungite from Karelia, and anthracite from Donbass are studied using Raman spectroscopy. Peaks at 1600 cm-1, indicating the presence of nanographite, are recorded in all samples. The anthracite sample from Donbass, 1330 cm-1, corresponds to the sp 3-line of carbon hybridization conforming to a nanodiamond. It is concluded that in nature diamonds can be formed at late stages of lithogenesis (catagensis, metagenesis), and for coals, it can occur at the zeolite stage of regional metamorphism of rocks, before the green schist stage.

  20. Constraints on Alpine Fault (New Zealand) Mylonitization Temperatures and Geothermal Gradient from Ti-in-quartz Thermobarometry

    OpenAIRE

    Kidder, Steven; Toy, Virginia; Prior, Dave; Little, Tim; MacRae, Colin

    2018-01-01

    We constrain the thermal state of the central Alpine Fault using approximately 750 Ti-in-quartz SIMS analyses from a suite of variably deformed mylonites. Ti-in-quartz concentrations span more than an order of magnitude from 0.24 to ~5 ppm, suggesting recrystallization of quartz over a 300° range in temperature. Most Ti-in-quartz concentrations in mylonites, protomylonites, and the Alpine Schist protolith are between 2 and 4 ppm and do not vary as a function of grain size or bul...

  1. Radioactivity measurements of soil samples from Raichur of Karnataka, India

    International Nuclear Information System (INIS)

    Rajesh, S.; Kerur, B.R.; Anilkumar, S.

    2016-01-01

    Radiations present in environment comprise the terrestrial and extraterrestrial radiations. Natural radioactivity measurement, radiation monitoring of the region, dose assessment and interpretation of radiological related parameters are crucial aspects from the public awareness and environmental safety point of view. It is found that values of the radiological parameters obtained for samples in the study area were found within acceptable or permissible limits. The estimated gamma absorbed dose rate was found to be in the range 32 - 162 nGy h -1 . Higher dose rate than that of the normal dose rate were observed in the regions where granitic, granitic gneiss and schist outcrops were prominent area

  2. Final Environmental Assessment for 2012-14 Capital Improvements Program (CIP) for Davis-Monthan Air Force Base (AFB), Tucson, Arizona

    Science.gov (United States)

    2012-03-01

    but most of the andesite and basaltic flows were fo1med in the last 50 million years. The oldest rocks in the Tucson Basin ru·e the metavolcanic...Pinal Schist, fo1med approximately 1.7 billion years ago (U.S. Geological Smvey 2003). Some basaltic flows occmTed as early as 4 million years ago and...pe1mits. ACMs are a pruticulru· concem for demolition projects because of potential exposme of workers to hazardous fibers released into the air

  3. Litiniferous pegmatites from Itinga-Aracuai region, Minas Gerais, Brazil

    International Nuclear Information System (INIS)

    Silva Sa, J.H. da.

    1977-01-01

    This work explains the study of more a hundred pegmatites from Itinga and Aracuai, in middle Jequitinhonha. This area have cassiterite, tantalite-columbite, semiprecious stones ad lithium minerals. The lithium ores are the most economic importance. The predominate rocks are quartz-mica schist, rich in cordierite. Geochronological dating, by the Rb-Sr method, show ages about 650 m.a. to schist and 520 m.a. to the granites. Was dated muscovites from two pegmatites by K-Ar method showing ages about 4677+- 18 m.a and 490 +- 12 m.a. The pegmatites was classified in simple and complex, based in mineralogical and structural criterion. In the complex pegmatites was determinated notable accessory minerological association, in which the principal are lithium ores-petalite, spodumene, lepidolite, ambligonite, the cesium ore-polucite-and cassiterite, tantalite-columbite, and great variety of turmaline. Genetically the pegmatites are related with the granites of this region, with present high tenor of the lithium, cesium and beryllium, comparate with the normal granites. (C.D.G.) [pt

  4. Mineralogy of asbestos from the metamorphic complex from north eastern Takab-NW Iran

    International Nuclear Information System (INIS)

    Hajialioghli, R.; Moazzen, M.

    2016-01-01

    The ultramafic rocks from the Takht-e-Soleyman metamorphic complex, in Precambrian age, are classified as serpentinized meta peridotites and serpentinites, based on degree of serpentinization. Serpentine forms more than 90 volume% of the serpentinites. On the basis of serpentine polymorphs, textural relations and micro-structure features, variety of serpentinites are determined as massive serpentinites, serpentinite schists and chrysotile-bearing serpentinites. Chrysotile in serpentinites has been formed due to static condition and brittle deformations. During static state chrysotile and lizardite after olivine and pyroxene are formed as pseudomorphic mesh and bastite textures in the massive serpentinites. Then serpentinization processes reactivated by formation and development of joints and fractures related to brittle deformations at the local sheared zones. Chrysotile occur as fine grained crystals in the serpentinite matrix and veinlets with mm thickness filling fractures of the chrysotile-bearing serpentinites. Slight thickness of chrysotile veinlet in the investigated serpentinites can be attributed to the olivine rich composition of protolite. Low amounts of Cr 2 O 3 in composition of the analyzed chrysotile supports low clinopyroxene and high olivine in protolite of serpentinites. Serpentinite schists are formed under ductile deformation condition at the regional sheared zones. Amphibole asbestos occur as veins having meter scale thickness filling of joints and fractures at the regional sheared zone. Length of thin and long asbestos amphibole arrives up to cm. On the basis of petrography, Raman spectroscopy, XRD and microprope analysis, both chrysotile- and amphibole asbestos have been recognized in the Takht-e-Soleyman serpentintes.

  5. Stable isotope study of serpentinization and metamorphism in the Highland Border Suite, Scotland, UK

    Energy Technology Data Exchange (ETDEWEB)

    Ikin, N.P. (University Coll., Cardiff (UK)); Harmon, R.S. (Southern Methodist Univ., Dallas, TX (USA))

    1983-02-01

    D/H and /sup 18/O//sup 16/O ratios have been measured for whole-rock samples and mineral separates from the mafic and ultramafic rocks of the Cambro-Ordovician Highland Border Suite. The H- and O-isotopic compositions of these rocks record individual stages in a relatively complex 500 Myr old hydrothermal/ metamorphic history. Lizardite serpentinites record a premetamorphic history and indicate that parent harzburgites, dunites, and pyroxenites were serpentinized through low-temperature interaction with meteoric waters during cooling. The other rocks of the Highland Border Suite record subsequent interaction with metamorphic fluids. Amphibolite facies hornblende schists were produced through thrust-related metamorphism of spilitic pillow lavas. During dehydration, D-enriched fluids were driven off from the spilites thus leaving the hornblende schists to equilibrate with a relatively D-depleted internal fluid reservoir. The expelled D-enriched fluids may have mixed with more typical Dalradian metamorphic waters which then exchanged with the remaining mafic rocks and lizardite serpentinites during greenschist facies regional metamorphism to produce antigorite serpentinites and greenschist metaspilites with similar H- and O-isotopic compositions. Serpentinites which have been only partially metamorphosed show intermediate H-isotopic compositions between that of metamorphic antigorite and non-metamorphic lizardite end members.

  6. Evaluating the effect of lithology on porosity development in ridgetops in the Appalachian Piedmont

    Science.gov (United States)

    Marcon, V.; Gu, X.; Fisher, B.; Brantley, S. L.

    2016-12-01

    Together, chemical and physical processes transform fresh bedrock into friable weathered material. Even in systems where lithology, tectonic history, and climatic history are all known, it is challenging to predict the depth of weathering because the mechanisms that control the rate of regolith formation are not understood. In the Appalachian Piedmont, where rates of regolith formation and erosion are thought to be in a rough steady state, the depth of weathering varies with lithology. The Piedmont provides a controlled natural environment to isolate the effects of lithology on weathering processes so we can start to understand the mechanisms that initiate and drive weathering. Weathering is deepest over feldspathic rocks (schist/granite) with regolith 20-30m thick and thinnest over mafic and ultramafic rocks (diabase/serpentinite) with regolith serpentinization reactions and lost from collapse during weathering. Serpentinite consists of easily weathered hydrous minerals with little quartz. Comparatively, rocks with more quartz (e.g. schist) have a supportive skeleton as the rock weathers. This quartz skeleton could prevent the collapse of pores and result in isovolumetric weathering. Non-isovolumetric weathering limits infiltration of reactive fluids deeper into the rock, minimizing regolith formation in serpentinite due to its lack of a quartz skeleton. Given this, fracture toughness may be an important parameter to consider in terms of predicting regolith thickness.

  7. A stable isotope study of serpentinization and metamorphism in the Highland Border Suite, Scotland, UK

    International Nuclear Information System (INIS)

    Ikin, N.P.; Harmon, R.S.

    1983-01-01

    D/H and 18 O/ 16 O ratios have been measured for whole-rock samples and mineral separates from the mafic and ultramafic rocks of the Cambro-Ordovician Highland Border Suite. The H- and O-isotopic compositions of these rocks record individual stages in a relatively complex 500 Myr old hydrothermal/ metamorphic history. Lizardite serpentinites record a premetamorphic history and indicate that parent harzburgites, dunites, and pyroxenites were serpentinized through low-temperature interaction with meteoric waters during cooling. The other rocks of the Highland Border Suite record subsequent interaction with metamorphic fluids. Amphibolite facies hornblende schists were produced through thrust-related metamorphism of spilitic pillow lavas. During dehydration, D-enriched fluids were driven off from the spilites thus leaving the hornblende schists to equilibrate with a relatively D-depleted internal fluid reservoir. The expelled D-enriched fluids may have mixed with more typical Dalradian metamorphic waters which then exchanged with the remaining mafic rocks and lizardite serpentinites during greenschist facies regional metamorphism to produce antigorite serpentinites and greenschist metaspilites with similar H- and O-isotopic compositions. Serpentinites which have been only partially metamorphosed show intermediate H-isotopic compositions between that of metamorphic antigorite and non-metamorphic lizardite end members. (author)

  8. Study geology and uranium mineralization of ririt-amir engkala - tiga dara sector West Kalimantan

    International Nuclear Information System (INIS)

    Bambang Soetopo

    2009-01-01

    The results of previous research from Ririt, Amir Engkala, Tiga Dara sector which consist of geology, geophysics and drilling data show that all of the areas has similar in geology and Uranium mineralization. The purpose of this study is to know the relationship between geological condition and Uranium mineralization in Ririt, Amir Engkala and Tiga Dara sector. In general the geology of Ririt and Amir Engkala is similar with Tiga Dara sector. Those areas consist of tourmaline quartzite, muscovite quartzite, meta ignimbrite, biotite quartz schist, muscovite quartz schist, and micro diorite. The direction of the stratification is NE - SW and dipping to SE and the direction of the stochasticity is W - E and dipping to N. The dextral faults have WNW-ESE and NNE - SSW trends, while the sinistral one is WSW - ENE direction. There are also a thrust fault and a normal fault with WSW-ESE and NW-SE striking respectively. Uranium mineralization as a uraninite fill in the stochasticity and fracture N2600-30° E37°-59° in orientation which associated with magnetite, chalcopyrite, pyrite, arsenopyrite,. rutile, ilmenite, tourmaline and quartz. Radiometric value of Uranium mineralization is in the range of 500-15.000 c/s. The mineral association and the present of calcite, gypsum and quartz veins suggest that Uranium mineralization was resulted by hydrothermal magmatic processes. (author)

  9. Tectono-metamorphic evolution of high-P/T and low-P/T metamorphic rocks in the Tia Complex, southern New England Fold Belt, eastern Australia: Insights from K-Ar chronology

    Science.gov (United States)

    Fukui, Shiro; Tsujimori, Tatsuki; Watanabe, Teruo; Itaya, Tetsumaru

    2012-10-01

    The Tia Complex in the southern New England Fold Belt is a poly-metamorphosed Late Paleozoic accretionary complex. It consists mainly of high-P/low-T type pumpellyite-actinolite facies (rare blueschist facies) schists, phyllite and serpentinite (T = 300 °C and P = 5 kbar), and low-P/high-T type amphibolite facies schist and gneiss (T = 600 °C and P Tia granodiorite). White mica and biotite K-Ar ages distinguish Carboniferous subduction zone metamorphism and Permian granitic intrusions, respectively. The systematic K-Ar age mapping along a N-S traverse of the Tia Complex exhibits a gradual change. The white mica ages become younger from the lowest-grade zone (339 Ma) to the highest-grade zone (259 Ma). In contrast, Si content of muscovite changes drastically only in the highest-grade zone. The regional changes of white mica K-Ar ages and chemical compositions of micas indicate argon depletion from precursor high-P/low-T type phengitic white mica during the thermal overprinting and recrystallization by granitoids intrusions. Our new K-Ar ages and available geological data postulate a model of the eastward rollback of a subduction zone in Early Permian. The eastward shift of a subduction zone system and subsequent magmatic activities of high-Mg andesite and adakite might explain formation of S-type granitoids (Hillgrove suite) and coeval low-P/high-T type metamorphism in the Tia Complex.

  10. Detailed prospective stages of inventory of U resources in Mentawa and Seruyan, Center of Kalimantan

    International Nuclear Information System (INIS)

    Ramadanus; Sudjiman; Agus, S.

    1996-01-01

    Indication of U mineralization in granite biotite 1.500 cps and metasilt boulders 500 cps - 15.000 cps was found in Mentawa River. This detailed examination was done with the aim to gather geological information and U mineralization and to obtain knowledge about potential U resources. Methods used were geological mapping, the radiometric measuring and peeling the chosen outcrop samples were taken from outcrop and anomaly boulders, and stream sediment as mud and heavy minerals. This research was backed up with laboratory analysis in the form of petrography, mineragraphy, autoradiography, total and mobile U content. The result of this research stratigraphy of Mentawa and Seruyan which consisted of schist and tonalite. Outcrop of U mineralization was found in schist in the from of uraninite generally, filled up SSE-NNW subvertical-vertical dipping. Boulder of U mineralizations was found in the from of uraninite, gumite and autonite associated with turmaline. Those U mineralizations mentioned were found in Mentawa Satu River and upper reaches of Rengka River with distribution width + 7 km 2

  11. FY 2000 report on the results of the data processing in the geothermal development promotion survey. Tertiary. No.B-7 Kuwanosawa area; 2000 nendo chinetsu kaihatsu sokushin chosa data shori hokokusho. No. B-7 Kuwanosawa chiiki (Dai 3 ji)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-01-01

    The comprehensive analysis was conducted of various data obtained in the geothermal development promotion survey conducted in the Kuwanosawa area, Yuzawa city, Akita prefecture, from FY 1998 to FY 2000. The geology of the Kuwanosawa area consists of the Pretertiary system and Quarternary system, through which intrusive rocks are recognized. Basement rocks are composed of the Paleozoic-origin crystalline schist and the Cretaceous-period granites which intruded into the schist. In the Kuwanosawa area, there were recognized no clear geothermal signs such as the discharge of geothermal fluids like hot spring, fumarolic gas, etc., places of high temperature and new geothermal alteration zones. The geothermal water of borehole N11-KN-1 is a low temperature/low CL concentration geothermal water which was stored in basement rocks, which is supposed to be the one conductively heated in the process of the meteoric water penetrating deep-underground. The geothermal system heat source in the Kuwanosawa area and the periphery is regarded as the relic magma which spewed out the volcanic rocks of Mt. Takamatsu-dake in the Quaternary period. However, the geothermal fluid included no components originating in high temperature volcanic emissions, and therefore, it is considered that the geothermal fluid was formed by the meteoric water conductively heated by volcanic heat source. (NEDO)

  12. 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.

  13. On most ancient geologic events on the Anabar Shield

    International Nuclear Information System (INIS)

    Melnikow, A.I.; Lepin, V.S.; Solodyankina, V.N.; Kolosnicyna, T.I.; Oxmann, V.S.; Petrov, A.F.

    1987-01-01

    The Anabar Shield is considered in geologic literature as one of the oldest formations of the Earth. In present work a special selection of two series of samples was undertaken: crystallic schists of the Daldynskaya Series and plagio-granito-gneisses from the basin of the Knyasevaya River. Concentrations of Rb, Sr, K and 87 Sr/ 86 Sr, 87 Rb/ 86 Sr isotope ratios were determined. A Rb-Sr isochron for plagio-granito-gneisses gives ages 1.1 and 1.8 by (depending on interpretation). According to the data obtained the plagio-granito-gneisses may not be regarded as oldest formations of the Earth. In contrast to these, the crystallic schists allow to obtain a reliable Rb-Sr isochron age of 3.8 ± 0.2 by with ( 87 Sr/ 86 Sr) 0 = 0.7010. Thus, on the Anabar shield one of the oldest events of the Earth is detected. It is stated that K/Rb and 87 Rb/ 86 Sr ratios are correlated and are quite specific for oldest formations of the Earth. (author)

  14. Provenance and depositional age of metavolcano-sedimentary sequences of the Santa Terezinha de Goias, based on Sm-Nd and U-Pb zircon single grain

    International Nuclear Information System (INIS)

    Dantas, Ellton Luiz; Jost, Hardy; Fuck, Reinhardt A.; Brod, Jose Afonso; Pimentel, Marcio Martins; Meneses, Paulo Roberto

    2001-01-01

    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)

  15. [NIR and XRD analysis of drill-hole samples from Zhamuaobao iron-graphite deposit, Inner Mongolia].

    Science.gov (United States)

    Li, Ying-kui; Cao, Jian-jin; Wu, Zheng-quan; Dai, Dong-le; Lin, Zu-xu

    2015-01-01

    The author analyzed the 4202 drill-hole samples from Zhamuaobao iron-graphite deposit by using near infrared spectroscopy(NIR) and X-ray diffraction(XRD) measuring and testing techniques, and then compared and summarized the results of two kinds of testing technology. The results indicate that some difference of the mineral composition exists among different layers, the lithology from upper to deeper is the clay gravel layer of tertiary and quaternary, mudstone, mica quartz schist, quartz actinolite scarn, skarnization marble, iron ore deposits, graphite deposits and mica quartz schist. The petrogenesis in different depth also shows difference, which may indicate the geological characteristic to some extent. The samples had mainly undergone such processes as oxidization, carbonation, chloritization and skarn alteration. The research results can not only improve the geological feature of the mining area, but also have great importance in ore exploration, mining, mineral processing and so on. What's more, as XRD can provide preliminary information about the mineral composition, NIR can make further judgement on the existence of the minerals. The research integrated the advantages of both NIR and XRD measuring and testing techniques, put forward a method with two kinds of modern testing technology combined with each other, which may improve the accuracy of the mineral composition identification. In the meantime, the NIR will be more wildly used in geography on the basis of mineral spectroscopy.

  16. Relationship between fluvial clastic sediment and source rock abundance in Rapti river basin of central Nepal Himalayas

    International Nuclear Information System (INIS)

    Tamrakar Naresh Kazi; Shresth Madhusudan Bhakta

    2008-01-01

    Many tributaries from carbonate sedimentary, metamorphic and igneous rocks of the Lesser Himalayan and clastic sedimentary rocks of the Sub-Himalayan Ranges carry gravelly sediments to the Rapti River. River bar sediments were analyzed for composition and texture to evaluate downstream changes in properties, and to establish relationship between proportion of clasts and the abundance of rock types in the source areas. Percent quartzite clast or granite clast increases whereas that of carbonate, schist or slate decreases along downstream. The largest grain size decreases downstream, whereas fatness index and sphericity tend to increase. Despite of little diminish in relative abundance of rock types in source areas along the river, the relative proportion of corresponding clast type shows rapid reduction (e.g. slate or phyllite or carbonate clasts) or rapid enhancement (e.g. granite clast). The relationships of quartzite clast and schist clasts with their corresponding source rocks are statistically significant suggesting that these clasts can provide clue to source rock abundance. About 85 to 94% of the gravel clasts represent rock types of the Lesser Himalayan Range suggesting that this range has been contributing enormous amount of sediments.

  17. 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.)

  18. A new mathematical approximation of sunlight attenuation in rocks for surface luminescence dating

    Energy Technology Data Exchange (ETDEWEB)

    Laskaris, Nikolaos, E-mail: nick.laskaris@gmail.com [University of the Aegean, Department of Mediterranean Studies, Laboratory of Archaeometry, 1 Demokratias Avenue, Rhodes 85100 (Greece); Liritzis, Ioannis, E-mail: liritzis@rhodes.aegean.gr [University of the Aegean, Department of Mediterranean Studies, Laboratory of Archaeometry, 1 Demokratias Avenue, Rhodes 85100 (Greece)

    2011-09-15

    The attenuation of sunlight through different rock surfaces and the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals clock resetting derived from sunlight induced eviction of electrons from electron traps, is a prerequisite criterion for potential dating. The modeling of change of residual luminescence as a function of two variables, the solar radiation path length (or depth) and exposure time offers further insight into the dating concept. The double exponential function modeling based on the Lambert-Beer law, valid under certain assumptions, constructed by a quasi-manual equation fails to offer a general and statistically sound expression of the best fit for most rock types. A cumulative log-normal distribution fitting provides a most satisfactory mathematical approximation for marbles, marble schists and granites, where absorption coefficient and residual luminescence parameters are defined per each type of rock or marble quarry. The new model is applied on available data and age determination tests. - Highlights: > Study of aattenuation of sunlight through different rock surfaces. > Study of the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals as a function of depth. > A Cumulative Log-Normal Distribution fitting provides the most satisfactory modeling for marbles, marble schists and granites. > The new model (Cummulative Log-Norm Fitting) is applied on available data and age determination tests.

  19. 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.

  20. A new mathematical approximation of sunlight attenuation in rocks for surface luminescence dating

    International Nuclear Information System (INIS)

    Laskaris, Nikolaos; Liritzis, Ioannis

    2011-01-01

    The attenuation of sunlight through different rock surfaces and the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals clock resetting derived from sunlight induced eviction of electrons from electron traps, is a prerequisite criterion for potential dating. The modeling of change of residual luminescence as a function of two variables, the solar radiation path length (or depth) and exposure time offers further insight into the dating concept. The double exponential function modeling based on the Lambert-Beer law, valid under certain assumptions, constructed by a quasi-manual equation fails to offer a general and statistically sound expression of the best fit for most rock types. A cumulative log-normal distribution fitting provides a most satisfactory mathematical approximation for marbles, marble schists and granites, where absorption coefficient and residual luminescence parameters are defined per each type of rock or marble quarry. The new model is applied on available data and age determination tests. - Highlights: → Study of aattenuation of sunlight through different rock surfaces. → Study of the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals as a function of depth. → A Cumulative Log-Normal Distribution fitting provides the most satisfactory modeling for marbles, marble schists and granites. → The new model (Cummulative Log-Norm Fitting) is applied on available data and age determination tests.

  1. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Portugal

    International Nuclear Information System (INIS)

    1977-10-01

    Portugal is situated on the western edge of the Iberian Meseta. At present, its reasonably assured reserves are about 7800 t of U (including 1000 t of U at more than 830/lb U 3 O 8 ) and 850 t of U in estimated additional reserves. This potential is divided between vein deposits and deposits located in the peribatholithic schists or enclaved in granite. Two main districts share these reserves - Beira at the centre of the country and Alto Alentejo in the east, approximately at the same latitude as Lisbon. In spite of the considerable prospecting activities authorized by Portugal in the Meseta area, the subject cannot yet be regarded as exhausted. Additional resources may still be located in the horizontal and vertical extensions of the vein mineralizations or schists from the already known deposits or outside the districts containing such deposits. Moreover, certain post-Palaeozoic sedimentary basins exhibit features favourable for the presence of uranium-bearing deposits and therefore deserve to be taken into consideration. However, there are as yet no examples of economic mineralization in such locations in Portugal. All things considered, we considered it reasonable to place Portugal in category No. 3 of the classiffication adopted by BJREP. (author)

  2. 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.)

  3. Results of Rb-Sr dating of metamorphic rocks of crystalline complexes of Male Karpaty Mts

    International Nuclear Information System (INIS)

    Bagdasaryan, G.P.; Gukasyan, P.Kh.; Cambel, B.; Veselsky, J.

    1983-01-01

    The paper follows up on a recently published paper on Rb-Sr isochrone dating of granitoid rocks of the Male Karpaty Mts. Data are given on comparative statistical analysis of isochrones obtained for the Bratislava and Modra massifs (isochrone of the latter is complemented with the analyses of two new samples) and the results of age determination of metasedimentary rocks of the Pezinok-Pernek zone and the Bratislava area by the Rb-Sr isochrone. Regression analysis shows that there is no statistically significant difference between the age of the Bratislava massif (347+-4 m.y.) and the Modra massif (326+-22 m.y.) and between their initial ratios 87 Sr/ 86 Sr (i.e., they are synchronous, having the same magma source) which makes it possible to calculate uniform value for age. Whole-rock samples of metamorphic and crystalline schists (gneisses) of the Male Karpaty Mts. also determine the isochrone corresponding to the age 387+-38 m.y. (2σ) and initial ratio ( 87 Sr/ 86 Sr)=0.7100+-0.00O8 (2σ). Rb-Sr isotope analyses of several pairs of biotite-crystalline schist (from which biotite was separated) point out that redistribution of Sr isotopes among the mineral phases of rocks takes place during the periplutonic metamorphism, while the whole-rock samples remain chemically closed systems. (author)

  4. Origin of acid orthoderived and paraderived geologic formations of the central part of the province of Limousin (France). A possible source for uraniferous leucogranite

    International Nuclear Information System (INIS)

    Bourguignon, A.

    1988-01-01

    Important metamorphic formations of the central part of the province of Limousin are studied by chemical investigations for characterization of their primary signature. Four large orthoderived formations are compared: Dronne, Meuzac, and Thaurion arcs and leptynite formations. The typology of the parent magmatism of orthogneiss and leptynite allows to find leack most of plutonic associations known in the Variscan chain (subalkaline, calcoalkaline, aluminous). Interpretation of primary geochemical fractionation in rocks from the Dronne are suggests cogenetism of the whole facies following a fractionated crystallization process. Moreover rocks from the Dronne arc have a peraluminous character with high U and Th content related to subalkaline magmatism which make of them a potential source of uraniferous peraluminous leucogranites. Paraderived formations are represented by 3 mica schist formations and 2 gneiss formations. Each unit is individualized by geochemical study of mica schist. Gneiss formation are chemically distinct. These differences confirm that they belong to distinct lithologic units. Trace elements are used to precise the paleogeotectonic context of original sediment deposition [fr

  5. Erosional stability of rehabilitated uranium mine structures incorporating natural landform characteristics, northern tropical Australia

    International Nuclear Information System (INIS)

    East, T.J.; Uren, C.J.; Noller, B.N.; Cull, R.F.; Curley, P.M.; Unger, C.J.

    1994-01-01

    Australian Government guidelines specify that tailings containment structures at rehabilitated uranium mines in the Alligator Rivers Region of tropical northern Australia should have an engineered structural life of 1000 years. As part of the containment structure design process, erosion plots incorporating both regional geomorphological characteristics (concave hillslope profiles and a weathering-resistant rock cover of schist) and more conventional engineering design parameters (straight slopes and mine waste rock) were constructed at the Ranger Uranium Mine. The plots were monitored for storm runoff, and concentrations of solutes, suspended solids and selected ions over successive wet seasons. The concave slopes (the hillslope analogues) had lower peak discharges and lower concentrations of suspended solids than the straight slopes. However, solute concentrations in runoff from the schist covered (hillslope) slopes were higher than from the waste rock covered plots. Solute (mainly magnesium sulfate) concentrations for both rock types decreased by about an order of magnitude over the wet season. High sulfate concentrations are also likely to decrease substantially after several wet seasons, due to settlement of the waste rock and a reduction in rates of weathering. Development of a vegetation cover on the rehabilitated landforms will reduce the high suspended sediment concentrations. These initial results suggest that rehabilitated uranium mine structures which utilise selected features of stable natural landforms in their design may have greater erosional stability than more conventionally engineered structures. (orig.)

  6. Empirical analysis of electromagnetic profiles for groundwater prospecting in rural areas of Ibadan, southwestern Nigeria

    Science.gov (United States)

    Ehinola, O. A.; Opoola, A. O.; Adesokan, H. A.

    2006-04-01

    The Slingram electromagnetic (EM) survey using a coil separation of 60 and 100 m was carried out in ten villages in the Akinyele area of Ibadan, southwestern Nigeria to aid in the development of groundwater. Five main rock types including an undifferentiated gneiss complex (Su), biotite-garnet schist/gneiss (Bs), quartzite and quartz schist (Q), migmatized undifferentiated biotite/hornblende gneiss (M) and pegmatite/quartz vein (P) underlie the study area. A total of 31 EM profiles was made to accurately locate prospective borehole sites in the field. Four main groups with different behavioural patterns were categorized from the EM profiles. Group 1 is characterized by a high density of positive (HDP) or a high density of negative (HDN) real and imaginary curves, Group 2 by parallel real and imaginary curves intersecting with negligible amplitude (PNA), Group 3 by frequent intersection of a high density of negative minima (FHN) real and imaginary curves, and Group 4 by separate and approximately parallel (SAP) real and imaginary curves. Qualitative pictures of the overburden thickness and the extent of fracturing have been proposed from these behavioural patterns. A comparison of the borehole yield with the overburden thickness and the level of fracturing shows that the borehole yield depends more on the fracture density than on the overburden thickness. The asymmetry of the anomaly was also found to be useful in the determination of the inclination of the conductor/fracture.

  7. Contribution to the geology of the Niari basin: sedimentology and metallogeny of the mining region

    International Nuclear Information System (INIS)

    Bigotte, G.

    1956-01-01

    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.)

  8. 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.

  9. 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)

  10. Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran

    Directory of Open Access Journals (Sweden)

    Taghipour Batoul

    2015-03-01

    Full Text Available The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj-Sirjan Zone (SSZ, within the NE-SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist and footwall (meta-limestone rocks. The pattern also reflects an enrichment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO42- and CO2-bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold mineralisation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG type shear zone and orogenic type gold mineralisation.

  11. Hydrogeologic field study of the Koongarra uranium deposit in the Northern Territory of Australia

    International Nuclear Information System (INIS)

    Marley, R.D.

    1990-01-01

    This study is focused on the hydrogeologic characterization of the more southwesterly of the two Koongarra orebodies. The general objective is to augment the current hydrogeologic understanding of groundwater flow so that realistic transport models can be developed. Water level, aquifer tests, and slug-test data indicate that the Koongarra uranium deposit is within a low permeability, semi-confined, fractured-schist aquifer. Water levels demonstrate semi-diurnal and diurnal fluctuations related to earth tides and evapotranspiration stresses. Hydraulic test data were analyzed with homogenous isotropic and homogenous anisotropic models which allowed parameter estimation for sub-regions of the study area. Dominant anisotropy is subparallel to lithologic layering and the reverse fault. Slug tests reveal regions controlled by low storage but highly conductive fractures and isolated regions of low conductivity. Hydraulic connection of the weathered zone with the underlying schist is dependent on clay content and fractures. Environmental isotopes indicate ground water has been isolated from the atmosphere for a least 40 years and possibly several thousand years in some locations. Water budget calculations indicate the majority of recharge must be from direct infiltration through the weathered profile to account for the calculated ground-water fluxes. 36 refs., 12 tabs., 52 figs

  12. 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.

  13. 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.

    2018-04-01

    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.

  14. Hydration of the Atlantis Massif: Halogen, Noble Gas and In-Situ δ18O Constraints

    Science.gov (United States)

    Williams, M. J.; Kendrick, M. A.; Rubatto, D.

    2017-12-01

    A combination of halogen (Cl, Br, I), noble gases (He, Ne, Ar, Kr and Xe) and in situ oxygen isotope analysis have been utilized to investigate the fluid-mobile element record of hydration and alteration processes at the Atlantis Massif (30°N on the Mid-Atlantic Ridge). The sample suite investigated includes serpentinite, talc-amphibole ± chlorite schist and hydrated gabbro recovered by seafloor drilling undertaken at sites on a transect across the Atlantis Massif during IODP Expedition 357. Serpentine mesh and veins analysed in-situ by SHRIMP SI exhibit δ18O from 6‰ down to ≈0‰, suggesting serpentinization temperatures of 150 to >280°C and water/rock ratios >5. Differences of 1.5-2.5‰ are observed between adjacent generations of serpentine, but the δ18O range is similar at each investigated drilling site. Halogen and noble gas abundances in serpentinites, talc-amphibole schist and hydrated gabbro have been measured by noble gas mass spectrometry of both irradiated and non-irradiated samples. Serpentinites contain low abundances of halogens and noble gases (e.g. 70-430 ppm Cl, 4.7-12.2 x 10-14 mol/g 36Ar) relative to other seafloor serpentinites. The samples have systematically different Br/Cl and I/Cl ratios related to their mineralogy. Serpentinites retain mantle-like Br/Cl with a wide variation in I/Cl that stretches toward seawater values. Talc-amphibole schists exhibit depletion of Br and I relative to Cl with increasing Cl abundances, suggesting tremolite exerts strong control on halogen abundance ratios. Serpentinites show no evidence of interaction with halogen-rich sedimentary pore fluids. Iodine abundances are variable across serpentinites, and are decoupled from Br and Cl; iodine enrichment (up to 530 ppb) is observed within relatively oxidised and clay-bearing samples. Serpentinized harzburgites exhibit distinct depletion of Kr and Xe relative to atmospheric 36Ar in seawater. Oxygen isotope compositions and low abundances of both halogens

  15. The magmatism and metamorphism at the Malayer area, Western Iran

    Science.gov (United States)

    Ahadnejad, V.; Valizadeh, M. V.; Esmaeily, D.

    2009-04-01

    The Malayer area is located in the NW-SE aligned Sanandaj-Sirjan metamorphic belt, western Iran and consists mainly of Mesozoic schists so-called Hamadan Phyllites, Jurassic to Tertiary intrusive rocks and related contact metamorphic aureoles, aplites and pegmatites. The Sanandj-Sirjan Zone is produced by oblique collisional event between Arabian plate and Central Iran microcontinent. Highest level of regional metamorphism in the area is greenschist facies and injection of felsic magmas is caused contact metamorphism. Magmatism is consist of a general northwest trend large felsic to intermediate intrusive bodies. The main trend of structural features i.e. faults, fractures and other structural features is NW-SE. The Malayer granitoid complex is ellipsoid in shape and has NW-SE foliation especially at the corners of the intrusions. Petrography of the magmatic rocks revealed recrystallization of quartz and feldspars, bending of biotite, and aligment of minerals paralle to the main trend of magmatic and metamorphic country rocks. These indicated that intrusion of felsic magma is coincide to the regional metamorphism and is syn-tectoinc. Non-extensive contact metamorphism aureoles and rareness of pegmatite and aplite in the area are interpreted as injection of felsic magmas into the high-strain metamorphic zone. The regional metamorphic rocks mainly consist of meta-sandstone, slate, phyllite, schist. These gray to dark metasedimentary rocks are consist of quartz, muscovite, turmaline, epidote, biotite and chlorite. Sheeted minerals form extended schistosity and study of porphyroblast-matrix relationships shows that injection of granitic magma into the country rocks is syn to post-tectonic. Syn-tectonic indicating porphyroblast growth synchronous with the development of the external fabric. The thermal contact area of the granite can be observed in the contact margin of granite and regional metamorphic rocks, where it produced hornfelses, andalusit-garnet schists and

  16. Source-to-Sink System Evolution as Recorded in Clastic Facies in Two New Zealand Examples: the Bounty System of South Island and the Waipaoa System of North Island

    Science.gov (United States)

    Marsaglia, K. M.

    2010-12-01

    New Zealand river sources and their submarine sinks are excellent examples for modeling source-to-sink systems. In particular, the sand fractions of these systems can be used as tracers to document links and/or disconnects between fluvial, shelf, slope, and bathyal components. Within any given system, the ability to use sand as a tracer depends on the nature of the rocks exposed in source river drainage basins. In evolving systems, the potential for erosional unroofing, change of outcrop lithology through time, can be important. Additionally, the ability of a given lithology to generate sediment of a certain size may also vary. For example in the New Zealand examples, Cenozoic mudstones generate mostly mud but can liberate recycled sand grains (if present), as well as a smaller proportion of mudstone lithic fragments depending on degree of mudstone induration; schist generates copious sand and quartz-vein pebbles; and thin-bedded sandy turbidites can generate significant gravel, as well as mud and sand. Sediment production mode also comes into play with glacial processes (South Island) generating rock flour, as well as coarser debris. The major outcropping unit across both islands is a sedimentary to metasedimentary forearc succession, the Torlesse Terrane. It served as the protolith of the Otago schist (South Island) and the source of detritus for Cretaceous and Cenozoic sedimentary units on both islands. Local magmatism also supplied sand-sized material: intraplate (South Island) volcanism produced intrabasinal epiclastic debris and magmatic arc (North Island) volcanism produced extrabasinal pyroclastic debris. Various lithologies have characteristic detrital signatures. For example, in the Cenozoic units of the Waipaoa system, Pliocene calcareous mudstone fragments are key lithic components in tracing sediment transport from source-to sink, whereas the major fingerprint of Otago schist input into the Bounty System of South Island is mica. Critical to defining

  17. Fate of Subducting Organic Carbon: Evidence from HP/UHP Metasedimentary Suites

    Science.gov (United States)

    Kraft, K.; Bebout, G. E.

    2017-12-01

    Community interest in deep-Earth C cycling has focused attention on extents of C release from subducting oceanic lithosphere and sediment and the fate of this released C. Many have suggested that, based on isotopic and other arguments, 20% of the C subducted into the deeper mantle is in reduced form (organic); however, individual margins show large variation in carbonate to organic C ratios. Despite the size of the potentially deeply subducted organic C reservoir, its fate in subducting sections remains largely unexplored, with most attention paid to release of carbonate C. To characterize the forearc behavior of organic C, metamorphosed to P-T as high as that beneath volcanic fronts, we evaluated records of reduced C (RC) contents and isotope compositions in HP/UHP metasediments: 1) Schistes Lustres/Cignana (SLC) suite (Alps; Cook-Kollars et al., 2014, Chem Geol) with abundant carbonate and resembling sediment entering the East Sunda trench; and (2) Franciscan Complex (FC), W. Baja Terrain (WBT), Catalina Schist (CS) metasediments (Sadofsky and Bebout, 2003, G3), largely sandstone-shale sequences containing very little carbonate. In general, more Al-rich samples (shaley) in the terrigenous metasedimentary suites have higher concentrations of RC, which in low-grade units preserves δ13C of its organic protoliths. Carbonate-poor rocks in the SLC suite, and at ODP Site 765, show correlated major element (Al, Mg, Mn, Ti, P) and RC contents (up to 1.2 wt.%) reflecting sandstone-shale mixture. In the FC, WBT, and CS, the more Al-rich samples contain up to 2 wt. % RC. In high-grade Catalina Schist, RC has elevated δ13C due to C loss in CH4 and high-grade Alps rocks show reduced RC wt. % normalized to Al content. We consider processes that could alter contents and isotopic compositions of RC in sediment, e.g., devolatilization, closed-system exchange with carbonate, redox reactions, isotopic exchange with C in externally-derived fluids. It appears that, on modern Earth

  18. 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

  19. Intra-Continental Deformation by Mid-Crustal Shearing and Doming in a Cenozoic Compressive Setting Along the Ailao Shan-Red River Shear Zone

    Science.gov (United States)

    Zhang, B.

    2016-12-01

    Large-scale lateral strike-slip shear zones have been a key point in the debate about the deformation mechanisms of Asia in response to the India-Asia collision. The exhumed gneiss has been attributed to lateral strike-slip shear zone. This hypothesis has been challenged by recent discoveries indicating that a contractional doming deformation prior to the initiation of lateral strike-slip shearing. The Cenozoic Xuelong Shan antiformal dome is located at the northern segment of the Ailao Shan-Red River shear zone. Subhorizontal foliation in the gneiss core are recognized, representing a broad top-to-NE shear initiated under amphibolite facies conditions and propagated into greenschist facies in the mantling schist and strike-slip shear zone. Quartz CPOs and opening angles of crossed girdle fabrics in quartz suggest that the deformation temperatures increased with increasing structural depth from 300-500 °C in the mantling schist to ≥650 °C in the gneissic core. This trend is mirrored by variations in the metamorphic grade of the syn-kinematic mineral assemblages and microstructures, which ranges from garnet + amphibole + biotite + sillimanite + rutite + feldspar in the core to garnet + staurolite + biotite + epidote + muscovite within the limb units. Five-stage deformation is identified: (1) a broad top-to-NE shear in the subhorizontal level (D1); (2) opposing reverse-sense shear along the two schist limbs of the dome during contraction-related doming (D2-D3); (3) sinistral strike-slip shearing within the eastern limb (D4); and (4) extensional deformation (D5). The antiformal dome formation had been roughly coeval with top-to-NE ductile shearing in the mid-crust at 32 Ma or earlier. The geometries of the antiformal dome in the Xuelong Shan dome are similar to those associated with the antiform in the Dai Nui Con Voi, Diancang Shan and Ailao Shan zones. It is likely that the complex massifs, which define a regional linear gneiss dome zone in Cenozoic intra

  20. Elastic properties and seismic anisotropy of the Seve Nappe Complex - Laboratory core measurements from the International Continental Drilling Project COSC-1 well, Åre, Sweden

    Science.gov (United States)

    Wenning, Q. C.; Almqvist, B. S. G.; Zappone, A. S.

    2015-12-01

    The COSC-1 scientific borehole was drilled in the summer of 2014 to ~2.5 km depth to study the structure and composition of the Middle Allochthon of the Central Scandinavian Caledonides. It crosscuts the amphibolite-grade lower part of the Seve nappe and intersects a mylonite zone in the lower 800 m of the borehole. We selected six core samples representing the primary lithologies in the COSC-1 borehole for laboratory investigation of elastic properties. The cores consisted of two amphibolites with differing grain sizes, a calc-silicate gneiss, a felsic gneiss, a coarse grained amphibole bearing gneiss, and a garnet bearing mylonitic schist from the basal shear zone. Both P- and S-waves were measured at ultrasonic frequency (1 MHz), and room temperature hydrostatic pressure conditions up to 260 MPa. Measurements were made along three mutually perpendicular directions, one perpendicular to foliation and two parallel to the foliation with one aligned with mineral lineation. Vp and Vs, anisotropy, and elastic properties are reported as an extrapolation of the high-pressure portion of the ultrasonic measurements back to the intersection with the zero pressure axis. The Vp and Vs in the direction perpendicular to foliation ranges from 5.51-6.67 km/s and 3.18-4.13 km/s, respectively. In the direction parallel to foliation the Vp and Vs ranges from 6.31-7.25 km/s and 3.52-4.35 km/s, respectively. Vp anisotropy ranges from 3% in the calc-silicate gneiss to 18% in mylonitic schist. Acoustic impedance estimations at lithostatic pressure conditions at base of the borehole (70 MPa) show that acoustic impedance contrast generating reflection coefficients between the basal shear zone and overlying units are significant enough to cause seismic reflections. Above the mylonite zone/shear zone, the reflectivity within the lower Seve nappe is due to the impedance contrast between the felsic gneiss and the amphibolite. This result fits with 3D seismic reflection imaging in the area of

  1. Geology, petrography and macro meso- aspects, and microstructural area of Salto del Penitente

    International Nuclear Information System (INIS)

    Guerrero Cherma, S.

    2016-05-01

    This work corresponds to a geological and structural study of multi scale approach conducted in a representative area of ​​the southwest sector Dom Feliciano Belt. The study area is located near the Salto del Penitente and presents an array of blocks with lithology and structural characteristics distinctive. A foundation block pre-Brasiliano, a strip of supra crustal rocks and granitoid non-cinematic. The base block, is constituted mainly of gneisses, migmatites, schists and quartzites, foliation has a preferential N259º / 70 (NW). The supra crustal correspond to a meta-volcano sedimentary green schist facies, sequence preferential foliation N040º / 75 ° (SE) and non-kinematic granitoid a granite-gneiss foliation mylonitic according to said preferential direction. The geological survey and the macro- and mesoestructural analysis, determines that the contact of these blocks is through shear zones. These, presented regional and preferential directions N040º and N020º. They are defined respectively as Shear Zone La Posada (informal) and Shear Zone Tips Sugar loaf, corresponding in the study area to the homonymous lineament Machado and Fragoso (1987). Microstructural analysis suggests in low temperature conditions (green schist facies lower) for the event that brings the ZCPPA and contacts Rocks pre-Brasiliano basement with supra crustal. Instead, this event is only significant in the ZCLP, which shows effects of deformation temperature under medium high (amphibolite facies). Based on these conditions, as well as the relations between the two cutting shear zones, a poly phase evolution for the proposed study area. The deformation conditions identified in the work area are correlated with regional events. Both the high temperature dextral event that brings Shear Zone Sarandi del Yi, during the collision Land Nico Perez with the Río de la Plata Craton between 630-590 Ma (Oriolo et al., 2016), as the (2009 Oyhantçabal et al.) sinistral event that gathers the

  2. preparation of beryllia n concentrate from beryllium minerals by ion exchange method

    International Nuclear Information System (INIS)

    Shoukry, M.M.; Atrees, M. Sh.; Hashem, M.D.

    2007-01-01

    The present work is concerned with the preparation of pure Beryllia concentrate from Zabara beryl mineralization in the mica schist of Wadi El Gemal area in the eastern desert. This has been possible through application of ion exchange techniques to selectively concentrate. This method is based on the fact that the beryllium complex of ethylene diamine tetra acetic acid (EDTA) at a ph of about 3.5, is much weaker than the corresponding complexes of iron and aluminum. It was, therefore, possible to effect a complete separation of beryllium from the latter on a cation exchange resin, the studied optimum conditions of separation include a contact time of 3 minute and ph of 3.5 for the selective separation of beryllium from its EDTA solution after a prior separation of alum

  3. U-Pb and Sm-Nd preliminary geochronologic data on the Yaounde series, Cameroon: re-interpretation of the granulitic rocks as the suture of a collision in the ''Centrafrican'' belt

    International Nuclear Information System (INIS)

    Schmus, W.R. Van; Penaye, J.; Toteu, S.F.; Nzenti, J.P.

    1993-01-01

    U-Pb on zircons and Sm-Nd on whole-rock analyses have been applied on the schists, micaschists and granulitic gneisses of the Yaounde series. The results fix the granulitic metamorphism in the Yaounde series at 620±10 Ma and the deposition of the series during the Upper Proterozoic. In addition, another remnant of Lower Proterozoic basement, previously recognized in northern Cameroon, has been identified at Kekem northwest of the Yaounde series. The Yaounde granulitic unit is re-interpreted as the suture of a Pan-African collision between a passive margin (Archean Congo craton and its Birrimian Nyong cover) to the south and an intensive granitized active margin (dismembered eburnian basement and Upper Proterozoic series) to the north. (author). 14 refs., 4 figs

  4. Discussion of metallogenic substance source of Xiangshan uranium orefield

    International Nuclear Information System (INIS)

    Shao Fei; Tang Xiangsheng; Zou Maoqin; Hu Maomei; He Xiaomei; Chen Xiaoming; Xu Hengli

    2008-01-01

    Analysis of uranium source is a key problem for study on uranium deposit genesis. Based on analysis of general implication for determination of uranium source on distribution characteristics of regional uranium abundance, according to temporal and spatial evolution of regional metallogenic substances in process of geological history, and combining with indication for analysis of uranium source by Pb isotopic composition of ores and REE geochemistry of both rocks and ores in Xiangshan orefield, Lower Cambrian strata are determined as regional uranium source bed, Xiangshan volcanic basin is the accumulation area for regional metallogenic substances, magma and hydrothermal solution of post magmatism are media for uranium. Magmatism realizes uranium migration from 'source' to 'accumulation'. In process of magmatic evolution, uranium transformed into gas phase to provide substance base for uranium mineralization. Fluid-rock interaction of post magmatism also promoted some uranium from schist of the basement and rhyodacite into metallogenic solution. (authors)

  5. Petrology and mapping of Fe and Ti occurences in Passira country, PE, Brazil

    International Nuclear Information System (INIS)

    Silva Filho, A.F. da; Pinho Guimaraes, I. de.

    1979-01-01

    The results of a geologic mapping realized at the scale of 1:25.000, for graduating in geology, the will show in this communication. The area mapped has 230 square kilometers and it is localized between the south lattitudes of 7 0 52'30'' and 8 0 42'45'' and the west greenwiches of 35 0 26'49'' and 35 0 33'30'', at the districts of Passira and Limoeiro-PE. At the area, are recorgnized migmatites granites, biotite schists, hornblende-gneisses, quartz-diorites and amphigolites. The iron titanium ore are fitted, like xenoliths, inside the amphibolites. The amphibolites have orthorocks type, and they are derived predominatly of the quartz-diorite unit, where they may be individualized cartographicaly. On the other side of the geological mapping, we did many thin sections and polished, chemical analyses of the ore bodyes, and the results will be disciminated [pt

  6. Plutonic mobilization, sodium metasomatism, propylitic wall-rock alteration and element partitioning from Hoehensteinweg uranium occurrence (Northeast Bavaria, F.R.G.)

    International Nuclear Information System (INIS)

    Dill, H.

    1983-01-01

    The investigated U deposit near Poppenreuth (Hoehensteinweg) in northeast Bavaria is situated among Upper Proterozoic biotite gneisses and mica schists with ENE- to NE-striking foliation. In this paper, the element distribution is determined of the elements involved in the U-Th petrogenic cycle (Zr, Ce, Th, U, P and Na); as are the mineralogical changes of the primary U minerals. The problem of lithogene element supply is studied. The area abundant in U is compared with other U-bearing sodium enriched host rocks in order to improve the selection of exploration target areas. Content: the primary U and Th minerals; plutonic mobilizates; episyenites and sodium metasomatites; propylitic rocks; U minerals and their relation to the primary U minerals; the origin of Hoehensteinweg uranium deposits. (Auth.)

  7. Plutonic mobilization, sodium metasomatism, propylitic wall-rock alteration and element partitioning from Hoehensteinweg uranium occurrence (Northeast Bavaria, F. R. G. )

    Energy Technology Data Exchange (ETDEWEB)

    Dill, H. (Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany, F.R.))

    1983-05-01

    The investigated U deposit near Poppenreuth (Hoehensteinweg) in northeast Bavaria is situated among Upper Proterozoic biotite gneisses and mica schists with ENE- to NE-striking foliation. In this paper, the element distribution is determined of the elements involved in the U-Th petrogenic cycle (Zr, Ce, Th, U, P and Na); as are the mineralogical changes of the primary U minerals. The problem of lithogene element supply is studied. The area abundant in U is compared with other U-bearing sodium enriched host rocks in order to improve the selection of exploration target areas. Content: the primary U and Th minerals; plutonic mobilizates; episyenites and sodium metasomatites; propylitic rocks; U minerals and their relation to the primary U minerals; the origin of Hoehensteinweg uranium deposits.

  8. Inheritance, Variscan tectonometamorphic evolution and Permian to Mesozoic rejuvenations in the metamorphic basement complexes of the Romanian Carpathians revealed by monazite microprobe geochronology

    Science.gov (United States)

    Săbău, Gavril; Negulescu, Elena

    2014-05-01

    South Carpathians contain lower Paleozoic or older units intruded by Ordovician granitoids, imbricated with juvenile Variscan slivers, the structural sequence differing in individual basement complexes. So, in the Leaota Massif the lowermost term of the sequence is prograde Variscan, tectonically overlain by reworked lower Paleozoic gneisses, supporting thrust sheets with very low- to low-grade Variscan schists. In the Făgăraş Massif a lower Paleozoic (Cumpăna) complex bearing a strong Variscan overprint, straddles Variscan juvenile rocks, and the lowermost visible structural level is assumed by upper Carboniferous to Permian juvenile medium-grade metamorphic schists. In the Lotru Metamorphic Suite of the Alpine Getic Nappe, the Variscan stacking is overprinted by post-orogenic differential uplift, documented by the correlation among younging ages, structural and metamorphic low-pressure overprints, recording often higher metamorphic temperatures. The most spectacular structure is Upper Jurassic in age, contains high-grade metamorphic rocks and peraluminous anatectic granitoids, is outlined by a deformed boundary evolving from ductile to brittle regime during cooling, and induces a thermal overprint in the neighbouring rocks. In the basement units thrust over the Getic Nappe, the Sibişel unit yielded Permian prograde peak metamorphic ages and Triassic post-peak overprints, while an adjacent gneissic unit (Laz) delivered an exclusively Cretaceous age pattern. Unexpectedly young metamorphic ages resulted also for the East Carpathians and the Apuseni Mountains. While most of the ages obtained so far correspond to Variscan retrogression of older basement units, the lowermost structural unit of the infra-Bucovinian nappe system in the East Carpathians yielded Upper Cretaceous metamorphic ages in apparently monometamorphic medium-grade schists. In the Apuseni Mountains, schists of the Baia de Arieş Unit display an Upper Jurassic age spectrum, corresponding to a clearly

  9. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Sikkim

    International Nuclear Information System (INIS)

    1977-11-01

    Sikkim is a country in the eastern Himalayas and is bound on the west by Nepal, on the north by Tibet, on the east by Bhutan and on the south by India. Precambrian Darjeeling gneiss forms the rim of the amphitheatre while schists of Late Precambrian to Lower Paleozoic rocks form tee habital interior. A small outcrop of carboniferous to Permain methomorphic rocks is preserved in the Tista Basin as well in a thin outcrop trust upon fluvitile beds of Sivalik which is mostly of Pliestocene age. Imbricate thrusts have stacked the rocks in a vast heap where reverse metamorphism is common. Ni information is available concerning uranium occurrences and resources as well as past and present explorations. The uranium potential of Sikkim is almost zero

  10. 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.

  11. Water - rock interaction in different rock environments

    International Nuclear Information System (INIS)

    Lamminen, S.

    1995-01-01

    The study assesses the groundwater geochemistry and geological environment of 44 study sites for radioactive waste disposal. Initially, the study sites were divided by rock type into 5 groups: (1) acid - intermediate rocks, (2) mafic - ultramafic rocks, (3) gabbros, amphibolites and gneisses that contain calc-silicate (skarn) rocks, (4) carbonates and (5) sandstones. Separate assessments are made of acid - intermediate plutonic rocks and of a subgroup that comprises migmatites, granite and mica gneiss. These all belong to the group of acid - intermediate rocks. Within the mafic -ultramafic rock group, a subgroup that comprises mafic - ultramafic plutonic rocks, serpentinites, mafic - ultramafic volcanic rocks and volcanic - sedimentary schists is also evaluated separately. Bedrock groundwaters are classified by their concentration of total dissolved solids as fresh, brackish, saline, strongly saline and brine-class groundwaters. (75 refs., 24 figs., 3 tabs.)

  12. Brazilian energy model

    Science.gov (United States)

    1981-05-01

    A summary of the energy situation in Brazil is presented. Energy consumption rates, reserves of primary energy, and the basic needs and strategies for meeting energy self sufficiency are discussed. Conserving energy, increasing petroleum production, and utilizing other domestic energy products and petroleum by-products are discussed. Specific programs are described for the development and use of alcohol fuels, wood and charcoal, coal, schist, solar and geothermal energy, power from the sea, fresh biomass, special batteries, hydrogen, vegetable oil, and electric energy from water power, nuclear, and coal. Details of the energy model for 1985 are given. Attention is also given to the energy demands and the structure of global energy from 1975 to 1985.

  13. Sedimentary processes in the Carnot Formation (Central African Republic) related to the palaeogeographic framework of Central Africa

    Science.gov (United States)

    Censier, Claude; Lang, Jacques

    1999-08-01

    The depositional environment, provenance and processes of emplacement of the detrital material of the Mesozoic Carnot Formation are defined, by bedding and sedimentological analysis of its main facies, and are reconstructed within the palaeogeographic framework of Central Africa. The clastic material was laid down between probably the Albian and the end of the Cretaceous, in a NNW-oriented braided stream fluvial system that drained into the Doba Trough (Chad) and probably also into the Touboro Basin (Cameroon). The material was derived from weathering of the underlying Devonian-Carboniferous Mambéré Glacial Formation and of the Precambrian schist-quartzite complex located to the south of the Carnot Formation. These results provide useful indications as to the provenance of diamonds mined in the southwest Central African Republic.

  14. Environmental geochemical study of Red Mountain--an undisturbed volcanogenic massive sulfide deposit in the Bonnifield District, Alaska range, east-central Alaska: Chapter I in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

    Science.gov (United States)

    Eppinger, Robert G.; Briggs, Paul H.; Dusel-Bacon, Cynthia; Giles, Stuart A.; Gough, Larry P.; Hammarstrom, Jane M.; Hubbard, Bernard E.

    2007-01-01

    The Red Mountain volcanogenic massive sulfide (VMS) deposit exhibits well-constrained examples of acid-generating, metal-leaching, metal-precipitation, and self-mitigation (via co-precipitation, dilution, and neutralization) processes that occur in an undisturbed natural setting, a rare occurrence in North America. The unmined pyrite-rich deposit displays a remarkable environmental footprint of natural acid generation, high metal concentrations, and exceedingly high rare-earth-element (REE) concentrations in surface waters. Dissolution of pyrite and associated secondary reactions under near-surface, oxidizing conditions are the primary causes for the acid generation and metal leaching. The deposit is hosted in Devonian to Mississippian felsic metavolcanic rocks of the Mystic Creek Member of the Totatlanika Schist.

  15. Carbonization

    Energy Technology Data Exchange (ETDEWEB)

    Hennebutte, H G; Goutal, E

    1921-07-04

    Materials such as coal, peat, or schist are subjected to a rising temperature in successive stages in apparatus in which the distillation products are withdrawn at each stage. For example in a three-stage process, the acid products of the first or low-temperature stage are fixed in a suitable reagent, the basic products from a second or higher-temperature stage are absorbed in an acid reagent, hydrocarbons being retained by solvents, while the third are subjected to a pyrogenation process carried out in a closed vessel. Wherein the material is subjected in stages to a rising temperature, the gasified products being withdrawn at each stage, and are prevented as far as possible from mixing with the carbonized products.

  16. 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

  17. PALEOARCHEAN MAFIC ROCKS OF THE SOUTHWESTERN SIBERIAN CRATON: PRELIMINARY GEOCHRONOLOGY AND GEOCHEMICAL CHARACTERIZATION

    Directory of Open Access Journals (Sweden)

    A. V. Ivanov

    2017-01-01

    Full Text Available The Siberian craton consists of Archean blocks, which were welded up into the same large unit by ca 1.9 Ga [Gladkochub et al., 2006; Rojas-Agramonte et al., 2011]. The history of the constituent Archean blocks is mosaic because of limited number of outcrops, insufficient sampling coverage because of their location in remote regions and deep forest and difficulties with analytical studies of ancient rocks, which commonly underwent metamorphic modifications and secondary alterations. In this short note, we report data on discovery of unusual for Archean mafic rocks of ultimate fresh appearance. These rocks were discovered within southwestern Siberian craton in a region near a boundary between Kitoy granulites of the Sharyzhalgai highgrade metamorphic complex and Onot green-schist belt (Fig. 1. Here we present preliminary data on geochronology of these rocks and provide their geochemical characterization.

  18. 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.

  19. Destructive hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Terrisse, H; Dufour, L

    1929-01-21

    Oils of high boiling point, e.g. gas oil, lamp oil, schist oil, brown coal tar etc., are converted into motor benzine by heating them at 200 to 500/sup 0/C under pressure of 5 to 40 kilograms/cm/sup 2/ in the presence of ferrous chloride and gases such as hydrogen, or water gas, the desulfurization of the oils proceeding simultaneously. One kilogram of lamp oil and 100 g. ferrous chloride are heated in an autoclave in the presence of water gas under a pressure of 18 kg/cm/sup 2/ to 380 to 400/sup 0/C. The gaseous products are allowed to escape intermittently and are replaced by fresh water gas. A product distilling between 35 and 270/sup 0/C is obtained.

  20. Construction of a differential thermal analysis installation; Realisation d'une installation d'analyse thermique differentielle

    Energy Technology Data Exchange (ETDEWEB)

    Branche, G; Chantret, F [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The authors are indicating the characteristics of a D.T.A. installation they built. Experimental rooms, ovens, thermal regulation, recording methods are thoroughly described, with outlining of the requirements to obtain a high sensitivity. Numerous D.T.A. curves relating to argillaceous substances, bituminous shales, and uraniferous compounds are given. (author) [French] Les auteurs donnent les caracteristiques de l'installation d'Analyse Thermique Differentielle qu'ils ont construits. Ils decrivent en detail les chambres d'experiences, les fours, la regulation thermique, l'enregistrement, en insistant sur les conditions necessaires pour obtenir une sensibilite elevee. Ils donnent de nombreuses courbes differentielles relatives des produits argileux, des schistes bitumineux et des composes uraniferes. (auteur)

  1. New K-Ar constraints on the onset of subsidence in the Canning Basin, Western Australia

    International Nuclear Information System (INIS)

    Shaw, R.D.; Tyler, I.M.; Griffin, T.J.; Webb, A.

    1992-01-01

    Structural mapping and reconnaissance K-Ar studies have helped to delineate and date the latest deformational stages (D4 and D5) in the King Leopold Orogen, to the north of the Canning Basin. The dates have been determined for schists selected from both contractional shear zones and from rocks metamorphosed to the lower greenschist facies during the final phase of basement deformation. These dates imply that the basement-deforming event started in the latest Precambrian to earliest Cambrian (ca 560 Ma), and that tectonism recurred in the latest Cambrian to earliest Ordovician (ca 500 Ma). The final contractional deformation is slightly older than the oldest-known sedimentary rocks in the basin (latest Tremadoc), and helps to define the time that basin subsidence started. 23 refs., 3 tabs., 2 figs

  2. Ca isotopes reveal weak control of tectonic uplift on long-term climate change

    Science.gov (United States)

    Moore, J.; Jacobson, A. D.; Holmden, C. E.; Craw, D.

    2010-12-01

    Ca-Mg silicate weathering consumes atmospheric CO2 over geological timescales (≥106 yr) whereas carbonate weathering has no effect. High Ca fluxes from active orogens have been used to argue that mountain uplift is a disproportionately large CO2 sink. To test this hypothesis, it is essential to determine proportions of Ca from silicate versus carbonate weathering. High precision measurement of Ca isotopes (δ44/40Ca) provides a novel method to directly quantify Ca sources. To this end, we examined δ44/40Ca in rivers draining the Southern Alps of New Zealand. The Southern Alps have large tectonic and climatic gradients but nearly constant bedrock chemistry. West of the main topographic divide, uplift and precipitation rates are high, and steep, fast-flowing rivers drain schist. East of the divide, uplift and precipitation rates are low, and low-gradient, braided rivers drain either schist or greywacke. Both schist and greywacke contain up to 3% hydrothermal and metamorphic calcite. Glaciers feed several schist and greywacke catchments. Examined as δ44/40Ca versus Sr/Ca, values measured for carbonate and silicate end-members define two-component mixing envelopes. Rivers west of the divide plot within the envelope, ruling out isotopic fractionation as a factor for these streams. Several rivers east of the divide are 40Ca enriched relative to the envelope. In-situ fractionation of stream water Ca cannot explain this pattern because fractionation is expected to preferentially remove 40Ca. We measured δ42/44Ca ratios to test if chemical weathering preferentially releases 40Ca. When examined as δ40/44Ca versus δ42/44Ca, the data only display mass-dependent isotope effects. Ca in grass and the exchangeable pool of shallow soils is enriched in 40Ca relative to waters and bedrock. This Ca defines a third mixing end-member that contributes 15-30% of the Ca in rivers east of the divide. Evidence of the plant-fractionated signal likely reflects water residence times

  3. The Geology of the Kivetty area

    International Nuclear Information System (INIS)

    Anttila, P.; Paulamaeki, S.; Lindberg, A.; Paananen, M.; Koistinen, T.; Front, K.; Pitkaenen, P.

    1992-05-01

    Teollisuuden Voima Oy (TVO) is preparing for the final disposal of spent nuclear fuel from the Olkiluoto nuclear power plant (TVO-I and TVO-II) deep in the Finnish bedrock. Kivetty in Konginkangas was one of the five areas selected in 1987 for preliminary site investigations for this purpose. The Kivetty area in Central Finland is located in a Svecokarelian granitoid environment consisting of a complex of synorogenic granitoids 1900 - 1860 million years in age. The bedrock consists almost entirely of plutonic rocks, i.e. gabbro, porphyritic granodiorite and granite, eguigranular granodiorite and granite, listed in order of age. The majority of the rock types are porphyritic in character, and supracrustal rocks such as quartz-feldspar schist and gneiss are found occasionally in small xenoliths

  4. Metallogenesis of the lode gold deposit in Ilesha area of southwestern Nigeria: inferences from lead isotope systematics

    International Nuclear Information System (INIS)

    Oyinloye, A.O.

    2006-01-01

    Studies were carried out on the geochemistry of 18 representative samples of the granite gneiss host rock, common Pb dates on six granite gneiss whole rock samples, six feldspar sample separates, and six samples from the lode gold deposit in the Ilesha schist belt. The AFM plot for the biotite granite gneiss indicated that its potlatch was derived from a subduction related tectonic setting. The granite gneiss had low U/Pb and Th/Pb ratios (0.10 to 0.31 and 0.33 to 1.31, respectively), and upper crystal Pb content of 30-47 ppm. The /sup 207/Pb/sup 204/Pb, /sup 206/Pb /sup 204/Pb, /sup 208/Pb/sup 204/Pb, were extremely homogeneous in the host rock, the feldspar, and the pyrite indicating derivation from a subduction related environment like a back arc or island arc. The two-stage Stacy and Kramers (1975) Pb-Pb model dating method of interpretation adopted in this study indicated that the granite gneiss was emplaced at 2750 +- 25 Ma in an orogen. On analysis, common Pb in pyrite yielded an average model age of 550 Ma. This Pb systematic indicated that Au was derived from the volcanics in the lIesha schist belt by hydrothermal leaching, transported through the same medium and deposited in the massive quartz veins as thio-complexes from which native gold was liberated through interaction of the ore fluid and spinals in the host rock. Studies were carried out on the geochemistry of 18 representative samples of the granite gneiss host rock, common Pb dates on six granite gneiss whole rock samples, six feldspar sample separates, and six samples from the lode gold deposit in the Ilesha schist belt. The AFM plot for the biotite granite gneiss indicated that its potlatch was derived from a subduction related tectonic setting. The granite gneiss had low U/Pb and Th/Pb ratios (0.10 to 0.31 and 0.33 to 1.31, respectively), and upper crustal Pb content of 30-47 ppm. The /sup 207/Pb /sup 204/Pb, /sup 206/Pb /sup 204/Pb, /sup 208/Pb /sup 204/Pb, were extremely homogeneous in the

  5. 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.

  6. 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

    High-precision 40Ar/39Ar dating of lamprophyre dike swarms in the Western Province of New Zealand reveals that these dikes were emplaced into continental crust prior to, during and after opening of the Tasman Sea between Australia and New Zealand. Dike ages form distinct clusters concentrated...... at the inception of opening of the Tasman Sea. Magmatic quiescence followed until ~72–68Ma,when another swarmof dikes was emplaced. The composition of the dikes reveals a dramatic change in primary melt sources while continental extension and lithospheric thinning were ongoing. The 102–100 Ma South Westland dikes...... 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)....

  7. Study on indoor radon concentration and gamma radiation dose rate in different rooms in some dwellings around Bharath Gold Mines Limited, Karnataka State, India

    International Nuclear Information System (INIS)

    Umesha Reddy, K.; Jayasheelan, A.; Sannappa, J.

    2012-01-01

    Indoor radon contributes significantly to the total radiation exposure caused to human beings. The indoor concentration of radon in different rooms in the same type of dwellings around Bharath Gold Mines Limited (BGML), Karnataka State (12°57' min N and 78°16' min E) were measured by using LR-115 (type-Il) Solid State Nuclear Track Detectors (SSNTDs). The maximum indoor radon concentration is observed in the bathroom and minimum in the hall. The maximum average indoor radon concentration is observed in the Champion and minimum in the BEML nagar. The indoor gamma radiation dose rate is also measured in these locations using scintillometer. The geology of this part forms predominantly Hornblende Schist, Granite gneiss, Champion gneiss, Quartzite etc. The indoor radon concentration shows good correlation with the indoor gamma radiation dose. (author)

  8. Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont

    Science.gov (United States)

    Cady, Wallace Martin; Albee, Arden Leroy; Chidester, A.H.

    1963-01-01

    The upper Missisquoi Valley and vicinity as described in this report covers an area of about 250 square miles at the headwaters of the Missisquoi River in north-central Vermont. About 90 percent of the area is forested and the remainder is chiefly farm land. The topography reflects the geologic structure and varied resistance of the bedrock to erosion. Most of the area is on the east limb of the Green Mountain anticlinorium, which is the principal structural feature of Vermont. The bedrock is predominantly sedimentary and volcanic rock that has been regionally metamorphosed. It was intruded before metamorphism by mafic and ultramafic igneous rocks, and after metamorphism by felsic and mafic igneous rocks. The metamorphosed sedimentary and volcanic rocks range in age from Cambrian(?) to Middle Silurian, the intrusive igneous rocks from probably Late Ordovician to probably late Permian. Metamorphism and principal folding in the region occurred in Middle Devonian time. The metamorphosed sedimentary and volcanic rocks make up a section at least 25,000 feet thick and can be divided into nine formations. The Hazens Notch formation of Cambrian(?) and Early Cambrian age is characterized by carbonaceous schist. It is succeeded in western parts of the area by the Jay Peak formation of Early Cambrian age, which is chiefly a schist that is distinguished by the general absence of carbonaceous zones; in central parts of the area the Hazens Notch formation is followed by the Belvidere Mountain amphibolite, probably the youngest of the formations of Early Cambrian age. The Ottauquechee formation, composed of carbonaceous phyllite and quartzite, and phyllitic graywacke, is of Middle Cambrian age. The Stowe formation of Late Cambrian(?) and Early(?) Ordovician age overlies the Ottauquechee and is predominantly noncarbonaceous schist, though it also contains greenstone and carbonaceous schist and phyllite. The Umbrella Hill formation of Middle Ordovician age is characteristically a

  9. Determination of gold by neutron activation analysis in some selected precambrian rocks from Eastern India

    International Nuclear Information System (INIS)

    Das, N.R.; Bhattacharyya, S.N.; Chakraborty, P.S.

    1976-01-01

    Gold was determined in epidiorite schist from Kunderkocha, in green phyllite from near Sausel in granodiorite from Kunderkocha and in galena quartz vein from Sausel by neutron activation analysis. The analysis was carried out both in destructive and non-destructive ways followed by γ-ray spectrometry. The process of preconcentration involves digestion of the rock samples with hydrofluoric acid and its dissolution in aqua regia solution, extraction of gold from the aqua regia solution by methylisobutyl ketone, back extraction of gold from the organic to the aqueous layer, and coprecipitation of gold by a known amount (0.7 g) of lead sulphide. The amounts of gold that were determined in the respective rock samples varied in the range 10 -4 -10 -6 %. Besides gold, some other trace constituents such as As, Ag, Sb, W, Se, La, Sn, etc. were also detected and their approximate order of occurence was determined. (T.G.)

  10. Geology and geochronology of the Sub-Antarctic Snares Islands/Tini Heke, New Zealand

    DEFF Research Database (Denmark)

    Scott, JM; Turnbull, IM; Sagar, MW

    2015-01-01

    are prismatic and yield an essentially unimodal age population of c. 116 Ma that is within error of the granodiorite. These properties suggest that the dated raft represents a meta-igneous rock despite its mica-rich nature. Some schistose rocks on the Western Chain contain coarse relict plagioclase phenocrysts...... and appear to have an igneous protolith. No conclusive metasedimentary rocks have been identified, although sillimanite-bearing mica-rich schist occurs on Rua. Deformation of the crystalline rocks occurred after Snares Granite intrusion and before cooling below muscovite K–Ar closure at 400 ± 50 °C at 95 Ma......The first comprehensive geological map, a summary of lithologies and new radiogenic isotope data (U–Pb, Rb–Sr) are presented for crystalline rocks of the Sub-Antarctic Snares Islands/Tini Heke, 150 km south of Stewart Island. The main lithology is Snares Granite (c. 109 Ma from U–Pb dating...

  11. Extent and character of early tertiary penetrative deformation, Sonora, Northwest Mexico

    Science.gov (United States)

    Anderson, T. H.

    1985-01-01

    Reconnaissance field work has led to the recognition of extensive Early Tertiary gneiss and schist which are distinguished by weakly developed to highly conspicous northeast to east-trending stretching lineation commonly accompanied by low-dipping foliation. This structural fabric has been imposed on Precambrian to Paleogene rocks. Regionally, minimum ages of deformation are based upon interpreted U-Pb isotopic ages from suites of cogenetic zircon from the Paleogene orthogneiss. Locally, the interpreted ages indicate that ductile deformation continued as late as Oligocene (Anderson and others, 1980; Silver and Anderson, 1984). The consistency of the deformational style is such that, although considerable variation in intensity exists, the fabric can be recognized and correlated in rocks away from the Paleogene orthogneiss.

  12. Coupling of Oceanic and Continental Crust During Eocene Eclogite-Facies Metamorphism: Evidence From the Monte Rosa Nappe, Western Alps, Italy

    Science.gov (United States)

    Lapen, T. J.; Johnson, C. M.; Baumgartner, L. P.; Skora, S.; Mahlen, N. J.; Beard, B. L.

    2006-12-01

    Subduction of continental crust to HP-UHP metamorphic conditions requires overcoming density contrasts that are unfavorable to deep burial, whereas exhumation of these rocks can be reasonably explained through buoyancy-assisted transport in the subduction channel to more shallow depths. In the western Alps, both continental and oceanic lithosphere has been subducted to eclogite-facies metamorphic conditions. The burial and exhumation histories of these sections of lithosphere bear directly on the dynamics of subduction and the stacking of units within the subduction channel. We address the burial history of the continental crust with high precision U-Pb rutile and Lu-Hf garnet geochronology of the eclogite-facies Monte Rosa nappe (MR), western Alps, Italy. U-Pb rutile ages from quartz-carbonate-white mica-rutile veins that are hosted within eclogite and schist of the MR, Gressoney Valley, Italy, indicate that it was at eclogite-facies metamorphic conditions at 42.6 +/- 0.6 Ma. The sample area (Indren glacier, Furgg zone; Dal Piaz, 2001) consists of eclogite boudins that are surrounded by micaceous schist. Associated with the eclogite and schist are quartz-carbonate-white mica-rutile veins that formed in tension cracks in the eclogite and along the contact between eclogite and surrounding schist. Intrusion of the veins occurred at eclogite-facies metamorphic conditions (480-570°C, >1.3-1.4 GPa) based on textural relations, oxygen isotope thermometry, and geothermobarometry. Lu-Hf geochronology of garnet from a chloritoid-talc-garnet-phengite-quartz-calcite-pyrite - chalcopyrite bearing boudin within talc-chloritoid whiteschists of the MR, Val d'Ayas, Italy (Chopin and Monie, 1984; Pawlig, 2001) yields an age of 40.54 +/- 0.36 Ma. The talc-chloritoid whiteschists from the area record pressures and temperatures of 1.6-2.4 GPa and 500-530°C (Chopin and Monie, 1984; Le Bayon et al., 2006) indicating near UHP metamorphic conditions. Based on the age, P-T, and textural

  13. Hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    1927-02-22

    Coal tar, mineral oils, bitumens, coal extraction products, hydrogenation products of coal, oil schists can be atomized and heated with steam to decompose pyrogenetically and form gases rich in olefins which may be heated with or without pressure and with or without catalysts to produce liquid hydrocarbons of low boiling point, some of which may be aromatic. The apparatus should be lined with copper, silica, or ferrosilicon to prevent contact of the bases with iron which causes deposition of soot. Catalysts used may be metal oxides, silica, graphite, active charcoal, mica, pumice, porcelain, barium carbonate, copper, silver, gold, chromium, boron, or their compounds. At temperatures from 300 to 400/sup 0/C, olefins are produced. At higher temperatures, naphthenes and benzene hydrocarbons are produced.

  14. Retort for distilling coal oil

    Energy Technology Data Exchange (ETDEWEB)

    Gibbon, J

    1865-12-20

    The construction of a retort for extracting or distilling coal oil or other products from cannel coal, shale, or schist, and more particularly of small coal or dust technically called slack, consists in applying self-acting feed and discharge apparatus to a revolving cylindrical wrought or cast iron retort, and constructing the inner surface of the cylindrical retort with a projecting ridge which encircles the interior of the retort in a spiral manner, the same as the interior of a female screw, and the ridge may be either cast upon or riveted on the internal surface, and is so arranged to cause the material to be operated upon to advance from one end of the retort to the other, as the retort revolves by following the course of the spiral screw or worm formed by the projecting ridge.

  15. Ca isotopes, chemical weathering, and geomorphic controls on long-term climate

    Science.gov (United States)

    Moore, J.; Jacobson, A. D.; Holmden, C. E.; Craw, D.

    2009-12-01

    Calcium isotope geochemistry (δ44Ca) offers a unique opportunity to directly quantify proportions of riverine Ca originating from silicate versus carbonate weathering, which is essential for understanding how geomorphic processes affecting landscape evolution, such as tectonic uplift and glaciation, influence the long-term cycling of atmospheric CO2. We measured the elemental and δ44Ca chemistry of river and rock samples from the New Zealand Southern Alps. In combination with our geochemical data, we used runoff and suspended sediment fluxes to elucidate relationships between chemical weathering, mechanical erosion, and long-term climate. The S. Alps have uniform bedrock chemistry but significant tectonic and climatic gradients. West of the main topographic divide, watersheds drain schist and experience high runoff, uplift, and erosion rates. East of the main divide, watersheds drain greywacke or schist and experience lower runoff, uplift, and erosion rates. Glaciated watersheds with high erosion rates are present throughout the mountain range. Both schist and greywacke contain up to 3% metamorphic and hydrothermal calcite. Waters exhibit two-component mixing between calcite and silicate end-members when plotted as δ44Ca versus Ca/Sr. Scatter about the mixing curve is generally smaller than the analytical uncertainty of the measurements and likely reflects variability of the end-member compositions rather than fractionation. We used the mixing relationships to calculate percentages of Ca from silicate weathering. Rivers draining greywacke average 27.6% of Ca from silicate weathering with glaciated and non-glaciated watersheds yielding 41.8 and 19.5%, respectively. Rivers draining schist average 9.8% with glaciated and non-glaciated watersheds yielding 17.7 and 3.9%, respectively. Although Ca fluxes are larger west of the main divide where erosion and runoff are higher, the percentage of Ca from silicate weathering is smaller. Hence, long-term atmospheric CO2

  16. Geology of dolomite-hosted uranium deposits at the Pitch Mine, Saguache County, Colorado

    International Nuclear Information System (INIS)

    Nash, J.T.

    1981-01-01

    Newly documented uranium ore in the Pitch mine occurs chiefly in brecciated Mississippian Leadville Dolomite along the Chester upthrust zone, and to a lesser extent in sandstone, siltstone, and carbonaceous shale of the Pennsylvanian Belden Formation and in Precambrian granitic rocks and schist. Uranium-mineralized zones are generally thicker, more consistent, and of higher grade in dolomite than in other hosts, and roughly 50 percent of the new reserves are in dolomite. Strong physical control by dolomite is evident, as this is the only rock type that is pervasively brecciated within the fault slices that make up the footwall of the reverse-fault zone. Other rocks tended to either remain unbroken or undergo ductile deformation. Chemical controls on uranium deposition are subtle and appear chiefly to involve coprecipitation of FeS 2 as pyrite and marcasite, suggesting that sulfide ion may be the reductant

  17. 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.

  18. Hydrochemical and isotopic properties of the groundwater in the middle part of the Tulian river watershed, Puerto Cortes, Honduras

    International Nuclear Information System (INIS)

    Contreras, Tirza C.; Vargas, Ingrid; Badilla, Elena

    2012-01-01

    The hydrochemical and isotopic properties of 11 springs are identified, including one thermal spring, in Tulian watershed, located in the city of Puerto Cortes, Cortes, Honduras. The relation in the water between the concentrations of the environmental stable isotopes, deuterium (2 H ) and oxygen - 18 (1 8O ), has been similar to the relation in global meteoric water, indicating that the water has a meteoric origin. Evaluation of the geochemical characteristics of the water reveals that these springs belong to the same hydrogeological system, which comprises a fractured schist and gneiss of the Esquistos Cacaguapa formation. The water of the evaluated springs has been mainly sodium bicarbonate and calcium bicarbonate. The isotopic contents have showed without a variation of δ 18 O as would be expected in the hot spring. (author) [es

  19. Microstructural analysis from archaeological sculptures of the Olmeca culture

    International Nuclear Information System (INIS)

    Rodriguez L, V.; Mendoza A, D.; Espinosa P, M.; Martinez C, G.

    1999-01-01

    This work presents the results obtained from the characterization of a series of samples belonging to different monuments of the Olmec culture. These monuments are exhibited in the archaeological site of La Venta, Tabasco, Mexico. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to determine the crystalline phases that characterise the samples, these phases are associated to different morphology. The elemental analysis exhibits the presence mainly of such elements as C, Si, O, Al, Na, Ca and in less abundance Ti, K, Cr, Ni and Mn were determined. The morphology is characterized by the presence of plane tabular structures, schists, extended slates and clusters of irregular grain. Such crystal phases as anorthite, albite, sanidine, zinnwaldite and clinochlore were identified. These phases are associated with such type of materials as feldspars and mica. All the identified phases are noted for presenting near perfect exfoliation. (Author)

  20. Contaminated Sites by Residues from Romanian Industry

    International Nuclear Information System (INIS)

    Aurelian, F.; Georgescu, D.; Vacariu, V.; Popescu, M.

    2001-01-01

    Full text: In Romania, the mining industries of ferrous ore, non-ferrous ore, bauxite, coal, chemical fertilisers, the extraction of natural gas and oil, etc. have a considerable weight in economy. The study lets us know that in these industries, in different by-products and waste from the process, some radionuclides come out. The preliminary data, which are determined in these industries, are compared with those data, which are published by the countries from EU. There were determined uranium, radium and thorium from ore and sterile (ferrous, non-ferrous, bauxite, talc, clay, asbestos, barytine, salt, coal and bituminous schist). Also, there have been determined the radium and the uranium content of waters from non-uraniferous mining sites. The level of radioactive noxa has been informative determined in each mine. The level of the concentrations requires a systematic research and an assessment of the risk and the impact against the environment, the workers, and the public. (author)

  1. Groundwater quality and hydrogeological characteristics of Malacca state in Malaysia

    Directory of Open Access Journals (Sweden)

    Shirazi Sharif Moniruzzaman

    2015-03-01

    Full Text Available Groundwater quality and aquifer productivity of Malacca catchment in Peninsular Malaysia are presented in this article. Pumping test data were collected from 210 shallow and 17 deep boreholes to get well inventory information. Data analysis confirmed that the aquifers consisting of schist, sand, limestone and volcanic rocks were the most productive aquifers for groundwater in Malacca state. GIS-based aquifer productivity map was generated based on bedrock and discharge capacity of the aquifers. Aquifer productivity map is classified into three classes, namely high, moderate and low based on discharge capacity. Groundwater potential of the study area is 35, 57 and 8% of low, moderate and high class respectively. Fifty two shallow and 14 deep aquifer groundwater samples were analyzed for water quality. In some cases, groundwater quality analysis indicated that the turbidity, total dissolved solids, iron, chloride and cadmium concentrations exceeded the limit of drinking water quality standards.

  2. 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

  3. Brazil Geologic Basic Survey Program - Limoeiro - Sheet SB.25-Y-C-V -Pernambuco State

    International Nuclear Information System (INIS)

    Barbosa, A.G.

    1991-01-01

    The Limoeiro map-sheet (SB.25-Y-C-V;1:100,000 scale), State of Pernambuco is delimited by the meridians 35 0 00'W to 35 0 30' W and parallels 7 0 30' S to 8 0 00' S. The sheet covers an area of about 3,000 km 2 . The basement rocks probable Archaean age consist of gneiss and migmatite. The basement rocks are overlain by Lower Proterozoic metasediments (schist and para gneiss), locally with flows (amphibolite), metamorphosed in the middle to high amphibolite facies. Geochemical surveys including stream sediment sampling and rock chip sampling were carried out. Ground geophysics included magnetometer, gravity and radiometric (scintillometer) surveys. A provisional metallogenetic map at 1:100,000 scale was prepared on which areas with potential for economic deposits of gold, apatite, barium copper, nickel, cobalt, zinc, niobium, iron, titanium and vanadium are shown. (author)

  4. Graphite content and isotopic fractionation between calcite-graphite pairs in metasediments from the Mgama Hills, Southern Kenya

    International Nuclear Information System (INIS)

    Arneth, J.D.; Schidlowski, M.; Sarbas, B.; Goerg, U.; Amstutz, G.C.

    1985-01-01

    Amphibolite-grade metasediments from the Mgama Hills region, Kenya, contain conspicuous quantities of graphite, most probably derived from organic progenitor materials,. The highest graphite contents are found in schists whereas calcite marbles intercalated in the sequence contain relatively low amounts. The graphitic constituents are consistently enriched in 13 C relative to common sedimentary organic material, with the highest isotopic ratios in graphite from the marbles. Carbon isotope fractionations between calcite and graphite mostly vary between 3.3 and 7.1 per mille, which comes close to both empirically recorded and thermodynamically calculated fractionations in the temperature range of the upper amphibolite facies. However, larger values occasionally encountered in the marbles suggest that complete isotopic equilibrium is not always attained in amphibolite-facies metamorphism. (author)

  5. Regional magnetic and gravity features of the Gibson Dome area and surrounding region, Paradox Basin, Utah : a preliminary report

    Science.gov (United States)

    Hildenbrand, T.G.; Kucks, R.P.

    1983-01-01

    Analyses of regional gravity and magnetic anomaly maps have been carried out to assist in the evaluation of the Gibson Dome area as a possible repository site for high-level radioactive waste. Derivative, wavelength-filtered, and trend maps were compiled to aid in properly locating major geophysical trends corresponding to faults, folds, and lithologic boundaries. The anomaly maps indicate that Paradox Basin is characterized by a heterogeneous Precambrian basement, essentially a metamorphic complex of gneisses and schist intruded by granitic rocks and mafic to ultramafic bodies. Interpreted Precambrian structures trend predominantly northwest and northeast although east-west trending features are evident. Prominent gravity lows define the salt anticlines. Structural and lithologic trends in the Gibson Dome area are closely examined. Of greatest interest is a series of circular magnetic highs trending west-northwest into the Gibson Dome area. Further study of the exact definition and geologic significance of this series of anomalies is warranted.

  6. Complex electric conductivity of rocks

    International Nuclear Information System (INIS)

    Rocha, B.R.P. da.

    1982-01-01

    Laboratory measurements of complex conductivity were made on 28 drill-core samples from area MM1-Prospect 1 of the Carajas Mining District. The objective of this research was to help interpret field geophysical survey of the area using Induced Polarization and AFMAG methods. A petrographic study of the samples was done, using thin sections, polished sections and X-ray diffraction. Copper content, in the form of sulfides, was determined using atomic absorption. As a result of the petrographic study, the samples were classified in five distinct groups: granite, biotite schist, amphibolite and magnetite quartzite-iron formation. The grade of Cu was variable in the five groups, ranging from 50 ppm to 6000 ppm. In conclusion, these measurements show that the field Induced Polarization and AFMAG anomalies near these three drill holes (F1, F2 and F3) are due primarily to the magnetic iron formation, and secondarily due to associated low-grade chalcopyrite mineralization. (author) [pt

  7. Geodynamic control of the chemical composition of Tertiary continental arc magmas of Ecuador?

    International Nuclear Information System (INIS)

    Chiaradia, M.; Fontbote, L

    2001-01-01

    Whereas an abundant literature has been produced on the Tertiary magmatism of the Central Andes, no comparable studies exist for the Tertiary continental magmatism of the Northern Andes in general and of Ecuador in particular. In this contribution we present the first extensive data on lead and strontium isotopes of Paleocene to Pliocene magmatic rocks of Ecuador together with their major, trace and rare earth element geochemistry. The main interest of carrying out a geochemical and isotopic investigation on the magmatism of Ecuador is that, different from the Central Andes, Ecuador consists of several accreted terranes both of continental and oceanic affinity. The fragmented nature of the recently assembled crust of Ecuador, composed of lithologies such as Paleozoic schists, Triassic anatexites, and Jurassic metabasalts, could have variably affected the chemistry of the Ecuadorian magmas (au)

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

    Directory of Open Access Journals (Sweden)

    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.

  9. SHRIMP U-Pb dating of detrital zircons in metamorphic rocks from northern Kyushu, western Japan

    International Nuclear Information System (INIS)

    Tsutsumi, Yukiyasu; Yokoyama, Kazumi; Terada, Kentaro; Sano, Yuji

    2003-01-01

    Radiometric ages of detrital zircons in psammitic schists from the Nagasaki, Kurume, Konoha and Kiyama areas, northern Kyushu, were obtained from 238 U/ 206 Pb ratio and isotopic compositions of Pb using a Sensitive High Resolution Ion Microprobe (SHRIMP II). Zircons from the Nagasaki, Kurume and Konoha areas show bimodal age distribution with peaks at ca. 1900 Ma and 250 Ma. It is suggested from this study that the older zircons were derived from Proterozoic landmass and the Korean Peninsula. Zircons from the Kiyama metamorphic rock show a different pattern with ages concentrated at 380-590 Ma. Such zircons are rare in rock samples from the Nagasaki, Kurume and Konoha areas, indicating that Kiyama rocks and a different origin than those from the other three areas. The youngest zircons from the Kiyama, Nagasaki, Kurume and Konoha areas show ages of 382±23 Ma, 238±13 Ma, 249±13 Ma, and 175±4 Ma, respectively, These data mark the upper age limit of their deposition. Since a continuous igneous activity occurred during the period from 300 to 170 Ma in Far East Asia, and the metamorphic age has been close to the zircon age of each area, these youngest ages for the Nagasaki, Kurume and Konoha areas are considered nearly contemporary to the depositional ages. An evaluation of the nature of metamorphism and available ages suggest the possibility that the Nagasaki metamorphic rocks as well as the schist from the Kurume area belong to the Suo zone of the Sangun belt, whereas the metamorphic rocks in the Konoha area may belong to the Ryoke belt or Suo zone of the Sangun belt. (author)

  10. Lead-Antimony Sulfosalts from Tuscany (Italy. XX. Members of the Jordanite–Geocronite Series from the Pollone Mine, Valdicastello Carducci: Occurrence and Crystal Structures

    Directory of Open Access Journals (Sweden)

    Cristian Biagioni

    2016-02-01

    Full Text Available A crystal-chemical study of historical specimens as well as new ones belonging to the jordanite–geocronite series from the Pollone baryte + pyrite ± (Pb-Zn-Ag ore deposit (Valdicastello Carducci, Apuan Alps, Tuscany, Italy has been performed. These crystals were collected in quartz extension veins embedded in three different occurrences: (i baryte + pyrite orebodies; (ii schist layers interbedded between baryte + pyrite orebodies; and (iii schists at the contact with pyrite-poor baryte orebodies. Electron-microprobe data indicated the occurrence of three distinct groups of compositions within the sample suite. These correspond to As-bearing geocronite, Sb-rich jordanite, and Sb-bearing jordanite, with mean compositions Pb14Sb3.8As2.2S23, Pb14Sb2.9As3.1S23, and Pb14Sb2.6As3.4S23, respectively. Crystals representative of these different compositions have been investigated through single-crystal X-Ray diffraction studies and their crystal structures have been solved to R1 = 0.078, 0.069, and 0.033, respectively. The unit-cell volume decreases passing through As-bearing geocronite (V = 2149.5(3 Å3 to Sb-bearing jordanite (V = 2132.3(3 Å3. The As-to-Sb substitution takes place preferentially at the Sb4 site; through the increasing of the Sb content, Sb can substitute As also at the As6 site. According to the structural study of the ore deposit, formation of jordanite–geocronite is subordinated to a late Alpine deformative D2 stage, which permitted in situ remobilization of preexisting sulfide ore in small quartz extension veins. Such a local recrystallization would explain the variability of the As/(As + Sb ratio of the members of the jordanite series, reflecting the heterogeneity of the orebody.

  11. Extensional ductile tectonics of the Sioule metamorphic series (Variscan French Massif Central)

    Science.gov (United States)

    Faure, M.; Grolier, J.; Pons, J.

    1993-09-01

    In the Northern part of the Variscan French Massif Central, the Sioule series, from top to bottom, consists of a pre-Viséan granite, migmatite, gneiss and mica schist. Two ductile deformations have been recognized. The earlier phase is characterized by a north-east-south-west trending stretching lineation; the second phase, characterized by a north-west-south-east trending mineral, stretching and crenulation lineation, is better marked in the lower mica schist part than in the upper granito-gneissic part. This second phase occurred during retrogression of the metamorphic rocks; related shear criteria indicate a top to the south-west shear. The Namurian-Westphalian magmatic bodies such as the Echassières leucogranite, Pouzol-Servant microgranite and numerous north-east -south-west trending microgranite dykes are emplaced in extensional fractures related to the same north-west-south-east maximum stretching direction. The asymmetrical shapes of the two granitic massifs indicate that they intruded towards the south-east. The synkinematic retrogression of the metamorphic rocks, the shape of the magmatic bodies and a re-examination of the numerous available data support the interpretation that the deformation is due to the extensional tectonic regime related to the Variscan crustal re-quilibration. This interpretation is in agreement with the correlation of the Sioule series with the Chavanon series. The two series belong to a unique tectono-metamorphic unit left-laterally offset by the Stephanian motion of the Sillon Houiller fault. This study also shows that the Sillon Houiller did not play a significant part during the Namurian-Westphalian extensional tectonics of the Massif Central.

  12. Blueschist facies fault tectonites from the western margin of the Siberian Craton: Implications for subduction and exhumation associated with early stages of the Paleo-Asian Ocean

    Science.gov (United States)

    Likhanov, Igor I.; Régnier, Jean-Luc; Santosh, M.

    2018-04-01

    The tectonic evolution of the Siberian Cratonic margins offers important clues for global paleogeographic reconstructions, particularly with regard to the complex geological history of Central Asia. The Yenisey Ridge fold-and-thrust belt at the western margin of the Siberian Craton forms part of the Central Asian Orogenic Belt (CAOB) and is a key to understand the Precambrian tectonic evolution of the Siberian Craton and crustal growth in the CAOB, the world's largest Phanerozoic accretionary orogenic belt. Here we report for the first time, the occurrence of glaucophane schist relics in tectonites within the Yenisey shear zone which provides insights on Chilean-type convergent boundary. We present results from isotope geochronology (SHRIMP zircon analysis and mica 40Ar/39Ar dating), coupled with P-T calculations derived from conventional geothermobarometry and pseudosections in the system NCKFMASH that suggest two superimposed metamorphic events. During the first stage, glaucophane schists formed at around 640-620 Ma at P-T conditions of 8-10 kbar and 400-450 °C. In the second stage, the rocks experienced dynamic metamorphism (c. 600 Ma) at 11-15 kbar/550-640 °C. The differences in P-T parameters between weakly deformed rocks and intensely deformed tectonites and P-T paths suggest distinct tectonic processes. Geochemical features of the mafic tectonites suggest N-MORB and E-MORB affinity, and the zircon U-Pb ages suggest formation of the protoliths at 701.6 ± 8.4. The sequence of spreading, subduction and shear deformation identified in our study correlate with the early stages of development of the Paleo-Asian Ocean at the western margin of the Siberian Craton and supports the spatial proximity of Siberia and Laurentia at 700-600 Ma, as proposed for the Late Neoproterozoic paleogeographic reconstructions and as robustly constrained from large igneous province (LIP) record.

  13. 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.

  14. The timing of tertiary metamorphism and deformation in the Albion-Raft River-Grouse Creek metamorphic core complex, Utah and Idaho

    Science.gov (United States)

    Strickland, A.; Miller, E.L.; Wooden, J.L.

    2011-01-01

    The Albion-Raft River-Grouse Creek metamorphic core complex of southern Idaho and northern Utah exposes 2.56-Ga orthogneisses and Neoproterozoic metasedimentary rocks that were intruded by 32-25-Ma granitic plutons. Pluton emplacement was contemporaneous with peak metamorphism, ductile thinning of the country rocks, and top-to-thewest, normal-sense shear along the Middle Mountain shear zone. Monazite and zircon from an attenuated stratigraphic section in the Middle Mountain were dated with U-Pb, using a SHRIMP-RG (reverse geometry) ion microprobe. Zircons from the deformed Archean gneiss preserve a crystallization age of 2532 ?? 33 Ma, while monazites range from 32.6 ?? 0.6 to 27.1 ?? 0.6 Ma. In the schist of the Upper Narrows, detrital zircons lack metamorphic overgrowths, and monazites produced discordant U-Pb ages that range from 52.8 ?? 0.6 to 37.5 ?? 0.3 Ma. From the structurally and stratigraphically highest unit sampled, the schist of Stevens Spring, narrow metamorphic rims on detrital zircons yield ages from 140-110 Ma, and monazite grains contained cores that yield an age of 141 ??2 Ma, whereas rims and some whole grains ranged from 35.5 ?? 0.5 to 30.0 ?? 0.4 Ma. A boudinaged pegmatite exposed in Basin Creek is deformed by the Middle Mountains shear zone and yields a monazite age of 27.6 ?? 0.2 Ma. We interpret these data to indicate two periods of monazite and metamorphic zircon growth: a poorly preserved Early Cretaceous period (???140 Ma) that is strongly overprinted by Oligocene metamorphism (???32-27 Ma) related to regional plutonism and extension. ?? 2011 by The University of Chicago.

  15. Basic rocks in Finland

    International Nuclear Information System (INIS)

    Piirainen, T.; Gehoer, S.; Iljina, M.; Kaerki, A.; Paakkola, J.; Vuollo, J.

    1992-10-01

    Basic igneous rocks, containing less than 52% SiO 2 , constitute an important part of the Finnish Archaean and Proterozoic crust. In the Archaean crust exist two units which contain the majority of the basic rocks. The Arcaean basic rocks are metavolcanics and situated in the Greenstone Belts of Eastern Finland. They are divided into two units. The greenstones of the lower one are tholeiites, komatiites and basaltic komatiites. The upper consists of bimodal series of volcanics and the basic rocks of which are Fe-tholeiites, basaltic komatiites and komatiites. Proterozoic basic rocks are divided into seven groups according to their ages. The Proterozoic igneous activity started by the volominous basic magmatism 2.44 Ga ago. During this stage formed the layered intrusions and related dykes in the Northern Finland. 2.2 Ga old basic rocks are situated at the margins of Karelian formations. 2.1 Ga aged Fe-tholeiitic magmatic activity is widespread in Eastern and Northern Finland. The basic rocks of 1.97 Ga age group are met within the Karelian Schist Belts as obducted ophiolite complexes but they occur also as tholeiitic diabase dykes cutting the Karelian schists and Archean basement. The intrusions and the volcanics of the 1.9 Ga old basic igneous activity are mostly encountered around the Granitoid Complex of Central Finland. Subjotnian, 1.6 Ga aged tholeiitic diabases are situated around the Rapakivi massifs of Southern Finland, and postjotnian, 1.2 Ga diabases in Western Finland where they form dykes cutting Svecofennian rocks

  16. 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.

  17. 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.

  18. PERMEABILITY OF SAVCIBEY DAM (BİLECİK AXIS LOCATION AND DESIGN OF GROUT CURTAIN

    Directory of Open Access Journals (Sweden)

    Mustafa Can Canoğlu

    2016-12-01

    Full Text Available This study comprise the design of the planned grout curtain in Savcıbey Dam (Söğüt/Bilecik in order to provide impermeability along the dam axis. Within the context of field studies, engineering geology map was generated, ground investigation drilling was realized and permeability tests were performed. Within the field studies, the joint conditions of the geological units (Triassic aged Bozuyük Metamorphic schists under the dam axis and its effect on permeability was observed considering the positions of the discontinuities with regard to the dam axis location. Orientation of discontinuities generally have strikes changing between N – S and NNE – SSW. 5 boreholes on dam axis, 2 boreholes on cofferdam, 3 boreholes on diversion tunnel and 2 boreholes on spillway total 245 m ground investigation borehole were drilled. In order to determine the permeability profile of dam axis and design the grout curtain, Lugeon tests in Bozuyük Metamorphic units observed in dam axis, falling head permeability tests in alluviums observed in thalveg and slope debris observed in right abutment were performed. Lugeon tests realized in Bozuyük Metamorphic units show that the unit is generally permeable and partly low permeable. Alluvium and slope debris are highly permeable. In addition, drilling works realized in dam axis shows that the augmentation of the weathering degree cause an increase of permeability in Triassic aged Bozüyük Metamorphic schists. As a result of these studies information about the permeability of Savcıbey Dam was collected and the grout curtain hole was designed. Accordingly, it is predicted that approximately 40 m depth of grout curtain from the stripping excavation with the depth of 1.50 m would prevent the possible leakages.

  19. 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.

  20. 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 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.

  1. 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

  2. Seismic imaging of the southern California plate-boundary around the South-Central Transverse Ranges using double-difference tomography

    Science.gov (United States)

    Share, P. E.; Ben-Zion, Y.; Thurber, C. H.; Zhang, H.; Guo, H.

    2017-12-01

    We derive P and S seismic velocities within and around the South-Central Transverse Ranges section of the San Andreas Fault (SAF), using a new double-difference tomography algorithm incorporating both event-pair and station-pair differential times. The event-pair data can determine high-resolution relative earthquake locations and resolve fine-scale structure in seismogenic zones, whereas station-pair data allow for better absolute locations and higher resolution of structure near the surface where stations are most dense. The tomographic results are based on arrival times of P and S waves generated by 17,753 M>1 local events from 1/1/2010 to 6/30/2015 recorded by 259 stations within a 222 km x 164 km region. The resulting P and S velocity models include low velocities along major fault segments and across-fault velocity contrasts. For example, at depths 50 km parallel to the SAF around Coachella Valley but offset to the NE by 13 km. This is interpreted to mark a dipping section of the SAF that separates granites at depth in the SW from gneisses and schists in the NE. Analysis of fault zone head waves propagating along these sections of the SAF and SJFZ show that major bimaterial interfaces are associated with the observed velocity contrasts. Additional features within the models include elongated low velocity anomalies extending from the SJFZ trifurcation area, which itself has associated low velocity at great depth (>14 km), to the Elsinore Fault in the SW. Moreover, a deep (>13 km) velocity contrast appears beneath the SBB with an east-west strike oblique to both the northern SJFZ and SAF traces. The latter is potentially related to the ancestral Banning Fault, which dips to the north, separating low velocity Pelona schist in the north from high velocity granites in the south.

  3. 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.

  4. Geology and geochronology of the sub-Antarctic Snares Islands/Tini Heke, New Zealand

    International Nuclear Information System (INIS)

    Scott, J.M.; Turnbull, I.M.; Sagar, M.W.; Tulloch, A.J.; Waight, T.E.; Palin, J.M.

    2015-01-01

    The first comprehensive geological map, a summary of lithologies and new radiogenic isotope data (U-Pb, Rb-Sr) are presented for crystalline rocks of the Sub-Antarctic Snares Islands/Tini Heke, 150 km south of Stewart Island. The main lithology is Snares Granite (c. 109 Ma from U-Pb dating of zircon), which intrudes Broughton Granodiorite (c. 114 Ma from U-Pb zircon) on Broughton Island. Rafts of schist within Snares Granite are common on the outlying Western Chain islets, and rare on North East and Broughton islands. Zircon grains extracted from one schistose raft on Broughton Island are prismatic and yield an essentially unimodal age population of c. 116 Ma that is within error of the granodiorite. These properties suggest that the dated raft represents a meta-igneous rock despite its mica-rich nature. Some schistose rocks on the Western Chain contain coarse relict plagioclase phenocrysts and appear to have an igneous protolith. No conclusive metasedimentary rocks have been identified, although sillimanite-bearing mica-rich schist occurs on Rua. Deformation of the crystalline rocks occurred after Snares Granite intrusion and before cooling below muscovite K-Ar closure at 400 ± 50 degrees C at 95 Ma. This period overlaps the age of extensional ductile shear zones on Stewart Island. The discovery of several basaltic dykes, which cut across fabrics and are unmetamorphosed, indicates that volcanic rocks are associated with all Sub-Antarctic island groups. The larger of the islands are overlain by peat, which on North East Island also contains gravel deposits. (author).

  5. Outline of Upper Precambrian and Lower Paleozoic evolution of the Iberian Peninsula according to U-Pb dating of zircons

    International Nuclear Information System (INIS)

    Lancelot, J.R.; Allegret, A.; Iglesias Ponce de Leon, M.

    1985-01-01

    In the northwestern part of the Iberian Peninsula, recent geological studies have defined the following stratigraphic sequence from bottom to top: basal orthogneiss of Miranda do Douro is overlain by a complex of schist and greywacke which have been assigned to the Cambrian or late Precambrian; these are followed by the Ollo de Sapo gneisses of volcanic-sedimentary origin which in turn are overlain by the fossiliferous layers of the lower Ordovician. The schist and greywacke complex and the lower part of the Ollo de Sapo Formation are transected by granitic dikes (Viana del Bollo orthogneiss). All these rocks were folded, faulted, metamorphosed, and intruded by granite plutons during Variscan times. The emplacement of the Miranda do Douro and Viana del Bollo orthogneisses have been respectively dated at 618+-9 Ma and 465+-10 Ma by the U-Pb method on zircons. These data yield lower and upper limits for the deposition of the Ollo de Sapo Formation and demonstrate the occurrence of a Precambrian basement (''Pan-African'' or ''Cadomian'' orogeny) in the Variscan belt in the northwestern part of the Iberian Peninsula. The emplacement of Viana del Bollo orthogneiss could be genetically related to the main phase of crustal thinning (470-520 Ma) characteristic of the Prevariscan evolution of western Europe. Typology and U-Pb data of the Ollo de Sapo zircons indicate the occurrence of inherited old Precambrian zircons and yield an age of 325+-3 Ma for the Variscan main thermal event in the area considered. Four possible evolutionary models for the U-Pb system of the Ollo de Sapo zircons are discussed. (orig.)

  6. Co-evolution of Vegetation, Sediment Transport and Infiltration on semi-arid hillslopes

    Science.gov (United States)

    Harman, C. J.; Troch, P. A.; Lohse, K. A.; Sivapalan, M.

    2011-12-01

    Soils in semi-arid landscapes can vary over very small distances, with a great deal of variation associated with 'resource islands' created and maintained by woody vegetation. The distinct physical and hydraulic properties that arise in these islands can lead to spatial patterns of infiltration that have been implicated in the maintenance of the vegetation populating the island. Less well understood are the roles that the small-scale variability in soils plays in determining the transport of sediments, water and sediment-bound carbon and nitrogen across hillslopes. Here we explore these relationships using a coupled field and modeling approach. Detailed field data from hillslopes underlain by both granite and schist parent materials in the Santa Catalina mountains (part of the JSC Critical Zone Observatory) suggest that soils under individual velvet mesquite (latin name) contain higher concentration of soil organic matter and have higher hydraulic conductivity and water holding capacity. Greater infiltration and increased roughness under the canopy appears to lead to the formation of mounds that alter overland flow lines around the area under the canopy, particularly in the finer schist soils. This diversion leads to a complex distribution of shear stresses across the hillslope, creating systematic patterns in the transport of carbon and nitrogen rich soils under the canopies. The relationship between the small scale mechanism and the emergent pattern dynamics in the temporal variability of materials delivered to the stream from the hillslope are also examined, and the implications of these results for the modeling of water, sediment and nutrient fluxes at hillslope scales will be discussed.

  7. Structural and geophysical interpretation of Roatan Island, Honduras, Western Caribbean

    Science.gov (United States)

    Sutton, Daniel Scott

    Roatan Island is the largest of the Bay Islands of Honduras. These islands form an emergent crest off the Caribbean coast of Honduras called the Bonacca Ridge. The Bartlett Trough to the north and subsequent Bonacca Ridge were likely formed due to the transform fault system of the Motagua-Swan Islands Fault System. This fault system forms the tectonic plate boundary between the North American and Caribbean plates. Although the timing and kinematics are poorly constrained, the Bay Islands and the Bonacca Ridge were likely uplifted due to transpression along this left-lateral strike-slip system. With limited regional exposures along the adjacent tectonic boundary, this study aimed to present a structural interpretation for Roatan. This new interpretation is further explained through regional considerations for a suggested geologic history of the northwestern Caribbean. In order to better constrain the kinematics of uplift and exhumation of Roatan Island, structural, gravity, and magnetic surveys were conducted. Principal attention was directed to the structural relationship between the geologic units and their relationship to one another through deformation. Resulting geologic cross-sections from this study present the metamorphic basement exposed throughout the island to be in a normal structural order consisting of biotite schist and gneiss, with overlying units of chlorite schist, carbonate, and conglomerate. These units have relatively concordant strike and dip measurements, consistent with resultant magnetic survey readings. Additionally, large and irregular bodies of amphibolite and serpentinite throughout the island are interpreted to have been emplaced as mafic and ultra-mafic intrusions in weakness zones along Early Paleogene transform system fault planes. The interpretation and suggested geologic history from this study demonstrate the importance of transpressive tectonics both local to Roatan and regionally throughout geologic history. Consideration of

  8. Petrography and geochemistry of lithic fragments in ignimbrites from the Mangakino Volcanic Centre : implications for the composition of the subvolcanic crust in western Taupo Volcanic Zone, New Zealand

    International Nuclear Information System (INIS)

    Krippner, S.J.P.; Briggs, R.M.; Wilson, C.J.N.; Cole, J.W.

    1998-01-01

    The Mangakino Volcanic Centre is the westernmost and oldest rhyolitic caldera volcano in the Taupo Volcanic Zone, North Island, New Zealand. The largest eruptions from Mangakino occurred in two periods of caldera-forming activity during the 1.68-1.53 Ma (Period I), and 1.21-0.95 Ma (Period IIA), producing several voluminous widespread welded and nonwelded ignimbrites and minor fall deposits. Other activity from Mangakino generated fall deposits and rhyolitic lava domes. Lithic fragments are common in all Mangakino ignimbrites (1-10 modal %), and consist of diverse lithologies including: rhyolite, dacite, andesite, and basaltic andesite lava, welded ignimbrite, tuff, volcanic breccia, biotite granite, granodiorite porphyry, siltstone, sandstone, greywacke, metagreywacke, metaconglomerate, biotite and hornblende-biotite schist. Lithic populations in Period I ignimbrites are dominated by andesite lavas, suggesting that there was a pre-existing andesite volcano in the Mangakino area, geochemically distinct from Titiraupenga and Pureora, the nearest roughly contemporaneous andesitic volcanoes. Later ignimbrites that erupted during Period IIA, contain predominantly rhyolitic lava lithics, implying that significant dome building activity occurred at Mangakino, which represented greater volumes of rhyolitic lava than previously described from the area. Petrographic, geochemical, and geophysical (density and magnetic susceptibility) data measured from the lithic fragments are used to propose a model for the shallow crust below Mangakino Volcanic Centre. This model postulates eruptions through a basement of Mesozoic biotite schists overlain by metagreywackes, a thin cover of Tertiary sandstones and siltsones, and an overlying volcanic succession of andesite, dacite and rhyolite lavas, welded ignimbrites, and lacustrine sediments. Ignimbrite eruptions incorporated comagmatic biotite granite fragments from the crystallised margins of the silicic magma chambers, and effectively

  9. Elastic wave velocities, chemistry and modal mineralogy of crustal rocks sampled by the Outokumpu scientific drill hole: Evidence from lab measurements and modeling

    Science.gov (United States)

    Kern, H.; Mengel, K.; Strauss, K. W.; Ivankina, T. I.; Nikitin, A. N.; Kukkonen, I. T.

    2009-07-01

    The Outokumpu scientific deep drill hole intersects a 2500 m deep Precambrian crustal section comprising a 1300 m thick biotite-gneiss series (mica schists) at top, followed by a 200 m thick meta-ophiolite sequence, underlain again by biotite gneisses (mica schists) (500 m thick) with intercalations of amphibolite and meta-pegmatoids (pegmatitic granite). From 2000 m downward the dominating rock types are meta-pegmatoids (pegmatitic granite). Average isotropic intrinsic P- and S-wave velocities and densities of rocks were calculated on the basis of the volume fraction of the constituent minerals and their single crystal properties for 29 core samples covering the depth range 198-2491 m. The modal composition of the rocks is obtained from bulk rock (XRF) and mineral chemistry (microprobe), using least squares fitting. Laboratory seismic measurements on 13 selected samples representing the main lithologies revealed strong anisotropy of P- and S-wave velocities and shear wave splitting. Seismic anisotropy is strongly related to foliation and is, in particular, an important property of the biotite gneisses, which dominate the upper and lower gneiss series. At in situ conditions, velocity anisotropy is largely caused by oriented microcracks, which are not completely closed at the pressures corresponding to the relatively shallow depth drilled by the borehole, in addition to crystallographic preferred orientation (CPO) of the phyllosilicates. The contribution of CPO to bulk anisotropy is confirmed by 3D velocity calculations based on neutron diffraction texture measurements. For vertical incidence of the wave train, the in situ velocities derived from the lab measurements are significantly lower than the measured and calculated intrinsic velocities. The experimental results give evidence that the strong reflective nature of the ophiolite-derived rock assemblages is largely affected by oriented microcracks and preferred crystallographic orientation of major minerals, in

  10. 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. Water-quality 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 drinking water 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

  11. 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

  12. 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

  13. 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 <8m thick mylonites in the SW, overlain by grey sericite-albite-graphite-schists (Flabouria Lithodeme); (2) Rizou Lithodeme - massive grey to BGC marble, with abundant

  14. 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

  15. 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

  16. Precambrian terranes of African affinities in the southeastern part of Brazil and Uruguay

    International Nuclear Information System (INIS)

    Basei, M.A.S; Junior, Siga; Harara, O.M; Preciozzi, F; Sato, K; Kaufuss, G

    2001-01-01

    The interest in correlating terranes at opposite margins of the South Atlantic Ocean reflects a natural curiosity of both researchers who work in the eastern South-America and who study southwestern Africa. On a large scale scenario the geology of this region is characterized by a central portion composed of Neo proterozoic-Cambrian belts (Dom Feliciano, Kaoko, Damara, Gariep, Saldania) having on each side old gneissic-migmatitic terrains on both continents (Luis Alves, Rio de La Plata, Kalahari and Congo). In South America the Neoproterozoic Dom Feliciano Belt (DFB) predominates in the eastern part of the region and is internally organized according to three different crustal segments characterized, from southeast to northwest, by a Granite belt (deformed I-type medium to high calc-alkaline granites and alkaline granitoid rocks; a Schist belt (volcano-sedimentary rocks metamorphosed from greenschist to amphibolite facies and intrusive granitoids), and a Foreland basin (anchimetamorphic sedimentary and volcanic rocks), the latter situated between the Schist belt and the Archean-Paleoproterozoic foreland. Despite discontinuously covered by younger sediments, the NS continuity of these three crustal segments is suggested by similar lithotypes, structural characteristics, ages and isotopic signature, as well as by the gravimetric data. The Major Gercino, Cordilheira, and Sierra Ballena shear zones are part of the major NE-SW lineaments that affect all southern Brazilian and Uruguayan Precambrian terrains. They separate the Dom Feliciano Schist Belt (supracrustal rocks of the Brusque-Porongos and Lavalleja groups), to the West, from the granitoids of the Granite belt, to the East. The shear zones are characterized by a regional NE trend and a resultant oblique direction of movement where ductile-brittle structures predominate. It is here postulated, as discussed later on, that this lineament separates terranes that are geologically, geo chronologically and isotopically

  17. 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

  18. 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

  19. Carbon Retention and Isotopic Evolution in Deeply Subducted Sediments: Evidence from the Italian Alps

    Science.gov (United States)

    Cook-Kollars, J.; Bebout, G. E.; Agard, P.; Angiboust, S.

    2012-12-01

    Subduction-zone metamorphism of oceanic crust and carbonate-rich seafloor sediments plays an important regulatory role in the global C cycle by controlling the fraction of subducting C entering long-term storage in the mantle and the fraction of subducting C emitted into the atmosphere in arc volcanic gases. Modeling studies suggest that the extent of decarbonation of subducting sediments could be strongly affected by extents of infiltration by external H2O-rich fluids and that, in cool subduction zones, the dehydration of subducting oceanic slabs may not release sufficient H2O to cause significant decarbonation of overlying sediments [Gorman et al. (2006), G-cubed; Hacker (2008), G-cubed]. Metasedimentary suites in the Western Alps (sampled from the Schistes Lustres, Zermatt-Saas ophiolite, and at Lago di Cignana) were subducted to depths corresponding to 1.5-3.2 GPa, over a range of peak temperatures of 350-600°C, and are associated with HP/UHP-metamorphosed Jurassic ophiolitic rocks [Agard et al. (2001), Bull. soc. geol. France; Frezzotti et al. (2011), Nature Geoscience]. These metasedimentary suites are composed of interlayered metapelites and metacarbonates and represent a range of peak P-T conditions experienced in modern, relatively cool subduction zones. Integrated petrologic and isotopic study of these rocks allows an analysis of decarbonation and isotopic exchange among oxidized and reduced C reservoirs along prograde subduction-zone P-T paths. Petrographic work on Schistes Lustres metacarbonates indicates only minor occurrences of calc-silicate phases, consistent with the rocks having experienced only very minor decarbonation during prograde metamorphism. Carbonate δ13CVPDB values (-1.5 to 1‰) are similar to values typical of marine carbonates. Higher grade, UHP-metamorphosed carbonates at Cignana show mineralogic evidence of decarbonation; however, the δ13C of the calcite in these samples remains similar to that of marine carbonate. With

  20. Toward a new tectonic model for the Late Proterozoic Araçuaí (SE Brazil)-West Congolian (SW Africa) Belt

    Science.gov (United States)

    Pedrosa-Soares, A. C.; Noce, C. M.; Vidal, Ph; Monteiro, R. L. B. P.; Leonardos, O. H.

    1992-08-01

    The Araçuaí Belt is a Late Proterozoic (Brasiliano Cycle) geotectonic unit which was developed along the southeastern margin of the São Francisco Craton (SE Brazil) and was formerly considered as being an ensialic orogen. It is correlated with the Pan-African West Congolian Belt (SW Africa) in many reports. In the western domain of the belt, the Macaúbas Group—the most important supracrustal sequence related to the evolution of the Araçuaí Belt —comprises the Terra Branca and Carbonita Formations, which consist of littoral glacial sediments to shelf turbidites. These formations grade upward and eastward to the Salinas Formation, consisting of distal turbidites related to submarine fans, pelagic sediments, and a rock association (the Ribeirão da Folha Facies) typical of an ocean-floor environment. Banded iron formations, metacherts, diopsidites, massive sulfides, graphite schists, hyperaluminous schists, and ortho-amphibolites, intercalated with quartz-mica schists and impure quartzites, characterize the most distinctive and restricted volcano-sedimentary facies yet found within the Salinas Formation. Ultramafic slabs were tectonically emplaced within the Ribeirão da Folha Facies. Eight whole rock samples of meta-ultramafic rocks and ortho-amphibolites yielded a SmNd isochronic age of 793 ± 90 Ma ( ɛNd(T) = +4.1 ± 0.6. MSWD = 1.76 ). The structures of the northern Araçuaí Belt are marked by a doen-dip stretching lineation (western domain) related to frontal thrusts which controlled tectonic transport from east to west; stretching lineation rakes decrease in the eastern tectonic domain, indicating dominant oblique to transcurrent motion; the northern arch of the belt is characterized by major high-dip transcurrent shear zones. Our tectonic model starts with marked fracturing, followed by rifting that took place in the São Francisco-Congo Craton around 1000 ± 100 Ma (ages of basic intrusions and alkaline anorogenic granites). A sinistral transfer

  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. 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

  3. Olivine CPO in non-deformed peridotite due to topotactic replacement of antigorite

    Science.gov (United States)

    Nagaya, Takayoshi; Wallis, Simon; Kobayashi, Hiroaki; Michibayashi, Katsuyoshi; Mizukami, Tomoyuki; Seto, Yusuke; Miyake, Akira; Matsumoto, Megumi

    2014-05-01

    Olivine crystallographic preferred orientation (CPO) is thought to be the main cause of seismic anisotropy in the mantle, and its formation is generally considered to be the result of plastic deformation of mantle by dislocation creep. Olivine CPO has been reproduced in laboratory deformation experiments and considerable success has been achieved in understanding the deformation conditions (e.g. stress, temperature and water content) under which different olivine CPO patterns develop. This opens the possibility of mapping conditions in the mantle using seismic anisotropy and has been the subject of considerable study. Here we report an alternative mechanism for olivine CPO without the need for deformation. This process may be important in understanding the seismic properties of mantle in convergent margins. Metamorphic studies show peridotite in the Happo area, central Japan, formed by the dehydration of antigorite-schist related to contact metamorphism around a granite intrusion. Both field and microstructural observations suggest the olivine has not undergone strong plastic deformation. This was confirmed by TEM work that shows the olivine has very low dislocation densities and lacks low angle tilt boundaries. Such tilt boundaries are general stable even after annealing. These features show that peridotite in the Happo area formed in the absence of solid-state deformation. The olivine of the Happo peridotite formed dominantly by the dehydration breakdown of antigorite schist. We propose that the olivine CPO formed as a result of topotactic replacement of antigorite by the newly formed olivine. EBSD measurements in samples where both antigorite and new olivine are present and in contact show a very close crystallographic relationship between the two minerals: the a-axes are parallel, and the b- and c-axes are perpendicular. We conclude the strong olivine CPO in the Happo area was inherited from the original CPO of the antigorite. Such a process is likely to also

  4. Geochemistry and mineralogy of the radioactive minerals associated with some pegmatite veins of the Ukma-Nawahatu Hursi sector, Purulia district, W.B., in the Precambrian Chhotanagpur Gneissic complex

    International Nuclear Information System (INIS)

    Baidya, Tapan Kumar

    2014-01-01

    Some barite-bearing pegmatites in the Ukma-Nawahatu-Hursi sector (23° 25 min - 26 sec N, 86° 02 min - 04 sec E) in Purulia dist., West Bengal, have association of radioactive minerals in the form of coarse-grained pitchblack lumps and irregular patches. The present author and his associates first reported the occurrence of this radioactive belt along a ENE-WSW shearzone during their fieldwork in November, 1978. Groundborne radiometric survey and isorad mapping has established a radioactive high zone of about 15 km length running through Ukma, Nawahatu and Hursi areas. Mineralogical studies of the radioactive minerals have revealed the occurrence of Chevkinite, Aeschynite, Brannerite, Allanite, Uraninite, Tyuyamunite, Davidite, Euxenite, Samarskite, Thorutite, Autunite, Cerianite, in association with quartz, barite, microcline as the principal minerals and various minor minerals like biotite, vermiculite, hornblende, augite, orthoclase, celsian, muscovite, calcite, epidote, zoisite, ilmenite, sphene, rutile, hematite, magnetite, anatase, galena and sodic plagioclase. The barite-bearing pegmatites occur as lenses or lenticular veins hosted by garnetiferous sillimanite-biotite-quartz-schist or occasionally by migmatite. Near Nawahatu the radioactive barite-pegmatite vein occurs at or near the junction between the footwall amphibolite and hangingwall garnetiferous schist. The pegmatite veins have followed mainly schistosity of the host rock and dip at 70°-80° towards south. Chemical analyses of individual radioactive minerals by SEM-EDX and also of the bulk radioactive lumps by ICP-MS have shown significant concentration of U, Tb and Rare earths. Minor and trace element analyses also record notable contents of Zr, Ga, Sc, Pb, Zn, Nb, Cu, Ni, V, Cr, As, W, Pd, Ag and TI. Details of chemical analytical data are presented here. Chemically active fluids generated during metamorphism, metasomatism and granitic activity appear to have played a significant role in the

  5. 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

  6. Late Cretaceous tectonothermal evolution of the southern Lhasa terrane, South Tibet: Consequence of a Mesozoic Andean-type orogeny

    Science.gov (United States)

    Dong, Xin; Zhang, Ze-ming; Klemd, Reiner; He, Zhen-yu; Tian, Zuo-lin

    2018-04-01

    The Lhasa terrane of the southern Tibetan Plateau participated in a Mesozoic Andean-type orogeny caused by the northward subduction of the Neo-Tethyan oceanic lithosphere. However, metamorphic rocks, which can unravel details of the geodynamic evolution, are rare and only exposed in the south-eastern part of the Lhasa terrane. Therefore, we conducted a detailed petrological, geochemical and U-Pb zircon geochronological study of the late Cretaceous metamorphic rocks and associated gabbros from the Nyemo inlier of the southern Lhasa terrane. The Nyemo metamorphic rocks including gneisses, schists, marbles and calc-silicate rocks, experienced peak amphibolite-facies contact metamorphism under P-T conditions of 3.5-4.0 kbar and 642-657 °C with a very high geothermal gradient of 45-50 °C/km, revealing a distinct deflection from the steady-state geotherm during low-pressure metamorphism. Inherited magmatic zircon cores from the metamorphic rocks yielded protolith ages of 197-194 Ma, while overgrowth zircon rims yielded metamorphic ages of ca. 86 Ma. Whole-rock chemistry and zircon Hf isotopes suggest that the protoliths of the gneisses and schists are andesites and tuffs of the early Jurassic Sangri Group, which were derived from a depleted mantle source of a continental arc affinity. The coeval intimately-associated gabbro (ca. 86 Ma) crystallized under P-T conditions of 3.5-5.3 kbar and 914-970 °C, supplying the heat flux high enough to cause the contact metamorphism of the Sangri Group rock types. We propose that the intrusion of the gabbro and a simultaneous pressure increase of up to 4.0 kbar, which is related to crustal thickening due to crustal overthrusting and the intrusion of mafic material, resulted in the late Cretaceous metamorphism of the early Jurassic Sangri Group during an Andean-type orogeny. Furthermore the Nyemo metamorphic rocks, which have previously been considered to represent slivers of the Precambrian metamorphic basement of the Lhasa terrane

  7. Triassic rejuvenation of unexposed Archean-Paleoproterozoic deep crust beneath the western Cathaysia block, South China

    Science.gov (United States)

    Li, Xi-Yao; Zheng, Jian-Ping; Xiong, Qing; Zhou, Xiang; Xiang, Lu

    2018-01-01

    Jurassic (ca. 150 Ma) Daoxian basalts from the western Cathaysia block (South China) entrained a suite of deep-seated crustal xenoliths, including felsic schist, gneiss and granulite, and mafic two-pyroxene granulite and metagabbro. Zircon U-Pb-Hf isotopic, whole-rock elemental and Sr-Nd-Pb isotopic compositions have been determined for these valuable xenoliths to reveal the poorly-known, unexposed deep crust beneath South China. Detrital zircons from the garnet-biotite schists show several populations of ages at 0.65-0.5 Ga, 1.1-0.75 Ga, 1.6-1.4 Ga, 1.8-1.7 Ga, 2.5-2.4 Ga, 2.8 Ga, and 3.5 Ga, representing a multi-sourced, meta-sedimentary origin with deposition time at the early Cambrian. One mafic granulite contains zircons with concordant U-Pb ages of Neoarchean ( 2520 Ma), as well as Hf model ages of 2.8-2.6 Ga and positive εHf(t) values (up to 6.3), suggesting an accretion of juvenile crust in Neoarchean, probably as the main framework of the lower crust. Geochemical and geochronological evidence shows the mafic granulite and metagabbro were produced by underplating of magmas derived from the depleted asthenosphere and mixed with EM2-type materials during the Late Triassic (205-196 Ma). This magmatic underplating also resulted in the widespread metamorphism of the mafic lower crust and felsic middle crust (e.g., the felsic granulite and gneiss) at 202-201 Ma. We suggest the existence of a highly evolved Archean-Paleoproterozoic basement beneath the western Cathaysia block, which experienced episodic accretion and reworking and the strong rejuvenation during the Triassic. A three-layered structure of the lower crust could exist beneath the Daoxian area during the Jurassic time: its upper layer is an evolved Archean-Paleoproterozoic basement; the middle hybrid layer represents a mixture of Archean-Paleoproterozoic basement with newly accreted/reworked Proterozoic to Phanerozoic materials; and the deeper layer consists of mafic granulites derived from the

  8. 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

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

    International Nuclear Information System (INIS)

    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

    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 UO_2(CO_3)_2"2"− and UO_2(CO_3)_3"4"− species in the alluvial fans under oxic conditions and suboxic conditions where reductions of Mn and NO_3"− 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. - Highlights:

  10. Heterogeneous arsenic enrichment in meta-sedimentary rocks in central Maine, United States

    Energy Technology Data Exchange (ETDEWEB)

    O' Shea, Beth, E-mail: bethoshea@sandiego.edu [Department of Marine Science and Environmental Studies, University of San Diego, 5998 Alcala Park, San Diego, CA 92110 (United States); Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 (United States); Stransky, Megan; Leitheiser, Sara [Department of Marine Science and Environmental Studies, University of San Diego, 5998 Alcala Park, San Diego, CA 92110 (United States); Brock, Patrick [School of Earth and Environmental Sciences, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367 (United States); Marvinney, Robert G. [Maine Geological Survey, 93 State House Station, Augusta, ME 04333 (United States); Zheng, Yan [School of Earth and Environmental Sciences, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367 (United States); Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 (United States)

    2015-02-01

    {sup −1} in meta-sedimentary rocks in central Maine. • Pyrite contains up to 1944 mg kg{sup −1} As in slates and phyllites. • Pyrite abundance decreases in schists and gneisses as pyrrhotite appears. • Arsenic is < 1 mg kg{sup −1} in pyrrhotite. • Non-sulfide arsenic minerals are possible hosts in schists and gneisses.

  11. Lithological model of the South China crust based on integrated geophysical data

    International Nuclear Information System (INIS)

    Zhao, Bing; Bai, Zhiming; Xu, Tao; Zhang, Zhi; Badal, José

    2013-01-01

    The structure and petrology of the earth's crust is critical to understand the growth and evolution of the continents. In this paper, we present the crustal lithological model along the 400-km-long seismic profile between Lianxian, near Hunan Province, and Gangkou Island, near Guangzhou City, South China. This model is based on an integrated geophysical data set including P-wave velocity (V P ), S-wave velocity (V S ), V P /V S ratio, mass density (ρ) and Lamé impedances (ρλ, ρµ), which are compared to those determined by laboratory measurements on a variety of crustal rock samples. The Bouguer gravity anomaly together with the seismic velocity enables us to constrain density. The heat flow and thermal field allow us to carry out corrections for temperature. Pressure correction is based on depth. We directly compare the property parameters determined from the South China seismic data with laboratory measurements made at the same conditions of pressure and temperature. Inversion of the available data for rock lithology indicates that there are substantial differences in the crustal lithology of the Yangtze and Cathaysia blocks. While the average lithology of the upper crust in both blocks is mainly characterized by granite–granodiorite and biotite gneiss, the granite–granodiorite layer is much thicker beneath the Cathaysia block. The middle crust in these two domains is not entirely similar, being granite–granodiorite and granite gneiss as the best fit for the Yangtze block, and granite gneiss and biotite gneiss for the Cathaysia block. The lower crust is composed of biotite gneiss, paragranulite and amphibolite for the Yangtze block, whereas biotite gneiss, paragranulite, diorite, mica quartz schist, amphibolite, green schist facies basalt and hornblende provide the best fit for the Cathaysia block. The results demonstrate that to the east of the Chenzhou–Linwu fault (CLF) that is the southern segment of the Jiangshan–Shaoxing fault, the lithology

  12. 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.

  13. Reconciling experimental and static-dynamic numerical estimations of seismic anisotropy in Alpine Fault mylonites

    Science.gov (United States)

    Adam, L.; Frehner, M.; Sauer, K. M.; Toy, V.; Guerin-Marthe, S.; Boulton, C. J.

    2017-12-01

    Reconciling experimental and static-dynamic numerical estimations of seismic anisotropy in Alpine Fault mylonitesLudmila Adam1, Marcel Frehner2, Katrina Sauer3, Virginia Toy3, Simon Guerin-Marthe4, Carolyn Boulton5(1) University of Auckland, New Zealand, (2) ETH Zurich, Switzerland, (3) University of Otago, New Zealand (4) Durham University, Earth Sciences, United Kingdom (5) Victoria University of Wellington, New Zealand Quartzo-feldspathic mylonites and schists are the main contributors to seismic wave anisotropy in the vicinity of the Alpine Fault (New Zealand). We must determine how the physical properties of rocks like these influence elastic wave anisotropy if we want to unravel both the reasons for heterogeneous seismic wave propagation, and interpret deformation processes in fault zones. To study such controls on velocity anisotropy we can: 1) experimentally measure elastic wave anisotropy on cores at in-situ conditions or 2) estimate wave velocities by static (effective medium averaging) or dynamic (finite element) modelling based on EBSD data or photomicrographs. Here we compare all three approaches in study of schist and mylonite samples from the Alpine Fault. Volumetric proportions of intrinsically anisotropic micas in cleavage domains and comparatively isotropic quartz+feldspar in microlithons commonly vary significantly within one sample. Our analysis examines the effects of these phases and their arrangement, and further addresses how heterogeneity influences elastic wave anisotropy. We compare P-wave seismic anisotropy estimates based on millimetres-scale ultrasonic waves under in situ conditions, with simulations that account for micrometre-scale variations in elastic properties of constitutent minerals with the MTEX toolbox and finite-element wave propagation on EBSD images. We observe that the sorts of variations in the distribution of micas and quartz+feldspar within any one of our real core samples can change the elastic wave anisotropy by 10

  14. 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

  15. 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

  16. 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

  17. Role of vegetation and edaphic factors in controlling diversity and use of different carbon sources in semi-arid ecosystems

    Science.gov (United States)

    Lohse, K. A.; McLain, J. E.; Harman, C. J.; Sivapalan, M.; Troch, P. A.

    2010-12-01

    Microbially-mediated soil carbon cycling is closely linked to soil moisture and temperature. Climate change is predicted to increase intra-annual precipitation variability (i.e. less frequent yet more intense precipitation events) and alter biogeochemical processes due to shifts in soil moisture dynamics and inputs of carbon. However, the responses of soil biology and chemistry to predicted climate change, and their concomitant feedbacks on ecosystem productivity and biogeochemical processes are poorly understood. We collected soils at three different elevations in the Santa Catalina Mountains, AZ and quantified carbon utilization during pre-monsoon precipitation conditions. Contrasting parent materials (schist and granite) were paired at each elevation. We expected climate to determine the overall activity of soil fungal and bacterial communities and diversity of soil C utilization, and differences in parent material to modify these responses through controls on soil physical properties. We used EcoPlateTM C utilization assays to determine the relative abundance of soil bacterial and fungal populations and rate and diversity of carbon utilization. Additional plates were incubated with inhibitors selective to fungal or bacterial activity to assess relative contribution of these microbial groups to overall C utilization. We analyzed soils for soil organic matter, total C and N, particle size analysis and soil moisture content via both gravimetric and volumetric methods to assess the influences of soil physical and chemical properties on the measured biological responses. Consistent with our expectations, overall microbial activity was highest at the uppermost conifer elevation sites compared to the middle and lower elevation sites. In contrast to our expectations, however, overall activity was lower at the mid elevation oak woodland sites compared to the low elevation desert sites. Also consistent with our expectations was the observation that overall activities

  18. 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 Stephanien inferieur. L'uranium n'y existe pas sous forme

  19. Isotopic ages of rocks along the Median Tectonic Line in the Yoshino area, Nara Prefecture

    International Nuclear Information System (INIS)

    Shibata, Ken; Sugiyama, Yuichi; Uchiumi, Shigeru; Takagi, Hideo.

    1988-01-01

    K-Ar, Rb-Sr and fission-track age determinations were carried out on rocks along the Median Tectonic Line (MTL) in the Yoshino area, Nara Prefecture. K-Ar ages on th Ryoke granitic rocks range from 35.3 to 75.9 Ma. Within about 1000 m of MTL the ages decrease toward MTL, probably caused by the hydrothermal alteration associated with cataclasis. The Takamiyama acidic rocks give a K-Ar age of 12.8 Ma. The cooling rate of the granitic rocks, calculated from K-Ar ages and closure temperatures of minerals, is 23 - 27degC/Ma. K-Ar ages for muscovites from pelitic schists in the Sambagawa belt are 62.3 - 69.4 Ma, whereas K-Ar whole-rock ages for phyllites in the Shimanto belt are 57.1 - 76.7 Ma; decrease in age is not observed even near MTL. Rb-Sr ages for muscovites from the schists are 70.4 and 72.5 Ma, which are assumed to indicate the time of metamorphism. The phyllites give a Rb-Sr whole-rock isochron age of 77.1±6.1 Ma, which is interpreted to represent the time of diagenesis or weak metamorphism. Fission-track ages for zircons from the Ryoke granitic rocks range from 37.0 to 68.2 Ma and decrease toward MTL. Fission-track ages of zircon are generally close to K-Ar ages of K-feldspar for the same rocks. From this fact the closure temperature for zircon is estimated to be lower than 200degC. The fine fractions (<2μm) separated from MTL fault gouges at Michaya and Takamiyama give K-Ar ages of 36.7 and 18.3 Ma, respectively. These ages probably represent the time of hydrothermal alteration following the major fault movement of MTL associated with cataclasis. (author)

  20. Insights into the structure and tectonic history of the southern South Island, New Zealand, from the 3-D distribution of P- and S-wave attenuation

    Science.gov (United States)

    Eberhart-Phillips, Donna; Reyners, Martin; Upton, Phaedra; Gubbins, David

    2018-05-01

    The Pacific-Australian plate boundary in the South Island of New Zealand is a transpressive boundary through continental lithosphere consisting of multiple terranes which were amalgamated during previous periods of subduction and plate reorganization. The style and locus of deformation within the present-day plate boundary is controlled by the mechanical behavior and distribution of these different lithospheric blocks. Geological studies are limited when it comes to illuminating lithospheric structure and rheology at depth. Imaging the 3-D seismic velocity and attenuation (1/Q), with distributed local earthquakes, helps unravel regional structure and variations in strength, fractures and fluids. We determine the 3-D distribution of Qp and Qs, which show much more variation than seismic velocity (Vp), underlining the utility of Q (1/attenuation). The Haast schist belt, previously shown as c. 25-km thick dry unit with moderate Vp and low Vp/Vs, is imaged with high Qs, and the highest Qs areas correlate with zones of higher grade schist. Below 25-km depth, the distribution of high Qp and Qs is markedly different from that of the overlying geological terranes. Both the strike and dip of the high Q regions indicate that they represent the subducted Hikurangi Plateau and its adjacent Cretaceous oceanic crust. The thickest part of the plateau, previously identified by Vp > 8.5 km/s from seismic tomography and P-wave precursors and associated with an eclogite layer at the base of the plateau, also has the highest Q. This confirms that the strong plateau extends southwestward as a narrow salient to the northern Fiordland subduction zone, where moderate-Q Eocene oceanic crust on the Australian plate is being subducted and bent to vertical. In the ductile crust, Q results suggest fluid saturation and elevated temperature conditions in the crustal root of the Southern Alps, and confirm that the shape of this crustal root is influenced by both the orientation and depth of the

  1. 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

  2. Chemistry of chromites from Arroio Grande Ophiolite (Dom Feliciano Belt, Brazil) and their possible connection with the Nama Group (Namibia)

    Science.gov (United States)

    Ramos, Rodrigo Chaves; Koester, Edinei; Porcher, Carla Cristine

    2017-12-01

    The present paper shows a mineral chemistry study in chromites found in serpentine-talc schists of the Arroio Grande Ophiolite, located in the southeastern Dom Feliciano Belt, near the Brazil/Uruguay border. Using electron microscope scanning and electron microprobe techniques, this study found a supra-subduction zone signature in the chromites, together with evidence of metasomatism. It corroborates previous hypothesis that suggested a supra-subduction zone origin for the protoliths of the Arroio Grande meta-igneous rocks and a metasomatic origin for the chromite-bearing magnesian schists. The studied chromites present high Cr# (0.65-0.77) and Fe2+# (0.88-0.95), low MgO (0.85-2.47 wt%) and TiO2 (0.01-0.19 wt%) and anomalous high concentration of ZnO (up to 1.97 wt%). The results were compared with chemical data from detrital chromites from the Schwarzrand and Fish River Subgroups of the Nama Group (Namibia), demonstrating that they are compositionally similar with those found in the latter. These chromites, in turn, are believed to have been derived from the oceanic Marmora Terrane (Gariep Belt) in the west (present-day coordinates). Taking into consideration that oceanic metamafites from both the latter and the Arroio Grande Ophiolite share common bulk-rock geochemical features (in this paper interpreted as fragments of the same paleo-ocean floor - the Marmora back-arc basin), it is possible to raise the hypothesis that detrital material derived from the studied ophiolite might also be found in Nama Group. It is reinforced by the fact that sediments (related to the Pelotas-Aiguá Batholith granitoids) derived from the easternmost Dom Feliciano Belt, i.e. the region where Arroio Grande Ophiolite is located, is found in both Schwarzrand and Fish River Subgroups. Thus, we suggest that Arroio Grande Ophiolite detrital sediments might also have contributed to the Nama Basin infilling during Late Ediacaran-Lower Cambrian.

  3. The early warning system of landslides and sediment runoffs using meteorological condition including rainfall-soil moisture index (Invited)

    Science.gov (United States)

    Kubota, T.; Silva, I. C.; Hasnawir, H.

    2009-12-01

    The research including observation of rain, soil moisture content and sediment discharge is conducted on a torrent in northern Kyushu whose geology consists of Paleozoic metamorphic rocks (mainly schist) and whose vegetation consists of mainly Japanese cypress and cedar. Soil depth is approximately 50cm in average and permeability k is 0.1~0.01 order. With data obtained by the observation for more than 4 years, standard rainfalls of warning and evacuation against the sudden sediment runoffs are analyzed. Then, the result was compared with the ones in Nuevo Leon Mexico (geology of schist, slate, k=0.01~0.001 order) and in southern Sulawesi Island Indonesia (volcanic geology, k=0.001~0.0001 order). Hitherto, various methods were proposed to analyze the warning critical standard for landslide disaster or large sediment discharge. In this study, we employed Hirano's element slope runoff theory, the Self Organized Criticality Assumption (SOC), and the Elementary Catastrophe Theory (ETC) to analyze the data, although the soil moisture fluctuation, meteorological condition such as upper air wind and dew point depression, the rainfall-soil moisture index provided by Japan Meteorological Agency was considered. The last one is a cutting edge technology based on the tank model calculation of soil moisture content combined with short term rainfall prediction which is a product of numerical simulation using radar image advection analysis compensated with surface rain data and with orographic rain effect. In Hirano's theory, we can describe the critical rain Rc and rain intensity Ric as following equation. Q/A/M/ cosθ = Ri ∫(r*cosθ)dt = Ri*R (1) ∴ Ric*Rc = C (2) Here, Q: sediment runoff or debris flow discharge, A: watershed area, M: function concerning with sediment deposit features on the upstream torrents or slopes (porosity, torrent bed slope gradient, sediment accumulation length and depth, cohesion), t: time, θ: torrent bed or hillside slope gradient, r: instant

  4. U-Pb ages of detrital zircon from Pegasus Group, Stewart Island

    International Nuclear Information System (INIS)

    Walker, N.; Tulloch, A.J.; Allibone, A.

    1998-01-01

    Stewart Island (New Zealand) is relatively unaffected by Cenozoic deformation related to the present-day plate boundary and has thus been a locale of investigations that focus on the relationship between Mesozoic continental margin magmatic rocks and the Western Province (WP) of NZ. Pegasus Group metasedimentary rocks represent the only candidate for WP equivalents on Stewart Island. We measured U-Pb and 207 Pb / 206 Pb ages of detrital zircons from the Pegasus Group in an effort to validate the correlation with the WP. On SI, Pegasus Group is exposed over a small area in the southern Tin Range where it forms amphibolite facies roof pendants and screens among plutons of mid Paleozoic to mid Cretaceous age. Mica schists predominate, with lesser amounts of psammite and metaquartzite and rare calcareous schist and amphibolite. Zircons were extracted from metaquarzite and 24 grains were chosen on the basis of morphology for geochronologic investigation. Sixteen single crystals were dated by U-Pb TIMS; 8 additional grains were studied by the total evaporation method described by Kober. Despite vigorous air abrasion prior to processing, the 16 grains measured by conventional U-Pb TIMS yielded slightly normally discordant ages that we interpret to reflect minor Pb-loss. The 8 grains studied by the total evaporation method yielded more than four analytically identical /sup 207 Pb / 206 Pb ages within each grain at progressively higher temperatures (1515-1580 degrees C) of evaporation. The results permit the following general conclusions: 1) the age range of 420-2700 Ma is grossly similar to that reported from the Greenland Group/Victoria Paragneiss (Ireland 1992) of the Buller Terrane, WP; 2) the zircon population is dominantly 530-680 Ma but a subsidiary population is 900-1100 Ma; 3) no zircons with ages that match the timing of the Ross Orogen (530-480 Ma) were identified; 4) two grains of 420 Ma and a 453 Ma are probably too young for the paleontogically

  5. 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 features, the mechanical degradation of the rocks overcomes their chemical decomposition. In the middle part of the river as result of almost abrupt passage between mountain and hilly terrains increases and concentration of radionuclides; effect of large quantities of clastic material deposited by torrents. The mechanical migration of resistant uranium, thorium and

  6. Mineral chemical and petrographic occurrences os iron of the south east of Uruguay (Nico Pere z terrane)

    International Nuclear Information System (INIS)

    Oyhantcabal, P.; Sanchez Bettucci, L.; Siegesmund, S.; Pineyro, D.

    2007-01-01

    Two iron-formation deposits from S E Uruguay were petrographic ally and mineralogically investigated (including microprobe mineral chemistry). The deposit from Piedra de Gigante (ANCAP) quarry is related to tectonic slivers of a platform succession in ortho gneiss of ca. 1750 Ma. Data of detrital zircon in this platform succession point to Meso- to Neo proterozoic age.The iron deposit of Piedra del Gigante (ANCAP) quarry belongs to a succession of mica schists, quartz-muscovite schists, marbles and basic rocks. Magnetite rich layers alternate with banded rocks rich in hematite, carbonate and amphibole. Carbonate is dolomite (Mg0.7Ca1.08Mn0.05Fe0.11(CO3)2) and the amphibole is a pale green tremolite (Na0,18Ca1,68Mn0,07Mg4,16Fe+++0,2Fe++0,55Al0,03(Si7,86Al0,13)O22(OH)2). This iron deposit shows strong deformation associated with martitization of magnetite and formation of specularite rich layers where relicts of magnetite (partly martitized) are occasionally observed. Available data are not conclusive about the genesis. The low iron-content of the amphibole together with dolomite in the mineral association cast doubts on a BIF-type origin, but low contents of Al2O3, V2O3, MnO and ZnO in magnetite do not indicate an igneous origin. High oxygen fugacity during martitization in medium-T metamorphic conditions could have determined that iron rich amphiboles were not formed as is normally expected in iron-formations. In the outcrop of Cerro la Higuerita (Grupo Arroyo del Soldado; Ediacaran) a succession of metapelites (bottom), iron rich pelites and iron formations (top) is observed. The metapelites contain evidences of volcanic contribution (phenochrysts of quartz and alkali feldspar as well as shards in the matrix) suggesting a volcanic source for the iron. This iron-formation contains magnetite pheno blasts (partly martitized) and fine disseminated laths of hematite in the matrix, together with grunerite (Na0,04Ca0,17 Mn0,02Mg1,36Fe5,35Al0,07(Si7,97Al0,03)O22(OH)2

  7. Studies on the recovery of uranium from low-grade ores in India

    International Nuclear Information System (INIS)

    Jayaram, K.M.V.; Dwivedy, K.K.; Deshpande, A.S.; Ramachar, T.M.

    1976-01-01

    Investigations were carried out to utilize the available para-marginal and low-grade ores - chlorite schists, amphibolites, carbonate ores, clays and quartzites - analysing between 0.027 and 0.08% U 3 O 8 . In addition, tests were undertaken on the technical and economic feasibility of recovering uranium as a byproduct from the copper flotation tailings and phosphorites. Heap and bacterial leaching tests were conducted on quartz-chlorite schists from the Singhbhum district, Bihar, analysing about 0.03% U 3 O 8 . Studies also showed that the ores harbour active Ferrobacillus ferrooxidans. Studies on 10-mesh samples of amphibolites from Inderwa, Bihar, (0.08% U 3 O 8 ) showed that only 32.8% recovery could be obtained by wet tabling and 85% by agitation leaching, while static leaching tests yielded 81% recovery in 24 hours of contact time. Similar tests on calcareous phyllites (0.05% U 3 O 8 ) with 30 kg/t Na 2 CO 3 and 8 kg/t NaHCO 3 yielded 86% uranium leachability at ambient temperature. Biogenic uraniferous clay from Udaisagar (0.029% U 3 O 8 ) yielded 43.3% uranium recovery using 1000 l/t of neutral water for 6 h. Percolation leaching tests were conducted with hard quartzites (0.06% U 3 O 8 ), and the results showed that 81% uranium could be recovered in 24 days. Although preliminary ore dressing studies on tailings obtained from the copper flotation (0.013% U 3 O 8 ) at Surda yielded a concentrate analysing 0.063% U 3 O 8 at 66% recovery, recent tests on the tailings from the copper concentrator indicated only 48% recovery at a grade of 0.112% owing to decrease in the feed grade. Studies on the utilization of large-capacity gravity machines and selective mining of uranium-rich copper lodes may render this source economic. Preliminary studies on a phosphorite sample containing 22.0% P 2 O 5 and 0.04% U 3 O 8 from the Mussorie area in Uttar Pradesh on calcination followed by scrubbing yielded a sand enriched in P 2 O 5 values (33.7% P 2 O 5 at 92.5% recovery) but

  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. 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.

  10. 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

  11. Contribution of the climatic transect approach application to the study of soil degradation in South of Spain.

    Science.gov (United States)

    Ruiz-Sinoga, José D.; Gabarrón-Galeote, Miguel A.; Cerdà, Artemi; Martínez-Murillo, Juan F.

    2014-05-01

    Since 1990s, the climatic transect approach has been widely applied to Mediterranean mountainous areas where climatic conditions are modified in few kilometres, from semiarid to humid conditions. The target in most of the cases was to evaluate the climatic change effect on the spatial variability of eco-geomorphological system, runoff and erosion and soil degradation processes, especially, in abandoned fields and Mediterranean rangeland. The Physical Geography and Land Management Research Group from the University of Málaga is applying this experimental approach since 2001. The study area corresponded to the Mediterranean Cordillera Bética in South of Spain, from the Strait of Gibraltar to Cabo de Gata, where a longitudinal climatic transect can be observed: from humid Mediterranean climate in the West (>1,500 mm/y) to nearly arid Mediterranean climate in the East (200 mm/y). More specifically, the investigations were focussed on the spatial and temporal variability of eco-geomorphological system (vegetation, soil and water relationship), runoff and erosion processes and controlling factors affecting to abandoned fields located in steep hillslopes of metamorphic and acid bedrocks (phyllites, schists and mica-schists) but differing in climatic conditions (humid, subhumid, dry and semiarid Mediterranean climate). The aim of this contribution is to share our findings and challenges from the last 13 years being some of the most important ones: i) Mediterranean summer drought homogenise the functioning of eco-geomorphological system independently of the geographical location along the climatic transect; ii) drought period affects more dramatically to humid and subhumid Mediterranean areas, especially, to the vegetation cover and pattern; iii) areas characterised by dry-Mediterranean climate are found as threshold areas and in risk of aridification due to Climate Change; iv) runoff and erosion processes can be similar in humid and semiarid abandoned lands as it has to

  12. Uranium exploration in albitised rocks of North Delhi Fold Belt in Rajasthan and Haryana, India

    International Nuclear Information System (INIS)

    Pandey, P.; Khandelwal, M.; Bhairam, C.; Parihar, P.

    2014-01-01

    Uranium deposits in Na-metasomatised granites and metasediments are reported from several places in the world. In India, uranium mineralization associated with soda metasomatic activity has been recognized at a number of places in North Delhi Fold Belt (NDFB) in Rajasthan and adjoining Haryana. Exploration activities for uranium in Khetri Sub Basin (KSB) of North Delhi Fold Belt (NDFB) in last six decades have resulted in locating number of uranium occurrences in the albitites and albitised metasediments at Sior, Siswali, Maonda, Hurra ki Dhani, Diara, Saladipura, Khandela, Rohil, Ghateshwar, Bichun, Sakhun, Ladera and Chota Udaipur in parts of Rajasthan and Dhancholi, Raghunathpura, Rambas and Gorir, in parts of Haryana. Incidentally, the occurrences fall along a NNE-SSW trending “Albitite line”, which comprises a 170 km long, structurally weak zone/lineament and axial trace of major folds in the KSB extending from Raghunathpura in Mahendragarh district of southern Haryana to Ladera-Sakun-Bichun in Rajasthan. Lithounits of KSB comprise lower Alwar Group consisting quartzite, amphibole quartzite, subordinate phyllite and schist and upper Ajabgarh Group consisting schist, phyllite, marble, quartzite and carbon phyllite. The post-Delhi magmatic activity in NDFB is represented by alkali granites, pegmatites, aplites and albitites. The rocks of Delhi supergroup have undergone low to medium grade metamorphism (amphibolite facies) and polyphase deformation. First two deformations with N-S to NNE-SSW axial plane are coaxial while the third phase have E-W axial plane. Prominent shear zones are developed along the N-S to NNE-SSW axial planes, characterized by intense silicification, brecciation and ferruginisation. The NE-SW trending disposition of albitised granites indicate that the metasomatic fluids originated during reactivation of the NE-SW trending Khetri lineament, caused pervasive albitisation of the preexisting rocks, the deformed lithounits providing conduits

  13. Late Cretaceous and Cenozoic exhumation history of the Malay Peninsula

    Science.gov (United States)

    François, Thomas; Daanen, Twan; Matenco, Liviu; Willingshofer, Ernst; van der Wal, Jorien

    2015-04-01

    The evolution of Peninsular Malaysia up to the collisional period in the Triassic is well described but the evolution since the collision between Indochina and the Sukhothai Arc in Triassic times is less well described in the literature. The processes affecting Peninsular Malaysia during the Jurassic up to current day times have to explain the emplacement multiple intrusions (the Stong Complex, and the Kemahang granite), the Jurassic/Cretaceous onland basins, the Cenozoic offshore basins, and the asymmetric extension, which caused the exhumation of Taku Schists dome. The orogenic period in Permo-Triassic times, which also formed the Bentong-Raub suture zone, resulted in thickening of the continental crust of current day Peninsular Malaysia due to the collision of the Indochina continental block and the Sukhothai Arc, and is related to the subduction of oceanic crust once present between these continental blocks. The Jurassic/Cretaceous is a period of extension, resulting in the onland Jurassic/Cretaceous basins, synchronous melting of the crust, resulting in the emplacement Stong Complex and the Kemahang granite and thinning of the continental crust on the scale of the Peninsular, followed by uplift of the Peninsular. Different models can explain these observations: continental root removal, oceanic slab detachment, or slab delamination. These models all describe the melting of the lower crust due to asthenospheric upwelling, resulting in uplift and subsequent extension either due to mantle convective movements or gravitational instabilities related to uplift. The Cenozoic period is dominated by extension and rapid exhumation in the area as documented by low temperature thermocrological ages The extension in this period is most likely related to the subduction, which resumed at 45 Ma, of the Australian plate beneath the Eurasian plate after it terminated in Cretaceous times due to the collision of an Australian microcontinental fragment with the Sunda margin in the

  14. 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 govern the halogen fluxes between the crust and the overlying mantle and/or the plate interface in subduction zones. Li and B are poorly stored in the oceanic crust (< 5 ppm). In subduction zones, prograde metamorphism of metagabbros is first marked by the crystallization of glaucophane at the expense of magmatic and amphibole coronas. This episode is accompanied with a decrease of halogen concentrations in amphiboles (< 200 ppm of F and Cl) suggesting that these elements can be transferred to the mantle wedge by fluids. In the Queyras Schistes Lustrés complex, the intense deformation and the abundant devolatilization of metasedimentary rocks produce large fluid flows that promote rock chemical hybridization (metasomatic mixing with hybrid composition between metasedimentary rock and metagabbro) at the metasedimentary rock

  15. Do diatoms percolate through soil and can they be used for tracing the origin of runoff?

    Science.gov (United States)

    De Graaf, Lenka; Cammeraat, Erik; Pfister, Laurent; Wetzel, Carlos; Klaus, Julian; Hissler, Christophe

    2015-04-01

    Tracers are widely used to study the movement of water in a catchment. Because of depletion of scientific possibilities with most common tracer types, we proposed the use of diatoms as a natural tracer. Paradoxical results on the contribution of surface runoff to the storm hydrograph were obtained in pioneer research on this idea. Diatom transport via the subsurface flow to the stream would explain this paradox. Prerequisite for this is vertical transport of diatoms through soils, which is the topic of this study. Emphasis is on percolation behavior (speed of percolation, speed of percolation over time, and species distribution) of Pseudostaurosira sp. and Melosira sp. (Bacillariophyceae) through undisturbed soil columns of contrasting substrates. Co-objective is to study the flowpaths of water through the soil columns. Natural undisturbed soil columns were sampled in the Attert basin (Luxembourg) on schist, marl and sandstone substrates. Rain simulation experiments were performed to study vertical diatom transport. Rhodamine dye experiments were carried out to gain insight in the active flowpaths of water, and breakthrough experiments were performed to study the responses of the soil columns to applied water. Diatoms were transported through the soil columns of the three substrates. A vast majority of diatom percolation took place within the first 15 minutes, percolation hereafter was marginal but nevertheless present. Peaks in diatom percolation corresponded with a high flux caused by the addition of the diatom culture, but seepage of diatoms along the sides is unlikely according to the species distribution and the rhodamine dye experiment. Pseudostaurosira sp. percolated significantly better than Melosira sp. Significantly more diatoms percolated through the marl columns compared to the schist columns and variance within the sandstone group was very high. Absolute differences between substrates however, were marginal. Most preferential flowpaths were observed in

  16. Brazil Geological Basic Survey Program - Lima Duarte - Sheet SF.23-X-C-VI - Minas Gerais State

    International Nuclear Information System (INIS)

    Pinto, C.P.

    1991-01-01

    The present report refers to the Lima Duarte sheet (SF.23-X-C-VI) systematic geological mapping, on the 1:100.000 scale. The surveyed area, localized in the Zona da Mata, Juiz de Fora micro-region, in South Minas Gerais, is dominantly composed by metamorphic rocks of the granulite and amphibolite facies and presents important diphtheritic process. An analysis of the Crustal Evolution Patterns based mostly on geological mapping, and gravimetric, air magneto metric and geochronologic data is given in the Chapter 6, Part II, of the text. Geophysical information is in the Chapter 5, Part II. Seventy two samples were analysed for oxides, trace-elements and REE, to provide litho environment and metallogenesis definition subsidies. Were studied 174 petrographic thin section, and 48 samples of quartzite and schist residual materials were analysed for heavy metals. Seven hundred and fifty outcrops were described. A geochemical survey, based on 81 pan concentrated samples and 277 stream sediments was carried out throughout the Sheet. The anomalies found in the stream sediments reflect the geochemical signature of the analysed elements for the litho types of the investigated terrains. (author)

  17. Ultramafic rocks of the western Idaho suture zone: Asbestos Peak and Misery Ridge

    Energy Technology Data Exchange (ETDEWEB)

    Godchaux, M.M. (Mount Holyoke Coll., South Hadley, MA (United States). Dept. of Geology); Bonnichsen, B. (Univ. of Idaho, Moscow, ID (United States))

    1993-04-01

    The Western Idaho Ultramafic Belt extends northward from the town of Weiser to the northern end of Dworshak Reservoir; in its northern portion most of the ultramafic bodies are localized along the suture zone where the Mesozoic oceanic accreted terranes meet the continental craton. Of the twenty bodies investigated, all are small, all are in fault contact with their metavolcanic and metasedimentary host rocks, all have been metamorphosed, and all display deformational fabrics in at least some portion of the outcrop area, suggesting that deformation continued after peak metamorphism. The degree of metamorphism ranges from incipient serpentinization to attainment of equilibrium in the upper amphibolite facies. Some bodies have been intruded by granitic dikes or pegmatite veins after emplacement, and have locally undergone contact metasomatism. Two particularly complex bodies, Asbestos Peak and Misery Ridge, were chosen for detailed petrographic and chemical study. Asbestos Peak is composed mostly of decussate anthophyllite-talc rock containing isolated patches of harzburgite protolith, and has blackwall border zones. Misery Ridge is composed mostly of coarse-grained sheared tremolite-talc schist without remnant protolith, and lacks true blackwall zones. Both bodies exhibit an unusual and enigmatic hornblende-poikiloblastic garnet-green spinel-skeletal ilmenite assemblage, present in some places as well-defined border zones and in other places as cross-cutting bodies.

  18. Bedrock Model of the Syyry area

    International Nuclear Information System (INIS)

    Saksa, P.; Kuivamaeki, A.; Kurimo, M.; Paananen, M.; Anttila, P.; Front, K.; Pitkaenen, P.; Hassinen, P.; Ylinen, A.

    1993-09-01

    Preliminary site investigations implemented in accordance with the research programme drawn up by Teollisuuden Voima Oy (TVO) were carried out at Syyry (in Finland) in 1987-1992. Models of the site were compiled and used for describing the rock types, fracturing, fracture structures and geohydrological conditions, the main emphasis being on the examination of the bedrock fracturing and related hydraulic conductivity. Three-dimensional models were used for the classification of the various properties of the bedrock structures. The descriptive models were gathered into a computer system to facilitate illustration and storage. The main rock type at Syyry is tonalite. A mica gneiss formation SE of the investigation site dips towards the NW and delimits the tonalite as far as the central part of the investigation site. The miga gneiss has a heterogeneous composition and includes intermediate layers consisting of quartz feldspar schist and amphibolite. There are mafic formations in the vicinity of the investigation site. The intrusive rocks have been deformed during three plastic and three mainly brittle deformation stages. (47 refs., 61 figs.)

  19. Measurements of hydraulic conductivity in deep bedrock at Palmottu, Outokumpu, Pori and Ylivieska

    International Nuclear Information System (INIS)

    Ahonen, L.

    1992-01-01

    Hydraulic conductivity of the bedrock was studied using a double packer equipment fitting the small-diameter drillholes (46 mm). Test method was a slug test, in which the pressure of the test section is reduced by removing water from a tube connected to the test section and, subsequently, monitoring the recovery of the original pressure. In the work, methods of interpretation suitable for the test method are examined, and compared by means of graphical simulations. Their relevance in the case of measurements in fractured crystalline bedrock are discussed. In the method of Hvorslev, the recovery rate is assumed to be directly proportional to residual drawdown and to the hydraulic conductivity of the test section and, consequently, the effect of specific storage is neglected. In other methods of interpretations (e.g. 'Cooper'- method), assuming radial flow from porous aquifer, specific storage is taken into consideration. Different methods of interpretation lead to dissimilar theoretical responses on recovery vs. time graphics. Skin-effect and outer boundary effects also have an influence on the shape of recovery curve. There is no major differences in K-values obtained by different methods of interpretation. The study sites represent different lithological environments, comprising migmatitic gneisses with granitic interlayers (Palmottu); a complex association of serpentine, black schist, quartzite, dolomite and scram (Outokumpu); arkosic sandstone (Pori); and mafic/ultramafic intrusion (Ylivieska)

  20. Alligator Rivers Analogue project. Geophysics, petrophysics and structure

    International Nuclear Information System (INIS)

    Emerson, D.W.; Mills, K.J.; Hallett, M.S.; Cao, L.Q.; Miyakawa, K.

    1992-01-01

    The geophysical and geological field work at Koongarra (including borehole core logging) showed that the site itself is a folded, faulted, variably fractured Precambrian psammitic and pelitic schist sequence with a quasi-horizontal weathered zone superimposed on the steeply dipping rock fabric. The site is flanked by a high resistivity younger sandstone unit to the northwest and by a magnetic amphibolite/ferricrete sequence to the far southeast. The data interpretations elicited the essential structural and broad lithological elements. Gravity, magnetic and electrical laboratory and field studies confirmed a broad folded fractured sequence of dipping layered host rocks weathered in their upper parts and trending in a southwest-northeast direction. Qualitatively interpreted anomalies indicated the trend of the main groundwater movement to the south where dolomites are thought to act as a sink. These drainage features have SP, resistivity and radiometric expression. The roles of the Kombolgie Sandstone as a source of water and the Koongarra Fault as a barrier or otherwise were not established owing to the lack of sufficient samples for testing and also on account of the difficulty of geophysical access over the site's rugged escarpment. 40 refs., 13 tabs., 69 figs

  1. 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.

  2. A kinetic study of cation release from a mixed mineral assemblage: implications for determination of uranium uptake

    International Nuclear Information System (INIS)

    Fenton, B.R.; Waite, T.D.

    1996-01-01

    The uptake of U(VI) as UO 2+ 2 on a natural complex mineral assemblage has been studied using batch selective chemical extraction techniques and secondary ion mass spectroscopy (SIMS). Sediments used in the study consisted of a quartz/mica schist collected from the locale of the Koongarra Uranium ore body, Alligator Rivers Uranium Province, Northern Territory, Australia. The bulk sediment was gravity separated into four size fractions, with attention focused on the nominally <25 μm and 250-1000 μm fractions of the bulk sample, in order to assess the effects of particle size on uranium uptake. Investigation of the kinetics of elemental release in the presence of selective extractants show that uranium is bound largely within the iron and aluminium oxyhydroxides of the assemblage, with a highly mobile fraction of this associated with aluminol sites. SIMS analysis of the natural substrate confirms that significant quantities of aluminium are present in surface layers. The effect of particle size on the uptake of uranium indicates very little change with respect to particle size. This finding may be attributed to the presence of highly porous surface coatings. (orig.)

  3. U-Pb SHRIMP and {sup 40}Ar/{sup 39}Ar constraints on the timing of mineralization in the Paleoproterozoic Caxias orogenic gold deposit, Sao Luis cratonic fragment, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Evandro Luiz, E-mail: evandro.klein@cprm.gov.br [Servico Geologico do Brasil (CPRM), Belem, PA (Brazil); Tassinari, Colombo Celso Gaeta, E-mail: ccgtassi@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Geociencias. Centro de Pesquisas Geocronologicas; Vasconcelos, Paulo Marcos, E-mail: paulo@earth.uq.edu.au [University of Queensland, School of Earth Sciences, Brisbane (Australia)

    2014-07-01

    Caxias is an orogenic gold deposit in the Sao Luis cratonic fragment, which is correlated with the Rhyacian terranes of the West-African Craton. The deposit postdates peak metamorphism (estimated at 2100 ± 15 Ma) and is hosted in a shear zone that cuts across schists of the Aurizona Group (2240 ± 5 Ma) and the Caxias Microtonalite. The emplacement age of the microtonalite, as determined in this work by SHRIMP U-Pb zircon dating, is 2009 ± 11 Ma and represents a latest age magmatic event in the Sao Luis cratonic fragment. Older zircon age of 2139 ± 10 Ma is interpreted as due to inheritance from the older granitoid or volcanic suites (magmatic sources?) or to contamination during emplacement. Lead isotope compositions indicate that the Pb incorporated in ore-related pyrite was probably sourced from regional, orogenic calc-alkaline granitoids of ca. 2160 Ma. Hydrothermal sericite from Caxias yielded a {sup 40}Ar/{sup 39}Ar plateau age of 1990 ± 30 Ma, which combined with the emplacement age of the Caxias Microtonalite brackets the age of gold mineralization between 2009 ± 11 and 1990 ± 30 Ma. (author)

  4. The U resources inventory at Tebalungkang sector, west Kalimantan systematic prospection stage

    International Nuclear Information System (INIS)

    Soetopo, B.; Suripto; Boman; Sajiyo

    1996-01-01

    The systematic prospection at Tebalungkang sector, West Kalimantan was carried out to characterize the occurrence of U mineralization and to invent the potential U resources at the area. The investigation was done on the basis of previous results, i.e. radiometric anomalous outcrops and boulders of 1000-7000 C/s. The methods for the investigation was systematic geological mapping and radiometric measurements of soil and tranced rocks and supported by mineralogical and geochemical analyses. The results of the investigation show that this area consists of metamorphic rocks, intruded by granite quartz-diorite batholites and dike of andesite and lamprophyre. From geological structure this is 30 o plunging from anticlin NE-SW and NNW-SSE, is crossed by NE-SW and E-W normal faults and NW-SE and WNW-ESE strike slip faults. Uranium mineralization appears in quartz-schist brecciated and quachitite (lamprophyre). The radioactive minerals were thorite and monazite, associated with rutile, ilmenite, magnetite, hematite, pyrite, calcopyrite, muscovite, apatite and allanite. The U content from rock samples has been found to be 4,5-54,75 ppm U

  5. Geologic evolution of Tucurui region - Para

    International Nuclear Information System (INIS)

    Silva Matta, M.A. da.

    1982-01-01

    The northern part of the Araguaia Belt is exposed in the Tucurui region and their stratigraphic, structural, metamorphic and magmatic features had been studied aiming at contributing for the understanding of the geological evolution of the area. Dating with R-Sr and K-At are also presented, allowing some association for the lythotype of Xingu complex and Araguaia Belt. The oldest stratigraphic unit of the area is represented by the Xingu Complex, composed by gneisses and granites and subordinated schists and anphibolites. Over this unit, during the niddle Proterozoic, the Tucurui group was developed. The bottom of this unit is composed by a sequence of tholeiitic basaltic flows which were here enclosed in the Caripe Formation. The Morrote Formation, is made up of graywackes, and constitutes the upper part of the Tucurui Group. The geossinolinal evolution of the Araguaia Belt took place during the Uruacuano Cycle. This geoteotonic unit is represented in the studied area by the Couto Magalhaes Formation (Tocantins Group) which comprises pelitic and psamitic metasediments. After the metamorphism of the Araguaia Belt, the Couto Magalhaes Formation acted as the place of mafic and ultramafic intrusion and, lately, the Tucurui Fault thrusted the metamorphic rocks of the Tocantins Group over the Tucurui Group lithetypes. (author)

  6. Contribution for geochronological evolution study of the Pianco-Alto Brigida fold belt system

    International Nuclear Information System (INIS)

    Brito Neves, B.B. de; Basei, M.A.S.; Van Schmus, W.R.

    1990-01-01

    The Proterozoic Painco-Alto Fold Belt is situated in the central portion of the Borborema Province and it probably is just a segment of a longer structural development encompassed between the Patos (N) and Pernambuco (S) lineaments. The geochronological study was carried out along a cross section in the central part of the belt (Paraiba State) where biotite-muscovite quartz schists are the predominating rock types, including intercalations of bi-modal volcanics, marbles and quartzites. These rocks were metamorphosed in the amphibolite facies, and they display a complex history of folding. Zircons of the acid volcanics (meta-rhyolytes where analysed through U/Pb method and they plot in a discordia diagram with superior intercept indicating ages around 1100 Ma. Whole rocks Rb/Sr analyses on the same meta-volcanics are indicating isochrons of 950Ma. These data are being respectively interpreted as ages of sedimentation (and volcanism) and regional metamorphism associated to the main (D sub(2)) phase of folding. One of the main purpose of this paper is to stress the importance of the ages around 950Ma, in the central domain of the Borborema Province, as result of regional folding and metamorphism. Some other occurence of ages in the 1000-900Ma range will be discussed as support for this interpretation from now on adopted. (author)

  7. Geologic feasibility of talc and serpentinite bodies from the Appalachian Mountain region of eastern United States with regard to siting of radioactive-waste repositories. Part I. Additional conclusions relating to ultramafic rocks. Part II. Field investigations of talc and serpentinite deposits. Supplementary report

    International Nuclear Information System (INIS)

    Wenner, D.B.

    1976-01-01

    Ultramafic rocks and serpentinites appear to have many favorable features that make them worthy of further consideration. Such rock types are widely distributed in this country and display wide variations in their physical properties, based largely on the degree of serpentinization and mineral content. For example, serpentinite has certain self-sealing and flowage characteristics that render it impermeable at depth, whereas unserpentinized ultramafic rocks are structurally very rigid and strong. Another favorable property of ultramafic rocks is the relatively low thermal expansion coefficient. Talc also has some favorable features and characteristics such as a high thermal stability and a low porosity and permeability. This present study has verified that very little ground water influx occurs in talcose rocks except in large fault zones. A major drawback for the usage of talc for containment of radioactive wastes is due to the relatively small sizes of most bodies. However, some of the large talc-carbonate units in the Missisquoi Valley Region of Vermont has potential. Consideration should also be given to other crystalline rocks as well, particularly schists, since they commonly contain micaceous materials which have similar properties to talc and serpentine. In considering various types of rocks for containment of radioactive wastes, the important properties are thermal conductivities, thermal expansion coefficients, thermal stabilities, and how high radiation fluxes affect these properties

  8. 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.

  9. Geochronological studies by Rb/Sr method in rocks of the Jundiai block and surroundings. [Ampario group

    Energy Technology Data Exchange (ETDEWEB)

    Wernick, E [Faculdade de Filosofia Ciencias e Letras de Rio Claro; Oliveira, M A.F. de; Kawashita, K; Cordani, U G [Sao Paulo Univ. (Brazil). Inst. de Geociencias; Delhal, J [Musee Royal de l' Afrique Centrale, Belgica

    1976-01-01

    Field and petrological data, as well as radiometric results performed in granulitic, gneissic, migmatitic, and granitic rocks from the 'Jundiai tectonic block' (States of Sao Paulo and Minas Gerais), show for that region the existence of two superposed orogeneses. To the older, of transamazonian age whole rock Rb-Sr isochron 2,010 m.y. Rb/sup 87//Sr/sup 86/ initial = 0.702), belongs the Amparo Group, composed of gneisses, migmatites, and granulites, with intercalation of quartzites, schists and calc-silicate rocks. To the younger, of brazilian age whole rock Rb-Sr isochron 690 m.y. (Sr/sup 87//Sr/sup 86/ initial = 0.702), are related the feldspathization and migmatization of the Amparo Group, as well as the intrusion of granitic bodies. Possibly, also the metasediments around Jacarei belong to the brazilian cycle. This pattern of geologic evolution is similar to that observed for the Serra dos Orgaos region (States of Rio de Janeiro and Minas Gerais).

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

    International Nuclear Information System (INIS)

    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

  11. Structural evolution of Halaban Area, Eastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Al-Amri, Yousef; Kassem1, Osama M. K.

    2017-04-01

    Neoproterozoic basement complex comprises a metamorphic/igneous suite (Abt schist and sheared granitoids) with syn-accretionary transpressive structures, unconformably overlain by a post-amalgamation volcanosedimentary sequence. This study aims to attempt to exposed post-accretionary thrusting and thrust-related structures at Halaban area, Eastern Arabian Shield. The Rf/ϕ and Fry methods are utilized on quartz and feldspar porphyroclasts, as well as on mafic crystals, such as hornblende and biotite, in eighteen samples. The X/Z axial ratios range from 1.12 to 4.99 for Rf/ϕ method and from 1.65 to 4.00 for Fry method. The direction of finite strain for the long axes displays clustering along the WNW trend (occasionally N) with slight plunging. Finite strain accumulated without any significant volume change contemporaneously with syn-accretionary transpressive structures. It indicates that the contacts between various lithological units in the Halaban area were formed under brittle to semi-ductile deformation conditions. The penetrative subhorizontal foliation was concurrent with thrusting and shows nearly the same attitudes of tectonic contacts with the overlying nappes. Keywords: Finite strain analysis, volcanosedimentary sequence, Halaban area, Eastern Arabian Shield, Saudi Arabia.

  12. Technology and function of grooved abraders in the early Neolithic of northwestern Europe

    Directory of Open Access Journals (Sweden)

    Caroline Hamon

    2016-10-01

    Full Text Available Found sporadically in late Palaeolithic and Mesolithic contexts, grooved abraders are among the most common tools found in Linear Pottery and Villeneuve-Saint-Germain settlements in north-western Europe (5,100-4,700 BCE. This paper presents an overview of the technical and functional characteristics of these tools in early Neolithic domestic contexts. Despite different blank morphologies and sizes, these tools tend to be relatively small in size and are generally not shaped. They are characterized by the use of a very specific raw material: low cohesive and generally ferruginous sandstones, chosen because their abrasiveness is enhanced through use. A classification of the different types of grooves is proposed, based on their shape, depth, section and localization. These characteristics are combined with use-wear analysis in order to propose a number of functional interpretations. Far from the widespread hypothesis that these tools functioned as shaft straighteners, we argue on the basis of the use-wear analysis and archaeological associations of items that these tools were primarily involved in the manufacture of bone and lithic tools, as well as of schist and limestone personal ornaments. They are evidence of the generalization and diversification of polishing and abrading techniques in the technical system of the first Neolithic populations. As such, they contribute to defining a whole new technical paradigm and are an essential element in any definition of the Neolithic.

  13. Geology and Geochemistry of some crystalline basement rocks in ilesha area, southwestern nigeria: implications on provenance and evolution

    International Nuclear Information System (INIS)

    Oyinloye, A.O.

    2007-01-01

    Geological and geochemical study of the basement complex rocks in ilesha schist belt revealed that amphibolite, hornblende gneiss and granite gneiss are the major constituents. The gneisses are composed of similar rock forming silicates with variations in abundance. The amphibolite being a mafic rock has different compositions, containing abundant pyroxene, actinolite and tremolite. Monazite is present in the mineralogy of all these rocks. Chemical composition of these rocks revealed that they are petrogenetically related. Geochemical diagrams, plotted from chemical composition of these rocks, REE fractionation trends and presence of monazite in their mineralogy reveal that all these rocks were derived from a mixed magma source which did not originate from a pure tipper mantle, but possibly from a back arc tectonic setting. The pattern of the REE, progressively increasing negative Eu/Eu anomaly, La/sub N//Yb/sub N/ from the amphibolite to the granite gneiss and marked Eu depletion tend to implicate evolution through fractionation of a mixed basaltic magma to form the precursor of these rocks. The amphibolite probably represents the sample of the original basaltic magma. (author)

  14. Gneiss Macuira: tectonic evolution of Paleozoic metamorphic rocks of the Alta Guajira, Colombia

    International Nuclear Information System (INIS)

    Lopez I; A Julian; Zuluaga C; A, Carlos

    2012-01-01

    The Macuira Gneiss is a Paleozoic metamorphic unit that outcrops in the Simarua, Jarara and Macuira ranges, Alta Guajira. It is composed by a lithologies metamorphosed under amphibolite facies P-T conditions and consist of amphibolitic and quartz feldspathic gneisses, amphibolites, schists, pegmatites, calc-silicated rocks and marbles, with migmatization evidences in gneisses and amphibolites. Five foliations (S1-5) and three folding events (F1-3) were identified and interpreted as product of two metamorphic events, developed in a progressive barrovian metamorphic gradient of intermediate pressure with intermediate P-T ratio, interpreted as product of continental collision tectonics. This unit is important in understanding of the tectonic evolution of the Alta Guajira and Caribbean because it records different deformational phases pre-, syn- and post-migmatitic, that could be related with different tectonic episodes: the first associated with the collision between Laurasia and Gondwana (Alleghanian Orogeny - Late Paleozoic), and the second related with the Caribbean Plate evolution (Andean Orogeny - Meso-Cenozoic).

  15. 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.

  16. The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)

    Science.gov (United States)

    Ahadnejad, Vahid; Hirt, Ann Marie; Valizadeh, Mohammad-Vali; Bokani, Saeed Jabbari

    2011-04-01

    The ammonium (NH4+) contents of the Malayer area (Western Iran) have been determined by using the colorimetric method on 26 samples from igneous and metamorphic rocks. This is the first analysis of the ammonium contents of Iranian metamorphic and igneous rocks. The average ammonium content of metamorphic rocks decreases from low-grade to high-grade metamorphic rocks (in ppm): slate 580, phyllite 515, andalusite schist 242. In the case of igneous rocks, it decreases from felsic to mafic igneous types (in ppm): granites 39, monzonite 20, diorite 17, gabbro 10. Altered granitic rocks show enrichment in NH4+ (mean 61 ppm). The high concentration of ammonium in Malayer granites may indicate metasedimentary rocks as protoliths rather than meta-igneous rocks. These granitic rocks (S-types) have high K-bearing rock-forming minerals such as biotite, muscovite and K-feldspar which their potassium could substitute with ammonium. In addition, the high ammonium content of metasediments is probably due to inheritance of nitrogen from organic matter in the original sediments. The hydrothermally altered samples of granitic rocks show highly enrichment of ammonium suggesting external sources which intruded additional content by either interaction with metasedimentary country rocks or meteoritic solutions.

  17. Influence of microwaves on the leaching kinetics of uraninite from a low grade ore in dilute sulfuric acid

    International Nuclear Information System (INIS)

    Madakkaruppan, V.; Pius, Anitha; Sreenivas, T.; Giri, Nitai; Sarbajna, Chanchal

    2016-01-01

    Highlights: • U leaching from a low-grade Si-rich ore studied in H_2SO_4 medium with (MW) irradiation. • MW heating is more efficient in terms of U recovery, kinetics and purity of liquor. • U leachability of 84% obtained in 90 min at 95 °C with 0.38 M H_2SO_4 at 450 mVwith MW heating • Conventional conductive heating gave about 74% leachability with less purity liquor. • U leaching was found follow product layer diffusion as controlling mechanism. - Abstract: This paper describes a study on microwave assisted leaching of uranium from a low-grade ore of Indian origin. The host rock for uranium mineralization is chlorite-biotite-muscovite-quartzo-feldspathic schist. The dominant presence of siliceous minerals determined leaching of uranium values in sulfuric acid medium under oxidizing conditions. Process parametric studies like the effect of sulfuric acid concentration (0.12–0.50 M), redox potential (400–500 mV), particle size (600–300 μm) and temperature (35°–95 °C) indicated that microwave assisted leaching is more efficient in terms of overall uranium dissolution, kinetics and provide relatively less impurities (Si, Al, Mg and Fe) in the leach liquor compared to conventional conductive leaching. The kinetics of leaching followed shrinking core model with product layer diffusion as controlling mechanism.

  18. Influence of microwaves on the leaching kinetics of uraninite from a low grade ore in dilute sulfuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Madakkaruppan, V. [Atomic Minerals Directorate for Exploration and Research, Begumpet, Hyderabad 500016 (India); Pius, Anitha, E-mail: dranithapius@gmail.com [Department of Chemistry, Gandhigram Rural Institute, Gandhigram, Dindigul District, Tamil Nadu 624302 (India); Sreenivas, T.; Giri, Nitai [Mineral Processing Division, Bhabha Atomic Research Center, AMD Complex, Begumpet, Hyderabad 500016 (India); Sarbajna, Chanchal [Atomic Minerals Directorate for Exploration and Research, Begumpet, Hyderabad 500016 (India)

    2016-08-05

    Highlights: • U leaching from a low-grade Si-rich ore studied in H{sub 2}SO{sub 4} medium with (MW) irradiation. • MW heating is more efficient in terms of U recovery, kinetics and purity of liquor. • U leachability of 84% obtained in 90 min at 95 °C with 0.38 M H{sub 2}SO{sub 4} at 450 mVwith MW heating • Conventional conductive heating gave about 74% leachability with less purity liquor. • U leaching was found follow product layer diffusion as controlling mechanism. - Abstract: This paper describes a study on microwave assisted leaching of uranium from a low-grade ore of Indian origin. The host rock for uranium mineralization is chlorite-biotite-muscovite-quartzo-feldspathic schist. The dominant presence of siliceous minerals determined leaching of uranium values in sulfuric acid medium under oxidizing conditions. Process parametric studies like the effect of sulfuric acid concentration (0.12–0.50 M), redox potential (400–500 mV), particle size (600–300 μm) and temperature (35°–95 °C) indicated that microwave assisted leaching is more efficient in terms of overall uranium dissolution, kinetics and provide relatively less impurities (Si, Al, Mg and Fe) in the leach liquor compared to conventional conductive leaching. The kinetics of leaching followed shrinking core model with product layer diffusion as controlling mechanism.

  19. Tectonic implications of the contrasting geochemistry of Damaran mafic volcanic rocks, South West Africa

    International Nuclear Information System (INIS)

    Miller, R.McG.

    1983-01-01

    Ortho-amphibolites occur in the southern and central parts of the north-east-trending branch of the Damara Orogen. The Matchless Member amphibolites are interbedded with quartzose mica schist. Mobility of Si, ΣFe, Mn, Mg, Ca, Na, K, P, CO 2 , H 2 O, Rb, Ba, Sr and possibly LREE and immobility of Co, V, Sc, Ga, Zr, Nb, Y and HREE are indicated during metamorphism and reaction with country rock. Central Zone amphibolites are alkaline. The stratigraphically lower amphibolites have a within-plate chemistry; their distribution and associated rock types indicate a continental origin. The Matchless amphibolites have an ocean-floor chemistry. The Damaran sedimentary and orogenic cycle was initiated by continental rifting in three parallel zones in which alkaline acid volcanics occur locally. Widespread subsidence of the rift zones and the intervening areas followed and led to deposition of carbonate and clastic rocks under shallow marine conditions. During renewed rifting, submarine, alkaline basic lavas were extruded. The Southern Margin Zone amphibolites are interbedded with continental slope mixtites and continental rise deep-water fans. Spreading led to continental breakup and the formation of oceanic crust

  20. Sedimentary uranium deposits in France and French Union

    International Nuclear Information System (INIS)

    Kervella, F.

    1958-01-01

    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) [fr

  1. The Statherian itabirite-bearing sequence from the Morro Escuro Ridge, Santa Maria de Itabira, Minas Gerais, Brazil

    Science.gov (United States)

    Silveira Braga, Flávia Cristina; Rosière, Carlos Alberto; Queiroga, Gláucia Nascimento; Rolim, Vassily Khoury; Santos, João Orestes Schneider; McNaughton, Neal Jesse

    2015-03-01

    The itabirite-bearing metasedimentary sequence from Morro Escuro Ridge comprises the basal units of the Espinhaço Supergroup and makes up a small tectonic inlier developed during one of the Brasiliano orogenic events (800-500 Ma), amongst horses of the Archean TTG gneisses, including sheared granites of the anorogenic Borrachudos Suite (˜1700 Ma). The metasedimentary rocks are comprised of low-to intermediate-amphibolite facies schists, quartzites, conglomerates and banded iron formation (itabirite) correlatable with the sequences of the Serro Group, which underlies the metasedimentary rocks of the Espinhaço Supergroup in the Serra da Serpentina Ridge. A maximum Statherian deposition age (1668 Ma) was established using SHRIMP U-Pb isotopic constraints on zircon grains from conglomerate and quartzite units overlying the itabirite. The itabirite is predominantly hematitic and its geochemical characteristics are typical of a Lake Superior-type BIF deposited in a platformal, suboxic to anoxic environment distant from Fe-bearing hydrothermal vents. Close to the contact zone with amphibolites of the Early Neoproterozoic Pedro Lessa mafic suite, an increase of the magnetite content and crystallization of metasomatic Mg-hornblende and Ce-allanite can be observed. These mineralogical changes developed preferentially along the igneous contact zone but are probably co-genetic with the formation of alteration haloes in zircon grains during the Neoproterozoic Brasiliano orogeny (506 ± 6 Ma).

  2. Studies on the radiation absorption characteristics of various rocks

    International Nuclear Information System (INIS)

    Rahman, K.N.; Abdullah, S.A.; Gazzaz, M.A.

    1984-05-01

    Radiation absorption characteristics of nine different rocks, namely, ferrugenous quartz, metabasalt, larvikite, coarse grained diorite, coarse grained granite, coarse grained alkali granite, marble, quartz mica schist, and metamorphosed rock are studied. The rocks were collected from Jeddah, Makkah, Mina and Taif areas. Special attention was given on the availability, compactness, physical formation and uniform composition in selecting the rocks. The rocks were identified by optical method and their elemental composition determined by chemical analysis. The data were used to calculate the effective atomic numbers, half value layers mass and linear attenuation coefficients. The half value layers and the linear attenuation coefficientsof these rocks were determined experimentally using Am-241, Cs-137,and Co-60 sources. The results are compared with those obtained by theoretical calculations and agrre within 10%. Most of the rocks show much higher radiation attenuation characteristics than the standard concrete. Rocks containing higher percentage of Fe, Ca, Ti, and Mn show much higher radiation absorption characteristics than concrete. Only granites are found to be almost equivalent to concrete. 12 Ref

  3. Pitchblende deposits at the Wood and Calhoun mines, Central City mining district, Gilpin County, Colorado

    Science.gov (United States)

    Moore, Frank R.; Butler, C.R.

    1952-01-01

    Pitchblende has been mined in commercial quantities from four gold- and silver-bearing pyrite-sphalerite-galena veins that occur in an area about one-half mile square on the south side of Quartz Hill, Central City district, Gilpin County, Colo. These veins are the Kirk, the German-Belcher, the Wood, and the Calhoun. Two of these veins, the Wood and the Calhoun, were studied in an attempt to determine the geologic factors favorable for pitchblende deposition. All accessible workings at the Wood and East Calhoun mines were mapped by tape and compass, and the distribution of radioactivity was studied in the field. Channel and chip samples were taken for chemical assay to compare radioactivity with uranium content. The pitchblende-bearing veins cat both pre-Cambrian granite gneiss and quartz-biotite schist; however, the gneiss was the more favorable host rock. Two bostonite porphyry dikes of Tertiary(?) age were crosscut by the Wood and Calhoun veins. The pitchblende occurs in lenses erratically distributed along the veins and in stringers extending outward from the veins. In the lenses it forms hard'. masses, but elsewhere it is Soft and powdery. The pitchblende is contemporaneous with the pyrite bat earlier than the sphalerite and galena in the same vein. All the observed pitchblende was at depths of less than 400 ft. The veins probably cannot be mined profitably for the pitchblende alone under present conditions.

  4. Araxa Group in the type-area: A fragment of Neoproterozoic oceanic crust in the Brasilia Fold Belt

    International Nuclear Information System (INIS)

    Seer, Hildor Jose; Brod, Jose Affonso; Fuck, Reinhardt Adolfo; Pimentel, Marcio Martins; Boaventura, Geraldo Resende; Dardenne, Marcel Auguste

    2001-01-01

    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 ε 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 ε 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)

  5. Sonication assisted dissolution of post-detonation nuclear debris using ammonium bifluoride

    Energy Technology Data Exchange (ETDEWEB)

    Mason, Christian A.; Brockman, John D. [Missouri Univ., Columbia, MO (United States). Research Reactor Center; Hubley, Nicholas T.; Wegge, Dana L. [Missouri Univ., Columbia, MO (United States). Dept. of Chemistry; Robertson, J. David [Missouri Univ., Columbia, MO (United States). Research Reactor Center; Missouri Univ., Columbia, MO (United States). Dept. of Chemistry

    2017-07-01

    There is significant interest in reducing the timeline for post detonation nuclear debris examination. A critical need is rapid dissolution of refractory nuclear debris to facilitate measurement of key radioisotopes and isotope ratios. Field deployable, rapid dissolution and analysis methods could significantly shorten the attribution analysis timeline. The current practice uses HF in combination with other acids to attack silicates and other refractory minerals expected in debris samples. However, techniques requiring HF are not amenable to use in the field. The fluorinating agent ammonium bifluoride (ABF) is a potential field deployable substitute for HF. In this work we report on the use of in-direct sonication with ABF as a means to improve low-temperature acid digestion of seven USGS and NIST geological reference materials. Using this method, elemental recoveries for USGS reference materials DNC-1a Dolerite, QLO-1a Quartz Latite, SDC-1 Mica Schist, and BHVO-2 Hawaiian Basalt were quantitative while the recovery of elements in USGS AGV-2 Andesite and NIST SRM 278 Obsidian and 1413 High Alumina Sand were low.

  6. Palaeoclimate significance of speleothems in crystalline rocks: a test case from the Late Glacial and early Holocene (Vinschgau, northern Italy)

    Science.gov (United States)

    Koltai, Gabriella; Cheng, Hai; Spötl, Christoph

    2018-03-01

    Partly coeval flowstones formed in fractured gneiss and schist were studied to test the palaeoclimate significance of this new type of speleothem archive on a decadal-to-millennial timescale. The samples encompass a few hundred to a few thousand years of the Late Glacial and the early Holocene. The speleothem fabric is primarily comprised of columnar fascicular optic calcite and acicular aragonite, both indicative of elevated Mg / Ca ratios in the groundwater. Stable isotopes suggest that aragonite is more prone to disequilibrium isotope fractionation driven by evaporation and prior calcite/aragonite precipitation than calcite. Changes in mineralogy are therefore attributed to these two internal fracture processes rather than to palaeoclimate. Flowstones formed in the same fracture show similar δ18O changes on centennial scales, which broadly correspond to regional lacustrine δ18O records, suggesting that such speleothems may provide an opportunity to investigate past climate conditions in non-karstic areas. The shortness of overlapping periods in flowstone growth and the complexity of in-aquifer processes, however, render the establishment of a robust stacked δ18O record challenging.

  7. Petrology and geochemistry of REE-rich Mafé banded iron formations (Bafia group, Cameroon)

    Science.gov (United States)

    Nkoumbou, Charles; Gentry, Fuh Calistus; Tchakounte Numbem, Jacqueline; Belle Ekwe Lobé, Yolande Vanessa; Nwagoum Keyamfé, Christin Steve

    2017-07-01

    Archaean-Paleoproterozoic foliated amphibole-gneisses and migmatites interstratified with amphibolites, pyroxeno-amphibolites and REE-rich banded-iron formations outcrop at Mafé, Ndikinimeki area. The foliation is nearly vertical due to tight folds. Flat-lying quartz-rich mica schists and quartzites, likely of Pan-African age, partly cover the formations. Among the Mafé BIFs, the oxide BIF facies shows white layers of quartz and black layers of magnetite and accessory hematite, whereas the silicate BIF facies is made up of thin discontinuous quartz layers alternating with larger garnet (almandine-spessartine) + chamosite + ilmenite ± Fe-talc layers. REE-rich oxide BIFs compositions are close to the East Pacific Rise (EPR) hydrothermal deposit; silicate BIFs plot midway between EPR and the associated amphibolite, accounting for a contamination by volcanic materials, in addition to the hydrothermal influence during their oceanic deposition. The association of an oceanic setting with alkaline and tholeiitic magmatism is typical of the Algoma-type BIF deposit. The REE-rich BIFs indices recorded at Mafé are interpreted as resulting from an Archaean-Paleoproterozoic mineralization.

  8. Geochemical provenance of anomalous metal concentrations in stream sediments in the Ashton 1:250,000 quadrangle, Idaho/Montana/Wyoming

    International Nuclear Information System (INIS)

    Shannon, S.S. Jr.

    1982-01-01

    Stream-sediment samples from 1500 sites in the Ashton, Idaho/Montana/Wyoming 1:250,000 quadrangle were analyzed for 45 elements. Almost all samples containing anomalous concentrations (exceeding one standard deviation above the mean value of any element) were derived from drainage basins underlain by Quaternary rhyolite, Tertiary andesite or Precambrian gneiss and schist. Aluminum, barium, calcium, cobalt, iron, nickel, magnesium, scandium, sodium, strontium, and vanadium have no andesite provenance. Most anomalous manganese, europium, hafnium, and zirconium values were derived from Precambrian rocks. All other anomalous elemental concentrations are related to Quaternary rhyolite. This study demonstrates that multielemental stream-sediment analyses can be used to infer the provenance of stream sediments. Such data are available for many parts of the country as a result of the National Uranium Resource Evaluation. This study suggests that stream-sediment samples collected in the Rocky Mountains can be used either as pathfinders or as direct indicators to select targets for mineral exploration for a host of metals

  9. The Suitable Geological Formations for Spent Fuel Disposal in Romania

    International Nuclear Information System (INIS)

    Marunteanu, C.; Ionita, G.; Durdun, I.

    2007-01-01

    Using the experience in the field of advanced countries and formerly Romanian program data, ANDRAD, the agency responsible for the disposal of radioactive wastes, started the program for spent fuel disposal in deep geological formations with a documentary analysis at the national scale. The potential geological formations properly characterized elsewhere in the world: salt, clay, volcanic tuff, granite and crystalline rocks,. are all present in Romania. Using general or specific selection criteria, we presently consider the following two areas for candidate geological formations: 1. Clay formations in two areas in the western part of Romania: (1) The Pannonian basin Socodor - Zarand, where the clay formation is 3000 m thick, with many bentonitic strata and undisturbed structure, and (2) The Eocene Red Clay on the Somes River, extending 1200 m below the surface. They both need a large investigation program in order to establish and select the required homogeneous, dry and undisturbed zones at a suitable depth. 2. Old platform green schist formations, low metamorphosed, quartz and feldspar rich rocks, in the Central Dobrogea structural unit, not far from Cernavoda NPP (30 km average distance), 3000 m thick and including many homogeneous, fine granular, undisturbed, up to 300 m thick layers. (authors)

  10. Evaluation of uranium anomalies in the McCaslin Syncline, northeastern Wisconsin

    International Nuclear Information System (INIS)

    Blackburn, W.H.; Mathews, G.W.

    1982-01-01

    On the basis of this investigation, the McCaslin area does not demonstrate sufficient recognition criteria to be considered favorable for the occurrence of uranium deposits that are analogous to quartz-pebble conglomerate deposits or unconformity-related deposits. Neither model is applicable because: (1) More often than not the conglomeratic lenses of the McCaslin Quartzite are polymictic. (2) Pyrite and chlorite are essentially lacking; (3) Pervasive chloritic and hematitic alteration are not present in the McCaslin district; (4) The maximum estimated age of the McCaslin is 1.9 b.y.; (5) The notable absence of anomalous uranium values in the basal McCaslin Quartzite, and especially where known faulting intersects the McCaslin, suggests that a process for concentrating uranium has not been effective in the area; (6) The Waupee Volcanics are not known to contain any extensive graphitic or chloritic schists, nor do they have more than normal amounts of uranium; (7) Uranium anomalies in stream-water, stream-sediment, and aerial surveys may be explained by uranium derived from the relatively uraniferous Hager Rhyolite, or other granitic intrusives related to the Wolf River batholith. The McCaslin area warrants no further investigation; it will not contribute any significant new potential the the NURE resource base. 3 figures, 3 tables

  11. 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.

  12. Modelling the productivity of Anatolian black pine plantations in Turkey

    Directory of Open Access Journals (Sweden)

    Şükrü Teoman Güner

    2016-01-01

    Full Text Available This study was carried out to determine the relationships between height growth (site index of Anatolian black pine (Pinus nigra Arnold. subsp. pallasina (Lamb. Holmboe and site factors of the plantation areas in Turkey. Data were collected from 118 sample plots by taking into consideration the variations of aspect, altitude, slope position, slope degree and site class. A representative tree for the productivity and soil samples were taken at each sample plot. Some chemical and physical properties of soil samples were determined in the laboratory. The relationships between site index values of the trees and site factors including parent material, soil, climate and topography were examined by using correlation, stepwise regression and regression tree analysis. Significant linear relations were found between site index of black pine and site factors being altitude, slope degree, slope position, annual rainfall, precipitation amount in the most drought month, solum depth and bedrock including granite, mica schist and dacite. Explanation variance percentage on the site index of black pine was found 54.4% by using regression tree analysis whereas explained variance become 34.7% by stepwise regression analysis.

  13. Biogeochemical control points in a water-limited critical zone

    Science.gov (United States)

    Chorover, J.; Brooks, P. D.; Gallery, R. E.; McIntosh, J. C.; Olshansky, Y.; Rasmussen, C.

    2017-12-01

    The routing of water and carbon through complex terrain is postulated to control structure evolution in the sub-humid critical zone of the southwestern US. By combining measurements of land-atmosphere exchange, ecohydrologic partitioning, and subsurface biogeochemistry, we seek to quantify how a heterogeneous (in time and space) distribution of "reactants" impacts both short-term (sub-)catchment response (e.g., pore and surface water chemical dynamics) and long-term landscape evolution (e.g., soil geochemistry/morphology and regolith weathering depth) in watersheds underlain by rhyolite and schist. Instrumented pedons in convergent, planar, and divergent landscape positions show distinct depth-dependent responses to precipitation events. Wetting front propagation, dissolved carbon flux and associated biogeochemical responses (e.g., pulses of CO2 production, O2 depletion, solute release) vary with topography, revealing the influence of lateral subsidies of water and carbon. The impacts of these episodes on the evolution of porous media heterogeneity is being investigated by statistical analysis of pore water chemistry, chemical/spectroscopic studies of solid phase organo-mineral products, sensor-derived water characteristic curves, and quantification of co-located microbial community activity/composition. Our results highlight the interacting effects of critical zone structure and convergent hydrologic flows in the evolution of biogeochemical control points.

  14. Geochemistry and genesis of the Pegmatite Limoeiro (Virgem da Lapa-MG-Brazil)

    International Nuclear Information System (INIS)

    Neves, J.M.C.; Soares, A.C.P.; Valle, R.R.

    1980-01-01

    The structure, mineralogy, geochemistry, and geological setting of the Pegmatite Limoeiro (Virgem da Lapa - MG) are presented. The country rock of this pegmatite is the Precambrian Macaubas quartz - biotite schist. The pegmatites of this region seem to be genetically related to the Coronel Murta granitoids which in the Streckeisen's diagram are scattered between granite and granodiorite. The structure of the Pegmatite Limoeiro is well displayed throught the quarring work and the following zones have been mapped: border zone, wall zone, intermediate zone, quartz core and the replacement bodies. A sample of twenty K,Na-feldspars specimens, collected according to the structure of the pegmatite, have been analysed for major elements and for Rb, Sr and Zr, using X-ray fluorescence spectrometry. Sequences of perthites from different zones, sampled all over the pegmatite, showed enrichment of Rb from the wall zone inward. This pattern supports the assumption that the studied pegmatite from Limoeiro crystallized in a restricted system from the contacts inward. The regional variation pattern of the ratios K/Rb and Rb/Ba seems to have metallogenetic implications as in other world pegmatite provinces. (Athor) [pt

  15. Petrology of the Fort Smith - Great Slave Lake radiometric high near Pilot Lake, N.W.T

    International Nuclear Information System (INIS)

    Burwash, R.A.; Cape, D.F.

    1981-01-01

    Near Pilot Lake, the east boundary of the Fort Smith - Great Slave Lake radiometric high coincides with the contact of a well-foliated, porphyroblastic microcline-plagioclase-quartz-garnet-biotite gneiss (Pilot Lake Gneiss) with a hybrid assemblage of quartzite, mica schist, garnet-cordierite gneiss, and minor amphibolite (Variable Paragneiss). Anomalously high concentrations of uranium and thorium are associated with mafic-rich, lenticular bodies with a mineral assemblage biotite + monazite + zircon + ilmenite + hematite +- plagioclase +- quartz, within both the Variable Paragneiss and the Pilot Lake Gneiss. Corundum and spinel occur in the mafic lenses and sillimanite, kyanite, and hypersthene in other inclusions of the Pilot Lake Gneiss. The ilmenite-magnetite--monazite-zircon-apatite assemblage is interpreted as a 'black sand' concentration in a clastic sedimentary sequence subsequently metamorphosed by a regional granulite facies event. A granite pluton intruded during the same orogenic cycle assimilated the clastic metasedimentary rocks containing black sand interlayers, becoming enriched in thorium from the monazite. A second metamorphic event at lower P-T conditions, accompanied by strong cataclasis, developed the texture of the Pilot Lake Gneiss as now observed. Shearing within the gneiss locally concentrated hematite + quartz + uranium. Regional tectonic extrapolations suggest that the pyroxene granulite event was Kenoran and the later amphibolite event Hudsonian. (author)

  16. Stable Isotopes (O, H, and S) in the Muteh Gold Deposit, Golpaygan Area, Iran

    International Nuclear Information System (INIS)

    Abdollahi, M. J.; Karimpour, M. H.; Kheradmand, A.; Zarasvandi, A. R.

    2009-01-01

    The Muteh gold district with nine gold deposits is located in the Sanandaj-Sirjan metamorphic zone. Gold mineralization occurs in a pre-Permian complex which mainly consists of green schists, meta-volcanics, and gneiss rocks. Shear zones are the host of gold mineralization. Gold paragenesis minerals include pyrite, chalcopyrite, pyrrhotite, and secondary minerals. Pyrites occur as pre-, syn-, and post-metamorphism minerals. To determine the source of the ore-bearing fluids, fifty samples were selected for petrographical and stable isotope studies. The mean values of 12.4 per mille , and -42 per mille for δ 18 O and δD isotopes, respectively, and a mean value of 7.75 per mille of calculated fractionation factors for δ 18 O H 2 O, from quartz veins indicate that metamorphic host rocks are the most important source for the fluids and gold mineralization. Three generations of pyrite can be distinguished showing a wide range of δ 34 S. Gold mineralization is closely associated with intense hydrothermal alteration along the ductile shear zones. The characteristics of the gold mineralization in the study area are similar to those of orogenic gold deposits elsewhere

  17. Ams Fabric and Deformation of The Jawornik Granitoids In The Zloty Stok - Skrzynka Deformation Zone (sudetes, SW Poland)- Preliminary Interpretations.

    Science.gov (United States)

    Werner, T.; Bialek, D.

    Jawornik granitoids comprise the NE-SW trending sequences of the 1cm up to 1 km thick granitoid veins surrounded by schists and gneisses of the Zloty Stok - Skrzynka deformation zone in Eastern Sudetes (SW Poland). According to conflicting theories granitoids are of magmatic origin or were formed from blastomylonitic rocks that underwent multiphase deformation. AMS studies were performed for the 53 sites lo- calized within granitoid veins and within the surrounding gneisses. AMS foliations for granitoid veins of various thickness as well as for gneisses dip at moderate to steep an- gles to N-NW. AMS lineations in the surrounding gneisses plunge subhorizontally to NE-SW that reflects the regional NE-SW shearing components. Magnetic lineations for sites within wider veins of granitoids plunge at low angles (mostly from S to W) but with more varying trends between sites. Mezoscopic tectonic foliations are record- able only in 50% of sites. They show good correlation with AMS planar fabric on the site scale. The uniformity of AMS fabric on the site scale and high AMS anisotropy within all sites (P of 1.05-1.30, T of 0.3-0.6 on average) suggest syntectonic gener- ation of granitoids. Further interpretations of the AMS and tectonic fabrics will be performed when microtectonic studies and chemical analyses results are available.

  18. Water level fluctuations due to earth tides in a well pumping from slightly fractured crystalline rock

    International Nuclear Information System (INIS)

    Marine, I.W.

    1975-01-01

    J At the Savannah River plant of the Atomic Energy Commission near Aiken, South Carolina, there are three distinct groundwater systems: the coastal plain sediments, the crystalline metamorphic rocks, and a buried Triassic basin. The coastal plain sediments include several Cretaceous and Tertiary granular aquifers and aquicludes, the total thickness being about 305 m. Below these sediments, water occurs in small fractures in crystalline metamorphic rock (hornblende schist and gneiss with lesser amounts of quartzite). Water level fluctuations due to earth tides are recorded in the crystalline metamorphic rock system and in the coastal plain sediments. No water level fluctuations due to earth tides have been observed in wells in the Triassic rock because of the very low permeability. The water level fluctuations due to earth tides in the crystalline rock are about 10 cm, and those in the sediments are about 1.8 cm. The use of water level fluctuations due to earth tides to calculate porosity appears to present practical difficulties both in the crystalline metamorphic rock system and in the coastal plain sediments. In a 1-yr pumping test on a well in the crystalline metamorphic rock the flow was controlled to within 0.1 percent of the total discharge, which was 0.94 1/s. The water level fluctuations due to earth tides in the pumping well were 10 cm, the same as when this well was not being pumped. (U.S.)

  19. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Vietnam

    International Nuclear Information System (INIS)

    1977-11-01

    The Chaine Annamatique represents the last of the three orogenic episodes that shook Indochina and forms most of Vietnam's boundary with Laos, In south Vietnam the mountains which have a north-south trend are formed of granites, gneisses and mica schists and are inseparable from the anti-hercynian formations. Iron ore, gold, lead, copper, tin, wolfraun, bismuth and molybdenium minerals are found. Plans had been made in 1960 to prospect for uranium but no information is available on whether that work was ever done. The only evidence of occurrences of nuclear raw materials is that titaniferous sands occur in several coastal regions and that uranium was once listed as having been produced in Forth Vietnam. Although the geology of Vietnam is not very conducive to the formation and preservation of uranium deposits it is possible that because of the granite terrain and presence of other metalliferous minerals, the Speculative Potential should be stated as in category 2 i.e. from 1,000 to 10,000 tonnes uranium. (author)

  20. 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.

  1. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Republic of Korea

    International Nuclear Information System (INIS)

    1977-12-01

    The Republic of Korea, occupies the southern end of the Korean peninsula. It has a long history of mining and mineral production, and has an active and fairly well equipped Geological Survey. The country in general is quite highly mineralized with many minerals including uranium although there has been no uranium production from it yet. Uranium occurs in granites, schists, and in black carbonaceous shales. The Korean Geological survey has estimated that one ore body contains 650 tonnes U in 1,600,000 tons of ore at an average grade of 0.047 percent U 3 O 8 . Many recent reports also indicate very large resources of uranium in very low grade ranges. The uranium potential for the Republic of Korea is considered in Category 2 (1,000 - 10,000 tonnes U) in the normal IUREP context. However, a very large resource may exist in the very low grades in black shales of the country. This resource is considered as in category 6 (500,000 to 1,000,000 tonnes U). (author)

  2. 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.

  3. Fabrics and deformational mechanisms in the high-pressure granulite of the Bacariza Formation (Cabo Ortegal Complex, NW Spain); Fabricas y mecanismos deformacionales en las granulitas de alta presion de la Formacion Bacariza (Complejo de Cabo Ortegal, NO de Espana)

    Energy Technology Data Exchange (ETDEWEB)

    Puelles, P.

    2009-07-01

    In the Cabo Ortegal Complex, mylonitic high-pressure granulites occur at the contacts between the HP granulitic Bacariza Formation and the adjacent units. This mylonitic stage is associated with the initial exhumation of the complex. The petrographic, microstructural and crystallographic analysis of the main constituent minerals in these rocks might provide valuable information on the deformation mechanisms operative at depth. Garnet accommodated part of the deformation by dislocation creep and rigid rotation, augite underwent dislocation creep accompanied by mass transfer and anisotropic growth while plagioclase, in turn, suffered dynamic subgrain rotation-recrystallization and climb-accommodated dislocation creep. Quartz fabrics developed under at least amphibolite-facies conditions. The shear sense criteria are consistent with a top-to-the-NE displacement of the hanging wall blocks. During their ascent to the surface, a static amphibolite-facies retrogressive stage was followed by plastic deformation accommodation under green schist- to lower amphibolite facies conditions. Deformation during the latest stages of exhumation was characterized by micro fracturing and seismic activity in conditions of high differential stresses and strain rates. (Author) 52 refs.

  4. Alligator Rivers Analogue project. Weathering and its effects on uranium redistribution

    International Nuclear Information System (INIS)

    Isobe, H.; Ohnuki, T.; Yanase, N.; Sato, T.; Kimura, H.; Sekine, K.; Nagano, T.; Klessa, D.A.; Conoley, C.; Nakashima, S.; Ewing, R.C.

    1992-01-01

    In the vicinity of the uranium ore deposit at Koongarra, quartz-chlorite schist, the ore host rock, has been subjected to weathering. Although quartz is resistant to weathering, chlorite has been altered to clays and iron minerals. The chlorite weathering and the uranium association with the weathered minerals are the main topics of this study. In order to clarify the weathering of chlorite and its effects on the redistribution of uranium, the processes, mechanisms, and kinetics of the chlorite weathering, and the uranium concentrations in minerals were examined by various methods: X-ray diffraction analysis, scanning electron microscopy, electron microprobe analysis, transmission electron microscopy, autoradiography, visible spectroscopy, alpha and gamma spectrometry. The observed results were compared to those calculated, based on two different models developed for the present study. Water-rock interactions have resulted in the weathering of chlorite and precipitation and sorption of uranyl from the groundwaters with the weathering products. It is concluded that the chlorite weathering affects the uranium retardation factor, and thus uranium redistribution at Koongarra. 55 refs., 20 tabs., 120 figs

  5. 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.

  6. Integrating Apparent Conductance in Resistivity Sounding to Constrain 2D Gravity Modeling for Subsurface Structure Associated with Uranium Mineralization across South Purulia Shear Zone, West Bengal, India

    Directory of Open Access Journals (Sweden)

    Arkoprovo Biswas

    2014-01-01

    Full Text Available South Purulia Shear Zone (SPSZ is an important area for the prospect of uranium mineralization and no detailed geophysical investigations have been carried out in this region. To delineate the subsurface structure in the present area, vertical electrical soundings using Schlumberger array and gravity survey were carried out along a profile perpendicular to the SPSZ. Apparent conductance in the subsurface revealed a possible connection from SPSZ to Raghunathpur. The gravity model reveals the presence of a northerly dipping low density zone (most likely the shear zone extending up to Raghunathpur under a thin cover of granitic schist of Chotanagpur Granite Gneissic Complex (CGGC. The gravity model also depicts the depth of the zone of density low within this shear zone at ~400 m near Raghunathpur village and this zone truncates with a steep slope. Integration of resistivity and gravity study revealed two possible contact zones within this low density zone in the subsurface at depth of 40 m and 200 m. Our study reveals a good correlation with previous studies in Raghunathpur area characterized by medium to high hydro-uranium anomaly. Thus the conducting zone coinciding with the low gravity anomaly is inferred to be a possible uranium mineralized zone.

  7. Periodic Hydraulic Testing for Discerning Fracture Network Connections

    Science.gov (United States)

    Becker, M.; Le Borgne, T.; Bour, O.; Guihéneuf, N.; Cole, M.

    2015-12-01

    Discrete fracture network (DFN) models often predict highly variable hydraulic connections between injection and pumping wells used for enhanced oil recovery, geothermal energy extraction, and groundwater remediation. Such connections can be difficult to verify in fractured rock systems because standard pumping or pulse interference tests interrogate too large a volume to pinpoint specific connections. Three field examples are presented in which periodic hydraulic tests were used to obtain information about hydraulic connectivity in fractured bedrock. The first site, a sandstone in New York State, involves only a single fracture at a scale of about 10 m. The second site, a granite in Brittany, France, involves a fracture network at about the same scale. The third site, a granite/schist in the U.S. State of New Hampshire, involves a complex network at scale of 30-60 m. In each case periodic testing provided an enhanced view of hydraulic connectivity over previous constant rate tests. Periodic testing is particularly adept at measuring hydraulic diffusivity, which is a more effective parameter than permeability for identify the complexity of flow pathways between measurement locations. Periodic tests were also conducted at multiple frequencies which provides a range in the radius of hydraulic penetration away from the oscillating well. By varying the radius of penetration, we attempt to interrogate the structure of the fracture network. Periodic tests, therefore, may be uniquely suited for verifying and/or calibrating DFN models.

  8. A Note on the Occurence of Permo-Carbonifergus in the Southeast of Afyon Region

    Directory of Open Access Journals (Sweden)

    Bilge ERİŞEN

    1982-12-01

    Full Text Available The fossils aged Permo-Carboniferous related with autochthonous Paleozoic basement were found out in the region between Degirmendere, Kızıldağ and Cumhuriyet villages in the southeast of Afyon (Fig. 1. Previous research carried out in this region and surroundings by Chaput (1931, Parejas (1941, Blumenthal (1947, Brennich (1954, Abdüsselamoğlu (1958, Brunn and others (1971. These researchers tried to find out the age of the Paleozoic basement by correlation for the lack of fossils.In 1971, in the southeast of Afyon, Permo-Carboniferous aged fossils were found in the Paleozoic formations during the studies aimed at geothermal energy researches. The report related to this subject has been registered in the archive of Mineral Research and Exploration Institute of Turkey (Erişen, 1972. In the research field, the Paleozoic basement which contains Permo-Carboniferous fossils has been covered with Pliocene layers and Quaternary deposits. The Paleozoic basement, in this region, is formed by; a Sultandede Schist, b Yalnızagaç Formation, c Karahasan Limestone. Among these, Yalnızağaç Formation and Karahasan Limestone contain Permo-Carboniferous fossils.

  9. 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.

  10. Characterization of cement-based ancient building materials in support of repository seal materials studies

    International Nuclear Information System (INIS)

    Roy, D.M.; Langton, C.A.

    1983-12-01

    Ancient mortars and plasters collected from Greek and Cypriot structures dating to about 5500 BC have been investigated because of their remarkable durability. The characteristics and performance of these and other ancient cementitious materials have been considered in the light of providing information on longevity of concrete materials for sealing nuclear waste geological repositories. The matrices of these composite materials have been characterized and classified into four categories: (1) gypsum cements; (2) hydraulic hydrated lime and hydrated-lime cements; (3) hydraulic aluminous and ferruginous hydrated-lime cements (+- siliceous components); and (4) pozzolana/hydrated-lime cements. Most of the materials investigated, including linings of ore-washing basins and cisterns used to hold water, are in categories (2) and (3). The aggregates used included carbonates, sandstones, shales, schists, volcanic and pyroclastic rocks, and ore minerals, many of which represent host rock types of stratigraphic components of a salt repository. Numerous methods were used to characterize the materials chemically, mineralogically, and microstructurally and to elucidate aspects of both the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical (mineralogical) and microstructural factors. Durability was found to be affected by matrix mineralogy, particle size and porosity, and aggregate type, grading, and proportioning, as well as method of placement and exposure conditions. Similar factors govern the potential for durability of modern portland cement-containing materials, which are candidates for repository sealing. 29 references, 29 figures, 6 tables

  11. Geochemistry of the Bossoroca greenstone belt, Southernmost Brazil

    International Nuclear Information System (INIS)

    Koppe, J.C.; Hartmann, L.A.

    1988-01-01

    The Bossoroca greenstone belt is situated in the center of the State of Rio Grande do Sul and has a north-south extension of 18 Km and an east-west of 12 Km. It comprises two sequences. The lower Arroio Lajeadinho Sequence is made up of ultramafic schists and serpentinites, besides amphibolite, meta basalts and mafic meta-volcanoclastic rocks and banded iron-formation; some chert and graphitic rocks also occur. The upper Campestre Sequence is made up of meta volcanoclastic rocks of basaltic to rhyolitic composition with predominance of andesite. They are N A 2 O-rich (5.0 wt%), K 2 O-poor (0.8 wt%), with high Na/K ratios. The REE patterns are rather flat, with small negative Eu anomaly, similar to andesite from Archean or younger greenstone belts. The major and trace elements in samples from the Campestre Sequence were determined by X-ray fluorescence analysis and the rare earth elements by induced coupled plasma. (author)

  12. International Uranium Resources Evaluation Project (IUREP) orientation phase mission summary report: Portugal

    International Nuclear Information System (INIS)

    1985-01-01

    A report has recently been published which describes the findings of the International Uranium Resources Evaluation Project (IUREP) mission to Portugal. The IUREP Orientation Phase mission to Portugal estimates that the Speculative Resources of that country fall within the range 20,000 to 80,000 tonnes uranium. The majority of this potential is expected to be located in intergranitic vein deposits and in pre-Ordovician schists, but other favourable geological environments include episyenites and Meso-Cainozoic continental sediments. The mission recommends that approximately US$25 million be spent on exploration in Portugal over the next 10 years. The majority of this ($18 million) would be spent on drilling, with a further $7 million on surface surveys and airborne radiometric surveys. It is the opinion of the IUREP Orientation Phase Mission that the considerable funding required for the outlined programme would most suitably be realized by inviting national or foreign commercial organisations to participate in the exploration effort under a partnership or shared production arrangements. (author)

  13. UTE park group and other meso proterozoic units of the Nico Perez terrane: Rodina connecting

    International Nuclear Information System (INIS)

    Gaucher, C; Chemale, F.; Bossi, J.; Sial, A.; Chiglino, L.

    2010-01-01

    The Parque UTE Group is a volcano sedimentary succession metamorphosed in green schist facies, comprising (from base to top): the Canada Espinillo Formation (prasinites, pelites, andesite s), the Mina Valencia Formation (dolostones, limestones, marls) and the Cerro del Mast il Formation (black pelites, limestones, acid tuffs). Thickness of the GPU exceeds 2.5 km; base and top are not exposed. U-Pb zircon ages for basic magmatic rocks at the base and rhyolites at the top yielded 1492±4 and 1429±21 Ma, respectively. 13C values of carbonates of the Pug are characterized by a plateau at +1‰ VPDB, bracketed between two negative excursions.These values are consistent with an early Mesoproterozoic depositional age. Detrital zircon age spectra show that the source area of the GPU was the Nico Perez Terrane, being thus native to the Rio de la Plata Craton (Rpc). A Mesoproterozoic tectonic event at 1.25 Ga, recorded at both sides of the Sarandi del Yi mega shear, is discussed. New U-Pb zircon ages are presented for the La China Complex at its type area, where a schistosity N60W cuts the metamorphic banding and is parallel to thrusts dated K-Ar at 1253±32 Ma. The ages obtained are: 3096±45 Ma (main metamorphic event) and 1252 Ma (lower intercept). These data confirm the occurrence of a Grenvillian-aged tectonic event in Uruguay, suggesting that the RPC was part of the super continent Rodinia

  14. Hydrologic information for land-use planning; Fairbanks vicinity, Alaska

    Science.gov (United States)

    Nelson, Gordon L.

    1978-01-01

    The flood plain on the Chena and Tanana Rivers near Fairbanks, Alaska, has abundant water in rivers and in an unconfined alluvial aquifer. The principal source of ground water is the Tanana River, from which ground water flows northwesterly to the Chena River. Transmissivity of the aquifer commonly exceed 100 ,000 sq ft. The shallow water table (less than 15 ft below land surface), high hydraulic conductivity of the sediments and cold soil give the flood plain a high susceptibility to pollution by onsite sewerage systems. The Environmental Protection Agency recommended maximum concentrations for drinking water may be exceeded in surface water for manganese and bacteria and in ground water for iron, manganese, and bacteria. Residents of the uplands obtain water principally from a widely-distributed fractured schist aquifer. The aquifer is recharged by local infiltration of precipitation and is drained by springs on the lower slopes and by ground-water flow to alluvial aquifers of the valleys. The annual base flow from basins in the uplands ranged from 3,000 to 100,000 gallons per acre; the smallest base flows occur in basins nearest the city of Fairbanks. The thick silt cover and great depth to the water table give much of the uplands a low susceptibility to pollution by onsite sewage disposal. Ground water is locally high in nitrate, arsenic, iron , and manganese. (Woodard-USGS)

  15. Distribution of K, Na, Th and U in sandstones and shales from western Shikoku, Japan

    International Nuclear Information System (INIS)

    Ishihara, Shunso; Sakamaki, Yukio; Mochizuki, Tsunekazu; Terashima, Shigeru; Endo, Yuji

    1981-01-01

    The regional variation of K, Na, Th and U distributions was studied on 58 sandstones, 81 shales and 3 green schists from the sedimentary terrains across western Shikoku. The geological structure of the studied district is explained. The regional characteristics of the sedimentary rocks are best demonstrated in the composition of the sandstones. The sandstones, in the source areas of which granitic and rhyolitic rocks exist and which have been deposited rapidly, were rich in K, whereas those derived mainly from mafic volcanic areas showed high Na content. The sandstones of the Shimanto Supergroup had the intermediate values, and K and K + Na contents became low in the south where the younger Upper Shimanto Group is exposed. Th and U in both sandstones and shales were highest in the Izumi Group, and generally low in the Shimanto Supergroup. The black shales of the Shimanto Supergroup did not show U-anomaly. In each group, highly matured rocks gave slightly higher Th/U ratio. Highly matured polycyclic sediments contained the least amount of radioactive elements. The radioactive anomaly due to the anomalous K contained in sericite, and that due to U in black shale were found in Chichibu and Sambosan belts. Similar anomaly was discovered in the foot wall of Mn deposits in the same zone. The possibility of anomalous U may be the least in the Shimanto Supergroup. (Kako, I.)

  16. The Rooiwater complex and associated rocks, Murchison granitoid-greenstone terrane, Kaapvaal Craton

    International Nuclear Information System (INIS)

    Vearncombe, J.R.; Walsh, K.L.

    1987-01-01

    The greater than 2625 Ma Rooiwater Complex is a thick, on-end differentiated basic igneous body exposed along the northern margin of the Murchison schist belt. It is metamorphosed to amphibolite facies and regionally retrograded and hydrothermally altered. Metamorphosed anorthosite, gabbro, pyroxenite, sulphide-bearing gabbros, thick magnetite layers, and granites are compatible with the hypothesis that the Complex is a layered intrusion, tectonically rotated and intruded by younger, genetically unrelated granites. Increasing TiO 2 and decreasing V 2 O 3 contents southwards in the magnetites layers combined with a general southern disposition of differentiated hornblende granite suggest that the Rooiwater Complex faces south. Although the Rubbervale Formation is pervasively deformed and metamorphosed at the greenschist facies, field relations and isotopic and rare earth element data tentatively suggest that a genetic relationship exists, the Rubbervale Formation being a possible roof to the Rooiwater intrusion, being derived from the same or a similar undepleted magmatic source. A paucity of ultramafic cumulates and up to 1,5 km of hornblende granites may relate to a source magma more felsic than that of other layered intrusions. In order to determine model ages for the Eden pluton, the Free State hornblende granite, the Quagga quartz amphibolite, the Rubbervale formation, and the Novengilla gabbro-anorthosite series. Rb-Sr and Pb isotopic analyses were undertaken

  17. Supracrustal suite of the Precambrian crystalline crust in the Ghor Province of Central Afghanistan

    Directory of Open Access Journals (Sweden)

    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.

  18. The discovery of hornblende-garnet-zoisite hornfels in the metamorphic basement of Xiangshan uranium ore field

    International Nuclear Information System (INIS)

    Jiang Zhenpin; Dong Yongjie; Yu Jianfa; Hu Rongquan; Wu Shuilin

    2007-01-01

    Some vein rocks are found among mica schist in the metamorphic rock area of the Xiangshan uranium ore field. They are petrologically denominated as hornblende-garnet-zoisite hornfels. The primitive rocks are basic vein rocks. The hornfels are formed under thermal metamorphism with the temperature about 640 degree C and belong to low-pressure faces. This is closed to the form condition of EarlyMiddle Proterozoic metamorphic rocks in the area. The metamorphism forming the hornfels means that the Early-Middle Proterozoic metamorphic rocks was superimposed to another thermal metamorphism and produced the second phase metamorphic minerals such as staurolite, almandine and biotite. The lattice of the second phase metamorphic mineral developed continuously with the first phase minerals. The overlapping metamorphism made the first phase metamorphic mineral suffer recrystallization, auto purification and idiomorphism. The discovery of hornfelsed basic rock veins discloses that strong geologic process with the activity of fault, magma and metamorphism were still taken placed in Paleozoic era within the metamorphic basement of the Xiangshan uranium ore field. (authors)

  19. 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.

  20. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Turkey

    International Nuclear Information System (INIS)

    1977-08-01

    Turkey has an area of 296 185 sq mi or 767 120 square kilometers. The geology is dominated lay Tertiary and post-Tertiary rocks which are very widespread but extensive outcrops of Mesozoic rocks also occur. Paleozoic rocks, mainly gneisses, mica schists and quartzites occur in the ancient massifs, principally the Istranca massif in Thrace, the Merideres massif in western Anatolia and the Karrshir massif in central Anatolia. Prospecting for uranium began in Turkey in 1953 and the Atomic Energy Raw Materials Division of the Maden Tetkikive Arama Enstitusu (M.T.A.) was founded in 1956. By 1962 a total of 78% of the whole country had been covered by serial radiometric reconnaissance prospecting. Uranium was discovered at Kasar in western Anatolia in 1961 and several hundred tons of reserves estimated two years later. Uranium prospecting was largely recessed from 1963 to 1967. IAEA/UNDP assistance was provided in 1962-63 and 1965 and between 1974 and 1977 in a detailed exploration programme in the Kasar area. In the whole country nearly 600 anomalies and occurrences had been identified by 1963. Several occurrences principally in Western Anatolia had been assigned a small reserve. A recent official estimate places the total national reserve at 3150 tonnes uranium in the less than 30% category of reasonably assured resources. A speculative Potential of between 30,000 and 50,000 tonnes uranium is considered to be reasonable. (author)

  1. 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.

  2. 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.

  3. The geological position, sedimentary record and composition of the Tylicz Conglomerate (Late Eocene-Oligocene): stratigraphical and paleogeographical implications (Magura Nappe, Polish Outer Carpathians)

    Science.gov (United States)

    Olszewska, Barbara; Oszczypko, Nestor

    2010-02-01

    During the Late Cretaceous to Paleogene the Magura Basin was supplied with clastic material from, non-existing today, source areas situated on the northern and southern margins of the basin. The northern source area is traditionally connected with Silesian Ridge, whereas the position of the southern one is still under discussion. The Upper Eocene-Oligocene pebbly mudstones of the Tylicz/Krynica facies zone contain exotic material derived from the south-Magura source area. The studied pebbles and clasts contain fragments of crystalline rocks, derived from a continental type of crust, and frequent clasts of Mesozoic to Paleogene deep and shallow-water limestones. Volcanites, rarely granitoides as well as schists, gneisses, quartzites and cataclasites were found in the group of crystalline exotic pebbles. The isotopic ages of "exotic" pebbles from the Tylicz section document a Variscan age of plutonic and metamorphic rocks. The composition of the Tylicz exotic conglomerates occupied the transitional position between the Jarmuta/Proč (Maastrichtian-Lower Eocene) and Strihovce (Eocene) exotic pebbles. The provenance of these rocks could be connected with Eocene exhumation of the SE sector of the Magura Basin basement. Another possibility can be explain by supply of siliciclastic material from a SE source area (Dacia and Tisza Mega-Units) and carbonate material from a S source area (ALCAPA Mega-Unit: Central Carpathian Block and Pieniny Klippen Belt).

  4. 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.

  5. The Cambrian cavalcades in the Cuchilla Dionisio sub ground. Uruguay

    International Nuclear Information System (INIS)

    Bossi, J.

    2010-01-01

    Most tratadistes consider that Sierra Ballena shear zone (SBSZ) is the western limit of an all octon block after the paper of Boss i and Gauche r (2004) showing a detailed geological map. The same method was applied to sporulation block in the Ne of Treinta y Tres city. It was obtained a 1/100.000 geological map with photo geology and 140 field data in an area of 3500 k m2. This document allowed to discover two kinds of mega - faults put in action at the same time (about 525 Ma): a mega shear zone N30E80E with proto - to ultramylonites similar to SBSZ and a regional thrust fault with vergence to NNW. The thrust fault has different features according to the affected type of rocks. At La Micaela, the mica schists are thrust ed by gneisses and migmatites. To the N W the gneisses became firstly sharply laminated and then, horizontal ultramylonites. Both kind of faulting produced at the same time may not be explained by an orthogonal collision and instead of it, is a naturalist proof of tangential collision and alcoholisation nature of the crustal block. In order to easily understand the new proposal it is necessary to change Paso del Dragón fm by Micaela fm, Cuchilla Dionisio Terrane by Treinta y Tres; Punta del Este Terrane by Punta del Este sub - terrane

  6. Stable Isotope Group progress report for the period July 1989-June 1990

    Energy Technology Data Exchange (ETDEWEB)

    Lyon, G L [Nuclear Sciences Group, DSIR Physical Sciences, Lower Hutt (New Zealand)

    1991-07-01

    The work of the stable isotope and geochronology laboratories in 1989-90 continued to emphasise geochemical and geological applications of mass spectrometry. Research included studies in mass spectrometer instrumentation, atmospheric science, isotope hydrology, geology and biology. A new sulphur isotope reference solid was prepared for international distribution. Geochronological research has included work on the dating and petrogenesis of Taupo Volcanic Zone eruptives, Coromandel Peninsula volcanics, Canterbury-Marlborough plutonics and volcanics, the Subantarctic Islands, West Coast granitoids and the schists and greywackes of New Zealand. Oxygen isotopes continue to be valuable in the study of geothermal systems and of a fossil geothermal system in Fiordland rocks. Geothermal studies have included work in El Salvador as well as a major new study of the Rotorua geothermal system. Atmospheric studies have concentrated on the applications of isotope ratios especially 13C/12C in the trace gases CH4 and CO. Groundwater research on the role of the unsaturated zone continued, and studies of the 14C and 13C content of deep groundwaters of Poverty Bay and Marlborough were carried out. Isotope variations in groundwater near faults are being monitored to look for earthquake precursors. (author). 45 refs., 1 fig.

  7. Application of kinematic vorticity techniques for mylonitized Rocks in Al Amar suture, eastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Hamimi, Z.; Kassem, O. M. K.; El-Sabrouty, M. N.

    2015-09-01

    The rotation of rigid objects within a flowing viscous medium is a function of several factors including the degree of non-coaxiality. The relationship between the orientation of such objects and their aspect ratio can be used in vorticity analyses in a variety of geological settings. Method for estimation of vorticity analysis to quantitative of kinematic vorticity number (Wm) has been applied using rotated rigid objects, such as quartz and feldspar objects. The kinematic vorticity number determined for high temperature mylonitic Abt schist in Al Amar area, extreme eastern Arabian Shield, ranges from ˜0.8 to 0.9. Obtained results from vorticity and strain analyses indicate that deformation in the area deviated from simple shear. It is concluded that nappe stacking occurred early during an earlier thrusting event, probably by brittle imbrications. Ductile strain was superimposed on the nappe structure at high-pressure as revealed by a penetrative subhorizontal foliation that is developed subparallel to tectonic contacts versus the underlying and overlying nappes. Accumulation of ductile strain during underplating was not by simple shear but involved a component of vertical shortening, which caused the subhorizontal foliation in the Al Amar area. In most cases, this foliation was formed concurrently with thrust sheets imbrications, indicating that nappe stacking was associated with vertical shortening.

  8. Tectonic setting and strain analysis of Halaban Area, Eastern Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Alamri, Y. A., II; Kassem, O. M. K.

    2016-12-01

    Finite strain technique was applied for Abt schist, sheared granitoids and volcanosedimentary rocks exposed at Halaban area, Eastern Arabian Shield. This study aims to attempt to decipher the relationship of these lithologies to nappe contacts and to clarify the nature of subhorizontal foliation pervasively recorded in the Halaban area. The Rf/φ and Fry methods are utilized on quartz and feldspar porphyroclasts, as well as on mafic crystals, such as hornblende and biotite, in eighteen samples. The X/Z axial ratios range from 1.12 to 4.99 for Rf/φ method and from 1.65 to 4.00 for Fry method. The direction of finite strain for the long axes displays clustering along the WNW trend (occasionally N) with slight plunging. The Z axes are subvertical and associated with a subhorizontal foliation. The data reveal oblate strain symmetry (flattening) and the strain magnitudes show no considerable increase towards the tectonic contacts. The obtained finite-strain data demonstrate that the sheared granitoids are mildly to moderately deformed. It is suggested that the accumulation of finite strain was not associated with any significant volume change. The penetrative subhorizontal foliation was concurrent with thrusting and shows nearly the same attitudes of tectonic contacts with the overlying nappes. Field relations and observations, together with finite stain data, are inconsistent with the proposed idea that nappes in orogens resulted from simple-shear deformation.

  9. Tectonic superposition of the Kurosegawa Terrane upon the Sanbagawa metamorphic belt in eastern Shikoku, southwest Japan

    International Nuclear Information System (INIS)

    Suzuki, Hisashi; Isozaki, Yukio; Itaya, Tetsumaru.

    1990-01-01

    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)

  10. Lavalleja group (Uruguay) a neoproterozoic metavolcanic-sedimentary sequence: ore deposits

    International Nuclear Information System (INIS)

    Sanchez Bettucci, L.; Preciozzi, F.; Ramos, V.

    2003-01-01

    The Lavalleja meta volcano-sedimentary Group, exposed along the Dom Feliciano Belt, is located in the southeast of Uruguay and formed by meta gabbros, basic and acid meta volcanic rocks. It was developed during late Proterozoic-Early Paleozoic Brasiliano orogeny. Based on the geochemical signature, Sánchez-Bettucci et al. (2001) suggested a back-arc basin tectonic setting. The metamorphic grade increases to the southeast, ranging from very low grade to lower green schist facies in the Minas formation, to lower amphibolite facies in the Fuente del Puma and Zanja del Tigre Formations (Sánchez-Bettucci et al., 2001). The metamorphic mineral assemblages correspond to a low-pressure regional metamorphism associated with a high thermal gradient (Sánchez-Bettucci et al., 2001).A compressive deformational event, that probably corresponds to the basin closure of the Lavalleja Group during a continental collision was recognized. The petrology, geochemistry, metamorphism grade, and tectonic setting are consistent with a back-arc basin as suggested by Sánchez-Bettucci et al. (2001)

  11. A Geomorfologia e a datação de gravuras de Foz Côa. Metodologia e desenvolvimento de um caso de investigação científica

    Directory of Open Access Journals (Sweden)

    Fernando Rebelo

    1997-06-01

    Full Text Available THE GEOMORPHOLOGY AND THE DATING OF THE ENGRAVINGS OF FOZ CÔA - METHODOLOGY AND DEVELOPMENT OF A SCIENTIFIC RESEARCH CASE - Several alternative interpretations of the age of the engravings at Foz Côa are presented. One derivation is based on the climatic and paleo-climatic characteristics of the area as well as the hydrological characteristics of the Côa River, especially its propensity for flooding. This interpretation involves the assumption that the smooth rock surface on which the engravings are found is of late-glacial origin. Another approach at establishing an age is based on the hardness of the rock schists and the near vertical slopes of the smooth surfaces in which the engravings are etched. And another interpretation is related to the burial of the engravings by debris flow and the effects of frost action on the rock surfaces. Evidence of the effects of ice on the rock surface along with the presence of periglacial deposits, similar to other known and previously-dated engravings, leads to the identification of a paleolithic age for the engravings found in the Foz Côa area.

  12. Potency of Thorium and Uranium in West Bangka Region

    International Nuclear Information System (INIS)

    Ngadenin; Heri Syaeful; Kurnia Setiawan Widana; Muhammad Nurdin

    2014-01-01

    Thorium and uranium in Bangka Island are mainly found in monazite mineral. In the geological point of view the monazite formed in S type granite, sandstones and alluvial deposits. In Bangka Barat where several S types granite and also alluvial deposits and this area considered as a potential area for monazite placer. S type granites are predicted as a source of monazite while alluvial deposits are considered as a dispersion place for deposition of monazite. The purpose of this study is to determine the geological information and to know the hypothetical potency of thorium and uranium resources in alluvial deposits. The methods used in this study are geological mapping, measurement of thorium and uranium contents in the rock, sampling of granite for petrographic analysis, sampling of heavy mineral in alluvial deposits for grain size analysis. Results of the research show that the lithology of West Bangka region composed of schist unit, meta-sandstone unit, granite intrusion, diabase intrusion, sandstone unit and alluvial deposits. Monazite is found in granite intrusion, sandstone unit and alluvial deposits. Evolving fault strand to northwest-southeast, northeast-southwest and west-east. The results of the grain size analysis of heavy mineral shows the average percentage of monazite in the heavy mineral is 6.34%. Other potential minerals contained in placer deposits are zircon 36.65%, ilmenite 19.67% and cassiterite 14.75%. (author)

  13. The Salinas formation in the type-area, Northeastern Minas Gerais: a proposal to review the stratigraphy of the Aracuai belt on sedimentary, metamorphic and U-Pb SHRIMP evidences

    International Nuclear Information System (INIS)

    Lima, Sirlene A. de Abreu; Pedrosa Soares, Antonio C.; Cordani, Umberto G.; Nutman, Allen

    2002-01-01

    The Salinas Formation has been considered to be a stratigraphic unit of the Macaubas Group. This group comprises the rift to passive margin sequences of the precursor basin of the Neo proterozoic Aracuai Orogeny, eastern Brazil. However, new road cuts show extensive and spectacular outcrops with very well-preserved sedimentary structures, allowing detailed studies in the type-locality of this formation, located in the Salinas town and surroundings, northeast Minas Gerais State. In its type-locality, the Salinas Formation consists of graywacke, pelite and clast-supported conglomerate, metamorphosed in the green schist facies. The sedimentary lithofacies are grouped into three facies association (shelf, slope and deep-sea), indicating sedimentation from shelf deposits to deep-water turbidites. The shelf sedimentation was influenced by storm-wave during deposition. The slump and deep-sea deposits were generated by gravitational flows and high- to low-concentration turbidity currents. Shelf sandstone, clast-supported conglomerate and proximal to distal turbidites outline a submarine fan system. U-Pb SHRIMP data from detrital zircons of graywacke samples indicate a maximum sedimentation age of ca. 568 Ma. Thus, the Salinas Formation is much younger than the Macaubas Group, and represents late orogenic deposits (ca. 568- 500 Ma). The distal, passive margin unit of the Macaubas Group is now called Ribeirao da Folha Formation (ca. 800 Ma). (author)

  14. 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.

  15. Geological and geophysical investigations at Sierra del Medio massif - Argentine

    International Nuclear Information System (INIS)

    Perucca, J.C.; Llambias, E.; Puigdomenech, H.H.; Cebrelli, E.; Castro, C.E.; Grassi, I.; Salinas, L.I.

    1987-01-01

    Geological investigations were performed at Sierra del Medio (Chubut Province), a mountainous massif of about 25 km by 8 km of migmatic origin, which emerges from a depressed tectonic trench or graben called Pampa de Gastre. The most ancient rocks belong to biotitic and anphibolic schist that passed almost entirely to tonalitoid migmatites with a second process producing granitic rocks. Boreholes were drilled on the basis of conclusions from Landsat satellites imagery and aerial photographic sets, folowed by field work on geological, petrographic, geophysical and hydrogeological features at surface, structural interpretation supported by geostatistical computations. Two sets of boreholes were drilled to investigate subsurface rock behaviour al 300 m depth and 800 m depth respectively, beginning at peripheral places and ending at the central part or selected site. Basic purposes of boreholes were to define structural and petrographic features of the rock massif by a good comprehension of master joints and faulting distribution with its belts of alteration mylonitization or brecciation, mechanical properties of samples, chemical composition and varitions, petrographic facies and mineralogy. Boreholes provided data to investigate joints, faults and dikes as general discontinuities for hydraulic research like permeability or effective hydraulic conductivity, and their geostatistical modelling. Boreholes are also being prepared for geophysical logging from which logthermal ones have already been completed. (Author) [es

  16. Age/isotopic characterisation of the Waipapa Group in Northland and Auckland, New Zealand, and implications for the status of the Waipapa Terrane

    International Nuclear Information System (INIS)

    Adams, C.J.; Maas, R.

    2004-01-01

    Rb-Sr ages of low-grade metasediments of the Waipapa Group (probable Permian-Jurassic) of Northland and Auckland range from Late Triassic (c. 209-217 Ma) to Middle Jurassic (c. 164-174 Ma), reflecting deformation and metamorphism during the Rangitata Orogeny. K-Ar ages indicate Middle Jurassic (c. 165-175 Ma) uplift and cooling of the western Omahuta-Puketi Forest block, and later, Middle-Late Jurassic (c. 150-160 Ma) cooling of the Helena Bay to Hunua Ranges eastern coastal block. In the intervening Western Bay of Islands block, there is evidence of local Early Cretaceous (c. 135 Ma) metamorphism. Rb-Sr whole-rock isochron age (t) and initial 87 Sr/ 86 Sr ratio (i) data support the assignment of Waipapa Group of the westernmost, Omahuta-Puketi block to the Caples Terrane. The remaining data have a consistent (t)-(i) signature, with (i) values 0.7039-0.7049, unlike Permian-Cretaceous Torlesse Supergroup metasediments with more radiogenic (i) values, typically >0.7060. They thus support the retention of a separate, Waipapa Terrane which continues southwards through central North Island to the Kaimanawa Ranges, and probably to Kapiti Island, and schist equivalents in eastern Marlborough. (author). 62 refs., 5 figs., 3 tabs

  17. 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)

  18. Analysis by neutronic activation of samples of a geologic formation of Cuba

    International Nuclear Information System (INIS)

    Capote Rodriguez, G.; Pena Fortes, B.; Padilla Alvarez, R.; Llanes Castro, A.I.; Perez Zayas, G.; Hernandez Rivero, A.T.; Lopez Reyes, M. C.; Ribeiro Guevara, S.; Molina Insfran, J.

    1997-01-01

    The analysis by neutronic activation (AAN) is an analytical non destructive technique of high accuracy and sensibility. These advantages are very utilized in the determination of geological multielemental samples. In the job 22 elements are determined in 9 geological samples pertaining to the complex of dams of acid composition that includes the graphitic micaceous schist and the quartzites of the Canada Formation, developed fundamentally in the fasteners of the anticlinal Victoria (Yac. of Wolframio Lela, Island of the Youth, Cuba) The results obtained are of great importance for the evaluation of the potentiality of these rocks as fountains or of uranium adjusting and for the geologic prognostic of the region in study. The irradiation of the samples was carried out during three campaigns, in two occasions (October 1992 and November 1994) in the reactor of investigations of the ININ of Mexico, with a flow of thermic neutrons of 10a the 13 n.s -1 cm -2 and in an occasion in the nuclear reactor of the CAB (september 1994), with a flow of thermic neutrons of 6x 10 to the 12 n.s-1. The results were processed with the program ACTAM in the CEADEN. (S. Grainger) [es

  19. Sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone terrane, western Dharwar Craton: Implications on pyroclastic volcanism and sedimentation in an active continental margin

    Science.gov (United States)

    Manikyamba, C.; Saha, Abhishek; Ganguly, Sohini; Santosh, M.; Lingadevaru, M.; Rajanikanta Singh, M.; Subba Rao, D. V.

    2014-12-01

    We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb-Cu-Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

  20. Indications of a major Neolithic trade route? An archaeometric geochemical and Sr, Pb isotope study on amphibolitic raw material from present day Europe

    International Nuclear Information System (INIS)

    Christensen, A.-M.; Holm, P.M.; Schuessler, U.; Petrasch, J.

    2006-01-01

    In order to interpret pre-historic cultural interactions, the provenance of amphibolitic raw material used for flat-axes and adzes in lower to middle Neolithic cultures throughout present day Germany were investigated by elemental and Sr, Pb isotopic methods. Within all settlements studied, a homogeneous actinolite-hornblende schist rock type (AHS) was found to be massively dominating, with a distinct petrography of needle-shaped actinolite interwoven with single larger grains of hornblende along with calcic plagioclase and large amounts of ilmenite. Geochemically, the AHS group is very homogeneous and has a signature of an enriched basaltic precursor with high concentrations of particularly the LIL-elements. The geochemical signature is relatively rare and can not be matched in nearby geological outcrops, wherefore the conclusion of 'imported material' is quickly reached. Strontium and Pb isotopic analyses of the AHS were compared to the isotopic composition of amphibolitic rocks with similar petrography and trace elemental signatures within possible archaeological trade regions. The isotopic data of the archaeological material point roughly to a Proterozoic age of the stone used; an age which can be reasonable matched to a single outcrop situated at Jistebsko within the Czech Republic. This area further shows archaeological traces of prehistoric mining. Based on petrographic, geochemical and isotopic evidence, this area is here presented as the provenance area of the stone raw material, which later spread throughout prehistoric Europe - establishing contact and trade routes between Neolithic cultures

  1. The Distribution, Character, and Rhenium Content of Molybdenite in the Aitik Cu-Au-Ag-(Mo Deposit and Its Southern Extension in the Northern Norrbotten Ore District, Northern Sweden

    Directory of Open Access Journals (Sweden)

    Christina Wanhainen

    2014-12-01

    Full Text Available Molybdenite in the Aitik deposit and its southern extension was studied through mineralogical/chemical analysis and laboratory flotation tests. It is demonstrated that molybdenite varies considerably in grain size, ranging from coarse (>20 μm to very fine (<2 μm and occurs predominantly as single grains in the groundmass of the rocks, as grain aggregates, and intergrown with chalcopyrite and pyrite. The dominating molybdenite-bearing rocks are the mica schists, the quartz-monzodiorite, and the Salmijärvi biotite-amphibole gneiss, the latter containing mostly medium-coarsegrained molybdenite. Later geological features, such as garnet-magnetite-anhydrite-K feldspar alteration and pegmatite dikes appear to be responsible for a significant part of the distribution pattern of molybdenite. Molybdenite grains contain up to 1587 ppm Re, with an average of 211 ± 10 ppm in Aitik molybdenite and 452 ± 33 ppm in Salmijärvi molybdenite. The higher Re concentrations are found in molybdenite associated with sericite- and quartz-amphibole-magnetite altered rocks, whereas low Re values occur in rocks in which potassic alteration is prominent. Molybdenite recovery is influenced by the mineralogy of the host rock and the alteration grade; hence both of these factors will have an impact on potential recoveries. The recovery of molybdenite was lower from flotation feeds with significant amounts of Mg-bearing clay-micas.

  2. 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.

  3. Poisson's Ratio and Auxetic Properties of Natural Rocks

    Science.gov (United States)

    Ji, Shaocheng; Li, Le; Motra, Hem Bahadur; Wuttke, Frank; Sun, Shengsi; Michibayashi, Katsuyoshi; Salisbury, Matthew H.

    2018-02-01

    Here we provide an appraisal of the Poisson's ratios (υ) for natural elements, common oxides, silicate minerals, and rocks with the purpose of searching for naturally auxetic materials. The Poisson's ratios of equivalently isotropic polycrystalline aggregates were calculated from dynamically measured elastic properties. Alpha-cristobalite is currently the only known naturally occurring mineral that has exclusively negative υ values at 20-1,500°C. Quartz and potentially berlinite (AlPO4) display auxetic behavior in the vicinity of their α-β structure transition. None of the crystalline igneous and metamorphic rocks (e.g., amphibolite, gabbro, granite, peridotite, and schist) display auxetic behavior at pressures of >5 MPa and room temperature. Our experimental measurements showed that quartz-rich sedimentary rocks (i.e., sandstone and siltstone) are most likely to be the only rocks with negative Poisson's ratios at low confining pressures (≤200 MPa) because their main constituent mineral, α-quartz, already has extremely low Poisson's ratio (υ = 0.08) and they contain microcracks, micropores, and secondary minerals. This finding may provide a new explanation for formation of dome-and-basin structures in quartz-rich sedimentary rocks in response to a horizontal compressional stress in the upper crust.

  4. 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.

  5. 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.

  6. Uranium prospect inventory on general prospection stage at Sigli sector Aceh

    International Nuclear Information System (INIS)

    Soetopo, Bambang; Sutriyono, Agus; Sajiyo

    2002-01-01

    This study based on the considering of the existence of reductive sedimentary rock and acid igneous rocks. The rocks could be favorable for uranium accumulation and source rocks respectively. The aim of this study is to understand the uranium geology, radiometric and geochemical anomalies distribution and it to delineate the prospective area to uranium accumulation. Method of this study field geological observations, radiometric measurements, stream sediment and heavy mineral concentrate sampling, mineralogical and geochemical laboratory analysis. Litho logically, the area composed of slate (Early Yurassic), schist and phyllite (Triassic) and meta calcareous marl (Cretaceous). Those rocks un conformably overly by black siltstone and sandstone (Eocene) conglomerate sandstone (Late Oligocene-Early Miocene) siltstone (Middle Miocene). Some intrusions have been identified as biotite granodiorite (Cretaceous) porphyritic granodiorite (Eocene) and Olivine basalt (Middle Miocene-late Miocene). The rock have been faulted by dextral strike slip fault NW-SE, thrust fault NW-SE, sinistral; strike slip fault NE-SW, and normal faults WNW-ESE. Radioactivity value of rocks range between 40-100 cps SPP2NF and it contains is range about 0.36-150.84 ppm U. The geochemical prospect area has been defined at the area of 93.186 km 2

  7. Thermo chronology by fission tracks of the conjugated rift margins of the Liguro-Provencal basin: Corsica and the Maures-Tanneron Massif

    International Nuclear Information System (INIS)

    Jakni, B.

    2000-01-01

    We have employed apatite fission-track (AFT) thermo-chronology on granitic and metamorphic samples taken from Corsican and Maures-Tanneron basement rocks as well as alpine 'schistes lustres' units in Corsica, in order to constrain the cooling histories and the tectonic evolution of the Liguro-Provencal basin margins. The AFT data indicate that: -) the Tanneron massif (AFT ages 145- 150 My) appears to record the earliest cooling history, reflecting thermal relaxation related to opening of the Tethys; -) the Maures basement (AFT ages 20-25 My) clearly records a thermo- tectonic evolution associated with Liguro-Provencal rifting; -) the island of Corsica, which was the main focus of this work and which shows a complex geomorphology and a poly-phased tectonic evolution. shows a remarkable zoning in the distribution of AFT ages, reflecting the signature of at least two post-Oligocene thermal events. Those events are related to the opening of Liguro-Provencal basin (20-25 My) in the west, and exhumation of the Hercynian basement related to Tyrrhenian extension (12- 16 My) in the east. In the east-Tenda shear zone, which forms the contact between the alpine units and Hercynian basement in northern Corsica, our results indicate that the Tenda Massif was being exhumed from about 21 Ma onwards. (author)

  8. 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)

  9. Infiltration-driven metamorphism, New England, USA: Regional CO2 fluxes and implications for Devonian climate and extinctions

    Science.gov (United States)

    Stewart, E. M.; Ague, Jay J.

    2018-05-01

    We undertake thermodynamic pseudosection modeling of metacarbonate rocks in the Wepawaug Schist, Connecticut, USA, and examine the implications for CO2 outgassing from collisional orogenic belts. Two broad types of pseudosections are calculated: (1) a fully closed-system model with no fluid infiltration and (2) a fluid-buffered model including an H2O-CO2 fluid of a fixed composition. This fluid-buffered model is used to approximate a system open to infiltration by a water-bearing fluid. In all cases the fully closed-system model fails to reproduce the observed major mineral zones, mineral compositions, reaction temperatures, and fluid compositions. The fluid-infiltrated models, on the other hand, successfully reproduce these observations when the XCO2 of the fluid is in the range ∼0.05 to ∼0.15. Fluid-infiltrated models predict significant progressive CO2 loss, peaking at ∼50% decarbonation at amphibolite facies. The closed-system models dramatically underestimate the degree of decarbonation, predicting only ∼15% CO2 loss at peak conditions, and, remarkably, global warming, sea level rise, and, perhaps, extinction in the mid- to late-Devonian.

  10. Uranium occurrence at Sao Teodosio farm, Currais Novos, Rio Grande do Norte, Brazil

    International Nuclear Information System (INIS)

    Favali, J.C.; Leal, J.R.L.V.

    1974-01-01

    The areas of certain radiometric anomalies discovered in Serido geosyncline were selected for intensive study because of the similarity of the geology to that of known uranium deposits in other parts of the world. The uranium mineralization at Sao Teodosio farm, near Currais Novos, RN, on the Serrinha anticline axis, occurs in alaskite similar to that at Rossing in Southwest Africa. The Rossing deposit is the best example of the model proposed by Armstrong (1974) as 'porphyry' uranium deposits. That uranium deposit presents low grade of uranium content, about 0,030% U 3 O 8 and hundred thousands tons of uranium oxide. At Sao Teodosio occurs 550 m.y. alaskitic pegmatitic granite and garnet-quartz-biotite-schists of Serido formation, Upper Precambrian. These older rocks are cut by diabases dykes of Upper Terciary age. Uranium mineralization is associated with pegmatitic granite bodies similar to dykes and sills. The most common uranium minerals are: uraninite, meta-autunite and uranophane. Oligoclase, microline and quartz are the most frequent minerals. Acessory minerals are magnetite, titanite and zircon. Uranium oxide content at Sao Teodosio is 0,023% and average thickness is 2,80 m [pt

  11. Stable Isotope Group progress report for the period July 1989-June 1990

    International Nuclear Information System (INIS)

    Lyon, G.L.

    1991-01-01

    The work of the stable isotope and geochronology laboratories in 1989-90 continued to emphasise geochemical and geological applications of mass spectrometry. Research included studies in mass spectrometer instrumentation, atmospheric science, isotope hydrology, geology and biology. A new sulphur isotope reference solid was prepared for international distribution. Geochronological research has included work on the dating and petrogenesis of Taupo Volcanic Zone eruptives, Coromandel Peninsula volcanics, Canterbury-Marlborough plutonics and volcanics, the Subantarctic Islands, West Coast granitoids and the schists and greywackes of New Zealand. Oxygen isotopes continue to be valuable in the study of geothermal systems and of a fossil geothermal system in Fiordland rocks. Geothermal studies have included work in El Salvador as well as a major new study of the Rotorua geothermal system. Atmospheric studies have concentrated on the applications of isotope ratios especially 13C/12C in the trace gases CH4 and CO. Groundwater research on the role of the unsaturated zone continued, and studies of the 14C and 13C content of deep groundwaters of Poverty Bay and Marlborough were carried out. Isotope variations in groundwater near faults are being monitored to look for earthquake precursors. (author). 45 refs., 1 fig

  12. Water-level fluctuations due to Earth tides in a well pumping from slightly fractured crystalline rock

    International Nuclear Information System (INIS)

    Marine, I.W.

    1975-01-01

    At the Savannah River plant of the Atomic Energy Commission near Aiken, South Carolina, there are three distinct groundwater systems: the coastal plain sediments, the crystalline metamorphic rocks, and a buried Triassic basin. The coastal plain sediments include several Cretaceous and Tertiary granular aquifers and aquicludes, the total thickness being about 305 m. Below these sediments, water occurs in small fractures in crystalline metamorphic rock (hornblende schist and gneiss with lesser amounts of quartzite). Water level fluctuations due to earth tides are recorded in the crystalline metamorphic rock system and in the coastal plain sediments. No water level fluctuations due to earth tides have been observed in wells in the Triassic rock because of the very low permeability. The water level fluctuations due to earth tides in the crystalline rock are about 10 cm, and those in the sediments are about 1.8 cm. The use of water level fluctuations due to earth tides to calculate porosity appears to present practical difficulties both in the crystalline metamorphic rock system and in the coastal plain sediments. In a 1-yr pumping test on a well in the crystalline metamorphic rock the flow was controlled to within 0.1 per cent of the total discharge, which was 0.94 l/s. The water level fluctuations due to earth tides in the pumping well were 10 cm, the same as when this well was not being pumped. (U.S.)

  13. Prescribed burning impact on forest soil properties--a Fuzzy Boolean Nets approach.

    Science.gov (United States)

    Castro, Ana C Meira; Paulo Carvalho, Joao; Ribeiro, S

    2011-02-01

    The Portuguese northern forests are often and severely affected by wildfires during the Summer season. These occurrences significantly affect and negatively impact all ecosystems, namely soil, fauna and flora. In order to reduce the occurrences of natural wildfires, some measures to control the availability of fuel mass are regularly implemented. Those preventive actions concern mainly prescribed burnings and vegetation pruning. This work reports on the impact of a prescribed burning on several forest soil properties, namely pH, soil moisture, organic matter content and iron content, by monitoring the soil self-recovery capabilities during a one year span. The experiments were carried out in soil cover over a natural site of Andaluzitic schist, in Gramelas, Caminha, Portugal, which was kept intact from prescribed burnings during a period of four years. Soil samples were collected from five plots at three different layers (0-3, 3-6 and 6-18) 1 day before prescribed fire and at regular intervals after the prescribed fire. This paper presents an approach where Fuzzy Boolean Nets (FBN) and Fuzzy reasoning are used to extract qualitative knowledge regarding the effect of prescribed fire burning on soil properties. FBN were chosen due to the scarcity on available quantitative data. The results showed that soil properties were affected by prescribed burning practice and were unable to recover their initial values after one year. Copyright © 2010 Elsevier Inc. All rights reserved.

  14. STUDY OF GAS POTENCY BASED ON GRAVITY ANOMALY MODELING AND SEISMIC PROFILE ANALYSIS AT BANGGAI-SULA BASIN

    Directory of Open Access Journals (Sweden)

    Ediar Usman

    2017-07-01

    Full Text Available Banggai-Sula Basin is one of the basins with character of the micro-continent derived from northern part of Australia. Some traces the migration in the central part of Papua are slate, schist, and gneiss, current movement is facilitated by the Sorong Fault, which runs from the northern part of Papua to eastern part of Sulawesi. Results of gravity anomaly model (2D and 3D, seepage distribution, seismic and fields existing of oil and gas production in the western part of the Banggai-Sula Basin obtained a new prospect area in the northern part of Peleng Island, western part of Banggai Island, southern part of Banggai-Taliabu Islands, western and eastern part of Sulabesi Island. The new prospect area is reflected in the centre with form of the low morphology on gravity model and prospect trap on seismic data in the western part of Tolo Bay. Results of chemical analysis on the source rock of Buya Formation on Tmax vs Hydrogen Index (Tmax vs HI Diagram shows the type III kerogen quality and the Oxygen Index vs Hydrogen Index (OI vs HI Diagram shows the gas prone Type II, so that giving the impression that this area has the potential to containing the gas. The quality of the gas is included in the category of immature to mature type.

  15. 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.

  16. Ultrasound-assisted extraction for total sulphur measurement in mine tailings

    International Nuclear Information System (INIS)

    Khan, Adnan Hossain; Shang, Julie Q.; Alam, Raquibul

    2012-01-01

    Highlights: ► We develop a total sulphur measuring procedure of mine tailings. ► Ultrasound is used in the sample pre-treatment process. ► 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 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 °C temperature and 1 ml of HNO 3 :1 ml of HCl, which can achieve 100% recovery for the selected CRM. Subsequently a fraction of the 2 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™-CNS method.

  17. Ultrasound-assisted extraction for total sulphur measurement in mine tailings.

    Science.gov (United States)

    Khan, Adnan Hossain; Shang, Julie Q; Alam, Raquibul

    2012-10-15

    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(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°C temperature and 1 ml of HNO(3):1 ml of HCl, which can achieve 100% recovery for the selected CRM. Subsequently a fraction of the 2(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™-CNS method. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Terminal storage of radioactive waste in geologic formations

    International Nuclear Information System (INIS)

    Lomenick, T.F.

    1976-01-01

    The principal aim of the National Waste Terminal Storage (NWTS) program is to develop pilot plants and, ultimately, repositories in several different rock formations in various parts of the country. Rocks such as salt, shale, limestone, granite, schists, and serpentinite may all qualify as host media for the disposition of radioactive wastes in the proper environments. In general, the only requirement for any rock formation or storage site is that it contain any emplaced wastes for so long as it takes for the radioactive materials to decay to innocuous levels. This requirement, though, is a formidable one as some of the wastes will remain active for periods of hundreds of thousands of years and the physical and chemical properties of rocks that govern circulating groundwater and hence containment, are difficult to determine and define. Nevertheless, there are many rock types and a host of areas throughout the country where conditions are promising for the development of waste repositories. Some of these are discussed below

  19. Cambrian horses in the field Dionisio Blade (Uruguay)

    International Nuclear Information System (INIS)

    Bossi, J.; Gaucher, C.

    2010-01-01

    The shear zone of Sierra Ballena (ZCSB) , is considered the western boundary of an allochthonous block by most writers from the definition of Land Blade Dionisio. The same method to the northern block NE of the city of Thirty- Three was applied. The geological map at 1:100,000 and 1:40,000 photogeology supported by field observations 140 covers an area of ​​3500 km2, allowed 525 Ma to discover that simultaneously produce sinistral megashear N30E, 80E and a mount (horse Amarillo ) with convergence towards the NNW . The megashear consists proto and ultramylonites petrológicamente being identical to ZCSB and age < 532 Ma The horse varies by rock type . On Micaela mica schist are ridden by gneisses and migmatites . In the center, the gneisses are rolled every few inches in W are ultramylonites sub - horizontal . The simultaneity of both phenomena is unexplained by head-on collision of cratons and explained by tangential collision from the SSE with tectonic transport to the north , representing a naturalistic aloctonía test

  20. Evaluation of hydrologic isolation from evidence in mine openings in igneous and metamorphic rocks in the Maritime Provinces of Canada

    International Nuclear Information System (INIS)

    Martinez, J.D.

    1975-09-01

    Conditions in the mines inspected ranged from very wet to very dry. The Heath Steele Mine certainly provided an example of severe leakage through either the country rock, the ore, or both. By way of contrast, the Brunswick Mine is very dry, particularly at the 2800 foot level. A note of caution is raised by this dissimilarity, inasmuch as the local geologic setting for both mines is very much alike. The Buchans Mine also provided evidence of dry conditions at the depth inspected (3215 ft). The Ming Mine at Baie Verte is also nearly dry with a decrease in water leakage with depth. It seems reasonable to tentatively conclude that mined openings in the rock types investigated (volcanics and sediments metamorphosed to a low or subgreen schist facies and intensely deformed) would provide hydraulic isolation at depths on the order of 2800-3200 feet below the surface or greater. It is disturbing to have found one mine that is very wet at shallow depths and to have received reports of some water problems in shaft construction. This report in conjunction with other more comprehensive studies should provide a point of departure for more detailed studies of the nature and causes of hydraulic isolation provided by igneous and metamorphic rocks. 27 figs

  1. Chlorine Isotope Evidence for Syn-Subduction Modification of Serpentinites by Interaction with Sediment-Derived Fluid

    Science.gov (United States)

    Selverstone, J.; Sharp, Z. D.

    2012-12-01

    High-pressure serpentinites and rodingites and high- to ultrahigh-pressure metasedimentary rocks from the Aosta region, Italy, preserve strikingly different chlorine isotope compositions that can be used to constrain the nature of fluid-rock interactions during subduction. Serpentinites and rodingitized gabbroic dikes subducted to 70-80 km have bulk δ37Cl values between -1.6 and +0.9‰ (median= -0.5‰, n=26 plus 5 replicates; one amphibole-vein outlier at -2.9‰). Serpentinite δ37Cl values are positively correlated with Cr ± Cl contents (r2= 0.97 and 0.58) and negatively correlated with CaO (r2=0.72). BSE imaging and X-ray mapping reveal up to three generations of compositionally distinct serpentine and chlorite in single samples. The youngest generation, which is most abundant, has the lowest chlorine content. Three rodingite samples contain abundant texturally early fluid inclusions. These samples were finely crushed and leached in 18 MΩ H2O to extract water-soluble chlorides. The leachates, which are assumed to record the compositions of the fluid inclusions, have δ37Cl values that are 0.7-1.5‰ lower than the corresponding bulk rock values. Leachate from the outlier amph-magnesite vein is indistinguishable from the bulk value at -2.7‰. There is almost no overlap between the Cl isotope compositions of HP serp/rod samples and associated HP/UHP metasedimentary rocks. Calcmica schists, diamond-bearing Mn nodules, and impure marbles subducted to >130 km and calcmica schists and Mn crusts transported to 70-80 km have δ37Cl values between -4.5 and -1.5‰ (median= -2.7‰, n=25 plus 7 replicates; two outlier points at -0.5‰). Primary fluid inclusions in the diamondiferous samples contain carbonate- and silicate-bearing aqueous fluids with very low chloride contents (Frezzotti et al., 2011, Nature Geosci). Taken together, these data record a history of progressive modification of serpentinites and rodingites by mixing with low-δ37Cl, low-Cl, high

  2. Oriented growth due to topotactic replacement of antigorite by olivine as a mechanism for the formation of B-type olivine CPO in convergent margins

    Science.gov (United States)

    Nagaya, T.; Wallis, S.; Kobayashi, H.; Michibayashi, K.; Mizukami, T.

    2012-12-01

    B-type olivine (Ol) CPO patterns are characterized by an a-axis concentration parallel to the intermediate principle axis of strain and have been proposed by many workers as the cause of seismic anisotropy in the mantle wedge of subduction zones that shows the fast direction perpendicular to the plate movement direction. Experimental work has shown that B-type Ol CPO can form by dislocation creep at relatively high stresses and in the presence of water. Natural examples of B-type Ol CPO have also been reported, but there are several discrepancies with the experimental results. 1) Some natural B-type CPO formed at relatively high temperatures and low stress outside the ranges predicted by experiments. 2) Natural examples lack evidence for the c-slip expected for the formation of B-type Ol CPO by dislocation creep. 3) The high shear stresses expected along subduction boundaries promote the formation of B-type Ol CPO, but these regions are also expected to be associated with the formation of serpentine minerals and even relatively small amounts prevent strong CPO patterns from forming because of grain-boundary sliding occurring between Ol and serpentine. We show B-type Ol CPO can form as a result of static topotactic growth of olivine after high-temperature breakdown of antigorite (Atg) schist. In the Happo-One region of the Hida Marginal belt, Japan, dehydration of foliated Atg produces non-deformed secondary Ol formed in veins or patches and peridotite-hornfels where the conversion is complete.The CPO of non-deformed Ol in veins and in the hornfels shows a strong B-type fabric. The veins show consistent Ol CPO irrespective of the vein orientation, implying the CPO is not related to the vein opening direction. The CPO of Atg bordering the vein Ol shows a strong concentration of c-axes at a high angle to the foliation and a strong alignment of b-axes parallel to the lineation. Numerous recent studies have shown this type of Atg CPO is the most widespread in the

  3. 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

  4. Malenco Serpentine: proposed as a candidate for "Global Heritage Stone Resource" designation

    Science.gov (United States)

    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

  5. 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

  6. Geological and Geochemical Criteria for the Estimation of the Area of The Lesser Hinggan for the Endogenous Gold Mineralization (The Far East, Russia)

    Science.gov (United States)

    Yurchenko, Yuriy

    2015-04-01

    The Area of the Lesser Hinggan in the middle of the XIX century has been known as one of the Gold areas of the Far East. Exploration of gold in different years were engaged by P.K. Yavorovskiy (1904), E.E. Anert (1928), G.V. Itsikson (1961), V.A. Buryak (1999, 2002, 2003), A.M. Zhirnov (1998, 2000, 2008), L.V. Eyrish (1960, 1964, 1995, 1999, 2002, 2008) and many others. But despite the abundance of factual materials in the problem of the gold metallogeny of the Lesser Hinggan are more aspects that still have not received a answer. Among them is the key issue about indigenous sources of the gold. First for the Lesser Hinggan area, structural-geochemical zoning at 1:200 000 scale was carried out based on the results of the precise analyses of over 2,600 soil and sediment stream samples. Three anomalous geochemical zones and nine anomalous geochemical clusters in their contours specialized for gold mineralization were revealed. Regional clarkes (fersms) for 19 chemical elements were calculated. Geological formations geochemically specialized for gold and their role in endogenous ore-forming processes were defined. Geochemical criteria for endogenous gold mineralization and its ore-formational affiliation were defined as well. Thus, from the geological and geochemical data, are the following signs of the gold mineralization of the Lesser Hinggan: 1. Some geological formations are geochemical specialized by the gold (carbon ("black") schists and ferruginous quartzite Vendian-Cambrian Hinggan series). They're considered as a source of the gold, involved in younger epigenetic processes of mobilization and redistribution of this element; 2. Contrasting geochemical anomalies of the gold and elements satellites in the secondary halos and stream sediments displayed in the contours of the geological formations of a wide age range - terrigenous-carbonate rocks of the Hinggan series, the Paleozoic granitoid massives, the Cretaceous volcanic fields ; 3. Samples of the native gold

  7. Transformation of graphite by tectonic and hydrothermal processes in an active plate boundary fault zone, Alpine Fault, New Zealand

    Science.gov (United States)

    Kirilova, Matina; Toy, Virginia; Timms, Nicholas; Halfpenny, Angela; Menzies, Catriona; Craw, Dave; Rooney, Jeremy; Giorgetti, Carolina

    2017-04-01

    Graphite is a material with one of the lowest frictional strengths, with coefficient of friction of 0.1 and thus in natural fault zones it may act as a natural solid lubricant. Graphitization, or the transformation of organic matter (carbonaceous material, or CM) into crystalline graphite, is induced by compositional and structural changes during diagenesis and metamorphism. The supposed irreversible nature of this process has allowed the degree of graphite crystallinity to be calibrated as an indicator of the peak temperatures reached during progressive metamorphism. We examine processes of graphite emplacement and deformation in the Alpine Fault Zone, New Zealand's active continental tectonic plate boundary. Raman spectrometry indicates that graphite in the distal, amphibolite-facies Alpine Schist, which experienced peak metamorphic temperatures up to 640 ◦C, is highly crystalline and occurs mainly along grain boundaries within quartzo-feldspathic domains. The subsequent mylonitisation in the Alpine Fault Zone resulted in progressive reworking of CM under lower temperature conditions (500◦C-600◦C) in a structurally controlled environment, resulting in spatial clustering in lower-strain protomylonites, and further foliation-alignment in higher-strain mylonites. Subsequent brittle deformation of the mylonitised schists resulted in cataclasites that contain over three-fold increase in the abundance of graphite than mylonites. Furthermore, cataclasites contain graphite with two different habits: highly-crystalline, foliated forms that are inherited mylonitic graphite; and lower-crystallinity, less mature patches of finer-grained graphite. The observed graphite enrichment and the occurrence of poorly-organised graphite in the Alpine Fault cataclasites could result from: i) hydrothermal precipitation from carbon-supersaturated fluids; and/or ii) mechanical degradation by structural disordering of mylonitic graphite combined with strain-induced graphite

  8. Occurrence of Cr-bearing beryl in stream sediment from Eskişehir, NW Turkey

    Directory of Open Access Journals (Sweden)

    Hülya Erkoyun

    2016-07-01

    Full Text Available Beryl crystals are found within stream sediments transecting schists in the northeast of Eskişehir, western Anatolia. This paper studied the Eskişehir beryl crystals with optical microscopy, scanning electron microscopy (SEM-EDX, infrared spectroscopy (IR and geochemical analyses. Beryl is accompanied by garnet, glaucophane, quartz, epidote, muscovite and chlorite in the stream sediments. The crystals are euhedral emerald (green gem beryl and light bluishgreen aquamarine, with ideal sharp IR bands. Wet chemical analysis of Eskişehir beryl yielded 61.28% SiO2, 15.13% Al2O3, 12.34% BeO, 0.18% Cr2O3, 1.49% MgO, 1.69% Na2O, 0.98% Fe2O3, and 0.008% V2O3, resulting in the formula (Al1.75Cr0.01Mg0.22Fe0.08(Be2.90Si6.00(Na0.32O18. Large Ion Lithophile Elements (LILE (barium, strontium, some transition metals (cobalt, except nickel and High Field Strength Elements (HFSE (niobium, zirconium, and yttrium in stream sediments that are associated with beryl exhibited low content about metamorphic rocks. Beryl formation appears to be controlled by upthrust faults and fractures that juxtaposed them with Cr-bearing ophiolitic units and a regime of metasomatic reactions. Such beryl crystals have also been found in detrital sediments that are derived from the schists.   Presencia de berilios relacionados con Cromo en corrientes sedimentarias de Eskisehir, noroeste de Turquía   Resumen Cristales de berilo fueron encontrados en sedimentos de corrientes que atraviesan en esquistos en el noreste de Eskisehir, al oeste de Anatolia. En este artículo se presentan resultados sobre el estudio de los cristales de berilio de Eskisehir con microscopio electrónico de barrido (SEM-EDX, del inglés Scanning Electron Microscopy, espectroscopia infrarroja y análisis geoquímicos. El berilio estaba acompañado de granate, glaucofana, cuarzo, epidota, moscovita, y clorito en las corrientes sedmientarias. Los cristales son esmeraldas de formas definidas (gema verde de

  9. 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

  10. 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

  11. 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

  12. 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)

  13. Preliminary Geologic Map of the San Fernando 7.5' Quadrangle, Southern California: A Digital Database

    Science.gov (United States)

    Yerkes, R.F.

    1997-01-01

    . The San Fernando area lies on the southern slopes of the San Gabriel Mountains. The basement rocks here include high-grade metamorphic rocks of Precambrian age. The mountains are largely composed of crystalline basement that includes the Pelona Scist of probable Mesozoic age that has been overthrust by Precambrian gneisses; the gneisses were subsequently intruded by Mesozoic plutons prior to overthrusting along the latest Cretaceous Vincent thrust. Gneisses of somewhat variable composition and possibly varying ages are found in four terranes, but not all are in contact with Pelona Schist. Large tracts of Precambrian (1.2 billion years old) andesine anorthosite are intrusive into 1.7 billion year-old Mendenhall gneiss, and are found in the western part of the San Gabriels. Mixed with these are younger marble, limestone, and schist of possible Paleozoic age found in association with plutons along the southern margin of the range. The older rocks are intruded by diorite, quartz diorite, and granodiorite of Jurassic age. Also present are siliceous sedimentary rocks of Jurassic age. A thick section of Tertiary sedimentary and volcanic rocks overlie these units. The sediments located south of the San Gabriel Fault are totally different in character from those on the northern range flank, and mostly resemble the western Transverse Ranges due to their deposition in the southeastern Ventura basin; approximately 3,000 m of these sediments are exposed north and west of the city of San Fernando in the Tujunga syncline. Some of the Tertiary rocks are Paleocene and Eocene in age, but the bulk of these rocks are Oligocene and Miocene in age. The Vasquez and Sespe Formations of basal basaltic volcanic and sandstone are Oligocene and lower Miocene in age. These are overlain by clastic rocks of Tick Canyon and Mint Canyon Formations of middle to late Miocene age. Above these rocks are the Castaic, Modelo, and Santa Margarita Formations of fossiliferous marine shale, sand

  14. 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