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Sample records for late archaean granitoids

  1. the origin of late archaean granitoids in the sukumaland greenstone

    African Journals Online (AJOL)

    Mgina

    melting at the base of a late Archaean thickened sub-arc basaltic crust. Melting to form the Suite 1 granitoids occurred in the eclogite stability field whereas Suite 2 formed by melting at shallower ... of TTG in terms of slab melting processes.

  2. On the metamorphic history of an Archaean granitoid greenstone terrane, East Pilbara, Western Australia, using the 40Ar/39Ar age spectrum technique

    International Nuclear Information System (INIS)

    Wijbrans, J.R.; McDougall, I.

    1987-01-01

    Age spectrum analyses of blue-green hornblendes from amphibolites from the Western Shaw Belt, East Pilbara, Western Australia, indicate an age of at least 3200 Ma for early regional metamorphism. Ages on hornblende and muscovite from the narrow contact zone with the adjacent Yule Batholith probably data updoming of the granitoid gneiss terranes at 2950 Ma. Hornblendes from within the Shaw Batholith and from a contact zone of a post-tectonic granitoid yield ages of 2840-2900 Ma, indicating either prolonged high temperatures within the granitoid gneiss terranes or a separate thermal pulse associated with the intrusion of post-tectonic granitoids. The preservation of very old hornblendes in a narrow greenstone belt surrounded by massive granitoid gneiss domes indicates that remarkable contrasts in metamorphic geotherms existed over short distances during the Late Archaean, suggesting that updoming occurred during a period of rapid tectonism. (orig.)

  3. On the metamorphic history of an Archaean granitoid greenstone terrane, East Pilbara, Western Australia, using the /sup 40/Ar//sup 39/Ar age spectrum technique

    Energy Technology Data Exchange (ETDEWEB)

    Wijbrans, J.R.; McDougall, I.

    1987-07-01

    Age spectrum analyses of blue-green hornblendes from amphibolites from the Western Shaw Belt, East Pilbara, Western Australia, indicate an age of at least 3200 Ma for early regional metamorphism. Ages on hornblende and muscovite from the narrow contact zone with the adjacent Yule Batholith probably data updoming of the granitoid gneiss terranes at 2950 Ma. Hornblendes from within the Shaw Batholith and from a contact zone of a post-tectonic granitoid yield ages of 2840-2900 Ma, indicating either prolonged high temperatures within the granitoid gneiss terranes or a separate thermal pulse associated with the intrusion of post-tectonic granitoids. The preservation of very old hornblendes in a narrow greenstone belt surrounded by massive granitoid gneiss domes indicates that remarkable contrasts in metamorphic geotherms existed over short distances during the Late Archaean, suggesting that updoming occurred during a period of rapid tectonism.

  4. Adakitic magmas: modern analogues of Archaean granitoids

    Science.gov (United States)

    Martin, Hervé

    1999-03-01

    Both geochemical and experimental petrological research indicate that Archaean continental crust was generated by partial melting of an Archaean tholeiite transformed into a garnet-bearing amphibolite or eclogite. The geodynamic context of tholeiite melting is the subject of controversy. It is assumed to be either (1) subduction (melting of a hot subducting slab), or (2) hot spot (melting of underplated basalts). These hypotheses are considered in the light of modern adakite genesis. Adakites are intermediate to felsic volcanic rocks, andesitic to rhyolitic in composition (basaltic members are lacking). They have trondhjemitic affinities (high-Na 2O contents and K 2O/Na 2O˜0.5) and their Mg no. (0.5), Ni (20-40 ppm) and Cr (30-50 ppm) contents are higher than in typical calc-alkaline magmas. Sr contents are high (>300 ppm, until 2000 ppm) and REE show strongly fractionated patterns with very low heavy REE (HREE) contents (Yb≤1.8 ppm, Y≤18 ppm). Consequently, high Sr/Y and La/Yb ratios are typical and discriminating features of adakitic magmas, indicative of melting of a mafic source where garnet and/or hornblende are residual phases. Adakitic magmas are only found in subduction zone environments, exclusively where the subduction and/or the subducted slab are young (subducted and where the adakitic character of the lavas correlates well with the young age of the subducting oceanic lithosphere. In typical subduction zones, the subducted lithosphere is older than 20 Ma, it is cool and the geothermal gradient along the Benioff plane is low such that the oceanic crust dehydrates before it reaches the solidus temperature of hydrated tholeiite. Consequently, the basaltic slab cannot melt. The released large ion lithophile element (LILE)-rich fluids rise up into the mantle wedge, inducing both its metasomatism and partial melting. Afterwards, the residue is made up of olivine+clinopyroxene+orthopyroxene, such that the partial melts are HREE-rich (low La/Yb and Sr

  5. Rock strength measurements on Archaean basement granitoids recovered from scientific drilling in the active Koyna seismogenic zone, western India

    Science.gov (United States)

    Goswami, Deepjyoti; Akkiraju, Vyasulu V.; Misra, Surajit; Roy, Sukanta; Singh, Santosh K.; Sinha, Amalendu; Gupta, Harsh; Bansal, B. K.; Nayak, Shailesh

    2017-08-01

    Reservoir triggered earthquakes have been occurring in the Koyna area, western India for the past five decades. Triaxial tests carried out on 181 core samples of Archaean granitoids underlying the Deccan Traps provide valuable constraints on rock strength properties in the Koyna seismogenic zone for the first time. The data include measurements on granite gneiss, granite, migmatitic gneiss and mylonitised granite gneiss obtained from boreholes KBH-3, KBH-4A, KBH-5 and KBH-7 located in the western and eastern margins of the seismic zone. Salient results are as follows. (i) Increase of rock strength with increasing confining pressure allow determination of the linearized failure envelopes from which the cohesive strength and angle of internal friction are calculated. (ii) Variable differential stresses at different depths are the manifestations of deformation partitioning in close association of fault zone(s) or localized fracture zones. (iii) Fractures controlled by naturally developed weak planes such as cleavage and fabric directly affect the rock strength properties, but the majority of failure planes developed during triaxial tests is not consistent with the orientations of pre-existing weak planes. The failure planes may, therefore, represent other planes of weakness induced by ongoing seismic activity. (iv) Stress-strain curves confirm that axial deformation is controlled by the varying intensity of pre-existing shear in the granitoids, viz., mylonite, granite gneiss and migmatitic gneiss. (v) Frequent occurrences of low magnitude earthquakes may be attributed to low and variable rock strength of the granitoids, which, in turn, is modified by successive seismic events.

  6. Magmatism during the accretion of the late Archaean Dharwar Craton (South India): sanukitoids and related rocks in their geological context.

    Science.gov (United States)

    Moyen, J.-F.; Martin, H.; Jayananda, M.; Peucat, J.-J.

    2003-04-01

    The South Indian Dharwar Craton assembled during the late-Archaean (ca. 2.5 Ga). This event was associated with intense granite genesis and emplacement. Based on petrography and geochemistry, 4 main types of late Archaean granitoids were distinguished: (1) Anatectic granites (and diatexites), formed by partial melting of TTG gneisses; (2) Classical TTGs; (3) Sanukitoids, generated by interaction between slab melts (TTG) and mantle peridotite; (4) The high HFSE Closepet granite, interpreted as derived from partial melting of a mantle metasomatized by slab melts (TTG). While the 3 later groups all are interpreted as resulting from slab melt/mantle wedge interactions, their differences are related to decreasing felsic melt/peridotite ratios during the ascent “slab melts” in the mantle wedge above an active subduction zone. Field data together with geochronology and isotope geochemistry allow to subdivide the Dharwar craton into three main domains: (1) The Western Dharwar Craton (WDC) is an old (3.3 2.9 Ga ), stable continental block with limited amounts of 2.5 Ga old anatectic granites. (2) The Eastern Dharwar Craton (EDC) is subdivided into two parts: (2a) West of Kolar Schist Belt, a region of 3.0-2.7 Ga old basement intruded by 2.5 Ga old anatectic granites; (2b) East of Kolar, an area featuring mainly 2.5 Ga old diatexites and granites, derived of partial melting of a newly accreted TTG crust. Anatectic granites are ubiquitous, and late in the cratonic evolution; they witnessed generalized melting of a juvenile crust. In contrast, deep-originated granites emplaced before this melting and are restricted to the boundaries between the blocks. This structure of distinct terranes separated by narrow bands operating as channels for deep-originated magmas provides independent evidences for a two-stage evolution: an arc accretion context for the TTG, sanukitoids and related rocks, immediately followed by high temperature reworking of the newly accreted craton

  7. A hitherto unknown river type from the Archaean at Bhurkuli (Jharkhand, E India

    Directory of Open Access Journals (Sweden)

    Loon A.J. (Tom van

    2017-06-01

    Full Text Available The Archaean granitoid pluton of the Singhbhum craton in E India is overlain by Archaean to Palaeoproterozoic metasediments. These sediments are still poorly known and their stratigraphy is under debate. Several scattered, most probably Meso- to Neoarchaean, conglomerates are present in the state of Jharkhand that differ so much in characteristics that they are probably not related to each other. The sedimentology of a series of conglomerate patches and layers near Bhurkuli has been investigated, including the characteristics of the clasts. It is deduced on the basis of these characteristics and the sedimentological context that the Bhurkuli conglomerates represent the channel facies of a river system that differed from the types of fluvial systems that exist nowadays.

  8. The Archaean Granny Smith gold deposit, western Australia: age and Pb-isotope tracer studies

    International Nuclear Information System (INIS)

    Ojala, V.J.; McNaughton, N.J.; Groves, D.I.; Ridley, J.R.; Fanning, C.M.

    1997-01-01

    The Granny Smith gold deposits are situated within a greenstone sequence in the Laverton-Leonora area of the Northeastern Goldfields Province of the Archaean Yilgarn Block, Western Australia. The greenstone sequence (U-Pb zircon age of 2677±6 Ma, felsic pyroclastic rock) was intruded by the Granny Smith Granodiorite at 2665±4 Ma. Gold mineralisation is located along a reactivated N-S Stricking, thrust which wraps around the granitoid intrusion, and within the granitoid intrusion. Initial lead-isotope compositions of the Granny Smith Granodiorite and ore-fluid Pb, estimated from K-feldspar and galena and lead tellurides, respectively, are slightly different. Calculations based on Pb isotope data for the host rocks, and the U-Pb zircon age of the Granny Smith Granodiorite, suggest that ore-fluid Pb was derived from a source with a similar initial lead-isotopic composition to the source of the Granny Smith Granodiorite but about 30 million years after the intrusion of the granitoid. The Pb-isotope data for granitoids of the Northeastern Goldfields fall in a distinct field different to that of the granitoids of the Norseman area and those from Kambalda to Menzies. (authors)

  9. Petrogenesis of shoshonitic granitoids, eastern India: Implications for the late Grenvillian post-collisional magmatism

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    B. Goswami

    2014-11-01

    Full Text Available Many elongated, lenticular plutons of porphyritic granitoids are distributed mainly near the southern and northern margin of the Chhotanagpur Gneissic Complex (CGC which belongs to the EW to ENE–WSW tending 1500 km long Proterozoic orogenic belt amalgamating the North and South Indian cratonic blocks. The late Grenvillian (1071 ± 64 Ma Raghunathpur porphyritic granitoid gneiss (PGG batholith comprising alkali feldspar granite, granite, granodiorite, tonalite, quartz syenite and quartz monzonite intruded into the granitoid gneisses of southeastern part of CGC in the Purulia district, West Bengal and is aligned with ENE–WSW trending North Purulia shear zone. Mineral chemistry, geochemistry, physical condition of crystallization and petrogenetic model of Raghunathpur PGG have been discussed for the first time. The petrographic and geochemical features (including major and trace-elements, mineral chemistry and 87Sr/86Sr ratio suggest these granitoids to be classified as the shoshonitic type. Raghunathpur batholith was emplaced at around 800 °C and at 6 kbar pressure tectonic discrimination diagrams reveal a post-collision tectonic setting while structural studies reveal its emplacement in the extensional fissure of North Purulia shear zone. The Raghunathpur granitoid is compared with some similar granitoids of Europe and China to draw its petrogenetic model. Hybridization of mantle-generated enriched mafic magma and crustal magma at lower crust and later fractional crystallization is proposed for the petrogenesis of this PGG. Mafic magma generated in a post-collisional extension possibly because of delamination of subducting slab. Raghunathpur batholith had emplaced in the CGC during the final amalgamation (∼1.0 Ga of the North and South Indian cratonic blocks. Granitoid magma, after its generation at depth, was transported to its present level along megadyke channel, ways within shear zones.

  10. Lead isotopes in archaean plutonic rocks

    International Nuclear Information System (INIS)

    Oversby, V.M.

    1978-01-01

    Archaean intrusive rocks have initial Pb isotopic compositions which show a varied and complex history for the source regions of the rocks. Even the oldest rocks from Greenland indicate heterogenous U and Pb distribution prior to 3800 m.y. ago. Source regions with μ values less than 7 must have played a significant role in the early history of the earth. By late Archaean time U/Pb ratios of source regions had increased substantially. Data from Australia and North America show distinct regional differences, both within and between continents. (Auth.)

  11. 207Pb-206Pb zircon ages of eastern and western Dharwar craton, southern India : Evidence for contemporaneous Archaean crust

    Science.gov (United States)

    Maibam, B.; Goswami, J. N.; Srinivasan, R.

    2009-04-01

    Dharwar craton is one of the major Archaean crustal blocks in the Indian subcontinent. The craton is comprised of two blocks, western and eastern. The western domain is underlain by orthogneisses and granodiorites (ca. 2.9-3.3 Ga) collectively termed as Peninsular Gneiss [e.g., 1] interspersed with older tracts of metasedimentary and metamorphosed igneous suites (Sargur Group and Dharwar Group; [2]). The eastern part of the craton is dominated by Late Archaean (2.50-2.75 Ga) granitoids and their gneissic equivalents. They are interspersed with schist belts (also of Sargur Group and Dharwar Group), which are lithologically similar to the Dharwar Supergroup in the western block, but are in different metamorphic dress. Here we report 207Pb-206Pb age of zircons separated from the metasedimentary and gneissic samples from the two blocks to constrain the evolution of the Dharwar craton during the early Archaean. Detrital zircons of the metasedimentary rocks from both the blocks show a wide range of overlapping ages between ~2.9 to >3.5 Ga. Zircon ages of the orthogneisses from the two blocks showed that most of the analysed grains of the eastern Dharwar block are found to be of the age as old as the western Dharwar gneisses. Imprints of younger events could be discerned from the presence of overgrowths in zircons from the studied samples throughout the craton. Our data suggest that crust forming cycles in the two blocks of the Dharwar craton occurred contemporaneously during the Archaean. References [1] Beckinsale, R.D., Drury, S.A., Holt, R.W. (1980) Nature 283, 469-470. [2] Swami Nath J., Ramakrishnan M., Viswanatha M.N. (1976) Rec. Geol. Surv. Ind., 107, 149-175.

  12. Percolation of diagenetic fluids in the Archaean basement of the Franceville basin

    Science.gov (United States)

    Mouélé, Idalina Moubiya; Dudoignon, Patrick; Albani, Abderrazak El; Cuney, Michel; Boiron, Marie-Christine; Gauthier-Lafaye, François

    2014-01-01

    The Palaeoproterozoic Franceville basin, Gabon, is mainly known for its high-grade uranium deposits, which are the only ones known to act as natural nuclear fission reactors. Previous work in the Kiéné region investigated the nature of the fluids responsible for these natural nuclear reactors. The present work focuses on the top of the Archaean granitic basement, specifically, to identify and date the successive alteration events that affected this basement just below the unconformity separating it from the Palaeoproterozoic basin. Core from four drill holes crosscutting the basin-basement unconformity have been studied. Dating is based on U-Pb isotopic analyses performed on monazite. The origin of fluids is discussed from the study of fluid inclusion planes (FIP) in quartz from basement granitoids. From the deepest part of the drill holes to the unconformable boundary with the basin, propylitic alteration assemblages are progressively replaced by illite and locally by a phengite + Fe chlorite ± Fe oxide assemblage. Illitic alteration is particularly strong along the sediment-granitoid contact and is associated with quartz dissolution. It was followed by calcite and anhydrite precipitation as fracture fillings. U-Pb isotopic dating outlines three successive events: a 3.0-2.9-Ga primary magmatic event, a 2.6-Ga propylitic alteration and a late 1.9-Ga diagenetic event. Fluid inclusion microthermometry suggests the circulation of three types of fluids: (1) a Na-Ca-rich diagenetic brine, (2) a moderately saline (diagenetic + meteoric) fluid, and (3) a low-salinity fluid of probable meteoric origin. These fluids are similar to those previously identified within the overlying sedimentary rocks of the Franceville basin. Overall, the data collected in this study show that the Proterozoic-Archaean unconformity has operated as a major flow corridor for fluids circulation, around 1.9 Ga. highly saline diagenetic brines; hydrocarbon-rich fluids derived from organic matter

  13. Electron probe micro analyser chemical zircon ages of the Khetri granitoids, Rajasthan, India: records of widespread late palaeoproterozoic extension-related magmatism

    International Nuclear Information System (INIS)

    Kaur, Parampreet; Chaudhri, Naveen; Biju-Sekhar, S.; Yokoyama, K.

    2006-01-01

    A number of granitoid plutons were emplaced in the northernmost entity of the Aravalli craton, the Khetri Copper Belt (KCB). We report here Th-U-Pb electron probe micro analyser chemical ages for zircon and monazite from two granitoid plutons of the north KCB, the Biharipur and Dabla. Zircons occurring in the granitoids depict well-developed magmatic zoning and are chronologically unzoned. Both the plutons and their diverse granitoid facies are coeval and provide ages around 1765-1710 Ma. Geochemical attributes of the studied plutons are typical of A-type within-plate granites and consistent with an extensional tectonic environment. Our new age data are comparable to the petrologically similar A-type granitoids of the Alwar region, which have provided zircon chemical ages around 1780-1710 Ma. These analogous ages imply a widespread late palaeoproterozoic extension-related plutonism in the northern part of the Aravalli craton. The monazites, which were recovered only from the mafic magmatic rocks of the Biharipur pluton, yielded an isochron age of 910 ±10 Ma, signifying an over- print of a younger neoproterozoic thermal event in the region. (author)

  14. Geodynamic evolution of the West Africa between 2.2 and 2 Ga: the Archaean style of the Birimian greenstone belts and the sedimentary basins in northeastern Ivory-Coast

    International Nuclear Information System (INIS)

    Vidal, M.; Pouclet, A.; Delor, C.; Simeon, Y.; Alric, G.

    1996-01-01

    The litho-structural features of Palaeo-proterozoic terrains of northeastern Ivory-Coast, greenstones belts and then sedimentary basin Birimian), are similar to those of Archaean terrains. Their early deformation is only voluminal deformation due to granitoid intrusions, mainly between 2.2 and 2.16 Ga. The shortening deformation (main deformation) is expressed by right folds and transcurrent shear zones ca 2.1 Ga. Neither thrust deformation nor high pressure metamorphic assemblages are known. This pattern of flexible and hot crust, at least between 2.2 and 2.16 Ga, is pole apart to a collisional pattern, proposed for West African Craton by some authors. The Archaean/Palaeo-proterozoic boundary would not represent a drastic change of the geodynamic evolution of the crust. (authors). 60 refs., 5 figs., 6 photos

  15. A-type granitoid in Hasansalaran complex, northwestern Iran: Evidence for extensional tectonic regime in northern Gondwana in the Late Paleozoic

    Science.gov (United States)

    Azizi, Hossein; Kazemi, Tahmineh; Asahara, Yoshihiro

    2017-07-01

    The Hasansalaran plutonic complex is one of the main intrusive bodies with a wide range of granite, monzonite, diorite and syenite that crop out in northwest Iran. This body includes Paleozoic granitoids that are surrounded and cut by Cretaceous granitoids. Zircon U-Pb age dating shows that the crystallization of this body occurred at 360 Ma ago in the Early Carboniferous. Whole rock compositions of the investigated intrusive body, show high contents of Ga (11.1-76.3 ppm), Zr (73.5-1280 ppm), Zn (43.7-358 ppm), Y(17.9-177 ppm), enrichment of rare earth elements (REEs) together with high Ga/Al ratios and a strong Eu negative anomaly, fairly consistent with typical A-type signature. The low εNd(t = 360 Ma) value (model for evolution of northwest Iran in the Late Paleozoic. Based on our model, the upwelling of a mantle plume, probably due to the proto-Tethys oceanic rollback activity beneath northern Gondwana, had a crucial role in the uplifting of the continental crust and resulted in the crystallization of A-type granitoids with some gabbroic rocks in northwest Iran.

  16. The evolutionary characteristics and study of uranium mineralization conditions of early precambrian basement and old granitoids in Northern Hebei province of China

    International Nuclear Information System (INIS)

    Xia Yuliang; Rong Jiashu; Lin Jinrong; Zheng Maogong; Wen Xiyuan

    1993-05-01

    Based on the systematic studies of petrology, geochemistry and isotope geochronology, the Early Precambrian metamorphic complex in Northern Hebei province of China can be divided into three different series, i.e. granulite series, khondalite series and amphibolitic-felsic rock series. The so called 'magmatic granitoids' in that area are actually some magmagranites with different ages and different geneses, and they are not formed by migmatization. Up to now, the discovered Huaian complex which was formed in 3.5 Ga ago is the oldest nuclear area in the northern margin of North-China Platform. The granulite series, khondalite series and amphibolitic-felsic rock series belong to Early Archaean (>3.0 +- 0.1 Ga), Middle Archaean (>2.7 +- 0.1 Ga) and Later Archaean (>2.4 +- 0.1 Ga) respectively. The geological time scale of the Early Precambrian for Northern Hebei Province has been built. According to the synthetic analyses of various factors there is no prospect of uranium mineralization in the ancient terrain. However, the Mesozoic volcanic basins covering over the Hercynian Period granites would be main goal for looking for large uranium deposits in north part in that area

  17. Oxidation state inherited from the magma source and implications for mineralization: Late Jurassic to Early Cretaceous granitoids, Central Lhasa subterrane, Tibet

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    Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; McInnes, Brent I. A.; Li, JinXiang; Zhao, JunXing

    2018-03-01

    Arc magmas are more oxidized than mid-ocean ridge basalts; however, there is continuing debate as to whether this higher oxidation state is inherited from the source magma or developed during late-stage magmatic differentiation processes. Well-constrained Late Jurassic to Early Cretaceous arc-related intermediate to felsic rocks derived from distinct magma sources provide us with a good opportunity to resolve this enigma. A series of granitoids from the western Central Lhasa subterrane were analyzed for whole-rock magnetic susceptibility, Fe2O3/FeO ratios, and trace elements in zircon. Compared to Late Jurassic samples (1.8 ± 2.0 × 10-4 emu g-1 oe-1, Fe3+/Fetotal = 0.32 ± 0.07, zircon Ce4+/Ce3+* = 15.0 ± 13.4), Early Cretaceous rocks show higher whole-rock magnetic susceptibility (5.8 ± 2.5 × 10-4 emu g-1 oe-1), Fe3+/Fetotal ratios (0.43 ± 0.04), and zircon Ce4+/Ce3+* values (23.9 ± 22.3). In addition, positive correlations among whole-rock magnetic susceptibility, Fe3+/Fetotal ratios, and zircon Ce4+/Ce3+* reveal a slight increase in oxidation state from fO2 = QFM to NNO in the Late Jurassic to fO2 = ˜NNO in the Early Cretaceous. Obvious linear correlation between oxidation indices (whole-rock magnetic susceptibility, zircon Ce4+/Ce3+*) and source signatures (zircon ɛHf(t), TDM C ages) indicates that the oxidation state was predominantly inherited from the source with only a minor contribution from magmatic differentiation. Thus, the sources for both the Late Jurassic and Early Cretaceous rocks were probably influenced by mantle wedge-derived magma, contributing to the increased fO2. Compared to ore-forming rocks at giant porphyry Cu deposits, the relatively low oxidation state (QFM to NNO) and negative ɛHf(t) (-16 to 0) of the studied granitoids implies relative infertility. However, this study demonstrates two potential fast and effective indices ( fO2 and ɛHf(t)) to evaluate the fertility of granitoids for porphyry-style mineralization. In an

  18. Melting of subducted continental crust: Geochemical evidence from Mesozoic granitoids in the Dabie-Sulu orogenic belt, east-central China

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    Zhao, Zi-Fu; Liu, Zhi-Bin; Chen, Qi

    2017-09-01

    Syn-collisional and postcollisional granitoids are common in collisional orogens, and they were primarily produced by partial melting of subducted continental crust. This is exemplified by Mesozoic granitoids from the Dabie-Sulu orogenic belt in east-central China. These granitoids were emplaced in small volumes in the Late Triassic (200-206 Ma) and the Late Jurassic (146-167 Ma) but massively in the Early Cretaceous (111-143 Ma). Nevertheless, all of them exhibit arc-like trace element distribution patterns and are enriched in Sr-Nd-Hf isotope compositions, indicating their origination from the ancient continental crust. They commonly contain relict zircons with Neoproterozoic and Triassic U-Pb ages, respectively, consistent with the protolith and metamorphic ages for ultrahigh-pressure (UHP) metaigneous rocks in the Dabie-Sulu orogenic belt. Some granitoids show low zircon δ18O values, and SIMS in-situ O isotope analysis reveals that the relict zircons with Neoproterozoic and Triassic U-Pb ages also commonly exhibit low δ18O values. Neoproterozoic U-Pb ages and low δ18O values are the two diagnostic features that distinguish the subducted South China Block from the obducted North China Block. Thus, the magma source of these Mesozoic granitoids has a genetic link to the subducted continental crust of the South China Block. On the other hand, these granitoids contain relict zircons with Paleoproterozoic and Archean U-Pb ages, which are present in both the South and North China Blocks. Taken together, the Mesozoic granitoids in the Dabie-Sulu orogenic belt and its hanging wall have their magma sources that are predominated by the continental crust of the South China Block with minor contributions from the continental crust of the North China Block. The Triassic continental collision between the South and North China Blocks brought the continental crust into the thickened orogen, where they underwent the three episodes of partial melting in the Late Triassic, Late

  19. Pine creek geosyncline

    International Nuclear Information System (INIS)

    Needham, R.S.; Ewers, G.R.; Ferguson, J.

    1988-01-01

    The Pine Creek Geosyncline is a 66,000 km 2 inlier of Early Proterozoic metasediments, mafic and felsic intrusives and minor extrusives, surrounding small late Archaean granitic domes. Economic uranium occurrences cluster into three fields, with the Alligator Rivers field being the most significant. The metasediments are alluvial and reduced shallow-water pelites and psammites. Evaporitic carbonate developed on shallow shelves around Archaean islands. Basin development and sedimentation (c. 2000-1870 Ma) were related to gradual subsidence induced by crustal extension. Facies variations and volcanism were in places controlled by the extensional faults. The rocks were metamorphosed to lower the high grade, complexly folded, and intruded by numerous granitoids from c. 1870 to 1730 Ma. Late orogenic felsic volcanics accumulated in local rift systems. Middle Proterozoic sandstone was deposited on a peneplaned and deeply weathered surface from about 1650 Ma. Uranium is enriched in some Archaean and Proterozoic igneous rocks, but there is no local or regional enrichment of the metasedimentary hosts or of the unconformably overlying sandstone. There is no regional gravity, magnetic or radiometric character attributable to the region's significance as a uranium province; contrasts with surrounding sedimentary basins reflect expected differences in rock properties between a heterogeneous igneous/metamorphic region and relatively homogeneous undeformed and unmineralized sediments. Uranium-enriched Archaean and Proterozoic granitoids and felsic volcanics with labile U are likely though not exclusive source rocks. U was probably transported in oxidized low temperature solutions as uranyl complexes and precipitated in reduced, structurally controlled, low-pressure traps. All uranium occurrences are broadly classified as 'Proterozoic unconformity related'. Greatest potential for further discovery is offered in the Alligator Rivers field, where perhaps at least 3 to 5.5 times the

  20. Petrography and geochronology of the Sao Jose dos Quatro Marcos granitoids, southwestern Mato Grosso, Brazil

    International Nuclear Information System (INIS)

    Carneiro, M.A.; Ulbrich, H.H.G.J.; Kawashita, K.

    1989-01-01

    An area of about 400Km 2 was mapped in the region of Sao Jose dos Quatro Marcos, southwestern State of Mato Grosso, western Brazil. Various granitoid rocks were recognized, intrusive into basement gneisses, and mapped as two distinct units, one of massive late granitoids (mostly 3a and 3b granites) and one of foliated granitoids, with oriented mafic minerals, consisting mainly of tonalites and, to a lesser degree, of granodiorites. The sequence of intrusion is from tonalites to granodiorites to late granites. Magmatic textures are usually preserved in the rocks, with the exception of some clearly recrystallized samples. Field aspects, as well as petrography and mineralogy, suggest a genetic relationship between the various granitoid types, showing overall features commonly cited as typical of 'I' lineages. A Rb/Sr whole-rock isochron obtained from 3b granites (six points) shows an age of 1,472 +- 19 Ma, and Sr 87 86 initial ratio of 0.7037 +- 0.0004; a nine point isochron (adding two tonalites and one granodiorite) yelds similar results (age of 1,505 +- 20 Ma, initial ratio of 0.7029+- 0.0003). The obtained ages confirm the existence of a thermal-magmatic event at about 1,500 Ma at the southern border of the Amazon Craton. (author) [pt

  1. Age of granitoids from the Kohut Veporic zone according to Rb-Sr isochrone analysis

    International Nuclear Information System (INIS)

    Cambel, B.; Bagdasaryan, G.P.; Gukasyan, R.K.; Dupej, J.

    1988-01-01

    Rb-Sr isochrone analyses of granitoid rocks from the southern part of the Veporic zone - the so-called Kohut zone - are presented. In this region, the Sinec (Rimavica) type of granitoids formerly considered to be Late Palaeozoic to Neoide, is found. The present isochrone research determines them as equivalents of granitoids of the Sihla type (387±27 m.y.). The Sinec (Rimavica) granite reaches an age of 392±5 m.y. This extended age must partly be attributed to additional processes which took place in the stage of retrograde alterations. The conclusions are of considerable importance in clarifying the metamorphic age and stratigraphy of the crystalline complex in the region of the southern Veporic zone. (author). 9 figs., 4 tabs., 38 refs

  2. Early tectonic history of the Marymia Inlier and correlation with the Archaean Yilgarn Craton, Western Australia

    International Nuclear Information System (INIS)

    Bagas, L.

    1999-01-01

    The Archaean granite-greenstone rocks of the Marymia Inlier outcrop within Proterozoic rocks forming the Capricorn Orogen. Five major deformation events are recognised in the rocks of the Plutonic Well and Baumgarten greenstone belts. The first two events were Late Archaean and synchronous with major epithermal gold mineralisation in the belts. Palaeoproterozoic extensional faulting was probably related to the early stages of the Capricorn Orogeny. The fourth event records a compressional phase of the Capricorn Orogeny associated with greenschist-facies metamorphism, whereas the last major event involved wrench faulting associated with minor folding. The Archaean tectonic history, rock types and timing of mineralisation strongly suggest that the Marymia Inlier is part of the Yilgarn Craton, and that each of the provinces in the craton experienced the same geological history since 2.72 Ga. The inlier is now interpreted to include two components, one is the eastern or northern extension of either the Narryer Terrane. Murchison Province or Southern Cross Province, and the other is the northwestern extension of the Eastern Goldfields Province. The Jenkin Fault, which was active in Proterozoic times, separates these two components. Copyright (1999) Blackwell Science Pty Ltd

  3. INTERACTIONS BETWEEN GABBROID AND GRANITOID MAGMAS DURING FORMATION OF THE PREOBRAZHENSKY INTRUSION, EAST KAZAKHSTAN

    Directory of Open Access Journals (Sweden)

    S. V. Khromykh

    2017-01-01

    Full Text Available The paper reports on studies of the Preobrazhensky gabbro‐granitoid intrusion, East Kazakhstan, com‐ posed of the rocks that belong to four phases of intrusion, from quartz monzonites and gabbroids to granite‐ leucogranites. Specific relationships between basite and granitoid rocks are usually classified as the result of interac‐ tions and mixing of liquid magmas, i.e. magma mingling and mixing. Basite rocks are represented by a series from biotite gabbros to monzodiorites. Granitoids rocks are biotite‐amphibole granites. Porphyric granosyenites, com‐ bining the features of both granites and monzodiorites, are also involved in mingling. It is established that the primary granitoid magmas contained granosyenite/quartz‐monzonite and occurred in the lower‐medium‐crust conditions in equilibrium with the garnet‐rich restite enriched with plagioclase. Monzodiorites formed during fractionation of the parent gabbroid magma that originated from the enriched mantle source. We propose a magma interaction model describing penetration of the basite magma into the lower horizons of the granitoid source, which ceased below the viscoplastic horizon of granitoids. The initial interaction assumes the thermal effect of basites on the almost crystal‐ lized granitic magma and saturation of the boundary horizons of the basite magma with volatile elements, which can change the composition of the crystallizing melt from gabbroid to monzodiorite. A ‘boundary’ layer of monzodiorite melt is formed at the boundary of the gabbroid and granitoid magmas, and interacts with granitoids. Due to chemical interactions, hybrid rocks – porphyric granosyenites – are formed. The heterogeneous mixture of monzodiorites and granosyenites is more mobile in comparison with the overlying almost crystallized granites. Due to contraction frac‐ turing in the crystallized granites, the heterogeneous mixture of monzodiorites and granosyenites penetrate into the

  4. Fossil Microorganisms in Archaean deposits of Northern Karelia

    Science.gov (United States)

    Astafieva, M. M.; Hoover, R. B.; Rozanov, A. Y.; Vrevskiy, A. B.

    2005-01-01

    Newly found biomorphic microstructures from the Upper Archaean (lopian) rocks from Northern Karelia are described. The presence of various microorganisms of bacterial nature and even cyanobacteria (and possibly eukaryotic forms) is suggested. The necessity of employing methods of electron microscopy, as well as traditional methods, while studying the very early manifestations of life in Archaean and Early Proterozoic is noted.

  5. The W (Sn-Mo)-specialized catinga suite and other granitoids of the Brusque Group, neo proterozoic of the state of Santa Catarina, Southern Brazil

    International Nuclear Information System (INIS)

    Castro, Neivaldo Araujo de; Crosta, Alvaro Penteado; Basei, Miguel Angelo Stipp

    1999-01-01

    The petrographic, geochemical and isotopic data on the granitoids intrusive in the Brusque Group, State of Santa Catarina, southern Brazil, are presented in this paper. These are late-to post-tectonic rocks, being the most evolved ones those that constitute the Catinga Suite. The granitoids intrusive in the southern domain of the Brusque Group are grayish rocks, in which biotite (when present) is practically the only mafic mineral. They are rather reduced, slightly alkalic, transitional between meta-and peraluminous. An acid subvolcanic pluton, the Ribeirao da Velha pluton, has similar petrographic and geochemical characteristics, and seems to be genetically related to these granitoids. LREE fractionation relative to HREE is incipient for the Catinga suite, and the REE patterns showing strong negative Eu anomaly. Initial 87 Sr/ 86 Sr ratios, from the literature for these granitoids are around 0.721 (Sao Joao Batista granitoid) and the only available t DM model age (Valsungana granitoid) points to a genesis from a continental crust of ca. 2020 Ma old. Gneiss-migmatitic rocks such as those that occur in the eastern portion of Brusque Group domain and as enclaves in the Nova Italia granitoid are strong candidates for protoliths of these granitoids. Little available information on the granitoids intrusive in the northern domain of the Brusque Group reports the presence of pink K-feldspar hornblende granitoids (Faxinal pluton) and light pink K-feldspar biotite granitoid (Guabiruba pluton). These granitoids are more enriched in K and more oxidized than those in the southern domain, and the LREE fractionation relative to HREE is strong, with the REE patterns showing incipient negative Eu anomaly. It is suggested that part of the Au concentrations found in the northern domain may be genetically associated with the granitoids, since they present characteristics favorable to promote Au mineralizations than the granitoids in the southern domain. Distinct protoliths and

  6. Late Archaean-early Proterozoic source ages of zircons in rocks from the Paleozoic orogen of western Galicia, NW Spain

    Energy Technology Data Exchange (ETDEWEB)

    Kuijper, R P; Priem, H N.A. [Laboratorium voor Isotopen-Geologie, Amsterdam (Netherlands); Den Tex, E [Rijksuniversiteit Utrecht (Netherlands). Inst. voor Aardwetenschappen

    1982-08-01

    U-Pb data are reported for nine suites of zircons and three monazites from the Paleozoic orogen in western Galicia: one paragneiss and six orthogneisses from the early Paleozoic basement, and two Carboniferous (ca. 310 Ma old) intrusions of two-mica granite. New whole-rock Rb-Sr analyses, along with earlier data, indicate an age of ca. 470-440 Ma (Ordovician) for the emplacement of the granitic precursors of the orthogneisses. Monazite from the paragneiss also yields an U-Pb age of ca. 470 Ma. From the high initial /sup 87/Sr//sup 86/Sr ratios an involvement of Precambrian continental crust material is evident in the generation of the early Paleozoic suite of granites, while the zircon U-Pb data give evidence of the presence of about 3.0-2.0 Ga old (late Archaean-early Proterozoic) components in the source material. Zircons from the oldest sedimentary rocks in the area, now present as catazonal paragneisses and a likely source for the granites, likewise reveal a provenance age of 3.0-2.0 Ga.

  7. Rb-Sr isochronous age of Vepor pluton granitoids

    International Nuclear Information System (INIS)

    Bagdasaryan, G.P.; Gykasyan, R.Kh.; Cambel, B.

    1986-01-01

    The result are presented of geochronological investigations of the Vepor pluton granitoids by the Rb-Sr isochronous method. The results prove the Variscan age of granodiorite magmatism of the Sihla type (387±27 m.y.) and the Early Variscan age of leucocratic granitoids of the Vepor and the Ipel types (284±22 m.y.). Since the initial ratio of 87 Sr/ 86 Sr in granitoids of the Sihla type is 0.7054 and of the Vepor type 0.7060, it can be assumed that during the formation of the granitoids of veporides there was an increased supply of matter from the main source affecting genesis of granitoids. The results prove a polyphase character of the Variscan granitoids of Veporicum. (author)

  8. The distribution of radioelements in archaean granites of the Kaapvaal Craton, with implications for the source of uranium in the Witwatersrand Basin

    International Nuclear Information System (INIS)

    Robb, L.J.; Meyer, M.; Ferraz, M.F.; Drennan, G.R.

    1989-05-01

    Approximately 500 samples from the Archaean granitic basement of the southern Kaapvaal Craton have been analysed, for U and Th. When viewed in conjunction with geological relationships, the radioelement distribution patterns in the Archaean basement provide contraints regarding the origin of uranium in the Witwatersrand Basin. Granites in the Baberton region are sub-divided into three magnetic cycles, the earliest cycle comprising tonalite-trondhjemite gneisses, the intermediate cycle comprising literally extensive K-rich batholiths and the final stage consisting of discrete intrusive granitic plutons. Uranium and thorium contents vary as a function of age and rock type, an increase progressively from the first cycle through to the third cycle. Certain of the late granite plutons may have been S-type in origin, have relatively low Th/U ratios, high U contents, and are characterized by accessory minerals dominated by monazite-like phases. The late granite plutons with highest radioelement contents appear to have formed circa 2,8 Ga, an age which coincides with granulite facies metamorphism and uranium-thorium depletion in the lower crust, as recrorded in the Vredeford crustal profile. Uranium has been leached from portions of the regolith profile, but also concentrated into leucoxene-rich zones derived from the breakdown of pre-existing titanium-bearing phases. The widespread development of an uraniferous leucoxene protore in weathered source rocks of the Witwatersrand Basin has relevance to the genesis of authigenic U-Ti phases (brannerite) in the reefs themselves. The study of radioelement distribution in Archaean granites adjacent to the Witwatersrand Basin provides a framework within which considerations regarding the origin of the uranium deposits in the basin can be viewed. The secular evolution of the Archaean granitic basement, hydrothermal processes, and palaeoweathering all played a role in the formation of the Witwatersrand deposits

  9. Archaean TTG of Vodlozero Terrain, Fennoscandian Shield

    Science.gov (United States)

    Chekulaev, Valery; Arestova, Natalia

    2014-05-01

    The Vodlozero terrain is the largest (about 270*240 km) early Archaean fragment of Fennoscandian Shield and composes its eastern part. The granitoids of TTG suite are predominant component of the terrain. The greenstone belts are placed along the margins of the terrain. Several stages of TTG formation can be distinguished in Achaean crust history. (1) The oldest TTG are trondhjemites and tonalities with age of 3240 Ma. They contain rare and small amphibolite inclusions of the same age. These TTG are characterized by high Sr (av. 412 ppm), Sr/Y (70), (La/Yb)n (54) and low Y (av. 7 ppm), Yb (0.32 ppm) and Nb (4 ppm). It was shown (Lobach-Zhuchenko et al., 2000), that the source of these TTG could be basic rocks, having composition similar with TH1 by K.Condie. (2) The tonalities and granodiorites with age of 3150 Ma are disposed near greenstone belts and contain compared to TTG of the first group less Sr (av. 250 ppm), Sr/Y (22), (La/Yb)n (18) and more K, Rb (av. 70 ppm), Ba (470 ppm), Y (11 ppm),Yb (1.16 ppm). TTG of both groups have identical T(DM)Nd (3250-3400 Ma) and differences in composition is evidently connected with lower level of source melting of the second group and also with K-metasomatism. The volcanics of the greenstone belts have age 3020 - 2940 Ma. Dykes of gabbro-amphibolites and andesites with the same age and composition cut TTG of the first and the second groups. The age of the third TTG group is about 2900 Ma ago. These rocks form leucosoma of migmatites within TTG of the second group. The composition of the third TTG and Nd isotope data suppose their origin by the melting of ancient TTG crust simultaneously with greenstone belt emplacement. The fourth TTG group with age 2780-2850 Ma forms a small intrusions, cutting older TTG and greenstone rocks. Their composition is similar to 3150 Ma TTG. Nd isotope data indicate that these TTG have younger (about 2850 Ma) source. Thus there are four TTG groups formed into interval more 400 Ma. The age and

  10. 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

    Directory of Open Access Journals (Sweden)

    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

  11. Cyclic formation and stabilization of Archean lithosphere by accretionary orogenesis: Constraints from TTG and potassic granitoids, North China Craton

    Science.gov (United States)

    Wang, Wei; Cawood, Peter A.; Liu, Shuwen; Guo, Rongrong; Bai, Xiang; Wang, Kang

    2017-09-01

    Accretionary orogens are major sites of modern continental growth, yet their role in the development of Archean continental crust remains enigmatic. Diverse granitoid suites from tonalite-trondhjemite-granodiorite (TTG) to potassic granitoids appeared during late Archean, representing a period of major continental formation and stabilization. In this study, whole-rock geochemical and zircon U-Pb and Lu-Hf isotopic data are reported for Neoarchean granitoid gneisses from the Northern Liaoning Terrane, northeastern North China Craton (NCC). Older granitoid gneisses ( 2592-2537 Ma) define three magmatic zones migrating from southeast to northwest, each showing a common magmatic evolution from high-pressure TTGs to medium-/low-pressure TTGs and potassic granitoids. They have depleted zircon ƐHf(t) of +0.5 to +8.7. Younger 2529-2503 Ma potassic granitoids and TTGs occur throughout the terrane, which are marked by variable zircon ƐHf(t) of -4.7 to +8.1, and are coeval with regional high-grade metamorphism. Petrogenetic modeling and changing Sr/Y and (La/Yb)N of the granitoids suggest that the crust experienced episodic thickening and thinning and became progressively evolved through development of potassic granitoids and sedimentary successions. The metavolcanic basement to the granitoids display tholeiitic to calc-alkaline affinities, together with the top-to-the-northwest thrusting and associated volcanogenic massive sulfide-type Cu-Zn deposits, suggesting cyclic crustal formation of Northern Liaoning within an accretionary orogen with a SE-dipping subduction polarity. Cyclic crustal thickening and thinning is related to tectonic switching from advancing to retreating relations between the downgoing and overriding plate. After 2530 Ma, this accretionary system accreted to the ancient continental nucleus of NCC (Anshan-Benxi Terrane), signifying final lithosphere stabilization.

  12. Zircon U-Pb ages and Hf isotopic compositions of neoarchaean granitoids from Karimnagar, Eastern Dharwar craton, Southern India: LA-ICPMS results

    International Nuclear Information System (INIS)

    Babu, E.V.S.S.K.; Vijaya Kumar, T.; Sreenivas, B.; Khadke, Namrata; Vijaya Gopal, B.; Bhaskar Rao, Y.J.

    2015-01-01

    The Archaean Dharwar and Bastar cratons of Peninsular India are separated by the NE-SW trending Godavari Graben. This zone is involved in recurrent rifting. It is generally believed that earlier phase of rifting dates back to Mesoproterozoic and the younger phase is related to the deposition of Permo-carboniferous coal-bearing sediments. A belt of high-grade rocks (∼ 150 x 45 km) - the Karimnagar granulite terrane (KGT) along the southern flank of the graben. The KGT comprises high-grade lithologies such as orthopyroxene-bearing quarto-feldspathic gneiss, amphibolite-granulite facies supracrustal belts that include metamorphosed quartz-arenites, pelites, carbonates, iron formation and mafic rocks as well as several zones of migmatite and younger granitoid intrusives. The study presented new LA-ICPMS zircon U-Pb age data for five granitoid (charnockite and granite) samples (KRN-90-24, KRN-90-30, KRN-13-02, KRN-13-03 and KRN-13-05; a closer constraint of the age crystallization of protoliths and high-grade metamorphism of felsic granulites and orthogneisses from the KGT. Hf isotopic compositions were also obtained for selected zircons from two samples (KRN-90-24 and KRN-90-30) using New Wave UP-213 Laser Ablation system coupled to Nu Plasma HR MC-ICPMS to constraint the nature of the felsic protoliths of the charnockite and granite gneisses in the KGT

  13. Deep and persistent melt layer in the Archaean mantle

    Science.gov (United States)

    Andrault, Denis; Pesce, Giacomo; Manthilake, Geeth; Monteux, Julien; Bolfan-Casanova, Nathalie; Chantel, Julien; Novella, Davide; Guignot, Nicolas; King, Andrew; Itié, Jean-Paul; Hennet, Louis

    2018-02-01

    The transition from the Archaean to the Proterozoic eon ended a period of great instability at the Earth's surface. The origin of this transition could be a change in the dynamic regime of the Earth's interior. Here we use laboratory experiments to investigate the solidus of samples representative of the Archaean upper mantle. Our two complementary in situ measurements of the melting curve reveal a solidus that is 200-250 K lower than previously reported at depths higher than about 100 km. Such a lower solidus temperature makes partial melting today easier than previously thought, particularly in the presence of volatiles (H2O and CO2). A lower solidus could also account for the early high production of melts such as komatiites. For an Archaean mantle that was 200-300 K hotter than today, significant melting is expected at depths from 100-150 km to more than 400 km. Thus, a persistent layer of melt may have existed in the Archaean upper mantle. This shell of molten material may have progressively disappeared because of secular cooling of the mantle. Crystallization would have increased the upper mantle viscosity and could have enhanced mechanical coupling between the lithosphere and the asthenosphere. Such a change might explain the transition from surface dynamics dominated by a stagnant lid on the early Earth to modern-like plate tectonics with deep slab subduction.

  14. First record of 1.2 Ga quartz dioritic magmatism in the Archaean Yilgarn Craton, Western Australia, and its significance

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Y.; McNaughton, N.J.; Groves, D.I.; Dunphy, J.M. [University of Western Australia, Nedlands, WA (Australia). Centre for Strategic Mineral Deposits, Department of Geology and Geophysics

    1999-06-01

    Ion microprobe (SHRIMP) U-Pb zircon dating. Pb-Nd isotope tracer studies and major, trace and rare-earth element analyses have identified, for the first time. a Mesoproterozoic (1.2 Ga) quartz diorite intrusion in the central part of the Archaean Yilgarn Craton. Western Australia The quartz diorite is characterised by intergrowths of quartz and plagioclase, having low A/CNK (0 8). low K{sub 2}O (0.28 wt%), Ba (54 ppm), Rb (11 ppm), Sr (92 ppm), Pb (13 ppm), U (1.7 ppm) and Th (6 ppm) contents, high Nd (41 ppm), Sm (10.5 ppm), Zr (399 ppm). Nb (18.5 ppm). Y (57.5 ppm) and Sc (19 ppm) contents. a low Pb isotope two-stage model {mu} value (6.3), and a primitive initial e{sub Nd} value (+3.4) at 1.2 Ga. It is interpreted that the 1.2 Ga quartz diorite was derived from a predominantly mantle source, with minor crustal contamination, possibly from the surrounding Archaean monzogranites or their source region, during magma ascent. The age (1215 {+-} 11 Ma) of the intrusion overlaps with the timing of a major continental collisional orogeny in the Albany-Fraser Orogen, about 400km south, and is broadly coeval with the diamond-bearing Argyle lamproites in the east Kimberley Block. This study extends the history of granitoid magmatism in the central craton by more than 1.0 billion years (2.6 to 1.2 Ga), and has implications for isotopic data interpretations of tectonothermal events in the craton. Copyright (1999) Blackwell Science Pty Ltd 33 refs., 3 tabs., 6 figs.

  15. Crustal melting and recycling: geochronology and sources of Variscan syn-kinematic anatectic granitoids of the Tormes Dome (Central Iberian Zone). A U-Pb LA-ICP-MS study

    Science.gov (United States)

    López-Moro, F. J.; López-Plaza, M.; Gutiérrez-Alonso, G.; Fernández-Suárez, J.; López-Carmona, A.; Hofmann, M.; Romer, R. L.

    2018-04-01

    In this study, we report U-Pb Laser Ablation ICP-MS zircon and ID-TIMS monazite ages for peraluminous granitoid plutons (biotite ± muscovite ± cordierite ± sillimanite) in the Tormes Dome, one of the gneiss-cored domes located in the Central Iberian Zone of the Variscan belt of northern Spain. Textural domains in zircon, interpreted to represent the magmatic crystallization of the granitoids (and one monazite fraction in the Ledesma pluton) yielded ages around 320 Ma, in agreement with other geochronological studies in the region. This age is interpreted to date the timing of decompression crustal melting driven by the extensional collapse of the orogenic belt in this domain of the Variscan chain of western Europe. In addition, there are several populations of inherited (xenocrystic) zircon: (1) Carboniferous zircon crystals (ca. 345 Ma) as well as one of the monazite fractions in the coarse-grained facies of the Ledesma pluton that also yielded an age of ca. 343 Ma. (2) Devonian-Silurian zircon xenocrysts with scattered ages between ca. 390 and 432 Ma. (3) Middle Cambrian-Ordovician (ca. 450-511 Ma). (4) Ediacaran-Cryogenian zircon ages (ca. 540-840 Ma). (5) Mesoproterozoic to Archaean zircon (900-2700 Ma). The abundance of Carboniferous-inherited zircon shows that crustal recycling/cannibalization may often happen at a fast pace in orogenic scenarios with only short lapses of quiescence. In our case study, it seems plausible that a "crustal layer" of ca. 340 Ma granitoids/migmatites was recycled, partially or totally, only 15-20 My after its emplacement.

  16. Gold contents of sulfide minerals in granitoids from southwestern New Brunswick, Canada

    Science.gov (United States)

    Yang, Xue-Ming; Lentz, David R.; Sylvester, Paul J.

    2006-07-01

    The abundance of gold and selected trace elements in magmatic sulfide and rock-forming minerals from Silurian-Devonian granitoids in southwestern New Brunswick were quantitatively analyzed by laser-ablation inductively coupled plasma mass-spectrometry. Gold is mainly hosted in sulfide minerals (i.e., chalcopyrite, pyrrhotite, and pyrite), in some cases perhaps as submicron inclusions (nanonuggets). Gold is below detection (caca % qGTbGaaeyzaiaabYgacaqG0baaaOGaeyypa0JaaGymaiaaiwdacaaI % WaGaeyySaeRaaGioaiaaiodacaGGSaGaaeiiaiaabggacaqGUbGaae % izaiaabccacaWGebWaa0baaSqaaiaabgeacaqG1baabaGaaeiCaiaa % bMhacaqGVaGaaeyBaiaabwgacaqGSbGaaeiDaaaakiabg2da9iaaio % dacaaI2aGaaGOmaiabgglaXkaaiMdacaaI2aaaaa!6E8F! D^{{{text{cpy/melt}}}}_{{{text{Au}}}}= 948 ± 269,{text{ }}D^{{{text{po/melt}}}}_{{{text{Au}}}} = 150 ± 83,{text{ and }}D^{{{text{py/melt}}}}_{{{text{Au}}}} = 362 ± 96. This result suggests that gold behavior in the granitoid systems is controlled by the conditions of sulfur saturation during magmatic evolution; the threshold of physiochemical conditions for sulfur saturation in the melts is a key factor affecting gold activity. Gold behaves incompatibly prior to the formation of sulfide liquids or minerals, but it becomes compatible at their appearance. Gold would be enriched in sulfur-undersaturated granitoid magmas during fractionation, partitioning into evolved magmatic fluids and favoring the formation of intrusion-related gold deposits. However, gold becomes depleted in residual melts if these melts become sulfur-saturated during differentiation, leading to gold precipitation in the early sulfide phases of a granitoid suite. Late-stage Cl-bearing magmatic-hydrothermal fluids with low pH and relatively high oxidation state derived from either progressively cooling magmas at depth or convective circulation of meteoric water buffered by reduced carbon-bearing sediments, may scavenge gold from early sulfide minerals. If a significant amount of gold produced in this

  17. Salinity of the Archaean oceans from analysis of fluid inclusions in quartz

    Science.gov (United States)

    Marty, Bernard; Avice, Guillaume; Bekaert, David V.; Broadley, Michael W.

    2018-05-01

    Fluids trapped in inclusions in well-characterized Archaean hydrothermal quartz crystals were analyzed by the extended argon-argon method, which permits the simultaneous measurement of chlorine and potassium concentrations. Argon and nitrogen isotopic compositions of the trapped fluids were also determined by static mass spectrometry. Fluids were extracted by stepwise crushing of quartz samples from North Pole (NW Australia) and Barberton (South Africa) 3.5-3.0-Ga-old greenstone belts. The data indicate that fluids are a mixture of a low salinity end-member, regarded as the Archaean oceanic water, and several hydrothermal end-members rich in Cl, K, N, and radiogenic parentless 40Ar. The low Cl-K end-member suggests that the salinity of the Archaean oceans was comparable to the modern one, and that the potassium content of the Archaean oceans was lower than at present by about 40%. A constant salinity of the oceans through time has important implications for the stabilization of the continental crust and for the habitability of the ancient Earth.

  18. Granites and granitoids of the southern region - Granite molybdenite system

    International Nuclear Information System (INIS)

    Issler, R.S.

    1987-01-01

    Economic concentrations of molybdenum are genetically closely associated with acidic and moderately acid granitoids-granites, granodiorites, monzonites and diorites, and are located in two geotectonic settings: subduction-related and rift-related. The aim of this paper is twofold, first succinctly approach the geology, tectonic setting and chemical parameters of the 'granite molybdenite system' as defined by Mutschler and/or alcali granite porphyry bodies emplaced in the North American continent for occasion of a Mesozoic-Fanerozoic extensile event; second to relate the computer-assisted evaluation of 422 major element chemical analysis of granites and granitoids of southern region of Brazil, using chemical fingerprints (SiO 2 ≥ 74. Owt%, Na 2 O ≤ 3.6wt%, K 2 O ≥ 4.5wt%), and K 2 O/Na 2 O ratio > 1.5 developed and testified from North American and Finnish occurrences, may locate molybdenite-bearing granite bodies with high exploration potential. These techniques suggest that some late Precambrian to early Paleozoic granite-rhyolite assemblages inserted at domains of the SG. 22/23 Curitiba/Iguape, SH. 21/22 Uruguaiana/Porto Alegre and SI.22 Lagoa Mirim Sheets, have exploration potential for molybdenum. (author) [pt

  19. Petrotectonic framework of granitoids and associated granulites at ...

    Indian Academy of Sciences (India)

    tion that wraps around the feldspar augen. The sheared granitoid ..... 1987) has been used to classify the granitoids ... The data for all the analyses used in the diagrams are given in table 1. ..... Different stages of crystal-plastic deformation are.

  20. Emplacement, petrological and magnetic susceptibility characteristics of diverse magmatic epidote-bearing granitoid rocks in Brazil, Argentina and Chile

    Science.gov (United States)

    Sial, A. N.; Toselli, A. J.; Saavedra, J.; Parada, M. A.; Ferreira, V. P.

    1999-03-01

    Magmatic epidote (mEp)-bearing granitoids from five Neoproterozoic tectonostratigraphic terranes in Northeastern (NE) Brazil, Early Palaeozoic calc-alkalic granitoids in Northwestern (NW) Argentina and from three batholiths in Chile have been studied. The elongated shape of some of these plutons suggests that magmas filled fractures and that dyking was probably the major mechanism of emplacement. Textures reveal that, in many cases, epidote underwent partial dissolution by host magma and, in these cases, may have survived dissolution by relatively rapid upward transport by the host magma. In plutons where such a mechanism is not evident, unevenly distributed epidote at outcrop scale is armoured by biotite or near-solidus K-feldspar aggregates, which probably grew much faster than epidote dissolution, preventing complete resorption of epidote by the melt. Al-in-hornblende barometry indicates that, in most cases, amphibole crystallized at P≥5 kbar. Kyanite-bearing thermal aureoles surrounding plutons that intruded low-grade metamorphic rocks in NE Brazil support pluton emplacement at intermediate to high pressure. mEp show overall chemical variation from 20 to 30 mol% (mole percent) pistacite (Ps) and can be grouped into two compositional ranges: Ps 20-24 and Ps 27-30. The highest Ps contents are in epidotes of plutons in which hornblende solidified under Pcorrosion of individual epidote crystals included in plagioclase in high-K calc-alkalic granitoids in NE Brazil, emplaced at 5-7 kbar pressure, yielded estimates of magma transport rate from 70 to 350 m year -1. Most of these plutons lack Fe-Ti oxide minerals and Fe +3 is mostly associated with the epidote structure. Consequently, magnetic susceptibility (MS) in the Neoproterozoic granitoids in NE Brazil, as well as Early Palaeozoic plutons in Argentina and Late Palaeozoic plutons in Chile, is usually low (3.0×10 -3 SI, typical of magnetite-series granitoids crystallized under higher oxygen fugacity. In NE

  1. Pre- and syn-Ross orogenic granitoids at Drake Head and Kartografov Island, Oates Coast, northern Victoria Land, East Antarctica

    International Nuclear Information System (INIS)

    Adams, C.J.; Roland, N.W.

    2002-01-01

    The majority of the Oates Coast, northern Victoria Land granitoids, typified by those at Drake Head and Kartografov Island (Harald Bay), are monzogranites with lesser granodiorites and minor quartz-monzodiorite and syenogranite. All are plagioclase-K-feldspar-biotite granitoids with additional muscovite, garnet and/or hornblende, and are subalkaline and peraluminous. Berg Granite typifies the early Ordovician, Granite Harbour Instrusive (GHI) suite of the Ross Orogen at the Oates Coast. Granitoids from Kartografov Island have higher amounts of Fe+Mg+Ti and an ambiguous Rb-Sr geochronology: they could be either pre-Ross Orogeny in age, or syn-Ross Orogeny and representing a lower structural level of GHI. The Drake Head granite gneiss has a fractionated leuco-granite composition similar to Berg Granite, and is intruded by granite and granodiorite. Rb-Sr ages indicate that all are Neoproterozoic, although the granite gneiss result is probably an errorchron age, reflecting its less uniform nature (granodiorite:649 ± 30 Ma, initial ratio 0.7065 +/- 6; granite gneiss: 682 ± 140 Ma, initial ratio 0.7107 ± 50). These late Neoproterozoic granitoids provide a source for distinctive detrital zircon age components in extensive early Paleozoic turbidites of Australia-New Zealand-Antarctica. (author). 24 refs., 5 figs., 1 tab

  2. Highly refractory Archaean peridotite cumulates: Petrology and geochemistry of the Seqi Ultramafic Complex, SW Greenland

    Directory of Open Access Journals (Sweden)

    Kristoffer Szilas

    2018-05-01

    Full Text Available This paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma for the Seqi Ultramafic Complex. The Seqi rocks represent a broad range of olivine-dominated plutonic rocks with varying modal amounts of chromite, orthopyroxene and amphibole, i.e. various types of dunite (s.s., peridotite (s.l., as well as chromitite. The Seqi Ultramafic Complex is characterised primarily by refractory dunite, with highly forsteritic olivine with core compositions having Mg# ranging from about 91 to 93. The overall high modal contents, as well as the specific compositions, of chromite rule out that these rocks represent a fragment of Earth's mantle. The occurrence of stratiform chromitite bands in peridotite, thin chromite layers in dunite and poikilitic orthopyroxene in peridotite instead supports the interpretation that the Seqi Ultramafic Complex represents the remnant of a fragmented layered complex or a magma conduit, which was subsequently broken up and entrained during the formation of the regional continental crust.Integrating all of the characteristics of the Seqi Ultramafic Complex points to formation of these highly refractory peridotites from an extremely magnesian (Mg# ∼ 80, near-anhydrous magma, as olivine-dominated cumulates with high modal contents of chromite. It is noted that the Seqi cumulates were derived from a mantle source by extreme degrees of partial melting (>40%. This mantle source could potentially represent the precursor for the sub-continental lithospheric mantle (SCLM in this region, which has previously been shown to be ultra-depleted. The Seqi Ultramafic Complex, as well as similar peridotite bodies in the Fiskefjord region, may thus constitute the earliest cumulates that formed during the

  3. Ar-Ar dating and petrogenesis of the Early Miocene Taşkapı-Mecitli (Erciş-Van) granitoid, Eastern Anatolia Collisional Zone, Turkey

    Science.gov (United States)

    Oyan, Vural

    2018-06-01

    The Early Miocene Taşkapı-Mecitli granitoid that is located in the northern section of the Eastern Anatolia Collision Zone has typical I-type, metaluminous and calk-alkaline characteristics. It also contains mafic microgranular / magmatic enclaves (MMEs). New Ar-Ar dating results show that the age of the Taşkapı-Mecitli granitoid is ∼23 Ma and it crystallised in the Early Miocene, in contrast to its previously known Cretaceous age. Identical crystallisation ages (∼23 Ma), similar mineral assemblages and geochemical compositions, and indistinguishable isotopic compositions of MMEs and host rocks imply that the MMEs are most consistent with a cumulate origin formed at earlier stages of the same magmatic system that produced the Taşkapı-Mecitli granitoid. MELTS modelling suggests that magma of the Taşkapı-Mecitli granitoid was the result of fractionation under a crustal pressure of 4 kbar, with a H2O content of 1.5%. EC-AFC model calculation reveals that the Taşkapı-Mecitli granitoid includes from 0.5% to 2% crustal assimilation rates. These rates indicate that crustal contamination can be negligible when compared to fractional crystallisation in the evolution of the magma beneath the Taşkapı-Mecitli granitoid. The partial melting model calculations and MORB-normalised trace element concentrations of the least evolved samples of the Taşkapı-Mecitli granitoid are consistent with those of mafic melts obtained from partial melting of interacting mantle- lower crust with a melting degree of 18%. The age (23 Ma) of the post- or syn-collisional Taşkapı-Mecitli granitoid suggests that the collision between Arabian and Eurasian plates could be before/around ∼23 Ma (Late Oligocene to Early Miocene).

  4. Trace element characteristics of mafic and ultramafic meta-igneous rocks from the 3.5 Ga. Warrawoona group: evidence for plume-lithosphere interaction beneath Archaean continental crust

    International Nuclear Information System (INIS)

    Bolhar, R.; Hergt, J.; Woodhead, J.

    1999-01-01

    Full text: Magnesian- to Fe-rich tholeiitic basalts represent the dominant lithology in the Marble Bar Greenstone Belt, E-Pilbara Craton, and are locally associated with komatiitic basalts and rare komatiitic cumulates. Based on trace element characteristics, the extrusive and intrusive rocks from all three major stratigraphic units can be subdivided into LREE enriched and unfractionated to weakly LREE depleted groups. The former group is characterized by La/Sm pm = 1.7-4.6, Gd/Yb pm = 1.23.2 and Nb/Th pm 0.1-0.5, while the latter rocks possess ratios of La/Sm pm = 0.5-1.7, Gd/Yb pm = 0.8-1.9 and Nb/Th pm = 0.4-1.3. Nb/La -Nb/Th relationships in the LREE enriched samples indicate 7-28% contamination by crustal material similar in composition to Pilbara granitoids. LREE enrichment and strong negative HFSE anomalies, along with MgO = 2.2-22.0 wt% and SiO 2 = 39.2-63.5 wt%, have been observed in numerous Archaean greenstone belts, and can be successfully modeled in this study by AFC processes. In contrast, strong HFSE depletion combined with unfractionated to slightly depleted LREE in rocks of the latter group require different processes. Melting of mantle material previously depleted by melt extraction, enrichment of LILE and LREE relative to the HFSE in an arc-like environment and HFSE fractionation as a result of garnet retention in the melting source cannot account for negative Nb, Ta, Ti, P and strong positive Pb anomalies. Introduction of small amounts of crustal material into a depleted or primitive mantle, as possibly indicated by Nb/Ta ratios between 12 and 18, also fails to reproduce the trace element abundances of the second group of rocks. Recycling of oceanic crust previously processed through a subduction zone (low Th/Nb, La/Nb) and sub-arc lithospheric mantle (high Th/Nb, La/Nb), and subsequent mixing into the Archaean mantle has been recently invoked by several workers (e.g. Kerrich et al., EPSL, 168, 101-115; 1999) to explain the origin of

  5. Effect of thicker oceanic crust in the Archaean on the growth of continental crust through time

    International Nuclear Information System (INIS)

    Wilks, M.E.

    1988-01-01

    Present crustal evolution models fail to account for the generation of the large volume of continental crust in the required time intervals. All Archaean plate tectonic models, whether invoking faster spreading rates, similar to today's spreading rates, or longer ridge lengths, essentially propose that continental crust has grown by island arc accretion due to the subduction of oceanic crust. The petrological differences that characterize the Archaean from later terrains result from the subduction of hotter oceanic crust into a hotter mantle. If the oceanic crust was appreciably thicker in the Archaean, as geothermal models would indicate, this thicker crust is surely going to have an effect on tectonic processes. A more valid approach is to compare the possible styles of convergence of thick oceanic crust with modern convergence zones. The best modern analog occurs where thick continental crust is colliding with thick continental crust. Oceanic crustal collision on the scale of the present-day Himalayan continental collision zone may have been a frequent occurrence in the Archaean, resulting in extensive partial melting of the hydrous underthrust oceanic crust to produce voluminous tonalite melts, leaving a depleted stabilized basic residuum. Present-day island arc accretion may not have been the dominant mechanism for the growth of the early Archaean crust

  6. Potassium-argon ages of two granitoids northwest of Kumasi, Ghana

    International Nuclear Information System (INIS)

    Agyei, E.K.

    1989-01-01

    Four granitic samples from two granitoids northwest of Kumasi,Ghana, have been dated using the conventional K-Ar method. Two samples NB1 NB2 from a road-cutting at Nyamebekyere village, located about 60 km from Kumasi on the Kumasi-Sunyani road gave biotite ages of 2144+/= 11 Ma and 2144+/=7 Ma, respectively. The biotite ages for two samples NTN1 and NTN2 from Kassardjan quarry, located about 3 km south of the Kumasi-Sunyani road at Ntensere village some 20 km northwest of Kumasi were 2070+/= 10 Ma and 2099+/=14 Ma, respectively. A hornblende age of 2169+/=26 Ma was obtained for NTN2 which suggests a slow cooling during the uplift of the granitoid. Although the biotite ages obtained here for the two G2 granitoids are older than most of the reported biotite ages which happen to be for G1 granites, it is too premature to generalize that G2 granitoids are older than G1 granitoids. (author). 21 refs. 1 fig. 1 tab

  7. Stable isotope composition and volume of Early Archaean oceans

    DEFF Research Database (Denmark)

    Pope, Emily Catherine; Rosing, Minik Thorleif; Bird, Dennis K.

    via biogenic methanogenesis [2]. Mass balance considerations within the Earth system places a cumulative upper limit on elemental hydrogen loss to space of ~1.8x1022mol elemental hydrogen H, constraining maximum Archaean atmospheric methane levels at ~3.8Ga to

  8. Mafic microgranular enclave swarms in the Chenar granitoid stock, NW of Kerman, Iran: evidence for magma mingling

    Science.gov (United States)

    Arvin, M.; Dargahi, S.; Babaei, A. A.

    2004-10-01

    Mafic microgranular enclaves (MME) are common in the Early to Middle Miocene Chenar granitoid stock, northwest of Kerman, which is a part of Central Iranian Eocene volcanic belt. They occur individually and in homogeneous or heterogeneous swarms. The MME form a number of two-dimensional structural arrangements, such as dykes, small rafts, vortices, folded lens-shapes and late swarms. The enclaves are elongated, rounded to non-elongated and subrounded in shape and often show some size-sorting parallel to direction of flow. Variation in the elongation of enclaves could reflect variations in the viscosity of the enclave, the time available for enclave deformation and differential strain during flow of the host granitoid magma. The most effective mechanism in the formation of enclave swarms in the Chenar granitoid stock was velocity gradient-related convection currents in the granitoid magma chamber. Gravitational sorting and the break-up of heterogeneous dykes also form MME swarms. The MME (mainly diorite to diorite gabbro) have igneous mineralogy and texture, and are marked by sharp contacts next to their host granitoid rocks. The contact is often marked by a chilled margin with no sign of solid state deformation. Evidence of disequilibrium is manifested in feldspars by oscillatory zoning, resorbed rims, mantling and punctuated growth, together with overgrowth of clinopyroxene/amphibole on quartz crystals, the acicular habit of apatites and the development of Fe-Ti oxides along clinopyroxene cleavages. These observations suggest that the MMEs are derived from a hybrid-magma formed as a result of the intrusion of a mafic magma into the base of a felsic magma chamber. The density contrast between hybrid-magma and the overlying felsic magma was reduced by the release of dissolved fluids and the ascent of exsolved gas bubbles from the mafic magma into the hybrid zone. Further convection in the magma chamber dispersed the hybridized magma as globules in the upper parts of

  9. Stagnant lids and mantle overturns: Implications for Archaean tectonics, magmagenesis, crustal growth, mantle evolution, and the start of plate tectonics

    Directory of Open Access Journals (Sweden)

    Jean H. Bédard

    2018-01-01

    Full Text Available The lower plate is the dominant agent in modern convergent margins characterized by active subduction, as negatively buoyant oceanic lithosphere sinks into the asthenosphere under its own weight. This is a strong plate-driving force because the slab-pull force is transmitted through the stiff sub-oceanic lithospheric mantle. As geological and geochemical data seem inconsistent with the existence of modern-style ridges and arcs in the Archaean, a periodically-destabilized stagnant-lid crust system is proposed instead. Stagnant-lid intervals may correspond to periods of layered mantle convection where efficient cooling was restricted to the upper mantle, perturbing Earth's heat generation/loss balance, eventually triggering mantle overturns. Archaean basalts were derived from fertile mantle in overturn upwelling zones (OUZOs, which were larger and longer-lived than post-Archaean plumes. Early cratons/continents probably formed above OUZOs as large volumes of basalt and komatiite were delivered for protracted periods, allowing basal crustal cannibalism, garnetiferous crustal restite delamination, and coupled development of continental crust and sub-continental lithospheric mantle. Periodic mixing and rehomogenization during overturns retarded development of isotopically depleted MORB (mid-ocean ridge basalt mantle. Only after the start of true subduction did sequestration of subducted slabs at the core-mantle boundary lead to the development of the depleted MORB mantle source. During Archaean mantle overturns, pre-existing continents located above OUZOs would be strongly reworked; whereas OUZO-distal continents would drift in response to mantle currents. The leading edge of drifting Archaean continents would be convergent margins characterized by terrane accretion, imbrication, subcretion and anatexis of unsubductable oceanic lithosphere. As Earth cooled and the background oceanic lithosphere became denser and stiffer, there would be an increasing

  10. Crustal evolution of granitoids and gneisses from the Cambaizinho belt, southern Brazil: Review zircon Pb-Pb evaporation ages and Pb-Nd-Sr isotopes

    International Nuclear Information System (INIS)

    Remus, M.V.D; Macambira, M.B; Hartmann, L.A.; Beilfuss, M

    2001-01-01

    Deformed granitoids and gneisses from the Cambai Complex (900-700 Ma) along Cambaizinho Creek and in the Vila Nova do Sul region, state of Rio Grande do Sul, Brazil, were formed in a remarkably short time, about 10 m.y., between 704±13 and 697±3 Ma. The data base of this work includes eighteen zircon Pb/Pb evaporation analyses, five Pb isotope in feldspar and whole rock. The oldest known rocks in the region are polydeformed dioritic gneisses dated by conventional U-Pb zircon at 704±13 Ma. New Pb-Pb zircon evaporation data on the late transcurrent, less deformed and more evolved granitoids (Sanga do Jobim Granitoids) yield a 697± Ma age and indicates that the evolution of the plutonic magmatism in the area was nearly contemporaneous. These data contrast with previous interpretations based on Rb-Sr data which considered that these rock associations were formed during a longer time period (700-640 Ma). All these granitoids intruded the supracrustal sequence. These granitoids yield a minimum age of about 700 Ma for the formation of the supracrustal sequence and its regional dynamothermal metamorphism. Lead isotope composition of K-feldspar from Sanga do Jobim Granitoids plot close to, but slightly below the lead isotope evolution curve of orogeny in the Zartmann and Doe model (1981). This indicates that the setting for these granitoids was that of a juvenile magmatic arc. These new data plus previous data in the region also corroborate that the crustal evolution involved juvenile crust accreted between 760-700 Ma. In contrast, the Cacapava and Sao Sepe Granites intruded the supracrustal sequences along the eastern side of the Sao Gabriel Block at 562 Ma and 550 Ma, respectively, and show Pb and Nd isotope signatures from an old basement. This evidence suggests that the juvenile terrane was thrusted over the older basement situated along the eastern part of the shield during the Dom Feliciano collisional orogeny at about 620-590 Ma (au)

  11. Distribution of natural radioactive elements in Western Carpathians granitoids

    International Nuclear Information System (INIS)

    Katlovsky, V.

    1979-01-01

    The content of natural radioactive elements was determined using the 1024-channel analyser NTA-512 B with NaI(Tl) scintillators or with a Ge(Li) detector. The following groups of samples were processed: 1. granitoids, pegmatites and weathered rocks in the Small Carpathians; 2. acid magmatites of exotic rocks of the klippen zone; 3. granitoids of the Western Carpathians. The results of the measurements are summed up. (Ha)

  12. Geodynamic evolution of the West and Central Pilbara Craton in Western Australia : a mid-Archaean active continental margin

    NARCIS (Netherlands)

    Beintema, K.A.

    2003-01-01

    The Archaean era lasted for about one third of the Earth's history, from ca 4.0 until 2.5 billion years ago. Because the Archaean spans such a long time, knowledge about this era is for understanding the evolution of the Earth until the present day, especially because it is the time

  13. The age of Male Karpaty Mts. granitoid rocks determined by Rb-Sr isochrone method

    International Nuclear Information System (INIS)

    Badgasaryan, G.P.; Gukasyan, R.Kh.; Veselsky, J.

    1982-01-01

    The results are presented of nuclear geochronological datings of Male Karpaty Mts. granitoids by Rb-Sr isochrone method. Using the method the age of Bratislava massif granitoids was established to be 347+-4 mil. y. at ( 87 Sr/ 86 Sr)=0.7076+-0.0013 and the age of Modra massif granitoids to be 324+-18 mil. y. at ( 87 Sr/ 86 Sr)=0.7075+-0.00032 (2σ). The relative agreement of age of both massifs as well as the agreement of the primary ratio ( 87 Sr/ 86 Sr) 0 not only testifies to their continuity in age but also in genesis. The same relations also confirm the genetic dependence of pegmatites and leucocratic granitoids on fundamental types of granitoids building up the Bratislava and Modra massifs. (author)

  14. Geochemistry and petrogenesis of the Kolah-Ghazi granitoid assemblage, south of Esfahan

    Directory of Open Access Journals (Sweden)

    Jamshid Ahmadian

    2018-04-01

    , andalusite and sillimanite, the predominance of ilmenite, A/CNK values (A/CNK >1, and crondom contents (more than 3% in norm suggest that the Kolah-Ghazi plutonic assemblage can be classified as S-type granitoids. Moreover, all of the Kolah-Ghazi samples plot on the S-type field of the granite classification diagrams (Whalen et al., 1987; Chappell and White, 1992 which is in good agreement with mineralogical evidences. The sedimentary source, mostly shale and greywacke, can be suggested for Kolah-Ghazi melts according to the Rb/Sr vs. Rb/Ba diagram (Sylvester, 1998. Several discrimination diagrams such as Rb vs. Ta+Yb (Pearce et al., 1984 and R1-R2 (Batchelor and Bowden, 1985 were used to determine the tectonic setting of the Kolah-Ghazi granitoids. The Kolah-Ghazi samples lied between the fields of magmatic arc and syn-collisional granitoids in the discrimination diagrams. The geochemistry of the studied samples suggest a syntectonic environment for the Kolah-Ghazi granitoids which may be related to the late Cimmerian orogenic phase. References Batchelor, R.A. and Bowden, P., 1985. Petrogenetic interpretation of granitoid rock series using multicationic parameters. Chemical Geology, 48(1: 43–55. Chappell, B.W. and White, A.J.R., 1992. I- and S-type granites in the Lachlan Fold Belt. Transactions of the Royal Society of Edinburgh, Earth Sciences, 83: 1–2. Pearce, J.A., Harris, N.B.W. and Tindle, A.G., 1984. Trace Element Discrimination Diagrams for the Tectonic Interpretation of Granitic Rocks. Journal of Petrology, 25(4: 956–983. Sylvester, P.J., 1998. Post-collisional strongly peraluminous granites. Lithos, 45(1-4: 29–44. Whalen, J.B., Currie, K.L. and Chappell, B.W., 1987. A-type granites: geochemical characteristics, discrimination and petrogenesis. Contributions to Mineralogy and Petrology, 95(4: 407–419.

  15. Geodynamic evolution of the West and Central Pilbara Craton in Western Australia : a mid-Archaean active continental margin

    NARCIS (Netherlands)

    Beintema, K.A.

    2003-01-01

    The Archaean era lasted for about one third of the Earth's history, from ca 4.0 until 2.5 billion years ago. Because the Archaean spans such a long time, knowledge about this era is for understanding the evolution of the Earth until the present day, especially because it is the time offormation of

  16. DURATION OF GRANITOID MAGMATISM IN PERIPHERAL PARTS OF LARGE IGNEOUS PROVINCES (BASED ON 40AR/39AR ISOTOPIC STUDIES OF ALTAI PERMIAN-TRIASSIC GRANITOIDS

    Directory of Open Access Journals (Sweden)

    O. A. Gavryushkina

    2017-01-01

    Full Text Available In large igneous provinces (LIP of fold areas, granitoid rocks are dominant, while mantle-derivated rocks play a subordinate role in rock formation. If magma emissions are impulsive, it may take 25–30 million years for a LIP to form and take shape. In this paper, we present the results of 40Ar/39Ar isotopic studies of Permian-Triassic grani­toids in the Altai region, Russia, and clarify the evolution of this region located at the periphery of the Siberian LIP. These granitoids are very diverse and differ not only in their rock set, but also in the composition features. In the study region, the granodiorite-granite and granite-leucogranite association with the characteristics of I- and S-types as well rare metal ore-bearing leucogranites are observed along with gabbro- and syenite-granite series, including mafic and intermediate rocks with the A2-type geochemical features. The 40Ar/39Ar data obtained in our study suggest that most of the studied granitoids intruded within a short period of time, 254–247 Ma. This timeline is closely related to the formation of granitoids in theKuznetsk basin and dolerite dikes in the Terekta complex (251–248 and 255±5 Ma, respectively, as well as intrusions of lamproite and lamprophyre dikes of the Chuya complex (245–242 and 237–235 Ma. Thus, we conclude that the Altai Permian-Triassic granitoids are varied mainly due to the evolution of mafic magmatism.

  17. Rb-Sr isochrone dating of granitoids from Tribec Mts

    International Nuclear Information System (INIS)

    Bagdasaryan, G.P.; Gukasyan, R.Kh.; Cambel, B.; Broska, I.

    1990-01-01

    The results of Rb-Sr isochrone dating of granitoids from the Tribec-Zobor crystalline complex region are presented. Whole-rock Rb-Sr isochrone indicates an age of 352±5 m.y., the initial ratio being ( 87 Sr/ 86 Sr) 0 =0.70582±0.00008, which approaches the hitherto published initial ratios from the Tatric-Veporide part of the crystalline complex. This indicates a common source of granitoid rocks over the entire region studied. (author). 2 figs., 1 tab., 15 refs

  18. Asteroids and Archaean crustal evolution: Tests of possible genetic links between major mantle/crust melting events and clustered extraterrestrial bombardments

    Science.gov (United States)

    Glikson, A. Y.

    1992-01-01

    Since the oldest intact terrestrial rocks of ca. 4.0 Ga and oldest zircon xenocrysts of ca. 4.3 Ga measured to date overlap with the lunar late heavy bombardment, the early Precambrian record requires close reexamination vis a vis the effects of megaimpacts. The identification of microtektite-bearing horizons containing spinals of chondritic chemistry and Ir anomalies in 3.5-3.4-Ga greenstone belts provides the first direct evidence for large-scale Archaean impacts. The Archaean crustal record contains evidence for several major greenstone-granite-forming episodes where deep upwelling and adiabatic fusion of the mantle was accompanied by contemporaneous crustal anatexis. Isotopic age studies suggest evidence for principal age clusters about 3.5, 3.0, and 2.7 (+/- 0.8) Ga, relics of a ca. 3.8-Ga event, and several less well defined episodes. These peak events were accompanied and followed by protracted thermal fluctuations in intracrustal high-grade metamorphic zones. Interpretations of these events in terms of internal dynamics of the Earth are difficult to reconcile with the thermal behavior of silicate rheologies in a continuously convecting mantle regime. A triggering of these episodes by mantle rebound response to intermittent extraterrestrial asteroid impacts is supported by (1) identification of major Archaean impacts from microtektite and distal ejecta horizons marked by Ir anomalies; (2) geochemical and experimental evidence for mantle upwelling, possibly from levels as deep as the transition zone; and (3) catastrophic adiabatic melting required to generate peridotitic komatites. Episodic differentiation/accretion growth of sial consequent on these events is capable of resolving the volume problem that arises from comparisons between modern continental crust and the estimated sial produced by continuous two-stage mantle melting processes. The volume problem is exacerbated by projected high accretion rates under Archaean geotherms. It is suggested that

  19. Petrography, geochemistry and tectonic setting of Rigi granitoid body (east of Lut Block, Central Iran)

    International Nuclear Information System (INIS)

    Ghonjalipour, R.; Biabangard, H.; Ahmadi, A.

    2016-01-01

    The Rigi Granitoid Mountain is located in 5 Km West of Dehsalm and 85 Km West of Nehbandan city, southeast of Birjand province and east of Lut Block. This granitoid with Eocene-Oligocene age was penetrated into sedimentary rocks (shale, limestone and sandstone) and changes theses rocks to skarn, hornfels and calcsilicate rocks. This granitoid consist of granodiorite, quartz monzonite and syenogranite with plagioclase, orthose, biotite, hornblende and quartz minerals. Sericite, chlorite, and Magnetite are secondary mineral in these rocks. Geochemical properties this pluton showes that it subalkaline and has metaluminous. Geochemical diagrams and presence of hornblende mineral in this pluton shows that belong to I-type granite. The rocks in granitoid pluton are enrichment LREE compare to HREE, high contents of LILE relative to HFSE and negative anomalies of Nb, Ti and P show it granitoid related to subduction zone. Also, tectonomagmatic diagrams improve that this pluton has belong to active continental margin.

  20. Old inherited zircons in two synkinematic variscan granitoids: the 'granite du Pinet' and the 'Orthogneiss de Marvejols' (Southern French Massif Central)

    International Nuclear Information System (INIS)

    Pin, C.

    1981-01-01

    Two granitic bodies outcropping in the metamorphic basement of the Southern French Massif Central have been studied with the zircon U-Pb method: the Pinet granite (Rouergue area) and the Marvejols orthogneisses (Serie du Lot). It is shown that neither of them are pre-Variscan intrusions but that they were emplaced synkinematically, during the early stages of the Hercynian tectonometamorphic event. As numerous other S-type granitoids, both formations are characterized by an important inherited zircon component, whose apparent age is 1800 +- 200 m.y. Lower intersections with the Concordia curve allow to settle an emplacement age around 350-360 m.y., although the Pinet zircons display a complex pattern, owing both to heterogeneity of the inherited component and to late isotopic disturbances. Regional consequences of the synkinematic character of these S-type granitoids are outlined. It is shown that inherited zircons occurences often hinder accurate dating and the possible petrogenetic significance of the old proterozoic component is discussed. (orig.)

  1. A-type and I-type granitoids and mylonitic granites of Hassan Salaran area of SE Saqqez, Kurdistan, Iran

    Science.gov (United States)

    Abdullah, Fakhraddin Mohammad; Saeed Ahmad, Sheler

    2014-05-01

    The Hassan Salarn area is located 20km to southeast of Saqqez city in Kurdistan Province, western Iran. In this area there are two distinct granitic rock suites consisting A-type and I-type granites and also mylonitic granites. These A-type and I-type granites have various petrological and geochemical characteristics. They also have different origins and petrogenesis. A-type granitoids comprise alkali feldspar granite, syenogranite and quartz alkali feldspar syenite, whereas I-type granitoids are composed of monzogranite, granodiorite and tonalite. Geochemically, A-type granitoids are peralkaline and acmite-normative but I-type granitoids are subalkaline (calc-alkaline), metaluminous and diopside-normative. A-type granitoids are also ferroan alkali and ferroan alkali-calcic whereas I-type granitoids are magnesian and calcic. A-type granitoids resemble to within plate granites and post-orogenic granites whereas I-type granitoids resemble to volcanic arc granites. A-type granitoids contain higher concentrations of alkalies, Zr, Rb, Nb, Y, Th, Ce, high FeO/MgO ratios and lower concentrations of Mg, Ca and Sr, resembling post-orogenic A-type granites. It is possible that heat from a mantle-derived magma which intruded into the lower crust, and/or rapid crustal extension have been essential generation of approriate melts producing A-type granitoids. Thus we can conclude that A-type granitoids were generated from a mixed mantle-crust source. Negative Nb anomalies and low contents of Ti and P probably indicate a subduction-related origin for protolith of I-type granitoids. Negative Nb anomalies and enrichment in Ce relative to its adjacent elements can be related to involvement of continental crust in magmatic processes. I-type granitoids are also enriched in Rb, Ba, K, Th, Ce and depleted in Nb, Zr and Y, indicating that they have had interacted with crust. I-type granitoids may result from contamination of mantle-derived magmas by continental crust during a subduction

  2. Petrochemical and Tectonogenesis of Granitoids in the Wuyo-Gubrunde Horst, Northeastern Nigeria: Implication for Uranium Enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Bolarinwa, Anthony Temidayo, E-mail: atbola@yahoo.com; Bute, Saleh Ibrahim [University of Ibadan, Department of Geology (Nigeria)

    2016-06-15

    The Wuyo-Gubrunde Horst in the northeastern Nigeria consists of migmatite gneiss, unaltered, altered, and sheared porphyritic granites, pegmatites, aplites, basalts, and sandstone. Uranium has been reported in rhyolite, sheared rocks, and sandstone within the area. The petrogenesis of the granitoids and associated rocks in the area was evaluated in the light of new geochemical data, which showed that the U content of altered porphyritic granite is highest and hydrothermal-related. The granitoids are metaluminous, sub-alkaline, and S-type granite, and have evolved by partial melting of crustal material emplaced at moderate depth of 20–30 km in a syn-to late-collisional within-plate tectonic setting. The negative Eu/Eu* anomaly and high (La/Yb){sub N} ratio of the granitoids indicate magma fractionation. The low SiO{sub 2} (<53%) and high Fe{sub 2}O{sub 3} (10%) of the altered porphyritic granite compared to other similar rock units suggest pervasive alteration. The associated basalts are tholeiitic, emplaced within continental plate tectonic setting, and enriched in Ni, V, Nb, Sr, and light rare earth elements, and they have SiO{sub 2}, Fe{sub 2}O{sub 3}, V, Th, and Co contents that are similar to those of the altered porphyritic granites. The U occurrence in the Wuyo-Gubrunde Horst is believed to be sourced from the adjoining Bima sandstone in the Benue Trough, which locally contains carbonaceous zones with anomalously high concentrations of U. The Fe{sup 2+}/Fe{sup 3+} redox fronts formed by alteration of the iron-rich basalts provided the requisite geochemical barrier for U-bearing hydrothermal fluid, causing enrichment of U leached and mobilized from the sandstone through fractures in the rocks.

  3. Interaction between felsic granitoids and basic dykes in ...

    Indian Academy of Sciences (India)

    37

    Many workers gave detailed petrographical and geochemical data of the ... greenstone complex (Malviya et al., 2006; Kumar et al., 2013; Singh and ...... Mafic rock shows lobate shape pointing towards granitoids (marked by the white arrows);.

  4. SHRIMP zircon dating of granitoids from Myanmar: constraints on the tectonic evolution of Southeast Asia

    International Nuclear Information System (INIS)

    Barley, M.E.; Pickard, A.L.; Zaw, K.; University of Tasmania, Hobart, TAS

    1999-01-01

    Full text: Situated south of the eastern syntaxis of the Himalayas, Myanmar occupies a key position in the tectonic evolution of Southeast Asia. However, there is almost no modern geochronology for this region. In this contribution we present new SHRIMP zircon dates for granitoids from the Shan Scarp (Mogok Metamorphic Belt), Taninthayi (Tenasserim) Region in the Myeik (Mergui) Archipelago and Central Valley (Western Myanmar) regions of Myanmar. The oldest ages obtained were from Jurassic granitoids, gneisses and amphibolites interlayered with marbles that were metamorphosed and deformed during the Eocene-Oligiocene and Miocene in the Mogok Metamorphic Belt. The occurrence of mid-Jurassic metamorphosed igneous rocks in the Mogok Metamorphic Belt is similar to that in the Hunza Karakoram and confirms interpretations that the southern margin of Asia became an Andean-type convergent margin at that time. Ages between 120 and 80 Ma for l-type granitoids intruding the Mogok Metamorphic Belt, Myeik Archipelago and Western Myanmar confirm that an up to 200km wide mid Cretaceous magmatic belt extended along the Eurasian margin from Tibet to Sumatra. Fractionated l-Type granitoids, that locally host Sn-W mineralisation, were emplaced in the Myeik Archipelago (and adjacent Thailand) in the latest Cretaceous to Early Eocene (80 to 50 Ma). These granitoids formed a wide convergent margin magmatic belt as the Indian plate rapidly approached Eurasia. Deformation and high-grade metamorphism occurred in the Mogok Metamorphic Belt during the Eocene-Oligiocene as the collision between India and Eurasia initiated crustal thickening prior to extrusion, or rotation, of Indochina and northward movement of Western Myanmar. Arc magmatism continued in Western Myanmar with emplacement of granitoids in the Central Valley. Deformation, extensional uplift and further granitoid magmatism occurred in the Mogok Metamorphic Belt during the Early Miocene northward movement of Western Myanmar

  5. Granitoids of South Korea and Southwest Japan. Trace element evidence regarding their differentiation

    International Nuclear Information System (INIS)

    Tsusue, Akio; Mizuta, Toshio; Tamai, Tadaharu.

    1994-01-01

    Although we have already published our trace element data for granitoids of South Korea and Southwest Japan, and we have interpreted REE patterns and Ba, Rb and Sr relationships of the granitoids (Tsusue et al., 1986, 1987a, 1987b, 1988), we intend to review briefly the trace element data of South Korea and Southwest Japan in this report. (J.P.N.)

  6. Manganiferous minerals of the epidote group from the Archaean basement of West Greenland

    DEFF Research Database (Denmark)

    Katerinopoulou, Anna; Balic Zunic, Tonci; Kolb, Jochen

    2014-01-01

    The chemical compositions and crystal structures of Mn3+-containing minerals from the epidote group in Greenland rocks are investigated and described in detail. They occur in hydrothermally altered Archaean mafic sequences within the gneissic complex of the North Atlantic craton of West Greenland...

  7. Oxygen isotope regional pattern in granitoids from the Cachoeirinha Belt, northeast Brazil

    International Nuclear Information System (INIS)

    Sial, A.N.

    1984-01-01

    Four groups of granitoids are present within the Cachoeirinha belt and in the adjacent migmatitic basement, between 37 0 and 40 0 W long. and 7 0 and 8 0 15' S lat., States of Pernambuco and Paraiba: a) K 2 O - enriched, very porphyritic; b) a calc-alkalic slightly porphyritic group; c) group with trondjemitic affinities; and d) peralkalic group. Petrology and oxygen isotope geochemistry for over 100 samples from these groups were studied. Almost all plutons for which 5 or more samples were analyzed, exhibit a total range of gamma 18 O less than 2% o. A broad range of mean oxygen isotope composition is observed, varying from 6.93 to 12.79% o. There is a systematic regional trend in which the calc-alkalic granitoids (conceicao-type) found within the Cachoeirinha space are the most 18 O - enriched rocks (10.6 to 12.9% o) while the lowest mean gamma 18 O values (4.5 to 9.7% o) are found in the K 2 O - enriched granitoids (Itaporanga-type). Intermediate gamma 18 O values were recorded in the bodies with trondhjemitic affinities (8.9 to 9.8% o) which intruded metasediments of the Salgueiro Group and in the peralkalic granitoids of Catingueira (8.1 to 9.8% o) which intruded Cachoeirinha metamorphics. Among the potassic granitoids, mean gamma 18 O increases from Bodoco to Itaporanga (from west to east). As a whole, the W.R. gamma 18 O of these plutons correlate with the type of grade of metamorphism of the host rocks and, therefore, with the tectonic framework, increasing from those which intruded the gneiss-migmatites to those which intruded the low-grade metamorphics of the Cachoeirinha Group. The possible origin of each rock group is discussed in light of the oxygen isotope geochemistry. (Author) [pt

  8. Geological, petrogical and geochemical characteristics of granitoid rocks in Burma: with special reference to the associated WSn mineralization and their tectonic setting

    Science.gov (United States)

    Zaw, Khin

    The granitoid rocks in Burma extend over a distance of 1450 km from Putao, Kachin State in the north, through Mogok, Kyaukse, Yamethin and Pyinmana in the Mandalay Division, to Tavoy and Mergui areas, Tenasserim Division, in the south. The Burmese granitoids can be subdivided into three N-S trending, major belts viz. western granitoid belt, central graniotoid belt and eastern granitoid belt. The Upper Cretaceous-Lower Eocene western belt granitoids are characterized by high-level intrusions associated with porphyry Cu(Au) related, younger volcanics; these plutonic and volcanic rocks are thought to have been emplaced as a magmatic-volcanic arc (inner magmatic-volcanic arc) above an east-dipping, but westwardly migrating, subduction zone related to the prolonged plate convergence which occurred during Upper Mesozoic and Cenozoic. The central granitoid belt is characterized by mesozonal, Mostly Upper Cretaceous to Lower Eocene plutons associated with abundant pegmalites and aplites, numerous vein-type W-Sn deposits and rare co-magmatic volcanics. The country rocks are structurally deformed, metamorphic rocks of greenschist to upper amphibolite facies ranging in age as early as Upper Precambrian to Upper Paleozoic and locally of fossiliferous, metaclastic rocks (Mid Jurassic to Lower Cretaceous). Available K/Ar radiometric data indicate significant and possibly widespread thermal disturbances in the central granitoid belt during the Tertiary (mostly Miocence). In this study, the distribution, lithological, textural and structural characteristics of the central belt granitoids are reviewed, and their mineralogical, petrological, and geochemical features are presented. A brief description of W-Sn ore veins associated with these granitoid plutons is also reported. Present geological, petrological and geochemical evidences demonstrate that the W-Sn related, central belt granitoids are mostly granodiorite and granite which are commonly transformed into granitoid gneisses

  9. Polycyclic migmatites from southern of Minas Gerais state and adjacent parts: structural/petrographic characterization and geochronological data

    International Nuclear Information System (INIS)

    Artur, A.C.; Wernick, E.; Kawashita, K.

    1990-01-01

    The geology of the southern part of the State of Minas Gerais and adjacent parts of the State of Sao Paulo (SE Brazil) is built up by gray gneisses (Barbacena and Amparo Complexes), pink gneisses (Pinhal Complex) and granulites (Guaxupe Complex) areas, the oldest of them of Archaean ages. Structural, petrographic, geochronological and geologic data indicate that in fact each of those complexes is the result of a long evolution including successive phases of deformation, anatexis and intrusions. The extensive migmatization of the Archaean rocks during the Lower and Upper Proterozoic combined with the intrusion of huge granitoid bodies suggest that the considered region has been involved in successively continental approaches by subduction/collision processes. (author)

  10. Petrology of Oligocene Ghaleh Yaghmesh granitoids in the west of Yazd province

    Directory of Open Access Journals (Sweden)

    Bahareh Fazeli

    2017-02-01

    Full Text Available Introduction The generation and evolution of granitic magmas has been a hot debated subject among petrologists. The diversity of their origin has led different authors to propose that these rocks are not simple in their origin and might be generated in more ways than one. In the past several decades, many petrologists used a variety characteristics to subdivide the granitoid rocks. Such proposals have of course been forward by Chappell and White (1974 for the granitoids of Eastern Australia. They divided these granitoids into two distinct types (I-and S-type granitic rocks, which they interpreted as being derived from igneous and sedimentary source rocks, respectively. The Ghaleh Yaghmesh plutonic massif is located in the most western part of Yazd and it forms a part of the Urumieh-Dokhtar magmatic belt. The belt is response to subduction of Neo-Tethyan oceanic crust beneath central Iran (Alavi, 1994. During Cretaceous-Late Tertiary, numerous granitoid bodies were exposed in this belt, many of which have been studied by a number of workers (e.g. Sepahi and Malvandi, 2008; Honarmand et al., 2013; Kananian et al., 2014. The massif composed of diorite, quartzdiorite, tonalite, granodiorite and granite (Oligocene intruded into the Eocene volcanic and pyroclastic rocks including rhyolite, rhyodacite, andesitic, rhyodacitic and rhyolitic tuff. The main purpose of the present paper is to describe the petrography, and whole rock geochemistry of the Ghaleh Yaghmish granitoids as well as discussing their petrogenetic and tectonic significance in the light of the regional geological framework of the study area. Materials and methods After field studies and sampling, fifty thin sections were prepared for petrographic study. Twenty-one fresh samples were selected for XRF chemical analysis performed at the Southern Methodist University (Dallas - USA. Thin polished sections of granodiorite rocks were prepared for composition determining and structure formula

  11. 222Rn activity concentration differences in groundwaters of three Variscan granitoid massifs in the Sudetes (NE Bohemian Massif, SW Poland)

    International Nuclear Information System (INIS)

    Przylibski, Tadeusz A.; Gorecka, Joanna

    2014-01-01

    Based on research conducted in three Variscan granitoid massifs located within the crystalline Bohemian Massif, the authors confirmed that the higher the degree of their erosional dissection, the smaller the concentration of 222 Rn in groundwaters circulating in these massifs. This notion implies that radon waters and high-radon waters, from which at least some of the dissolved radon should be removed before feeding them as drinking water to the water-supply system, could be expected in granitoid massifs which have been poorly exposed by erosion. At the same time, such massifs must be taken into account as the areas of possible occurrence of radon medicinal waters, which in some countries can be used for balneotherapy in health resorts. Slightly eroded granitoid massifs should be also regarded as very probable radon prone areas or areas of high radon potential. - Highlights: • The concentration of 222 Rn in groundwater depends on the zone of the granitoid massif which is exposed on the ground surface. • The highest 222 Rn concentrations occur in the least eroded granitoid massifs, the lowest in massifs with exposed root parts. • The stronger the erosional dissection of a granitoid massif, the lower 222 Rn concentration in groundwaters in this massif. • Not all granitoid massifs are areas with groundwaters containing high concentrations of 222 Rn. • The least eroded granitoid massifs are radon prone areas with the occurrence of high-radon and radon groundwaters

  12. Diversity, origin and tectonic significance of the Mesoarchean granitoids of Ourilândia do Norte, Carajás province (Brazil)

    Science.gov (United States)

    da Silva, Luciano Ribeiro; de Oliveira, Davis Carvalho; dos Santos, Maria Nattânia Sampaio

    2018-03-01

    This study investigates the diversity, origin and tectonic significance of the Ourilândia do Norte Mesoarchean granitoids, emplaced near Rio Maria-Carajás domains boundary, southeastern Amazonian Craton (Brazil). In this area, previous works has identified sanukitoids (∼2.87 Ga), (quartz) diorites of BADR affinity and undifferentiated leucogranites, with charnockites cross-cutting the other granitoids. New geological mapping data allowed to differentiate three new groups of granitoids: (i) biotite monzogranites (BMzG); (ii) epidote-biotite granodiorites (EBGd); and (iii) porphyritic granitoids (pGrt). Thus, this paper aims to define their classification, nature, formation processes and deformation aspects, and discuss the relations between plutonism and deformation for the Ourilandia do Norte granitoids. The petrographic data showed that each one of these groups can be subdivided into two facies. The BMzG is differentiated into equigranular (eBMzG) and heterogranular (hBMzG) and the EBGd into heterogranular (hEBGd) and sparsely porphyritic (spTEBGd). These granitoids constitute two batholiths separated by a rock strip of sanukitoid and BADR affinities. Both are largely dominated by BMzG rocks, with less abundant EBGd lenses. The pGrt is individualized in porphyritic granodiorites (pBHGd) and trondhjemites (pEBTd), which occur as smaller bodies. Structurally, the central portions these plutons represent lower strain domains, while their borders are marked by large-scale shear zones, where occur submagmatic and mylonitic fabrics of ENE-WSW main direction and subvertical dip, respectively. The meso- and microstructural data indicate that the rocks studied are syn-to late-tectonic and were affected by high temperature deformation (>500 °C) and low differential stress, in a sinistral transpression regime, indicating that both fabrics are related to the a same deformational event. Geochemically, except the pEBTd facies that has sodic affinity, the Ourilândia do

  13. The tardi-Pan-African granitoids of South-Westerner Anti-Atlas (Morocco: Evolution from magnesian to ferroan type. Example of the Ifni inlier

    Directory of Open Access Journals (Sweden)

    El Aouli, E. H.

    2007-06-01

    Full Text Available The study of the neoproterozoic granitoids in the Ifni Inlier and those of the other inliers in south-westerner Anti-Atlas shows that this magmatism evolves from magnesian to ferroan type. In the Ifni inlier, these granitoids outcrop within the sedimentary and volcanogenic formations of the Ouarzazate Super- Group SGO (615 to 540 My. They belong to two distinct magmatic episodes (i an early one composed of magnesian granitoids with alkali-calcic and metaluminous to slightly aluminous character (quartz bearing diorite, granodiorite and monzogranite intrusive in the lower formations of the SGO, and (ii a late episode associated to the summit of the SGO volcanites, which includes granites and sub-volcanic syenogranites of iron-bearing type and alkali-calcic to alkaline affinity. These magmatisms resulting from the partial melting of mixed material mark the end of the last Panafrican episode and would be set up in a transition from orogenic to anorogenic settings which announce the Paleozoic cycle. They would be contemporary to posterior with the exhumation of the extensive metamorphic domes of the Western Anti-Atlas.El estudio de los granitoides neoproterozoicos de la “boutonnière” (complejo plutono-metamórfico profundo con geometría subcircular de Ifni y de los de otras “boutonnières” del dominio suroccidental del Anti-Atlas, demuestra que este magmatismo evoluciona desde un tipo magnésico hacia un tipo férrico. En la “boutonnière” de Ifni, estos granitoides afloran en el interior de formaciones sedimentarias y volcano-sedimentarias del Supergrupo de Ouarzazate SGO (615 a 540 Ma. Pertenecen a dos episodios magmáticos diferentes (i un episodio precoz compuesto de granitoides magnésicos, calcoalcalinos y metaluminosos a poco aluminosos (dioritas con cuarzo, granodioritas y monzogranitos que intruyen en las formaciones inferiores del SGO, (ii un episodio tardío asociado con un vulcanismo terminal a techo del

  14. The Rb/Sr ages for granitoids of the Middle Chukotka: a new approach to the geological history of the region

    International Nuclear Information System (INIS)

    Efremov, S.V.; Kozlov, V.D.; Sandimirova, G.P.

    2000-01-01

    For studying the history of geological evolution of the Middle Chukotka in the Mesozoic by the method of Rb-Sr dating the age of granitoids in the region was determined. It was ascertained that the granitoids have different genetic nature, their formation involving the most intensive tectonic restructuring. Magmatism was manifested in two stages. Formation of the first stage granitoids (126-144 mln. years) relates to orogenesis, while that of the second stage granitoids (∼ 80 mln. years) - to the process of the Chukotka folded region activation [ru

  15. Greenland from Archaean to Quaternary, Descriptive text to the 1995 Geological Map of Greenland 1:2 500 000, 2nd edition

    Directory of Open Access Journals (Sweden)

    Kalsbeek, Feiko

    2009-11-01

    Full Text Available The geological development of Greenland spans a period of nearly 4 Ga, from Eoarchaean to the Quaternary. Greenland is the largest island on Earth with a total area of 2 166 000 km2, but only c. 410 000 km2 are exposed bedrock, the remaining part being covered by a major ice sheet (the Inland Ice reaching over 3 km in thickness. The adjacent offshore areas underlain by continental crust have an area of c. 825 000 km2. Greenland is dominated by crystalline rocks of the Precambrian shield, which formed during a succession of Archaean and Palaeoproterozoic orogenic events and stabilised as a part of the Laurentian shield about 1600 Ma ago. The shield area can be divided into three distinct types of basement provinces: (1 Archaean rocks (3200–2600 Ma old, with local older units up to >3800Ma that were almost unaffected by Proterozoic or later orogenic activity; (2 Archaean terrains reworked during the Palaeoproterozoic around 1900–1750 Ma ago; and (3 terrains mainly composed of juvenile Palaeoproterozoic rocks (2000–1750 Ma in age.Subsequent geological developments mainly took place along the margins of the shield. During the Proterozoic and throughout the Phanerozoic major sedimentary basins formed, notably in North and North-East Greenland, in which sedimentary successions locally reaching 18 km in thickness were deposited. Palaeozoic orogenic activity affected parts of these successions in the Ellesmerian fold belt of North Greenland and the East Greenland Caledonides; the latter also incorporates reworked Precambrian crystalline basement complexes. Late Palaeozoic and Mesozoic sedimentary basins developed along the continent–ocean margins in North, East and West Greenland and are now preserved both onshore and offshore. Their development was closely related to continental break-up with formation of rift basins. Initial rifting in East Greenland in latest Devonian to earliest Carboniferous time and succeeding phases culminated with the

  16. Study of rare earth elements for the characterization and metalogenetic evaluation of granitoids of the paranaense shield

    International Nuclear Information System (INIS)

    Chiodi Filho, C.; Santos, J.F. dos; Moretzsohn, J.S.

    1989-01-01

    REE geochemistry combined with major and trace elements data, provide some diagnostic criteria regarding the origin, the geotectonic setting and the metallogenesis of granitoid intrusions in the Parana Shield. The intrusions were grouped as mantle (Sintexis Series) and crustal (Transformation Series) origins. The two lineages include six suites, with pre, syn, tardi-to-post and post-collisional emplacement. From the metallogenetic standpoint, the 'Sintexis' granitoids can be labelled as ''0Mo-W-Cu-Au porphyry-granites''and the 'Transformation' granitoids as Sn-W greisengranites. (author) [pt

  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. Petrogenesis of Jurassic granitoids at the northeastern margin of the North China Craton: New geochemical and geochronological constraints on subduction of the Paleo-Pacific Plate

    Science.gov (United States)

    Liu, Jin; Zhang, Jian; Liu, Zhenghong; Yin, Changqing; Zhao, Chen; Peng, Youbo

    2018-06-01

    At the junction between the North China Craton (NCC) and the Central Asian Orogenic Belt (CAOB), northern Liaoning province, NE China, there are widespread Jurassic igneous rocks. The tectonic setting and petrogenesis of these rocks are unresolved. Zircon U-Pb dating, whole-rock geochemistry, and Hf isotopic compositions of Jurassic granitoids were investigated to constrain their ages and petrogenesis in order to understand the tectonic evolution of the Paleo-Pacific Ocean along the northeastern margin of the NCC. Geochronological data indicate that magmatism occurred between the early and late Jurassic (180-156 Ma). Despite the wide range in ages of the intrusions, Jurassic granitoids were likely derived from a similar or common source, as inferred from their geochemical and Hf isotopic characteristics. Compared to the island arc andesite-dacite-rhyolite series, the Jurassic granitoids are characterized by higher SiO2, Al2O3, and Sr contents, and lower MgO, FeOT, Y, and Yb contents, indicating that the primary magmas show typical characteristics of adakitic magmas derived from partial melting of thickened lower crust. These findings, combined with their εHf(t) values (+1.4 to +5.4) and two-stage model ages (1515-1165 Ma), indicate the primary magmas originated from partial melting of juvenile crustal material accreted during the Mesoproterozoic. They are enriched in large-ion lithophile elements (e.g., Rb, K, Th, Ba, and U) and light rare-earth elements (REE), and depleted in high-field-strength elements (e.g., Nb, Ta, Ti, and P) and heavy REE. Based on these findings and previous studies, we suggest that the Jurassic adakitic granitoids (180-156 Ma) were formed in an active continental margin and compressive tectonic setting, related to subduction of the Paleo-Pacific Plate.

  19. Petrology, geochronology, geochemistry and petrogenesis of Bajestan granitoids, North of Ferdows, Khorasan Razvi Province

    Directory of Open Access Journals (Sweden)

    Reyhaneh Ahmadirouhani

    2017-02-01

    Full Text Available Introduction The investigated area is situated in the south west of the Khorasan Razavi Province along the North West of the Lut Block. Different types of metal ore bodies along with non-metal deposits have already been documented in the Lut Block (Karimpour et al., 2008. Most of the study area is covered with granitoid rocks. Metamorphic rocks with unknown age are present in the north of the area. Skarns are observed in contact with fault zones and intrusive bodies. Eocene volcanic rocks with andesite and andesibasalt composition are located in the east and north east of the area (Ahmadirouhani et al., 2015. The study area that is a part of the Lut Block has a high potentials for Cu, Fe, Au, and Barite mineralization along the observed alteration zones. In the present study, the petrography, petrogenesis, Sr–Nd isotopes, and U–Pb zircon age of acidic granitoids in the east of Bajestan were investigated. Materials and methods In the current study, 400 rock samples were collected from the field and 170 thin sections were prepared for petrography studies. Thirty samples of volcanic rocks, intrusions, and dykes were analyzed using XRF at the Geological Survey of Iran. Twenty-five samples were selected for the elemental analysis using ICP-MS by the Acme Lab Company (Canada, 16 samples of them were related to acidic intrusive bodies and dykes. In addition, zircon crystals from four samples of the granitoids bodies were collected for U–Pb dating. Approximately 50 zircon grains (i.e. euhedral, clear, uncracked crystals with no visible heritage cores and no inclusions were hand-picked from each sample. Through cathodoluminescence imaging, the internal structure and the origin of zircon grains were examined at the Geological Survey of Vienna, Austria. Moreover, zircons were dated using the (LA-ICP-MS method at the Laboratory of Geochronology, the University of Vienna, Austria using the methodology outlined in Klötzli et al., (2009. Sr and Nd

  20. Permo-Triassic arc-like granitoids along the northern Lancangjiang zone, eastern Tibet: Age, geochemistry, Sr-Nd-Hf isotopes, and tectonic implications

    Science.gov (United States)

    Wang, Xinyu; Wang, Shifeng; Wang, Chao; Tang, Wenkun

    2018-05-01

    Large volumes of Permo-Triassic granitoids are exposed along the Northern Lancangjiang zone, eastern Tibet, and these rocks provide insights into the tectonic evolution of the Paleo-Tethys Ocean. We conducted detailed geological fieldwork and geochemical analysis of the Xiaochangdu and Kagong plutons that crop out along the Northern Lancangjiang magmatic belt. Zircon U-Pb data constrain the emplacement of the Xiaochangdu quartz diotites to between 263 and 257 Ma, and the Kagong granites and diorites to between 234 and 232 Ma. The Xiaochangdu quartz diorites are enriched in light rare earth (LREE) and large ion lithophile elements (LILE), depleted in high field strength elements (HFSE), have low (87Sr/86Sr)i ratios, and near-positive εNd(t) (-0.26 to 1.58) and εHf(t) (0.68-8.83) values, similar to typical subduction- related mantle-derived arc magmas. They are also characterized by high Al2O3 concentrations and low Nb/U (3.48-7.59) and Ce/Pb (3.22-4.86) ratios, indicating that their mantle source was modified by subducted pelagic sediments; Coeval granites and diorites from the Kagong pluton exhibit low A/CNK values, high LREE/HREE (heavy rare earth element) ratios, enrichment in LILE, and depletion in HFSE, also characteristic of typical arc magmas. Their variable SiO2 contents (57%- 75%), (87Sr/86Sr)i ratios, and εNd(t) (1.02-4.49) and εHf(t) (2.52-6.93) values, and relatively high zircon saturation temperatures (721-827 °C), suggest underplating of mantle-derived mafic melts beneath the lower crust. Their magmatic evolution can be explained using a MASH model. In combination with regional geological studies, our geochemical and geochronological results suggest that the late Permian Xiaochangdu and Late Triassic Kagong arc-like granitoids represent a section of a Permo-Triassic magmatic arc that was associated with the eastward subduction of the Paleo-Tethys oceanic slab beneath the Northern Qiangtang-Changdu terrane. Combined with other geological evidence

  1. In search of Archean basement from Rio Maria region, southeastern of Para State

    International Nuclear Information System (INIS)

    Macambira, M.B.; Lancelot, J.

    1991-01-01

    The Rio Maria Region, southeastern part of the Amazonian craton (Brazil), displays a typical Archaean granite-greenstone association intruded by Proterozoic granites. The greenstone is crosscut by Archaean granitoids, such as the Rio Maria granodiorite. Clear field contacts between the Xingu gneisses and the granodiorite are lacking, making it difficult to determine the stratigraphic sequence. U-Pb data for zircons from the Xingu gneiss and the Rio Maria granodiorite provide upper intercept ages of 2971 +30/ -28 Ma and 2874 +9/ -10 Ma respectively on the Concordia diagram. 2.97 Ga is the most ancient age ever obtained on zircons from gneisses of the Amazonian craton. It provides an upper limit for the beginning of the continental crust formation in this part of the craton. (author)

  2. Rare earth element lithogeochemistry of granitoid mineral deposits

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, R.P.; Fryer, B.J. (Memorial Univ. of Newfoundland, St. John' s (Canada). Dept. of Earth Sciences)

    1983-12-01

    As a monitor of the processes involved in the formation of granitoid mineral deposits the coherent group behaviour of the rare earth elements (REE) actively reflects changing fluid characteristics. For example, in the porphyry environment, magmatic-hydrothermal fluids produce potassic alteration with strong enrichment in the light rare earth elements, reflecting their high pH, low fluid/rock ratios, and the dominant role of Cl/sup -/ complexing in metal (i.e. Cu, Au) transport. With increasing fluid/rock ratios and decreasing pH accompanying the progressive involvement of meteoric fluids (and the production of propylitic, argillic, and phyllic alteration) anionic species such as F/sup -/ and CO/sub 3//sup 2 -/ become important in metal (e.g. Mo, W) transport through complexing, and their activity in the hydrothermal fluids is illustrated by mobilization of the heavy rare earth elements. The relative involvement of Cl/sup -/ versus F/sup -/ versus CO/sub 3//sup 2 -/ in metal transport in other granite-related systems can also be monitored through REE behaviour. Hence granitoid tin-tungsten mineralization and associated greisenization typically exhibit heavy rare earth enrichment and evidence the importance of F/sup -/ and CO/sub 3//sup 2 -/ in metal transport. Similarly, heavy rare earth element enrichment in hydrothermal uranium deposits can be related to the transport of uranium as carbonate complexes. REE are widely accepted as powerful tools in the study of rock petrogenesis, but their use has been neglected in the investigation of mineral deposits. The recognition of the systematic variation of REE distributions in granitoid mineral deposits suggests that the application of REE geochemistry, particularly when integrated with fluid inclusion and isotope studies, can provide l) an effective method for identifying the physiochemical controls of metal transport and 2) a useful criterion of elucidating metal distribution.

  3. Rare earth element lithogeochemistry of granitoid mineral deposits

    International Nuclear Information System (INIS)

    Taylor, R.P.; Fryer, B.J.

    1983-01-01

    As a monitor of the processes involved in the formation of granitoid mineral deposits the coherent group behaviour of the rare earth elements (REE) actively reflects changing fluid characteristics. For example, in the porphyry environment, magmatic-hydrothermal fluids produce potassic alteration with strong enrichment in the light rare earth elements, reflecting their high pH, low fluid/rock ratios, and the dominant role of Cl - complexing in metal (i.e. Cu, Au) transport. With increasing fluid/rock ratios and decreasing pH accompanying the progressive involvement of meteoric fluids (and the production of propylitic, argillic, and phyllic alteration) anionic species such as F - and CO 3 2- become important in metal (e.g. Mo, W) transport through complexing, and their activity in the hydrothermal fluids is illustrated by mobilization of the heavy rare earth elements. The relative involvement of Cl - versus F - versus CO 3 2- in metal transport in other granite-related systems can also be monitored through REE behaviour. Hence granitoid tin-tungsten mineralization and associated greisenization typically exhibit heavy rare earth enrichment and evidence the importance of F - and CO 3 2- in metal transport. Similarly, heavy rare earth element enrichment in hydrothermal uranium deposits can be related to the transport of uranium as carbonate complexes. REE are widely accepted as powerful tools in the study of rock petrogenesis, but their use has been neglected in the investigation of mineral deposits. The recognition of the systematic variation of REE distributions in granitoid mineral deposits suggests that the application of REE geochemistry, particularly when integrated with fluid inclusion and isotope studies, can provide l) an effective method for identifying the physiochemical controls of metal transport and 2) a useful criterion of elucidating metal distribution

  4. U-Pb SHRIMP data and geochemical characterization of granitoids intruded along the Coxixola shear zone, Provincia Borborema, NE Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, Ignez de Pinho; Silva Filho, Adejardo Francisco da; Silva, Francis M.J.V. da, E-mail: ignez@ufpe.br [Universidade Federal de Pernanmbuco (UFPE), Recife, PE (Brazil). Dept. de Geologia; Armstrong, Richard [Australian National University (Australia)

    2011-07-01

    A large volume of granitic magmatism associated with large scale shear zone and metamorphism under high-T amphibolite facies conditions characterize the Brasiliano Orogeny in the Borborema Province, NE Brazil. Granitoids from two plutons and later dykes intruded along the Coxixola shear zone show distinct crystallization ages and geochemical signature. The oldest granitoids (618 ± 5 Ma), Serra de Inacio Pereira Pluton are coeval with the peak of regional metamorphism and they were probably originated by melting of a paleoproterozoic source. The granitoids from the Serra do Marinho Pluton show crystallization age of 563 ± 4 Ma and geochemical signature of post-collisional A-type granites. The later dykes have crystallization age of 526 ± 7 Ma, geochemical signature of A-type granitoids. (author)

  5. Archaean ultra-depleted komatiites formed by hydrous melting of cratonic mantle.

    Science.gov (United States)

    Wilson, A H; Shirey, S B; Carlson, R W

    2003-06-19

    Komatiites are ultramafic volcanic rocks containing more than 18 per cent MgO (ref. 1) that erupted mainly in the Archaean era (more than 2.5 gigayears ago). Although such compositions occur in later periods of Earth history (for example, the Cretaceous komatiites of Gorgona Island), the more recent examples tend to have lower MgO content than their Archaean equivalents. Komatiites are also characterized by their low incompatible-element content, which is most consistent with their generation by high degrees of partial melting (30-50 per cent). Current models for komatiite genesis include the melting of rock at great depth in plumes of hot, diapirically rising mantle or the melting of relatively shallow mantle rocks at less extreme, but still high, temperatures caused by fluxing with water. Here we report a suite of ultramafic lava flows from the Commondale greenstone belt, in the southern part of the Kaapvaal Craton, which represents a previously unrecognized type of komatiite with exceptionally high forsterite content of its igneous olivines, low TiO(2)/Al(2)O(3) ratio, high silica content, extreme depletion in rare-earth elements and low Re/Os ratio. We suggest a model for their formation in which a garnet-enriched residue left by earlier cratonic volcanism was melted by hydration from a subducting slab.

  6. Les granitoïdes néoprotérozoïques de Khzama, Anti-Atlas central, Maroc: marqueurs de l'évolution d'un magmatisme d'arc à un magmatisme alcalineNeoproterozoic granitoids from Khzama, central Anti-Atlas, Morocco: evolution markers from arc magmatism to alkaline magmatism

    Science.gov (United States)

    El-Khanchaoui, T.; Lahmam, M.; El-Boukhari, A.; El-Beraaouz, H.

    2001-05-01

    Petrological study and zircon typology provide important information that is related to the classification and genesis of Neoproterozoic granitoids in the Khzama area (northeast Siroua). The Pan-African granitoids show a transition from island-arc magmatism to alkaline magmatism. A space and time zonation of magmatism from the north to the south is evident. Early Pan-African granitoids were generated from various magma sources through different petrogenetic mechanisms. The first association corresponds to the low-K calc-alkaline plutons of Ait Nebdas, the second one correponds to high-K calc-alkaline post-collisional granites (Tamassirte-Tiferatine and Ifouachguel). Finally, shoshonitic magmatism (Irhiri) ends the magmatic evolution of the region. Thus, the late Pan-African granitic plutonism began with calc-alkaline associations and ended with K-alkaline magmatism in a transtensional setting, heralding the onset of the Moroccan Palæozoic cycle.

  7. Indoor radon related to uranium in granitoids of the Central Bohemian plutonic complex

    International Nuclear Information System (INIS)

    Barnet, I.; Fojtikova, I.

    2004-01-01

    The study is based on the indoor radon data (one year measurements, Kodak LR 115 track etch detectors), vectorized geological maps 1:50000, vectorized coordinates of dwellings and uranium data for granitoid types of the Central Bohemian Plutonic Complex (CBPC). Using ArcGis 8.2 programme, the position of 16145 dwellings was linked to a geological database covering the CBPC (approx. 3200 km 2 ), and the type of underlying rock type was specified for each house. The resulting databases enabled us to calculate the mean EEC indoor Rn data for particular granitoid types and to study the relationship between the indoor Rn and the U concentrations. The petrogenetically variable CBPC was emplaced during Variscan orogenesis (330-350 Ma) and is among the most radioactive rock types within the Bohemian Massif. A long-term process of CBPC genesis resulted in more than 20 granitoid types, differing by their petrogenetic characteristics as well as mineralogical and chemical composition, including uranium concentration. The relation between the mean indoor radon values and uranium concentrations in particular rock types was examined. A positive regression between indoor Rn and uranium as the source of Rn soil gas clearly demonstrates how regional geology influences the indoor radon activity concentration in dwellings. The highest indoor Rn concentrations were observed in the Sedlcany granodiorite and Certovo bremeno syenite, where also the highest gamma dose rates (150-210 nGy.h -1 ) within all granitoid types in the Czech Republic were observed. The two rock types differ from other granitoids by a relatively high zircon concentration, which is the main source of U and subsequently of soil gas Rn being released from the bedrock. The lower indoor Rn values of Certovo bremeno syenite which do not correspond with the high U concentrations can be explained by a relatively low permeability of its clayey weathering crust. This feature was also observed for soil gas radon concentration

  8. Granitoid magmatism of Alarmaut granite-metamorphic dome, West Chukotka, NE Russia

    Science.gov (United States)

    Luchitskaya, M. V.; Sokolov, S. D.; Bondarenko, G. E.; Katkov, S. M.

    2009-04-01

    -metamorphic domes at Russian North-East. Paper 2. Magmatism, metamorphism and migmatization in Late Mesozoic domes // Pacific geology. 1996. V. 15. № 1. P. 84-93. (in Russian) 13. Bering Strait Geologic Field Party, Koolen metamorphic complex, NE Russia: implications for the tectonic evolution of the Bering Strait region // Tectonics, vol. 16, no. 5, p. 713-729 14. Bondarenko G.E., Luchitskaya M.V. Mesozoic tectonic evolution of Alarmaut rise // Byul. MOIP. Otd. Geol. V. 78. Is. 3. P. 25-38. (in Russian) 15. Katkov S.M., Strikland A., Miller E.L. Age of granite batholiths in the Anyui-Chukotka Foldbelt // Doklady. Earth Sciences. 2007. Vol. 414. № 4. P. 515-518. 16. Amato J.M., Wright J.E. Potassic mafic magtism in the Kigluaik gneiss dome, northern Alaska: a geochemical study of arc magmatism in an extensional tectonic setting // J. Geophys. Res. 1997. Vol.102. N B4. P.8065-8084 17. Tikhomirov P.L., Luchitskaya M.V., Kravchenko-Berezhnoy I.R. Comparison of Cretaceous granitoids of the Chaun tectonic zone to those of the Taigonos Peninsula, NE Asia: rock chemistry, composition of rock forming minerals, and conditions of formation // Stephan Mueller series. Geology and Tectonic Origins of Northeast Russia: A Tribute to Leonid Parfenov (in press) 28. Velikoslavinsky S.D. Geochemical typification of acid magmatic rocks of leading geodynamic settings // Petrology. 2003. V. 11. № 4. P.363-380. (in Russian) 19. Pearce J.A. Sources and settings of granitic rocks // Episodes. 1996. V. 19. N. 4. P. 120-125

  9. Tectonic implications of U-Pb (zircon) Geochronology of Chor Granitoids of the Lesser Himalaya, Himachal Pradesh, NW Himalaya

    Science.gov (United States)

    Singh, P.; Bhakuni, S. S.

    2017-12-01

    Granitoids of various ages ranging from Proterozoic to Tertiary occur throughout the Himalayan fold-thrust belt. The occurrence of the Neoproterozoic granitoids are very less in the Himalayan orogen. One of the best example of Neoproterozoic granitoids is Chor granitoids, which are the intrusive granite bodies in the Paleoproterozoic of the Lesser Himalayan Crystallines of the Jutogh Group. In the central part these granites are non-foliated homogeneous that are porphyritic and peraluminous in nature (Singh et al., 2002; Bhargava et al., 2014, 2016), whereas in the peripheral part these are foliated showing south directed shear sense of movement. In this work we present the U-Pb (zircon) geochronology of two different granites samples of the Chor granitoids of Himachal Pradesh, NW Himalaya. The Jutogh Group of rocks is thrust over the Lesser Himalayan Sequence along the Jutogh Thrust or MCT. The geochronology of the Chor Granitoids and Lesser Himalayan Crystallines and their relationship with each other, including with the Indian shield are sparsely obscure. U-Pb zircon geochrnological age populations from these granitoids yield ages between 780 and 980 Ma. One sample gives the prominent age spectra for 206Pb/238U with weighted mean age of 908.3 ± 6.7 Ma (2σ) MSWD = 2.4 (n = 18). Similarly another sample gives the age of crystallization with weight mean age of 917 ± 17 Ma (2σ) MSWD = 3 (n = 11) and Th/U ratios of both samples are >0.1, indicating their magmatic origin. As a result of ductile shearing of granites along the MCT during the Cenozoic Himalayan Orogeny, the age has reduced to 780 Ma. The Neoproterozoic age of Chor granite matches with the Neoproterozoic detrital zircon age (800 to 1000 Ma by Parrish and Hodges 1996, Decelles et al., 2000) of the HHC. On the basis of U-Pb (zircon) geochronological ages, it is revealed that the source of zircons of the Chor granite and HHC rocks was the northern margin of the Pan-African orogen. The Chor granitoids was

  10. Origin of the mafic microgranular enclaves (MMEs) and their host granitoids from the Tagong pluton in Songpan-Ganze terrane: An igneous response to the closure of the Paleo-Tethys ocean

    Science.gov (United States)

    Chen, Qiong; Sun, Min; Zhao, Guochun; Yang, Fengli; Long, Xiaoping; Li, Jianhua; Wang, Jun; Yu, Yang

    2017-10-01

    The Songpan-Ganze terrane is mainly composed of a Triassic sedimentary sequence and late Triassic-Jurassic igneous rocks. A large number of plutons were emplaced as a result of tectono-magmatic activity related to the late stages of Paleo-Tethys ocean closure and ensuing collision. Granitoids and their hosted mafic enclaves can provide important constraints on the crust-mantle interaction and continental crustal growth. Mesozoic magmatism of Songpan-Ganze remains enigmatic with regard to their magma generation and geodynamic evolution. The Tagong pluton (209 Ma), in the eastern part of the Songpan-Ganze terrane, consists mainly of monzogranite and granodiorite with abundant coeval mafic microgranular enclaves (MMEs) (ca. 208-209 Ma). The pluton comprises I-type granitoid that possesses intermediate to acidic compositions (SiO2 = 61.6-65.8 wt.%), high potassium (K2O = 3.2-4.1 wt.%), and high Mg# (51-54). They are also characterized by arc-type enrichment of LREEs and LILEs, depletion of HFSEs (e.g. Nb, Ta, Ti) and moderate Eu depletions (Eu/Eu* = 0.46-0.63). Their evolved zircon Hf and whole-rock Nd isotopic compositions indicate that their precursor magmas were likely generated by melting of old lower continental crust. Comparatively, the MMEs have lower SiO2 (53.4-58.2 wt.%), higher Mg# (54-67) and show covariation of major and trace elements, coupled with field and petrographic observations, such as the disequilibrium textures of plagioclase and amphibole, indicating that the MMEs and host granitoids were originated from different magma sources but underwent mafic-felsic magma mixing process. Geochemical and isotopic data further suggest that the precursor magma of the MMEs was formed in the continental arc setting, mainly derived from an ancient metasomatized lithospheric mantle wedge. The Triassic granitoids from the Songpan-Ganze terrane show remarkable temporal-spatial-petrogenetic affinities to the counterparts of subduction zones in the Yidun and Kunlun arc

  11. Constraining the potential temperature of the Archaean mantle: A review of the evidence from komatiites

    Science.gov (United States)

    Nisbet, E. G.; Cheadle, M. J.; Arndt, N. T.; Bickle, M. J.

    1993-09-01

    The maximum potential temperature of the Archaean mantle is poorly known, and is best constrained by the MgO contents of komatiitic liquids, which are directly related to eruptive temperatures. However, most Archaean komatiites are significantly altered and it is difficult to assess the composition of the erupted liquid. Relatively fresh lavas from the SASKMAR suite, Belingwe Greenstone Belt, Zimbabwe (2.7 Ga) include chills of 25.6 wt.% MgO, and olivines ranging to Fo 93.6, implying eruption at around 1520°C. A chill sample from Alexo Township, Ontario (also 2.7 Ga) is 28 wt.% MgO, and associated olivines range to Fo 94.1, implying eruption at 1560°C. However, inferences of erupted liquids containing 32-33 wt.% MgO, from lavas in the Barberton Greenstone Belt, South Africa (3.45 Ga) and from the Perseverance Complex, Western Australia (2.7 Ga) may be challenged on the grounds that they contain excess (cumulate) olivine, or were enriched in Mg during alteration or metamorphism. Re-interpretation of olivine compositions from these rocks shows that they most likely contained a maximum of 29 wt.% MgO corresponding to an eruption temperature of 1580°C. This composition is the highest liquid MgO content of an erupted lava that can be supported with any confidence. The hottest modern magma, on Gorgona Island (0.155 Ga) contained 18-20% MgO and erupted at circa 1400°C. If 1580°C is taken as the temperature of the most magnesian known eruption, then the source mantle from which the liquids rose would have been at up to 2200°C at pressures of 18 GPa corresponding to a mantle potential temperature of 1900°C. These temperatures are in excess of the mantle temperatures predicted by secular cooling models, and thus komatiites can only be formed in hot rising convective jets in the mantle. This result requires that Archaean mantle jets may have been 300°C hotter than the Archaean ambient mantle temperature. This temperature difference is similar to the 200-300

  12. A petrochemical investigation of a group of granitoids in the Cnydas area, West of Upington

    International Nuclear Information System (INIS)

    Jankowitz, J.A.C.

    1981-01-01

    Detailed mapping in the eastern Namaqualand Metamorphic Complex west of Upington, indicates that the Cnydas batholith can be divided into ten different granitoidal phases. The classification is based on the intrusive field relationships supported by variation in mineralogy, texture, petrography and geochemistry. A differentiation sequence from granodiorite through mesocratic granite to leucogranite is proposed on the basis of geochemical evidence. The chemistry and petrography suggests an I-type origin for these granitoids

  13. Lithogeochemistry of rare-earth elements in the characterization of granitoids from the Cachoeirinha belt, Northeast Brazil

    International Nuclear Information System (INIS)

    Sial, A.N.

    1984-01-01

    Detailed rare-earth element study on about 40 samples from 14 granitic bodies distributed within and in adjacent areas of the Cachoeirinha belt, states of Pernambuco and Paraiba, between 37 0 and 40 0 W long. and 7 0 and 8 0 15' lat., was performed. These bodies include potassic, calc-alkalic, and peralkalic granitic associations, besides one with trondhjemitic affinities. The REE patterns for the potassic granitoids (Bodoco, Serra da Lagoinha and Itaporanga) which pierced basement migmatites, are strongly fractionated, mutually similar, LREE-enriched, and lack En anomaly. The calc-alkalic granitoids (Conceicao-type) intruded the low-grade metamorphics, and display strongly fractionated REE patterns, LREE-enriched relative to HREE, and exhibit a discrete, yet significative negative Eu anomaly. The granitoids with trondhjemitic affinities (Serrita-type) which intruded the Salgueiro schists, exhibit Σ REE much lower than in the previously mentioned granituids - REE patterns are strongly fractionated, LREE - enriched in relation to HREE, with discrete positive Eu anomaly and HREE approaching chondrite abundances. REE patterns of the peralkalic granitoids (Catingueira-type) ressemble those of rocks with trondhjemitic affinities and show a discrete positive Eu anomaly. The REE geochemistry agrees essentially with the major chemistry of the 4 granitoid associations, and is consistent with the 18 O/ 1 6O behavior which of ten varies sympathetically with Σ REE and S;O 2 . The presence of magmatic epidote, a high pressure phase, in three of these associations suggests that these rocks crystallized at a relatively great depth. (D.M.) [pt

  14. Petrology and Geochemistry of Shakh Sefid Granitoid and related skarn in the North of Rayen (southeastern of Kerman

    Directory of Open Access Journals (Sweden)

    Habib biabangard

    2017-11-01

    Full Text Available The Shakh Sefid Granitoid pluton and related Skarn are located 80 Km in the southeastern of Kerman and 20 Km north of Rayen. This area   is geologically located in the southeastern of the Lut block in the Central Iran. The Shakh Sefid Granitoid with Eocene-Oligocene age cuts the Cretaceous sedimentary rocks and led to the formation of Skarn. The granitoids are granite and granodiorite in composition composing of quartz, plagioclase, orthoclase, as primary minerals, biotite as minor and chlorite and sericite as secondary minerals. The sedimentary rocks are shale, sandstone, siltstone and limestone. Metamorphic rocks are marble and Skarns. The Skarn is calcic type. Garnet (grossular-andradite, tremolite and magnetite are the main minerals that are often accompanied with hematite, goethite and limonite. Pyrite, chalcopyrite and copper carbonate (malachite and azurite are the other minerals in Skarn. Geochemical studies show that the amount of major and minor elements of granitoid with increasing SiO2 content do not change due to the uniform mass, low dispersion of elements which result from heterogeneous textures and low alteration zone. Spider diagrams from minor elements normalized to Chondrite and primitive mantle show enrichment of all elements except for Ti, positive anomalies of Th, Pb and negative anomalies of Ti, P and Sr for the Sakh Sefid granitoids are probably due to crustal contamination. They are enriched in light rare earth elements (LREE between 10 to 100 times and heavy elements (HREE enrichment between 1 to 10 times compared to the reference (chondrite and regular pattern with approximately the same slope , the parallel trends indicate that the granitoid rocks share  a common source rock . The Shakh Sefid granitoid is I-type, metaluminous to peraluminous belonging to an active continental margin. Mineral and Mineralization in Kuh Shakh Sefid skarn is remarkably similar to iron skarn deposits. Minerals such as garnet and

  15. Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archaean biomass - the "hydrothermal pump hypothesis"

    Science.gov (United States)

    Duda, Jan-Peter; Thiel, Volker; Bauersachs, Thorsten; Mißbach, Helge; Reinhardt, Manuel; Schäfer, Nadine; Van Kranendonk, Martin J.; Reitner, Joachim

    2018-03-01

    Archaean hydrothermal chert veins commonly contain abundant organic carbon of uncertain origin (abiotic vs. biotic). In this study, we analysed kerogen contained in a hydrothermal chert vein from the ca. 3.5 Ga Dresser Formation (Pilbara Craton, Western Australia). Catalytic hydropyrolysis (HyPy) of this kerogen yielded n-alkanes up to n-C22, with a sharp decrease in abundance beyond n-C18. This distribution ( ≤ n-C18) is very similar to that observed in HyPy products of recent bacterial biomass, which was used as reference material, whereas it differs markedly from the unimodal distribution of abiotic compounds experimentally formed via Fischer-Tropsch-type synthesis. We therefore propose that the organic matter in the Archaean chert veins has a primarily microbial origin. The microbially derived organic matter accumulated in anoxic aquatic (surface and/or subsurface) environments and was then assimilated, redistributed and sequestered by the hydrothermal fluids (hydrothermal pump hypothesis).

  16. Field, geochemistry and Sr-Nd isotopes of the Pan-African granitoids from the Tifnoute Valley (Sirwa, Anti-Atlas, Morocco): a post-collisional event in a metacratonic setting

    Science.gov (United States)

    Toummite, A.; Liegeois, J. P.; Gasquet, D.; Bruguier, O.; Beraaouz, E. H.; Ikenne, M.

    2013-10-01

    In the Tifnoute Valley, three plutonic units have been defined: the Askaoun intrusion, the Imourkhssen intrusion and the Ougougane group of small intrusions. They are made of quartz diorite, granodiorite and granite and all contain abundant mafic microgranular enclaves (MME). The Askaoun granodiorite and the Imourkhssen granite have been dated by LA-ICP-MS on zircon at 558 ± 2 Ma and 561 ± 3 Ma, respectively. These granitic intrusions are subcontemporaneous to the widespread volcanic and volcano-detrital rocks from the Ouarzazate Group (580-545 Ma), marking the post-collisional transtensional period in the Anti-Atlas and which evolved towards alkaline and tholeiitic lavas in minor volume at the beginning of the Cambrian anorogenic intraplate extensional period. Geochemically, the Tifnoute Valley granitoids belong to an alkali-calcic series (high-K calc-alkaline) with typical Nb-Ta negative anomalies and no alkaline affinities. Granitoids and enclaves display positive ɛNd-560Ma (+0.8 to +3.5) with young Nd-TDM between 800 and 1200 Ma and relatively low 87Sr/86Sr initial ratios (Sri: 0.7034 and 0.7065). These values indicate a mainly juvenile source corresponding to a Pan-African metasomatized lithospheric mantle partly mixed with an old crustal component from the underlying West African Craton (WAC). Preservation in the Anti-Atlas of pre-Pan-African lithologies (c. 2.03 Ga basement, c. 800 Ma passive margin greenschist-facies sediments, allochthonous 750-700 Ma ophiolitic sequences) indicates that the Anti-Atlas lithosphere has not been thickened and was never an active margin during the Neoproterozoic. After a transpressive period, the late Ediacaran period (580-545 Ma) is marked by movement on near vertical transtensional faults, synchronous with the emplacement of the huge Ouarzazate Group and the Tifnoute Valley granitoids. We propose here a geodynamical model where the Tifnoute Valley granitoids as well as the Ouarzazate Group were generated during the post

  17. Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life

    Science.gov (United States)

    Heinrich, Christoph A.

    2015-03-01

    The Witwatersrand Basin in South Africa is one of the best-preserved records of fluvial sedimentation on an Archaean continent. The basin hosts the worlds biggest gold resource in thin pebble beds, but the process for gold enrichment is debated. Mechanical accumulation of gold particles from flowing river water is the prevailing hypothesis, yet there is evidence for hydrothermal mobilization of gold by fluids invading the metasedimentary rocks after their burial. Earth's atmosphere three billion years ago was oxygen free, but already sustained some of the oldest microbial life on land. Here I use thermodynamic modelling and mass-balance calculations to show that these conditions could have led to the chemical transport and precipitation of gold in anoxic surface waters, reconciling the evidence for fluvial deposition with evidence for hydrothermal-like chemical reactions. I suggest that the release of sulphurous gases from large volcanic eruptions created acid rain that enabled the dissolution and transport of gold in surface waters as sulphur complexes. Precipitation of the richest gold deposits could have been triggered by chemical reduction of the dissolved gold onto organic material in shallow lakes and pools. I conclude that the Witwatersrand gold could have formed only during the Archaean, after the emergence of continental life but before the rise of oxygen in the Earth's atmosphere.

  18. Genesis of Neoproterozoic granitoid magmatism in the Eastern Aracuai Fold Belt, eastern Brazil: field, geochemical and Sr-Nd isotopic evidence

    International Nuclear Information System (INIS)

    Celino, Joil Jose; Botelho, Nilson Francisquini; Pimentel, Marcio Martins

    2000-01-01

    The Neoproterozoic granitoid magmatism of the Aracuai Fold Belt (AFB) is an important element for the discussion of the evolution of this belt and its relationships with the African counterpart, the West Congo Belt. In the eastern part of the AFB, four different granitoid suites were recognized. The Nanuque Suite (NQS) comprises syn-tectonic peraluminous cordierite-bearing monzogranites. The Sao Paulinho Suite (SPS) consists of Th-rich peraluminous two mica or biotite-only granitoids. Calc-alkalic granitoids with magmatic epidote were grouped into the Itagimirim Suite (ITS) and post-tectonic charnockitic rocks were grouped into the Salomao Suite (SLS). Sm-Nd mineral isochron and Rb- isochron yielded ages of yielded ages of respectively 761 Ma and 714 Ma for the Nanuque and Sao Paulino suites. The general Sr-Nd isotopic characteristics of the granitoid suites and some country rocks indicate that the parental magmas were mostly the product of melting of the Paraiba do Sul metasediments. The chronological and genetic evolution the Neoproterozoic plutonism can be envisaged in a model of est-dipping subduction zone, followed by a continental collision between the Brasiliano/Pan-African (Brazil) and Congo (Africa cratons and final episodes of uplift and collapse. (author)

  19. Why Archaean TTG cannot be generated by MORB melting in subduction zones

    Science.gov (United States)

    Martin, Hervé; Moyen, Jean-François; Guitreau, Martin; Blichert-Toft, Janne; Le Pennec, Jean-Luc

    2014-06-01

    Until recently it was assumed that the Archaean continental crust (made of TTGs: tonalites, trondhjemites, and granodiorites) was generated through partial melting of MORB-like basalts in hot subduction environments, where the subducted oceanic crust melted at high pressure, leaving a garnet-bearing amphibolitic or eclogitic residue. However, recent geochemical models as well as basalt melting experiments have precluded MORB as a plausible source for TTGs. Rather, geochemical and experimental evidences indicate that formation of TTG required a LILE-enriched source, similar to oceanic plateau basalts. Moreover, subduction is a continuous process, while continental growth is episodic. Several “super-growth events” have been identified at ~ 4.2, ~ 3.8, ~ 3.2, ~ 2.7, ~ 1.8, ~ 1.1, and ~ 0.5 Ga, which is inconsistent with the regular pattern that would be expected from a subduction-driven process. In order to account for this periodicity, it has been proposed that, as subduction proceeds, descending residual slabs accumulate at the 660-km seismic discontinuity. When stored oceanic crust exceeds a certain mass threshold, it rapidly sinks into the mantle as a cold avalanche, which induces the ascent of mantle plumes that in turn produce large amounts of magmas resulting in oceanic plateaus. However, melting at the base of thick oceanic plateaus does not appear to be a realistic process that can account for TTG genesis. Modern oceanic plateaus contain only small volumes (≤ 5%) of felsic magmas generally formed by high degrees of fractional crystallization of basaltic magmas. The composition of these felsic magmas drastically differs from that of TTGs. In Iceland, the interaction between a mantle plume and the mid-Atlantic ridge gives rise to an anomalously (Archaean-like) high geothermal gradient resulting in thick basaltic crust able to melt at shallow depth. Even in this favorable context though, the characteristic Archaean TTG trace element signature is not being

  20. Granitoides paleozoicos de la Sierra de Narváez, Sistema de Famatina, Argentina: Hibridización de magmas en un margen continental activo

    Directory of Open Access Journals (Sweden)

    Cisterna, C. E.

    1992-12-01

    Full Text Available The granitoids from the Sierra de Narváez were investigated for their geochemical and petrographical characteristics. They are composed of calc-alkaline granites, granodiorites and tonalites, similar to the other paleozoic granitoids of the Famatina System. These rocks are intrusive in the Las Planchadas (volcanic rocks and Suri (sedimentary rocks Formations, which are probably cogenetic with the granitoids within the same magmatic cycle.The study of the granitoids reveals the close relationship between their composition and the abundance of the enclosed magmatic inclusions. The latter represent rocks and granodioritic tonalitic and diorite composition, and have a great number of mineralogical characteristic that suggest the presence of two magmas, mafic and felsic for the origin of such enclaves.The close chemical relationship existing between the inclusions and their host rocks shows that the mafic and felsic components are compositionally modified and that the granitoids are more or less hybridized.Trace elements discrimination diagrams have been used as a tools for fingerprinting the tectonic setting of the Sierra de Narváez granitoids. The geochemistry as well as the geologic relations of the granitoids with the roughly coeval ordovician vulcanism indicate a volcanic arc environment.Las rocas que afloran en el extremo septentrional de la Sierra de Narváez están representadas por una asociación de monzogranitos, granodioritas y tonalitas que definen una serie calcoalcalina, de características similares a las de otros intrusivos del Paleozoico del Sistema de Famatina. Estos granitoides se hallan intruyendo las Formaciones Las Planchadas y Suri, representadas por vulcanitas y metasedimentitas, respectivamente, y corresponderían a un mismo evento magmático del Paleozoico Inferior.Los granitoides estudiados presentan abundantes inclusiones ígneas de composición granodiorítica o tonalítica y diorítica. La estrecha relación que

  1. Direct evidence for the origin of low-18O silicic magmas: Quenched samples of a magma chamber's partially-fused granitoid walls, Crater Lake, Oregon

    International Nuclear Information System (INIS)

    Bacon, C.R.; Adami, L.H.; Lanphere, M.A.

    1989-01-01

    Partially fused granitoid blocks were ejected in the climactic eruption of Mount Mazama, which was accompanied by collapse of Crater Lake caldera. Quartz, plagioclase, and glass in the granitoids have much lower δ 18 O values (-3.4 to +4.9per mille) than any fresh lavas of Mount Mazama and the surrounding region (+5.8 to +7.0per mille). Oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at T≥900deg C following subsolidus exchange with hydrothermal fluids of meteoric origin. Assimilation of ≅ 10-20% of material similar to these granitoids can account for the O and Sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber, many of which have δ 18 O values ≅ 0.5per mille or more lower than comparable lavas of Mount Mazama. The O isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids (dominantly granodiorite) are similar to those of erupted juvenile magmas. The granitoid blocks from Crater Lake serve as direct evidence for the origin of 18 O depletion in large, shallow silicic magma bodies. (orig.)

  2. Petrogenesis of Luchuba and Wuchaba granitoids in western Qinling: geochronological and geochemical evidence

    Science.gov (United States)

    Kong, Juanjuan; Niu, Yaoling; Duan, Meng; Zhang, Yu; Hu, Yan; Li, Jiyong; Chen, Shuo

    2017-12-01

    The West Qinling Orogenic Belt (WQOB) is a major portion of the Qinling-Dabie-Sulu Orogen and holds essential information for understanding the prolonged evolution of the northeastern branch of the Paleo-Tethys in East Asia. This study focuses on the petrogenesis of granitoids from Luchuba and Wuchaba plutons in the WQOB. We obtained zircon U-Pb ages of 211 ± 1.4 Ma for the Luchuba pluton and 218.7 ± 1.3 Ma for the Wuchaba pluton, which are the same as the proposed timing of continental collision at ˜220 Ma. We thus interpret the granitoids to represent a magmatic response to the collision between the North China Craton (NCC) and the Yangtze Block (YB). The two plutons are metaluminous to weakly peraluminous I-type granitoids. Samples from the two plutons show strong light rare earth element (REEs) enrichment and weak heavy REE depletion, with varying negative Eu anomalies, which is most consistent with significant plagioclase fractionation although the possible effect of plagioclase as residual phase in the magma source region cannot be ruled out. In primitive mantle normalized multi-element variation diagrams, nearly all the samples show negative Nb, Ta, P and Ti anomalies and relative enrichment in Rb, Pb, U and K. These characteristics resemble those of the average continental crust. The Luchuba pluton has lower (87Sr/86Sr)i (0.7051 to 0.7104), higher ɛNd(t) (-8.11 to -5.73) and ɛHf(t) (-6.70 to -1.65) than mature continental crust ([87Sr/86Sr] i > 0.72, ɛNd(t) pluton also has lower (87Sr/86Sr)i (0.7069 to 0.7080), higher ɛNd(t) (-9.86 to -3.34) and ɛHf(t) (-5.69 to 1.58) than mature continental crust. We conclude that the Luchuba and Wuchaba granitoids in the WQOB are best explained as resulting from fractional crystallization with crustal assimilation of parental magmas derived from melting of Mianlue oceanic crust under amphibolite facies conditions during the initial stage of continental collision between the North China Craton and the Yangtze Block

  3. Recycling of the Archaean continental crust: the case study of the Gavião, State of Bahia, NE Brazil

    Science.gov (United States)

    Pinto, M. Santos; Peucat, J. J.; Martin, H.; Sabaté, P.

    1998-09-01

    The Gavião block, located to the west of the São Francisco Craton (State of Bahia, NE Brazil), is the oldest crustal block so far recognised in South America—3.42 Ga. In its southern part, the Gavião block has been divided into three domains on the basis of 207Pb/ 206Pb dating on single zircons and monazites combined with Sr and Nd isotopic data and major and trace element geochemical modelling. These are: (1) an Archaean juvenile domain which consists of grey gneisses (Bernada massif) which evidence mantle extraction around 3.3 Ga; (2) an Archaean domain (3.24-3.16 Ga) either recycled, or juvenile with crustal contamination, consisting of trondhjemitic grey gneisses (Aracatu massif) and K-rich calc-alkaline granitic gneisses (Mariana and Serra do Eixo massifs); (3) a Paleoproterozoic recycled domain consisting mainly of the Umburanas granites, which yielded inherited zircons ages ranging from 3.1 to 2.8 Ga, whereas the monazite age is ca 2.0 Ga. The Aracatu and Mariana massifs are cut by granites at ca 2.0 Ga the same age of the Serra da Franga massif. The Gavião block is a type example of Archaean continental crust (3.2 Ga) that has been recycled through partial melting events mainly in Paleoproterozoic times during the Transamazonian orogeny (2.0-2.1 Ga). Brasiliano cooling ages are recorded by the Rb-Sr system of biotite-whole rock pairs ca 500 Ma.

  4. The mechanics of granitoid systems and maximum entropy production rates.

    Science.gov (United States)

    Hobbs, Bruce E; Ord, Alison

    2010-01-13

    A model for the formation of granitoid systems is developed involving melt production spatially below a rising isotherm that defines melt initiation. Production of the melt volumes necessary to form granitoid complexes within 10(4)-10(7) years demands control of the isotherm velocity by melt advection. This velocity is one control on the melt flux generated spatially just above the melt isotherm, which is the control valve for the behaviour of the complete granitoid system. Melt transport occurs in conduits initiated as sheets or tubes comprising melt inclusions arising from Gurson-Tvergaard constitutive behaviour. Such conduits appear as leucosomes parallel to lineations and foliations, and ductile and brittle dykes. The melt flux generated at the melt isotherm controls the position of the melt solidus isotherm and hence the physical height of the Transport/Emplacement Zone. A conduit width-selection process, driven by changes in melt viscosity and constitutive behaviour, operates within the Transport Zone to progressively increase the width of apertures upwards. Melt can also be driven horizontally by gradients in topography; these horizontal fluxes can be similar in magnitude to vertical fluxes. Fluxes induced by deformation can compete with both buoyancy and topographic-driven flow over all length scales and results locally in transient 'ponds' of melt. Pluton emplacement is controlled by the transition in constitutive behaviour of the melt/magma from elastic-viscous at high temperatures to elastic-plastic-viscous approaching the melt solidus enabling finite thickness plutons to develop. The system involves coupled feedback processes that grow at the expense of heat supplied to the system and compete with melt advection. The result is that limits are placed on the size and time scale of the system. Optimal characteristics of the system coincide with a state of maximum entropy production rate. This journal is © 2010 The Royal Society

  5. Petrogenesis of late Paleozoic-to-early Mesozoic granitoids and metagabbroic rocks of the Tengchong Block, SW China: implications for the evolution of the eastern Paleo-Tethys

    Science.gov (United States)

    Zhu, Ren-Zhi; Lai, Shao-Cong; Qin, Jiang-Feng; Zhao, Shao-Wei

    2018-03-01

    mantle-derived material associated with late Permian-to-Early Triassic subduction of the Paleo-Tethys, and a second stage that generated granitoid magmas by the partial melting of crustal-derived sources during the Late Triassic collision between the Lhasa and Tengchong blocks and the northern margin of the Australian continent. These rocks, therefore, provide evidence of a systematic late Permian-to-Late Triassic transition from a pre-collision/volcanic arc setting through a collisional setting to a final within-plate phase of magmatism. The previous research involving bulk-rock Sr-Nd analyses of units from the southern Sanjiang orogenic belt and zircon Hf isotopic analyses of units from the Tengchong Block suggests that these areas may record similar magmatic evolutionary trends from mantle- to crustal-derived sources during the evolution of the eastern Paleo-Tethys.

  6. Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archaean biomass – the “hydrothermal pump hypothesis”

    Directory of Open Access Journals (Sweden)

    J.-P. Duda

    2018-03-01

    Full Text Available Archaean hydrothermal chert veins commonly contain abundant organic carbon of uncertain origin (abiotic vs. biotic. In this study, we analysed kerogen contained in a hydrothermal chert vein from the ca. 3.5 Ga Dresser Formation (Pilbara Craton, Western Australia. Catalytic hydropyrolysis (HyPy of this kerogen yielded n-alkanes up to n-C22, with a sharp decrease in abundance beyond n-C18. This distribution ( ≤  n-C18 is very similar to that observed in HyPy products of recent bacterial biomass, which was used as reference material, whereas it differs markedly from the unimodal distribution of abiotic compounds experimentally formed via Fischer–Tropsch-type synthesis. We therefore propose that the organic matter in the Archaean chert veins has a primarily microbial origin. The microbially derived organic matter accumulated in anoxic aquatic (surface and/or subsurface environments and was then assimilated, redistributed and sequestered by the hydrothermal fluids (hydrothermal pump hypothesis.

  7. Geochemistry of the Serifos calc-alkaline granodiorite pluton, Greece: constraining the crust and mantle contributions to I-type granitoids

    Science.gov (United States)

    Stouraiti, C.; Baziotis, I.; Asimow, P. D.; Downes, H.

    2017-11-01

    The Late Miocene (11.6-9.5 Ma) granitoid intrusion on the island of Serifos (Western Cyclades, Aegean Sea) is composed of syn- to post-tectonic granodiorite with quartz monzodiorite enclaves, cut by dacitic and aplitic dikes. The granitoid, a typical I-type metaluminous calcic amphibole-bearing calc-alkaline pluton, intruded the Cycladic Blueschists during thinning of the Aegean plate. Combining field, textural, geochemical and new Sr-Nd-O isotope data presented in this paper, we postulate that the Serifos intrusion is a single-zoned pluton. The central facies has initial 87Sr/86Sr = 0.70906 to 0.7106, ɛNd(t) = - 5.9 to - 7.5 and δ18Οqtz = + 10 to + 10.6‰, whereas the marginal zone (or border facies) has higher initial 87Sr/86Sr = 0.711 to 0.7112, lower ɛ Nd(t) = - 7.3 to - 8.3, and higher δ18Οqtz = + 10.6 to + 11.9‰. The small range in initial Sr and Nd isotopic values throughout the pluton is paired with a remarkable uniformity in trace element patterns, despite a large range in silica contents (58.8 to 72 wt% SiO2). Assimilation of a crustally derived partial melt into the mafic parental magma would progressively add incompatible trace elements and SiO2 to the evolving mafic starting liquid, but the opposite trend, of trace element depletion during magma evolution, is observed in the Serifos granodiorites. Thermodynamic modeling of whole-rock compositions during simple fractional crystallization (FC) or assimilation-fractional crystallization (AFC) processes of major rock-forming minerals—at a variety of pressure, oxidation state, and water activity conditions—fails to reproduce simultaneously the major element and trace element variations among the Serifos granitoids, implying a critical role for minor phases in controlling trace element fractionation. Both saturation of accessory phases such as allanite and titanite (at SiO2 ≥ 71 wt%)(to satisfy trace element constraints) and assimilation of partial melts from a metasedimentary component (to

  8. Transformation of juvenile Izu-Bonin-Mariana oceanic arc into mature continental crust: An example from the Neogene Izu collision zone granitoid plutons, Central Japan

    Science.gov (United States)

    Saito, Satoshi; Tani, Kenichiro

    2017-04-01

    Granitic rocks (sensulato) are major constituents of upper continental crust. Recent reviews reveal that the average composition of Phanerozoic upper continental crust is granodioritic. Although oceanic arcs are regarded as a site producing continental crust material in an oceanic setting, intermediate to felsic igneous rocks occurring in modern oceanic arcs are dominantly tonalitic to trondhjemitic in composition and have lower incompatible element contents than the average upper continental crust. Therefore, juvenile oceanic arcs require additional processes in order to get transformed into mature continental crust enriched in incompatible elements. Neogene granitoid plutons are widely exposed in the Izu Collision Zone in central Japan, where the northern end of the Izu-Bonin-Mariana (IBM) arc (juvenile oceanic arc) has been colliding with the Honshu arc (mature island arc) since Middle Miocene. The plutons in this area are composed of various types of granitoids ranging from tonalite to trondhjemite, granodiorite, monzogranite and granite. Three main granitoid plutons are distributed in this area: Tanzawa plutonic complex, Kofu granitic complex, and Kaikomagatake granitoid pluton. Tanzawa plutonic complex is dominantly composed of tonalite and trondhjemite and characterized by low concentration of incompatible elements and shows geochemical similarity with modern juvenile oceanic arcs. In contrast, Kofu granitic complex and Kaikomagatake granitoid pluton consists mainly of granodiorite, monzogranite and granite and their incompatible element abundances are comparable to the average upper continental crust. Previous petrogenetic studies on these plutons suggested that (1) the Tanzawa plutonic complex formed by lower crustal anatexis of juvenile basaltic rocks occurring in the IBM arc, (2) the Kofu granitic complex formed by anatexis of 'hybrid lower crust' comprising of both basaltic rocks of the IBM arc and metasedimentary rocks of the Honshu arc, and (3) the

  9. Did the formation of D″ cause the Archaean-Proterozoic transition?

    Science.gov (United States)

    Campbell, Ian H.; Griffiths, Ross W.

    2014-02-01

    The MgO content of the highest MgO plume-related komatiites and picrites remained constant at 32±2.5% between 3.5 and 2.7 Ga, then fell to 21±3% by ca. 2.0 Ga, a value similar to the present day value. Because there is a linear relationship between the liquidus temperature of dry magmas and their MgO content this observation implies that the temperature of mantle plumes changed little between 3.5 and 2.7 Ga, and then fell by 200-250 °C between 2.7 and 2.0 Ga to a temperature similar to that of present plumes. We suggest that Archaean plumes originate from the core-mantle boundary and that their temperature remained constant because the temperature of the outer core was buffered by solidification of the Fe-Ni inner core. At about 2.7 Ga dense former basaltic crust began to accumulate at the core and eventually covered it to produce an insulating layer that reduced the heat flux out of the core and lowered the temperature of mantle plumes. The temperature of mantle plumes fell as the dense layer above the core thickened until it exceeded the critical thickness required for convection. Because heat is transferred rapidly across the convecting part of the insulating layer, any further increase in its thickness by the addition more basaltic material has no influence on the temperature at the top of the layer, which is the source of Post-Archaean mantle plumes. We equate the dense layer above the core with the seismically identified layer D″. Our analyses suggest the drop in plume temperatures produced by a dense insulating layer above the core will be about 40% once it starts to convect, which is consistent with the observed drop inferred from the decrease in the MgO content of komatiites and picrites at that time.

  10. Geochemical and biologic constraints on the Archaean atmosphere and climate – A possible solution to the faint early Sun paradox

    DEFF Research Database (Denmark)

    Rosing, Minik Thorleif; Brid, Dennis K.; Sleep, Norman H.

    into account the apparent growth of Earth continents (Collerson and Kamber 1999) and the absence of land vegetation during the Precambrian for the evolution of the surface albedo, and a model for the abundance and properties of clouds that takes into account the lower abundance of biogenic cloud condensation......There is ample geological evidence that Earth’s climate resembled the present during the Archaean, despite a much lower solar luminosity. This was cast as a paradox by Sagan and Mullen in 1972. Several solutions to the paradox have been suggested, mostly focusing on adjustments of the radiative...... properties of Earth’s atmosphere e.g. Kasting (1993), by increasing the mixing ratio of CO2 and/or adding various other greenhouse gasses. We have used banded iron formation (BIF), which are chemical sediments precipitated out of the Archaean ocean to characterize the composition of the atmosphere...

  11. An isotopic study of granitoids in the Litchfield Block, Northern Territory

    International Nuclear Information System (INIS)

    Page, R.W.; Bower, M.J.; Guy, D.B.

    1984-01-01

    The Litchfield Block contains a variety of granitoids, gneissic rocks, and migmatites that are intrusive into metasediments of probable Early Proterozoic age at the western margin of the Pine Creek Inlier. Isotopic data, which include U-Pb measurements on cogenetic zircon and xenotime and Rb-Sr total-rock measurements on the least metamorphosed granodiorites, show that these rocks crystallised from mantle-derived melts between 1840 Ma and 1850 Ma ago. Radiogenic Pb was lost from zircon in the early Palaeozoic (about 435 Ma), but xenotime remained a closed system until recent time. Many granitoids in the Litchfield Block have a gneissic fabric imposed during greenschist to amphibolite-grade regional metamorphism. This disturbance allowed partial isotopic re-equilibration of Rb-Sr total-rock systems, at about 1770 +- 16 Ma. As this igneous and metamorphic evolution is mirrored in other parts of the Pine Creek Inlier, the Halls Creek Inlier, and many other orogenic belts in northern Australia, its recognition and isotopic definition in the Litchfield Block further emphasise the magnitude and chronological integrity of this early Proterozoic tectonic event

  12. Chemical Zoning of Feldspars in Lunar Granitoids: Implications for the Origins of Lunar Silicic Magmas

    Science.gov (United States)

    Mills, R. D; Simon, J. I.; Alexander, C.M. O'D.; Wang, J.; Christoffersen, R.; Rahman, Z..

    2014-01-01

    Fine-scale chemical and textural measurements of alkali and plagioclase feldspars in the Apollo granitoids (ex. Fig. 1) can be used to address their petrologic origin(s). Recent findings suggest that these granitoids may hold clues of global importance, rather than of only local significance for small-scale fractionation. Observations of morphological features that resemble silicic domes on the unsampled portion of the Moon suggest that local, sizable net-works of high-silica melt (>65 wt % SiO2) were present during crust-formation. Remote sensing data from these regions suggest high concentrations of Si and heat-producing elements (K, U, and Th). To help under-stand the role of high-silica melts in the chemical differentiation of the Moon, three questions must be answered: (1) when were these magmas generated?, (2) what was the source material?, and (3) were these magmas produced from internal differentiation. or impact melting and crystallization? Here we focus on #3. It is difficult to produce high-silica melts solely by fractional crystallization. Partial melting of preexisting crust may therefore also have been important and pos-sibly the primary mechanism that produced the silicic magmas on the Moon. Experimental studies demonstrate that partial melting of gabbroic rock under mildly hydrated conditions can produce high-silica compositions and it has been suggested by that partial melting by basaltic underplating is the mechanism by which high-silica melts were produced on the Moon. TEM and SIMS analyses, coordinated with isotopic dating and tracer studies, can help test whether the minerals in the Apollo granitoids formed in a plutonic setting or were the result of impact-induced partial melting. We analyzed granitoid clasts from 3 Apollo samples: polymict breccia 12013,141, crystalline-matrix breccia 14303,353, and breccia 15405,78

  13. Some genetic aspects of hydrothermal uranium deposits in the Bakulja granitoide (Serbia)

    International Nuclear Information System (INIS)

    Jelenkovic, Rade

    1998-01-01

    This paper discusses the influence of temperature and the way of hydrothermal fluids flow in function of both the degree of tectonized granitoid and the origin of solutions, and partly the processes accompanying mineralization expressed through physico-chemical, mineralogical and mechanical alterations of the mother rock. It has been concluded that heat energy exchange is in function of: 1) petrochemical characteristic of a rock the hydrothermal fluids flow through; 2) degree of tectonization of the surrounding mineralized rocks; 3) volume and morphology of the fissured-porous space; 4) form of uranium bonding in mineral carriers; 5) degree of uranium leaching in hydrothermal solutions; 6) the way of hydrothermal fluids flow, and 7) coefficient of heat exchange expressed by distribution of heat energy within a fluid-rock system. It has also been established that contraction of granite volume results from physico-chemical processes that take place within a granitoid-hydrothermal fluid system and its quantification has been carried out. (Author)

  14. Petrological mineralogical and geochemical characterization of the granitoids and fracture fillings developed in Ratones Mines (Spain)

    International Nuclear Information System (INIS)

    Buil Gutierrez, B.

    2002-01-01

    The petrological, mineralogical and geochemical characterisation of the granitoids and fracture fillings developed in the Ratones Mine (Caceres, Spain) has been done in order to understand rock-water interaction processes which control water geochemical parameters. Special interest has been devoted to the analysis and interpretation of REE patterns in the solid phase (granitoids and fracture fillings) because they constitute geochemical tracers in water-rock interaction process. Moreover, REE are considered as actinide analogues. In order to characterise the solid phase (granitoids and fracture fillings) several investigation scales (system, outcrop, whole rock, mineral and geochemical components) have been considered and different types of samples have been analysed. These factors control the methodological approach used in this investigation. The analytical methods we have used in this investigation are microscope, qualitative and semi-quantitative methods (XRD, SEM,EDAX) and quantitative methods (ICP-MS, XRF, EM, LAM-IC-MS). The bulk of the granitoids located around the Ratones Mine Belongs to the alkaline feldspar granite-sienogranite lihotype and they show a peraluminous and subalkaline pattern. From the mineralogical point of view, they are composed by quartz, K-feldspar (Or>90%), showing sericitation, moscovitization and turmolinization altherations, alkaline plagioclase (An-=-3%), usually altered to sericite, saussirite and less frequently affected by moscovitization processes, Fe-Al biotite, frequently affected by chloritization processes and sometimes replaced by muscovite, and finally muscovite (>2% celadonite and <4% paragonite) both of primary and secondary origin. The differences observed between the different lithotypes are related with the modal proportion of the principal minerals,with the presence or absence of certain accessory minerals ( turmaline, cordierite), with specific textural patterns, grain size and also with the richness in specific

  15. Late Paleozoic-Early Mesozoic tectonic evolution of the Paleo-Asian Ocean: geochronological and geochemical evidence from granitoids in the northern margin of Alxa, Western China

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    Sha, Xin; Wang, Jinrong; Chen, Wanfeng; Liu, Zheng; Zhai, Xinwei; Ma, Jinlong; Wang, Shuhua

    2018-03-01

    The Paleo-Asian Ocean (Southern Mongolian Ocean) ophiolitic belts and massive granitoids are exposed in the Alxa block, in response to oceanic subduction processes. In this work, we report petrographic, geochemical, and zircon U-Pb age data of some granitoid intrusions from the northern Alxa. Zircon U-Pb dating for the quartz diorite, tonalite, monzogranite, and biotite granite yielded weighted mean 206Pb/238U ages of 302±9.2 Ma, 246.5±4.6 Ma, 235±4.4 Ma, and 229.5±5.6 Ma, respectively. The quartz diorites ( 302 Ma) exhibit geochemical similarities to adakites, likely derived from partial melting of the initially subducted Chaganchulu back-arc oceanic slab. The tonalites ( 246.5 Ma) display geochemical affinities of I-type granites. They were probably derived by fractional crystallization of the modified lithospheric mantle-derived basaltic magmas in a volcanic arc setting. The monzogranites ( 235 Ma) are characterized by low Al2O3, but high Y and Yb with notably negative Eu anomalies. In contrast, the biotite granites ( 229.5 Ma) show high Al2O3 but low Y and Yb with steep HREE patterns and the absence of negative Eu anomalies. Elemental data suggested that the biotite granites were likely derived from a thickened lower crust, but the monzogranites originated from a thin crust. Our data suggested that the initial subduction of the Chaganchulu oceanic slab towards the Alxa block occurred at 302 Ma. This subduction process continued to the Early Triassic ( 246 Ma) and the basin was finally closed before the Middle Triassic ( 235 Ma). Subsequently, the break-off of the subducted slab triggered asthenosphere upwelling (240-230 Ma).

  16. Geología de la parte sur de la Sierra de San Luis y granitoides asociados, Argentina

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    Llambías, E. J.

    1992-12-01

    Full Text Available The lower Palaeozoic basement of the southern part of Sierra de San Luis, Argentina, is made up of metamorphic rocks, granitoids and ultramafic rocks. The metamorphic grade ranges from the lower limit of greenschist facies through the upper limit of amphibolite facies, in apparent transition. The lower grade metamorphic rocks include slates, metavolcanics, metaconglomerates, quartzites and phyllites. Rocks with intermediate metamorphism are biotite-quartz-oligoclase schists with abundant pegmatoid veins. The higher grade metamorphism is represented by gneisses, amphibolites and migmatites, to which mafic and ultramafic bodies are associated. Three deformation phases have been recognized, being the last one (D3, of ordovician age, responsible of the most marked structures.The granitoids were grouped into pre-, syn- and post-kynematic bodies respect to D3. The pre-kynematic granitoids are located within the belt of lower grade metamorphic rocks and are composed of tonalites, granodiorites and monzogranites, strongly deformed. Their age is unknown. The syn-kynematic bodies are mainly garnet-moscovite-bearing leucogranodiorites. They show low thermal and rheological contrasts respect to the country rocks, and the age is 454 ± 21 m.a. The post-kynematic granitoids are mainly monzogranites with K-feldspar megacrysts and abundant sphene. They are subcircular and discordant, and are associated with an extensional regime. Their age is comprised between 423 and 320 m.a., and corresponds to the end of the Famatinian cycle.El basamento cristalino de la parte sur de la Sierra de San Luis, de edad Paleozoico Inferior, está constituido por rocas metamórficas, granitoides y rocas ultramáficas. El grado de metamorfismo varía desde la parte baja de esquistos verdes hasta la parte alta de la facies anfibolita, siendo sus relaciones de aparente transicionalidad. Las rocas con menor grado metamórfico consisten en pizarras, metavolcanitas, metaconglomerados

  17. Mineral chemistry and geochemistry of the Late Neoproterozoic Gabal Abu Diab granitoids, Central Eastern Dessert, Egypt: Implications for the origin of rare metal post-orogenic A-type granites

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    Sami, Mabrouk; Ntaflos, Theodoros; Farahat, Esam S.; Ahmed, Awaad F.; Mohamed, Haroun A.

    2015-04-01

    The Neoproterozoic Gabal Abu Diab pluton is a part of the Arabian Nubian shield (ANS) continental crust and located in the Central Eastern Desert (CED) of Egypt. It constitutes multiphase granitic pluton intruded into granodiorite and metagabbro-diorite rocks with sharp and nonreactive contacts. Based on field observations, colors, structural variations and petrographic investigations, this granitic outcrop consists of an inner core of two-mica granite (TMG) followed outward by garnet bearing muscovite granite (GBMG) and albite granite (AG). Petrographical study indicated that medium to coarse-grained TMG is dominated by K-feldspar (Or88-98), quartz, plagioclase (albite, An0-7), muscovite and biotite with hypidiomorphic texture. With exception the appearance of garnet and the disappearance of biotite the GBMG resembles the TGM, while AG is leucocratic without any mafic mineral. The main accessories are zircon, Nb and Ta-bearing rutile, columbite, ilmenorutile, ilmenite, magnetite and apatite. This mineralogical similarity and the existence of columbite group minerals (CGM) in all granitoids, indicates a cogenetic relationship. Microprobe analyses reveal that, besides the CGM, rutile and ilmenite are the main repository phases for Nb-Ta-Ti. Columbite-(Mn) exists as individual subhedral crystals (up to 100μm in size) or intimate intergrowth with Nb-bearing rutile and/or ilmenite. The CGM are represented mostly by columbite-(Mn) with Ta/(Ta+Nb) and Mn/(Mn+Fe) ratio ranging from 0.02-0.08 and 0.4-0.9, respectively suggesting extreme degree of magmatic fractionation. Rutile contains significant amounts of Ta (up to 4 wt.% Ta2O5) and Nb (up to 22 wt.% Nb2O5). Biotites are phlogopite-annite in composition (Ann47-60Phlog40-53,on average) and are enriched with AlIV that characterize peraluminous granites. Garnets contain 60-69 mol.% spessartine and 28-36 mol.% almandine where, the ratio of spessartine and almandine together exceeds 95 mole percent, similar to garnet occur

  18. New monazite U-Pb age constraints on the evolution of the Paleoproterozoic Vaasa granitoid batholith, western Finland

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    A.K. Kotilainen

    2016-09-01

    Full Text Available The Vaasa batholith, western Finland, is a large, peraluminous granitoid pluton that crystallized at 1.88–1.87 Ga during the culmination of the Svecofennian orogeny. The batholith has gradual contacts, through metatexites and diatexites, with the enveloping metasedimentary rocks of the Bothnian Belt. We present ID-TIMS U-Pb age data on monazite from granitoids and xenoliths of the Vaasa batholith and combine these with published U–Pb zircon ages in order to shed further light on the evolution of the Vaasa batholith. The apparent monazite ages for seven of the examined samples are 1870–1863 Ma, and 1855±3 Ma for one further sample from the southern part of the batholith. Combined with pre-existing data, the monazite ages of the granitoids are 9 to 18 Ma (face values or 3 to 9 Ma (external errors considered younger than the U–Pb zircon crystallization ages from respective samples. Our new data suggest slow cooling for the Vaasa batholith – the closure/saturation temperature of the monazite U–Pb system was probably reached in ~10 m.y. after the crystallization of magmatic zircon in the examined rocks.

  19. Protoliths of enigmatic Archaean gneisses established from zircon inclusion studies: Case study of the Caozhuang quartzite, E. Hebei, China

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    Allen P. Nutman

    2014-07-01

    Full Text Available A diverse suite of Archaean gneisses at Huangbaiyu village in the North China Craton, includes rare fuchsite-bearing (Cr-muscovite siliceous rocks – known as the Caozhuang quartzite. The Caozhuang quartzite is strongly deformed and locally mylonitic, with silica penetration and pegmatite veining common. It contains abundant 3880–3600 Ma and some Palaeoarchaean zircons. Because of its siliceous nature, the presence of fuchsite and its complex zircon age distribution, it has until now been accepted as a (mature quartzite. However, the Caozhuang quartzite sample studied here is feldspathic. The shape and cathodoluminescence petrography of the Caozhuang quartzite zircons show they resemble those found in immature detrital sedimentary rocks of local provenance or in Eoarchaean polyphase orthogneisses, and not those in mature quartzites. The Caozhuang quartzite intra-zircon mineral inclusions are dominated by quartz, with lesser biotite, apatite (7% and alkali-feldspar, and most inclusions are morphologically simple. A Neoarchaean orthogneiss from near Huangbaiyu displays morphologically simple inclusions with much more apatite (73%, as is typical for fresh calc-alkaline granitoids elsewhere. Zircons were also examined from a mature conglomerate quartzite clast and an immature feldspathic sandstone of the overlying weakly metamorphosed Mesoproterozoic Changcheng System. These zircons have oscillatory zoning, showing they were sourced from igneous rocks. The quartzite clast zircons contain only rare apatite inclusions (<1%, with domains with apatite habit now occupied by intergrowths of muscovite + quartz ± Fe-oxides ± baddeleyite. We interpret that these were once voids after apatite inclusions that had dissolved during Mesoproterozoic weathering, which were then filled with clays ± silica and then weakly metamorphosed. Zircons in the immature feldspathic sandstone show a greater amount of preserved apatite (11%, but with petrographic

  20. Ordovician A-type granitoid magmatism on the Ceará Central Domain, Borborema Province, NE-Brazil

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    Castro, Neivaldo A.; Ganade de Araujo, Carlos E.; Basei, Miguel A. S.; Osako, Liliane S.; Nutman, Alan A.; Liu, Dunyi

    2012-07-01

    We present field relationships, major and trace element geochemistry and U-Pb SHRIMP and ID-TIMS geochronology of the A-type Ordovician Quintas pluton located in the Ceará Central Domain of the Borborema Province, in northeastern Brazil. This pluton presents a concentric geometry and is composed mainly of syenogranite, monzogranite, quartz syenite to quartz monzodiorite, monzogabbro and diorite. Its geochemical characteristics [SiO2 (52-70%), Na2O/K2O (1.55-0.65), Fe2O3/MgO (2.2-7.3), metaluminous to sligthly alkaline affinity, post-collisional type in (Y + Nb) × Rb diagram, and A-type affinity (Ga > 22 ppm, Nb > 20 ppm, Zn > 60 ppm), REE fractioned pattern with negative Eu anomaly] are coherent with post-collisional A2-type granitoids. However, the emplacement of this pluton is to some extent temporally associated with the deposition of the first strata of the Parnaíba intracratonic basin, attesting also to a purely anorogenic character (A1-type granitoid). The emplacement of this pluton is preceded by one of the largest known orogenesis of the planet (Neoproterozoic Pan-African/Brasiliano) and, if it is classified as an A2-type granitoid, it provides interesting constraints about how long can last A2-type magmatic activity after a major collisional episode, arguably triggered by disturbance of the underlying mantle, a topic extensively debated in the geoscience community.

  1. Review of the geochemistry and metallogeny of approximately 1.4 Ga granitoid intrusions of the conterminous United States

    Science.gov (United States)

    du Bray, Edward A.; Holm-Denoma, Christopher S.; Lund, Karen; Premo, Wayne R.

    2018-03-27

    The conterminous United States hosts numerous volumetrically significant and geographically dispersed granitoid intrusions that range in age from 1.50 to 1.32 billion years before present (Ga). Although previously referred to as A-type granites, most are better described as ferroan granites. These granitoid intrusions are distributed in the northern and central Rocky Mountains, the Southwest, the northern midcontinent, and a swath largely buried beneath Phanerozoic cover across the Great Plains and into the southern midcontinent. These intrusions, with ages that are bimodally distributed between about 1.455–1.405 Ga and 1.405–1.320 Ga, are dispersed nonsystematically with respect to age across their spatial extents. Globally, although A-type or ferroan granites are genetically associated with rare-metal deposits, most U.S. 1.4 Ga granitoid intrusions do not contain significant deposits. Exceptions are the light rare-earth element deposit at Mountain Pass, California, and the iron oxide-apatite and iron oxide-copper-gold deposits in southeast Missouri.Most of the U.S. 1.4 Ga granitoid intrusions are composed of hornblende ± biotite or biotite ± muscovite monzogranite, commonly with prominent alkali feldspar megacrysts; however, modal compositions vary widely. These intrusions include six of the eight commonly identified subtypes of ferroan granite: alkali-calcic and calc-alkalic peraluminous subtypes; alkalic, alkali-calcic, and calc-alkalic metaluminous subtypes; and the alkalic peralkaline subtype. The U.S. 1.4 Ga granitoid intrusions also include variants of these subtypes that have weakly magnesian compositions. Extreme large-ion lithophile element enrichments typical of ferroan granites elsewhere are absent among these intrusions. Chondrite-normalized rare-earth element patterns for these intrusions have modest negative slopes and moderately developed negative europium anomalies. Their radiogenic isotopic compositions are consistent with mixing involving

  2. Abundances of chemical elements in granitoids of different geological ages and their characteristics in China

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    Changyi Shi

    2011-04-01

    Full Text Available Actual granitoid analytical data of 767 composited samples are presented here. The data source is 6080 samples collected mainly from 750 large- to middle-sized granitoid bodies across China. Data from the composited samples, which includes that of 70 elements, is analyzed according to geological age — Archeozoic (Ar, Proterozoic (Pt, Eopaleozoic (Pz1, Neopaleozoic (Pz2, Mesozoic (Mz, and Cenozoic (Cz — and three major compositional varieties, e.g. alkali-feldspar granite, syenogranite and adamellite. Petrochemical parameters, trace-element content and rare-earth element (REE distributions of the different rock types and geological ages are characterized, and change tendencies through Archean to Cenozoic time are recorded. The comprehensive analytical data presented here has not been previously published. This significant data set can be used as fundamental information in studies of basic China geology, magma petrogenesis, ore exploration and geochemistry.

  3. New isotopic and field evidence for the ages and distribution of Archaean rocks in east Antarctica

    International Nuclear Information System (INIS)

    Kinny, P.D.; Delor, C.P.

    1990-01-01

    The Precambrian shield of East Antarctica is composed of a number of recognised Archaean cratonic nuclei surrounded by Proterozoic metamorphic complexes. Poor exposure, inaccessibility and the effects of multiple tectonothermal overprints combine to confound the knowledge of the early history of these terranes. Against this, it is shown how recent advances in zircon geochronology allied with new petrological, geochemical and field observations have resulted in major revisions to the chronostratigraphy of several key areas, including Napier Complex of Enderby Land, Vestfold Hills and Rauer Group. 11 refs

  4. A basin on an unstable ground: Correlation of the Middle Archaean Moodies Basin, Barberton Greenstone Belt, South Africa

    Science.gov (United States)

    Ohnemueller, Frank; Heubeck, Christoph; Kirstein, Jens; Gamper, Antonia

    2010-05-01

    time and immediately predates the initiation of basin shortening. Basin compartmentalization was likely due to the movement along a group of major faults (Sheba, Haki, Barbrook, Saddleback Faults) between the present Saddleback and Eureka Synclines, creating at least two subbasins in late Moodies time. Even though sediment provenance thus became localized, intensive Archaean weathering likely contributed to generate petrographically similar quartz-rich sandstones in fault-bounded minibasins. The late-Moodies minibasins may have become connected occasionally, allowing concurrent deposition of thin BIFs. A similar phase of movement along the major transcurrent Inyoka Fault may be responsible for the distinct petrographic character of Moodies sandstones south of that fault.

  5. Devonian granitoids and their hosted mafic enclaves in the Gorny Altai terrane, northwestern Central Asian Orogenic Belt: crust-mantle interaction in a continental arc setting

    Science.gov (United States)

    Chen, Ming; Sun, Min

    2016-04-01

    Granitoids are a major component in the upper continental crust and hold key information on how did the continental crust grow and differentiate. This study focuses on the Yaloman intrusive complex from the Gorny Altai terrane, northwestern Central Asian Orogenic Belt (CAOB). The association of granitoids and mafic enclaves can provide important clues on the source nature, petrogenetic processes and geodynamic setting of the Yaloman intrusive complex, which in turn will shed light on the crustal evolution in the northwestern CAOB. Zircon U-Pb dating shows that the granitoids, including quartz diorites and granodiorites, were emplaced in ca. 389-387 Ma. The moderate Na2O + K2O contents and low A/CNK values indicate that these rocks belong to the sub-alkaline series with metaluminous to weakly peraluminous compositions. The granitoids yield two-stage zircon Hf model ages of ca. 0.79-1.07 Ga and whole-rock Nd model ages of ca. 0.90-0.99 Ga, respectively, implying that they were mainly sourced from Neoproterozoic juvenile crustal materials. The mafic enclaves show an almost identical crystallization age of ca. 389 Ma. The identification of coarse-grained xenocrysts and acicular apatites, together with the fine-grained texture, makes us infer that these enclaves are likely to represent magmatic globules commingled with the host magmas. The low SiO2 and high MgO contents of the mafic enclaves further suggest that substantial mantle-derived mafic melts were probably involved in their formation. Importantly, the SiO2 contents of the granitoids and mafic enclaves are well correlated with other major elements and most of the trace elements. Also a broadly negative correlation exists between the SiO2 contents and whole-rock epsilon Nd (390 Ma) values of the granitoids. Given the observation of reversely zoned plagioclases within the granitoids and the common occurrence of igneous mafic enclaves, we propose that magma mixing probably played an important role in the formation

  6. Les granitoïdes hercyniens post-collisionnels du Maroc oriental : une province magmatique calco-alcaline à shoshonitiqueThe post-collisional Hercynian granitoids from eastern Morocco: a calc-alkaline to shoshonitic magmatic province

    Science.gov (United States)

    El Hadi, Hassan; Tahiri, Abdelfatah; Reddad, Aicha

    2003-11-01

    The post-collisional Hercynian granitoids crop out in the easternmost part of the Moroccan Hercynian belt. Petrographical and geochemical studies show a composition similarity in the various granitoids. The granitoids belong to per-aluminous and metaluminous magmatic associations. They have evolved according to a scheme similar to high-K calc-alkaline to shoshonitic associations. To cite this article: H. El Hadi et al., C. R. Geoscience 335 (2003).

  7. Signature of breccia complex/iron oxide- type U-REE mineralisation in the Khairagarh basin with special reference to Dongargaon- Lohara area, central India

    International Nuclear Information System (INIS)

    Hansoti, S.K.; Sinha, D.K.

    1995-01-01

    The Khairagarh basin having late Archaean- early Proterozoic basement is filled up by middle Proterozoic Khairagarh group volcano - sedimentary sequence, laid in the Kotri rift zone (KRZ) with imprints of repetitive volcanic, plutonic and tectonic activities. A strong thermal imprint of ∼ 1.5 Ga has been recorded in rocks of the basin that could be an effect of copious outpouring of basalts, dacites, ignimbrites, together with the emplacements of stocks of gabbros, gabbroic dolerites, dolerites, granites, granophyres, felsites, aplites, and quartz veins. Some of the basement rocks are enriched in Fe, Cu and other base metals and have been emplaced and assimilated by the volcano- plutonic rocks of the Nandgaon group and Malanjkhand granitoids. The Nandgaon group rocks and the Malanjkhand granitoids have anomalous intrinsic abundance of U, REE, Cu, Fe and quite a few metals in different sectors. Thermo-tectonic (∼ 1.5 Ga) reactivation event(s) along the KRZ apart from facilitating formation of agglomerates, ignimbrites and tectonic breccias has promoted emplacement of plutonic and subvolcanic phases and their metasomatising and hydrothermal metal bearing fluids. In the Malanjkhand complex sector Cu±Mo±Fe±Ag±Au±REE±Zn metallisation and in the Dongargarh Massif sector U±Th±F±Fe±Pb±Zn±Cu±REE±Zr metallisation are manifested. The detection of Fe+U+REE ±Cu±Ni metallisation in the Bortalao sandstones of the Dongargaon - Lohara area, located in between Malanjkhand ore zone and the Chandidongri (Dongargarh granite hosted) fluorite-rich and Pb±Zn±Cu±U - bearing ore zone, considered to lie on the same (Malanjkhand - Chandidongri) fault/shear lineament is rated highly significant. This observation supports the prognosis that the terrain lying in between the Dongargarh Massif and the Malanjkhand Granitoid complex should be the locus for the mixing of the respective metal bearing fluids and such a terrain therefore should be considered as a first order

  8. From steep feeders to tabular plutons - Emplacement controls of syntectonic granitoid plutons in the Damara Belt, Namibia

    Science.gov (United States)

    Hall, Duncan; Kisters, Alexander

    2016-01-01

    Granitoid plutons in the deeply eroded south Central Zone of the Damara Belt in Namibia commonly show tabular geometries and pronounced stratigraphic controls on their emplacement. Subhorizontal, sheet-like pluton geometries record emplacement during regional subhorizontal shortening, but the intrusion of spatially and temporally closely-related granitoid plutons at different structural levels and in distinct structural settings suggests independent controls on their levels of emplacement. We describe and evaluate the controls on the loci of the dyke-to-sill transition that initiated the emplacement of three syntectonic (560-530 Ma) plutons in the basement-cover stratigraphy of the Erongo region. Intrusive relationships highlight the significance of (1) rigidity anisotropies associated with competent sedimentary packages or pre-existing subhorizontal granite sheets and (2) rheological anisotropies associated with the presence of thick ductile marble horizons. These mechanical anisotropies may lead to the initial deflection of steep feeder conduits as well as subsequent pluton assembly by the repeated underaccretion of later magma batches. The upward displacement of regional isotherms due to the heat advection associated with granite emplacement is likely to have a profound effect on the mechanical stratification of the upper crust and, consequently, on the level at which granitoid pluton emplacement is initiated. In this way, pluton emplacement at progressively shallower crustal depths may have resulted in the unusually high apparent geothermal gradients recorded in the upper crustal levels of the Damara Belt during its later evolution.

  9. Geochemical characteristics of granitoids and related mafic granulites from the Pan-African Dahomeyide belt, southeastern Ghana

    International Nuclear Information System (INIS)

    Aidoo, F.

    2012-07-01

    The Dahorneyide orogenic belt marks the southeastern limit of the West Africa craton (WAC). The belt consists of three structural units which include the deformed eastern edge of the WAC with its cover rocks made up of the Togo and the Buern Structural Units (external nappes), a suture zone assemblage of mafic and ultramafic rocks, and granitoid gneiss-rnigmatite assemblages (east of the suture zone). Geochemical and petrographic characteristics of the granitoids from the external nappes and mafic and ultramafic granulites roeks from the suture zone have been studied with the objective of inferring their petrogenesis and tectonic setting in which they were formed. Twenty five (25) representative samples were selected for petrographic studies and fifteen samples for major and trace elements composition using ICP-AES and ICP-MS respectively. The granitoids gneisses are mainly biotite muscovite gneisses, migmatites and granodiorites made up of quartz (25-68%), biotite (7-30%), plagioclase (8-40%), muscovite (4-20%) with some few pyroxene, sericite and calcite observed in some oF the samples. Within these rocks is an amphibole rich gneiss composed of about 45% amphiboles. The granitoid gneisses contain SiO 2 content of 40.60-68.90 wt. % with low Mg# of 36-46. Geochernically, they are classified as I-type, mctaluminous to peraluminous, magnessian to ferroan, calcic to calc alkali granitoids. They exhibit fractionated REE patterns with (La/Sm) N = 1.80-5.85 and (La/Yb) N = 3.76-76.30, and negative to positive Eu anomalies (Eu/Eu*'' = 0.68-2.10. The primitive mantle-normalised, trace element patterns show that the granitoid gneisses are characterised by enrichment in LILE relative to HFSE and in LREE relative HREE. They display subduction-related trace element characteristics of positive Ba and negative Ti, Ta, Nb and Hf anomalies. The mafic granulites are composed of quartz (16-43%), hornblende (12-45%), plagioclase (13-23%), pyroxene (13-17%), garnet (4

  10. Petrology of the Porriño late-Variscan pluton from NW Iberia. A model for post-tectonic plutons in collisional settings

    Energy Technology Data Exchange (ETDEWEB)

    González Menéndez, L.; Gallastegui, G.; Cuesta, A.; Montero, P.; Rubio-Ordoñez, A.; Molina, J.F.; Bea, F.

    2017-07-01

    The Variscan orogen of NW Iberia contains abundant syn- and post-tectonic granitoids. The post-tectonic granitoids are metaluminous to slightly peraluminous, I-type granites, monzogranites ± granodiorites ± tonalites. The Porriño pluton studied here is a representative example. It consists of two units: i) a pink-red, peraluminous, biotite granite and ii) a gray, metaluminous to peraluminous, biotite (± amphibole ± titanite) monzogranite, including maficintermediate enclaves. SHRIMP U-Pb dating yielded 290-295Ma ages for all the units. The mineralogy and geochemistry show that the pink-red granite has features of I- and A-type granites, whereas the gray monzogranite and enclaves are I-types. Sr isotopes show scattered values for the pink-red granite (87Sr/86Sr295Ma ≈ 0.702-0.710) and uniform values for the gray monzogranite and enclaves (87Sr/86Sr295Ma≈ 0.705-0.706). Geochemical results indicate a peritectic entrainment of clinopyroxene + orthopyroxene ± Ca-plagioclase ± ilmenite ± garnet, and minor accessory phases (± zircon ± titanite ± apatite) into a melt similar to the leucocratic gray monzogranite. A mafic-intermediate source is proposed for the gray monzogranite and its enclaves. Restitic protoliths generated granitic melts with A-type features such as the pink-red granite. The I-type nature of many post-tectonic granitoids could be explained by the previous extraction of S-type syn-tectonic granites that left restites and less fertile rocks. Late orogenic new melting affected the previously unmelted and more mafic lithologies of the lower-middle crust, and gave rise to I-type granitoids. Repeated melting events affecting such lithologies and previous restites could have generated granitic melts with A-type features.

  11. Multiple sources of magmatism. granitoids from southeast Kohistan, NW Himalayas, Pakistan

    International Nuclear Information System (INIS)

    Khan, M. A.; Qazi, M. S.

    2005-01-01

    The Kohistan island arc terrane in the northwestern Himalayas of N. Pakistan is sandwiched between the Indian and Karakoram plated. The base of the arc is occupied by a major stratiform ultramafic-gabbroic complex (the Sapat-Babusar complex), which overrides the crust of the Indian plate along the Indus suture (i.e., the Main Mantle Thrust; MMT). It was intruded into the base of a thick pile of metavolcanics (the Kamila belt), which comprise a tectonic collage of MORB-type tholeiitic basalts, island-arc tholeiites and calc-alkaline andesites. The Chilas complex, comprising ultramafic and gabbronorite rocks, is also intrusive into the Kamila belt, it is emplaced onto the top rather than the base of the Kamila belt. A sizeable proportion of granitoid rocks are present in the south-eastern part of Kohistan, which intruded the Kamila amphibolites. These are predominantly dioritic in composition, but include gabbros, granodiorites, granites and trondhjemites. The granitoids occur in two types. (1) large sheet-like lenticular masses, and (2) minor intrusives in the form of veints, sills or dykes. Three large sheets like bodies are mapped. All these bodies are composite, comprising gabbros, diorite/tonalite, granodiorite and granite. The minor intrusion of granitic and trondhjemitic composition are abundantly present in the form of veins, sills and dykes; and are characterized by variation in distribution. Strong shearing transformed the rocks into blastomylonite gneisses. The mineral assemblage consists of quartz, plagioclase, emphibole, epidote, chlorite, biotite, muscovite, sphene, magnetite and apatite. (author)

  12. Multiple sources of magmatism: granitoids from southeast kohistan, nw himalayas Pakistan

    International Nuclear Information System (INIS)

    Sayab, M.; Qazi, M.S.

    2005-01-01

    The Kohistan island arc terrane in the northwestern Himalayas of N. Pakistan is sandwiched between the Indian and Karakoram plates. The base of the arc is occupied by a major stratiform ultramafic-gabbroic complex (the Sapat-Babusar complex). which overrides the crust of the Indian plate along the Indus suture (i. e., the Main Mantle Thrust; MMT). It was intruded into the base of a thick pile of metavolcanics (the Kamila belt), which comprise a tectonic collage of MORB-type tholeiitic basalts, island-arc tholeiites and calc-alkaline andesites. The Chilas complex, comprising ultramafic and gabbronorite rocks, is also intrusive into the Kamila belt. It is emplaced onto the top rather than the base of the Kamila belt. A sizeable proportion of granitoid rocks are present in the south-eastern part of Kohistan. Which intruded the Kamila amphibolites. These are predominantly dioritic in composition but include gabbros, granodiorites, granites and trondhjemites. The granitoids occur in two types: (I) large sheet-like lenticular masses, and (2) minor intrusives in the form of veins sills or dykes. Three large sheets like bodies are mapped. All these bodies are composite, comprising gabbros, diorite/tonalite. granodiorite and granite. The minor intrusions of granitic and trondhjemitic composition are abundantly present in the form of veins, sills and dykes and are characterized by variation in distribution. Strong shearing transformed the rocks into blastomylonite gneisses. The mineral assemblage consists of quartz, plagioclase, Amphibole, epidote, chlorite, biotite, muscovite, sphene, magnetite and apatite. (author)

  13. Oxygen and U-Th isotopes and the timescales of hydrothermal exchange and melting in granitoid wall rocks at Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Ankney, Meagan E.; Bacon, Charles R.; Valley, John W.; Beard, Brian L.; Johnson, Clark M.

    2017-01-01

    We report new whole rock U-Th and in-situ oxygen isotope compositions for partially melted (0–50 vol% melt), low-δ18O Pleistocene granitoid blocks ejected during the ∼7.7 ka caldera-forming eruption of Mt. Mazama (Crater Lake, Oregon). The blocks are interpreted to represent wall rocks of the climactic magma chamber that, prior to eruption, experienced variable amounts of exchange with meteoric hydrothermal fluids and subsequent partial melting. U-Th and oxygen isotope results allow us to examine the timescales of hydrothermal circulation and partial melting, and provide an “outside in” perspective on the buildup to the climactic eruption of Mt. Mazama. Oxygen isotope compositions measured in the cores and rims of individual quartz (n = 126) and plagioclase (n = 91) crystals, and for transects across ten quartz crystals, document zonation in quartz (Δ18OCore-Rim ≤ 0.1–5.5‰), but show homogeneity in plagioclase (Δ18OCore-Rim ≤ ±0.8‰). We propose that oxygen isotope zonation in quartz records hydrothermal exchange followed by high-temperature exchange in response to partial melting caused by injection of basaltic to andesitic recharge magma into the deeper portions of the chamber. Results of modeling of oxygen diffusion in quartz indicates that hydrothermal exchange in quartz occurred over a period of ∼1000–63,000 years. Models also suggest that the onset of melting of the granitoids occurred a minimum of ∼10–200 years prior to the Mazama climactic eruption, an inference which is broadly consistent with results for magnetite homogenization and for Zr diffusion in melt previously reported by others.Uranium-thorium isotope compositions of most granitoid blocks are in 238U excess, and are in agreement with a 238U enriched array previously measured for volcanic rocks at Mt. Mazama. Uranium excess in the granitoids is likely due to enrichment via hydrothermal circulation, given their low δ18O values. The sample with the

  14. Signature of breccia complex/iron oxide- type U-REE mineralisation in the Khairagarh basin with special reference to Dongargaon- Lohara area, central India

    Energy Technology Data Exchange (ETDEWEB)

    Hansoti, S K; Sinha, D K [Department of Atomic Energy, Nagpur (India). Atomic Minerals Div.

    1995-10-01

    The Khairagarh basin having late Archaean- early Proterozoic basement is filled up by middle Proterozoic Khairagarh group volcano - sedimentary sequence, laid in the Kotri rift zone (KRZ) with imprints of repetitive volcanic, plutonic and tectonic activities. A strong thermal imprint of {approx} 1.5 Ga has been recorded in rocks of the basin that could be an effect of copious outpouring of basalts, dacites, ignimbrites, together with the emplacements of stocks of gabbros, gabbroic dolerites, dolerites, granites, granophyres, felsites, aplites, and quartz veins. Some of the basement rocks are enriched in Fe, Cu and other base metals and have been emplaced and assimilated by the volcano- plutonic rocks of the Nandgaon group and Malanjkhand granitoids. The Nandgaon group rocks and the Malanjkhand granitoids have anomalous intrinsic abundance of U, REE, Cu, Fe and quite a few metals in different sectors. Thermo-tectonic ({approx} 1.5 Ga) reactivation event(s) along the KRZ apart from facilitating formation of agglomerates, ignimbrites and tectonic breccias has promoted emplacement of plutonic and subvolcanic phases and their metasomatising and hydrothermal metal bearing fluids. In the Malanjkhand complex sector Cu{+-}Mo{+-}Fe{+-}Ag{+-}Au{+-}REE{+-}Zn metallisation and in the Dongargarh Massif sector U{+-}Th{+-}F{+-}Fe{+-}Pb{+-}Zn{+-}Cu{+-}REE{+-}Zr metallisation are manifested. The detection of Fe+U+REE {+-}Cu{+-}Ni metallisation in the Bortalao sandstones of the Dongargaon - Lohara area, located in between Malanjkhand ore zone and the Chandidongri (Dongargarh granite hosted) fluorite-rich and Pb{+-}Zn{+-}Cu{+-}U - bearing ore zone, considered to lie on the same (Malanjkhand - Chandidongri) fault/shear lineament is rated highly significant. (Abstract Truncated)

  15. Petrological mineralogical and geochemical characterization of the granitoids and fracture fillings developed in Ratones Mines (Spain); Caracterizacion petrologica, mineralogica, geoquimica y evaluacion del comportamiento geoquimico de las REE en la fase solida (granitoides y rellenos fisurales) del sistema de interaccion agua-roca delentorno de la Mina Ratones

    Energy Technology Data Exchange (ETDEWEB)

    Buil Gutierrez, B [Ciemat. Madrid (Spain)

    2002-07-01

    The petrological, mineralogical and geochemical characterisation of the granitoids and fracture fillings developed in the Ratones Mine (Caceres, Spain) has been done in order to understand rock-water interaction processes which control water geochemical parameters. Special interest has been devoted to the analysis and interpretation of REE patterns in the solid phase (granitoids and fracture fillings) because they constitute geochemical tracers in water-rock interaction process. Moreover, REE are considered as actinide analogues. In order to characterise the solid phase (granitoids and fracture fillings) several investigation scales (system, outcrop, whole rock, mineral and geochemical components) have been considered and different types of samples have been analysed. These factors control the methodological approach used in this investigation. The analytical methods we have used in this investigation are microscope, qualitative and semi-quantitative methods (XRD, SEM,EDAX) and quantitative methods (ICP-MS, XRF, EM, LAM-IC-MS). The bulk of the granitoids located around the Ratones Mine Belongs to the alkaline feldspar granite-sienogranite lihotype and they show a peraluminous and subalkaline pattern. From the mineralogical point of view, they are composed by quartz, K-feldspar (Or>90%), showing sericitation, moscovitization and turmolinization altherations, alkaline plagioclase (An-=-3%), usually altered to sericite, saussirite and less frequently affected by moscovitization processes, Fe-Al biotite, frequently affected by chloritization processes and sometimes replaced by muscovite, and finally muscovite (>2% celadonite and <4% paragonite) both of primary and secondary origin. The differences observed between the different lithotypes are related with the modal proportion of the principal minerals,with the presence or absence of certain accessory minerals ( turmaline, cordierite), with specific textural patterns, grain size and also with the richness in specific

  16. Late Variscan, Permo-Carboniferous, Al-K plutonism in the South Portuguese Zone: El Crispinejo cordierite-bearing granite

    Energy Technology Data Exchange (ETDEWEB)

    Díez Montes, A.; Valverde-Vaquero, P.; Rey-Moral, C.; Sánchez García, L.

    2017-07-01

    The El Crispinejo granite forms part of a small, but distinctive late intrusive suite of cordierite-bearing peraluminous granites in the South Portuguese Zone (SPZ). This granite has the best outcrop relationships of the suite. It cross-cuts different members of the Sierra Norte Batholith of the SPZ and the Carboniferous Volcano-Sedimentary Complex of the Iberian Pyrite Belt, producing contact metamorphism. This late pluton has a high K content which results in a contrasting geophysical response (K-Th-U) with respect to the surrounding trondhjemitic granitoids of the TTG suite of the Sierra Norte Batholith. A concordant monazite-zircon U-Pb ID-TIMS age of 300.5 +0.5/-1.5Ma demonstrates Permo-Carboniferous age for this late Variscan magmatic event. The granite is associated with a series of ore showings (F-Pb-Zn and Sn-W) which are completely different from the nearby, massive sulphide and manganese ore deposits of the Iberian Pyrite Belt, indicating the unique character of this intrusion.

  17. Unusual Rb-Sr data on the age of two typical peralkaline granitoid plutons in West Transbeikalia

    International Nuclear Information System (INIS)

    Litvinovskij, B.A.; Posokhov, V.F.; Zanvilevich, A.N.

    1995-01-01

    Rb-Sr isotope study of two typical plutons in West Transbaikalia (Bryansk and Kharitonov) has been carried out. For alkaline and peralkaline suits of the Bryansk pluton the obtained data are 287 ± m.y., I Sx =0.7054 ± 3 and 285 ± 1 m.y., I Sr =0.7037 ± 3 respectively. Rb-Sr age of peralkaline syenites and granites from the Kharitonov pluton are in more or less consistency with those on the Malokunal pluton (233 ± 5 m.y.) and much less than the age of the Khorinsk pluton (253 ± 3 m.y.). Taking into account the K-Ar data on amphibole from the peralkaline granitoids it is concluded that probable age of these rocks span the interval 250-220 m.y. However results obtained from the Bryansk pluton suggest that within the Mongolia-Transbaikalia belt one more stage of peralkaline granitoid generation i.e. the Early Permian stage could be manifested as well. 20 refs.; 5 figs.; 3 tabs

  18. U-Th-Pb systematics of some granitoids from the northeastern Yilgarn Block, Western Australia and implications for uranium source rock potential

    Energy Technology Data Exchange (ETDEWEB)

    Stuckless, J S; Nkomo, I T [Geological Survey, Denver, CO (USA); Bunting, J A [Geological Survey of Western Australia, Perth

    1981-11-01

    The Mount Boreas-type granite and spatially associated syenitic granitoid of Western Australia yield Pb-Pb ages of 2370 +- 100 Ma and 2760 +- 210 Ma, respectively. Th-Pb ages, although less precise, are concordant with these ages, and therefore the apparent ages are interpreted to be the crystallisation ages for these two units. U-Pb ages are variable and for the most part anomalously old, which suggests a Cainozoic uranium loss. However, this loss is generally small (3..mu..g/g); therefore, neither granitoid in its fresh state provides a good source for nearby calcrete-hosted uranium deposits. The possibility remains that the Mount Boreas-type granite that has been completely weathered during the Tertiary could have been a source for the calcrete-type uranium deposits in W.A. Although the Mount Boreas-type granite is highly fractionated, it does not bear a strong geochemical imprint of a sedimentary precursor. This feature contrasts it with apparently fresh granitoids from other parts of the world that have lost large amounts of uranium (approx. 20..mu..g/g) and are associated with large roll-type and other low temperature-type uranium deposits.

  19. Geochemistry and petrogenesis of Mesoproterozoic A-type granitoids from the Danish island of Bornholm, southern Fennoscandia

    DEFF Research Database (Denmark)

    Johansson, Åke; Waight, Tod Earle; Andersen, Tom

    2016-01-01

    Granitoids and gneisses from the Danish island of Bornholm have been investigated using whole rock geochemistry, Sr and Nd isotope geochemistry and Hf isotopes in zircon. Recent U–Pb dating shows that the rocks were formed during a short time interval at 1.45 to 1.46 Ga, penecontemporaneous...

  20. Granitoids of the Dry Valleys area, southern Victoria Land, Antarctica : plutons, field relationships, and isotopic dating

    International Nuclear Information System (INIS)

    Allibone, A.H.; Cox, S.C.; Johnstone, R.D.

    1993-01-01

    Detailed mapping throughout much of the Dry Valleys area indicates the region is underlain by 15 major granitoid plutons and numerous smaller plugs and dikes. Intrusive relationships of these plutons and dikes indicate repeated intrusion of superficially similar granitoids at different times. Sufficient internal lithologic variation occurs within individual plutons, to allow correlation with several of the previously defined granitoid units based on lithologic character. Consequently, previous subdivision schemes based on lithology are no longer tenable and are here replaced with a subdivision scheme based on the identification of individual plutons. The elongate, concordant Bonney, Denton, Cavendish, and Wheeler Plutons, which range in composition between monzodiorite and granodiorite, are the oldest relatively undeformed plutons in the Dry Valleys area. Each pluton is characterised by flow alignment of K-feldspar megacrysts, hornblende, biotite, and mafic enclaves. Field relationships and radiometric dating indicate these are deep-level plutons, emplaced synchronous with upper amphibolite facies metamorphism of the adjacent Koettlitz Group between 589 and 490 Ma ago. Elongate, discordant plutons of equigranular homogeneous biotite granodiorite and granite (Hedley, Valhalla, St Johns, Suess) were subsequently emplaced by stoping at a relatively high crustal level at 490 Ma. These eight plutons are cut by numerous swarms of Vanda mafic and felsic porphyry dikes. The ovoid, discordant, high level Pearse, Nibelungen, Orestes, Brownworth, Swinford, and Harker Plutons, emplaced between c. 486 and 477 Ma, display mutually crosscutting relationships with the youngest of the Vanda dikes. These younger plutons range in composition between monzonite and granite. Some are characterised by K-feldspar megacrystic textures superficially similar to some of the oldest concordant plutons. (author). 57 refs.; 2 tabs.; 4 figs

  1. Geochemical evidence for Paleozoic crustal growth and tectonic conversion in the Northern Beishan Orogenic Belt, southern Central Asian Orogenic Belt

    Science.gov (United States)

    Yuan, Yu; Zong, Keqing; He, Zhenyu; Klemd, Reiner; Jiang, Hongying; Zhang, Wen; Liu, Yongsheng; Hu, Zhaochu; Zhang, Zeming

    2018-03-01

    The Beishan Orogenic Belt is located in the central southernmost part of the Central Asian Orogenic Belt (CAOB), which plays a key role in understanding the formation and evolution of the CAOB. Granitoids are the documents of crustal and tectonic evolution in orogenic belts. However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Paleozoic granitoids in the Northern Beishan Orogenic Belt (NBOB). The present study reveals significant differences concerning the petrogenesis and tectonic setting of early and late Paleozoic granitoids from the NBOB. The early Paleozoic granitoids from the 446-430 Ma Hongliuxia granite complex of the Mazongshan unit and the 466-428 Ma Shibanjing complex of the Hanshan unit show classic I-type granite affinities as revealed by the relative enrichment of LILEs and LREEs, pronounced depletions of Nb, Ta and Ti and the abundant presence of hornblende. Furthermore, they are characterized by strongly variable zircon εHf(t) values between - 16.7 and + 12.8 and evolved plagioclase Sr isotopic compositions of 0.7145-0.7253, indicating the involvement of both juvenile and ancient continental crust in the magma source. Thus, we propose that the early Paleozoic granitoids in the NBOB were generated in a subduction-related continental arc setting. In contrast, the late Paleozoic 330-281 Ma granitoids from the Shuangjingzi complex of the Hanshan unit exhibit positive zircon εHf(t) values between + 5.8 and + 13.2 and relatively depleted plagioclase Sr isotopic compositions of 0.7037-0.7072, indicating that they were mainly formed by remelting of juvenile crust. Thus, an intra-plate extensional setting is proposed to have occurred during formation of the late Paleozoic granitoids. Therefore, between the early and late Paleozoic, the magma sources of the NBOB granitoids converted from the reworking of both juvenile and ancient crusts during a subduction-induced compressional setting to the remelting of

  2. Evolution of the Gondwanaland Archaean Shield: ion microprobe zircon dating and southwestern Australia/Wilkes Land, Antartica

    International Nuclear Information System (INIS)

    Lovering, J.F.; Comaford, D.J.

    1979-01-01

    The ion microprobe has been used to study 207 Pb/ 206 Pb ages on 20μm-sized sites on single zircon grains from coastal rocks on either side of the rift in the Gondwanaland Archaean Shield between southwestern Australia and Wilkes Land, Antarctica. The ages on individual sites on zircon grains from a variety of rock types from southwestern Australia show a range from 1600 m.y. to about 3400 m.y., with an inverse dependence on the uranium abundance at each site. Ages of zircons from rocks from the Antartic region show a range from 1600 m.y. to 3100 m.y

  3. Molybdenite Re/Os dating, zircon U-Pb age and geochemistry of granitoids in the Yangchuling porphyry W-Mo deposit (Jiangnan tungsten ore belt), China: Implications for petrogenesis, mineralization and geodynamic setting

    Science.gov (United States)

    Mao, Jingwen; Xiong, Bikang; Liu, Jun; Pirajno, Franco; Cheng, Yanbo; Ye, Huishou; Song, Shiwei; Dai, Pan

    2017-08-01

    The Yangchuling W-Mo deposit, located in the Jiangnan porphyry-skarn (JNB) tungsten ore belt, is the first recognized typical porphyry W-Mo deposit in China in the 1980's. Stockworks and disseminated W-Mo mineralization occur in the roof pendant of a 0.3 km2 monzogranitic porphyry stock that intruded into a granodiorite stock, hosted by Neoproterozoic phyllite and slate. LA-ICPMS zircon U-Pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143.8 ± 0.5 Ma and 149.8 ± 0.6 Ma, respectively. Six molybdenite samples yielded a Re-Os weighted mean age of 146.4 ± 1.0 Ma. Geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements (LILE) relative to high field strength elements (HFSE), indicating a peraluminous nature (A/CNK = 1.01-1.08). Two granitoids are characterized by a negative slope with significant light REE/heavy REE fractionation [(La/Yb)N = 8.38-23.20] and negative Eu anomalies (Eu/Eu* = 0.69-0.76). The P2O5 contents of the Yangchuling granitoids range from 0.12% to 0.17% and exhibit a negative correlation with SiO2, reflecting that they are highly fractionated I-type. They have high initial 87Sr/86Sr ratios (0.7104-0.7116), low negative εNd(t) (- 5.05 to - 5.67), and homogeneous εHf(t) between - 1.39 and - 2.17, indicating similar sources. Additionally, two-stage Nd model ages (TDM2) of 1.3-1.4 Ga and two-stage Hf model ages (TDM2) of 1.2-1.3 Ga are consistent, indicating that Neoproterozoic crustal rocks of the Shuangqiaoshan Group could have contributed to form the Yangchuling magmas. Considering the two groups of parallel Late Mesozoic ore belts, namely the Jiangnan porphyry-skarn tungsten belt (JNB) in the south and the Middle-Lower Yangtze River porphyry-skarn Cu-Au-Mo-Fe ore belt (YRB) in the north, the Nanling granite-related W-Sn ore belt (NLB) in the south, the neighboring Qin-Hang porphyry-skarn Cu-Mo-hydrothermal Pb-Zn-Ag ore belt (QHB

  4. Granitoids of the Dry Valleys area, southern Victoria Land : geochemistry and evolution along the early Paleozoic Antarctic Craton margin

    International Nuclear Information System (INIS)

    Allibone, A.H.; Cox, S.C.; Smillie, R.W.

    1993-01-01

    Field relationships and geochemistry indicate granitoid plutons of the Dry Valleys area comprise at least three petrogenetically distinct suites. The older Dry Valleys 1a (DV1a) suite, comprising the Bonney, Catspaw, Denton, Cavendish, and Wheeler Plutons and hornblende-biotite orthogneisses, and Dry Valleys 1b (DV1b) suite, comprising the Hedley, Valhalla, St Johns, Dun, Calkin, and Suess Plutons, biotite granitoid dikes and biotite orthogneisses, were emplaced before prominent swarms of Vanda mafic and felsic dikes. Both the DV1a and DV1b suites are time transgressive, with older intrusions in each suite being emplaced during the later stages of deformation of the Koettlitz Group. Younger granitoids that postdate the majority of the Vanda dikes include: the Dry Valleys 2 (DV2) suite, comprising the Pearse and Nibelungen Plutons plus several smaller, unnamed plugs; and the Harker, Swinford, Orestes, and Brownworth Plutons with identical field relationships and enclaves but distinct chemistries. Chemical characteristics and limited Rb-Sr isotopic dating indicate plutonism before c. 500 Ma was dominated by the Cordilleran I-type DV1a suite, inferred to have developed during melting above a west-dipping subduction zone along the Antarctic Craton margin. The chemical characteristics of the DV1b suite indicate large-scale melting of a quartzo-feldspathic protolith lacking residual plagioclase, but containing refractory garnet. Potential DV1b suite source rocks include metamorphosed immature sediments, possibly underplated along the subduction zone associated with DV1a magmatism, or older granitoid orthogneisses. Major DV1b plutonism at 490 Ma marks the end of subduction-related plutonism in southern Victoria Land. Younger DV2 alkali-calcic, Caledonian I-type plutonism is inferred to have formed in response to uplift and extension between 480 and 455 Ma. Lack of DV2 suite correlatives and Vanda mafic and felsic dikes in northern Victoria Land suggests significantly

  5. Permian alkali granitoids of the transbaikal region (new Rb-Sr dates)

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanov, M K; Ryakhovskij, V M; Abramov, A V

    1984-01-01

    Rubidium-strontium isotopic investigations of granitoids from Khorinsk and Middle Oninsk massifs were conducted. Isochrones for two chief-modifications of rocks - subalkaline syenites and alkaline granites-were constructed. The age of syenites is determined to be (293 + 20) x 10/sup 6/ at (/sup 87/Sr//sup 86/Sr)/sub 0/=0.7044 +- 0.0106 that of alkaline granites - (253 +- 3) x 10/sup 6/ at (/sup 87/Sr//sup 86/Sr)/sub 0/=0.7077 +- 0.0033. Analytical data for determination of rubidium-strontium age of rocks of the mentioned massits are presented as well.

  6. Sr and Nd isotopic compositions, age and petrogenesis of A-type granitoids of the Vernon Supersuite, New Jersey Highlands, USA

    Science.gov (United States)

    Volkert, R.A.; Feigenson, M.D.; Patino, L.C.; Delaney, J.S.; Drake, Avery A.

    2000-01-01

    Voluminous late Mesoproterozoic monzonite through granite of the Vernon Supersuite underlies an area of approximately 1300 km2 in the Highlands of northern New Jersey. The Vernon Supersuite consists of hastingsite ?? biotite-bearing granitoids of the Byram Intrusive Suite (BIS) and hedenbergite-bearing granitoids of the Lake Hopatcong Intrusive Suite (LHIS). These rocks have similar major and trace element abundances over a range of SiO2 from 58 to 75 wt.%, are metaluminous to weakly peraluminous, and have a distinctive A-type chemistry characterized by high contents of Y, Nb, Zr, LREE, and Ga/Al ratios, and low MgO, CaO, Sr and HREE. Whole-rock Rb-Sr isochrons of BIS granite yield an age of 1116 ?? 41 Ma and initial 87Sr/86Sr ratio of 0.70389, and of LHIS granite an age of 1095 ?? 9 Ma and initial 87Sr/86Sr ratio of 0.70520. Both suites have similar initial 143Nd/144Nd ratios of 0.511267 to 0.511345 (BIS) and 0.511359 to 0.511395 (LHIS). Values of ??(Nd) are moderately high and range from +1.21 to +2.74 in the BIS and +2.24 +2.95 in the LHIS. Petrographic evidence, field relationships, geochemistry, and isotopic data support an interpretation of comagmatism and the derivation of both suites from a mantle-derived or a juvenile lower crustal parent with little crustal assimilation. Both suites crystallized under overlapping conditions controlled by P-T-f(H(2)O). Lake Hopatcong magma crystallized at a liquidus temperature that approached 900??C and a pressure of about 6 kbar, and remained relatively anhydrous throughout its evolution. Initial P-T conditions of the Byram magma were ??? 850??C and about 5.5 kbar. BIS magma was emplaced contemporaneous with, or slightly preceding LHIS magma, and both magmas were emplaced during a compressional tectonic event prior to granulite facies metamorphism that occurred in the Highlands between 1080 and 1030 Ma. (C) 2000 Elsevier Science B.V. All rights reserved.

  7. Geological evolution of the Neoproterozoic Bemarivo Belt, northern Madagascar

    Science.gov (United States)

    Thomas, Ronald J.; De Waele, B.; Schofield, D.I.; Goodenough, K.M.; Horstwood, M.; Tucker, R.; Bauer, W.; Annells, R.; Howard, K. J.; Walsh, G.; Rabarimanana, M.; Rafahatelo, J.-M.; Ralison, A.V.; Randriamananjara, T.

    2009-01-01

    show characteristics of arc-related magmatism, but include both calc-alkaline and tholeiitic compositions. It is not certain when the two Bemarivo terranes were juxtaposed, but ages from metamorphic rims on zircon suggest that both the northern and southern terranes were accreted to the northern cratonic margin of Madagascar at about 540-530 Ma. Terrane accretion included the assembly of the Archaean Antongil and Antananarivo cratons and the high-grade Neoproterozoic Anaboriana Belt. Late- to post-tectonic granitoids of the Maevarano Suite, the youngest plutons of which gave ca. 520 Ma ages, intrude all terranes in northern Madagascar showing that terrane accretion was completed by this time. ?? 2009 Natural Environment Research Council (NERC).

  8. Geochronology, geochemistry, and Sr-Nd-Pb-Hf isotopes of the Zhunsujihua granitoid intrusions associated with the molybdenum deposit, northern Inner Mongolia, China: implications for petrogenesis and tectonic setting

    Science.gov (United States)

    Zhang, Xiaojun; Lentz, David R.; Yao, Chunliang; Liu, Rui; Yang, Zhen; Mei, Yanxiong; Fan, Xianwang; Huang, Fei; Qin, Ying; Zhang, Kun; Zhang, Zhenfei

    2018-03-01

    The Zhunsujihua porphyry molybdenum deposit, located in northern Inner Mongolia of China that belongs to Central-Asian Orogenic Belt (CAOB), is the only Mo deposit formed in the late Carboniferous in this area so far. Its mineralization is mainly restricted to the Zhunsujihua granitoid intrusions, which are composed of the main granodiorite (GD) and crosscutting, virtually coeval minor syn-ore leucogranite (LG) and diorite porphyry (DP) dykes. LA-ICP-MS zircon U-Pb dating yields crystallization ages of 300.0 ± 2.0, 299.3 ± 2.0, and 299.0 ± 2.6 Ma for the GD, LG, and DP, respectively. The major and trace element lithogeochemical data show that the GD and LG are metaluminous to weakly peraluminous, high-K calc-alkaline series with I-type granite characteristics, strongly oxidized, with low concentrations of Ba, Nb, Sr, P, and Ti and elevated K and Rb contents, indicating typical arc magmatic features. The LG is a product derived by extensive fractional crystallization of a parental magma similar to the GD as evident from the lower Eu/Eu*, Nb/Ta, Zr/Hf, and T Zr. The moderately altered DP exhibits high concentrations of K, Rb, Cs, LREE, Y, and low Sr/Y, with a positive ɛ Nd (300 Ma), which indicates a mantle or juvenile source associated with an arc setting. The Sr-Nd-Hf isotope data show low I Sr (0.70406-0.70461) and moderate ɛ Nd (300 Ma) (-0.9 to 1.5) for the GD and LG, and relatively high ɛ Hf (300 Ma) values (-3.6 to +11.2) for the GD, suggesting the magma mainly originated from the juvenile lower crust that was derived from depleted mantle, with a minor component of ancient continental crust. Lead isotope data have characteristics of a lower crust source with minor contamination by upper crustal material. Combined with previous research, the Zhunsujihua granitoid intrusions developed in an intracontinental volcanic arc (Uliastai) associated with northward subduction of the Paleo-Asian Ocean plate during late Carboniferous to early Permian; this suggests

  9. A review of the ascent and emplacement of granitoid bodies into the crust

    Directory of Open Access Journals (Sweden)

    Katarína Bónová

    2005-03-01

    Full Text Available This paper relates to basic information (i.e. mechanical aspects of ascent, indicators faciliting the discriminability of various ascent styles about the models of ascent and emplacement of granitoid bodies, since the purely mechanical aspect of intrusion of magmas is a fascinating subject and it has generated a considerable controversy over many years. Individual models are demonstrated by world-known occurrences and examples from Western Carpathian’s region. The conditions of magma migration are demonstrated as well.

  10. Age, geochemical affinity and geodynamic setting of granitoids and felsic volcanics in the basement of Wrangel Island

    Science.gov (United States)

    Luchitskaya, Marina; Moiseev, Artem; Sokolov, Sergey; Tuchkova, Marianna; Sergeev, Sergey

    2016-04-01

    Granitoids and basic rocks of Wrangel Island are the components of Precambrian metamorphic basement, exposed in the anticlinorium in the central part of the island and named as Wrangel complex (Kameneva, 1970; Ageev, 1979; Til'man et al., 1964, 1970; Ganelin, 1989; Kos'ko et al., 1993, 2003). The latter is composed of volcanic, volcaniclastic and clastic rocks metamorphosed in greenshist to locally lower amphibolite facies (Kos'ko et al., 2003; Cecile et al., 1991). Obtained earlier datings of granitoids and basic rocks from Wrangel complex display a wide scatter: 609-700 Ma, U-Pb zircon (Cecile et al., 1991; Kos'ko et al., 1993); 590 Ma, Pb-Pb zircon; 574, 575 Ma, K-Ar whole rock; 475 Ma, Rb-Sr muscovite (Kos'ko et al., 2003). Our previous U-Pb SHRIMP datings indicate the episode of granitoid activity in 681-707 Ma (Luchitskaya et al., 2014). Here we present new results from zircon SIMS and LA-ICP-MS U-Pb dating and geochemical data for granites and felsic volcanics of Wrangel complex. Granites of Wrangel complex in the area of Khishchnikov River form small tabular bodies less than 30 meters in thickness. They range from slightly recrystallized muscovite granites to gneissic and mylonitic ones. Felsic and basic volcanics are exposed in the central part of Wrangel Island (rivers Neizvestnaya and Krasnyy Flag). Their interrelations are unknown and earlier they were considered as single bymodal assemblage of C1 sequence (Kos'ko et. al., 1993, 2003). Samples were collected in the area of Pervaya Mountain, visible thickness of volcanics ~100 meters. Basalts are overlain by conglomerates with detrite zircons no younger than 550 Ma (Moiseev et al., 2009, 2015). Wheited mean ages of zircons from muscovite granites and mylonitic ones are 592.9±6.7 Ma (n=10) and 692.9±5.0 Ma (n=30); in two samples we suppose the age of crystallization ~700 Ma. Wheited mean ages of zircons from felsic volcanics are 594.4±7.1 Ma (n=10) and 598.6±7.5 Ma (n=10). Granites and felsic

  11. Contribution to the geologic evolution from the Eastern part of Central Amazonia Province by Rb-Sr geochronology from the Carajas Mineral Province and the Sao Felix do Xingu region, Para State

    International Nuclear Information System (INIS)

    Pereira, Edilea Dutra.

    1992-01-01

    This work deals with a Rb/Sr geochronological study carried on granitoids and granulites of the Carajas Mineral Province (Rio Maria, Serra dos Gradaus and Serra do Pium regions) and Sao Felix do Xingu regions. The Manelao and Ourilandia granitoids of the Sao Felix do Xingu region are associated with the greenstone terrains of the Tucuma Group, and yield an age of 2749 ± 24 Ma with an initial ratio of 0.07028 ± 19, and 2677 ± 50 Ma with an initial ratio of 0.07016 ± 22, respectively. In the Rio Maria region, an age of 2541 ± 74 Ma with an initial ratio of 0.7104 ± 343 was obtained on the Mata Surrao Granite located near the Marajoara Village. This age confirms an archaean monzogranitic magmatism in this region. In the Gradaus area, the Cumaru Granodiorite give an mineral age of 2577 ± 27 Ma similar to the age obtained by whole rock method. Finally, Rb/Sr ages were obtained from granulitic rocks of the Pium Complex located at the Serra do Pium and near the Catete River. Samples of the Serra do Pium yielded ages of 2325 ± 71 Ma (whole rock) and 1857 ± 48 (minerals). Samples from the Catete River area give a whole rock age of 2018 ± 25 Ma with an initial ratio of 0.7039 ± 25. These data show that the Rb/Sr system in these granulitic rocks suffered changes during the Early Proterozoic times. The geochronological data here obtained confirm promptly an Archaean evolution in the studied regions, besides give rise the discussion about the problem related to the Transamazonian Event inside them. (author). 92 refs., 32 figs., 10 tabs

  12. Repeated granitoid intrusions during the Neoproterozoic along the western boundary of the Saharan metacraton, Eastern Hoggar, Tuareg shield, Algeria: An AMS and U-Pb zircon age study

    Science.gov (United States)

    Henry, B.; Liégeois, J. P.; Nouar, O.; Derder, M. E. M.; Bayou, B.; Bruguier, O.; Ouabadi, A.; Belhai, D.; Amenna, M.; Hemmi, A.; Ayache, M.

    2009-09-01

    The N-S oriented Raghane shear zone (8°30') delineates the western boundary of the Saharan metacraton and is, with the 4°50' shear zone, the most important shear zone in the Tuareg shield. It can be followed on 1000 km in the basement from southern Aïr, Niger to NE Hoggar, Algeria. Large subhorizontal movements have occurred during the Pan-African orogeny and several groups of granitoids intruded during the Neoproterozoic. We report U-Pb zircon datings (laser ICP-MS) showing that three magmatic suites of granitoids emplaced close to the Raghane shear zone at c. 790 Ma, c. 590 and c. 550 Ma. A comprehensive and detailed (158 sites, more than 1000 cores) magnetic fabric study was performed on 8 plutons belonging to the three magmatic suites and distributed on 200 km along the Raghane shear zone. The main minerals in all the target plutons do not show visible preferential magmatic orientation except in narrow shear zones. The AMS study shows that all plutons have a magnetic lineation and foliation compatible with the deformed zones that are zones deformed lately in post-solidus conditions. These structures are related to the nearby mega-shear zones, the Raghane shear zone for most of them. The old c. 793 Ma Touffok granite preserved locally its original structures. The magnetic structures of the c. 593 Ma Ohergehem pluton, intruded in the Aouzegueur terrane, are related to thrust structures generated by the Raghane shear zone while it is not the case of the contemporaneous plutons in the Assodé-Issalane terrane whose structures are only related to the subvertical shear zones. Finally, the c. 550 Ma granite group has magnetic structure related to the N-S oriented Raghane shear zone and its associated NNE-SSW structures when close to them, but NW-SE oriented when further. These NW-SE oriented structures appear to be characteristic of the late Neoproterozoic evolution of the Saharan metacraton and are in relation to the convergence with the Murzuq craton. This

  13. Geochronology, petrogenesis and metallogeny of Piaotang granitoids in the tungsten deposit region of South China

    International Nuclear Information System (INIS)

    He Zhenyu; Xu Xisheng; Wang Xudong; Yu Yao; Zou Haibo

    2010-01-01

    The tungsten deposit region of South China is well known as the world's leading tungsten (W) producer. The Piaotang tungsten deposit in the region is such a representative large-scale quartz vein type tungsten polymetallic deposit that is closely associated with granitoids. In the present study we present precise LA-ICP-MS zircon U-Pb dating and LA-MC-ICPMS zircon Hf isotopic data for the samples from exposed quartz diorite body and buried granite stock in the Piaotang tungsten deposit area. Zircon U-Pb dating results indicate that the quartz diorite body was formed in Early Paleozoic time at 439±2 Ma, whereas the granite body was emplaced in EarlyYanshanian time at 158±3 Ma. Both the quartz diorite and granite have negative ε Hf (t) values, with similar two-stage zircon Hf model ages ranging from 1.8 to 2.1 Ga. Through integration of our new data with the isotope data of Precambrian basement rocks in western Cathaysia, we suggest that the Paleoproterozoic Hf model ages (1.8-2.1 Ga) might be an average age which resulted from mixing of continental materials of different ages. Both the Piaotang Early Paleozoic quartz diorite and Early Yanshanian granite are produced by reworking of the heterogeneous Neoproterozoic crust. Our zircon ages, together with the geochemical data and geological features and ore-forming ages of this tungsten deposit, indicate that the buried Early Yanshanian granite, rather than the exposed quartz diorite, is genetically associated with tungsten mineralization. The distinct metallogeny difference between the Piaotang Early Paleozoic quartz diorite and Early Yanshanian granite can be ascribed to the different degrees of magma differentiation. The Early Yanshanian granite is highly differentiated rock and similar to the other W-Sn deposits generating granitoids in South China. The extents of magma differentiation depend on the tectonic setting and the mechanism of magma generation. On the basis of the relationship between two different

  14. Behaviour of {sup 238}U, {sup 234}U, {sup 228}Ra and {sup 226}Ra in rock alterations: study of Morungaba granitoids, SP-Brazil and ground water in its fractures; Comportamento de {sup 238}U, {sup 234}U, {sup 228}Ra e {sup 226}Ra na alteracao de rochas: estudo dos granitoides de Morungaba (SP) e aguas subterraneas de suas fraturas

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Rosana N. dos [Pontificia Univ. Catolica de Sao Paulo, SP (Brazil). Dept. de Fisica]. E-mail: rosana@pucsp.br; Marques, Leila S. [Sao Paulo Univ., SP (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas. Dept. de Geofisica]. E-mail: leila@iag.usp.br

    2005-07-01

    This work presents the first results obtained on the investigation of the behavior of uranium and radium radioisotopes in the processes of weathering and rock-water interaction of Morungaba granitoids belonging to Meridional Pluton (Valinhos Town-SP-Brazil). Specific activities of {sup 238}U, {sup 234}U, {sup 228}Ra and {sup 226}Ra were determined in non altered granitoids (Group A), as well as in those affected by different degrees of weathering (Groups B, C and D). The uranium specific activities were determined by alpha spectrometry method, whereas for the determination of radium isotopes high resolution gamma-ray spectrometry technique was employed. The data indicate that {sup 238}U and {sup 234}U are in radioactive equilibrium in the fresh analyzed granitoids, but show a slight depletion of {sup 234}U in relation to {sup 238}U in the weathered rocks. The ({sup 226}Ra/{sup 238}U) and ({sup 226}Ra/{sup 234}U) activity ratios of all investigated rocks are similar, showing a significant {sup 226}Ra depletion, which is probably caused by its preferential leaching. These results indicate that even samples macroscopically classified as fresh rocks, their systems have been opened for some geochemical changes. The high ({sup 234}U/{sup 238}U) activity ratios of groundwaters which are found in the fractures of these granitoids suggest their prolonged residence times in the aquifer and/or their percolation by other rocks presenting different geochemical properties. (author)

  15. Geology and geochemistry of Massangana Granitoid Complex, Brazil, and its relation with tin mineralization

    International Nuclear Information System (INIS)

    Romanini, S.J.

    1982-01-01

    The geochemical and petroLogical characteristics of the Massangana Granitoid Complex, situated in the Rondonia Federal Territory, Brazil, aiming to discriminate the tin mineralized granitic rocks from the no mineralized ones. The collected samples consists of examples in tin mineralized and sterile phases. The elements traces were determined by x-ray fluorescence analysis, emission spectrography, molecular absorption spectrophotometry and atomic absorption spectrophotometry. The complex edifying evolved in four sucessive episodes called Massangana Phase, Bom Jardim Phase, Sao domingos Phase and Taboca Phase ordered stratigraphycally in this sequence. (author/M.C.K.) [pt

  16. Rb/Sr geochronology in whole rocks and minerals of the Cumaru granodiorite, Serra dos Gradaus, Para state, Brazil

    International Nuclear Information System (INIS)

    Lafon, J.M.; Scheller, T.; Pereira, E.D.; Macambira, J.B.

    1990-01-01

    The Cumaru granodiorite occurs in the Serra dos Gradaus region, southeastern part of the Metallogenic Province of Carajas, Para. Rb-Sr systematics have been provided in whole rocks and minerals for samples of the Cumaru granodiorite thus an age of 2543 ± 53 Ma, with an initial isotopic ratio of 0.70311 ± 34 (MSWD+1.87) was obtained for whole rocks samples. Taking in account that these rocks are not affected by metamorphism and/or deformation, we consider the age of 2543 ± 53 Ma as an emplacement age corresponding to the crystallization of the body. Such an age confirms the existence of a late Archaean plutonic event in the Serra dos Gradaus area and the interpretation of the Cumaru granodiorite as a contemporaneous and cogenetic body of the Juruena type granites (Ca. 2000 Ma old), as proposed previously, must be definitively abandoned. Therefore, Archaean ages for the greenstone belt sequence (Gradaus group) as well as for the Xingu complex in this area are also confirmed, although by indirect evidence. The age obtained implies that the latter represents an Archaean metamorphic basement in the Serra dos Gradaus region rather than the reworking of the late archaean granitics rocks during the Transmazonian orogenic event. The initial isotopic ratio of 0.70311 ± 34 is close to a mantellic or low time of crustal residence source material ratios at the end of Archaean times. Therefore, comparison with isotopic initial ratios of other granitic rocks which occur in the Rio Maria region identifies an evolution line with a Rb-Sr ratio of 0.25 for a crustal source material that would have separated from mantle about 2.8 Ga ago. (author)

  17. Earth's oldest stable crust in the Pilbara Craton formed by cyclic gravitational overturns

    Science.gov (United States)

    Wiemer, Daniel; Schrank, Christoph E.; Murphy, David T.; Wenham, Lana; Allen, Charlotte M.

    2018-05-01

    During the early Archaean, the Earth was too hot to sustain rigid lithospheric plates subject to Wilson Cycle-style plate tectonics. Yet by that time, up to 50% of the present-day continental crust was generated. Preserved continental fragments from the early Archaean have distinct granite-dome/greenstone-keel crust that is interpreted to be the result of a gravitationally unstable stratification of felsic proto-crust overlain by denser mafic volcanic rocks, subject to reorganization by Rayleigh-Taylor flow. Here we provide age constraints on the duration of gravitational overturn in the East Pilbara Terrane. Our U-Pb ages indicate the emplacement of 3,600-3,460-million-year-old granitoid rocks, and their uplift during an overturn event ceasing about 3,413 million years ago. Exhumation and erosion of this felsic proto-crust accompanied crustal reorganization. Petrology and thermodynamic modelling suggest that the early felsic magmas were derived from the base of thick ( 43 km) basaltic proto-crust. Combining our data with regional geochronological studies unveils characteristic growth cycles on the order of 100 million years. We propose that maturation of the early crust over three of these cycles was required before a stable, differentiated continent emerged with sufficient rigidity for plate-like behaviour.

  18. Archaean Gold Mineralization in an Extensional Setting: The Structural History of the Kukuluma and Matandani Deposits, Geita Greenstone Belt, Tanzania

    Directory of Open Access Journals (Sweden)

    Shimba D. Kwelwa

    2018-04-01

    Full Text Available Three major gold deposits, Matandani, Kukuluma, and Area 3, host several million ouncez (Moz of gold, along a ~5 km long, WNW trend in the E part of the Geita Greenstone Belt, NW Tanzania. The deposits are hosted in Archaean volcanoclastic sediment and intrusive diorite. The geological evolution of the deposits involved three separate stages: (1 an early stage of syn-sedimentary extensional deformation (D1 around 2715 Ma; (2 a second stage involving overprinting ductile folding (D2–4 and shearing (D5–6 events during N-S compression between 2700 and 2665 Ma, coeval with the emplacement of the Kukuluma Intrusive Complex; and (3 a final stage of extensional deformation (D7 accommodated by minor, broadly east-trending normal faults, preceded by the intrusion of felsic porphyritic dykes at ~2650 Ma. The geometry of the ore bodies at Kukuluma and Matandani is controlled by the distribution of magnetite-rich meta-ironstone, near the margins of monzonite-diorite bodies of the Kukuluma Intrusive Complex. The lithological contacts acted as redox boundaries, where high-grade mineralization was enhanced in damage zones with higher permeability, including syn-D3 hydrothermal breccia, D2–D3 fold hinges, and D6 shears. The actual mineralizing event was syn-D7, and occurred in an extensional setting that facilitated the infiltration of mineralizing fluids. Thus, whilst gold mineralization is late-tectonic, ore zone geometries are linked to older structures and lithological boundaries that formed before gold was introduced. The deformation-intrusive history of the Kukuluma and Matandani deposits is near identical to the geological history of the world-class Nyankanga and Geita Hill deposits in the central part of the Geita Greenstone Belt. This similarity suggests that the geological history of much of the greenstone belt is similar. All major gold deposits in the Geita Greenstone Belt lack close proximity to crustal-scale shear zones; they are associated

  19. High Sr/Y rocks are not all adakites!

    Science.gov (United States)

    Moyen, Jean-François

    2010-05-01

    The name of "adakite" is used to describe a far too large group of rocks, whose sole common feature is high Sr/Y and La/Yb ratios. Defining adakites only by this criterion is misleading, as the definition of this group of rocks does include many other criteria, including major elements. In itself, high (or commonly moderate!) Sr/Y ratios can be achieved via different processes: melting of a high Sr/Y (and La/Yb) source; deep melting, with abundant residual garnet; fractional crystallization or AFC; or interactions of felsic melts with the mantle, causing selective enrichment in LREE and Sr over HREE. A database of the compositions of "adakitic" rocks - including "high silica" and "low silica" adakites, "continental" adakites and Archaean adakites—was assembled. Geochemical modeling of the potential processes is used to interpret it, and reveals that (1) the genesis of high-silica adakites requires high pressure evolution (be it by melting or fractionation), in equilibrium with large amounts of garnet; (2) low-silica adakites are explained by garnet-present melting of an adakite-metasomatized mantle, i.e at depths greater than 2.5 GPa; (3) "Continental" adakites is a term encompassing a huge range of rocks, with a corresponding diversity of petrogenetic processes, and most of them are different from both low- and high- silica adakites; in fact in many cases it is a complete misnomer and the rocks studied are high-K calc-alkaline granitoids or even S-type granites; (4) Archaean adakites show a bimodal composition range, with some very high Sr/Y examples (similar to part of the TTG suite) reflecting deep melting (> 2.0 GPa) of a basaltic source with a relatively high Sr/Y, while lower Sr/Y rocks formed by shallower (1.0 GPa) melting of similar sources. Comparison with the Archaean TTG suite highlights the heterogeneity of the TTGs, whose composition spreads the whole combined range of HSA and Archaean adakites, pointing to a diversity of sources and processes

  20. Late Archaean mantle metasomatism below eastern Indian craton ...

    Indian Academy of Sciences (India)

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

    crop NDD display mainly four distinct orientations viz., N-S, NNE-SSW, ...... also be trapped either along the grain boundary ... faster plate movements, high angle subduction would be ..... istry of oxide minerals in polymictic xenoliths from the.

  1. Late Mesozoic basin and range tectonics and related magmatism in Southeast China

    Directory of Open Access Journals (Sweden)

    Dezi Wang

    2012-03-01

    Full Text Available During the Late Mesozoic Middle Jurassic–Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic (Type I and intra-continental extensional basins (Type II. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tuffs and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous–Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geodynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc extensional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range

  2. Lithogeochemistry of the main unities of Pelotas batholith from Rio Grande do Sul State

    International Nuclear Information System (INIS)

    Figueiredo, M.C.H. de; Cesar, A.R.S.; Kronberg, B.I.

    1990-01-01

    The Pelotas batholith is composed predominantly of a Cambrian multi-intrusive granitic complex (Dom Feliciano Granitic Suite) associated to rhyolitic dike swarms and small basic plutons. The Piratini Gneisses (Late Riphean -Vendian) correspond to calcalkaline dioritic-tonalitic-granodioritic orthogneisses with chemical features of pre-collisional granitoids related to oceanic crust subduction (B-subduction) under an active continental margin. The Pinheiro Machado Granitoids (Vendian) are alkali-calcic granodiorite-monzogranites with Caledonian-type characteristics, but appear to also correspond to pre-collisional granitoids as a latter and more mature phase in the evolution of the magmatic arc. The Dom Feliciano Granitic Suite (Cambrian) is subdivided into porphyritic and equigranular facies, with predominance of monzogranites and syenogranites, respectively, with alkali-calcic late-orogenic characteristics. While the Rb/Sr isotopic data is consistent with the proposed evolution, the Nd model ages range from 2.0 - 1.2 Ga. This may reflect episodes of Sm/Nd fractionation within a lithospheric mantle instead of the accretion age of the granitoids. These apparent ages, which are also obtained in Parana and Karroo continental basalts, probably indicate coupled evolution of the continental crust and lithospheric mantle. In the suggested model, the Piratini Gneisses were orginated by differentiation of basic magmas formed by partial melting of lithospheric mantle, induced by dehydration of subducted oceanic crust, while the more mature arc granitoids had increasing crustal contamination or mingling-mixing with crustal melts and finally, in the late-and post-orogenic stages, partial melting of continental crust predominates. (author)

  3. Geochronology of granitoids and gnaisses from the Rio Maria, Mata Geral farm and Itacaiunas river regions, southern Para, Brazil

    International Nuclear Information System (INIS)

    Montalvao, R.M.G. de; Tassinari, C.C.G.; Bezerra, P.E.L.; Prado, P.

    1984-01-01

    Granitoids and gneisses occurring at Rio Maria, Mata Geral farm and Itacaiunas river regions, southern Para, underwent radiometric age determinations by Rb/Sr method using conventional isochrons. Results obtained from the Rio Maria and Mata Geral farm regions allowed te establishment of a reference 2,600 my Rb/Sr isochron with an initial Sr 87 /Sr 86 ratio of 0.7009. This result resembles the one obtained for granitoids and gneisses hosting rocks of the Serra do Inaja greenstone belt, located some what south of this area, which yielded, in Rb/Sr isochron, a radiometric age of 2,696 + - 79 my with an initial Sr 87 /Sr 86 ratio of 0.701. Results obtained from the Itacaiunas river region allowed for the establishment of a Rb/Sr referential isochron of 2,480 + - 40 my wth an initial Sr 87 /.Sr 86 ratio of 0.7072. Due to low initial ratios, it is suggested that the rocks from the Rio Maria, Mata Geral farm and Serra do Inaja regions formed from Mafic crust or superior mantle reworking, while those from the Itacaiunas river region, due to a high initial ratio, result from reworking at high crustal levels. (Author) [pt

  4. The geochemistry and geochronology of some proterozoic granitoid rocks from the Natal structural and metamorphic province, Southeastern Africa

    International Nuclear Information System (INIS)

    Kerr, A.; Milne, G.C.; Eglington, B.M.

    1987-01-01

    The Natal Structural and Metamorphic Province is thought to be an eastern extension of the Namaqua Metamorphic Province. Until recently few geochemical and isotopic data have been available on many of the rocks of this mobile belt. This paper presentes initial geochemical and geochronological information on the granitoids and associated rocks from three areas NSMP. Together, these areas provide a traverse through central and southern parts of the Mapumulo Group. Supracrustal gneisses, of uncertain age, are the oldest rocks in all areas, while the granitic intrusives range from 1,200-850 Ma, with a tendency for younger dates towards dates towards the south. Low initial 87 Sr/ 86 Sr ratios for these plutonic units suggest that the rocks were the products of partial melting of a relatively juvenile (circa 1,400 Ma) protolith. A type granites are common within the NSMP and give a range of ages, indicating that conditions suitable for their formation persited in this part of the African continent for an extended period of time. Economic deposits are lacking in eastern (Natal) sector of the mobile belt. Reconnaissance studies, however indicate that syn-tolate-Kinematic granitoids, intruded circa 1,000 Ma, are enriched in uranium and thorium irrespective of bulk chemistry, textural nature,mineralogy,structural setting, and isotopic characteristics. (author) [pt

  5. The possibility of use of Kremicj granitoid (Serbia) as an architectural stone

    International Nuclear Information System (INIS)

    Kureshevicj, Lidja

    2010-01-01

    The stone from the granitoid pluton of Kremić in southern Serbia has been examined in order to evaluate the possibility of its use as an architectural stone. Both field observations and laboratory testing of specimens have been performed. Although the specimens were collected from the field surface level, their physicomechanical lab test results have shown that the rock mass itself fulfils all the requirements for use as an architectural stone set by the State through Serbian standards. Also, the stone quality is higher in deeper ground levels, where the weathering agents have less intense effects. This stone does not have high ornamental properties, but it has a finegrained texture and low mica content which has a positive effect on its technical characteristics and susceptibility to processing. (Author)

  6. Metasedimentary, granitoid, and gabbroic rocks from central Stewart Island, New Zealand

    International Nuclear Information System (INIS)

    Allibone, A.H.; Tulloch, A.J.

    1997-01-01

    A NNE-NE trending strip, 3-8 km wide, extending from the Freshwater valley across Mt Rakeahua Table Hill, and Mt Allen to the northern end or the Tin Range was mapped at a scale of 1:12,500 to locate and investigate the boundary between the Median Tectonic Zone (MTZ) and Western Province on Stewart Island. A NNE-trending fault, herein termed the Escarpment Fault, separates predominantly ductily deformed rocks on its south side from essentially undeformed rocks to the north. North of the Escarpment Fault, a small (2-3 km 2 ) pluton of alkali-feldspar granite (Freds Camp) intruded gabbroic rocks tentatively considered to be associated with gabbro/anorthosite/diorite of the Rakeahua pluton, centred on Mt Rakeahua. Both units were subsequently intruded by I-type biotite granite of the South West Arm pluton. South of the Escarpment Fault the oldest intrusions are biotite tonalite-granite orthogneisses (Ridge and Table Hill plutons) intercalated with the sillimanite-cordierite-bearing Pegasus Group metasedimentary rocks, considered to represent the Western Province. They contain titanite, allanite, and magmatic epidote-bearing assemblages, implying affinities with I-type granitoids. These older granitoids have been affected by at least three phases of ductile deformation. Immediately south of the Escarpment Fault, the Escarpment pluton (hornblende, biotite, quartz, monzonite-quartz monzodiorite) only exhibit effects of the third phase of deformation. Minor gabbroic intrusives concordant with the S 3 fabric intrude the Pegasus Group and intercalated orthogneisses. Plutons of two-mica, garnet ±cordierite granite (Blaikies and Knob) and younger biotite-titanite-magmatic epidote granite (Campsite) cut fabrics associated with the third phase of ductile deformation. Preliminary U-Pb dating indicate Devonian-Carboniferous, Jurassic, and Early Cretaceous emplacement ages for Ridge Orthogneiss, Freds Camp pluton, South West Arm pluton, and Blaikies pluton, respectively. South

  7. Weathering profiles in granitoid rocks of the Sila Massif uplands, Calabria, southern Italy: New insights into their formation processes and rates

    Science.gov (United States)

    Scarciglia, Fabio; Critelli, Salvatore; Borrelli, Luigi; Coniglio, Sabrina; Muto, Francesco; Perri, Francesco

    2016-05-01

    In this paper we characterized several weathering profiles developed on granitoid rocks in the Sila Massif upland (Calabria, southern Italy), integrating detailed macro- and micromorphological observations with physico-mechanical field tests and petrographic, mineralogical and geochemical analyses. We focused our attention on the main weathering and pedogenetic processes, trying to understand apparent discrepancies between weathering grade classes based on field description and geomechanical properties, and two common weathering indices, such as the micropetrographic index (Ip) and the chemical index of alteration (CIA). Our results showed that sericite on plagioclase and biotite chloritization, that represent inherited features formed during late-stage hydrothermal alteration of granitoid rocks, may cause an overestimation of the real degree of weathering of primary mineral grains under meteoric conditions, especially in lower weathering grade classes. Moreover, the frequent identification of Fe-Mn oxides and clay coatings of illuvial origin (rather than or in addition to those formed in situ), both at the macro- and microscale, may also explain an overestimation of the weathering degree with respect to field-based classifications. Finally, some apparent inconsistencies between field geomechanical responses and chemical weathering were interpreted as related to physical weathering processes (cryoclastism and thermoclastism), that lead to rock breakdown even when chemical weathering is not well developed. Hence, our study showed that particular caution is needed for evaluating weathering grades, because traditional field and geochemical-petrographic tools may be biased by inherited hydrothermal alteration, physical weathering and illuvial processes. On the basis of chronological constraints to soil formation obtained from a 42 ka-old volcanic input (mixed to granite parent materials) detected in the soil cover of the Sila Massif upland, a first attempt to estimate

  8. The late-Variscan peraluminous Valdepeñas pluton (southern Central Iberian Zone)

    Energy Technology Data Exchange (ETDEWEB)

    Errandonea-Martín, J.; Carracedo-sánchez, M.; Sarrionandia, F.; Santos Zalduegui, J.F.; García de Madinabeitia, S.; Gil-Ibarguchi, J.I.

    2017-07-01

    The Valdepeñas pluton is the easternmost outcrop of the Cáceres-Valdepeñas magmatic alignment (southern Central Iberian Zone). This massif is constituted by a cordierite-bearing porphyritic monzogranite and may be grouped within the so-called “Serie Mixta” granitoids. The Valdepeñas monzogranite is of magnesian [FeOt/(FeOt+MgO)~0.76], alkali-calcic [(Na2O+K2O)–CaO=7.8–8.5] and peraluminous (A/CNK=1.14–1.20). Multielemental- and REE-normalized patterns are comparable to those of similar rocks in the Nisa- Alburquerque-Los Pedroches magmatic alignment, and slightly differ from those of the Montes de Toledo batholith, both in the southern Central Iberian Zone. The U-Pb zircon age of 303±3Ma is consistent with the late-orogenic character of the intrusion and is in accordance with most of the granitic peraluminous intrusions in the southern Central Iberian Zone. 86Sr/87Sr300Ma ratios (0.707424–0.711253), εNd300Mavalues (-5.53 to -6.68) and whole-rock major and trace element compositions of the studied rocks, suggest that the parental magma of the Valdepeñas monzogranite could derive from a crustal metaigneous source. The U-Pb ages (552–650Ma) of inherited zircon cores found in Valdepeñas monzogranite samples match those often found in Lower Paleozoic metavolcanics and granitic orthogneisses of Central Iberia and, furthermore, point to Upper Neoproterozoic metaigneous basement rocks as possible protoliths at the magma source. Based on the solubility of monazite in peraluminous melts, the estimated emplacement temperature of the studied monzogranite is 742–762ºC. The results obtained in this work would contribute to a better understanding of the origin of the “Serie Mixta” granitoids.

  9. Geochemical evidence for subduction in the early Archaean from quartz-carbonate-fuchsite mineralization, Isua Supracrustal Belt, West Greenland

    DEFF Research Database (Denmark)

    Pope, Emily Catherine; Rosing, Minik Thorleif; Bird, Dennis K.

    Quartz, carbonate and fuchsite (chromian muscovite) is a common metasomatic assemblage observed in orogenic gold systems, both in Phanerozoic convergent margin settings, and within supracrustal and greenstone belts of Precambrian rocks. Geologic and geochemical observations in younger orogenic...... systems suggest that ore-forming metasomatic fluids are derived from subduction-related devolitilization reactions, implying that orogenic Au-deposits in Archaean and Proterozoic supracrustal rock suites are related to subduction-style plate tectonics beginning early in Earth history. Justification...... with Phanerozoic orogenic deposits and that this type of metasomatism is a unique result of subduction-related processes. Fuchsite from the ISB has a δ18O and δD of 7.7 to 17.9‰ and -115 to -61‰, respectively. δ18O of quartz from the same rocks is between 10.3 and 18.6‰. Muscovite-quartz oxygen isotope thermometry...

  10. Metasomatic processes in the orthogneiss-hosted Archaean peridotites of the Fiskefjord region, SW Greenland

    Science.gov (United States)

    Szilas, K.; Cruz, M. F.; Grove, M.; Morishita, T.; Pearson, D. G.

    2016-12-01

    Field observations and preliminary geochemical data are presented for large (>500x1000m) peridotite enclaves from the Fiskefjord region of SW Greenland. These ultramafic complexes are dominated by dunite, amphibole-harzburgite, lesser amounts of norite and horizons of stratiform chromitite and are therefore interpreted as cumulate rocks[1]. The ultramafic enclaves are hosted by intrusive tonalitic orthogneiss, which provide U-Pb zircon minimum age constraints of ca. 2980 Ma, whereas preliminary Re-Os isotope data on the dunite and chromitite yield TRD ages of ca. 3300 Ma[2]. Dunite has highly forsteritic olivine compositions with Mg# mostly around 92 to 93, which is uncorrelated with the bulk-rock mg# or modal chromite contents. This indicates that the primary olivine records equilibration with a highly magnesian parental magma, which may have been responsible for the strong depletion of the SCLM in this region. Amphibole and phlogopite is mostly associated with granitoid sheets or infiltrating veins in the dunite and appear to replace chromite. Argon dating (40Ar/39Ar) of the phlogopite yields ages ranging from ca. 3400 Ma to ca. 1750 Ma, with most ages clustering around 3000 Ma. This is consistent with formation of the phlogopite and amphibole by metasomatic processes involving reaction between granitoid-derived siliceous fluids and the ultramafic rocks. The older 40Ar/39Ar age plateaus most plausibly represent excess Ar, potentially inherited from the nearby Itsaq Gneiss Complex (3900 to 3600 Ga) based on its proximity. The youngest 40Ar/39Ar age plateaus on the other hand may potentially signify the closure-age for this system, which could have important implications for determining the exhumation history of the North Atlantic craton. References [1] Szilas, K., Kelemen, P. B., & Bernstein, S. (2015). Peridotite enclaves hosted by Mesoarchaean TTG-suite orthogneisses in the Fiskefjord region of southern West Greenland. GeoResJ, 7, 22-34. [2] Szilas, K., van

  11. Evolution of Brasiliano-age granitoid types in a shear-zone environment, Umarizal-Caraubas region, Rio Grande do Norte, northeast Brazil

    Science.gov (United States)

    Galindo, A. C.; Dall'Agnol, R.; McReath, I.; Lafon, J. M.; Teixeira, N.

    1995-01-01

    A sequence of Brasiliano-age granitoid types is exposed in a small area near the cities of Umarizal and Caraúbas in Rio Grande do Norte State, Northeast Brazil. Porphyritic K-alkali-calcic monzogranite is an important facies of the oldest Caraúbas intrusion (RbSr whole rock isochron age of ca. 630 Ma), which suffered solid-state deformation due to movements on a major NE-trending shear zone. The intrusion of the Prado and part of the Quixaba bodies was probably controlled by the shear zone. These two bodies include mafic/intermediate rocks, some of which contain two pyroxenes, and have hybrid, partly alkaline and partly shoshonitic geochemical characteristics. Rock types and ages are similar to those of some Pan-African occurrences in southwestern Nigeria. The Tourão body, intruded at ca. 590 Ma, presents preferred mineral orientations which are probably largely magmatic, since little evidence is found for widespread solid-state deformation. On the other hand, its intrusion may have been facilitated by the presence of the shear-zone faults. The rocks form a monomodal felsic K-alkali-calcic suite. With the exception of the Quixaba body, all these earlier granitoids are magmatic epidote- and magnetite-bearing porphyritic monzogranites with trace element geochemical characteristics of modern syn-collisional granites. The latest intrusion at ca. 545 Ma is mainly represented by potassic quartz syenites and related rocks, some of which contain fayalite or ferrohypersthene. These rocks possess neither well developed mineral orientations of magmatic origin nor signs of solid-state deformation. They are mineralogically similar to, but younger than some of the "bauchites" of central Nigeria. Geochemical signatures are comparable with those of modern within-plate granites. All granitoids present high ( 87Sr/ 86Sr)i ratios which range from 0.708 to 0.712, and increase with decreasing age. Such ratios are compatible with important or dominant crustal contributions. On the

  12. The differentiation process of the I-type granitoids in southwest Japan and New South Wares in Australia

    Science.gov (United States)

    Kawakatsu, K.; Iwamoto, Y.; Ebisu, S.; Hasegawa, M.; Hiraiwa, N.; Kawakatsu, T.; Kitano, A.; Masuta, T.; Ootsubo, H.; Wakazono, R.

    2013-12-01

    Cretaceous-Paleogene Granitoids in the inner zone of southwest Japan have been divided into two series: the magnetite series that is distributed mainly in the San-in belt and the ilmenite series that is distributed mainly in San-yo belt. For 8 years, we have been investigating the two series to clear their processes of magmatic differentiation. Recently, we discovered oscillatory zoned structure, exsolution lamellae of amphibole, and relics of pyroxene left in the core of amphibole from Harima granodiorite, Nunobiki granodiorite (San-yo belt) and Daito-Yokota quartz diorite (San-in belt). The amphibole that has microstructure coexists with magnetite, ilmenite and pyrrhotite. We compared the two series for crystallization and re-equilibrium by ion substitution using the microstructure of the amphibole as 'time measure' during the differentitation process of acidic magma. While magnetites and ilmenites coexist with the core of the amphiboles, the oxygen fugacity of the San-yo belt magma was low until the later stage of magmatic differentiation where H2S from the Earth's crust mixed with it. In the subsolidus process, hydrothermal solutions circulated. On the other hand, the oxygen fugacity of the San-in belt magma began to rise in the early stage of magmatic differentiation. In the later stage, mafic magma was contaminated with SO2. The rims of amphiboles coexist with pyrrhotites in both of belts. Furthermore, the re-equilibrium of minerals underwent progressive oxidation and hydrothermal fluid circulated actively in the subsolidus process. Bingie Bingie Point at New South Wares (Eurobodalla National Park) is a peninsula about a meter around. The plutonic rocks were formed in the Devonian period and belong to the magnetite series. They are classified I-type granitoids such as those found in the inner zone of southwest Japan. They have only trace amounts of oxide minerals and pyrrhotite. The amphiboles of the granitoids have oscillatory zoned structures at pale green

  13. Geocronología y geoquímica isotópica (Sr, Nd) de los granitoides de Pola de Allande (Asturias): ¿Relictos de un arco magmático cadomiense en la Zona Asturoccidental Leonesa?

    OpenAIRE

    Gutiérrez Alonso, Gabriel; Fernández Suárez, Javier

    1998-01-01

    [ES] Los granitoides pre-Variscos de Pola de Allande se sitúan en el Antiforme del Narcea, en el límite entre las zonas Cantábrica y Asturoccidental Leonesa de la cadena Varisca Ibérica. Estos granitoides, formados por tonalitas y granodioritas con afinidades geoquímicas de arco magmático, intruyeron en sedimentos siliciclásticos Neoproterozoicos y fueron posteriormente afectados por la deformación tangencial Varisca. La datación U-Pb de circones de dos intrusiones por el método de Ablación L...

  14. High but balanced sedimentation and subsidence rates (Moodies Group, Barberton Greenstone Belt), followed by basin collapse: Implication for Archaean tectonics

    Science.gov (United States)

    Heubeck, Christoph; Lowe, Donald R.; Byerly, Gary R.

    2010-05-01

    Archaean tectonophysical models distinguish between thick, rigid and thin, mobile crust; from these the major mechanisms and rates for continental growth are derived. Archaean sedimentary rocks, preserved in metamorphosed and highly deformed greenstone belts, can contribute to constrain these models by estimating subsidence rates, derived from the combination of facies changes and precise age dates. Largely siliciclastic strata of the Moodies Group form the topmost unit of the Barberton Supergroup of the Barberton Greenstone Belt (BGB), South Africa, represent one of the world's oldest unmetamorphosed quartz-rich sedimentary sequences, and reach ca. 3500m thick (Lowe and Byerly, 2007). Large parts of the Moodies Group were deposited in apparent sedimentary continuity in alluvial, fluvial, shoreline and shallow-marine environments (e.g., Eriksson, 1979; Heubeck and Lowe, 1994). Distinctive sources and variations in facies indicate that Moodies deposition occurred at times in several basins. In several now tectonically separated regions, a regional basaltic lava (unit MdL of Anhaeusser, 1968) separates a lower unit (ca. 2000m thick and possibly representing an extensional setting) from an upper unit (ca. 1500m thick and characterized by progressive unconformities, rapidly changing facies, thicknesses, and sandstone petrographic composition). Single zircons separated from a felsic air-fall tuff of the middle Moodies Group and immediately overlying the basaltic lava in the Saddleback Syncline were dated on the Stanford-USGS SHRIMP RG. Out of 24 dated grains, two near-concordant groups have mean ages of 3230,6+-6,1Ma (2σ; n=9) and 3519+-7 Ma (2σ; n=9), respectively. We interpret the former age as representing the depositional age of the tuff, the latter as representing inherited zircons from underlying Onverwacht-age basement. The interpreted depositional age of the Moodies tuff is indistinguishable from numerous similar ages from felsic and dacitic volcanics at the

  15. Geochemical studies, magmatic evolution, microstructures and replacement mechanisms in Jebale-Barez granitoid Complex (East and Southeast Jiroft

    Directory of Open Access Journals (Sweden)

    Jamal Rasouli

    2017-08-01

    Full Text Available Introduction The Jebale-Barez Plutonic Complex (JBPC is composed of many intrusive bodies and is located in the southeastern province of Kerman on the longitude of the 57◦ 45 ' east to 58◦ 00' and Northern latitudes 28◦ 30' to 29◦ 00'. The petrologic composition is composed of granodiorite, quartzdiorite, granite, alkali-granite, and trace amounts of tonalite with dominant granodiorite composition. Previously, the JBPC was separated into three plutonic phases by Ghorbani (2014. The first plutonic phase is the main body of the complex with composition of quartz-diorite to granodiorite. After differentiation of magma in the magmatic chamber, the porphyritic and not fully consolidated magmas have intruded into the main body. Their compositions were dominantly granodiorite and granite that are defined as the second plutonic phase. Finally, the last phase was started by an intrusion of the holo- leucogranite into the previous bodies. This plutonic activity was pursued by the minor Quaternary basaltic volcanism that shows metamorphic haloes in the contacts. They are dominantly porphyric leucogranites. However, some bodies show dendritic texture that may imply the existence of silicic fluids in the latest crystallization stages. Materials and methods In this article different analysis methods were used. For example, we used a total of two hundred samples of the various granitoids that were selected for common thin section study. Forty four representative samples from the different granitic rocks were selected for whole rock chemical analyses. The analyses of both major and trace elements were performed at the Department of Earth Sciences, the University of Perugia, Italy. The analysis for all major elements was carried out by an X-ray fluorescence spectrometry (XRF using a tube completed with a Rn and W anode under conditions with acceleration voltage of 40-45 kV and electric current ranging from I=30-35 mA. After calcination of powdered

  16. Geological evolution of the center-southern portion of the Guyana shield based on the geochemical, geochronological and isotopic studies of paleoproterozoic granitoids from southeastern Roraima, Brazil; Evolucao geologica da porcao centro-sul do escudo das Guianas com base no estudo geoquimico, geocronologico e isotopico dos granitoides paleoproterozoicos do sudeste de Roraima, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, Marcelo Esteves

    2006-07-01

    This study focuses the granitoids of center-southern portion of Guyana Shield, southeastern Roraima, Brazil. The region is characterized by two tectonic-stratigraphic domains, named as Central Guyana (GCD) and Uatuma-Anaua (UAD) and located probably in the limits of geochronological provinces (e.g. Ventuari-Tapajos or Tapajos-Parima, Central Amazonian and Maroni-Itacaiunas or Transamazon). The aim this doctoral thesis is to provide new petrological and lithostratigraphic constraints on the granitoid rocks and contribute to a better understanding of the origin and geo dynamic evolution of Guyana Shield. The GCD is only locally studied near to the UAD boundary, and new geological data and two single zircon Pb-evaporation ages in mylonitic biotite granodiorite (1.89 Ga) and foliated hastingsite-biotite granite (1.72 Ga) are presented. These ages of the protholiths contrast with the lithostratigraphic picture in the other areas of Cd (1.96-1.93 Ga). Regional mapping, petrography, geochemistry and zircon geochronology carried out in the Urad have showed widespread Paleoproterozoic calc-alkaline granitic magmatism. These granitoid rocks are distributed into several magmatic associations with different Paleoproterozoic (1.97-1.89 Ga) ages, structural and geochemical affinities. Detailed mapping, petrographic and geochronological studies have distinguished two main sub domains in the UAD. In the northern UAD, the high-K calc-alkaline Martins Pereira (1.97 Ga) and Serra Dourada S-type granites (1.96 Ga) are affected by NE-SW and E-W ductile dextral shear-zones, showing coexistence of magmatic and deformational fabrics related to heterogeneous deformation. Inliers of basement (2.03 Ga) crop out northeast of this area, and are formed by meta volcano-sedimentary sequence (Cauarane Group) and TTG-like calc-alkaline association (Anaua Complex). Xenoliths of meta diorites (Anaua Complex) and para gneisses (Cauarane Group) reinforce the intrusive character of Martins Pereira

  17. Geochemistry Petrography, thermobarometry and investigation of magmatic series in Mirabad- Chehel Khane granitoid body (east of Bouin– Miandasht, Isfahan province

    Directory of Open Access Journals (Sweden)

    Seyed Mohsen Tabatabaei Manesh

    2017-11-01

    Full Text Available On the base of petrology, the Mirabad- Chehel Khane granitoid, east of Bouin-Miandasht, dominantly consists of syenogranite, monzogranite, alkali granite and granodiorites. The main minerals of these rocks are quartz, alkali feldspar (Orthoclase, plagioclase (Albite - Oligoclase, biotite, ± amphibole with minor amount of allanite, zircon, titanite, apatite, ± tourmaline.  The biotite from the granites are Fe-rich type (annite and primary magmatic in origin. The composition of the biotites studied principally falls in the calc-alkaline subduction related I-type granite on the tectonomagmatic discrimination diagrams, which stand on their major element oxides. Which is consistent with the nature of their host rocks. The studied amphiboles are classified as calcic (ferro-hornblende which points to the I-type nature of the granitoid.  The tourmaline composition plots on the schorl - foitite field. The temperature for the alteration, on the base of chlorite composition from the syenogranite, is estimated around 350°C and from the monzogranite rocks about 341°C.  Based on the application of Al-in amphibole, a 3 Kbar pressure was determined for the syenogranite unit corresponding to the depth of 8-11 Km for the emplacement of the pluton. Hornblende- plagioclase thermometer shows 694 to 700°C for the equilibrium of these two minerals.

  18. Geotectonic evolution of granitoid-greenstone belts from Crixas, Guarinos, Pilar de Goias - Hidrolina (Goias), Brazil

    International Nuclear Information System (INIS)

    Montalvao, R.M.G. de.

    1985-01-01

    The area in discussion, in a geologic context, constitutes one of the most interesting and complex, within the South American Platform, in Brazilian territory, over which granitoid-greenstone belts are outstanding. The Goiano Complex is the oldest unit in the geologic column herein adopted and composed largely of granitoids, gneiss and migmatites, in the amphibolite facies. Dated samples of the complex have shown two isochrones of Rb/Sr reference, the oldest one is 2.926 +- 65 m.y. and the 87 Sr/ 86 Sr initial ratio of 0.7001 and the youngest on of 2.471 + 20 m.y. and 87 Sr/ 86 Sr initial ratio of 0.701. Although the initial ratios data of the Rb/Sr isochron, as well as the parameters in the Pb/Pb analyses may indicate material of mantle source, it may be interpreted, with the help of field data, that the youngest values may indicate the reworking of crustal sialic rocks formed 2.925 +- 65 m.y. ago (oldest isochron), with primitive material contribution. Before such reworking volcanic-sedimentary sequence was deposited over the already formed sialic crust, and it is denominated Pilar de Goias Supergroup which characterizes the Greenstone Belts in the region. The Archean age for the supergroup was evident through the age results of its ultramafic rocks, showing 2.600 m.y. isochron age, with Sm/Nd methods. Besides the geochronology and field studies, basic information for the construction of the geologic column herein presented, there has been done petrographic and litho geochemical studies, both in the Goiano Complex and Pilar de Goias Supergroup, as for the Pilar de Goias Supergroup, the studies were concentrated on its mafic-ultramafic rocks. (author)

  19. Metal availability and the expanding network of microbial metabolisms in the Archaean eon

    Science.gov (United States)

    Moore, Eli K.; Jelen, Benjamin I.; Giovannelli, Donato; Raanan, Hagai; Falkowski, Paul G.

    2017-09-01

    Life is based on energy gained by electron-transfer processes; these processes rely on oxidoreductase enzymes, which often contain transition metals in their structures. The availability of different metals and substrates has changed over the course of Earth's history as a result of secular changes in redox conditions, particularly global oxygenation. New metabolic pathways using different transition metals co-evolved alongside changing redox conditions. Sulfur reduction, sulfate reduction, methanogenesis and anoxygenic photosynthesis appeared between about 3.8 and 3.4 billion years ago. The oxidoreductases responsible for these metabolisms incorporated metals that were readily available in Archaean oceans, chiefly iron and iron-sulfur clusters. Oxygenic photosynthesis appeared between 3.2 and 2.5 billion years ago, as did methane oxidation, nitrogen fixation, nitrification and denitrification. These metabolisms rely on an expanded range of transition metals presumably made available by the build-up of molecular oxygen in soil crusts and marine microbial mats. The appropriation of copper in enzymes before the Great Oxidation Event is particularly important, as copper is key to nitrogen and methane cycling and was later incorporated into numerous aerobic metabolisms. We find that the diversity of metals used in oxidoreductases has increased through time, suggesting that surface redox potential and metal incorporation influenced the evolution of metabolism, biological electron transfer and microbial ecology.

  20. Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing

    Energy Technology Data Exchange (ETDEWEB)

    Galán, G.; Enrique, P.; Butjosa, L.; Fernández-Roig, L.

    2017-07-01

    Olivine hornblendites (cortlandtites) form part of the Montnegre mafic complex related to late-Variscan I-type granitoids in the Catalan Coastal Ranges. Two generations of spinel are present in these hornblendites: Spl1 forms euhedral crystals included in both olivine and Spl2. Spl2 forms euhedral to anhedral crystals associated with phlogopite and fibrous colourless amphibole forming pseudomorphs after olivine. Compositions of Spl1 are picotite-Al chromite (Fe#: 77.78-66.60; Cr#: 30.12-52.22; Fe3+/R3+: 6.99-21.89; 0.10< TiO2%< 0.62). Compositions of Spl2 are pleonaste (Fe#: 37.86-52.12; Cr#: 1.00-15.45; Fe3+/R3+: 0.31-5.21; TiO2% <0.10%). The two types of spinel follow a CrAl trend, mainly due to the substitution (Fe2+)-1Cr-1= MgAl, which is interpreted as the result of mixing between two different mantle-derived melts. The compositions of early Spl1 crystals included in olivine are characteristic of Al-rich basalts. More aluminous Spl2 would result from reaction of olivine with a less evolved, Al and K-rich mantle-derived melt after new refilling of the magma chamber or channel. As a whole, spinels from similar examples of Variscan olivine hronblendites also follow a CrAl trend with high Fe# and starting at higher Cr# than other trends of this type. Cr# heterogeneity in the early spinels from these Variscan hornblendites would be inherited from the variable Al content of the mafic melts involved in their genesis.

  1. Petrogenesis and geodynamic implications of Ediacaran highly fractionated A-type granitoids in the north Arabian-Nubian Shield (Egypt): Constraints from whole-rock geochemistry and Sr-Nd isotopes

    Science.gov (United States)

    Sami, Mabrouk; Ntaflos, Theodoros; Farahat, Esam S.; Mohamed, Haroun A.; Hauzenberger, Christoph; Ahmed, Awaad F.

    2018-04-01

    Mineral chemistry, whole-rock geochemical and Sr-Nd isotopic data are reported for the Abu-Diab granitoids in the northern Arabian-Nubian Shield (ANS) of Egypt, to investigate their petrogenesis and geodynamic significance. Gabal Abu-Diab constitute a multiphase pluton, consisting largely of two-mica granites (TMGs) enclosing microgranular enclaves and intruded by garnet bearing muscovite granites (GMGs) and muscovite granites (MGs). The granitoids are weakly peraluminous (A/CNK = 1.01-1.12) and show high SiO2 (>72.9 wt%) and alkali (K2O + Na2O = 8.60-9.13) contents. The geochemical features show that they are post-collisional and highly fractionated A-type granitoids. Compared to their host TMGs, the microgranular enclaves are strongly peraluminous (A/CNK = 1.18-1.24) with lower SiO2 and higher abundances of trace elements. The TMGs are depleted in Ba, Nb, P and Ti and are enriched in LREEs relative to HREEs with weakly negative Eu anomalies (Eu/Eu* = 0.45-0.64). In contrast, the GMGs and MGs are extremely depleted in Ba, Sr and Ti and have tetrad-type REE patterns (TE1-3 = 1.1-1.3) with strongly pronounced negative Eu anomalies (Eu/Eu* = 0.03-0.26), similar to rare metals bearing granites. The Ediacaran (585 ± 24 Ma) TMGs, are characterized by restricted and relatively low initial 87Sr/86Sr ratios (0.70337-0.70382) that suggests their derivation from a depleted mantle source, with little contamination from the older continental crust. In contrast, the GMGs and MGs have extremely high 87Rb/86Sr and 87Sr/86Sr ratios that reflect the disturbance of the Rb-Sr isotopic system and may give an indication for magmatic-fluid interaction. However, all the granitoids display positive εNd(t) (4.41-6.57) and depleted mantle model ages TDM2 between 777 and 956 Ma, which indicate their derivation from a Neoproterozoic juvenile magma sources and preclude the occurrence of pre-Neoproterozoic crustal rocks in the ANS. The microgranular enclaves represent globules of hot mafic

  2. Metallogenetic characterization of granitoid rocks through geochemical prospection: the Lagoa Real example related to uranium mineralization in Bahia state, Brazil; Caracterizacao metalogenetica de corpos gratinoides atraves de prospeccao geoquimica: o exemplo da suite intrusiva Lagoa Real relacionada a mineralizacoes de uranio no Estado da Bahia

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, J.E., E-mail: cprmsa@bahianet.com.br [Servico Geologico do Brasil (GEREMI/SUREG/SA/CPRM), Salvador, BA (Brazil)

    2011-07-01

    Within a broad metallogenetic evaluation program carried out by CPRM - Geological Survey of Brazil in covenant with the CBPM - Companhia Baiana de Pesquisa Mineral in the central part of the Sao Francisco Craton, the Lagoa Real granitoid rocks was one of the selected targets. The work included geochemical exploration supplemented by follow-in survey and integrated 1:200.000 scale geochemical cartography. The Lagoa Real granitoid was recognized with composition ranging from monzogranitic to alcaligranitic type. The geochemical surveying led to the definition of the metallogenetic specialization of the granitoid rock, with characteristic geochemical and mineralogic associations. These associations are related to uranium mineralization. The genetic model using stream sediment and pan concentrate data, show similarity with the metallogenetic model of zonal partitioning proposed by Routhier (1963), for plutonogenic lode deposits with potential for Sn, W, Nb, Be, REE, Au, and U. In this work emphasis is given to the importance of the integrated use of different prospective methods toward the evaluation of granitoid systems, particularly the combination of geochemical surveying methods with results for a better understanding of the geologic and metallogenetic settings. (author)

  3. Variation of stable silicon isotopes. Analytical developments and applications in Precambrian geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Abraham, Kathrin

    2010-05-28

    regarded as the most likely source of silica for the silicification process. Calculations show that classical water-rock interaction can not influence the silicon isotope variation due to the very low concentration of Si in seawater (49 ppm). The data are consistent with a two end-member component mixture between basalt and chert. The secular increase in chert isotope composition through time is confirmed by the present data. Possible factors that could account for different gradients of δ{sup 30}Si vs. δ{sup 18}O are changes of seawater isotope signature, the water temperature or secondary alteration. The last section describes potential changes in the source of Granitoids in the Archaean: the Si isotope perspective. Sodic tonalite-trondhjemite-granodiorite (TTG) intrusive units make up large components of the Archaean crust. In contrast, today's continental crust is more potassic in composition (GMS group: granite-monzonite-syenite). Processes that lead to this changeover from ''sodic'' to ''potassic'' crust are the subject of this section. Silicon isotope measurements were combined with major and trace element analyses on different generations of TTG and GMS group intrusive units from 3.55 to 3.10 Ga from the study area. δ{sup 30}Si-values show a slight temporal increase during different pluton generations, with sodic intrusive units demonstrating the lowest Si-isotope composition. The small increase in silicon isotope composition with time might be due to different temperature conditions in the source of granitoids, with Na-rich, light δ{sup 30}Si granitoids emerging at higher temperatures. A similarity in δ{sup 30}Si between Archaean K-rich plutons and Phanerozoic K-rich plutons is confirmed.

  4. Variation of stable silicon isotopes. Analytical developments and applications in Precambrian geochemistry

    International Nuclear Information System (INIS)

    Abraham, Kathrin

    2010-01-01

    likely source of silica for the silicification process. Calculations show that classical water-rock interaction can not influence the silicon isotope variation due to the very low concentration of Si in seawater (49 ppm). The data are consistent with a two end-member component mixture between basalt and chert. The secular increase in chert isotope composition through time is confirmed by the present data. Possible factors that could account for different gradients of δ 30 Si vs. δ 18 O are changes of seawater isotope signature, the water temperature or secondary alteration. The last section describes potential changes in the source of Granitoids in the Archaean: the Si isotope perspective. Sodic tonalite-trondhjemite-granodiorite (TTG) intrusive units make up large components of the Archaean crust. In contrast, today's continental crust is more potassic in composition (GMS group: granite-monzonite-syenite). Processes that lead to this changeover from ''sodic'' to ''potassic'' crust are the subject of this section. Silicon isotope measurements were combined with major and trace element analyses on different generations of TTG and GMS group intrusive units from 3.55 to 3.10 Ga from the study area. δ 30 Si-values show a slight temporal increase during different pluton generations, with sodic intrusive units demonstrating the lowest Si-isotope composition. The small increase in silicon isotope composition with time might be due to different temperature conditions in the source of granitoids, with Na-rich, light δ 30 Si granitoids emerging at higher temperatures. A similarity in δ 30 Si between Archaean K-rich plutons and Phanerozoic K-rich plutons is confirmed.

  5. Tectonomagmatic evolution of the proto Andean Margin: Geochemical characterization and zircon U-Pb geochronologic constraints from the Ecuadorian Eastern Cordilleran granitoids

    Science.gov (United States)

    Buchwaldt, R.; Toulkeridis, T.

    2013-05-01

    The timing of pan-Pacific Gondwanide Orogeny in the proto-Andes, and its driving mechanisms are still highly debated and relies predominantly upon whole-rock Rb-Sr and K-Ar chronology and rudimentary mineralogy and geochemistry. In order to decipher these uncertainties we have studied the composition, age and provenance of granitoids along the strike of the Eastern Cordillera of Ecuador and related these deep-seated and surface tectonic processes attending the Late Cretaceous-Palaeogene history of the northern Andes. The plutonic rocks constitute a metaluminous to peraluminous (A/CNK ~ 0.8-1.2), calc-alkaline suite. A unimodal and wide compositional range of the intrusives (49-78 wt. % SiO2) is characteristic of this I-type orogenic suites. Mantle-normalized trace element patterns reveal typical subduction-related signature. Chondrite-normalized REE patterns do not show significant HREE fractionation suggesting the absence of high-pressure residual mineralogy in the source and formation in a "normal thickness", garnet-free crust. Slight Eu anomalies, lowering Sr contents, and concave-up REE patterns of samples dioritic in composition indicate a model involving fractionation of plagioclase, amphibole and pyroxene from a basaltic parent. The analyzed zircon crystals are colorless - transparent ranging in size from 50 to 250 μm. In CL images, 95% of the zircons exhibit oscillatory zonation, characteristic of a magmatic origin. This observation is consistent with the REE zircon composition showing a are characteristic steep positive slope from La to Lu with a significantly positive Ce-anomaly and slight negative Eu-anomaly. There is very little variation in Hf isotopic composition with most of the crust maintains near chondritic Zr/Hf ratios of around 35-40. Our results indicate the development of two tectonic episodes; with the first varying between 210-250 Ma and the second approximate 170-180 Ma. These results are consistent with similar events observed throughout

  6. [Analysis of X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry of Pangxidong Composite Granitoid Pluton and Its Implications for Magmatic Differentiation].

    Science.gov (United States)

    Zeng, Chang-yu; Ding, Ru-xin; Li, Hong-zhong; Zhou, Yong-zhang; Niu, Jia; Zhang, Jie-tang

    2015-11-01

    Pangxidong composite granitoid pluton located in the southwestern margin of Yunkai massif. The metamorphic grade of this pluton increases from outside to inside, that is, banded-augen granitic gneisses, gneissoid granites and granites distribute in order from edge to core. X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry are conducted to study the geochemical characteristics of the three types of rocks. The result shows that all the three types of rocks are peraluminous rocks and their contents of main elements and rare earth elements change gradually. From granitic gneisses to granites, the contents of Al₂O₃, CaO, MgO, TiO₂, total rare earth elements and light rare earth elements increase, but the contents of SiO₂ and heavy rare earth elements decrease. It is suggested that the phylogenetic relationship exists between granitic gneisses, gneissoid granites and granites during the multi-stage tectonic evolution process. Furthermore, the remelting of metamorphosed supracrustal rocks in Yunkai massif is probably an important cause of granitoid rocks forming. The evolutionary mechanism is probably that SiO₂ and heavy rare earth elements were melt out from the protolith and gradually enriched upward, but Al₂O₃, CaO, MgO, TiO₂ and light rare earth elements enriched downward.

  7. Rb-Sr isochronous dating of granitoids of Dumbier zone of Low Tatras (Western Carpathians)

    International Nuclear Information System (INIS)

    Bagdasaryan, G.P.; Gukasyan, R.Kh.; Cambel, B.; Vesel'skij, J.

    1985-01-01

    The results are discussed of isotopic-geochronological research and age determination of characteristic samples of granitoid rocks, obtained by the Rb/Sr isochronous method. The samples were biotite granodiorites and granites taken from various parts of the Dumbier massif and small granite bodies of the Kralicka type. Rb/Sr isochrones of the rock samples show identical age values: 362+-21 m.y. for the Dumbier massif and 365+-17 m.y. correspnding to the Middle - Upper Devonian. Initial 87 Sr/ 86 Sr ratios equal to 0.7079 and 0.7157, respectively, allow to make a presumption that the rocks of the Dumbier massif may have been derived both from crustal and from mantle sources while granites of the Kralicka type are close to the rocks of the crustal origin

  8. Late Cretaceous evolution of the northern Sistan suture zone ...

    Indian Academy of Sciences (India)

    Department of Geology, Birjand University, Birjand, Iran. ∗ ... Anisotropy of magnetic susceptibility (AMS) survey supported by field and ...... the ca. 1.45 Ga Karlshamn granitoid pluton, southeastern. Sweden, during .... Vernon R H 2004 A Practical Guide to Rock Microstructure;. UK, Cambridge University Press, 594p.

  9. The Sr:Ba:Rb ratio and zircon typology in granitoid complexes of Sao Paulo, Parana and Minas Gerais states (Brazil)

    International Nuclear Information System (INIS)

    Wernick, E.; Galembeck, T.M.B.; Artur, A.C.; Rigo Junior, L.; Weber-Diefenbach, K.

    1990-01-01

    Chemical (Sr: Ba: Rb) and zircon typology data from the Nazare Paulista, Mairipora/Cantareira, Cunhaporanga, Tres Corregos, Morungaba, Socorro, Itu, Graciosa and Serra Carambei granitoid complexes from the states of Minas Gerais, Sao Paulo and Parana (SE/S Brazil) are presented and discussed. By the zircon typology method these complexes are reffered, respectively, to the 2nd crustal, 3rd crustal/low temperature C-A, low temperature C-A, medium temperature C-A, medium/high temperature C-A, K-SA/Alkaline and alkaline serie which are considered as generated under increasing temperature associated with a progressive major participation of mantellic material. All these series, with the exception of the medium to high temperature calc-alkaline complexes Socorro and Morungaba whose chemical data come from several laboratories, display different positions and behaviour in the Sr: Ba: Rb diagram which reinforce the use of the zircon typology method in the study of granitoids. From the 2nd crustal serie up to the medium temperature C-A serie the complexes show a regular shift in their chemical composition which became progressively richer in Sr and depleted in Rb. The highly differentiades hypersolvus Serra do Carambei granite is strongly enriched in Rb and impoverish in Ba with respect to the Itu and the Graciosa complex which itself is slighly more depleted in Sr than the Itu granite. (author)

  10. Petrochemical and Mineralogical Constraints on the Source and Processes of Uranium Mineralisation in the Granitoids of Zing-Monkin Area, Adamawa Massif, NE Nigeria

    International Nuclear Information System (INIS)

    Haruna, I. V.; Orazulike, D. M.; Ofulume, A. B.; Mamman, Y. D.

    2011-01-01

    Zing-Monkin area, located in the northern part of Adamawa Massif, is underlain by extensive exposures of moderately radioactive granodiorites, anatectic migmatites, equigranular granites, porphyritic granites and highly radioactive fine-grained granites with minor pegmatites. Selected major and trace element petrochemical investigations of the rocks show that a progression from granodiorite through migmatite to granites is characterised by depletion of MgO, CaO, Fe 2 O 3, Sr, Ba, and Zr, and enrichment of SiO 2 and Rb. This trend is associated with uranium enrichment and shows a chemical gradation from the more primitive granodiorite to the more evolved granites. Electron microprobe analysis shows that the uranium is content in uranothorite and in accessories, such as monazite, titanite, apatite, epidote and zircon. Based on petrochemical and mineralogical data, the more differentiated granitoids (e.g., fine-grained granite) bordering the Benue Trough are the immediate source of the uranium prospect in Bima Sandstone within the Trough. Uranium was derived from the granitoids by weathering and erosion. Transportation and subsequent interaction with organic matter within the Bima Sandstone led to precipitation of insoluble secondary uranium minerals in the Benue Trough.

  11. A prolonged granitoid formation in Saglek Block, Labrador: Zonal growth and crustal reworking of continental crust in the Eoarchean

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Komiya

    2017-03-01

    We made a detailed sketch of a small outcrop in St. John's Harbour South (SJHS area, and classified the orthogneisses and mafic enclaves into seven generations based on the geologic occurrence. The first and second generations comprise mafic rocks and lack magmatic zircons. We conducted CL imaging and U-Pb dating of zircons from the third, sixth and seventh generation of the orthogneisses to estimate the protolith ages at 3902 ± 25, 3892 ± 33 and 3897 ± 33 Ma for each, supporting the presence of the over 3.9 Ga Iqaluk Gneiss. The geological occurrence that the mafic rocks occur as enclaves within the 3.9 Ga Iqaluk Gneiss indicates that they are the oldest supracrustal rocks in the world. Our geochronological and geological studies show the Uivak Gneiss is quite varied in lithology and age from 3.6 to >3.9 Ga, and tentatively classified into six groups based on their ages. The oldest Uivak Gneiss components including the Iqaluk Gneiss are present around the SJHS area, and the orthogneisses become young as it is away. The lines of evidence of overprinting of younger granitoid on older granitoid in small outcrops and geological-map scale as well as presence of inherited zircons even in the oldest suite suggests that crustal reworking played an important role on erasing the ancient crusts.

  12. Geological evolution of the center-southern portion of the Guyana shield based on the geochemical, geochronological and isotopic studies of paleoproterozoic granitoids from southeastern Roraima, Brazil

    International Nuclear Information System (INIS)

    Almeida, Marcelo Esteves

    2006-01-01

    This study focuses the granitoids of center-southern portion of Guyana Shield, southeastern Roraima, Brazil. The region is characterized by two tectonic-stratigraphic domains, named as Central Guyana (GCD) and Uatuma-Anaua (UAD) and located probably in the limits of geochronological provinces (e.g. Ventuari-Tapajos or Tapajos-Parima, Central Amazonian and Maroni-Itacaiunas or Transamazon). The aim this doctoral thesis is to provide new petrological and lithostratigraphic constraints on the granitoid rocks and contribute to a better understanding of the origin and geo dynamic evolution of Guyana Shield. The GCD is only locally studied near to the UAD boundary, and new geological data and two single zircon Pb-evaporation ages in mylonitic biotite granodiorite (1.89 Ga) and foliated hastingsite-biotite granite (1.72 Ga) are presented. These ages of the protholiths contrast with the lithostratigraphic picture in the other areas of Cd (1.96-1.93 Ga). Regional mapping, petrography, geochemistry and zircon geochronology carried out in the Urad have showed widespread Paleoproterozoic calc-alkaline granitic magmatism. These granitoid rocks are distributed into several magmatic associations with different Paleoproterozoic (1.97-1.89 Ga) ages, structural and geochemical affinities. Detailed mapping, petrographic and geochronological studies have distinguished two main sub domains in the UAD. In the northern UAD, the high-K calc-alkaline Martins Pereira (1.97 Ga) and Serra Dourada S-type granites (1.96 Ga) are affected by NE-SW and E-W ductile dextral shear-zones, showing coexistence of magmatic and deformational fabrics related to heterogeneous deformation. Inliers of basement (2.03 Ga) crop out northeast of this area, and are formed by meta volcano-sedimentary sequence (Cauarane Group) and TTG-like calc-alkaline association (Anaua Complex). Xenoliths of meta diorites (Anaua Complex) and para gneisses (Cauarane Group) reinforce the intrusive character of Martins Pereira

  13. Characteristics of the Late Devonian Tsagaan Suvarga Cu-Mo deposit, Southern Mongolia

    Science.gov (United States)

    Tungalag, Naidansuren; Jargalan, Sereenen; Khashgerel, Bat-Erdene; Mijiddorj, Chuluunbaatar; Kavalieris, Imants

    2018-05-01

    The Late Devonian Tsagaan Suvarga deposit (255 Mt at 0.55% Cu, 0.02% Mo) is located on the NW margin of the Tsagaan Suvarga Complex (TSC), which extends ENE over 15 × 10 km and comprises mainly medium-grained equigranular hornblende-biotite quartz monzonite and monzodiorite. Distinct mineralized intrusions are inferred from distribution of Cu-Mo mineralization but are not clearly discernible. The Tsagaan Suvarga Complex is a window within Carboniferous volcanic and sedimentary rocks, and wall rocks to the TSC are not known or exposed in the nearby district. Whole-rock analyses and Sr-Nd isotopes, 87Sr/86Sr0 = 0.7027 to 0.7038 (n = 12) and ɛNd0 = + 4.26 to + 2.77 (n = 12), show that the granitoids are subduction-related I-type, high K-calc-alkaline to shoshonitic series and derived from a mantle source. They exhibit fractionated light rare earth elements, without depleted Eu and depleted middle heavy rare earth elements and Y, typical of oxidized, fertile porphyry magmatic suites. Early porphyry-style quartz veins include A- and B-type. Molybdenite occurs in monomineralic veins (1-5 mm) or A veins. Copper mineralization occurs mainly as chalcopyrite and subordinate bornite, disseminated and associated with quartz-muscovite veins. Pyrite (vol%) content is less than chalcopyrite and bornite combined. Deep oxidation to about 50 m depth has formed zones of malachite and covellite in late fractures. The most important alteration is actinolite-biotite-chlorite-magnetite replacing hornblende and primary biotite. Quartz-K-feldspar alteration is minor. Late albite replaces primary K-feldspar and enhances sodic rims on plagioclase crystals. Quartz-muscovite (or sericitic alteration) overprints actinolite-biotite and porphyry-type quartz veins. Field observations and petrographic studies suggest that the bulk of the chalcopyrite-bornite mineralization at the Tsagaan Suvarga formed together with coarse muscovite alteration.

  14. ∼2.5 Ga late cratonisation events in Dharwar craton: insights from the gold mineralisation ages

    International Nuclear Information System (INIS)

    Srinivasa Sarma, D.; Ram Mohan, M.; McNaughton, Neal

    2013-01-01

    The history of volcanism, granitic magmatism, and gold mineralization is defined by U-Pb geochronology of magmatic zircons and hydrothermal monazite and xenotime respectively. The felsic volcanic host rocks from Hutti greenstone belt have a U-Pb zircon age of 258 ±7 Ma, about 40 m.y. older than the age of gold mineralization at 2547±10 Ma determined from hydrothermal monazite in the Hutti gold deposit. The syntectonic Kavital granitoid in the Hutti greenstone belt has a U-Pb zircon age of 2545±7 Ma, which overlaps with the timing of gold deposition and is consistent with structural interpretations. Zircon U-Pb ages for a felsic volcanic rock (2,588±10 Ma) and an intrusive granite (e''2,555±6 Ma) in the Gadag greenstone belt in the Western Dharwar Craton. In situ U-Pb dating of monazite and xenotime in gold reefs of the Gadag (2,522±6 Ma) and Ajjanahalli (2,520±9 Ma) gold deposits reveal a previously undated episode of gold mineralization at 2.52 Ga, substantially younger than the 2.55 Ga Hutti deposit in the eastern Dharwar Craton. The Hutti, Gadag and Ajjanahalli gold geochronology suggests that gold mineralization occurred throughout the Dharwar craton some 80 to 120 m.y. later than the major peak of Late Archean world-class orogenic gold mineralization in most other Archean cratons. Although gold mineralization across the craton postdates most of the magmatic activity and metamorphism at upper crustal levels, widespread thermal reworking of the lower middle crust, involving partial melting, metamorphism, and lower crustal granitoid intrusion, occurred concurrently with gold mineralization. It is likely that the large-scale hydrothermal fluid flow that produced widespread gold deposition was also part of this tectono-thermal event during the final stages of cratonization of the Dharwar Craton in southern India. (author)

  15. Geochronology Intermediary Laboratory implantation at the Rio Grande do Norte Federal University: the dating of the Serrinha Granitoid (RN) and the correlate Brasiliana extensional deformation; Implantacao do Laboratorio Intermediario de Geocronologia na UFRN: a datacao do granitoide de Serrinha (RN) e da deformacao extensional brasiliana correlata

    Energy Technology Data Exchange (ETDEWEB)

    Macedo, Maria Helena F.; Sa, Emanuel F. Jardim de; Souza, Zorano S. [Pernambuco Univ., Recife, PE (Brazil). Nucleo de Pesquisa em Geodinamica e Geofisica; Mendes, Franklin S. [Pernambuco Univ., Recife, PE (Brazil). Curso de Quimica; Ramalho, Karlos A.C. [Pernambuco Univ., Recife, PE (Brazil). Curso de Geologia

    1997-12-31

    The article describes the activities developed by the Geochronology Intermediary Laboratory at the Federal University of the Rio Grande do Norte, a Brazilian university, where there were the preoccupation of establishing strategies for a geochronological development. It relates the Rubidium-Strontium (Rb/Sr) and Samarium-Neodymium (Sm/Nd) methods, describing the analysis realized in these methodologies. Afterward, it presents the geological and petrographic situation of the Granitoide de Serrinha, located at Rio Grande do Norte State, Brazil and its geochronological data 8 refs., 2 figs.

  16. Structural and metamorphic evolution of the Mid-Late Proterozoic Rayner Complex, Cape Bruce, East Antarctica

    International Nuclear Information System (INIS)

    Dunkley, D.J.; Clarke, G.L.; White, R.W.

    2002-01-01

    Granulite to transitional granulite facies gneisses exposed at Cape Bruce, Rayner Complex, East Antarctica, record three main orogenic/magmatic phases: (1) intrusion of c. 1000-980 Ma felsic orthogneisses into Mid-Proterozoic metasediments, contemporary with the development of north-trending reclined to recumbent folds; (2) extensive c. 980-900 Ma felsic magmatism, including equivalents of the Mawson Charnockite, which accompanied the development of upright, east-northeast-trending folds; and (3) ultramylonite zones of uncertain age. The first two phases are known as the Rayner Structrual Episode, the effects of which are similar in rocks to the east of Cape Bruce, at Mawson, and in the northern Prince Charles Mountains. Archaean rocks immediately to the west of Cape Bruce were tectonically reworked during the Rayner Structural Episode. The first orogenic phase is inferred to represent the collision between a wedge-shaped Proterozoic block comprising rocks of the Mawson Coast and Eastern Ghats Province, with the Archaean Napier Complex. The second orogenic phase included a major period of crustal growth through emplacement of the Mawson Charnockite and equivalents. (author). 41 refs., 6 figs., 1 tab

  17. An Archaean Tonalite-Trondhjemite-Granodiorite Association of the Kursk Block (Voronezh Massif): Composition, Age, and Correlation with the Ukrainian Shield

    Science.gov (United States)

    Savko, K. A.; Samsonov, A. V.; Larionov, A. N.; Korish, E. Kh.; Bazikov, N. S.

    2018-01-01

    Framing of the Archaean greenstone belts of the Kursk Block (KB) of the East Sarmatia preserves rocks of the TTG association: those do not form massifs with distinct boundaries, but occur as fields gradually transiting into gneisses and migmatites. According to Sm-Nd isotope-geochemical data, the TTG are characterized by positive values of ɛNd(2960) = +0.3…+1.6 and protolith model ages of T Nd( DM) = 3100-3200 Ma. Magmatic protoliths of the Kursk Block TTG were formed about 2960 Ma by melting from a juvenile basite source. These age estimates are significantly younger than heterochronous (3.19, 3.13 and 3.07 Ga) TTGs of the Middle Dnieper granite-greenstone terrane. On the other hand, the similarity of ɛNd(T) implies a single source of their protoliths. Consequently, the KB TTGs, apparently, are a result of transformation of an older sial crust preserved within the Middle Dnieper Block.

  18. A cryptic Early Palaeozoic event in the Narcea Antiform? 40Ar/39Ar amphibole data in the Puente de Selce granitoid

    OpenAIRE

    Gutiérrez Alonso, Gabriel; Fernández Suárez, J.; Keppie, J. D.; Ortega Rivera, M. A.; Lee, J. K. W.; Murphy, J. B.

    2005-01-01

    Las edades 40Ar/39Ar obtenidas a partir de anfíboles del granitoide Neoproterozoico de Puente de Selce, localizado en el Antiforme del Narcea junto con la existencia de fábricas de deformación relictas generadas en condiciones de media-alta temperatura en las mismas rocas puede ser interpretada como debida a un evento críptico de edad Paleozoico Inferior fuertemente retrabajado durante la deformación varisca. La naturaleza y la cinemática de este posible evento no pueden precisars...

  19. A Field Trip to the Archaean in Search of Darwin’s Warm Little Pond

    Directory of Open Access Journals (Sweden)

    Bruce Damer

    2016-05-01

    Full Text Available Charles Darwin’s original intuition that life began in a “warm little pond” has for the last three decades been eclipsed by a focus on marine hydrothermal vents as a venue for abiogenesis. However, thermodynamic barriers to polymerization of key molecular building blocks and the difficulty of forming stable membranous compartments in seawater suggest that Darwin’s original insight should be reconsidered. I will introduce the terrestrial origin of life hypothesis, which combines field observations and laboratory results to provide a novel and testable model in which life begins as protocells assembling in inland fresh water hydrothermal fields. Hydrothermal fields are associated with volcanic landmasses resembling Hawaii and Iceland today and could plausibly have existed on similar land masses rising out of Earth’s first oceans. I will report on a field trip to the living and ancient stromatolite fossil localities of Western Australia, which provided key insights into how life may have emerged in Archaean, fluctuating fresh water hydrothermal pools, geological evidence for which has recently been discovered. Laboratory experimentation and fieldwork are providing mounting evidence that such sites have properties that are conducive to polymerization reactions and generation of membrane-bounded protocells. I will build on the previously developed coupled phases scenario, unifying the chemical and geological frameworks and proposing that a hydrogel of stable, communally supported protocells will emerge as a candidate Woese progenote, the distant common ancestor of microbial communities so abundant in the earliest fossil record.

  20. The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archaean rocks.

    Science.gov (United States)

    Rizo, Hanika; Boyet, Maud; Blichert-Toft, Janne; O'Neil, Jonathan; Rosing, Minik T; Paquette, Jean-Louis

    2012-11-01

    The first indisputable evidence for very early differentiation of the silicate Earth came from the extinct (146)Sm-(142)Nd chronometer. (142)Nd excesses measured in 3.7-billion-year (Gyr)-old rocks from Isua (southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean eon (about 4,570-4,000 Gyr ago). As dictated by mass balance, the differentiation event responsible for the formation of the Isua early-depleted reservoir must also have formed a complementary enriched component. However, considerable efforts to find early-enriched mantle components in Isua have so far been unsuccessful. Here we show that the signature of the Hadean enriched reservoir, complementary to the depleted reservoir in Isua, is recorded in 3.4-Gyr-old mafic dykes intruding into the Early Archaean rocks. Five out of seven dykes carry (142)Nd deficits compared to the terrestrial Nd standard, with three samples yielding resolvable deficits down to -10.6 parts per million. The enriched component that we report here could have been a mantle reservoir that differentiated owing to the crystallization of a magma ocean, or could represent a mafic proto-crust that separated from the mantle more than 4.47 Gyr ago. Our results testify to the existence of an enriched component in the Hadean, and may suggest that the southwest Greenland mantle preserved early-formed heterogeneities until at least 3.4 Gyr ago.

  1. Backarc extension, detachments and granitoids in the Aegean, their relations to slab tear and asthenospheric flow

    Science.gov (United States)

    Jolivet, Laurent; Menant, Armel; Rabillard, Aurélien; Arbaret, Laurent; Augier, Romain; Gumiaux, Charles

    2013-04-01

    The Cycladic granitoids (Ikaria, Mykonos, Naxos, Kos, Lavrion, Serifos, Tinos) intruded the Aegean crust during a rather short period (17-10 Ma) compared to the much longer Oligo-Miocene crustal thinning phase (35 Ma to the Present). Their geochemical characteristics show that their sources have changed through time and space, with a progressive decreasing component of continental crust contamination with time and from east to west. They all interacted with large-scale detachments, namely the North Cycladic Detachment System (NCDS) in the north and the West Cycladic Detachment System (WCDS) in the south. In Mykonos, Naxos, Serifos and Ikaria the plutons are also associated with a high-temperature metamorphic dome of Miocene age. Their intrusion period roughly covers the same time window as the fast clockwise rotation of the western Aegean evidenced by paleomagnetic measurements and they are contemporaneous with a surge of alkaline volcanism in the eastern Aegean that can be related to a slab tear imaged below western Anatolia. The continental crust component in the Middle Miocene Cycladic plutons is not found in the early Miocene plutons of the northern Aegean, like in Kavala and Vrondou. They thus probably record a quite sudden thermal event in the Cyclades that led to the partial melting of the extending deep crust. We propose a model involving slab tear starting at ~17 Ma, fast retreat of the slab west of the tear and southwestward influx of hot asthenospheric material below the Aegean crust, leading to melting of the lower crust. Partial melting of the whole lower crust above the hot asthenospheric flow could explain the flat Moho observed below the Cyclades. The close proximity of plutons with the detachments suggests that their ascent toward the upper crust is favoured by the extreme extension at work there. The first granitoids in the region of the tear (Ikaria) are the richest in crustal component and this component decreases while the crust thins more and

  2. A cryptic Early Palaeozoic event in the Nacea Antiform? 40Ar/39Ar amphibole data in the Puente de Selce granitoid

    OpenAIRE

    Gutiérrez Alonso, Gabriel; Fernández Suárez, Javier; Ortega Rivera, M. A.; Lee, J. k. W.; Murphy, J. B.

    2005-01-01

    Las edades 40Ar/39Ar obtenidas a partir de anfíboles del granitoide Neoproterozoico de Puente de Selce, localizado en el Antiforme del Narcea junto con la existencia de fábricas de deformación relictas generadas en condiciones de media-alta temperatura en las mismas rocas puede ser interpretada como debida a un evento críptico de edad Paleozoico Inferior fuertemente retrabajado durante la deformación varisca. La naturaleza y la cinemática de este posible evento no pueden precisarse pero si se...

  3. Forty years of TTG research

    Science.gov (United States)

    Moyen, Jean-François; Martin, Hervé

    2012-09-01

    TTGs (tonalite-trondhjemite-granodiorite) are one of the archetypical lithologies of Archaean cratons. Since their original description in the 1970s, they have been the subject of many studies and discussions relating to Archaean geology. In this paper, we review the ideas, concepts and arguments brought forward in these 40 years, and try to address some open questions — both old and new. The late 1960s and the 1970s mark the appearance of "grey gneisses" (TTG) in the scientific literature. During this period, most work was focused on the identification and description of this suite, and the recognition that it is a typical Archaean lithology. TTGs were already recognised as generated by melting of mafic rocks. This was corroborated during the next decade, when detailed geochemical TTG studies allowed us to constrain their petrogenesis (melting of garnet-bearing metamafic rocks), and to conclude that they must have been generated by Archaean geodynamic processes distinct from their modern counterparts. However, the geodynamic debate raged for the following 30 years, as many distinct tectonic scenarios can be imagined, all resulting in the melting of mafic rocks in the garnet stability field. The 1990s were dominated by experimental petrology work. A wealth of independent studies demonstrated that melting of amphibolites as well as of mafic eclogites can give rise to TTG liquids; whether amphibolitic or eclogitic conditions are more likely is still an ongoing debate. From 1990s onwards, one of the key questions became the comparison with modern adakites. As originally defined these arc lavas are reasonably close equivalents to Archaean TTGs. Pending issues largely revolve around definitions, as the name TTG has now been applied to most Archaean plutonic rocks, whether sodic or potassic, irrespective of their HREE contents. This leads to a large range of petrogenetic and tectonic scenarios; a fair number of which may well have operated concurrently, but are

  4. Textures, trace element compositions, and U-Pb ages of titanite from the Mangling granitoid pluton, East Qinling Orogen: Implications for magma mixing and destruction of the North China Craton

    Science.gov (United States)

    Hu, Hao; Li, Jian-Wei; McFarlane, Christopher R. M.; Luo, Yan; McCarron, Travis

    2017-07-01

    /Ce ratios compared to those from the monzogranite (type 2 and type 4). These compositional differences suggest that titanite grains from the MMEs and the host monzogranite crystallized from different magmas. Type 3 titanite contains abundant Fe-Ti oxide inclusions and is characterized by dissolution and reprecipitation textures; the composition of its core and rims are comparable to those of type 1 and type 4 titanites, respectively. The compositional variation between the core and rims of the type 3 titanite grains implies that they were re-equilibrated with high temperature mafic magma and then continued to crystallize within the granitic magmas with low fO2. The textural, geochronological, and geochemical data of titanite grains can be best explained in term of mixing of mafic and felsic magmas. We conclude that both the fine-grained MMEs and the host monzogranite are hybrid products of mafic and felsic end-member magmas. When combined with other geological and geochronological data in the North China Craton, our results suggest that the widespread late Jurassic to early Cretaceous granitoid intrusions were generated in an extensional setting related to craton destruction.

  5. Uranium in accessory sphene from granitoids and its behaviour during mineral's alteration (Muzbekskij pluton at Mogol-Tau, Central Asia)

    International Nuclear Information System (INIS)

    Simonova, L.I.; Maksimova, I.G.; Nad'yarnykh, V.G.; Voronikhin, V.A.

    1982-01-01

    Uranium behaviour in accessory spbene and products of its alteration at different stages of granitoid transformation with characteristic association of zirconium-apatite-sphene and magnetite of accessory minerals, is shown. The products of sphene alteration (due to propylitization of granatoids the sphene is replaced by leucoxene) are determined by MS-46 electron probe microanalyzer and MA-1 lazer microanalyzer. Uranium distribution in leucoxene is studied by the method of fragmentary radiography. Leucoxene pseudomorphoses at a high oxygen potential are capable of giving into solution Uranium previously sorbed by leucoxene. This fact should be taken into account when determining source of metal of hydrogenous deposits

  6. 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

  7. Geological, geochemical and isotopic characteristics of the Archaean Kaap Valley pluton, Barberton mountain land, South Africa

    International Nuclear Information System (INIS)

    Robb, L.J.; Barton, J.M. Jr.; Kable, E.J.D.; Wallace, R.C.

    1984-01-01

    The Kaap Valley pluton consists predominantly of a homogeneous weakly foliated, hornblende-bearing tonalite. It is among the oldest granitoid bodies yet recognized in the environs of the Barberton greenstone belt, yielding 207 Pb/ 206 Pb mineral ages of about 3300 Ma and a Rb-Sr whole rock isochron age of about 3500 Ma. The Kaap Valley pluton is distinctive in many respects. Whereas all other gneiss plutons in the area are characterized by a trondhjemitic bulk composition with mafic mineralogies dominated by biotite, the Kaap Valley pluton is tonalitic in bulk composition with hornblende (plus minus minor biotite) as its major mafic phase. In this paper, the results of a detailed geological, geochemical and Pb-isotopic study of the Kaap Valley pluton are presented. Questions relating to the origin of the body are considered, with an emphasis on the formation of a tonalitic magma which is more mafic than those typically encountered in the region. Although exposure does not permit a detailed structural study of the gneiss pluton consideration is given to its mode of emplacement

  8. Refining Raindrop Paleobarometry: A Satus Report

    Science.gov (United States)

    Zimmerman, J. K.; Som, S. M.

    2016-12-01

    In the late Archaean eon, a sun that was approximately 20% dimmer than today's was still able to warm the Earth to the point where there was liquid water. This is known as the `Faint Young Sun' paradox. Explanations of this paradox include a denser atmosphere rich in nitrogen1 or higher greenhouse gas concentrations. Recent work has suggested that the partial pressure of nitrogen in the late Archean was less than modern values, up to a maximum of 0.5 bar 2.7 billion years ago2. In the current work, we have compiled several global datasets on modern raindrop size and rainfall rate. Together with existing scaling on how raindrop size affects the size of resultant craters3, we use the full distribution of fossilized raindrop craters found in the Ventersdorp Supergroup, South Africa to draw conclusions about the difference in terminal velocity through the Archaean atmosphere as compared to today, in addition to inferences on rainfall rate that formed the Ventersdorp imprints. The calculated value of the terminal velocity places bounds on the range of possible densities of the Archaean atmosphere during Ventersdorp deposition. 1 Goldblatt, C., et al. "Nitrogen-enhanced greenhouse warming on early Earth." Nature Geoscience 2 (2009): 891-896. 2 Som, S., et al. "Earth's air pressure 2.7 billion years ago constrained to less than half of modern levels." Nature Geoscience (2016). 3 Som, S., et al. "Air density 2.7 billion years ago limited to less than twice modern levels by fossil raindrop imprints." Nature 484.7394 (2012): 359-362.

  9. Metallogenetic systems associated with granitoid magmatism in the Amazonian Craton: An overview of the present level of understanding and exploration significance

    Science.gov (United States)

    Bettencourt, Jorge Silva; Juliani, Caetano; Xavier, Roberto P.; Monteiro, Lena V. S.; Bastos Neto, Artur C.; Klein, Evandro L.; Assis, Rafael R.; Leite, Washington Barbosa, Jr.; Moreto, Carolina P. N.; Fernandes, Carlos Marcello Dias; Pereira, Vitor Paulo

    2016-07-01

    The Amazonian Craton hosts world-class metallogenic provinces with a wide range of styles of primary precious, rare, base metal, and placer deposits. This paper provides a synthesis of the geological database with regard to granitoid magmatic suites, spatio temporal distribution, tectonic settings, and the nature of selected mineral deposits. The Archean Carajás Mineral Province comprises greenstone belts (3.04-2.97 Ga), metavolcanic-sedimentary units (2.76-2.74 Ga), granitoids (3.07-2.84 Ga) formed in a magmatic arc and syn-collisional setting, post-orogenic A2-type granites as well as gabbros (ca. 2.74 Ga), and anorogenic granites (1.88 Ga). Archean iron oxide-Cu-Au (IOCG) deposits were synchronous or later than bimodal magmatism (2.74-2.70 Ga). Paleoproterozoic IOCG deposits, emplaced at shallow-crustal levels, are enriched with Nb-Y-Sn-Be-U. The latter, as well as Sn-W and Au-EGP deposits are coeval with ca. 1.88 Ga A2-type granites. The Tapajós Mineral Province includes a low-grade meta-volcano-sedimentary sequence (2.01 Ga), tonalites to granites (2.0-1.87 Ga), two calc-alkaline volcanic sequences (2.0-1.95 Ga to 1.89-1.87 Ga) and A-type rhyolites and granites (1.88 Ga). The calc-alkaline volcanic rocks host epithermal Au and base metal mineralization, whereas Cu-Au and Cu-Mo ± Au porphyry-type mineralization is associated with sub-volcanic felsic rocks, formed in two continental magmatic arcs related to an accretionary event, resulting from an Andean-type northwards subduction. The Alta Floresta Gold Province consists of Paleoproterozoic plutono-volcanic sequences (1.98-1.75 Ga), generated in ocean-ocean orogenies. Disseminated and vein-type Au ± Cu and Au + base metal deposits are hosted by calc-alkaline I-type granitic intrusions (1.98 Ga, 1.90 Ga, and 1.87 Ga) and quartz-feldspar porphyries (ca. 1.77 Ga). Timing of the gold deposits has been constrained between 1.78 Ga and 1.77 Ga and linked to post-collisional Juruena arc felsic magmatism (e.g., Col

  10. Two-phase southward subduction of the Mongol-Okhotsk oceanic plate constrained by Permian-Jurassic granitoids in the Erguna and Xing'an massifs (NE China)

    Science.gov (United States)

    Liu, Huichuan; Li, Yinglei; He, Hongyun; Huangfu, Pengpeng; Liu, Yongzheng

    2018-04-01

    Geodynamics of the Mongol-Okhotsk oceanic plate southward subduction are still pending problems. This paper presents new zircon LA-ICP-MS U-Pb age and whole-rock geochemical data for the middle Permian to Middle Jurassic granitoids in the western Erguna and central Xing'an massifs. 267-264 Ma, 241 Ma and 173 Ma I-type granites, and 216 Ma A-type granites were identified in the Erguna and Xing'an massifs (NE China). The I-type granites were produced by partial melting of the lower mafic crust. The 216 Ma A-type granites were derived from partial melting of crustal materials with tonalitic to granodioritic compositions. The 267-264 Ma and 241 Ma I-type granites were generated in an Andean-type arc setting, wheras the 216 Ma A-type and 173 Ma granites were formed in supra subduction extensional setting. We summarized previous age data of the middle Permian to Middle Jurassic magmtaic rocks in the Erguna and Xing'an Massifs and identified two isolated phases of magmatic activity including the ca. 267-225 Ma and ca. 215-165 Ma periods, with a significant magmatic gap at ca. 225-215 Ma. These middle Permian to Middle Jurassic magmatic rocks are closely related to the southward subduction of the Mongol-Okhotsk ocean. A two-stage tectonic evolutionary model was proposed to account for these geological observations in the Erguna and Xing'an massifs, involving Permian to Middle Triassic continuous southward subduction of the Mongol-Okhotsk oceanic plate and Late Triassic to Jurassic slab-rollback and supra subduction extension.

  11. The Kovdor-2015 experiment: study of the parameters of a conductive layer of dilatancy-diffusion nature (DD Layer) in the Archaean crystalline basement of the Baltic Shield

    Science.gov (United States)

    Zhamaletdinov, A. A.; Velikhov, E. P.; Shevtsov, A. N.; Kolobov, V. V.; Kolesnikov, V. E.; Skorokhodov, A. A.; Korotkova, T. G.; Ivonin, V. V.; Ryazantsev, P. A.; Birulya, M. A.

    2017-06-01

    This paper addresses the Kovdor-2015 Experiment involving frequency electromagnetic soundings of the Archaean basement of the Earth's crust in the southwestern part of the Kola Peninsula. Eleven soundings were carried out using two transmitting arrangements, 85 km apart. Each arrangement consisted of two mutually orthogonal grounded electric dipoles of 1.5 km long. The distances between the source and the receiver were 25 and 50 km. Interpretation of the results took into account the influence of displacement currents and static distortions. It is found that there is an intermediate conductive layer of the dilatancy-diffusion nature (DD layer) with a longitudinal conductivity of about one siemens at depths ranging from 1.5-2 to 5-7 km. The results are interpreted in the terms of geodynamics.

  12. 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.

  13. Using apatite to discriminate synchronous ore-associated and barren granitoid rocks: A case study from the Edong metallogenic district, South China

    Science.gov (United States)

    Duan, Deng-Fei; Jiang, Shao-Yong

    2018-06-01

    In order to find criteria to discriminate the synchronous ore-associated and barren granitoid rocks, we have determined apatite chemistry associated with ore-associated (Cu-Au) and barren granitoid rocks in the Edong district of the Middle and Lower Yangtze River metallogenic belt, South China. Both rock types give zircon U-Pb ages between 135.0 and 138.7 Ma. Apatite has a higher volatile and Li content (Cl: 0.19-0.57 wt%, average 0.35 wt%, SO3: 0.08-0.71 wt%, average 0.32 wt%, Li: 0.49-7.99 ppm, average 3.23 ppm) in ore-associated rocks than those in barren rocks (Cl: 0.09-0.31 wt%, average 0.16 wt%, SO3: 0.06-0.28 wt%, average 0.16 wt%, Li: 0.15-0.89 ppm, average 0.36 ppm). Apatite (La/Yb)N ratios and Eu/Eu* values are relatively high and show wider variation in ore-associated rocks than those in barren rocks. Apatite (La/Sm)N and (Yb/Sm)N show positive correlation in ore-associated rocks but negative in barren rocks. The higher volatile content occurs in ore-associated magma, favoring Cu-Au transportation and deposition. Furthermore, amphibole fractional crystallization in ore-associated magma further enriched the ore elements in the residual melt. Barren rocks may have undergone fluid exsolution before emplacement, which makes it barren in Cl, S and ore elements (Cu, S). These signatures emphases the significance of volatile and magma evolution in mineralization and indicate that analyses of magmatic apatite can serve to distinguish ore-associated from barren intrusions.

  14. Rifting an Archaean Craton: Insights from Seismic Anisotropy Patterns in E. Africa

    Science.gov (United States)

    Ebinger, C. J.; Tiberi, C.; Currie, C. A.; van Wijk, J.; Albaric, J.

    2016-12-01

    Few places worldwide offer opportunities to study active deformation of deeply-keeled cratonic lithosphere. The magma-rich Eastern rift transects the eastern edge of the Archaean Tanzania craton in northeastern Tanzania, which has been affected by a large-scale mantle upwelling. Abundant xenolith locales offer constraints on mantle age, composition, and physical properties. Our aim is to evaluate models for magmatic fluid-alteration (metasomatism) and deformation of mantle lithosphere along the edge of cratons by considering spatial variations in the direction and magnitude of seismic anisotropy, which is strongly influenced by mantle flow patterns along lithosphere-asthenosphere topography, fluid-filled cracks (e.g., dikes), and pre-existing mantle lithosphere strain fabrics. Waveforms of teleseismic earthquakes (SKS, SKKS) recorded on the 39-station CRAFTI-CoLiBREA broadband array in southern Kenya and northern Tanzania are used to determine the azimuth and amount of shear-wave splitting accrued as seismic waves pass through the uppermost mantle and lithosphere at the craton edge. Lower crustal earthquakes enable evaluation of seismic anisotropy throughout the crust along the rift flanks and beneath the heavily intruded Magadi and Natron basins, and the weakly intruded Manyara basin. Our results and those of earlier studies show a consistent N50E splitting direction within the craton, with delay times of ca. 1.5 s, and similar direction east of the rift in thinner Pan-African lithosphere. Stations within the rift zone are rotated to a N15-35E splitting, with the largest delay times of 2.5 s at the margin of the heavily intruded Magadi basin. The short length scale of variations and rift-parallel splitting directions are similar to patterns in the Main Ethiopian rift attributed to melt-filled cracks or oriented pockets rising from the base of the lithosphere. The widespread evidence for mantle metasomatism and magma intrusion to mid-crustal levels suggests that

  15. Geochronology Intermediary Laboratory implantation at the Rio Grande do Norte Federal University: the dating of the Serrinha Granitoid (RN) and the correlate Brasiliana extensional deformation

    International Nuclear Information System (INIS)

    Macedo, Maria Helena F.; Sa, Emanuel F. Jardim de; Souza, Zorano S.; Mendes, Franklin S.; Ramalho, Karlos A.C.

    1997-01-01

    The article describes the activities developed by the Geochronology Intermediary Laboratory at the Federal University of the Rio Grande do Norte, a Brazilian university, where there were the preoccupation of establishing strategies for a geochronological development. It relates the Rubidium-Strontium (Rb/Sr) and Samarium-Neodymium (Sm/Nd) methods, describing the analysis realized in these methodologies. Afterward, it presents the geological and petrographic situation of the Granitoide de Serrinha, located at Rio Grande do Norte State, Brazil and its geochronological data

  16. Cuddapah basin and its environs as first-order uranium target in the Proterozoics of India

    International Nuclear Information System (INIS)

    Sharma, Mithilesh; Rai, A.K.; Nagabhushana, J.C.; Vasudeva Rao, M.; Sinha, R.M.

    1995-01-01

    In peninsular India the middle Proterozoic intracratonic Cuddapah basin and its environs possess good geological favorability for several types of uranium deposits. Investigations so far have revealed the strata bound carbonate-hosted uranium mineralization in the Vempalle dolomitic limestone (e.g. Tummallapalle) and in the Pulivendla quartzite, confined to the lower part of the Cuddapah supergroup, and the structurally controlled uranium mineralization in the late Archaean/early Proterozoic granitoids and metamorphics along eastern (e.g. Kasturigattu), south-western (e.g. Sanipaya and T-Sanipaya and T-Sundapalle), and northern margins (e.g. Lambapur-Yellapur) of the Cuddapah basin. Based on the present level of work within the Cuddapah Basin and its environs, the following favourable locales and prospecting techniques have been suggested to identify the unconformity/vein-type high grade uranium deposits. (i) Detailed geological examination of the contact of basement with mid-Proterozoic Gulcheru/Nagari quartzite for locating unconformity-type uranium mineralisation. (ii) Extensive ground radiometric survey along the unconformity between basement granite and outliers of Srisailam formation, Banganpalle formation, Cumbum/Pullampet formation and Bairenkonda formation along northern and eastern margins of Cuddapah basin. (iii) Examination of the contact zone of the igneous intrusives (syenite and granite) into the Cumbum formation of central and northeastern parts of the basin e.g. Chelima - Giddalur area. (iv) Geophysical survey like resistivity (viz. SP, IP, TEM) to (a) delineate the concealed sulphide-rich zones along the prominent structures of the basinal margins and (b) study the possible existence under cover of quartzite and their subsurface behaviour for the fracture zones identified in the T. Sundapalle-Sanipaya, Pincha, Maddireddigaripalle, Chakrayapeta and Vepamanipeta areas. (author). 22 refs., 1 fig., 3 tabs

  17. The 226Ra isotope activities in ground water samples drawn of two wells from the Meridional Pluton, Morungaba Granitoids, eastern Sao Paulo State; Atividades do 226Ra em aguas subterraneas extraidas de dois pocos localizados no pluton meridional, granitoides de Morungaba, SP

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, Fabio de Oliveira; Silva Junior, Mario Goncalves da; Bertolla, Luciana; Ribeiro, Fernando Brenha [Sao Paulo Univ., SP (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas. Dept. de Geofisica]. E-mail: brenha@iag.usp.br

    2005-07-01

    The 226Ra activities, both in solution and associated with suspended solids, were measured in ground water samples drawn from two wells drilled in a fractured granitic aquifer from the Meridional Pluton, Morungaba Granitoids, eastern Sao Paulo State. The 226Ra isotope activities were measured in a sequence of samples collected about one month apart between March, 2003 and April 2004. The 226Ra activities were measured by radon gas emanometry. The mean dissolved 226Ra activity concentration activities observed in the two wells were (44.9 {+-} 7.1) mBq/L and (51.6 {+-} 8.8) mBq/L. The 226Ra activity of the suspend solids in a liter of these waters varied between (0,6 {+-} 0,1) mBq and (13 {+-} 1) mBq, respectively. (author)

  18. Petrology and U-PB geochronology of the Robertson River Igneous Suite, Blue Ridge province, Virginia - Evidence for multistage magmatism associated witn an early episode of Laurentian rifting

    Science.gov (United States)

    Tollo, R.P.; Aleinikoff, J.N.

    1996-01-01

    The Late Neoproterozoic (735-702 Ma) Robertson River Igneous Suite includes at least eight plutons ranging in composition from syenogranite to alkali feldspar granite to alkali feldspar syenite. These plutons intruded Mesoproterozoic (1.2-1.0 Ga) gneissic basement of the Blue Ridge anticlinorium in northern and central Virginia during an early episode of Laurentian rifting. Robertson River plutons range in composition from metaluminous to peralkaline and, relative to other granite types, exhibit compositional characteristics of A-type granitoids including (1) marked enrichment in Nb, Zr, Y, REE (except Eu), and Ga, (2) high Ga/Al and FeO(total)/MgO, and (3) depletion of Ba and Sr. High Ga/Al ratios are particularly diagnostic of the suite and serve as an effective discriminant between originally metaluminous and peralkaline bulk compositions, providing a useful proxy for widely used indicators based on major elements that are prone to remobilization. U-Pb isotopic analyses of zircons indicate that the suite was emplaced in two pulses, occurring at 735 to 722 and 706 to 702 Ma. Metaluminous magmas were emplaced during both pulses, formed most of the main batholith, and fractionated as independent, time-correlative groups. Peralkaline magmas were emplaced only during the final pulse, formed a volcanic center that erupted unknown quantities of rhyolite, and experienced a style of fractionation similar to the metaluminous types. Differences in Ce/Nb, Y/Nb, and Yb/Ta ratios suggest that the metaluminous and peralkaline magmas were derived from different sources. The Robertson River Igneous Suite is part of a regional group of Late Neoproterozoic (760-700 Ma) plutons including at least 20 other A-type granitoid bodies exposed throughout the Laurentian terrane of Virginia and northwestern North Carolina. Like the Robertson River, most of the other granitoids are metaluminous in composition, typically form multi-intrusive, elongate plutons, and are not geographically

  19. A tale of 10 plutons - Revisited: Age of granitic rocks in the White Mountains, California and Nevada

    Science.gov (United States)

    McKee, E.H.; Conrad, J.E.

    1996-01-01

    40Ar/39Ar incremental heating analysis and conventional K-Ar age determinations on plutonic rocks of the White Mountains define two stages of magmatic emplacement: Late Cretaceous, between ca. 90 Ma and 75 Ma, and Middle-Late Jurassic, between ca. 180 and 140 Ma. The Jurassic stage can be divided into two substages, 180-165 Ma and 150-140 Ma. Thermal effects of the younger plutons on the older granitoids partially to completely reset ages, making it difficult to determine the age of emplacement and cooling of several of the plutons even by 40Ar/39Ar incremental heating analyses. New data together with published ages and regional geochronological synthesis of the Sierra Nevada batholith indicate that regions within the batholith have coherent periods or episodes of magmatic activity. In the White Mountains and Sierra Nevada directly to the west there was little or no activity in Early Jurassic and Early Cretaceous time; magmatism took place during relatively short intervals of 15 m.y. or less in the Middle and Late Jurassic and Late Cretaceous periods. The new K-Ar and 40Ar/39Ar analyses of granitoids from the White Mountains help, but do not completely clarify the complex history of emplacement, cooling, and reheating of the batholith.

  20. Early Archaean collapse basins, a habitat for early bacterial life.

    Science.gov (United States)

    Nijman, W.

    For a better definition of the sedimentary environment in which early life may have flourished during the early Archaean, understanding of the basin geometry in terms of shape, depth, and fill is a prerequisite. The basin fill is the easiest to approach, namely from the well exposed, low-grade metamorphic 3.4 - 3.5 Ga rock successions in the greenstone belts of the east Pilbara (Coppin Gap Greenstone Belt and North Pole Dome) in West Australia and of the Barberton Greenstone Belt (Buck Ridge volcano-sedimentary complex) in South Africa. They consist of mafic to ultramafic volcanic rocks, largely pillow basalts, with distinct intercalations of intermediate to felsic intrusive and volcanic rocks and of silicious sediments. The, partly volcaniclastic, silicious sediments of the Buck Ridge and North Pole volcano-sedimentary complexes form a regressive-transgressive sequence. They were deposited close to base level, and experienced occasional emersion. Both North Pole Chert and the chert of the Kittys Gap volcano-sedimentary complex in the Coppin Gap Greenstone Belt preserve the flat-and-channel architecture of a shallow tidal environment. Thickness and facies distribution appear to be genetically linked to systems, i.e. arrays, of syn-depositionally active, extensional faults. Structures at the rear, front and bottoms of these fault arrays, and the fault vergence from the basin margin towards the centre characterize the basins as due to surficial crustal collapse. Observations in the Pilbara craton point to a non-linear plan view and persistence for the basin-defining fault patterns over up to 50 Ma, during which several of these fault arrays became superposed. The faults linked high-crustal level felsic intrusions within the overall mafic rock suite via porphyry pipes, black chert veins and inferred hydrothermal circulations with the overlying felsic lavas, and more importantly, with the cherty sediments. Where such veins surfaced, high-energy breccias, and in the

  1. Selection for Protein Kinetic Stability Connects Denaturation Temperatures to Organismal Temperatures and Provides Clues to Archaean Life.

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    M Luisa Romero-Romero

    Full Text Available The relationship between the denaturation temperatures of proteins (Tm values and the living temperatures of their host organisms (environmental temperatures: TENV values is poorly understood. Since different proteins in the same organism may show widely different Tm's, no simple universal relationship between Tm and TENV should hold, other than Tm≥TENV. Yet, when analyzing a set of homologous proteins from different hosts, Tm's are oftentimes found to correlate with TENV's but this correlation is shifted upward on the Tm axis. Supporting this trend, we recently reported Tm's for resurrected Precambrian thioredoxins that mirror a proposed environmental cooling over long geological time, while remaining a shocking ~50°C above the proposed ancestral ocean temperatures. Here, we show that natural selection for protein kinetic stability (denaturation rate can produce a Tm↔TENV correlation with a large upward shift in Tm. A model for protein stability evolution suggests a link between the Tm shift and the in vivo lifetime of a protein and, more specifically, allows us to estimate ancestral environmental temperatures from experimental denaturation rates for resurrected Precambrian thioredoxins. The TENV values thus obtained match the proposed ancestral ocean cooling, support comparatively high Archaean temperatures, and are consistent with a recent proposal for the environmental temperature (above 75°C that hosted the last universal common ancestor. More generally, this work provides a framework for understanding how features of protein stability reflect the environmental temperatures of the host organisms.

  2. Anomalous uranium concentration in Archaean basement Shear at Dhani Basri and its significance on Southern Margin of Alwar sub-basin, Rajasthan

    International Nuclear Information System (INIS)

    Panigrahi, B.; Shaji, T.S.; Sharma, G.S.; Yadav, O.P.; Nanda, L.K.

    2008-01-01

    Prominent shear zones cutting through the basement and cover rocks of Delhi Supergroup have been recognized in Dhani Basri - Ramewala sector of Dausa district, Rajasthan. One such shear zone traversing the granite gneiss (Archaean basement) has been observed at Dhani Basri. The sheared rock is exposed in the form of a small hump and gives appearance of quartzite due to intense silicification. Grab samples collected from the shear zone rock analysed upto 93 ppm U 3 O 8 and <10 ppm ThO 2 , which is anomalous in comparison to unsheared rock which analysed 51 ppm eU 3 O 8 , upto 5 ppm U 3 O 8 and 80 ppm ThO 2 . Gamma-ray logging of boreholes drilled by GSI across this shear zone indicated uranium mineralization of the order of 0.030% eU 3 O 8 x 5.40 m and the primary radioactive mineral has been identified as uraninite. The extension of Dhani Basri shear zone inside the cover rocks of Meso-Proterozoic Delhi Supergroup of rocks of Alwar sub-basin is of paramount importance in locating unconformity related as well as hydrothermal vein type uranium mineralization. (author)

  3. Emergence of silicic continents as the lower crust peels off on a hot plate-tectonic Earth

    Science.gov (United States)

    Chowdhury, Priyadarshi; Gerya, Taras; Chakraborty, Sumit

    2017-09-01

    The rock record and geochemical evidence indicate that continental recycling has been occurring since the early history of the Earth. The stabilization of felsic continents in place of Earth's early mafic crust about 3.0 to 2.0 billion years ago, perhaps due to the initiation of plate tectonics, implies widespread destruction of mafic crust during this time interval. However, the physical mechanisms of such intense recycling on a hotter, (late) Archaean and presumably plate-tectonic Earth remain largely unknown. Here we use thermomechanical modelling to show that extensive recycling via lower crustal peeling-off (delamination but not eclogitic dripping) during continent-continent convergence was near ubiquitous during the late Archaean to early Proterozoic. We propose that such destruction of the early mafic crust, together with felsic magmatism, may have caused both the emergence of silicic continents and their subsequent isostatic rise, possibly above the sea level. Such changes in the continental character have been proposed to influence the Great Oxidation Event and, therefore, peeling-off plate tectonics could be the geodynamic trigger for this event. A transition to the slab break-off controlled syn-orogenic recycling occurred as the Earth aged and cooled, leading to reduced recycling and enhanced preservation of the continental crust of present-day composition.

  4. The study of the mineralogy and rare earth elements behavior in the hydrothermal alteration zones of the Astaneh granitoid massif (SW Arak, Markazi province, Iran)

    International Nuclear Information System (INIS)

    Esmaeily, D.; Afshooni, S. Z.; Valizadeh, M. V.

    2009-01-01

    The Astaneh granitoid massif is located about 40 km to Arak city, central Iran, is a part of Sanandaj-Sirjan structural zone. These intrusive rocks which are mainly composed of gronodioritic rocks, widely affected under hydrothermal alteration. The alteration zones, on the basis of field studies and mineralogy as well as the study of the REE behavior, are investigated in this paper. Eight alteration zones including phyllic (sericitic) with quartz, sericite and pyrite; chloritic with quartz, sericite and chlorite; propylitic with chlorite, epidot, calcite and albite; argillic with clay minerals (chlorite and illite); silicic with abundant quartz; albitic with albite, chlorite and quartz; hematitisation with hematite, Fe-carbonates (ankerite and siderite) and tourmalinisation with tourmaline (dravite) are identified. The results demonstrate notable differences in the REE behavior in the different alteration zones. Accordingly, comparison with the fresh rocks, in the phyllic (sericitic) alteration, LREE are enriched, but HREE, except Yb which enriched, unchanged. Also in chloritic alteration zone, LREEs are depleted, but HREEs represent different behaviors. In the argillic and propylitic alteration zones, all REE are depleted, but compared with HREE, the LREE represent more depletion. In the silicic and hematitisation alteration zones, compared with HREE, the LREE are enriched. Finally, in the albitic and tourmalinisation alteration zones all REE are depleted. These features indicate that the behavior of REE in the hydrothermal alteration zones of the Astaneh granitoid rocks is mainly controlled by p H, availability of complexing ions in the fluid as well as the presence of secondary phases as host REE minerals

  5. Petrology and isotope systematics of magma mushes: some porphyritic granitoids of northeastern Brazil

    International Nuclear Information System (INIS)

    McMurry, J.; Long, L.E.; Sial, A.N.

    1987-01-01

    More than 80 coarsely porphyritic granitoid plutons with K-feldspar megacrysts (Itaporanga-type granites) intrude metamorphic rocks of Northeastern Brazil. Textural evidence for filter pressing and flow foliation indicates that these bodies were emplaced as viscous, crystal-laden mushes. A representative Itaporanga-type pluton, the Monte das Gameleiras intrusion, consists of a variety of rock types with SiO 2 ranging from 49.5 to 71.6 weight percent. Chemically and petrographically, this hornblende-bearing pluton has I-type characteristics with some S-type affinities. Whole-rock oxygen isotope data are in keeping with the distribution of δO 18 , for unaltered granitic rocks. Similarly, REE data suggest a single magmatic process, at least for the more felsic rock types, without post-intrusive effects. A 5-point, whole-rock Rb-Sr isochron for the Monte das Gameleiras pluton gives t = 511 ± 26 Ma andan initial, 87 Sr/ 86 Sr = 0.7099 ± 0.0004. This is contrasted with disparate ages calculated from texturally similar bodies such as the Fazenda Nova pluton, for which a 5-point whole-rock isochron gives t = 630 ± 24 Ma with initial 87 Sr/ 86 Sr = 0.7065 ± 0.0005, and the type locality Itaporanga pluton, for which a 6-point isochron gives t= 625 ± 22 Ma. (author) [pt

  6. The Pedregal granite (Portugal: petrographic and geochemical characterization of a peculiar granitoid

    Directory of Open Access Journals (Sweden)

    Ferreira, J. A.

    2014-12-01

    Full Text Available The Pedregal granite outcrops in the Central Iberian Zone, northern Portugal, in the eastern border of a synorogenic variscan granite-migmatite complex sub-concordant with the regional metamorphic structures. It is a granitoid (ca. 3 km2 with an elongated NW-SE shape intruded in staurolite-micaschist and banded gneiss-migmatite rocks, with local igneous breccias in the contact. The country rocks belong to a metapelitic and metasammitic sequence of Edicarian-Cambrian age, known as the “Complexo Xisto-Grauváquico” (CXG which shows a main regional foliation with a NW-SE to NNW-SSE direction. The Pedregal granite is peraluminous (its A/CNK parameter ranges from 1.18 to 1.62, with a magnesian and alkali to alkali-calcic signature. The peculiar features of the granite are high contents of Zr (389 to 435 ppm and a LREE flat pattern, which are uncommon characteristics for granitic rocks, as well as the corroded shape of the biotite, and the large amount of secondary muscovite. These peculiar features distinguish it from the adjacent synorogenic granites. The field, petrographical and chemical features of the Pedregal granite are in accordance with a second phase of partial melting of a residuum, depleted by melt segregation during a first melting episode with the involvement of peritectic garnet and abundant residual biotite with LREE- and Zr-bearing accessory minerals. Besides, the intrusive character of the granite, and the presence of metasedimentary xenoliths point out to a secondary diatexite.El granito de Pedregal aflora en la Zona Centro-Ibérica, en el norte de Portugal, en el borde oriental de un complejo granito-migmatítico sinorogénico varisco, subconcordante con las estructuras metamórficas regionales. Es un granitoide (ca. 3 km2 de forma elongada NW-SE, que intruye en micaesquistos estaurolíticos y en rocas gneissico- migmatíticas bandeadas, con brechas ígneas locales en el contacto. Las rocas encajantes pertenecen a una

  7. Late Archaean tectonics and sedimentation of the South Rand area, Witwatersrand basin

    International Nuclear Information System (INIS)

    Spencer, R.M.

    1992-01-01

    The sedimentary fill of the southern part of the northeastern Witwatersrand basin consists of four unconformity bounded mega sequences. Early sedimentation took place in a stable, epi continental basin characterized by amphidromic flow. Gradual transgression to distal shelf facies was followed by gradual emergence to intertidal facies. Unconformity Bounded Mega sequence 2 shows that the basin underwent regression, in which discrete uplifts provided a source of granite-greenstone-derived sediment to associated braid plain aprons. Thereafter the basin subsided into a system almost identical to that in which Unconformity Bounded Mega sequence 1 developed. Unconformity Bounded Mega sequence 3 was deposited in a similar marine environment, on an angular unconformity in the east. Regional uplift occurred to the northwest of the basin. Unconformity Bounded Mega sequence 4 records progradation of a perennial braid plain controlled by uplift in the east, and by the minor influence of an uplift to the northwest. Rapid transgression resulted in submarine fan facies development, after which rapid emergence was controlled by uplift in the east, and to a lesser extent, the north. The braid plain was the site of extrusion of komatiitic lavas of the lower Ventersdorp Supergroup and was subsequently smothered by the sustained outpouring of a two kilometer-thick pile of basalts. Crustal extension climaxed after extrusion of felsic volcanics. This extension is antithetic to regional down-to-the-northwest, lower Ventersdorp Supergroup rifting. The last conspicuous phase of Precambrian tectonics is the superposition of a right-lateral wrench system on the early structural framework, after deposition of the lower Transvaal Sequence. Analysis of the samples was carried out by X-ray fluorescence spectrometry. 243 refs., 119 figs., 8 tabs

  8. Pseudotachylitic breccia from the Dhala impact structure, north-central India: Texture, mineralogy and geochemical characterization

    Science.gov (United States)

    Pati, J. K.; Reimold, W. U.; Greshake, A.; Schmitt, R. T.; Koeberl, C.; Pati, P.; Prakash, K.

    2015-05-01

    Pseudotachylitic breccia (PTB) occurs in a drill core from the crater floor of the 11 km diameter, Proterozoic Dhala impact structure, India. PTBs were intersected in late Archean granitoids between 348.15 m and 502.55 m depth in the MCB-10 drill core from the center of the Dhala structure. The breccias comprise both cataclastic-matrix as well as melt breccias. The presence of microlites and vesicles in the groundmass and a widely observed flow fabric in the PTB support the presence of melt in the groundmass of some samples. Clasts in PTB are derived from the Archean granitoid basement. PTB matrix, the matrix of impact melt breccia also occurring between 256.50 m and 502.55 m depth, and the target granitoids vary in terms of silica, total alkali, magnesium and iron oxide contents. Chondrite-normalized REE patterns of PTB and target granitoids are similar, but the elemental abundances in the PTB are lower. The restricted size of PTB as veins and pods of up to 2.5 cm width, their occurrence at varied depths over a core length of 150 m, the clast population, and the chemical relationships between PTB and their host rocks all suggest the derivation of these breccias locally from the fractured basement granitoids involving in-situ melting. We favor that this took place due to rapid decompression during the collapse and modification stage of impact cratering, with, locally, additional energy input from frictional heating. Locally, amphibolite and dioritic mylonite occur in the host granitoids and their admixture could have contributed to the comparatively more mafic composition of PTB. Alteration of these crater floor rocks could have involved preferential reduction of silica and alkali element abundances, possibly due to impact-induced hydrothermal activity at crater floor level. This process, too, could have resulted in more mafic compositions.

  9. Shear Wave Velocity Structure of Southern African Crust: Evidence for Compositional Heterogeneity within Archaean and Proterozoic Terrains

    Energy Technology Data Exchange (ETDEWEB)

    Kgaswane, E M; Nyblade, A A; Julia, J; Dirks, P H H M; Durrheim, R J; Pasyanos, M E

    2008-11-11

    Crustal structure in southern Africa has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations spanning much of the Precambrian shield of southern Africa. 1-D shear wave velocity profiles obtained from the inversion yield Moho depths that are similar to those reported in previous studies and show considerable variability in the shear wave velocity structure of the lower part of the crust between some terrains. For many of the Archaean and Proterozoic terrains in the shield, S velocities reach 4.0 km/s or higher over a substantial part of the lower crust. However, for most of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain, as well as for the western part of the Tokwe terrain, mean shear wave velocities of {le} 3.9 km/s characterize the lower part of the crust along with slightly ({approx}5 km) thinner crust. These findings indicate that the lower crust across much of the shield has a predominantly mafic composition, except for the southwest portion of the Kaapvaal Craton and western portion of the Zimbabwe Craton, where the lower crust is intermediate-to-felsic in composition. The parts of the Kaapvaal Craton underlain by intermediate-to-felsic lower crust coincide with regions where Ventersdorp rocks have been preserved, and thus we suggest that the intermediate-to-felsic composition of the lower crust and the shallower Moho may have resulted from crustal melting during the Ventersdorp tectonomagmatic event at c. 2.7 Ga and concomitant crustal thinning caused by rifting.

  10. Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

    International Nuclear Information System (INIS)

    Deckart, Katja; Godoy, Estanislao; Bertens, Alfredo; Jerez, Daniela; Saeed, Ayesha

    2010-01-01

    Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were undertaken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32 o and 34 o S. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Meson Alto massif), 10.3±0.2 Ma (La Gloria pluton), 14.9±0.2 Ma/14.9±0.1 Ma (Yerba Loca stock) and 11.2±0.1 Ma/14.7±0.1 Ma (San Francisco Batholith). Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32 o S, slightly younger mineralized porphyries at Rio Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758- 0.512882), plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial εHf-data variation for the younger age group (10-12 Ma; 7.04-9.54) and show a more scattered range for the older one (14-15 Ma; 8.50-15.34); both sets plot between the DM and CHUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Rio Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening across the NE

  11. Characterisation and genesis of the Singhbhum uranium province, India

    International Nuclear Information System (INIS)

    Mahadevan, T.M.

    1988-01-01

    The Singhbhum Uranium province is characterised by the late Archaean predominantly granitic Singhbhum Craton and the associated Proterozoic mobile belts, the boundaries of which are marked by major crustal dislocations. The Singhbhum craton had two-phase evolution during the time range 4000-2900 million years and its stabilisation around 2900 million years was marked by the emplacement of K-rich granitoids and the early crustal enrichment of uranium. Two distinctive types of uranium mineralisation occur in the Province - (i) the early Quartz Pebble Conglomerate (QPC) type and (ii) the later economically most significant shear-controlled hydrothermal type. The QPC type is confined to the cratonic volcano-sedimentary basins, characterised by basal fluvial high-energy deposits, near-continental volcanics and banded iron formations spanning the time band of 2900-2500 million years. The shear controlled hydrothermal mineralisation is predominantly developed in a 200 km-long arcuate zone of intense and deep tectonisation, acid-(?) alkaline-basic magmatism, hydrothermal activity and metallogenesis. This shear zone represents a belt of intense crust-mantle interaction. Uranium mineralisation is polyphasic, polymetallic. The mineralogy is complex and the chemistry of the ores is greatly influenced by the lithology of the host rocks involved in the shear. Part of the shear zone grazing the Dhanjori, predominantly volcanic supra-crustals is richer in U, Cu, Ni, Mo and also contains minor Bi, Au, Ag, Te and Se, while the western trans-Dhanjori sector of the shear zone characterised by schists and quartzites with lesser volcanic component is relatively poorer in these metals. The ore bodies in the trans-Dhanjori sector are more peneconcordant, gradational, stratabound and have spherical variograms, while those in the Dhanjori sector are transgressive, sharp, highly mobilised, vein type with Dewijsian variograms. A synthesis leads to the conclusion that uranium mineralisation is

  12. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil; Petrologia e geocronologia (U/Pb-Sm/Nd) do Granito Passagem, Complexo Granitoide Pensamiento, SW do Craton Amazonico (MT)

    Energy Technology Data Exchange (ETDEWEB)

    Jesus, Gisely Carmo de, E-mail: giselycarmo@hotmail.co [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Programa de Pos-Graduacao em Geociencias; Sousa, Maria Zelia Aguiar de, E-mail: mzaguiar@terra.com.b [Universidade Federal de Mato Grosso(ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Recursos Minerais; Ruiz, Amarildo Salina; Matos, Joao Batista de, E-mail: asruiz@gmail.co, E-mail: jmatos@cpd.ufmt.b [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Geologia Geral

    2010-09-15

    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  13. Semi-brittle flow of granitoid fault rocks in experiments

    Science.gov (United States)

    Pec, Matej; Stünitz, Holger; Heilbronner, Renée.; Drury, Martyn

    2016-03-01

    Field studies and seismic data show that semi-brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so-called frictional-viscous transition. To understand the physical and chemical processes accommodating semi-brittle flow, we have performed an experimental study on synthetic granitoid fault rocks exploring a broad parameter space (temperature, T = 300, 400, 500, and 600°C, confining pressure, Pc ≈ 300, 500, 1000, and 1500 MPa, shear strain rate, γṡ ≈ 10-3, 10-4, 10-5, and 10-6 s-1, to finite shear strains, γ = 0-5). The experiments have been carried out using a granular material with grain size smaller than 200 µm with a little H2O added (0.2 wt %). Only two experiments (performed at the fastest strain rates and lowest temperatures) have failed abruptly right after reaching peak strength (τ ~ 1400 MPa). All other samples reach high shear stresses (τ ~ 570-1600 MPa) then weaken slightly (by Δτ ~ 10-190 MPa) and continue to deform at a more or less steady state stress level. Clear temperature dependence and a weak strain rate dependence of the peak as well as steady state stress levels are observed. In order to express this relationship, the strain rate-stress sensitivity has been fit with a stress exponent, assuming γ˙ ∝ τn and yields high stress exponents (n ≈ 10-140), which decrease with increasing temperature. The microstructures show widespread comminution, strain partitioning, and localization into slip zones. The slip zones contain at first nanocrystalline and partly amorphous material. Later, during continued deformation, fully amorphous material develops in some of the slip zones. Despite the mechanical steady state conditions, the fabrics in the slip zones and outside continue to evolve and do not reach a steady state microstructure below γ = 5. Within the slip zones, the fault rock material progressively transforms from a crystalline solid to an amorphous material. We

  14. Natural radioactivity (226Ra, 232Th and 40K) and assessment of radiological hazards in the Kestanbol granitoid, Turkey.

    Science.gov (United States)

    Canbaz, Buket; Cam, N Füsun; Yaprak, Günseli; Candan, Osman

    2010-09-01

    The surveys of natural gamma-emitting radionuclides in rocks and soils from the Ezine plutonic area were conducted during 2007. Direct dose measurement using a survey meter was carried out simultaneously. The present study, which is part of the survey, analysed the activity concentrations of (238)U, (232)Th and (40)K in granitoid samples from all over the region by HPGe gamma spectrometry. The activity concentrations of (226)Ra ranged from 94 to 637 Bq kg(-1), those of (232)Th ranged from 120 to 601 Bq kg(-1)and those of (40)K ranged from 1074 to 1527 Bq kg(-1) in the analysed rock samples from different parts of the pluton. To evaluate the radiological hazard of the natural radioactivity in the samples, the absorbed dose rate (D), the annual effective dose rate, the radium equivalent activity (Ra(eq)) and the external (H(ex)) hazard index were calculated according to the UNSCEAR 2000 report. The thorium-to-uranium concentration ratios were also estimated.

  15. Crustal basement controls granitoid magmatism, and implications for generation of continental crust in subduction zones: A Sr-Nd-Hf-O isotopic study from the Paleozoic Tongbai orogen, central China

    Science.gov (United States)

    Wang, Hao; Wu, Yuan-Bao; Yang, Jin-Hui; Qin, Zheng-Wei; Duan, Rui-Chun; Zhou, Lian; Yang, Sai-Hong

    2017-06-01

    Ascertaining the petrogenesis of granitoid rocks in subduction zones holds the key for understanding the processes of how continental crust is produced. The synchronous Taoyuan and Huanggang plutons occur in two different geological units of the Paleozoic Tongbai orogen of central China. They provide an optimal opportunity for a study to address the role of the crustal basement in generating voluminous granitoid magmatism in subduction zones. The Taoyuan and Huanggang plutons have identical U-Pb zircon crystallization ages of 440-444 Ma, which are temporally related to northward subduction of the Paleotethyan Ocean. The Taoyuan samples show high SiO2 (73.36-79.16%) and low Al2O3 (12.00-13.45%) contents, Mg numbers (20.6-38.2), and Sr/Y (2.04-10.1) and (La/Yb)N (2.34-7.32) ratios with negative Eu anomalies (Eu/Eu* = 0.33-0.93). They yielded positive εNd(t) (+ 3.0 to + 6.7) and εHf(t) (+ 11.8 to + 13.2) values, elevated initial Sr isotopic ratios (0.7040-0.7057) and relatively low zircon δ18O values of 4.62-5.39‰. These suggest that they were produced through partial melting of hydrothermally altered lower crust of the accreted Erlangping oceanic arc. In contrast, the Huanggang samples exhibit variable whole-rock geochemical and isotopic compositions with SiO2 contents of 57.01-64.42 wt.%, initial Sr isotopic ratios of 0.7065-0.7078, and εNd(t) values of - 5.7 to - 9.4. Additionally, they have high zircon δ18O values of 7.57-8.45‰ and strongly negative zircon εHf(t) values of - 14.4 to - 10.5. They were suggested to have been mainly derived from ancient continental crust of the Kuanping crustal unit with the addition of 20-40% juvenile, mantle-derived material. Accordingly, the granitoids in both oceanic and continental arcs are likely to be mainly derived from intracrustal melting of their crustal basement. It is revealed by the Huanggang pluton that little net continental crust growth occurs in continental arcs, and addition of new volume of continental

  16. Major uranium provinces: Yilgarn block and Gascoyne Province, Western Australia

    International Nuclear Information System (INIS)

    Butt, C.R.M.

    1988-01-01

    The Archaean Yilgarn Block and the adjacent Proterozoic Gascoyne Province, Western Australia, form the basement and source rocks for numerous occurrences of surficial uranium mineralization, the largest being the Yeelirrie deposit (35 million tonnes at 0.15% U 3 O 8 ). The mineralization, almost exclusively in the form of carnotite, has been deposited in the regolith and appears to be less than 1 Ma old, with some deposits still forming. The nature and distribution of the mineralization are controlled by basement and surface geology, geomorphology, hydrology and climate, being restricted to deeply weathered, semi-arid terrain with granitoid source rocks. A few small occurrences in the Gascoyne Province may be pedogenic in origin but the majority, in the north of Yilgarn Block, occur in unrejuvenated palaeodrainage channels now choked by colluvial, alluvial and chemical sediments. These sediments, which are aquifers for the present, predominantly sub-surface, drainage, can exceed 10-15 m. Uranium released from the weathering granitoids has been transported in groundwaters in uranyl carbonate complexes and precipitated as carnotite where, (i) concentrations of uranium and potassium have been elevated by evaporation and, (ii) dissolved vanadium has been oxidized to the 5-valent state. Precipitation is in calcretes and associated sediments in the drainage axes, in 'chemical deltas' where the drainages enter playas and in the playas themselves. This style of mineralization was first recognized in 1969-1970 as the result of investigations into the source of radiometric anomalies delineated by airborne surveys. The majority of discoveries have similarly been by radiometric surveys but hydrogeochemical surveys have promise and may become important in future search for blind mineralization and/or young deposits not in radioactive equilibrium. (author). 61 refs, 6 figs

  17. Petrology and geochemistry of the orbicular granitoid of Caldera, northern Chile. Models and hypotheses on the formation of radial orbicular textures

    Science.gov (United States)

    Díaz-Alvarado, Juan; Rodríguez, Natalia; Rodríguez, Carmen; Fernández, Carlos; Constanzo, Ítalo

    2017-07-01

    The orbicular granitoid of Caldera, located at the northern part of the Chilean Coastal Range, is a spectacular example of radial textures in orbicular structures. The orbicular body crops out as a 375 m2 tabular to lensoidal intrusive sheet emplaced in the Lower Jurassic Relincho pluton. The orbicular structures are 3-7 cm in diameter ellipsoids hosted in a porphyritic matrix. The orbicules are comprised by a Qtz-dioritic core (3-5 cm in diameter) composed by Pl + Hbl + Qtz + Bt ± Kfs with equiaxial textures and a gabbroic shell (2-3 cm in diameter) characterized by feathery and radiate textures with a plagioclase + hornblende paragenesis. The radial shell crystals are rooted and orthogonally disposed in the irregular contact with the core. The radial shell, called here inner shell, is in contact with the granodioritic equiaxial interorbicular matrix through a 2-3 mm wide poikilitic band around the orbicule (outer shell). The outer shell and the matrix surrounding the orbicules are characterized by the presence of large hornblende and biotite oikocrystals that include fine-grained rounded plagioclase and magnetite. The oikocrystals of both the outer shell and the matrix have a circumferential arrangement around the orbicule, i.e. orthogonal to the radial inner shell. The coarse-grained granodioritic interorbicular matrix present pegmatitic domains with large acicular hornblende and K-feldspar megacrysts. This work presents a review of the textural characteristics of the orbicules and a complete new mineral and whole-rock geochemical study of the different parts of the orbicular granitoid, together with thermobarometric and crystallographic data, and theoretical modeling of the crystallization and element partitioning processes. We propose a model for the formation of the orbicular radial textures consisting of several processes that are suggested to occur fast and consecutively: superheating, volatile exsolution, undercooling, geochemical fractionation and

  18. A radiological survey of the Eğrigöz granitoid, Western Anatolia/Turkey.

    Science.gov (United States)

    Canbaz Öztürk, B; Yaprak, G; Çam, N F; Candan, O

    2015-06-01

    A radiological survey of the granitoid areas throughout Western Anatolia was conducted during 2007-14. As a part of this radiological survey, this article presents results obtained from Eğrigöz pluton, which lies in the northeastern region of Western Anatolia. In the investigated area, the activity measurements of the natural gamma-emitting radionuclides ((226)Ra, (232)Th and (40)K) in the granitic rock samples and soils have been carried out by means of the NaI(Tl) gamma-ray spectrometry system. The activity concentrations of the relevant natural radionuclides in the granite samples appeared in the ranges as follows: (226)Ra, 28-95 Bq kg(-1); (232)Th, 50-122 Bq kg(-1) and (40)K, 782-1365 Bq kg(-1), while the typical ranges of the (226)Ra, (232)Th and (40)K activities in the soil samples were found to be 7-184, 11-174 and 149-1622 Bq kg(-1), respectively. Based on the available data, the radiation hazard parameters associated with the surveyed rocks/soils are calculated. The corresponding absorbed dose rates in air from all those radionuclides were always much lower than 200 nGy h(-1) and did not exceed the typical range of worldwide average values noted in the UNSCEAR (2000) report. Furthermore, the data are also used for the mapping of the surface soil activity of natural radionuclides and the corresponding gamma dose rates of the surveyed area. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  19. Uranium distributions in the mineral constituents of granitoid rocks and the associated pegmatites at Wadi Abu Had, north eastern desert, Egypt

    International Nuclear Information System (INIS)

    Nossair, L.M.; Moharem, A.F.; Abdel Warith, A.

    2007-01-01

    Wadi Abu Had area is located at the northern part of the Eastern Desert of Egypt. It covers about 55 km2 of the crystalline basement rocks stretching between latitudes 28o 15'- 28o 25' N and longitudes 32o 25' - 32o 35' E. Abu Had younger granites are fertile (uraniferous) granites as they possess U-contents greater than 11 ppm. Their associated pegmatites show higher U-contents than those of granitoid rocks and hosting secondary uranium minerals. Numerous unzoned and zoned pegmatite pockets are associated with the marginal parts of granodiorite and within younger granites. Zoned pegmatites are the most radioactive ones. They are composed of extremely coarse-grained milky quartz core, intermediate zone of mica and wall zone of feldspars. An alteration zone with secondary uranium minerals (uranophane and beta-uranophane) is found at the contact between quartz core and the intermediate zone.

  20. Age and geochemistry of Neoproterozoic granitoids in the Songnen-Zhangguangcai Range Massif, NE China: Petrogenesis and tectonic implications

    Science.gov (United States)

    Luan, Jin-Peng; Xu, Wen-Liang; Wang, Feng; Wang, Zhi-Wei; Guo, Peng

    2017-10-01

    This study presents new zircon U-Pb ages and geochemical data for Neoproterozoic granitoids in the Songnen-Zhangguangcai Range Massif (SZRM) of NE China. This dataset provides insights into the Neoproterozoic tectonic setting of the SZRM and the links between this magmatism and the evolution of the Rodinia supercontinent. The zircon U-Pb dating indicates that the Neoproterozoic magmatism within the SZRM can be subdivided into two stages: (1) a ∼917-911 Ma suite of syenogranites and monzogranites, and (2) an ∼841 Ma suite of granodiorites. The 917-911 Ma granitoids contain high concentrations of SiO2 (67.89-71.18 wt.%), K2O (4.24-6.91 wt.%), and Al2O3 (14.89-16.14 wt.%), and low concentrations of TFe2O3 (1.63-3.70 wt.%) and MgO (0.53-0.88 wt.%). They are enriched in the light rare earth elements (LREE) and the large ion lithophile elements (LILE), are depleted in the heavy REE (HREE) and the high field strength elements (HFSE; e.g., Nb, Ta, and Ti), and have slightly positive Eu anomalies, indicating that they are geochemically similar to high-K adakitic rocks. They have zircon εHf (t) values and TDM2 ages from -4.4 to +1.5 and 1915 Ma to 1592 Ma, respectively, suggesting that they were derived from a primary magma generated by the partial melting of ancient thickened lower crustal material. In comparison, the 841 Ma granodiorites contain relatively low concentrations of Al2O3 (14.50-14.58 wt.%) and K2O (3.27-3.29 wt.%), relatively high concentrations of TFe2O3 (3.78-3.81 wt.%) and the HREE, have negative Eu anomalies, and have zircon εHf (t) values and TDM2 ages from -4.7 to +1.0 and 1875 to 1559 Ma, respectively. These granodiorites formed from a primary magma generated by the partial melting of ancient crustal material. The ∼917-911 Ma magmatism within the SZRM is inferred to have formed in an orogenic setting, whereas the ∼841 Ma magmatism formed in an anorogenic setting related to either a post-orogenic tectonic event or the onset of Neoproterozoic

  1. THE GEOCHEMISTRY AND AGES OF ROCKS IN THE FOOTWALL OF THE BUTULIYN-NUR AND ZAGAN METAMORPHIC CORE COMPLEXES (NORTH MONGOLIA – WESTERN TRANSBAIKALIA

    Directory of Open Access Journals (Sweden)

    T. V. Donskaya

    2014-01-01

    Full Text Available This article reviews data on ages of rocks in the footwall of the Butuliyn-Nur and Zagan metamorphic core complexes (MCC and provides new data on the geochemistry of the rock complexes. It is noted that the oldest rocks are mylonitized gneisses on rhyolites (554 Ma in the footwall of the Butuliyn-Nur MCC. The Late Permian – Triassic (249–211 Ma igneous rocks are ubiquitous in the footwall of the Butuliyn-Nur and Zagan MCC. The youngest rocks in the studied MCC are the Jurassic granitoids (178–152 Ma of the Naushki and Verhnemangirtui massifs. In the footwall of the Butuliyn-Nur and Zagan MCC, the most common are granitoids and felsic volcanic rocks (249–211 Ma with many similar geochemical characteristics, such as high alkalinity, high contents of Sr and Ba, moderate and low concentrations of Nb and Y. Considering the contents of trace elements and REE, the granitoids and the felsic volcanic rocks are similar to I-type granites. Specific compositions of these rocks suggest that they might have formed in conditions of the active continental margin of the Siberian continent over the subducting oceanic plate of the Mongol-Okhotsk Ocean. The granitoids of the Naushki and Verhnemangirtui massifs, which are the youngest of the studied rocks (178–152 Ma, also have similar geochemical characteristics. In both massif, granitoids are ferriferous, mostly alkaline rocks. By contents of both major and trace elements, they are comparable to A-type granites. Such granitoids formed in conditions of intracontinental extension while subduction was replaced by collision. Based on ages and geochemical characteristics of the rocks in the footwall of the Butuliyn-Nur and Zagan MCC, a good correlation is revealed between the studied rocks  and the rock complexes of the Transbaikalian and North-Mongolian segments of the Central Asian fold belt (CAFB, and it can thus be suggested that the regions under study may have a common evolutionary history.

  2. Geochemistry and Nd-Sr isotopic signatures of the Pensamiento Granitoid Complex, Rondonian-San Ignacio Province, eastern precambrian shield of Bolivia: petrogenetic constraints for a mesoproterozoic magmatic arc setting;Geoquimica e assinaturas Nd-Sr do Complexo Granitoide Pensamiento, provincia Rondoniana-San Ignacio, pre-cambriano de Bolivia Oriental: caracterizacao petrogenetica de um arco magmatico no mesoproterozoico

    Energy Technology Data Exchange (ETDEWEB)

    Matos, Ramiro, E-mail: rmatoss@igc.usp.b [Universidad Mayor de San Andre (UMSA), La Paz (Bolivia, Plurinational State of). Inst. de Investigaciones Geologicas y del Medio Ambiente; Teixeira, Wilson; Bettencourt, Jorge Silva, E-mail: wteixeir@usp.b, E-mail: jsbetten@usp.b [Universidade de Sao Paulo (IGC/USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica; Geraldes, Mauro Cesar, E-mail: geraldes@uerj.b [Universidade do Estado do Rio de Janeiro (FG/UERJ), RJ (Brazil). Faculdade de Geologia

    2009-07-01

    The Pensamiento Granitoid Complex (PGC), located in the northern part of the eastern Precambrian shield of Bolivia, is tectonically assigned to the Rondonian-San Ignacio Province (1.55 - 1.30 Ga) of the Amazonian Craton that is made up by Archean and Proterozoic provinces. The Proterozoic ones result from accretionary orogens that become successively younger south westwards, such as the Rondonian/San Ignacio (1.37 - 1.32 Ga) and the Sunsas orogenies (1.20 - 1.00 Ga). The PGC crops out mainly on the 'Paragua craton' bounded to the south by the Sunsas belt, and composed of granites and subvolcanic terms, and subordinately of syenites, granodiorites, tonalites, trondhjemites and diorites as orogenic representatives of the Rondonian/San Ignacio Orogeny, intrusive into the Lomas Maneches (ca. 1.68 Ga) and Chiquitania (ca. 1.7 Ga) complexes. Thirteen whole rock chemical analyses for major, trace and REE elements were performed for the La Junta, San Martin, Diamantina, Porvernir, San Cristobal, Piso Firme plutons of the PGC. The negative trends of MgO, Al{sub 2}O{sub 3} and CaO contents with increasing SiO{sub 2} suggest that fractional crystallization played an important role in the petrogenesis of the investigated rocks. The data also indicate a mainly peraluminous, sub-alkaline to high-K calc-alkaline composition, and fractionated LREE/HREE patterns are consistent with a magmatic arc character for these plutons. SHRIMP U-Pb zircon ages of the La Junta and San Martin syn- to late-kinematic plutons are 1347 {+-} 21 Ma and 1373 {+-} 20 Ma respectively, and the Sm-Nd T{sub DM} model ages are between 1.9 to 2.0 Ga, while {epsilon}{sub Nd(1330)} values range from +1.8 to -4.3, respectively. In addition, the late- to post-kinematic Diamantina pluton yields SHRIMP U-Pb zircon age of 1340 {+-} 20 Ma, and variable Sm-Nd T{sub DM} model ages (1.6 to 1.9 Ga) and {epsilon}{sub Nd(1330)} values (+0.4 to -1.2) that are comparable with previous results found for other coeval

  3. Association of the Purana basins and the middle Proterozoic mobile belts in peninsular India: implications on targeting uranium deposits

    International Nuclear Information System (INIS)

    Kale, V.S.

    1995-01-01

    The disparate Archaean Cratonic Nuclei of the Indian peninsular shield coalesced together through late Archaean - Palaeoproterozoic accretionary tectonic events. The subsequent Mesoproterozoic and Neoproterozoic sequences are preserved either in the Purana basins or in the middle Proterozoic mobile belts (MPMB). The latter contain deformed and metamorphosed supracrustal sequences; and can be ascribed to compressive tectonic regimes. The Purana basins on the other hand represent shallow marine, epicratonic, passive-margin sequences deposited in an extensional tectonic regime. Major deformational events and metamorphism of the MPMB are known to have taken place around 1600 ±200 Ma and 900 ± 100 Ma. These two periods coincide with the ages of initiation and major intrabasinal breaks in the growth of the Purana basins. The contemporary juxtapositioning of these two dissimilar tectonic regimes in peninsular India, is examined within the framework of the available data on them and the current models of Proterozoic tectonics. Its implications on uranium mineralization and possible regions for targeting exploration activities are discussed on this basis. (author). 112 refs., 4 figs

  4. Comparison of the behaviour of rare earth elements in surface waters, overburden groundwaters and bedrock groundwaters in two granitoidic settings, Eastern Sweden

    International Nuclear Information System (INIS)

    Roennback, Pernilla; Astroem, Mats; Gustafsson, Jon-Petter

    2008-01-01

    This work, which was done within the Swedish nuclear waste management program, was carried out in order to increase the understanding of the mobility and fate of rare earth elements (REEs) in natural boreal waters in granitoidic terrain. Two areas were studied, Forsmark and Simpevarp, one of which will be selected as a site for spent nuclear fuel. The highest REE concentrations were found in the overburden groundwaters, in Simpevarp in particular (median ΣREE 52 μg/L), but also in Forsmark (median ΣREE 6.7 μg/L). The fractionation patterns in these waters were characterised by light REE (LREE) enrichment and negative Ce and Eu anomalies. In contrast, the surface waters had relatively low REE concentrations. They were characterised either by an increase in relative concentrations throughout the lanthanide series (Forsmark which has a carbonate-rich till) or flat patterns (Simpevarp with carbonate-poor till), and had negative Ce and Eu anomalies. In the bedrock groundwaters, the concentrations and fractionation patterns of REEs were entirely different from those in the overburden groundwaters. The median La concentrations were low (just above 0.1 μg/L in both areas), only in a few samples were the concentrations of several REEs (and in a couple of rare cases all REEs) above the detection limit, and there was an increase in the relative concentrations throughout the lanthanide series. In contrast to these large spatial variations, the temporal trends were characterised by small (or non existent) variations in REE-fractionation patterns but rather large variations in concentrations. The Visual MINTEQ speciation calculations predicted that all REEs in all waters were closely associated with dissolved organic matter, and not with carbonate. In the hydrochemical data for the overburden groundwater in particular, there was however a strong indication of association with inorganic colloids, which were not included in the speciation model. Overall the results showed

  5. Late Paleozoic to Triassic magmatism in the north-central High Andes, Chile: New insights from SHRIMP U-Pb geochronology and O-Hf isotopic signatures in zircon

    Science.gov (United States)

    Hernández González, Álvaro; Deckart, Katja; Fanning, Mark; Arriagada, César

    2014-05-01

    The Chilean High Andes (28o- 31oS) comprises a vast number of late Paleozoic - Triassic granitoids which give information about the last stages of Gondwana assemblage. Particularly, previous studies determined two tectonic configurations during this time: subduction related compressional setting (late Carboniferous - Late Permian) and non-subduction post-collisional extensional setting (Late Permian - Triassic), as the last stage of Gondwana assemblage. However, new O-Hf isotopic data along new U-Pb SHRIMP ages in zircon have shown that this model should be modified and updated to the new analytical data available. δ18O values indicate a strong change in the tectonic configuration approximately 270 Ma (earliest middle Permian) and thus, units can be divided into 2 mayor groups: late Carboniferous to earliest middle Permian and middle Permian to Triassic. The oldest group shows slightly low values of ɛHfi (ca. +1 to -4) with high δ18O (ca. >6.5 o/oo), indicating an elevated supracrustal component and the addition of less radiogenic continental-like material, which along significant residence time (TDM2: Mesoproterozoic) can be interpreted as magmas formed at depth in a subduction-related continental arc, and contaminated with supracrustal material and/or oceanic sediments transported through the subducted slab to the mantle-wedge. Subsequently, middle Permian - Triassic rocks show a wider range of ɛHfi values (ca. +3 to -3) with relatively low, mantle-like δ18O (ca. 4.5-6.5 o/oo), indicating a source of magmas without the addition of supracrustal material for some plutons, whilst for others, a slight input. The higher positive values of ɛHfi can be related to the influence of new juvenile material in the source of some magmas. This isotopic data can be interpreted as rocks formed as the result of melting of an old thinned mafic crust (with mantle-like δ18O values characteristic of this type of rocks) with limited addition of supracrustal material; in

  6. Post-collisional magmatism in the central East African Orogen: The Maevarano Suite of north Madagascar

    Science.gov (United States)

    Goodenough, K.M.; Thomas, Ronald J.; De Waele, B.; Key, R.M.; Schofield, D.I.; Bauer, W.; Tucker, R.D.; Rafahatelo, J.-M.; Rabarimanana, M.; Ralison, A.V.; Randriamananjara, T.

    2010-01-01

    Late tectonic, post-collisional granite suites are a feature of many parts of the Late Neoproterozoic to Cambrian East African Orogen (EAO), where they are generally attributed to late extensional collapse of the orogen, accompanied by high heat flow and asthenospheric uprise. The Maevarano Suite comprises voluminous plutons which were emplaced in some of the tectonostratigraphic terranes of northern Madagascar, in the central part of the EAO, following collision and assembly during a major orogeny at ca. 550 Ma. The suite comprises three main magmatic phases: a minor early phase of foliated gabbros, quartz diorites, and granodiorites; a main phase of large batholiths of porphyritic granitoids and charnockites; and a late phase of small-scale plutons and sheets of monzonite, syenite, leucogranite and microgranite. The main phase intrusions tend to be massive, but with variably foliated margins. New U-Pb SHRIMP zircon data show that the whole suite was emplaced between ca. 537 and 522 Ma. Geochemically, all the rocks of the suite are enriched in the LILE, especially K, and the LREE, but are relatively depleted in Nb, Ta and the HREE. These characteristics are typical of post-collisional granitoids in the EAO and many other orogenic belts. It is proposed that the Maevarano Suite magmas were derived by melting of sub-continental lithospheric mantle that had been enriched in the LILE during earlier subduction events. The melting occurred during lithospheric delamination, which was associated with extensional collapse of the East African Orogen. ?? 2009 Natural Environment Research Council.

  7. Petrogenesis of Malaysian tin granites: geochemistry, fractional crystallization, U-Pb zircon geochronology and tectonic setting

    Science.gov (United States)

    Wai-Pan Ng, Samuel; Searle, Mike; Whitehouse, Martin; Chung, Sun-Lin; Ghani, Azman; Robb, Laurence; Sone, Masatoshi; Oliver, Grahame; Gardiner, Nick; Roselee, Mohammad

    2014-05-01

    The Malaysian tin granites forming the backbone of the Thai-Malay Peninsula has been long recognized with two distinct granitic provinces:- 1. Early Permian to Late Triassic Eastern Province with mainly "I-type" (Hbl)-Bt granites with associated Cu-Au deposits, with subordinate Bt granites hosting limited Sn-W deposits, and 2. Late Triassic Main Range Province with mainly "S-type" Bt granites with associated Sn-W deposits, and subordinate (Hbl)-Bt granites. New geochemical data show that Chappell and White's (1974) I-S granite classification adopted in the existing model does not adequately distinguish the granites from one another as previously implied. Trace element geochemistry and Sr-Nd isotopic compositions show that the Malaysian tin granites in both provinces have transitional I-S characteristics. In addition, they inherited within-plate signature from Cambro-Ordovician Gondwana-related source rocks. Previous ages were obtained by whole rock Rb-Sr and biotite K-Ar geochronology in the 70s and 80s, dating methods that may not accurately represent the crystallization age of granites. We re-sampled the entire Malaysian Peninsula and 40 samples were collected for high-precision U-Pb SIMS dating on extracted zircon grains in order to better constrain the magmatic and tectonic evolution of Southeast Asia. The crystallization ages of the Eastern Province granitoids have been constrained ranging from 220 to 290 Ma, while the Main Range (Western) Province granitoids have ages ranging from 200 to 230 Ma. A progressive westward younging trend is apparent across the Eastern Province, but becomes less obvious in the Main Range Province. Our model suggests two east dipping subduction zones. We suggest that subduction roll-back along the Bentong-Raub suture might account for the westward younging trend, in the Eastern province. A second Late Triassic east-dipping subduction zone beneath western Malaysia is proposed in order to explain the "I-type" components to the Main

  8. Western cratonic domains in Uruguay: geochronology

    International Nuclear Information System (INIS)

    Preciozzi, F.; Peel, E.; Muzio, E.; Ledesma, R.; Guerequiz, R.

    2001-01-01

    The western cratonic domains in Uruguay are divided into three major units: Piedra Alta Terrane, Valentines Block and Pavas Block. Piedra Alta Terrane lacks of evidence of Neoproterozoic orogenesis (deformation, metamorphism or magmatism). Sarandí del Yi - Arroyo Solís Grande shear zone, separates it from Valentines Block. Valentines Block is separated from Pavas Block by Cueva del Tigre shear zone. Magmatic rocks with different ages, compositions and emplacements occur all over the Piedra Alta Terrane distributed in three metamorphic belts (Arroyo Grande, San José and Montevideo) as well as in the Central Gneissic-Migmatitic Complex (Figure 1). Samples from the Gneissic-Migmatitic complex, late tectonic granitoids and basic rocks associated to the metamorphic belts were analyzed using Rb/Sr, U/Pb, K/Ar and Sm/Nd methodologies. The age ranges obtained for granitoids

  9. The alkaline peralkaline granitic post-collisional Tin Zebane dyke swarm (Pan-African Tuareg shield, Algeria): prevalent mantle signature and late agpaitic differentiation

    Science.gov (United States)

    Hadj-Kaddour, Zakia; Liégeois, Jean-Paul; Demaiffe, Daniel; Caby, Renaud

    1998-12-01

    The Tin Zebane dyke swarm was emplaced at the end of the Pan-African orogeny along a mega-shear zone separating two contrasting terranes of the Tuareg shield. It is located along the western boundary of the Archaean In Ouzzal rigid terrane, but inside the adjacent Tassendjanet terrane, strongly remobilized at the end of the Precambrian. The Tin Zebane swarm was emplaced during post-collisional sinistral movements along the shear zone at 592.2±5.8 Ma (19WR Rb-Sr isochron). It is a dyke-on-dyke system consisting of dykes and stocks of gabbros and dykes of metaluminous and peralkaline granites. All rock types have Sr and Nd isotopic initial ratios (Sr i=0.7028 and ɛNd=+6.2) typical of a depleted mantle source, similar to the prevalent mantle (PREMA) at that period. No crustal contamination occurred in the genesis of the Tin Zebane swarm. Even the samples showing evidence of fluid interaction (essentially alkali mobility) have the same isotopic signature. The peralkaline granites have peculiar geochemical characteristics that mimic subduction-related granites: this geochemical signature is interpreted in terms of extensive differentiation effects due to late cumulates comprising aegirine, zircon, titanite, allanite and possibly fergusonite, separated from the liquid in the swarm itself due to magmatic flow turbulence. The Tin Zebane dyke swarm is thus of paramount importance for constraining the differentiation of mantle products to generate highly evolved alkaline granites without continental crust participation, in a post-collisional setting.

  10. Exploring Late Globalization

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    2016-01-01

    literature on late globalization from sociocultural and economic perspectives. It illustrates in a vignette the character and features of late globalization observable in the withdrawal from foreign locations or deinternationalization of universities, as late globalizing entitis. The paper discusses...

  11. Age revision of the Neotethyan arc migration into the southeast Urumieh-Dokhtar belt of Iran: Geochemistry and U-Pb zircon geochronology

    Science.gov (United States)

    Hosseini, Mohammad Reza; Hassanzadeh, Jamshid; Alirezaei, Saeed; Sun, Weidong; Li, Cong-Ying

    2017-07-01

    The Urumieh-Dokhtar magmatic belt of Central Iran runs parallel to the Zagros orogenic belt and has been resulted from Neotethys ocean subduction underneath Eurasia. The Bahr Aseman volcanic-plutonic complex (BAC), covering an area 2000 km2 in the Kerman magmatic belt (KMB) in the southern section of the Urumieh-Dokhtar belt, has long been considered as the earliest manifestation of extensive Cenozoic arc magmatism in KMB. The nature and timing of the magmatism, however, is poorly constrained. An area 1000 km2, in BAC and adjacent Razak volcaniclastic complex and Jebal Barez-type granitoids, was mapped and sampled for geochemistry and geochronology. Andesite and basaltic andesite are the main volcanic components in the study area; plutonic bodies vary from tonalite to quartz diorite, granodiorite and biotite-granite. The rocks in BAC display dominantly normal calc-alkaline character. On spider diagrams, the rocks are characterized by enrichments in LILE relative to HFSE and enrichments in LREE relative to HREE. These features suggest a subduction related setting for the BAC. LaN/YbN ratios for the intrusive and volcanic rocks range from 1.41 to 5.16 and 1.01 to 6.42, respectively. These values are lower than those for other known granitoids in KMB, namely the abyssal, dominantly Oligocene Jebal Barez-type (LaN/YbN = 1.66-9.98), and the shallow, dominantly late Miocene Kuh Panj-type (LaN/YbN = 12.97-36.04) granitoids. This suggests a less evolved magma source for the BAC igneous rocks. In Y vs. Nb and Th/Yb vs. La/Yb discrimination diagrams, an island-arc setting is defined for the BAC rocks. The rocks further plot in primitive island-arc domain in Nb vs. Rb/Zr and Y/Nb vs. TiO2 diagrams. The BAC volcanic and plutonic rocks yielded zircon U-Pb ages of 78.1 to 82.7 Ma and 77.5 to 80.8 Ma, respectively. Zircon U-Pb dating of volcanic rocks and granitoids from the adjacent Razak complex and the Jebal Barez-type granitoids indicated 48.2 Ma and 26.1 Ma ages

  12. Magmatism and polymetallic mineralization in southwestern Qinzhou-Hangzhou metallogenic belt, South China

    Science.gov (United States)

    Huang, Xudong; Lu, Jianjun; Wang, Rucheng; Ma, Dongsheng

    2016-04-01

    As Neoproterozoic suture zone between the Yangtze Block and Cathaysia Block, Qinzhou-Hangzhou metallogenic belt is one of the 21 key metallogenic belts in China. Intensive multiple-aged felsic magmatism and related polymetallic mineralization take place in this belt. Although Neoproterozoic, Paleozoic, Triassic granites and associated deposits have been found in southwestern Qinzhou-Hangzhou metallogenic belt, Middle-Late Jurassic (150-165 Ma) magmatism and related mineralization is of the most importance. Three major kinds of Middle-Late Jurassic granitoids have been distinguished. (Cu)-Pb-Zn-bearing granitoids are slightly differentiated, calc-alkaline and metaluminous dioritic to granodioritic rocks. Sn-(W)-bearing granites contain dark microgranular enclaves and have high contents of REE and HFSE, suggesting affinities of aluminous A-type (A2) granites. W-bearing granites are highly differentiated and peraluminous rocks. (Cu)-Pb-Zn-bearing granitoids have ɛNd(t) values of -11 ˜ -4 and ɛHf(t) values of -12 ˜ -7, corresponding to TDMC(Nd) from 1.4 to 1.8 Ga and TDMC(Hf) from 1.6 to 2.0 Ga, respectively. The ɛNd(t) values of W-bearing granites vary from -11 to -8 with TDMC(Nd) of 1.6 ˜ 1.9 Ga and ɛHf(t) values change from -16 to -7 with TDMC(Hf) of 1.5 ˜ 2.0 Ga. Compared with (Cu)-Pb-Zn-bearing granitoids and W-bearing granites, the Sn-(W)-bearing granites have higher ɛNd(t) (-8 ˜ -2) and ɛHf(t) (-8 ˜ -2) values and younger TDMC(Nd) (1.1 ˜ 1.6 Ga) and TDMC(Hf) (1.2 ˜ 1.8 Ga) values, showing a more juvenile isotopic character. Sn-(W)-bearing granites originate from partial melting of granulitized lower crust involved with some mantle-derived materials. W-bearing granites are derived from partial melting of crust. (Cu)-Pb-Zn-bearing granitoids are also derived from crust but may be influenced by more mantle-derived materials. For (Cu)-Pb-Zn deposits, skarn and carbonate replacement are the most important mineralization types. Cu ore bodies mainly

  13. The Sao Jose do Rio Pardo mangeritic-granitic suite, south eastern Brazil

    International Nuclear Information System (INIS)

    Campos Neto, M.C.; Figueiredo, M.C.H.; Janasi, V.A.; Basei, M.A.S.; Fryer, B.J.

    1988-01-01

    In the Sao Jose do Rio Pardo region, Sao Paulo and Minas Gerais States, occur some intrusive, folded tabular bodies of mangerites associated with hornblende granitoids. The country rocks correspond to a complex association of gneisses and migmatites, locally with granulite facies assemblages. Both the magnerites and hornblende granitoids present a tectonic foliation with mineral flattening and stretching. Petrographically the mangeritic rocks are mainly dark green quartz mangerites with mesoperthite, plagioclase, quartz, hypersthene, clinopyroxene and variable amounts of hornblende, with zircon as conspicuous acessory. The pink hornblende granitoids are mainly granite s.s. exhibiting higher quartz and amphibole contents and lacking pyroxenes. Hololeucocratic alkali feldspar granites are locally associated to the hornblende granites. The textures of the mangerites and granites almost always show an important metamorphic overprinting, with relictic mesoperthite and pyroxene crystal into a granoblastic matrix. The magneritic-granitic suite is characterized by relatively high Fe/(Fe + Mg), K and HFS elements and low Ca contents, being comparable to typical anorogenic magneritic-granitic suites from Svcandinavia and North America. The Rb/Sr data indicate a Late Proterozoic metamorphic isotopic rehomogenization (930 Ma, Ro = 0.706). Geological evidence suggest that the intrusive age could be Middle Proterozoic, wich is reinforced by another Rb-Sr value of about 1300 Ma. (author) [pt

  14. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil

    International Nuclear Information System (INIS)

    Jesus, Gisely Carmo de; Sousa, Maria Zelia Aguiar de; Ruiz, Amarildo Salina; Matos, Joao Batista de

    2010-01-01

    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  15. New SHRIMP zircon results from Broken Hill: towards robust stratigraphic and event timing

    International Nuclear Information System (INIS)

    Page, R.W.; Stevens, B.P.J.

    1999-01-01

    ∼1700-1715 Ma felsic volcaniclastic and intrusive rocks in the Olary region. Potosi Gneiss lithotypes in the Parnell Formation (middle Broken Hill Group) and Hores Gneiss (upper Broken Hill Group) were interpreted as felsic volcaniclastic rocks with depositional ages of 1693±5 and 1689±5 Ma (Page and Laing, 1992). We have now substantiated the Hores Gneiss age (1686±3 Ma) which, together with a new depositional age of 1690-1695 Ma for tuffaceous metasediments in the lower Broken Hill Group, support the conclusion that the Broken Hill Group (excluding some amphibolite intrusions) is a coherent depositional package. Suggestions by Nutman and Ehlers (1998b) that the mapped Hores Gneiss comprises later intrusions (from 1690 Ma to 1640-1660 Ma old) and underwent high-grade metamorphism at 1640-1660 Ma are at variance with our data and the conclusions we draw here. Our age for the Rasp Ridge Gneiss (1682±3 Ma) indicates that this felsic magmatism postdates middle Broken Hill Group, and was possibly coeval with Hores Gneiss. Work is in progress on Sundown Group rocks to determine maximum depositional ages and provenance using immature psammopelitic lithologies. Some sediments contain a small component of detrital zircons as young as ca. 1690-1700 Ma, but major sediment input is from terrains ca. 1790 Ma and 1820-1860 Ma old, as well as older Palaeoproterozoic and late Archaean sources. Tuffaceous siltstones in the middle Paragon Group, both in northern Broken Hill Block and Euriowie Inlier, record similar detrital zircon ages to the Sundown Group, but in addition they include pristine, unabraded zircons which date deposition at no older than 1656±5 Ma. Similar lithologies in the Dalnit Bore Metasediments (upper Paragon Group) provide a maximum depositional age of 1642±5 Ma. Progress towards dating deformational events has been focussed on obtaining zircon ages for granitoid intrusions which bracket the deformations. This enables us to possibly constrain the D 2

  16. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally

  17. Late Carboniferous to Late Permian carbon isotope stratigraphy

    DEFF Research Database (Denmark)

    Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria

    2015-01-01

    An integrated study of the litho-, bio-, and isotope stratigraphy of carbonates in the Southern Alps was undertaken in order to better constrain δ13C variations during the Late Carboniferous to Late Permian. The presented high resolution isotope curves are based on 1299 δ13Ccarb and 396 δ13Corg...

  18. Primordial crustal growth in northern Nigeria: preliminary Rb-Sr and Sm-Nd constraints from Kaduna migmatite-gneiss complex

    International Nuclear Information System (INIS)

    Dada, S. S.; Briqueu, L.; Birck, J. L.

    1998-01-01

    The Kaduna Migmatite-Gneiss Complex in the central area of the Northern shield includes variably migmatised granitotrondhjemitic gneisses and amphibolite of hitherto unknown age. The amphibolite enclaves and dykes are metatholeiites with comparatively unfractionated rare-earth patterns. The two main rock units (TTG and amphibolite) exhibit complementary geochemical signatures in the normalised abundance patterns of relatively incompatible elements and suggest possible derivation of the gneisses from subduction related mafic material. Sm-Nd and Rb-Sr isotopic data document early Archaean crustal formation of new crust and its subsequent late Archaean differentiation. These preliminary results form an evidence for a more extended crustal history in the heart of the Pan-African domain (ca. 600 Ma.). They suggest the differentiation of juvenile crustal protolith from a chondritic reservoir about 3.5 Ga. for the gneiss-amphibolite bimodal suite. A tectonothermal event about 3.1-3.0 Ga led to the emplacement of an early gneiss as indicated from Rb-Sr and U-Ph zircon analyses. Subsequent differentiation and/or reworking around 2.8-2.7 Ga is coherent with the Liberian orogeny within the West African- Latino American subregion

  19. Geochemistry and Nd-Sr isotopic signatures of the Pensamiento Granitoid Complex, Rondonian-San Ignacio Province, eastern precambrian shield of Bolivia: petrogenetic constraints for a mesoproterozoic magmatic arc setting

    International Nuclear Information System (INIS)

    Matos, Ramiro; Teixeira, Wilson; Bettencourt, Jorge Silva; Geraldes, Mauro Cesar

    2009-01-01

    The Pensamiento Granitoid Complex (PGC), located in the northern part of the eastern Precambrian shield of Bolivia, is tectonically assigned to the Rondonian-San Ignacio Province (1.55 - 1.30 Ga) of the Amazonian Craton that is made up by Archean and Proterozoic provinces. The Proterozoic ones result from accretionary orogens that become successively younger south westwards, such as the Rondonian/San Ignacio (1.37 - 1.32 Ga) and the Sunsas orogenies (1.20 - 1.00 Ga). The PGC crops out mainly on the 'Paragua craton' bounded to the south by the Sunsas belt, and composed of granites and subvolcanic terms, and subordinately of syenites, granodiorites, tonalites, trondhjemites and diorites as orogenic representatives of the Rondonian/San Ignacio Orogeny, intrusive into the Lomas Maneches (ca. 1.68 Ga) and Chiquitania (ca. 1.7 Ga) complexes. Thirteen whole rock chemical analyses for major, trace and REE elements were performed for the La Junta, San Martin, Diamantina, Porvernir, San Cristobal, Piso Firme plutons of the PGC. The negative trends of MgO, Al 2 O 3 and CaO contents with increasing SiO 2 suggest that fractional crystallization played an important role in the petrogenesis of the investigated rocks. The data also indicate a mainly peraluminous, sub-alkaline to high-K calc-alkaline composition, and fractionated LREE/HREE patterns are consistent with a magmatic arc character for these plutons. SHRIMP U-Pb zircon ages of the La Junta and San Martin syn- to late-kinematic plutons are 1347 ± 21 Ma and 1373 ± 20 Ma respectively, and the Sm-Nd T DM model ages are between 1.9 to 2.0 Ga, while ε Nd(1330) values range from +1.8 to -4.3, respectively. In addition, the late- to post-kinematic Diamantina pluton yields SHRIMP U-Pb zircon age of 1340 ± 20 Ma, and variable Sm-Nd T DM model ages (1.6 to 1.9 Ga) and ε Nd(1330) values (+0.4 to -1.2) that are comparable with previous results found for other coeval plutons. The Porvenir, San Cristobal and Piso Firme plutons

  20. Geochronology of Hydrothermal Processes Leading to the Formation of the Au–U Mineralization at the Rompas Prospect, Peräpohja Belt, Northern Finland: Application of Paired U–Pb Dating of Uraninite and Re–Os Dating of Molybdenite to the Identification of Multiple Hydrothermal Events in a Metamorphic Terrane

    Directory of Open Access Journals (Sweden)

    Ferenc Molnár

    2017-09-01

    Full Text Available The Peräpohja belt comprises a greenschist to amphibolite facies; multiply-folded supracrustal sequence of quartzites; mafic volcanics; carbonate rocks; black shales; mica schists and greywackes deposited from ca. 2.44 Ga to 1.92 Ga; during protracted rifting of the Archaean basement. Metamorphism and multiple folding of the basin fill occurred during the Svecofennian orogeny (1.92–1.80 Ga. The Rompas Au–U mineralization is hosted within deformed and metamorphosed calcsilicate veins in mafic volcanics. Textural evidence suggests that deposition and periods of uraninite re-mobilization were followed by localized hydrocarbon-bearing fluid flow which produced pyrobitumen crusts around grains of uraninite. Gold precipitated during the latest hydrothermal event at around 1.75 Ga. In situ U–Pb dating of uraninite by laser ablation inductively coupled mass spectroscopy (LA-ICP-MS, and Re–Os dating of molybdenite, indicate that primary hydrothermal uranium mineralization forms two age clusters; about 2.03–2.01 and 1.95–1.94 Ga. Resetting of the U–Pb system and precipitation of new generations of uraninite are associated with major deformation and metamorphic stages of the Svecofennian orogeny at 1.91–1.89 Ga, 1.85 Ga, and 1.80 Ga. Gold deposition was synchronous with the emplacement of the 1.75–1.78 Ga late/post-orogenic granitoids. The gold-producing hydrothermal event is also recorded by Re–Os dating of molybdenite from the gold-bearing Mg-metasomatized metasedimentary and metavolcanic units at the Palokas prospect; a few kilometres from Rompas. Results of this study confirm that some domains in the structure of uraninite may preserve the original crystallization age, despite an overprinting amphibolite facies metamorphic and other hydrothermal events. The study supports the utility of in situ U–Pb dating of uraninite and the ability of Re–Os dating to assist in sorting out different hydrothermal events in areas with complex

  1. Updating the Geologic Barcodes for South China: Discovery of Late Archean Banded Iron Formations in the Yangtze Craton.

    Science.gov (United States)

    Ye, Hui; Wu, Chang-Zhi; Yang, Tao; Santosh, M; Yao, Xi-Zhu; Gao, Bing-Fei; Wang, Xiao-Lei; Li, Weiqiang

    2017-11-08

    Banded iron formations (BIFs) in Archean cratons provide important "geologic barcodes" for the global correlation of Precambrian sedimentary records. Here we report the first finding of late Archean BIFs from the Yangtze Craton, one of largest Precambrian blocks in East Asia with an evolutionary history of over 3.3 Ga. The Yingshan iron deposit at the northeastern margin of the Yangtze Craton, displays typical features of BIF, including: (i) alternating Si-rich and Fe-rich bands at sub-mm to meter scales; (ii) high SiO 2  + Fe 2 O 3total contents (average 90.6 wt.%) and Fe/Ti ratios (average 489); (iii) relative enrichment of heavy rare earth elements and positive Eu anomalies (average 1.42); (iv) and sedimentary Fe isotope compositions (δ 56 Fe IRMM-014 as low as -0.36‰). The depositional age of the BIF is constrained at ~2464 ± 24 Ma based on U-Pb dating of zircon grains from a migmatite sample of a volcanic protolith that conformably overlied the Yingshan BIF. The BIF was intruded by Neoproterozoic (805.9 ± 4.7 Ma) granitoids that are unique in the Yangtze Craton but absent in the North China Craton to the north. The discovery of the Yingshan BIF provides new constraints for the tectonic evolution of the Yangtze Craton and has important implications in the reconstruction of Pre-Nuna/Columbia supercontinent configurations.

  2. Rb-Sr ages and initial 87Sr/86Sr ratios of late paleozoic granitic rocks from northern Chile

    International Nuclear Information System (INIS)

    Shibata, Ken; Ishihara, Shunso; Ulriksen, C.E.

    1984-01-01

    Rb-Sr whole-rock isochron ages were determined on three suites of so-called Paleozoic granitic rocks from northern coastal Chile. The granitic rocks from the Valparaiso and Ci Funcho areas are dated as 296.3 +- 5.4 Ma and 262.2 +- 4.6 Ma, respectively, which are in accord with geologically estimated age. The rocks from the Chanaral area is dated as 212.8 +- 8.6 Ma, which is correlated close to the Triassic-Jurassic boundary age. A K-Ar age of 196 +- 6 Ma was obtained on biotite in granite from Esmeralda between Ci Funcho and Chanaral. These age results demonstrate that no Precambrian plutonism occurred in the studied area, and that so-called Paleozoic granitic rocks in the Ci Funcho-Chanaral area are divided into Permian and early Mesozoic in age. Initial 87 Sr/ 86 Sr ratios of the ilmenite-series granitic rocks from the coastal region are 0.70641 (Valparaiso), 0.70635 (Ci Funcho) and 0.70455 (Chanaral). These relatively low ratios deny substantial crustal contribution to the granitoids. The initial ratios of magnetite-series granitoids from porphyry- and manto-type mineralized areas (Chiquicamata, El Salvador and Tocopilla) are as low as 0.70344 to 0.70464. (author)

  3. The precambrian crustal evolution and mineralization cycle of uranium in the northeast of norern China platform

    International Nuclear Information System (INIS)

    Guo Zhitian.

    1986-01-01

    According to the evolution history of the crust the region is divided into three Precambrian structural structural units: (1) Archaean craton; (2) Early Proterozoic zone of fold; (3) Middle-late Proterozoic depression zone. The Archaean-craton mainly consists of granite complex and metasediments. They form the first generation of uranium sources. Proterozoic is characterized by the obvious cycle of sedimentation which consists of the second generation of uranium source. There were multiplestage and congenetic nature in the formation of uranium deposit. The mineralization of uranium coincides with geotectonicdeveloping stage -- igneous activity -- metamorphism in their time. The formation of uranium deposits generally underwent the weathering and erosion of original uraniferous bodies-the migration, redeposition and reformed concentration by metamorphism and metamorphosed hydrothermal solution, and the mineralization was not only of intermittence, but also of inheritance. The evolutional process of forming uranium deposits undergoing various geological function of a structural cycle in the uranium geochemical anomalous area is called uranium mineralizational cycle. The Northeast of Northern China Platform had undergone multiple times structural movements causing migration and concentration of uranium and having mutiple cycle mineralizational character. Corresponding to the three main developing stages of the crustal evolution the Precambrian uranium mineralization in the Northeast of northern China platform area may be divided into three cycles: Late Archaeozoic mineralizational cycle, Early Proterozoic mineralizational cycle, and Middle Proterozoic mineralizational cycle. It is possible to search for potential uranium metallogenetic provinces to study the crustal evolution and the multiple cycle characters of uranium minerogenetic process in the Northern China platform

  4. Mass changes during hydrothermal alteration/mineralization in the gold-bearing Astaneh granitoid, western Iran

    Science.gov (United States)

    Zahra Afshooni, Seyedeh; Esmaeily, Dariush

    2010-05-01

    The Astaneh granitoid massif, located in western Iran, is a part of Sanandaj-Sirjan structural Zone. This body, mainly consist of granodioritic rocks, is widely affected under hydrothermal alteration and four alteration zones including phyllic (sericitic), chloritic, propylitic and argillic zones could be identified in this area. Four main mineralization- related alteration episodes have been studied in terms of mass transfer and element mobility during the hydrothermal evolution of Astaneh deposit. In order to illustrate these changes quantitatively, isocon plots have been applied. Isocon plots illustrate that Al, Ti, Ga and Tm was relatively immobile during alteration and that mass were essentially conserved during alteration. Phyllic alteration was accompanied by the depletion of Na and Fe and the enrichment of Si and Cu. The loss of Na and Fe reflects the sericitization of alkali feldspar and the destruction of ferromagnesian minerals. The addition of Si is consistent with widespread silicification wich is a major feature of phyllic alteration. All of the HFSE (except in Y), were enriched but all REEs were depleted in this zone. The overall obtained results show that major oxides such as SiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5 and TiO2 and also LOI show dissimilar behaviors in the different zones. All of the LFSE, HFSE and FTSM (except in Cu and Mo) were depleted in argillic alteration but show dissimilar behaviors in the other alteration zones. The results shown strong depletion in REE, in particular LREE, in all of the alteration facies (except in chloritic zone), equivalent fresh rocks. In chloritic zone, compared with HREE, the LREE represent more enrichment.

  5. THE GEOCHEMICAL CHARACTERISTIC OF MAJOR ELEMENT OF GRANITOID OF NATUNA, SINGKEP, BANGKA AND SIBOLGA

    Directory of Open Access Journals (Sweden)

    Ediar Usman

    2017-07-01

    Full Text Available A study of geochemical characteristic of major elelemnt of granitoid in Western Indonesia Region was carried out at Natuna, Bangka, Singkep and Sibolga. The SiO2 contents of the granites are 71.16 to 73.02 wt%, 71.77 to 75.56wt% and 71.16 to 73.02wt% at Natuna, Bangka, and Singkep respectively, which are classified as acid magma. While in Sibolga the SiO2 content from 60.27 to 71.44wt%, which is classified as intermediate to acid magma. Based on Harker Diagram, the granites from Natuna, Bangka and Singkep as a co-genetic. In other hand the Sibolga Granite show as a scatter pattern. Granites of Natuna, Bangka and Singkep have the alkaline-total (Na2O + K2O between 6.03 to 8.51 wt% which are classified as granite and alkali granite regime. K2O content ranges from 3.49 to 5.34 wt% and can be classified as calc-alkaline type. The content of alkaline-total of Sibolga granite between 8.12 to 11.81 wt% and classified as a regime of syenite and granite. The range of K2O is about 5.36 to 6.94wt%, and assumed derived from high-K magma to ultra-potassic types. Granites of Natuna, Bangka and Singkep derived from the plutonic rock types and calc-alkaline magma, while Sibolga granite magma derived from K-high to ultra-potassic as a granite of islands arc. Based on the chemical composition of granite in Western Indonesian Region can be divided into two groups, namely Sibolga granite group is representing the Sumatera Island influenced by tectonic arc system of Sumatera Island. Granites of Bangka and Singkep are representing a granite belt in Western Indonesian Region waters which is influenced by tectonic of back arc.

  6. New data on barguzinsky granitoids age of the Angaro-Vitimsky batholith

    International Nuclear Information System (INIS)

    Budnikov, S.V.; Kovalenko, V.I.; Yarmolyuk, V.V.

    1995-01-01

    The age batholith rocks was studied by the Sm-Nd and U-Pb methods in terms of zircon. The boundary of masses being of Late carboniferous age of batholith rocks has been defined. Early and Middle Proterozoic age is possible for magmatic rocks of this part of batholith. 12 refs.; 3 refs.; 1 tab

  7. The uranium cycle

    International Nuclear Information System (INIS)

    Ferguson, J.

    1988-01-01

    In identifying uranium provinces, and, more importantly, mineralized zones within these provinces, it is of paramount importance to attempt to trace the geochemical behaviour of an element through all stages of Earth's evolution. Aspects that need to be addressed in this regard include solar abundance levels and fractionation processes during accretion, changing patterns of crustal evolution, effects of an evolving atmosphere, and the weathering cycle. Abundance patterns and partition coefficients of some of the siderophile elements in mantle rocks lend support to a multistage accretionary process. Lack of a terrestrial record in the first 500 Ma necessitates that lunar models be invoked, which suggests that early fractionation of a mafic/ultramafic magma resulted in an anorthositic crust. Fractionation of the mantle and transfer of materials to the upper levels must be central to any model invoked for development of the crust. Given high heat flow conditions in the early Archaean it would seem inescapable that the process of sea floor spreading and plate tectonics was an ongoing process. If the plate tectonic model is taken back to 3500 Ma, and assuming current speading rates, then about half of the mantle has passed through the irreversible differentiation cycle. Arguments in support of recycled material must be balanced against mantle metasomatism effects. With the associated advent of partial melting of the mantle material a partitioning of minor and trace elements into the melt fraction would take place. The early primitive mafic and ultramafic komatiites exemplify this feature by concentrating U and Th by a factor of 5 compared to chondritic abundances. It is of tantamount importance to understand the generation of the magmas in order to predict which are the 'fertile' bodies in terms of radioelement concentrations. In that the granitoid magmas image their source compositions, the association of high radioelements will primarily be source-dependent. Uranium

  8. Determination of emplacement mechanism of Zafarghand granitoid Pluton (Southeast of Ardestan by using anisotropy of magnetic susceptibility method (AMS

    Directory of Open Access Journals (Sweden)

    Mahmoud Sadeghian

    2017-03-01

    Full Text Available Zafarghand granitoid pluton with compositional range from gabbro to granite and early to middle Miocene age cropped out about 35 km of SE Ardestan. This pluton intrudedthe Eocene volcanic and volcanosedimentary rocks of the Urumieh - Dokhtar structuralzone. In this research, for the first time, the emplacement mechanism of Zafarghandgranitoidic pluton method has been investigated using of anisotropy of magneticsusceptibility (AMS. Based on field observations, as well as petrography andinterpretations of magnetic parameters, Zafarghand pluton divided into 5 domains (1A,1B, 2, 3, 4 and 5. Domain 1, in turn, is divided into 1A and 1B. Domains 2 and 4 arelithologically, gabbro to quartzdiorite and have been emplaced first. They have playedas feeder zones. Domains 1A, 1B, 3, and 5 are dominantly granodioritic to graniticcomposition and have been emplaced as a big and low dip magmatic flow (or possibly as a sill. The occurrence of gabbro to quartzdiorite as well as grandiorite, granite andtonalite in the margin borders of the body, are all indication of magma mixing. It isshould be noted that during emplacement of the pluton studied, fractionalcrystallization, magma mixing and crustal contamination contributed to its generationand the evolution as well.

  9. Granitoid-associated gold mineralization in Egypt: a case study from the Atalla mine

    Science.gov (United States)

    Zoheir, Basem; Deshesh, Fatma; Broman, Curt; Pitcairn, Iain; El-Metwally, Ahmed; Mashaal, Shabaan

    2018-06-01

    Gold-bearing sulfide-quartz veins cutting mainly through the Atalla monzogranite intrusion in the Eastern Desert of Egypt are controlled by subparallel NE-trending brittle shear zones. These veins are associated with pervasive sericite-altered, silicified, and ferruginated rocks. The hosting shear zones are presumed as high-order structures of the Najd-style faults in the Central Eastern Desert ( 615-585 Ma). Ore minerals include an early pyrite-arsenopyrite (±pyrrhotite) mineralization, partly replaced by a late pyrite-galena-sphalerite-chalcopyrite (±gold/electrum ± tetrahedrite ± hessite) assemblage. Gold occurs as small inclusions in pyrite and arsenopyrite, or more commonly as intergrowths with galena and sphalerite/tetrahedrite in microfractures. Arsenopyrite geothermometry suggests formation of the early Fe-As-sulfide mineralization at 380-340 °C, while conditions of deposition of the late base metal-gold assemblage are assumed to be below 300 °C. Rare hessite, electrum, and Bi-galena are associated with sphalerite and gold in the late assemblage. The early and late sulfide minerals show consistently a narrow range of δ34S ‰ (3.4-6.5) that overlaps with sulfur isotopic values in ophiolitic rocks. The Au-quartz veins are characterized by abundant CO2 and H2O ± CO2 ± NaCl inclusions, where three-dimensional clusters of inclusions show variable aqueous/carbonic proportions and broad range of total (bimodal) homogenization temperatures. Heterogeneous entrapment of immiscible fluids is interpreted to be caused by unmixing of an originally homogenous, low salinity ( 2 eq. mass % NaCl) aqueous-carbonic fluid, during transition from lithostatic to hydrostatic conditions. Gold deposition occurred generally under mesothermal conditions, i.e., 1.3 kbar and 280 °C, and continued during system cooling to chemistry of the ore fluids.

  10. Structural control of weathering processes within exhumed granitoids: Compartmentalisation of geophysical properties by faults and fractures

    Science.gov (United States)

    Place, J.; Géraud, Y.; Diraison, M.; Herquel, G.; Edel, J.-B.; Bano, M.; Le Garzic, E.; Walter, B.

    2016-03-01

    In the latter stages of exhumation processes, rocks undergo weathering. Weathering halos have been described in the vicinity of structures such as faults, veins or dykes, with a lateral size gradually narrowing with depth, symmetrically around the structures. In this paper, we describe the geophysical characterisation of such alteration patterns on two granitoid outcrops of the Catalan Coastal Ranges (Spain), each of which is affected by one major fault, as well as minor faults and fractures. Seismic, electric and ground penetrating radar surveys were carried out to map the spatial distribution of P-wave velocity, electrical resistivity and to identify reflectors of electromagnetic waves. The analysis of this multi-method and complementary dataset revealed that, at shallow depth, geophysical properties of the materials are compartmentalised and asymmetric with respect to major and subsidiary faults affecting the rock mass. This compartmentalisation and asymmetry both tend to attenuate with depth, whereas the effect of weathering is more symmetric with respect to the major structure of the outcrops. We interpret such compartmentalisation as resulting from the role of hydraulic and mechanical boundaries played by subsidiary faults, which tend to govern both the chemical and physical alterations involved in weathering. Thus, the smoothly narrowing halo model is not always accurate, as weathering halos can be strongly asymmetrical and present highly irregular contours delimiting sharp contrasts of geophysical properties. These results should be considered when investigating and modelling fluid storage and transfer in top crystalline rock settings for groundwater applications, hydrocarbon or geothermal reservoirs, as well as mineral deposits.

  11. 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).

  12. Early Permian intrusions of the Alai range: Understanding tectonic settings of Hercynian post-collisional magmatism in the South Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Konopelko, D.; Wilde, S. A.; Seltmann, R.; Romer, R. L.; Biske, Yu. S.

    2018-03-01

    We present geochemical and Sr-Nd-Pb-Hf isotope data as well as the results of single grain U-Pb zircon dating for ten granitoid and alkaline intrusions of the Alai segment of Kyrgyz South Tien Shan (STS). The intrusions comprise four geochemically contrasting series or suites, including (1) I-type and (2) shoshonitic granitoids, (3) peraluminous granitoids including S-type leucogranites and (4) alkaline rocks and carbonatites, closely associated in space. New geochronological data indicate that these diverse magmatic series of the Alai segment formed in a post-collisional setting. Five single grain U-Pb zircon ages in the range 287-281 Ma, in combination with published ages, define the main post-collisional magmatic pulse at 290-280 Ma, which is similar to ages of post-collisional intrusions elsewhere in the STS. An age of 287 ± 4 Ma, obtained for peraluminous graniodiorite of the Liayliak massif, emplaced in amphibolite-facies metamorphic rocks of the Zeravshan-Alai block, is indistinguishable from ca. 290 Ma age of peraluminous granitoids emplaced coevally with Barrovian-type metamorphism in the Garm block, located ca. 40 km south-west of the research area. The Sr-Nd-Pb-Hf isotopic compositions of the studied intrusions are consistent with the reworking of crustal material with 1.6-1.1 Ga average crustal residence times, indicating the formation of the Alai segment on a continental basement with Mesoproterozoic or older crust. The pattern of post-collisional magmatism in the Alai segment, characterized by emplacement of I-type and shoshoninitic granitoids in combination with coeval Barrovian-type metamorphism, is markedly different from the pattern of post-collisional magmatism in the adjacent Kokshaal segment of the STS with predominant A-type granitoids that formed on a former passive margin of the Tarim Craton. We suggest that during the middle-late Carboniferous the Alai segment probably comprised a microcontinent with Precambrian basement located between

  13. Petrology and geochemistry of Granitoids at Khanchay-Aliabad region, Tarom sub-zone, East of Zanjan

    Directory of Open Access Journals (Sweden)

    Arefeh Saiedi

    2018-03-01

    Full Text Available Khanchay-Aliabad area as a part of Tarom magmatic belt contains some shallow depth intrusions which are intruded the Eocene volcanic- sedimentary rocks and have very close association with Cu mineralization. The Eocene volcanic- sedimentary rocks include alternation of basalt, basaltic andesite and andesite, various kinds of tuff, tuffaceous sandstone, sandstone, siltstone and occasionally shale. Petrographical studies demonstrate that intrusions are pyroxene quartz monzonite and olivine gabbro in composition. The Khanchay pyroxene quartz monzonite have porphyritic to porphyroidic, hetero-granular to sereitic, ophitic and sub- ophitic textures and composed of plagioclase, clinopyroxene, hornblende, quartz, K-feldspar and biotite. The Aliabad pyroxene quartz monzonite shows porphyritic to porphyroidic textures composing of plagioclase, clinopyroxene and hornblende in the quartz- feldspatic matrix. The Khanchay olivine gabbro is characterized by the presence of coarse grained granular, ophitic and sub- ophitic textures as well as the occurrence of plagioclase, clinopyroxene and olivine. Geochemical studies indicate that the Khanchay- Aliabad pyroxene quartz monzonitic intrusions have SiO2 content varying from 59.58 to 61.34 %. These intrusions have high- K calc- alkaline nature and are classified as I-type metaluminous granitoids. Their similar patterns on spider diagrams are indication of genetic relation of these intrusions. On these diagrams LILEs (Ba, K, Th and Pb enrichment along with negative anomalies of HFSEs (Nb and Ti are observed. Moreover, the Chondrite normalized REE patterns demonstrate LREE enrichment with high ratio of LREE/HREE and Lan/Ybn ratio ranging from 3.08 to 3.72. The overall  field investigation, petrological and geochemical studies as well as  tectonic setting discrimination diagrams confirm that the Khanchay- Aliabad high-K intrusions were formed from a subduction related metasomatized lithospheric mantle in a post

  14. Lateness to School Remediation Game

    Science.gov (United States)

    Ugwuegbulam, Charles N.; Ibrahim, Haj. Naheed

    2015-01-01

    Primary and secondary school in Nigeria encourage punctuality to school yet a good number of the learners came late to school. This is especially true in the case of day students. Learners who come late to school are usually punished in one way or the other yet the lateness to school phenomenon still persist. Lateness to school behaviour affects…

  15. Mechanisms for strain localization within Archaean craton: A structural study from the Bundelkhand Tectonic Zone, north-central India

    Science.gov (United States)

    Sarkar, Saheli; Patole, Vishal; Saha, Lopamudra; Pati, Jayanta Kumar; Nasipuri, Pritam

    2015-04-01

    The transformation of palaeo-continents involve breakup, dispersal and reassembly of cratonic blocks by collisional suturing that develop a network of orogenic (mobile) belts around the periphery of the stable cratons. The nature of deformation in the orogenic belt depends on the complex interaction of fracturing, plastic deformation and diffusive mass transfer. Additionally, the degree and amount of melting during regional deformation is critical as the presence of melt facilitates the rate of diffusive mass transfer and weakens the rock by reducing the effective viscosity of the deformed zone. The nature of strain localization and formation of ductile shear zones surrounding the cratonic blocks have been correlated with Proterozoic-Palaeozoic supercontinent assembly (Columbia, Rodinia and Gondwana reconstruction). Although, a pre-Columbia supercontinent termed as Kenorland has been postulated, there is no evidence that supports the notion due to lack of the presence of shear zones within the Archaean cratonic blocks. In this contribution, we present the detailed structural analysis of ductile shear zones within the Bundelkhand craton. The ductlile shear zone is termed as Bundelkhand Tectonic Zone (BTZ) that extends east-west for nearly 300 km throughout the craton with a width of two-three kilometer . In the north-central India, the Bundelkhand craton is exposed over an area of 26,000 sq. The craton is bounded by Central Indian Tectonic zone in the south, the Great Boundary fault in the west and by the rocks of Lesser Himalaya in the north. A series of tonalite-trondjhemite-granodiorite gneiss are the oldest rocks of the Bundelkhand craton that also contains a succession of metamorphosed supracrustal rocks comprising of banded iron formation, quartzite, calc-silicate and ultramafic rocks. K-feldspar bearing granites intrude the tonalite-trondjhemite-granodiorite and the supracrustal rocks during the time span of 2.1 to 2.5 Ga. The TTGs near Babina, in central

  16. Constraints and prospects of uranium exploration in Himalaya

    International Nuclear Information System (INIS)

    Singh, Rajendra

    1994-01-01

    Exploration for uranium in the Himalaya over the last thirty years has brought to light five distinct types of mineralisation, namely, vein-type, hydrothermal shear controlled-type, disseminated-type, syngenetic-type, and sandstone-type. The first three are associated with lower to middle proterozoic metasedimentary rocks, metabasic rocks, and granitoids of the lesser Himalaya in close proximity to the main central thrust (MCT). The carbonaceous slates of Haimanta group (late proterozoic to eocambrian) and the Mussoorie phosphorites (eocambrian) represent the syngenetic types. The sandstone-type is associated with the late tertiary Siwaliks of the northwestern Himalaya. The constraints in geology and uranium exploration in the Himalaya have been briefly discussed and principal uranium occurrences in relation to their tectonic environment and genesis listed. The need for geochemical characterization of the Himalayan granitoids and the metabasics related to known uranium mineralisation and new areas have been suggested. Integrated application of radiometric, geochemical and geophysical methods of prospecting and remote sensing techniques in regional geological correlation, identification of subtle rock alterations associated with mineralized zones, geologic structures, and deep crustal lineaments have been advocated. A case for the exploration of the areas of lesser Himalaya outside the MCT has been made out so as to locate hitherto unknown types of uranium deposits including, strata bound, metamorphic, and intra granitic types, possibly with better depth persistence. (author). 57 refs., 1 fig., 2 tabs

  17. 7 CFR 920.112 - Late payments.

    Science.gov (United States)

    2010-01-01

    ... Miscellaneous Provisions § 920.112 Late payments. Pursuant to § 920.41(a), interest will be charged at a 1.5 percent monthly simple interest rate. Assessments for kiwifruit shall be deemed late if not received... late charge will be assessed when payment becomes 30 days late. Interest and late payment charges shall...

  18. The contribution of remote sensing to an understanding of the geology of Gabon

    International Nuclear Information System (INIS)

    Bassot, J.P.

    1988-01-01

    A major remote-sensing operation involving radar imagery and airbone magnetism and spectrometry has been successfully conducted in Gabon. The three methods used give complementary results. Lateral radar imagery and radiometry (U, K, Th) have supplied much new information on the Upper and Lower Proterozoic, but in areas affected by intense peneplanation and lateritisation they are less effective. Conversely, Airbone magnetism gives a deeper vision into the ground: particularly it revealed that the extent of greenstone belts had been significantly underestimated on existing geological maps. In addition, the trends in these belts have given a new insight into late Archaean tectonics in northern Gabon [fr

  19. Late magmatic controls on the origin of schorlitic and foititic tourmalines from late-Variscan peraluminous granites of the Arbus pluton (SW Sardinia, Italy): Crystal-chemical study and petrological constraints

    Science.gov (United States)

    Bosi, Ferdinando; Naitza, Stefano; Skogby, Henrik; Secchi, Francesco; Conte, Aida M.; Cuccuru, Stefano; Hålenius, Ulf; De La Rosa, Nathaly; Kristiansson, Per; Charlotta Nilsson, E. J.; Ros, Linus; Andreozzi, Giovanni B.

    2018-05-01

    Tourmalines from the late-Variscan Arbus pluton (SW Sardinia) and its metamorphic aureole were structurally and chemically characterized by single-crystal X-ray diffraction, electron and nuclear microprobe analysis, Mössbauer, infrared and optical absorption spectroscopy, to elucidate their origin and relationships with the magmatic evolution during the pluton cooling stages. The Arbus pluton represents a peculiar shallow magmatic system, characterized by sekaninaite (Fe-cordierite)-bearing peraluminous granitoids, linked via AFC processes to gabbroic mantle-derived magmas. The Fe2+-Al-dominant tourmalines occur in: a) pegmatitic layers and pods, as prismatic crystals; b) greisenized rocks and spotted granophyric dikes, as clots or nests of fine-grained crystals in small miaroles locally forming orbicules; c) pegmatitic veins and pods close to the contacts within the metamorphic aureole. Structural formulae indicate that tourmaline in pegmatitic layers is schorl, whereas in greisenized rocks it ranges from schorl to fluor-schorl. Tourmalines in thermometamorphosed contact aureole are schorl, foitite and Mg-rich oxy-schorl. The main substitution is Na + Fe2+ ↔ □ + Al, which relates schorl to foitite. The homovalent substitution (OH) ↔ F at the O1 crystallographic site relates schorl to fluor-schorl, while the heterovalent substitution Fe2+ + (OH, F) ↔ Al + O relates schorl/fluor-schorl to oxy-schorl. Tourmaline crystallization in the Arbus pluton was promoted by volatile (B, F and H2O) enrichment, low oxygen fugacity and Fe2+ activity. The mineralogical evolutive trend is driven by decreasing temperature, as follows: sekaninaite + quartz → schorl + quartz → fluor-schorl + quartz → foitite + quartz. The schorl → foitite evolution represents a distinct trend towards (Al + □) increase and unit-cell volume decrease. These trends are typical of granitic magmas and consistent with Li-poor granitic melts, as supported by the absence of elbaite and other

  20. U-Pb zircon geochronology, Sr-Nd isotope geochemistry, and petrogenesis of oxidant granitoids at Keybarkuh, southwest of Khaf

    Directory of Open Access Journals (Sweden)

    Ehsan Salati

    2012-10-01

    Full Text Available Keybarkuh area is located 70 km southwest of Khaf, Khorasan Razavi province. The study area is situated in northeastern Lut block. The rock units in the area are Paleozoic metamorphic rocks and Cretaceous to Tertiary subvolcanic intrusions intruded as dike, stock and batholith; their composition varies from granite to diorite. Based on magnetic susceptibility, the intrusive rocks are divided into oxidant and reduced series. In this study, the oxidant intrusions are discussed. These intrusions are mostly high-K to shoshonitic and also meta-aluminous type. Their magma formed in subduction magmatic arc and they belong to I-type granitoid series. Enrichment of Large Ion Lithophile Elements (LILE such as Rb, Cs, K, Ba, and Th relative to High Field Stength Elements (HFSE such as Nb, Zr, and Ti supported the idea. Enrichment of Light Rare Earth Elements (LREE and depletion of Heavy Rare Earth Elements (HREE are also typical of subduction magmatism. Negative anomalies of Eu/Eu* can be attributed to the presence of residual plagioclase in a mantle source and contamination of magma by reduced continental crust. The amount of Nb > 11 ppm, lower ratio of Zr/Nb 0.706, initial 143Nd/144Nd (> 0.512 and εNd (< -3.5 indicate that magma contaminated by reduced continental crust. Hornblende biotite granodiorite porphyry dated using U-Pb zircon geochronology at 43.44 Ma (Middle Eocene. Based on calculated TDM, magma derived from ancient slab with 820 Ma age in the Keybarkuh area, was affected by the highest continental crust contamination during its ascent.

  1. Late effects from hadron therapy

    Energy Technology Data Exchange (ETDEWEB)

    Blakely, Eleanor A.; Chang, Polly Y.

    2004-06-01

    Successful cancer patient survival and local tumor control from hadron radiotherapy warrant a discussion of potential secondary late effects from the radiation. The study of late-appearing clinical effects from particle beams of protons, carbon, or heavier ions is a relatively new field with few data. However, new clinical information is available from pioneer hadron radiotherapy programs in the USA, Japan, Germany and Switzerland. This paper will review available data on late tissue effects from particle radiation exposures, and discuss its importance to the future of hadron therapy. Potential late radiation effects are associated with irradiated normal tissue volumes at risk that in many cases can be reduced with hadron therapy. However, normal tissues present within hadron treatment volumes can demonstrate enhanced responses compared to conventional modes of therapy. Late endpoints of concern include induction of secondary cancers, cataract, fibrosis, neurodegeneration, vascular damage, and immunological, endocrine and hereditary effects. Low-dose tissue effects at tumor margins need further study, and there is need for more acute molecular studies underlying late effects of hadron therapy.

  2. Isotopic geochronology of the Western Carpathian crystalline complex: the present state

    International Nuclear Information System (INIS)

    Cambel, B.; Kral, J.

    1989-01-01

    Main events in the Western Carpathian crystalline complex documented by the U-Th-Pb, Rb-Sr, K-Ar and FT methods are as follows: Regional metamorphism of sedimentary rocks from the Tatric unit documented by isotopic homogenization of the 87 Sr/ 86 Sr ratio took place 400 million years ago (Silurian-Devonian boundary). Subsequent metamorphism of these rocks is associated with intrusions of granitoid bodies. The age of rhyolite volcanism of Gelnica sequence in the Gemericum is identical with that of the first stage of regional metamorphism. Granitoid plutonism covers a long time interval ranging from 390 to 280 million years. The presence of late Alpine granites has not yet been proved. Cooling of rocks from the crystalline complex to a temperature of ca. 270 degC was attained in the Tatric rocks ca. 300 million years ago and in the Veporic (Gemeric) rocks ca. 90-120 million years ago. The latest post-orogenic uplift differs in the Tatricum (most often Miocene) and the Veporicum (Upper Cretaceous). (author). 8 fis., 1 tab., 51 refs

  3. Piedra lata terrane of Uruguay: Rb-Sr geochronological data of two new paleoproterozoic (transamazonian) granitoids

    International Nuclear Information System (INIS)

    Cingolani, C; Bossi, J; Varela, R; Maldonado, S.; Pineyro, D.; Schipilov, A

    2001-01-01

    The Precambrian basement of Uruguay consists of three major terranes separated and crosscut by wide NE-striking subvertical transcurrent shear zones. The western terrane as a part of the Rio de la Plata Craton is known as the Piedra Alta Terrane (PAT). This is separated from the Nico Perez Terrane by the Sarandi del Yi-Piri olis subvertical shear zone (Bossi et al., 1993). A mafic dykes complex intruded the PAT at 1.8 Ga and was not later deformed. The PAT has equivalent rocks in the igneous-metamorphic basement of Tandilia region and the Martin Garcia Island, Buenos Aires Province, Argentina (Dalla Salda et al., 1988; Cingolani and Dalla Salda, 2000). The PAT shows no evidence of the Neoproterozoic orogenies and is considered a best preserved Paleoproterozoic block (Transamazonian Cycle). It contains three E-W trending belts of volcano-sedimentary rocks with low grade metamorphism. These are from south to north: Pando, San Jose and Andresito belts (Bossi et al., 1996). Associated with them, three granitic-gneissic zones he Ecilda Paullier, Florida and Feliciano- were recognized with magmatic intrusives emplaced at different crustal levels. The San Jose belt is the largest supracrustal unit and contains abundant volcanic and volcaniclastic rocks of low grade metamorphic (Paso Severino Fm.) with sheets of granitic rocks intercalated (Mutti et al., 1996; Bossi et al., 1996). The associated granitic rocks are of large areal extension, mostly granodiorites and tonalites, and minor monzogranite and gabbro (e.g. Cerro Rospide region), including xenoliths from Paso Severino Fm. Towards the north of the San Jose belt an important Florida granitized zone is developed in the central part of the PAT, where the Pintos massif was recognized. The main purpose of this contribution is to offer new Rb-Sr geochronological data from two granitoid units, The Cerro Rospide intrusive in Paso Severino Fm. and Pintos massif included in medium grade migmatic-metamorphic complex and its

  4. Personality in Late Midlife

    DEFF Research Database (Denmark)

    Mortensen, Erik Lykke; Flensborg-Madsen, Trine; Molbo, Drude

    2014-01-01

    To analyze associations in late midlife between sex, age, education and social class, and the Big Five personality traits; to analyze associations between personality traits and cognitive ability in late midlife; and to evaluate how these associations are influenced by demographic factors....

  5. Trace element and Sr-Nd-Pb isotope geochemistry of Rungwe Volcanic Province, Tanzania: Implications for a superplume source for East Africa Rift magmatism

    Directory of Open Access Journals (Sweden)

    Paterno R Castillo

    2014-09-01

    Full Text Available The recently discovered high, plume-like 3He/4He ratios at Rungwe Volcanic Province (RVP in southern Tanzania, similar to those at the Main Ethiopian Rift in Ethiopia, strongly suggest that magmatism associated with continental rifting along the entire East African Rift System (EARS has a deep mantle contribution (Hilton et al., 2011. New trace element and Sr-Nd-Pb isotopic data for high 3He/4He lavas and tephras from RVP can be explained by binary mixing relationships involving Early Proterozoic (+/- Archaean lithospheric mantle, present beneath the southern EARS, and a volatile-rich carbonatitic plume with a limited range of compositions and best represented by recent Nyiragongo lavas from the Virunga Volcanic Province also in the Western Rift. Other lavas from the Western Rift and from the southern Kenya Rift can also be explained through mixing between the same endmember components. In contrast, lavas from the northern Kenya and Main Ethiopian rifts can be explained through variable mixing between the same mantle plume material and the Middle to Late Proterozoic lithospheric mantle, present beneath the northern EARS. Thus, we propose that the bulk of EARS magmatism is sourced from mixing among three endmember sources: Early Proterozoic (+/- Archaean lithospheric mantle, Middle to Late Proterozoic lithospheric mantle and a volatile-rich carbonatitic plume with a limited range of compositions. We propose further that the African Superplume, a large, seismically anomalous feature originating in the lower mantle beneath southern Africa, influences magmatism throughout eastern Africa with magmatism at RVP and Main Ethiopian Rift representing two different heads of a single mantle plume source. This is consistent with a single mantle plume origin of the coupled He-Ne isotopic signatures of mantle-derived xenoliths and/or lavas from all segments of the EARS (Halldorsson et al., 2014.

  6. Insights into crystal growth rates from a study of orbicular granitoids from western Australia

    Science.gov (United States)

    Zhang, J.; Lee, C. T.

    2017-12-01

    The purpose of this study is to develop new tools for constraining crystal growth rate in geologic systems. Of interest is the growth of crystals in magmatic systems because crystallization changes the rheology of a magma as well as provides surfaces on which bubbles can nucleate. To explore crystal growth in more detail, we conducted a case study of orbicular granitoids from western Australia. The orbicules occur as spheroids dispersed in a granitic matrix. Most orbicules have at least two to three concentric bands, composed of elongate and radially oriented hornblende surrounded by interstitial plagioclase. We show that mineral modes and hence bulk composition at the scale of the band is homogeneous from rim to core. Crystal number density decreases and crystal size increases from rim to core. These observations suggest that the orbicules crystallized rapidly from rim to core. We hypothesize that the orbicules are blobs of hot dioritic liquid injected into a cold granitic magma and subsequently cooled and solidified. Crystals stop growing when the mass transport rate tends to zero due to the low temperature. We estimated cooling timescales based on conductive cooling models, constraining crystal growth rates to be 10-6 to 10-5 m/s. We also show that the oscillatory banding is controlled by disequilibrium crystallization, wherein hornblende preferentially crystallizes, resulting in the diffusive growth of a chemical boundary layer enriched in plagioclase component, which in turns results in crystallization of plagioclase. We show that the correlation between the width of each crystallization couplet (band) with distance from orbicule rim is linear, with the slope corresponding to the square root of the ratio between chemical diffusivity in the growth medium and thermal diffusivity. We estimate chemical diffusivity of 2*10-7 m2/s, which is remarkably fast for silicate liquids but reasonable for diffusion in hot aqueous fluids, suggesting that crystallization

  7. Heat flow, heat generation and crustal thermal structure of the northern block of the South Indian Craton

    Science.gov (United States)

    Gupta, Mohan L.; Sharma, S. R.; Sundar, A.

    Heat flow values and heat generation data calculated from the concentration of heat producing radioactive elements, U, Th and K in surface rocks were analyzed. The South Indian Craton according to Drury et al., can be divided into various blocks, separated by late Proterozoic shear belts. The northern block comprises Eastern and Western Dharwar Cratons of Rogers (1986), Naqvi and Rogers (1987) and a part of the South Indian granulite terrain up to a shear system occupying the Palghat-Cauvery low lands. The geothermal data analysis clearly demonstrates that the present thermal characteristics of the above two Archaean terrains of the Indian and Australian Shields are quite similar. Their crustal thermal structures are likely to be similar also.

  8. Heat flow, heat generation and crustal thermal structure of the northern block of the South Indian Craton

    Science.gov (United States)

    Gupta, Mohan L.; Sharma, S. R.; Sundar, A.

    1988-01-01

    Heat flow values and heat generation data calculated from the concentration of heat producing radioactive elements, U, Th and K in surface rocks were analyzed. The South Indian Craton according to Drury et al., can be divided into various blocks, separated by late Proterozoic shear belts. The northern block comprises Eastern and Western Dharwar Cratons of Rogers (1986), Naqvi and Rogers (1987) and a part of the South Indian granulite terrain up to a shear system occupying the Palghat-Cauvery low lands. The geothermal data analysis clearly demonstrates that the present thermal characteristics of the above two Archaean terrains of the Indian and Australian Shields are quite similar. Their crustal thermal structures are likely to be similar also.

  9. Late effects of childhood leukemia therapy.

    Science.gov (United States)

    Fulbright, Joy M; Raman, Sripriya; McClellan, Wendy S; August, Keith J

    2011-09-01

    As survival rates for children treated for childhood cancers become significantly better, the focus is increasingly on determining the late effects of treatments and the best ways to monitor for them and prevent their occurrence. This review focuses on recent literature discussing the late effects of treatment in patients treated for acute myeloid leukemia and acute lymphoblastic leukemia during childhood. The late effects of therapy for childhood leukemia include secondary malignancy, cardiotoxicity, obesity, endocrine abnormalities, reproductive changes, neurocognitive deficits, and psychosocial effects. As clinicians have become more aware of the late effects of therapy, treatment regimens have been changed to decrease late effects, but patients still require long-term follow-up for their prevention and treatment.

  10. Geological and geophysical investigations in the selection and characterization of the disposal site for high-level nuclear waste in Finland

    Energy Technology Data Exchange (ETDEWEB)

    Paulamaki, S.; Paananen, M.; Kuivamaki, A. [Geological Survey of Finland, Espoo (Finland); Wikstrom, L. [Posiva Oy, Olkiluoto (Finland)], e-mail: seppo.paulamaki@gtk.fi

    2011-07-01

    Two power companies, Teollisuuden Voima Oy (TVO) and Fortum Power and Heat Oy, are preparing for the final disposal of spent nuclear fuel deep in the Finnish bedrock. In the initial phase of the site selection process in the late 1970s and early 1980s, the Geological Survey of Finland (GTK) examined the general bedrock factors that would have to be taken into account in connection with final disposal with reference to the international guidelines adapted to Finnish conditions. On the basis of extensive basic research data, it was concluded that it is possible to find a potential disposal site that fulfils the geological safety criteria. In the subsequent site selection survey covering the whole of Finland, carried out by GTK in 1983-1985, 101 potential investigation areas were discovered. Eventually, five areas were selected by TVO for preliminary site investigations: Romuvaara and Veitsivaara in the Archaean basement complex, Kivetty and Syyry in the Proterozoic granitoid area, and Olkiluoto (TVO's NPP site) in the Proterozoic migmatite area. The preliminary site investigations at the selected sites in 1987-1992 comprised deep drillings together with geological, geophysical, hydrogeological and hydrogeochemical investigations. A conceptual geological bedrock model was constructed for each site, including lithology, fracturing, fracture zones and hydrogeological conditions. On the basis of preliminary site investigations, TVO selected Romuvaara, Kivetty and Olkiluoto for detailed site investigations to be carried out during 1993-2000. After the feasibility studies, the island of Haestholmen, where Fortum's Loviisa nuclear power plant is located, was added to the list of potential disposal sites. In the detailed site investigations, additional data on bedrock were gathered, the previous conceptual geological, hydrogeological and hydrogeochemical models were complemented, the rock mechanical properties of the bedrock were examined, and the constructability

  11. Geological and geophysical investigations in the selection and characterization of the disposal site for high-level nuclear waste in Finland

    Energy Technology Data Exchange (ETDEWEB)

    Paulamaki, S; Paananen, M; Kuivamaki, A [Geological Survey of Finland, Espoo (Finland); Wikstrom, L. [Posiva Oy, Olkiluoto (Finland)], e-mail: seppo.paulamaki@gtk.fi

    2011-07-01

    Two power companies, Teollisuuden Voima Oy (TVO) and Fortum Power and Heat Oy, are preparing for the final disposal of spent nuclear fuel deep in the Finnish bedrock. In the initial phase of the site selection process in the late 1970s and early 1980s, the Geological Survey of Finland (GTK) examined the general bedrock factors that would have to be taken into account in connection with final disposal with reference to the international guidelines adapted to Finnish conditions. On the basis of extensive basic research data, it was concluded that it is possible to find a potential disposal site that fulfils the geological safety criteria. In the subsequent site selection survey covering the whole of Finland, carried out by GTK in 1983-1985, 101 potential investigation areas were discovered. Eventually, five areas were selected by TVO for preliminary site investigations: Romuvaara and Veitsivaara in the Archaean basement complex, Kivetty and Syyry in the Proterozoic granitoid area, and Olkiluoto (TVO's NPP site) in the Proterozoic migmatite area. The preliminary site investigations at the selected sites in 1987-1992 comprised deep drillings together with geological, geophysical, hydrogeological and hydrogeochemical investigations. A conceptual geological bedrock model was constructed for each site, including lithology, fracturing, fracture zones and hydrogeological conditions. On the basis of preliminary site investigations, TVO selected Romuvaara, Kivetty and Olkiluoto for detailed site investigations to be carried out during 1993-2000. After the feasibility studies, the island of Haestholmen, where Fortum's Loviisa nuclear power plant is located, was added to the list of potential disposal sites. In the detailed site investigations, additional data on bedrock were gathered, the previous conceptual geological, hydrogeological and hydrogeochemical models were complemented, the rock mechanical properties of the bedrock were examined, and the constructability and the

  12. Geochronology, radiogenic isotope geochemistry, and petrogenesis of Sang bast Paleo-tethys monzogranite, Mashhad, Iran

    International Nuclear Information System (INIS)

    Karimpour, M. H.; Farmer, G.L.; Stern, C.R.

    2010-01-01

    The study area is located in northeastern Iran (south of Mashhad). Paleo-Tethys Ocean opened during Silurian time and subduction under Turan plate was started in Late Devonian. By Late Triassic (225 Ma) there was no Paleo-Tethys left on an Iranian transect, therefore Turan plate obducted over Iran Plate. Two stages of low grade regional metamorphism are exposed, that are related to Hercynian (Late Paleozoic) and Cimmerian (Jurassic) oro genies. The Paleo-Tethys remnants (meta-ophiolite and meta-flysch) were intruded by Sang bast monzogranite. Chemically, monzogranite is moderately peraluminous S-type granitoid. It has low values of magnetic susceptibility [(5 to 11) * 10 -5 SI] therefore it is classified as belonging to the ilmenite-series of reduced type granitoids. Monzogranite is characterized by strong light rare earth element enrichment and less low heavy rare earth element. All samples have very small negative Eu anomalies (Eu/Eu * = 0.62 to 0.88). Total rare earth element content of monzogranite is between 212-481 ppm. The result of U-Pb zircon age dating of monzogranite is 201.3 ± 3.6 Ma (Upper Triassic, Rhaetian time). The initial 87 Sr/ 86 Sr and 143 Nd/ 144 Nd ratios for monzogranite is (0.706776 and 0.512219) when recalculated to an age of 201 Ma, consistent with the new radiometric. The initial 87 Sr/ 86 Sr and 143 Nd/ 144 Nd ratios for slate is (0.720613 and 0.511601) respectively when recalculated to an age of 201 Ma, consistent with the new radiometric results. Initial εNd isotope values for monzogranite is -3.13 and the slate is -15.19. Based on radiogenic isotopic data and rare earth element monzogranite magma originated either from lower continental crust which was very different from slate or it is originated from mantle and contaminated in continental crust during ascending.

  13. Geochronology and geochemistry of Mesozoic intrusive rocks in the Xing'an Massif of NE China: Implications for the evolution and spatial extent of the Mongol-Okhotsk tectonic regime

    Science.gov (United States)

    Li, Yu; Xu, Wen-Liang; Tang, Jie; Pei, Fu-Ping; Wang, Feng; Sun, Chen-Yang

    2018-04-01

    This study presents new zircon U-Pb-Hf and whole-rock geochemical data for intrusive rocks in the Xing'an Massif of NE China, with the aim of furthering our understanding of the evolution and spatial influence of the Mongol-Okhotsk tectonic regime. Zircon U-Pb dating indicates that five stages of Mesozoic magmatism are recorded in the Xing'an Massif, namely during the Middle Triassic ( 237 Ma), the Late Triassic ( 225 Ma), the Early Jurassic ( 178 Ma), the Middle Jurassic ( 168 Ma), and the late Early Cretaceous ( 130 Ma). The Middle Triassic-Early Jurassic intrusive rocks in the Xing'an Massif are dominantly granodiorites, monzogranites, and syenogranites that formed from magma generated by partial melting of newly accreted continental crust. Geochemistry of the Middle Triassic-Early Jurassic granitoid suites of the Xing'an Massif indicates their formation at an active continental margin setting, related to the southwards subduction of the Mongol-Okhotsk oceanic plate. The Middle Jurassic monzogranites in the Xing'an Massif are geochemically similar to adakites and have εHf(t) values (+3.8 to +5.8) and Hf two-stage model ages (TDM2; 979-850 Ma) that are indicative of derivation from magma generated by partial melting of thickened juvenile lower crust. The Middle Jurassic monzogranites formed in a compressional setting related to the closure of the Mongol-Okhotsk Ocean. The late Early Cretaceous intrusive rocks in the Xing'an Massif are dominated by A-type granitoids that are associated with bimodal volcanic rocks, suggesting their formation in an extensional environment related to either (i) delamination of a previously thickened region of the crust, associated with the Mongol-Okhotsk tectonic regime; (ii) the subduction of the Paleo-Pacific Plate; or (iii) the combined influence of these two tectonic regimes.

  14. Multiple crust reworking in the French Armorican Variscan belt: implication for the genesis of uranium-fertile leucogranites

    Science.gov (United States)

    Ballouard, C.; Poujol, M.; Zeh, A.

    2018-03-01

    Muscovite peraluminous granites (MPGs) form by partial melting of the continental crust and can be related to metalliferous deposits such as tin, tungsten, and uranium (U). Metal enrichment in MPGs commonly results from fractional crystallization, but the metal contents of the source play a major role for their fertility. Between ca. 320 and 300 Ma (Late Carboniferous), the French Armorican Variscan belt was intruded by numerous U-fertile MPGs that contain inherited zircon grains with a wide range of ages from Archean-to-Carboniferous. U-Pb and Hf isotopic data of zircon grains from Brioverian-to-Carboniferous sediments, Cambrian-to-Early Carboniferous granitoids, and Late Carboniferous MPGs indicate that the crust of the Armorican Massif is made up by detritus mainly derived from the West African craton (3500-1600 Ma; T DM = 3.8-2.3 Ga), Grenvillian belt (1200-900 Ma; T DM = 2.7-1.2 Ga), and Avalonian-Cadomian belt (800-550 Ma; T DM = 2.5-0.8 Ga) and that the crust was affected by magmatic events at 510-470 Ma (T DM = 1.6-0.6 Ga), 410-330 Ma (T DM = 1.6-1 Ga), and 320-300 Ma. Furthermore, they reveal that the Late Carboniferous MPGs were mainly formed by partial melting of Brioverian sediments with Cambro-Ordovician and Devonian-Carboniferous granitoids, which are all genetically linked with each other and characterized by Th/U < 4. The new data suggest that the U-fertile MPGs result from multiple reworking of U-rich Brioverian sediments, deposited ca. 550 Ma ago on the northern margin of Gondwana, and partially molten during several Paleozoic events, causing a successive increase in U content in the middle-upper crust.

  15. LATE VISION: PROCESSES AND EPISTEMIC STATUS

    Directory of Open Access Journals (Sweden)

    Athanassios eRaftopoulos

    2011-12-01

    Full Text Available In this paper, I examine the processes that occur in late vision and address the problem of whether late vision should be construed as a properly speaking perceptual stage, or as a thought-like discursive stage. Specifically, I argue that late vision, its (partly conceptual nature notwithstanding, neither is constituted by nor does it implicate what I call pure thoughts, that is, propositional structures that are formed in the cognitive areas of the brain through, and participate in, discursive reasoning and inferences. At the same time, the output of late vision, namely an explicit belief concerning the identity and category membership of an object (that is, a recognitional belief or its features, eventually enters into discursive reasoning. Using Jackendoff’s distinction between visual awareness, which characterizes perception, and visual understanding, which characterizes pure thought, I claim that the contents of late vision belong to visual awareness and not to visual understanding and that although late vision implicates beliefs, either implicit or explicit, these beliefs are hybrid visual/conceptual constructs and not pure thoughts. Distinguishing between these hybrid representations and pure thoughts and delineating the nature of the representations of late vision lays the ground for examining, among other things, the process of conceptualization that occurs in visual processing and the way concepts modulate perceptual content affecting either its representational or phenomenal character. I also do not discuss the epistemological relations between the representations of late vision and the perceptual judgments they ‘support’, or ‘guide’ or ‘render possible’ or ‘evidence’ or ‘entitle’. However, the specification of the epistemology of late vision lays the ground for attacking that problem as well.

  16. Petrogenesis of Mesozoic granites in the Xitian, South China: Evidence from whole-rock geochemistry and zircon isotopes

    Science.gov (United States)

    Liu, Q.; Sun, J.; He, M.; Hou, Q.; Niu, R.

    2017-12-01

    Mesozoic granitoids are widespread in southeastern China, which accompanied with lots of world-famous polymetallic deposits. The mineralization is believed to be related to the Mesozoic granitic magmatism. However, the petrogenesis of these granites and their relation to the mineralization are still debated. As a typical granitic pluton, Xitian granites from the eastern Hunan Province are formed during this period and associated with tungsten-tin deposit. Whole-rock geochemical, SIMS zircon geochronology and oxygen isotopes, as well as LA-ICPMS zircon Lu-Hf isotopic analyses, were carried out on a suite of rocks from Xitian granitic pluton to constrain their magmatic sources and petrogenesis. Xitian granitic pluton is mainly composed of biotite adamellite, biotite granite, fine-grained granite. SIMS and LA-ICPMS U-Pb dating of zircons indicate that there are two episodes of these rocks, i.e., Late Triassic granites (227-233Ma) and Late Jurassic granites (150-154Ma). The Xitian granites are silica-rich, potassic and weakly peraluminous. Petrographic and geochemical features show that they are highly fractionated I-type granites. The combined elemental and isotopic results indicated that the Late Triassic granite in Xitian area experienced a process of crystal fractionation of crustal-derived magmas coupled with strong assimilation of the surrounding rocks. The occurrence of Jurassic granitoids in Xitian area is attributed to ascending of mantle-derived magmas, which provide heat for partial melting of crustal materials. The Late Jurassic granite may be derived from juvenile crust or partial melting of ancient crustal rocks, whereas high degrees of crystal fractionation further enriched tungsten-tin in the evolved granitic rocks. This work was financially supported by the Research Cooperation between Institute and University of Chinese Academy of Sciences grant (Y552012Y00), Public Welfare Project of the Ministry of land and Resources of China (201211024

  17. Late prematurity: a systematic review

    Directory of Open Access Journals (Sweden)

    Luís Carlos Machado Júnior

    2014-06-01

    Full Text Available Objective: this study aimed to review the literature regarding late preterm births (34 weeks to 36 weeks and 6 days of gestation in its several aspects. Sources: the MEDLINE, LILACS, and Cochrane Library databases were searched, and the references of the articles retrieved were also used, with no limit of time. Data synthesis: numerous studies showed a recent increase in late preterm births. In all series, late preterm comprised the majority of preterm births. Studies including millions of births showed a strong association between late preterm birth and neonatal mortality. A higher mortality in childhood and among young adults was also observed. Many studies found an association with several neonatal complications, and also with long-term disorders and sequelae: breastfeeding problems, cerebral palsy, asthma in childhood, poor school performance, schizophrenia, and young adult diabetes. Some authors propose strategies to reduce late preterm birth, or to improve neonatal outcome: use of antenatal corticosteroids, changes in some of the guidelines for early delivery in high-risk pregnancies, and changes in neonatal care for this group. Conclusions: numerous studies show greater mortality and morbidity in late preterm infants compared with term infants, in addition to long-term disorders. More recent studies evaluated strategies to improve the outcomes of these neonates. Further studies on these strategies are needed.

  18. Excess Ar in biotites from the Broderick Falls (Webuye) area, western Kenya: implications for the tectonothermal history of the Mozambique Belt and its Archaean foreland

    Science.gov (United States)

    Shibata, K.; Suwa, K.; Uchiumi, S.; Agata, T.

    1996-10-01

    RbSr whole rock and KAr mineral age determinations were made on rocks from the Broderick Falls (Webuye) area, western Kenya. Granitic rocks yielded a RbSr whole rock isochron age of 2555 ± 101 Ma with an initial {87Sr}/{86Sr} ratio of 0.70121 ± 0.00038. This age represents the time of granitoid emplacement. KAr mineral ages range from 574 to 3420 Ma, which is very variable with respect to mineral type and locality. Mylonitic granodiorite very close to the Nandi Escarpment gave a KAr age of 916 Ma from biotite, suggesting the time of the activity of the Nandi Fault, which may be an earlier phase of the Pan-African Orogeny. Ages of biotites in a zone between 4 and 6 km northeast of the Nandi Fault are anomalously high compared to those of coexisting hornblende and the RbSr isochron age, confirming the existence of excess 40Ar in biotite. Excess 40Ar was probably introduced into biotite under the appropriate temperature conditions prevailing near the Nandi Fault. Taramite, a rare sodic-calcic amphibole, was found in a cordierite-biotite gneiss of the Kavirondian Supergroup and gave a typical Pan-African KAr age of 574 Ma. The last Pan-African metamorphism occurred in the terrane east of the Surongai Thrust.

  19. Geochemical criteria for distinguishing magmatic and metasomatic albite-enrichment in granitoids — examples from the Ta-Li granite Yichun (China) and the Sn-W deposit Tikus (Indonesia)

    Science.gov (United States)

    Schwartz, M. O.

    1992-03-01

    Two examples of albite-rich granitoids of different genesis are discussed: the Ta-Li granite at Yichun (China) exhibits dominantly igneous textures, and the sodium-enrichment zone in biotite granite of the Sn-W deposit at Tikus is characterized by metasomatic textures. The Yichun stock shows a magmatic evolution from biotite-muscovite granite to lepidolite granite with an increase of Na2O and F concentrations and a decrease of CaO and Sr concentrations. The composition of the different granite phases is close to pseudoternary minima in the haplogranite-H2O(-Li-F) system. The composition of the F-rich albitization zone at Tikus deviates strongly from the pseudoternary minima and shows a tendency to become monomineralic (nearly pure albitite). CaO and Sr concentrations are increased or remain unchanged with respect to the unaltered biotite granite at Tikus. Albitization produced by fluid-rock interaction in F-rich systems is characterized by that CaO or Sr released by the breakdown of plagioclase in the granite protolith, are fixed in newly formed fluorite or albite, respectively.

  20. Early mantle differentiation: constraint from 146Sm-142Nd systematics

    International Nuclear Information System (INIS)

    Caro, G.

    2005-07-01

    We present new ultra-high precision 142 Nd/ 144 Nd measurements of early Archaean rocks using the new generation thermal ionization mass spectrometer TRITON. Repeated measurements of the Ames Nd standard demonstrate that the 142 Nd/ 144 Nd ratio can be determined with external precision of 2 ppm (2s), allowing confident resolution of anomalies as small as 5 ppm. A major analytical improvement lies in the elimination of the double normalization procedure required to correct our former measurements from a secondary mass fractionation effect. Our new results indicate that metasediments, meta-basalts and orthogneisses from the 3.6 - 3.8 Ga West Greenland craton display positive 142 Nd anomalies ranging from 8 to 15 ppm. Using a simple two-stage model with initial e 143 Nd value of 1.9 ± 0.6 e-units, coupled 147 Sm- 143 Nd and 146 Sm- 142 Nd chronometry constrains mantle differentiation to 50 to 200 Ma after formation of the solar system. This chronological constraint is consistent with differentiation of the Earth's mantle during the late stage of crystallization of a magma ocean. We have developed a two-box model describing 142 Nd and 143 Nd isotopic evolution of depleted mantle during the subsequent evolution of the crust-mantle system. Our results indicate that early terrestrial proto-crust had a lifetime of ca. 500 Ma in order to produce the observed Nd isotope signature of Archaean rocks. In the context of this two box mantle-crust system, we model the evolution of isotopic and chemical heterogeneity of depleted mantle as a function of the mantle stirring time. Using the dispersion of 142 Nd/ 144 Nd and 143 Nd/ 144 Nd ratios observed in early Archaean rocks, we constrain the stirring time of early Earth's mantle to 100 - 150 Ma, a factor of 5 to 10 shorter than stirring time inferred from modern oceanic basalts. (author)

  1. Early mantle differentiation: constraint from {sup 146}Sm-{sup 142}Nd systematics; Radioactivite eteinte du {sup 146}Sm et differenciation precoce du manteau terrestre

    Energy Technology Data Exchange (ETDEWEB)

    Caro, G

    2005-07-15

    We present new ultra-high precision {sup 142}Nd/{sup 144}Nd measurements of early Archaean rocks using the new generation thermal ionization mass spectrometer TRITON. Repeated measurements of the Ames Nd standard demonstrate that the {sup 142}Nd/{sup 144}Nd ratio can be determined with external precision of 2 ppm (2s), allowing confident resolution of anomalies as small as 5 ppm. A major analytical improvement lies in the elimination of the double normalization procedure required to correct our former measurements from a secondary mass fractionation effect. Our new results indicate that metasediments, meta-basalts and orthogneisses from the 3.6 - 3.8 Ga West Greenland craton display positive {sup 142}Nd anomalies ranging from 8 to 15 ppm. Using a simple two-stage model with initial e{sup 143}Nd value of 1.9 {+-} 0.6 e-units, coupled {sup 147}Sm-{sup 143}Nd and {sup 146}Sm-{sup 142}Nd chronometry constrains mantle differentiation to 50 to 200 Ma after formation of the solar system. This chronological constraint is consistent with differentiation of the Earth's mantle during the late stage of crystallization of a magma ocean. We have developed a two-box model describing {sup 142}Nd and {sup 143}Nd isotopic evolution of depleted mantle during the subsequent evolution of the crust-mantle system. Our results indicate that early terrestrial proto-crust had a lifetime of ca. 500 Ma in order to produce the observed Nd isotope signature of Archaean rocks. In the context of this two box mantle-crust system, we model the evolution of isotopic and chemical heterogeneity of depleted mantle as a function of the mantle stirring time. Using the dispersion of {sup 142}Nd/{sup 144}Nd and {sup 143}Nd/{sup 144}Nd ratios observed in early Archaean rocks, we constrain the stirring time of early Earth's mantle to 100 - 150 Ma, a factor of 5 to 10 shorter than stirring time inferred from modern oceanic basalts. (author)

  2. Detrital zircon ages in Buller and Takaka terranes, New Zealand : constraints on early Zealandia history

    International Nuclear Information System (INIS)

    Adams, C.J.; Mortimer, N.; Campbell, H.J.; Griffin, W.L.

    2015-01-01

    Detrital zircon ages are presented for 34 early Palaeozoic sandstones from Buller and Takaka terranes, New Zealand, and formerly adjacent parts of Australia-Antarctica. The Buller-Takaka datasets always have two major groups: Ordovician-late Neoproterozoic, 444-700 Ma (but mainly 540-700 Ma), termed 'Gondwana Assembly' (GA), and early Neoproterozoic-Mesoproterozoic, 700-1600 Ma (but mainly 900-1200 Ma), termed 'Rodinia Assembly' (RA). In both terranes, significant age components within these groups are strikingly similar and also have RA/GA ratios, 0.6-1.8. The Cambrian volcanic arc of the Takaka Terrane has contributed little to the zircon patterns. Proportions of Late Cambrian-Early Ordovician zircons, characteristic of granitoid sources in the Ross-Delamerian Orogen are low. The zircons are predominantly reworked with contemporary zircons only evident in a few Buller datasets. The zircon patterns suggest that two major sources (late Mesoproterozoic and late Neoproterozoic), enduring over 120 Ma, were widely distributed and it is postulated they form Precambrian basement beneath southern Zealandia. (author).

  3. Coping – Late Side Effects

    Science.gov (United States)

    Cancer treatment can cause late side effects that may not show up for months or years after treatment. These late effects may include heart and lung problems, bone loss, eye and hearing changes, lymphedema, and other problems

  4. Geological and geochemical characteristics of the Heerenveen and Mpuluzi batholiths south of the Barberton greenstone belt and preliminary thoughts on their petrogenesis

    International Nuclear Information System (INIS)

    Anhaeusser, C.R.; Robb, L.J.

    1982-01-01

    The Archaean granitic terrane south and south-west of the Barberton greenstone belt consists predominantly of an older suite of tonalitic and trondhjemitic gneisses into which have been emplaced two large multi-component granitoid bodies known as the Heerenveen and Mpuluzi batholiths. Although geochronologic and Sr-isotopic studies demonstrate that there is little distinction between the ages and initial ratios of the various phases associated with these batholiths, each body displays contrasting textural and geochemical characteristics. The oldest phase is represented by coarse porphyritic granitic rocks into which is intruded a medium-to-fine-grained homogeneous granodioritic phase. Both phases are components of a bimodal association that is, in turn, intruded by a third phase which includes medium-grained pink or grey granodiorite and adamellite dykes feeding a homogeneous sheet-like carapace over-lying the coarser porphyritic granites. A fourth phase, consisting predominantly of potassic migmatites and gneisses, occurs in the areas rimming the batholiths and represents the product of interaction between the batholith magmas and components of the pre-existing crust in the region. Geochemically, the Heerenveen batholith has trondhjemitic affinities whereas the Mpuluzi batholith consists predominantly of potassic granites. Together with the Nelspruit batholith north of the Barberton greenstone belt the three granitic bodies show a progression in actual values of K 2 O, Na 2 O, Rb, and Sr with the Nelspruit body having chemical characteristics intermediate between the two

  5. Geochemistry and petrogenesis of Neoproterozoic Mylliem ...

    Indian Academy of Sciences (India)

    the Mylliem granitoids is depicted by (Ce/Yb)N values, which show a range of 1.39 to 1.65. ... granitoid pluton intrusive into the Shillong Group ..... vs. SiO2 diagram (Frost et al 2001) (figure 6a). MALI of Mylliem granitoids ranges from 4.46.

  6. Cohort Profile: The Danish Testicular Cancer Late Treatment Effects Cohort (DaTeCa-LATE

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    Michael Kreiberg

    2018-02-01

    Full Text Available The cohort was set up in order to analyze late effects in long-term testicular cancer survivors (TCS and to contribute to the design of future follow-up programs addressing and potentially preventing late effects. Data for this cross-sectional study were collected between January 1, 2014, and December 31, 2016, among living Danish TCS and 60% agreed to participate in the cohort (N = 2,572. Mean time since testicular cancer (TC diagnosis was 18 years (range 7–33 and mean age of participants was 53 years (range 25–95. Data consist of results of a questionnaire with patient reported outcomes which covers a broad range of items on late-effects. The study also included data obtained through linkages to Danish registries, a biobank, and clinical data from hospital files and pathology reports originating from the Danish Testicular Cancer Database (DaTeCa. The treatment during the observation period has been nearly the same for all stages of TC and is in agreement with today’s standard treatment, this allows for interesting analysis with a wide timespan. We have extensive data on non-responders and are able to validate our study findings. Data from a Danish reference population (N = 162,283 allow us to compare our findings with a Danish background population. The cohort can easily be extended to access more outcomes, or include new TCS. A limitation of the present study is the cross-sectional design and despite the large sample size, The Danish Testicular Cancer Late Treatment Effects Cohort (DaTeCa-LATE lacks statistical power to study very rare late effects. Since it was voluntary to participate in the study we have some selection bias, for instance, we lack responders who were not in a paired relationship, but we would still argue that this cohort of TCSs is representative for TCSs in Denmark.Collaboration and data accessResearches interested in collaboration with the DaTeCa-LATE study group please contact Professor Gedske Daugaard

  7. IVUS Findings in Late and Very Late Stent Thrombosis. A Comparison Between Bare-metal and Drug-eluting Stents.

    Science.gov (United States)

    Fuentes, Lara; Gómez-Lara, Josep; Salvatella, Neus; Gonzalo, Nieves; Hernández-Hernández, Felipe; Fernández-Nofrerias, Eduard; Sánchez-Recalde, Ángel; Alfonso, Fernando; Romaguera, Rafael; Ferreiro, José Luis; Roura, Gerard; Teruel, Luis; Gracida, Montserrat; Marcano, Ana Lucrecia; Gómez-Hospital, Joan-Antoni; Cequier, Ángel

    2018-05-01

    Stent thrombosis (ST) is a life-threatening complication after stent implantation. Intravascular ultrasound is able to discern most causes of ST. The aim of this study was to compare intravascular ultrasound findings between bare-metal stents (BMS) and drug-eluting stents (DES) in patients with late (31 days to 1 year) or very late ST (> 1 year). Of 250 consecutive patients with late or very late ST in 7 Spanish institutions, 114 patients (45.5% BMS and 54.5% DES) were imaged with intravascular ultrasound. Off-line intravascular ultrasound analysis was performed to assess malapposition, underexpansion, and neoatherosclerosis. The median time from stent implantation to ST was 4.0 years with BMS and 3.4 years with DES (P = .04). Isolated malapposition was similarly observed in both groups (36.5% vs 46.8%; P = .18) but was numerically lower with BMS (26.6% vs 48.0%; P = .07) in patients with very late ST. Isolated underexpansion was similarly observed in both groups (13.5% vs 11.3%; P = .47). Isolated neoatherosclerosis occurred only in patients with very late ST and was more prevalent with BMS (22.9%) than with DES (6.0%); P = .02. At 2.9 years' follow-up, there were 0% and 6.9% cardiac deaths, respectively (P = .06) and recurrent ST occurred in 4.0% and 5.2% of patients, respectively (P = .60). Malapposition was the most common finding in patients with late and very late ST and is more prevalent with DES in very late ST. In contrast, neoatherosclerosis was exclusively observed in patients with very late ST and mainly with BMS. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  8. Late-onset Huntington's disease: diagnostic and prognostic considerations.

    Science.gov (United States)

    Koutsis, Georgios; Karadima, Georgia; Kladi, Athina; Panas, Marios

    2014-07-01

    To address diagnostic and prognostic issues in patients with late-onset Huntington's disease (HD). We analyzed a cohort of 41 late-onset (≥60 years) HD patients and compared them to 39 late-onset patients referred for HD testing that were negative for the HD-expansion and to 290 usual-onset (20-59 years) HD patients. Disease severity was assessed by the Total Functional Capacity Scale. Late-onset HD comprised 11.5% of our HD cohort. In total, 70.7% of late-onset HD patients had positive family history compared to 15.4% of late-onset expansion-negative patients (p < 0.001). Clinical features at onset or presentation could not usefully distinguish between late-onset expansion-positive and negative patients, excepting hemichorea, which was absent from the HD group (p = 0.024). Chorea was the first clinical feature in 53.7% and a presenting feature in 90.2% of late-onset HD. The mutation hit rate for late-onset patients was 51.3%, lower than in usual-onset patients (p = 0.04). Frequencies of chorea, cognitive impairment and psychiatric manifestations at onset or presentation were not significantly different between late-onset and usual-onset HD patients. Gait unsteadiness however was more common at presentation in late-onset HD (p = 0.007). Late-onset HD patients reached a severe stage of illness on average 2.8 years earlier than usual-onset HD patients (p = 0.046). A positive family history suggestive of HD, although absent in a third of patients, remains a helpful clue in diagnosing late-onset HD. Prognosis of late-onset HD in terms of Total Functional Capacity appears no better and shows a trend of being somewhat less favorable compared to usual-onset HD. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Late effects on normal tissues: oesophagus

    International Nuclear Information System (INIS)

    Pavy, J.J.; Bosset, J.F.

    1997-01-01

    Radiation-induced late effects of oesophagus are observed after treatment of various cancers. Acute reactions, mainly oesophagitis, are well known and accurately described; late effects share, for most of these, a common consequence: alteration of the main oesophageal function, namely to conduct the food bolus; clinically they are impaired in terms of mobility and stenosis. More rarely, ulcerations and pseudodiverticulae can be observed. Chemotherapy further increases the risk of late effects, especially in case of concomitant chemo-radiotherapy. All numbers and statistical data on oesophagus late effects should be regarded with caution due to recent changes in the therapeutic attitudes (more and more combined chemotherapy-radiotherapy) and some progress in given cancer locations. A common scale like the LENT-SOMA should enable the clinician to better know these late effects on oesophagus which is required to initiate effective prevention measures and adapted treatments. (authors)

  10. Late onset endophthalmitis

    Directory of Open Access Journals (Sweden)

    Abdulaziz AlHadlaq

    2016-04-01

    Full Text Available We report an extremely rare presentation of late-onset endophthalmitis in a young adult patient with an unexposed Ahmed tube implant. The implant was inserted 11 years prior to presentation. There was no history of trauma or any obvious exposure on clinical examination and the tube plate was filled with purulent material. After aqueous and vitreous tap, the patient underwent intracameral, intravitreal subconjunctival antibiotic injections and was started on systemic antibiotics with good response. Endophthalmitis associated with tube drainage device can present as late as 11 years and even without an unexposed tube.

  11. Gratkorn - A new late Middle Miocene vertebrate fauna from Styria (Late Sarmatian, Austria)

    Science.gov (United States)

    Gross, M.; Böhme, M.; Prieto, J.

    2009-04-01

    Integrated stratigraphic approaches provide precise correlations of global standard stages with regional Paratethys stages. Nevertheless, higher resolution stratigraphic matching of terrestrial deposits remains challenging due to the lack of a practical continental biostratigraphy. The mostly used tool for biostratigraphic correlation of non-marine deposits in the Old World is still the concept of Neogene Mammal-zones (MN-zones). However, at higher biostratigraphic resolution (reptiles (scincids, lacertids, gekkonids, anguids, varanids, colubrids, testudinids, emydids), birds (coliiformes), rodents and lagomorphs (cricetids, glirids, eomyids, sciurids, castorids), insectivores and chiropterans (erinaceids, soricids, talpids), and large mammals (suids, tragulids, moschids, cervids, ?palaeomerycids, equids, chalicotheriids, rhinos, proboscidians, carnivors). Litho- and biostratigraphy (terrestrial gastropods) as well as magnetostratigraphic data and the sequence stratigraphic and geodynamic frame indicate an age of 12-12.2 Ma (early Late Sarmatian s.str., chron 5An.1n) for the locality. Therefore, Gratkorn is one of richest and most complete fauna of the late Middle Miocene of Central Europe and will be confidentially one of the key faunas for a high-resolution continental biostratigraphy and the comprehension of the faunal succession and interchanges near the Middle/Late Miocene transition. Acknowledgements This is a preliminary overview of the Gratkorn vertebrate fauna. Several taxa are still under investigation. We are especially grateful to Gudrun Daxner-Höck, Ursula Göhlich (both Natural History Museum Vienna) and Getrud Rössner (University of Munich) for their comments to the rodents, ruminants, proboscidians and bird remains. References Böhme, M., Ilg, A., Winklhofer, M. 2008. Late Miocene "washhouse" climate in Europe.- Earth and Planetary Science Letters, 275: 393-401. Gross, M., 2008. A limnic ostracod fauna from the surroundings of the Central

  12. Diurnal phase of late-night against late-afternoon of stratiform and convective precipitation in summer southern contiguous China

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rucong [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); China Meteorological Administration, LaSW, Chinese Academy of Meteorological Sciences, Beijing (China); Yuan, Weihua [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); Graduate School of the Chinese Academy of Sciences, Beijing (China); Li, Jian [China Meteorological Administration, LaSW, Chinese Academy of Meteorological Sciences, Beijing (China); Fu, Yunfei [Chinese Academy of Sciences, LASG, Institute of Atmospheric Physics, Beijing (China); University of Science and Technology of China, Laboratory of Satellite Remote Sensing and Climate Environment, Hefei, Anhui (China)

    2010-09-15

    Using the tropical rainfall measuring mission (TRMM) Precipitation Radar (PR) observations combined with the surface rain gauge data during 1998-2006, the robust diurnal features of summer stratiform and convective precipitation over the southern contiguous China are revealed by exploring the diurnal variations of rain rate and precipitation profile. The precipitation over the southern contiguous China exhibits two distinguishing diurnal phases: late-night (2200-0600 LST) and late-afternoon (1400-2200 LST), dependent on the location, precipitation type and duration time. Generally, the maximum rain rate and the highest profile of stratiform precipitation occur in the late-afternoon (late-night) over the southeastern (southwestern) China, while most of the stratiform short-duration rain rate tends to present late-afternoon peaks over the southern China. For convective precipitation, the maximum rain rate and the highest profile occur in the late-afternoon over most of the southern contiguous China, while the convective long-duration rain rate exhibits late-night peaks over the southwestern China. Without regional dependence, the convective precipitation exhibits much larger amplitude of diurnal variations in both near surface rain rate and vertical extension compared with stratiform precipitation and the convective rain top rises most rapidly between noon and afternoon. However, there are two distinctive sub-regions. The diurnal phases of precipitation there are very weakly dependent on precipitation type and duration time. Over the eastern periphery of the Tibetan Plateau, the maximum rain rate and the highest profile of either convective or stratiform precipitation occur in the late-night. Over the southeastern coastal regions, both the near surface rain rate and rain top of convective and stratiform precipitation peak in the late-afternoon. (orig.)

  13. Pukala intrusion, its age and connection to hydrothermal alteration in Orivesi, southwestern Finland

    Directory of Open Access Journals (Sweden)

    Matti Talikka

    2005-01-01

    Full Text Available The Pukala intrusion is situated in the Paleoproterozoic Svecofennian domain of the Fennoscandian Shield in the contact region between the Central Finland Granitoid Complex and the Tampere Belt. The acid subvolcanic intrusion, which is in contact or close to severalaltered domains, mainly consists of porphyritic granodiorite and trondhjemite. The Pukala intrusion was emplaced into volcanic sequence in an island-arc or fore-arc setting before or during the early stages of the main regional deformation phase of the Svecofennian orogeny. On the basis of the geochemical data, the Pukala intrusion is a peraluminous volcanic-arc granitoid. After crystallisation at 1896±3 Ma, multiphase deformation and metamorphismcaused alteration, recrystallisation, and orientation of the minerals, and tilted the intrusion steeply towards south. The 1851±5 Ma U-Pb age for titanite is connected to the late stages of the Svecofennian tectonometamorphic evolution of the region. Several hydrothermally altered domains are located in the felsic and intermediate metavolcanic rocks of the Tampere Belt within less than one kilometre south of the Pukala intrusion. Alteration is divided into three basic types: partial silica alteration, chlorite-sericite±silica alteration, and sericite alteration in shear zones. The first two types probably formed during the emplacement and crystallisation of the Pukala intrusion, and the third is linked to late shearing. Intense sericitisation and comb quartz bands in the contact of theintrusion and the altered domain at Kutemajärvi suggest that the hydrothermal system was driven by the Pukala intrusion.

  14. Geology, petrology and geochemistry of the Cacapava do Sul Granitic complex, RS

    International Nuclear Information System (INIS)

    Nardi, L.V.S.; Bitencourt, M. de F.

    1989-01-01

    The Cacapava do Sul Granitic Complex comprises mainly hornblende and biotite-rich granodioritic rocks, leucogranitoids which may contain muscovite and garnet, and transitional types of granitoids. The available data suggest that it is a diapiric intrusion synchronous, with the second regional metamorphism and deformation phase, inprinted on the country rocks and on the batholith itself. Geochemical evidences are consistent with a comagmatic character for the granitic rocks and also indicate calc-alkaline affinity, with an origin either from partial melting of the lower crust or from differentiation of mantle-derived basaltic magmas, with crustal contamination. The geochemical features indicate strong similarities with orogenic granitoids intruded in highly mature arcs. The re-evaluation of Rb-Sr data indicates an age of 549 Ma and initial ratio of 0.7051 for the leucogranites. The available data suggest that the studied complex has been emplaced during the late stages of the Brasiliano Cycle, which were marked by the development of ensialic basins and shear zones, with associated granitic magmatism. In its early stages, this orogeny may be interpreted according to the classical model, involving subduction of oceanic crust. (author) [pt

  15. The late administration of surfactant

    African Journals Online (AJOL)

    HMD and 4 as having congenital pneumonia. Overall there was a significant and sustained improvement ... 3 infants weighing> 2 400 g with congenital pneumonia responded to a single delayed dose of SRT. Late SRT is ..... pneumonia and meconium aspiration syndrome.' It does not appear that late SRT compromised the ...

  16. Geochemical and isotopic characterization of the granitic magmatism along the Remígio - Pocinhos shear zone, Borborema Province, NE Brazil

    Science.gov (United States)

    de Lima, Jefferson V.; Guimarães, Ignez de P.; Santos, Lucilene; Amorim, José Victor A.; Farias, Douglas José S.

    2017-04-01

    Two granitoid plutons (Pilõezinhos and Curral de Cima) intruded along the Remígio - Pocinhos shear zone, eastern part of the Borborema Province. The Pilõezinhos and Curral de Cima granites were dated at 566 ± 3 Ma and 618 ± 5 Ma respectively. The granitoids from both plutons have distinct initial 143Nd/144Nd ratios, expressed by εNd(t) values, i.e. the granitoids of Pilõezinhos pluton have lower εNd(t) values (-15.47 to -15.81) and negative εHf (t = 570 Ma) values (-16.0 to -18.6), while the granitoids of the Curral de Cima pluton have εNd(t) values between -1.12 and -5.23. The granitoids of the Curral de Cima pluton are epidote bearing, magnesian calcalkaline I-type granitoids, crystallized under high fO2 conditions. The granitoids of the Pilõezinhos pluton are alkaline, low-fO2, ferroan, ilmenite-series, A2-type granite intrusions. The geochemical and isotopic signatures suggest that the origin of magma of the Curral de Cima granitoids involved mixing/mingling at depth between crustal and mantle magmas, associated to decompression (lateral escape) during the convergent stage of Brasiliano/Pan/African orogeny, which lead the asthenosphere melts to rise into the lower crust. The source of magma of the granitoids of the Pilõezinhos pluton involved a strong crustal component with geochemical and isotopic signatures similar to the orthogneisses of the Serrinha-Pedro Velho Complex, and small mantle component. The emplacement of the Pilõezinhos pluton is associated to an extensional space formed during high-T strike-slip shearing developed by the synchronic movement of the Matinhas sinistral shear zone and Remígio - Pocinhos dextral shear zone.

  17. Late Onset Bipolar Disorder: Case Report

    OpenAIRE

    Filipa Araújo; Adriana Horta

    2016-01-01

    Background: Bipolar disorder affects approximately 1% of the population, with diagnosis often being made during late adolescence and early adulthood, and only rarely (0.1%) in the elderly. Late onset bipolar disorder in the elderly has a impact on the nature and course of bipolar disorder. Aims: The authors report a case of bipolar disorder emerging in late life  (76years old) with no cleary identified organic cause. Conclusion: This case highlights the importance of a broad different...

  18. 48 CFR 852.273-70 - Late offers.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Late offers. 852.273-70... SOLICITATION PROVISIONS AND CONTRACT CLAUSES Texts of Provisions and Clauses 852.273-70 Late offers. As prescribed in 873.110(a), insert the following provision: Late Offers (JAN 2003) This provision replaces...

  19. Isotope geochemistry of brasiliano age, coarsely porphyritic, K-calc-alkalic granitoids and associated K-diorites, northeast Brazil

    International Nuclear Information System (INIS)

    Sial, A.N.; Mariano, G.; Ferreira, V.P.

    1989-01-01

    Several porphyritic, K-calc-alkalic were syntectonically intruded in NE Brazil during the Brasiliano orogeny. They show bi-(qz) diorite and coarsely porphyritic granodiorite to qz monzonite ('Itaporanga-type') in commingling zones on a scale of cm to m irrespective of whether plutons are at the margins of the NE-trending Cachoeirinha-Salgueiro Fold Belt (CSF) or intruded metasediments of the Serido Fold Belt (SFB). The bi(qz) diorites are found in magmatic or stromatic structures and narrow dikes wich intruded the felsic facies. SiO 2 in the porphyritic facies ranges from 61 to 72% with K 2 O usually > Na 2 O. K-diorities exhibit SiO 2 from 50 to 58%, MgO from 2 to 10% and K 2 O from 2 to 5%. Both facies are usually Ba and Sr-enriched, with similar, highly fractionated REE patterns, lacking free of Eu anomaly. Quartz 180 values are considered homogeneous on the scale of these intrusions in the CSF, (8 to 10 per milSMOW). Bi-(qz) diorites exhibit slightly higher 180 (9.5 to 10.5 per milSMOW). In the SFB both facies are lower than 180. The oxygen isotope data for the porphyritic facies are compatible with I-type source with some metasedimentary component of variable proportion. As bi(qz) diorites were formed pre- to post-porphyritic facies intrusion, their high LREE, K and 180 reflect their source rather than the interaction with the potassic felsic magma. Preliminarly sulfur isotope values suggest that porphyritic facies of granitoids in the SBF are lower in 34S than those in the CSF. Rb and Sr isotopes reflect source heterogeneity, complicated by mixing relations. Ages span from 510 to 630 Ma suggesting that the Itaporanga-type association was formed during uplift and cooling of the Pan-African I and onset of the Pan-African II orogenies, recognized in West Africa. (author) [pt

  20. Proterozoic rifting and major unconformities in Rajasthan, and their implications for uranium mineralisation

    International Nuclear Information System (INIS)

    Sinha-Roy, S.

    2004-01-01

    Evolution of the Precambrian terrain in Rajasthan has taken place via crustal consolidation of the basement at ca. 2.9 Ga, its cratonisation at ca. 2.5 Ga, through protracted tectonostratigraphic evolution of the Proterozoic cover sequences, following repeated rifting and Wilson cycles in the Aravalli and Delhi foldbelts. Consequently, the Proterozoic rift basins are characterised by growth faults and pull-aparts, and multitier volcanose dimentary sequences that contain a number of unconformities and stratigraphic breaks. The Archaean basement of the Mewar terrain that witnessed end-Archaean K-magmatism and ductile shearing, led to the creation of a possible uranium province, namely uranium enriched basement. This province acted as the source of remobilised uranium and its concentration at suitable multilevel structural and stratigraphic traps within the Proterozoic rift basins to give rise to unconformity-related syngenetic uranium mineralisation. Late Neoproterozoic to Pan-African tectonothermal reworking of the basement rocks produced fracture zones and caused Na-metasomatism giving rise to albitite-related uranium mineralisation. Based on an analysis of Proterozoic rift kinematics and lithofacies characteristics, five possible uranium-enriched stratigraphic horizons have been identified in the Aravalli and its equivalent sequences as well as in the North Delhi foldbelt sequences. From a regional synthesis, ten possible uranium metallogenic events, spanning ca. 2.5-0.5 Ga, are recognised in Rajasthan. These uranium events have predictive value for delineation of target areas for exploration. (author)

  1. Late Effects of Polio: An Overview

    Science.gov (United States)

    ... Polio Wellness Retreats For Health Professionals The Late Effects of Polio: An Overview FRENCH | GERMAN | PORTUGUESE POLIOMYELITIS ( ... largest and most inclusive category is called Late Effects of Polio or Polio Sequelae and is defined ...

  2. Pb and O isotope systematics in granulite facies xenoliths, French Massif Central: Implications for crustal processes

    International Nuclear Information System (INIS)

    Downes, H.; Kempton, P.D.; Harmon, R.S.; Briot, D.; Leyreloup, A.F.

    1991-01-01

    Pb and O isotope data are represented for a suite of granulite facies xenoliths found within Tertiary alkaline volcanic rocks of the Massif Central, France. The suite consists of ultramafic and mafic cumulates, metagabbros which are considered to represent basic liquids, felsic meta-igneous lithologies (charnockites) and metasediments. Ranges of δ 18 O values are +6.9 to +9.8per mille for mafic xenoliths, +9.3 to +10.2per mille for felsic meta-igneous samples and +6.1 to +11.8per mille for the metasediments. By comparison, δ 18 O values for mantle peridotites from the same region range from +5.1 to +6.9per mille, whilst local Hercynian granitoids vary from +8.6 to +12.0per mille. The 206 Pb/ 204 Pb ratios of the granulite xenoliths are between 17.77 and 19.19, 207 Pb/ 204 Pb ratios vary from 15.51 to 15.69, and 208 Pb/ 204 Pb ratios range from 38.07 to 40.07. In general, metasedimentary granulites have the more radiogenic Pb isotope compositions, whereas mafic meta-igneous samples are less radiogenic. These isotopic characteristics can be explained as the result of the interaction of mafic magmas with the metasedimentary crust into which they intruded. The release of heat also provoked melting of the more fusible parts of the lower crust and led to the formation of late-orogenic Hercynian granitoids. However, an additional component which provides less radiogenic Pb is also needed in the source of the granitoids; this may be the felsic meta-igneous xenoliths or middle/upper crustal gneisses. (orig.)

  3. Relationships between the Brook Street Terrane and Median Tectonic Zone (Median Batholith) : evidence from Jurassic conglomerates

    International Nuclear Information System (INIS)

    Tulloch, A.J.; Kimbrough, D.L.; Landis, C.A.; Mortimer, N.; Johnston, M.R.

    1999-01-01

    U-Pb zircon ages of 237-180 Ma and c. 280 Ma of seven granitoid clasts from the Rainy River Conglomerate which lies within the eastern Median Tectonic Zone (Median Batholith) in Nelson, and the Barretts Formation of the Brook Street Terrane in Southland, constrain the depositional ages of both units to be no older than c. 180-200 Ma (Early Jurassic). The minimum age of the Rainy River Conglomerate is constrained by the 147 +2 -1 Ma (Latest Jurassic) emplacement age of the One Mile Gabbronorite (new name: previously western Buller Diorite). The ages and chemistry of five of the granitoid clasts are broadly compatible with derivation from rocks that are now represented by Triassic plutons of the Median Tectonic Zone (Median Batholith), although ages as young as 180 Ma are slightly outside the range of the latter as currently exposed in New Zealand. The age (273-290 Ma, 237 +/- 3 Ma) and chemistry of the other two clasts (one each from Rainy River Conglomerate and Barretts Formation) suggest derivation from the Brook Street Terrane. Similarity in stratigraphic age, depositional characteristics, granitoid clast ages and composition between Rainy River Conglomerate and Barretts Formation suggests that they are broadly correlative and collectively overlapped a combined Brook Street Terrane - Median Batholith (MTZ) before the Late Jurassic (147 +2 -1 Ma). Sedimentary overlap may also have continued across to Middle Jurassic conglomeratic strata in the Murihiku Terrane to the east of the Brook Street Terrane. A U-Pb zircon age of 261 +/- 2 Ma is reported for Pourakino Trondhjemite of the Brook Street Terrane. (author). 56 refs., 10 figs., 4 tabs

  4. Nephrogenic systemic fibrosis: late skin manifestations

    DEFF Research Database (Denmark)

    Bangsgaard, Nannie; Marckmann, Peter; Rossen, Kristian

    2009-01-01

    BACKGROUND: Nephrogenic systemic fibrosis (NSF) is a serious disease that occurs in patients with severe renal disease and is believed to be caused by gadolinium-containing contrast agents. A detailed description of the late skin manifestations of NSF is important to help dermatologists...... and nephrologists recognize the disease. OBSERVATIONS: We studied 17 patients with NSF late in the disease. All patients showed epidermal atrophy and hairlessness of the affected regions, primarily the lower legs. Affected areas were symmetrically distributed and hyperpigmented in most cases. Eleven patients showed......: This descriptive case series of patients with NSF gives a detailed clinical picture of the skin manifestations late in the disease. It demonstrates that the clinical picture in the late stage has a varied presentation and that NSF has a significant effect on the quality of life....

  5. Late somatic effects

    International Nuclear Information System (INIS)

    Gilbert, E.S.

    1989-01-01

    Late effects are by definition effects that occur at least one year, and in most cases decades, after the time of exposure. The late effects considered in this chapter are limited to latent cancer incidence and mortality, and benign thyroid disease. A model is provided for estimating risks of late effects resulting from the radiation exposure likely to be received in the event of a nuclear power plant accident. It is assumed that exposure to high-LET radiation would be negligible in such an accident, and thus only risks from low-LET exposure are evaluated. Separate estimates are provided for risks of leukemia, bone cancer, lung cancer, gastrointestinal cancers, thyroid cancer, skin cancer, and the residual group of all other cancers; estimates of leukemia and other cancers due to in utero exposure are also provided. Risks are expressed in absolute terms as the number of cancer deaths (or cases) per million persons exposed to a particular dose. Because the time of death is also important in assessing the impact of an accident, and because the quality of life after the occurrence of cancer will often be reduced, the number of years of life lost and the number of years of life lived after the occurrence of cancer are also estimated

  6. Radiobiological considerations of late effects arising from radiotherapy

    International Nuclear Information System (INIS)

    Kogelnik, H.D.; Kaercher, K.H.

    1977-01-01

    A variety of clinical and experimental data are reviewed to investigate the different factors leading to appearance of late complications. Higher individual doses per fraction are related to an increase in the incidence and severity of late effects and massive dose techniques result in catastrophic late complications. There is no apparent relation between the severity of initial skin reactions and late effects, indicating that matching of acute radiation reactions on skin or mucous membranes cannot be extrapolated to late damage in connective tissues and organs. The probability of late tissue injury increases with the volume of tissue irradiated. Several phenomena, e.g. parenchymal cell depletion, vascular injury and fibrocyte dysfunction, are likely to operate together as well as separately in the pathogenesis of late effects. The late complications of radiotherapy develop in cells with a slow proliferation, and this is consistent with the hypothesis that parenchymal cell killing may be the basis for the injury. The response of cells with a slow proliferation to a course of fractionated irradiation differs from that of rapidly proliferative cells in three biological processes: repair of potentially lethal damage, redistribution and regeneration. (author)

  7. Migration of fluids as a tool to evaluate the feasibility of the implantation of geological radioactive wastes repositories (RARN) in granitoid rocks: tests on granites submitted to natural deformation vs. not deformed

    International Nuclear Information System (INIS)

    Lopes, Nilo Henrique Balzani; Barbosa, Pedro Henrique Silva; Santos, Alanna Leite dos; Amorim, Lucas Eustáquio Dias; Freitas, Mônica Elizetti de; Rios, Francisco Javier

    2017-01-01

    Fluid composition and migration studies in granitoid rocks subjected to deformation events are a factor that should be considered in the selection of geologically favorable areas for RANR construction, and may be an excellent complement to engineering barrier designs. The research objective was to develop an academic approach, comparing the behavior of deformed and non-deformed granites, not being related to any CNEN project of deploying repositories. It is concluded that in the choice of suitable sites for the construction of repositories, granite bodies that are submitted to metamorphic / deformation / hydrothermal events or that are very fractured should be disregarded. The domes of granite batholith that have undergone hydraulic billing should also be discarded. It has been found that, because of the warming caused by radioactive decay reactions, there is a real possibility that the release of potentially abrasive fluids contained in the minerals can reach and corrode the walls of the repositories and / or packaging

  8. Polyphase Neoproterozoic orogenesis within the east Africa- Antarctica orogenic belt in central and northern Madagascar

    Science.gov (United States)

    Key, R.M.; Pitfield, P.E.J.; Thomas, Ronald J.; Goodenough, K.M.; Waele, D.; Schofield, D.I.; Bauer, W.; Horstwood, M.S.A.; Styles, M.T.; Conrad, J.; Encarnacion, J.; Lidke, D.J.; O'connor, E. A.; Potter, C.; Smith, R.A.; Walsh, G.J.; Ralison, A.V.; Randriamananjara, T.; Rafahatelo, J.-M.; Rabarimanana, M.

    2011-01-01

    Our recent geological survey of the basement of central and northern Madagascar allowed us to re-evaluate the evolution of this part of the East Africa-Antarctica Orogen (EAAO). Five crustal domains are recognized, characterized by distinctive lithologies and histories of sedimentation, magmatism, deformation and metamorphism, and separated by tectonic and/or unconformable contacts. Four consist largely of Archaean metamorphic rocks (Antongil, Masora and Antananarivo Cratons, Tsaratanana Complex). The fifth (Bemarivo Belt) comprises Proterozoic meta-igneous rocks. The older rocks were intruded by plutonic suites at c. 1000 Ma, 820-760 Ma, 630-595 Ma and 560-520 Ma. The evolution of the four Archaean domains and their boundaries remains contentious, with two end-member interpretations evaluated: (1) all five crustal domains are separate tectonic elements, juxtaposed along Neoproterozoic sutures and (2) the four Archaean domains are segments of an older Archaean craton, which was sutured against the Bemarivo Belt in the Neoproterozoic. Rodinia fragmented during the early Neoproterozoic with intracratonic rifts that sometimes developed into oceanic basins. Subsequent Mid- Neoproterozoic collision of smaller cratonic blocks was followed by renewed extension and magmatism. The global 'Terminal Pan-African' event (560-490 Ma) finally stitched together the Mid-Neoproterozoic cratons to form Gondwana. ?? The Geological Society of London 2011.

  9. Genetic models and their impact on uranium exploration in the Athabasca sandstone basin, Saskatchewan, Canada

    International Nuclear Information System (INIS)

    Strnad, J.G.

    1980-01-01

    While the Beaverlodge area of Northern Saskatchewan became an important uranium-producing district during the 1950s, the Athabasca sandstone basin, located in the immediate vicinity, was considered to be non-prospective in Canada's regional assessment. Twenty years later, with the introduction of the supergene model into the basin's exploration strategy, the favourability of the host-rock for uranium deposits was shown. However, in some instances the search for local targets was enriched by implementing non-supergene models. Most geologists originally favoured the Middle Proterozoic (sub-Helikian) unconformity as a unique ore-controlling feature. Later, the concept of Lower Proterozoic (Aphebian) syngenetic protore, as represented by graphite-bearing strata in Archaean proximity, was added. In the author's view the combination of these factors is productive only within specialized segments of Archaean-Lower Proterozoic (Archaean-Aphebian) contact zones. (author)

  10. The first 800 million years of earth's history

    Science.gov (United States)

    Smith, J. V.

    1981-01-01

    It is pointed out that there is no direct geological information on the first 750 Ma of earth history. Consequently the reported study is based on controversial inferences drawn from the moon, other planets and meteorites, coupled with backward extrapolation from surviving terrestrial rocks, especially those of Archaean age. Aspects of accretion are considered, taking into account cosmochemical and cosmophysical evidence, a new earth model, and convection systems. Attention is given to phase-equilibrium constraints, estimates of heat production, the bombardment history of the moon and implications for the earth, and the nature of the early crust. From a combination of physical, chemical, and petrological arguments, it is concluded that the earth's surface underwent intense volcanism in the pre-Archaean era, and that the rock types were chemically similar to those found in the early Archaean era.

  11. Late style as exile: De/colonising the life course.

    Science.gov (United States)

    Hartung, Heike

    2016-12-01

    In the collection of essays On Late Style, Edward Said reflects on the new idiom achieved by great artists in their work near the end of their lives as "late style." Drawing on Adorno's essay on Beethoven's late style, Said also focuses on the aesthetic aspects of lateness. Defining the late works of artists as "a form of exile," however, Said moves beyond Adorno's aesthetic conception of late style. Highlighting the artist's abandonment of communication with the established social order, who achieves a contradictory, alienated relationship with it instead, Said compares artistic lateness with the experience of the subject in exile. Drawing on the analogy provided by Said, this article argues that the relationship between "self" and "other" in the different theoretical contexts of Postcolonial Studies and Age Studies can be usefully combined in the composite concept of "late style as exile." In order to explore how the concept of lateness correlates with that of exile, this contribution turns to theoretical and autobiographical texts by Edward Said. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Spatiotemporal evolution of magmatic pulses and regional metamorphism during a Cretaceous flare-up event: Constraints from the Ryoke belt (Mikawa area, central Japan)

    Science.gov (United States)

    Takatsuka, Kota; Kawakami, Tetsuo; Skrzypek, Etienne; Sakata, Shuhei; Obayashi, Hideyuki; Hirata, Takafumi

    2018-05-01

    The spatiotemporal relationship between granitoid intrusions and low-pressure/temperature type regional metamorphism in the Ryoke belt (Mikawa area) is investigated to understand the tectono-thermal evolution of the upper- to middle-crust during a Cretaceous flare-up event at the Eurasian active continental margin. Three plutono-metamorphic stages are recognized; (1) 99-84 Ma: intrusion of granitoids (99-95 Ma pulse) into the upper crust and high-T regional metamorphism reaching sillimanite-grade (97.0 ± 4.4 Ma to 88.5 ± 2.5 Ma) in the middle crust, (2) 81-75 Ma: intrusion of gneissose granitoids (81-75 Ma Ma pulse) into the middle crust at 19-24 km depth, and (3) 75-69 Ma: voluminous intrusions of massive to weakly-foliated granitoids (75-69 Ma pulse) at 9-13 km depth and formation of contact metamorphic aureoles. Cooling of the highest-grade metamorphic zone below the wet solidus of granitic rocks is estimated at 88.5 ± 2.5 Ma. At ca. 75 Ma, the upper-middle crustal section underwent northward tilting, resulting in the exhumation of regional metamorphic zones to 9-13 km depth. Although the highest-grade metamorphic rocks and the 99-95 Ma pulse granitoids preserve similar U-Pb zircon ages, the absence of spatial association suggests that the regional metamorphic zones were mainly produced by a transient thermal anomaly in the mantle and thermal conduction through the crust, supplemented by localized advection due to granitoid intrusions. The successive emplacement of granitoids into shallow, deep and shallow levels of the crust was probably controlled by the combination of change in thermal structure of the crust and tectonics during granitoid intrusions.

  13. Diabetes mellitus: a predictor for late radiation morbidity

    International Nuclear Information System (INIS)

    Herold, David M.; Hanlon, Alexandra L.; Hanks, Gerald E.

    1999-01-01

    Purpose: Given the high frequency of diabetes, as well as prostate cancer in the elderly population, we sought to determine whether diabetic patients treated with three-dimensional conformal external-beam radiotherapy (3DCRT) had an increased risk of late gastrointestinal (GI) or genitourinary (GU) complications. Methods and Materials: Nine-hundred forty-four prostate cancer patients were treated between April 1989 and October 1996 using 3DCRT. Median patient age was 69 years (range 48-89), median center of prostate dose was 7211 cGy (range 6211-8074) and median follow-up was 36 months (range 2-99). Patients were evaluated every 6 months with digital rectal examinations, serum PSAs and symptom questionnaires. Radiation morbidity was quantified using Radiation Therapy Oncology Group (RTOG) and modified Late Effects Normal Tissue Task Force (LENT) scales. Patients with a preexisting history of either Type I or Type II diabetes mellitus were coded as diabetics. Results: One hundred twenty-one patients had diabetes (13% of total). Rates of acute morbidity did not differ between diabetics and nondiabetics; however, diabetics experienced significantly more late grade 2 GI toxicity (28% vs. 17%, p = 0.011) and late grade 2 GU toxicity (14% vs. 6%, p 0.001). There was a trend toward increased late grade 3 and 4 GI complications in diabetics, but not for late grade 3 and 4 GU complications; however, the total number of recorded events for these categories was small. Examining the onset of late toxicity, diabetics developed GU complications earlier than nondiabetics (median: 10 months vs. 24 months, p = 0.02). Considering age, dose, rectal blocking, field size, and history of diabetes in a stepwise multivariate regression model for late grade 2 GI toxicity, dose (p 0.0001), diabetes (p = 0.0110), and rectal blocking (p = 0.0163) emerged independently predictive for complications. For late grade 2 GU toxicity, only the presence of diabetes remained independently significant

  14. Late Budgets

    DEFF Research Database (Denmark)

    Andersen, Asger Lau; Lassen, David Dreyer; Nielsen, Lasse Holbøll Westh

    are negative rather than positive; and when there is divided government. We test the hypotheses of the model using a unique data set of late budgets for US state governments, based on dates of budget approval collected from news reports and a survey of state budget o¢ cers for the period 1988...

  15. Early- versus Late-Onset Dysthymia

    Science.gov (United States)

    Sansone, Lori A.

    2009-01-01

    In the current Diagnostic and Statistical Manual of Mental Disorders, dysthymic disorder is categorized as either early-onset or late-onset, based upon the emergence of symptoms before or after the age of 21, respectively. Does this diagnostic distinction have any meaningful clinical implications? In this edition of The Interface, we present empirical studies that have, within a single study, compared individuals with early-versus late-onset dysthymia. In this review, we found that, compared to those with late-onset dysthymia, early-onset patients are more likely to harbor psychiatric comorbidity both on Axis I and II, exhibit less psychological resilience, and have more prominent family loadings for mood disorders. These findings suggest that this distinction is meaningful and that the early-onset subtype of dysthymia is more difficult to effectively treat. PMID:20049145

  16. Comparing Measures of Late HIV Diagnosis in Washington State

    Directory of Open Access Journals (Sweden)

    Laura Saganic

    2012-01-01

    Full Text Available As more US HIV surveillance programs routinely use late HIV diagnosis to monitor and characterize HIV testing patterns, there is an increasing need to standardize how late HIV diagnosis is measured. In this study, we compared two measures of late HIV diagnosis, one based on time between HIV and AIDS, the other based on initial CD4+ results. Using data from Washington's HIV/AIDS Reporting System, we used multivariate logistic regression to identify predictors of late HIV diagnosis. We also conducted tests for trend to determine whether the proportion of cases diagnosed late has changed over time. Both measures lead us to similar conclusions about late HIV diagnosis, suggesting that being male, older, foreign-born, or heterosexual increase the likelihood of late HIV diagnosis. Our findings reaffirm the validity of a time-based definition of late HIV diagnosis, while at the same time demonstrating the potential value of a lab-based measure.

  17. Late-Stage Caregiving

    Science.gov (United States)

    ... Caregiving Middle-Stage Caregiving Late-Stage Caregiving Behaviors Aggression & Anger Anxiety & Agitation Depression Hallucinations Memory Loss & Confusion Repetition Sleep Issues & Sundowning Suspicion & Delusions Wandering Abuse Start Here What You Need to Know Online ...

  18. Late Onset Bipolar Disorder: Case Report

    Directory of Open Access Journals (Sweden)

    Filipa Araújo

    2016-07-01

    Full Text Available Background: Bipolar disorder affects approximately 1% of the population, with diagnosis often being made during late adolescence and early adulthood, and only rarely (0.1% in the elderly. Late onset bipolar disorder in the elderly has a impact on the nature and course of bipolar disorder. Aims: The authors report a case of bipolar disorder emerging in late life  (76years old with no cleary identified organic cause. Conclusion: This case highlights the importance of a broad differential diagnosis and pharmacologic management when approaching new-onset manic/depressive symptoms among geriatric patients.

  19. The polyimage poetics in Ibsen's late plays

    Directory of Open Access Journals (Sweden)

    Wang Yuli

    2015-02-01

    Full Text Available The unique poetics of polyimage implied in Ibsen’s late plays can be excavated with aesthetic reading. The term polyimage is coined to describe Ibsen’s original design in aesthetic form and ingenious realm in aesthetic reaction in his late plays; that is, beyond an imagery realm, another imagery realm exists, which construct a deep vision of significance. In each of the excellent late plays, what Ibsen creates is one or more veiled holistic imagery realms in addition to an ordinary entire imagery realm perceived by most audiences. The “layers of imagery realm” result from Ibsen’s “double self-examinations”, including self-examination of soul and of art. It is these “double self-examinations” that make polyimage possible in his late plays and generates the attribute of “meta-art” in these works. Compared with polyphony in Dostoevsky’s novels, the polyimage in Ibsen’s late plays contains a unique modernity, which is of great significance to modern artistic creation.

  20. A low-angle normal fault and basement structures within the Enping Sag, Pearl River Mouth Basin: Insights into late Mesozoic to early Cenozoic tectonic evolution of the South China Sea area

    Science.gov (United States)

    Ye, Qing; Mei, Lianfu; Shi, Hesheng; Shu, Yu; Camanni, Giovanni; Wu, Jing

    2018-04-01

    The basement structure of the Cenozoic Enping Sag, within the Pearl River Mouth Basin on the northern margin of South China Sea, is revealed by borehole-constrained high-quality 3D seismic reflection data. Such data suggest that the Enping Sag is bounded in the north by a low-angle normal fault. We interpret this low-angle normal fault to have developed as the result of the reactivation of a pre-existing thrust fault part of a pre-Cenozoic thrust system. This is demonstrated by the selective reactivation of the pre-existing thrust and by diffuse contractional deformation recognized from the accurate analysis of basement reflections. Another significant result of this study is the finding of some residual rift basins within the basement of the Enping Sag. Both the thrust system and the residual basins are interpreted to have developed after the emplacement of continental margin arc-related granitoids (J3-K1) that define the basement within the study area. Furthermore, seismic sections show that the pre-existing residual rift basins are offset by the main thrust fault and they are both truncated by the Tg unconformity. These structural relationships, interpreted in the frame of previous studies, help us to reconstruct a six-event structural evolution model for the Enping Sag from the late Mesozoic to the early Cenozoic. In particular, we interpret the residual rift basins to have formed as the result of back-arc extension due to the slab roll-back of the Paleo-Pacific Plate subduction in the early K2. The thrust system has recorded a compressional event in the late K2 that followed the back-arc extension in the SCS area. The mechanism of this compressional event is still to be clarified, and might be related to continuous subduction of the Paleo-Pacific Plate or to the continent-continent collision between a micro-continental block and the South China margin.

  1. Geodynamic controls on the contamination of Cenozoic arc magmas in the southern Central Andes: Insights from the O and Hf isotopic composition of zircon

    Science.gov (United States)

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Dhuime, Bruno; Elliott, Tim; Litvak, Vanesa D.; Alonso, Ricardo; Hinton, Richard

    2015-09-01

    Subduction zones, such as the Andean convergent margin of South America, are sites of active continental growth and crustal recycling. The composition of arc magmas, and therefore new continental crust, reflects variable contributions from mantle, crustal and subducted reservoirs. Temporal (Ma) and spatial (km) variations in these contributions to southern Central Andean arc magmas are investigated in relation to the changing plate geometry and geodynamic setting of the southern Central Andes (28-32° S) during the Cenozoic. The in-situ analysis of O and Hf isotopes in zircon, from both intrusive (granitoids) and extrusive (basaltic andesites to rhyolites) Late Cretaceous - Late Miocene arc magmatic rocks, combined with high resolution U-Pb dating, demonstrates distinct across-arc variations. Mantle-like δ18O(zircon) values (+5.4‰ to +5.7‰ (±0.4 (2σ))) and juvenile initial εHf(zircon) values (+8.3 (±0.8 (2σ)) to +10.0 (±0.9 (2σ))), combined with a lack of zircon inheritance suggests that the Late Cretaceous (∼73 Ma) to Eocene (∼39 Ma) granitoids emplaced in the Principal Cordillera of Chile formed from mantle-derived melts with very limited interaction with continental crustal material, therefore representing a sustained period of upper crustal growth. Late Eocene (∼36 Ma) to Early Miocene (∼17 Ma) volcanic arc rocks present in the Frontal Cordillera have 'mantle-like' δ18O(zircon) values (+4.8‰ (±0.2 (2σ) to +5.8‰ (±0.5 (2σ))), but less radiogenic initial εHf(zircon) values (+1.0 (±1.1 (2σ)) to +4.0 (±0.6 (2σ))) providing evidence for mixing of mantle-derived melts with the Late Paleozoic - Early Mesozoic basement (up to ∼20%). The assimilation of both Late Paleozoic - Early Mesozoic Andean crust and a Grenville-aged basement is required to produce the higher than 'mantle-like' δ18O(zircon) values (+5.5‰ (±0.6 (2σ) to +7.2‰ (±0.4 (2σ))) and unradiogenic, initial εHf(zircon) values (-3.9 (±1.0 (2σ)) to +1.6 (±4.4 (2

  2. Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics Granitoides estériles del Mioceno en la franja metalogénica de los Andes Centrales, Chile: geoquímica e isotopía de Nd-Hf y U-Pb

    Directory of Open Access Journals (Sweden)

    Katja Deckart

    2010-01-01

    Full Text Available Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were under-taken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32° and 34°S. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Mesón Alto massif, 10.3±0.2 Ma (La Gloria pluton, 14.9±0.2 Ma/14.9±0.1 Ma (Yerba Loca stock and 11.2±0.1 Ma/14.7±0.1 Ma (San Francisco Batholith. Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32°S, slightly younger mineralized porphyries at Río Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758-0.512882, plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial εHf i-data variation for the younger age group (10-12 Ma; 7.04-9.54 and show a more scattered range for the older one (14-15 Ma; 8.50-15.34; both sets plot between the DM and CLTUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Río Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening

  3. Evaluating late detection capability against diverse insider adversaries

    International Nuclear Information System (INIS)

    Sicherman, A.

    1987-01-01

    The threat of theft or diversion of special nuclear material (SNM) by insiders is a key concern for safeguards planners. Different types of employees having varying degrees of access to both SNM and safeguards systems pose a difficult challenge for theft detection. Safeguards planners rely on physical security, material control, and accountability to provide detection of a theft attempt. When detection occurs too late to prevent a theft, it is called a late detection or late alarm. Activities or events that many provide late detection usually belong to material control and accountability (MC ampersand A) activities. A model has been developed for evaluating the probability of late detection as a function of time elapsed since the theft. Late detection capability is beneficial if it is timely enough to improve the ability to determine the cause of an alarm, speed recovery of SNM, prevent an incorrect response to a threat demand, or promote assurance that no theft has occurred in the absence of an alarm. The model provides insight into the effectiveness of late detection safeguards components in place and helps to identify areas where the MC ampersand A can be most effectively improved

  4. Late-Onset Asthma

    DEFF Research Database (Denmark)

    Ulrik, Charlotte Suppli

    2017-01-01

    Late-onset asthma is common, associated with poor outcome, underdiagnosed and undertreated, possibly due to the modifying effect of ageing on disease expression. Although the diagnostic work-up in elderly individuals suspected of having asthma follows the same steps as in younger individuals (case......, to objectively confirm asthma. If necessary, a trial of oral or inhaled corticosteroid might be necessary. Asthma can be diagnosed when increased airflow variability is identified in a symptomatic patient, and if the patient does not have a history of exposure, primarily smoking, known to cause chronic...... obstructive pulmonary disease, the diagnosis is asthma even if the patient does not have fully reversible airflow obstruction. Pharmacological therapy in patients with late-onset asthma follows international guidelines, including treatment with the lowest effective dose of inhaled corticosteroid to minimize...

  5. Late onset depression: A recent update

    Directory of Open Access Journals (Sweden)

    Ananya Mahapatra

    2015-01-01

    Full Text Available Late onset depression has recently emerged as a serious mental health issue in the geriatric population with significant public health implications. It is often challenging to diagnose and treat this entity. Various theories have been postulated to elucidate the etiology of late onset depression, but a unifying hypothesis is lacking. Although the vascular hypothesis is most researched; a complex interaction of multiple vulnerability factors is the current focus of attention. Numerous psychosocial variables have been implicated to play a significant role in predicting the onset and severity of late-life depression. Phenomenological differences have been delineated from depression occurring at a younger age, but the findings are equivocal. A better understanding of the natural trajectory of depression in the elderly is required for early diagnosis and effective treatment. This review attempts to summarize the current status of evidence regarding epidemiology, etiology, clinical features, and treatment options available for late-onset depression.

  6. Petrogenesis of the middle Jurassic appinite and coeval granitoids in the Eastern Hebei area of North China Craton

    Science.gov (United States)

    Fan, Wenbo; Jiang, Neng; Xu, Xiyang; Hu, Jun; Zong, Keqing

    2017-05-01

    An integrated study of zircon U-Pb ages and Hf-O isotopic compositions, whole rock elemental and Sr-Nd isotope geochemistry was conducted on three lithologically diverse middle Jurassic plutons from the Eastern Hebei area of the North China Craton (NCC), in order to reveal both their petrogenesis and possible tectonic affinity. The three plutons have consistent magmatic zircon U-Pb ages from 167 ± 1 Ma to 173 ± 1 Ma. The Nianziyu pluton has typical characteristics of appinite with low SiO2 (43.7-52.6%), high Ca, Mg, Fe and H2O contents. It possesses subduction-related trace element patterns, enriched Nd-Hf isotopic signatures as well as elevated zircon δ18O values (6.2-7.2‰), arguing for an enriched mantle source metasomatized by fluids related to subduction. The Shuihutong monzogranites have high silica (SiO2 = 75.4-75.9%) and alkali contents, low Ca contents and striking negative Ba, Sr and Eu anomalies. Samples from the pluton have more evolved Nd-Hf isotopic values and are considered to be most likely derived from anatexis of ancient lower continental crust. Hybridization between mantle- and ancient lower crust-derived magmas is proposed for the mafic microgranular enclave-bearing Baijiadian granitoids, which are characterized by variable εNd (t) and εHf(t) values. Integrated with the regional geologic history, we suggest that the formation of the three middle Jurassic plutons were related to the subduction of the Paleo-Pacific ocean plate beneath the NCC. Their petrogenetic differences reflect complex magmatic processes in subduction settings involving melting of multiple sources, possible partly facilitated by fluid metasomatism and water-rich magma injection, accompanied with various degrees of magma mixing. The appearance of middle Jurassic appinitic rocks leads us to propose that the NCC destruction and lithosphere thinning were facilitated and controlled by the weakening of the lithospheric mantle after hydration because of the subduction of the

  7. Childhood abuse in late-life depression

    NARCIS (Netherlands)

    Comijs, Hannie C; van Exel, Eric; van der Mast, Roos C; Paauw, Anna; Oude Voshaar, Richard; Stek, Max L

    Background: Little is known about the role of childhood abuse in late-life depression. The aim of the study is therefore to study whether childhood abuse is associated with late-life depression according to its onset, and which clinical characteristics play a role in this association. Methods: Data

  8. Late presentation of HIV infection: a consensus definition

    DEFF Research Database (Denmark)

    Antinori, A; Coenen, T; Costagiola, D

    2010-01-01

    clinical definition of late presentation. The objective of this article is to present a consensus definition of late presentation of HIV infection. Methods Over the past year, two initiatives have moved towards a harmonized definition. In spring 2009, they joined efforts to identify a common definition...... of what is meant by a 'late-presenting' patient. Results Two definitions were agreed upon, as follows. Late presentation: persons presenting for care with a CD4 count below 350 cells/muL or presenting with an AIDS-defining event, regardless of the CD4 cell count. Presentation with advanced HIV disease...... able to implement this definition (either on its own or alongside their own preferred definition) when reporting surveillance or research data relating to late presentation of HIV infection....

  9. Rare metal granites in the structures of the Russian sector of Pacific ore belt

    Directory of Open Access Journals (Sweden)

    В. И. Алексеев

    2016-08-01

    Full Text Available Data are presented on the geology of areas of rare metal granites proliferation in the Russian sector of the Pacific Ore Belt that make one take a fresh look at the East Asian granitoid area to update its metallogeny. History is reviewed of studying rare metal granites of the Russian Far East. As a rule, these are found in the vicinity of major tungsten-stanniferous ore deposits, except much later than discovering the former, at the stages of their assessment and survey. Rare earth granites are usually missed by the geologists during the early stages of regional geological surveys due to their small size, weak eroding and external similarity with earlier granites. Using the examples of the Central Polousny, Badzhal and Kuyviveem-Pyrekakay regions the structural and geological conditions are characterized of localization of rare metal granites. Comparative analysis of geological situations made it possible to formulate the areal character of manifestation of rare metal granites; their confinedness to late Mesozoic orogenic arched uplifts of bogen structures above deep granitoid batholiths; positioning in the areas where longitudinal and transversal deep laying faults cross; gravitation to the environs of pre-Cambrian median masses. Similarity of structural-geological conditions for manifestation of the well-studied ore-containing granites serves to confirm the hypothesis on the joint stage of late Cretaceous rare metal magmatism in the Russian sector of the Pacific Ore Belt and the existence in the region of a magmatic super-province – the Far East belt of rare metal granites that includes the Novosibirsk-Chukotka, the Yana-Kolyma and the Sikhote-Alin rare metal – granite provinces.

  10. Late washing filter cleaning cycle demonstration

    International Nuclear Information System (INIS)

    Meyer, M.L.; McCabe, D.J.

    1992-01-01

    The DWPF Late Washing Facility will filter cesium and potassium tetraphenyl borate (TPB) solids using a Mott sintered metal filter, identical to the filter now used in the In-tank Precipitation Facility. The purpose of the late wash step is primarily to remove the nitrite salts from the slurry prior to delivery to DWPF. Periodic chemical cleaning of the filter will be required, presumably after each batch although the actual required frequency could not be determined on the lab-scale. Minimization of chemical cleaning solution volumes is key to maximizing the attainment of the Late Wash facility. This report summarizes work completed in experiments designed to identify minimum cleaning solution requirements

  11. Paleointensity determination on Neoarchaean dikes within the Vodlozerskii terrane of the Karelian craton

    Science.gov (United States)

    Shcherbakova, V. V.; Lubnina, N. V.; Shcherbakov, V. P.; Zhidkov, G. V.; Tsel'movich, V. A.

    2017-09-01

    The results of paleomagnetic studies and paleointensity determinations from two Neoarchaean Shala dikes with an age of 2504 Ma, located within the Vodlozerskii terrane of the Karelian craton, are presented. The characteristic components of primary magnetization with shallow inclinations I = -5.7 and 1.9 are revealed; the reliability of the determinations is supported by two contact tests. High paleointensity values are obtained by the Thellier-Coe and Wilson techniques. The calculated values of the virtual dipole moment (11.5 and 13.8) × 1022 A m2 are noticeably higher than the present value of 7.8 × 1022 A m2. Our results, in combination with the previous data presented in the world database, support the hypothesized existence of a period of high paleointensity in the Late Archaean-Early Proterozoic.

  12. Comparative Earth history and Late Permian mass extinction

    Science.gov (United States)

    Knoll, A. H.; Bambach, R. K.; Canfield, D. E.; Grotzinger, J. P.

    1996-01-01

    The repeated association during the late Neoproterozoic Era of large carbon-isotopic excursions, continental glaciation, and stratigraphically anomalous carbonate precipitation provides a framework for interpreting the reprise of these conditions on the Late Permian Earth. A paleoceanographic model that was developed to explain these stratigraphically linked phenomena suggests that the overturn of anoxic deep oceans during the Late Permian introduced high concentrations of carbon dioxide into surficial environments. The predicted physiological and climatic consequences for marine and terrestrial organisms are in good accord with the observed timing and selectivity of Late Permian mass extinction.

  13. The development of continental crust through geological time: the South African case

    International Nuclear Information System (INIS)

    Dia, A.; Allegre, C.J.; Erlank, A.J.

    1990-01-01

    Nd isotopic compositions and 147 Sm/ 144 Nd ratios were measured in fifty-eight South African shales and greywackes with depositional ages ranging from 0.2 to 3.3 b.y. Elements such as the rare earths, which are poorly soluble in water and not fractionated during exogeneous processes, preserve the signature of the original crustal source. The 147 Sm/ 144 Nd ratios appear to be approximately constant throughout the time interval sampled. We calculated Nd model ages of crustal differentiation. Knowing that the shales represent a true blend of different continental areas we consider these model ages representative of the mean ages of their primitive continental sources. Then, using the inverse technique developed by Allegre and Rousseau in 1984, we computed a growth curve for the continental crust in South Africa. Two periods of important crustal genesis (Archaean and around 1.5 b.y.) can be compared with the observed geology and with other continental crust growth curves obtained in previous studies in southern Africa and in Australia. The observation of large variations in the MgO content and Ni, Cr, U and Th concentrations between Archaean South African shales and post-Archaean samples compared to the constancy of the 147 Sm/ 144 Nd ratios leads us to propose that the Archaean crust was composed of both granite (70.5%) and a mafic component (29.5%) which could have been komatiite. The small dispersion of 147 Sm/ 144 Nd ratios suggests that erosion and sedimentation processes yielded homogeneous Archaean shales. The present-day continental crust is much more heterogeneous, because it has undergone several episodes of recycling. Thus recent shales are characterized by more variable 147 Sm/ 144 Nd ratios. (orig.)

  14. Sr-Nd isotope systematics of xenoliths in Cenozoic volcanic rocks from SW Japan

    International Nuclear Information System (INIS)

    Kagami, Hiroo; Iwata, Masatoshi; Iizumi, Shigeru; Nureki, Terukazu.

    1993-01-01

    Based on new and previously published Sr and Nd isotope data, we examined the petrogenetic relationship between deep crust- and upper mantle-derived xenoliths contained in Cenozoic volcanic rocks and Cretaceous-Paleogene granitoid rocks in SW Japan. The deep crust- and upper mantle-derived mafic to ultramafic xenoliths contained in Cenozoic volcanic rocks from SW Japan have comparable initial Sr and Nd isotope ratios to the Cretaceous-Paleogene granitoid rocks in their respective districts. This may suggest that these xenoliths were genetically related to the Cretaceous-Paleogene granitoid rocks in SW Japan, and that regional variations in Sr and Nd isotope ratios observed in the granitoid rocks are attributed to differences in the geochemistry of the magma sources. (author)

  15. Geochronology and geochemistry of the Borohoro pluton in the northern Yili Block, NW China: Implication for the tectonic evolution of the northern West Tianshan orogen

    Science.gov (United States)

    Wang, Meng; Zhang, Jinjiang; Zhang, Bo; Liu, Kai; Chen, Youxin; Zheng, Yanrong

    2018-03-01

    The closure of the North Tianshan Ocean between the Junggar Terrane and the Yili Block is a longtime debated issue in literature, because of the different understanding of the Carboniferous volcanic rocks in the northern margin of the Yili Block. This study presents new geochronological and whole-rock geochemical data for the granitic rocks from the Borohoro pluton to provide constraints on the tectonic regime for the northern West Tianshan during the Carboniferous. LA-ICP-MS U-Pb dating results reveal two magmatic phases for the Borohoro pluton. The former magmatic activity in the Early Carboniferous formed the fine-grained granodiorite (332 Ma). The later magmatic activity occurred during the Late Carboniferous (305-300 Ma), forming a diversity of granitic rocks, involving quartz diorite, granodiorite and granite. Geochemical and mineralogical studies reveal that the studied granitic rocks from the Borohoro pluton all belong to metaluminous to weakly peraluminous, calc-alkaline I-type granites. They are characterized by enrichment in LILEs relative to HFSEs, and depletion of Nb, Ti and P, typical of continental arc-type granites. The intermediate SiO2, high Al2O3, and relatively low Fe2O3T, MgO and TiO2 contents reflect that these granitic rocks are mainly crust-derived. But the high Mg# values for most samples and the occurrence of microgranular mafic enclaves indicate that their magma sources were mixed by mantle-derived components. Especially, the Late Carboniferous rocks define an elegant mixing trend in both the Rb-Rb/V and the 1/V-Rb/V diagrams, consistent with mixing between magmas from subcontinental lithospheric mantle and mafic lower crust. Taking into consideration of the facts that all the Devonian to Carboniferous granitoids belong to calc-alkaline I-type granites, and granitoids of A-type didn't appear until the Early Permian, we suggest that the subduction of the North Tianshan Ocean continued to the Late Carboniferous, generating the granitic

  16. Elemental and Sr-Nd isotopic geochemistry of Cretaceous to Early Paleogene granites and volcanic rocks in the Sikhote-Alin Orogenic Belt (Russian Far East): implications for the regional tectonic evolution

    Science.gov (United States)

    Zhao, Pan; Jahn, Bor-ming; Xu, Bei

    2017-09-01

    The Sikhote-Alin Orogenic Belt in Russian Far East is an important Late Mesozoic to Early Cenozoic accretionary orogen related to the subduction of the Paleo-Pacific Plate. This belt was generated by successive accretion of terranes made of accretionary prisms, turbidite basins and island arcs to the continental margin of northeastern Asia (represented by the Bureya-Jiamusi-Khanka Block) from Jurassic to Late Cretaceous. In order to study the tectonic and crustal evolution of this orogenic belt, we carried out zircon U-Pb dating, and whole-rock elemental and Sr-Nd isotopic analyses on granites and volcanic rocks from the Primorye region of southern Sikhote-Alin. Zircon dating revealed three episodes of granitoid emplacement: Permian, Early Cretaceous and Late Cretaceous to Early Paleogene. Felsic volcanic rocks (mainly rhyolite, dacite and ignimbrite) that overlay all tectonostratigraphic terranes were erupted during 80-57 Ma, postdating the accretionary process in the Sikhote-Alin belt. The Cretaceous-Paleogene magmatism represents the most intense tectonothermal event in the Sikhote-Alin belt. Whole-rock major and trace elemental data show arc-like affinity for granitoids and volcanic rocks, indicating that they were likely generated in a supra-subduction setting. Their initial 87Sr/86Sr ratios range from 0.7048 to 0.7114, and εNd(t) values vary from +1.7 to -3.8 (mostly < 0). Thus, the elemental and Sr-Nd isotopic data suggest that the felsic magmas were generated by partial melting of source rocks comprising mantle-derived juvenile component and recycled crustal component. In addition to the occurrence in the Sikhote-Alin orogenic belt, Cretaceous to Early Paleogene magmatic rocks are also widespread in NE China, southern Korean peninsula, Japanese islands and other areas of Russian Far East, particularly along the coastal regions of the Okhotsk and Bering Seas. These rocks constitute an extended magmatic belt along the continental margin of NE Asia. The

  17. The late-M dwarfs

    International Nuclear Information System (INIS)

    Bessell, M.S.

    1991-01-01

    Far-red spectra and VRIJHK photometry have been obtained for a sample of late-M dwarfs selected on the basis of large reduced red magnitudes from the LHS Catalog. Half of the stars in the three faintest 1 mag bins are late-M stars, the other red stars are metallic-hydride subdwarfs. Relations between various colors for the late-M dwarfs are investigated. Of all the colors I - K most reliably correlates with spectral type. FeH bands near 9900 A are clearly seen in the spectra of all dwarf stars later than M5. Two stars cooler than VB10, and similar in temperature to LHS2924 have been identified; both have H-alpha in emission and appear variable in magnitude and R - I color; one is a flare star. The other stars are of earlier spectral type and resemble W359 and VB8. The observed MI, I - K main sequence is in good agreement with the IG theoretical main sequence of Stringfellow, and the faintest stars could be about 0.09 solar mass red dwarfs or lower mass brown dwarfs. 65 refs

  18. Quantification of late complications after radiation therapy

    International Nuclear Information System (INIS)

    Jung, Horst; Beck-Bornholdt, Hans-Peter; Svoboda, Vladimir; Alberti, Winfried; Herrmann, Thomas

    2001-01-01

    Background: An increasing number of patients survive cancer after having received radiation therapy. Therefore, the occurrence of late normal tissue complications among long-term survivors is of particular concern. Methods: Sixty-three patients treated by radical surgery and irradiation for rectal carcinoma were subjected to an unconventional sandwich therapy. Preoperative irradiation was given in four fractions of 5 Gy each applied within 2 or 3 days; postoperative irradiation consisted mostly of 15x2 Gy (range, 20-40 Gy). A considerable proportion of these patients developed severe late complications (Radiother Oncol 53 (1999) 177). The data allowed a detailed analysis of complication kinetics, leading to a new model which was tested using data from the literature. Results: Data on late complications were obtained for eight different organs with a follow-up of up to 10 years. For the various organs, the percentage of patients being free from late complications, plotted as a function of time after start of radiation therapy, was adequately described by exponential regression. From the fit, the parameter p a was obtained, which is the percentage of patients at risk in a given year of developing a complication in a given organ during that year. The rate p a remained about constant with time. Following sandwich therapy, the annual incidence of complications in the bladder, ileum, lymphatic and soft tissue, and ureters was about the same (p a =10-14%/year), whereas complications in bone or dermis occurred at lower rates (4.7 or 7.5%/year, respectively). Discussion: Numerous data sets collected from published reports were analyzed in the same way. Many of the data sets studied were from patients in a series where there was a high incidence of late effects. Three types of kinetics for the occurrence of late effects after radiotherapy were identified: Type 1, purely exponential kinetics; Type 2, exponential kinetics, the slope of which decreased exponentially with time

  19. Late post-operative hypoxaemia and organ dysfunction

    DEFF Research Database (Denmark)

    Kehlet, H; Rosenberg, J

    1995-01-01

    an adverse effect of tissue hypoxia on wound healing and on resistance to bacterial wound infections. Finally, mental confusion and surgical delirium may be related to inadequate arterial oxygenation during the late post-operative period. Late post-operative constant and episodic hypoxaemia may therefore......Constant and episodic hypoxaemia are common after major operations in the late post-operative period in the surgical ward. Recent studies have shown that hypoxaemia may be related to the development of myocardial ischaemia and cardiac arrhythmias. Experimental and clinical studies have demonstrated...

  20. Recent casualties of late globalization

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    2016-01-01

    In this essay I will expand my thoughts on universities as ‘late globalizers’ and the impact ‘being late’ has on university internationalization or globalization activities. In my earlier essay I viewed universities as ‘late globalizers’ and briefly introduced the impact of being ‘late’, e.g., wi.......g., withdrawal or de-internationalization of universities due to incompatibility between university autonomy and the context in the target country or universities unwillingness to compromise on their freedom and autonomy....

  1. Pathological review of late cerebral radionecrosis

    International Nuclear Information System (INIS)

    Yoshii, Yoshihiko

    2008-01-01

    Late cerebral radionecrosis may be considered to be a specific chronic inflammatory response, although it is unknown whether the initial damage by brain irradiation is to an endothelial cell or a glial cell. I discuss the pathological specificity of late cerebral radionecrosis by studying the published literature and a case that I experienced. In late cerebral radionecrosis, there are typical coagulation necrosis areas containing fibrinoid necrosis with occlusion of the lumina and poorly active inflammatory areas with many inflammatory ghost cells, focal perivascular lymphocytes, hyalinized vessels, and telangiectatic vascularization near and in the necrotic tissue, and more active inflammatory areas formed as a partial rim of the reactive zone by perivascular lymphocytes, much vascularization, and glial fibrillary acidic protein (GFAP)-positive astrocytes at the corticomedullary border adjacent to necrotic tissue in the white matter. It is difficult to believe that coagulation necrosis occurs without first disordering the vascular endothelial cells because fibrinoid necrosis is a main feature and a diffusely multiple lesion in late cerebral radionecrosis. Because various histological findings do develop, progress, and extend sporadically at different areas and times in the irradiated field of the brain for a long time after radiation, uncontrolled chronic inflammation containing various cytokine secretions may also play a key role in progression of this radionecrosis. Evaluation of the mechanism of the development/aggravation of late cerebral radionecrosis requires a further study for abnormal cytokine secretions and aberrant inflammatory reactions. (author)

  2. Zircon U-Pb geochronology and Sr-Nd-Pb-Hf isotopic constraints on the timing and origin of Mesozoic granitoids hosting the Mo deposits in northern Xilamulun district, NE China

    Science.gov (United States)

    Shu, Qihai; Lai, Yong; Zhou, Yitao; Xu, Jiajia; Wu, Huaying

    2015-12-01

    Located in the east section of the Central Asian orogen in northeastern China, the Xilamulun district comprises several newly discovered molybdenum deposits, primarily of porphyry type and Mesozoic ages. This district is divided by the Xilamulun fault into the southern and the northern parts. In this paper, we present new zircon U-Pb dating, trace elements and Hf isotope, and/or whole rock Sr-Nd-Pb isotopic results for the host granitoids from three Mo deposits (Yangchang, Haisugou and Shabutai) in northern Xilamulun. Our aim is to constrain the age and petrogenesis of these intrusions and their implications for Mo mineralization. Zircon U-Pb LA-ICP-MS dating shows that the monzogranites from the Shabutai and Yangchang deposits formed at 138.4 ± 1.5 and 137.4 ± 2.1 Ma, respectively, which is identical to the molybdenite Re-Os ages and coeval well with the other Mo deposits in this region, thereby indicating an Early Cretaceous magmatism and Mo mineralization event. Zircon Ce/Nd ratios from the mineralized intrusions are significantly higher than the barren granites, implying that the mineralization-related magmas are characterized by higher oxygen fugacity. These mineralized intrusions share similar zircon in-situ Hf and whole rock Sr-Nd isotopic compositions, with slightly negative to positive εHf(t) ranging from - 0.8 to + 10.0, restricted εNd(t) values from - 3.7 to + 1.6 but a little variable (87Sr/86Sr)i ratios between 0.7021 and 0.7074, indicative of formation from primary magmas generated from a dominantly juvenile lower crust source derived from depleted mantle, despite diverse consequent processes (e.g., magma mixing, fractional crystallization and crustal contamination) during their evolution. The Pb isotopes (whole rock) also show a narrow range of initial compositions, with (206Pb/204Pb)i = 18.03-18.88, (207Pb/204Pb)i = 15.48-15.58 and (208Pb/204Pb)i = 37.72-38.28, in agreement with Sr-Nd-Hf isotopes reflecting the dominance of a mantle component

  3. Late induced abortion.

    Science.gov (United States)

    Savage, W

    1990-09-01

    In the UK in 1988, 13.3% of abortions were performed at 13 weeks' gestation or later. Reasons for this delay, in addition to the diagnosis through amniocentesis of a fetal abnormality, include late recognition of pregnancy, a change of mind about completing the pregnancy, a failure of primary care physicians to entertain the diagnosis of pregnancy, travel or financial problems, and referral difficulties and scheduling delays. Women with little education and very young women are most likely to present for late abortions. From 13-16 weeks, dilatation and evacuation is the safest method of pregnancy termination. The procedure can be made easier through preparation of the cervix with a prostaglandin pessary or Foley catheter. After 16 weeks, an instillation method is recommended; prostaglandin administration can be intro- or extra-amniotic. Complication rates at 13-19 weeks are 14.5/1000 for vaginal methods of abortion and 7.2/1000 for prostaglandin methods. The risk of complications is 3 times higher for women who have 2nd-trimester abortions through the National Health Service. Although it is not realistic to expect that late abortions ever can be eliminated, improved sex education and contraceptive reliability as well as reforms in the National Health Service could reduce the number substantially. To reduce delay, it is suggested that the National Health Service set up satellite day care units and 1-2 central units in each region to deal quickly with midtrimester abortions. Delays would be further reduced by legislation to allow abortion on request in at least the 1st trimester of pregnancy.

  4. Lost Terranes of Zealandia: possible development of late Paleozoic and early Mesozoic sedimentary basins at the southwest Pacific margin of Gondwanaland, and their destination as terranes in southern South America Terrenos perdidos de Zealandia: posible desarrollo de cuencas sedimentarias del Paleozoico tardío y Mesozoico temprano en el margen suroccidental del Pacífico de Gondwana y su destino como terrenos en el sur de América del Sur

    Directory of Open Access Journals (Sweden)

    Christopher J Adams

    2010-07-01

    Full Text Available Latest Precambrian to Ordovician metasedimentary successions and Cambrian-Ordovician and Devonian-Carboniferous granitoids form the major part of the basement of southern Zealandia and adjacent sectors of Antarctica and southeast Australia. Uplift/cooling ages of these rocks, and local Devonian shallow-water cover sequences suggest that final consolidation of the basement occurred through Late Paleozoic time. A necessary consequence of this process would have been contemporaneous erosion and the substantial development of marine sedimentary basins at the Pacific margin of Zealandia. These are found nowhere at the present day, suggesting that the basins have been lost by tectonic erosion, perhaps in a margin-parallel dextral translation similar to late Paleozoic-Mesozoic suspect terranes of New Zealand. Aprobable detrital zircon age pattern is assembled for these lost Zealandia sediments, and then compared with those of pre-Jurassic (probable Triassic to Devonian metasedimentary rocks in the Chilean archipelago. Significant Mesoproterozoic, latest Neoproterozoic-Cambrian and Devonian-Carboniferous detrital zircon age components are common to both, thus supporting a possible Chilean terrane destination for these 'lost terranes of Zealandia'.Las sucesiones metasedimentarias del Precámbrico tardío al Ordovícico y granitoides del Cámbrico-Ordovícico y Devónico-Carbonífero constituyen la mayor parte del basamento del sur de Zealandia y sectores adyacentes de la Antartica y el sudeste de Australia. Las edades de enfriamiento/alzamiento de estas rocas y la cobertura local de secuencias de aguas someras del Devónico, sugieren que la consolidación definitiva del basamento se produjo durante el Paleozoico tardío. Una consecuencia necesaria de este proceso habría sido la erosion contemporánea y el desarrollo sustancial de cuencas sedimentarias marinas en el margen del Pacífico de Zealandia. Estas no se encuentran en ninguna parte en la

  5. Neoarchean granite-greenstone belts and related ore mineralization in the North China Craton: An overview

    Directory of Open Access Journals (Sweden)

    Li Tang

    2018-05-01

    Full Text Available Tectonic processes involving amalgamations of microblocks along zones of ocean closure represented by granite-greenstone belts (GGB were fundamental in building the Earth's early continents. The crustal growth and cratonization of the North China Craton (NCC are correlated to the amalgamation of microblocks welded by 2.75–2.6 Ga and ∼2.5 Ga GGBs. The lithological assemblages in the GGBs are broadly represented by volcano-sedimentary sequences, subduction-collision related granitoids and bimodal volcanic rocks (basalt and dacite interlayered with minor komatiites and calc-alkalic volcanic rocks (basalt, andesite and felsic rock. The geochemical features of meta-basalts in the major GGBs of the NCC display affinity with N-MORB, E-MORB, OIB and calc-alkaline basalt, suggesting that the microblocks were separated by oceanic realm. The granitoid rocks display arc signature with enrichment of LILE (K, Rb, Sr, Ba and LREE, and depletion of HFSE (Nb, Ta, Th, U, Ti and HREE, and fall in the VAG field. The major mineralization includes Neoarchean BIF-type iron and VMS-type Cu-Zb deposits and these, together with the associated supracrustal rocks possibly formed in back-arc basins or arc-related oceanic slab subduction setting with or without input from mantle plumes. The 2.75–2.60 Ga TTG rocks, komatiites, meta-basalts and metasedimentary rocks in the Yanlingguan GGB are correlated to the upwelling mantle plume with eruption close to the continental margin within an ocean basin. The volcano-sedimentary rocks and granitoid rocks in the late Neoarchean GGBs display formation ages of 2.60–2.48 Ga, followed by metamorphism at 2.52–2.47 Ga, corresponding to a typical modern-style subduction-collision system operating at the dawn of Proterozoic. The late Neoarchean komatiite (Dongwufenzi GGB, sanukitoid (Dongwufenzi GGB and Western Shandong GGB, BIF (Zunhua GGB and VMS deposit (Hongtoushan-Qingyuan-Helong GGB have closer connection to a combined

  6. The LATEA metacraton (Central Hoggar, Tuareg shield, Algeria): behaviour of an old passive margin during the Pan-African orogeny

    Science.gov (United States)

    Liégeois, Jean Paul; Latouche, Louis; Boughrara, Mustapha; Navez, Jacques; Guiraud, Michel

    2003-10-01

    Historically, the Tuareg shield is divided into three parts bordered by mega-shear zones with the centre, the Central Polycyclic Hoggar, characterized by Archaean and Palaeoproterozoic lithologies. Nearly 10 years ago, the Tuareg shield was shown to be composed of 23 displaced terranes [Geology 22 (1994) 641] whose relationships were deciphered in Aı̈r to the SE [Precambr. Res. 67 (1994) 59]. The Polycyclic Central Hoggar terranes were characterized by the presence of well preserved Archaean/Palaeoproterozoic and Neoproterozoic lithologies. We show here that the terranes from Central Hoggar (Laouni, Azrou-n-Fad, Tefedest, Egéré-Aleksod) belonged to a single old passive margin, to which we gave the acronym name LATEA, which behaved as a craton during the Mesoproterozoic and the Early-Middle Neoproterozoic but was partly destabilized and dissected during the Late Neoproterozoic as a consequence of its involvement as a passive margin in the Pan-African orogen. An early Pan-African phase consisted of thrust sheets including garnet-bearing lithologies (eclogite, amphibolite, gneiss) that can be mapped and correlated in three LATEA terranes. In the Tin Begane area, P- T- t paths have been established from >15 kbar--790 °C (eclogite) to 4 kbar--500 °C (greenschist retrogression) through 12 kbar--830 °C (garnet amphibolite) and 8 kbar--700 °C (garnet gneiss), corresponding to the retrograde path of a Franciscan-type loop. Sm-Nd geochronology on minerals and laser ablation ICP-MS on garnet show the mobility of REE, particularly LREE, during the retrograde greenschist facies that affects, although slightly, some of these rocks. The amphibolite-facies metamorphism has been dated at 685 ± 19 Ma and the greenschist facies at 522 ± 27 Ma. During the thrust phase, the Archaean-Palaeoproterozoic basement was only locally affected by the Pan-African tectonics. LATEA behaved as a craton. Other juvenile terranes were also thrust early onto LATEA: the Iskel island arc at

  7. [Cause of late death in liver transplant recipients].

    Science.gov (United States)

    Coelho, Júlio Cézar Uili; Parolin, Mônica B; Matias, Jorge Eduardo Fouto; Jorge, Fernando Marcus Felipe; Canan Júnior, Lady Wilson

    2003-01-01

    The objective is to present the causes of late death in patients subjected to liver transplantation. A total of 209 patients were subjected to 223 liver transplantations (14 retransplantations). The computerized study protocol sheets were evaluated to determine the causes of late death (> 6 months after transplantation). Of the 209 patients, 30 had late death. Ductopenic rejection (chronic rejection) was the most common cause and it was observed in 10 patients. Time after transplantation at the moment of death of this group of patients varied from 11 to 57 months, with an average of 29 months. Seven patients died at the hospital admission of hepatic retransplantation. Other causes of late death were sepsis, lymphoproliferative disease, chronic renal insufficiency, and hepatic insufficiency. The most common cause of late death after liver transplantation is ductopenic rejection, followed by complications of retransplantation and sepsis. Death owing to ductopenic rejection may occur even many years after transplantation.

  8. U-Pb (LA-ICPMS) zircon ages and Nd isotopes for granitoids of the Tamboril-Santa Quiteria Complex, Ceara Central Domain: implication for neoproterozoic syncollisional magmatism in north Borborema Province, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Felipe Grandjean da; Araujo, Carlos Eduardo Ganade de; Vasconcelos, Antonio Maurilio, E-mail: felipe.costa@cprm.gov.br, E-mail: caegeo@gmail.com, E-mail: maurilio.vasconcelos@cprm.gov.br [Servico Geologico do Brasil (CPRM), Fortaleza, CE (Brazil); Amaral, Wagner da Silva, E-mail: wamaral@ufc.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Geologia; Rodrigues, Joseneusa Brilhante, E-mail: joseneusa.rodrigues@cprm.gov.br [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil)

    2013-06-15

    The Tamboril-Santa Quiteria Complex (TSQC) is one of the largest Neoproterozoic plutonic manifestations in the north Borborema Province (NE Brazil). It represents an anatectic/igneous association characterized by a number of magmatic pulses that occurred in the 650-610 Ma interval. In this paper, we present U-Pb (LA-MC-ICP-MS) zircon ages and Nd isotopes for quartz monzonite and quartz diorites of the southern part of TSQC. The quartz monzonite belong to a hybrid granitoid association, including monzonite, syenites and quartz syenites, all with abundant mafic magmatic enclaves. A quartz monzonite sample yielded a U-Pb zircon age of 634 {+-} 10 Ma and a TDM age of 2.69 Ga. The quartz diorites are much more homogeneous in composition and yielded a U-Pb zircon age of 618 {+-} 23 Ma and a TDM age of 2.19 Ga. The presence of coeval mantle-derived magmatism and diatexites (crustal anatexis) post-dating high-pressure metamorphism (ca. 650 Ma), and together with high-temperature metamorphism (ca. 630-610 Ma), suggests that this large magmatic manifestation evolved in a collisional setting, probably related to slab break off during the Western Gondwana amalgamation. (author)

  9. Requests for late termination of pregnancy: Tower Hamlets, 1983.

    OpenAIRE

    Savage, W

    1985-01-01

    The case histories of all women seeking late (more than 20 weeks' gestation) abortion in the NHS district of Tower Hamlets in 1983 were assessed. Of 12 women requesting late abortion, seven underwent termination of pregnancy. All the women had severe social or psychological problems, or both. The main reasons for late presentation were denial of pregnancy, youth, and mental disorder. In a small group of atypical women late abortion seems to be justified for reasons other than fetal abnormality.

  10. Are we ready to predict late effects?

    DEFF Research Database (Denmark)

    Salz, Talya; Baxi, Shrujal S; Raghunathan, Nirupa

    2015-01-01

    BACKGROUND: After completing treatment for cancer, survivors may experience late effects: consequences of treatment that persist or arise after a latent period. PURPOSE: To identify and describe all models that predict the risk of late effects and could be used in clinical practice. DATA SOURCES:...

  11. Radiation therapy and late reactions in normal tissues

    International Nuclear Information System (INIS)

    Aoyama, Takashi; Kuroda, Yasumasa

    1998-01-01

    Recent developments in cancer therapy have made us increasingly aware that the quality of life of a patient is as valuable as other benefits received from therapy. This awareness leads to an emphasis on organ and/or function preservation in the course of therapy. In line with this new thinking, greater consideration is placed on radiation therapy as an appropriate modality of cancer therapy. Possible complications in normal tissues, especially those of late reaction type after the therapy must be overcome. This review, therefore, focuses on recent progress of studies on mechanisms of the complications of the late reaction type. An observation of a clinical case concerning a late reaction of spinal cord (radiation myelopathy) and surveys of experimental studies on the mechanisms of late reactions (including radiation pneumonitis and lung fibrosis, and radiation response of vascular endothelial cells) provide a hypothesis that apoptosis through the pathway starting with radiation-induced sphingomyelin hydrolysis may play an important role in causing a variety of late reactions. This insight is based on the fact that radiation also activates protein kinase C which appears to block apoptosis. The mechanisms of late reactions, therefore, may involve a balance between radiation-induced apoptotic death and its down regulation by suppressor mechanisms through protein kinase C. (author)

  12. Neurocognitive outcome in young adults born late-preterm.

    Science.gov (United States)

    Heinonen, Kati; Lahti, Jari; Sammallahti, Sara; Wolke, Dieter; Lano, Aulikki; Andersson, Sture; Pesonen, Anu-Katriina; Eriksson, Johan G; Kajantie, Eero; Raikkonen, Katri

    2018-03-01

    This study examined whether late-preterm birth (34+0 to 36+6wks+d gestational age) was associated with neurocognitive deficit in young adulthood, and whether small for gestational age (SGA) birth amplified any adversity. Participants derived from the prospective regional cohort study, the Arvo Ylppö Longitudinal Study (n=786; 398 females, 388 males) (mean age 25y 4mo, SD 8mo), born 1985 to 1986 late-preterm (n=119; 21 SGA, intelligence, executive functioning, attention, and memory, and reported their education. Those born late-preterm scored -3.71 (95% confidence interval [CI] -6.71 to -0.72) and -3.11 (95% CI -6.01 to -0.22) points lower on Full-scale and Verbal IQ than peers born at term. Compared with those born at term and appropriate for gestational age (≥-2 to increase the risk of poorer neurocognitive functioning in adulthood. But the double burden of being born late-preterm and SGA seems to increase this risk. Late-preterm birth did not increase the risk of poorer neurocognitive functioning in adulthood. But the double burden of being born late-preterm and being small for gestational age did increase this risk. © 2017 Mac Keith Press.

  13. Late-modern hipsters

    DEFF Research Database (Denmark)

    Andersen, Bjørn Schiermer

    2014-01-01

    The article deals with the cultural significance of a new figure in late-modern Western culture: the hipster. The current hipster culture, so I argue, can be used as a magnifying glass that makes impending changes to our conception of culture and of cultural development visible. It ushers...

  14. Paradoxical physiological transitions from aging to late life in Drosophila.

    Science.gov (United States)

    Shahrestani, Parvin; Quach, Julie; Mueller, Laurence D; Rose, Michael R

    2012-02-01

    In a variety of organisms, adulthood is divided into aging and late life, where aging is a period of exponentially increasing mortality rates and late life is a period of roughly plateaued mortality rates. In this study we used ∼57,600 Drosophila melanogaster from six replicate populations to examine the physiological transitions from aging to late life in four functional characters that decline during aging: desiccation resistance, starvation resistance, time spent in motion, and negative geotaxis. Time spent in motion and desiccation resistance declined less quickly in late life compared to their patterns of decline during aging. Negative geotaxis declined at a faster rate in late life compared to its rate of decline during aging. These results yield two key findings: (1) Late-life physiology is distinct from the physiology of aging, in that there is not simply a continuation of the physiological trends which characterize aging; and (2) late life physiology is complex, in that physiological characters vary with respect to their stabilization, deceleration, or acceleration in the transition from aging to late life. These findings imply that a correct understanding of adulthood requires identifying and appropriately characterizing physiology during properly delimited late-life periods as well as aging periods.

  15. Childhood abuse and late-life depression: Mediating effects of psychosocial factors for early- and late-onset depression.

    Science.gov (United States)

    Wielaard, Ilse; Hoyer, Mathijs; Rhebergen, Didi; Stek, Max L; Comijs, Hannie C

    2018-03-01

    Childhood abuse makes people vulnerable to developing depression, even in late life. Psychosocial factors that are common in late life, such as loneliness or lack of a partner, may explain this association. Our aim was to investigate whether the association between childhood abuse and depression in older adults can be explained by psychosocial factors. Cross-sectional data were derived from the Netherlands Study of Depression in Older Persons (aged 60-93), including 132 without lifetime depression, 242 persons with an early-onset depression (Childhood abuse (yes/no) and a frequency-based childhood abuse index were included. Multinomial regression and multivariable mediation analyses were used to examine the association between childhood abuse and the onset of depression, and the influence of loneliness, social network, and partner status. Multinomial regression analyses showed a significant association between childhood abuse and the childhood abuse index with early- and late-onset depression. Multivariable mediation analyses showed that the association between childhood abuse and early-onset depression was partly mediated by social network size and loneliness. This was particularly present for emotional neglect and psychological abuse, but not for physical and sexual abuse. No psychosocial mediators were found for the association between childhood abuse and late-onset depression. A smaller social network and feelings of loneliness mediate the association between childhood abuse and early-onset depression in older adults. Our findings show the importance of detecting childhood abuse as well as the age at depression onset and mapping of relevant psychosocial factors in the treatment of late-life depression. Copyright © 2018 John Wiley & Sons, Ltd.

  16. Late-onset CMV disease following CMV prophylaxis.

    LENUS (Irish Health Repository)

    Donnelly, C

    2012-02-01

    BACKGROUND: Cytomegalovirus (CMV) is the most common opportunistic infection after solid-organ transplantation, increasing morbidity and mortality. Three months of oral valganciclovir have been shown to provide effective prophylaxis. Late-onset CMV disease, occurring after the discontinuation of prophylaxis, is now increasingly recognised. AIMS: To investigate the incidence and the time of detection of CMV infections in liver transplant recipients who received CMV prophylaxis. METHODS: Retrospective review of 64 high- and moderate-risk patients with 1 year of follow-up. RESULTS: The incidence of CMV infection was 12.5%, with 4.7% disease. All cases of symptomatic CMV disease were of late-onset. CONCLUSIONS: The incidence of CMV infections in this study was low compared with literature reports; however, the late-onset disease is an emerging problem. Detection of late-onset disease may be delayed because of less frequent clinic follow-up visits. Increased regular laboratory monitoring may allow earlier detection at the asymptomatic infection stage.

  17. Progression of Late-Onset Stargardt Disease

    OpenAIRE

    Lambertus, Stanley; Lindner, Moritz; Bax, Nathalie M.; Mauschitz, Matthias M.; Nadal, Jennifer; Schmid, Matthias; Schmitz-Valckenberg, Steffen; den Hollander, Anneke I.; Weber, Bernhard H. F.; Holz, Frank G.; van der Wilt, Gert Jan; Fleckenstein, Monika; Hoyng, Carel B.

    2016-01-01

    Purpose: Identification of sensitive biomarkers is essential to determine potential effects of emerging therapeutic trials for Stargardt disease. This study aimed to describe the natural history of late-onset Stargardt, and demonstrates the accuracy of retinal pigment epithelium (RPE) atrophy progression as an outcome measure. Methods: We performed a retrospective cohort study collecting multicenter data from 47 patients (91 eyes) with late-onset Stargardt, defined by clinical phenotype...

  18. Observations of the late superhump in VW Hydri

    International Nuclear Information System (INIS)

    Van Der Woerd, H.; Van Der Klis, M.; Van Paradijs, J.; Beuermann, K.; Motch, C.

    1988-01-01

    This paper presents the results of simultaneous optical and near-IR photometry, optical fast spectroscopy, and Exosat X-ray observations of the dwarf nova VW Hyi, obtained simultaneously during three consecutive orbital cycles, approximately two days after the 1983 November superoutburst terminated. The optical data show clear evidence for a late superhump, which is shifted + 0.7 in phase relative to the orbital modulation. An attempt is made to derive from the observed spectral distribution the contribution of the late superhump. The orbital hump and the late superhump apparently are not related to each other. This important effect excludes all models, in which the late superhump phenomenon is interpreted in terms of variations in the bright-spot brightness. 43 references

  19. Fossil Microorganisms in Archaean

    Science.gov (United States)

    Astafleva, Marina; Hoover, Richard; Rozanov, Alexei; Vrevskiy, A.

    2006-01-01

    Ancient Archean and Proterozoic rocks are the model objects for investigation of rocks comprising astromaterials. The first of Archean fossil microorganisms from Baltic shield have been reported at the last SPIE Conference in 2005. Since this confeence biomorphic structures have been revealed in Archean rocks of Karelia. It was determined that there are 3 types of such bion structures: 1. structures found in situ, in other words microorganisms even-aged with rock matrix, that is real Archean fossils biomorphic structures, that is to say forms inhabited early formed rocks, and 3. younger than Archean-Protherozoic minerali microorganisms, that is later contamination. We made attempt to differentiate these 3 types of findings and tried to understand of burial of microorganisms. The structures belongs (from our point of view) to the first type, or real Archean, forms were under examination. Practical investigation of ancient microorganisms from Green-Stone-Belt of Northern Karelia turns to be very perspective. It shows that even in such ancient time as Archean ancient diverse world existed. Moreover probably such relatively highly organized cyanobacteria and perhaps eukaryotic formes existed in Archean world.

  20. Late effects of thoracic irradiation in children

    Energy Technology Data Exchange (ETDEWEB)

    Boelling, T.; Koenemann, S.; Ernst, I.; Willich, N. [Dept. of Radiotherapy, Univ. Hospital of Muenster (Germany)

    2008-06-15

    Purpose: to summarize the literature regarding the late effects of radiotherapy to the thorax in childhood and adolescence with special emphasis on cardiac and pulmonary impairment. Material und methods: the literature was critically reviewed using the PubMed {sup registered} database with the key words 'late effects', 'late sequelae', 'child', 'childhood', 'adolescence', 'radiation', 'radiotherapy', 'thorax', 'lung', 'heart', and 'pulmonary'. Results: 17 publications dealing with radiation-induced pulmonary and cardiac late sequelae in children could be identified and were analyzed in detail. 29 further publications with additional information were also included in the analysis. Pulmonary function impairment after mediastinal irradiation arose in one third of all pediatric patients, even when treatment was performed with normofractionated lower doses (15-25 Gy). Whole lung irradiation was regularly followed by pulmonary function impairment with differing rates in several reports. However, clinically symptomatic function impairment like dyspnea was less frequent. Irradiation of up to 25 Gy (single doses {<=} 2 Gy) to the heart showed little or no cardiac toxicity in analyses of irradiated children (median follow-up 1.3-14.3 years). Doses of > 25 Gy (single doses {<=} 2-3.3 Gy) led to several cardiac dysfunctions. However, new data from adults with longer follow-up may indicate threshold doses as low as 1 Gy. Impairment of skeletal growth, breast hypoplasia, and secondary malignancy were further potential late sequelae. Conclusion: several retrospective reports described radiation-associated late sequelae in children. However, there is still a lack of sufficient data regarding the characterization of dose-volume effects. (orig.)

  1. Takaka Fossil Cave : a stratified Late Glacial to Late Holocene deposit from Takaka Hill, New Zealand

    International Nuclear Information System (INIS)

    Worthy, T.H.; Roscoe, D.

    2003-01-01

    A rich terrestrial vertebrate fauna from the pitfall trap deposit of Takaka Fossil Cave on Takaka Hill, South Island, New Zealand, is described. Radiocarbon ages on moa bones bracket the onset of sedimentation in the site to between 12361 and 11354 14 C yrs BP. Euryapteryx geranoides was in the Late Glacial moa fauna that predates the onset of sedi-mentation in the site, but was absent in younger faunas. The moa Anomalopteryx didiformis was present in the Late Glacial fauna as well throughout the Holocene. A total of 1633 bones from 25 species of birds and a further 895 bones of 154 individuals of vertebrates other than birds (two species of frog, one tuatara, three lizards, two bats, and a rat) were identified in the total recovered fauna. A well-preserved partial skeleton of Haast's eagle (Harpagornis moorei) of Late Glacial age had severe arthritis. Unusually small specimens of Euryapteryx were morphologically diagnosed as E. geranoides, and confirmed as such by mitochondrial DNA analysis. The molluscan fauna contained two aquatic, troglobitic hydrobiids and 29 taxa of land snails. While there is little change in species diversity between lower and upper layers, there are marked changes in relative abundance of some taxa that suggest the environment was drier in the Early and Middle Holocene than it was in the Late Holocene. (author). 26 refs., 3 figs., 4 tabs

  2. The Berezitovoe gold-polymetallic deposit (Upper Amur region, Russia: Structure, mineralogy and genetic aspects

    Directory of Open Access Journals (Sweden)

    Alexandr S. Vakh

    2016-05-01

    Full Text Available The Berezitovoe deposit in the Sergachi volcano-plutonic and metallogenic belt preserves evidence for polymetallic mineralization of multiple stages. The steeply dipping garnet-tourmaline-muscovite-quartz metasomatites (with K-Ar ages of 132 ± 2.9 and 127 ± 4.4 Ma carry two distinct stages of mineralization developed at different times: (1 polymetallic mineralization and (2 gold-quartz. The deposit is located within Paleozoic gneissose granitoids of the Pikansky complex (dated as 379 ± 1.1 Ma by zircon U-Pb method intruded by early Cretaceous porphyry-like granites of the Haikta pluton (dated as 137 ± 0.67 Ma by zircon U-Pb method and late Cretaceous dikes of porphyrites, porphyries, and lamprophyres. Evidence suggests the action of late gold-bearing hydrothermal fluids on the early polymetallic ores and the selective mobilization of some elements from these lead to redeposition together with complex sulphosalts.

  3. Climate predictors of late quaternary extinctions

    DEFF Research Database (Denmark)

    Nogués-Bravo, David; Ohlemüller, Ralf; Batra, Persaram

    2010-01-01

    Between 50,000 and 3,000 years before present (BP) 65% of mammal genera weighing over 44 kg went extinct, together with a lower proportion of small mammals. Why species went extinct in such large numbers is hotly debated. One of the arguments proposes that climate changes underlie Late Quaternary...... extinctions, but global quantitative evidence for this hypothesis is still lacking. We test the potential role of global climate change on the extinction of mammals during the Late Quaternary. Our results suggest that continents with the highest climate footprint values, in other words, with climate changes...... of greater magnitudes during the Late Quaternary, witnessed more extinctions than continents with lower climate footprint values, with the exception of South America. Our results are consistent across species with different body masses, reinforcing the view that past climate changes contributed to global...

  4. Sirtinol abrogates late phase of cardiac ischemia preconditioning in rats.

    Science.gov (United States)

    Safari, Fereshteh; Shekarforoosh, Shahnaz; Hashemi, Tahmineh; Namvar Aghdash, Simin; Fekri, Asefeh; Safari, Fatemeh

    2017-07-01

    The aim of this study was to investigate the effect of sirtinol, as an inhibitor of sirtuin NAD-dependent histone deacetylases, on myocardial ischemia reperfusion injury following early and late ischemia preconditioning (IPC). Rats underwent sustained ischemia and reperfusion (IR) alone or proceeded by early or late IPC. Sirtinol (S) was administered before IPC. Arrhythmias were evaluated based on the Lambeth model. Infarct size (IS) was measured using triphenyltetrazolium chloride staining. The transcription level of antioxidant-coding genes was assessed by real-time PCR. In early and late IPC groups, IS and the number of arrhythmia were significantly decreased (P < 0.05 and P < 0.01 vs IR, respectively). In S + early IPC, incidences of arrhythmia and IS were not different compared with the early IPC group. However, in S + late IPC the IS was different from the late IPC group (P < 0.05). In late IPC but not early IPC, transcription levels of catalase (P < 0.01) and Mn-SOD (P < 0.05) increased, although this upregulation was not significant in the S + late IPC group. Our results are consistent with the notion that different mechanisms are responsible for early and late IPC. In addition, sirtuin NAD-dependent histone deacetylases may be implicated in late IPC-induced cardioprotection.

  5. 2D CFT partition functions at late times

    Science.gov (United States)

    Dyer, Ethan; Gur-Ari, Guy

    2017-08-01

    We consider the late time behavior of the analytically continued partition function Z( β + it) Z( β - it) in holographic 2 d CFTs. This is a probe of information loss in such theories and in their holographic duals. We show that each Virasoro character decays in time, and so information is not restored at the level of individual characters. We identify a universal decaying contribution at late times, and conjecture that it describes the behavior of generic chaotic 2 d CFTs out to times that are exponentially large in the central charge. It was recently suggested that at sufficiently late times one expects a crossover to random matrix behavior. We estimate an upper bound on the crossover time, which suggests that the decay is followed by a parametrically long period of late time growth. Finally, we discuss gravitationally-motivated integrable theories and show how information is restored at late times by a series of characters. This hints at a possible bulk mechanism, where information is restored by an infinite sum over non-perturbative saddles.

  6. Correlations between the North China Craton and the Indian Shield: Constraints from regional metallogeny

    Directory of Open Access Journals (Sweden)

    Caifeng Li

    2015-11-01

    Full Text Available The correlation between the North China Craton (NCC and the Indian Shield (IND has been a hot topic in recent years. On the basis of ore deposit databases, the NCC and IND have shown broad similarity in metallogenesis from the middle Archaean to the Mesoproterozoic. The two blocks both have three major metallogenic systems: (1 the Archaean BIF metallogenic system; (2 the Paleoproterozoic Cu-Pb-Zn metallogenic system; and (3 the Mesoproterozoic Fe-Pb-Zn system. In the north margin of the NCC and the west margin of the IND, the Archaean BIF-Au-Cu-Pb-Zn deposits had the same petrogenesis and host rocks, the Paleoproterozoic Cu-Pb-Zn deposits were controlled by active belts, and the Mesoproterozoic Fe-Pb-Zn deposits were mainly related to multi-stage rifting. Matching regional mineralization patterns and geological features has established the continental assembly referred to as “NCWI”, an acronym for the north margin of the NCC (NC and the west margin of the IND (WI during the middle Archaean to the Mesoproterozoic. In this assembly, the available geological and metallogenic data from the Eastern Block and active belts of NC fit those from the Dharwar craton and the Aravalli–Delhi–Vindhyan belt of WI, respectively. Moreover, the depositional model and environment of Paleoproterozoic metasedimentary manganese deposits in NCWI implied that the assembly may be located at low latitudes, where the conditions were favorable for dissolving ice and precipitating manganese deposits.

  7. Late effects of radiation therapy on the gastrointestinal tract

    International Nuclear Information System (INIS)

    Coia, Lawrence R.; Myerson, Robert J.; Tepper, Joel E.

    1995-01-01

    Late gastrointestinal complications of radiation therapy have been recognized but not extensively studied. In this paper, the late effects of radiation on three gastrointestinal sites, the esophagus, the stomach, and the bowel, are described. Esophageal dysmotility and benign stricture following esophageal irradiation are predominantly a result of damage to the esophageal wall, although mucosal ulcerations also may persist following high-dose radiation. The major late morbidity following gastric irradiation is gastric ulceration caused by mucosal destruction. Late radiation injury to the bowel, which may result in bleeding, frequency, fistula formation, and, particularly in small bowel, obstruction, is caused by damage to the entire thickness of the bowel wall, and predisposing factors have been identified. For each site a description of the pathogenesis, clinical findings, and present management is offered. Simple and reproducible endpoint scales for late toxicity measurement were developed and are presented for each of the three gastrointestinal organs. Factors important in analyzing late complications and future considerations in evaluation and management of radiation-related gastrointestinal injury are discussed

  8. Late Pleistocene dune activity in the central Great Plains, USA

    Science.gov (United States)

    Mason, J.A.; Swinehart, J.B.; Hanson, P.R.; Loope, D.B.; Goble, R.J.; Miao, X.; Schmeisser, R.L.

    2011-01-01

    Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20-25 ka are interbedded with loess south of the Sand Hills. Several of the large dunes sampled in the Sand Hills clearly contain a substantial core of Late Pleistocene sand; thus, they had developed by the Late Pleistocene and were fully mobile at that time, although substantial sand deposition and extensive longitudinal dune construction occurred during the Holocene. Many of the Late Pleistocene OSL ages fall between 17 and 14 ka, but it is likely that these ages represent only the later part of a longer period of dune construction and migration. At several sites, significant Late Pleistocene or Holocene large-dune migration also probably occurred after the time represented by the Pleistocene OSL ages. Sedimentary structures in Late Pleistocene eolian sand and the forms of large dunes potentially constructed in the Late Pleistocene both indicate sand transport dominated by northerly to westerly winds, consistent with Late Pleistocene loess transport directions. Numerical modeling of the climate of the Last Glacial Maximum has often yielded mean monthly surface winds southwest of the Laurentide Ice Sheet that are consistent with this geologic evidence, despite strengthened anticyclonic circulation over the ice sheet. Mobility of large dunes during the Late Pleistocene on the central Great Plains may have been the result of

  9. Late injury of cancer therapy on the female reproductive tract

    International Nuclear Information System (INIS)

    Grigsby, Perry W.; Russell, Anthony; Bruner, Deborah; Eifel, Patricia; Koh, Wui-Jin; Spanos, William; Stetz, Joann; Stitt, Judith Anne; Sullivan, Jessie

    1995-01-01

    The purpose of this article is to review the late effects of cancer therapy on the female reproductive tract. The anatomic sites detailed are the vulva, vagina, cervix, uterus, fallopian tubes, and ovaries. The available pathophysiology is discussed. Clinical syndromes are presented. Tolerance doses of irradiation for late effects are rarely presented in the literature and are reviewed where available. Management strategies for surgical, radiotherapeutic, and chemotherapeutic late effects are discussed. Endpoints for evaluation of therapeutic late effects have been formulated utilizing the symptoms, objective, management, and analytic (SOMA) format. Late effects on the female reproductive tract from cancer therapy should be recognized and managed appropriately. A grading system for these effects is presented. Endpoints for late effects and tolls for the evaluation need to be further developed

  10. Determined Initial lead for South Of Isua (SOI) terrain suggests a single homogeneous source for it and possibly other archaean rocks

    Science.gov (United States)

    Tera, F.

    2011-12-01

    other rocks from Isua Greenstone Belt (1) and Amîtsoq gneiss (4) fall inside the TULIP triangle of SOI, suggesting potential derivation of these Archaean rocks from the same homogeneous source.

  11. Palaeomagnetism and the continental crust

    Energy Technology Data Exchange (ETDEWEB)

    Piper, J.D.A.

    1987-01-01

    This book is an introduction to palaeomagnetism offering treatment of theory and practice. It analyzes the palaeomagnetic record over the whole of geological time, from the Archaean to the Cenozoic, and goes on to examine the impact of past geometries and movements of the continental crust at each geological stage. Topics covered include theory of rock and mineral magnetism, field and laboratory methods, growth and consolidation of the continental crust in Archaean and Proterozoic times, Palaeozoic palaeomagnetism and the formation of Pangaea, the geomagnetic fields, continental movements, configurations and mantle convection.

  12. Syn-collisional felsic magmatism and continental crust growth: A case study from the North Qilian Orogenic Belt at the northern margin of the Tibetan Plateau

    Science.gov (United States)

    Chen, Shuo; Niu, Yaoling; Xue, Qiqi

    2018-05-01

    The abundant syn-collisional granitoids produced and preserved at the northern Tibetan Plateau margin provide a prime case for studying the felsic magmatism as well as continental crust growth in response to continental collision. Here we present the results from a systematic study of the syn-collisional granitoids and their mafic magmatic enclaves (MMEs) in the Laohushan (LHS) and Machangshan (MCS) plutons from the North Qilian Orogenic Belt (NQOB). Two types of MMEs from the LHS pluton exhibit identical crystallization age ( 430 Ma) and bulk-rock isotopic compositions to their host granitoids, indicating their genetic link. The phase equilibrium constraints and pressure estimates for amphiboles from the LHS pluton together with the whole rock data suggest that the two types of MMEs represent two evolution products of the same hydrous andesitic magmas. In combination with the data on NQOB syn-collisional granitoids elsewhere, we suggest that the syn-collisional granitoids in the NQOB are material evidence of melting of ocean crust and sediment. The remarkable compositional similarity between the LHS granitoids and the model bulk continental crust in terms of major elements, trace elements, and some key element ratios indicates that the syn-collisional magmatism in the NQOB contributes to net continental crust growth, and that the way of continental crust growth in the Phanerozoic through syn-collisional felsic magmatism (production and preservation) is a straightforward process without the need of petrologically and physically complex processes.

  13. The late Cainozoic East Antarctic ice sheet

    International Nuclear Information System (INIS)

    Colhoun, E.A.

    1999-01-01

    A review, mainly of East Antarctic late Cainozoic (post 40 Ma) geological and geomorphological evidence, supports the hypothesis of the continuous presence of an ice sheet, of about the present size, since the late Miocene. Evidence is presented and the view advanced that, during the late Wisconsin maximum of isotope stage 2, ice was not nearly as thick or extensive over the continental shelf as required by the model of 'maximum' Antarctic glaciation. Some of the factors influencing the contribution of Antarctica to post-glacial sea-level rise are discussed. It is considered that Antarctica's contribution was probably considerably less than previously estimated. The dating of marine and freshwater sequences in the Vestfold and Bunger Hills is consistent with deglaciation around the Pleistocene Holocene boundary, after the Late Wisconsin maximum. A date of ∼25 ka BP from permafrost in the Larsemann Hills means that either the Larsemann Hills were not glaciated during the Late Wisconsin or the ice failed to erode much of the permafrost surface. The degree of weathering of rock and glacial drifts in the Vestfold, Larsemann and Bunger Hills suggests a long time for formation, perhaps considerably longer than indicated by the dated marine and freshwater sediment sequences. Cosmogenic isotope dating in the Vestfold Hills has provided equivocal ages for deglaciation. While the results could indicate deglaciation before 80 ka BP, they do not confirm such early deglaciation. If the ice cover was thin and failed to remove the previous rock exposure profile, then the assays could predate the last ice advance. Weathered iron crust fragments in the till suggest little erosion. The raised beaches of the oases are Holocene. Assuming they have been produced by post Late Wisconsin isostatic uplift and by the Holocene transgression, calculations show that the Antarctic continental ice sheet could not have been more than ∼500 m thicker in the inner shelf-coastal zone. The

  14. Late radiation effects in animals surviving lethal irradiation

    International Nuclear Information System (INIS)

    Dimitrov, L.A.

    1974-01-01

    Animals (rats, mice, dogs) survived lethal irradiation by means of prophylactic-therapeutic treatments or previously irradiated, were studied for late radiation effects: life span, cachexia and fat growing of hypophysical type, tissue or organ hypoplasia manifested by disturbed hemopoiesis, suppressed function of adrenal gland, etc., suppressed immune reactivity of the irradiated organism, atypical biochemical changes in DNA and protein metabolism, epilation, chronic dermatitis, ulcerations, reduced reproductivity or full sterility, damage of kidneys leading to nephrosclerosis, dishormonal states, cataracts, diffuse sclerotic processes, various kinds of malignant and non-malignant tumors. In these cases hemopoiesis compensated for a definite time peripheral blood composition, but during the late period it showed features of incompleteness: shorter life survival of erythrocytes and thrombocytes manifested by a decreased binding of labelled methionine in these blood elements, anemia and relative thrombocytopenia sometimes with an increased number of polychromatic erythrocytes in peripheral blood and a decreased number of reticulocytes at the same time; lymphopenia and relative leucopenia with an increased number of hypersegmented neutrophils. Decreased reproductivity and atypical biochemical changes available in the first generation of the irradiated animals showed the probable role of mutagenic factors in the emergence of some late radiation effects. A significant part of late radiation sequences were due to neuro-endocrine desintegrations which lead to a disturbed supply of the vessels and afterwards to their sclerosis. Some of the described late radiation effects were also observed in biological controls as festures of ageing while in irradiated animals they were manifested in an earlier period. After application of optimal amounts radioprotectors (AET, cysteamine, serotonin) a more marked protective effect is demonstrated in the early reactions (time survival

  15. The neuropsychology and neurobiology of late-onset schizophrenia and very-late-onset schizophrenia-like psychosis : a critical review

    OpenAIRE

    Assche, Van, Lies; Morrens, Manuel; Luyten, Patrick; Ven, Van de, Luc; Vandenbulcke, Mathieu

    2017-01-01

    Abstract: OBJECTIVE: The current review discusses neuropsychological profiles and the longitudinal course of cognitive dysfunction in Late Onset Schizophrenia (LOS) and Very-late-onset schizophrenia-like psychosis (VLOSLP), and attempts to clarify its neurobiological underpinnings. METHOD: A systematic literature search resulted in 29 publications describing original research on the neuropsychology of LOS/VLOSLP and 46 studies focussing on neurobiology. RESULTS: Although mildly progressive co...

  16. Use of petrophysical data for siting of deep geological repository of radioactive waste

    Science.gov (United States)

    Petrenko, Liliana; Shestopalov, Vyacheslav

    2017-11-01

    The paper is devoted to analyzing the petrophysical properties and petrographical characteristics of Volyn region with the view to choosing the least permeable and so the most suitable geological formation for the radioactive waste disposal. On a basis of the petrophysical estimations of the granitoids properties the argumentation of permeability has been developed for the petrotypes of Volyn region. Also method of classification of the petrotypes with their relative rate of suitability for radioactive waste disposal was developed. As a result of studying the perspectives were shown of the zhytomyr and korosten types of the granitoids as host rock for the radioactive waste disposal. According to the results of investigations performed by Swedish researchers a comparative analysis of rocks based on the age of formation, composition, structural features and some petrophysical properties of granitoids as host rocks for repository of radioactive waste was performed. Detail comparison the data of the granitoids of the Forsmark site in Sweden and the data of the granitoids of the Volyn megablock can be one of the next steps in researching the host rocks for the development of the RW disposal system in Ukraine.

  17. Use of petrophysical data for siting of deep geological repository of radioactive waste

    Directory of Open Access Journals (Sweden)

    Petrenko Liliana

    2017-01-01

    Full Text Available The paper is devoted to analyzing the petrophysical properties and petrographical characteristics of Volyn region with the view to choosing the least permeable and so the most suitable geological formation for the radioactive waste disposal. On a basis of the petrophysical estimations of the granitoids properties the argumentation of permeability has been developed for the petrotypes of Volyn region. Also method of classification of the petrotypes with their relative rate of suitability for radioactive waste disposal was developed. As a result of studying the perspectives were shown of the zhytomyr and korosten types of the granitoids as host rock for the radioactive waste disposal. According to the results of investigations performed by Swedish researchers a comparative analysis of rocks based on the age of formation, composition, structural features and some petrophysical properties of granitoids as host rocks for repository of radioactive waste was performed. Detail comparison the data of the granitoids of the Forsmark site in Sweden and the data of the granitoids of the Volyn megablock can be one of the next steps in researching the host rocks for the development of the RW disposal system in Ukraine.

  18. K-Ar age and tectonic setting of brannerite-mineralized Futagojima granodiorite, Koshiki Islands, Southern Kyushu

    International Nuclear Information System (INIS)

    Ishihara, Shunso; Shibata, Ken; Terashima, Shigeru

    1984-01-01

    Futagojima granodiorite, which was previously thought to be a part of Cretaceous Ryoke granitoids, is turned out to be upper Miocene granitoids (7.5 Ma). The granodiorite contains magnetite and is depleted in lithophile components. This is characteristics of magnetite-series granitoids in the Green Tuff terrains. All the Miocene granitoids in Koshiki Islands are relatively mafic consisting of hornblende-bearing facies such as quartz diorite, tonalite and granodiorite; thus belonging to I-type magnetite series. These rocks are considered to have generated at depth and formed along a rift zone during Miocene time (13 - 7 Ma). Thus, Koshiki Islands may represent an aborted rift at margin of the Danjo basin. Miocene granitoids of Koshiki Islands are small stocks but magmatic-hydrothermal ore deposits are only seen in Futagojima. This localization of mineralization is explained by a high degree of magmatic fractionation, which is only observed in Futagojima and by a low rate of erosion to preserve the mineralized horizons. Mineralization here is unique having brannerite-magnetite and chalcopyrite-molybdenite-quartz assemblages. No gold and silver were detected from the vein-type deposit. (author)

  19. Stratigraphic and tectonic revision of Cerro Olivo Complex located of Southeastern of Uruguay

    International Nuclear Information System (INIS)

    Masquelin, E.

    2004-01-01

    This paper presents a stratigraphic and tectonic revision of Cerro Olivo Complex, located in the Southeastern part of the Uruguayan Predevonian Shield. This informal lithostratigraphic unit constitutes the country rock for the emplacement of late-orogenic granitoids, during Neoproterozoic to Cambrian times. This unit groups all the lithodemes affected by deformation and metamorphism. Recent studies indicate the presence of straight gneisses of quartzo-feldspathic composition in the coast of Maldonado Department. These rocks were interpreted as the result of intense deformation in high temperature. These tectonites base a new stratigraphic insight for the complex. They allow their lithotypes to be organized by petrotectonic features, being a function of PT conditions for every last strain process [es

  20. Response in the late phase to a radiological emergency

    International Nuclear Information System (INIS)

    Morrey, M.; Nisbet, A.; Thome, D.; Savkin, M.; Hoe, S.; Brynildsen, L.

    2004-01-01

    This paper looks at the key issues that need to be addressed during the transition from the emergency phase to the late phase of a radioactive release, and the development of the initial late phase strategy. It discusses the extent to which current national plans and international advice address the needs of decision makers following contamination of inhabited areas and food production systems. Based on this the following recommendations are made: (1) the issues that will arise at the start of the late phase response to a radioactive release require preparation work in advance of any release; (2) this preparation should consider the adequacy of legislation, technical data and modelling, options for waste storage and disposal, resources for monitoring and implementing clean up; (3) late phase preparedness requires regular exercising and (4) the possibility of terrorist releases adds further emphasis to the need for preparedness for the late phase. (authors)

  1. Paradox of Prescribing Late Chemotherapy: Oncologists Explain.

    Science.gov (United States)

    Bluhm, Minnie; Connell, Cathleen M; De Vries, Raymond G; Janz, Nancy K; Bickel, Kathleen E; Silveira, Maria J

    2016-12-01

    The value of chemotherapy for patients with cancer in the last weeks of life warrants examination. Late chemotherapy may not improve survival or quality of life but typically precludes hospice enrollment and may result in additional symptoms, increased use of other aggressive treatments, and worsening quality of life. Few studies have explored oncologists' rationales for administering chemotherapy near death. This study examines the self-reported factors that influence oncologists' decisions about late chemotherapy. In-depth individual interviews were conducted with 17 oncologists through a semistructured interview guide. Interviews were audio recorded and transcribed verbatim. Transcripts were coded and analyzed using conventional content analysis, a qualitative method that allows the detection and analysis of patterns in the data. Clinical factors take priority in determining late chemotherapy decisions when clear treatment choices exist. When clinical factors are ambiguous, emotion becomes a highly salient influence. Oncologists view late chemotherapy to be patient driven and use it to palliate emotional distress and maintain patient hope even when physical benefit is unexpected. Oncologists experience unique and difficult challenges when caring for dying patients, including emotionally draining communication, overwhelming responsibility for life/death, limitations of oncology to heal, and prognostic uncertainty. These challenges are also eased by offering late chemotherapy. The findings reveal a nuanced understanding of why oncologists find it difficult to refuse chemotherapy treatment for patients near death. Optimal end-of-life treatment decisions require supportive interventions and system change, both of which must take into account the challenges oncologists face.

  2. Migration of fluids as a tool to evaluate the feasibility of the implantation of geological radioactive wastes repositories (RARN) in granitoid rocks: tests on granites submitted to natural deformation vs. not deformed; A migração de fluidos como ferramenta de avaliação da viabilidade da implantação de repositórios de rejeitos radioativos geológicos (RARN) em rochas granitoides: testes em granitos submetidos a deformação natural vs. não deformados

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Nilo Henrique Balzani; Barbosa, Pedro Henrique Silva; Santos, Alanna Leite dos; Amorim, Lucas Eustáquio Dias; Freitas, Mônica Elizetti de; Rios, Francisco Javier, E-mail: javier@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Lab. de Caracterização Mineralógica e Metalogênese

    2017-07-01

    Fluid composition and migration studies in granitoid rocks subjected to deformation events are a factor that should be considered in the selection of geologically favorable areas for RANR construction, and may be an excellent complement to engineering barrier designs. The research objective was to develop an academic approach, comparing the behavior of deformed and non-deformed granites, not being related to any CNEN project of deploying repositories. It is concluded that in the choice of suitable sites for the construction of repositories, granite bodies that are submitted to metamorphic / deformation / hydrothermal events or that are very fractured should be disregarded. The domes of granite batholith that have undergone hydraulic billing should also be discarded. It has been found that, because of the warming caused by radioactive decay reactions, there is a real possibility that the release of potentially abrasive fluids contained in the minerals can reach and corrode the walls of the repositories and / or packaging.

  3. Big Java late objects

    CERN Document Server

    Horstmann, Cay S

    2012-01-01

    Big Java: Late Objects is a comprehensive introduction to Java and computer programming, which focuses on the principles of programming, software engineering, and effective learning. It is designed for a two-semester first course in programming for computer science students.

  4. New Rb-Sr isotopic ages and geochemistry of granitic gneisses from southern Bastar: implications for crustal evolution

    International Nuclear Information System (INIS)

    Sarkar, G.; Gupta, S.N.; Bishui, P.K.

    1994-01-01

    Deformed gneisses from the southern Bastar craton yield Rb-Sr whole-rock ages of 2560 Ma and 2659 Ma with initial Sr ratios ranging between 0.70899 and 0.70726 respectively. The isotopic data are found to be scattered even at the outcrop scale which possibly indicate large-scale reworking of the gneisses during the period. The high initial Sr ratios that associate with scattering of the isotopic data reflect reworking of older gneisses. Geochemically, these gneisses are considered to be derived from an amphibolitic or basaltic protolith. The 2095 Ma (initial Sr ratio of 0.74312) old leucocratic granite intrusive into these gneisses represent early Proterozoic magmatic activity. Based on the available isotopic and geochemical data, it is suggested that the Bastar craton represents a polyphase, multicomponent terrain developed by repeated magmatism at a much earlier, probably during mid-Archaean, time and was extensively reworked during the time span between end-Archaean and early Proterozoic period. This reworking may be synchronous with coalescing of smaller crustal components possibly during the end-Archaean time. (author). 21 refs., 5 figs., 2 tabs

  5. Late Embryogenesis Abundant Proteins

    NARCIS (Netherlands)

    Shih, M.D.; Hoekstra, F.A.; Hsing, Y.I.C.

    2008-01-01

    During the late maturation stage of seed development, water content decreases greatly. One of the most striking characteristics of mature orthodox seeds is their ability to withstand severe desiccation. Mechanisms of plant drought/desiccation tolerance have been studied by numerous groups, and a

  6. Late Globalization and Evolution and Metamorphoses of Industries

    DEFF Research Database (Denmark)

    Boujarzadeh, Behnam; Turcan, Romeo V.; Dholakia, Nikhilesh

    2016-01-01

    In this paper we explore the effect of late globalization on evolution of industries. Specifically we investigate the impact of late globalization on the evolution and metamorphoses of Danish Textile and Fashion Industry (DTFI). Using historical data, we survey the development of DTFI between 1945...

  7. Late baryogenesis faces primordial nucleosynthesis

    International Nuclear Information System (INIS)

    Delbourgo-Salvador, P.; Audouze, J.; Salati, P.

    1991-11-01

    Since the sphalleron mechanism present in the standard theory of electro-weak interactions violates B+L, models have been suggested where baryogenesis takes place at late epochs and is concomitant with primordial nucleosynthesis. The possibility for the baryon asymmetry to be generated was numerically investigated at the same time as the light elements are cooked. The primordial yields of D, 3 He, 4 He and 7 Li were shown to exceed the upper limits inferred from observation, unless baryogenesis is anterior to the freeze-out of the weak interactions. This implies strong constraints on scenarios where the baryon asymmetry originates from the late decay of massive gravitinos. (author) 18 refs., 6 figs

  8. Late somatic sequelae after treatment of childhood cancer in Slovenia

    Directory of Open Access Journals (Sweden)

    Erman Nuša

    2012-05-01

    Full Text Available Abstract Background This is a long-term follow-up clinical study of adolescents and adults, survivors of childhood cancer. We evaluate and analyze the late somatic sequelae of childhood cancer treatment. Many such studies are susceptible to a strong selection bias, i.e., they employ a limited non-systematic sample of patients, based on a clinical hospital that provided the cancer treatment or performed the follow-up. To address the issue of selection bias, we perform here an analysis of late sequelae on a systematic database of the entire population of the children treated for cancer in Slovenia. Due to the specifics of cancer treatment procedures in Slovenia, they have all been treated and followed-up in the same clinic. Methods The data are based on the centralized registry of cancer patients in Slovenia and present a controlled and homogeneous collection. Late sequelae are evaluated following a modified CTCAE, i.e., the National Cancer Institute’s Common Terminology Criteria for Adverse Events version 3.0. We use survival analysis method to estimate the incidence of and risk for late sequelae, where the time variable is measured in years from the diagnosis date, while we follow the event of incidence of late sequelae scored other than none. Survival analysis is performed using KaplanMeier estimator and Cox regression model. Results The incidence of mild, moderate, or severe late sequelae of childhood cancer treatment significantly decreased from 75% in the group of patients diagnosed before 1975 to 55% for those diagnosed after 1995. The Cox regression analysis of the risk factors for the incidence of late sequelae identifies three significant factors: treatment modalities, age at diagnosis, and primary diagnosis. Conclusions The change of treatment modalities in terms of replacement of surgery and radiotherapy with chemotherapy is the main reason for the decrease of the incidence and the risk for late sequelae of childhood cancer treatment

  9. Lattice-preferred orientations of late-Variscan granitoids derived from neutron diffraction data: implications for magma emplacement mechanisms

    Czech Academy of Sciences Publication Activity Database

    Müller, A.; Leiss, B.; Ullemeyer, K.; Breiter, Karel

    2011-01-01

    Roč. 100, č. 7 (2011), s. 1515-1532 ISSN 1437-3254 Institutional research plan: CEZ:AV0Z30130516 Keywords : neutron diffraction * lattice-preferred orientation * shape-preferred orientation * magma tic flow * Podlesí granite * Meissen massif Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.342, year: 2011

  10. The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes

    Science.gov (United States)

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Litvak, Vanesa D.; Poma, Stella; Alonso, Ricardo N.; Hinton, Richard; EIMF

    2016-10-01

    The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29-31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ U-Pb dating of magmatic zircon, combined with Ar-Ar dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data. A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous ( 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle. The Late Oligocene ( 26 Ma) to Early Miocene ( 17 Ma), and Late Miocene ( 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the Permian-Triassic (P

  11. The Pan-African continental margin in northeastern Africa: Evidence from a geochronological study of granulites at Sabaloka, Sudan

    International Nuclear Information System (INIS)

    Kroener, A.

    1987-01-01

    Ion microprobe zircon ages, a Nd model age and Rb-Sr whole-rock dates are reported from the high-grade gneiss terrain at Sabaloka on the River Nile north of Khartoum, formally considered to be part of the Archaean/early Proterozoic Nile craton. The granulites, which are of both sedimentary and igneous derivation, occur as remnants in migmatites. Detrital zircon ages range from ≅ 1000 to ≅ 2650 Ma and prove the existence of Archaean to late Proterozoic continental crust in the sedimentary source region. The Nd model age for one sedimentary granulite is between 1.26 (T CHUR ) and 1.70 (T DM ) Ga and provides a mean crustal residence age for the sedimentary precursor. Igneous zircons in enderbitic gneiss crystallized at 719±81 Ma ago, an age that also corresponds to severe Pb loss in the detrital zircons and whic probably reflects the granulite event at Sabaloka. The Rb-Sr data indicate isotropic homogenization at about 700 Ma ago in the granulites and severe post-granulite disturbance at ≅ 570 Ma in the migmatites. We associate this disturbance with hydration, retrograde metamorphism and anatexis that produced undeformed granites ≅ 540 Ma ago. The ≅ 700 Ma granulite event at Sabaloka suggests that this part of the Sudan belongs to the Pan-African Mozambique belt while the ancient Nile craton lay farther west. The gneisses studied here may represent the infrastructure of the ancient African continental margin onto which the juvenile arc assemblage of the Arabian-Nubian shield was accreted during intense horizontal shortening and crustal interstacking of a major collision event. (orig.)

  12. Late complications after radiotherapy for prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Jung, H. [University Hospital Hamburg-Eppendorf (Germany). Inst. of Biophysics and Radiobiology; University Hospital Hamburg-Eppendorf (Germany). Lab. of Radiobiology and Experimental Radiooncology; Beck-Bornholdt, H.P. [University Hospital Hamburg-Eppendorf (Germany). Inst. of Biophysics and Radiobiology; Svoboda, V. [University Hospital Hamburg-Eppendorf (Germany). Inst. of Biophysics and Radiobiology; Portsmouth Oncology Centre, Saint Mary' s Hospital (United Kingdom). Dept. of Radiotherapy; Alberti, W. [University Hospital Hamburg-Eppendorf (Germany). Dept. of Radiotherapy and Radiooncology; Herrmann, T. [Technical Univ. Dresden (Germany). Dept. of Radiotherapy and Radiooncology

    2012-11-15

    Background: The aim of the present study was to analyze in detail the time course of the incidence of radiation-induced late effects. For this purpose, unpublished data of patients treated by radiation therapy in Hamburg in the late 1980s were analyzed. Relatively large volumes were exposed to comparatively high doses, thus leading to a high rate of treatment-related side effects. Patients and methods: A total of 180 consecutive patients received radiotherapy for prostate cancer. The median age was 66 years (range 41-88 years). The median of the maximum dose was 77.5 Gy (range 56.3-95 Gy) and overall treatment time was 51 days (range 28-128 days). Endpoints analyzed were late complications of grade 3 or higher, overall and disease-free survival, local tumor control, and distant metastases. Data analysis was actuarial and the log-rank test was used to compare the various subgroups. Results After 2 years, 80.5 {+-} 3.2% of the patients were without any complications of grade 3 or higher, and after 5 years a constant level of 70.3 {+-} 4.0% was approached. When multiple lesions occurred per patient, the later events were disregarded. A total of 66 complications occurred in 42 patients. The percentage of patients being free from late complications, plotted as a function of time after start of radiation therapy, was adequately described by an exponential function and a constant fraction. Complications approached a constant level of 70.3% at a rate of 5.3% per month. This means that patients who will develop a complication do so at exponential kinetics and at a relatively high rate, whereas about 70% of the patients will never experience a late effect even over long observation periods. After subdividing the maximum dose into three equal dose groups of 55 patients each (< 73.3 Gy, 73.3-80 Gy, > 80 Gy), the constant fraction decreased from 85.7 to 72.8% and 52.2%, whereas the incidence rate was 4.3%, 7.7%, and 5.6% per month and, thus, almost independent of radiation dose

  13. Late Career Decision-Making: A Qualitative Panel Study

    NARCIS (Netherlands)

    Wilmar Schaufeli; Annet de Lange; Juhani Ilmarinen; Per Erik Solem; Trude Furunes; Reidar Mykletun; Astri Syse

    2015-01-01

    The aim of this longitudinal qualitative interview study (3 waves of interviews) was to examine the nature of older workers’ late career decision-making processes, including the main drivers and obstacles for prolonging working life or retiring. Late career decision-making is regarded as a process

  14. Mobile ICT Acceptance in Late Adopter Countries

    DEFF Research Database (Denmark)

    Gimpel, Gregory; Sudzina, Frantisek; Petrovcikova, Katarina

    2014-01-01

    Despite the rapid global diffusion of the smartphone, some countries have experienced much slower uptake of the technology. The low smartphone penetration within Slovakia provides the opportunity to explore what drives smartphone use in late majority countries. Slovakia is a central European nation...... and part of the Eurozone. It has advanced telecommunications infrastructure and is subject to the same telecommunications regulations as other EU members. While neighbours have high smartphone penetration, Slovakia is a late majority adopter. This study uses Triandis’ theory of interpersonal behavior...... to investigate the question: What drives the use of smartphones in late majority countries? By studying the differences between current and potential smartphone users, the study revisits Karahanna et al.’s research question: Do potential adopters and users of IT hold the same behavioral and normative beliefs...

  15. Late presentation of developmental dysplasia of the hip.

    LENUS (Irish Health Repository)

    Gul, R

    2012-02-03

    BACKGROUND: A neonatal screening programme for developmental dysplasia of the hip (DDH) is ongoing in Cork. Despite early screening, infants continue to present at later ages with DDH. The impact of late diagnosis is significant. Established DDH causes significant morbidity and may have major medicolegal implications. AIM: To identify the reasons for the late presentation of DDH in the presence of a screening programme. METHODS: In a retrospective study all cases of late DDH presenting from 1988 to 2000 were identified using inpatient database. RESULTS: Forty-nine cases of DDH were diagnosed. The mean age of diagnosis was 14.8 months (range 6-47). Multiple risk factors were identified in four patients only. More than one risk factor was identified in 10 patients. CONCLUSION: Despite screening, children continue to present with late DDH. In this study, only 14 patients had multiple risk factors and only four patients had more than two risk factors, highlighting the low incidence of suspicion in this patient group.

  16. WILDFIRES IN THE LATE PALAEOZOIC AND MESOZOIC OF THE SOUTHERN ALPS THE LATE PERMIAN OF THE BLETTERBACH-BUTTERLOCH AREA (NORTHERN ITALY

    Directory of Open Access Journals (Sweden)

    DIETER UHL

    2012-07-01

    Full Text Available For the first time fossil macroscopic remains of charcoal as direct evidence of palaeo-wildfires from the Late Permian Gröden Formation of the Bletterbach-Butterloch area in Northern Italy is described. The charcoal consists of pycnoxylic wood and originates from gymnosperms, but a more specific affiliation is not possible due to the fragmentary nature of the material. On a global scale our knowledge about Late Permian fire-ecology is still rather scarce and this finding helps to fill one of the numerous geographical gaps in our current knowledge about Late Permian wildfires. 

  17. Late effecten van kankerbehandeling

    NARCIS (Netherlands)

    Langeveld, Nelia E.

    2004-01-01

    In dit artikel wordt ingegaan op de lange termijn effecten van kanker op de kinderleeftijd. Vervolgens wordt een kort overzicht gegeven van de belangrijkste late gevolgen die kunnen optreden na een oncologische behandeling met radio- en/of chemotherapie toegepast in de kinderleeftijd. Er wordt kort

  18. Late Raphael

    OpenAIRE

    Henry, Tom F. K.; Joannides, Paul; González Mozo, Ana; Martín, Bruno

    2012-01-01

    Exhibition catalogue (co-authored with P. Joannides) in English, Spanish and French by the Museo del Prado and the Musée du Louvre, 2012. English edition, publisher: Museo Nacional del Prado (ISBN 978-84-8480-237-2). 382 pages, of which 300 were co-authored with P. Joannides. This publication was the catalogue of the major exhibtion of Raphael's late work which was at the Prado and the Louvre in 2012-13. The exhibition was seen by more than 650,000 visitors, and was widely reviewed in the int...

  19. Late Babylonian Astrology

    Science.gov (United States)

    Steele, John M.

    The last five centuries BC saw the development of several new forms of astrology in Babylonia. Key to these new astrological techniques was the invention of the zodiac in about 400 BC. These new forms of astrology include personal horoscopes, astral medicine, and the exploitation of geometrical relationships between the position of heavenly bodies. Several Late Babylonian astrological doctrines were later adopted within Greek astrology.

  20. Late-modern transformation of Islam or Islamic transformation of Late-modern Religiosity?

    DEFF Research Database (Denmark)

    Riexinger, Martin Thomas

    2017-01-01

    The Turkish author Muhammed Bozdağ, who has no formal religious education, has been popular since the late 1990s because of his self-help seminars and self-help books. Though they are based on the adaptation of Western New Age-inspired models, Bozdağ uses many of the models’ parascientific concepts...

  1. SHRIMP U-Pb zircon dating of Archean core complex formatio and pancratonic strike-slip deformation in the East Pilbara Granite-Greenstone Terrain

    NARCIS (Netherlands)

    Zegers, T.E.; Nelson, D.R.; Wijbrans, J.R.; White, S.H.

    2001-01-01

    Sensitive high-resolution ion microprobe (SHRIMP) U-Pb dating of zircons from granitic rocks in the East Pilbara Granite-Greenstone Terrain has provided time constraints for main tectonic events in the Shaw Granitoid Complex and has shown that deformation was intricately related to granitoid

  2. Anatomy of the late radiation encephalopathy

    Energy Technology Data Exchange (ETDEWEB)

    De Reuck, J; vander Eecken, H

    1975-01-01

    The clinico-pathological data and the topography of the lesions were determined in 13 cases of late radiation encephalopathy. In one case the arterial vascularisation was studied by the translucidation technique after filling of the blood vessels with a colloidal barium sulphate solution. The radiation lesions consisted of areas of focal necrosis and of diffuse demyelination and necrosis of the deep cerebral structures and the brain stem. Demyelination was predominantly present in cases of late appearance of the neurological symptoms while necrosis was found in cases with a short latency period. The cerebral cortex and the arcuate fibres were always the most preserved structures. The topography of the focal lesions in the cerebral hemispheres and in the brain stem corresponded well to the vascular supply areas of the deep perforating arteries, while the diffuse lesions always had a predominant distribution in the periventricular arterial end- and border-zones. These observations were also confirmed by a post mortem angiographic study. The present report argues once more for a vascular aetiology as cause of the late radiation encephalopathy.

  3. PRR11 regulates late-S to G2/M phase progression and induces premature chromatin condensation (PCC)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chundong; Zhang, Ying; Li, Yi; Zhu, Huifang; Wang, Yitao; Cai, Wei [Department of Biochemistry and Molecular Biology, Chongqing Medical University, Chongqing 400016 (China); Molecular Medicine and Cancer Research Center, Chongqing Medical University, Chongqing 400016 (China); Zhu, Jiang [Molecular Medicine and Cancer Research Center, Chongqing Medical University, Chongqing 400016 (China); Ozaki, Toshinori [Laboratory of DNA Damage Signaling, Chiba Cancer Center Research Institute, 666-2 Nitona, Chuohku, Chiba 260-8717 (Japan); Bu, Youquan, E-mail: buyqcn@aliyun.com [Department of Biochemistry and Molecular Biology, Chongqing Medical University, Chongqing 400016 (China); Molecular Medicine and Cancer Research Center, Chongqing Medical University, Chongqing 400016 (China)

    2015-03-13

    Recently, we have demonstrated that proline-rich protein 11 (PRR11) is a novel tumor-related gene product likely implicated in the regulation of cell cycle progression as well as lung cancer development. However, its precise role in cell cycle progression remains unclear. In the present study, we have further investigated the expression pattern and functional implication of PRR11 during cell cycle in detail in human lung carcinoma-derived H1299 cells. According to our immunofluorescence study, PRR11 was expressed largely in cytoplasm, the amount of PRR11 started to increase in the late S phase, and was retained until just before mitotic telophase. Consistent with those observations, siRNA-mediated knockdown of PRR11 caused a significant cell cycle arrest in the late S phase. Intriguingly, the treatment with dNTPs further augmented PRR11 silencing-mediated S phase arrest. Moreover, knockdown of PRR11 also resulted in a remarkable retardation of G2/M progression, and PRR11-knockdown cells subsequently underwent G2 phase cell cycle arrest accompanied by obvious mitotic defects such as multipolar spindles and multiple nuclei. In addition, forced expression of PRR11 promoted the premature Chromatin condensation (PCC), and then proliferation of PRR11-expressing cells was massively attenuated and induced apoptosis. Taken together, our current observations strongly suggest that PRR11, which is strictly regulated during cell cycle progression, plays a pivotal role in the regulation of accurate cell cycle progression through the late S phase to mitosis. - Highlights: • PRR11 started to increase in the late S phase and was retained until just before mitotic telophase. • PRR11-knockdown caused a significant cell cycle arrest in the late S phase and G2 phase. • The treatment with dNTPs further augmented PRR11 silencing-mediated S phase arrest. • PRR11-knockdown led to multipolar spindles and multiple nuclei. • Forced expression of PRR11 promoted the PCC and inhibited

  4. PRR11 regulates late-S to G2/M phase progression and induces premature chromatin condensation (PCC)

    International Nuclear Information System (INIS)

    Zhang, Chundong; Zhang, Ying; Li, Yi; Zhu, Huifang; Wang, Yitao; Cai, Wei; Zhu, Jiang; Ozaki, Toshinori; Bu, Youquan

    2015-01-01

    Recently, we have demonstrated that proline-rich protein 11 (PRR11) is a novel tumor-related gene product likely implicated in the regulation of cell cycle progression as well as lung cancer development. However, its precise role in cell cycle progression remains unclear. In the present study, we have further investigated the expression pattern and functional implication of PRR11 during cell cycle in detail in human lung carcinoma-derived H1299 cells. According to our immunofluorescence study, PRR11 was expressed largely in cytoplasm, the amount of PRR11 started to increase in the late S phase, and was retained until just before mitotic telophase. Consistent with those observations, siRNA-mediated knockdown of PRR11 caused a significant cell cycle arrest in the late S phase. Intriguingly, the treatment with dNTPs further augmented PRR11 silencing-mediated S phase arrest. Moreover, knockdown of PRR11 also resulted in a remarkable retardation of G2/M progression, and PRR11-knockdown cells subsequently underwent G2 phase cell cycle arrest accompanied by obvious mitotic defects such as multipolar spindles and multiple nuclei. In addition, forced expression of PRR11 promoted the premature Chromatin condensation (PCC), and then proliferation of PRR11-expressing cells was massively attenuated and induced apoptosis. Taken together, our current observations strongly suggest that PRR11, which is strictly regulated during cell cycle progression, plays a pivotal role in the regulation of accurate cell cycle progression through the late S phase to mitosis. - Highlights: • PRR11 started to increase in the late S phase and was retained until just before mitotic telophase. • PRR11-knockdown caused a significant cell cycle arrest in the late S phase and G2 phase. • The treatment with dNTPs further augmented PRR11 silencing-mediated S phase arrest. • PRR11-knockdown led to multipolar spindles and multiple nuclei. • Forced expression of PRR11 promoted the PCC and inhibited

  5. Fluid geochemistry associated associated to rocks: preliminary tests om minerals of granite rocks potentially hostess of radioactive waste repository; Geoquimica de fluidos associados a rochas: testes preliminares em minerais de rochas granitoides potencialmente hospedeiras de repositorios de rejeitos radioativos

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, Lucas E.D.; Rios, Francisco J.; Oliveira, Lucilia A.R. de; Alves, James V.; Fuzikawa, Kazuo; Garcia, Luiz; Ribeiro, Yuri, E-mail: LDAmorim@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Matos, Evandro C. de [Industrias Nucleares do Brasil S.A. (INB), Caetite, BA (Brazil)

    2009-07-01

    Fluid inclusions (FI) are micro cavities present on crystals and imprison the mineralizer fluids, and are formed during or posterior to the mineral formation. Those kind of studies are very important for orientation of the engineer barrier projects for this purpose, in order to avoid that the solutions present in the mineral FI can affect the repository walls. This work proposes the development of FI micro compositional studies in the the hostess minerals viewing the contribution for a better understanding of the solution composition present in the metamorphosis granitoid rocks. So, micro thermometric, microchemical and characterization of the material confined in the FI, and the hostess minerals. Great part of the found FI are present in the quartz and plagioclase crystals. The obtained data on the mineral compositions and their inclusions will allow to formulate hypothesis on the process which could occurs at the repository walls, decurrens from of the corrosive character (or not) of the fluids present in the FI, and propose measurements to avoid them

  6. LATE RENAL GRAFT REJECTION: PATHOLOGY AND PROGNOSIS

    Directory of Open Access Journals (Sweden)

    E.S. Stolyarevich

    2014-01-01

    Full Text Available Rejection has always been one of the most important cause of late renal graft dysfunction. Aim of the study was to analyze the prevalence of different clinico-pathological variants of rejection that cause late graft dysfunction, and evaluate their impact on long-term outcome. Materials and methods. This is a retrospective study that analyzed 294 needle core biopsy specimens from 265 renal transplant recipients with late (48,8 ± 46,1 months after transplantation allograft dysfunction caused by late acute rejection (LAR, n = 193 or chronic rejection (CR, n = 78 or both (n = 23. C4d staining was performed by immunofl uorescence (IF on frozen sections using a standard protocol. Results. Peritubular capillary C4d deposition was identifi ed in 36% samples with acute rejection and in 62% cases of chronic rejection (including 67% cases of transplant glomerulopathy, and 50% – of isolated chronic vasculopathy. 5-year graft survival for LAR vs CR vs their combination was 47, 13 and 25%, respectively. The outcome of C4d– LAR was (p < 0,01 better than of C4d+ acute rejection: at 60 months graft survival for diffuse C4d+ vs C4d− was 33% vs 53%, respectively. In cases of chronic rejection C4d+ vs C4d– it was not statistically signifi cant (34% vs 36%. Conclusion. In long-term allograft biopsy C4d positivity is more haracteristic for chronic rejection than for acute rejection. Only diffuse C4d staining affects the outcome. C4d– positivity is associated with worse allograft survival in cases of late acute rejection, but not in cases of chronic rejection. 

  7. Inflammatory markers of radiation-induced late effects

    International Nuclear Information System (INIS)

    Dubner, D.; Gallegos, C.; Michelin, S.; Portas, M.

    2011-01-01

    Up to now there is no established parameters for the follow-up of delayed radiation injuries. Late toxicity is generally irreversible and can have devastating effects on quality of life of people exposed either accidentally or during therapeutic radiation treatments. Histologically, late manifestations of radiation damage include fibrosis, necrosis, atrophy and vascular lesions. Although many etiologies have been suggested regarding these late toxicities, persistent inflammation has been described as playing a key role. The recruitment of leukocytes from circulating blood is decisive in the inflammatory reaction. All the steps in the recruitment cascade are orchestrated by cell-adhesion molecules (CAMs) on both leukocytes and endothelial cells, and different subsets of CAMs are responsible for different steps in extravasation. A link between radiation –induced inflammatory processes and alterations in T-cell immunity are still demonstrable in the blood of A-bomb survivors. The following study was conducted to examine the response of the immune system in the inflammatory reactions in patients with late skin injuries after radiotherapy or interventional fluoroscopy procedures. The expression of adhesion molecules ICAM1 and β1-integrin on granulocytes and lymphocytes, as well as changes in subpopulations of T lymphocytes and the level of C-reactive protein, a well- studied inflammatory marker were evaluated. (authors)

  8. Late Jute seed production in cropland agroforestry system

    Directory of Open Access Journals (Sweden)

    Kazi Noor-E-Alam Jewel

    2015-12-01

    Full Text Available Farmers were not self-sufficient in jute seed production and cultivation to avoid use exotic jute seed from different resources. Though the conventional method of jute seed production was not enough to meet the demand of farmers because of shrinkage of jute seed production land. So, late jute seed production technique was applied in agroforestry systems at both established and newly developed orchards. The study was conducted in the selected three sites of Rangpur, Dinajpur and Faridpur. Both White (Corchorus capsularis L.cv. CVL-1 and Tossa (two popular cultivars, eg., Corchorus olitorius L. cv. O-9897, and cv. O-72 varieties were used for to evaluate the late jute seed production in cropland agroforestry in 2011- 2013. It was observed that 600 kg ha-1 to 725 kg ha-1 of jute seed was produced in different types of orchard plantation. Seeds from Litchi orchard showed the higher fiber yield (1051.11, 2511.11 and 3555.56 kg ha-1 at Rangpur, Dinajpur and Faridpur, respectively than the mango orchard. Nutrient contents of soil in three sits were improved significantly due to the cultivation of late jute seed production. Moreover, late jute seed production in early stages of orchard plantation was more profitable and late jute can be produced economically for five to seven years depending on the plantations type and age.

  9. Late Palaeozoic plants.

    Science.gov (United States)

    Feng, Zhuo

    2017-09-11

    Land plants are one of the major constituents of terrestrial ecosystems on Earth, and play an irreplaceable role in human activities today. If we are to understand the extant plants, it is imperative that we have some understanding of the fossil plants from the deep geological past, particularly those that occurred during their early evolutionary history, in the late Palaeozoic. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. A case of late-onset oligomeganephronia

    Directory of Open Access Journals (Sweden)

    Rafael José Vargas Alves

    2012-12-01

    Full Text Available A 33-year old caucasian man was investigated for pain in the right flank, proteinuria, hemathuria and an elevated serum creatinine level. He also presented an abnormal ultrasonography, which revealed asymmetric kidneys. Through renal biopsy, the diagnosis of oligomeganephronia (OMN was confirmed. OMN is a very rare form of renal hypoplasia, and late-onset in adulthood is even rarer. In the pediatric population, OMN leads to end-stage-renal-failure(ESRF in a few years. This is the sixth case related in the literature of a late-onset OMN who have not yet developed ESRF.

  11. Late-time cosmological phase transitions

    International Nuclear Information System (INIS)

    Schramm, D.N.

    1990-11-01

    It is shown that the potential galaxy formation and large-scale structure problems of objects existing at high redshifts (Z approx-gt 5), structures existing on scales of 100M pc as well as velocity flows on such scales, and minimal microwave anisotropies (ΔT/T) approx-lt 10 -5 can be solved if the seeds needed to generate structure form in a vacuum phase transition after decoupling. It is argued that the basic physics of such a phase transition is no more exotic than that utilized in the more traditional GUT scale phase transitions, and that, just as in the GUT case, significant random gaussian fluctuations and/or topological defects can form. Scale lengths of ∼100M pc for large-scale structure as well as ∼1 M pc for galaxy formation occur naturally. Possible support for new physics that might be associated with such a late-time transition comes from the preliminary results of the SAGE solar neutrino experiment, implying neutrino flavor mixing with values similar to those required for a late-time transition. It is also noted that a see-saw model for the neutrino masses might also imply a tau neutrino mass that is an ideal hot dark matter candidate. However, in general either hot or cold dark matter can be consistent with a late-time transition. 47 refs., 2 figs

  12. Psychiatry: life events and social support in late life depression

    Directory of Open Access Journals (Sweden)

    Clóvis Alexandrino-Silva

    2011-01-01

    Full Text Available OBJECTIVES: To examine the association of life events and social support in the broadly defined category of depression in late life. INTRODUCTION: Negative life events and lack of social support are associated with depression in the elderly. Currently, there are limited studies examining the association between life events, social support and late-life depression in Brazil. METHODS: We estimated the frequency of late-life depression within a household community sample of 367 subjects aged 60 years or greater with associated factors. ''Old age symptomatic depression'' was defined using the Composite International Diagnostic Interview 1.1 tool. This diagnostic category included only late-life symptoms and consisted of the diagnoses of depression and dysthymia as well as a subsyndromal definition of depression, termed ''late subthreshold depression''. Social support and life events were assessed using the Comprehensive Assessment and Referral Evaluation (SHORT-CARE inventory. RESULTS: ''Old age symptomatic depression'' occurred in 18.8% of the patients in the tested sample. In univariate analyses, this condition was associated with female gender, lifetime anxiety disorder and living alone. In multivariate models, ''old age symptomatic depression'' was associated with a perceived lack of social support in men and life events in women. DISCUSSION: Social support and life events were determined to be associated with late-life depression, but it is important to keep in mind the differences between genders. Also, further exploration of the role of lifetime anxiety disorder in late-life depression may be of future importance. CONCLUSIONS: We believe that this study helps to provide insight into the role of psychosocial factors in late-life depression.

  13. Carbonatite magmatism in northeast India

    Science.gov (United States)

    Kumar, D.; Mamallan, R.; Dwivedy, K. K.

    The Shillong Plateau of northeast India is identified as an alkaline province in view of the development of several carbonatite complexes e.g. the Sung Valley (Jaintia Hills), Jasra (Karbi-Anglong), Samchampi and Barpung (Mikir Hills) and lamprophyre dyke swarms (Swangkre, Garo-Khasi Hills). On the basis of limited KAr data, magmatic activity appears to have taken place over a protracted period, ranging from the Late Jurassic to the Early Cretaceous. The carbonatite complexes of the Shillong Plateau share several common traits: they are emplaced along rift zones, either within Archaean gneisses or Proterozoic metasediments and granites, and exhibit enrichment in the light rare-earth elements, U, Th, Nb, Zr, Ti, K and Na. The enrichment in incompatible trace elements can best be accounted for if the parental magmas were of alkali basaltic type (e.g. mela-nephelinite or carbonate-rich alkali picrite).

  14. Multiple determinants controlling activation of yeast replication origins late in S phase.

    Science.gov (United States)

    Friedman, K L; Diller, J D; Ferguson, B M; Nyland, S V; Brewer, B J; Fangman, W L

    1996-07-01

    Analysis of a 131-kb segment of the left arm of yeast chromosome XIV beginning 157 kb from the telomere reveals four highly active origins of replication that initiate replication late in S phase. Previous work has shown that telomeres act as determinants for late origin activation. However, at least two of the chromosome XIV origins maintain their late activation time when located on large circular plasmids, indicating that late replication is independent of telomeres. Analysis of the replication time of plasmid derivatives containing varying amounts of chromosome XIV DNA show that a minimum of three chromosomal elements, distinct from each tested origin, contribute to late activation time. These late determinants are functionally equivalent, because duplication of one set of contributing sequences can compensate for the removal of another set. Furthermore, insertion of an origin that is normally early activated into this domain results in a shift to late activation, suggesting that the chromosome XIV origins are not unique in their ability to respond to the late determinants.

  15. Predicting late restenosis after coronary angioplasty by very early (12 to 24 h) thallium-201 scintigraphy: Implications with regard to mechanisms of late coronary restenosis

    International Nuclear Information System (INIS)

    Hardoff, R.; Shefer, A.; Gips, S.; Merdler, A.; Flugelman, M.Y.; Halon, D.A.; Lewis, B.S.

    1990-01-01

    To examine whether late coronary restenosis may be predicted by abnormalities of myocardial perfusion in the early hours after successful percutaneous transluminal coronary angioplasty and to study in greater detail the mechanisms involved in the development of late coronary restenosis after angioplasty, a prospective study was undertaken in 90 consecutive patients. Thallium-201 scintigrams were recorded at rest and during the stress of atrial pacing, 12 to 24 h after angioplasty, and the results were related to the findings at angiography in 70 patients undergoing late cardiac catheterization. A reversible thallium-201 perfusion defect was found in 39 (38%) of 104 myocardial regions supplied by the dilated coronary vessel and identified a subset of patients at high risk of late (6 to 12 months) angiographic restenosis (sensitivity 77%, specificity 67%). In contrast, late coronary restenosis developed in only 7 (11%) of 65 vessels and in 5 (14%) of 37 patients with a nonischemic thallium-201 scintigram on day 1 (p less than 0.005). Multivariate logistic regression analysis of 14 possible preangioplasty and periangioplasty clinical and angiographic variables selected reversible perfusion defect on the thallium-201 scintigram on day 1 (p = 0.016) and immediate postangioplasty residual coronary narrowing (p = 0.004) as significant independent predictors of late restenosis, with younger patient age as an additional less powerful predictor (p less than 0.05). The findings have important implications regarding the pathogenesis of late coronary restenosis in patients undergoing successful angioplasty and they imply that in the majority of these patients pathophysiologic events in the early minutes and hours after angioplasty may determine the development of late restenosis

  16. Reproductive rights: Current issues of late abortion

    Directory of Open Access Journals (Sweden)

    Mujović-Zornić Hajrija

    2009-01-01

    Full Text Available This article considers the legal issues surrounding induced late abortion in cases when severe medical, therapeutic or ethical reasons have not been in dispute. Generally discussing the essential question about abortion today, it means not anymore legality of abortion but, in the first place, safety of abortion. From the aspect of woman health the most important aim is to detect and avoid possible risks of medical intervention, such as late abortion present. This is the matter of medical law context and also the matter of the woman's reproductive rights, here observed through legislation and court practice. The gynecologist has an obligation to obtain the informed consent of each patient. Information's should be presented in reasonably understandable terms and include alternative modes of treatment, objectives, risks, benefits, possible complications, and anticipated results of such treatment. Pregnant woman should receive supportive counseling before and particularly after the procedure. The method chosen for all terminations should ensure that the fetus is born dead. This should be undertaken by an appropriately trained practitioner. Reform in abortion law, making it legally accessible to woman, is not necessarily the product of a belief in woman's rights, but can be a means of bringing the practice of abortion back under better control. Counseling and good medical practice in performing late abortion are the instruments to drive this point even further home. It does not undermine the woman who wants to make a positive decision about her life and its purpose is not to produce feelings of insecurity and guilt. It concludes that existing law should not be changed but that clear rules should be devised and board created to review late term abortion. In Serbia, this leads to creation and set up guidelines for reconciling medical justification for late abortion with existing law, especially with solutions which brings comparative law. .

  17. Heterogeneity of late-life depression : relationship with cognitive functioning

    NARCIS (Netherlands)

    Korten, Nicole C M; Penninx, Brenda W J H; Kok, Rob M; Stek, Max L; Oude Voshaar, Richard C; Deeg, Dorly J H; Comijs, Hannie C

    BACKGROUND: Late-life depression is a heterogeneous disorder, whereby cognitive impairments are often observed. This study examines which clinical characteristics and symptom dimensions of late-life depression are especially impacting on specific cognitive domains. METHODS: Cross-sectional data of

  18. Heterogeneity of late-life depression : relationship with cognitive functioning

    NARCIS (Netherlands)

    Korten, Nicole C. M.; Penninx, Brenda W. J. H.; Kok, Rob M.; Stek, Max L.; Oude Voshaar, Richard; Deeg, Dorly J. H.; Comijs, Hannie C.

    Background: Late-life depression is a heterogeneous disorder, whereby cognitive impairments are often observed. This study examines which clinical characteristics and symptom dimensions of late-life depression are especially impacting on specific cognitive domains. Methods: Cross-sectional data of

  19. Petrología y geoquímica del granito Los Cuartos, Tafí del Valle, Tucumán, noroeste de Argentina: integración al esquema magmático regional

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    López, J. P.

    2010-12-01

    Full Text Available Los Cuartos Granite crops out on the western flank of the Cumbres Calchaquíes, east of Tafí del Valle, Tucumán Province, Argentina. It has a granitic to granodioritic composition, of two micas, being biotite dominant. The granite is medium grained and inequigranular, with rare K-feldspar megacrysts. It contains host-rock xenoliths with different degrees of assimilation. The granite intrusion produced con tact metamorphism in the surrounding basement, with development of andalucite porphyroblasts and poikiloblastic biotite. The granite is calk-alkaline and peraluminous, and is K- and P-rich and Ca- and Na poor compared to other granitoids of the region. The pluton shows late-tectonic features with regard to the regional deformation. The granite possibly intruded during the Ordovician (Famatinian Cycle and its emplacement was structurally controlled by the Tafí Megafracture. Los Cuartos Granite and other intrusive bodies of the region share similar petrographical, geochemical, structural and geochronological characteristics.

    El Granito Los Cuartos aflora sobre la ladera occidental de Cumbres Calchaquíes, al E de la localidad de Tafí del Valle, provincia de Tucumán, Argentina. Es de composición granítica a granodiorítica, con desarrollo de dos micas, predominando la biotita. Es de grano medio e inequigranular, con megacristales de feldespato potásico raros o ausentes. Contiene xenolitos de la roca de caja con diferentes grados de digestión. Este cuerpo desarrolla fenómenos de metamorfismo de contacto en el basamento al que intruye, con desarrollo de porfiroblastos de andalucita y biotita poiquiloblástica. El granitoide presenta características calcoalcalina, peraluminosos, rico en K y P y con contenidos comparativamente más bajos en Ca y Na que los granitoides del área; poseen rasgos tardío-tectónicos con respecto a la deformación y su emplazamiento se habría producido durante el Ordovícico (Ciclo Famatiniano.

  20. Diabetes mellitus is associated with late-onset post-stroke depression.

    Science.gov (United States)

    Zhang, Yu; He, Ji-Rong; Liang, Huai-Bin; Lu, Wen-Jing; Yang, Guo-Yuan; Liu, Jian-Rong; Zeng, Li-Li

    2017-10-15

    To explore the associated factors of late-onset post-stroke depression (PSD). A total of 251 patients with acute ischemic stroke were recruited. The evaluation of depression was performed 2 weeks after ischemia. 206 patients showing no depression in 2 weeks were followed up. They were divided into late-onset PSD group and non-depressed group by clinical interview with Hamilton depression scale score 3 months after stroke. On the first day following hospitalization, the clinical data including age, gender, educational level and vascular risk factors were recorded. The severity, etiological subtype and location of stroke were evaluated. The inflammatory mediators, glucose and lipid levels were recorded on the day of admission. The association between clinical factors and late-onset PSD was explored by logistic regression analysis. The ROC analysis was performed to evaluate the predicting power of the clinical factors. 187 of 206 patients completed the assessment 3 months after stroke. 19 (10.16%) patients were diagnosed as late onset PSD. Diabetes mellitus was an independent risk factor for late-onset PSD (OR 2.675, p = 0.047). ROC analysis demonstrated that glucose and HbA1C could predict late-onset PSD with specificity of 84.4%. The sample of our study was small. The results should be further confirmed in a larger cohort of patients with acute ischemic stroke. The acute ischemic stroke patients with diabetes mellitus were more tendered to suffer late-onset PSD. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Late prematurity: a systematic review

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    Luís Carlos Machado, Júnior

    2014-05-01

    Full Text Available Objective: this study aimed to review the literature regarding late preterm births (34 weeks to 36 weeks and 6 days of gestation in its several aspects. Sources: the MEDLINE, LILACS, and Cochrane Library databases were searched, and the references of the articles retrieved were also used, with no limit of time. Data synthesis: numerous studies showed a recent increase in late preterm births. In all series, late preterm comprised the majority of preterm births. Studies including millions of births showed a strong association between late preterm birth and neonatal mortality. A higher mortality in childhood and among young adults was also observed. Many studies found an association with several neonatal complications, and also with long-term disorders and sequelae: breastfeeding problems, cerebral palsy, asthma in childhood, poor school performance, schizophrenia, and young adult diabetes. Some authors propose strategies to reduce late preterm birth, or to improve neonatal outcome: use of antenatal corticosteroids, changes in some of the guidelines for early delivery in high-risk pregnancies, and changes in neonatal care for this group. Conclusions: numerous studies show greater mortality and morbidity in late preterm infants compared with term infants, in addition to long-term disorders. More recent studies evaluated strategies to improve the outcomes of these neonates. Further studies on these strategies are needed. Resumo: Objetivo: revisar a literatura sobre prematuridade tardia (nascimentos de 34 semanas a 36 semanas e seis dias em seus vários aspectos. Fonte dos dados: buscas nas bases MEDLINE, LILACS e Biblioteca Cochrane, sem limite de tempo, e nas referências bibliográficas dos artigos encontrados. Síntese dos dados: muitos estudos mostram aumento na taxa de prematuridade tardia nos últimos anos. Em todas as séries, os prematuros tardios correspondem à maioria dos nascimentos prematuros. Estudos envolvendo análises de milhões de

  2. Late adverse reactions to intravascular iodinated contrast media

    International Nuclear Information System (INIS)

    Webb, Judith A.W.; Stacul, Fulvio; Thomsen, Henrik S.; Morcos, Sameh K.

    2003-01-01

    Late adverse reactions to intravascular iodinated contrast media are defined as reactions occurring 1 h to 1 week after contrast medium injection. They have received increasing interest over the past decade, but their prevalence remains uncertain and their pathophysiology is not fully understood. The Contrast Media Safety Committee of the European Society of Urogenital Radiology decided to review the literature and to issue guidelines. An extensive literature search was carried out and summarized in a report. Based on the available information, simple guidelines have been drawn up. The report and guidelines were discussed at the 8th European Symposium on Urogenital Radiology in Genoa. Late adverse reactions after intravascular iodinated contrast medium include symptoms such as nausea, vomiting, headache, itching, skin rash, musculoskeletal pain, and fever. A significant proportion of these reactions is unrelated to the contrast medium; however, allergy-like skin reactions are well-documented side effects of contrast media with an incidence of approximately 2%. Late reactions appear to be commoner after non-ionic dimers. The majority of late skin reactions after contrast medium exposure are probably T-cell-mediated allergic reactions. Patients at increased risk of late skin reactions are those with a history of previous contrast medium reaction and those on interleukin-2 treatment. Most skin reactions are self-limiting and resolve within a week. Management is symptomatic and similar to the management of other drug-induced skin reactions. (orig.)

  3. LATE DEVONIAN-CARBONIFEROUS CONODONTS FROM EASTERN IRAN

    Directory of Open Access Journals (Sweden)

    MEHDI YAZDI

    1999-07-01

    Full Text Available Conodont data from acid-leaching 110 samples from two Late Devonian-Carboniferous areas in the Shotori Range (Tabas region of eastern Iran are presented. At Howz-e-Dorah, a section (88 samples commencing high in the Bahram Formation (Givetian-early Frasnian extended through the Shishtu Formation (Frasnian, Early hassi Zone or older, to latest Tournaisian, anchoralis-latus Zone and the Sardar Formation (earliest Visean, texanus Zone, to late Namurian, sinuatus-corrugatus-sulcatus Zone and into the Jamal Formation (Permian. Four less exhaustively sampled sections (22 samples show the Kale Sardar area to be tectonically more complicated than the Howz-e-Dorah area. Useful marker horizons in the Howz-e-Dorah section, well constrained by conodont data, are: the early Frasnian (no older than Early hassi Zone biostromal beds of the Shishtu Formation, an early Famennian (Late triangularis to Early crepida interval of oolitic limestone, a cyclothem sequence straddling the Early Carboniferous-Late Carboniferous boundary, and an Early Permian interval of siliceous sand ("the white quartzite" of previous authors. Additionally, several iron-rich horizons, readily traceable from locality to locality, are well constrained by conodont ages. Eighty-five conodont species/subspecies are documented representing 24 genera.. Two new species, Polygnathus capollocki and Polygnathus ratebi and one new subspecies, Icriodus alternatus mawsonae are described. 

  4. Late endosomal cholesterol accumulation leads to impaired intra-endosomal trafficking.

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    Komla Sobo

    Full Text Available BACKGROUND: Pathological accumulation of cholesterol in late endosomes is observed in lysosomal storage diseases such as Niemann-Pick type C. We here analyzed the effects of cholesterol accumulation in NPC cells, or as phenocopied by the drug U18666A, on late endosomes membrane organization and dynamics. METHODOLOGY/PRINCIPAL FINDINGS: Cholesterol accumulation did not lead to an increase in the raft to non-raft membrane ratio as anticipated. Strikingly, we observed a 2-3 fold increase in the size of the compartment. Most importantly, properties and dynamics of late endosomal intralumenal vesicles were altered as revealed by reduced late endosomal vacuolation induced by the mutant pore-forming toxin ASSP, reduced intoxication by the anthrax lethal toxin and inhibition of infection by the Vesicular Stomatitis Virus. CONCLUSIONS/SIGNIFICANCE: These results suggest that back fusion of intralumenal vesicles with the limiting membrane of late endosomes is dramatically perturbed upon cholesterol accumulation.

  5. Vaginal bleeding in late pregnancy

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000627.htm Vaginal bleeding in late pregnancy To use the sharing ... JavaScript. One out of 10 women will have vaginal bleeding during their 3rd trimester. At times, it ...

  6. Structural analysis and magmatism characterization of the Major Gercino shear zone, Santa Catarina State, Brazil

    International Nuclear Information System (INIS)

    Passarelli, Claudia Regina

    1996-01-01

    This work describes the geometric and kinematic characteristics of the Major Gercino Shear Zone (MGSZ) in the Canelinha-Garcia area. This shear zone is one of the major lineaments that affect all southern Brazilian precambrian terrains. In Santa Catarina State, it separates, along its whole extension, the supracrustal rocks of the Brusque belt (northern part) from the Granitoid belt (southern). This zone is characterized by a regional NE trend and a dextral sense of movement where ductile-brittle structures predominate. The MGSZ is composed of two mylonitic belts separated by granitoid rocks probably associated to the development of the shear zone. Both shear zones show cataclastic to ultra mylonitic rocks, but mylonites and protomylonites conditions at high strain rate. The calc-alkaline granitoids present in the area can be grouped in two granitoid associations with meta to peraluminous affinities. The Rolador Granitoid Association is characterized by grayish porphyritic biotite-monzogranites and the Fernandes Granitoid Association by coarsed-grained to porphyritic pinkish amphibole-syenogranites. The U-Pb and Rb-Sr ages range from 670 to 590 Ma with the Sr 87 / Sr 86 initial ratios suggesting a crustal contribution in the generation of these rocks. The importance of the pure shear component is also emphasized by the results of the Fry method. Many z axes of the strain ellipses are at high angle to the shear foliation. Symmetric porphyroclasts also corroborate this hypothesis. The micaceous minerals formed during the shear development indicate K-Ar ages around 555 ± 15 Ma. Brittle reactivations of the shear zone have been placed by K-Ar in fine-fraction materials at Triassic time (215 ± 15 Ma.)

  7. Late Cretaceous vicariance in Gondwanan amphibians.

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    Ines Van Bocxlaer

    Full Text Available Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions.

  8. Late-onset ADHD in adults: milder, but still dysfunctional.

    Science.gov (United States)

    Karam, Rafael G; Bau, Claiton H D; Salgado, Carlos A I; Kalil, Katiane L S; Victor, Marcelo M; Sousa, Nyvia O; Vitola, Eduardo S; Picon, Felipe A; Zeni, Gregory D; Rohde, Luis A; Belmonte-de-Abreu, Paulo; Grevet, Eugenio H

    2009-04-01

    The requirement in classificatory systems that some impairment from attention-deficit/hyperactivity disorder (ADHD) symptoms starts before 7 years of age (age of onset of impairment criteria - AOC) has been harshly criticized. Although there is evidence that late-onset ADHD is a valid diagnosis, little is known about the role of age of onset of impairment on the clinical profile of adult patients. The diagnoses of 349 adults with ADHD followed DSM-IV criteria. ADHD and oppositional defiant disorder (ODD) were evaluated with the K-SADS-E, and other comorbidities with the SCID-IV and the MINI. Subjects were divided in early and late-onset groups (age of onset of impairment between 7 and 12 years old). The effect of age of onset over clinical and demographic characteristics was tested by regression models. Late-onset subjects were diagnosed later (P=0.04), had a lower frequency of problems with authority and discipline (P=0.004), and lower scores in SNAP-IV (Pactivities (P=0.03). On the other hand, late-onset patients presented a higher prevalence of comorbid general anxiety disorder (GAD) (P=0.01). Both groups had a similar profile in the remaining comorbidities and sociodemographic characteristics. This study provides initial evidence that adults with late-onset ADHD have less severity, lower frequency of externalizing symptoms and increased comorbidity with GAD, but similar profile in other comorbidities. In addition, the data suggest that late-onset patients have a higher probability of delayed diagnosis despite the significant impairment of their condition.

  9. Increased number of applications for late termination of pregnancy in Denmark

    DEFF Research Database (Denmark)

    Theibel, Sara Sofie; Petersson, Birgit H; Christensen, Anne Vinggaard

    2014-01-01

    INTRODUCTION: Last year, it was 40 years since the introduction of legal abortion until the 12th week of gestation and the possibility of late termination of pregnancy in Denmark. The aim of this study was to describe the development in applications for late termination of pregnancy in the 1986......%. CONCLUSION: Significant changes in the women's age and the reasons they provide when applying for late termination of pregnancy have been observed from 1986 to 2011. Further investigation of this subject will contribute to securing the best possible conditions for women going through late termination...

  10. Late Carboniferous Monzonite-Granosyenite Magmatism in the Northern Balkhash Region (Central Kazakhstan)

    Science.gov (United States)

    Ermolov, P. V.; Degtyarev, K. E.; Salnikova, E. B.; Tretyakov, A. A.; Kotov, A. B.; Anisimova, I. V.; Plotkina, Yu. V.

    2018-02-01

    U-Pb dating of the Torangalyk Complex (Northern Balkhash) yielded a Late Carboniferous age of 305 ± 2 Ma. Taking into account the previous data, a new scheme for Late Paleozoic granitic magmatism in this region has been proposed. It includes the Early Carboniferous granite-granodiorite Balkhash Complex, Late Carboniferous monzonite-granosyenite Kokdombak and Torangalyk complexes, and the Late Carboniferous-Early Permian granite-leucogranite Akchatau Complex.

  11. Late Cretaceous neosuchian crocodiles from the Sultanate of Oman

    NARCIS (Netherlands)

    Buscalioni, Angela D.; Schulp, Anne S.; Jagt, John W M; Hanna, Samir S.; Hartman, Axel Frans

    Two apparently new crocodilian taxa from the Late Cretaceous (Late Campanian-Maastrichtian) Al-Khod Conglomerate of the Sultanate of Oman are described. The fragmentary state of preservation precludes formal naming, yet enables comparisons to be made with other taxa. One is a short-snouted

  12. LATE NEUROSYPHILIS: TRENDS AND CHALLENGES.

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    Ivan Dimitrov

    2015-09-01

    Full Text Available Background: Syphilis is not only a disease of historical importance. It has been recognized that nowadays, in the era of AIDS, it still remains a serious challenge. For the last two decades there has been a resumption of neurosyphilis cases. This has revived the interest in the diagnostic and therapeutic challenges that the disease presents to clinical practice and to healthcare systems. Material/Methods: We present the overall picture of newly registered cases of syphilis in Varna municipality between 2009 and 2013, and report a case of neurosyphilis diagnosed at the first clinic of neurological diseases of St. Marina University Hospital during this period. Results: For the 5-year period, newly registered cases of syphilis in Varna have shown a tendency towards a decrease. Patients were typically in the early stages of the disease, primary and secondary. Late manifestations dropped from 29 in 2009 to 0 in 2010, but increased again to 15 in 2013. Only 1 case of neurosyphilis was registered during the 5-year period, in 2013. Conclusions: Neurological syndromes observed in cases of late neurosyphilis, presenting in different clinical forms, require a broad spectrum of differential diagnoses. Attention in everyday clinical practice should be focused on these cases which, though rare, are of high medical and social importance. Clinical cases of late neurosyphilis are often atypical and the early consideration of serologic tests or even biopsy may be of critical importance.

  13. Late radiation injury to muscle and peripheral nerves

    International Nuclear Information System (INIS)

    Gillette, E. L.; Mahler, P. A.; Powers, B. E.; Gillette, S. M.; Vujaskovic, Z.

    1995-01-01

    Late radiation injury to muscles and peripheral nerves is infrequently observed. However, the success of radiation oncology has led to longer patient survival, providing a greater opportunity for late effects to develop, increase in severity and, possibly, impact the quality of life of the patient. In addition, when radiation therapy is combined with surgery and/or chemotherapy, the risk of late complications is likely to increase. It is clear that the incidence of complications involving muscles and nerves increases with time following radiation. The influence of volume has yet to be determined; however, an increased volume is likely to increase the risk of injury to muscles and nerves. Experimental and clinical studies have indicated that the (α(β)) ratio for muscle is approximately 4 Gy and, possibly, 2 Gy for peripheral nerve, indicating the great influence of fractionation on response of these tissues. This is of concern for intraoperative radiation therapy, and for high dose rate brachytherapy. This review of clinical and experimental data discusses the response of muscle and nerves late after radiation therapy. A grading system has been proposed and endpoints suggested

  14. The Main Shear Zone in Sør Rondane: A key feature for reconstructing the geodynamic evolution of East Antarctica

    Science.gov (United States)

    Ruppel, Antonia; Läufer, Andreas; Lisker, Frank; Jacobs, Joachim; Elburg, Marlina; Damaske, Detlef; Lucka, Nicole

    2013-04-01

    Structural investigations were carried out along the Main Shear Zone (MSZ) of western Sør Rondane (22°-25°E, 71.5°-72.5°S) to gain new information about the position of the East-/West-Gondwana suture and the ancient plate tectonic configuration during Gondwana amalgamation. The WSW-ENE striking MSZ divides south-western Sør Rondane in a northern amphibolite-facies terrane and a southern tonalite-trondhjemite-granodiorite (TTG) terrane. The structure can be traced over a distance of ca. 100 km and reaches several hundred meters in width. It is characterized by a right-lateral sense of movement and marked by a transpressional and also transtensional regime. Ductilely deformed granitoids (ca. 560 Ma: SHRIMP U-Pb of zircon) and ductile - brittle structures, which evolved in a transitional ductile to brittle regime in an undeformed syenite (ca. 499-459 Ma, Ar-Ar mica), provide a late Proterozoic/ early Paleozoic time limit for the activity of the shear zone (Shiraishi et al., 2008; Shiraishi et al., 1997). Documentation of ductile and brittle deformation allows reconstructing up to eight deformation stages. Cross-cutting relationships of structural features mapped in the field complemented by published kinematic data reveal the following relative age succession: [i] Dn+1 - formation of the main foliation during peak metamorphism, [ii] Dn+2 - isoclinal, intrafolial folding of the main foliation, mostly foliation-parallel mylonitic shear zones (1-2 meter thick), [iii] Dn+3 - formation of tight to closed folds, [iv] Dn+4 - formation of relatively upright, large-scale open folds, [v] Dn+5 - granitoid intrusion (e.g. Vengen granite), [vi] Dn+6 - dextral shearing between amphibolite and TTG terranes, formation of the MSZ, [vii] Dn+7 - intrusion of late- to post-tectonic granitoids, first stage of brittle deformation (late shearing along MSZ), intrusion of post-kinematic mafic dykes, [viii] Dn+8 - second stage of brittle deformation including formation of conjugate fault

  15. Late radiation effects in animals surviving lethal irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrov, L A

    1974-01-01

    Animals (rats, mice, dogs) survived lethal irradiation by means of prophylactic-therapeutic treatments or previously irradiated, were studied for late radiation effects: life span, cachexia and fat growing of hypophysical type, tissue or organ hypoplasia manifested by disturbed hemopoiesis, suppressed function of adrenal gland, etc., suppressed immune reactivity of the irradiated organism, atypical biochemical changes in DNA and protein metabolism, epilation, chronic dermatitis, ulcerations, reduced reproductivity or full sterility, damage of kidneys leading to nephrosclerosis, dishormonal states, cataracts, diffuse sclerotic processes, various kinds of malignant and non-malignant tumors. In these cases hemopoiesis compensated for a definite time peripheral blood composition, but during the late period it showed features of incompleteness: shorter life survival of erythrocytes and thrombocytes manifested by a decreased binding of labelled methionine in these blood elements, anemia and relative thrombocytopenia sometimes with an increased number of polychromatic erythrocytes in peripheral blood and a decreased number of reticulocytes at the same time; lymphopenia and relative leucopenia with an increased number of hypersegmented neutrophils. Decreased reproductivity and atypical biochemical changes available in the first generation of the irradiated animals showed the probable role of mutagenic factors in the emergency of some late radiation effects. A significant part of late radiation sequences were due to neuro-endocrine disintegrations. Some of the described late radiation effects were also observed in biological controls as features of ageing. After application of radioprotectors (AET, cysteamine, serotonin) a more marked protective effect is demonstrated in the early reactions (time survival till 30th day, DNA and protein metabolism, immune reactions) of the lethally irradiated animals.

  16. Fluid inclusion study of radioactive granite and cherty cataclasite in the Southeastern part of Nanded district, Maharashtra: implications for the uranium mineralisation

    International Nuclear Information System (INIS)

    Banerjee, Rahul; Shivkumar, K.; Thomas, Tresa; Thomas, Jugina; Pandian, M.S.

    2013-01-01

    Southeastern part of Nanded district, Maharashtra exposes Palaeoproterozoic granitoids, representing the younger phase of Peninsular Gneissic Complex (PGC), mark the northeastern extension of Eastern Dharwar Craton. These granitoids are predominantly pink/grey granites, which are traversed by younger phosphatic cherty cataclasites close to the Deccan Trap capping. They are also affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations, especially close to fault/shear zones. A number of N-S to NNE-SSW, NE-SW, NW-SE and E-W trending lineaments marked by faults/fractures/shear zones and dykes are delineated in this granitic terrain. Among these, NE-SW and NNE-SSW faults/shear zones affecting granitoids and cherty cataclasites in Shahpur-Sujayatpur and Thadisaoli area have recorded significant uranium anomalies (Granitoids: upto 1% U 3 O 8 and 0.20% ThO 2 ; Cherty cataclasites upto 0.11% U 3 O 8 and <0.005% ThO 2 ) and enrichment in rare metal and rare earth element content (Nb-77ppm, Y-111 ppm, Zr-432ppm; n=9 and total REE-1167ppm; n=3). Presence of discrete uranium/thorium minerals (uraninite, b-uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite are responsible for radioactivity in granitoids while phosphatic material accounts for radioactivity in cherty cataclasites

  17. Toward late career transitioning: a proposal for academic surgeons.

    Science.gov (United States)

    Richards, Robin; McLeod, Robin; Latter, David; Keshavjee, Shaf; Rotstein, Ori; Fehlings, Michael G; Ahmed, Najma; Nathens, Avery; Rutka, James

    2017-09-01

    In the absence of a defined retirement age, academic surgeons need to develop plans for transition as they approach the end of their academic surgical careers. The development of a plan for