Thrust tectonics in crystalline domains: The origin of a gneiss dome

Science.gov (United States)

Greiling, R. O.

1997-12-01

Structural geological field work, microscopic and magnetic fabric studies have been applied in order to assess the structural origin of a gneiss dome, based on a regional example from the Neoproterozoic Pan-African Belt of NE Africa, the Wadi Hafafit Culmination (WHC). The culmination is dominated by a number of major shear zones, which form both the boundaries between the gneissic core and surrounding low grade successions as well as those of minor structural units within the gneisses. These shear zones form a linked fault system, which, based on shear criteria, fault-bend fold and overall geometric interrelationships, can be classified as an antiformal stack. The relative age sequence of the shear zones/thrusts with the highest thrust oldest and the lowermost youngest points to a forward-propagating thrust system. This, together with the shear criteria, exclude an origin of the WHC as a metamorphic core complex, where the highest shear zone should be youngest. The geometry of the WHC antiformal stack is documented by maps and sections as well as section balancing and restoration. Microscopic work showed brittle deformation in feldspar and dynamic recrystallization in quartz ribbons. The asymmetry of the fabric confirmed the macroscopically determined shear sense. However, there is one example of an earlier, perhaps extensional shear movement. Mylonitic foliation and transport-parallel lineation have also been determined by magnetic fabric studies. The observations suggest that thrusts may cut across both previously folded crystalline rocks as well as homogeneous granitoid plutonic bodies. According to the regional tectonic picture the large-scale structure of the gneiss dome originated after a phase of (late-orogenic) extensional collapse. It is speculated that during late-orogenic cooling the upper part of the lithosphere was sufficiently strong to allow brittle thrusting whilst the lithosphere as a whole was still weak enough to allow large-scale compressional

Constraints from geochemistry and oxygen isotopes for the hydrothermal origin of orthoamphibole mafic gneiss in the New Jersey Highlands, north-central Appalachians, USA

Science.gov (United States)

Volkert, Richard A.; Peck, William H.

2017-12-01

Rare exposures of orthoamphibole mafic (Oam) gneiss of Mesoproterozoic age in the north-central Appalachians are confined to the northwestern New Jersey Highlands where they form thin lens-shaped bodies composed of gedrite and sparse anthophyllite, oligoclase (An13-An20), biotite, magnetite, and local fluorapatite, rutile, and ilmenite. The gneiss is penetratively foliated and has sharp, conformable contacts against enclosing supracrustal paragneiss and marble. Orthoamphibole mafic gneiss is characterized by low SiO2 (48 ± 2.5 wt%), CaO (1.9 ± 1.3 wt%), and high Al2O3 (18 ± 1.2 wt%), Fe2O3 (10.5 ± 1.6 wt%), and MgO (12 ± 2.3 wt%). Trace element abundances overlap those of unaltered amphibolites in the study area and, coupled with δ18O values of 9.45 ± 0.6‰ (VSMOW) from gedrite separates, support an origin from a basalt protolith. The geochemical and isotopic data are consistent with the formation of Oam gneiss through sea floor hydrothermal alteration of basalt at low temperature of 150-200 °C. Mass-balance calculations indicate gains during alteration mainly in MgO and Al2O3 and losses in CaO, Sr, and light rare earth elements. Our results are compatible with the pre-metamorphic alteration of the basalt protoliths through chloritization and plagioclase dissolution that produced a Mg-rich and Ca-poor rock. Subsequent metamorphism of this chlorite-rich rock to the current mineral assemblage of Oam gneiss took place at ca. 1045 Ma, during the Ottawan phase of the Grenvillian Orogeny. The close spatial association in the study area of Oam gneiss bodies and sulfide occurrences suggests an affinity to the style of mineralization associated with volcanogenic massive sulfide (VMS)-type deposits.

Durability analysis of gneiss using wear resistance

Directory of Open Access Journals (Sweden)

José Luiz Ernandes Dias Filho

2014-01-01

Full Text Available This paper presents a study conducted in gneiss in Santo Antonio de Pádua, RJ, BR, including durability analysis of the rock using slake durability test. Rocks in the region of Pádua are mostly used for ornamental purposes. A lab equipment was developed to evaluate the influence of rotation in the test, allowing for the speed variation of 7 RPM to 238 RPM. This study could be implemented in a wide variety of rock materials, targeting them according to their lifetime in the project. With variation of the wear levels, increasing weight loss was observed until the inertia moment in which the sample holds to the machine wall. The results indicate an increase in linear mass loss. These procedures allow a more precise analysis of durability than can be applied in different different regions of the world.

Effect of Hydrograph Separation on Suspended Sediment Concentration Predictions in a Forested Headwater with Thick Soil and Weathered Gneiss Layers

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Naoki Kabeya

2014-06-01

Full Text Available Two-component hydrograph separation using oxygen-18 concentrations was conducted at a sediment runoff observation weir installed in a small subcatchment of a forested gneiss catchment in Japan. The mean soil thickness of this catchment is 7.27 m, which comprises 3.29 m of brown forest soil (A and B layers and a 3.98-m layer of heavily weathered gneiss. Data were collected for a storm on 20–21 May 2003, and the percentage of event water separated by the stable isotope ratio in comparison with the total rainfall amount was about 1%. This value is within the ratio of a riparian zone in a drainage area. Temporal variation of suspended sediment concentration exhibited higher correlation with the event water component than with the total runoff or pre-event water component. This shows that the riparian zone causes rainwater to flow out quickly during a rain event, and that this is an important area of sediment production and transportation in a forested headwater with thick soil and weathered gneiss layers.

Scandian Ultrahigh-Pressure Metamorphism of Proterozoic Basement Rocks on Fjortoft and Otroy, Western Gneiss Region, Norway

NARCIS (Netherlands)

Carswell, D.A.; van Roermund, H.L.M.; Wiggers de Vries, D.F.

2006-01-01

Electron microprobe mineral composition data are presented for samples of exsolved and recrystallized garnet websterites within the mantle-derived peridotite bodies and of external orthopyroxene eclogite lenses directly enclosed within the gneisses on the islands of Fjørtoft and Otrøy in the Western

U-Pb dating of deformed mafic dyke and host gneiss: implications for understanding reworking processes on the western margin of the Archaean U3o8 Block, NE Sao Francisco Craton, Brazil

International Nuclear Information System (INIS)

Oliveira, Elson Paiva

2000-01-01

U-Pb ages of deformed mafic dyke and host migmatitic grey gneiss from the transition zone between the Archaen Uaua Block and the Caldeirao Belt are presented. Titanites from the metamorphic dyke's margin and zircons from the gneiss were dated at 2,039 ± 2 Ma and 2,956 ± 39 Ma, respectively. The Sm-Nd data (T DM =2,965 Ma and ε Nd(t) =1.69) on the gneiss, coupled with the U-Pb data on both dyke and gneiss, suggest than an Archaen granodioritic batholith, probably originated at an andean-type continental margin, was intruded by mafic dykes, and subsequently was reworked during the Paleoproterozoic collisional event associated with the development of the Salvador-Curaca Orogen. (author)

Experimental Researches on Long-Term Strength of Granite Gneiss

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Lin Liu

2015-01-01

Full Text Available It is important to confirm the long-term strength of rock materials for the purpose of evaluating the long-term stability of rock engineering. In this study, a series of triaxial creep tests were conducted on granite gneiss under different pore pressures. Based on the test data, we proposed two new quantitative methods, tangent method and intersection method, to confirm the long-term strength of rock. Meanwhile, the isochronous stress-strain curve method was adopted to make sure of the accuracy and operability of the two new methods. It is concluded that the new methods are suitable for the study of the long-term strength of rock. The effect of pore pressure on the long-term strength of rock in triaxial creep tests is also discussed.

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

Science.gov (United States)

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

2017-12-01

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

REE distributions in a high-grade Archaean gneiss complex in Scotland: Implications for the genesis of ancient sialic crust

International Nuclear Information System (INIS)

Drury, S.A.

1978-01-01

Seventeen rocks from the Lewisian Gneiss of the Inner Hebrides of Scotland, which represent three distinct lithological types at granulite to greenschist facies of metamorphism show rare-earth element patterns which seem not to have been disturbed by their complex metamorphic history. Some indication of their origin can be obtained by simple geochemical models. (Auth.)

A geochemical and Pb, Sr isotopic study of the evolution of granite-gneisses from the Bastar craton, Central India

International Nuclear Information System (INIS)

Sarkar, G.; Paul, D.K.; Misra, V.P.; de Laeter, J.R.; Mc Naughton, N.J.

1990-01-01

Preliminary Pb-Pb and Rb-Sr geochronology of granitic and gneissic rocks from the Sukma area of the Bastar craton, Central India, provides important constraints on crustal evolution. Much of the craton is made up of felsic orthogneisses and younger granitic intrusives, compositionally ranging from tonalite to granite. Pb-Pb isotopic data suggest the presence of ca. 3.0 Ga old gneisses. Younger granitic intrusives have been dated at ca. 2.6 Ga which represents a widespread resetting and/or emplacement event. Comparison of the Pb-Pb and Rb-Sr whole rock ages suggests that the latter were more perturbed after the gneiss-forming or emplacement events. All rock suites show significant geological scatter of isotopic data probably because of sampling on a regional scale, and reflect multi-stage isotopic evolution in a complex terrain. The present isotopic data indicate the presence of Archaean rock in the Bastar craton and suggest temporal similarity with the oldest crustal rocks in the Singhbhum and Dharwar cratons. (author). 18 refs., 4 tabs., 8 figs

Notes on epilithic and epigeic lichens from granite and gneiss outcrops in mountains of Makedonia, Greece, with emphasis on northern species

DEFF Research Database (Denmark)

Christensen, Steen

2014-01-01

The epilithic and epigeic lichen flora of eight localities with granite and gneiss outcrops in the mountains of Makedonia, N Greece has been investigated. Of the 46 taxa reported, seven species are new to Greece, viz.: Brodoa oroarcti­ca, Candelariella coralliza, Cetraria ericetorum, Lecanora...

Geodynamic evolution of the Pan-African lower crust in Sri Lanka : structural and petrological investigations into a high-grade gneiss terrain

NARCIS (Netherlands)

Kriegsman, L.

1993-01-01

Some main objectives of present-day geological research are to assess the role of the lower crust in collision and extensional tectonics and to unravel the mechanism and timing of crustal growth. Both objectives require input from the study of high-grade gneiss terrains, notably data concerning

Metamorphic history and age of aluminous gneisses of the Belomorian belt of the Baltic shield

International Nuclear Information System (INIS)

Bibikova, E.V.; Borisova, E.Yu.; Makarov, V.A.; Drugova, G.M.

1997-01-01

Metamorphic conditions and age are determined for the early metamorphic stage of aluminous gneisses in the Chupa nappe in the Belomorian Mobile Belt. The granulite-facies metamorphic conditions during Late Archean time are determined based on the composition of garnet and biotie from the metapelites. The early metamorphic stage was dated at 2860 ± 30 Ma based on the U-Pb systematics of granulitic zircon from the metapelites. The U-Pb isotopic system of the zircon was strongly affected by Svecogennian metamorphism (at 1750 Ma). The geodynamic evolution of the Belomorian Mobile Belt is discussed in light of the data of this work

Summary report - development of laboratory tests and the stress- strain behaviour of Olkiluoto mica gneiss

International Nuclear Information System (INIS)

Hakala, M.; Heikkilae, E.

1997-05-01

This work summarizes the project aimed at developing and qualifying a suitable combination of laboratory tests to establish a statistically reliable stress-strain behaviour of the main rock types at Posiva Oy's detailed investigation sites for disposal of spent nuclear fuel. The work includes literature study of stress-strain behaviour of brittle rock, development and qualification of laboratory tests, suggested test procedures and interpretation methods and finally testing of Olkiluoto mica gneiss. The Olkiluoto study includes over 130 loading tests. Besides the commonly used laboratory tests, direct tensile tests, damage controlled tests and acoustic emission measurements were also carried out. (orig.) (54 refs.)

Elastic anisotropy of layered rocks: Ultrasonic measurements of plagioclase-biotite-muscovite (sillimanite) gneiss versus texture-based theoretical predictions (effective media modeling)

Czech Academy of Sciences Publication Activity Database

Ivankina, T. I.; Zel, I. Yu.; Lokajíček, Tomáš; Kern, H.; Lobanov, K. V.; Zharikov, A. V.

712/713, 21 August (2017), s. 82-94 ISSN 0040-1951 R&D Projects: GA MŠk LH13102 Institutional support: RVO:67985831 Keywords : compositional layering * crystallographic texture * effective elastic properties calculation * neutron diffraction * plagioclase-biotite-muscovite (sillimanite) gneiss * velocity measurements Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.693, year: 2016

Summary report - development of laboratory tests and the stress- strain behaviour of Olkiluoto mica gneiss

Energy Technology Data Exchange (ETDEWEB)

Hakala, M.; Heikkilae, E. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Rock Engineering

1997-05-01

This work summarizes the project aimed at developing and qualifying a suitable combination of laboratory tests to establish a statistically reliable stress-strain behaviour of the main rock types at Posiva Oy`s detailed investigation sites for disposal of spent nuclear fuel. The work includes literature study of stress-strain behaviour of brittle rock, development and qualification of laboratory tests, suggested test procedures and interpretation methods and finally testing of Olkiluoto mica gneiss. The Olkiluoto study includes over 130 loading tests. Besides the commonly used laboratory tests, direct tensile tests, damage controlled tests and acoustic emission measurements were also carried out. (orig.) (54 refs.).

Rb-Sr dating of strain-induced mineral growth in two ductile shear zones in the western gneiss region of Nord-Troendelag, Central Norway

International Nuclear Information System (INIS)

Piasecki, M.A.; Cliff, R.A.

1988-01-01

In the Bjugn district of the northern part of the Western Gneiss Region, Nord-Troendelag, a basement gneiss-cover nappe boundary is marked by a thick zone of ductile shearing. In this zone a layer-parallel mylonitic fabric with related new mineral growth overprints and retrogresses a previous fabric associated with a granulite facies mineral assemblage. Related minor shear belts contain abundant new minerals and vein systems, including pegmatites, believed to represent strain-induced products formed at the time of the shearing movements. Central parts of two large muscovite books from such a pegmatite yielded Rb-Sr, Early to Middle Devonian ages of 389±6 Ma and 386±6 Ma, interpreted as indicating the approximate time of pegmatite formation and of the shearing. Small, matrix-size muscovite and biotite grains from the host mylonite gave ages of 378±6 Ma and 365±5 Ma, respectively, supposed to relate to post-shearing uplift and cooling

The complex systematics of zircons in migmatitic gneisses: An example from an Archean migmatite along the Patos Shear Zone, Borborema Province, NE Brazil

International Nuclear Information System (INIS)

Costa, A.C.D; Hackspacher, P.C; Dantas, E.L; Fetter, A.H.

2001-01-01

The Northem Tectonic Domain Borborema Province, in Northeast of Brazil records a complex history of tectonic activity ranging from 3.4 Ga to 0.6 Ga (Brito Neves, 1995 and Dantas, 1996). U-Pb systematics of zircons from a migmatitic gneiss just north of the Patos Shear Zone provide an excellent example of the difficulties encountered using conventional single-grain U/Pb zircon geochronology in polydeformed gneiss terranes. Our conventional single grain zircon analyses of a migmatite yielded Archean ages between ca. 3.3 at 2.8 a, as well as some highly discordant Paleoproterozoic ages. Subsequent cathodoluminescence images of these zircon grains showed complex internal structures that possibly record up to 4 separate stages of zircon growth. With such internal complexity, is impossible resolve primary crystallization ages as well as the ages of subsequent overgrowth events using conventional single grain analyses. Such resolution will require analyses of the individual grain domains using the SHRIMP method (au)

Petrological and geochemical features of the early Paleozoic granitic gneisses and iron ores in the Tianhu iron deposit, Eastern Tianshan, NW China: Implications for ore genesis

Science.gov (United States)

Zheng, Jiahao; Mao, Jingwen; Yang, Fuquan; Chai, Fengmei; Shen, Ping

2017-08-01

This paper reports whole-rock geochemical, zircon U-Pb and Hf isotopic data for ore-hosted granitic gneisses, mineral compositions of oxides, and sulfur isotopic data for sulfides in iron ores from the Tianhu deposit, central part of the Eastern Tianshan. Our results can provide crucial constraints on the genesis of granitic gneisses and early Paleozoic tectonic setting of the Eastern Tianshan. LA-ICP-MS U-Pb dating on magmatic zircons yielded weighted mean 206Pb/238U ages of 463 to 438 Ma, interpreted as the crystallization ages of the granitic protoliths and the formation ages of the Tianhu Group. Zircon U-Pb age of ore-hosted granitic gneiss (ca. 459 Ma) can provide reliable constrains on upper limit for iron mineralization age in the Tianhu deposit. Geochemical characteristics suggest that the protoliths of the Tianhu granitic gneisses are metaluminous to weakly peraluminous high-K calc-alkaline granitic rocks, exhibiting typical subduction-related features such as strong enrichment in LREE and LILE and depletion in HFSE. Zircon Hf isotopic compositions show a positive trend from 463 to 438 Ma, indicating that 460 Ma magmas came from both ancient and juvenile sources, whereas 438 Ma magmas involved more juvenile material. Some early Paleozoic granitoids were recently identified in the Eastern Tianshan with the ages between ca. 475 and ca. 425 Ma. The formation of these early Paleozoic granitoids was in response to subduction processes, suggesting that subduction of Junggar Ocean probably began in the Early Ordovician and lasted until Late Silurian. Pyrite and pyrrhotite in iron ores have δ34SCDT values from + 4.6 to + 15.7‰, which are consistent with the marine source, but inconsistent with the magmatic source or those involved evaporites in skarn iron deposit. Geological, geochemical, and isotopic data suggest that the Tianhu iron ores were formed by volcano-sedimentary processes in a subduction environment during the early Paleozoic time, and Tianhu is a

Preliminary radiometric analyses of zircons from the Mount Copeland syenite gneiss, Shuswap metamorphic complex, British Columbia

International Nuclear Information System (INIS)

Okulitch, A.V.; Laveridge, W.D.; Sullivan, R.W.

1981-01-01

The isotopic ratios resulting from Pb and U analyses on three zircon fractions from syenite gneiss intrusive into metasediments of the Shuswap Metamorphic Complex are collinear on a concordia plot and yield upper and lower intercepts of about 773 Ma and 70 Ma. The upper intercept is tentatively interpreted as the minimum age of emplacement. The lower intercept is suggested to be the time of uplift and cooling associated with tectonic denudation of the Shuswap Complex. The implied age of the country rocks is pre-late Proterozoic and they may be correlatives of the Purcell Supergroup. (auth)

Measurements of cesium and strontium diffusion in biotite gneiss

International Nuclear Information System (INIS)

Skagius, K.; Neretnieks, I.

1988-01-01

A significant retardation of radionuclides transported by flowing water from an underground repository can be expected if the nuclides are able to diffuse into the water filled micropores in the rock. This diffusion into the pores will also increase the surface available to interactions between the nuclides in the ground water and the rock material, such as sorption. To calculate the retardation, it is necessary to know the sorption properties and the diffusivities in the rock matrix for the radionuclides. Diffusion experiments with cesium and strontium in biotite gneiss samples have been performed. Both the transport of strontium and cesium through rock samples and the concentration profiles of cesium and strontium inside rock samples have been determined. The result shows that diffusion of cesium and strontium occurs in the rock material. A diffusion model has been used to evaluate the diffusivity. Both pore diffusion and surface diffusion had to be included in the model to give good agreement with the experimental data. If surface diffusion is not included in the model, the effective pore diffusivity that gives the best fit to the experimental data is found to be higher than expected from earlier measurement of iodide diffusion in the same type of rock material. This indicates that the diffusion of cesium and strontium (sorbing components) in rock material is caused by both pore diffusion and surface diffusion acting in parallel

Diffusion measurements of cesium and strontium in biotite gneiss

International Nuclear Information System (INIS)

Skagius, K.; Neretnieks, I.

1985-01-01

A significant retardation of radionuclides transported by flowing water from an underground repository can be expected if the nuclides are able to diffuse into the water filled micropores in the rock. This diffusion into the pores will also increase the surface available to interaction between the nuclides in the groundwater and the rock material, such as sorption. To calculate the retardation it is necessary to know the sorption properties and the diffusivities in the rock matrix for the radionuclides. Diffusion experiments with cesium and strontium in biotite gneiss samples have been performed. Both the transport of strontium and cesium through rock samples and the concentration profiles of cesium and strontium inside rock samples have been determined. The result show that diffusion of cesium and strontium occurs in the rock material. A diffusion model has been used to evaluate the diffusivity. Both pore diffusion and surface diffusion had to be included in the model to give good agreement with the experimental data. If surface diffusion is not included in the model, the effective pore diffusivity that gives the best fit to the experimental data is found to be higher than expected from earlier measurements of iodide diffusion in the same type of rock material. This indicates that the diffusion of cesium and strontium (sorbing components) in rock material is caused by both pore diffusion and surface diffusion acting in parallel. (author)

Nd-Sr isotopic geochemistry and U-Pb geochronology of the Fe granitic gneiss and Lajedo Granodiorite: implications for paleoproterozoic evolution of the Mineiro Belt, southern Sao Francisco craton, Brazil

Energy Technology Data Exchange (ETDEWEB)

Teixeira, Wilson [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias. Centro de Pesquisas Geocronologicas]. E-mail: wteixeir@usp.br; Avila, Ciro Alexandre [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Museu Nacional. Dept. de Geologia e Paleontologia]. E-mail: avila@mn.ufrj.br; Nunes, Luciana Cabral [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias]. E-mail: luciana@igc.usp.br

2008-07-01

The Fe granitic gneiss and Lajedo granodiorite belong to a voluminous felsic-mafic plutonism, tectonically linked to Paleoproterozoic magmatic evolution of the Mineiro Belt, southern portion of the Sao Francisco Craton, central-eastern Brazil. The Fe pluton is located north of the Lenheiros shear zone and is intrusive with respect to the Rio das Mortes greenstone belt and pyroxenite - gabbroic bodies, as indicated by xenoliths of gneiss and amphibolite, in the first case, and pyroxenite in the latter. The Lajedo granodiorite is located south of the Lenheiros shear zone and cuts the metamafic rocks of the Forro peridotite - pyroxenite and mafic and intermediate rocks of the Nazareno greenstone belt, as evidenced by xenoliths from the latter unit. The modal composition of the Fe granitic gneiss lies within the ranges of monzogranite and syenogranite. It is peraluminous and shows a large variation in K{sub 2}O content, which implies a middle-K calc-alkaline to high-K calc-alkaline tendency. The Lajedo modal composition is consistent with granodioritic and tonalitic compositions. It indicates a predominantly peraluminous composition and calc-alkaline character. The U-Pb zircon crystallization age of the Fe granitic gneiss is 2191 {+-} 9 Ma, whereas the Lajedo granodiorite yields 2208 {+-} 26 Ma. The Nd/Sr characteristics of the Fe and Lajedo plutons are consistent with mixtures of enriched mantle (EMI-type), DMM and crustal components during magma genesis in a plutonic arc setting, while the low {sup 87}Sr/{sup 86}Sri ratios point to contribution of mafic rock protoliths during magma genesis. This is also in accordance with the characteristic xenoliths observed within the investigated plutons from the Nazareno and Rio das Mortes greenstone belts. The Fe granitic gneiss and Lajedo granodiorite show tectonic characteristics which are comparable to those of nearby coeval plutons: Brito quartz-diorite (2221 +- 2 Ma), Brumado de Cima granodiorite (2219 {+-} 2 Ma), Brumado

Nd-Sr isotopic geochemistry and U-Pb geochronology of the Fe granitic gneiss and Lajedo Granodiorite: implications for paleoproterozoic evolution of the Mineiro Belt, southern Sao Francisco craton, Brazil

International Nuclear Information System (INIS)

Teixeira, Wilson; Avila, Ciro Alexandre; Nunes, Luciana Cabral

2008-01-01

The Fe granitic gneiss and Lajedo granodiorite belong to a voluminous felsic-mafic plutonism, tectonically linked to Paleoproterozoic magmatic evolution of the Mineiro Belt, southern portion of the Sao Francisco Craton, central-eastern Brazil. The Fe pluton is located north of the Lenheiros shear zone and is intrusive with respect to the Rio das Mortes greenstone belt and pyroxenite - gabbroic bodies, as indicated by xenoliths of gneiss and amphibolite, in the first case, and pyroxenite in the latter. The Lajedo granodiorite is located south of the Lenheiros shear zone and cuts the metamafic rocks of the Forro peridotite - pyroxenite and mafic and intermediate rocks of the Nazareno greenstone belt, as evidenced by xenoliths from the latter unit. The modal composition of the Fe granitic gneiss lies within the ranges of monzogranite and syenogranite. It is peraluminous and shows a large variation in K 2 O content, which implies a middle-K calc-alkaline to high-K calc-alkaline tendency. The Lajedo modal composition is consistent with granodioritic and tonalitic compositions. It indicates a predominantly peraluminous composition and calc-alkaline character. The U-Pb zircon crystallization age of the Fe granitic gneiss is 2191 ± 9 Ma, whereas the Lajedo granodiorite yields 2208 ± 26 Ma. The Nd/Sr characteristics of the Fe and Lajedo plutons are consistent with mixtures of enriched mantle (EMI-type), DMM and crustal components during magma genesis in a plutonic arc setting, while the low 87 Sr/ 86 Sri ratios point to contribution of mafic rock protoliths during magma genesis. This is also in accordance with the characteristic xenoliths observed within the investigated plutons from the Nazareno and Rio das Mortes greenstone belts. The Fe granitic gneiss and Lajedo granodiorite show tectonic characteristics which are comparable to those of nearby coeval plutons: Brito quartz-diorite (2221 +- 2 Ma), Brumado de Cima granodiorite (2219 ± 2 Ma), Brumado de Baixo

Evolution of the Archean continental crust in the nucleus of the Yangtze block: Evidence from geochemistry of 3.0 Ga TTG gneisses in the Kongling high-grade metamorphic terrane, South China

Science.gov (United States)

Qiu, Xiao-Fei; Ling, Wen-Li; Liu, Xiao-Ming; Lu, Shan-Song; Jiang, Tuo; Wei, Yun-Xu; Peng, Lian-Hong; Tan, Juan-Juan

2018-04-01

Archean Tonalite-Trondhjemite-Granodiorite (TTG) rocks are scattered within the Kongling high-grade metamorphic terrane (KHMT) in the northern South China block. A comprehensive geochronological and geochemical study is carried out on the Taoyuan granitic gneisses, a newly recognized TTG suite in the northwestern KHMT. This suite has long been regarded as a Mesoproterozoic magmatic pluton, but U-Pb zircon ages of 2994 ± 22 Ma and 2970 ± 15 Ma are obtained by LA-ICP-MS method in this study. The Taoyuan gneiss suite is trondhjemitic in composition, and has high SiO2 (67.80-74.93 wt.%), Na2O (5.11-5.81 wt.%) contents with Na2O/K2O ratios greater than unity, and low Ni (2.56-7.61 ppm), Cr (1.26-7.67 ppm), Yb (0.32-0.82 ppm) and Y (4.48-11.5 ppm) contents. Plots show large variation in La/Yb and Sr/Y ratios and pronounced depletion in Nb, Ta and Ti in the primitive mantle-normalized spiderdiagram. The gneiss suite also displays two-stage Nd model ages close to its crystallization age with corresponding εNd(t) values of -2.5 to +3.5. It is thus suggested that the Taoyuan gneisses, in fact, is part of the Archean Kongling basement complex. Geochemical evidence implies that the TTG rocks may be derived from partial melting of subducted oceanic crust from a garnetiferous amphibolite source with residual assemblage of garnet + amphibole + plagioclase. Our study further indicates that the nucleus of the Yangtze block might experience a juvenile continental crustal growth during Mesoarchean. We also suggest that the Yangtze block may have its own crustal evolutionary history independent from the North China craton and the Tarim block before Paleoproterozoic.

Evaluating the controls on Tourmaline Crystallization in the mylonitic granite-gneiss pluton in the Northeastern of Jan mine (Lorestan province

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Arezoo Moradi

2017-02-01

Full Text Available Introduction The study area is a part of the Sanandaj- Sirjan zone that is located in the NW of Azna city and NE of the dimension stone mine of Jan between 49° 11' 41"and 49° 16' 07" E longitude and 33° 36'35" and 33° 38'12" N latitude., A pluton of mylonitic granite-gneiss is exposed in the area which contains abundant tourmalines as black and patchy or subgrain association. Geochemically, the studied granite-gneiss is A-type, peraluminous to slightly metaluminous and calc – alkaline to slightly alkaline (Moradi et al., 7. The electron microprobe analyses of the tourmalines display shorl-dravite in composition with more tendency to shorl (Moradi et al., 2015. In this paper we try to study the petrological sites of tourmaline formation with associated minerals, controller factors of crystallization using mineral chemistry of tourmaline, comprehensive behavior of trace elements in the tourmaline, synthetic phase diagrams and finally relationships between the associated minerals. Materials and methods The results of trace-element and major-element analyses were obtained from one polished thin section including 2 tourmaline grains. Major-element analyses of tourmaline were obtained at Oklahama City University of America using the JEOL 8200 electron microprobe with a spot size of 5 μm and trace-element analyses were performed on just a sample by Laser Ablation-Inductively Coupled Plasma-Mass Spectroscopy (LA-ICP-MS a 193nm ArF excimer laser ablation system (MicroLas GeoLas 200Q in combination with a quadrupole ICP-MS (Micromass Platform ICP at Utrecht University of Netherland. Representative EMP and LA-ICP-MS analyses of tourmaline samples are presented in Tables1 and 2. Results The results of LA-ICP-MS on tourmalines of Jan mine in the North east of mylonitic granite-gneiss body show that distribution and diffusion of trace elements during the growth of tourmaline trend is positive on the plots of binary Mn versus Fetot / (Fetot +Mg and it

Gneisses of Brazil's cultural heritage buildings and its most frequent degradations

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Gilberto Costa, Antônio

2017-04-01

Macroscopic descriptions of cultural heritage buildings constructed using gneisses in the cities of Rio de Janeiro, Belo Horizonte and Ouro Preto, Brazil, allowed to identify alterations and degradations, in part conditioned by the mineralogical composition and the structures present in these stone materials. It is important to emphasize that: - some changes still begin in the environments where these materials were formed, experiencing an intensification from the processes of extraction, processing and application; - modifications occurring after the applications are understood herein as degradations. The studied gneisses present banding consisting of parts with different thicknesses and mineralogical contents. Due to these differentiated contents, clear bands were identified and constituted essentially by felsic minerals, such as feldspars and quartz, as well as dark bands formed by mafic minerals represented by: biotite, garnets, amphiboles, such as hornblende or pyroxene (hyperstene). In addition to these minerals, low contents of oxides and sulphides were found. Also under the influence of this distribution of minerals, planar structures or foliations, more or less developed, that can be very penetrative have been identified, mainly when these rocks were submitted to the performance of milonitization processes. From the set of changes and degradations observed stand out those related to the decomposition of minerals that make up these materials. In these cases, feldspars and other silicates, such as micas, amphiboles and pyroxenes, were decomposed due to the hydrolysis and products were generated which compromised the resistance of these stone materials, leading to their consequent disintegration. On the other hand, the presence of expansive clays in these products, caused volume increases which also contributed to the expansion of the weathered surface layer (blistering). This process may result detachments in the form of scales to cavities in cases of

Long-range laser scanning and 3D imaging for the Gneiss quarries survey

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Schenker, Filippo Luca; Spataro, Alessio; Pozzoni, Maurizio; Ambrosi, Christian; Cannata, Massimiliano; Günther, Felix; Corboud, Federico

2016-04-01

In Canton Ticino (Southern Switzerland), the exploitation of natural stone, mostly gneisses, is an important activity of valley's economies. Nowadays, these economic activities are menaced by (i) the exploitation costs related to geological phenomena such as fractures, faults and heterogeneous rocks that hinder the processing of the stone product, (ii) continuously changing demand because of the evolving natural stone fashion and (iii) increasing administrative limits and rules acting to protect the environment. Therefore, the sustainable development of the sector for the next decades needs new and effective strategies to regulate and plan the quarries. A fundamental step in this process is the building of a 3D geological model of the quarries to constrain the volume of commercial natural stone and the volume of waste. In this context, we conducted Terrestrial Laser Scanning surveys of the quarries in the Maggia Valley to obtain a detailed 3D topography onto which the geological units were mapped. The topographic 3D model was obtained with a long-range laser scanning Riegl VZ4000 that can measure from up to 4 km of distance with a speed of 147,000 points per second. It operates with the new V-line technology, which defines the surface relief by sensing differentiated signals (echoes), even in the presence of obstacles such as vegetation. Depending on the esthetics of the gneisses, we defined seven types of natural stones that, together with faults and joints, were mapped onto the 3D models of the exploitation sites. According to the orientation of the geological limits and structures, we projected the different rock units and fractures into the excavation front. This way, we obtained a 3D geological model from which we can quantitatively estimate the volume of the seven different natural stones (with different commercial value) and waste (with low commercial value). To verify the 3D geological models and to quantify exploited rock and waste volumes the same

The UHP metamorphic Seve Nappe Complex of the Swedish Caledonides - a new occurrence of the microdiamond-bearing gneisses and their exhumation

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Klonowska, Iwona; Janák, Marian; Majka, Jarosław; ‎ Froitzheim, Nikolaus; Gee, David G.

2015-04-01

The ultra-high pressure metamorphism (UHPM) in the Seve Nappe Complex of the Swedish Caledonides has been recently recognized within several lithologies including gneisses, eclogites and garnet pyroxenites (e.g. Janák et al. 2013, Klonowska et al. 2014a, Majka et al. 2014). Thermodynamic modelling and thermobarometric calculations indicate peak pressure conditions of >3GPa at c. 800-900°C (reaching the diamond stability field) for eclogites and garnet pyroxenites from northern Jämtland (e.g. Klonowska et al. 2014b). In addition to this, the first microdiamonds were found in paragneisses from the Snasahögarna Mt. in central Jämtland (Majka et al. 2014). Here we report a new discovery of microdiamond together with moissanite (SiC) from one of the world's most famous localities for thrusting, Mount Åreskutan, where long transport distances were recognized already in the 19th century (Törnebohm 1888). Garnet porphyroblasts in gneisses from the Åreskutan Mt. contain abundant mineral inclusions, mainly graphite, carbonates and quartz, together with fluid inclusions of CO2 concentrated in swarms. Among these inclusions three microdiamonds were found in two gneiss samples. In one of the samples moissanite was also discovered. Both minerals were identified by micro-Raman spectroscopy. In addition to these 'swarm' inclusions, biotite, kyanite, rutile, feldspars, zircon, monazite, ±phengite, ±muscovite, ±spinel, ±ilmenite, ±apatite occur in garnets. Phase equilibrium modelling for the phengite-bearing gneiss confirms its UHP history at temperatures of c. 800°C. Recent discoveries of UHP metamorphism within the Seve Nappe Complex derived from the Baltican outer margin (part of the Middle Allochthon) challenged us to present a new tectonic model incorporating exhumation of the deeply subducted continental rocks together with mantle lithosphere peridotites. Majka et al. (2014) introduced a new "under-pressure"-driven exhumation mechanism of rocks buried in

Mineralogy and mineral chemistry of rare-metal pegmatites at Abu Rusheid granitic gneisses, South Eastern Desert, Egypt

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Mohamed Fahmy Raslan

2011-12-01

Full Text Available The Abu Rushied area, situated in the South Eastern Desert of Egypt is a distinctive occurrence of economically important rare-metal mineralization where the host rocks are represented by granitic gneisses. Correspondingly, mineralogical and geochemical investigation of pegmatites pockets scattered within Abu Rusheid granitic gneisses revealed the presence of Hf-zircon, ferrocolumbite and uranyl silicate minerals (uranophane and kasolite. Electronmicroprobe analyses revealed the presence of Nb-Ta multioxide minerals (ishikawaite, uranopyrochlore, and fergusonite, uraninite, thorite and cassiterite as numerous inclusions in the recorded Hf-zircon and ferrocolumbite minerals.Abu Rusheid pegmatites are found as small and large bodies that occur as simple and complex (zoned pegmatites.Abu Rusheid rare-metal pegmatites occur as steeply dipping bodies of variable size, ranging from 1 to 5 m in width and 10 to 50 m in length. The zoned pegmatites are composed of wall zone of coarser granitic gneisses, intermediated zone of K-feldspar and pocket of mica (muscovite and biotite, and core of quartz and pocket ofmica with lenses of rare metals.The zircon is of bipyramidal to typical octahedral form and short prisms. Because the zircon of the investigated Abu Rushied pegmatite frequently contains hafnium in amounts ranging between 2.31 and 11.11%, the studied zircon was designated as Hf-rich zircon. This zircon commonly exhibits a normal zoning with rims consistentlyhigher in Hf than cores. The bright areas in the crystal either in core or rim showed a remarkable enrichment in hafnium content (8.83–11.11% with respect to the dark zones (3.19%. The investigated ferroclumbite commonly exhibits zoning; the dark zone is low in the Ta and U but the light zone is enriched in Ta (13% and U (1%. EMPAanalyses indicate the chemical composition of ishikawaite with U ranging from 0.68 to 0.79 per formula unit.Uranopyrochlore species has dominant uranium in the A

U-Pb ages for two tonalitic gneisses, pegmatitic granites, and K-feldspar porphyries, Olkiluoto study site, Eurajoki, SW Finland

International Nuclear Information System (INIS)

Maenttaeri, I.; Lindberg, A.; Aaltonen, I.

2007-08-01

Secondary ion microprobe zircon U-Pb ages have been determined for two tonalitic gneisses, two pegmatitic granites, and two potassium feldspar porphyry samples from the Olkiluoto study site, Eurajoki, S-W Finland. Moreover, monazites from the Kfeldspar porphyries were dated using TIMS U-Pb method. The tonalitic gneiss A1879 TTG 1 reveals bimodal zircon population and for A1880 TTG it is homogeneous. The samples yield similar overlapping concordia ages of 1851 ± 5 Ma and 1856 ± 5 Ma, respectively. The pegmatitic granite samples A1881 PGR 1 and A1883 PGR 2 have mostly zircons resembling those of the TTG's. The supposed pegmatitic zircons with high U and low Th are strongly altered. The zircon U-Pb data of A1881 PGR 1 plot roughly in two separate lines on a concordia diagram. The apparently younger ∼1.79 Ga data are all from the high U and low Th/U zircons and therefore certainly set the minimum age for the A1881 PGR 1. It is suggested, that the ∼1.85 Ga data comprise analyses from inherited zircons as it include both lower and higher Th/U zircons and 1.85 Ga coevals with age of the tonalitic gneisses. Thus, the apparent age for the A1881 PGR 1 is ∼1.79 Ga. The U-Pb data of sample A1883 PGR 2 also divide into two groups. The higher Th/U, inherited zircons determine an age of 1852 ± 9 Ma which is the same as that of the TTG's. The low Th/U zircon data scatter and the age of 1.83 Ga for A1883 PGR 2 is only poorly determined. The both potassium feldspar porphyry samples A1882 KFP 1 and A1884 KFP 2 reveal heterogeneous zircon populations. The A1882 KFP 1 zircons showing magmatic zoning in BSE images conceivably determine a concordia age of 1842± 6 Ma for the rock. In addition to that a few ∼1.9 Ga inherited zircon and metamorphic low Th/U rims with ages between 1.88 Ga and 1.83 Ga were detected. The age for the youngest metamorphic zircon rims overlaps with that of the magmatic zircons. The zircons in the other KFP sample A1884 show a wide range of ages

Geology, geochemistry, and geochronology (U-Pb) of the Rio Fortuna Gneiss - Serra do Bau intrusive Suite - Paragua Terrane SW Amazonian Craton

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Faria, Debora Almeida; Ruiz, Amarildo Salina; Matos, Joao Batista; Sousa, Maria Zelia Aguiar de; Lima, Gabrielle Aparecida de [Research Group on Crustal and Tectonic Evolution, Guapore, RS (Brazil); Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Instituto de Ciencias Exatas e da Terra; Inst. Nacional de Ciencia e Tecnologia de Geociencias da Amazonia (GEOCIAM), Belem, PA (Brazil); Moacir Jose Buenano Macambira, E-mail: defaal.debora@gmail.com, E-mail: gabilimagel@gmail.com, E-mail: asruiz@gmail.com, E-mail: jmatos@ufmt.br, E-mail: prof.mzaguiar@gmail.com, E-mail: moamac@ufpa.br [Research Group on Crustal and Tectonic Evolution, Guapore, RS (Brazil); Universidade Federal do Para (UFPA), Belem, PA (Brazil)

2014-07-01

The Rio Fortuna Gneiss crops out in the Serra Santa Barbara, near the Fortuna military headquarters, on the Brazil-Bolivia border. These orthogneisses are located in a portion of the Paragua terrain affected by the Sunsas Orogeny (1.0-0.9 Ga.). They are classified as monzo to granodiorite orthogneisses and underwent at least three episodes of deformation. The U-Pb zircon age of 1,711 ± 13 Ma obtained by laser ablation MC-ICP-MS is interpreted as the crystallization age of this orthogneiss. Geochemically, these rocks form a sequence comprising acidic subalkaline magmatism, calc-alkalic-type high-K, and metaluminous to peraluminous. (author)

Charnockitic ortho gneisses and mafic granulites of Cerro Olivo complex, proterozoic basement of SE Uruguay, Part 1: Geology

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Masquelin, H.

2008-01-01

Charnockitic ortho gneisses and mafic granulite s exposed in the Cerro Bori Block, in the center of Punta del Este terrain, were the first document occurrence of granulitic rocks from SE sector of the Uruguayan Shield. We present here their main geological features, with the purpose to suggest some petrologic and structural interesting problems for a future lithogeochemical, mineral chemistry, stable isotopes and fluid inclusion studies about these rocks. We propose some speculation form field-based studies considering a cognate magmatic origin of both kinds of rocks, previous to a homogeneous granulitic metamorphism. Some structural evidences indicate that after their uplift, these rocks were located on over thickened crust, at great to medium deepness. A cataclasis during anatexis and amphibolite-facies mineral association stabilization are common phenomena. Other evidences suggest a polycyclic character for the regional geologic evolution

Characteristics and mode of emplacement of gneiss domes and plutonic domes in central-eastern Pyrenees

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Soula, Jean-Claude

Gneiss domes and plutonic granitoid domes make up almost 50% of the pre-Hercynian terrains in the Central and Eastern Pyrenees. From a structural study of the shape and internal structure of the domes and of their relationships with the enclosing rocks, it can be shown that both types of domes were emplaced diapirically during the major regional deformation phase and the peak of regional metamorphism. The study also shows that the internal structure, the overall shape and general behaviour relative to the host rocks are similar for plutonic domes and for gneiss domes. This appears to be in good agreement with H. Ramberg's (1967, Gravity Deformation and the Earth's Crust. Academic Press, London; 1970, Model studies in relation to intrusion of plutonic bodies. In: Mechanisms of Igneous Intrusion (edited by Newall, G. & Rast, N.) Geol. J. Spec. Issue2, 261-286.) model studies showing that dome or mushroom-like structures, similar to those observed, develop when there is a small viscosity ratio between the rising body and its enclosing medium. This implies a high crystal content for the granitoid magma. This crystal content has been estimated by (i) calculating the viscosity and density in natural conditions from petrological data for the magma considered as a suspension, using the model and program of J. P. Carron et al. (1978 Bull Soc. géol. Fr.20, 739-744.); (ii) using the recent results of experimental deformation of partially melted granites of I. van der Molen & M. S. Paterson (1979, Contr. Miner. Petrol.70, 299-318.) and (ii) comparing the preceding results with the data obtained by deformation experiments on rocks similar to those enclosing the domes. The minimum crystal content for the development of a dome-like structure has been, thus, estimated to about 70%, i.e. a value very close to that estimated by van der Molen & Paterson (1979) to be the critical value separating the granular framework flow from suspension-like behaviour. The effect of small

Factor value determination and applicability evaluation of universal soil loss equation in granite gneiss region

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Wen-hai Zhang

2009-06-01

Full Text Available Six types of runoff plots were set up and an experimental study was carried out to examine natural rate of soil and water loss in the granite gneiss region of northern Jiangsu Province in China. Through correlation analysis of runoff and soil loss during 364 rainfall events, a simplified and convenient mathematical formula suitable for calculating the rainfall erosivity factor (R for the local region was established. Other factors of the universal soil loss equation (USLE model were also determined. Relative error analysis of the soil loss of various plots calculated by the USLE model on the basis of the observed values showed that the relative error ranged from -3.5% to 9.9% and the confidence level was more than 90%. In addition, the relative error was 5.64% for the terraced field and 12.36% for the sloping field in the practical application. Thus, the confidence level was above 87.64%. These results provide a scientific basis for forecasting and monitoring soil and water loss, for comprehensive management of small watersheds, and for soil and water conservation planning in the region.

Microstructural finite strain analysis and 40Ar/39Ar evidence for the origin of the Mizil gneiss dome, eastern Arabian Shield, Saudi Arabia

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Al-Saleh, Ahmad M.; Kassem, Osama M. K.

2012-07-01

The Mizil antiform is a gneiss-cored culmination situated near the northern end of the Ar Rayn island arc terrane, which is the easternmost exposed tectonic unit of the Arabian Shield. This domal structure has a mantle of metamorphosed volcanosedimentary rocks belonging to the Al-Amar Group, and an igneous interior made up of foliated granodiorite-tonalite with adakitic affinity. The gneissic core has a SHRIMP U-Pb zircon age of 689 ± 10 Ma making it the oldest rock unit in the Ar Rayn terrane. An adakite diapir, formed by the melting of the subducted crust of a young marginal basin, and rising through the volcanosedimentary succession of the Ar Rayn island arc is thought to have caused the observed doming. Relatively uniform strain throughout the dome combined with strong vertical shortening and the roughly radial pattern of stretching lineation is consistent with diapirism; the absence of strain localization rules out detachment faulting as a causative mechanism. Amphibolites from the metamorphic envelope have an 40Ar/39Ar age of 615 ± 2 Ma; the age gap between core and cover is thought to reflect the resetting of metamorphic ages during the final suturing event, a phenomenon that is often observed throughout the eastern shield. Aeromagnetic anomalies beneath the Phanerozoic sedimentary cover indicate the presence of a collage of accreted terranes east of the Ar Rayn terrane that were probably amalgamated onto the Arabian margin during the latest stages of the closure of the Mozambique ocean; culminant orogeny is believed to have taken place between 620 and 600 Ma as these terrane collided with a major continental mass to the east referred to here as the eastern Arabian block (EAB). The Mizil gneiss dome is therefore considered to have formed in a convergent contractional setting rather than being the outcome of extensional post-orogenic collapse.

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

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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)

Gneisses (Serizzi and Beole) of the Verbano-Cusio-Ossola district (Piedmont, Northern Italy): possible candidates for the designation of "Global Heritage Stone province"

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Antonella Dino, Giovanna; Borghi, Alessandro; Cavallo, Alessandro; Primavori, Piero

2016-04-01

The Verbano-Cusio-Ossola quarrying district (Piedmont, northern Italy) produces many different ornamental stones (granites, gneisses, marbles): two really important categories are represented by Serizzo and Beola gneisses. Several varieties of Serizzo and Beola crop out in the upper and middle Ossola Valley: Serizzo derives from the Antigorio, Monte Leone and Monte Rosa Penninic Units, whereas Beola from the Monte Leone, Orselina-Moncucco-Isorno and Monte Rosa Penninic Units, as well from the Fobello-Rimella schists (Austroalpine). The Serizzo, represented by a group of foliated granitoid orthogneisses (Serizzo Antigorio, Serizzo Formazza, Serizzo Sempione and Serizzo Monte Rosa varieties), is probably the most important and extensively exploited ornamental stones from the VCO province (about 70% of the VCO stone production). The quarries are mostly concentrated in the Antigorio and Formazza valleys, where the Antigorio nappe has a sub-horizontal attitude and reaches its greatest thickness (up to 1000 m). This stone was largely used to produce columns since the end of XV century (e.g. the old Ospedale Maggiore in Milano, now University of Milano) and later on it was replaced with granites. It was also used in the building structure of the Duomo di Milano, for the plinth and the piers. Nowadays, thanks to its good wear resistance and low cost, it is mainly used in polished slabs for paving: a recent application is the Frankfurt airport floor. Beola is the name of a group of heterogeneous orthogneisses with mylonitic foliation and strong mineralogical lineation (Beola Grigia, Bianca, Ghiandonata, Striata varieties), easy to split into thin slabs with hammer and chisel, occurring in the middle Ossola Valley, between Vogogna and Montecrestese. The quarries of Beola are probably the oldest of the Ossola Valley, although the precise period in which the stone started to be exported is unknown. The Beola trade probably started at the end of the XIII century, with the

Experimental and petrological constraints on local-scale interaction of biotite-amphibole gneiss with H2O-CO2-(K, NaCl fluids at middle-crustal conditions: Example from the Limpopo Complex, South Africa

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Oleg G. Safonov

2012-11-01

Full Text Available Reaction textures and fluid inclusions in the ∼2.0 Ga pyroxene-bearing dehydration zones within the Sand River biotite-hornblende orthogneisses (Central Zone of the Limpopo Complex suggest that the formation of these zones is a result of close interplay between dehydration process along ductile shear zones triggered by H2O-CO2-salt fluids at 750–800 °C and 5.5–6.2 kbar, partial melting, and later exsolution of residual brine and H2O-CO2 fluids during melt crystallization at 650–700 °C. These processes caused local variations of water and alkali activity in the fluids, resulting in various mineral assemblages within the dehydration zone. The petrological observations are substantiated by experiments on the interaction of the Sand River gneiss with the H2O-CO2-(K, NaCl fluids at 750 and 800 °C and 5.5 kbar. It follows that the interaction of biotite-amphibole gneiss with H2O-CO2-(K, NaCl fluids is accompanied by partial melting at 750–800 °C. Orthopyroxene-bearing assemblages are characteristic for temperature 800 °C and are stable in equilibrium with fluids with low salt concentrations, while salt-rich fluids produce clinopyroxene-bearing assemblages. These observations are in good agreement with the petrological data on the dehydration zones within the Sand River orthogneisses.

Revisiting elastic anisotropy of biotite gneiss from the Outokumpu scientific drill hole based on new texture measurements and texture-based velocity calculations

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Wenk, H.-R.; Vasin, R. N.; Kern, H.; Matthies, S.; Vogel, S. C.; Ivankina, T. I.

2012-10-01

A sample of biotite gneiss from the Outokumpu deep drilling project in Finland was investigated by Kern et al. (2008) for crystal preferred orientation and elastic anisotropy. Considerable differences between measured acoustic velocities and velocities calculated on the basis of texture patterns were observed. Measured P-wave anisotropy was 15.1% versus a Voigt average yielding 7.9%. Here we investigate the same sample with different methods and using different averaging techniques. Analyzing time-of-flight neutron diffraction data from Dubna-SKAT and LANSCE-HIPPO diffractometers with the Rietveld technique, much stronger preferred orientation for biotite is determined, compared to conventional pole-figure analysis reported previously. The comparison reveals important differences: HIPPO has much better counting statistics but pole figure coverage is poor. SKAT has better angular resolution. Using the new preferred orientation data and applying a self-consistent averaging method that takes grain shapes into account, close agreement of calculated and measured P-wave velocities is observed (12.6%). This is further improved by adding 0.1 vol.% flat micropores parallel to the biotite platelets in the simulation (14.9%).

Modeling the effects of structure on seismic anisotropy in the Chester gneiss dome, southeast Vermont

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Saif, S.; Brownlee, S. J.

2017-12-01

Compositional and structural heterogeneity in the continental crust are factors that contribute to the complex expression of crustal seismic anisotropy. Understanding deformation and flow in the crust using seismic anisotropy has thus proven difficult. Seismic anisotropy is affected by rock microstructure and mineralogy, and a number of studies have begun to characterize the full elastic tensors of crustal rocks in an attempt to increase our understanding of these intrinsic factors. However, there is still a large gap in length-scale between laboratory characterization on the scale of centimeters and seismic wavelengths on the order of kilometers. To address this length-scale gap we are developing a 3D crustal model that will help us determine the effects of rotating laboratory-scale elastic tensors into field-scale structures. The Chester gneiss dome in southeast Vermont is our primary focus. The model combines over 2000 structural data points from field measurements and published USGS structural data with elastic tensors of Chester dome rocks derived from electron backscatter diffraction data. We created a uniformly spaced grid by averaging structural measurements together in equally spaced grid boxes. The surface measurements are then projected into the third dimension using existing subsurface interpretations. A measured elastic tensor for the specific rock type is rotated according to its unique structural input at each point in the model. The goal is to use this model to generate artificial seismograms using existing numerical wave propagation codes. Once completed, the model input can be varied to examine the effects of different subsurface structure interpretations, as well as heterogeneity in rock composition and elastic tensors. Our goal is to be able to make predictions for how specific structures will appear in seismic data, and how that appearance changes with variations in rock composition.

Petrology of Olkiluoto

International Nuclear Information System (INIS)

Kaerki, A.; Paulamaeki, S.

2006-11-01

The rocks of Olkiluoto fall into four main groups: (1) gneisses, (2) migmatitic gneisses, (3) TGG-gneisses (TGG = tonalite-granodiorite-granite) and 4) pegmatitic granites. In addition, narrow diabase dykes occur sporadically. The gneisses include homogeneous mica-bearing quartz gneisses, banded mica gneisses and hornblende or pyroxene-bearing mafic gneisses. The migmatitic gneisses, which typically comprise 20 - 40% leucosome, can be divided into three subgroups in terms of their migmatite structures: veined gneisses, stromatic gneisses and diatexitic gneisses. The leucosomes of the veined gneisses show vein-like, more or less elongated traces with some features similar to augen structures. Planar leucosome layers characterize the stromatic gneisses, while the migmatite structure of the diatexitic gneisses is asymmetric and irregular. The TGG gneisses are medium-grained, relatively homogeneous rocks that can show a blastomylonitic foliation, but they can also resemble plutonic, unfoliated rocks. The pegmatitic granites are leucocratic, very coarse-grained rocks, which may contain large garnet, tourmaline and cordierite phenocrysts. Mica gneiss inclusions are typical of the larger pegmatitic bodies. Gneisses, which are weakly or not at all migmatitic, make ca. 9% of the bedrock. Migmatitic gneisses make up over 64% of the volume of the Olkiluoto bedrock, with the veined gneisses accounting for 43%, the stromatic gneisses for 0.4% and the diatexitic gneisses for 21%, based on drill core logging. Of the remaining lithologies, TGG gneisses constitute 8% and pegmatitic granites almost 20% by volume. The supracrustal rocks of Olkiluoto can be divided into four series by reference to whole rock chemical composition: a T series, S series, P series and basic, volcanogenic gneisses. Rocks of the T, S and P series seem to make up 42%, 12% and 26%, respectively, of the volume of central part of the island of Olkiluoto, in addition to which, pegmatitic granites and diabases

Release of uranium through cataclastic deformation of Mansehra granite gneiss and its precipitation in the overlying intramontane basin in northern Pakistan

International Nuclear Information System (INIS)

Butt, K.A.

1989-01-01

The Mansehra pluton belongs to a discontinuous belt of two mica granites of the Lesser Himalayas. The Mansehra granite is generally foliated except in the area around Mansehra. Several phases of granitic activity have been reported from the Mansehra Complex. Shams and Rahman have demonstrated that the younger phases tend to be enriched in Na 2 O. Ashraf extensively studied minor bodies ranging from albitites through aplites to pegmatites and suggested a late stage albitization event. The northern edge of this sheet-like granitic mass has undergone extensive cataclastic deformation, resulting in the formation of shear zones, mylonites and cataclasites. A chemical comparison of crushed granite with granite outside the shear zone suggests little chemical reconstitution in terms of major elements during cataclastic deformation. A huge shear zone in albitized granite gneiss has yielded secondary uranium minerals at water seepages, suggesting a liberation of uranium. Hydrogeochemical surveys of the crushed granite and adjoining areas suggest that uranium from crushed granite was easily leachable in comparison with rocks outside the shear zone. The uranium thus liberated was trapped in a Pleistocene sequence of clays and unsorted fluviatile sand overlying the granite and country rock metamorphics. (author). 17 refs, 2 figs, 2 tabs

Assessment of Blasting Performance Using Electronic Vis-à-Vis Shock Tube Detonators in Strong Garnet Biotite Sillimanite Gneiss Formations

Science.gov (United States)

Sharma, Suresh Kumar; Rai, Piyush

2016-04-01

This paper presents a comparative investigation of the shock tube and electronic detonating systems practised in bench blasting. The blast trials were conducted on overburden rocks of Garnet Biotite Sillimanite Gneiss formations in one of the largest metalliferous mine of India. The study revealed that the choice of detonating system was crucial in deciding the fragment size and its distribution within the blasted muck-piles. The fragment size and its distribution affected the digging rate of excavators. Also, the shape of the blasted muck-pile was found to be related to the degree of fragmentation. From the present work, it may be inferred that in electronic detonation system, timely release of explosive energy resulted in better overall blasting performance. Hence, the precision in delay time must be considered in designing blast rounds in such overburden rock formations. State-of-art image analysis, GPS based muck-pile profile plotting techniques were rigorously used in the investigation. The study revealed that a mean fragment size (K50) value for shock tube detonated blasts (0.55-0.59 m) was higher than that of electronically detonated blasts (0.43-0.45 m). The digging rate of designated shovels (34 m3) with electronically detonated blasts was consistently more than 5000 t/h, which was almost 13 % higher in comparison to shock tube detonated blasts. Furthermore, favourable muck-pile shapes were witnessed in electronically detonated blasts from the observations made on the dozer performance.

A practical assessment of aquifer discharge for regional groundwater demand by characterizing leaky confined aquifer overlain on a Mesozoic granitic gneiss basement

Science.gov (United States)

Shih, David Ching-Fang

2018-04-01

Due to increasing population worldwide, there is an urgent need to manage these important but diminishing groundwater resources efficiently to ensure their continued availability. The major innovative design of this study is to provide a practical assessment process for groundwater discharge under a regional demand by characterizing the nature of leaky confined aquifers overlain on a Mesozoic granitic gneiss basement which involves the important groundwater system in the Kinmen region (Taiwan, ROC) and the assessment of adoptable groundwater discharge in aquifer is needed. The storage coefficient presents an order of one in a thousand and hydraulic conductivity is approximately at the order of 1-8 m/d and 0.4-0.9 m/d for aquifer and aquitard respectively. Groundwater discharge and admissible number of pumping well is suggested considering scheduled maximum groundwater volume and head decline change for eastern and western studied area respectively. The safety subjected to the conservative issue is then addressed by the use of scheduled maximum groundwater volume. It reveals that the safety can be ensured using the indicator as scheduled maximum groundwater volume with predefined scenarios. The result can be utilized practically for developing management strategy of groundwater resources due to the applicability and novel of method.

Geochronology of Zircon in Eclogite Reveals Imbrication of the Ultrahigh-Pressure Western Gneiss Region of Norway.

Science.gov (United States)

Young, D. J.; Kylander-Clark, A. R.; Root, D. B.

2014-12-01

Eclogite provides the only record of kinematic events at the deepest levels of orogens. Integrating the U-Pb geochronology and trace element chemistry of zircon in eclogite reveals the most complete view of the PTt history, yet low concentrations of uranium and zirconium and drier compositions that hinder zircon growth at peak conditions render it a challenging rocktype for this approach. The iconic Western Gneiss Region (WGR) in Norway is one of the largest terranes of deeply subducted continental rocks in the world, and contains many indicators of ultrahigh-pressure metamorphic conditions (P>2.8 GPa) that developed during the Siluro-Devonian Caledonian Orogeny. A metamorphic transition from amphibolite-facies to ultrahigh-pressure eclogite facies broadly coincides with a km-scale shear zone that underlies the majority of the WGR. A critical unknown is the timing of movement on this feature, which emplaced allochthonous units above the Baltica basement, but might also have accommodated late-orogenic exhumation of the WGR from mantle depths. We carried out laser ablation split-stream ICPMS (LASS) and selected multigrain TIMS analyses of zircons from eleven eclogites across the southern WGR, of which eight are located within or above the shear zone. LASS spots on polished grains mostly yield weakly discordant Proterozoic intrusive ages, and often minimal indication of a Caledonian (U)HP metamorphic overprint. Direct ablation into unpolished zircon reveals thin rims of Caledonian age in some cases. Overall, the dataset shows that all samples began zircon growth at approximately the same time (ca. 430-420 Ma). Eclogite from lower levels of the shear zone does not contain any dates younger than ca. 410 Ma, however, while eclogite from higher levels continued growth until ca. 400 Ma. We interpret this to result from thrusting of the WGR above cooler basement after 410 Ma, terminating new zircon crystallization within the shear zone but allowing limited further growth in

Reorientation of lineation in the Central Crystalline Zone, Munsiari ...

Indian Academy of Sciences (India)

with some relevant microstructures and stretching lineations. In this study, although it has been men- .... middle unit (Unit II) is constituted of gneiss, augen gneiss, granitic gneiss, muscovite gneiss, and biotite gneiss. ... mylonites, the middle unit by gneissic rocks and the upper unit by schistose rocks. As such, the rocks.

Timing of metamorphism and exhumation in the Nordøyane ultra-high-pressure domain, Western Gneiss Region, Norway: New constraints from complementary CA-ID-TIMS and LA-MC-ICP-MS geochronology

Science.gov (United States)

Butler, J. P.; Jamieson, R. A.; Dunning, G. R.; Pecha, M. E.; Robinson, P.; Steenkamp, H. M.

2018-06-01

We present the results of a combined CA-ID-TIMS and LA-MC-ICP-MS U-Pb geochronology study of zircon and associated rutile and titanite from the Nordøyane ultra-high-pressure (UHP) domain in the Western Gneiss Region (WGR) of Norway. The dated samples include 4 eclogite bodies, 2 host-rock migmatites, and 2 cross-cutting pegmatites and leucosomes, all from the island of Harøya. Zircon from a coesite eclogite yielded an age of ca. 413 Ma, interpreted as the time of UHP metamorphism in this sample. Zircon data from the other eclogite bodies yielded metamorphic ages of ca. 413 Ma, 407 Ma, and 406 Ma; zircon trace-element data associated with 413 Ma and 407 Ma ages are consistent with eclogite-facies crystallization. In all of the eclogites, U-Pb dates from zircon cores, interpreted as the times of protolith crystallization, range from ca. 1680-1586 Ma, consistent with Gothian ages from orthogneisses in Nordøyane and elsewhere in the WGR. A zircon core age of ca. 943 Ma from one sample agrees with Sveconorwegian ages of felsic gneisses and pegmatites in the western part of the area. Migmatites hosting the eclogite bodies yielded zircon core ages of ca. 1657-1591 Ma and rim ages of ca. 395-392 Ma, interpreted as the times of Gothian protolith formation and Scandian partial melt crystallization, respectively. Pegmatite in an eclogite boudin neck yielded a crystallization age of ca. 388 Ma, interpreted as the time of melt crystallization. Rutile and titanite from 3 samples (an eclogite and two migmatites) yielded concordant ID-TIMS ages of 378-376 Ma. The results are similar to existing U-Pb data from other Nordøyane eclogites (415-405 Ma). In combination with previous pressure-temperature data from the coesite eclogite, these ages indicate that peak metamorphic conditions of 3 GPa/760 °C were reached ca. 413 Ma, followed by decompression to 1 GPa/810 °C by ca. 397 Ma and cooling below ca. 600 °C by ca. 375 Ma. The results are compatible with protracted UHP

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

International Nuclear Information System (INIS)

Chatterjee, S.K.

1984-01-01

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

Himalayan gneiss dome formation in the middle crust and exhumation by normal faulting: New geochronology of Gianbul dome, northwestern India

Science.gov (United States)

Horton, Forrest; Lee, Jeffrey; Hacker, Bradley; Bowman-Kamaha'o, Meilani; Cosca, Michael A.

2015-01-01

A general lack of consensus about the origin of Himalayan gneiss domes hinders accurate thermomechanical modeling of the orogen. To test whether doming resulted from tectonic contraction (e.g., thrust duplex formation, antiformal bending above a thrust ramp, etc.), channel flow, or via the buoyant rise of anatectic melts, this study investigates the depth and timing of doming processes for Gianbul dome in the western Himalaya. The dome is composed of Greater Himalayan Sequence migmatite, Paleozoic orthogneiss, and metasedimentary rock cut by multiple generations of leucogranite dikes. These rocks record a major penetrative D2 deformational event characterized by a domed foliation and associated NE-SW–trending stretching lineation, and they are flanked by the top-down-to-the-SW (normal-sense) Khanjar shear zone and the top-down-to-the-NE (normal sense) Zanskar shear zone (the western equivalent of the South Tibetan detachment system). Monazite U/Th-Pb geochronology records (1) Paleozoic emplacement of the Kade orthogneiss and associated granite dikes; (2) prograde Barrovian metamorphism from 37 to 33 Ma; (3) doming driven by upper-crustal extension and positive buoyancy of decompression melts between 26 and 22 Ma; and (4) the injection of anatectic melts into the upper levels of the dome—neutralizing the effects of melt buoyancy and potentially adding strength to the host rock—by ca. 22.6 Ma on the southwestern flank and ca. 21 Ma on the northeastern flank. As shown by a northeastward decrease in 40Ar/39Ar muscovite dates from 22.4 to 20.2 Ma, ductile normal-sense displacement within the Zanskar shear zone ended by ca. 22 Ma, after which the Gianbul dome was exhumed as part of a rigid footwall block below the brittle Zanskar normal fault, tilting an estimated 5°–10°SW into its present orientation.

Rb-Sr geochronology of the rocks of the Himalayas, Eastern Nepal, (1)

International Nuclear Information System (INIS)

Kai, Kunio

1981-01-01

Rb-Sr isotopic measurements were carried out for whole rock and small sliced rock from the Himalayan gneiss which constitutes the metamorphosed basement of the Tethyan sediments. The results of the measurements on whole rock from the Barun migmatite, the Barun gneiss and the Irkhua gneiss indicate that complete Sr isotopic redistribution occurred about 520 m.y. ago. This age is interpreted as the time of the regional metamorphism. The analytical results of the small sliced slabs of the Himalayan gneiss indicate that Sr isotopic redistribution occurred among the sliced slabs 33.3 +- 13.2 m.y. ago. This age is interpreted as the time of the metamorphism in the sillimanite-amphibolite facies. The high initial 87 Sr/ 86 Sr ratio of 0.7372 +- 0.0031 from the Barun migmatite of the Himalayan gneiss suggests the Precambrian Origin of the source rocks. The analytical results on the sliced slab of the Barun migmatite indicate that the original age of the rocks is about 800 m.y. The rock is interpreted as the remobilized Precambrian crustal rock. The high initial 87 Sr/ 86 Sr ratio of the Barun gneiss and the Irkhua gneiss of the Himalayan gneiss (0.7234 +- 0.0013) indicates also the Precambrian origin of the source rocks. (author)

The post collisional metamorphic evolution from Ultra High Temperature to Amphibolite facies metamorphism in the Odesan area during the Triassic collision between the North and South China cratons.

Science.gov (United States)

Lee, Byung Choon; Oh, Chang Whan; Kim, Tae Sung; Yi, Kee Wook

2015-04-01

The Odaesan Gneiss Complex (OGC) is the eastern end of the Hongseong-Odesan collision belt in Korean Peninsula which is the extension of the Dabie-Sulu collision belt between the North and South China blocks. The OGC mainly consists of banded and migmatitic gneiss with porphyritic granitoid and amphibolite. The banded gneiss can be subdivided into garnet-biotite and garnet-orthopyroxene banded gneisses. The highest metamorphic P/T conditions of the migmatitic and garnet-biotite banded gneiss were 760-820°C/6.3-7.2kbar and 810-840°C/7.2-7.8kbar respectively. On the other hand, the garnet-orthopyroxene banded gneiss records 940-950°C/10.5-10.7kbar that is corresponded to UHT metamorphic condition. These data indicate that the peak UHT metamorphic condition of the study area was preserved only within the garnet-orthopyroxene banded gneiss because its lower water content than other gneisses and UHT metamorphic mineral assemblage was completely replaced by the granulite facies metamorphism in other gneisses due to their higher water content than the garnet-orthopyroxene banded gneiss. Finally all gneisses experienced amphibolite facies retrograde metamorphism which is observed locally within rocks, such as garnet rim and surrounding area. The peak UHT metamorphism is estimated to occur at ca. 250-230 Ma using SHRIMP zircon U-Pb age dating and was caused by the heat supplied from asthenospheric mantle through the opening formed by slab break-off during early post collision stage. The calculated metamorphic conditions represent that geothermal gradient of the study area during the post collision stage was 86°C/kbar indicating the regional low-P/T metamorphic event. Besides the Triassic metamorphic age, two Paleoproterozoic metamorphic ages of ca. 1930 and 1886 Ma are also recognized by the SHRIMP age dating from the banded gneisses and Paleoproterozoic emplacement age of ca. 1847 Ma is identified from the porphyritic granitoid which formed in the within plate tectonic

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

International Nuclear Information System (INIS)

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

1981-01-01

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

Origin of an unusual monazite-xenotime gneiss, Hudson Highlands, New York: SHRIMP U-Pb geochronology and trace element geochemistry

Science.gov (United States)

Aleinikoff, John N.; Grauch, Richard I.; Mazdab, Frank K.; Kwak, Loretta; Fanning, C. Mark; Kamo, Sandra L.

2012-01-01

A pod of monazite-xenotime gneiss (MXG) occurs within Mesoproterozoic paragneiss, Hudson Highlands, New York. This outcrop also contains granite of the Crystal Lake pluton, which migmatized the paragneiss. Previously, monazite, xenotime, and zircon from MXG, plus detrital zircon from the paragneiss, and igneous zircon from the granite, were dated using multi-grain thermal ionization mass spectrometry (TIMS). New SEM imagery of dated samples reveals that all minerals contain cores and rims. Thus TIMS analyses comprise mixtures of age components and are geologically meaningless. New spot analyses by sensitive high resolution ion microprobe (SHRIMP) of small homogeneous areas on individual grains allows deconvolution of ages within complexly zoned grains.Xenotime cores from MXG formed during two episodes (1034 ± 10 and 1014 ± 3 Ma), whereas three episodes of rim formation are recorded (999 ± 7, 961 ± 11, and 874 ± 11 Ma). Monazite cores from MXG mostly formed at 1004 ± 4 Ma; rims formed at 994 ± 4, 913 ± 7, and 890 ± 7 Ma. Zircon from MXG is composed of oscillatory-zoned detrital cores (2000-1170 Ma), plus metamorphic rims (1008 ± 7, 985 ± 5, and ∼950 Ma). In addition, MXG contains an unusual zircon population composed of irregularly-zoned elongate cores dated at 1036 ± 5 Ma, considered to be the time of formation of MXG. The time of granite emplacement is dated by oscillatory-zoned igneous cores at 1058 ± 4 Ma, which provides a minimum age constraint for the time of deposition of the paragneiss.Selected trace elements, including all REE plus U and Th, provide geochemical evidence for the origin of MXG. MREE-enriched xenotime from MXG are dissimilar from typical HREE-enriched patterns of igneous xenotime. The presence of large negative Eu anomalies and high U and Th in monazite and xenotime are uncharacteristic of typical ore-forming hydrothermal processes. We conclude that MXG is the result of unusual metasomatic processes during high grade

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

Directory of Open Access Journals (Sweden)

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

Untitled

Indian Academy of Sciences (India)

Figure 7. Broad hinge Zone of a D, fold in calc gneiss, showing axial planar cleavage at very high angle to stratification (pen parallel to cleavage). Figure 8. Calc gneiss showing ribbing lineation due to. interSection of stratification and axial planar cleavage plunging to the right (parallel to pen). Figure 9. Sillimanite gneiss ...

U-Pb zircon geochronology and Sm-Nd-Pb isotopic constraint for precambrian plutonic rocks in the northeastern part of Ryeongnam massif, Korea

International Nuclear Information System (INIS)

Chang, Ho-Wan

2003-01-01

The Ryeongnam massif is composed of Precambrian gneisses, Paleozoic and Mesozoic sedimentary rocks and extensive Triassic-Jurassic plutonic rocks of felsic to mafic composition. In the northeast Ryeongnam massif, the oldest rocks belong to the Sobaegsan gneiss complex, which is composed of orthogneisses, paragneisses and mafic plutonic rocks. U-Pb zircon ages for the felsic and mafic intrusive bodies within the Sobaegsan gneiss complex are: the Icheon granite gneiss, 2357±43 and 2342±47 Ma; the Buncheon granite gneiss, 1963±5 Ma; the Pyeonghae granite gneiss, 1936±21 Ma; the Ogbang amphibolite, 1918±10 Ma; the Imwon leucogranite gneiss, 1826±20 Ma. The Hyeondong biotite schist, which is intruded by the Buncheon granite gneiss and the Ogbang amphibolite, yielded an age of 2271±44 Ma. The Nd-Sm-Pb isotopic data indicate that the felsic plutonic rocks are derived from an older Archean crust. The Nd T DM ages are Archean, and the εNd values are negative for the felsic rocks and positive for the amphibolite. Common Pb isotope compositions also indicate a crustal source for the felsic intrusives. The U-Pb ages of Precambrian rocks of the Ryeongnam massifs are similar to those in the Gyeonggi massif, and may have a similar crustal evolutionary history. The Precambrian rocks of South Korea could be related either to the North China block or to the South China block, as the isotope ages and patterns are not unique to either block. Similarly, a geologic correlation with Japan, although possible, is tenuous at present. (author)

Timing of metamorphism of the Lansang gneiss and implications for left-lateral motion along the Mae Ping (Wang Chao) strike-slip fault, Thailand

Science.gov (United States)

Palin, R. M.; Searle, M. P.; Morley, C. K.; Charusiri, P.; Horstwood, M. S. A.; Roberts, N. M. W.

2013-10-01

The Mae Ping fault (MPF), western Thailand, exhibits dominantly left-lateral strike-slip motion and stretches for >600 km, reportedly branching off the right-lateral Sagaing fault in Myanmar and extending southeast towards Cambodia. Previous studies have suggested that the fault assisted the large-scale extrusion of Sundaland that occurred during the Late Eocene-Early Oligocene, with a geological offset of ˜120-150 km estimated from displaced high-grade gneisses and granites of the Chiang Mai-Lincang belt. Exposures of high-grade orthogneiss in the Lansang National Park, part of this belt, locally contain strong mylonitic textures and are bounded by strike-slip ductile shear zones and brittle faults. Geochronological analysis of monazite from a sample of sheared biotite-K-feldspar orthogneiss suggests two episodes of crystallization, with core regions documenting Th-Pb ages between c. 123 and c. 114 Ma and rim regions documenting a significantly younger age range between c. 45-37 Ma. These data are interpreted to represent possible magmatic protolith emplacement for the Lansang orthogneiss during the Early Cretaceous, with a later episode of metamorphism occurring during the Eocene. Textural relationships provided by in situ analysis suggest that ductile shearing along the MPF occurred during the latter stages of, or after, this metamorphic event. In addition, monazite analyzed from an undeformed garnet-two-mica granite dyke intruding metamorphic units at Bhumipol Lake outside of the Mae Ping shear zone produced a Th-Pb age of 66.2 ± 1.6 Ma. This age is interpreted to date the timing of dyke emplacement, implying that the MPF cuts through earlier formed magmatic and high-grade metamorphic rocks. These new data, when combined with regional mapping and earlier geochronological work, show that neither metamorphism, nor regional cooling, was directly related to strike-slip motion.

Pb-Pb geochronology in zircon of the basement rocks of the southern portion of the Araguaia Belt - Paraiso do Tocantins region, Brazil

International Nuclear Information System (INIS)

Arcanjo, Silvia Helena de Souza; Moura, Candido Augusto Veloso

2000-01-01

Recent geochronological studies of the basement orthogneisses of the northern region of the Araguaia belt showed the occurrence of both Archean (2.85 Ga) and Early Proterozoic (1.85 Ga) rocks. The oldest gneisses were grouped in the Colmeia Complex, the younger were named the Cantao Gneiss. In the southern portion of the Araguaia belt, the basement sequences include metavolcanic-sedimentary rocks, tonalitic, calc-silicate, and alkaline gneisses, and granitic rocks. All of these sequences have been considered as Archean in age, although no geochronological data are available to test this hypothesis. The metavolcanic-sedimentary rocks are included in the Rio do Coco Group, while the granitic rocks are represented by the Serrote and Matanca granites. The tonalitic and calc-silicate gneisses were grouped with Colmeia and Rio do Mangues Complexes, and the alkaline gneisses in the Monte Santo Suite. These gneisses were investigated geochronologically by single zircon Pb-evaporation methods in order to define their stratigraphic interrelationships, and to contribute to a greater understanding of the geological evolution of this crustal segment. The single zircon ages of the tonalitic and calc-silicate gneisses range between 1.8 and 2.1 Ga. An age of about 1.0 Ga, was obtained for the alkaline gneisses of Serra da Estrela (Monte Santo Suite). These data along with the single zircon age of 1.85 Ga. published for the Serrote Granite, indicate the widespread occurrence of Proterozoic rocks in the basement of the southern part of Araguaia belt. However, the existence of Arquean sequences in this region can not be discarded since the volcanic-sedimentary rocks of the Rio do Coco Group have not as yet been dated. The correlation of tonalitic and calc-silicate gneisses with the Colmeia Complex was not confirmed, so these gneisses have been grouped with the Early proterozoic Rio dos Mangues Complex. Thus, it is suggested that a significant part of the basement of the southern

The geological processes time scale of the Ingozersky block TTG complex (Kola Peninsula)

Science.gov (United States)

Nitkina, Elena

2013-04-01

Ingozersky block located in the Tersky Terrane of the Kola Peninsula is composed of Archean gneisses and granitoids [1; 5; 8]. The Archaean basement complexes on the regional geological maps have called tonalite-trondemit-gneisses (TTG) complexes [6]. In the previous studies [1; 3; 4; 5; 7] within Ingozersky block the following types of rocks were established: biotite, biotite-amphibole, amphibole-biotite gneisses, granites, granodiorites and pegmatites [2]. In the rocks of the complex following corresponding sequence of endogenous processes observed (based on [5]): stage 1 - the biotitic gneisses formation; 2 - the introduction of dikes of basic rocks; 3 phase - deformation and foliation; 4 stage - implementation bodies of granite and migmatization; 5 stage - implementation of large pegmatite bodies; stage 6 - the formation of differently pegmatite and granite veins of low power, with and without garnet; stage 7 - quartz veins. Previous U-Pb isotopic dating of the samples was done for biotite gneisses, amphibole-biotite gneisses and biotite-amphibole gneisses. Thus, some Sm-Nd TDM ages are 3613 Ma - biotite gnesses, 2596 Ma - amphibole-biotite gnesses and 3493 Ma biotite-amphibole gneisses.. U-Pb ages of the metamorphism processes in the TTG complex are obtained: 2697±9 Ma - for the biotite gneiss, 2725±2 and 2667±7 Ma - for the amphibole-biotite gneisses, and 2727±5 Ma for the biotite-amphibole gneisses. The age defined for the biotite gneisses by using single zircon dating to be about 3149±46 Ma corresponds to the time of the gneisses protolith formation. The purpose of these studies is the age establishing of granite and pegmatite bodies emplacement and finding a geological processes time scale of the Ingozerskom block. Preliminary U-Pb isotopic dating of zircon and other accessory minerals were held for granites - 2615±8 Ma, migmatites - 2549±30 Ma and veined granites - 1644±7 Ma. As a result of the isotope U-Pb dating of the different Ingozerskogo TTG

Geological mapping of investigation trench OL-TK9 at the Olkiluoto study site, Eurajoki, SW Finland

International Nuclear Information System (INIS)

Nordbaeck, N.; Talikka, M.

2006-07-01

Geological mapping of trench OL-TK9 was carried out the by the Geological Survey of Finland at the Olkiluoto study site, Eurajoki, southwestern Finland, as a part of Posiva Oy's site investigation programme for the development of an underground repository for nuclear waste. The NW-SE striking trench, which is about 371 metres in length and 0.4-2.5 metres in width, is situated to the west from the OL-TK3 in the northwestern part of the study site. The rock types were determined macroscopically and the main rock types were further investigated microscopically. On the basis of the migmatite structure, the migmatitic gneisses at Olkiluoto can be divided into three groups: veined gneiss, stromatic gneiss and diatexitic gneiss. Most of the migmatitic gneisses in the trench are veined gneisses and only a few short sections of the diatexitic gneiss or K-feldspar porphyry exist. Stromatic gneisses were not encountered. The leucosome of the veined gneiss show vein like, more or less linear traces with some features similar to large-scale augen structures, whereas the migmatitic structure of the diatexitic gneiss is more asymmetric and irregular. The southernmost part of the trench is dominated by mica gneiss and pegmatitic granite. The mica gneiss is homogenous mica-rich rock that contains less than 10 % granite leucosome material. The pegmatitic granite shows variations in grain size, colour, and mode of occurrence. The veined gneiss dominates the central part of the trench. The northernmost part of the trench is mainly comprised of tonalitic-granodioritic-granitic gneiss, which has an igneous character. Most rocks in the trench are altered, the intensity of the alteration varies from weak to strong, and the most common alteration type is chloritisation. The intense alteration has resulted in pervasive softening and weathering of the bedrock in places and up to four meters thick layers of strongly weathered rocks were observed on the edges of the trench. The foliation S2B

Evaluation of the geological, geophysical and hydrogeological conditions at Fjaellveden

International Nuclear Information System (INIS)

Ahlbom, K.; Carlsson, L.; Carlsten, L.E.; Duran, O.; Larsson, N.Aa.; Olsson, O.

1983-05-01

The Fjaellveden study site has a flat topography and a high per-centage of outcrops. The main type of rock in the area is veined gneiss with a north-east structural strike and vertical dip. The veined gneiss contains sulphide minerals, primarily pyrite and pyrrhotite, in the form of fracture minerals and as impregnations. In conformity with the gneiss structure there are strata of granite gneiss. The rock mass has a fracture frequency of 4.0 fractures per metre within the upper 100 metres. The frequency decreases with increasing depth and below the 300 m level it is 1.8 fractures per metre. The Fjaellveden study site is delimited to the north-east and south-west by regional fracture zones, 80-90 m wide and dipping approx 75degree towards the south-west. The fracture zones contain wide sections of crushed and clay-altered rock, mylonites and breccias. The regional zones delimit a block at least 3times3 km large. This block contains only local fracture zones. Drill hole examinations indicate that the fracture zones are small and of a mean width of 5 m. Within the upper 100-200 metres horizontal fractures can be found. Common fracture minerals in fracture zones are calcite, kaolinite, chlorite and illite. Existing granite gneiss strata possess higher hydraulic conductivity than the surrounding veined gneiss. At a depth of 500 m the granite gneiss has a hydraulic conductivity than the surrounding veined gneiss. At a depth of 500 m the granite gneiss has a hydraulic conductivity of 3times10 -9 m/s, the corresponding value in the surrounding bedrock being 2times10 -11 m/s. For the rock mass as a whole, the hydraulic conductivity decreases from approx 10 -8 m/s at the surface rock to approx 10 -11 m/s at a depth of 600 m. The hydraulic conductivity in the local fracture zones in the Fjaellveden area is 5times10 -9 m/s at the 500 m level. The flat topography of the area implies that the hydraulic gradients in the bedrock are small. This has also been recorded by means of

Zircon (Hf, O isotopes) as melt indicator: Melt infiltration and abundant new zircon growth within melt rich layers of granulite-facies lenses versus solid-state recrystallization in hosting amphibolite-facies gneisses (central Erzgebirge, Bohemian Massif)

Science.gov (United States)

Tichomirowa, Marion; Whitehouse, Martin; Gerdes, Axel; Schulz, Bernhard

2018-03-01

In the central Erzgebirge within the Bohemian Massif, lenses of high pressure and ultrahigh pressure felsic granulites occur within meta-sedimentary and meta-igneous amphibolite-facies felsic rocks. In the felsic granulite, melt rich parts and restite form alternating layers, and were identified by petrology and bulk rock geochemistry. Mineral assemblages representing the peak P-T conditions were best preserved in melanocratic restite layers. In contrast, in the melt rich leucocratic layers, garnet and related HP minerals as kyanite are almost completely resorbed. Both layers display differences in accessory minerals: melanosomes have frequent and large monazite and Fe-Ti-minerals but lack xenotime and apatite; leucosomes have abundant apatite and xenotime while monazite is rare. Here we present a detailed petrographic study of zircon grains (abundance, size, morphology, inclusions) in granulite-facies and amphibolite-facies felsic gneisses, along with their oxygen and hafnium isotope compositions. Our data complement earlier Usbnd Pb ages and trace element data (REE, Y, Hf, U) on zircons from the same rocks (Tichomirowa et al., 2005). Our results show that the degree of melting determines the behaviour of zircon in different layers of the granulites and associated amphibolite-facies rocks. In restite layers of the granulite lenses, small, inherited, and resorbed zircon grains are preserved and new zircon formation is very limited. In contrast, new zircons abundantly grew in the melt rich leucocratic layers. In these layers, the new zircons (Usbnd Pb age, trace elements, Hf, O isotopes) best preserve the information on peak metamorphic conditions due to intense corrosion of other metamorphic minerals. The new zircons often contain inherited cores. Compared to cores, the new zircons and rims show similar or slightly lower Hf isotope values, slightly higher Hf model ages, and decreased oxygen isotope ratios. The isotope compositions (Hf, O) of new zircons indicate

The ONKALO area model. Version 1

International Nuclear Information System (INIS)

Kemppainen, K.; Ahokas, T.; Ahokas, H.; Paulamaeki, S.; Paananen, M.; Gehoer, S.; Front, K.

2007-11-01

The geological model of the ONKALO area consists of three submodels: the lithological model, the brittle deformation model and the alteration model. The lithological model gives properties of definite rock units that can be defined on the basis the migmatite structures, textures and modal compositions. The brittle deformation model describes the results of brittle deformation, where geophysical and hydrogeological results are added. The alteration model describes occurrence of different alteration types and its possible effects. The rocks of Olkiluoto can be divided into two major classes: (1) supracrustal high-grade metamorphic rocks including various migmatitic gneisses, tonalitic-granodioriticgranitic gneisses, mica gneisses, quartz gneisses and mafic gneisses, and (2) igneous rocks including pegmatitic granites and diabase dykes. The migmatitic gneisses can further be divided into three subgroups in terms of the type of migmatite structure: veined gneisses, stromatic gneisses and diatexitic gneisses. On the basis of refolding and crosscutting relationships, the metamorphic supracrustal rocks have been subject to polyphased ductile deformation, including five stages. In 3D modelling of the lithological units, an assumption has been made, on the basis of measurements in outcrops, investigation trenches and drill cores, that the pervasive, composite foliation produced as a result a polyphase ductile deformation has a rather constant attitude in the ONKALO area. Consequently, the strike and dip of the foliation has been used as a tool, through which the lithologies have been correlated between the drillholes and from the surface to the drillholes. The bedrock in the Olkiluoto site has been subject to extensive hydrothermal alteration, which has taken place at reasonably low temperature conditions, the estimated temperature interval being from slightly over 300 deg C to less than 100 deg C. Two types of alteration can be observed: (1) pervasive (disseminated

Air abrasion experiments in U-Pb dating of zircon

Science.gov (United States)

Goldich, S.S.; Fischer, L.B.

1986-01-01

Air abrasion of zircon grains can remove metamict material that has lost radiogenic Pb and zircon overgrowths that were added during younger events and thereby improve the precision of the age measurements and permit closer estimates of the original age. Age discordance that resulted from a single disturbance of the U-Pb isotopic decay systems, as had been demonstrated by T.E. Krogh, can be considerably reduced, and, under favorable conditions, the ages brought into concordancy. Two or more events complicate the U-Pb systematics, but a series of abrasion experiments can be helpful in deciphering the geologic history and in arriving at a useful interpretation of the probable times of origin and disturbances. In east-central Minnesota, U.S.A., Penokean tonalite gneiss is dated at 1869 ?? 5 Ma, and sheared granite gneiss is shown to have been a high-level granite intrusion at 1982 ?? 5 Ma in the McGrath Gneiss precursor. Tonalite gneiss and a mafic granodiorite in the Rainy Lake area, Ontario, Canada, are dated at 2736 ?? 16 and 2682 ?? 4 Ma, respectively. The tonalitic phase of the Morton Gneiss, southwestern Minnesota, is dated at 3662 ?? 42 Ma. ?? 1986.

Geological mapping of investigation Trench OL-TK13 at the Olkiluoto study site, Eurajoki, SW Finland

International Nuclear Information System (INIS)

Talikka, M.

2007-04-01

Geological mapping of investigation trench OL-TK13 was carried out by the Geological Survey of Finland at the Olkiluoto study site, Eurajoki, as a part Posiva Oy's site investigation programme for the development of an underground repository for nuclear waste. The east-west striking, ca. 250 m long trench is located in the vicinity of boreholes OL-KR23 and OL-KR27, ca. 250 m east of the ONKALO research facility. The mapping was performed from washed bedrock surface and rock types were determined macroscopically. The main rock types in OL-TK13 are diatexitic gneiss, veined gneiss, pegmatitic granite and K-feldspar porphyry. Mica gneiss and granite/granitized mica gneiss exist to a lesser extent. The diatexitic gneiss is the dominant rock type in the western part and the veined gneiss in the eastern part of the trench. The veined gneiss consists of pelitic mica gneiss paleosome and pegmatitic granite leucosome veins that are parallel to the foliation. In the diatexitic gneiss, the proportion of the leucosome veins and patches is over 50 % and the rock has an ambiguous texture. The pegmatitic granite also occurs as wider sections in the western part of the trench. The K-feldspar porphyry is characterized by potassium feldspar phenocrysts (diameter 4 deformation phase. The migmatitic gneisses were folded during the D 3 deformation phase resulting in small scale, tight and asymmetrical F 3 folds plunging moderately to the NE. During the fracture mapping, all fractures longer than one metre and all fractures intersecting the central thread were investigated. Measurements including orientation, length, fillings, Jr-value, Ja-value and undulation were recorded for a total of 860 fractures. The mean fracture density is 3.5 fracture/m. From the orientation data, three fracture sets were identified: (1) fractures parallel to the foliation, (2) subvertical N-S trending factures and (3) fractures dipping steeply to the N. ∼45 % of all fractures are 0.5-1.5 m in length and �

Fluid-present melting of meta-igneous rocks and the generation of leucogranites – Constraints from garnet major and trace element data, Lu-Hf whole rock-garnet ages and whole rock Nd-Sr-Hf-O isotope data

NARCIS (Netherlands)

Jung, C.; Jung, S.; Nebel, O.; Hellebrand, E.; Masberg, P.; Hoffer, E.

2009-01-01

Pan-African high-grade metamorphism in the Proterozoic Damara orogen (Namibia) led to formation of garnet-bearing leucosomes in potassic meta-igneous gneisses producing a meta-igneous migmatite. In addition, the migmatite (gneiss (mesosome) plus leucosome) was intruded by small-scale leucogranitic

Rb-Sr systematics of granitoids of the central gneissic complex, Arunachal Himalaya: implications on tectonism, stratigraphy and source

International Nuclear Information System (INIS)

Dikshitulu, G.R.; Dhana Raju, R.; Pandey, B.K.; Krishna, Veena

1995-01-01

Precambrian central gneissic complex (CGC) in the Kameng district of Arunachal Pradesh comprises the oldest Sela group thrusting over the Bomdila group, with the Salari group being the youngest. Augen gneiss of the Bomdila group, granite of the Salari group and hornblende granite gneiss of the Sela group define Rb-Sr isochron ages of 1914±23, 1536±60 and 481± 23 Ma, respectively. The 481 Ma age on the hornblende gneiss from the oldest Sela group is attributed to the resetting of Rb-Sr clock due to tectonic imprint of the main central thrust (MCT). The 1914 Ma age of the augen gneiss, the oldest reported so far from the Arunachal Himalaya, is either the emplacement age or latest metamorphic event. The 1536 Ma old emplacement age of the granite intruding the black shale of the Salari group disproves the hitherto considered Gondwana age for the black shale, and, thus, necessitates revision in its chronostratigraphy ( 87 Sr/ 86 Sr), of the hornblende granite gneiss and Salari granite is high (0.719 and 0.709) indicating a crustal source for these, whereas it is low for the augen gneiss (0.703) suggesting an inherited signature of the upper mantle source together with some crustal contamination. Rb-Sr whole-rock isochron ages from the Arunachal Himalaya are correlatable with those reported from other parts of the Indian Himalaya. These cumulatively point to at least three major periods of activity in the Himalaya at ca. 2060±250, 1530±90 and 530± 75 Ma. (author). 22 refs., 2 figs., 3 tabs

Rb-Sr systematics of granitoids of the central gneissic complex, Arunachal Himalaya: implications on tectonism, stratigraphy and source

Energy Technology Data Exchange (ETDEWEB)

Dikshitulu, G R; Dhana Raju, R [Dept. of Atomic Energy, Bangalore (India). Atomic Minerals Division; Pandey, B K; Krishna, Veena [Department of Atomic Energy, Hyderabad (India). Atomic Minerals Div.

1995-01-01

Precambrian central gneissic complex (CGC) in the Kameng district of Arunachal Pradesh comprises the oldest Sela group thrusting over the Bomdila group, with the Salari group being the youngest. Augen gneiss of the Bomdila group, granite of the Salari group and hornblende granite gneiss of the Sela group define Rb-Sr isochron ages of 1914{+-}23, 1536{+-}60 and 481{+-} 23 Ma, respectively. The 481 Ma age on the hornblende gneiss from the oldest Sela group is attributed to the resetting of Rb-Sr clock due to tectonic imprint of the main central thrust (MCT). The 1914 Ma age of the augen gneiss, the oldest reported so far from the Arunachal Himalaya, is either the emplacement age or latest metamorphic event. The 1536 Ma old emplacement age of the granite intruding the black shale of the Salari group disproves the hitherto considered Gondwana age for the black shale, and, thus, necessitates revision in its chronostratigraphy ({sup 87}Sr/{sup 86}Sr), of the hornblende granite gneiss and Salari granite is high (0.719 and 0.709) indicating a crustal source for these, whereas it is low for the augen gneiss (0.703) suggesting an inherited signature of the upper mantle source together with some crustal contamination. Rb-Sr whole-rock isochron ages from the Arunachal Himalaya are correlatable with those reported from other parts of the Indian Himalaya. These cumulatively point to at least three major periods of activity in the Himalaya at ca. 2060{+-}250, 1530{+-}90 and 530{+-} 75 Ma. (author). 22 refs., 2 figs., 3 tabs.

Geological Model of the Olkiluoto Site. Version 2.0

International Nuclear Information System (INIS)

Aaltonen, I.

2010-10-01

The rocks of Olkiluoto can be divided into two major classes: 1) supracrustal high-grade metamorphic rocks including various migmatitic gneisses, tonalitic-granodioriticgranitic gneisses, mica gneisses, quartz gneisses and mafic gneisses, and 2) igneous rocks including pegmatitic granites and diabase dykes. The migmatitic gneisses can further be divided into three subgroups in terms of the type of migmatite structure: veined gneisses, stromatic gneisses and diatexitic gneisses. On the basis of refolding and crosscutting relationships, the metamorphic supracrustal rocks have been subjected to polyphased ductile deformation, consisting of five stages, the D2 being locally the most intensive phase, producing thrust-related folding, strong migmatisation and pervasive foliation. In 3D modelling of the lithological units, an assumption has been made, on the basis of measurements in the outcrops, investigation trenches and drill cores, that the pervasive, composite foliation produced as a result of polyphase ductile deformation has a rather constant attitude in the ONKALO area. Consequently, the strike and dip of the foliation has been used as a tool, through which the lithologies have been correlated between the drillholes and from the surface to the drillholes. In addition, the largest ductile deformation zones and tectonic units are described in 3D model. The bedrock at the Olkiluoto site has been subjected to extensive hydrothermal alteration, which has taken place at reasonably low temperature conditions, the estimated temperature interval being from slightly over 300 deg C to less than 100 deg C. Two types of alteration can be observed: firstly, pervasive alteration and secondly fracturecontrolled alteration. Clay mineralisation and sulphidisation are the most prominent alteration events in the site area. Sulphides are located in the uppermost part of the model volume following roughly the foliation and lithological trend. Kaolinite is also mainly located in the

An exotic terrane in the Sulu UHP region, China

Science.gov (United States)

Chu, W.; Zhang, R.; Tsujimori, T.; Liou, J. G.

2004-12-01

The Haiyangsuo region of about 15 km2 along the coast in the NE part of the Triassic Sulu UHP terrane occurs three major rock types: amphibolitized metagabbro, gneiss and granitic dikes. Three different gneisses were observed in the field: A) Light color felsic gneiss is the dominant country rock and contains Qtz, Pl, Ms and Bi. B) Dark color plagioclase-amphibole gneiss occurs as thin layers within country rock; C) Granulite facies rock occurs as discontinuous lens. The amphibolitized metagabbros intrude into the gneisses as massive bodies (several m to hundreds of m in size) and thin dikes. Both metamorphic intrusives and gneisses are cross-cut by granitic dikes. The amphibolitized metagabbro was divided into three types: coronal metagabbro, transitional rock and garnet amphibolite: 1) Coronal metagabbro preserves gabbroic texture and primary assemblage of Opx+Cpx+Pl+Amp+Ilm. Most pyroxene grains are partially rimmed by thin corona of Amp+Ab+Qtz. Garnet occurs as fine-grained coronas at interface between plagioclase, pyroxene or ilmenite. 2) Transitional rocks contain similar assemblage and texture but most orthopyroxenes were partially or totally replaced by Amp+Qtz; garnet increases in content and size. Some gabbroic textures are preserved, but calcic plagioclase was replaced by zoisite, albite and muscovite. 3) Garnet amphibolite occurs at the margins of intrusive bodies and boudins where only minor relict clinopyroxenes preserve. Garnet coronal chains are not clear any more. Granitic dikes show pronounced deformation with mylonitic texture and contain 40-50% quartz porphyroclasts. Zircon separates from 2 metagabbros, 4 gneisses and 1 granitic rock were dated by using Stanford SHRIMP-RG. Metagabbroic zircons are angular and fractured shapes. The upper-intercept ages of gneisses rang from 1730 to about 2400 Ma, indicating variable protoith age. The 2 garnet amphibolites have upper-intercept ages 1734±5Ma and 1735±21Ma respectively. They are much older than

Geological model of the Olkiluoto site. Version 1.0

International Nuclear Information System (INIS)

Mattila, J.; Aaltonen, I.; Kemppainen, K.

2008-01-01

The rocks of Olkiluoto can be divided into two major classes: (1) supracrustal high-grade metamorphic rocks including various migmatitic gneisses, tonalitic-granodioriticgranitic gneisses, mica gneisses, quartz gneisses and mafic gneisses, and (2) igneous rocks including pegmatitic granites and diabase dykes. The migmatitic gneisses can further be divided into three subgroups in terms of the type of migmatite structure: veined gneisses, stromatic gneisses and diatexitic gneisses. On the basis of refolding and crosscutting relationships, the metamorphic supracrustal rocks have been subjected to polyphased ductile deformation, consisting of five stages, the D2 being locally the most intensive phase, producing thrust-related folding, strong migmatisation and pervasive foliation. In 3D modelling of the lithological units, an assumption has been made, on the basis of measurements in the outcrops, investigation trenches and drill cores, that the pervasive, composite foliation produced as a result of polyphase ductile deformation has a rather constant attitude in the ONKALO area. Consequently, the strike and dip of the foliation has been used as a tool, through which the lithologies have been correlated between the drillholes and from the surface to the drillholes. The bedrock at the Olkiluoto site has been subjected to extensive hydrothermal alteration, which has taken place at reasonably low temperature conditions, the estimated temperature interval being from slightly over 300 deg C to less than 100 deg C. Two types of alteration can be observed: (1) pervasive (disseminated) alteration and (2) fracture-controlled (veinlet) alteration. Kaolinisation and sulphidisation are the most prominent alteration events in the site area. Sulphides are located in the uppermost part of the model volume following roughly the lithological trend (slightly dipping to the SE). Kaolinite is also located in the uppermost part, but the orientation is opposite to the main lithological trend

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

International Nuclear Information System (INIS)

Oyinloye, A.O.

2006-01-01

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

PETROCHEMISTRY, Pb ISOTOPE SYSTEMATICS, AND ...

African Journals Online (AJOL)

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

338-IJBCS-Article-Dr Alexandre NONO

African Journals Online (AJOL)

Dr Gatsing

vaste ensemble constitué d'un socle granito-gneissique (gneiss, granitoïdes, amphibolites), recouvert par un manteau volcanique (basaltes, trachytes, rhyolites, ignimbrites), mis en place selon la tectonique de la Chaîne. Panafricaine Nord-Equatoriale et de la Ligne Volcanique du Cameroun. Les gneiss et migmatites sont ...

STRUCTURAL EVOLUTION OF THE KILOMBERO

African Journals Online (AJOL)

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

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

International Nuclear Information System (INIS)

Oyinloye, A.O.

2007-01-01

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

Matrix diffusion in crystalline rocks: coupling of anion exclusion, surface diffusion and surface complexation

International Nuclear Information System (INIS)

Olin, M.; Valkiainen, M.; Aalto, H.

1997-12-01

This report includes both experimental and modelling parts. Also, a novel approach to the diffusion experiments is introduced, where ions of the same electric charge diffuse in opposite directions through the same rock sample. Six rock-types from Olkiluoto radioactive waste disposal investigation site were used in the experiments: granite, weathered granite, mica gneiss, weathered mica gneiss, tonalite and altered mica gneiss/migmatite. The experiments consisted of the determination of the effective diffusion coefficient and the rock capacity factor for tritium, chloride (Cl-36) and sodium (Na-22). The modelling consisted of a chemical model for small pores (< 100 nm), a model for counter ion diffusion and models for the laboratory experiments

Evolution of the Dharwar Craton: a terrain of early Archean crustal stability, long term orogenic cycles and large scale palaeobiological activity

International Nuclear Information System (INIS)

Srinivasan, R.; Naqvi, S.M.

1988-01-01

Traceable history of the Dharwar Craton goes back to approximately 3400 m.y. old tonalitic to trondhjemitic fundamental gneiss whose REE composition indicates its derivation from a preexisting basalt which apparently had very short time of crustal residence. The fundamental gneiss is preserved only as rare relicts in the vast gneissic complex of the Indian Peninsula (the Peninsular Gneiss), and as pebbles in the conglomerates of the Archean Dharwar sequence. Study of these relicts, shows evidence of a deformation episode prior to the deposition of the high- and low-grade Dharwar supracrustal sequence. The Dharwar supracrustal sequence is briefly described. Geochemistry of the volcanic and sedimentary rocks of the Dharwar supracrustal belts are examined

Matrix diffusion in crystalline rocks: coupling of anion exclusion, surface diffusion and surface complexation

Energy Technology Data Exchange (ETDEWEB)

Olin, M.; Valkiainen, M.; Aalto, H. [VTT Chemical Technology, Espoo (Finland)

1997-12-01

This report includes both experimental and modelling parts. Also, a novel approach to the diffusion experiments is introduced, where ions of the same electric charge diffuse in opposite directions through the same rock sample. Six rock-types from Olkiluoto radioactive waste disposal investigation site were used in the experiments: granite, weathered granite, mica gneiss, weathered mica gneiss, tonalite and altered mica gneiss/migmatite. The experiments consisted of the determination of the effective diffusion coefficient and the rock capacity factor for tritium, chloride (Cl-36) and sodium (Na-22). The modelling consisted of a chemical model for small pores (< 100 nm), a model for counter ion diffusion and models for the laboratory experiments. 21 refs.

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.

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)

Geological model of the ONKALO area version 0

International Nuclear Information System (INIS)

Paananen, M.; Paulamaeki, S.; Gehoer, S.; Kaerki, A.

2006-03-01

The geological model of the ONKALO area is composed of four submodels: ductile deformation model, lithological model, brittle deformation model and alteration model. The ductile deformation model describes and models the products of polyphase ductile deformation, which facilitates the definition of dimensions and geometrical properties of individual lithological units determined in the lithological model. The lithological model describes the properties of rock units that can be defined on the basis the migmatite structures, textures and modal compositions. The brittle deformation model describes the products of multiple phases of brittle deformation, and the alteration model describes the types, occurrence and the effects of the hydrothermal alteration. On the basis of refolding and crosscutting relationships, the metamorphic supracrustal rocks have been subject to five stages of ductile deformation. This resulted in a pervasive, composite foliation which shows a rather constant attitude in the ONKALO area. Based on observations in outcrops, investigation trenches and drill cores, 3D modelling of the lithological units is carried out assuming that the contacts are quasiconcordant. Using this assumption, the strike and dip of the foliation has been used as a tool to correlate the lithologies between the drillholes, and from surface and tunnel outcrops to drillholes. Consequently, the strike and dip of the foliation has been used as a tool, through which the lithologies have been correlated between the drillholes and from surface to drillholes. The rocks at Olkiluoto can be divided into two major groups: (1) supracrustal high-grade metamorphic rocks including various migmatitic gneisses, homogeneous tonaliticgranodioritic- granitic gneisses, mica gneisses and quartzitic gneisses, and mafic gneisses, (2) igneous rocks, including pegmatitic granites and diabase dykes. The migmatitic gneisses can further be divided into three subgroups in terms of the type of migmatite

The strain-dependent spatial evolution of garnet in a high- P ductile shear zone from the Western Gneiss Region (Norway): a synchrotron X-ray microtomography study

Energy Technology Data Exchange (ETDEWEB)

Macente, A. [School of Geosciences, University of Edinburgh, The King' s Building James Hutton Road Edinburgh EH9 3FE UK; Fusseis, F. [School of Geosciences, University of Edinburgh, The King' s Building James Hutton Road Edinburgh EH9 3FE UK; Menegon, L. [School of Geography, Earth and Environmental Sciences, Faculty of Science and Engineering, Plymouth University, Fitzroy Drake Circus Plymouth Devon PL4 8AA UK; Xianghui, X. [Argonne National Laboratory, 9700 S. Cass Ave Building 431-B003 Argonne IL USA; John, T. [Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstr. 74-100 12249 Berlin Germany

2017-03-27

Reaction and deformation microfabrics provide key information to understand the thermodynamic and kinetic controls of tectono-metamorphic processes, however they are usually analysed in two dimensions, omitting important information regarding the third spatial dimension. We applied synchrotron-based X-ray microtomography to document the evolution of a pristine olivine gabbro into a deformed omphacite-garnet eclogite in four dimensions, where the 4th dimension is represented by the degree of strain. In the investigated samples, which cover a strain gradient into a shear zone from the Western Gneiss Region (Norway), we focused on the spatial transformation of garnet coronas into elongated clusters of garnets with increasing strain. Our microtomographic data allowed quantification of garnet volume, shape and spatial arrangement evolution with increasing strain. We combined microtomographic observations with light microscope- and backscatter electron images as well as electron microprobe- (EMPA) and electron backscatter diffraction (EBSD) analysis to correlate mineral composition and orientation data with the X-ray absorption signal of the same mineral grains. With increasing deformation, the garnet volume almost triples. In the low strain domain, garnets form a well interconnected large garnet aggregate that develops throughout the entire Page 1 of 52 sample. We also observed that garnet coronas in the gabbros never completely encapsulate olivine grains. In the most highly deformed eclogites, the oblate shapes of garnet clusters reflect a deformational origin of the microfabrics. We interpret the aligned garnet aggregates to direct synkinematic fluid flow and consequently influence the transport of dissolved chemical components. EBSD analyses reveal that garnet show a near-random crystal preferred orientation that testifies no evidence for crystal plasticity. There is, however evidence for minor fracturing, neo-nucleation and overgrowth. Microprobe chemical analysis

On the geology of the uranium mineralization in the Swiss Alps

International Nuclear Information System (INIS)

Gillieron, F.

1988-01-01

Numerous radiometric anomalies and several uranium occurrences were found in the Swiss Alps by systematic prospecting of selected areas carried out between 1957 and 1984. Most of the uranium indications lie in a rather narrow belt that follows roughly the valleys of the Rhone und of the Rhine Anterior, from Martigny onto Ilanz and extending northwards towards the Lake of Walenstadt. The uranium occurrences were found in the following geological environments: - permocarboniferous continental, variably metamorphosed series, belonging either to the formation of the 'Verrucano' or to the Penninic St. Bernhard nappe; - muscovite-chlorite-albite gneisses belonging to the pre-Westphalian basement of the St. Bernhard nappe; - muscovite-chlorite gneisses and phyllites of the Hercynian Tavetsch massiv; - muscovite-biotite gneisses within the southern border of the Aar massif; - Vallorcine granite of the Auguilles-Rouges massiv and polymetamorphic biotite gneisses along its northwestern contact zone. The possible geological (or 'in situ') resources are estimated to be 50-250 tonnes uranium in each one of the investigated mineralization zones of some importance; the respective estimated grades are 50-250 ppm U. Therefore the occurrences are actually of no economic value. (author) 25 figs., 1 tab., refs

Investigation of Fault Zones In The Penninic Gneiss Complex of The Swiss Central Alps Using Tomograhic Inversion of The Seismic Wavefield Along Tunnels

Science.gov (United States)

Giese, R.; Klose, C.; Otto, P.; Selke, C.; Borm, G.

Underground seismic investigations have been carried out since March 2000 in the Faido adit of the Gotthard Base Tunnel (Switzerland) and the Piora exploration adit. Both adits cut metamorphic rock formations of the Leventina and Lucomagno Gneiss Complexes. The seismic measurements in the Faido Adit were carried out every 200 m during the excavation work with the Integrated Seismic Imaging System (ISIS) developed by the GeoForschungsZentrum Potsdam in cooperation with Amberg Measuring Technique, Switzerland. This system provides high resolution seismic images via an array of stan- dard anchor rods containing 3D-geophones which can be installed routinely during the excavation process. The seismic source is a repetitive pneumatic impact hammer. For each measurement in the Faido adit, seismic energy was transmitted from 30 to 50 source points distributed along the tunnel wall at intervals of 1.0 to 1.5 m. In the Piora exploration adit a 2D grid of 441 source points distributed along a distance of 147 tunnel meters were measured. In both adits the shots were recorded by arrays of 8 to 16 three - component geophone anchor rods glued into 2 m deep boreholes at intervals of 9 m - 10 m. The total length of all profiles was about 850 m. Seismic sections show first P-wave energy at frequencies up to 2 kHz and S-wave energy up to 1.3 kHz. Reflection energy was observed from distances of up to 350 m for P-waves and 200 m for S-waves. The dominant frequencies of reflective energy were found between 600 and 800 Hz for P-waves and between 200 and 400 Hz for S-waves. The corresponding wave lengths were 8 to 10 m. We used the first arrival times of P- and S- waves to calculate tomographic inversions. The 2D-velocity models for P- and S-waves in the Faido adit revealed a near field of 2 to 3 m from the tunnel surface which is characterized by strong velocity variations: 3000 to 5700 m/s for P-wave velocity (Vp) and 2000 to 3000 m/s for S-wave velocity (Vs). High velocity zones

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.

Poly-phase Deformation Recorded in the Core of the Coast Plutonic Complex, Western British Columbia

Science.gov (United States)

Hamblock, J. M.; Andronicos, C. L.; Hurtado, J. M.

2006-05-01

The Coast Plutonic Complex of western British Columbia constitutes the largest batholith within the North American Cordillera. The field area for this study is Mt. Gamsby, an unexplored region above the Kitlope River, east of the Coast Shear Zone and at the southern end of the Central Gneiss Complex. The dominant lithologies on Mt. Gamsby include amphibolite and metasedimentary gneiss, gabbro-diorite, and orthogneiss. The amphibolite gneiss contains alternating amphibolite and felsic layers, with chlorite and epidote pervasive in some regions and garnet rare. This unit is commonly migmatized and contains various folds, boudins, and shear zones. The metasedimentary gneiss contains quartz, k-spar, graphite, chlorite, and perhaps cordierite, but appears to lack muscovite and aluminosilicates. The gabbro-diorite is salt and pepper in color and contains ca. 50% pyroxene and plagioclase. The orthogneiss is light in color and plagioclase-rich, with a texture varying from coarse-grained and undeformed to mylonitic. In some regions, this unit contains abundant mafic enclaves. At least four deformational events (D1-4) are observed. The second generation of folding, F2, is dominant in the area and resulted in the production of a large synform during sinistral shearing. The S1 foliation is observed only in the amphibolite gneiss and is orthogonal to S2, creating mushroom- type fold interference patterns. S2 foliations strike NW-SE and dip steeply to the SW, suggesting SW-NE directed shortening. L2 lineations developed on S2 plunge shallowly to the NW and SE, implying strike-slip motion. Although both dextral and sinistral motions are indicated by shear band data, sinistral motion is dominant. The average right and left lateral shear band orientation is nearly identical to S2, suggesting that right and left lateral shearing were synchronous. Foliations within the orthogneiss are parallel to the axes of S2 folds and boudins in the amphibolite gneiss, suggesting that emplacement

Mechanical properties of granitic rocks from Gideaa, Sweden

International Nuclear Information System (INIS)

Ljunggren, C.; Stephansson, O.; Alm, O.; Hakami, H.; Mattila, U.

1985-10-01

The elastic and mechanical properties were determined for two rock types from the Gideaa study area. Gideaa is located approximately 30 km north-east of Oernskoeldsvik, Northern Sweden. The rock types that were tested were migmatitic gneiss and migmatitic granite. The following tests were conducted: - sound velocity measurements; - uniaxial compression tests with acoustic emission recording; - brazilian disc tests; - triaxial tests; - three point bending tests. All together, 12 rock samples were tested with each test method. Six samples of these were migmatic gneiss and six samples were migmatitic granite. The result shows that the migmatitic gneiss has varying strength properties with low compressive strength in comparison with its high tensile strength. The migmatitic granite, on the other hand, is found to have parameter values similar to other granitic rocks. With 15 refs. (Author)

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.

Geological model of the Olkiluoto site Version O

International Nuclear Information System (INIS)

Paulamaeki, S.; Paananen, M.; Gehoer, S.

2006-05-01

The geological model of the Olkiluoto site consists of four submodels: the lithological model, the ductile deformation model, the brittle deformation model and the alteration model. The lithological model gives properties of definite rock units that can be defined on the basis the migmatite structures, textures and modal compositions. The ductile deformation model describes and models the products of polyphase ductile deformation, which enables to define the dimensions and geometrical properties of individual lithological units determined in the lithological model. The brittle deformation model describes the products of multiple phases of brittle deformation. The alteration model describes the types, occurrence and the effects of the hydrothermal alteration. The rocks of Olkiluoto can be divided into two major classes: (1) supracrustal high-grade metamorphic rocks including various migmatitic gneisses, tonalitic-granodioriticgranitic gneisses, mica gneisses, quartz gneisses and mafic gneisses, and (2) igneous rocks including pegmatitic granites and diabase dykes. The migmatitic gneisses can further be divided into three subgroups in terms of the type of migmatite structure: veined gneisses, stromatic gneisses and diatexitic gneisses. On the basis of refolding and crosscutting relationships, the metamorphic supracrustal rocks have been subject to polyphased ductile deformation, including five stages. In 3D modelling of the lithological units, an assumption has been made, on the basis of measurements in outcrops, investigation trenches and drill cores, that the pervasive, composite foliation produced as a result a polyphase ductile deformation has a rather constant attitude in the ONKALO area. Consequently, the strike and dip of the foliation has been used as a tool, through which the lithologies have been correlated between the drillholes and from the surface to the drillholes. The bedrock in the Olkiluoto site has been subject to extensive hydrothermal alteration

geological mapping of the Onkalo open cut

Energy Technology Data Exchange (ETDEWEB)

Talikka, M. [Geological Survey of Finland, Espoo (Finland)

2005-11-15

Posiva Oy and Geological Survey of Finland carried out geological mapping of the ONKALO open cut in the latter half of the year 2004. The study area is located on the Olkiluoto Island in Eurajoki, SW Finland. The study included geological mapping, stereo-photography, and interpretation of 3D images. Fieldwork was carried out during the construction work. The main rock types are vein migmatite and grey gneiss with variation to granitic grey gneiss. The contacts of the rock types are gradual. The vein migmatite consists of fine- to medium-grained mica gneiss paleosome and granite or granite pegmatite neosome. The proportion of the neosome material varies between 15 and 35 percent and the neosome occurs as veins and bands up to ten centimetres in thickness. The granite I granite pegmatite is medium- to coarse-grained and not orientated. Main minerals in the mica gneiss are plagioclase, biotite, quartz, and in the granite / granite pegmatite potassium feldspar, plagioclase, and quartz. The grey gneiss is medium grained and fairly homogenous comprising mainly plagioclase, biotite, and quartz. The granitic grey gneiss contains also potassium feldspar crystals up to five cm in length. The rocks within the study area are generally well preserved. There is, however, a zone of strongly weathered rocks east of the ONKALO open cut. The main structural feature in the study area is S{sub 2} foliation, which is seen in the orientation of biotite grains. The degree of the foliation is weak to medium in the vein migmatite and weak to non-existence in the grey gneiss. The foliation (S{sub 2}) dips 20-70 deg to southeast with an average direction of 150/45 deg. The migmatisation took place during the second deformation phase and possibly proceeded along the lithologic layers. The neosome veins bend irregularly and folding is present in places. The fold axis of the small scale, isoclinal folds dip 50-70 deg to northeast. In fracture mapping a total of 231 fractures were measured

geological mapping of the Onkalo open cut

International Nuclear Information System (INIS)

Talikka, M.

2005-11-01

Posiva Oy and Geological Survey of Finland carried out geological mapping of the ONKALO open cut in the latter half of the year 2004. The study area is located on the Olkiluoto Island in Eurajoki, SW Finland. The study included geological mapping, stereo-photography, and interpretation of 3D images. Fieldwork was carried out during the construction work. The main rock types are vein migmatite and grey gneiss with variation to granitic grey gneiss. The contacts of the rock types are gradual. The vein migmatite consists of fine- to medium-grained mica gneiss paleosome and granite or granite pegmatite neosome. The proportion of the neosome material varies between 15 and 35 percent and the neosome occurs as veins and bands up to ten centimetres in thickness. The granite I granite pegmatite is medium- to coarse-grained and not orientated. Main minerals in the mica gneiss are plagioclase, biotite, quartz, and in the granite / granite pegmatite potassium feldspar, plagioclase, and quartz. The grey gneiss is medium grained and fairly homogenous comprising mainly plagioclase, biotite, and quartz. The granitic grey gneiss contains also potassium feldspar crystals up to five cm in length. The rocks within the study area are generally well preserved. There is, however, a zone of strongly weathered rocks east of the ONKALO open cut. The main structural feature in the study area is S 2 foliation, which is seen in the orientation of biotite grains. The degree of the foliation is weak to medium in the vein migmatite and weak to non-existence in the grey gneiss. The foliation (S 2 ) dips 20-70 deg to southeast with an average direction of 150/45 deg. The migmatisation took place during the second deformation phase and possibly proceeded along the lithologic layers. The neosome veins bend irregularly and folding is present in places. The fold axis of the small scale, isoclinal folds dip 50-70 deg to northeast. In fracture mapping a total of 231 fractures were measured. Field

A low-δ18O intrusive breccia from Koegel Fontein, South Africa: Remobilisation of basement that was hydrothermally altered during global glaciation?

Science.gov (United States)

Olianti, Camille A. E.; Harris, Chris

2018-02-01

The Cretaceous Koegel Fontein igneous complex is situated on the west coast of South Africa, and has a high proportion of rocks with abnormally low δ18O values. The rocks with the lowest δ18O values (- 5.2‰) belong to intrusive matrix-supported breccia pipes and dykes, containing a variety of clast types. The breccia rocks range in SiO2 from 44 to 68 wt% and their whole-rock δ18O values vary between - 5.2‰ and + 1.8‰. The major and trace element composition of the breccia rocks is consistent with them containing variable proportions of clasts of Cretaceous intrusive rocks and basement gneiss and the matrix being fluidized material derived from the same source as the clasts. Based on the nature of the clasts contained in the breccia, it was emplaced just prior to intrusion of the main Rietpoort Granite at 134 Ma. All components of the breccia have low δ18O value and, at least in the case of the gneiss clasts, this predates incorporation in the fluidized material. Although the early Cretaceous appears to have been a period of cold climate, it is unlikely that the δ18O values of ambient precipitation ( - 10‰) would have been low enough to have generated the required 18O-depletion. The basement gneiss was probably 2-3 km below the Cretaceous surface, minimizing the possibility of interaction with isotopically unmodified meteoric water, and there is no evidence for foundered blocks of cover rocks in the breccia. There is, therefore, no evidence for downwards movement of material. We favour a model where basement gneiss interacted with extremely 18O-depleted fluid during crustal reworking at 547 Ma, a time of global glaciation. Low-δ18O metamorphic fluids produced by dehydration melting of 18O-depleted gneiss became trapped and, as the fluid pressure increased, failure of the seal resulted in explosive upwards movement of fluidized breccia. Migration was along pre-existing dykes, incorporating fragments of these dykes, as well as the country rock gneiss.

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.)

Charnockites and granites of the western Adirondacks, New York, USA: a differentiated A-type suite

Science.gov (United States)

Whitney, P.R.

1992-01-01

Granitic rocks in the west-central Adirondack Highlands of New York State include both relatively homogeneous charnockitic and hornblende granitic gneisses (CG), that occur in thick stratiform bodies and elliptical domes, and heterogeneous leucogneisses (LG), that commonly are interlayered with metasedimentary rocks. Major- and trace-element geochemical analyses were obtained for 115 samples, including both types of granitoids. Data for CG fail to show the presence of more than one distinct group based on composition. Most of the variance within the CG sample population is consistent with magmatic differentiation combined with incomplete separation of early crystals of alkali feldspar, plagioclase, and pyroxenes or amphibole from the residual liquid. Ti, Fe, Mg, Ca, P, Sr, Ba, and Zr decrease with increasing silica, while Rb and K increase. Within CG, the distinction between charnockitic (orthopyroxene-bearing) and granitic gneisses is correlated with bulk chemistry. The charnockites are consistently more mafic than the hornblende granitic gneisses, although forming a continuum with them. The leucogneisses, while generally more felsic than the charnockites and granitic gneisses, are otherwise geochemically similar to them. The data are consistent with the LG suite being an evolved extrusive equivalent of the intrusive CG suite. Both CG and LG suites are metaluminous to mildly peraluminous and display an A-type geochemical signature, enriched in Fe, K, Ce, Y, Nb, Zr, and Ga and depleted in Ca, Mg, and Sr relative to I- and S-type granites. Rare earth element patterns show moderate LREE enrichment and a negative Eu anomaly throughout the suite. The geochemical data suggest an origin by partial melting of biotite- and plagioclase-rich crustal rocks. Emplacement occurred in an anorogenic or post-collisional tectonic setting, probably at relatively shallow depths. Deformation and granulite-facies metamorphism with some partial melting followed during the Ottawan phase

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.

Geology and mineral occurences of braquiantidinal do Lontra - GO

International Nuclear Information System (INIS)

Macambira, J.B.

1983-01-01

This work involved the geological mapping (in the scale 1:60.000) of an area of 800 square kilometers in the nortwestern part of the state of Goias, near and east of the Araguaia river. Based on the stratigraphy, metamorphism, geochronology, magmatism and mineral deposits hypotheses on the geological evolution of the region are discussed. The area studied belongs to the Precambrian Araguaia Fold Belt. The oldest rocks identified are trondhjemitic gneisses and on these rocks was deposited a sedimentary sequence with minor volcanics of a geosynclinal type. The stratigraphic column of Abreu (1978) was adopted with minor modifications. The basement, of transamazonic age (2000 Ma), consists mostly of gneiss, migmatite, granite gneiss and amphibolite. The metasediments belongs to the lower unit (Estrondo Group) of the Supergroup Baixo Araguaia. The Estrondo Group, of brasilian age (600 Ma), consists in the area of the lowermost Morro do Campo Formation, mainly quartzite and amphibolite, which give the high relief of the brachyanticlines of Lontra and Ramal do Lontra.(author)

The geologic investigation of the bedrock and the tectonic and geophysical surveys at Kynnefjaell

International Nuclear Information System (INIS)

Ahlbom, K.; Ahlin, S.; Eriksson, L.; Samuelsson, L.

1980-05-01

The geologic survey took place at a selected area of Kynnefjaell. The result is given on geologic and tectonic maps. Two kinds of rock dominate, namely (a) sedimentary veined gneiss and (b) gneissic granite. The strike is in the N-S direction. A symmetric folds dip to the last. The fissure zones are oriented in the N-S and NE-SW directions. The latter zones are considered to be Precambrian shear zones with a dip to the NW. The dip of the fissure zones with the direction N-S is difficult to ascertain. The frequency of fissures is the same for granite and gneiss. The length of fissures is longer in the gneissic granite than in the sedimentary veined gneiss. The measurement of stress shows its main direction to be WNW-NW to ESE-SE. The fissure zones are at right or blunt-ended angles to the main stress direction. (G.B.)

Relative chronology in high-grade crystalline terrain of the Eastern Ghats, India: new insights

Science.gov (United States)

Bhattacharya, S.; Kar, R.; Saw, A. K.; Das, P.

2011-01-01

The two major lithology or gneiss components in the polycyclic granulite terrain of the Eastern Ghats, India, are the supracrustal rocks, commonly described as khondalites, and the charnockite-gneiss. Many of the workers considered the khondalites as the oldest component with unknown basement and the charnockite-protoliths as intrusive into the khondalites. However, geochronological data do not corroborate the aforesaid relations. The field relations of the hornblende- mafic granulite with the two gneiss components together with geocronological data indicate that khondalite sediments were deposited on older mafic crustal rocks. We propose a different scenario: Mafic basement and supracrustal rocks were subsequently deformed and metamorphosed together at high to ultra-high temperatures - partial melting of mafic rocks producing the charnockitic melt; and partial melting of pelitic sediments producing the peraluminous granitoids. This is compatible with all the geochronological data as well as the petrogenetic model of partial melting for the charnockitic rocks in the Eastern Ghats Belt.

Le district aurifère de Challant (Val d'Aoste-Italie) : gîtologie, géochimie et métallogénie de l'or

OpenAIRE

Richard , Annick

1981-01-01

In the auriferous Monte Rosa Province , the Challant district appears as a geological unit and is situated near the Arcesa island. These rocks are paleozoic gneiss surrounded by the Piemonte ophiolite nappe. The district extends South of Ranzola major fault which is the North limit of gneiss . They are typical epigenetic lodes : it may be assumed that their period of deposition fell between 50 and 30 My. It is possible to range the hundred of deposits in two types : quartz, native gold and lo...

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Outcome of the geological mapping of the ONKALO underground research facility access tunnel, chainage 1980-3116

International Nuclear Information System (INIS)

Nordbaeck, N.

2010-06-01

This report describes the lithology and geological structures of the ONKALO underground rock characterization facility access tunnel in chainage 1980-3116. This part of the tunnel was excavated and mapped from spring 2007 to autumn 2008. The bedrock is very heterogeneous and mainly composed of veined gneiss and diatexitic gneiss, but many felsic dykes and sections of pegmatitic granite also occur. In addition, small sections of mica gneiss and K-feldspar porphyry are present. There are also numerous inclusions of mica gneiss, quartz gneiss and skarn. The foliation dips moderately towards SE. 14 fold axes and axial planes were measured from the ONKALO tunnel in chainage 1980-3116 and all have been interpreted to belong to deformation phase D 3 . The measured fold axes have various orientations, but most have moderate plunges and ENE- or WSW-trending ones dominate. The axial planes typically dip moderately towards SE. An almost vertical lineation was also measured from mica gneiss on two locations. A total of 7668 fractures were measured. Three main fracture sets were distinguished from the measured orientations: set 1 fractures are vertical and strike approximately NS, set 2 fractures are more or less horizontal and set 3 fractures are vertical and ENEWSW- striking. The most common filling minerals are calcite, pyrite, chlorite, kaolinite, epidote, muscovite, quartz, biotite, and illite. Of the measured fractures, 579 were slickensided. The slickensided fractures are mainly either sub-vertical N-S-trending (set 1) or sub-vertical NE-SW-trending, with dip to SE. Slickenside surfaces show N-S- and NE-SW-trending lineations, with shallow dip. The slickensided fractures are mostly strike-slip faults with both sinistral and dextral sense of movement. The chainage 1980- 3116 contains 170 tunnel-crosscutting fractures. The orientation is mostly vertical N-Sstriking, sub-horizontal or vertical E-W- trending. 27 deformation zone intersections were also observed, 23 brittle

O Gnaisse Facoidal: a mais Carioca das Rochas.

Directory of Open Access Journals (Sweden)

Kátia Leite Mansur

2008-09-01

Full Text Available The city of Rio de Janeiro is known by its natural beauties. The mountains and the sea make the city the postcard ofBrazil. The sculpture of the carioca landscape is closely related to the augen gneiss, very resistant rock to the weatheringand, for this reason, it stands out in the relief. It gives form for Sugar Loaf and Corcovado, for example. Augen gneisswas used in the construction of most of the historical buildings of the city, including museums and churches, manyof them were built in the 19th century. It was used in the sculpture of ornaments, facades and frames of doors andwindows. The exploitation of the augen gneiss was presented by Jean Baptiste Debret in his book "Voyage Pittoresque etHistorique au Brésil". A picture of quarry is presented at Morro da Glória and describes the extraction method by slavelabor. He informes that the augen gneiss is softer, less expensive and more easily exploited. It was destined, mainly, tothe parts of the buildings that should be sculpted. This rock is still present in an important event of the history of thebrazilian arts. Pedra do Sal, a stairway sculpted in the augen gneiss Downtown, was the place that African people metin the past to tell their histories, to do religious cults and to sing. In these meetings in Pedra do Sal samba was born.

A system of nomenclature for rocks in Olkiluoto

International Nuclear Information System (INIS)

Mattila, J.

2006-06-01

Due to international interest in the Finnish deep repository project at Olkiluoto (SW Finland) and the need for collaboration between scientists involved in site investigations for the disposal of spent nuclear fuel in other countries, a well-documented system of rock nomenclature is required, based on existing classification schemes and international recommendations. The BGS (British Geological Survey) rock classification scheme is the most comprehensive rock classification scheme and the basic principles behind it are utilised for the system of nomenclature for rocks in Olkiluoto. The BGS classification system is based on the use of descriptive names and a clear hierarchy, making it possible to classify rocks at different levels depending on the specific goals of the study, the level of available information, and the expertise of the user. Each rock type is assigned a root name, which is based on structural and textural characteristics or modal compositions of the rock and the root names are refined with qualifier terms as prefixes. Qualifier terms refer to the structure or modal composition of the rock. The bedrock at the Olkiluoto site consists of metamorphic and igneous rocks. The metamorphic rocks consist of migmatitic gneisses and (non-migmatitic) gneisses, which are further divided according to their structural characteristics and modal compositions, the former into stromatic, veined, diatexitic gneisses, the latter into mica, quartz, mafic and TGG gneisses. Igneous rocks consist of pegmatitic granites, K-feldspar porphyry and diabases. (orig.)

Petrologic and zircon U-Pb geochronological characteristics of the pelitic granulites from the Badu Complex of the Cathaysia Block, South China

Science.gov (United States)

Zhao, Lei; Zhou, Xiwen; Zhai, Mingguo; Liu, Bo; Cui, Xiahong

2018-06-01

The recognition of the Indosinian Orogeny in the South China block has been controversial and difficult because of strong weathering and thick cover. High temperature (HT) and high pressure (HP) metamorphic rocks related to this orogeny were considered to be absent from this orogenic belt until the recent discovery of eclogite and granulite facies meta-igneous rocks, occurring as lenses within the meta-sedimentary rocks of the Badu Complex. However, metamorphic state of these meta-sedimentary rocks is still not clear. Besides, there have been no geochronological data of HT pelitic granulites previously reported from the Badu Complex. This paper presents petrographic characteristics and zircon geochronological results on the newly discovered kyanite garnet gneiss, pyroxene garnet gneiss and the HT pelitic granulites (sillimanite garnet gneiss). Mineral assemblages are garnet + sillimanite + ternary feldspar + plagioclase + quartz + biotite for the HT pelitic granulite, kyanite + ternary feldspar + garnet + sillimanite + plagioclase + quartz + biotite for the kyanite garnet gneiss, and garnet + biotite + pyroxene + plagioclase + ternary feldspar + quartz for the pyroxene garnet gneiss, respectively. Decompressional coronas around garnet grains can be observed in all these pelitic rocks. Typical granulite facies mineral assemblages and reaction textures suggest that these rocks experienced HP granulite facies metamorphism and overprinted decompression along a clockwise P-T loop. Results from integrated U-Pb dating and REE analysis indicate the growth of metamorphic zircons from depleted heavy REE sources (100-50 chondrite) compared with detrital zircons derived from granitic sources (typically > 1000 chondrite). Metamorphic zircons in HP granulite exhibit no or subdued negative Eu anomalies, which perhaps indicate zircon overgrowth under eclogite facies conditions. The zircon overgrowth ages range from 250 to 235 Ma, suggesting that HP granulite (eclogite) to

On most ancient geologic events on the Anabar Shield

International Nuclear Information System (INIS)

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

1987-01-01

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

Thermal conductivity of water-saturated rocks from the KTB pilot hole at temperatures of 25 to 300°C

Science.gov (United States)

Pribnow, D.; Williams, C.F.; Sass, J.H.; Keating, R.

1996-01-01

The conductivitites of selected gneiss (two) and amphibolite (one) core samples have been measured under conditions of elevated temperature and pressure with a needle-probe. Water-saturated thermal conductivity measurements spanning temperatures from 25 to 300??C and hydrostatic pressures of 0.1 and 34 MPa confirm the general decrease in conductivity with increasing temperature but deviate significantly from results reported from measurements on dry samples over the same temperature range. The thermal conductivity of water-saturated amphibolite decreases with temperature at a rate approximately 40% less than the rate for dry amphibolite, and the conductivity of water-saturated gneiss decreases at a rate approximately 20% less than the rate for dry gneiss. The available evidence points to thermal cracking as the primary cause of the more rapid decrease in dry thermal conductivity with temperature. The effects of thermal cracking were also observed in the water-saturated samples but resulted in a net decrease in room-temperature conductivity of less than 3%. These results highlight the importance of duplicating in-situ conditions when determining thermal conductivity for the deep crust.

40Ar/39Ar incremental-release ages of biotite from a progressively remetamorphosed Archean basement terrane in southwestern Labrador

International Nuclear Information System (INIS)

Dallmeyer, R.D.

1982-01-01

Gneisses within Archean basement terrane adjacent to the southwestern portion of the Labrador Trough were variably retrograded during a regional metamorphism of Grenville age (ca. 1000 Ma). Bioties from non-retrograded segments of the gneiss terrane record 40 Ar/ 39 Ar plateau and isochron ages which date times of cooling following an episode of the Kenoran orogeny (2376-2391 Ma). A suite of gneiss samples displaying varying degrees of retrograde alteration was collected across the Grenville metamorphic gradient. Bioties in these samples show no petrographic evidence of retrograde alteration, however they do record internally discordant 40 Ar/ 39 Ar age spectra. Although the extent of internal discordance is variable, the overall character of the release patterns is similar with younger apparent ages recorded in intermediate-temperature gas fractions. The total-gas dates range from 2257+-27 Ma (northwest) to 1751+-23 Ma (southeast), suggesting that variable quantities of radiogenic argon were lost from the Archean biotites during Grenville metamorphism. The 'saddle-shaped' nature of the discordant spectra indicates that argon loss was not accomplished through single-stage, volume diffusion processes. (orig./ME)

Detrital zircon and igneous protolith ages of high-grade metamorphic rocks in the Highland and Wanni Complexes, Sri Lanka: Their geochronological correlation with southern India and East Antarctica

Science.gov (United States)

Kitano, Ippei; Osanai, Yasuhito; Nakano, Nobuhiko; Adachi, Tatsuro; Fitzsimons, Ian C. W.

2018-05-01

The high-grade metamorphic rocks of Sri Lanka place valuable constraints on the assembly of central parts of the Gondwana supercontinent. They are subdivided into the Wanni Complex (WC), Highland Complex (HC) and Vijayan Complex (VC), but their correlation with neighbouring Gondwana terranes is hindered by a poor understanding of the contact between the HC and WC. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating of remnant zircon cores from 45 high-grade metamorphic rocks in Sri Lanka reveals two domains with different age characteristics that correlate with the HC and WC and which help constrain the location of the boundary between them. The HC is dominated by detrital zircon ages of ca. 3500-1500 Ma from garnet-biotite gneiss, garnet-cordierite-biotite gneiss, some samples of garnet-orthopyroxene-biotite gneiss and siliceous gneiss (interpreted as paragneisses) and igneous protolith ages of ca. 2000-1800 Ma from garnet-hornblende-biotite gneiss, other samples of garnet-orthopyroxene-biotite gneiss, garnet-two-pyroxene granulite, two-pyroxene granulite and charnockite (interpreted as orthogneisses). In contrast, the WC is dominated by detrital zircon ages of ca. 1100-700 Ma from paragneisses and igneous protolith ages of ca. 1100-800 Ma from orthogneisses. This clearly suggests the HC and WC have different origins, but some of our results and previous data indicate their spatial distribution does not correspond exactly to the unit boundary proposed in earlier studies using Nd model ages. Detrital zircon and igneous protolith ages in the HC suggest that sedimentary protoliths were eroded from local 2000-1800 Ma igneous rocks and an older Paleoproterozoic to Archean craton. In contrast, the WC sedimentary protoliths were mainly eroded from local late Mesoproterozoic to Neoproterozoic igneous rocks with very minor components from an older 2500-1500 Ma craton, and in the case of the WC precursor sediments there was possibly

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

Full text: Zircon U-Pb SHRIMP geochronology is a powerful means of elucidating geological ages, providing that it is integrated with unequivocal field constraints, and providing that the fundamental assumptions which are behind any isotopic dating methods are geologically validated. In an attempt to better quantify the timing of Broken Hill's complex history and to reduce some current uncertainties, we report initial results from a new U-Pb SHRIMP investigation. This program was planned within the background of our own disparate stratigraphic and structural approaches to Broken Hill geology, and with objectives to (a) benchmark our new age results with those of previous workers as well as our own previous work in the Broken Hill Group, (b) evaluate and test the evidence for reported Archaean basement terrain, (c) date stratigraphic units in the upper parts of the Willyama Supergroup, (d) better constrain the timing of deformational events. Our U-Pb SHRIMP work on zircons from layered paragneisses in the Redan Geophysical Zone near Farmcote was catalysed by Nutman and Ehlers' (1998a) preferred interpretation that these 'strondhjemitic' gneisses represent an original ∼2650 Ma protolith. Our work finds zircon provenance age signatures typical of almost all ca. 1700 Ma metasediments, whether in the Broken Hill Block or other Australian Palaeoproterozoic settings. This therefore suggests that the rocks are not Archaean basement, but are part of a Thackaringa Group package possibly deposited about 1705-1710 Ma ago. New SHRIMP work on the Alma Gneiss provides a magmatic age of 1704±3 Ma, and a minimum stratigraphic age for host Thackaringa Group. This result is within error of our ages for other granitoids (1703±3 Ma, 1704±3 Ma) in the same stratigraphic position near Farmcote. As the Thackaringa Group is no more than 1000-1500 metres thick and includes 1710-1700 Ma detrital zircons, pan of the Alma Gneiss intrusion may well have been shallowly intruded, and akin to

Groundwater chemistry at depth in granites and gneisses

International Nuclear Information System (INIS)

Jacks, G.

1978-04-01

The place considered for a radioactive waste storage is beneath a local water divide along the eastcoast of southern and central Sweden. pH is fixed by the carbonate system and the ground waters can be expected to be saturated with respect to calcite. pH may vary from about 7,2 to about 8,5 with the most probable value around 8. The content of Cl - is difficult to asses as it is associated with the presence of relict sea water. Relict sea waters are linked to the postglacial clays and low sections of the terrain. Near local water divides the content of Cl - is low approaching the atmospheric contribution or below 10 mg/l. The content of F - is restricted by the solubility of fluorspar and may be about 7 mg/l as a maximum, but normally 3,5 mg/l or lower. SO 4 - seems to be of the same order as the atmospheric contribution or about 15 mg/l. In the deep boreholes sampled so far the contents have been lower. The partial pressure of oxygen in the ground water should be very low. An increasing ironcontent towards depth is likely. Organic substance in the order of a few tenths of mg/l may be present. The local heating of the water close to the storage may bring about precipitation of calcite while the subsequent cooling when the water leaves the storage may result in precipitation of aluminiumsilicates. This may have a sealing effect of the rock

Garnet-sillimanite bearing gneisses from Darjeeling, eastern Himalaya

Indian Academy of Sciences (India)

Centre of Advanced Study in Geology, Banaras Hindu University, Varanasi 221 005, India. ∗Corresponding author. e-mail: ... consistent TWEEQU programme and Perple X software in the KFMASH model system, the combina- tion of these three ... Generalized geological map of the Himalayas. The location of Darjeeling is ...

U–Pb, Rb–Sr, and U-series isotope geochemistry of rocks and fracture minerals from the Chalk River Laboratories site, Grenville Province, Ontario, Canada

International Nuclear Information System (INIS)

Neymark, L.A.; Peterman, Z.E.; Moscati, R.J.; Thivierge, R.H.

2013-01-01

Highlights: • AECL evaluates Chalk River Laboratories site as potential nuclear waste repository. • Isotope-geochemical data for rocks and fracture minerals at CRL site are reported. • Zircons from gneiss and granite yielded U–Pb ages of 1472 ± 14 and 1045 ± 6 Ma. • WR Rb–Sr and Pb–Pb systems do not show substantial large-scale isotopic mobility. • U-series and REE data do not support oxidizing conditions at depth in the past 1 Ma. - Abstract: As part of the Geologic Waste Management Facility feasibility study, Atomic Energy of Canada Ltd. (AECL) is evaluating the suitability of the Chalk River Laboratories (CRL) site in Ontario, situated in crystalline rock of the southwestern Grenville Province, for the possible development of an underground repository for low- and intermediate-level nuclear waste. This paper presents petrographic and trace element analyses, U–Pb zircon dating results, and Rb–Sr, U–Pb and U-series isotopic analyses of gneissic drill core samples from the deep CRG-series characterization boreholes at the CRL site. The main rock types intersected in the boreholes include hornblende–biotite (±pyroxene) gneisses of granitic to granodioritic composition, leucocratic granitic gneisses with sparse mafic minerals, and garnet-bearing gneisses with variable amounts of biotite and/or hornblende. The trace element data for whole-rock samples plot in the fields of within-plate, syn-collision, and volcanic arc-type granites in discrimination diagrams used for the tectonic interpretation of granitic rocks. Zircons separated from biotite gneiss and metagranite samples yielded SHRIMP-RG U–Pb ages of 1472 ± 14 (2σ) and 1045 ± 6 Ma, respectively, in very good agreement with widespread Early Mesoproterozoic plutonic ages and Ottawan orogeny ages in the Central Gneiss Belt. The Rb–Sr, U–Pb, and Pb–Pb whole-rock errorchron apparent ages of most of the CRL gneiss samples are consistent with zircon U–Pb age and do not indicate

Geological mapping of investigation trench OL-TK19 at the Olkiluoto study site, Eurajoki, SW Finland

Energy Technology Data Exchange (ETDEWEB)

Eroma, E.; Nordbaeck, N.; Engstroem, J. [Geological Survey of Finland, Espoo (Finland)

2014-12-15

In October 2012, the geological mapping of investigation trench OL-TK19 was carried out by the Geological Survey of Finland at the Olkiluoto study site. The SE-NW trending, ca. 85 m long trench is located in the central part of the Olkiluoto Island next to investigation trenches OL-TK18 and OL-TK4. The lithology in investigation trench OL-TK19 is of heterogeneous character, with rock type varying from veined gneiss, diatexitic gneiss to pegmatitic granite, along with portions of mica gneiss and K-feldspar porphyritic gneiss. In addition, inclusions of mica gneiss, quartz gneiss and skarn are encountered. The rocks have been subjected to a multiphase ductile deformation and the trench is situated in an area where the latest ductile deformation phase, D4 prevails. The investigation trench can be divided into three domains according to its dominant deformation phase and foliation; the eastern part of the trench is dominated by the D3 deformation phase whereas the middle and western parts are dominated by the D4 deformation phase. The S3 foliation has a more ENE-WSW oriented direction whereas the S4 is trending NE-SW. In addition to this difference in orientation, the different structural signature of these two deformation types is observed, the S3 foliation is defined by smaller scaled granitic leucosome veining whereas the S4 foliation is intensely sheared and have a schistose character. During the fracture mapping, all fractures intersecting the central thread were investigated and a total of 132 fractures were recorded. The average fracture frequency 1.53 fractures/m. On the basis of fracture orientations, three fracture sets can be defined. The first set is vertical and NW-SE trending, second set strikes NE-SW with a moderate dip towards the SE and the third set is vertical and NE-SW trending. The median fracture length is 1.38 m and most fractures do not exceed 0.5 m in length, the longest measured fracture being 5.30 m in length. Fracture fillings are mostly

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

Science.gov (United States)

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

2015-12-01

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

Extrapolation of tectonic boundaries across the Labrador shelf: U-Pb geochronology of well samples

International Nuclear Information System (INIS)

Wasteneys, H.A.; Krogh, T.E.

1996-01-01

Near Saglek Fiord, a northerly trending boundary between the early Archean Saglek block and the middle Archean Hopedale block extends between drill sites which, respectively, sampled Uivak amphibolite gneiss with U-Pb zircon intercept ages of 3742 ± 12 and 2752 ± 42 Ma, and migmatitic Lister gneiss with concordant ages of 3213 -4 +21 Ma for restite and 2552 -21 +4 Ma for leucosome. Titanite ages of ca. 2508 Ma are common to both rocks. A nearby metapsammitic gneiss has detrital zircon and monazite ages of 2681 ± 5, 2700 ± 4, ca. 2730, and 2750 ± 2 Ma representing high-grade metamorphism related to the Hopedale-Saglek collision and metamorphic monazite of ca. 2560 Ma age representing metamorphism of the sediment during reactivation of the Saglek-Hopedale suture. Two hundred kilometres southeast, a gneissic granite records a protolith age of 3170 Ma and Late Proterozoic Pb loss. Near the Nain-Makkovik boundary, 1269 ± 4 Ma zircons indicate a significant extension of the Nain Plutonic Suite. South of the Makkovik boundary, a foliated granite yielded an upper intercept age defining intrusion at 1895 ± 8 Ma and concordant 1872 ± 5 Ma titanite ages that date subsequent metamorphism. Discordant U-Pb ages from an alkali-feldspar granite also constrain crystallization to ca. 1890 Ma and together with the gneiss represent the previously defined Iggiuk event in the Kaipokok domain. Wells near the southerly end of the transect record 1801 ± 5, 1813 ± 3, and 1806 ± 8 Ma ages, respectively, that are typical of the synorogenic granitoid suite representing the Cape Harrison domain of southern Makkovik Province. (author). 46 refs., 1 tab., 5 figs

Geologic study of Kettle dome, northeast Washington. Final report

International Nuclear Information System (INIS)

1980-10-01

This geologic study of Kettle dome, northeast Washington, encompasses an area of approximately 800 square miles (2048 sq km). The evaluation of uranium occurrences associated with the igneous and metamorphic rocks of the dome and the determination of the relationship between uranium mineralization and stratigraphic, structural, and metamorphic features of the dome are the principal objectives. Evaluation of the validity of a gneiss dome model is a specific objective. The principal sources of data are detailed geologic mapping, surface radiometric surveys, and chemical analyses of rock samples. Uranium mineralization is directly related to the presence of pegmatite dikes and sills in biotite gneiss and amphibolite. Other characteristics of the uranium occurrences include the associated migmatization and high-grade metamorphism of wallrock adjacent to the pegmatite and the abrupt decrease in uranium mineralization at the pegmatite-gneiss contact. Subtle chemical characteristics found in mineralized pegmatites include: (1) U increase as K 2 O increases, (2) U decreases as Na 2 O increases, and (3) U increases as CaO increases at CaO values above 3.8%. The concentration of uranium occurrences in biotite gneiss and amphibolite units results from the preferential intrusion of pegmitites into these well-foliated rocks. Structural zones of weakness along dome margins permit intrusive and migmatitic activity to affect higher structural levels of the dome complex. As a result, uranium mineralization is localized along dome margins. The uranium occurrences in the Kettle dome area are classified as pegmatitic. Sufficient geologic similarities exist between Kettle dome and the Rossing uranium deposit to propose the existence of economic uranium targets within Kettle dome

Uranium geology of the eastern Baker Lake basin, District of Keewatin, Northwest Territories

International Nuclear Information System (INIS)

Miller, A.R.

1980-01-01

Proterozoic sequences associated with major unconformities are potential uranium metallogenic provinces. Late Aphebian to Paleohelikian Dubawnt Group contintental clastic sedimentary and subaerial alkaline volcanic rocks and underlying Archean gneisses, District of Keewatin, Northwest Territories, represent one such uraniferous metallogenic province. Three types of uranium mineralization are present in the eastern Baker Lake basin, which extends from Christopher Island at the eastern end of Baker Lake southwestwards to the western limit of Thirty Mile Lake. The three uranium associations are: 1) fracture controlled mineralization in the Dubawnt Group and basement gneisses (U-Cu-Ag-Au-Se or U-Cu-Pb-Mo-Zn), 2)diatreme breccia mineralization in basement gneisses (U-Cu-Zn), and 3) impregnation and microfracture mineralization in altered arkose peripheral to lamprophyre dykes(U-Cu-Ag). Hydrothermal fracture related mineralization is controlled by northwest- and east-northeast-trending fault-fracture zones. Diatreme breccia mineralization results from the channelling of groundwaters through highly permeable brecciated gneiss. Mineralization within the altered Kazan arkose peripheral to alkaline dyke complexes formed by a two stage process. Iron and copper sulphides and silver were deposited within the outer portions of the thermal aureole in response to a temperature and Eh gradient across a convective cell created by the thermal anomaly of the dyke complex. The epigenetic sulphide mineralization subsequently provided the reducing environment for precipitation of uranium from groundwater. All three uranium associations show a close spatial distribution to the basal Dubawnt unconformity. The lithological and structural relationships of the Dubawnt Group rocks, types of mineralization and associated alteration assemblages are strikingly similar to the Beaverlodge district, Saskatchewan. (author)

Shear zone-related pseudotachylite occurences from the northern Transvaal

International Nuclear Information System (INIS)

Reimold, W.U.; Meyer, F.M.

1990-01-01

Pseudotachylite from the Sand River localities displays very variable composition when formed in Sand River Gneiss, but is less variable when originating from diabase. Comparison of individual pseudotachylite (granitic) host rock pairs shows consistent depletion and enrichment. Rather high LoI values indicate significant secondary alteration for some specimens. The chemical variations agree well with the theory that pseudotachylite in granitic-granodioritic environment is formed by preferential melting of hydrous ferromagnesian minerals plus varied proportions of feldspar components. 'Basaltic' pseudotachylite is characterised by increase of SiO 2 and K 2 O, which is also known from other occurences. With respect to most trace elements, pseudotachylite is generally enriched. Comparison of all pseudotachylite analyses with Sand River Gneiss data reveals that mixing on a dm scale cannot be completely excluded, but 'basaltic' pseudotachilyte obtained in granodioritic host rock has not assimilated more than approximately 5% of felsic material. The cataclastic breccias chemically compare well with undeformed Sand River Gneiss. These results agree well with current theory on pseudotachylite formation, but at the Geocongress a larger data base will be discussed. 1 fig., 6 refs

Geology and geochronology of Mata Surrao granites - South-West of Rio Maria - Para State, Brazil

International Nuclear Information System (INIS)

Duarte, K.D.; Pereira, E.D.; Dall'Agnol, R.; Lafon, J.M.

1991-01-01

This paper summarize the preliminary data about a geological mapping on the scale 1:50.000 located at an area in the southeastern part of the Para State. The recognized units comprise the Mata Surrao granite, which is within the typical Archean Granite-Greenstone Terrain of Rio Maria, and has mainly a monzogranitic composition. Its foliation is restricted to the north and east borders. The mapped host rocks are represented by Tonalitic Ortho gneisses, Gneisses with Pegmatites, Migmatite Gneisses, both latter show different deformation rates. Rb/Sr on whole rock systematics had been applied for the Mata Surrao granite and yield an age of 2541 ± 74 Ma with Sr initial ratio of 0.71040 ± 343 (MSWD = 2.81). This data revealed another Archean granitic body (strictu sensu) related to the Rio Maria Granite-Greenstone Terrain. Such age can be interpreted either as the crystallization age of this granitic body, or a renewed one caused by the thermo tectonic event that affected the region at the end of Archean time. It can be deduced from the initial ratio that an important crustal contribution controlled the Mata Surrao granite genesis. (author)

Radon exposed workplaces in Bavarian public water supplies

International Nuclear Information System (INIS)

Heinrich, T.; Huebel, K.; Schindlmeier, W.

1998-01-01

From April 1996 to July 1996 a radon-screening in 112 Bavarian water supplies was carried out to determine the radon concentration in workplaces. In some regions with granit or gneiss stones as underground a considerable radiation exposure to the employees in public water supplies can be expected. The median of the measured radon concentration in relevant workplaces is found to be 4000 Bq/m 3 in the areas with granite or gneiss. This is approximately the fourfold of the median measured in a reference area with sandstone as underground. In some workplaces radon concentrations of more than 100000 Bq/m 3 can be found. (orig.) [de

National Dam Safety Program. Lindys Lake Dam (NJ00201), Passaic River Basin, Branch of West Brook, Passaic County, New Jersey. Phase 1 Inspection Report.

Science.gov (United States)

1980-02-01

shallow ground moraine over rock. The downstream channel is described as swamp. The rock is described on Geologic Overlay Sheet 22, as hornblende granite ...DAM 410-04’ hqa Scale: I" =I Mite LEGEND: PRECAMBRIAN gh Mostly Hornblende Granite and Gneiss. hqa Hyperstene-Quartz- And esine.-Gneiss. GEOLOGIC MAP L...A.J. 0o2o/) S CZ6 -§&S5 /,r/ C,4 7-1 ,4V-etaoe Dep4e&/LaL L* rt~~~c~~t4’A aeS’ OP~ ~ A AI 3CD PS?7V7,/ & zAer ’, ! v’.’:7- z - 6 c ,, ,, ,,g

Metasomatic Reaction Zones as Monitors of Trace Element Transfer at the Slab-Mantle Interface: the Case of the Hochwart Peridotite (Ulten Zone, Italy)

Science.gov (United States)

Marocchi, M.; Hermann, J.; Bargossi, G. M.; Mair, V.; Morten, L.

2006-12-01

Ultramafic blocks belonging to the Hochwart peridotite outcrop (Ulten Zone, Italian Alps) preserve a series of metasomatic mineral zones generated by infiltration of Si-rich hydrous fluids which occurred at the gneiss- peridotite interface. The age of the high pressure metamorphism for the Hochwart complex has been constrained at 330 Ma (Tumiati et al., 2003, EPSL, 210, 509-526). The country rocks are stromatic gneisses consisting mainly of quartz, K-feldspar, garnet, kyanite, biotite and muscovite. The ultramafic body consists of strongly serpentinized metaperidotites which are exposed as a hectometre-size lens along a steep gully, associated to monomineralic zones that developed at the contact between the peridotite body and the garnet gneiss country rocks. The composition of the metasomatic zones has been investigated in detail and records an order of metasomatic zoning formed by phlogopite-rich to tremolite-anthophyllite-rich rocks going from the host gneiss towards the peridotite. In some cases, the ultramafics fade into the gneisses developing serpentine and talc which has replaced, presumably at lower temperatures, the serpentine matrix and occurs in association with chlorite. Phlogopite aggregates (phlogopitite) with accessory minerals (quartz + zircon + apatite) and metabasic pods (phlogopite and hornblende) also occur. Black tourmaline (schorl-dravite solid solution) has been found for the first time in the contact near the phlogopite zone, suggesting an external addition of elements (boron and fluorine) to the system at high temperature. The formation of the metasomatic zones composed exclusively of hydrous phases must have involved extensive H2O-metasomatism as already documented for the Ulten peridotites. The source for these fluids can be a system of trondhjemitic-pegmatitic dikes cutting the peridotite that would have channelled aqueous fluids into the ultramafic rocks. Whole-rock geochemistry and trace element (LA ICP-MS) composition of hydrous

Regional characterization of suspected land Punta del Este ( east of the Republica Oriental del Uruguay )

International Nuclear Information System (INIS)

Preciozzi, F.; Sanchez Bettucci, L.; Oyhantcabal, P.; Pecoits, E.; Aubet, N.; Peel, E.; Basei, M.

2003-01-01

Field Suspect Punta del Este (TSPE) is located in the easternmost portion of Uruguay (Figure 1). This is bounded to the west by Shear Zone Punta del Este-Cordillera (Masquelin, 1990; Preciozzi et al., 1999; 2002), while the east with Rocha makes Formation (Hasui et al, 1975;.. Sanchez-Bettucci and Mezzano, 1993). The TSPE is represented by gneisses and Migmatites formed in the range of 1100 and 630 Ma (Preciozzi et al, in prep.) and have been intensively reworked during Rio Doce orogeny (ca. 600 Ma). Field Suspect Punta del Este (TSPE) is separated from the Neoproterozoic granitoids or granitoids by central Shear Zone Punta del Este-Cordillera represented by a thin strip of mylonite s and gneisses mylonitic able to anatexis. Granitoids are sub alkaline trend throughout of this guideline. The mylonitic foliation has a general direction between N15ºE and N40ºE with sub vertical slope where development ductile quartz and muscovite bands observed (Figure 2). The base of TSPE consists essentially of porphyritic granitoids deformed with biotite and muscovite, and ortho gneisses oftalmíticos granitoids, showing an attenuation of that reaching isotropic deformation terms. From studies in zircons from a sample of ortho gneisses (UCUR 03) by U / Pb conventional and SHRIMP ages of 753 ± 14 Ma for the edge obtained (consistent with the conventional age) and 1000 Ma for zircon center. This has allowed us to recognize in the protoliths one Grenvillian heritage in this area, preserved during crustal melting processes. Also, new U / Pb (Preciozzi et al., In prep.) Data show a orogénesis penicontemporánea to the Brasiliano cycle would be responsible for most of the generation of the rocks that make up the TSPE

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

Science.gov (United States)

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

2009-07-01

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

Bedrock model of the Olkiluoto area

International Nuclear Information System (INIS)

Saksa, P.; Paananen, M.; Paulamaeki, S.; Anttila, P.; Front, K.; Pitkaenen, P.; Hassinen, P.; Ylinen, A.

1993-07-01

Site investigations were carried out at Olkiluoto (in Finland) in 1987-1992 in accordance with an investigation programme drawn up by Teollisuuden Voima Oy (TVO). The site was modelled in terms of rock types, fracturing, fracture structures and geohydrological conditions, the main focus of examination was on fracturing and associated hydraulic conductivity. The various properties of the bedrock structures were classified by means of a three-dimensional model. The descriptions of the models were gathered in a computer system for illustration and storage purposes. The rock types at Olkiluoto are migmatite, which may be divided into mica gneiss and veined gneiss, and also tonalite and coarse-grained migmatite granite (pegmatite). (64 refs., 65 figs.)

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)

[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.

U-Th/He ages of fluorite mineralizations of the Tangua alkaline intrusion; Idades U-Th/He das mineralizacoes de fluorita da intrusao alcalina de Tangua

Energy Technology Data Exchange (ETDEWEB)

Geraldes, M.C.; Vargas, T., E-mail: geraldes@uerj.br, E-mail: vargas@uerj.br [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Faculdade de Geologia; Evans, N., E-mail: Noreen.Evans@csiro.au [CSIRO and Curtin University for Technology, Western Australia (Australia); Nummer, A.R., E-mail: nummer@ufrrj.br [Universidade Federal Rural do Rio de Janeiro (DEGEOC/IA/UFRRJ), RJ (Brazil)

2015-07-01

The Tangua massif is part of a group of alkaline complexes that occurs in an extensive zone of faults and E-W lineaments and includes the Brazilian Southeastern Rift. This work presents U-He ages of the fluorite mineralization. The Tangua alkaline massif is emplaced in coarse-grained biotite gneiss (Oriental Domain, central portion of the Ribeira belt). Cataclastic gneiss with intense weathering are restricted to the intrusion contacts. The alkaline body is comprised of pulaskites and umptekites, nephelinesyenites, foiaites, and pseudoleucite foiaites and is cut by phonolite dykes, trachytes and alkaline lamprophyres. In the locality of Barbosao, veins of fluorite occur, accompanied by silica and pyrite within trachyte dykes. These veins are parallel to the gneiss foliation (N 50 - 70 E) with an average thickness of 30 cm and the fluorite contains limonite and manganese oxides inclusions. The U-He ages range from <2Ma to 73Ma. The older age is coherent with 80-65 ma range of K-Ar ages reported in the literature. The veins of fluorite crosscut the lithologies associated with shear zones, and are important to economic exploration in the region. The petrographic and U-Th/He sating studies indicate the fluorite formation coeval to alkaline intrusion and meteoric water fluid circulation recently. (author)

Studies on radioactivity distribution and radioactive mineral identification in uranium ores from Espinharas (PB), Brazil

International Nuclear Information System (INIS)

Oliveira, G.N.M. de.

1979-01-01

Studies about the identification of radioactive minerals in uranium bearing rocks from Espinharas (PB), Brazil are presented. Autoradiography with α-sensitive nuclear emulsions was utilized for determining radioctivity distributions and for localizing radioactive minerals, in combination with microscopy, X-ray diffractometry, PIXE and eletron microprobe analysis for its identification. Mineralized gneisse and feldspatic rock, the two principal samples studied, show distinct differences in radioactive distribution patterns, however the main carriers for U and Th seem to be the same. Microanalysis shows that elements are associated with Si, Ca, Fe and Al an some trace elements like Y, Zr, Ti, etc. U and Th are distributed uniformly in feldspatic rock and inhomogeneously in mineralized gneisse, indicating that the zonary structure of the radioactive cristals, frequently observed in gneisse, could be due to variable U:Th ratios. Chemical analysis, X-ray diffraction datas and microscopic studies indicates that the principal carrier for radioactivity in the rocks of Espinharas is a silicate mineral of U and Th, probably situaded in the series of transition: Coffinite -> uraninite, thorogummite -> thorianite. Some additional experiments about leachability of uranium with diluted sulfuric acid are reported, which confirm the different nature of radioactivity distribution in feldspatic and gneissic rocks. (author) [pt

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

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

The influence of the coarse aggregates from different mineralogy on the mechanical properties of the high-performance concrete; A influencia de agregados graudos de diferentes mineralogias nas propriedades mecanicas do concreto de alto desempenho

Energy Technology Data Exchange (ETDEWEB)

Magalhaes, A.G.; Calixto, J.M. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia de Estruturas], e-mail: aldo@dees.ufmg.br; Franca, E.P. [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil). Dept. de Materiais de Construcao; Aguilar, M.T.P. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Materiais de Construcao; Vasconcelos, W.L. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Metalurgica e de Materiais

2006-07-01

Concrete in normal conditions is a versatile and strong construction material. However under certain environmental conditions it may deteriorate in a short period of time. This fact has led researchers in recent times to develop the high-performance concrete. In this scenario, the aim of this paper is to present the effects of the different types of coarse aggregate on the mechanical properties of high performance concrete. Limestone, granite, gneiss and basalt were used as coarse aggregates. Their characterization consisted of chemical analysis, x-ray diffraction and optical microscopy. The compressive strength and the modulus of elasticity were the investigated mechanical properties. The test results indicate expressively the better performance of the concretes fabricated with basalt, granite and gneiss aggregates. (author)

The influence of the coarse aggregates from different mineralogy on the mechanical properties of the high-performance concrete

International Nuclear Information System (INIS)

Magalhaes, A.G.; Calixto, J.M.; Franca, E.P.; Aguilar, M.T.P.; Vasconcelos, W.L.

2006-01-01

Concrete in normal conditions is a versatile and strong construction material. However under certain environmental conditions it may deteriorate in a short period of time. This fact has led researchers in recent times to develop the high-performance concrete. In this scenario, the aim of this paper is to present the effects of the different types of coarse aggregate on the mechanical properties of high performance concrete. Limestone, granite, gneiss and basalt were used as coarse aggregates. Their characterization consisted of chemical analysis, x-ray diffraction and optical microscopy. The compressive strength and the modulus of elasticity were the investigated mechanical properties. The test results indicate expressively the better performance of the concretes fabricated with basalt, granite and gneiss aggregates. (author)

characterization of terrain and biotite gneiss-derived lateritic soils

African Journals Online (AJOL)

DJFLEX

2010-04-08

Apr 8, 2010 ... from 23m above mean sea level in the lowlying areas to. 41m (msl) for the high rise area is decorated on the eastern part with Inselbergs of ..... through landfill liners Florida centre for solid and hazardous waste management ...

Some geotechnical properties of a cement-stabilized granite-gneiss ...

African Journals Online (AJOL)

This was with a view to determining the influence of cement on some engineering properties of the soil. ... the maximum Dry Density and the percentage cement of the samples compacted at the West African and Modified American Association of State Highways and Transportation Officials (AASHTO) levels respectively.

petrography and mineral chemistry of the pelitic and semi-pelitic ...

African Journals Online (AJOL)

Mgina

SEMI-PELITIC GNEISSES OF THE MERELANI TANZANITE MINING. AREA ... and thin sections were prepared with ... Six samples were chosen for chemical ... were also determined by X-ray fluorescence ..... metamorphosed iron formation.

Field occurrences and petrology of eclogites from the Dabie Mountains, Anhui, central China

Science.gov (United States)

Wang, X.; Jing, Y.; Liou, J. G.; Pan, G.; Liang, W.; Xia, M.; Maruyama, S.

1990-11-01

Four distinct types of eclogites are recognized according to their field occurrences and mineral parageneses in a gneiss terrane of the Dabie Mountains, a collision zone between the Sino-Korean and Yangtze cratons in central China. Some eclogites contain coesite and its quartz pseudomorphs enclosed in garnet and omphacite. Type I eclogites occur as layers in serpentinites and contain garnet, clinopyroxene, orthopyroxene, phengite, rutile, and coesite pseudomorph. Type II eclogites occur as lenticular bodies inside serpentinites and contain garnet, clinopyroxene, quartz, rutile, and edenitic hornblende. Type III eclogites occur as blocks of 2 cm to 20 m in size in a matrix of hornblende gneiss and biotite gneiss, and Type IV eclogites occur as thin layers interbedded with amphibolites. P- T estimates for these different eclogites indicate that they were formed under different physical conditions. All the eclogites were affected by later regional metamorphism for which the P- T conditions are estimated. This paper provides an introduction to the abundant eclogites from central China which have not been reported previously in Western literature. Specifically, the mode of field occurrence, petrography, mineral chemistry and formation conditions of the four types of eclogites are described. The paper is thus designed to establish a petrological framework for future detailed studies of the eclogites and their country rocks in an ancient zone of collision.

Rb/Sr and K/Ar determinations of Monguba and Pendanga rocks,Ceara

International Nuclear Information System (INIS)

Torquato, J.R.F.; Pedreira, L.H.; Kawashita, K.; Barbosa, H.S.P.

1986-01-01

In this paper we describe the petrography and geochronology of rocks from two quarries near the City of Fortaleza/Ceara. One, the Pedreira Monguba, is formed, basically, by rocks of the granitic to monzogranitic type. Its isochrone age is 672 +- 46 m.y. with an initial ratio of 0.7036 +- 0.0005. Datinfs of biotite by the K/Ar method gave values of 522+- 19m.y. for the consolidation of the region. For comparison with the other components of the same morphologic unit, the Massif of Maranguape, we designed a reference isochrone with all values available from the literature (for granite, gneisses and migmatites) and obtained a straight line parallel to the first, but with a higher initial ratio of 0.709, demonstrating the strong influence of the Brasiliano Cycle in this region. The other quarry, Pedreira Pendanga, is composed of gneisses and migmatized gneisses and forms an open chemical system. It was possible, however, to verify that its age is equal or greater than 2150+- 71 m.y. and that all of its rocks have suffered strong metamorphism during the Brasiliano Cycle as in shown by the K/Ar ages of biotites of 541+- 3 m.y. A discussion of sampling problems is given and the influence of a granitic intrusion on the chemical opening of the system is evidenced. (author) [pt

Metamorphism, metasomatism and mineralization at Lagoa Real, Bahia, Brazil

International Nuclear Information System (INIS)

Lobato, L.M.

1985-09-01

Uranium deposits cumulatively in the 100,000 tonne U 3 O 8 range occur within ductile shear zones transecting Archean basement gneisses of the Sao Francisco Craton, at the Lagoa Real region of south-central Bahia, Brasil. The gneisses, dated at 2.6-3.0Ga, are at amphibolite and granulite facies and overlie to the west, the Proterozoic Espinhaco metasedimentary sequence along a thrust fault. Petrography and mineral chemistry show that in the zones of alteration/mineralization, the original K-feldspar + quartz + albite/oligoclase + hastingsite assemblage, is replaced by albite + aegirine - angite + andradite + hematite assemblages, with or without uraninite. This information along with oxygen isotope, whole rock geochemistry and fluid inclusion studies indicate that the alteration process involves removal of Si, K, Rb, Ba and addition of Na under oxidizing conditions. V, Pb and Sr were introduced along with U via interaction with saline SO 2 - rich, isotopically light fluids under varying water/rock ratios and at temperatures of 500 - 550 0 C. 87 Sr/ 86 Sr systematics suggest that it is unlikely that Sr, and by extension uranium, were introduced by fluids originating from the basement gneisses. Geological constraints and the general alteration pattern are consistent with the release of the mineralizing fluids in response to the overloading of the basement rocks onto the Sedimentary Espinhaco via a thrust mechanism. (Author) [pt

The geochemical chararateristics of the marble deposits east of ...

African Journals Online (AJOL)

), marbles were investigated with the view to establishing marble occurrences and their geochemical characteristics. Crystalline rocks of the Nigerian Basement Complex (migmatite – gneiss complex) underlie the area. Ten marble bodies were ...

Petrography and geochemistry of five granitic plutons from south central Uruguay: contribution to the knowledge of the Piedra Alta terrane

International Nuclear Information System (INIS)

Preciozzi, F.

2005-01-01

Granitoid rocks in south-central Uruguay are largely concentrated in three east-west trending metamorphic belts, known as (from south to north) the Montevideo Belt, the San José Belt and the Arroyo Grande Belt. These belts are separated from one another by intervening bands of gneisses of granitic composition. The whole assemblage, the gneisses as well as the metamorphic belts and their associated granites, collectively constitute the Piedra Alta Terrane. Five of these granite plutons, two from the San José Belt and three from the Arroyo Grande Belt, have been studied in some detail and the chemical composition of 86 samples (major elements as well as a selected suite of trace elements) have been determined. These data, as well as Rb-Sr isotopic data, show that these plutons are typically composite in nature, and that the various units range in age from 1900 Ma to 2500 Ma. The older ages were obtained from the main units of the plutons themselves whereas the younger ages are from late dykes which were emplaced into the plutons and which are clearly not related to them. The plutons are predominantly, but not exclusively, of calc-alkaline affinity and are typically synorogenic whereas the dykes are post-orogenic and are either calc-alkaline or alkaline in composition. These data have been incorporated into a tectonic model for the Piedra Alta Terrane which is considerably different from that heretofore proposed. The essential features of the geological history of the area are: 1) development of an older ''basement'' of granitic gneisses 2) deposition, upon or adjacent to this gneisses basement, of a typical Archean greenstone belt assemblage (no komatiites so far reported) 3) Paleo-proterozoic metamorphism, followed by syn-tectonic to post-tectonic intrusion of the plutonic rocks 4) major tectonic dislocation(s) associated with the Transamazonian orogeny 5) dyke emplacement (post-orogenic to anorogenic) following the Transamazonian orogeny

Geological 3D model of the investigation niche in ONKALO, Olkiluoto, southwestern Finland

Energy Technology Data Exchange (ETDEWEB)

Koittola, N.

2014-07-15

The main goal of this Master of Science Thesis was to create a geological 3D-model of the investigation niche 3 and its surroundings. The model were created for the needs of the rock mechanical back analysis. This study is a part of Posiva's regional studies for characterization of the bedrock. Totally 4 models were created: lithological model, foliation model, fracture model, and physical rock property model. Besides the modeling, there was also made a study of the migmatite structures in the niche. Used geological and geophysical methods were drill core loggings, tunnel mapping, ground penetration radar, mise-a-la-masse and drill hole geophysics. Four rock types exist at the niche area: veined gneiss, pegmatite granite, diatexitic gneiss and quartz gneiss. The lithological units were modeled primary with the drill core loggings, tunnel mapping and ground penetrating radar. The major lithological units followed the main foliation direction (south dipping). So the continuations were fairly easy to model in the walls and roof, where the data was lacking. Foliation and fractures were modeled as discs, with mid-points at the measurement points of the structure. There were two main foliation directions 164/46 and 62/39. Fractures were more scattered but three fracture sets can be separated: 156/34, 270/85 and 342/83. The first set is mainly from the drill core loggings, second and third from tunnel mapping. Used methods in foliation model were drill core loggings, tunnel mapping and drill hole geophysics. In fracture model used data was from drill core loggings, tunnel mapping, mise-a-la-masse measurements and drill core geophysic. Four anomalous zones were detected with the drill hole geophysics. Three of these zones were associated with intensely fractured zones and one was connected to exceptionally high mica content in the gneiss. Rocks of Olkiluoto are divided into gneisses and magmatic rocks in the geological mapping. Actually almost all Olkiluoto

Geological 3D model of the investigation niche in ONKALO, Olkiluoto, southwestern Finland

International Nuclear Information System (INIS)

Koittola, N.

2014-07-01

The main goal of this Master of Science Thesis was to create a geological 3D-model of the investigation niche 3 and its surroundings. The model were created for the needs of the rock mechanical back analysis. This study is a part of Posiva's regional studies for characterization of the bedrock. Totally 4 models were created: lithological model, foliation model, fracture model, and physical rock property model. Besides the modeling, there was also made a study of the migmatite structures in the niche. Used geological and geophysical methods were drill core loggings, tunnel mapping, ground penetration radar, mise-a-la-masse and drill hole geophysics. Four rock types exist at the niche area: veined gneiss, pegmatite granite, diatexitic gneiss and quartz gneiss. The lithological units were modeled primary with the drill core loggings, tunnel mapping and ground penetrating radar. The major lithological units followed the main foliation direction (south dipping). So the continuations were fairly easy to model in the walls and roof, where the data was lacking. Foliation and fractures were modeled as discs, with mid-points at the measurement points of the structure. There were two main foliation directions 164/46 and 62/39. Fractures were more scattered but three fracture sets can be separated: 156/34, 270/85 and 342/83. The first set is mainly from the drill core loggings, second and third from tunnel mapping. Used methods in foliation model were drill core loggings, tunnel mapping and drill hole geophysics. In fracture model used data was from drill core loggings, tunnel mapping, mise-a-la-masse measurements and drill core geophysic. Four anomalous zones were detected with the drill hole geophysics. Three of these zones were associated with intensely fractured zones and one was connected to exceptionally high mica content in the gneiss. Rocks of Olkiluoto are divided into gneisses and magmatic rocks in the geological mapping. Actually almost all Olkiluoto's rocks are

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

International Nuclear Information System (INIS)

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

2012-01-01

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

A preliminary study on the geochemical environment for deep geological disposal of high level radioactive waste in Korea

International Nuclear Information System (INIS)

Kim, Chun Soo; Bae, Dae Seok; Kim, Kyung Su; Koh, Yong Kwon; Park, Byoung Yun

2000-03-01

Geochemical study on the groundwater from crystalline rocks (granite and gneiss) for the deep geological disposal of high-level radioactive waste was carried out in order to elucidate the hydrogeochemical and isotope characteristics and geochemical evolution of the groundwater. Study areas are Jungwon, Chojeong, Youngcheon and Yusung for granite region, Cheongyang for gneiss region, and Yeosu for volcanic region. Groundwaters of each study areas weree sampled and analysed systematically. Groundwaters can be grouped by their chemistry and host rock. Origin of the groundwater was proposed by isotope ( 18 O, 2 H, 13 C, 34 S, 87 Sr, 15 N) studies and the age of groundwater was inferred from their tritium contents. Based ont the geochemical and isotope characteristics, the geochemical evolutions of each types of groundwater were simulated using SOLVEQ/CHILLER and PHREEQC programs

Geological, Geochemical 1 and Rb-Sr isotopic studies on tungsten 2 ...

Indian Academy of Sciences (India)

37

Geological, Geochemical and Rb-Sr isotopic studies on tungsten. 1 mineralised ..... From the field relations it is demonstrated that SG (biotite-bearing granitic gneiss) and. 120 ..... cases Ba) and vice-versa for the low concentration. 291.

Can groundwater be successfully implemented as a bulk water ...

African Journals Online (AJOL)

that groundwater can be developed as a potential viable bulk-water supply source. This paper attempts .... fracturing, even when using conventional geophysical methods. Gneiss and/or ..... will start to be self-sufficient in about 2018 and 2019.

Detachment folding of partially molten crust in accretionary orogens: A new magma-enhanced vertical mass and heat transfer mechanism

Czech Academy of Sciences Publication Activity Database

Lehmann, J.; Schulmann, K.; Lexa, O.; Závada, Prokop; Štípská, P.; Hasalová, Pavlína; Belyanin, G.; Corsini, M.

2017-01-01

Roč. 9, č. 6 (2017), s. 889-909 ISSN 1941-8264 Institutional support: RVO:67985530 Keywords : continental crust * shear-zone * gneiss domes Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.662, year: 2016

Preliminary report on diatoms from the deep lake terraces, Vestfold Hills, Antarctica

Digital Repository Service at National Institute of Oceanography (India)

Setty, M.G.A.P.; Kellogg, D.E.; Kellogg, T.B.

with fragments of pyroxenite, quartzite, permatite, gneiss, and glacial debris. Halite and mirabilite crystals are common. A general study of foraminifera of the lake sediments of the Vestfold Hills was made and the results are presented here...

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.

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

International Nuclear Information System (INIS)

Simoes, L.S.A.

1984-01-01

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

Measurement of activity concentration of 222Rn in ground waters drawn from two wells drilled in the Amparo Complex metamorphic rocks, municipio de Amparo, SP

International Nuclear Information System (INIS)

Oliveira, Igor Jose Chaves de

2008-01-01

A sampling system was assembled for field 222 Rn activity concentration measurements in ground waters. The system consists of a sampling flask that prevents the contact between the water sample and the atmosphere and a closed line for radon extraction from water. The system, its operation and calibration, are described in full detail, as well as, the conversion of the measured alpha counting rates in activity concentrations. The assembled system was used in 222 Rn activity concentrations measurements in ground waters drawn from two wells drilled in the Amparo Complex metamorphic rocks. The wells are located at the urban area of the city of Amparo and are exploited for public use water. One well, named Vale Verde, is 56 meters deep and crosses 18 meters of soil, 26 meters of quartz rich gneiss and 12 meters of biotite-gneiss. The other well, named Seabra, is 117 meters deep, crosses 28 meters of soil and weathered rocks and ends in granite-gneiss. The mean activity concentrations for the year long observation were (377 +- 25) Bq/dm 3 , for Seabra well, and (1282 +- 57) Bq/dm3, for the Vale Verde well. The 222 Rn activity concentrations fall in the activity concentration range reported in the literature for similar geology areas and are larger than the concentrations found neighboring areas of the same metamorphic Complex. The seasonal activity concentration variations seem to correlate with rain fall variations in the study area. (author)

Isotopic age determineations on granitic and gneissic rocks from the Ubendian-Usagaran System in southern Tanzania

International Nuclear Information System (INIS)

Priem, H.N.A.; Boelrijk, N.A.I.M.; Hebeda, E.H.; Verdurmen, E.A.Th.; Verschure, R.H.; Oen, I.S.; Westra, L.

1979-01-01

Isotopic age measurements on granites and gneisses are reported from the Ubendian-Usagaran System in southern Tanzania. For the Lukumburu-Wino Granites a Rb-Sr whole-rock isochron (9 points) of 1771 +- 145 Ma with initial 87 Sr/ 86 Sr of 0.704 +- 0.003 was obtained (γ 87 Rb = 1.42 10 -11 a -1 ; errors 95% confidence level). Two samples from neighbouring granites and three gneisses from the contact zone of the Lukumburu-Wino Granites also fit to this isochron; inclusion into the isochron calculation yields an age of 1747 +- 85 Ma with the same initial Sr composition. Five parts of a banded Usagaran gneiss sample produce an isochron of 589 +- 70 Ma with initial 87 Sr/ 86 Sr of 0.7194 +- 0.0005. This internal isochron is interpreted as reflecting Sr isotopic equilibration through the sample during the main phase (or one of the main phases) of the Pan-African thermotectonic episode. Rb-Sr and K-Ar ages of 17 micas show a general resetting by the Pan-African thermotectonic episode. The Rb-Sr ages of the muscovites and the biotites average 528 Ma and 463 Ma, respectively, and are interpreted as reflecting subsequent stages in the cooling history after the termination of the event. Biotites have K-Ar ages persistently higher than the corresponding Rb-Sr ages, possibly reflecting a high partial 40 Ar pressure through the crust during the resetting of the biotite K-Ar systems. (Auth.)

Bedrock model of the Romuvaara area

International Nuclear Information System (INIS)

Saksa, P.; Paananen, M.; Paulamaeki, S.; Anttila, P.; Pitkaenen, P.; Front, K.; Vaittinen, T.

1992-05-01

Site for the final disposal of the spent nuclear fuel investigations implemented in accordance with the research programme drawn up by Teollisuuden Voima Oy were carried out at Romuvaara, Kuhmo, in 1987 - 1991. Model of the site were compiled and used for describing the rock types, fractures, fracturing structures and geohydrological conditions, the main emphasis being on the examination of the bedrock fracturing and related hydraulic conductivity. Three-dimensional models were used for the classification of the various properties of the bedrock structures. The descriptive models were gathered together in a computerized system to facilitate illustration and strage. The rock types at Romuvaara are gneiss, mica gneiss, leucotonalite gneiss, amphibolite, granodiorite and metadiabase. The structural model for fracturing at the site contains 19 zones described in terms of a number of properties. The fracturing observed at Romuvaara ranges from local occurences of dence fracturing to significant, altered fracture zones. The structural model includes deduced values for hydraulic conductivity, deduced points of flow in the boreholes and measured hydraulic heads.Various classifications were used for assessment of hydraulic conductivity in the zones and solid bedrock, and in both cases conductivity was found to diminish with depth. Measured hydraulic heads were mostly found to support structural interpretation. The results were used for estimation of a three-dimensional hydraulic head distribution. Results from pumping tests carried out in the significant flow zone support the geometric interpretation

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

Science.gov (United States)

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

2006-04-01

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

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

Science.gov (United States)

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

2018-03-01

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

Water - rock interaction in different rock environments

International Nuclear Information System (INIS)

Lamminen, S.

1995-01-01

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

A preliminary study on the geochemical environment for deep geological disposal of high level radioactive waste in Korea

Energy Technology Data Exchange (ETDEWEB)

Kim, Chun Soo; Bae, Dae Seok; Kim, Kyung Su; Koh, Yong Kwon; Park, Byoung Yun

2000-03-01

Geochemical study on the groundwater from crystalline rocks (granite and gneiss) for the deep geological disposal of high-level radioactive waste was carried out in order to elucidate the hydrogeochemical and isotope characteristics and geochemical evolution of the groundwater. Study areas are Jungwon, Chojeong, Youngcheon and Yusung for granite region, Cheongyang for gneiss region, and Yeosu for volcanic region. Groundwaters of each study areas weree sampled and analysed systematically. Groundwaters can be grouped by their chemistry and host rock. Origin of the groundwater was proposed by isotope ({sup 18}O, {sup 2}H, {sup 13}C, {sup 34}S, {sup 87}Sr, {sup 15}N) studies and the age of groundwater was inferred from their tritium contents. Based ont the geochemical and isotope characteristics, the geochemical evolutions of each types of groundwater were simulated using SOLVEQ/CHILLER and PHREEQC programs.

Rock Rb-Sr ages from Bananal region - Sao Paulo State, Brazil

International Nuclear Information System (INIS)

Dias Neto, C.M.; Tassinari, C.G.C.; Silva, M.E.

1996-01-01

New Rb-Sr whole rock isochron ages have been determined for the main lithological units that occur in Sao Paulo and Rio de Janeiro States. These rocks belong to Serra do Mar domain. The purpose of this work is to characterize the sequence of the geological events as well as the possible relationship between the different rocks. The geochronological data suggest that the paragneisses and the basement rocks, represented by ortho gneisses nuclei, were generated under amphibolite conditions around 700 Ma. At the same time the leucogranites were generated by partial melting processes and injected into both gneiss types. Tarditectonic granitic magmatic activities took place within ductile shear zones. One of the granites, the Getulandia granite, yielded an age of 514 Ma, falling in the range of the late Brasiliano Cycle which extended into the Middle Cambrian. (author). 9 figs., 1 tab

An overview of uranium, rare metal and REE mineralisation in the crystallines of Sonbhadra district, Uttar Pradesh, India

International Nuclear Information System (INIS)

Parihar, P.

2014-01-01

Uranium and REE mineralisation hosted by the Proterozoic migmatites and younger intrusives is identified over 350 km"2 in Son Valley area, Sonbhadra district, Uttar Pradesh, which forms the northwestern extension of Chotanagpur Granite Gneiss Complex (CGGC). The rocks exposed include banded gneisses and metasedimentary enclaves, overlain by the Mahakoshal supracrustals and sediments of the Vindhyan Supergroup in the north and Gondwana Supergroup in the south. The craton had undergone repeated rifting, giving rise to intracratonic rift basins for the development of cover rock sequences of arkosic to psammo-pelitic metasediments, which now occur as migmatites comprising pegmatoid leucosomes and biotite melanosomes and associated mesosomes. These intracratonic zones are parallel to the Lower Proterozoic Mahakoshal supracrustals. Anorogenic, rift related plutons of alkali granite of middle Proterozoic age are seen emplaced within Mahakoshal supracrustals, which at places like Kundabhati and Sonwani are episyenitised.

Characteristics of pegmatoidal granite exposed near Bayalan, Ajmer ...

Indian Academy of Sciences (India)

near Bayalan, Ajmer district, Rajasthan. Nilanjan ... eastern flank of the South Delhi Fold Belt (Sinha. Roy 1984 .... gneisses in a lit-par-lit manner producing alternate layers of granite and ... shows a point concentration (table 1) with a mean.

Rafineeritud naudingud : kuumaveeallikad Valsis (Šveits)

Index Scriptorium Estoniae

1998-01-01

Peter Zumthori (sünd. 1943) projekteeritud, 1997. a. valminud supelasutusest Alpides Valsi kuurordis. Kalju sisse uuristatud veekompleksi ehitusmaterjaliks on kivim gneiss. 1997. a. Euroopa parima ehitise tiitli sai napilt Valsi supelasutuse ees Pariisi uus rahvusraamatukogu (arhitekt D. Perrault).

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

Science.gov (United States)

2010-02-08

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

Characterisation and monitoring of the Excavation Disturbed Zone (EDZ) in fractured gneisses of the Roselend underground laboratory: permeability measurements, transport property changes and related radon bursts

Science.gov (United States)

Wassermann, Jérôme; Sabroux, Jean-Christophe; Richon, Patrick; Pontreau, Sébastien; Guillon, Sophie; Pili, Eric

2010-05-01

The Roselend tunnel was drilled in the fifties by blasting in the micashists, granites and gneisses of the Méraillet massif (French Alps). It is situated on the shore of the Roselend reservoir Lake near its dam. Several tectonic shear fractures related to the Alpine orogeny intersect the dead end tunnel (with length of 128 m and section about 2 m), indeed the fracture density varies from 0.45 to 1 fracture per meter along the tunnel (Dezayes and Villemin 2002). Some fractures are partially or totally filled with secondary minerals. The flow rates of percolating water through the fractured medium are seasonal dependent. Large fractures drain a large fluid volume unlike small ones that drain limited fluid volume (Patriarche et al. 2007). The Roselend underground laboratory allows the study of the geochemical and geophysical responses of a fractured rock mass to periodic sollicitations due to water level variations of the nearby Roselend reservoir Lake. The tunnel was instrumented in the nineties to understand the relationship between radon (Rn-222) concentration and water level variations of the Roselend reservoir Lake (Trique et al. 1999). In order to characterize the geometry and the extent of the EDZ, core drilling and permeability measurements through pneumatic testing are performed along the Roselend tunnel. Drilled core analysis consists of direct observations at a macroscopic scale of fractures (density of fractures from EDZ) and also at a microscopic scale via thin sections. Method of pressure build-up in wells (Jakubick and Franz 1993, Bossart et al. 2002) is used to determine permeability profile along each borehole and hence to precise the extent and geometry of the EDZ. A strong correlation is observed between permeability profiles and the density of fractures estimated from core analysis. The extent of the EDZ appears to be about one tunnel radius i.e. one meter around the tunnel corridor. Another experiment consisting of continuous differential

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

International Nuclear Information System (INIS)

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

1991-01-01

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

Nd isotopes, U-Pb single grain and SHRIMP zircon ages from basement rocks of the Tocantin Province

International Nuclear Information System (INIS)

Fuck, R.A.; Dantas, E.L.; Pimentel, M.M.; Junges, S.L.; Moraes, R

2001-01-01

Large areas of the northern part of the Brasilia Belt, Tocantins Province, central Brazil, are underlain by basement granite-gneiss terrain and associated volcano-sedimentary sequences, as well as felsic and mafic-ultramafic intrusions. The basement rocks are covered by the late Paleoproterozoic-Mesoproterozoic rift-related Arai and Natividade groups and intruded by 1.77 to 1.58 Ga an orogenic granites of the Goias Tin Province (Pimentel and Botelho, 2001). To the southwest they are un conformably overlain by the low-grade late Proterozoic Paranoa Group, whereas to the east they are in faulted contact with the Neoproterozoic Bambui Group at the western edge of the Sao Francisco Craton. To the north they are covered by Phanerozoic sediments of the Parnaiba and Sanfranciscana basins. Despite their large extension, granite-gneiss and associated supracrustals of SE Tocantins and NE Goias are still poorly known. Previous regional Rb-Sr and K-Ar isotopic studies indicated dominant early Proterozoic ages and late Proterozoic cooling ages (Hasui, et al. 1980, Fernandes et al. 1982). More detailed studies in the Almas-Dianopolis area (Costa, 1984) came up with similar results, although the region was interpreted as underlain by Archean granite-greenstone terrain, following previous suggestions by Costa et al. (1976). Recent work recognized the presence of two suites of deformed granitoids (Cruz and Kuyumjian, 1996, 1998). The oldest suite intruded the supracrustals and comprises hornblende-bearing tonalite gneiss, with minor trondhjemite, granodiorite, and quartz diorite. The younger suite comprises oval shaped biotite-bearing tonalite, trondhjemite, and granodiorite intrusions. Both suites display low-K calc-alkaline affinity, the younger being more Al-rich. Both are interpreted as TTG suites and were dated at 2,2 Ga using U-Pb SHRIMP (Cruz et al 2000). In the Porto Nacional area, Gorayeb et al. (2000) determined single zircon Pb-evaporation ages of 2.15 Ga in granulites

SECULAR CHANGES IN RELATIONSHIPS BETWEEN PLATE-TECTONIC AND MANTLE-PLUME ENGENDERED PROCESSES DURING PRECAMBRIAN TIME

Directory of Open Access Journals (Sweden)

M. V. Mints

2016-01-01

Full Text Available Paradoxically, the lists of “proxies” of both plate- and plume-related settings are devoid of even a mention of the high-grade metamorphic rocks (granulite, amphibolite and high-temperature eclogite facies. However, the granulite-gneiss belts and areas which contain these rocks, have a regional distribution in both the Precambrian and the Phanerozoic records. The origin and evolution of the granulite-gneiss belts correspond to the activity of plumes expressed in vigorous heating of the continental crust; intraplate magmatism; formation of rift depressions filled with sediments, juvenile lavas, and pyroclastic flow deposits; and metamorphism of lower and middle crustal complexes under conditions of granulite and high-temperature amphibolite facies that spreads over the fill of rift depressions also. Granulite-gneiss complexes of the East European Craton form one of the main components of the large oval intracontinental tectonic terranes of regional or continental rank. Inclusion of the granulite-gneiss complexes from Eastern Europe, North and South America, Africa, India, China and Australia in discussion of the problem indicated in the title to this paper, suggests consideration of a significant change in existing views on the relations between the plate- and plume-tectonic processes in geological history, as well as in supercontinent assembly and decay. The East European and North American cratons are fragments of the long-lived supercontinent Lauroscandia. After its appearance at ~2.8 Ga, the crust of this supercontinent evolved under the influence of the sequence of powerful mantle plumes (superplumes up to ~0.85 Ga. During this time Lauroscandia was subjected to rifting, partial breakup and the following reconstruction of the continent. The processes of plate-tectonic type (rifting with the transition to spreading and closing of the short-lived ocean with subduction within Lauroscandia were controlled by the superplumes. Revision of the

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

Science.gov (United States)

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

2017-04-01

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

Humic acids quality of Cambisols developed on gneiss and amphibolite

Czech Academy of Sciences Publication Activity Database

Pospíšilová, Ľ.; Žigová, Anna; Šťastný, Martin; Liptaj, T.

2012-01-01

Roč. 9, č. 4 (2012), s. 503-510 ISSN 1214-9705 R&D Projects: GA ČR GA526/08/0434 Institutional support: RVO:67985831 Keywords : Cambisols * parent material * arable soil, * grassland soil * X-ray diffraction * humic acids * SRATR FTIR and 13C NMR spectroscopy Subject RIV: DF - Soil Science Impact factor: 0.530, year: 2011 http://www.irsm.cas.cz/materialy/acta_content/2012_04/8.Pospisilova.pdf

Pb–Pb zircon ages of Archaean metasediments and gneisses from ...

Indian Academy of Sciences (India)

eastern parts of the Dharwar craton took place over similar time interval starting in the Mesoarchaean at ca. .... the age of the Bababudan Group between 2.91 and. 2.72 Ga. ..... All the samples were processed using a standard technique to ...

Mafic rocks from Erinpura gneiss terrane in the Sirohi region ...

Indian Academy of Sciences (India)

1Department of Geology, University of Rajasthan, Jaipur 302 004, India. 2GeoZentrum .... from massive to foliated types wherein the gener- ally steep foliations show ... ered for kinematic analyses of the shear movement. These features are ...

Mapping of groundwater potential zones in Salem Chalk Hills, Tamil Nadu, India, using remote sensing and GIS techniques.

Science.gov (United States)

Thilagavathi, N; Subramani, T; Suresh, M; Karunanidhi, D

2015-04-01

This study proposes to introduce the remote sensing and geographic information system (GIS) techniques in mapping the groundwater potential zones. Remote sensing and GIS techniques have been used to map the groundwater potential zones in Salem Chalk Hills, Tamil Nadu, India. Charnockites and fissile hornblende biotite gneiss are the major rock types in this region. Dunites and peridodites are the ultramafic rocks which cut across the foliation planes of the gneisses and are highly weathered. It comprises magnesite and chromite deposits which are excavated by five mining companies by adopting bench mining. The thickness of weathered and fracture zone varies from 2.2 to 50 m in gneissic formation and 5.8 to 55 m in charnockite. At the contacts of gneiss and charnockite, the thickness ranges from 9.0 to 90.8 m favoring good groundwater potential. The mine lease area is underlined by fractured and sheared hornblende biotite gneiss where groundwater potential is good. Water catchment tanks in this area of 5 km radius are small to moderate in size and are only seasonal. They remain dry during summer seasons. As perennial water resources are remote, the domestic and agricultural activities in this region depend mainly upon the groundwater resources. The mines are located in gently slope area, and accumulation of water is not observed except in mine pits even during the monsoon period. Therefore, it is essential to map the groundwater potential zones for proper management of the aquifer system. Satellite imageries were also used to extract lineaments, hydrogeomorphic landforms, drainage patterns, and land use, which are the major controlling factors for the occurrence of groundwater. Various thematic layers pertaining to groundwater existence such as geology, geomorphology, land use/land cover, lineament, lineament density, drainage, drainage density, slope, and soil were generated using GIS tools. By integrating all the above thematic layers based on the ranks and

Geodynamic evolution and crustal growth of the central Indian Shield

Indian Academy of Sciences (India)

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

mantle interaction in the generation of the granitoids. The low values of Mg#, Ni, Cr, Sr and high values of SiO2 in the gneisses in turn overrules such melt-mantle interaction. 1. Introduction. The formation and growth of continental crust.

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

African Journals Online (AJOL)

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

Geochronological data on the Amsinassene-Tefedest Block (Central Hoggar, Algerian Sahara) and evidence for its polycyclic evolution

International Nuclear Information System (INIS)

Vialette, Y.; Vitel, G.

1979-01-01

The history of the Amsinassene-Tefedest Block, in the central Hoggar domain, is characterized by a polycyclic evolution. The unreliable 1970 Ma age obtained on the Arechchoum gneisses, known to be Suggarian-Eburnean, might represent the effect of the Eburnean orogeny. A Rb/Sr whole-rock age on the leucocratic fractions of gneisses point to a kibaran migmatization. This age confirms the existence of a Kibaran orogeny shown in the Aleksod area. The Pharusian-Pan African cycle, in this domain, is characterized by the emplacement of huge granitic bodies during two distinct magnetic phases: one of Late Proterozoic age (670 Ma) or Imezzarian phase, the other of Cambrian age as shown by the 546 and 515 Ma Rb/Sr whole-rock ages obtained on late kinematic granitic plutons, Iskelian phase. The younger mineral ages (470-430 Ma) indicate late vertical uplift of the central Hoggar. (Auth.)

The geology of the Romuvaara area

International Nuclear Information System (INIS)

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

1990-12-01

Teollisuuden Voima Oy (TVO) is preparing for the final disposal of spent uranium fuel from the Olkiluoto nuclear power plant deep in the Finnish bedrock. The report presents a summary of the geological conditions at Romuvaara in Kuhmo, which was one of the five areas selected in 1987 for the preliminary site investigations. The Romuvaara site and its surroundings belong to the Archaean basement complex, the age of the oldest parts of which is over 2800 Ma. The bedrock consists mainly of migmatic banded gneisses (tonalite, leucotonalite and mica gneiss). These rock types are intersected by granodiorite and metadiabase dykes. Proterozoic metadiabases represent the youngest rock unit in the area. Except for the metadiabase, the rocks have undergone a multiphase Archaean deformation. The bedrock structures are interpreted as representing six deformation phases, after which sharp faults developed during at least four further movement phases

The foundation of the units 2 and 3 of the nuclear power plant Angra dos Reis/Brasil

International Nuclear Information System (INIS)

Bokemeyer, R.; Linder, W.R.

1979-01-01

The report describes the extraordinarily difficult and comprehensive foundation activities which started in Summer 1977. Because of the high building weight, and the gigantic soft superimposed layers prevailing on the site, a bay, a foundation on more than 2500 large-scale drilling posts for both units is planned. The posts have to be inserted into loose marine sediments, gneiss decomposition grounds and weather-worn rocks down to an average of 36 m, and often down to 60 m, into competent rocks, mostly gneiss or granite. Because of the size and the changing consistency of the weather-worn rocks and the great amount of the hard boulders which are deposited in the soft layers enormous technical difficulties have to be surmounted as the drilling work has to be accomplished within a very short time. It has not been necessary yet to cope with difficulties of this dimension. (orig./HP) [de

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

International Nuclear Information System (INIS)

Barbosa, A.G.

1991-01-01

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

The ongoing search for the oldest rock on the Danish island of Bornholm: new U-Pb zircon ages for a quartz-rich xenolith and country rock from the Svaneke Granite

DEFF Research Database (Denmark)

Waight, Tod Earle; Serre, Simon H.; Næsby, Sebastian H.

2017-01-01

Previous geochronological studies on the Danish island of Bornholm have not identified any rocks older than c. 1.46 Ga. New LA-ICP-MS U-Pb zircon ages are presented for a xenolith within, and the country rock gneiss adjacent to, the Svaneke Granite on Bornholm. The xenolith is fine......-grained and quartz-rich and was likely derived from either a quartz-rich sedimentary protolith or a hydrothermally altered felsic volcanic rock. The relatively fine-grained felsic nature of the country rock gneiss and the presence of large zoned feldspars that may represent phenocrysts suggest its protolith may have...... been a felsic volcanic or shallow intrusive rock. A skarn-like inclusion from a nearby locality likely represents an originally carbonate sediment and is consistent with supracrustal rocks being present at least locally. Zircon data from the xenolith define an upper intercept age of 1483 ± 12 Ma (2σ...

Compact rock material gas permeability properties

Energy Technology Data Exchange (ETDEWEB)

Wang, Huanling, E-mail: whl_hm@163.com [Key Laboratory of Coastal Disaster and Defence, Ministry of Education, Hohai University, Nanjing 210098 (China); LML, University of Lille, Cite Scientifique, 59655 Villeneuve d’Ascq (France); Xu, Weiya; Zuo, Jing [Institutes of Geotechnical Engineering, Hohai University, Nanjing 210098 (China)

2014-09-15

Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO{sub 2,} shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10{sup −19} m{sup 2}; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10{sup −17} m{sup 2}; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens’ permeability evolution is related to the relative particle movements and microcrack closure.

Rb-Sr measurements on metamorphic rocks from the Barro Alto Complex, Goias, Brazil

International Nuclear Information System (INIS)

Fuck, R.A.; Neves, B.B.B.; Cordani, U.G.; Kawashita, K.

1988-01-01

The Barro Alto Complex comprises a highly deformed and metamorphosed association of plutonic, volcanic, and sedimentary rocks exposed in a 150 x 25 Km boomerang-like strip in Central Goias, Brazil. It is the southernmost tip of an extensive yet discontinuous belt of granulite and amphibolite facies metamorphic rocks which include the Niquelandia and Cana Brava complexes to the north. Two rock associations are distinguished within the granulite belt. The first one comprises a sequence of fine-grained mafic granulite, hypersthene-quartz-feldspar granulite, garnet quartzite, sillimanite-garnet-cordierite gneiss, calc-silicate rock, and magnetite-rich iron formation. The second association comprises medium-to coarse-grained mafic rocks. The medium-grade rocks of the western/northern portion (Barro Alto Complex) comprise both layered mafic rocks and a volcanic-sedimentary sequence, deformed and metamorphosed under amphibolite facies conditions. The fine-grained amphibolite form the basal part of the Juscelandia meta volcanic-sedimentary sequence. A geochronologic investigation by the Rb-Sr method has been carried out mainly on felsic rocks from the granulite belt and gneisses of the Juscelandia sequence. The analytical results for the Juscelandia sequence are presented. Isotope results for rocks from different outcrops along the gneiss layer near Juscelandia are also presented. In conclusion, Rb-Sr isotope measurements suggest that the Barro Alto rocks have undergone at least one important metamorphic event during Middle Proterozoic times, around 1300 Ma ago. During that event volcanic and sedimentary rocks of the Juscelandia sequence, as well as the underlying gabbro-anorthosite layered complex, underwent deformation and recrystallization under amphibolite facies conditions. (author)

Anisotropy effect on strengths of metamorphic rocks

Directory of Open Access Journals (Sweden)

Ahmet Özbek

2018-02-01

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

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

NARCIS (Netherlands)

Salemink, J.

1985-01-01

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

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

Science.gov (United States)

2012-08-28

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

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

African Journals Online (AJOL)

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

Cranberry magnetite deposits Avery County, N.C., and Carter County, Tenn.

Science.gov (United States)

Kline, M.H.; Ballard, T.J.

1948-01-01

The Cranberry magnetite deposits occur in pre-Cambrian granite-gneiss in a belt extending from 3 miles southeast of Cranberry, N.C., to about 6 miles southwest of Magnetic City, Tenn. The belt forms a curve, elongated to the north, approximately 26 miles in length.

pdf2xml

International Development Research Centre (IDRC) Digital Library (Canada)

Leur croissance a obligé certaines d'entre elles ( Rio de Janeiro, Maceió, Recife ...... gneiss, divers types de migmatites et par des intrusions granitiques isolées. ...... de minéraux micacés ( surtout muscovite et biotite, mais également sericite, ...

Geochemistry of the Bayonplutonic Complex – Western Cameroon ...

African Journals Online (AJOL)

The BayonNeoproterozoic plutonic complex located in Western Cameroon intrudes gneisses of Paleo to Neo Proterozoic age. The complex is composed of gabbro, monzogabbro and monzonites frequently crosscut by trachytic and granitic veins. The primary mineral assemblages of the gabbro and monzogabbro is ...

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

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Earth System Science. Dhruba Mukhopadhyay. Articles written in Journal of Earth System Science. Volume 109 Issue 1 March 2000 pp 22-38. Anasagar gneiss: A folded granitoid pluton in the Phanerozoic South Delhi Fold Belt, central Rajasthan · Dhruba Mukhopadhyay Tapas Bhattacharyya ...

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

This region comprises sedimentary rocks, metasediments, granites and gneisses that bear characteristic GR dose values and U/Th ratios corresponding with their specific geological history. A-type Malani granites and rhyolitic derivates, also referred as high heat production granites, show distinct differences as compared to ...

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African Journals Online (AJOL)

collision models, between the Congo Craton and an active continental block in the .... Description of the Bouguer anomaly ... dients, which occur over these basic intrusive rocks, ... Profile B: Fig. 5 a: Residual Anomaly Profile. African Formations; 5: gneiss forma- ..... wedged against the Pan African plate (Kennedy, 1964).

U–Pb zircon and biostratigraphic data of high‐pressure/ low‐temperature metamorphic rocks of the Talea Ori : tracking the Paleotethys suture in central Crete, Greece

NARCIS (Netherlands)

Zulauf, G.; Dörr, W.; Krahl, J.; Lahaye, Y.; Chatzaras, V.; Xypolias, P.

2016-01-01

Inherited deformation microfabrics of detrital quartz grains and U–Pb (Laser ablation (LA)-ICPMS and ID TIMS) ages of detrital zircons separated from the Phyllite–Quartzite Unit s.l. of the Talea Ori, central Crete, suggest strikingly different source rocks. Albite gneiss of the lower Rogdia Beds

Tibetan garnet records early Eocene initiation of thickening in the Himalaya

DEFF Research Database (Denmark)

Smit, Matthijs Arjen; Hacker, Bradley; Lee, Jeffrey

2014-01-01

Tectonic reconstructions of the Himalayan orogeny depend on the age at which crustal thickening commenced. To investigate this age, we analyzed garnet from middle crustal rocks exposed in the north Himalayan Mabja and Kangmar gneiss domes of Tibet using Lu-Hf geochronology. Garnet yielded Lu-Hf a...

Age of origin of the polymetamorphosed Copperton Formation, Namaqua-Natal Province, determined by single grain zircon Pb-Pb dating

International Nuclear Information System (INIS)

Cornell, D.H.; Griffin, G.; Kroener, A.; Humphreys, H.

1990-01-01

The Copperton Formation of the Areachap Group in the Northern Cape Province is a strongly metamorphosed, predominantly metavolcanic unit which contains several massive sulphide deposits. Previous work on this unit has established a complex metamorphic history, the four main phases of which are fairly well dated by a combination of methods; however, the age of origin is still poorly constrained. Zircons extracted from the Smouspan Gneiss Member of the Copperton formation are euhedral and show a crystal habit which indicates an igneous and probably volcanic origin, with no discernable metamorphic component. Whole-grain thermal evaporation on four such zircon grains yielded a precise set of 207 Pb/ 206 Pb data which establishes a 1 285 ± 14 Ma age for the origin of the Smouspan Gneiss and Copperton Formation. Indications of a ∼1 600 Ma age from other parts of the Areachap Group should be treated with caution until more reliable data are obtained. 9 figs., 2 tabs., 29 refs

Placer mineral resources of Tamil Nadu

International Nuclear Information System (INIS)

Anil Kumar, V.

2016-01-01

Tamil Nadu, the southernmost state with second longest coast line in India has many placer heavy mineral deposits. These deposits contain economically important light heavy minerals like ilmenite, rutile, leucoxene, monazite, zircon, garnet, sillimanite, kyanite and non-economic minerals like pyroxenes, amphiboles and magnetite along with associated accessory minerals like staurolite, epidote, spinel, biotite and tourmaline. Geologically, granulitic rocks, principally Khondalites (garnet-sillimanite-graphite gneisses), charnockites and granitic gneisses bordered by sedimentary rocks are exposed along the eastern coastal plains of the Tamil Nadu. The principal highland areas, as for example, Shavaroys, Nilgiris, Palni-Kodaikanal Hills and Cardomom hills consists primarily of Charnockites. The margins of highland show a gradation into less metamorphosed rocks generally of amphibolite facies. The khondalites are found south of Kodaikanal massif. Anorthosites and layered mafic complexes occur at Sittampundi, Kadavur areas. Alkaline rocks and carbonatites are prominent at Simalpatti, Sevattur and Sivamalai. Coastal sedimentaries include, Gondwanas, Cretaceous, Tertiary and Quaternary rocks along with lateritic soils and beach sands

Geotechnical evaluation of rocks and soils in Catoca kimberlitic mining complex (Angola

Directory of Open Access Journals (Sweden)

Domingos M. Dos Santos Neves-Margarida

2012-10-01

Full Text Available Landslides and rock sliding occur very frequently in the mining area of Catoca, located in Angola. Therefore, a physical/mechanical and geotechnical characterization of the massif and the rock matrix was carried out adopting the landslide classifications as proposed by Hutchinson and Varnes. The safety factor was applied based on the structural weakness coefficient (λ; resulting in 0.70 in surface rocks, sandstones and intraformational sands; 0.58 in oversaturated eluvial gneiss; 0.50 in cracked gneiss and 0.47 in the ore compound of weathered, moist kimberlitic porphyric and weathered porphyric kimberlite. These results indicate the low strength of the massif and the need to reformulate the activities in the mine and the construction of more stable slopes. It could also be observed that deformation of rocks in the slopes and the cuts in the Catoca mine is conditioned by the movement of underground water within the rock massif itself.

3.3 Ga SHRIMP U-Pb zircon age of a felsic metavolcanic rock from the Mundo Novo greenstone belt in the São Francisco craton, Bahia (NE Brazil)

Science.gov (United States)

Peucat, J. J.; Mascarenhas, J. F.; Barbosa, J. S. F.; de Souza, S. L.; Marinho, M. M.; Fanning, C. M.; Leite, C. M. M.

2002-07-01

Felsic metavolcanics associated with supracrustal rocks provide U-Pb zircon and Sm-Nd TDM ages of approximately 3.3 Ga, which establish an Archean age of the Mundo Novo greenstone belt. A granodioritic gneiss from the Mairi complex, located on the eastern boundary of the Mundo Novo greenstone belt, exhibits a zircon evaporation minimum age of 3.04 Ga and a Nd model age of 3.2 Ga. These results constrain the occurrence of at least three major geological units in this area: the Archean Mundo Novo greenstone belt, the Archean Mairi gneisses, and the adjoining Paleoproterozoic (<2.1 Ga) Jacobina sedimentary basin. The Jacobina basin follows the same trend as the Archean structure, extending southward to the Contendas-Mirante belt, in which a similar Archean-Paleoproterozoic association appears. We postulate that during the Paleoproterozoic in the eastern margin of the Gavião block, these Archean greenstone belts constituted a zone of weakness along which a late-stage orogenic sedimentary basin developed.

New Sm/Nd and U/Pb geochronological constraints of the Archean to neoproterozoic evolution of the Amparo basement complex of the Central Ribeira Belt, Southeastern Brazil

International Nuclear Information System (INIS)

Fetter, A.H.; Hackspacher, P.C.; Ebbert, H.D; Dantas, E.L; Costa, A.C.D. da

2001-01-01

The Amparo Basement Complex is a distinctive collage of migmatitic tronjhemitetonalite- granodiorite (TTG) orthogneisses that represents the older basement exposures within the Central Ribeira Belt, a Late Neoproterozoic (ca. 600 Ma) collisional belt in southeastern Brazil. These basement gneisses are overlain by Mesoproterozoic to Neoproterozoic supracrustal sequences, and intruded by Neoproterozoic collisional granitoids. Pioneering Rb/Sr, Pb/Pb and K/Ar geochronological studies of the Amparo Complex, e.g. (Wernick et al., 1981; Wernick and Oliveira, 1986; Arthur, 1988; Tassinari, 1988; Campos Neto, 1991) provided some initial insights into the antiquity and geologic evolution of the complex, but little about the crustal evolution of the constituent gneisses. Furthermore, the susceptibility of these systems to partial isotopic resetting, left some doubt about the timing and true number of geologic events recorded by these polydeformed rocks. Recent Sm/Nd whole rock (Dantas et al., 2000) and new U/Pb single crystal zircon and monazite data obtained from the Amparo Complex, however, now furnish information on the crustal growth history of the basement and provide precise age constraints on the timing of events related to the geologic evolution of the complex. Based on these new data, it appears that the oldest rocks within the complex are polymigmatized tronjhemitic gneisses located near the town of Amparo. The oldest phase of this migmatite yields a U/Pb zircon age of 3,024 +/- 9 Ma. Sm/Nd data from this locale yields a Nd T(DM) model age of 3.28 Ga suggesting that the genesis of this crustal unit involved some input from yet older crust. Data from banded tonalitic gneisses collected ca. 50 km south of Amparo indicate that subsequent Archean crustal growth around the older core occurred around 2.77 Ga (U/Pb zircon age of 2,772 +/- 26 Ma. A Nd T(DM) model age of 3.02 Ga obtained from these tonalites also indicate enrichment from older crustal sources during their

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...

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

African Journals Online (AJOL)

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

Petrology of the Northern Adula Region, Switzerland (with particular reference to the Glaucophane-Bearing Rocks)

NARCIS (Netherlands)

Plas, van der L.

1959-01-01

Geological and petrographical investigations were carried out in the northern part of the so-called Adula Nappe, one of the deepest Pennine nappes. The area under consideration lies in the SE of Switzerland, near Vals, S of Ilanz. This area is situated north of the Lepontinic gneiss-region, the

Mafic dykes at the southwestern margin of Eastern Ghats belt ...

Indian Academy of Sciences (India)

Ghats belt: Evidence of rifting and collision. S Bhattacharya. 1,∗ ... 1.3 Ga, which may have been initiated by intra-plate volcanism. 1. Introduction ... tively, is described as a compressional orogen. Keywords. ... charnockite gneiss, around Naraseraopet, AP (b) Thin mafic ... Sometimes orthopyroxene also occurs at margin of.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Earth System Science. Bibhuti Gogoi. Articles written in Journal of Earth System Science. Volume 123 Issue 5 July 2014 pp 959-987. Geochemical constraints on the evolution of mafic and felsic rocks in the Bathani volcanic and volcano-sedimentary sequence of Chotanagpur Granite Gneiss ...

Title Qualitative stability assessment of cut slopes along the national ...

Indian Academy of Sciences (India)

64

Qualitative stability assessment of cut slopes along the national highway- 05 around Jhakri area, .... The rock types in the area are augen migmatite, biotite gneiss, quartz ..... slopes using quantified method (Sonmez and Ulusay 1999, 2002). Finally a .... through numerical simulation is suggested by many researchers. 1. 2. 3.

Geochemistry and petrology of mafic Proterozoic and Permian dykes on Bornholm, Denmark:

DEFF Research Database (Denmark)

Holm, Paul Martin; Pedersen, Lise E.; Højsteeen, Birte

2010-01-01

More than 250 dykes cut the mid Proterozoic basement gneisses and granites of Bornholm. Most trend between NNW and NNE, whereas a few trend NE and NW. Field, geochemical and petrological evidence suggest that the dyke intrusions occurred as four distinct events at around 1326 Ma (Kelseaa dyke...

Petrology and geochemistry of a boninite dyke from the western ...

Indian Academy of Sciences (India)

26

extensive extraction of tholeiitic melt (Crawford et al. 1989). .... within Amgaon gneisses of western Bastar craton (Figure 1). This part of ..... higher CaO are the characteristics of the nearby Dongargarh boninite from the same Bastar. 260 ..... Purushottam D and Linga D 2016 Geochemical characteristics of gold bearing. 448.

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.)

Geochronological dating in polycyclic rocks: alternative interpretation to data from Serido (RN-PB) Brazil

International Nuclear Information System (INIS)

McReath, I.; Sa, E.F.J. de

1979-01-01

Recent studies revealed a polycyclic history of deformation and metamorphism in the Serido, region, with a minimum of three regionally important events (F 1-3 ) the earliest of which is restricted to gneisses interpreted as basement (Caico Group). A relation between these phases and a complex series of granitic rocks is possible, the oldest generations (G 1-2 ) being gneissified. K/Ar ages normally reflect the regional uplift and other events toward the close of the Brasilian orogeny. Some of the older dates in the 700 - 1.400 m.y. range encountered in intrusives and metamophites may be due to parcial overprinting of earlier events. Reference Rb/Sr isochrons for widely dispersed G 3 granites need checking, but give creditable Brasilian ages. Rb/Sr studies of Serido Group metasediments show disequilibrium with a dispersion of points between a reference Brasilian isochron and one at 2.0 b.y. Parcial rejuvenation during the Brasilian orogeny of older rock series seems the best current explanation, although locally metasomatism may have had some influence, while some effect of initial disequilibrium may also be present. Gneisses yield Rb/Sr isochron ages of ca.2.7 and 1.9 b.y. Unpublished diagrams (B.B.B. Neves, written comm.) show a similar dispersion to that encountered for the Serido Group, and this might be explained in a similar fashion. It should be noted, however, that the distinction between high-grade cover, instrusive orthogneisses and basement is difficult, and that in these analyses some of the former gneisses could have been included. The possible existence of some event at ca.1.1 b.y needs verification. (author) [pt

Cordilleran metamorphic core complexes and their uranium favorability. Final report

International Nuclear Information System (INIS)

Coney, P.J.; Reynolds, S.J.

1980-11-01

The objective of this report is to provide a descriptive body of knowledge on Cordilleran metamorphic core complexes including their lithologic and structural characteristics, their distribution within the Cordillera, and their evolutionary history and tectonic setting. The occurrence of uranium in the context of possibility for uranium concentration is also examined. Chapter 1 is an overview of Cordilleran metamorphic core complexes which describes their physical characteristics, tectonic setting and geologic history. This overview is accompanied by a tectonic map. Chapter 2 is a discussion of the mantled gneiss dome concept. The purpose of including this work is to provide a basic history of this concept and to describe the characteristics and distribution of gneiss domes throughout the world to enable one to compare and contrast them with the metamorphic core complexes as discussed in this report. Some gneiss domes are known producers of uranium (as are also some core complexes). Chapter 3 is an examination of the effects of the core complex process on adjacent sedimentary and volcanic cover terranes. Also included is a discussion of the kinematic significance of these cover terranes as they are related to process within the cores of the complexes. Some of the cover terranes have uranium prospects in them. Chapter 4 is a detailed discussion of uranium in Cordilleran metamorphic core complexes and includes the conceptual basis for the various types of occurrences and the processes that might favor concentration of uranium. The report is supported by a 5-part Appendix. The majority of the core complexes discussed in this report either do not appear or are not recognizable on existing published geologic maps

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

Science.gov (United States)

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

2011-01-01

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

Strike-slip linked core complexes: A new kinematic model of basement rock exhumation in a crustal-scale fault system

Science.gov (United States)

Meyer, Sven Erik; Passchier, Cees; Abu-Alam, Tamer; Stüwe, Kurt

2014-05-01

Metamorphic core complexes usually develop as extensional features during continental crustal thinning, such as the Basin and Range and the Aegean Terrane. The Najd fault system in Saudi Arabia is a 2000 km-long and 400 km-wide complex network of crustal-scale strike-slip shear zones in a Neoproterozoic collision zone. Locally, the anastomosing shear zones lead to exhumation of lower crustal segments and represent a new kinematic model for the development of core complexes. We report on two such structures: the Qazaz complex in Saudi Arabia and the Hafafit complex in Egypt. The 15 km-wide Qazaz complex is a triangular dome of gently dipping mylonitic foliations within the 140 km-long sinistral strike-slip Qazaz mylonite zone. The gneissic dome consists of high-grade rocks, surrounded by low-grade metasediments and metavolcanics. The main SE-trending strike-slip Qazaz shear zone splits southwards into two branches around the gneiss dome: the western branch is continuous with the shallow dipping mylonites of the dome core, without overprinting, and changes by more than 90 degrees from a NS-trending strike-slip zone to an EW-trending 40 degree south-dipping detachment that bounds the gneiss dome to the south. The eastern SE-trending sinistral strike-slip shear zone branch is slightly younger and transects the central dome fabrics. The gneiss dome appears to have formed along a jog in the strike-slip shear zone during 40 km of horizontal strike-slip motion, which caused local exhumation of lower crustal rocks by 25 km along the detachment. The eastern shear zone branch formed later during exhumation, transacted the gneiss dome and offset the two parts by another 70 km. The Hafafit core complex in Egypt is of similar shape and size to the Qazaz structure, but forms the northern termination of a sinistral strike-slip zone that is at least 100 km in length. This zone may continue into Saudi Arabia as the Ajjaj shear zone for another 100 km. The NW trending strike slip

Detrital Zircons From the Jack Hills and Mount Narryer, Western Australia: Geochronological, Morphological, and Geochemical Evidence for Diverse >4000 Ma Source Rocks

Science.gov (United States)

Crowley, J. L.; Myers, J. S.; Sylvester, P. J.; Cox, R. A.

2004-05-01

Detrital zircons from all major clastic units in the Jack Hills and Mount Narryer metasedimentary belts, Western Australia, were analyzed for morphology, internal zoning, inclusion mineralogy, age, and trace element concentrations (latter two obtained by laser-ablation microprobe ICPMS). The results show that zircons were derived from a wide diversity of rocks, including previously described, >4000 Ma grains that are older than any known terrestrial rocks. In three metaconglomerate samples from the western Jack Hills, 4200-3800 Ma zircons ("old grains") comprise 14% of the population, 3800-3600 Ma grains form only 2%, and 3550-3250 Ma zircons ("young grains") are dominant with a significant peak at 3380 Ma. Old and young grains are interpreted as being from similar rock types because they are indistinguishable in trace element concentrations, size (several hundred microns), morphology (subequant, typically fragmented), internal zoning (typically both oscillatory and sector), and U concentration (50-200 ppm). Many of these properties suggest an intermediate plutonic source, whereas an evolved granitic source was previously interpreted from rare-earth element and oxygen isotope data. Detrital zircons in quartzites and metaconglomerates at Mount Narryer differ significantly from zircons from the western Jack Hills. Old grains comprise only 3% (most of which are 4200-4100 Ma), 3800-3600 Ma zircons form 31%, and there are peaks at 3650, 3600, and 3500 Ma. Old and young grains have similar properties that suggest granitic sources, such as elongate prismatic morphology, oscillatory zoning, high U concentrations (100-600 ppm), and xenotime and monazite inclusions. Trace element concentrations are broadly similar to those in Jack Hills zircons, with notable exceptions being generally higher U, smaller Ce and Eu anomalies, and lower Nb/Ta. It is considered unlikely that Jack Hills zircons were derived from granitic gneisses that surround the metasedimentary belts because

Journal of Applied Science, Engineering and Technology - Vol 3, No ...

African Journals Online (AJOL)

Some geotechnical properties of a cement-stabilized granite-gneiss-derived lateritic soil from Ile-Ife, Southwestern Nigeria · EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. GO Adeyemi, RA Owosanya, FC Anokwu, 8-12. http://dx.doi.org/10.4314/jaset.v3i2.38243 ...

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

NARCIS (Netherlands)

Maar, P.A. van der

1981-01-01

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

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

NARCIS (Netherlands)

van der Maar, P.A.

1981-01-01

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

Provenance of sandstone on the western flank of Anambra Basin ...

African Journals Online (AJOL)

Petrographic and heavy mineral studies were carried out on clastic deposits that crop out in Ikpeshi, Auchi and Fugar localities in order to determine the provenance of the ... The heavy mineral suites and the petrographic signatures of the sandstones suggest derivation mainly from acid igneous rocks, gneisses and older ...

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

African Journals Online (AJOL)

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

An Overview of the Soutpansberg Sedimentary and Volcanic Rocks

Directory of Open Access Journals (Sweden)

J.W. Bristow

1986-11-01

Full Text Available Volcanic and sedimentary rocks occupy a faulted graben within the previously uplifted and eroded high-grade gneiss terrain of the Limpopo Mobile Belt. The rocks comprise the Soutpansberg Group and represent an important sequence of Proterozoic rocks. Their general geology and volcanology is summarised in this paper.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Classical field method, conic sections method and Ramsay's fold classification method were applied to (i) have the general orientation of folds, (ii) analyze the fold shapes and (iii) classify the geometry of the folded bands. Fold axes in banded amphibole gneiss plunge moderately (<15◦) towards the NNE or SSW.

Compositional differences between roof and floor rocks of the Skaergaard Intrusion

DEFF Research Database (Denmark)

Salmonsen, Lars Peter; Tegner, Christian; Barfod, Gry

2014-01-01

of stoped gneissic blocks. Our new Sr and Nd data of the Upper Border Series exclude this as a first order process as has been shown before. Mixing models suggest that the Layered and Upper Border Series assimilated less than 3 percent Precambrian host gneiss. Furthermore, no correlation exists between...

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

African Journals Online (AJOL)

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

Investigation of the subsurface features of the basement complex of ...

African Journals Online (AJOL)

3D seismic reflection survey was recently carried out within the Zaria area of the basement complex of northern Nigeria, in order to investigate the complexity of the subsurface features within the basement. The geology of the survey area was characterized by gneisses and low grade meta-sedimentary rocks that form the ...

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Granulite facies metamorphism of the complex initiated with breaking down of biotite to produce garnet and cordierite in the pelitic gneisses. Geothermobarometric calculations indicate metamorphic conditions of 720°C/6.2 kbar, followed by a retrograde (687°C/4.9 kbar) to very late retro-grade stages of metamorphism ...

U-Pb GEOCHRONOLOGY OF METASEDIMENTARY SCHISTS IN ...

African Journals Online (AJOL)

PROF EKWUEME

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

Migmatization and low-pressure overprinting metamorphism as record of two pre-Cretaceous tectonic episodes in the Santander Massif of the Andean basement in northern Colombia (NW South America)

Science.gov (United States)

Zuluaga, C. A.; Amaya, S.; Urueña, C.; Bernet, M.

2017-03-01

The core of the Santander Massif in the northern Andes of Colombia is dominated by migmatitic gneisses with a 7.5 kbar. Lithologies are overprinted by low-pressure metamorphism, related to extensive Jurassic intrusions and linked with growth of cordierite and equilibration of low-pressure mineral assemblages, recorded metamorphic conditions are Pangaea.

PROCESS TEST WORK FOR THE RECOVERY OF TANTALITE ...

African Journals Online (AJOL)

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

The Dora-Maira Unit (Italian Cottian Alps): a reservoir of ornamental stones locally and worldwide employed since Roman age

Science.gov (United States)

Borghi, Alessandro; Cadoppi, Paola; Antonella Dino, Giovanna

2015-04-01

The Dora-Maira is a geological unit belonging to the Penninic Domain of the Western Alps (NW Italy), which covers over 1000 km2 from the Susa to the Maira valleys, in the inner part of the Cottian Alps. It consists of different superposed complexes made of micaschists, fine-grained gneisses, quartzites, impure and dolomitic marbles, metabasites and various types of orthogneisses deriving from metamorphic transformation, during alpine orogeny, of a Palaeozoic upper continental crust and its Mesozoic carbonate cover. Thanks to the presence of different varieties of rocks, the Dora-Maira Unit can be considered as a reservoir of ornamental stones, locally employed, since Roman age, for military and religious buildings. Furthermore, these materials were used in Piedmont region for the construction of important historical palaces (17th and 18th centuries). Several varieties of gneisses, quartzites and marbles, exploited in the past and up to now, come from the Paleozoic basement. The most famous variety of gneiss is the so called "Luserna stone", a leucocratic gneiss characterized by a mylonitic fabric deriving from highly differentiated granitoids of Permian age. The first traces of Luserna Stone exploitation arise to the medieval age in the Pellice Valley). This material was widely employed in Turin, from Savoia kingdom period up to know. The very peculiar and precious application of Luserna stone were: Royal Palace and Venaria Reale Palace, Mole Antonelliana. Recently, it has been employed for the construction of Turin Metro stations (launched in 2006). Other varieties of orthogneisses, not yet exploited, are: Borgone and Vaie Stones, Villarfocchiardo and Cumiana Stones. They were used for the realization of the columns characterising the façade of several churches in Turin and in the piers of different bridges over the Po River. Another gneiss variety, with dioritic composition, is the Malanaggio Stone employed in the Fenestrelle Fortress. As for the palaeozoic

Application of the Rb-Sr, Pb-Pb and Sm-Nd systems on the Salobe 3A polymetallic deposit, Carajas Mineral Province, Para, Brazil; Aplicacao dos sistemas Rb-Sr, Pb-Pb e Sm-Nd do deposito polimetalico do Salobo 3A, Provincia Mineral de Carajas, Para

Energy Technology Data Exchange (ETDEWEB)

Mellito, Katia Maria

1998-07-01

The Salobo 3A polymetallic Cu (Au-Mo-Ag) deposit, located in the northern part of the Carajas Mineral Province, Para, consists of a metavolcano-sedimentary sequence represented by iron formation, amphibolite, schist and quartzite of the Igarape Salobo Group. This rock sequence rest uncomformably on the gneissic basement of the Xingu Complex. The copper mineralization hosted by iron formation consists of bornite-chalcocite and bornite-chalcopyrite disseminations associated with magnetite. The geochronological data determined through the application of the Rb-Sr, Sm-Nd and Pb-Pb methods, contribute to characterize the complex evolution of both the geological setting and the cupriferous mineralization of the Salobo deposit. The 3.11-2.92 Ga interval (T{sub DM}, Sm-Nd, whole rock) represents the age of the igneous protholith of the gneiss. The {epsilon}{sub Nd} values calculated for the time of the gneiss formation (2859 Ma) vary between +1.02 and -1.08, and indicate a short period between the mantle-crust differentiation epoch and the gneiss formation. Moreover, the {epsilon}{sub Nd} parameter suggest a mantle source with late crustal contamination. The application of the leaching technique allows a gradual extraction of Pb at each leaching step and it was applied to chalcocite and magnetite. The 2762 {+-} 180 Ma and 2776 {+-} 240 Ma ages determined on those minerals are interpreted to be close to the epoch of the formation of the copper mineralization with Uu and Th enrichment and of the iron formation deposition, respectively, in a conventional setting. The leaching technique was also applied to tourmaline from gneiss and quartzite, and the age near to 2400 Ma was attributed to its formation. The random variability of the Pb isotope compositions of the tourmaline together with its petrographic characteristics suggest the boron source is not associated with the metassedimentary rocks of the Igarape Salobo Group. The Sm-Nd mineral isochron attributed to schists

Core drilling of deep drillhole OL-KR57 at Olkiluoto in Eurajoki 2011-2012

International Nuclear Information System (INIS)

Toropainen, V.

2012-07-01

As a part of the confirming site investigations at Olkiluoto, Suomen Malmi Oy (Smoy) core drilled 401.71 m and 45.01 m deep drillholes, OL-KR57 and OL-KR57B, at Olkiluoto in September 2011 - January 2012. The diameter of the drillholes is 75.7 mm. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the returning and drilling water were recorded. The drill rig was computer controlled and the computer recorded drilling parameters during drilling. The objective of the measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volumes of the used drilling, flushing and washing water were 350 m3 and 30 m3 in the drillholes OL-KR57 and OL-KR57B, respectively. The measured volumes of the returning water in the drillholes were 328 m 3 and 16.8 m 3 , respectively. The deviations of the drillholes were measured with the deviation measuring instruments EMS and Gyro. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength was 123.9 MPa, the average Young's Modulus was 42.6 GPa and the average Poisson's ratio was 0.23. The main rock types are veined and diatexitic gneisses, mica gneiss and tonaliticgranodioritic- granitic gneiss. The average fracture frequency is 2.5 pcs/m in drillhole OL-KR57 and 3.3 pcs/m in the drillhole OL-KR57B. The average RQD values are 95.0 % and 93.0 %. Seven separate fractured zones were interpreted from OL-KR57 and three fractured zones from OL-KR57B. (orig.)

The Alto Moxoto Terrain in Eastern Paraiba ('Caldas Brandao Massif')

International Nuclear Information System (INIS)

Neves, Benjamim Bley de Brito; Campos Neto, Mario da Costa; Souza, Solange Lucena de; Schmus, William Randall Van; Fernandes, Tania Maria Gomes

2001-01-01

The Alto Moxoto Terrane (TAM), at the east of Paraiba State is mostly composed of sheared ortho gneisses, porphyritic granodioritic gneisses and it bears an imbricated sheet of Al-rich (garnet-biotite-sillimanite) gneisses, deeply affected by migmatization phenomena. This litho-structural assemblage is drawing a regional asymmetric anti formal structure, with its axial zone running parallel to the B R-230 highway (E-W trending). It is limited in both, north (Alto Pajeu terrane) and south (Rio Capibaribe terrane) sides by important shear zones, which are feather faults connected with the development of the Pernambuco lineament, to the southwest. The adopted designation of 'terrane' is based upon its singular geological features, in terms of lithological and structural characteristics, Paleoproterozoic in age and sharp limits with the different confining terranes. TAM is here considered as a mega-fragment of the Atlantica Super continent, that was built up by the Paleoproterozoic Collage ('Transamazonian') and that was preserved in the framework of West Gondwana (Brasiliano/Pan African Collage) as a 'terrane'. This terrane shows conspicuous continuity to the far interior of the province, to the southwestern part of Pernambuco State, and so doing, it demonstrates that the former designation of 'Caldas Brandao Massif must be ruled out, as obsolete for many reasons. Geochronological determinations using Rb-Sr, Sm-Nd and U-Pb methods confirm the Paleoproterozoic age of this terrane, with the presence of some Archean protoliths as well as the various degrees of structural reworking and isotopic reseting promoted by the Brasiliano Cycle. This cycle was responsible for some intrusive granites, for most of the general geological features, like usual informal limits and even the present shape of the TAM, a typical reworked 'basement inlier'. (author)

Core drilling of deep drillhole OL-KR57 at Olkiluoto in Eurajoki 2011-2012

Energy Technology Data Exchange (ETDEWEB)

Toropainen, V. [Suomen Malmi Oy, Espoo (Finland)

2012-07-15

As a part of the confirming site investigations at Olkiluoto, Suomen Malmi Oy (Smoy) core drilled 401.71 m and 45.01 m deep drillholes, OL-KR57 and OL-KR57B, at Olkiluoto in September 2011 - January 2012. The diameter of the drillholes is 75.7 mm. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the returning and drilling water were recorded. The drill rig was computer controlled and the computer recorded drilling parameters during drilling. The objective of the measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volumes of the used drilling, flushing and washing water were 350 m3 and 30 m3 in the drillholes OL-KR57 and OL-KR57B, respectively. The measured volumes of the returning water in the drillholes were 328 m{sup 3} and 16.8 m{sup 3}, respectively. The deviations of the drillholes were measured with the deviation measuring instruments EMS and Gyro. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength was 123.9 MPa, the average Young's Modulus was 42.6 GPa and the average Poisson's ratio was 0.23. The main rock types are veined and diatexitic gneisses, mica gneiss and tonaliticgranodioritic- granitic gneiss. The average fracture frequency is 2.5 pcs/m in drillhole OL-KR57 and 3.3 pcs/m in the drillhole OL-KR57B. The average RQD values are 95.0 % and 93.0 %. Seven separate fractured zones were interpreted from OL-KR57 and three fractured zones from OL-KR57B. (orig.)

Sorption and diffusion of cobalt, strontium, cesium and americium in natural fissure surfaces and drill core cups studied by autoradiography, 1

International Nuclear Information System (INIS)

Pinnioja, S.; Kaemaeraeinen, E.L.; Jaakkola, T.; Siitari, M.; Muuronen, S.; Lindberg, A.

1985-06-01

A method based on autoradiography was developed to determine the diffusion of radionuclides into the rock matrix. To investigate the diffusion the samples, which has been in contact with radioactive tracer solution up to 6 months, were splitted by sawing. From the autoradiograms of the cross sections the penetration depths of radionuclides were determined and the apparent diffusion coefficient Dsup(a) calculated. The filled and unfilled natural fissure surfaces chosen to this study were bars of drilling cores and drill core cups of tonalite, mica gneiss and rapakivi granite. After contact time of 3 months the highest penetration depths of cesium were observed for natural fissure surface sample of rapakivi granite up to 2.5 mm and of mica gneiss up to 3.7 mm. For strontium the penetration depths of 6 mm and 11 mm for unfilled and filled natural fissure samples of rapakivi granite were found. Dsup(a)-values for cesium varied between 1.5 x 10 -15 and 3.2 x 10 -14 , for strontium between 3.5 x 10 -14 and 2.1 x 10 -13 m 2 /s. D-value obtained for cobalt (drill core cup sample, tonalite) was 5.4 x 10 -17 m 2 /s. 241 Am was only sorbed on the surface of the sample and thus no apparent diffusion coefficient could be calculated. Filling materials, chlorite and secondary minerals in tonalite and rapakivi granite increased diffusion into the mother rock. Radionuclides were sorbed both into the filling material and through fillers into the rock matrix. Cs and Sr penetrated though calcite filling material in mica gneiss into the mother rock. Calcite didn't influence on diffusion of radionuclides. Penetration depths of Cs and Sr were about the same for filled and unfilled samples

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

Science.gov (United States)

Richards, Lawrence Edward

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

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

Science.gov (United States)

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

2018-03-01

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

Using the magmatic record to constrain the growth of continental crust-The Eoarchean zircon Hf record of Greenland

Science.gov (United States)

Fisher, Christopher M.; Vervoort, Jeffrey D.

2018-04-01

Southern West Greenland contains some of the best-studied and best-preserved magmatic Eoarchean rocks on Earth, and these provide an excellent vantage point from which to view long-standing questions regarding the growth of the earliest continental crust. In order to address the questions surrounding early crustal growth and complementary mantle depletion, we present Laser Ablation Split Stream (LASS) analyses of the U-Pb and Hf isotope compositions of zircon from eleven samples of the least-altered meta-igneous rocks from the Itsaq (Amîtsoq) Gneisses of the Isukasia and Nuuk regions of southern West Greenland. This analytical technique allows a less ambiguous approach to determining the age and Hf isotope composition of complicated zircon. Results corroborate previous findings that Eoarchean zircon from the Itsaq Gneiss (∼3.85 Ga to ∼3.63 Ga) were derived from a broadly chondritic source. In contrast to the Sm-Nd whole rock isotope record for southern West Greenland, the zircon Lu-Hf isotope record provides no evidence for early mantle depletion, nor does it suggest the presence of crust older than ∼3.85 Ga in Greenland. Utilizing LASS U-Pb and Hf data from the Greenland zircons studied here, we demonstrate the importance of focusing on the magmatic (rather than detrital) zircon record to more confidently understand early crustal growth and mantle depletion. We compare the Greenland Hf isotope data with other Eoarchean magmatic complexes such as the Acasta Gneiss Complex, Nuvvuagittuq greenstone belt, and the gneissic complexes of southern Africa, and all lack zircons with suprachondritic Hf isotope compositions. In total, these data suggest only a very modest volume of crust was produced during (or survived from) the Hadean and earliest Eoarchean. There remains no record of planet-scale early Earth mantle depletion in the Hf isotope record prior to 3.8 Ga.

Scintilometry in pegmatitcs of the region of Cristais

International Nuclear Information System (INIS)

Marinho, J.M.L.

1981-01-01

The objective of this paper is to show the use of cintilometry in the delimitation of pegmatites of the region of Cristais, northeast of Ceara State. It is a part of the Project Litium-Ce and it receives a financial aid from FINEP. Four on-the-spot surveys have been made with a rectangules 5 x 15 m mesh on heterogeneous and little or not exploited pegmatite revealed on the surface by a residual mantle of milky quartz and slabs of muscovite. A cintilometer Saphyro Srat, model SPP-2 was used for readings in counts per second (c/s). Three of the surveys were performed on medium-sized pegmatites ( 5 - 15 m of width) and show that their measurement are in the 15-60 c/s range while those on the host rock (biotite-gneiss) vary from 70 to 130 c/s. One of the surveys was made over a pegmatitic dyke, with 1,5 meter width, in a sand-covered area of 1 meter, and it shows that the portion of the pegmatite may hardly by suggested, pointing out only at the southwest corner of the area the presence of biotite-gneiss through the increase in the readings. The cintilometry may be used on a more detailed scale in areas with superficial signs of the presence of pegmatites, in order to determine their position and to guide a superficial prospection. The low value reading (15 - 60 c/s) on the pegmatites are bound to be related to the absence of U and Th minerals and to the presence of a nucleus of quartz and albite, replacing largely the potassium feldspars. The reading in the 70 - 130 c/s range on the biotite-gneiss should be linked with the presence in their mineralogic composition of biotite muscovite, potassium feldspars and zircon. A sandy corer disguises the anomalies. (author) [pt

Browse Title Index

African Journals Online (AJOL)

Items 101 - 150 of 228 ... Vol 5, No 1 (2007), Laboratory modelling of the electrical resistivity response of Near-surface geological contacts, Abstract. H O Ogundipe, A I Idornigie, M O Olorunfemi. Vol 9, No 1 (2011), Lateritic weathering of granite-gneiss in Obudu Plateau, south eastern Nigeria, Abstract PDF. FA Ushie, OL Anike.

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

Bedrock Model of the Syyry area

International Nuclear Information System (INIS)

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

1993-09-01

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

Sorption of iodine neptunium, technetium, thorium and uranium on rocks and minerals

International Nuclear Information System (INIS)

Koskinen, A.; Alaluusua, M.; Pinnioja, S.; Jaakkola, T.; Lindberg, A.

1985-12-01

Sorption of Tc, I, Th, U and Np were studied using the radionuclides Tc-99, I-125, Th-234, U-233 and Np-237. Samples were selected to represent common rocks and minerals in Finnish bedrock. The determination of Ksub(a)-values for Th, U and Np in porphyric granite, granodiorite, tonalite, mica gneiss, biotite, quartz, hornblende, K-feldspar and plagioclase were performed by the autoradiographic method. To complete the earlier studies the Ksub(d)-values of Tc, I, Th, U and Np for crushed tonalite and mica gneiss samples were determined by the batch method. The order of sorption tendency was Ksub(a)(Np) -4 to 4.9x10 -4 m 3 /m 2 , 0.7x10 -4 to 4.2x10 -4 m 3 /m 2 , 650x10 -4 to 1970x10 -4 m 3 /m 2 for Np, U and Th, respectively. For crushed samples the sorption tendency was Ksub(d)(Tc) 3 ml/g being more than three orders of magnitude higher than those of other elements examined

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

International Nuclear Information System (INIS)

Bourguignon, A.

1988-01-01

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

Phosphorus-uranium occurrences of Serrotes Baixos, state of Ceara, Brazil

International Nuclear Information System (INIS)

Favali, J.C.; Muniz Netto, R.; Alcantara e Silva, J.R. de; Oliveira, J.A.D. de

1984-01-01

The Serrotes Baixos phosphorus-uranium showing is located 28 Km south of Santa Quiteria and it is geologically related to the Complexo Tamboril/Santa Quiteria rocks (Transamazonico Cycle) which are represented by a migmatitic-granitic basement and relicts of gneisses and ectinict lithologies (calc-silicated rocks, marbles, etc.). Granodiorite granites and gabbros were formed by plutonic activity occurring in the area. Four folding phases were identified: the first two systems are isoclinal recumbent folds and the last two are subvertical open folds. The faults are mainly transcurrent in nature and were reactivated as gravity faults around the end of the Brasiliano Cycle. The phosphorus-uranium mineralization occurs, at the surface, related to episyenites and, at depth, associated to the brecciated calc-silicated rocks. The mineralization (collophane/apatite with uranium) also occurs as stockworks in marbles and as disseminations in gneisses. The Serrotes Baixos area mineralization appears to be more phosphatic and less uraniferous when compared to the Itataia mine concentrations. It also shows higher thorium values as well. (Author) [pt

The geology of Pedra Verde region, Ceara, Brazil

International Nuclear Information System (INIS)

Korpershoek, H.R.; Mendonca, J.A.C. de; Torquato, J.R.

1979-01-01

The upper Proterozoic Mambira Formation (≥ 1.1000 m.y.) consists of > 1000 m of micaschists with subordinate quartzites and limestones, its upper part, the ''Pedra Verde Phyllite'', is composed of phyelitic slump breccias, with abundance of pyrite. The Mambira formation crops out in the west flank of the tope Anticline, formed by ∼ 600 m of quartzites with sillimanite and/or andalusite (Sao Joaquim Formation), underlain by granitoid gneisses, representing the amphibolite facies. The contact between the Sao Joaquim and Mabira Formations appears to be tectonic. The folding and the metamorphism of the latter date from the Brazilian Cycle, which also affected the gneisses, causing homogeneization of the whole-rock K/Ar ages around 500 m.y. After erosion of some 10.000 m of sedimentary re-activation of the faults, which may already have formed during the deposition of the Mambira Formation resulted in the development of the Ubari Graben. The above formations are unconformably overlain by 300-350 m of subhorizontal Shallow-Marine sandstones belonging to the Serra Grande Formation, of upper silurian to lower devonian ages [pt

Cambrian horses in the field Dionisio Blade (Uruguay)

International Nuclear Information System (INIS)

Bossi, J.; Gaucher, C.

2010-01-01

The shear zone of Sierra Ballena (ZCSB) , is considered the western boundary of an allochthonous block by most writers from the definition of Land Blade Dionisio. The same method to the northern block NE of the city of Thirty- Three was applied. The geological map at 1:100,000 and 1:40,000 photogeology supported by field observations 140 covers an area of ​​3500 km2, allowed 525 Ma to discover that simultaneously produce sinistral megashear N30E, 80E and a mount (horse Amarillo ) with convergence towards the NNW . The megashear consists proto and ultramylonites petrológicamente being identical to ZCSB and age < 532 Ma The horse varies by rock type . On Micaela mica schist are ridden by gneisses and migmatites . In the center, the gneisses are rolled every few inches in W are ultramylonites sub - horizontal . The simultaneity of both phenomena is unexplained by head-on collision of cratons and explained by tangential collision from the SSE with tectonic transport to the north , representing a naturalistic aloctonía test

Sm-Nd isochrone of 2,1 Ga in ores of two samples from Santa Maria Chico Granulite Complex

International Nuclear Information System (INIS)

Hartmann, L.A.

1987-01-01

Sm and Nd isotopes were determined on garnet and plagioclasse from a metapelite and on garnet and clinopyroxene from a mafic gneiss. The age of this metamorphic event in the Santa Maria Chico Granulite Complex is 2.1 Ga. The age of generaion of the protoliths is 2.6 Ga, as determined on total rock samples. (author) [pt

Minor elements, HREE and d18O distribution in UHP garnets from the Dora-Maira massif (western Alps)

Science.gov (United States)

Brunet, F.; Chazot, G.; Vielzeuf, D.; Chopin, C.

2003-04-01

The spatial distribution of minor elements, HREE and δ18O in garnet can be used as a probe of the availability and mobility of those elements and isotopes at the time of crystal growth, provided that the initial record was not significantly modified by intracrystalline diffusion and that growth took place under nearly constant pressure and temperature conditions. Garnets from three different Dora-Maira rock-types have been studied, (1) nearly pure pyrope (GT1) from the magnesian coesite-bearing quartzites, (2) almandine/pyrope dominant garnets (GT2) from jadeite-quartzite veins which crosscut the Mg-quartzite body, (3) almandine/grossular dominant garnets (GT3) from the country-rock gneiss, sampled in the vicinity of the quartzites. In GT1, minor elements are mainly Fe, Na and P. Na and P are incorporated according to a Na^+ + P5+ = Me2+ + Si4+ substitution with P_2O_5 contents up to 2000 to 2500 ppm. HREE concentrations obtained by LA-ICP-MS, vary by 2 orders of magnitude from core to rim. The δ18O ratio (Cameca 1270, Nancy), around 5 ppm (SMOW), is constant within error throughout the analysed crystals. In GT2, the situation is different since HREE concentrations appear remarkably constant within a given crystal and from one crystal to the other. In contrast with GT1, Na in GT2 is partly charge-balanced by yttrium incorporation. The δ18O ratio in GT2 of around 7 ppm is close to that encountered in GT3 (gneiss) between 7 and 8 ppm. In GT3, phosphorus content is close to detection limit (P_2O_5 below 300 ppm). HREE concentrations are highly variable from one crystal to the other and unfortunately, the size of garnet crystals does not allow profiling. Although δ18O ratio in garnet is imposed by the bulk-rock isotopic composition, HREE distribution is dominated by element availability through the fluid composition and/or absence/presence of accessory phases. The decrease in HREE and P concentration from GT1 cores to rims suggest that these elements are

Origin of radon concentration of Csalóka Spring in the Sopron Mountains (West Hungary)

International Nuclear Information System (INIS)

Freiler, Ágnes; Horváth, Ákos; Török, Kálmán; Földes, Tamás

2016-01-01

We examined the Csalóka Spring, which has the highest radon concentration in the Sopron Mountains (West Hungary) (, yearly average of 227 ± 10 Bq L"−"1). The main rock types here are gneiss and micaschist, formed from metamorphism of former granitic and clastic sedimentary rocks respectively. The aim of the study was to find a likely source of the high radon concentration in water. During two periods (2007–2008 and 2012–2013) water samples were taken from the Csalóka Spring to measure its radon concentration (from 153 ± 9 Bq L"−"1 to 291 ± 15 Bq L"−"1). Soil and rock samples were taken within a 10-m radius of the spring from debrish and from a deformed gneiss outcrop 500 m away from the spring. The radium activity concentration of the samples (between 24.3 ± 2.9 Bq kg"−"1 and 145 ± 6.0 Bq kg"−"1) was measured by gamma-spectroscopy, and the specific radon exhalation was determined using radon-chamber measurements (between 1.32 ± 0.5 Bq kg"−"1 and 37.1 ± 2.2 Bq kg"−"1). Based on these results a model calculation was used to determine the maximum potential radon concentration, which the soil or the rock may provide into the water. We showed that the maximum potential radon concentration of these mylonitic gneissic rocks (c_p_o_t = 2020 Bq L"−"1) is about eight times higher than the measured radon concentration in the water. However the maximum potential radon concentration for soils are significantly lower (41.3 Bq L"−"1) Based on measurements of radon exhalation and porosity of rock and soil samples we concluded that the source material can be the gneiss rock around the spring rather than the soil there. We determined the average radon concentration and the time dependence of the radon concentration over these years in the spring water. We obtained a strong negative correlation (−0.94 in period of 2007–2008 and −0.91 in 2012–2013) between precipitation and radon concentration. - Highlights: • A yearly dataset

Subsolidus migmatization in high-grade meta-tuffs (Kurkijärvi, southwest Finland)

Science.gov (United States)

Blom, K. A.

1988-07-01

The phenomenon of migmatization was studied in Precambrian metavolcanic gneisses of calc-alkaline chemistry, outcropping along a prograde amphibolite/granulite facies transition in the West Uusimaa Complex of SW Finland. This paper discusses one of the studied gneiss levels (a garnet-bearing Qtz/Plag/Ksp/Bio-gneiss) which was observed to transsect the metamorphic isograd pattern at almost right angle. The gneiss was studied for structures, whole-rock chemistry (major, trace and REE), mineral content, microtextures, plagioclase anorthite content and fluid inclusions. Data concerning the latter four subjects are presented. Migmatization proved to: (1) have occurred parallel to compositional banding of the rocks; (2) have produced identical leucosome/melanosome/mesosome mineral parageneses; (3) have initiated feldspar/garnet-poikiloblasthesis (and occasionally biotite porphyroblasthesis) in leucosome, and biotite-/garnet-poikiloblasthesis in melanosome; (4) have caused entrapment of unstrained quartz blebs carrying isolated (primary) two-phase pure H 2O fluid inclusions of unique filling degree range in the above-mentioned feldspar- and garnet-poikiloblasts; (5) have occurred post-D 1/pre-D 2, synchronous to amphibolitefacies metamorphism, in the subsolidus regime; (6) have been affected by D 2 in the way of localized mylonitization of the melanosome, and quartz migration (exudation) from adjacent mesosome into leucosome; and (7) have had some control by the biotite content of the original compositionally banded rock. Initial leucosome formation appears to have been controlled by the pre-leucosome biotite content: the recalculated modal biotite content of the leucosome/melanosome combination conspicuously is in the range of 5-20 vol.% of biotite. Final extent of the leucosome shows on its turn a marked correlation with mesosome modal biotite content. Because leucosomes occur carrying a recalculated modal biotite content equalling adjacent mesosome biotite content, a

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

These are asymmetrical folds with alternate flat and steep, locally overturned, limbs and have consistent easterly vergence. F3 folds are upright and coaxial with F2. F4 puckers and large scale warps have E-W to ESE-WNW subvertical axial planes. The gneiss is exposed in the core of an F3 arch on the flat limb of a major ...

Heat production in an Archean crustal profile and implications for heat flow and mobilization of heat-producing elements

Energy Technology Data Exchange (ETDEWEB)

Ashwal, L.D.; Morgan, P.; Kelley, S.A.; Percival, J.A.

1987-10-01

We have measured concentrations of heat producing elements (Th, U, and K) in 58 samples representative of the main lithologies in a 100 km transect of the Superior Province of the Canadian Shield, from the Michipicoten (Wawa) greenstone belt, near Wawa, Ontario, through a domal gneiss terrane of amphibolite grade, to the granulite belt of the Kapuskasing Structural Zone, near Foleyet. (orig./SHOE).

Precambrain Rb-Sr isochron ages from the crystalline complexes of inner Forsblads Fjord, East Greenland fold belt

International Nuclear Information System (INIS)

Rex, D.C.; Gledhill, A.R.; Higgins, A.K.

1977-01-01

Several collections of samples were made from crystalline units in inner Forsblads Fjord in 1974. Results of whole rock Rb-Sr analyses on two of these collections are presented, and give an Archaean age for banded gneisses and a middle Proterozoic age for quartzitic metasediments. These ages confirm the occurence of major Precambrian complexes within the East Greenland Caledonian fold belt. (author)

Neoproterozoic metamorphic events in the kekem area (central ...

African Journals Online (AJOL)

2009-06-11

Jun 11, 2009 ... 4-3-1. Metasedimentary rocks. Representative major and trace element compositions of metasediments are given in Table 6. These rock types define a chemical trend parallel to that of average shales. (Fig 5), but with a slightly lower Al2O3/SiO2 ratio. Sillimanite-garnet-biotite gneisses display Fe2O3, MgO.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Paharpur gabbroic intrusive is an arcuate body running east–west paralleling the foliation of Chhotanagpur Granite Gneiss which acts as country rock. The main gabbroic body is intruded by a number of dolerite dykes running north–south. It is composed of clinopyroxene (Wo48En40Fs12–Wo51En40Fs09, mg no. 72–82) ...

Core drilling of drillhole ONK-PVA11 in ONKALO at Olkiluoto 2014

Energy Technology Data Exchange (ETDEWEB)

Toropainen, V. [Drillcon SMOY, Espoo (Finland)

2014-12-15

Suomen Malmi Oy (Smoy) core drilled a drillhole for groundwater monitoring station in ONKALO at Eurajoki, Olkiluoto in 2014. The groundwater monitoring stations are used for monitoring changes in groundwater conditions. The drillhole ONK-PVA11 was drilled in February 2014. The length of the drillhole is 30.05 metres. The drillhole is 75.7 mm by diameter. The drillhole ONK-PVA11 was drilled in the left wall of the ONK-TT-4399 (tunnel chainage 50) between the demonstration tunnel ONK-TDT-4399-44 and 56 openings. The hydraulic DE 130 drilling rig was used. The drilling water was taken from the ONKALO drilling water pipeline and premixed sodium fluorescein was used as a label agent in the drilling water. The drillhole was measured with EMS deviation survey tool. In addition to drilling the drillcore was logged and reported by geologist. Geological logging included the following parameters: lithology, foliation, fracture parameters, fractured zones, core loss, weathering, fracture frequency, RQD and rock quality. The main rock types in the drillcore are veined gneiss, diatexitic gneiss and pegmatitic granite. The average fracture frequency in drill core is 2.3 pcs/m and the average RQD value 95.2 %. (orig.)

The presence of hydrocarbons in southeast Norway

DEFF Research Database (Denmark)

Hanken, Niels Martin; Hansen, Malene Dolberg; Kresten Nielsen, Jesper

Hydrocarbons, mostly found as solid pyrobitumen, are known from more than 30 localities in southeast Norway. They occur as inclusions in a wide range of "reservoir rocks" spanning from Permo-Carboniferous breccias to veins (vein quartz and calcite veins) in Precambrian granites, gneisses and amph......Hydrocarbons, mostly found as solid pyrobitumen, are known from more than 30 localities in southeast Norway. They occur as inclusions in a wide range of "reservoir rocks" spanning from Permo-Carboniferous breccias to veins (vein quartz and calcite veins) in Precambrian granites, gneisses......, indicating that Alum Shale was the most important source rock. Petrographic investigations combined with stable isotope analyses (d13C and d18O) of the cement containing pyrobitumen indicate two phases of hydrocarbon migration. The first phase probably took place in Upper Silurian to Lower Devonian time......, when the Alum Shale entered the oil window. These hydrocarbons are mostly found as pyrobitumen in primary voids and calcite cemented veins in Cambro-Silurian sedimentary deposits. The second phase is probably of Late Carboniferous/Permian age and was due to the increased heat flow during the formation...

Granulitic orthogneisses geochemistry of Caraiba complex, in Riachao do Jacuipe region - Bahia state, Brazil

International Nuclear Information System (INIS)

Teixeira, L.R.; Mello, R.C.

1990-01-01

This paper describes the granulitic orthogneisses of the Riachao do Jacuipe unit (Caraiba Complex) petrographicaly classified as tonalitic (predominating), trondhjemitic, granodioritic and quartz dioritic hyperstene gneisses. The chemical composition of the orthogneisses is dominantly tonalitic/granodioritic, that is typical of a calc-alkaline parentage depleted in K and enriched in Al sub(2) O sub(3). Their geochemical characteristics are very similar to those of the grey gneisses of other regions of the world, usually named TTG (tonalite-trondhhemite-granodiorite). In the sequence of orthogneiss coexist rocks both normal and depleted in LILE. The patterns of distribution of highly fractioned REE (La/YbN ratio up to 102) with Eu anomaly small or absent points against a direct mantle origin. On the other hand the only Rb-Sr age determination in the se rocks gives an age of 2,35 Ga with an initial ratio (Ro) of 0,702. This initial ratio suggests that the rocks did not originated from reworking of a much older continental crust. The available data suggest that the granulitized orthogneisses of the Caraiba Complex were formed by partial melt of basaltic material (amphibalitized oceanic crust). (author)

Geology and geochemistry of the Middle Proterozoic Eastern Ghat mobile belt and its comparison with the lower crust of the Southern Peninsular shield

Science.gov (United States)

Rao, M. V. Subba

1988-01-01

Two prominent rock suites constitute the lithology of the Eastern Ghat mobile belt: (1) the khondalite suite - the metapelites, and (2) the charnockite suite. Later intrusives include ultramafic sequences, anorthosites and granitic gneisses. The chief structural element in the rocks of the Eastern Ghats is a planar fabric (gneissosity), defined by the alignment of platy minerals like flattened quartz, garnet, sillimanite, graphite, etc. The parallelism between the foliation and the lithological layering is related to isoclinal folding. The major structural trend (axial plane foliation trend) observed in the belt is NE-SW. Five major tectonic events have been delineated in the belt. A boundary fault along the western margin of the Eastern Ghats, bordering the low grade terrain has been substantiated by recent gravity and the deep seismic sounding studies. Field evidence shows that the pyroxene granulites (basic granulites) post-date the khondalite suite, but are older than the charnockites as well as the granitic gneisses. Polyphase metamorphism, probably correlatable with different periods of deformation is recorded. The field relations in the Eastern Ghats point to the intense deformation of the terrain, apparently both before, during and after metamorphism.

Report on earth science studies at the Mt. Riiser-Larsen area, Amundsen Bay, Enderby Land, 2000-2001 (JARE-42

Directory of Open Access Journals (Sweden)

Minoru Funaki

2003-03-01

Full Text Available Five members of the summer party of the 42nd Japanese Antarctic Research Expedition (JARE-42 stayed in the Mt. Riiser-Larsen area, Amundsen Bay, Enderby Land, Antarctica, from December 18, 2000 to February 18, 2001 for paleomagnetism, geochronology, electromagnetic and magnetic surveys. A resident hut was built beside the generator hut constructed by JARE-38 in the camp. For the paleomagnetic study, 741 samples from 86 sites were collected in addition to the data of susceptibility and distribution of magnetite-quartz gneiss. 187 samples of felsic gneisses and basic dike rocks were collected for the geochronology. The high conductivity layer between 8 and 28 km was elucidated by the magnetotelluric method applied to samples obtained from 5 sites on the moraine field and 1 site on Richardson Lake. Strong magnetic anomalies up to 7000 nT were observed along gneissosity and dike intrusions by the magnetic survey. The weather was relatively mild during 63 days, although the maximum wind speed reached 50.7m/s. The camp was maintained without major accidents or trouble. After the work was completed, the camp facilities at Mt. Riiser-Larsen and Tonagh Island were completely withdrawn for environmental protection.

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

Core drilling of drillhole ONK-PVA11 in ONKALO at Olkiluoto 2014

International Nuclear Information System (INIS)

Toropainen, V.

2014-12-01

Suomen Malmi Oy (Smoy) core drilled a drillhole for groundwater monitoring station in ONKALO at Eurajoki, Olkiluoto in 2014. The groundwater monitoring stations are used for monitoring changes in groundwater conditions. The drillhole ONK-PVA11 was drilled in February 2014. The length of the drillhole is 30.05 metres. The drillhole is 75.7 mm by diameter. The drillhole ONK-PVA11 was drilled in the left wall of the ONK-TT-4399 (tunnel chainage 50) between the demonstration tunnel ONK-TDT-4399-44 and 56 openings. The hydraulic DE 130 drilling rig was used. The drilling water was taken from the ONKALO drilling water pipeline and premixed sodium fluorescein was used as a label agent in the drilling water. The drillhole was measured with EMS deviation survey tool. In addition to drilling the drillcore was logged and reported by geologist. Geological logging included the following parameters: lithology, foliation, fracture parameters, fractured zones, core loss, weathering, fracture frequency, RQD and rock quality. The main rock types in the drillcore are veined gneiss, diatexitic gneiss and pegmatitic granite. The average fracture frequency in drill core is 2.3 pcs/m and the average RQD value 95.2 %. (orig.)

The life forms of lichens on different substrates in Yelanetsko-Ingulskiy region (Mikolayivska and Kirovogradska oblast, Ukraine

Directory of Open Access Journals (Sweden)

Tatyana O. Boiko

2012-03-01

Full Text Available The article reveals the issue of distribution of lichens life forms on different substrates, which are present in the Yelanetsko- Ingulskiy region. The largest number of life forms of the lichens is characteristic for granite outcrops, and the lowest – for gneisses. This fact is associated with features of substrate morphostructure and density, microclimatic conditions of different ecotopes in which lichens grow.

Mikroskopische Studien ueber Gesteine aus den Molukken. 2. Gesteine von Seran. Mit einem französischen Résumé

NARCIS (Netherlands)

Schroeder van der Kolk, J.L.C.

1899-01-01

Dans les pages précédentes j’ai décrit quelques uns des nombreux échantillons de roche recueillis par M. Martin pendant son voyage de Séran (Céram). Les types suivants en sont les plus intéressants, les granites à cordiérite, les diorites les péridotites, les andésites à augite, les gneiss, les

Geologic setting of the St. Catherine basement rocks, Sinai, Egypt

OpenAIRE

Abdel Maksoud, M. A. [محمد علي عبدالمقصود; Khalek, M. L. Abdel; Oweiss, K. A.

1993-01-01

St. Catherine area, some 900 km in size, is dominated by basement rocks Encompassing old continental gneisses, metasediments, greenstone belt, calc-alkaline granites (G-II-granites), rift-related volcanics (RV), and anorogenic within plate granites (G-III-granites). The greenstone belt is composed of subduction-related volcanics (SV) intercalated with metasediments. These volcanics split into older group (moderately metamorphosed) and younger group (slightly metamorphosed). The calc-alkaline ...

Reactivation of the Archean-Proterozoic suture along the southern margin of Laurentia during the Mazatzal orogeny: Petrogenesis and tectonic implications of ca. 1.63 Ga granite in southeastern Wyoming

Science.gov (United States)

Jones, Daniel S.; Barnes, Calvin G.; Premo, Wayne R.; Snoke, Arthur W.

2013-01-01

The presence of ca. 1.63 Ga monzogranite (the “white quartz monzonite”) in the southern Sierra Madre, southeastern Wyoming, is anomalous given its distance from the nearest documented plutons of similar age (central Colorado) and the nearest contemporaneous tectonic margin (New Mexico). It is located immediately south of the Cheyenne belt—a ca. 1.75 Ga Archean-Proterozoic tectonic suture. New geochronological, isotopic, and geochemical data suggest that emplacement of the white quartz monzonite occurred between ca. 1645 and 1628 Ma (main pulse ca. 1628 Ma) and that the white quartz monzonite originated primarily by partial melting of the Big Creek Gneiss, a modified arc complex. There is no evidence that mafic magmas were involved. Open folds of the ca. 1750 Ma regional foliation are cut by undeformed white quartz monzonite. On a regional scale, rocks intruded by the white quartz monzonite have experienced higher pressure and temperature conditions and are migmatitic as compared to the surrounding rocks, suggesting a genetic relationship between the white quartz monzonite and tectonic exhumation. We propose that regional shortening imbricated the Big Creek Gneiss, uplifting the now-exposed high-grade rocks of the Big Creek Gneiss (hanging wall of the thrust and wall rock to the white quartz monzonite) and burying correlative rocks, which partially melted to form the white quartz monzonite. This tectonism is attributed to the ca. 1.65 Ga Mazatzal orogeny, as foreland shortening spread progressively into the Yavapai Province. Mazatzal foreland effects have also been described in the Great Lakes region and have been inferred in the Black Hills of South Dakota. We suggest that the crustal-scale rheologic contrast across the Archean-Proterozoic suture, originally developed along the southern margin of Laurentia, and including the Cheyenne belt, facilitated widespread reactivation of that boundary during the Mazatzal orogeny. This finding emphasizes the degree to

Lead-lead isotope method. Application to migmatites and associaded rocks of the region of Sao Jose dos Campos, SP

International Nuclear Information System (INIS)

Babinski, M.

1988-01-01

Establishment of chemical and analytical procedures, preparation and purification of reagents and the mounting of a clean laboratory (class 100) for the Pb-Pb isotope dating of whole rock and mineral samples are discussed in this work. Two different methods of dissolution of rock samples and chemical separation of lead using anionic resin were tried in a conventional chemical laboratory using analytical grade reagents. The samples analysed were paleossome and neossome of migmatites from Sao Jose dos Campos, SP, and from the results obtained the analytical method to be employed was chosen. The results obtained by this method agree well with those of the Geochronology Laboratory at Oxford, for the same samples. Applying the established analytical procedure, migmatites and associated gneisses from the region of Sao Jose dos Campos were dated by Pb/Pb method. Some of the samples were also dated by Rb-Sr method. The lead-lead isochron age of 2355 +- 85 M.a. (μ 1 = 8.33) for the paleossome may be interpreted as the age of the metamorphism for these rocks, which were formed probably during the Archean. The age data for the phacoidal gneisses show a similar geological evolution, whereas the 2414 +- 800 M.A. Pb-Pb isochron age for the protomylonitic gneisses indicates a disturbed Pb-Pb isotope system. The neossome samples define a Pb-Pb isochron age of 1388 +- 290 M.A. (μ1 = 8.15), which may be interpreted as the age of migmatization. The calculated Pb-Pb ages for two alkali feldspars from the migmatites are devoid of any geological significance. The age values obtained by the Rb-Sr isotope system for the neossome and paleossome of the migmatites agree with the Pb/Pb data within experimental errors. However, the study shows that results of the Rb-Sr data alone cannot be interpreted unambiguously with out comparison with data from other isotope systems. (author) [pt

Geology and mineral deposits of an area in the Departments of Antioquia and Caldas (Subzone IIB), Colombia

Science.gov (United States)

Feininger, Tomas; Barrero L., Dario; Castro, Nestor; Hall, R.B.

1973-01-01

The Inventario Minero National (IMN), a four-year cooperative geologic mapping and mineral resources appraisal project, was accomplished under an agreement between the Republic of Colombia and the U. S. Agency for International Development from 1964 through 1969. Subzone IIB, consisting essentially of the east half of Zone comprises nearly 20,000 km2 principally in the Department of Antioquia but including also small parts of the Departments of Caldas and Tolima. The rocks in IIB range from Precambrian to Holocene. Precambrian feldspar-quartz gneiss occupies a mosaic of fault-bounded blocks intruded by igneous rocks between the Oto fault and the Rio Magdalena. Paleozoic rocks are extensive, and include lightly metamorphosed graptolite-bearing Ordovician shale at Cristalina, and a major suite of graphitic quartz-mica schist, feldspathic and aluminous gneiss, quartzite, marble, amphibolite, and other rocks. Syntectonic intrusive gneiss included many of the older rocks during a late Paleozoic(?) orogeny, which was accompanied by Abukuma-type metamorphosing from lowermost greenschist to upper amphibolite facies. A Jurassic diorite pluton bounded by faults cuts volcanic rocks of unknown age east of the Otu fault. Cretaceous rocks are major units. Middle Cretaceous carbonaceous shale, sandstone, graywacke, conglomerate, and volcanic rocks are locally prominent. The Antioquian batholith (quartz diorite) of Late Cretaceous age cuts the middle Cretaceous and older rocks. A belt of Tertiary nonmarine clastic sedimentary rocks crops out along the Magdalena Valley. Patches of Tertiary alluvium are locally preserved in the mountains. Quaternary alluvium, much of it auriferous, is widespread in modern stream valleys. Structurally IIB constitutes part of a vast complex synclinorium intruded concordantly by syntectonic catazonal or mesozonal felsic plutons, and by the later epizonal post-tectonic Antioquian batholith. Previously unrecognized major wrench faults are outstanding

The 'Pajeu-Paraiba System' and the Sao Jose do Campestre 'Massif' in Eastern Borborema

International Nuclear Information System (INIS)

Neves, Benjamim Bley de Brito; Campos Neto, Mario da Costa

2001-01-01

The best areas of exposures of the Pajeu-Paraiba Folding System (SPP) are in the western hinterland of Pernambuco, but the northern part of it - the so-called Alto Pajeu Terrane (TAP) - reaches the coastal zone of Paraiba (east of the 36 deg 00 ' W). This supra crustal terrane is positioned between important regional shear zones that separate it from high grade gneiss domains. To the north, there is the Rio Grande do Norte Terrane (RON)- separated by the Patos Lineament- and to the south there is the exposition of another important fraction of the basement of SPP, the Alto Moxoto Terrane (TAM). Both RON and TAM are considered mega-fragments of a previous Paleo proterozoic super continent, while TAP is assumed as a descendant segment of the Meso-Neo proterozoic orogenic belt, probably part of the super continent of that time (Rodinia). All these Nterranes are now juxtaposed and they were deeply reworked by the development of the Brasiliano Cycle, during the amalgamation of the Western Gondwana super continent. The TAP is mostly composed of muscovite-biotite gneisses (a), garnet-biotite-schists (b), intruded by augen-gneisses of granitic and syenogranitic composition (c) which are lithological assemblages of Eoneoproterozoic age (Cariris Velhos Cycle). They were diversely reworked and penetrated by granitoids (d) of the Brasiliano Cycle (as well as RGN has been), specially plutonic rocks of the end of Neo proterozoic III. These predominant rock-units (a, b, c) are positioned between major regional dextral shear zones, and their regional features are drawing an wide fan-sinformal structure, due to the Brasiliano reworking. Geochronological determinations -Rb-Sr, Sm-Nd and U-Pb methods- confirm the Paleoproterozoic age of the RGN and its reworking during the Brasiliano, as well as the early Neo proterozoic age (Cariris Velhos Cycle) for the main rock units of TAP. Granitic plutonism and processes of shearing are common events of the Brasiliano Cycle for both, RGN and

Coexistence of enriched and modern-like 142Nd signatures in Archean igneous rocks of the eastern Kaapvaal Craton, southern Africa

Science.gov (United States)

Schneider, Kathrin P.; Hoffmann, J. Elis; Boyet, Maud; Münker, Carsten; Kröner, Alfred

2018-04-01

The short-lived 146Sm-142Nd isotope system is an important tool for tracing Hadean crust-mantle differentiation processes and constraining their imprint on much younger rocks from Archean cratons. We report the first comprehensive set of high-precision 142Nd analyses for granitoids and amphibolites of the Ancient Gneiss Complex (AGC; Swaziland) and the oldest metavolcanic units of the Barberton Greenstone Belt (BGB; South Africa). The investigated samples span an age range from 3.66 Ga to 3.22 Ga and are representative of major geological units of the AGC and the lower Onverwacht Group of the BGB. Measured samples yielded μ142Nd values in the range from -8 ppm to +3 ppm relative to the JNdi-1 terrestrial standard, with typical errors smaller than 4.4 ppm. The distribution of the μ142Nd values for these 17 measured samples is bimodal with ten samples showing a tendency towards slightly negative μ142Nd anomalies, whereas seven samples have 142Nd similar to the terrestrial reference. The only confidently resolvable μ142Nd anomalies were found in a 3.44 Ga Ngwane Gneiss sample and in amphibolites of the ca. 3.45 Ga Dwalile Greenstone Remnant, revealing μ142Nd values ranging from - 7.9 ± 4.4 to - 6.1 ± 4.3 ppm. The μ142Nd deficits do not correlate with age, lithological unit, or sample locality. Instead, our results reveal that two distinct mantle domains were involved in the formation of the AGC crust. The two reservoirs can be distinguished by their μ142Nd signatures. Mantle-derived rocks tapped the enriched reservoir with negative μ142Nd at least until 3.46 Ga, whereas the granitoids preserved a negative μ142Nd signature that formed by incorporation of older AGC crust at least until 3.22 Ga. The oldest gneisses with no μ142Nd anomaly are up to 3.64 Ga in age, indicating that a modern terrestrial 142Nd reservoir was already present by early Archean times.

The provenance and Sm/Nd Model ages of siliciclastic supracrustal rocks of the Faina and Santa Rita Greenstone belts, Goias, Brazil

International Nuclear Information System (INIS)

Resende, Marcelo Goncalves; Jost, Hardy; Lima, Bruno Eustaquio Moreira; Teixeira, Alexandre de Amorim

1999-01-01

The Faina and Santa Rita greenstone belts are two N 60 deg C W trending synclinoria separated by a N 30 deg C E strike-slip fault and rest allochtonous on the adjacent Uva and Caicara granite-gneiss complexes. The belts are made up of lower metakomatiites, followed by metabasalts and thick metasedimentary sequences deposited under contrasting paleogeographic settings. In Faina, the sequence consists of two complete shelf cycles, the first resting on basalts by an erosional unconformity. In Santa Rita, the basalts give gradually place to carbonaceous metashales, unconformably overlain by metarhythmites. Provenance based on trace element geochemistry, mineral chemistry of chloride and muscovite, source-are modeling and REE elements indicate that protoliths of the first shelf cycle of Faina and the carbonaceous metashales of Santa Rita formed under the influence of a source area dominated by mafic ultramafic rocks, whilst during the sedimentation of the second shelf cycle and the metarhythmites of Santa Rita the source-area was dominated by TTG granitoids. Sm-Nd model ages of the lower sedimentary packages vary between 3.0 and 2.8 Ga and the upper between 2.7 and 2.6 Ga. These intervals coincide, respectively, with the estimated age of the underlying, and with the Sm-Nd, Rb-Sr e U-Pb ages of the main granitoids and gneisses of the adjacent complexes. The same data indicate that, during the sedimentation of the first shelf cycle of Faina and the carbonaceous metashales of Santa Rita, both basins had independent source-areas, but shared the same source during the upper sections. Weathering nature and intensity of the source-area calculated by means of geochemical a data suggest that the dramatic change of provenance from the lower to the upper sections is due to the shift from tectonically stable to unstable regimes, interpreted as resulting from the emergence of the island arc whose roots are represented by the adjacent granite-gneiss complexes. (author)

The provenance and Sm/Nd Model ages of siliciclastic supracrustal rocks of the Faina and Santa Rita Greenstone belts, Goias, Brazil; Proveniencia e idades modelo Sm/Nd das rochas siliciclasticas arqueanas dos greenstone belts de Faina e Santa Rita, Goias

Energy Technology Data Exchange (ETDEWEB)

Resende, Marcelo Goncalves [Universidade Catolica de Brasilia, DF (Brazil); Jost, Hardy [Brasilia Univ., DF (Brazil). Inst. de Geociencias; Lima, Bruno Eustaquio Moreira; Teixeira, Alexandre de Amorim

1999-09-01

The Faina and Santa Rita greenstone belts are two N 60 deg C W trending synclinoria separated by a N 30 deg C E strike-slip fault and rest allochtonous on the adjacent Uva and Caicara granite-gneiss complexes. The belts are made up of lower metakomatiites, followed by metabasalts and thick metasedimentary sequences deposited under contrasting paleogeographic settings. In Faina, the sequence consists of two complete shelf cycles, the first resting on basalts by an erosional unconformity. In Santa Rita, the basalts give gradually place to carbonaceous metashales, unconformably overlain by metarhythmites. Provenance based on trace element geochemistry, mineral chemistry of chloride and muscovite, source-are modeling and REE elements indicate that protoliths of the first shelf cycle of Faina and the carbonaceous metashales of Santa Rita formed under the influence of a source area dominated by mafic ultramafic rocks, whilst during the sedimentation of the second shelf cycle and the metarhythmites of Santa Rita the source-area was dominated by TTG granitoids. Sm-Nd model ages of the lower sedimentary packages vary between 3.0 and 2.8 Ga and the upper between 2.7 and 2.6 Ga. These intervals coincide, respectively, with the estimated age of the underlying, and with the Sm-Nd, Rb-Sr e U-Pb ages of the main granitoids and gneisses of the adjacent complexes. The same data indicate that, during the sedimentation of the first shelf cycle of Faina and the carbonaceous metashales of Santa Rita, both basins had independent source-areas, but shared the same source during the upper sections. Weathering nature and intensity of the source-area calculated by means of geochemical a data suggest that the dramatic change of provenance from the lower to the upper sections is due to the shift from tectonically stable to unstable regimes, interpreted as resulting from the emergence of the island arc whose roots are represented by the adjacent granite-gneiss complexes. (author)

Fission track dating of zircon: a multichronometer

International Nuclear Information System (INIS)

Carpena, J.

1992-01-01

Scattering in Fission Track ages of zircons of a single rock is possible when they present morphological and geochemical variations, if the greatest care is not taken in the choice of the etching conditions and the counting of tracks. The Fission Track study of two heterogeneous populations of zircons from the Mont Blanc granite and from the Gran Paradiso gneisses allows to show that zircon may work as a multichronometer

Untitled

Indian Academy of Sciences (India)

vestigations particularly because of the close association of charnockites with diopside-gneisses and calc-silicate rocks. The petrogenetic history of these rocks is also discussed. 17°. ÇAI. c. --5; Lt CAT E ROCKS O SCALE | N MILES !/2 44'. O 1 C P 5 ; D E - Gº! E! S$8 S b=c, |. HYPER S THE # E-GRA iſ ºf L fºrt. 5 w. K: #A p.

Migmatitic rocks southwest of the Barberton greenstone belt

International Nuclear Information System (INIS)

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

1981-01-01

A geologic survey was done on the migmatitic rocks southwest of the Barberton greenstone belt. A table is given on the chemical analyses of components from migmatic outcrops in this area, as well as on the chemical analyses of some selected rock types found in greenstone xenoliths, together with leuco-biotite tomalite/tronomjemite gneisses in the area surrounding the Boesmanskop syenite pluton. Isotope dating was also used in the survey

Model galena ages from Karnataka and surrounding ages

Energy Technology Data Exchange (ETDEWEB)

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

1977-02-01

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

Cerro Largo South orientation

International Nuclear Information System (INIS)

Pradier, B.

1982-01-01

This work is about Cerro Largo South orientation. The site is located in the northeast of Uruguay in the south of Melo city, Department of Cerro Largo. The study was carried out in the young edge socket in the East side of a small valley. This metamorphic socket constituted by gneisses and crystalline limestone are in contact with upper carboniferous formations and basal deposits composed by sandstones and conglomerates

Petrography, geochemistry and regional significance of crystalline ...

Indian Academy of Sciences (India)

and K2O content. To demonstrate the nature of these rocks, A/CNK ratios were derived (where molecular A/CNK= {mol. [Al2O3/(CaO+Na2O+. K2O)]}, which range between 1.24 and 2.37. (UG: 1.39–0.37, DP: 1.28–1.45, BMG: ..... The petrographic studies and the age determination of. Koidal gneiss, Kumaon Himalaya; Curr.

Mining technology development for hard rock excavation

International Nuclear Information System (INIS)

Hustrulid, W.; Cudnick, R.; Trent, R.; Holmberg, R.

1980-01-01

A research facility has been established in the granitic gneiss of the CSM Experimental Mine at Idaho Springs, Colorado, for the purpose of evaluating/developing mining, geologic and geotechnical procedures appropriate for use in establishing nuclear waste repositories in hard rock. An experimental room has been excavated using careful blasting procedures. The extent and magnitude of blast damage is being evaluated. Structural geology is being mapped to assess continuity

Age determination and development of experimental methods for quaternary fault and formation

International Nuclear Information System (INIS)

Lee, Kwang Sik; Choi, M. S.; Kim, J. M.

2004-02-01

Late cretaceous to early tertiary movement ages were constrained by Rb-Sr and K-Ar dating of fault rocks near the Uljin Nuclear Power Plants. These ages are well reproducible and consistent with geologic context. Tectonic evolution of the northeastern Yeongnam massif, the site of the Uljin Nuclear Power Plants, was investigated on the basis of Rb-Sr, Sm-Nd and Pb isotopic systematics and geochemistry of precambrian basement rocks including the Hosanri Formation, Buncheon granite gneiss, biotite granite gneiss, and Hongjesa granite. The optical ages from the Suryum fault outcrop represent the younger limit of sedimentation timing because they are simply based upon the present-day water content. The lower, Qt 2 terrace at about 18m elevation is correlated with Marine Isotopic Stage (MIS) 5a, although its apparent optical age was consistently reported from 71 to 48 ka. Correlation of shoreline elevations indicates the correspondence of the Qt 3a terrace to MIS 5e, which is supported by stratigraphically concordant optical ages for aeolian sand dunes at the north of the Suryum site. This time scale yields an uplift rate of 0.266 m/ka, requiring the revision of conventional view that the Korean peninsula is tectonically very stable

Geologic map of the Harvard Lakes 7.5' quadrangle, Park and Chaffee Counties, Colorado

Science.gov (United States)

Kellogg, Karl S.; Lee, Keenan; Premo, Wayne R.; Cosca, Michael A.

2013-01-01

The Harvard Lakes 1:24,000-scale quadrangle spans the Arkansas River Valley in central Colorado, and includes the foothills of the Sawatch Range on the west and Mosquito Range on the east. The Arkansas River valley lies in the northern end of the Rio Grande rift and is structurally controlled by Oligocene and younger normal faults mostly along the west side of the valley. Five separate pediment surfaces were mapped, and distinctions were made between terraces formed by the Arkansas River and surfaces that formed from erosion and alluviation that emanated from the Sawatch Range. Three flood deposits containing boulders as long as 15 m were deposited from glacial breakouts just north of the quadrangle. Miocene and Pliocene basin-fill deposits of the Dry Union Formation are exposed beneath terrace or pediment deposits in several places. The southwestern part of the late Eocene Buffalo Peaks volcanic center, mostly andesitic breccias and flows and ash-flow tuffs, occupy the northeastern corner of the map. Dated Tertiary intrusive rocks include Late Cretaceous or early Paleocene hornblende gabbro and hornblende monzonite. Numerous rhyolite and dacite dikes of inferred early Tertiary or Late Cretaceous age also intrude the basement rocks. Basement rocks are predominantly Mesoproterozoic granites, and subordinately Paleoproterozoic biotite gneiss and granitic gneiss.

New SHRIMP U-Pb zircon ages of the metapelitic granulites from NW of Madurai, Southern India

International Nuclear Information System (INIS)

Prakash, D.

2010-01-01

Zircon cathodoluminescent imaging and SHRIMP U-Pb dating were carried out for metapelitic rocks (sapphirine-hearing granulites and garnet-cordierite gneisses) from the NW of Madurai, Southern India. The cathodoluminescence images reveal the complex, inhomogeneous internal structure having irregular-shaped core and overgrowths. Zircon grains have obliterated oscillatory zoning. SHRIMP U-Pb chronological results yield ages of 550 ± 15 Ma and 530 ± 50 Ma as a time of metamorphic overprint, and the age of 2509 ± 12 Ma and 2509 ± 30 Ma corresponding to a timing of protolith formation for sapphirine-bearing granulites and garnet-cordierite gneisses respectively. Zircon ages reflect that continental crust in the NW of Madurai region resulted from the recycling of Archaean protolith of an igneous origin similar to the preserved crust in the southern part of Dharwar craton. The present SHRIMP U-Pb zircon ages are in close agreement with earlier published Nd isotopic data which suggest an extended precrustal history of their protoliths. The abraded zircon grains indicate multiple recycling and repeated metamorphism that has ultimately resulted in present day continental crust exposed in Madurai region. These SHRIMP U-Pb zircon ages from metapelitic UHT granulites are also significant to understanding the architecture of the SGT during the amalgamation of Gondwana in Neoproterozoic time. (author)

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

International Nuclear Information System (INIS)

1980-10-01

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

Rock weathering by indigenous heterotrophic bacteria of Bacillus spp. at different temperature: a laboratory experiment

Science.gov (United States)

Štyriaková, I.; Štyriak, I.; Oberhänsli, H.

2012-07-01

The bio-weathering of basalt, granite and gneiss was experimentally investigated in this study. These rock-forming minerals weathered more rapidly via the ubiquitous psychrotrophic heterotrophic bacteria . With indigenous bacteria of Bacillus spp. from sediments of Lake Baikal, we traced the degradation process of silicate minerals to understand the weathering processes occurring at the change temperature in the subsurface environment with organic input. The bacteria mediated dissolution of minerals was monitored with solution and solid chemistry, X-ray analyses as well as microscopic techniques. We determined the impact of the bacteria on the mineral surface and leaching of K, Ca, Mg, Si, Fe, and Al from silicate minerals. In the samples the release of major structural elements of silicates was used as an overall indicator of silicate mineral degradation at 4°C and 18°C from five medium exchanges over 255 days of rock bioleaching. The increase of temperature importantly affected the efficiency of Fe extraction from granite and basalt as well as Si extraction from granite and gneiss. In comparison with elemental extraction order at 4°C, Ca was substituted first by Fe or Si. It is evident that temperature influences rock microbial weathering and results in a change of elements extraction.

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

Directory of Open Access Journals (Sweden)

Syafrizal

2017-07-01

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

The Atuba complex: a paleoproterozoic belt intensively reworked in the neoproterozoic era

International Nuclear Information System (INIS)

Siga Junior, O.; Basei, M.A.S.; Machiavelli, A.; Harara, O.M.; Reis Neto, J.M.

1996-01-01

Studies of terranes between the northern Ribeira and southern Dom Feliciano Belts allow the characterization of three geotectonic domains with different evolutions: the Luis Alves, Curitiba and Paranagua terranes. The Atuba complex occurs in Curitiba Domain, which has a northwestern limit with metasediments of the Acungui and Setuva Groups and a southwestern limit with the granulitic gneisses of the Luis Alves domains. The contacts are expressive shear zones. The predominant rocks of the Curitiba Domain are banded, migmatitic gneisses in amphibolite grade with biotite-amphibolite gneissic mesosomes and tonalitic/graodioritic leucosomes, here called the Atuba complex. The migmatites are Paleoproterozoic (2.000±200 Ma) and remigmatized in Neoproterozoic (600±20 Ma). During the latter period temperatures reached more than 500 0 C. The structural pattern indicated shear-controlled tectonics with an important lateral component, and low-angle, south-southeastward transport direction. The terranes of the Atuba complex appear to represent deep-level rocks which were migmatized, granitized and then added to the border of the Luis Alves Microplate during the Neoproterozoic. This late Neoproterozoic tectonic scheme which continued to the Cambro-Ordoviciano seems to be the result of larger scale processes of continental agglutination which ended with the formation of western Gondwanaland. (author). 17 figs., 2 tabs

The Atuba complex: a paleoproterozoic belt intensively reworked in the neoproterozoic era; O complexo Atuba: um cinturao paleoproterozoico intensamente retrabalhado no neoproterozoico

Energy Technology Data Exchange (ETDEWEB)

Siga Junior, O.; Basei, M.A.S.; Machiavelli, A.; Harara, O.M. [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias; Reis Neto, J.M. [Parana Univ., Curitiba, PR (Brazil). Dept. de Geologia

1996-11-01

Studies of terranes between the northern Ribeira and southern Dom Feliciano Belts allow the characterization of three geotectonic domains with different evolutions: the Luis Alves, Curitiba and Paranagua terranes. The Atuba complex occurs in Curitiba Domain, which has a northwestern limit with metasediments of the Acungui and Setuva Groups and a southwestern limit with the granulitic gneisses of the Luis Alves domains. The contacts are expressive shear zones. The predominant rocks of the Curitiba Domain are banded, migmatitic gneisses in amphibolite grade with biotite-amphibolite gneissic mesosomes and tonalitic/graodioritic leucosomes, here called the Atuba complex. The migmatites are Paleoproterozoic (2.000{+-}200 Ma) and remigmatized in Neoproterozoic (600{+-}20 Ma). During the latter period temperatures reached more than 500{sup 0} C. The structural pattern indicated shear-controlled tectonics with an important lateral component, and low-angle, south-southeastward transport direction. The terranes of the Atuba complex appear to represent deep-level rocks which were migmatized, granitized and then added to the border of the Luis Alves Microplate during the Neoproterozoic. This late Neoproterozoic tectonic scheme which continued to the Cambro-Ordoviciano seems to be the result of larger scale processes of continental agglutination which ended with the formation of western Gondwanaland. (author). 17 figs., 2 tabs.

Age determination and development of experimental methods for quaternary fault and formation

Energy Technology Data Exchange (ETDEWEB)

Lee, Kwang Sik; Choi, M. S.; Kim, J. M. [Korea Basic Science Institute, Daejeon (Korea, Republic of)] (and others)

2004-02-15

Late cretaceous to early tertiary movement ages were constrained by Rb-Sr and K-Ar dating of fault rocks near the Uljin Nuclear Power Plants. These ages are well reproducible and consistent with geologic context. Tectonic evolution of the northeastern Yeongnam massif, the site of the Uljin Nuclear Power Plants, was investigated on the basis of Rb-Sr, Sm-Nd and Pb isotopic systematics and geochemistry of precambrian basement rocks including the Hosanri Formation, Buncheon granite gneiss, biotite granite gneiss, and Hongjesa granite. The optical ages from the Suryum fault outcrop represent the younger limit of sedimentation timing because they are simply based upon the present-day water content. The lower, Qt{sub 2} terrace at about 18m elevation is correlated with Marine Isotopic Stage (MIS) 5a, although its apparent optical age was consistently reported from 71 to 48 ka. Correlation of shoreline elevations indicates the correspondence of the Qt{sub 3a} terrace to MIS 5e, which is supported by stratigraphically concordant optical ages for aeolian sand dunes at the north of the Suryum site. This time scale yields an uplift rate of 0.266 m/ka, requiring the revision of conventional view that the Korean peninsula is tectonically very stable.

Araguaia fold belt, new geochronological data

International Nuclear Information System (INIS)

Lafon, J.M.; Macambira, J.B.; Macambira, M.J.B.; Moura, C.A.V.; Souza, A.C.C.

1990-01-01

The northern part of the Araguaia Fold Belt (AFB) outcrops in a N-S direction for about 400 km in the state of Tocantins. Dome-like structures occur in this fold belt also in a N-S direction. Both deformation and metamorphism increase from the West to the East. The basement of the AFB consist of Colmeia complex and Cantao gneiss, which crop out mainly in the core of the dome-like structures. The supracrustals rocks of the fold belt belongs to the Baixo Araguaia supergroup which is divided into the lower Estrondo group and the upper Tocantins group. Preliminary Sm-Nd data from the Colmeia complex (Grota Rica dome) gave Archean model ages of 2.8 Ga (TNd sub(DM)) while Rb-Sr data in the same rocks give an age of 2530 ± 200 Ma. In the others dome-like structures, the Rb-Sr systematics gave ages for the Colmeia a complex of 2239 ± 47 Ma (Colmeia structure) and 1972 ± 46 Ma (Lontra structure). These younger ages are believed to represent partial to total isotopic resetting of the Rb-Sr system during the Transamazonian Event. The Rb-Sr studies of the Cantao gneiss gave an age of 1774 ± 31 Ma. (author)

Punta del Este terrane : a better knowledge

International Nuclear Information System (INIS)

Preciozzi, F.; Sanchez Bettucci, L; Basei, M.

2002-01-01

Field Punta del Este (TPE) is constituted by a series of gneisses and migmatites formed in the range of 1000 and 900 Ma, and have been intensely reworked during Rio Doce orogeny (ca. 600-500 Ma). This cortical segment represents high-grade metamorphic terrain, correlatable with complex gneiss Southwest Africa, particularly with Kibariáno Belt - Namaqualanos recognized in the southwestern portion of Africa (Namibia). U-Pb zircon ages in tonalite granitoids indicate values ​​between 1000 and 900 Ma and were interpreted as indicating the time of generation of these rocks. This should also be the age of high-grade metamorphism that affected a large part of the gneissic rocks of the region. Moreover, the anatectic related mobilized leucosomes ages of migmatites gave ca. 520-540 Ma, indicating that the metamorphic conditions (overlapping) during the Rio Doce orogeny reached at least the amphibolite facies. The metasedimentary cover TPE occurs in the vicinity of the towns of La Paloma Rocha. These are represented by a siliciclastic metasedimentary sequence represented by Rocha Formation. Despite the poly phase deformation and low grade metamorphism affecting this training, primary structures are common such as stratification plano-parallel, cross-bedding, hummock y and massive levels with gradational stratification

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

International Nuclear Information System (INIS)

Daziano, C.; Ayala, R.

2010-01-01

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

First thermo-chronological data; Premieres donnees thermo-chronologiques sur les socles sarde et kabylo-peloritain submerges dans le canal de Sardaigne (Mediterranee occidentale)

Energy Technology Data Exchange (ETDEWEB)

Bouillin, J.P.; Poupeau, G.; Tricart, P.; Bigot-Cormier, F.; Mascle, G. [Grenoble-1 Univ., 38 (France). Laboratoire de geodynamique des chaines alpines; Torelli, L. [Universita degli studi di Parma (Italy). Dept. di Scienze della Terra; Compagnoni, R.; Mascle, J.; Pecher, A.; Peis, D.; Rekhiss, F.; Rolfo, F

1998-04-01

Granite and gneiss sampled from the submarine fault scarps of the Sardinia Channel were dated using the apatite fission-track method. One sample provides an age of 22.8 {+-} 1.3 Ma, which is in the range of the cooling ages of the Calabrian-Peloritan basement, where cooling is due to erosion. Three other samples have ages around 10 Ma, probably due to a tectonic denudation during the Tortonian extension in the Sardinia Channel. (authors)

The Caledonian tectonomagmatic evolution of the Orkney Islands, Scotland

OpenAIRE

Bjerga, Audun Dalene

2017-01-01

The geology of the Orkney Islands is dominated by well-studied Devonian sedimentary rocks deposited in the Orcadian basin. However, on the islands of Mainland Orkney and Graemsay there are small, relatively poorly studied outcrops of the underlying basement. Based on comparison with rocks in mainland Scotland this basement has been suggested to comprise pre-Caledonian para-gneisses and Caledonian granites. This has, however, never been documented. Here the contact relationships in the basemen...

A NEW INVESTIGATION OF VIETNAM’S BERYL

Directory of Open Access Journals (Sweden)

Nguyen Van Binh

2017-11-01

Full Text Available The paper presents briefly new investigation of Vietnam beryl group, especially some characteristics of regional geology of Song Chay granite massif and new find of big crystals of beryl in them. The green beryl is found in quartz - mica - tourmaline, mica - feldspar – quartz pegmatite bodies in the south part of Song Chay granite - gneiss massif near Na Chi and Tan Nam villages, Quang Binh district, Ha Giang province.

Radiocrystallographic study of titanites from Xerem, Rio de Janeiro

International Nuclear Information System (INIS)

Baptista, A.; Baptista, N.R.

1987-01-01

The conclusions of the radiocrystallographic studies in titanite crystals - CaTi[SiO 4 ] (0,0H,F) from two rocks with different petrogenesis, from Xerem, Rio de Janeiro State are described. The rocks was granite and nepheline-gneiss and the Spetrochemical analysis showed different compositions to crystals from each one of the rocks. This different composition was eough to development of comparative study using optical determination and petrographic analysis. (C.D.G.) [pt

Geological Mapping of Investigation Trenches OL-TK15 and OL-TK16 at the Olkiluoto Study Site, Eurajoki, SW Finland

International Nuclear Information System (INIS)

Vaarma, M.; Vuokko, J.

2009-07-01

Geological mapping of investigation trenches OL-TK15 and OL-TK16 was carried out by the Geological Survey of Finland (GTK) at the Olkiluoto study site as a part of Posiva Oy's site investigation program for the development of an underground repository for nuclear waste. OL-TK15 is ca. N-S striking and ca. 95 m long, and OL-TK16 is ca. E-W striking and ca. 172 m long. The trenches were cleaned with pressure washer and pressurized air. The rock types were determined in field by naked eyes. Five samples from OL-TK15 and 10 samples from OL-TK16 were thin sectioned and investigated microscopically. In addition, petrophysical measurements were carried out by GTK geophysical laboratory for these samples. The bedrock within the excavation trenches OL-TK15 and OL-TK16 consists mainly of veined gneiss (VGN) with intercalations of mica gneiss (MGN), and mafic gneiss (MFGN) of amphibolite, amphibolite-gneiss, and skarn gneiss. The VGN is frankly solid or intact, fine grained and weakly banded and multiple intruded by granitic and pegmatitic veins and veinlets. Narrow scrappy zones occupied by dark dots of highly altered pseudomorphs after cordierite and/or garnet tend to be common in places. In addition, VGN contains rounded oblong mafic to intermediate fragments due to boudination of competent layers and/or dykes. Some rather narrow pegmatitic and quartz veins cut the previous tectonic structures. The prevailing tectonic structures are strong pervasive foliation and conformal veining of several generations mostly granitic in composition. The strike of the foliation and banding and veining as well, varies a little from NNE to ENE and the dip is ca. 40 - 50 degrees to SE sector, respectively. The younger folding has bent the older foliation and neosomic veining mostly with dextral monoclinic style so that in many places there occur tight kinky nodes and rootles augen like knots showing dextral rotation, too. Due to brittle deformation, there are some shear zones and zones with

Summary of petrophysical analysis of Olkiluoto. Core samples 1990-2008

International Nuclear Information System (INIS)

Heikkinen, E.; Oehman, I.; Paulamaeki, S.; Saeaevuori, H.; Vuoriainen, S.; Aaltonen, I.

2009-04-01

Posiva prepares for disposal of spent nuclear fuel in deep geological repository at Olkiluoto, Eurajoki. This is in accordance of the application filed in 1999, the Decision in Principle of the State Council in 2000, and ratification by the Parliament in 2001.The site characterization has included comprehensive geological, hydrological and geophysical investigations airborne, on ground and in drillholes since 1988. Petrophysical analysis has been carried out to enhance knowledge on physical properties in rock mass. Also the large scale geophysical interpretations will essentially benefit on this knowledge. This report is associated with and covering the 2005-2008 sampling campaign (932 samples), but also pre-existing results (506 samples from 1990 - 2004) are discussed in the report. Data has been acquired from non-broken core samples, and of representative locations of lithological units. Samples have been taken at 10-30 m interval from all core sections. Selecting the samples and analysis has been carried out for different purposes during campaigns. Altogether there are 1438 samples from drillholes OL-KR1 - OL-KR39 and ONK-PH01-PH07. Petrophysical measurements included density, susceptibility and remanence (partly oriented), resistivity, IP value (frequency effect), P-wave velocity and porosity. Sample data was analyzed for distributions and mutual relations. Petrophysical signatures of different parameters were assessed by lithology. Mineral composition and texture will affect to petrophysical results. Deformation and alteration cause an overprint to lithology specific values. In petrophysical sense, granite pegmatite is distinguished from all other rock types. It is of rather high resistivity and P-wave velocity, and low density and susceptibility. Other distinct lithological unit is mafic gneisses. They are described by high density and Pwave velocity, and also increased susceptibility, IP value and resistivity. The tonaliticgranodioritic- granitic gneiss

Geological mapping of investigation trench OL-TK18 at the Olkiluoto study site, Eurajoki, SW Finland

Energy Technology Data Exchange (ETDEWEB)

Engstroem, J. [GTK Geological Survey of Finland, Espoo (Finland)

2012-04-15

Survey of Finland at the Olkiluoto study site, Eurajoki, as part of Posiva Oy's site investigation programme for the development of an underground repository for nuclear waste. The E-W striking, ca. 55 m long trench is located in the central part of the Olkiluoto Island adjacent to investigation trenches OL-TK12 and OL-TK4. The trench was cleaned with a pressure washer and pressurized air. The rock types were determined macroscopically. The rock types in investigation trench OL-TK18 is of heterogeneous character, with a large variation in their composition. The rocks vary from tonalitic-granodioritic gneiss to diatexitic gneiss, with portions of K-feldspar porphyritic gneiss. Inclusions of mica gneiss and a well-preserved schollen migmatite is encountered. The trench ends in a feldspar-rich pegmatoid. The most dominant tectonic feature is D{sub 4} ductile deformation domain and associated S{sub 4} foliation. This domain and hence the S{sub 4} foliation is striking NE-SW with a moderate dip towards SE. Both ends of the trench are dominated by the earlier deformation phase, showing S{sub 3} foliation striking ENE-WSW and roughly dipping towards the S. The S{sub 3} foliation is associated with small-scaled granitic leucosome veining, while the S{sub 4} foliation have a schistose character and it is more sheared. D{sub 4} ductile deformation domain is also characterised by a sheared blastomylonitic rock having growth of roundish feldspar porphyroblasts and BTschlierens indicating high alteration of the protolith. During the fracture mapping, all fractures intersecting the central thread were investigated and a total of 117 fractures were recorded. The average fracture frequency of the trench is 2.11 fractures/m. On the basis of fracture orientations one main set can be distinguished striking NE-SW (foliation parallel) with a moderate dip towards the SE. The median fracture trace length is 1.6 m and over half of the fractures exceed 1.5 m trace length, the longest

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

International Nuclear Information System (INIS)

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

2000-01-01

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

Evolution of supercritical fluid in deeply subducted continental crust: a case study of composite granite-quartz veins in the Sulu belt, China

Science.gov (United States)

Wang, S.; Wang, L.; Brown, M.

2016-12-01

Although fluid plays a key role in element transport and rock strength during subduction to and exhumation from ultrahigh pressure (UHP) metamorphic conditions, the source of supercritical fluid at P above the second critical endpoints (SCE) and the subsequent evolution are not well constrained. To provide insight into the evolution of supercritical fluid in continental subduction zones, we undertook an integrated study of composite granite-quartz veins in retrogressed and migmatitic UHP eclogite at General's Hill, N of Qingdao, in the central Sulu belt. The composite veins are irregularly distributed in the eclogite, which occurs as blocks within gneiss. The granite component is enriched in large ion lithophile elements and light rare earth elements but depleted in high field strength elements and heavy rare earth elements, indicating crystallization from a melt phase of crustal origin. Additionally, the granite contains high modal phengite (22-30 vol%) and clinozoisite/epidote (3-10 vol%), implying precipitation from a H2O-rich silicate melt. By contrast, the quartz component is dominated by SiO2 (99.10 wt%), and contains low total rare earth elements (ΣREE = 0.46 ppm), indicating precipitation from an aqueous fluid. The crystallization age of the composite veins is 221 ± 2 Ma, which is younger than the UHP metamorphism in the Sulu belt at ca 230 Ma, consistent with formation during exhumation. Initial 176Hf/177Hf ratios and δ18O values of metamorphic zircons from the composite veins, and Sr-Nd isotope compositions of the granites all lie between values for eclogite and gneiss, indicating a mixed source. Accordingly, we propose that a supercritical fluid generated from the gneiss and the included blocks of eclogite at P-T conditions above the SCE for both compositions became trapped in the eclogite during exhumation. At P below the SCE for the hydrous granite system, the mixed supercritical fluid separated into immiscible aqueous melt and aqueous fluid and

Origin and evolution of multi-stage felsic melts in eastern Gangdese belt: Constraints from U-Pb zircon dating and Hf isotopic composition

Science.gov (United States)

Guo, Liang; Zhang, Hong-Fei; Harris, Nigel; Pan, Fa-Bin; Xu, Wang-Chun

2011-11-01

This integrated study of whole rock geochemistry, zircon U-Pb dating and Hf isotope composition for seven felsic rocks from the Nyingchi Complex in eastern Himalayan syntaxis has revealed a complex magmatic history for the eastern Gangdese belt. This involves multiple melt sources and mechanisms that uniquely identify the tectonic evolution of this part of the Himalayan orogen. Our U-Pb zircon dating reveals five stages of magmatic or anatectic events: 165, 81, 61, 50 and 25 Ma. The Jurassic granitic gneiss (165 Ma) exhibits εHf(t) values of + 1.4 to + 3.5. The late Cretaceous granite (81 Ma) shows variable εHf(t) values from - 0.9 to + 6.2, indicating a binary mixing between juvenile and old crustal materials. The Paleocene granodioritic gneiss (61 Ma) has εHf(t) values of + 5.4 to + 8.0, suggesting that it originated from partial melting of a juvenile crustal material. The Eocene anatexis is recorded in the leucosome, which has Hf isotopic composition similar to that of the Jurassic granite, indicating that the leucosome could be derived from partial melting of the Jurassic granite. The late Oligocene biotite granite (25 Ma) shows adakitic geochemical characteristics, with Sr/Y = 49.3-56.6. The presence of a large number of inherited zircons and negative εHf(t) values suggest that it sourced from anatexis of crustal materials. In contrast to the Gangdese batholiths that are mainly derived from juvenile crustal source in central Tibet, the old crustal materials play an important role for the magma generation of the felsic rocks, suggesting the existence of a crustal basement in the eastern Gangdese belt. These correspond to specific magmatic evolution stages during the convergence between India and Asia. The middle Jurassic granitic gneiss resulted from the northward subduction of the Neo-Tethyan oceanic slab. The late Cretaceous magmatism is probably related to the ocean ridge subduction. The Paleocene-Eocene magmatism, metamorphism and anatexis are

Molybdenum mineralization at Alpeiner Scharte, Tyrol (Austria): results of in-situ U-Pb zircon and Re-Os molybdenite dating

International Nuclear Information System (INIS)

Langthaler, K.J.; Raith, J.G.; Cornell, D.H.; Stein, H.J.; Melcher, F.

2004-01-01

Vein-type Mo mineralization at Alpeiner Scharte occurs in the Penninic units of the western Tauern Window in the Eastern Alps. Three types of previously undated metagranitoids (central gneisses) are distinguished and preserve intrusive contacts with pre-Alpine metamorphosed supracrustal rocks. The granitic protoliths represent fractionated late to post-orogenic, calc-alkaline, I-type magmas with minor S-type components. The Mo veins are restricted to a biotite and alkali feldspar-rich gneiss variety and occur in E-W trending normally sub-vertical quartz veins with adjacent thin discontinuous garnet- and biotite-rich zones; the latter are interpreted as metamorphosed vein selvages. Prior to this work the age of the intrusive host rocks as well as the age of Mo mineralization were unknown. The pre-Alpine Mo deposit and its host rocks were affected by four Alpine deformation events (D 1 -D 4 ) and Young-Alpine regional metamorphism. The P-T conditions of this metamorphic event were ∼ 550 o C and ∼ 8 kbar and are in agreement with results of previous regional studies. Zircon grains from two orthogneiss samples were dated with the U-Pb method using ion probe techniques. Zircons from the metagranitic host rock of the Mo-veins yielded an emplacement age of 306.8 ± 3.8 Ma (2σ). A second sample from a more leucocratic gneiss lacking Mo-veins gave 305.0 ± 6.6 Ma (2 σ). Re-Os dating of molybdenite from the veins yielded an age of 306.8 ± 3.1 Ma in good agreement with the U-Pb zircon ages. This study confirms one of two alternative hypotheses discussed in the literature. lt supports the idea that vein-type Mo-mineralization in the western Tauern Window is genetically related to Late Carboniferous (Westphalian) granitoids that were emplaced during the late to post-orogenic stage of the Variscan orogeny. They do not constitute an Alpine metamorphic-hydrothermal deposit. This study further confirms the strength of the Re-Os molybdenite chronometer, in that it was

Sorption of cesium in intact rock

International Nuclear Information System (INIS)

Puukko, E.

2014-04-01

The mass distribution coefficient K d is used in performance assessment (PA) to describe sorption of a radionuclide on rock. The R d is determined using crushed rock which causes uncertainty in converting the R d values to K d values for intact rock. This work describes a method to determine the equilibrium of sorption on intact rock. The rock types of the planned Olkiluoto waste disposal site were T-series mica gneiss (T-MGN), T-series tonalite granodiorite granite gneiss (T-TGG), P-series tonalite granodiorite granite gneiss (P-TGG) and pegmatitic granite (PGR). These rocks contain different amount of biotite which is the main sorbing mineral. The sorption of cesium on intact rock slices was studied by applying an electrical field to speed up migration of cesium into the rock. Cesium is in the solution as a noncomplex cation Cs + and it is sorbed by ion exchange. The tracer used in the experiments was 134 Cs. The experimental sorption on the intact rock is compared with values calculated using the in house cation exchange sorption model (HYRL model) in PHREEQC program. The observed sorption on T-MGN and T-TGG rocks was close to the calculated values. Two PGR samples were from a depth of 70 m and three samples were from a depth of 150 m. Cesium sorbed more than predicted on the two 70 m PGR samples. The sorption of Cs on the three 150 m PGR samples was small which was consistent with the calculations. The pegmatitic granite PGR has the smallest content of biotite of the four rock types. In the case of P-TGG rock the observed values of sorption were only half of the calculated values. Two kind of slices were cut from P-TGG drill core. The slices were against and to the direction of the foliation of the biotite rims. The sorption of cesium on P-TGG rock was same in both cases. The results indicated that there was no effect of the directions of the electric field and the foliation of biotite in the P-TGG rock. (orig.)

Early lineations in a later shear zone: case study from the Eastern Ghats Belt, India

Science.gov (United States)

Bose, S.; Gupta, S.

2016-12-01

In polydeformed gneissic terranes, ductile shear zones may cut across rocks with older penetrative fabrics. Earlier lineations in later ductile shear zones need to be identified to avoid incorrect kinematic interpretation. To investigate the fate of early lineations during later ductile shearing, the Mahanadi Shear Zone (MSZ) from the Eastern Ghats Belt (EGB) in India is taken as a case study. The EGB is a Proterozoic granulite terrane correlated with Indo-Antarctica collision. The MSZ lies within the EGB, but is oriented almost perpendicular to the trend of the belt. The penetrative structural fabric in the EGB is NE-SW trending and dipping SE. However, a broad swing in structural trend from NE-SW to WNW-ESE can be detected near the MSZ from satellite imagery. In mylonitised rocks of the shear zone, a discrepancy between the shear zone lineation and inferred shear sense leads to uncertainty in kinematic interpretation of the shear zone. The EGB rock types include charnockites, quartzofeldspathic gneisses and garnet-sillimanite-bearing metapelitic gneisses (khondalites). Outside the MSZ, gneisses preserve an earlier, dominantly down-dip intersection lineation. Sillimanite needles in khondalites are aligned parallel to this lineation, while quartz and garnet are also annealed into the granulite facies fabric. In the vicinity of the shear zone, evidence of dextral non-coaxial shearing progressively increases but the lineation distribution is scattered. Quartz grains show strong undulose extinction caused by strain at lower temperatures, and crystallographic c-axis fabric analyses using EBSD indicate deformation by basal c-slip mechanism. Preferred alignment of the sillimanite needles is disrupted in khondalites within the MSZ because of partial rotation of the needles towards the sub-horizontal movement direction, with the extent of rotation of the needles being apparently controlled by grain size. Some sillimanite needles also appear to have undergone

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

Science.gov (United States)

Zhang, B.

2016-12-01

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

Geologic map of the Big Delta B-2 quadrangle, east-central Alaska

Science.gov (United States)

Day, Warren C.; Aleinikoff, John N.; Roberts, Paul; Smith, Moira; Gamble, Bruce M.; Henning, Mitchell W.; Gough, Larry P.; Morath, Laurie C.

2003-01-01

New 1:63,360-scale geologic mapping of the Big Delta B-2 quadrangle provides important data on the structural setting and age of geologic units, as well as on the timing of gold mineralization plutonism within the Yukon-Tanana Upland of east-central Alaska. Gold exploration has remained active throughout the region in response to the discovery of the Pogo gold deposit, which lies within the northwestern part of the quadrangle near the south bank of the Goodpaster River. Geologic mapping and associated geochronological and geochemical studies by the U.S. Geological Survey (USGS) and the Alaska Department of Natural Resources, Division of Mining and Water Management, provide baseline data to help understand the regional geologic framework. Teck Cominco Limited geologists have provided the geologic mapping for the area that overlies the Pogo gold deposit as well as logistical support, which has lead to a much improved and informative product. The Yukon-Tanana Upland lies within the Tintina province in Alaska and consists of Paleozoic and possibly older(?) supracrustal rocks intruded by Paleozoic (Devonian to Mississippian) and Cretaceous plutons. The oldest rocks in the Big Delta B-2 quadrangle are Paleozoic gneisses of both plutonic and sedimentary origin. Paleozoic deformation, potentially associated with plutonism, was obscured by intense Mesozoic deformation and metamorphism. At least some of the rocks in the quadrangle underwent tectonism during the Middle Jurassic (about 188 Ma), and were subsequently deformed in an Early Cretaceous contractional event between about 130 and 116 Ma. New U-Pb SHRIMP data presented here on zircons from the Paleozoic biotite gneisses record inherited cores that range from 363 Ma to about 2,130 Ma and have rims of euhedral Early Cretaceous metamorphic overgrowths (116 +/- 4 Ma), interpreted to record recrystallization during Cretaceous west-northwest-directed thrusting and folding. U-Pb SHRIMP dating of monazite from a Paleozoic

The geology and mineral deposits of Tantalite Valley, Warmbad district, South West Africa

International Nuclear Information System (INIS)

Von Backstroem, J.W.

1976-04-01

The Tantalite Valley Complex, a poorly mineralised (Cu and Ni sulphides) body of roughly concentric peridotite-gabbroid intrusions was emplaced along a major zone of dislocation (the Tantallite Valley Lineament) into a metasedimentary sequence of migmatites and gneisses which, together with the complex, have experienced a complex metamorphic and tectonic history. A number of large mineralised pegmatites (producers of minerals of Nb, Ta, Bi, Li and Be over the past two decades), was intruded about 1000 Ma ago [af

Geology and fluorspar deposits, Northgate district, Colorado

Science.gov (United States)

Steven, Thomas A.

1960-01-01

The fluorspar deposits in the Northgate district, Jackson County, Colo., are among the largest in Western United States. The mines were operated intermittently during the 1920's and again during World War II, but production during these early periods of operation was not large. Mining was begun on a larger scale in 1951, and the district has assumed a prominent position among the fluorspar producers in the United States. Within the Northgate district, Precambrian metamorphic and igneous rocks crop out largely in the Medicine Bow Mountains, and later sedimentary rocks underlie North Park and fill old stream valleys in the mountains. The metamorphic rocks constitute a gneiss complex that formed under progressively changing conditions of regional metamorphism. They consist principally of hornblende-plagioclase gneiss (hornblende gneiss), quartz monzonite gneiss, pegmatite, biotite-garnet-quartz-plagioclase gneiss (biotite-garnet gneiss), hornblende-biotite-quartz-plagioclase gneiss (hornblende-biotite gneiss) and mylonite gneiss. The igneous rocks comprise some local fine-grained dacite porphyry dikes near the west margin of the district, and a quartz monzonitic stock and associated dikes in the central and eastern parts of the district. The sedimentary rocks in the district range in age from Permian to Recent. Folded Permian and Mesozoic rocks underlie the basin of North Park, and consist in sequence from oldest to youngest, of Satanka(?) shale (0-50 feet of brick-red shale) and Forelle(?) limestone (8-15 feet of pink to light-gray laminated limestone) of Permian age, Chugwater formation of Permian and Triassic age (690 feet of red silty shale and sandstone), Sundance formation of Late Jurassic age (145 feet of sandstone containing some shale and limestone), Morrison formation of Late Jurassic age (445 feet of variegated shale and minor sandstone and limestone), Dakota group as used by Lee (1927), now considered to be of Early Cretaceous age in this area (200

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

Science.gov (United States)

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

1952-01-01

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

Sediment underthrusting within a continental magmatic arc: Coast Mountains batholith, British Columbia

Science.gov (United States)

Pearson, David M.; MacLeod, Douglas R.; Ducea, Mihai N.; Gehrels, George E.; Jonathan Patchett, P.

2017-10-01

Though continental magmatic arcs are factories for new continental crust, a significant proportion of continental arc magmas are recycled from supracrustal material. To evaluate the relative contributions of retroarc underthrusting and trench side partial sediment subduction for introducing supracrustal rocks to the middle and lower crust of continental magmatic arcs, we present results from the deeply exposed country rocks of the Coast Mountains batholith of western British Columbia. Prior work demonstrates that these rocks underwent widespread partial melting that contributed to the Coast Mountains batholith. We utilize U-Pb zircon geochronology, Sm-Nd thermochronology, and field-based studies to document the protoliths and early burial history of amphibolite and granulite-facies metasedimentary rocks in the Central Gneiss Complex. U-Pb detrital zircon data from the structurally highest sample localities yielded 190 Ma unimodal age peaks and suggest that retroarc rocks of the Stikine terrane constitute a substantial portion of the Central Gneiss Complex. These supracrustal rocks underwent thrust-related burial and metamorphism at >25 km depths prior to 80 Ma. These rocks may also be underlain at the deepest exposed structural levels by Upper Cretaceous metasedimentary rocks, which may have been emplaced as a result of trench side underplating or intraarc burial. These results further our understanding of the mechanisms of material transport within the continental lithosphere along Cordilleran subduction margins.

Geochemical and mineralogical study of selected weathered samples from Olkiluoto site

International Nuclear Information System (INIS)

Lindberg, A.

2009-02-01

Optical microscopy, chemical analyses and X-ray diffraction method were used to study the influence of weathering from 11 drill core samples from shallow depths (< 25 m). The samples, 4 to 22 cm in length were drilled from Olkiluoto study site, Eurajoki, and they represent the common rock types of local bedrock: mica gneiss, tonalitic and granodioritic gneiss. Two of the samples were macroscopically unweathered and 9 of them were remarkably altered. The alteration was shown as porosity, the abundance of chlorite instead of biotite and pink, unclear feldspars. Many samples also contained red-brown hematite and fractures, some of them coated with secondary minerals, even clay. Microscopically the most visible feature of weathering was the total alteration of plagioclase and cordierite to sericite. In many samples also biotite was richly altered to chlorite and opaque minerals. Microfractures were common and they were filled by hematite, kaolinite and fine-grained muscovite (sericite). Hematite was, in some cases, also largely replacing the weathered minerals, feldspars and cordierite. Chemical alteration was not clear, because the alteration of main minerals have produced secondary minerals with almost the same chemical composition without any reasonable depleting or enrichment of certain elements. X-ray diffraction determination of samples proved, that often plagioclase was replaced by mica and biotite by chlorite. In some cases the samples contained products of chemical weathering, kaolinite and smectite. (orig.)

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1997-05-27

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

Structural and kinematic analysis from Montevideo Formation rocks

International Nuclear Information System (INIS)

Masquelin, E.; Gutierrez, L.; Sienra, M.

2004-01-01

The main purpose of this work is to bring new advances about structural and kinematic analysis from Montevideo Formation rocks. This information was collected by means of the classic methodology used for metamorphic terrains: (i) to recognize the nature of the protoliths, (ii) to discriminate the diversity of intrusive rocks and their relative age, (iii) to evaluate the intensity of strain, and (iv) to find the relationship between this strain and related displacements, in accordance to the unified theory for ductile shear zones. The exposed results show that there are not enough evidences to prove that the layering found in para-amphibolites and para-gneisses is the bedding surface. Although various lava primary structures were presented, these structures do not bring the bedding plane directly, and sedimentary structures are suspicious. In the other hand, the strain has proved to be very intense, by the development of isoclinal folds (may be intrafolial), highly strained veins of plagioclase-bearing gneiss and the boudinage of the duplicated sequence parallel to the axes of D2 later folds. The D2 fold axes parallel direction could be acted as the transport direction of a major strike-slip shear zone, striking N70 0 E. The fact is that various ductile flow vorticity indicators were found in para-amphibolites showing a dextral shear sense [es

Transpressional granite-emplacement model: Structural and magnetic study of the Pan-African Bandja granitic pluton (West Cameroon)

Science.gov (United States)

Sandjo, A. F. Yakeu; Njanko, T.; Njonfang, E.; Errami, E.; Rochette, P.; Fozing, E.

2016-02-01

The Pan-African NE-SW elongated Bandja granitic pluton, located at the western part of the Pan-African belt in Cameroon, is a K-feldspar megacryst granite. It is emplaced in banded gneiss and its NW border underwent mylonitization. The magmatic foliation shows NE-SW and NNE-SSW strike directions with moderate to strong dip respectively in its northern and central parts. This mostly, ferromagnetic granite displays magnetic fabrics carried by magnetite and characterized by (i) magnetic foliation with best poles at 295/34, 283/33 and 35/59 respectively in its northern, central and southern parts and (ii) a subhorizontal magnetic lineation with best line at 37/8, 191/9 and 267/22 respectively in the northern, central and southern parts. Magnetic lineation shows an `S' shape trend that allows to (1) consider the complete emplacement and deformation of the pluton during the Pan-African D 2 and D 3 events which occurred in the Pan-African belt in Cameroon and (2) reorganize Pan-African ages from Nguiessi Tchakam et al. (1997) compared with those of the other granitic plutons in the belt as: 686 ±17 Ma (Rb/Sr) for D 1 age of metamorphism recorded in gneiss; and the period between 604-557 Ma for D 2-D 3 emplacement and deformation age of the granitic pluton in a dextral ENE-WSW shear movement.

Rubidium in the food chain

Energy Technology Data Exchange (ETDEWEB)

Anke, M. [Inst. of Nutrition and Environment, Friedrich Schiller Univ., Jena (Germany); Angelow, L. [Inst. of Nutrition and Environment, Friedrich Schiller Univ., Jena (Germany)

1995-05-01

In spite of its abundant occurrence in the earth`s crust (310 mg Rb/kg) and its composition of a stable (72.2%) and a radioactive (27.8%) isotope, rubidium (Rb) belongs to the forgotten ultratrace elements. The interest in this ultratrace element grew considerably after Rb deficiency experiments with goats had shown that their growth was depressed, that > 80% of them aborted their kids. The geological origin of the site takes significant effect on the Rb content of the flora. Granite and gneiss weathering soils produce the by far Rb-richest plant populations, and drinking water. The water of the gneiss sites contained 18 {mu}g Rb/l, that of diluvial sands 3 {mu}g/l. Herbivores store most Rb whereas carnivores and omnivores accumulate significantly less Rb. The analysis of 137 foodstuffs and beverages in 15-fold repetition showed that the starch- and sugar-rich cereals, pasta, bread and confectionary are poor in Rb (1 mg/kg dry mater (DM)). Fruit and vegetables accumulate between 5 and > 60 mg Rb/kg (asparagus). Boiling drastically reduces the Rb content of vegetables. Animal foodstuffs are relatively poor in Rb. Poultry meat as well as freshwater fish are relatively rich in Rb. Coffee (40 mg/kg DM) and black tea (100 mg Rb/kg DM) store much Rb, 85% of which pass into the beverage. (orig.)

Gas-charged sediments on the inner continental shelf off western India

Digital Repository Service at National Institute of Oceanography (India)

Karisiddaiah, S.M.; Veerayya, M.; Vora, K.H.; Wagle, B.G.

the enormous reserves of methane hydrates in the Arctic (Nisbet, 1989) and elsewhere. Owens et al. (1991) observed that the northern Arabian Sea is an oceanic region of unusually high methane concentrations and fluxes to the atmo- sphere. In view... The western continental shelf of India between IO°N and 22°N is bordered by the Deccan Traps (volcanic rocks) of Cretaceous age towards the north of Goa, whereas Peninsular gneisses, char- nockites and various schistose formations of Archaean age...

Lead isotopic study of aplites from the Precambrian basement rocks near Ibadan, southwestern Nigeria

International Nuclear Information System (INIS)

Oversby, V.M.

1975-01-01

Pb isotopic compositions for three total-rock samples of aplite and their constituent K-feldspars from the Nigerian basement assemblage near Ibadan show lead homogenization during the Pan-African thermo-tectonic event. A secondary isochron formed by the K-feldspars data points is used to calculate a primary age of about 2750 m.y. for the aplites. The aplites do not register any Pb isotopic effect from the intrusion of granite gneiss in the area at 2330m.y. (Auth.)

Surficial clay mineral distribution on the southwestern continental margin of India: Evidence of input from the Bay of Bengal

Digital Repository Service at National Institute of Oceanography (India)

Chauhan, O.S.; Gujar, A.R.

LATERITE 3922 MIOCENE SANDSTONE (~) ARCHEANS ( GRANITE GNEISS I' --J CHARNOKITES ~ KHONOALITES) ~J 3940 -t- -4- -t- -t- ~ .. t Jr -4- + + + + Jr -t- Jr + Jr -t- -t- 4- -t- 4- Jre" + -t- + 4- + -t-.. + + 4- WADGE BANK INDIA -~ + + + + *4 t... et al., 1990). In the southern region, the shelf is marked by a low gradient physiographic feature, i.e. Wadge Bank (gradient 1:756), which has considerably enhanced the width of the shelf. The shelf break is shallowest in this region...

The geology of the Vaalputs radioactive waste disposal site, with implications for granite-charnockite relationships and crustal evolution in western Namaqualand

International Nuclear Information System (INIS)

Andreoli, M.A.G.; Brynard, H.J.; Anderson, N.J.B.; Hart, R.J.; Moore, J.M.; Welke, H.

1990-01-01

The Precambrian geology of the Valputs site is characterized by extensive sheets of Spektakel Suite syntectonic granite gneisses. Experimental methods used for the geological evaluation of the Vaalputs site included semi-regional and site-specific mapping. All main rock types were petrologically and geochemically classified. In addition, preliminary Rb-Sr whole-rock ages were calculated for the main lithotypes, together with Sm-Nd dating. The investigations for the licensing of the Vaalputs site have revealed numerous intriguing aspects of the crustal history in southwestern Namaqualand. 10 refs

O Gnaisse Facoidal: a mais Carioca das Rochas.

OpenAIRE

Kátia Leite Mansur; Ismar Souza Carvalho; Carlos Fernando Moura Delphim; Emilio Velloso Barroso

2008-01-01

The city of Rio de Janeiro is known by its natural beauties. The mountains and the sea make the city the postcard ofBrazil. The sculpture of the carioca landscape is closely related to the augen gneiss, very resistant rock to the weatheringand, for this reason, it stands out in the relief. It gives form for Sugar Loaf and Corcovado, for example. Augen gneisswas used in the construction of most of the historical buildings of the city, including museums and churches, manyof them were built in t...

U-Pb SHRIMP and Sm-Nd geochronology of the paleoproterozoic Silvania magmatic arc in the neoproproterozoic Brasilia Belt, Goias, Central Brazil

International Nuclear Information System (INIS)

Fischel, D.P.; Pimentel, M.M.; Fuck, R.A; Armstrong, R

2001-01-01

The Brasilia Belt is a large Neoproterozoic orogen formed along the western margin of the Sao Francisco/Congo Craton in central Brazil. It comprises: (i) a thick Meso-Neoproterozoic metasedimentary/sedimentary pile with eastward tectonic vergence; (ii) a large Neoproterozoic juvenile arc in the west (Goias Magmatic Arc); and (iii) a micro-continent (or exotic sialic terrain) formed by Archean rock units (the Crixas -Goias granitegreenstones) and associated Proterozoic formations (Almeida et al. 1981, Fuck et al. 1993,1994, Pimentel et al. 2000a, b). The sialic basement on which the Brasilia Belt sediments were deposited is poorly understood, despite being well exposed in some areas of Goias and Tocantins. Gneiss and volcano-sedimentary units form most of this basement. Early studies have suggested that these rock units are dominantly Archean ( Danni et al. 1982, Marini et al. 1984). However, recent Sm- Nd isotopic studies have indicated that most of them are Paleoproterozoic (Sato 1998, Pimentel et al. 1999a, 2000b). Granite gneiss to the south and east of the Barro Alto mafic-ultramafic layered complex has been dated at 2128+/- 15 Ma (Correia et al. 1997). Calc-alkaline granite gneiss from Almas-Dianopolis is dated at ca. 2.2-2.45 Ga old (U-Pb SHRIMP on zircon and titanite, Cruz et al. 2000). The latter is probably the western extension of Paleoproterozoic rocks which underlie the San Francisco Craton to the east of the northern part of the Brasilia Belt. In central Goias, a large part of the Brasilia Belt is underlain by high-grade metamorphic rocks known as the Anapolis-Itaucu Complex, together with surrounding greenschist to amphibolite facies Mesoto Neoproterozoic cover metasediments of the Araxa group. These rocks represent the main constituent of the internal zone of the Brasilia Belt (Fuck et al. 1994, Pimentel et al. 2000b). Between the Araxa Group, and the easternmost part of the Anapolis-Itaucu Complex a volcano-sedimentary association known as Silvania

Fluid inclusions in minerals associated to uranium mineralization in Jazida do Engenho (anomaly 09), Lagoa Real uranium province - Bahia, Brazil; Inclusoes fluidas nos minerais associados a mineralizacao uranifera da Jazida do Engenho (Anomalia 09), provincia uranifera de Lagoa Real, BA

Energy Technology Data Exchange (ETDEWEB)

Souza, Aurelio da Silva de

2009-07-01

The Engenho deposit (anomaly 09) is south-eastern from Cachoeira Mine (anomaly 13), in the northern part of the Province. The uranium mineralization is associated to 'albitites' (over 70% of albite/oligoclase). Epidosites with uranium may also occur. The 'albitite' main minerals are pyroxene, gamet, albite/oligoclase feldspar, amphibole and biotite. Pyroxene, gamet, plagioclase, titanite and epidote are the minerals associated to the uranium mineralization. The fluids related to pyroxene, gamet and epidote are aqueous-saline, primary and with no carbonic phases and are constant, with small variations. They all present medium to high salinity (14 to 18wt% NaCl eq.), the higher values being related to pyroxene and the lower ones related to gamet and epidote. The fluids associated to albite/oligoclase, although aqua-saline and with no carbonic phases, show salinities much lower than in pyroxene, gamet and epidote, suggesting a intense dilution process indicating dilution toward the later minerals phases. The data suggest the pyroxene formation process occurring under a 3,5 kbar pressure condition which corresponds to approximately 10km depth. The dispersion on Th in albites, due probably to the overheating and non elastic increase in volume, precluded a reliable pressure calculation. The IF's microscopy m plagioclase gneiss (albitites host-rocks) suggests the probability of primary carbonic fluids associated to these minerals. The fluids with CO{sub 2} showed in the gneiss maybe also be present in the albitites, probably as late or intergranular fluids. This assumption is based on the fact that signs of carbonic gases were shown during crushing tests. These tendencies suggest the occurrence of two albitization phases in this Lagoa Real area: one associated to a fluid composed by H{sub 2}O + CO{sub 2} + salts (in the gneiss host) and another (in the albitite) formed by an aqueous-saline phase. The data indicate the Brasiliano event as a thermal

Concentration of 226Ra in rocks of the southern part of Lower Silesia (SW Poland)

International Nuclear Information System (INIS)

Przylibski, Tadeusz Andrzej

2004-01-01

The aim of the article is to present a preliminary description of rocks in the southern part of Lower Silesia and the Sudety Mountains in particular, with regard to 226 Ra content. The research demonstrates that the average content of this isotope was 40.4 Bq/kg in the rocks of the southern part of Lower Silesia, and 41.7 Bq/kg in the rocks of the Sudetes. These values are slightly higher than the mean 226 Ra content in the upper part of the Earth's crust, while the measured maximum content of this isotope (244 Bq/kg) is more than twice as high as the upper range of the values most frequently recorded in the upper part of the Earth's crust. The minimum values were lower than the detection limit, which was about 1 Bq/kg. These results reflect the mosaic-like geological structure of Lower Silesia, and particularly the Sudety Mountains, the occurrence of SiO 2 -rich igneous rocks and the products of their metamorphism, as well as numerous manifestations of uranium mineralisation or even deposital concentrations of this element. The rocks with the highest 226 Ra contents include (in decreasing order): aplites, granites, gneisses and leucogranites, granite-gneisses, granodiorites and rhyolites, and, finally, mudstones. The lowest values of 226 Ra content, on the other hand, were measured in sandstones, marls and conglomerates, and extremely low - in marbles and quartzites. The results show that background values of 226 Ra content in the rocks of the southern part of Lower Silesia fall within a range from several to about 100 Bq/kg, which is the same as the range most frequently recorded in the upper part of the Earth's crust. Distribution of these values has log-normal character. The research demonstrates that the southern part of Lower Silesia, and the Sudetes in particular, may be marked by an increased radon potential. Particularly liable areas are: the Karkonosze granite massif, especially in its border zones, the Ladek-Snieznik and the Izera massifs, especially in

Fluid inclusions in minerals associated to uranium mineralization in Jazida do Engenho (anomaly 09), Lagoa Real uranium province - Bahia, Brazil

International Nuclear Information System (INIS)

Souza, Aurelio da Silva de

2009-01-01

The Engenho deposit (anomaly 09) is south-eastern from Cachoeira Mine (anomaly 13), in the northern part of the Province. The uranium mineralization is associated to 'albitites' (over 70% of albite/oligoclase). Epidosites with uranium may also occur. The 'albitite' main minerals are pyroxene, gamet, albite/oligoclase feldspar, amphibole and biotite. Pyroxene, gamet, plagioclase, titanite and epidote are the minerals associated to the uranium mineralization. The fluids related to pyroxene, gamet and epidote are aqueous-saline, primary and with no carbonic phases and are constant, with small variations. They all present medium to high salinity (14 to 18wt% NaCl eq.), the higher values being related to pyroxene and the lower ones related to gamet and epidote. The fluids associated to albite/oligoclase, although aqua-saline and with no carbonic phases, show salinities much lower than in pyroxene, gamet and epidote, suggesting a intense dilution process indicating dilution toward the later minerals phases. The data suggest the pyroxene formation process occurring under a 3,5 kbar pressure condition which corresponds to approximately 10km depth. The dispersion on Th in albites, due probably to the overheating and non elastic increase in volume, precluded a reliable pressure calculation. The IF's microscopy m plagioclase gneiss (albitites host-rocks) suggests the probability of primary carbonic fluids associated to these minerals. The fluids with CO 2 showed in the gneiss maybe also be present in the albitites, probably as late or intergranular fluids. This assumption is based on the fact that signs of carbonic gases were shown during crushing tests. These tendencies suggest the occurrence of two albitization phases in this Lagoa Real area: one associated to a fluid composed by H 2 O + CO 2 + salts (in the gneiss host) and another (in the albitite) formed by an aqueous-saline phase. The data indicate the Brasiliano event as a thermal event without a predominant fluid

The geology of the Cluff Lake uranium deposits

International Nuclear Information System (INIS)

Harper, C.T.

1978-01-01

The uranium deposits discovered by Amok (Canada) Ltd. in the Cluff Lake area of northwestern Saskatchewan occur at or near the southern edge of the uplifted basement core of the Carswell circular structure. Two types of mineralization, distinguishable by their geological and structural setting and mineral paragenesis, have been recognized. The N-Claude type is characterized by a relatively simple mineral assemblage, consisting of uraninite or pitchblende with coffinite, and is accompanied by variable amounts of graphite and organic matter, and Fe, Cu, Pb and Mo sulphides. Both N and Claude orebodies occur within quartzofeldpathic gneisses of the basement core. On the other hand, the D-type ore has a complex mineral assemblage consisting of: uraninite, pitchblende, tucholite and coffinite, along with native gold and selenium; gold tellurides, and selenides of Pb, Bi, Ni and Co; sulphides of Fe, Cu and Pb; and organic matter. The D orebody occurs within carbonaceous shales at the base of the Athabasca Formation as well as in fault zones in regolithic quartzofeldspathic gneisses above the inverted unconformity. An age of 1050 m.y., which is consistent with a period (circa 1200-1000 m.y.) of widespread hydrothermal activity and uranium mineralization or reworking within and adjacent to the Athabasca Basin, has been obtained from uranium mineralization from the D orebody. Later reworking (circa 470 m.y.) of the mineralization occurred at the intersection of older mineralized shear zones with radial faults produced during meteorite impact. (auth)

The regional geological and structural setting of the uraniferous granitic provinces of Southern Africa

International Nuclear Information System (INIS)

Jacob, R.E.; Corner, B.; Brynard, H.J.

1986-01-01

Uranium-bearing granites, comprising both potentially economic deposits and source rocks for uranium deposits is duricrustal and sedimentary sequences, are confined chiefly to the mobile belts of Southern Africa and to the Cape granites emplaced during late Precambrian times. The direct uranium potential of the mobile belts, i.e. the Damara, Namaqua-Natal and Limpopo belts, decreases with an increase in the age of associated ensialic diastrophism. This review paper is thus mainly confined to the Damara Belt, although a brief discussion of the potential of the Namaqua Belt is presented. Aspects of the Damara Belt that are discussed in detail, with particular reference to the occurrence of uraniferous granite, include regional tectonic setting, stratigraphy, structure, metamorphism and the patterns and origin of the uranium mineralization. Initial concentrations of uranium in basement and Nosib rocks have led, through ultrametamorphism and fractionation, to uraniferous granites of both economic and sub-economic grade. These granites, in turn, have acted as source of secondary mineralization in overlying superficial calcareous and gypsiferous deposits. The Damara Belt thus provides a good example of multicyclic processes of ore formation. With regard to the uraniferous granites of Namaqualand it is concluded that the porphyroblastic gneisses and late-intrusive Concordia granites, although not of direct economic interest, represent major sources of uranium for secondary superficial deposits. Smaller bodies of late-phase differentiates associated with the Concordia granitic gneiss may themselves, however, represent potentially economically viable deposits

Uranium geology and prospecting in Greenland

International Nuclear Information System (INIS)

Steenfelt, A.; Neilson, B.L.; Secher, K.

1977-01-01

The Geological Survey of Greenland is responsible for most of the uranium and thorium prospecting activity in Greenland, which involves airborne gamma spectrometry and scintillometry, geochemical sampling, geological investigations and ground scintillometry. Since 1971 large areas of east and west Greenland have been investigated by aerial surveys, geochemical sampling and most of the detailed scintillometric work having been restricted to small areas in east Greenland. Anomalous radioactivity in west Greenland is recorded from carbonatite intrusions, and from units in Proterozoic and Archaean gneisses. No mineralization has been found to date. In south Greenland investigations have been centred on the uranium and thorium deposit at Kvanefjeld, which is situated in a corner of the Ilimaussaq alkaline intrusion. The coincidence of favourable conditions during the differentiation and crystallization of the magma led to an extreme enrichment of uranium and thorium in the rocks that were last formed - the lujavrites. The deposit comprises parts of the lujavrites and a secondary enrichment zone in the contact between lujavrite and basaltic cover rocks. Reasonably assured reserves are 5800 t U with a grade of 310 ppm U. In the Caledonides of east Greenland some gneisses in basement cores, a dark siltstone in late Precambrian sediments and the Devonian acid magmatic rocks are characterized by a higher radiation level. A number of small mineral occurrences have been found, the majority of which are associated with the Devonian acid magmatic rocks. (author)

The Cambrian cavalcades in the Cuchilla Dionisio sub ground. Uruguay

International Nuclear Information System (INIS)

Bossi, J.

2010-01-01

Most tratadistes consider that Sierra Ballena shear zone (SBSZ) is the western limit of an all octon block after the paper of Boss i and Gauche r (2004) showing a detailed geological map. The same method was applied to sporulation block in the Ne of Treinta y Tres city. It was obtained a 1/100.000 geological map with photo geology and 140 field data in an area of 3500 k m2. This document allowed to discover two kinds of mega - faults put in action at the same time (about 525 Ma): a mega shear zone N30E80E with proto - to ultramylonites similar to SBSZ and a regional thrust fault with vergence to NNW. The thrust fault has different features according to the affected type of rocks. At La Micaela, the mica schists are thrust ed by gneisses and migmatites. To the N W the gneisses became firstly sharply laminated and then, horizontal ultramylonites. Both kind of faulting produced at the same time may not be explained by an orthogonal collision and instead of it, is a naturalist proof of tangential collision and alcoholisation nature of the crustal block. In order to easily understand the new proposal it is necessary to change Paso del Dragón fm by Micaela fm, Cuchilla Dionisio Terrane by Treinta y Tres; Punta del Este Terrane by Punta del Este sub - terrane

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

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

Science.gov (United States)

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

1979-01-01

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

Controls of Soil Spatial Variability in a Dry Tropical Forest.

Directory of Open Access Journals (Sweden)

Sandeep Pulla

Full Text Available We examined the roles of lithology, topography, vegetation and fire in generating local-scale (<1 km2 soil spatial variability in a seasonally dry tropical forest (SDTF in southern India. For this, we mapped soil (available nutrients, Al, total C, pH, moisture and texture in the top 10 cm, rock outcrops, topography, all native woody plants ≥1 cm diameter at breast height (DBH, and spatial variation in fire frequency (times burnt during the 17 years preceding soil sampling in a permanent 50-ha plot. Unlike classic catenas, lower elevation soils had lesser moisture, plant-available Ca, Cu, Mn, Mg, Zn, B, clay and total C. The distribution of plant-available Ca, Cu, Mn and Mg appeared to largely be determined by the whole-rock chemical composition differences between amphibolites and hornblende-biotite gneisses. Amphibolites were associated with summit positions, while gneisses dominated lower elevations, an observation that concurs with other studies in the region which suggest that hillslope-scale topography has been shaped by differential weathering of lithologies. Neither NO3(--N nor NH4(+-N was explained by the basal area of trees belonging to Fabaceae, a family associated with N-fixing species, and no long-term effects of fire on soil parameters were detected. Local-scale lithological variation is an important first-order control over soil variability at the hillslope scale in this SDTF, by both direct influence on nutrient stocks and indirect influence via control of local relief.

Geochemical characterization of rare earth elements from fluorite deposits of Tangua district - RJ

International Nuclear Information System (INIS)

Coelho, C.E.S.; Dardenne, M.A.

1987-01-01

The Tangua fluorite vein-type deposits are related to an alkaline complex of the same name, and situated in the District of Itaborai, in the State of Rio de Janeiro. The plutonic body of nepheline syenites (Tangua Massif) intrudes basement gneisses, with dykes and sills of trachitic and phonolitic nature of hundreds of meters in length and centimeters to tens of meters in thickness. The fluorite veins are emplaced both in gneisses and alkaline rocks (plutonic body and dykes) in NE-ENE structures created or reactivated during the opening of the South Atlantic Ocean. The geochemical study of rare earth elements reveals that these mineralizations show very low contents in these elements, and a relatively high fractionation spectres. In the deposit environment, four mineralization phases were differenciated, with the first one being considered as the initial solution; the second one characterized by a new europium rich-solution; the third one, representing the evolution of this new solution, but in a reducing environment, with precipitation of pyrite; and the last one, representing a new batch of the initial solution. As a consequence of the REE's and fluid inclusions studies, we are able to suggest an origen by weathering of the country rocks due to superficial meteorics solutions along faults and fractures, that when heated in deep environments, promote lixiviation of silica and fluorine and precipitate the fluorites when their ascending movement comes to an end. (author) [pt

Core drilling of deep drillhole OL-KR54 at Olkiluoto in Eurajoki 2010

International Nuclear Information System (INIS)

Toropainen, V.

2010-11-01

As a part of the confirming site investigations at Olkiluoto, Suomen Malmi Oy (Smoy) core drilled a 500.18 m deep drillhole with a diameter of 75.7 mm at Olkiluoto in July - August 2010. The identification number of the drillhole is OL-KR54. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the returning and drilling water were recorded. The drill rig was computer controlled and the computer recorded drilling parameters during drilling. The objective of the measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volume of the used drilling, washing and flushing water was 382 m 3 . The measured volume of the returning water in the drillhole was 334 m 3 . The deviation of the drillhole was measured with the deviation measuring instruments EMS and Gyro. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength was 111.5 MPa, the average Young's Modulus was 43.7 GPa and the average Poisson's ratio was 0.17. The main rock types are diatexitic and veined gneisses, pegmatitic granite and mafic gneiss. The average fracture frequency is 1.6 pcs/m and the average RQD value is 97.6 %. Nine fractured zones were penetrated by the drillhole. (orig.)

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

International Nuclear Information System (INIS)

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

1990-01-01

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

The millstone industry a summary of research on quarries and producers in the United States, Europe and elsewhere

CERN Document Server

Hockensmith, Charles D

2009-01-01

Since prehistoric times, the process of cutting rock to make millstones has been one of the most important industries in the world. The first part of this book compiles information on the millstone industry in the United States, which dates between the mid-1600s and the mid-1900s. Primarily based on archival research and brief accounts published in geological and historical volumes, it focuses on conglomerate, granite, flint, quartzite, gneiss, and sandstone quarries in different regions and states. The second part focuses on the millstone quarrying industry in Europe and other areas.

Geology and Geochemistry of the Poco de Fora region-Curaca river valley-Bahia-Brazil

International Nuclear Information System (INIS)

Figueiredo, M.C.H. de.

1976-01-01

In the Poco de Fora region level rocks of light metamorphism, from Caraiba group, corresponding to: - a meta-sedimentar sequence from Lower Pre-cambrian (Archean) - maphic-ultramaphic bodies with Fe and Cu sulphides of volcanogenic origin, and - sienitic ortho-gneiss. Geological, petrographic, geochemistry and geochronological studies were done. The sienitic-intrusion, from the upper crust, occur during the Archean-beginning of the Proterozoic. All the region was re-mobilized, and the sienitic was metamorphosed during Transamazonic Orogeny (2.200 to 1.800 m.y.). (C.D.G.) [pt

Oxigen isotope compositions as indicators of epidote granite genesis in the Borborema Provinces, NE Brazil

International Nuclear Information System (INIS)

Ferreira, V.P.; Valley, J.W; Sial, A.N; Spicuzza, M.J

2001-01-01

Neoproterozoic magmatic epidote-bearing granitoids intrude low-grade metapelites in the Cachoeirinha-Salgueiro terrane (CST), and gneisses and migmatites in the Serido terrane (ST), in the Borborema structural province, northeastern Brazil. Granitoids in both terranes contain biotite and hornblende, and are metaluminous, calc-alkalic, and oxidized I-type granites according to White's (1992) classification. However, in spite of these similarities, this work shows that mineral oxygen isotope data from plutons of the two terranes indicate different magma sources, and that magmatic epidote besides crystallizing at different pressure conditions, can have variable isotopic composition (au)

Calculation of the water permeability in large scale at a rock cavern in Blekinge, Sweden

International Nuclear Information System (INIS)

Lindblom, U.; Granero, J.J.

1979-08-01

A contract for KBS, Hagconsult has interpreted water leakage date for rock chambers near the harbor of Karlshamn in Southern Sweden. The storage plant consists of four separate rock chambers, each with a ca cross sectional area of 600 m 2 and a volume of 400.000 m 3 . The bedrock consists of gray, fine-grained gneiss, named ''Blekinge kustgnejs''. Through a simple potential flow analysis, utilizing homogeneous and isotropic rock conditions, the gross hydraulic conductivity of the rock mass was estimated at 1 x 10 -8 m/s. (author)

New airborne geophysical data from the Waterberg coalfield. South Africa's major future energy source

CSIR Research Space (South Africa)

Fourie, CJS

2008-11-01

Full Text Available Formation (110m thick in the south) • Recent cover is from the weathering of gneiss of the Limpopo Mobile Belt and the Karoo rock in the north; but from Waterberg sandstones in the south • Intrusive rocks – the most important of these rocks are those... 2) shows the northern contact of the Ellisras Basin clearly. It also shows the large block faulting and radioactive material eroding from the source (Waterberg Sandstones) in the south into the sediment load of the north-flowing Mokolo River...

Detailed petrographic-structural study of an outcrop of Crystalline Basement of Montevideo

International Nuclear Information System (INIS)

Pascale, A.; Oyhantçabal, P.

2010-01-01

Preliminary data analysis of detailed outcrop Punta Virgilo, located on the S E coast of the department of Montevideo are presented. The investigated outcrop includes gneisses, amphibolite s and several generations of pegmatite and aplite dikes of Paleoproterozoic metamorphic basement, plus a set of dikes emplaced lamprófido exhumed once the area. Petrographic and microstructural studies of metamorphic units allowed to determine the conditions of metamorphism and deformation temperature between 520-720 ° C and pressure between 2 and 6 kbar (depth of 10 to 23 km)

Regional setting, distribution and genesis of surficial uranium deposits in calcretes and associated sediments in Western Australia

International Nuclear Information System (INIS)

Butt, C.R.M.; Mann, A.W.; Horwitz, R.C.

1984-01-01

Surficial uranium deposits in Western Australia are largely in the Yilgarn Block in areas of Archean granitoids and greenstones, and in the Gascoyne Province in Proterozoic granites and gneisses. The region has had a long weathering history marked by continuous planation developing a regolith up to 100 metres thick. The distribution of calcrete type uranium deposits is controlled by geologic as well as weathering, erosion and climatic factors. Valley, playa and terrace deposits are recognized. The principal known surficial uranium deposit, Yeelirrie, occurs in the Yilgarn block as a valley deposit. (author)

Low-degree partial melting of metapelites - another possible implement for selective concentration of uranium: Example from the Rozna uranium deposit, Bohemian Massif

International Nuclear Information System (INIS)

Leichmann, J.; Matula, M.; Broska, I.; Holeczy, D.

2002-01-01

Monazite, as the main carrier of U and Th in host biotite gneiss at the Rozna uranium deposit, was replaced by allanite during the process of partial melting. The transformation was accompanied by a release of U, and to a lesser extent of Th, from the monazite lattice. The liberated U and Th crystallized in the extracted granitic melt mainly in the form of thorogummite or cheralite. The granites are depleted in HFS and LREE. Garnet-poor granites are depleted in HREE as well, whereas garnet-rich types are enriched in HREE. (author)

A desk study of surface diffusion and mass transport in clay

International Nuclear Information System (INIS)

Cook, A.J.

1989-01-01

Research into the properties of clays as barrier materials for nuclear waste disposal has led to the realization that they have important transport properties which are relatively insignificant in most other geological materials. Sorption has always been regarded as a purely retarding mechanism, but laboratory experiments over the past decade have indicated that surface diffusion of sorbed cations is a potentially significant transport mechanism in both compacted montmorillonite, and biotite gneiss. The present desk study about these issues was part of the CEC coordinated project Mirage-Second phase, research area Natural analogues

Geological mapping of investigation trench OL-TK14 at the Olkiluoto study site, Eurajoki, SW Finland

International Nuclear Information System (INIS)

Nordbaeck, N.

2007-12-01

Geological mapping of investigation trench OL-TK14 was carried out by the Geological Survey of Finland at the Olkiluoto study site, Eurajoki, as part of Posiva Oy's site investigation programme for the development of an underground repository for nuclear waste. The E-W striking, ca. 215 m long trench is located in the eastern part of the Olkiluoto Island adjacent to boreholes OL-KR40 and OL-KR45. The trench was cleaned with a pressure washer and pressurized air. The rock types were determined macroscopically. Five samples were also investigated microscopically. The main rock type in the trench is veined gneiss. A few less than 0.5 m wide coarsegrained pegmatitic granite dykes are also encountered. Furthermore a large number of mica gneiss, quartz gneiss and skarn inclusions are present in the veined gneiss, being often elongated and parallel to the foliation. The most dominant tectonic feature is the foliation S2 and associated intense granitic leucosome veining. The foliation strikes ENE-WSW and dips steeply towards SES. Intensely to moderately banded rocks dominate the trench. The sparse F3 folds observed in OL-TK14 are small-scale tight folds in leucosome veins. A large-scale (10 m) open bending of the foliation that could be a result of D4 folding was also observed. Shearbands and other signs of ductile shearing were observed on many locations in the trench and in the eastern part there is a high-grade ductile shear zone intersection. During the fracture mapping, all fractures intersecting the central thread were investigated and a total of 684 fractures were recorded. The average fracture density of the trench is 3.18 fractures/m. On the basis of fracture orientations three main sets can be distinguished: 1) a set striking N-S with vertical dip, 2) a ENE-WSW striking set with varying dips towards the SSE (parallel to the foliation) and 3) a NE-SW striking set with sub-vertical dip towards the SE or the NW. Most of the measured fractures are short due to the

Do the eclogites of the Variscan Malpica-Tuy shear zone in NW Spain point to continental subduction?

Science.gov (United States)

Li, Botao; Massonne, Hans-Joachim

2014-05-01

High-pressure (HP: P > 10 kbar) rocks such as eclogite typically occur in suture zones of collided continental plates in Phanerozoic times. In case of an extended area at the surface of a denuded orogen with HP and even ultrahigh pressure (UHP) metamorphic rocks, they are often interpreted as the result of continental subduction. We have tested this idea for the HP-UHP area of the Malpica-Tuy zone of the Variscan orogen, which was formed by the collision of Gondwana and Laurussia. For the test, we have initially studied an eclogite and its surrounding gneiss of this zone in detail. The eclogite contains the assemblage garnet, omphacite, amphibole, rutile, ilmenite, clinozoisite/epidote, quartz, and phengite with Si-contents as high as 3.45 per formula unit (pfu) in inner portions and 3.27-3.35 pfu in rims. Garnet exhibits chemical zonation with Gro25Alm55Pyr15Spe5, Gro29Alm57Pyr13Spe1, and Gro23Alm56Pyr20Spe1 as inner core, mantle, and outermost rim compositions, respectively. The gneiss is a former medium-grained granite now composed of quartz, plagioclase, K-feldspar, biotite, phengite, garnet, clinozoisite/epidote, titanite, apatite and ilmenite. Phengite shows Si contents between 3.40 (core) and 3.00 (rim) pfu. Garnet is chemically zoned with Gro69.6Alm27Pyr0.4Spe3, Gro65.5Alm32.5Pyr0.5Spe1.5, Gro65.7Alm31.7Pyr0.6Spe2, and Gro56.6Alm41.6Pyr1.2Spe0.6 as core, mantle, rim and outermost rim compositions, respectively. P-T pseudosections were calculated with the PERPLEX computer program in the system Na2O-K2O-CaO-FeO-O2-MnO-MgO-Al2O3-SiO2-TiO2-H2O for the bulk-rock compositions of the studied eclogite and gneiss. These pseudosections were contoured by isopleths of various parameters such as molar fractions of garnet components. Based on this contouring a P-T path was derived that starts at HP conditions for both lithologies. Garnet began to form at 22 kbar and 565°C in the eclogite. Subsequently, the temperatures increased to 585°C and the pressure decreased to

The Greenland analogue project, sub-project C 2008 field and data report

International Nuclear Information System (INIS)

Aaltonen, I.; Lehtinen, A.; Lintinen, P.; Ruskeeniemi, T.; Douglas, B.; Liljedahl, L. C.; Frape, S.; Henkemans, E.; Hobbs, M.; Klint, K.E.

2010-10-01

to bedrock. It is plausible that the actual depth is closer to the deeper end of the estimate. The deep borehole at Ilulissat evidenced that permafrost extends down to 215 m in similar climatic conditions and rock types as observed in Kangerlussuaq. The rocks in the investigation area are predominantly felsic or mafic Archaean orthogneisses that were reworked under high grade metamorphism in the Palaeoproterozoic. Microscopically the mafic rock types are variably orientated amphibole and/or pyroxene gneisses. The felsic rocks are typically quartz-feldspar gneisses. Geochemically the felsic rocks are similar to their counterparts in the Posiva and SKB sites. This is also the case with some of the mafic rocks, while the darkest gneisses at Kangerlussuaq differ clearly. The primary structures in the Kangerlussuaq area are of ductile to semi-ductile nature, which appear as folded or sheared zones of various types of gneiss. These structures are mainly healed and old fractures and faults have been re-crystallised, while brittle structures such as open faults and fractures are regarded to have formed in a younger shallow, colder and hence more rigid environment. Glacial meltwater in study area have very low conductivities (1-6μS/cm) in the sub- and supraglacial flows and conductivities of less than 450μS/cm are measured in the spring and till-plain lakes likely fed by meltwater. Isotopically, glacial meltwaters are typified by depleted δ 18 O and δ 2 H signatures and tritium values that are low or non-detect. (orig.)

Early Miocene rapid exhumation in southern Tibet: Insights from P-T-t-D-magmatism path of Yardoi dome

Science.gov (United States)

Wang, Jia-Min; Wu, Fu-Yuan; Rubatto, Daniela; Liu, Kai; Zhang, Jin-Jiang; Liu, Xiao-Chi

2018-04-01

Reconstructing the evolution of Gneiss domes within orogenic belts poses challenges because domes can form in a variety of geodynamic settings and by multiple doming mechanisms. For the North Himalayan gneiss domes (NHGD), it is debated whether they formed during shortening, extension or collapse of the plateau, and what is the spatial and temporal relationship of magmatism, metamorphism and deformation. This study investigates the Yardoi dome in southern Tibet using field mapping, petrography, phase equilibria modelling and new monazite ages. The resulting P-T-time-deformation-magmatism path for the first time reveals the spatial and temporal relationship of metamorphism, deformation and magmatism in the Yardoi dome: a) the dome mantle recorded prograde loading to kyanite-grade Barrovian metamorphic conditions of 650 ± 30 °C and 9 ± 1 kbar (M2) in the Early Miocene (18-17 Ma); b) the main top-to-the-north deformation fabric (D2) formed syn- to post-peak-metamorphism; c) the emplacement of leucorgranites related to doming is syn-metamorphism at 19-17 Ma. The link between the detachment shear zone in the Yardoi dome and the South Tibetan detachment system (STDS) is confirmed. By comparing with orogen-scale tectonic processes in the Himalaya, we suggest that north-south extension in a convergent geodynamic setting during Early Miocene accounts for formation of the Yardoi dome. In a wider tectonic context, the Early Miocene rapid exhumation of deep crustal rocks was contemporaneous with the rapid uplift of southern Tibet and the Himalayan orogen.

Core drilling of deep drillhole OL-KR56 at Olkiluoto in Eurajoki 2011 - 2012

Energy Technology Data Exchange (ETDEWEB)

Toropainen, V. [Suomen Malmi Oy, Espoo (Finland)

2012-07-15

As a part of the confirming site investigations at Olkiluoto, Suomen Malmi Oy (Smoy) core drilled a 1201.65 m deep drillhole with a diameter of 75.7 mm at Olkiluoto in October 2011 - January 2012. The identification number of the drillhole is OL-KR56. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the returning and drilling water were recorded. The drill rig was computer controlled and the computer recorded drilling parameters during drilling. The objective of the measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volume of the used drilling, washing and flushing water was 1628 m{sup 3}. The measured volume of the returning water in the drillhole was 1142 m{sup 3}. The deviation of the drillhole was measured with the deviation measuring instruments Reflex EMS and Reflex Gyro. The main rock types are veined and diatexitic gneisses, pegmatitic granite and mica gneiss. The average fracture frequency is 2.4 pcs/m and the average RQD value is 96.2 %. Fifty fractured zones were penetrated by the drillhole. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength was 120.0 MPa, the average Young's Modulus was 38.3 GPa and the average Poisson's ratio was 0.22. (orig.)

Identification of different generations of albite through microchemical fingerprint by LA-ICP-MS

Energy Technology Data Exchange (ETDEWEB)

Amorim, Lucas E.D.; Rios, Francisco J.; Freitas, Monica E.; Palmieri, Helena E.L.; Geraldes, Mauro C.; Matos, Evando C. de, E-mail: ledamorim@cdtn.br, E-mail: javier@cdtn.br, E-mail: monicaef@gmail.com, E-mail: help@cdtn.br, E-mail: geraldes@uerj.br, E-mail: carele@inb.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Universidade Estadual do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil); Indústrias Nucleares do Brasil (INB), Caetité, BA (Brazil)

2017-07-01

The Lagoa Real Uranium Province located in the south-central part of the Bahia-BR, in the central portion of the San Francisco Craton, is composed of an association of Paleoproterozoic metagranitoids, alkali-gneisses, and albitites (barren and mineralized). Intense action of metamorphic and metasomatic processes characterize this region. These processes culminated in the transformation of granites into gneisses, albitites and U mineralization in some albitites bodies. There are three types of metagranites, Lagoa do Barro (1,77Ga), Juazerinho (1,75Ga) and São Timóteo (1,74Ga). In view of this information, we aimed to verify if the albite formed by metamorphism in the metagranites has the same fingerprint of the albite present in the barren albitites. We used a LA-ICP-MS system for this. The results allowed the determination of albites fingerprint, allowing the differentiation of at least two generations. The Sr / U ratio allows characterizing these generations. The albitites have albite with minimal microchemical variation. The metagranites Lagoa do Barro and São Timóteo has similar generation of albite. The Juazerinho presents two generations of albite, one with similar to São Timóteo, Lagoa do Barro and albitites and another generation with distinctly higher concentrations of Sr and U. These results show that the same event that generated the albitite's albite interfered with the formation of the metagranite's albite, but another event culminated with the formation of the second generation of the albite in the Juazerinho. (author)

Core drilling of REPRO drillholes in ONKALO at Olkiluoto 2010-2011

International Nuclear Information System (INIS)

Toropainen, V.

2012-05-01

Suomen Malmi Oy (Smoy) core drilled ten drillholes for the Posiva's Experiments to investigate Rock Matrix Retention Properties (REPRO) in ONKALO at Eurajoki, 2010 - 2011. The drillholes are used for geological characterization, hydrological and geophysical studies and instrumenting in research for retention of radionuclides to rock matrix. The drillhole ONK-PP240 was drilled in March 2010 and the drillholes ONKPP318... 324 and ONK-PP326...327 in October - December 2011. The lengths of the drillholes range from 4.90 to 21.65 metres. The drillholes are 56.5 mm by diameter. The drillhole ONK-PP240 was drilled for pretesting in the investigation niche 4 at access tunnel chainage 3747 and the rest of the drillholes in the investigation niche 5 at access tunnel chainage 4219. The hydraulic DE 130 drilling rig was used. The starting directions of the close spaced drillholes were controlled with an aligner assembly to be as parallel as possible. The drilling water was taken from the ONKALO drilling water pipeline and premixed sodium fluorescein was used as a label agent in the drilling water. The drillholes were measured with EMS deviation survey tool. In addition to drilling the drillcores were logged and reported by geologist. Geological logging included the following parameters: lithology, foliation, fracture parameters, fractured zones, core loss, weathering, fracture frequency, RQD and rock quality. The main rock types in the drillholes are veined gneiss, pegmatitic granite and quartz gneiss (skarn rock). The average fracture frequency in drill cores is 1.2 pcs/m and the average RQD value 98.6 %. (orig.)

Core drilling of REPRO drillholes in ONKALO at Olkiluoto 2010-2011

Energy Technology Data Exchange (ETDEWEB)

Toropainen, V. [Suomen Malmi Oy, Espoo (Finland)

2012-05-15

Suomen Malmi Oy (Smoy) core drilled ten drillholes for the Posiva's Experiments to investigate Rock Matrix Retention Properties (REPRO) in ONKALO at Eurajoki, 2010 - 2011. The drillholes are used for geological characterization, hydrological and geophysical studies and instrumenting in research for retention of radionuclides to rock matrix. The drillhole ONK-PP240 was drilled in March 2010 and the drillholes ONKPP318... 324 and ONK-PP326...327 in October - December 2011. The lengths of the drillholes range from 4.90 to 21.65 metres. The drillholes are 56.5 mm by diameter. The drillhole ONK-PP240 was drilled for pretesting in the investigation niche 4 at access tunnel chainage 3747 and the rest of the drillholes in the investigation niche 5 at access tunnel chainage 4219. The hydraulic DE 130 drilling rig was used. The starting directions of the close spaced drillholes were controlled with an aligner assembly to be as parallel as possible. The drilling water was taken from the ONKALO drilling water pipeline and premixed sodium fluorescein was used as a label agent in the drilling water. The drillholes were measured with EMS deviation survey tool. In addition to drilling the drillcores were logged and reported by geologist. Geological logging included the following parameters: lithology, foliation, fracture parameters, fractured zones, core loss, weathering, fracture frequency, RQD and rock quality. The main rock types in the drillholes are veined gneiss, pegmatitic granite and quartz gneiss (skarn rock). The average fracture frequency in drill cores is 1.2 pcs/m and the average RQD value 98.6 %. (orig.)

Paleomagnetic evidence for the continuity and independent movement of a distinct major crustal block in the southern Appalachians

International Nuclear Information System (INIS)

Ellwood, B.B.

1982-01-01

The magnetization of 22 granitic and gneissic southern Appalachian rock units, with estimated cooling ages of 415--250 m.y., has been determined. Included are 842 samples from 114 sites within 19 granites (100 sites) and 3 gneisses (14 sites) located in North Carolina, South Carolina, and Georgia. Data for units which cooled to temperatures 0 C between 350--240 m.y., a period of apparently only slight North American plate motion, can be divided into two groups. A mean paleopole calculated for the first of these groups, group A (derived from six granites and gneisses 365--325 m.y. in age), located in the vicinity of Atlanta, Ga., is coincident with well-defined Lower Carboniferous North American paleopoles. Site paleolatitude is estimated to be approx.11 0 S. Group B granites (six units) range in age from 350--250 m.y., are located to the SE of an arc drawn from Columbia, S.C., through Athens, Ga., to Macon, Ga., are apparently anomalous, and lie in a crustal block >20,000 km 2 in size. A mean paleopole for this group, with corrections for maximum tilt estimates, exhibits good precision but has a paleosite latitude of approx.10 0 N. Without tilt correction the paleopole for group B still exhibits an anomalous paleosite latitude of approx.4 0 N. These data indicate that the group B block (Elberton-Sparta Crustal Block) lying to the SE has an apparent paleosite latitude corresponding to magnetization at a location to the north of the zone containing group A units

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)

Identification of different generations of albite through microchemical fingerprint by LA-ICP-MS

International Nuclear Information System (INIS)

Amorim, Lucas E.D.; Rios, Francisco J.; Freitas, Monica E.; Palmieri, Helena E.L.; Geraldes, Mauro C.; Matos, Evando C. de

2017-01-01

The Lagoa Real Uranium Province located in the south-central part of the Bahia-BR, in the central portion of the San Francisco Craton, is composed of an association of Paleoproterozoic metagranitoids, alkali-gneisses, and albitites (barren and mineralized). Intense action of metamorphic and metasomatic processes characterize this region. These processes culminated in the transformation of granites into gneisses, albitites and U mineralization in some albitites bodies. There are three types of metagranites, Lagoa do Barro (1,77Ga), Juazerinho (1,75Ga) and São Timóteo (1,74Ga). In view of this information, we aimed to verify if the albite formed by metamorphism in the metagranites has the same fingerprint of the albite present in the barren albitites. We used a LA-ICP-MS system for this. The results allowed the determination of albites fingerprint, allowing the differentiation of at least two generations. The Sr / U ratio allows characterizing these generations. The albitites have albite with minimal microchemical variation. The metagranites Lagoa do Barro and São Timóteo has similar generation of albite. The Juazerinho presents two generations of albite, one with similar to São Timóteo, Lagoa do Barro and albitites and another generation with distinctly higher concentrations of Sr and U. These results show that the same event that generated the albitite's albite interfered with the formation of the metagranite's albite, but another event culminated with the formation of the second generation of the albite in the Juazerinho. (author)

Electron microprobe Th-U-Pb monazite dating and metamorphic evolution of the Acaiaca Granulite Complex, Minas Gerais, Brazil

Energy Technology Data Exchange (ETDEWEB)

Medeiros Junior, Edgar Batista; Marques, Rodson Abreu, E-mail: edgarjr@ymail.com, E-mail: rodson.marques@ufes.br [Universidade Federal do Espirito Santo (UFES), Alegre, ES (Brazil). Departamento de Geologia; Jordt-Evangelista, Hanna; Queiroga, Glaucia Nascimento, E-mail: hanna@degeo.ufop.br, E-mail: glauciaqueiroga@yahoo.com.br [Universidade Federal de Ouro Preto (UFOP), Ouro Preto, MG (Brazil). Escola de Minas. Departamento de Geologia; Schulz, Bernhard, E-mail: bernhard.schulz@mineral.tu-freiberg.de [TU Bergakademie - Institute of Mineralogy, Freiberg - Saxony (Germany)

2016-01-15

The Acaiaca Complex (AC) is located in southeastern Minas Gerais state, and comprises felsic, mafic, ultramafic, and aluminous granulite as well as lower grade gneisses and mylonite. The complex is distributed over an area of ca. 36 km by 6 km, surrounded by amphibolite facies gneisses of the Mantiqueira Complex (MC). The discrepancy in the metamorphic grade between both complexes led to the present study aiming to understand the metamorphic history of the AC by means of geothermobarometry calculations and electron microprobe Th-U-Pb monazite dating. Estimates of the metamorphic conditions of the granulite based on conventional geothermobarometry and THERMOCALC resulted in temperatures around 800 deg C and pressures between of 5.0 and 9.9 kbar and a retro metamorphic path characterized by near-isobaric cooling. Part of the granulite was affected by anatexis. The melting of felsic granulite resulted in the generation of pegmatites and two aluminous lithotypes. These are: 1) garnet-sillimanite granulite with euhedral plagioclase and cordierite that show straight faces against quartz, and is the crystallization product of an anatectic melt, and 2) garnet-kyanite-cordierite granulite, which is probably the restite of anatexis, as indicated by textures and high magnesium contents. Th-U-Pb monazite geochronology of two granulite samples resulted in a metamorphic age around 2060 Ma, which is similar to the age of the MC registered in the literature. The similar Paleoproterozoic metamorphic ages of both complexes lead to the conclusion that the Acaiaca Complex may be the high grade metamorphic unit geochronological related to the lower grade Mantiqueira Complex. (author)

Geochronological {sup 40}Ar/{sup 39}Ar data on the submarine fault-scarps in the Sardinia channel (western mediterranean); Donnees geochronologiques {sup 40}Ar/{sup 39}Ar sur les socles sarde et kabylo-peloritain submerges dans le canal de Sardaigne (mediterranee occidentale)

Energy Technology Data Exchange (ETDEWEB)

Bouillin, J.P.; Tricart, P.; Mascle, G. [Grenoble-1 Univ., 38 - Grenoble (France). Laboratoire de Geodynamique des Chaines Alpines, CNRS UPRES-A5025; Monie, P. [Montpellier-2 Univ., 34 (France). Laboratoire de Geochronologie, Geochimie et de petrologie, UMR 5567; Rolfo, F. [Universita Torino, (Italy). Dipt. di Scienze Mineralogiche et Petrologiche; Torelli, L. [Parma Univ. (Italy). Ditp. di Scienze della Terra

1999-04-01

Granite and gneiss have been sampled on the submarine fault scarps of the Sardinia Channel and have been dated using the {sup 40}Ar/{sup 39}Ar method. The majority of rocks partially preserve Hercynian ages. Some of them display Lower Cretaceous ages. In addition, Upper Eocene-Oligocene argon resetting is recorded only in rocks from the southeast sector of the Channel. We thus propose that the basement of the Sardinia Channel occupied a shallow position within the stack of the Alpine tectonic units, behind the more deformed front of the internal zones of the Maghrebide Chain. (authors) 20 refs.

Geochronological 40Ar/39Ar data on the submarine fault-scarps in the Sardinia channel (western mediterranean)

International Nuclear Information System (INIS)

Bouillin, J.P.; Tricart, P.; Mascle, G.; Monie, P.; Rolfo, F.; Torelli, L.

1999-01-01

Granite and gneiss have been sampled on the submarine fault scarps of the Sardinia Channel and have been dated using the 40 Ar/ 39 Ar method. The majority of rocks partially preserve Hercynian ages. Some of them display Lower Cretaceous ages. In addition, Upper Eocene-Oligocene argon resetting is recorded only in rocks from the southeast sector of the Channel. We thus propose that the basement of the Sardinia Channel occupied a shallow position within the stack of the Alpine tectonic units, behind the more deformed front of the internal zones of the Maghrebide Chain. (authors)

Time constraints on the tectonic evolution of the eastern Sierras Pampeanas (Central Argentina)

DEFF Research Database (Denmark)

Siegesmund, Siegfried; Steenken, A; Martino, R D

2010-01-01

The application of the SHRIMP U/Pb dating technique to zircon and monazite of different rock types of the Sierras de Córdoba provides an important insight into the metamorphic history of the basement domains. Additional constraints on the Pampean metamorphic episode were gained by Pb/Pb stepwise...... leaching (PbSL) experiments on two titanite and garnet separates. Results indicate that the metamorphic history recorded by Crd-free gneisses (M2) started in the latest Neoproterozoic/earliest Cambrian (553 and 543 Ma) followed by the M4 metamorphism at ~530 Ma that is documented in the diatexites. Zircon...

Oxygen 18 isotopic analysis of sub-glacial concentrations of the Laurentide Ice Sheet

Energy Technology Data Exchange (ETDEWEB)

Hillaire-Marcel, C [Quebec Univ., Montreal (Canada); Cailleux, A [Observatoire de Paris, Section de Meudon, 92 (France); Soucy, J

1979-07-01

Calcareous concretions occuring on Grenvillian gneiss have been discovered north of Hull, Quebec. Their structure and isotopic composition (delta/sub PDB//sup 18/O approximately equal to -26%; delta/sub PDB//sup 13/C approximately equal to 0%; /sup 14/C age > 35,000 BP) indicate subglacial conditions of precipitation. It is concluded that they were deposited at the base of the Laurentide ice sheet. Assuming equilibrium conditions with the subglacial film of water during precipitation of calcite, it is possible to define a -27.5 to -31.8% (vs. 'standard mean ocean water' (SMOW)) range for the oxygen-18 content of ice.

Complementary radiochronological study of the Francevillian series and its environment

International Nuclear Information System (INIS)

Bonhomme, M.; Leclerc, J.; Weber, F.

The use of the K-Ar method to date biotites extracted from two gneiss samples from the Chaillu Massif shows that the substratum of the Francevillian did not undergo metamorphosis after 2,700 MY. The age of the dolorite veins is pinpointed by the method of the K-Ar internal isochrone at about 1,000 MY. A program is in progress to give a more precise Rb-Sr isochrone than the one published in 1965, and to try, by standard geochronological methods, to remove the uncertainty in the 1,800 to 2,000 MY estimated age of the nuclear reaction

A further radiochronological study of the Francevillian series and its environment

International Nuclear Information System (INIS)

Bonhomme, M.; Weber, F.

1978-01-01

Dating, by the K-Ar method, of biotites extracted from two gneiss samples from the Chaillu Massif shows that the basement of the Francevillian basin did not undergo metamorphism after 2700 million years. The age of the dolerite veins, determined by the K-Ar internal isochrone method, is approximately 1000 million years. A programme is under way to give a more precise Rb-Sr isochrone than that published in 1965 and to try and remove, by conventional geochronological methods, the uncertainty regarding whether 1800 or 2000 million years is the age of the nuclear reaction. (author)

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

International Nuclear Information System (INIS)

Abreu Machado, G.; Schorscher, H.

1998-01-01

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

Investigations of possibilities to dispose of spent nuclear fuel in Lithuania: a model case. Volume 1, Suitability of Geological Environment in Lithuania for Disposal of Spent Nuclear Fuel

International Nuclear Information System (INIS)

Motiejunas, S.; Satkunas, J.

2005-01-01

This Volume contains an overview of geological structure with respect to its relevance for waste disposal conditions and characteristics of crystalline rocks in Lithuania with respect to its relevance for waste disposal. The most prospective rock types are represented by cratonic (anorogenic) granitoid intrusions that in some places compose rather large massifs. These rocks are the least damaged by tectonic activity. Furthermore, the lithology variations at short distances are only minor that makes exploration much easier. Yet, other rock types (gneisses, mafic intrusions, migmatites) compose someplace only weakly fractured blocks that also may be prospective for repository

Core drilling of deep borehole OL-KR43 at Olkiluoto in Eurajoki 2006

Energy Technology Data Exchange (ETDEWEB)

Niinimaeki, R. [Suomen Malmi Oy, Espoo (Finland)

2006-12-15

Posiva Oy submitted an application to the Finnish Government in May 1999 for the Decision in Principle to choose Olkiluoto in the municipality of Eurajoki as the site of the final disposal facility for spent nuclear fuel. A positive decision was made at the end of 2000 by the Government. The Finnish Parliament ratified the decision in May 2001. The decision makes it possible for Posiva to focus the confirming bedrock investigations at Olkiluoto, where in the next few years an underground rock characterisation facility, ONKALO, will be constructed. As a part of the investigations Suomen Malmi Oy (Smoy) core drilled 1000.26 m and 45.01 m deep boreholes with a diameter of 75.7 mm at Olkiluoto in July - October 2006. The identification numbers of the boreholes are OL-KR43 and OL-KR43B, respectively. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the drilling water and the returning water were recorded. The drill rig was computer controlled and during drilling the computer recorded drilling parameters. The objective of all these measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volumes of the used drilling and flushing water were 1103 m{sup 3} and 16 m{sup 3} in boreholes OL-KR43 and OL-KR43B, respectively. Measured volumes of the returning water were 916m{sup 3} in borehole OL-KR43 and 13m{sup 3} in borehole OL-KR43B. The deviation of the boreholes was measured with the deviation measuring instruments EMS and Maxibor. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength is about 131 MPa, the average Young's Modulus is 37 GPa and the average Poisson's ratio is 0.19. The main rock types are veined gneiss, diatexitic gneiss

Field occurrence and geochemical characteristics of the baryte mineralization in Lessel and Ihugh areas, Lower Benue Trough, Nigeria

Science.gov (United States)

Labe, Ngukposu A.; Ogunleye, Paul O.; Ibrahim, Aliyu A.

2018-06-01

The Lessel and Ihugh areas are underlain by Precambrian rocks comprising of banded gneiss, medium-grained muscovite granite, coarse-grained biotite muscovite granite, and Turonian arenaceous Lessel Sandstone in the Lower Benue Trough, southeastern Nigeria. Baryte mineralization occurs at Lessel-Mbagwa, Ihugh and Bunde commonly as vein and cavity type deposits within NE-SW and NW-SE trending fracture zones. Major oxides and trace element analysis of baryte and the host rocks was undertaken using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), in order to establish the geochemical characteristics and to constrain the origin of the baryte mineralization. The data revealed enrichment in Ba and Sr and depletion in SiO2, TiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, LILEs, HFSEs relative to background values obtained from sandstones and granitic rocks in the area. Baryte mineralization from Lessel-Mbagwa, Bunde and Ihugh is marked by positive Gd (17.1-21.4) and negative Eu (0.02-0.05) anomalies. Negative Ce anomaly (0.06) is evident in barytes from Lessel-Mbagwa and Bunde whereas baryte from Ihugh is characterized by positive Ce anomaly (1.3). The structurally controlled nature of the mineralization, depleted major and trace elements concentration in the barytes in addition to REE anomalies indicate that mixing of a strongly differentiated residual Ba-bearing fluid and sulphur-rich seawater occurred under low temperature and oxidizing-reducing conditions. The tectonic event which occurred during the Santonian to Early Campanian reactivated the NE-SW, NW-SE structural pathways in the basement gneiss and also created similar structures in the Turonian Lessel Sandstone.

Geology and U-Pb geochronology of the Kipawa Syenite Complex - a thrust related alkaline pluton - and adjacent rocks in the Grenville Province of western Quebec

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Van Breemen, O.; Currie, K.L. [Geological Survey of Canada, Ottawa, Ontario (Canada)]. E-mail: ovanbree@nrcan.gc.ca

2004-07-01

The Kipawa Syenite Complex, a thin, folded sheet of amphibole syenite, quartz syenite and minor nepheline syenite, lies along a west-vergent thrust separating a lower slice comprising the Kikwissi granodiorite and biotite tonalite dated at 2717 {sub -11}{sup +15} Ma, and unconformably overlying metasedimentary rocks from an overlying slice containing the Red Pine Chute orthogneiss, an alkali granite gneiss, and the Mattawa Quartzite. The syenite complex, dated at 1033 {+-} 3 Ma, lies within the lower slice but has metasomatically altered the overlying slice. Texturally guided U-Pb spot analyses on partially metasomatised zircons from the alkali granite gneiss yield a cluster of {sup 207}G'Pb/{sup 206}Pb ages at 1389 {+-} 8 Ma, interpreted as the time of igneous crystallization and four ages overlapping the time of syenite emplacement, interpreted as in situ, metasomatic growth. The highest structural slice comprises garnet amphibolite separated from lower slices by the Allochthon Boundary Thrust. Metamorphic grade increases upward from greenschist grade in the biotite tonalite to amphibolite grade (690 {sup o}C, 9 kbar (1 kbar = 100 MPa)) at the lower boundary of the alkali granite. Emplacement of the Kipawa Syenite Complex took place after assembly of the thrust stack had begun and after emplacement of the allochthon or hot slab responsible for the inverted metamorphic gradient. Origin of the syenite is tentatively ascribed to anatexis of material metasomatized by flow of alkaline solutions along a major shear surface. Crystallization of new zircon in the margins of the syenite shows that metasomatism continued from ca. 1035 to 990 Ma, redistributing alkalies, fluorine, rare-earth elements and zirconium. (author)

Geochemistry, petrography, and zircon U-Pb geochronology of Paleozoic metaigneous rocks in the Mount Veta area of east-central Alaska: implications for the evolution of the westernmost part of the Yukon-Tanana terrane

Science.gov (United States)

Dusel-Bacon, Cynthia; Day, Warren C.; Aleinikoff, John N.

2013-01-01

We report the results of new mapping, whole-rock major, minor, and trace-element geochemistry, and petrography for metaigneous rocks from the Mount Veta area in the westernmost part of the allochthonous Yukon–Tanana terrane (YTT) in east-central Alaska. These rocks include tonalitic mylonite gneiss and mafic metaigneous rocks from the Chicken metamorphic complex and the Nasina and Fortymile River assemblages. Whole-rock trace-element data from the tonalitic gneiss, whose igneous protolith was dated by SHRIMP U–Pb zircon geochronology at 332.6 ± 5.6 Ma, indicate derivation from tholeiitic arc basalt. Whole-rock analyses of the mafic rocks suggest that greenschist-facies rocks from the Chicken metamorphic complex, a mafic metavolcanic rock from the Nasina assemblage, and an amphibolite from the Fortymile River assemblage formed as island-arc tholeiite in a back-arc setting; another Nasina assemblage greenschist has MORB geochemical characteristics, and another mafic metaigneous rock from the Fortymile River assemblage has geochemical characteristics of calc-alkaline basalt. Our geochemical results imply derivation in an arc and back-arc spreading region within the allochthonous YTT crustal fragment, as previously proposed for correlative units in other parts of the terrane. We also describe the petrography and geochemistry of a newly discovered tectonic lens of Alpine-type metaharzburgite. The metaharzburgite is interpreted to be a sliver of lithospheric mantle from beneath the Seventymile ocean basin or from sub-continental mantle lithosphere of the allochthonous YTT or the western margin of Laurentia that was tectonically emplaced within crustal rocks during closure of the Seventymile ocean basin and subsequently displaced and fragmented by faults.

Iso-Naakkima, a circular structure filled with Neoproterozoic sediments, Pieksämäki, southeastern Finland

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Elo, S.

1993-06-01

Full Text Available A circular Bouguer gravity anomaly with a minimum of -4.0 mGal and halfamplitude width of 2 km was recognized at Lake Iso-Naakkima (62°11'N, 27°09'E, southeastern Finland. The gravity low is associated with subdued aeromagnetic signature and notable airborne and ground electromagnetic anomalies that indicate low bedrock resistivity. The drilling record beneath the recent (Quaternary glacial sediments, 25-40 m thick, reveals a 100 m thick sequence of unmetamorphosed shale, siltstone, quartz sandstone, kaolinitic clay and conglomeratic sandstone that rest on a weathered mica gneiss basement. The upward fining sequence is characterized by red colour, high kaolinite content, and tilted, distorted and brecciated beds. According to the geophysical modelling the diameter of the whole basin is 3 km and that of the sedimentary rocks 2 km, and the depth is 160 m. Shock lamellas in quartz clasts of the basal conglomeratic sandstone, almost omnipresent kink banding in micas of the rocks beneath the basin floor and the occurrence of polymictic dike breccia in the underlying mica gneiss suggest shock metamorphism. It was concluded that the basin originated by a meteorite impact. However, the impact-generated rocks were subsequently eroded before the sedimentation and only minor marks of shock metamorphism were preserved. Lateritic weathering took place prior to deposition of the sediments. Quartz sandstone and siltstone are interpreted as fluvial deposits and the thinly laminated shales as transgressi ve lacustrine or lagoonal deposits. The microfossil assemblage in the shale includes sphaeromorphs of acritarchs from Late Riphean (Neoproterozoic. Postdepositional subsidence of the Iso-Naakkima basin, shown by tilted sediments, preserved the sequence from further erosion.

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.

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

Science.gov (United States)

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

1999-01-01

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

New geological model of the Lagoa Real uraniferous albitites from Bahia (Brazil)

Science.gov (United States)

de Oliveira Chaves, Alexandre

2013-09-01

New evidence supported by petrography (including mineral chemistry), lithogeochemistry, U-Pb geochronology by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and physicochemical study of fluid and melt inclusions by LA-ICP-MS and microthermometry, point to an orogenic setting of Lagoa Real (Bahia-Brazil) involving uraniferous mineralization. Unlike the previous models in which uraniferous albitites represent Na-metasomatised 1.75 Ga anorogenic granitic rocks, it is understood here that they correspond to metamorphosed sodium-rich and quartz-free 1.9 Ga late-orogenic syenitic rocks (Na-metasyenites). These syenitic rocks are rich not only in albite, but also in U-rich titanite (source of uranium). The interpretation of geochemical data points to a petrogenetic connection between alkali-diorite (local amphibolite protolith) and sodic syenite by fractional crystallization through a transalkaline series. This magmatic differentiation occurred either before or during shear processes, which in turn led to albitite and amphibolite formation. The metamorphic reactions, which include intense recrystallization of magmatic minerals, led uraninite to precipitate at 1.87 Ga under Oxidation/Reduction control. A second population of uraninites was also generated by the reactivation of shear zones during the 0.6 Ga Brasiliano Orogeny. The geotectonic implications include the importance of the Orosirian event in the Paramirim Block during paleoproterozoic Săo Francisco Craton edification and the influence of the Brasiliano event in the Paramirim Block during the West-Gondwana assembly processes. The regional microcline-gneiss, whose protolith is a 2.0 Ga syn-collisional potassic granite, represents the albitite host rock. The microcilne-gneiss has no petrogenetic association to the syenite (albitite protolith) in magmatic evolutionary terms.

Timing and conditions of peak metamorphism and cooling across the Zimithang Thrust, Arunachal Pradesh, India

Science.gov (United States)

Warren, Clare J.; Singh, Athokpam K.; Roberts, Nick M. W.; Regis, Daniele; Halton, Alison M.; Singh, Rajkumar B.

2014-07-01

The Zimithang Thrust juxtaposes two lithotectonic units of the Greater Himalayan Sequence in Arunachal Pradesh, NE India. Monazite U-Pb, muscovite 40Ar/39Ar and thermobarometric data from rocks in the hanging and footwall constrain the timing and conditions of their juxtaposition across the structure, and their subsequent cooling. Monazite grains in biotite-sillimanite gneiss in the hanging wall yield LA-ICP-MS U-Pb ages of 16 ± 0.2 to 12.7 ± 0.4 Ma. A schistose gneiss within the high strain zone yields overlapping-to-younger monazite ages of 14.9 ± 0.3 to 11.5 ± 0.3 Ma. Garnet-staurolite-mica schists in the immediate footwall yield older monazite ages of 27.3 ± 0.6 to 17.1 ± 0.2 Ma. Temperature estimates from Ti-in-biotite and garnet-biotite thermometry suggest similar peak temperatures were achieved in the hanging and footwalls (~ 525-650 °C). Elevated temperatures of ~ 700 °C appear to have been reached in the high strain zone itself and in the footwall further from the thrust. Single grain fusion 40Ar/39Ar muscovite data from samples either side of the thrust yield ages of ~ 7 Ma, suggesting that movement along the thrust juxtaposed the two units by the time the closure temperature of Ar diffusion in muscovite had been reached. These data confirm previous suggestions that major orogen-parallel out-of-sequence structures disrupt the Greater Himalayan Sequence at different times during Himalayan evolution, and highlight an eastwards-younging trend in 40Ar/39Ar muscovite cooling ages at equivalent structural levels along Himalayan strike.

Generation and emplacement of shear-related highly mobile crustal melts: the synkinematic leucogranites from the Variscan Tormes Dome, Western Spain

Science.gov (United States)

López-Moro, Francisco Javier; López-Plaza, Miguel; Romer, Rolf L.

2012-07-01

The Tormes dome consists of S-type granites that intruded into Ordovician augen gneisses and Neoproterozoic-Lower Cambrian metapelites/metagreywackes at different extents of migmatization. S-type granites are mainly equigranular two-mica granites, occurring as: (1) enclave-laden subvertical feeder dykes, (2) small external sill-like bodies with size and shape relations indicative for self-similar pluton growth, and (3) as large pluton bodies, emplaced at higher levels than the external ones. These magmas were highly mobile as it is inferred from the high contents of fluxing components, the disintegration and alignment of pelitic xenoliths in feeder dykes and at the bottom of some sill-like bodies. Field relations relate this 311 Ma magmatism (U-Pb monazite) to the regional shearing of the D3 Variscan event. Partial melting modeling and the relatively high estimated liquidus temperatures indicate biotite-dehydration partial melting (800-840°C and 400-650 MPa) rather than water-fluxed melting, implying that there was no partial melting triggered by externally derived fluids in the shear zones. Instead, the subvertical shear zones favored extraction of melts that formed during the regional migmatization event around 320 Ma. Nd isotope variation among the granites might reflect disequilibrium partial melting or different protoliths. Mass-balance and trace element partial melting modeling strongly suggest two kinds of fertile crustal protoliths: augen gneisses and metapelites. Slight compositional variation among the leucogranites does not reflect different extent of protolith melting but is related to a small amount of fractional crystallization (bodies. The lower extent of fractional crystallization and the higher-pressure emplacement conditions of the sill-like bodies support a more restricted movement through the crust than for batholitic leucogranites.

Structural, petrological and geochronological analysis of the lithotypes from the Pien region (Parana State, Brazil) and adjacences

International Nuclear Information System (INIS)

Harara, Ossama Mohamed

1996-01-01

The Pien area presents the major geotectonic domains separated by the Pien Shear Zone (PSZ). The northern one is the Rio Pien Granite-Mylonitic Suite composed by calc-alkaline granitoids of Neoproterozoic age. The southern domain is represented by the Amphibolite-Granulite where high grade metamorphism took place at the end of paleoproterozoic time. Considering the identified lithotypes, their geochemical affinity (particularly the Ti, Cr, Ni and REE content) and the geological context observed in the area, a geotectonical model of active continental margin related to subduction SSZ (Supra-Subduction Zone) is proposed. K-Ar on plagioclase from gabbronorites gave Neoproterozoic ages although Sm-Nd whole rock isochron yielded Paleoproterozoic ages. Based in geochemical data, it is proposed that the biotite gneiss and biotite-amphibole-gneiss which occur near the PSZ have a shoshonitic to high-K calc-alkaline features which are characteristic of active continental margins. K-Ar on biotite extracted from these rocks, gave Neoproterozoic ages. The available radiometric data for the Rio Pien mylonitic granitoids show that between 650-595 Ma the generation, deformation and cooling below the isotherm of 250 deg C occurred. On the other hand, the geochronological data for the Agudos do Sul Massif are in the 590-570 Ma interval showing its younger generation. The Sr 87 / Sr 86 initial ratios for both granitoids suggest more involvement of the continental crust in the origins of Agudos do Sul granitic Massif. The analyses of the entire set of the available data for the Pien area allows the suggestion of a geotectonic scenery related to the evolution of an active continental margin during the collages associated to the Brasiliano Cycle

Columbite-Group Minerals from New York Pegmatites: Insights from Isotopic and Geochemical Analyses

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Marian V. Lupulescu

2018-05-01

Full Text Available Columbite crystals from niobium-yttrium-fluorine (NYF pegmatites lacking zircon or containing metamict cyrtolite were analyzed for major and minor elements (Electron Microprobe (EMP, trace elements (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS, and U-Pb geochronology (Laser AblationMulti-Collector-Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICP-MS. All four pegmatite localities sampled are hosted by the Proterozoic Fordham gneiss and/or Paleozoic Bedford gneiss (Columbite-(Fe; Kinkel and Baylis localities and the Manhattan Schist of Lower Paleozoic age (Columbite-(Mn; Fort George and Harlem River Drive localities and yield Neoacadian ages. The weighted average U-Pb ages are 372.2 ± 8.2 Ma (Baylis Quarry, 371.3 ± 7.3 and 383.4 ± 8.9 Ma (Kinkel Quarry; 383 ± 15 Ma (185th St. and Harlem River Drive; and 372 ± 10 Ma (Fort George. A partial metamict zircon (“cyrtolite” from the Kinkel Quarry yielded a weighted average U-Pb age of 376.9 ± 4.3 Ma. The Neoacadian ages obtained agree with those determined by thermal ionization mass spectrometry (TIMS for zircon from Lithium-Cesium-Tantalum (LCT pegmatites from Connecticut and Maine. No pegmatites temporally associated with the Taconic orogeny were found. The size, lack of common Pb, uniform U concentrations across crystal cross-sections, sufficient but moderate uranium concentrations, lack of metamictization, and consistency in U-Pb isotopic ratios for columbite samples BCB-COL, NYSM #25232, and NYSM #525.8 suggests they show promise as potential standards for oxide mineral LA-MC-ICP-MS geochronological analyses, however, additional characterization using ID-TIMS would be necessary to develop as such.

The dehydration, rehydration and tectonic setting of greenstone belts in a portion of the northern Kaapvaal Craton, South Africa

Science.gov (United States)

Vanreenen, D. D.; Barton, J. M., Jr.; Roering, C.; Vanschalkwyk, J. C.; Smit, C. A.; Debeer, J. D.; Stettler, E. H.

1986-01-01

High-grade gneiss terranes and low-grade granite-greenstone terranes are well known in several Archaean domains. The geological relationship between these different crustal regions, however, is still controversial. One school of thought favors fundamental genetic differences between high-grade and low-grade terranes while others argue for a depth-controlled crustal evolution. The detailed examination of well-exposed Archaean terranes at different metamorphic grades, therefore, is not only an important source of information about the crustal levels exposed, but also is critical to the understanding of the possible tectonic and metamorphic evolution of greenstone belts with time. Three South African greenstone belts are compared.

Investigation of Alaska's uranium potential

International Nuclear Information System (INIS)

Eakins, G.R.

1975-01-01

Of the various geographical regions in Alaska that were examined in an exhaustive literary search for the possibility of uranium--either vein type or sedimentary--six offer encouragement: the Copper River Basin, the alkaline intrusive belt of west-central Alaska and Selawik Basin area, the Seward Peninsula, the Susitna Lowland, the coal-bearing basins of the north flank of the Alaska Range, the Precambrian gneisses of the USGS 1:250,000 Goodnews quadrangle, and Southeastern Alaska, which has the sole operating uranium mine in the state. Other areas that may be favorable for the presence of uranium include the Yukon Flats area, the Cook Inlet Basin, and the Galena Basin

Bouguer images of the North American craton and its structural evolution

Science.gov (United States)

Arvidson, R. E.; Bowring, S.; Eddy, M.; Guinness, E.; Leff, C.; Bindschadler, D.

1984-01-01

Digital image processing techniques have been used to generate Bouguer images of the North American craton that diplay more of the granularity inherent in the data as compared with existing contour maps. A dominant NW-SE linear trend of highs and lows can be seen extending from South Dakota, through Nebraska, and into Missouri. The structural trend cuts across the major Precambrian boundary in Missouri, separating younger granites and rhyolites from older sheared granites and gneisses. This trend is probably related to features created during an early and perhaps initial episode of crustal assembly by collisional processes. The younger granitic materials are probably a thin cover over an older crust.

Geology and age of the Lac a la Perdrix fenite, southern Gatineau district, Quebec

International Nuclear Information System (INIS)

Hogarth, D.D.

1996-01-01

The Lac a Ia Perdrix fenite lies in the Central Metasedimentary Belt of the Grenville Province. This 30 m wide fenite, adjacent to a narrow calciocarbonatite sill, replaces diopside-oligoclase gneiss and is composed of magnesio-arfvedsonite, aegirine, microcline, albite, and fluorapatite. Near the contact with carbonatite, it contains appreciable monazite and barite whereas aegirine virtually disappears. Fenitization probably took place early in the igneous stage of carbonatite development. A Pb/U monazite age of 1026 ± 2 Ma is thought to date fenite formation. Together with published data, this age shows that carbonatite intruded metamorphic rocks near the close of the Grenville Orogeny. (author). 33 refs., 4 tabs., 5 figs

Bedrock model of the Veitsivaara area

International Nuclear Information System (INIS)

Saksa, P.; Kuivamaeki, A.; Kurimo, M.; Anttila, P.; Front, K.; Pitkaenen, P.; Korkealaakso, J.; Vaittinen, T.

1993-07-01

Site investigations were carried out at Veitsivaara, in 1987-1991 in accordance with an investigation programme for radioactive waste disposal drawn up by Teollisuuden Voima Oy (TVO). The site was modelled in terms of rock types, fracturing, fracture structures and geophysical conditions, the main focus of examination was on fracturing and associated hydraulic conductivity. The various properties of the bedrock structures were classified by means a three-dimensional model. The descriptions of the models were stored in a computer system for illustration purposes. The rock types at Veitsivaara are tonalite gneiss, Tuliniemet potassium granite, amphipolite, granite porphyry and metadiabase, the last two of which occur in dykes

Geology and age of the Lac a la Perdrix fenite, southern Gatineau district, Quebec

Energy Technology Data Exchange (ETDEWEB)

Hogarth, D D [Ottawa Univ., ON (Canada). Dept. of Geology; VanBreemen, O [Geological Survey of Canada, Ottawa, ON (Canada)

1997-12-31

The Lac a Ia Perdrix fenite lies in the Central Metasedimentary Belt of the Grenville Province. This 30 m wide fenite, adjacent to a narrow calciocarbonatite sill, replaces diopside-oligoclase gneiss and is composed of magnesio-arfvedsonite, aegirine, microcline, albite, and fluorapatite. Near the contact with carbonatite, it contains appreciable monazite and barite whereas aegirine virtually disappears. Fenitization probably took place early in the igneous stage of carbonatite development. A Pb/U monazite age of 1026 {+-} 2 Ma is thought to date fenite formation. Together with published data, this age shows that carbonatite intruded metamorphic rocks near the close of the Grenville Orogeny. (author). 33 refs., 4 tabs., 5 figs.

Geologic map of the Hiller Mountain Quadrangle, Clark County, Nevada, and Mohave County, Arizona

Science.gov (United States)

Howard, Keith A.; Hook, Simon; Phelps, Geoffrey A.; Block, Debra L.

2003-01-01

Map Scale: 1:24,000 Map Type: colored geologic map The Hiller Mountains Quadrangle straddles Virgin Canyon in the eastern part of Lake Mead. Proterozoic gneisses and granitoid rocks underlie much of the quadrangle. They are overlain by upper Miocene basin-filling deposits of arkosic conglomerate, basalt, and the overlying Hualapai Limestone. Inception of the Colorado River followed deposition of the Hualapai Limestone and caused incision of the older rocks. Fluvial gravel deposits indicate various courses of the early river across passes through highlands of the Gold Butte-Hiller Mountains-White Hills structural block. Faults and tilted rocks in the quadrangle record tectonic extension that climaxed in middle Miocene time.

A study on mineralization U,REE and related processes in anomaly No.6 Khoshomy area central Iran

International Nuclear Information System (INIS)

Heidaryan, F.

2005-01-01

Uranium mineralization in Khoshomy prospect, located in central. part of Iran, with 303-15000 (cps) and 14 to 4000 (ppm) released, The main rock types include: gneiss, granite, pegmatite and migmatite, that influenced by pegmatite-albitic vines (quartz-heldespatic). Acidic and basic dykes, granodioritic, units and dolomite and marble have been seen. The alteration associated with the mineralization is potassic, argillic, propylitic, carbonization, silisificaition and hematitizaition. Uranium mineralization occurred in a hydrothermal phase with Cu, Mo, Ni and Au elements. Uranium primary minerals include pitchblende, coffinite, uraninite; and uranium secondary minerals include uranophane and . boltwoodite. REE mineralization occurred by the potassic phase in peginatitization process

New data on structure and radiological age of formations of Lapland granulite belt (Kandalaksha Shore of the White Sea)

Energy Technology Data Exchange (ETDEWEB)

Sukhanov, M K; Terekhov, E N; Levitskij, V I

1987-01-01

The structure and radiological age of granulite belt rocks along the White Sea shore from West to East have been investigated by the uranium-lead thermoisochronous method. The age of granulite metamorphism in the White Sea shore and Kola blocks, which separate the granulite belt, is estimated as 2.5-2.7 milliard years; the boundary for metamorphic transformations (1.8 milliard years) is distinctly fixed for granulite belt rocks. The most ancient values for ages have been obtained by zircons of biotite gneisses -2.7-2.8 milliard years, and from granite shingles in conglomerates, in zircons of which the value of 2.9 milliard years is fixed.

Radioactivity measurements of soil samples from Raichur of Karnataka, India

International Nuclear Information System (INIS)

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

2016-01-01

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

Reassessment of the geologic evolution of selected precambrian terranes in Brazil, based on new SHRIMP U-Pb data, part 3: Borborema, Southern Mantiqueira and Rio Negro-Juruena provinces; Reavaliacao da evolucao geologica em terrenos pre-cambrianos brasileiros com base em novos dados U-Pb SHRIMP, parte 3: Provincias Borborema, Mantiqueira Meridional e Rio Negro-Juruena

Energy Technology Data Exchange (ETDEWEB)

Silva, Luiz Carlos da; Pimentel, Marcio [Brasilia Univ., DF (Brazil). Inst. de Geociencias]. E-mail: luizcarlos@aneel.gov.br; Scandolara, Jaime; Ramgrab, Gilberto [Centro de Pesquisas e Recursos Minerais, Brasilia, DF (Brazil); Wildner, Wilson; Sander, Andrea [Centro de Pesquisas e Recursos Minerais, Porto Alegre, RS (Brazil); Angelim, Luiz Alberto de Aquino [Centro de Pesquisas e Recursos Minerais, Recife, PE (Brazil); Vasconcelos, Antonio Maurilio [Centro de Pesquisas e Recursos Minerais, Fortaleza, CE (Brazil); Rizzoto, Gilmar; Quadros, Marcio Luiz do Espirito Santo [Centro de Pesquisas e Recursos Minerais, Porto Veolho, RO (Brazil); Armstrong, Richard [Australian National Univ., Canberra (Australia). Research School of Earth Sciences; Rosa, Ana Lucia Zucatti da [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

2002-12-15

This paper discusses new SHRIMP U-Pb data for 17 key-exposures (mostly granites and ortho gneisses) from the Borborema, Southern Mantiqueira (Pelotas Orogen) and Rio Negro-Juruena provinces. In the Borborema Province (Ceara state) two samples from the Cruzeta Complex TTG ortho gneisses, ascribed to the Paleoproterozoic basement, were studied. One revealed Paleoarchean crystallization minimum age of ca. 3270 Ma. Accordingly, the gneiss is interpreted as the oldest continental crustal remnant already recognised in Ceara. The other sample, from the Saboeiro-Aiuaba Granite gave a crystallization age of ca. 625 Ma, suggesting the correlation of this syn-orogenic pluton with the Brasiliano II orogenic system (climax at 630 Ma). In the Paraiba state the granodioritic gneiss pluton ascribed to the Mesoproterozoic Sume Complex showed a crystallization age of ca. 640 Ma, also indicating that its evolution is associated with the Brasiliano II orogenic system. In the Pernambuco state one widespread ortho gneissic unit within the Pernambuco-Alagoas Massif (Belem do Sao Francisco Complex), mapped as a component of the Meso proterozoic Cariris Velho Orogen, yielded a crystallization age of ca. 2079 Ma and metamorphic overprinting at ca. 655 Ma (1{sigma}), without evidence of a Mesoproterozoic (Cariris Velhos) reworking. In the southern part of the province, near the northern margin of the Sao Francisco Craton, the Santa Maria da Boa Vista (S-type) orthogneiss yielded a crystallisation age of ca. 3070 Ma. In the southern Mantiqueira Province/Pelotas Orogen a foliated granitic pluton (mylonitic) from the Florianopolis Batholith showed Paleoproterozoic protolithic age of ca. 2175 Ma and imprecise Brasiliano age on reprecipitated overgrowths. Both results match previous ages obtained on the orthogneisses protoliths from the Aguas Mornas complex, the main exposure of reworked basement within the batholith. The large, zoned calc-alkaline pluton of the Maruim Suite, confirmed its

Preliminary Geologic Map of the San Fernando 7.5' Quadrangle, Southern California: A Digital Database

Science.gov (United States)

Yerkes, R.F.

1997-01-01

. The San Fernando area lies on the southern slopes of the San Gabriel Mountains. The basement rocks here include high-grade metamorphic rocks of Precambrian age. The mountains are largely composed of crystalline basement that includes the Pelona Scist of probable Mesozoic age that has been overthrust by Precambrian gneisses; the gneisses were subsequently intruded by Mesozoic plutons prior to overthrusting along the latest Cretaceous Vincent thrust. Gneisses of somewhat variable composition and possibly varying ages are found in four terranes, but not all are in contact with Pelona Schist. Large tracts of Precambrian (1.2 billion years old) andesine anorthosite are intrusive into 1.7 billion year-old Mendenhall gneiss, and are found in the western part of the San Gabriels. Mixed with these are younger marble, limestone, and schist of possible Paleozoic age found in association with plutons along the southern margin of the range. The older rocks are intruded by diorite, quartz diorite, and granodiorite of Jurassic age. Also present are siliceous sedimentary rocks of Jurassic age. A thick section of Tertiary sedimentary and volcanic rocks overlie these units. The sediments located south of the San Gabriel Fault are totally different in character from those on the northern range flank, and mostly resemble the western Transverse Ranges due to their deposition in the southeastern Ventura basin; approximately 3,000 m of these sediments are exposed north and west of the city of San Fernando in the Tujunga syncline. Some of the Tertiary rocks are Paleocene and Eocene in age, but the bulk of these rocks are Oligocene and Miocene in age. The Vasquez and Sespe Formations of basal basaltic volcanic and sandstone are Oligocene and lower Miocene in age. These are overlain by clastic rocks of Tick Canyon and Mint Canyon Formations of middle to late Miocene age. Above these rocks are the Castaic, Modelo, and Santa Margarita Formations of fossiliferous marine shale, sand

Petrogenesis of low-δ18O quartz porphyry dykes, Koegel Fontein complex, South Africa

Science.gov (United States)

Harris, Chris; Mulder, Kwenidyn; Sarkar, Saheli; Whitehead, Benjamin; Roopnarain, Sherissa

2018-04-01

This paper investigates the origin of low-δ18O quartz porphyry dykes associated with the 144-133 Ma Koegel Fontein Igneous Complex, which was intruded during the initial phase of breakup of Africa and South America. The 25-km diameter Rietpoort Granite is the largest and youngest phase of activity, and is roofed by a 10-km diameter pendant of gneiss. Quartz porphyry (QP) dykes, up to 15 m in width, strike NW-SE across the complex. The QP dykes that intruded outside the granite have similar quartz phenocryst δ18O values (average 8.0‰, ± 0.7, n = 33) to the granite (average 8.3 ± 1.0, n = 7). The QP dykes that intruded the roof pendant have quartz phenocrysts with more variable δ18O values (average 1.6‰, ± 2.1, n = 55). In some cases quartz phenocrysts have δ18O values as low as - 2.5‰. The variation in δ18O value within the quartz crystal population of individual dykes is small relative to the overall range, and core and rim material from individual quartz phenocrysts in three samples are identical within error. There is no evidence that quartz phenocryst δ18O values have been affected by fluid-rock interaction. Based on a Δquartz-magma value of 0.6‰, magma δ18O values must have been as low as - 3.1‰. Samples collected along the length of the two main QP dykes that traverse the roof pendant have quartz phenocryst δ18O values that range from + 1.1 to + 4.6‰, and - 2.3 to + 5.6‰, respectively. These δ18O values correlate negatively ( r = - 0.96) with initial 87Sr/86Sr, which can be explained by the event that lowered δ18O values of the source being older than the dykes. We suggest that the QP dykes were fed by magma produced by partial melting of gneiss, which had been variably altered at high temperature by 18O-depleted meteoric water during global glaciation at 550 Ma. The early melts had variable δ18O value but as melt pockets interconnected during melting, the δ18O values approached that of average gneiss. Variable quartz phenocryst �

Characterization and monitoring of the excavation damaged zone in fractured gneisses of the Roselend tunnel, French Alps

Science.gov (United States)

Wassermann, J.; Sabroux, J. C.; Pontreau, S.; Bondiguel, S.; Guillon, S.; Richon, P.; Pili, E.

2011-04-01

The Roselend dead-end tunnel was excavated in the last fifties by blasting in the Méraillet crystalline rock mass located on the shore of an artificial reservoir lake in the French Alps. Successive emptying and filling of the reservoir lake induce mechanical deformation of the rock mass. Thus, this tunnel is an exceptional place to study the evolution of the damaged zone (due to the excavation, and named EDZ) under a periodic mechanical or hydraulic loading. From the perspective of radioactive waste isolation in deep geological strata, the EDZ transport properties, and their evolution with time, are of major importance. The purpose of this study is, on the one hand, to quantify the transport properties of the EDZ of the Roselend tunnel through permeability measurements and drill core observations; on the other hand, to monitor the response of the EDZ to external solicitations via borehole pressure measurements. The air permeability has been deduced from pneumatic tests performed along several boreholes. The permeability profiles and the observation of drill cores lead to an estimation of the extent of the EDZ, of about 1 m around the tunnel. The response of the EDZ to barometric pumping has been observed through borehole pressure monitoring. Time-lag and attenuation of the barometric signal that propagates into the EDZ have been measured at a metric scale. The identification of potential time-lag and attenuation variations needs further investigations, the long time series of borehole pressure monitoring shows pressure increase probably due to percolating water during successive snow cover and thawing periods as observed in the Roselend area during winter.

The Katmandu and Gosainkund nappes, central Nepal Himalaya (cartography, structure, metamorphism, geochemistry and radio-chronology)

International Nuclear Information System (INIS)

Rai, S.M.

1998-10-01

In central Nepal, a multidisciplinary study has been carried out to characterize and distinguish the crystalline nappes of Katmandu and Gosainkund from the Midland formations. Two principal deformations are recorded: one ductile, syn-metamorphic, marked by microstructures (stretching lineation, S-C structures, etc. ), another, post-metamorphic, recorded by an anticline, roughly EW -directed, and by NNE-SSW -directed folds. The syn-metamorphic P-T conditions show differences between Katmandu Crystalline Nappe (900-720 MPa; 700-480 deg C) and Gosainkund Crystalline Nappe (890-580 MPa; 750-590 deg C). They exhibit well preserved inverted metamorphism between the Upper Midland Formations (750 Mpa; 560 deg C) and the Gosainkund Nappe. In central Nepal, the augen gneisses and the 'Lesser Himalayan' Cambro-Ordovician granites bear similar petrographic and geochemical characteristics which suggest a common origin. However, the geological setting and age of the Proterozoic Ulleri augen gneiss rule out correlation with these formations. 40 Ar/ 39 Ar analyses of muscovite, indicate cooling ages younger from south to north: 22 to 13 Ma in the Katmandu Nappe, 16 to 5 Ma in the Gosainkund Nappe, and 12 to 6 Ma in the Midland Formation. The principal points summarized by this study are the following: clear distinction between two nappes marked by their litho-stratigraphy and metamorphism; the ductile movement of MCT in the north of Katmandu is blocked since approximately 25 Ma; the late emplacement and late or common post metamorphic history of the two nappes; but earlier cooling history of the Katmandu nappe; the present uplift of the Katmandu region, underlined by the intense micro-seismicity, concerns indifferently the two nappes that form a single tectonic block at present; the combined uplift of the two nappes is due to the displacement on a ramp of major decollement surface. (author)

Field characteristics, petrography, and geochronology of the Hohonu Batholith and the adjacent Granite Hill Complex, North Westland, New Zealand

International Nuclear Information System (INIS)

Waight, T.E.; Weaver, S.D.; Ireland, T.R.; Maas, R.; Muir, R.J.; Shelley, D.

1997-01-01

Detailed geological mapping, petrography, geochemistry and geochronological studies in the Hohonu Batholith, North Westland, have identified 10 granitoid plutons emplaced during three intrusive episodes. The earliest episode is represented by a single dated Paleozoic pluton, Summit Granite (new) (381.2 ± 7.3 Ma), which is correlated with a discrete pulse of Mid-Late Devonian plutonism recognised in the Karamea Batholith. The undated Mount Graham Granite (new) is also likely to be Paleozoic, based on chemical and petrographic characteristics. The bulk of the batholith (seven plutons) was emplaced in the mid Cretaceous (114-109 Ma) and comprises two related, yet distinct, geochemical suites, which correlate with the previously defined Rahu Suite. The plutons identified are (from north to south): Pah Point Granite; Jays Creek Granodiorite (new); Uncle Bay Tonalite; Te Kinga Monzogranite; Deutgam Granodiorite; Turiwhate Granodiorite (new); and Arahura Granite (new). Mid-Cretaceous plutonism in the Western Province is considered to be the result of crustal thinning and extension following overthickening during collision of the Early Cretaceous Median Tectonic Zone volcanic arc. Late Cretaceous alkaline activity is represented by the emplacement of the A-type French Creek Granite at 1.7 ± 1.8 Ma, contemporaneous with intrusion of a major swarm of doleritic-lamprophyric dikes - the Hohonu Dike Swarm. These events correlate with the first appearance of oceanic crust in the Tasman Sea. The Granite Hill Complex is a suite of amphibolite facies gneisses occurring as an uplifted wedge between the Alpine Fault nd the Hohonu Batholith. These gneisses are considered to represent an extension of the Fraser Complex to the south. A detailed understanding of their geological affinities and history is yet to be established. (author). 66 refs., 7 figs., 3 tabs

DEPOSITIONAL ENVIRONMENTS OF SUPRACRUSTAL METASEDIMENTARY SEQUENCE AND POSSIBLE MODEL FOR ZINC MINERALIZATION OF RIO CLARO AREA, RIO DE JANEIRO STATE (BRAZIL

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Ronaldo Mello Pereira

2016-10-01

Full Text Available This work focuses on Neoproterozoic supracrustal rocks related to Andrelandia megasequence, which are superimposed on the basis represented by neoarchean granulites and palaeoproterozoic ortogneiss, in order to define palaeoenvironments of deposition of metasedimentary rocks and typological model of zinc mineralization of Rio Claro, Rio de Janeiro State, SE of Brazil. Three stratigraphic units in the area were considered for the studies: Valadão, São Roque and Lidice. Valadão unit was divided into three subunits: psamitic, psamitic / pelitic and pelitic. On the whole, it represents a turbiditic sequence influenced by underwater hydrothermal exhalations that led to the formation of quartzite with magnetite, considered as banded iron formations. São Roque Unit is composed of four subunits (São Roque I, II, III and IV and presents a typical pattern of deposition of low energy environments, in marine deep basins. Gondite, coticules levels and (Mn-almandine present in the local gneiss mark the manganese exalative contribution in that unit. Lídice unit has different sedimentation palaeoenvironments and is subdivided into Lídice I, II and III. Lídice subunits I and II exhibit quartzite interleaved with pelitic rocks and graphite gneiss, suggesting deposition in deeper environments of the basin, probably related to turbidity currents. In Lídice III subunit, more carbonated and with more quartz, limestone quartzite stand out, which enclose mineralized zones, reflecting depositional environment in shallow platform, possibly involving evaporitic environment, sabkha type. Sulfite mineralization of Rio Claro, associated with platformal rocks intensely metamorphosed and deformed, as well as its local geological context, features similarities with sedimentary exhalative deposits (SEDEX Zn-Pb-Ag model, Shuswap and Monashee type, present in Monashee and Shuswap Complexes of British Columbia in Canada.

Genetic aspects of uranium mineralization in the Himalaya

International Nuclear Information System (INIS)

Saraswat, A.C.; Mahadevan, T.M.

1989-01-01

The Himalayan Uranium Province hosts five major types of uranium mineralization: (1) stratiform remobilized (Proterozoic), (2) structurally controlled hydrothermal (Proterozoic), (3) black shale-phosphorite (Palaeozoic-Mesozoic), (4) sandstone (Siwalik belt, Tertiary), and (5) primary disseminations in granitoids (Tertiary). Evaluation of the genetic aspects of these types has led to the identification of distinct spatial (lithostratigraphic and tectonic units) and temporal relations among them. The sandstone types are confined to the Tertiary (Middle Miocene to Pleistocene) molasse formations found south of th Main Boundary Thrust (MBT). Between the MBT and the Main Central Thrust, in the Lesser Himalaya, mineralization hosted in the Chail quartzite-phyllite ± metabasic sequences is of stratiform remobilized type. The structurally controlled hydrothermal type is confined to Dalings and gneisses. Syngenetic uranium in black shale-phosphorite sequences of Palaeozoic-Mesozoic age is found on the southern fringes of the Lesser Himalaya, bordering the MBT. Disseminated uranium occurs in the Tertiary and Proterozoic(?) granitoids of the Greater Himalaya and Ladakh. Rb-Sr geochronological data on host rocks and U-Pb dates on uraninites from some areas indicate that uranium mineralization in stratiform remobilized and structurally controlled types hosted by the Chails, Dalings and gneisses is essentially Precambrian and thus existed much before the Himalayan Orogeny. The Himalayan Orogeny, however, appears to have aided in further remobilization. The sandstone type mineralization in the Siwalik, on the other hand, is directly related to the process of formation of the foredeep and molasse sedimentation and subsequent uplift and epigenesis of the uranium mineralization, all of which are directly relatable to the evolution of the Himalaya. The relevance of deep seated lineament structures to mineralization, particularly of uranium, needs to be evaluated critically, as most

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.

Structural, petrological and geochronological analysis of the lithotypes from the Pien region (Parana State, Brazil) and adjacences; Analise estrutural, petrologica e geocronologica dos litotipos da Regiao de Pien (PR) e adjacencias

Energy Technology Data Exchange (ETDEWEB)

Harara, Ossama Mohamed

1996-12-31

The Pien area presents the major geotectonic domains separated by the Pien Shear Zone (PSZ). The northern one is the Rio Pien Granite-Mylonitic Suite composed by calc-alkaline granitoids of Neoproterozoic age. The southern domain is represented by the Amphibolite-Granulite where high grade metamorphism took place at the end of paleoproterozoic time. Considering the identified lithotypes, their geochemical affinity (particularly the Ti, Cr, Ni and REE content) and the geological context observed in the area, a geotectonical model of active continental margin related to subduction SSZ (Supra-Subduction Zone) is proposed. K-Ar on plagioclase from gabbronorites gave Neoproterozoic ages although Sm-Nd whole rock isochron yielded Paleoproterozoic ages. Based in geochemical data, it is proposed that the biotite gneiss and biotite-amphibole-gneiss which occur near the PSZ have a shoshonitic to high-K calc-alkaline features which are characteristic of active continental margins. K-Ar on biotite extracted from these rocks, gave Neoproterozoic ages. The available radiometric data for the Rio Pien mylonitic granitoids show that between 650-595 Ma the generation, deformation and cooling below the isotherm of 250 deg C occurred. On the other hand, the geochronological data for the Agudos do Sul Massif are in the 590-570 Ma interval showing its younger generation. The Sr{sup 87} / Sr{sup 86} initial ratios for both granitoids suggest more involvement of the continental crust in the origins of Agudos do Sul granitic Massif. The analyses of the entire set of the available data for the Pien area allows the suggestion of a geotectonic scenery related to the evolution of an active continental margin during the collages associated to the Brasiliano Cycle 201 refs., 130 figs., 6 tabs., 2 maps

Uranium in the north of Côte d'Ivoire: the case of Odienné

International Nuclear Information System (INIS)

Koffi, K.

2014-01-01

This work is a contribution to a better knowledge of Precambrian formations of Odienne region (Côte d’Ivoire), through their petrography and geochemistry. Those formations may be divided into two main groups: - first the metamorphic rocks constituted of Liberian rock relics, volcanic and volcano-sedimentary complex of Birimian age, ortho-gneiss and amphibolites considered either as Ante-Eburnean or early from the Eburnean cycle; - second, the plutonic rocks which are mainly made of granitoids. The discovery of aluminous gneiss of granulite facies within the Liberian formations, petrographically and chemically similar to those described in the Man region, and the presence of magnetite containing quartzites, are evidences of the existence of Liberian basement in the Odienne region. All the features of the Odienne Eburnean volcanism, as shown by the study made on the volcanic and volcano-sedimentary complex, allow us to connect it to the calco-alkaline series. In the present case, a formation model related to the big cutting accidents seems to fit best. As for the granitoids, they show: • a cataclais characterized by mineral torsions or breakages, a frequent mineral lineation, and an ondulating extinction; these are evidences of a syncinematic set-up; • a high content of Na_2O that seems to be expressed by a very important plagioclasic charge; • an evolution wholly silico-potassic in nature; all the samples studied vary from a quartzic-diorite pole to a granitic pole, with the majority of the compositions found in the granodiorite and adamellite domains ; the magma which generated those granitoids is of the calco-alkaline type; • relatively low average uranium and thorium contents; most of the radioactivity of those rocks is concentrated in the biotite or in the accessory minerals (generally in the form of inclusions in the biotite). (author)

Complementary investigations of the bedrock in the Finnsjoe and Karlshamn areas, Sweden

International Nuclear Information System (INIS)

Olkiewicz, A.; Scherman, S.; Kornfaelt, K.-A.

1979-02-01

In its statement of the 1978-10-05 the government decided that the KBS' reports I and II did not prove the existance of a''sufficiently large'' geological formation with the qualities which were required in the KBS risk analysis. The government therefore demanded further investigations. Complementary investigations were carried out in two areas, Finnsjoen in northwestern Uppland and Sternoe in southwestern Blekinge, Sweden. This report comprises mapping of the drillcores and extended geological mapping of the actual investigated areas. Measurements of borehole-deviation as well as surface-geophysical investigations from the Finnsjoen area are enclosed. The mapping of the four drill-cores in the Finnsjoe area shows that the cores are dominated by a slightly gneissic granodiorite. Of secondary importance occurs a young red homogenous granite. The frequency of fractures and fracture sets is high and evenly distributed. The tectonized parts are very often red coloured, foliated and containing many calcite healed fractures. The mapping also shows that mylonites and breccias are common in connection with more disturbed zones. Fractures are usually lined with calcite and chlorite. The mapping of these five new boreholes at Sternoe (one of the holes an extension of Ka 1 from earlier investigations) shows quite a complex picture of the bedrock. This is probably an effect of granitization of the coastal gneiss. Close to the surface coastal gneiss is dominating, in the deeper sections granitic material, gneissgranite and granite, are dominating. Pegmatites are common in the shallow sections of the area investigated. The frequency of fractures and fracture sets are very low. The only exception is one core, Ka 4, drilled in close connection with a thrust-zone in ''Munkahusviken''. Coatings of fracture surfaces are dominated by calcite and gypsum. (author)

Geochronological data for lithostratigraphic complexes of a crystalline basement from the South regions of Minas Gerais and adjacent areas of the Sao Paulo state

International Nuclear Information System (INIS)

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

1988-01-01

New geochronological data (Rb/Sr, Pb/Pb) for the Amparo and Pinhal Complexes, southern State of Minas Gerais and adjacent areas of the State of Sao Paulo are presented and discussed with respect to other lithostratigraphic complexes which there occur. Among the different complexes considered, 4 are composed mainly by rock belonging to typical infrastructure associations. They are the Barcelona, the Guaxupe, the Amparo and the Pinhal complexes. The Barbacena Complex is a typical gray gneiss complex and geochronological data by different methods confirm its Archean age. The Guaxupe Complex is composed mainly by different types of charnockitic rocks and an Archean age is assumed on geotectonic basis due to its neighboring association with the gray gneiss/greenstone belt, a though confirming geochronological data are still missing, a normal feature in this type of mobile belts which generally show a complex, polycyling evolution. Geochronological data by different methods on diverse rock types indicates that the Amparo and Pinhal complexes are respectively of Lower an Upper proterozoic age. Geochronological, geological and petrographic data reveal that both complexes are composed mainly by 3 basic rock associations: a-mainly derived magmatic rocks including mafic/ultramafic ones as well as calc-alkaline, subalcaline and even alkaline granitoids; b-orthogneisses, migmatites and crustal granites derived by metamorphic processes acting on older, pre-existing rocks; corthogneisses and migmatites resulting from metamorphic processes acting on magmatic rocks intruded during the same tecto-metamorphic cycle during which its transformation took place. The results suggest a polycyclic evolution by successive tecto-metamorphic events which affected the older rocks of the considered are either by the reworking of enclosing rocks around pericratonic continental main magmatic arcs or by the remobilisation of older basement rocks during continental collisions. (author) [pt

Seismic tomography for charaterization of an ore vein in the research and education mine Reiche Zeche

Science.gov (United States)

Winter, Sebastian; Schlüter, Ralf; Hlousek, Felix; Buske, Stefan

2017-04-01

A test site for the design, implementation and operation of an underground in-situ bioleaching unit has been installed by the „Biohydrometallurgical Center for Strategic Elements" at the research and education mine "Reiche Zeche" of Technical University Bergakademie Freiberg. For this purpose an ore vein block will be developed and mined with the bio-hydrometallurgical in-situ leaching technology. As a site survey an underground seismic tomography experiment has been performed to investigate the spatial distribution of the ore vein within this block consisting mainly of gneiss and with dimensions of about 30 x 10 meters. The experiment was performed with a sledgehammer as source and 76 three-component receivers with source and receiver point intervals of about 1 m surrounding the approximately rectangular block. High precision laser scanning was performed to obtain accurate source and receiver positions which was particularly necessary to obtain reliable results due to the generally high wave velocities of the gneiss. The resulting seismic data set showed a high signal-to-noise ratio with clear first arrivals which were picked for all source and receiver combinations and subsequently used as input to a first-arrival tomographic inversion scheme. The resulting velocity model has very good ray coverage and shows well resolved high- and low-velocity regions within the block. These regions can be clearly assigned to mapped outcrops of the ore vein along the galleries surrounding the block, including a correlation of low velocities to fractured rock parts as well as high velocities to the undisturbed ore vein core, respectively. In summary the obtained velocity model and the inferred spatial distribution of the ore vein provides a good basis for planning and implementing the actual ore mining step using the envisaged bioleaching technology.

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

Directory of Open Access Journals (Sweden)

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.

Structural, petrological and geochronological analysis of the lithotypes from the Pien region (Parana State, Brazil) and adjacences; Analise estrutural, petrologica e geocronologica dos litotipos da Regiao de Pien (PR) e adjacencias

Energy Technology Data Exchange (ETDEWEB)

Harara, Ossama Mohamed

1997-12-31

The Pien area presents the major geotectonic domains separated by the Pien Shear Zone (PSZ). The northern one is the Rio Pien Granite-Mylonitic Suite composed by calc-alkaline granitoids of Neoproterozoic age. The southern domain is represented by the Amphibolite-Granulite where high grade metamorphism took place at the end of paleoproterozoic time. Considering the identified lithotypes, their geochemical affinity (particularly the Ti, Cr, Ni and REE content) and the geological context observed in the area, a geotectonical model of active continental margin related to subduction SSZ (Supra-Subduction Zone) is proposed. K-Ar on plagioclase from gabbronorites gave Neoproterozoic ages although Sm-Nd whole rock isochron yielded Paleoproterozoic ages. Based in geochemical data, it is proposed that the biotite gneiss and biotite-amphibole-gneiss which occur near the PSZ have a shoshonitic to high-K calc-alkaline features which are characteristic of active continental margins. K-Ar on biotite extracted from these rocks, gave Neoproterozoic ages. The available radiometric data for the Rio Pien mylonitic granitoids show that between 650-595 Ma the generation, deformation and cooling below the isotherm of 250 deg C occurred. On the other hand, the geochronological data for the Agudos do Sul Massif are in the 590-570 Ma interval showing its younger generation. The Sr{sup 87} / Sr{sup 86} initial ratios for both granitoids suggest more involvement of the continental crust in the origins of Agudos do Sul granitic Massif. The analyses of the entire set of the available data for the Pien area allows the suggestion of a geotectonic scenery related to the evolution of an active continental margin during the collages associated to the Brasiliano Cycle 201 refs., 130 figs., 6 tabs., 2 maps

Core drilling of deep drillhole OL-KR50 at Olkiluoto in Eurajoki 2008

International Nuclear Information System (INIS)

Toropainen, V.

2009-02-01

As a part of the confirming site investigations at Olkiluoto, Suomen Malmi Oy (Smoy) core drilled 939.33 m and 45.44 m deep drillholes with a diameter of 75.7 mm at Olkiluoto in September - November 2008. The identification numbers of the drillholes are OL-KR50 and OL-KR50B, respectively. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the returning and drilling water were recorded. The drill rig was computer controlled and the computer recorded drilling parameters during drilling. The objective of the measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volumes of the used drilling and washing water were 1135 m 3 and 20 m 3 in the drillholes OL-KR50 and OL-KR50B, respectively. The measured volume of the returning water in the drillhole OL-KR50 was 954 m 3 . The deviation of the drillholes was measured with the deviation measuring instruments EMS and Maxibor II. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength was 129.7 MPa, the average Young's Modulus was 45.8 GPa and the average Poisson's ratio was 0.15. The main rock types were veined and diatexitic gneisses, pegmatitic granite and tonaliticgranodioritic-granitic gneiss. The average fracture frequency is 2.0 pcs/m in drillhole OL KR50 and 3.6 pcs/m in the drillhole OL-KR50B. The average RQD values are 96.1 % and 94.3 %, respectively. 39 fractured zones were penetrated by drillhole OL-KR50 and four by drillhole OL-KR50B. (orig.)

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

Stages of material transformations of Archean-Proterozoic rocks (Central-Karelian domain)

International Nuclear Information System (INIS)

Vinogradov, V.I.; Buyakajte, M.I.; Kolodyazhnyj, S.Yu.; Leonov, M.G.; Orlov, S.Yu.

2001-01-01

The age of the Archean-Proterozoic rocks from the south-east part of the Central-Karelian domain was determined by the method of Rb-Sr dating. It was ascertained that the age of the least tectonized rocks of granite-greenstone Archean foundation makes up 2800±70 mln. years at initial strontium isotopic ratio of 0.7022±0.0007. Gneisses of mainly plagiogranite composition, their age 1930±118 mln. years and strontium isotopic ratio 0.7170±0.0026, constitute the second group of the rocks. It is shown that isotopic age defined for the two groups of rocks agrees well with major geological events on the Baltic shield and planet as a whole [ru

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

Science.gov (United States)

Anderson, T. H.

1985-01-01

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

An integrated study of aerospace data for uranium exploration in the Magajhi-Kotapali shear zone, Surguja district, Madhya Pradesh, India

International Nuclear Information System (INIS)

Chaturvedi, A.K.; Kak, S.N.

1993-01-01

Lower Proterozoic granite gneiss and associated cataclastic rocks of Surguja crystalline complex record uranium mineralisation along the WNW-ESE trending Magajhi-Kotapali shear zone. Extension of the shear zone and cross faults trending NE-SW were established using enhanced satellite data. On integrating it with aeroradiometric data, it has been found that uranium mineralisation is shear controlled and occur around the zone of intersection between the WNW-ESE trending shear and the NE-SW faults. The study has narrowed down the target area for detailed ground investigations and finally resulted in locating promising areas such as Chathila Pahar, Haskepi, Jarhakhar-Semarkhar, and Tilti forest with good extensions along the shear zone. (author). 18 refs., 5 figs

Mechanical characterization of rocks at high strain rate

Directory of Open Access Journals (Sweden)

Konstantinov A.

2012-08-01

Full Text Available The paper presents the dynamic characterization in tension and compression of three rocks, Carrara marble, Onsernone gneiss and Peccia Marble, at high strain-rates. Two versions of a Split Hopkinson Bar have been used. The version for direct tension tests is installed at the DynaMat Laboratory of the University of Applied Sciences of Southern Switzerland, while the traditional version in compression is installed at the Laboratory of Dynamic Investigation of Materials of Lobachevsky State University. Results of the tests show a significantly strain-rate sensitive behaviour, exhibiting dynamic strength increasing with strain-rate. The experimental research has been developed in the frame of the Swiss-Russian Joint Research Program.

Strain localization in the lower crust: brittle precursors versus lithological heterogeneities (Musgrave Ranges, Central Australia)

Science.gov (United States)

Hawemann, Friedrich; Mancktelow, Neil; Wex, Sebastian; Pennacchioni, Giorgio; Camacho, Alfredo

2016-04-01

The Davenport shear zone in Central Australia is a strike-slip ductile shear zone developed during the Petermann Orogeny (~ 550 Ma). The conditions of shearing are estimated to be amphibolite-eclogite facies (650 °C, 1.2 GPa). The up to seven kilometre thick mylonite zone encloses several large low strain domains with excellent exposure, thus allowing a thorough study of the initiation of shear zones. Quartzo-feldspathic gneisses and granitoids inherit a suite of lithological heterogeneities such as quartz-rich pegmatites, mafic layers and dykes. When in a favourable orientation to the shortening direction, these rheologically different pre-existing layers might be expected to localize deformation. However, with the singular exception of long, continuous and fine-grained dolerite dykes, this is not observed. Quartz-rich pegmatites are mostly unsheared, even if in a favourable orientation, and sometimes boudinaged or folded. There are instead many shear zones only a few mm to cm in width, extending up to tens of metres, which are in fact oriented at a very high angle to the shortening direction. Parallel to these, a network of little to moderately overprinted brittle fractures are observed, commonly marked by pseudotachylyte (pst) and sometimes new biotite. Shear reactivation of these precursor fractures is generally limited to the length of the initial fracture and typically re-uses and shears the pst. The recrystallized mineral assemblage in the sheared pst consists of Cpx+Grt+Fsp±Ky and is the same to that in the adjacent sheared gneiss, with the same PT estimates (650 °C, 1.2 GPa). In some cases, multiple generations of cross-cutting and sheared pst demonstrate alternating fracture and flow during progressive shear zone development and a clear tendency for subsequent pst formation to also localize in the existing shear zone. The latest pst may be both unsheared and unrecrystallized (no grt) and is probably related to a late stage, still localized within the

ONKALO POSE experiment. Phase 3: execution and monitoring

International Nuclear Information System (INIS)

Valli, J.; Hakala, M.; Wanne, T.; Kantia, P.; Siren, T.

2014-01-01

In-depth knowledge of the in situ stress state at the Olkiluoto site is critical for stability assessment both prior to and after deposition of spent nuclear fuel in order to understand and avoid potential damage to the rock at the site. Posiva's Olkiluoto Spalling Experiment (POSE) was designed specifically for this purpose with three primary goals: establish the in situ spalling/damage strength of Olkiluoto migmatitic gneiss, establish the state of in situ stress at the -345 m depth level and act as a Prediction-Outcome (P-O) exercise. Phases 1 and 2 of POSE are outlined in WR 2012-60. The objectives of the third phase of the POSE experiment are the same as the original objectives outlined above. This report outlines the execution and results of the third phase of the POSE experiment. The third phase of the experiment involved internally heating the third experimental hole (ONK-EH3) of the POSE niche in order to cause a symmetrical thermal stress increase around the hole due to the thermal expansion of rock. This thermomechanically induced stress increase, coupled with the estimated existing in situ stress state, should cause the maximum principal stress around the hole to exceed the predicted spalling strength of the rock around the hole. ONK-EH3 is located almost completely in pegmatitic granite. Four fractures near the top of the hole were mapped after boring ONK-EH3, and a tensile failure located at the contact between mica-rich gneiss and pegmatitic granite was observed 18 months after boring, prior to the experiment. Based on predictive calculations and the estimated in situ state of stress, the maximum principal stress magnitude should reach ca. 100 MPa when the temperature was just below 100 deg C after 12 weeks of heating. There were problems with the heater control unit at the beginning of the experiment, after which heating proceeded according to plan. The crack damage threshold of pegmatitic granite has been determined to be 85 ±17 MPa at Olkiluoto

Cachoeira Uranium Deposit, Lagoa Real, Bahia, Brazil – Kinematic, compositional and fluid evolution

International Nuclear Information System (INIS)

Pires, F.; Miano, S.

2014-01-01

The Cachoeira uranium albitite-type deposit occurs in a steep dip shear zone aligned with several other similar uranium deposits in the Lagoa Real Province. Uranium resources are estimated as about 90,000 t U_3O_8 [~76,000 t U] grading 2500 ppm U_3O_8 [~2100 ppm U]. Uraniferous albitite occupies a 15 m-thick strongly mylonitized shear zone structurally enclosed within “zebra” biotite gneiss. Uranium albitite mineralization forms cigar-shaped (prolate) and secondarily pancake-shaped (oblate) bodies composed of albite-hornblende-garnet-uraninite-magnetite ore grading to quartz-free skarntype rock with fluorite-kyanite-calcite-quartz concordant veins and pockets formed by late hydrothermal process. Brown chalcedony was the latest mineral to form. Fine-grained, disseminated uraninite is distributed and concentrated in the mafic portions of the gneiss consisting of hornblende andradite- sphene-apatite-epidote forming 30% and albite portions consisting of 70% of the albitite, which allows its gravitational treatment, thus decreasing acid leaching. While the host rock was severely affected by K-metasomatism the uraninite zone was deposited together with hornblende by Na- and Ca-metasomatism. Another reaction involves garnet crystallization exclusively together with uraninite, which liberates sílica and oxygen, differently from previous reaction which consumes silica and oxygen. Both reactions involve magnetite. The destabilization of biotite at the ore zone implies in the formation of GSPO-biotite overgrowing the LPO-biotite previously formed at host rock, due to the excess of K in the system. Magnetite is absent. The reaction represents the K-metasomatism at the host zebra gneiss: biotite + plagioclase + pyroxene + UO_2Cl"+ + Ca_2"+ = hornblende + uraninite + kyanite + quartz. The excess of Ca is allocated in the sphene, apatite and epidote structures. Consumption of Ca results in rutile deposition. As fluid composition was complex F and CO_2 were enriched in the

Grain-scale Sr isotope heterogeneity in amphibolite (retrograded UHP eclogite, Dabie terrane): Implications for the origin and flow behavior of retrograde fluids during slab exhumation

Science.gov (United States)

Guo, Shun; Yang, Yueheng; Chen, Yi; Su, Bin; Gao, Yijie; Zhang, Lingmin; Liu, Jingbo; Mao, Qian

2016-12-01

To constrain the origin and flow behavior of amphibolite-facies retrograde fluids during slab exhumation, we investigate the textures, trace element contents, and in situ strontium (Sr) isotopic compositions (using LA-MC-ICP-MS) of multiple types of epidote and apatite in the UHP eclogite and amphibolites from the Hualiangting area (Dabie terrane, China). The UHP epidote porphyroblasts in the eclogite (Ep-E), which formed at 28-30 kbar and 660-720 °C, contain high amounts of Sr, Pb, Th, Ba, and light rare earth elements (LREEs) and have a narrow range of initial 87Sr/86Sr ratios (0.70431 ± 0.00012 to 0.70454 ± 0.00010). Two types of amphibolite-facies epidote were recognized in the amphibolites. The first type of epidote (Ep-AI) developed in all the amphibolites and has slightly lower trace element contents than Ep-E. The Ep-AI has a same initial 87Sr/86Sr ratio range as the Ep-E and represents the primary amphibolite-facies retrograde product that is associated with an internally buffered fluid at 8.0-10.3 kbar and 646-674 °C. The other type of epidote (Ep-AII) occurs as irregular fragments, veins/veinlets, or reaction rims on the Ep-AI in certain amphibolites. Elemental X-ray maps reveal the presence of Ep-AI relics in the Ep-AII domains (appearing as a patchy texture), which indicates that Ep-AII most likely formed by the partial replacement of the Ep-AI in the presence of an infiltrating fluid. The distinctly lower trace element contents of Ep-AII are ascribed to element scavenging by a mechanism of dissolution-transport-precipitation during replacement. The Ep-AII in an individual amphibolite exhibits large intra- and inter-grain variations in the initial 87Sr/86Sr ratios (0.70493 ± 0.00030 to 0.70907 ± 0.00022), which are between those of the Ep-AI and granitic gneisses (wall rock of the amphibolites, 0.7097-0.7108). These results verify that the infiltrating fluid was externally derived from granitic gneisses. The matrix apatite in the amphibolites has

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

Science.gov (United States)

Negrel, Philippe; Pauwels, Hélène

2017-04-01

manure, water originating in the upper compartment of the aquifer in weathered rock (alterite) and water from the lower compartment of the aquifer, mainly comprising fissured fresh rock. The interaction with alterite thus led to higher Sr- isotope ratios (around 0.730) in the water because of the weathering of residual minerals whereas interaction in the fissured part implies that the Sr-isotope characteristics of waters are more related to the weathering of whole rock with a lower value. Secondly, an extensive approach was done by enlarging to Africa (granite-gneiss and schists 2200 - 700 Ma of the Congo Basin), French Guiana (Archaen gneiss 3400-2700Ma and granite-gneiss rocks 2300-1900Ma) and India (Archean granites 2500Ma and Palaeoproterozoic granodiorite and schists 3100 - 1600Ma) considering both surface and groundwater. Here, the weathering processes concern older silicate environments and such weathered silicates yield to clearly higher Sr- isotope ratios (up to 0.745). The Sr-isotope tracing defines and identifies the relative signature of water origin between alterite and rain or agricultural practice (India), between alterite and underlying weathered-fissured and fractured bedrock (Africa) and between the three end-members in French Guiana.

Using mineral equilibria to estimate H2O activities in peridotites from the Western Gneiss Region of Norway

NARCIS (Netherlands)

Kang, Patricia; Lamb, William M.; Drury, Martyn

2017-01-01

The Earth's mantle is an important reservoir of H2O, and even a small amount of H2O has a significant influence on the physical properties of mantle rocks. Estimating the amount of H2O in rocks from the Earth's mantle would, therefore, provide some insights into the physical properties of this

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

International Nuclear Information System (INIS)

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

1993-01-01

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

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

International Nuclear Information System (INIS)

1977-11-01

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

Rb-Sr geochronology from Barro Alto Complex, Goias: metamorphism evidence of high degree and continental collision around 1300 Ma ago in Central Brazil

International Nuclear Information System (INIS)

Fuck, R.A.; Neves, B.B.B.; Cordani, U.G.; Kawashita, K.

1989-01-01

Rb-Sr geochronologic investigation carried out on rocks from the Barro Alto Complex, Goias, yielded iso chronic ages of 1266 +- 17 Ma, for felsic rocks from the granulite belt and 1330 +- 67 Ma, for gneisses belonging to the Juscelandia Sequence. Rb-Sr isotope measurements suggest that Barro Alto rocks have undergone an important metamorphic event during middle Proterozoic times, around 1300 Ma ago. During that event, volcanic and sedimentary rocks of Juscelandia Sequence, as well as the underlying gabbros-anorthosite layered complex, underwent deformation and recrystallization under amphibolite facies conditions. Deformation and metamorphism took place during the collision of two continental blocks, which resulted in a southeastward directed thrust complex, allowing the exposure of granulite slices from the middle-lower crust of the overthrusted block. (author)

The Geology of the Kivetty area

International Nuclear Information System (INIS)

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

1992-05-01

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

Structural investigation of the Grenville Province by radar and other imaging and nonimaging sensors

Science.gov (United States)

Lowman, P. D., Jr.; Blodget, H. W.; Webster, W. J., Jr.; Paia, S.; Singhroy, V. H.; Slaney, V. R.

1984-01-01

The structural investigation of the Canadian Shield by orbital radar and LANDSAT, is outlined. The area includes parts of the central metasedimentary belt and the Ontario gneiss belt, and major structures as well-expressed topographically. The primary objective is to apply SIR-B data to the mapping of this key part of the Grenville orogen, specifically ductile fold structures and associated features, and igneous, metamorphic, and sedimentary rock (including glacial and recent sediments). Secondary objectives are to support the Canadian RADARSAT project by evaluating the baseline parameters of a Canadian imaging radar satellite planned for late in the decade. The baseline parameters include optimum incidence and azimuth angles. The experiment is to develop techniques for the use of multiple data sets.

The use of gamma spectrometry in mapping alteration zones in Olkiluoto

International Nuclear Information System (INIS)

Ojala, J.V.; Turunen, P.; Eilu, P.; Julkunen, A.; Gehoer, S.

2007-08-01

In the Olkiluoto site, a detailed gammaspectrometry log from the drill hole OL-KR27 was used to estimate the concentrations of K, Th and U. The gamma spectrometry results, lithological variations, and kaolinite and illite alteration visually mapped from the drill hole were compared. The result indicate that the Th/K ratio correlates best with lithology and that, in most cases, the changes in the ratio indicate lithological contacts and rising or falling trends of Th/K ratio with some peaks have some correlation with the kaolinite-illite alteration. From the result it is suggested that that very variable Th/K ratio is a reasonably good indicator of alteration zones even in the migmatic gneiss area in the Olkiluoto site. (orig.)

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

International Nuclear Information System (INIS)

Dill, H.

1983-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1983-05-01

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

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

International Nuclear Information System (INIS)

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

1990-01-01

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

The occurrence of rare earth elements in some Finnish mires

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Yliruokanen, I.

1995-12-01

Full Text Available The content of the more abundant rare earths (RE (Y, La, Ce, Pr, Nd and Sm in the ash of 399 peat samples from 26 Finnish mires was determined by X-ray fluorescence spectrometry. The content of all rare earths (La-Lu, Y in 29 samples was also determined by spark source mass spectrometry. The median RE contents in peat ashes from areas where the bedrock consists of rapakivi granite, granite or archean gneiss are reported. Detailed data concerning the individual mires are also presented. The highest RE contents were found in samples from rapakivi granite areas where a strong negative Eu anomaly was also observed. The RE contents were in general highest at the basal peat layers.

A desk study of surface diffusion and mass transport in clay

International Nuclear Information System (INIS)

Cook, A.J.

1988-09-01

The concept of a geological barrier to radionuclide migration from theoretical radioactive waste repositories has drawn attention to the physico-chemical properties of clays, which are traditionally regarded as retarding media. This report addresses the different mechanisms of transport of radionuclides through clay and in particular focuses on the surface diffusion movement of sorbed cations. The relative contributory importance of the different transport mechanisms is governed by the pore size distributions and interconnections within the clay fabric. Surface diffusion data in the literature have been from experiments using compacted montmorillonite and biotite gneiss. A possible programme of laboratory work is outlined, based on diffusion experiments, which describes the way of measuring the effect of surface diffusion more accurately in clays, mudstones and shales. (author)

Isotopic and chemical evidence for three accretionary magmatic arcs ( 1.79 - 1.42 Ga) in the SW Amazon Craton, Mato Grosso State, Brazil

International Nuclear Information System (INIS)

Geraldes, Mauro Cesar; Teixeira, Wilson; Schmus, William Randall van

2000-01-01

Twenty-one U/Pb ages of granitoids in the SW Amazon craton define three crustal accretionary events during the Paleo-and Mesoproterozoic that represent significant portions of the Rio Negro-Juruena Province and the Rondonian/San Ignacio province. Two events refer to the Rio Negro-Juruena province: The Alto Jauru greenstone belt comprises acid volcanics and tonalite to granite gneisses with U/Pb ages from 1790 to 1750 Ma. Sm/Nd isotopic data (e N -d (t) from +2.6 to +2.2 and T DM from 2.0 to 1.80 Ga) indicate a volcanic arc with juvenile signatures for these units. The second event (Cachoeirinha arc) comprises granites to tonalites with U/Pb ages from 1580 to 1530 Ma. Sm/Nd results. (author)

Deep Boreholes Seals Subjected to High P, T conditions – Preliminary Experimental Studies

Energy Technology Data Exchange (ETDEWEB)

Caporuscio, Florie Andre [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Norskog, Katherine Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Maner, James Lavada [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-01-18

The objective of this planned experimental work is to evaluate physio-chemical processes for ‘seal’ components and materials relevant to deep borehole disposal. These evaluations will encompass multi-laboratory efforts for the development of seals concepts and application of Thermal-Mechanical-Chemical (TMC) modeling work to assess barrier material interactions with subsurface fluids, their stability at high temperatures, and the implications of these processes to the evaluation of thermal limits. Deep borehole experimental work will constrain the Pressure, Temperature (P, T) conditions which “seal” material will experience in deep borehole crystalline rock repositories. The rocks of interest to this study include the silicic (granitic gneiss) end members. The experiments will systematically add components to capture discrete changes in both water and EBS component chemistries.

SHRIMP chronology of the Magallanes Basin basement, Tierra del Fuego: Cambrian plutonism and Permian high-grade metamorphism Geocronología SHRIMP del basamento de la Cuenca de Magallanes, Tierra del Fuego: plutonismo Cámbrico y metamorfismo Pérmico de alto grado

Directory of Open Access Journals (Sweden)

Francisco Hervé

2010-07-01

Full Text Available Five new SHRTMP U-Pb zircon ages are reported for gneisses and foliated plutonic rocks belonging to the Tierra del Fuego igneous and metamorphic basement complex (TFIMC, obtained from the bottom of borehole cores through the Magallanes Basin. Three of the samples yielded weighted mean 206Pb/238U ages (523±7 Ma, 522±6 Ma and 538±6 Ma, interpreted as indicating Early Cambrian igneous crystallization of the host rocks. A migmatitic gneiss shows peaks at ca. 950-1,100 Ma and 560-650 Ma from inherited zircon grains in addition to two grains with ages of ca. 525 Ma, suggesting involvement of Grenvillian and Brasiliano material in the protolith of a Cambrian migmatite. A cordierite-sillimanite-garnet gneiss contains igneous zircons of Cambrian age and a population of U-rich metamorphic Permian zircons, indicating that a Permian high-grade metamorphic and anatectic (P=2-3 kbar, T=730-770°C event affected the Cambrian igneous rocks or sedimentary rocks derived from them. Cambrian/Ediacaran plutonic rocks are known from the basement of NW Argentina, the Sierra de la Ventana, the Cape Fold Belt in South Africa, and the Ross Orogen in Antarctica. The Permian metamorphic event is coeval with the deformation and low-grade metamorphism of the sedimentary successions that overlie the basement in many of these areas. In Tierra del Fuego at least 8 to 12 km of cover rocks were removed following the high-grade Permian metamorphic episode and the unconformable deposition of the Tobífera Formation volcanic rocks in the Middle to Late Jurassic. This eroded cover could nave been an important source of detritus for the conglomeratic Permian and Triassic? Successions of neighboring regions in South America, Africa and Antarctica.Cinco nuevas edades radiométricas logradas mediante análisis U-Pb en circón utilizando el SHRIMP, fueron determinadas en gneises y rocas plutónicas foliadas obtenidas desde el fondo de pozos de sondajes en la Cuenca de Magallanes y

Geophysical Investigation using Two Dimensional Electrical Resistivity Tomography method to delineate Subsurface Geological Structures at Dudhkoshi-II (230 MW) Hydroelectric Project, Solukhumbu District, Eastern Nepal

Science.gov (United States)

Ghimire, H.; Bhusal, U. C.; Khatiwada, B.; Pandey, D.

2017-12-01

Geophysical investigation using two dimensional electrical resistivity tomography (2D-ERT) method plays a significant role in determining the subsurface resistivity distribution by making measurement on the ground surface. This method was carried out at Dudhkoshi-II (230 MW) Hydroelectric Project, lies on Lesser Himalayan region of the Eastern Nepal to delineate the nature of the subsurface geology to assess its suitability for the construction of dam, desanding basin and powerhouse. The main objective of the proposed study consists of mapping vertical as well as horizontal variations of electrical resistivity to enable detection of the boundaries between unconsolidated materials and rocks of the different resistivity, possible geologic structures, such as possible presence of faults, fractures, and voids in intake and powerhouse area. For this purpose, the (WDJD-4 Multi-function Digital DC Resistivity/IP) equipment was used with Wenner array (60 electrodes). To fulfill these objectives of the study, the site area was mapped by Nine ERT profiles with different profile length and space between electrodes was 5 m. The depth of the investigation was 50 m. The acquired data were inverted to tomogram sections using tomographic inversion with RES2DINV commercial software. The Tomography sections show that the subsurface is classified into distinct geo-electric layers of dry unconsolidated overburden, saturated overburden, fractured rock and fresh bedrock of phyllites with quartzite and gneiss with different resistivity values. There were no voids and faults in the study area. Thickness of overburden at different region found to be different. Most of the survey area has bedrock of phyllites with quartzite; gneiss is also present in some location at intake area. Bedrock is found at the varies depth of 5-8 m at dam axis, 20-32 m at desanding basin and 3-10 m at powerhouse area. These results are confirmed and verified by using several boreholes data were drilled on the

Recycling argon through metamorphic reactions: The record in symplectites

Science.gov (United States)

McDonald, Christopher S.; Regis, Daniele; Warren, Clare J.; Kelley, Simon P.; Sherlock, Sarah C.

2018-02-01

The 40Ar/39Ar ages of metamorphic micas that crystallized at high temperatures are commonly interpreted as cooling ages, with grains considered to have lost 40Ar via thermally-driven diffusion into the grain boundary network. Recently reported laser-ablation data suggest that the spatial distribution of Ar in metamorphic micas does not always conform to the patterns predicted by diffusion theory and that despite high metamorphic temperatures, argon was not removed efficiently from the local system during metamorphic evolution. In the Western Gneiss Region (WGR), Norway, felsic gneisses preserve microtextural evidence for the breakdown of phengite to biotite and plagioclase symplectites during near isothermal decompression from c. 20-25 to c. 8-12 kbar at 700 °C. These samples provide an ideal natural laboratory to assess whether the complete replacement of one K-bearing mineral by another at high temperatures completely 'resets' the Ar clock, or whether there is some inheritance of 40Ar in the neocrystallized phase. The timing of the high-temperature portion of the WGR metamorphic cycle has been well constrained in previous studies. However, the timing of cooling following the overprint is still much debated. In-situ laser ablation spot dating in phengite, biotite-plagioclase symplectites and coarser, texturally later biotite yielded 40Ar/39Ar ages that span much of the metamorphic cycle. Together these data show that despite residence at temperatures of 700 °C, Ar is not completely removed by diffusive loss or during metamorphic recrystallization. Instead, Ar released during phengite breakdown appears to be partially reincorporated into the newly crystallizing biotite and plagioclase (or is trapped in fluid inclusions in those phases) within a close system. Our data show that the microtextural and petrographic evolution of the sample being dated provides a critical framework in which local 40Ar recycling can be tracked, thus potentially allowing 40Ar/39Ar dates

Isotope characteristics of the sulphide-bearing sequence of the areachap group in the Boksputs area, North-West Cape

International Nuclear Information System (INIS)

Cilliers, F.H.

1987-06-01

The Boksputs stratiform sulphide deposit is situated in the eastern marginal zone of the Namaqua Province, South Africa, within the Boksputs Formation (previously termed Jannelsepan Formation). Pyrite, chalcopyrite and sphalerite are the most abundant minerals in the disseminated and thinly banded ore. The sulphide mineralization and host rocks have been deformed by at least four phases of folding followed by shearing and faulting. Major and trace element abundances (including REE), U-Pb and Sm-Nd isotope systematics indicate that changes owing to metamorphism are essentially isochemical in the amphibolite, which was derived from a mantle source. U-Pb isotope analysis were carried out on 24 amphibolite, 6 gneiss, 6 quartz-monzodiorite and 7 pyrite samples while Sm-Nd isotope analyses were performed on 6 amphibolite samples. A Pb-Pb isochron age of 1665 ± 140 Ma for the amphibolite samples indicates that the metavolcanic succession was extruded or emplaced before the Namaqua tectogenesis. The 1271 ± 53 Ma isochron age obtained for the gneiss samples is thus interpreted as a reset age, reflecting the Namaqualand metamorphic episode. It is proposed that the Boksputs mineralization like the Prieska Cu-Zn ore body, Areachap ore and Kielder sulphides, formed approximately 1500 to 1600 Ma ago as a syngenetic exhalative deposit, in a tectonic environment dominated by mantle derived tholeiitic volcanism with contemporaneous sedimentation. It is suggested that the hydrothermal fluid responsible for mineralization originated from a primary source, which must have been homogeneous, with respect to lead isotopic composition, over a large distance. The diversity of the volcano-sedimentary successions below the different ore bodies and overall similarity in Pb isotopic character, negates the possibility that the metals were leached from these rocks and a source related to a deep seated magma of mantle origin is proposed. It is concluded that Pb isotope systematics can be used

Microstructures of the Kirsehir Complex, Central Turkey

Science.gov (United States)

ISIK, V.; Caglayan, A.; Uysal, T.; Bolhar, R.

2011-12-01

Turkey is positioned on the boundary between the Eurasian and African/Arabian plates, providing an ideal natural laboratory for learning passive and active earth processes such as deformation, metamorphism, earthquakes and volcanism. Central Turkey historically has played an important role in evolution of the Alpine orogeny. The Kirsehir Complex is one of three Mesozoic-Early Tertiary metamorphic and plutonic mid-crustal basement units exposed in central Turkey. The most common lithology of the metamorphites are the banded gneisses, which are intercalated with layers of schists, amphibolites and quartzite, and marbles representing the structurally the highest metamorphites of the study area. The metamorphites are characterized by multiple folding episodes and overprinting faults (thrust, normal and strike-slip). These metamorphites reached peak metamorphic conditions of upper amphibolite facies, as indicated by local presence of clinopyroxene, sillimanite, hornblende, andalusite and garnet. Later, retrograde greenschist facies conditions were attained characterized by the alteration of feldspar and mafic minerals to muscovite and chlorite/actinolite, respectively. The microstructures of selected minerals can be used to bracket the metamorphic grade during which microstructure formed. Quartz displays undulose extinction, deformation bands, subgrains and deformation lamellae, and recrystallisation. The presence of lobate grain boundaries of quartz indicates that GBM recrystallisation occurred. Undulose extinction and recrystallisation are common in micas. Recrystallisation, core-mantle structures in feldspar, myrmekites in K-feldspars within the gneisses suggest that deformation occurred within the amphibolite facies. Garnet occurs as slightly elliptical porphroclats. Sillimanite is present as fibrolite growing near biotite and microboudinaged. Andalusite porphyroblast/porphroclats are elongate and microboudinaged. Kinematic indicators (asymmetric mantled grains, S

Age and origin of anorthosites, charnockites, and granulites in the Central Virginia Blue Ridge: Nd and Sr isotopic evidence

Science.gov (United States)

Pettingill, H.S.; Sinha, A.K.; Tatsumoto, M.

1984-01-01

Rb-Sr isotopic data for anorthosites, charnockites, ferrodioritic to quartz monzonitic plutons, and high-grade gneisses of the Blue Ridge of central Virginia show evidence of post-emplacement metamorphism, but in some cases retain Grenville ages. The Pedlar River Charnockite Suite yields an isochron age of 1021 +/-36 Ma, (initial 87Sr/86Sr ratio of 0.7047 +/-6), which agrees with published U-Pb zircon ages. Five samples of that unit which contain Paleozoic mylonitic fabrics define a regression line of 683 Ma, interpreted as a mixing line with no age significance. Samples of the Roseland Anorthosite Complex show excessive scatter on a Rb-Sr evolution diagram probably due to Paleozoic (475 m.y.) metamorphism. Data from the ferrodioritic to quartz monzonitic plutons of the area yield an age of 1009 +/-26 Ma (inital ratio=0.7058 +/-4), which is in the range of the U-Pb zircon ages of 1000-1100 Ma. The Stage Road Layered Gneiss yields an age of 1147 +/-34 Ma (initial ratio of 0.7047 +/- 5). Sm-Nd data for the Pedlar River Charnockite Suite reflect a pre-Grenville age of 1489 +/-118 Ma (e{open}Nd=+6.7 +/-1.2). Data for the Roseland Anorthosite Complex and the ferrodioritic to quartz monzonitic plutons yield Grenville isochron ages of 1045 +/44 Ma (e{open}Nd=+1.0 +/-0.3) and 1027 +/-101 Ma (e{open}Nd=+1.4 +/-1.0), respectively. Two Roseland Anorthosite samples plot far above the isochron, demonstrating the effects of post-emplacement disturbance of Sm-Nd systematics, while mylonitized Pedlar River Charnockite Suite samples show no evidence of Sm-Nd redistribution. The disparity of the Sm-Nd age and other isotopic ages for the Pedlar River Charnockite Suite probably reflects a Sm-Nd "source" age, suggesting the presence of an older crust within this portion of the ca. 1 Ga old basement. ?? 1984 Springer-Verlag.

Reconnaissance geology of the Thaniyah Quadrangle, sheet 20/42 C, Kingdom of Saudi Arabia

Science.gov (United States)

Greene, Robert C.

1983-01-01

The Thaniyah quadrangle, sheet 20/42 C, is located in the transition zone between the Hijaz Mountains and the Najd Plateau of southwestern Saudi Arabia between lat 20?00' and 20?30' N., long 42?00' to 42?30' E. The quadrangle is underlain by Precambrian metavolcanic, metasedimentary, plutonic, and dike rocks. Metavolcanic rocks consist of metamorphosed basalt and andesite with minor dacite and rhyolite and underlie three discontinuous northwest-trending belts. Metasedimentary rocks are confined to small areas underlain by quartzite, metasandstone, marble, and calc-silicate rock. Plutonic rocks include an extensive unit of tonalite and quartz diorite and a smaller unit of diorite and quartz diorite, which occupy much of the central part of the quadrangle. A small body of diorite and gabbro and a two-part zone of tonalite gneiss are also present. All of these plutonic rocks are assigned to the An Nimas batholith. Younger plutonic rocks include extensive graphic granite and rhyolite in the northeastern part of the quadrangle and several smaller bodies of granitic rocks and of gabbro. The metavolcanic rocks commonly have strong foliation with northwest strike and steep to vertical dip. Diorite and quartz diorite are sheared and brecciated and apparently syntectonic. Tonalite and quartz diorite are both foliate and nonfoliate and were intruded in episodes both preceding and following shearing. The granitic rocks and gabbro are post-tectonic. Trends of faults and dikes are mostly related to the Najd faulting episode. Radiometric ages, mostly from adjacent quadrangles, suggest that the An Nimas batholith is 835 to 800 Ma, gabbro and granite, except the graphic granite and rhyolite unit, are about 640 to 615 Ma, and the graphic granite and rhyolite 575 to 565 Ma old. Metavolcanic rocks similar to those hosting copper and gold mineralization in the Wadi Shuwas mining district adjacent to the southwestern part of the quadrangle are abundant. An ancient copper mine was

Distribution of radionuclides and radiation levels in some district of Karnataka State, India - a review

International Nuclear Information System (INIS)

Sannappa, J.

2015-01-01

Radiation is a form of energy that can be travelled through the medium in the form of waves or particles. The heat, sound and light are different forms of radiations that peoples can feel or see but there are other kinds of radiations that human senses cannot detect. Indeed we are constantly receiving such invisible radiation from the sky, earth crust, air, food and even our own body. Such radiations can be divided into ionizing and non ionizing radiation. The exposure of human beings to ionizing radiation from natural sources is a continuing and inescapable feature of life on earth. Our environment contains natural radionuclides in variable amounts. A large number of natural radioactivity measurements were conducted throughout world, in order to know their distribution and to assess their radiological health hazards. Karnataka state has 30 districts and having 74,051 sq m area and it is having various geological formations. The Archean complex made up of Dharwad schists and granitic gneisses, these cover around 60% of the area of the state and it consists of gneisses, granite and charnockite rocks. Some of the minerals found in this region are dolomite, lime stone, gabbro, quartzite, pyroxenite, manganese and iron ore and metabasalt. In addition the proposed uranium mining region is also present in Googi region of Yadagiri district. In many places Iron and manganese mining activities, crushing and quarrying activities are continuously going on. It is expected that such mining and extraction activities can enhance the natural radiation level in the environment. Hence there is a need to estimate the environmental radiation levels in the habitats of these areas. Our research group along with many researches in the Karnataka state initiated systematic study on the dose received by the population in some district of different environmental matrixes and more data are reported in Karnataka state, which have been reviewed and compiled in this paper. (author)

Geochronologic Constraints on the Location of the Sino-Korean/Yangtze Suture and Evolution of the Northern Dabie Shan

Science.gov (United States)

Bryant, D. L.; Ayers, J. C.; Gao, S.; Miller, C. F.; Zhang, H.

2002-05-01

The Northern Dabie Complex (NDC) has been proposed to be either a Paleozoic magmatic arc, an exhumed piece of subducted continental crust, or young crust produced almost entirely by Cretaceous extensional magmatism. Ion microprobe zircon 238U-206Pb ages of separates from NDC gneisses center around 689Ma (+/- 31(95%CL)), consistent with the characteristic zircon dates of the Yangtze Craton [1]. Field observations also show that these gneisses, ranging from granitic to dioritic composition, make up a sizeable area ( ~30%) of the NDC. Zircon separates from the Baimajian granitoid, the largest of the widespread Cretaceous intrusions in the NDC, have yielded ages clustered around 677Ma (+/- 79), and 120Ma (+/- 3.4), the latter of which agrees with ion probe Th-Pb monazite ages. The ~700Ma age indicates that this intrusion may be linked with partial melting of underlying Yangtze crust, while the 120Ma age is the age of its crystallization. Granitic intrusions from Sanzushi and Yerenshai in the Dabie ultrahigh-pressure (UHP) region also show clusters of ages at 714Ma (+/- 55) from zircon cores, as well as rims around 250Ma (+/- 38), which is interpreted as the time of collision of the two continental blocks. These age data support the hypothesis set forth by Zhang et al. [2] using Sm-Nd and Pb isotopic data, that the Yangtze block lies beneath the exhumed UHP belt and outcrops as the NDC, which lies between the UHP belt and the Sino-Korean/Yangtze suture. The Baimajian granitoid, however, also shows a range of older zircon core ages from 1.4-2.0Ga, which may represent the early stages of formation of the Yangtze craton. Zhang et al. [2] suggested craton formation at 1.6-2.4Ga but few such ages have been reported for rocks of the Yangtze or Sino-Korean cratons. 1. Hacker, et al. (2000) Journal of Geophysical Research. Vol. 105. p. 13,339. 2. Zhang, et al. (In press) Chemical Geology.

Development of autoradiographic method for measuring sorption of radionuclides on natural fracture surfaces

International Nuclear Information System (INIS)

Muuronen, S.

1983-11-01

On the basis of positive results about sorption of radionuclides in rock thin sections an autoradiographic method applicable for measurement sorption of radionuclides on rough rock surfaces was developed. There is no method available because 1) a plane film cannot be used because due to the roughness of rock surfaces 2) rock samples used in this investigation cannot be studied with microscopes and 3) autoradiogram cannot be studied fixed on the surface of a rock sample because the colours of the minerals in the sample will interfere with the interpretation. This report discusses experimental work done to find an useful proedure. In the development of the method main emphasis was put on investigation of the following steps: 1) preparation of the sample for equilibration and spiking; 2) properties of the covering paint for the rock surface and 3) testing of autoradiographic methods using different nuclear emulsions. As the result of these experiments promising autoradiograms with gel emulsion for sawed rock surfaces and with stripping film for rough rock surfaces were obtained. The mineralogic disribution of sorbed activity is easily seen in autoradiograms. Much work must still be done to get reliable quantitative information from autoradiograms. For developing of the autoradiographic method sawed plane rock samples of quartz feldspar intergrowth, pegmatite and limestone were used. In addition core samples of tonalite and mica gneiss from Olkiluoto were utilized. The distribution coefficients (Ksub(a)) obtained for cesium were 560 x 10 -4 and 620 x 10 -4 m 3 /m 2 for tonalite and mica gneiss, respectively. The results are little higher but of the same order of magnitude as obtained by the autoradiographic method using rock thin sections and by the batch method using crused samples. The natural fracture surface sorption study is a logical step in determining the scaling factor from laboratory to field studies. Field data will be needed to determine whether laboratory

Geologic map of the Strawberry Butte 7.5’ quadrangle, Meagher County, Montana

Science.gov (United States)

Reynolds, Mitchell W.; Brandt, Theodore R.

2017-06-19

The 7.5′ Strawberry Butte quadrangle in Meagher County, Montana near the southwest margin of the Little Belt Mountains, encompasses two sharply different geologic terranes.  The northern three-quarters of the quadrangle are underlain mainly by Paleoproterozoic granite gneiss, across which Middle Cambrian sedimentary rocks rest unconformably.  An ancestral valley of probable late Eocene age, eroded northwest across the granite gneiss terrane, is filled with Oligocene basalt and overlying Miocene and Oligocene sandstone, siltstone, tuffaceous siltstone, and conglomerate.  The southern quarter of the quadrangle is underlain principally by deformed Mesoproterozoic sedimentary rocks of the Newland Formation, which are intruded by Eocene biotite hornblende dacite dikes.  In this southern terrane, Tertiary strata are exposed only in a limited area near the southeast margin of the quadrangle.  The distinct terranes are juxtaposed along the Volcano Valley fault zone—a zone of recurrent crustal movement beginning possibly in Mesoproterozoic time and certainly established from Neoproterozoic–Early Cambrian to late Tertiary time.  Movement along the fault zone has included normal faulting, the southern terrane faulted down relative to the northern terrane, some reverse faulting as the southern terrane later moved up against the northern terrane, and lateral movement during which the southern terrane likely moved west relative to the northern terrane.  Near the eastern margin of the quadrangle, the Newland Formation is locally the host of stratabound sulfide mineralization adjacent to the fault zone; west along the fault zone across the remainder of the quadrangle are significant areas and bands of hematite and iron-silicate mineral concentrations related to apparent alteration of iron sulfides.  The map defines the distribution of a variety of surficial deposits, including the distribution of hematite-rich colluvium and iron-silicate boulders.  The southeast

Evaluation of the geological, geophysical and hydrogeological conditions at Gideaa

International Nuclear Information System (INIS)

Ahlbom, K.; Albino, B.; Carlsson, L.; Nilsson, G.; Olsson, O.; Stenberg, L.; Timje, H.

1983-05-01

The Gideaa study site has a flat topography, insignificant soil depth and a high percentage of outcrops. The dominating rock type in the area is veined gneiss of norht-east structural strike and small dip. The fracture frequency in the rock mass is more than 4.0 fractures per metre down to a depth of 400 m. Below the 500 m level, the fracture frequency is 2.0 fractures per metre. Within the study site there are defined local fracture zones at a mutual distance of 400-800 m. These local fracture zones delimit a triangular block of rock with a top surface of 1.8 km 2 . This bloc is transversed by two local fracture zones, approx 4 m wide. The fracture zones are steeply dipping with the exception of two subhorizontal fracture zones in the northern and eastern parts of the area which are dipping outwards from the study site. Horizontal fractures of vast lateral extent can be found in the upper 100-200 metres. Frequently occurring fracture minerals in the fracture zones are calcite, kaolinite, chlorite, laumontite, pyrite and the clay minerals illite and smectite. At a depth of 500 m the granite gneiss has a hydraulic conductivity of 1.5 x 10 -10 m/s, that of the surrounding bedrock being 2 x 10 -11 m/s. this implies anisotropic hydraulic properties in the rock mass with a higher hydraulic conductivity horizontally. In the rock mass as a whole, i.e. by forming the average of all data from both rock types, the hydraulic conductivity decreases from c. 4 x 10 -9 m/s at 100 m depth to c. 2 x 10 -11 m/s at a depth of 500 m. The hydraulic conductivity in the local fracture zones at Gideaa is 9 x 10 -11 m/s at a depth of 500 m. The hydraulic conductivity in the fracture zones decreases with increaseing depth in the same way as that of the rock mass

A 3D Magnetotelluric Perspective on the Galway Granite, Western Ireland

Science.gov (United States)

Farrell, Thomas; Muller, Mark; Vozar, Jan; Feely, Martin; Hogg, Colin

2017-04-01

Magnetotelluric (MT) and audi-magnetotelluric (AMT) data were acquired at 75 locations across the exposed calc-alkaline Caledonian Galway granite batholith and surrounding country rocks into which the granite intruded. The Galway granite is located in western Ireland on the north shore of Galway bay, and has an ESE-WNW long axis. The granite is cut by trans-batholith faults, the Shannawona Fault Zone (SFZ) in the western part of the batholith, which has a NE-SW trend, and the Bearna Fault Zone (BFZ) in the eastern sector that has a NW-SE trend. Geobarometry data indicate that the central granite block between these fault zones has been uplifted, with the interpretation being that the granite in this central block is thinned. To the west of the SFZ, much of the Galway granite is below sea level, with the majority of the southern granite contact also beneath the sea in Galway bay. To the east of the batholith, the Carboniferous successions, consisting of mainly limestone with shale, overlie the basement rocks. The country rock to the north includes the metagabbro-gneiss suite, which itself intruded the deformed Dalradian successions that were deposited on the Laurentian margin of the Iapetus Ocean. The deformation of the Dalradian rocks, the intrusion of the metagabbro-gneiss suite and the intrusion of the Galway granite were major events in the protracted closure of the Iapetus Ocean. It is clear from geological mapping, from geobarometry and from the present submergence by the sea of a large part of the Galway granite, that inversion of MT data in this structurally complex geology is likely to require a 3D approach. We present a summary of 3D inversion of the Galway MT and AMT data. The study shows that the structure of the Galway granite is quite different from the pre-existing perspective. The central block, thought by its uplifting to be thinned, is shown to be the thickest part of the batholith. A geological model of granite intrusion is offered to explain this

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

Science.gov (United States)

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

2018-01-01

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

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

Science.gov (United States)

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

2018-04-01

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

A new geological framework for south-central Madagascar, and its relevance to the "out-of-Africa" hypothesis

Science.gov (United States)

Tucker, R.D.; Roig, J.Y.; Macey, P.H.; Delor, C.; Amelin, Y.; Armstrong, R.A.; Rabarimanana, M.H.; Ralison, A.V.

2011-01-01

The Precambrian shield of south-central Madagascar, excluding the Vohibory region, consists of three geologic domains, from north to south: Antananarivo, Ikalamavony-Itremo, and Anosyen-Androyen. The northern Antananarivo domain represents the Neoarchean sector of the Greater Dharwar Craton amalgamated at 2.52-2.48. Ga. The Greater Dharwar Craton is overlain by several groups of Meso- to Neoproterozoic supracrustal rocks (Ambatolampy, Manampotsy, Ampasary, Sahantaha, and Maha Groups) each with a common and diagnostic signature of Paleoproterozoic detrital zircons (2.2-1.8. Ga). The central domain (Ikalamavony-Itremo) consists of two distinct parts. The Itremo Sub-domain, in the east, is a structurally intercalated sequence of Neoarchean gneiss and shallow marine metasedimentary rocks of Paleo-Mesoproterozoic age (Itremo Group), the latter with Paleoproterozoic detrital zircons ranging in age between 2.2 and 1.8. Ga. The Ikalamavony Sub-domain, to the west, contains abundant volcano-clastic metasediments and lesser quartzite (Ikalamavony Group), formed between 1.03. Ga and 0.98. Ga, and intruded by igneous rocks (Dabolava Suite) of Stenian-Tonian age. Structurally intercalated with these are sheets of Neoarchean gneiss (~2.5. Ga) and Neoproterozoic metaclastic rocks (Molo Group). Like the Itremo Group, quartzite of the Ikalamavony Group has detrital zircons of Paleoproterozoic age (2.1-1.8. Ga). The southern domain of Anosyen-Androyen consists of a newly recognized suite of Paleoproterozoic igneous rocks (2.0-1.8. Ga), and stratified supracrustal rocks also having Paleoproterozoic detrital zircons (2.3-1.8. Ga). The contact between the Anosyen-Androyen and Ikalamavony-Itremo domains, formerly known as the Ranotsara-Bongolava shear zone, is a tightly folded and highly flattened boundary that was ductilely deformed in Ediacaran time. It is roughly equivalent to the Palghat-Cauvery shear zone in south India, and it defines approximately the boundary between the Archean

Avalonian (Pan-African) mylonitic deformation west of Boston, U.S.A.

Science.gov (United States)

Rast, N.; Skehan, J. W.

1995-07-01

West of Boston, Mass., Castle and others (1976) recognized an up to 5km wide, possibly folded, NE-SW trending Burlington Mylonite Zone. We have extended mapping south into Natick and Framington quadrangles, and supplemented it by fixing local directions of tectonic motion, which are more variable than reported by Goldstein (1989). In Natick the mylonite zone is partly migmatized and converted into blastomylonites, forming the lithodemic Rice Gneiss and is intersected by the Dedham Granite dated ca 630 Ma. The granite also invades deformed, folded, and commonly mylonitized Westboro Quartzite. Thus mylonitization, folding, and formation of migmatitic blastomylonites are all earlier than ca 630 Ma, and can collectively be attributed to the main phase of the Avalonian orogeny that in Africa is referred to as the Pan-African I. The sense of movements in the Rice Gneiss is generally sinistral strike-slip with a NE-SW trend of foliation. Other local mylonites have more variable directions of motion. A narrower E-W zone of mylonitization has been recognized by Grimes (M.S. thesis 1993, Boston College) and named the Nobscot Shear Zone. It affects the Milford Granite, also about 630 Ma in age, while similar but narrow shear zones affect other local granites including the Dedham. These zones, dipping steeply north and including the Nobscot, are less intensely mylonitized and are not associated with migmatites. Their age is not known, but since they affect only Precambrian rocks, they are assumed to be late Proterozoic. We attribute these zones to the second stage of the Avalonian or the Pan-African II. The older rocks west of Boston are widely affected by numerous brittle faults. These are all of unknown age, but probably Phanerozoic. The most significant brittle fault in the Burlington area is the mid to late Paleozoic Bloody Bluff Fault. We do not associate large scale mylonitization with that fault, because the mylonites are commonly cut by undeformed or little deformed

Rock stress measurements in ONKALO underground characterisation facility at Olkiluoto at depth of 120 m

International Nuclear Information System (INIS)

Fecker, E.

2007-04-01

In November and December 2006 overcoring stress measurements have been conducted in the boreholes ONK-PP74, ONK-PP75 and ONK-PP77 in a niche of the access tunnel of the ONKALO underground characterisation facility at the Olkiluoto site. Measurements have been done using the CSIRO 3D stress measuring cell. This cell is one of the mostly used cells in the whole world for estimation of the state of stress in rock when doing the borehole measurements. The boreholes are at a depth of about 120 m under the ground surface. The rock where the measurements have been conducted is a foliated migmatitic gneiss (subtypes veined and diatexitic gneiss). Parallel to the overcoring measurements a glue test has been conducted in the laboratory to check the quality of the bonding of the stress cells to the rock. The result showed that the glue makes a good contact between the rock and the stress cell, but air bubbles, which have normally been observed within the glue and at the edges, proved this time to be disadvantageous. Normally such air bubbles have dimensions of about one millimetre, but sometimes certain bubbles may become notably bigger. In the ONKALO overcored probes sawn apart such air bubbles were found both in wet and dry probe conditions. In the test series eight stress measurements have been provided, three of them failed for technical reasons. At one of these three tests the glue has extruded too early, at the other two tests the overcoring was not conducted deep enough. At the remaining five tests in spite of the glue test results a calculation of the stress tensor could be made. Four of these five measurements can be seen as relatively successful. The results of these measurements show a major principal stress of 14.8 MPa in average, trending northwest - southeast, and with a dipping of 11 degrees in average. (orig.)

Core drilling of deep drillhole OL-KR47 at Olkiluoto in Eurajoki 2007-2008

International Nuclear Information System (INIS)

Toropainen, V.

2008-02-01

As a part of the confirming site investigations for ONKALO rock characterisation facility, Suomen Malmi Oy (Smoy) core drilled 1008.76 m and 44.31 m deep drillholes with a diameter of 75.7 mm at Olkiluoto in October 2007 - January 2008. The identification numbers of the drillholes are OL-KR47 and OL-KR47B, respectively. A set of monitoring measurements and samplings from the drilling and returning water was carried out during the drilling. Both the volume and the electric conductivity of the returning and drilling waters were recorded. The drill rig was computer controlled and during drilling the computer recorded drilling parameters. The objective of all these measurements was to obtain more information about bedrock and groundwater properties. Sodium fluorescein was used as a label agent in the drilling water. The total volumes of the used drilling and flushing water were 1229 m 3 and 13.6 m 3 in drillholes OL-KR47 and OL-KR47B, respectively. Measured volume of the returning water in drillhole OL-KR47 was 1125 m 3 , water did not return in drillhole OL-KR47B. The deviation of the drillholes was measured with the deviation measuring instruments EMS and Maxibor II. Uniaxial compressive strength, Young's Modulus and Poisson's ratio were measured from the core samples. The average uniaxial compressive strength is 92.1 MPa, the average Young's Modulus is 32.5 GPa and the average Poisson's ratio is 0.33. The main rock types are diatexitic and veined gneisses, pegmatitic granite and tonaliticgranodioritic- granitic gneiss. The average fracture frequency is 2.2 pcs / m in drillhole OL-KR47 and 3.4 pcs / m in drillhole OL-KR47B. The average RQD values were 95.3 % and 94.1 %. In drillhole OL-KR47 46 fractured zones and in drillhole OL-KR47B two fractured zones were penetrated during drilling work. (orig.)

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

International Nuclear Information System (INIS)

Guerrero Cherma, S.

2016-05-01

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

Surficial uranium deposits in Algeria

International Nuclear Information System (INIS)

Mokaddem, M.; Fuchs, Y.

1984-01-01

Along southern border of the Hoggar (Algeria) Precambrian shield, Lower Palaeozoic sediments lie unconformably on weathered metamorphic rocks. Along the eastern border of the Tin Seririne basin some good examples of the weathered rocks underneath the unconformity are exposed. The palaeosurface is a peneplain with only minor topographical reliefs from one to a few metres high. The nature and intensity of the weathering process was controlled by the topography, and the existence of badly drained areas is particularly important. At one such area the Tahaggart uranium ore deposit was discovered. The uranium ore consists mainly of torbernite and autunite. The deposit is present in the weathered gneiss underneath the palaeosurface. Mineralogical and geochemical observations indicated that the ore deposit was formed during the period of weathering which was controlled by climatological and palaeotopographical factors. (author)

Fissure fillings from Finnsjoen and Studsvik Sweden

International Nuclear Information System (INIS)

Tullborg, E.-L.; Larsson, S.Aa.

1982-12-01

Samples were taken from cores and collected at different levels. The bedrock at Finnsjoen is a Svecokarelian granite-granodiorite, the most frequent mineral in the fissures being calcite. The water from boreholes have a mean S 18 O value of -12 per thousand and saturated by calcite. Isotopically three different groups of calcite have been distinguished. Ages of 29+-13x10 3 years to 79+-25x10 3 years were estimated. Two generations of quartz were recognized the minerals prehnite and lanmontite were found Most fissure filling materials have cation exchange capacities. The bedrock at Studsvik is a Svecokarelian gneiss of sedimentary type which is migmatized with calcite and chlorite as fissure filling minerals. Most fissure fillings are thin and simple Claby minerals of smectite type are also frequent. (G.B.)

Radon in waters from health resorts of the Sudety Mountains (SW Poland)

International Nuclear Information System (INIS)

Ciezkowski, W.; Przylibski, T.A.

1997-01-01

This paper discusses the geological background related to the presence of selected radon waters in the Sudety Mountains. Special attention is paid to radon waters whose chemical composition is formed within metamorphic rocks (mainly gneisses). The physical, chemical, and isotopic characteristics of the waters of Ladek Zdroj, Czerniawa Zdroj and Swieradow Zdroj are presented. The rocks at these locations are briefly characterized by their U, Th, and Ra contents. It was found that the basic role in enrichment of these waters with radon is played by the 100 m deep near-surface zone. This is related to the increased emanation coefficient in this zone as a consequence of weathering processes. It is also shown that the residence time of water in the rocks is not important for radon genesis. (author)

Geology and structural outline of the Lagoa Real Complex, BA, Brazil

International Nuclear Information System (INIS)

Cruz, Simone Cerqueira Pereira; Cunha, Jose Carlos; Marinho, Moacir Moura; Noce, Carlos Mauricio

2007-01-01

The Lagoa Real Complex is constituted by 1.7 Ga granitoids that occur along the Paramirim valley. The granitoids are formed by the Sao Timoteo Granite and a set of alkali-gneisses that were crystallized during a compressional sin-metamorphic deformation episode. The carried out structural analysis has identified two deformation patterns. The compressional episode is represented by shear zones, compositional layering, milonite foliation and folds. The extensional episode is characterized by the nucleation of normal shear zones. The geometric patterns of the finite deformation are similar to the ones that occur in the Ituacu synclinal where the Salitre e Bebedouro formations of Una Group outcrop. An ancient geometric pattern was not found in the area; consequently we propose that the deformation episodes were related to the neoproterozoic Orogeny. (author)

Terahertz lens made out of natural stone.

Science.gov (United States)

Han, Daehoon; Lee, Kanghee; Lim, Jongseok; Hong, Sei Sun; Kim, Young Kie; Ahn, Jaewook

2013-12-20

Terahertz (THz) time-domain spectroscopy probes the optical properties of naturally occurring solid aggregates of minerals, or stones, in the THz frequency range. Refractive index and extinction coefficient measurement reveals that most natural stones, including mudstone, sandstone, granite, tuff, gneiss, diorite, slate, marble, and dolomite, are fairly transparent for THz frequency waves. Dolomite in particular exhibits a nearly uniform refractive index of 2.7 over the broad frequency range from 0.1 to 1 THz. The high index of refraction allows flexibility in lens designing with a shorter accessible focal length or a thinner lens with a given focal length. Good agreement between the experiment and calculation for the THz beam profile confirms that dolomite has high homogeneity as a lens material, suggesting the possibility of using natural stones for THz optical elements.

Geology of the Amelang Formation, western Dronning Maud Land

International Nuclear Information System (INIS)

Lindsay, P.; Coraker, M.C.; Millsteed, B.

2002-01-01

Vertical successions (>80 m thick) of the Permian Amelang Formation were studied in the southern Kirwannveggen, western Dronning Maud Land. Geochemical and petrographic results indicate that the dominant provenance of the formation was the Sverdrupfjella gneiss. A paleocurrent change in the formation and a difference in the clay mineralogy suggest the formation could be divided into two members. The thin coal seams have a rank of sub-bituminous B with associated maximum maturation temperatures of 80 degrees C. Palynological evindence indicates a Sakmarian (Early Permian) age for samples taken from immediately above the thickest coal seam. Sinusoidal trace fossils have a similar amplitude and wavelength to modern and Eocene Diptera traces, suggesting that traces which would normally be termed Cochlichnus may have been formed by Ceratopognid larvae. (author)

Pb isotopes during crustal melting and magma mingling - A cautionary tale from the Miki Fjord macrodike, central east Greenland

DEFF Research Database (Denmark)

Waight, Tod Earle; Lesher, Charles

2010-01-01

Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field...... grain boundaries during disequilibrium melting of the host rock by the mafic magma. The crustal melt involved in magma interactions was therefore heterogeneous with respect to Pb isotopes on a metre-scale. These results illustrate the difficulties inherent in interpreting isotopic variations...... in contaminated mafic magmas even when the end-members are well constrained by field relations. We show that the Pb isotopic composition of the crustal contaminants and contamination trajectories for the Miki Fjord hybrid magmatic lithologies are markedly different from regional basement gneisses and contaminated...

A study based on trace elements of differentiated metabasic rocks from the Machado-MG region

International Nuclear Information System (INIS)

Choudhuri, A.; Carvalho, S.G. de.

1983-01-01

Large metabasic intrusive bodies occur in the Precambrian gneiss-migmatite basement around Poco Fundo - Campestre - Machado Triangle, south Minas Gerais. Separate occurrences consisting in each case of pyroxenite, metagabbro and amphibolite seem to be related to each other as is evident from their mineralogy, texture and trends of trace element concentration when plotted against their mg number (Mg/MgO + FeO mol.). Furthermore, their trace elements indicate that these rocks belong to a differentiated sequence resulting from separation of pyroxenes in situ. In spite of their high large ion lithophile element contents comparable to calc-alcaline rocks, the metabasic rocks show close resemblance to present-day mid-ocean ridge basalts when these are plotted in relevant variation diagrams. The tectonic implication of the observations is, however, not yet clear. (Author) [pt

Bulk rock elastic moduli at high pressures, derived from the mineral textures and from extrapolated laboratory data

International Nuclear Information System (INIS)

Ullemeyer, K; Keppler, R; Lokajíček, T; Vasin, R N; Behrmann, J H

2015-01-01

The elastic anisotropy of bulk rock depends on the mineral textures, the crack fabric and external parameters like, e.g., confining pressure. The texture-related contribution to elastic anisotropy can be predicted from the mineral textures, the largely sample-dependent contribution of the other parameters must be determined experimentally. Laboratory measurements of the elastic wave velocities are mostly limited to pressures of the intermediate crust. We describe a method, how the elastic wave velocity trends and, by this means, the elastic constants can be extrapolated to the pressure conditions of the lower crust. The extrapolated elastic constants are compared to the texture-derived ones. Pronounced elastic anisotropy is evident for phyllosilicate minerals, hence, the approach is demonstrated for two phyllosilicate-rich gneisses with approximately identical volume fractions of the phyllosilicates but different texture types. (paper)

In-situ load-deformation characterization of the CSM/OCRD jointed test block

International Nuclear Information System (INIS)

Richardson, A.M.; Hustrulid, W.; Brown, S.; Ubbes, W.

1985-01-01

An extensive ambient-temperature test series has recently been completed on a block of Precambrian Gneiss at the Colorado School of Mines (CSM) Experimental Mine in Idaho Springs, Colorado. Block tests came into existence out of a desire to test a relatively large volume of rock and thereby minimize the scaling problems encountered when laboratory test results are used to obtain modeling parameters for full-size structures. A typical block test involves isolation of a large, approximately two-meter cube of rock by cutting slots on four sides and inserting flatjacks for loading. Much interest has recently centered around block tests as a promising method for in-situ characterization of rock-masses for licensing future commercial nuclear-waste repositories in crystalline rock. To date only a few block tests have been conducted

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Petrographic characterization and preliminary lithogeochemistry of albitites from Folha Bramado, northwest of Bahia state, Brazil

International Nuclear Information System (INIS)

Burgos, Cristina Maria; Pinho, Ivana Conceicao de Araujo; Martins, Adriano Alberto Marques; Teixeira, Leo Rodrigues; Oliveira, Rita Cunha Leal Menezes de; Cruz Filho, Basilio Elesbao da; Wosniak, Ricardo

2011-01-01

The mapping geological works carried out by CPRM, in the scope of the Brumado-Condeuba Project, had proceeded to the sampling from granitoids in the 'Folha Brumado'. The majority of the samples were classified as biotite gneiss and two of them recognized as albitites. Lithogeochemical data had proved that the rocks are alkaline, metaluminous, potash-rich (except for the two classified as albitites that are soda-rich), enriched in rare earth elements, with negative anomaly in europium and typical standards of A-type granitoids. They had been located in the field of the within-plate granites in the discrimination diagrams for the tectonic interpretation. The albitites of the 'Folha Brumado' are similar to the albitites that had been described in the Uranium Province of Lagoa Real. (author)

A study on the U speciation in groundwater of a hard rock aquifer in South India

International Nuclear Information System (INIS)

Thivya, C.; Chidambaram, S.; Thilagavathi, R.; Nepolian, M.; Adithya, V.S.; Tirumalesh, K.; Prasanna, M.V.

2015-01-01

Speciation of uranium indicates the contribution of this ion into different species. An attempt has been made to study the spatial and temporal variations of U speciation in the hard rock aquifer of South India. The major rock types have granulite facies with high grade metamorphic rocks and younger intrusive. It also comprises of Fissile hornblende biotite gneiss, Charnockite, Quartzite, Granite and Flood Plain Alluvium. A total of 108 samples were collected from the handpumps of the study area for two seasons (Pre monsoon and South West monsoon). The groundwater samples were analysed for U and other ions like Ca 2+ , Mg 2+ , Na + and K + , HCO 3 - , Cl - , SO 4 2- , PO 4 3- , NO 3 - , F - , H 4 SiO 4 , pH, EC and TDS using standard procedures

Study of the properties of biotitico-quartzitic gneisses from locality Braniskoin natural form and after remelting in atmospheric conditions

Directory of Open Access Journals (Sweden)

Zacharov Michal

2000-03-01

Full Text Available This paper deals with the changes of structural and physico-chemical properties after remelting of a temperature over 1615 °C. The following properties were analysed: chemical composition and microscopic changes in the structure of mineral.

On thermal properties of hard rocks as a host environment of an underground thermal energy storage

Science.gov (United States)

Novakova, L.; Hladky, R.; Broz, M.; Novak, P.; Lachman, V.; Sosna, K.; Zaruba, J.; Metelkova, Z.; Najser, J.

2013-12-01

With increasing focus on environmentally friendly technologies waste heat recycling became an important issue. Under certain circumstances subsurface environment could be utilized to accommodate relatively large quantity of heat. Industrial waste heat produced during warm months can be stored in an underground thermal energy storage (UTES) and used when needed. It is however a complex task to set up a sustainable UTES for industrial scale. Number of parameters has to be studied and evaluated by means of thermohydromechanical and chemical coupling (THMC) before any UTES construction. Thermal characteristics of various rocks and its stability under thermal loading are amongst the most essential. In the Czech Republic study two complementary projects THMC processes during an UTES operation. The RESEN project (www.resen.cz) employs laboratory tests and experiments to characterise thermal properties of hard rocks in the Bohemian Massif. Aim of the project is to point out the most suitable rock environment in the Bohemian Massif for moderate to ultra-high temperature UTES construction (Sanyal, 2005). The VITA project (www.geology.cz/mokrsko) studies THM coupling in non-electrical temperature UTES using long term in-situ experiment. In both projects thermal properties of rocks were studied. Thermal conductivity and capacity were measured on rock samples. In addition an influence of increasing temperature and moisture content was considered. Ten hard rocks were investigated. The set included two sandstones, two ignibrites, a melaphyr, a syenite, two granites, a gneiss and a serpentinite. For each rock there were measured thermal conductivity and capacity of at least 54 dried samples. Subsequently, the samples were heated up to 380°C in 8 hours and left to cool down. Thermal characteristics were measured during the heating period and after the sample reached room temperature. Heating and cooling cycle was repeated 7 to 10 times to evaluate possible UTES-like degradation of

Microchemistry, geochemistry and geochronology of the Lagoa Real Uranium Province (BA) magmatic association: petrological and evolutionary significance

International Nuclear Information System (INIS)

Amorim, Lucas Eustaquio Dias

2016-01-01

The Lagoa Real Uranium Province (PULR) is located in the center-south of the Bahia State, in the central part of Sao Francisco Craton and consists of an association of Paleoproterozoic meta-granites, alkali-gneiss, albitites, meta-leucodiorite and charnockites. This work has as objective the studies of the magmatic association, trying to understand its petrological and evolutionary meaning. For this purpose, representative bodies were sampled in order to develop unpublished studies of litogeochemistry, isotopes, geochronology and mineral chemistry. These analyzes were performed in: different preserved granitoid facies (Lagoa do Barro, Sao Timoteo, Juazeirinho and late pegmatitic phases), the meta-leucodiorites and charnockite. The data obtained using several modern methodologies, such as geochronology and mineral chemistry by LA-ICP-MS, provided results that allowed the characterization of two magmatic lithologies not described in the literature (Juazeirinho granite e late pegmatitic phases), and also a lithology preliminarily described (Lagoa do Barro granite). Moreover, these data contributed to elucidate the origin and meaning of the leucodiorite and charnoquito varieties, and made it possible to verify new compositional and mineral chemistry tendencies of Sao Timoteo granite. The data presented show that the studied granites were affected by albititization events (tardi or post-magmatic), which have different micro-chemical characteristics from the processes of albite formation related to the non-mineralized albitites bodies. Three albititization events were identified: a) An event that affected the granites characterized by the formation of albite with Rb and U, (b) Another event related to fluids associated with late pegmatitic bodies that formed albite with high levels of U, Rb and Ba, and partially affected the granites of the next pegmatoids portions; and (c) a final albititization event that caused the formation of the albite gneiss bodies, with albite

Preliminary hydrogeochemical analysis of springs in the region of Aguas de Lindoia, Brazil

International Nuclear Information System (INIS)

Szikszay, M.; Teissedre, J.-M.

1978-01-01

The sources of waters in the region of Aguas de Lindoia, Sao Paulo, Brazil are analysed from the chemical and geological point of view. A totality of 26 springs gas been studied, all belonging to the crystalline complex of metamorphic rocks known under the name of Amparo gneisses. All of these springs are of feeble discharge with exception of those of the 'Balneario de Aguas de Lindoia' which are also hypothermal. From the chemical viewpoint, all waters have similar characteristics as much in major elements as in trace elements. According to their composition, they can be classified as bicarbonated sodic, calcic and magnesian waters. Some of them are mixed or chloro-sodic. Only the radioactivity at the spring permits to consider them as mineral waters, having in view their low concentration in dissolved solids. (Author) [pt

Hydrogeologic characterization of the Cachoeira Deposit Massif, Caetite, state of Bahia, Brazil

International Nuclear Information System (INIS)

Bottura, J.A.; Albuquerque Filho, J.L.; Ojima, L.M.

1984-01-01

The hydrogeologic applications for the characterization of rock massifs in future mining activity areas are presented. The study was performed in the Cachoeira uranium deposit (Anomaly no.13 - Lagoa Real Project) located in the south-central portion of the state of Bahia, Caetite municipality, belonging to the Brazilian Nuclear Enterprise - NUCLEBRAS. The massif occuring in the area is composed of a group or series of rocks classified generically as gneisses, displaying different geotechnical classes. In order to consubstantiate the hydrogeologic/ hydrogeotechnical characterization, pumping and infiltration tests were performed, as well as periodic water level measurements in piezometers and drill-holes. In this manner, a hydrogeotechnical classification was made possible and a quantitative evaluation of the volume of water that will be drained was elaborated, orviding necessary contributions for research diggings and exploration. (D.J.M.) [pt

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

International Nuclear Information System (INIS)

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

2018-01-01

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

Deep groundwater chemistry

International Nuclear Information System (INIS)

Wikberg, P.; Axelsen, K.; Fredlund, F.

1987-06-01

Starting in 1977 and up till now a number of places in Sweden have been investigated in order to collect the necessary geological, hydrogeological and chemical data needed for safety analyses of repositories in deep bedrock systems. Only crystalline rock is considered and in many cases this has been gneisses of sedimentary origin but granites and gabbros are also represented. Core drilled holes have been made at nine sites. Up to 15 holes may be core drilled at one site, the deepest down to 1000 m. In addition to this a number of boreholes are percussion drilled at each site to depths of about 100 m. When possible drilling water is taken from percussion drilled holes. The first objective is to survey the hydraulic conditions. Core drilled boreholes and sections selected for sampling of deep groundwater are summarized. (orig./HP)

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

DEFF Research Database (Denmark)

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

2012-01-01

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

The Seis Lagos Carbonatite Complex

International Nuclear Information System (INIS)

Issler, R.S.; Silva, G.G. da.

1980-01-01

The Seis Lagos Carbonatite Complex located about 840 Km from Manaus, on the northwestern part of the Estado do Amazonas, Brazil is described. Geological reconnaissance mapping by Radam Project/DNPM, of the southwestern portion of the Guianes Craton, determined three circular features arranged in a north-south trend and outcroping as thick lateritic radioactive hills surrounded by gneisses and mignatites of the peneplained Guianense Complex. Results of core drilling samples analysis of the Seis Lagos Carbonatite Complex are compared with some igneous rocks and limestones of the world on the basis of abundance of their minor and trace elements. Log-log variation diagram of strontium and barium in carbonatite and limestone, exemplifield by South Africa and Angola carbonatites, are compared with the Seis Lagos Carbonatite Complex. The Seis Lagos Carbonatite Complex belongs to the siderite-soevite type. (E.G.) [pt

Elastic anisotropy of Tambo gneiss from Promontogno, Switzerland: a comparison of crystal orientation and microstructure-based modelling and experimental measurements

Czech Academy of Sciences Publication Activity Database

Vasin, R. N.; Kern, H.; Lokajíček, Tomáš; Svitek, Tomáš; Lehmann, E.; Mannes, D. C.; Chaouche, M.; Wenk, H.-R.

2017-01-01

Roč. 209, č. 1 (2017), s. 1-20 ISSN 0956-540X R&D Projects: GA MŠk LH13102; GA ČR GA13-13967S; GA ČR(CZ) GA16-03950S Institutional support: RVO:67985831 Keywords : numerical solutions * microstructures * elasticity and anelasticity * seismic anisotropy * acoustic properties Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.414, year: 2016

Can we rely on Swedish granites and gneisses as sage host rock for hazardous waste disposal during future geological periods?

International Nuclear Information System (INIS)

Morfeldt, C.O.; Morfeldt, D.

1991-01-01

The rapid growth of our industrial societies, together with an increased awareness and sense of responsibility towards the environment in most countries, has made us being to understand the urgency of halting and preventing further pollution and destruction of irreparable environments. The main issue sat present focus on neutralizing the harmful effects of toxic waste by isolating it from the biosphere for long periods of time, perhaps for many hundreds of thousands of years. These issues no longer focus on radioactive substances and their harmful ionizing radiation effects but also on heavy alloys and chemical pollutants generated during transformation processes of different types of waste, or through incineration of waste. Ash and sedimentary deposits from sewage plants for example, also contain heavy alloys. (au)

Geology of quadrangles H-12, H-13, and parts of I-12 and I-13, (zone III) in northeastern Santander Department, Colombia

Science.gov (United States)

Ward, Dwight Edward; Goldsmith, Richard; Cruz, Jaime B.; Restrepo, Hernan A.

1974-01-01

A program of geologic mapping and mineral investigation in Colombia was undertaken cooperatively by the Colombian Instituto Nacional de Investigaciones Geologico-Mineras (formerly known as the Inventario Minero Nacional), and the U. S. Geological Survey; by the Government of Colombia and the Agency for International Development, U. S. Department of State. The purpose was to study, and evaluate mineral resources (excluding of petroleum, coal, emeralds, and alluvial gold) of four selected areas, designated Zones I to IV, that total about 70,000 km2. The work in Zone III, in the Cordillera Oriental, was done from 1965 to 1968. The northeast trend of the Cordillera Oriental of Colombia swings abruptly to north-northwest in the area of this report, and divides around the southern end of the Maracaibo Basin. This section of the Cordillera Oriental is referred to as the Santander Massif. Radiometric age determinations indicate that the oldest rocks of the Santander massif are Precambrian and include high-grade gneiss, schist, and migmatite of the Bucaramanga Formation. These rocks were probably part of the Precambrian Guayana Shield. Low- to medium-grade metamorphic rocks of late Precambrian to Ordovician age .include phyllite, schist, metasiltstone, metasandstone, and marble of the Silgara Formation, a geosynclinal series of considerable extent in the Cordillera Oriental and possibly the Cordillera de Merida of Venezuela. Orthogneiss ranging from granite to tonalite is widely distributed in the high- and medium-grade metamorphic rocks of the central core of the massif and probably represents rocks of two ages, Precambrian and Ordovician to Early Devonian. Younger orthogneiss and the Silgara are overlain by Middle Devonian beds of the Floresta Formation which show a generally low but varying degree of metamorphism. Phyllite and argillite are common, and infrequent marble and other calcareous beds are fossiliferous. Except for recrystallization in limestones of !the

Forming chemical composition of surface waters in the Arctic as "water - rock" interaction. Case study of lake Inari and river Paz

Science.gov (United States)

Mazukhina, Svetlana; Sandimirov, Sergey; Pozhilenko, Vladimir; Ivanov, Stanislav; Maksimova, Viktoriia

2017-04-01

Due to the depletion of fresh water supplies and the deterioration of their quality as a result of anthropogenic impact on the Arctic ecosystems, the research questions of forming surface and ground waters, their interactions with the rocks, development of the foundations for their rational use and protection are of great fundamental and practical importance. The aim of the work is to evaluate the influence of the chemical composition of rocks of the northern part of the Fennoscandian (Baltic) shield on forming surface waters chemical composition (Lake Inari, river Paz) using physical-chemical modeling (Chudnenko, 2010, Selector software package). River Paz (Paatsjoki) is the largest river in North Fennoscandia and flows through the territory of three countries - Finland, Russia and Norway. It originates from Lake Inari, which a large number of streams and rivers flow into, coming from the mountain range of the northern Finland (Maanselkä hill). Within the catchment of inflows feeding the lake Inari and river Paz in its upper flow there are mainly diverse early Precambrian metamorphic and intrusive rocks of the Lapland granulite belt and its framing, and to a lesser extent - various gneisses and migmatites with relicts of amphibolites, granitic gneisses, plagioclase and plagio- and plagiomicrocline granites, and quartz diorites of Inari terrane (Meriläinen, 1976, fig 1; Hörmann et al, 1980, fig 1; Geologicalmap, 2001). Basing on the techniques developed earlier (Mazukhina, 2012), and the data of monitoring of the chemical composition of surface waters and investigation of the chemical composition of the rocks, physical-chemical modeling (FCM) (Selector software package) was carried out. FCM includes 34 independent components (Al-B-Br-Ar-He-Ne-C-Ca-Cl-F-Fe-K-Mg-Mn-N-Na-P-S-Si-Sr-Cu-Zn-Ni-Pb-V-Ba-Co-Cr-Hg-As-Cd-H-O-e), 996 dependent components, of them 369 in aqueous solution, 76 in the gas phase, 111 liquid hydrocarbons, and 440 solid phases, organic and mineral

Pre-Alpine contrasting tectono-metamorphic evolutions within the Southern Steep Belt, Central Alps

Science.gov (United States)

Roda, Manuel; Zucali, Michele; Li, Zheng-Xiang; Spalla, Maria Iole; Yao, Weihua

2018-06-01

In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are preserved. Between Valtellina and Val Camonica, a poly-metamorphic rock association occurs, which belongs to the Austroalpine units and includes two classically subdivided units: the Languard-Campo nappe (LCN) and the Tonale Series (TS). The outcropping rocks are low to medium grade muscovite, biotite and minor staurolite-bearing gneisses and micaschists, which include interlayered garnet- and biotite-bearing amphibolites, marbles, quartzites and pegmatites, as well as sillimanite-bearing gneisses and micaschists. Permian intrusives (granitoids, diorites and minor gabbros) emplaced in the metamorphic rocks. We performed a detailed structural, petrological and geochronological analysis focusing on the two main lithotypes, namely, staurolite-bearing micaschists and sillimanite-bearing paragneisses, to reconstruct the Variscan and Permian-Triassic history of this crustal section. The reconstruction of the tectono-metamorphic evolution allows for the distinction between two different tectono-metamorphic units during the early pre-Alpine evolution (D1) and predates the Permian intrusives, which comprise rocks from both TS and LCN. In the staurolite-bearing micaschists, D1 developed under amphibolite facies conditions (P = 0.7-1.1 GPa, T = 580-660 °C), while in the sillimanite-bearing paragneisses formed under granulite facies conditions (P = 0.6-1.0 GPa, T> 780 °C). The two tectono-metamorphic units coupled together during the second pre-Alpine stage (D2) under granulite-amphibolite facies conditions at a lower pressure (P = 0.4-0.6 GPa, T = 620-750 °C) forming a single tectono-metamorphic unit (Languard-Tonale Tectono-Metamorphic Unit), which comprised the previously distinguished LCN and TS. Geochronological analyses on zircon rims indicate ages ranging between 250 and 275 Ma for D2, contemporaneous with the emplacement of Permian intrusives. This event developed under

In-situ 40Ar/39Ar Laser Probe Dating of Micas from Mae Ping Shear Zone, Northern Thailand

Science.gov (United States)

Lin, Y. L.; Yeh, M. W.; Lo, C. H.; Lee, T. Y.; Charusiri, P.

2012-04-01

The Mae Ping Shear Zone (MPSZ, also known as Wang Chao Fault Zone), which trends NW-SE from Myanmar to central Thailand, was considered as the southern boundary of the SE extrusion of Indochina and Sibumasu block during the Cenozoic escape tectonic event of SE asia. Many analyses of 40Ar/39Ar dating on biotite and K-feldspar, K/Ar dating on biotite and illite, zircon fission-track and apatite fission-track dating had been accomplished to constrain the shearing period. Nevertheless, it is hard to convince that the ages could represent the end of the shearing since none of the dated minerals have been proved to be crystallized syn-tectonically. Meta-granitoid and gneiss from the MPSZ were analyzed in this study by applying in-situ 40Ar/39Ar laser probe dating with combination of petrology and micro-structural analysis in the purpose to decipher the geological significance of the dates. Plagioclase was replacing K-feldspar for K-feldspar was cut and embayed by plagioclase observed by SEM + EDS. Muscovite in the granitoid own fish shapes of sinistral sense of shearing, and are always in contact with plagioclase and quartz, which suggests that the muscovite crystallized from the dissolving K-feldspar under amphibolite facies condition. 117 spots on 12 muscovite fishes yield ages from 44 Ma to 35 Ma and have a mean age of 40 Ma. Since the growth condition of the muscovite is higher than the closure temperature, thus we can interpret these muscovite ages as cooling ages. Hence left-lateral shearing of the MPSZ can be deduced as syn- to post-muscovite growth and uplifted the crystalline rocks within the shear zone. The ages of matrix biotite in gneiss has a mean age of 35 Ma, which is consistent with the cooling path reconstructed from previous studies. While the ages of inclusion biotite in the K-feldspar phenocryst scatter from 40 to 50 Ma due to the isotopes were not totally re-equilibrated during the shearing. Consequently, the left-lateral shearing of the MPSZ was

Zircon trace element and isotopic (Sr, Nd, Hf, Pb) effects of assimilation-fractional crystallization of pegmatite magma: A case study of the Guangshigou biotite pegmatites from the North Qinling Orogen, central China

Science.gov (United States)

Yuan, Feng; Liu, Jia-Jun; Carranza, Emmanuel John M.; Zhang, Shuai; Zhai, De-Gao; Liu, Gang; Wang, Gong-Wen; Zhang, Hong-Yuan; Sha, Ya-Zhou; Yang, Shang-Song

2018-03-01

Evidence for open-system magmatic processes related to wallrock assimilation accompanied by fractional crystallization (AFC) is present in the Guangshigou biotite pegmatites, North Qinling Orogen. The biotite pegmatite-gneiss contacts generally coincide with the greatest enrichment of U and Th. Zircon Usbnd Pb dating constrains the crystallization ages of the biotite pegmatite (rim zone-415 ± 2.6 Ma; internal zone-413.5 ± 2.5 Ma), in line with a pyrite Pbsbnd Pb isochron age (413 ± 22 Ma). Metamict areas in zircon show generally elevated concentrations of trace elements and expulsion of radioactive Pb. Internal zone samples, representing uncontaminated magma, have negative to positive zircon ( 413 Ma) εHf(t) (- 1.53 - + 3.24), low εNd(t) values (- 2.4), and old Hf and Nd model ages (tDM2 = 1.5-1.19 Ga, T2DM = 1.35 Ga, respectively), indicating a dominantly recycled Mesoproterozoic lower crustal material with involvement of some juvenile materials in the source region. The magmatic oxygen fugacity (fO2) and crystallization temperatures ranges from - 24.81 to - 13.34 of log fO2 and 570 °C to 793 °C, respectively. Compared to the internal zone, pegmatite rim samples display a variable and lower εNd(t) values (- 3.9 to - 2.8) and T2DM (1.47-1.37 Ga), but similar Hf isotopic compositions, favouring a three-component isotopic mixing model (recycled Mesoproterozoic lower crust materials, juvenile materials, and host gneiss). Pronounced variations of Ti, Y, U, Th, Hf, and REE concentrations in zircon from grain to grain in individual samples and from area to area within individual grains suggest a fluctuating crystallization environment in hybridized magma from which the rim-hosted zircons crystallized. Variable and high radiogenic Pb ratios of pyrites forming in the hybridized magma were inherited from the matrix. Zircons from both zones exhibit similar Hf isotope patterns, indicating the rim-hosted zircons crystallized during the early stage of hybridization of

What is the Emerging Knowledge of the Early Earth from the Oldest (>3.6 Ga) Rocks?

Science.gov (United States)

Bennett, V. C.; Nutman, A. P.

2016-12-01

Eoarchean to Hadean rocks are direct samples of early Earth chemistry and conditions and provide the ground-truth for models of early Earth formation, environments and evolution. Intensive investigations by many groups reveal rocks of this age comprise only one millionth of Earth's surface and are found in 9 areas of varying extent distributed worldwide. This record is of variable fidelity however, owing to metamorphic overprinting. The majority of the oldest rocks are high grade gneisses with protoliths from mid-crustal levels; the more rare supracrustal assemblages reflect early Earth's surface conditions and processes. First-order observations from supracrustal sequences at several localities and from 3.6 Ga to ≥3.9 Ga in age provide abundant evidence of liquid water at the Earth's surface with pillow basalts and chemical sedimentary rocks in the form of cherts, banded Fe formations and carbonates. Trace element patterns of these sedimentary rocks strongly resemble modern seawater compositions, except for the absence of redox sensitive Ce anomalies. Evidence for early life remains controversial and is mainly in the form of stable isotopic signatures of C and Fe. Our recent work from newly-discovered, exceptionally well-preserved 3.7 Ga sedimentary rocks and the deformed unconformity they rest on has provided the first evidence of Eoarchean intense weathering and shallow water sedimentary processes. Whilst the major and trace element compositions of Eoarchean gneisses have analogs in younger rocks in accord with a continuum of crust formation processes, radiogenic isotopic signatures from both long and short half-life decay schemes record an image of the Earth in transition from early differentiation processes, likely associated with planetary accretion and formation, to more modern styles. Most Eoarchean rocks possess extinct nuclide anomalies in the form of 142Nd and 182W isotopic signatures that are absent in modern terrestrial samples, and developed from

Strides in Preservation of Malawi's Natural Stone

Science.gov (United States)

Kamanga, Tamara; Chisenga, Chikondi; Katonda, Vincent

2017-04-01

The geology of Malawi is broadly grouped into four main lithological units that is the Basement Complex, the Karoo Super group, Tertiary to Quaternary sedimentary deposits and the Chilwa Alkaline province. The basement complex rocks cover much of the country and range in age from late Precambrian to early Paleozoic. They have been affected by three major phases of deformation and metamorphism that is the Irumide, Ubendian and The Pan-African. These rocks comprise gneisses, granulites and schists with associated mafic, ultramafic, syenites and granite rocks. The Karoo System sedimentary rocks range in age from Permian to lower Jurassic and are mainly restricted to two areas in the extreme North and extreme Alkaline Province - late Jurassic to Cretaceous in age, preceded by upper Karoo Dolerite dyke swarms and basaltic lavas, have been intruded into the Basement Complex gneisses of southern Malawi. Malawi is endowed with different types of natural stone deposits most of which remain unexploited and explored. Over twenty quarry operators supply quarry stone for road and building construction in Malawi. Hundreds of artisanal workers continue to supply aggregate stones within and on the outskirts of urban areas. Ornamental stones and granitic dimension stones are also quarried, but in insignificant volumes. In Northern Malawi, there are several granite deposits including the Nyika, which is the largest single outcrop occupying approximately 260.5 km2 , Mtwalo Amazonite an opaque to translucent bluish -green variety of microcline feldspar that occurs in alkali granites and pegmatite, the Ilomba granite (sodalite) occurring in small areas within biotite; apatite, plagioclase and calcite. In the Center, there are the Dzalanyama granites, and the Sani granites. In the South, there are the Mangochi granites. Dolerite and gabbroic rocks spread across the country, treading as black granites. Malawi is also endowed with many deposits of marble. A variety of other igneous

New Zircon U-Pb Age Constrain of the Origin of Devil's River Uplift (SW Texas) and Insights into the Late Proterozoic and Paleozoic Evolution of the Southern Margin of Laurentia

Science.gov (United States)

Rodriguez, E.; Dickerson, P. W.; Stockli, D. F.

2017-12-01

The Devils River Uplift (DRU) in SW Texas records the evolution of the southern Laurentian margin from Grenvillian orogenesis and assembly of Rodinia, to its fragmentation by rifting, and to the amalgamation of Pangaea. It was cored by a well (Shell No. 1 Stewart), penetrating Precambrian gneisses and Cambrian metasediments and sandstones. New zircon LA-ICP-MS data from a total of 10 samples elucidate the crystallization and depositional ages, as well as the detrital provenance, of Precambrian and Cambrian rocks from the DRU. Zircons from five Precambrian crystalline basement samples (6000-9693') yield uniform U-Pb crystallization ages of 1230 Ma that are similar to ages for young gneisses of the Valley Spring Domain (Llano uplift) in central Texas, where they mark the cessation of arc magmatism within the Grenville orogenic belt. The 1230 Ma igneous basement is overlain by L.-M. Cambrian metasedimentary rocks ( 4000-6000') with maximum depositional ages of 533-545 Ma. Detrital zircons from Cambrian strata are dominated by a 1070-1080 Ma population, likely derived from basement units exposed in Texas (Llano uplift, Franklin Mts.), with minor contributions from local 1230 Ma Precambrian basement and the 1380-1500 Ma Granite Rhyolite Province. The L.-M. Cambrian interval is dominated (>80%) by Neoproterozoic detrital magmatic zircons with two major distinct age clusters at 570-700 Ma and 780-820 Ma, supporting a two-stage Rodinia rift model and providing strong evidence for major Cryogenian-Eocambrian intraplate magmatism along the southern margin of Rodinia. Moreover, detrital zircon signatures for L.-M. and U. Cambrian strata strongly correlate with those from the Cuyania terrane of W. Argentina - notably the W. Sierras Pampeanas (Sa. Pie de Palo, Sa. de Maz): 1230 Ma from metasandstones (PdP); 1081-1038 Ma from metasiliciclastics (PdP, SdM); Cryogenian-Eocambrian [774 & 570 Ma] plutons (SdM, PdP). In summary, these new zircon U-Pb data from DRU in SW Texas show