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

International Nuclear Information System (INIS)

Silva Sa, J.H. da.

1977-01-01

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

Mineralogy and Radioactivity of Some Pegmatite Bodies, Southeastern Sinai, Egypt

International Nuclear Information System (INIS)

Elnahas, H.A.

2012-01-01

The area under consideration constitutes the extreme eastern part of the Kid metamorphic belt in Sinai Peninsula. The Neoproterozoic rock units exposed there comprise gneisses, migmatites, old granitoids and monzogranites. Most of the pegmatite bodies encountered in the monzogranite rocks occur as plug-like bodies and veins of variable dimensions. These studied pegmatites are mainly of the simple unzoned type. They are composed of intergrowths of smoky quartz and pink K-feldspar with some accumulations of micas which host most of radioactive mineralizations. Radiomertrically, the concentration of eU ranges between 41 and 117ppm with an average of 73ppm, while eTh varies between 160 and 433ppm with an average of 223ppm. The Ra content reaches up to 94ppm with an average of 62ppm. The radioelements variation diagrams illustrate that the distribution of radioelements is due to both magmatic origin and hydrothermal redistribution. The high level of radioactivity in the studied granitic pegmatites is mainly resulted from the presence of ishikawaite, thorite, uranothorite, thorianite, zircon, fiptafite and fluorite. Most of the studied radioactive minerals commonly occur in the metamict state. Other accessory minerals like anatase, hematite and magnetite are also recorded. The study reports for the first time the presence of Ishikawaite-Th, where Th prevails U. Ishikawaite-Th grains contain exsolution intergrowths of ishikawaite-U and thorianite.

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

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.

New Rb-Sr isotopic ages and geochemistry of granitic gneisses from southern Bastar: implications for crustal evolution

International Nuclear Information System (INIS)

Sarkar, G.; Gupta, S.N.; Bishui, P.K.

1994-01-01

Deformed gneisses from the southern Bastar craton yield Rb-Sr whole-rock ages of 2560 Ma and 2659 Ma with initial Sr ratios ranging between 0.70899 and 0.70726 respectively. The isotopic data are found to be scattered even at the outcrop scale which possibly indicate large-scale reworking of the gneisses during the period. The high initial Sr ratios that associate with scattering of the isotopic data reflect reworking of older gneisses. Geochemically, these gneisses are considered to be derived from an amphibolitic or basaltic protolith. The 2095 Ma (initial Sr ratio of 0.74312) old leucocratic granite intrusive into these gneisses represent early Proterozoic magmatic activity. Based on the available isotopic and geochemical data, it is suggested that the Bastar craton represents a polyphase, multicomponent terrain developed by repeated magmatism at a much earlier, probably during mid-Archaean, time and was extensively reworked during the time span between end-Archaean and early Proterozoic period. This reworking may be synchronous with coalescing of smaller crustal components possibly during the end-Archaean time. (author). 21 refs., 5 figs., 2 tabs

Determining Age and Origin of Spodumene-Bearing Pegmatites in Southeastern Ireland

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Brown, A. A.; Barros, R.; Menuge, J. F.

2017-12-01

Exploration prospecting around Caldonian Leinster Granite has revealed pegmatite intrusions containing spodumene, a lithium ore, on the eastern margin of the Tullow Lowlands Pluton. Drill cores of these pegmatites have been extracted and studied due to increasing economic interest. Ages between 430 and 400 Ma for spodumene pegmatites have been previously determined using the in situ Rb-Sr isochron method [1]. Here we use the Sm-Nd isochron method to see if the less-mobile nature of REEs during contact metamorphism and deformation impacts ages. Suitable samples containing garnet and feldspar from spodumene and barren pegmatites were studied using regular microscopy and SEM; minerals were then isolated manually. After mineral dissolution and elemental separation via ion exchange columns, a Neptune MS measured Sm and Nd isotope ratios. Blank corrections were applied. Both types of pegmatites were used to calculate an isochron using Isoplot 3.7 [2] which yielded an initial 143Nd/144Nd ratio of 0.51190±0.00009, and an age of 414±52 Ma. Ages and ɛNd, relating to the initial Nd ratio, were compared with previous whole rock data of Leinster Granite [3] and Rb-Sr multimineral data [1]. Comparable ages from both methods likely represent crystallization age. At the minimum possible age considering uncertainty, the origins of pegmatites and granitic rocks are indistinguishable, but at the maximum age, pegmatites show lower ɛNd values suggesting heterogeneous sources. All representative data points held negative ɛNd values signifying crustal assimilation. The Sm-Nd method was found suitable for age/ source investigation; however, Leinster pegmatite garnet is particularly depleted in Nd (Microsoft Excel. Berkeley Geochronology Center Special Publication, 4 [3] Mohr, Peter (1991): "Cryptic Sr and Nd isotopic variation across the Leinster Granite, Southeast Ireland" Geology Magazine, Vol 128, 3, 251-256

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

Rare metal and rare earth pegmatites of Western India

International Nuclear Information System (INIS)

Maithani, P.B.; Nagar, R.K.

1999-01-01

Rajasthan Mica Belt in western India is one of the three major mica-producing Proterozoic pegmatite belts of India, the others being in Bihar and Andhra Pradesh. The pegmatites of these mica belts, in general, are associated with the rare metal (RM) and rare earth element (REE)-bearing minerals like columbite-tantalite, beryl, lepidolite and other multiple oxides. RM-REE pegmatites of Gujarat are devoid of commercially workable mica. These pegmatites are geologically characterised in this paper, based on their association with granite plutons geochemistry, and RM and REE potential. In addition to RM and RE-bearing pegmatites, granites of the Umedpur area, Gujarat also show anomalous concentration (0.97 wt%) of rare metals (6431 ppm Nb, 1266 ppm Ta, 454 ppm Sn, 173 ppm W), (1098 ppm Ce 1.36% Y 2 O 3 ) rare earths, and uranium (0.40% eU 3 O 8 ). Eluvial concentrations in the soil and panned concentrate (0.04-0.28 wt%) analysed up to 7.4%Nb 2 O 5 , 836 ppm Ta, and 1.31% Y. Discrete columbite-tantalite and betafite have been identified in these concentrates in addition to other minerals like zircon, rutile, sphene and xenotime. This area with discrete RM R EE mineral phases could be significant as a non-pegmatite source for rare metal and rare earths. (author)

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

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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

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...

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

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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

The role of pegmatites and acid fluids for REE/HFSE mobilization in the Strange Lake peralkaline granitic pluton, Canada

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Gysi, A. P.; Williams-Jones, A.

2012-12-01

The Strange Lake pluton in Canada is a mid-Proterozoic peralkaline granitic intrusion that is host to a world-class rare earth element (REE), yttrium (Y) and high-field strength element (HFSE) deposit containing more than 50 Mt ore at >1.5 wt.% REE and >3 wt.% Zr. The highest REE/HFSE concentrations are found in pegmatite-rich zones characterized by intense alteration. Previous studies of Strange Lake and other peralkaline and alkaline intrusions, such as Khan Bogd (Mongolia) and Tamazeght (Morocco) plutons have shown that hydrothermal alteration may play an important role in the mobility of the REE/HFSE. However, the fluid chemistry and conditions of alteration (i.e., P, T, pH, fO2, ligand activity) in these systems still need to be constrained to evaluate the importance and scale of such hydrothermal mobilization. We present new data from the B-zone, a pegmatite-rich zone located in NW Strange Lake. The pegmatites are generally zoned and form two main types. The border-type pegmatites consist of quartz, K-feldspar and hematized aegirine, whereas volatile-rich pegmatites consist of hydrothermal quartz and fluorite. Transitions between both types were also observed, with the K-feldspar being partly altered and replaced by Al-Si-rich phyllosilicates. The heavy (H)REE and Zr were primarily concentrated in zirconosilicates such as elpidite, now pseudomorphed by zircon or gittinsite, whereas light (L)REE and Y were concentrated in REE-F-(CO2)-minerals such as fluocerite and bastnäsite. Textural and mineralogical observations indicate that these minerals are primary and were partly to completely leached upon fluid-rock interaction in the pegmatites. Secondary phases include Ca-F-Y-rich minerals, mainly hydrothermal fluorite, that fill vugs and replaced primary REEHFSE minerals. The presence of hydrothermal fluorite veins, micro-veins, vugs and micro-breccia in the most altered parts of the B-zone are interpreted to reflect interaction of the rocks with a F-rich fluid

Difference of ore-bearing and non-ore-bearing pegmatite in the Guangshigou area and its research significance

International Nuclear Information System (INIS)

Zuo Wenqian; Zhang Zhanshi; Sha Yazhou; Rao Chaojun

2011-01-01

Guangshigou uranium deposit is one of the typical granite-pegmatite uranium deposits in China, the ore-body are located in the density zone of the outside contact zone of granite pluton. To distinguish the ore-bearing and Non-ore-bearing pegmatite is one of the most practices and have great significance for the effect of mineral exploration. Based on the field investigation and former research results, contrast research on the characteristics of the pegmatite on petrology, geophysical, geochemistry and stable isotopes have been carried out. It is pointed out that the ore-bearing pegmatite differ from the non-ore-bearing one from macro-and-micro-view in Guangshigou Uranium deposits, the main characteristics are summarized; the macro-and-micro signs are established, the genetic difference between the ore-bearing and non-ore-bearing pegmatite are discussed primarily. The achievements would be helpful for prospecting and researching of this type uranium deposits in China. (authors)

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

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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

Genesis and petrology of Late Neoproterozoic pegmatites and aplites associated with the Taba metamorphic complex in southern Sinai, Egypt

Energy Technology Data Exchange (ETDEWEB)

Abdelfadil, K.M.; Asimow, P.D.; Azer, M.K.; Gahlan, H.A.

2016-07-01

We present new field, petrographical, mineralogical and geochemical data from late Neoproterozoic pegmatites and aplites in southern Sinai, Egypt, at the northernmost limit of the Arabian-Nubian Shield. The pegmatites cross-cut host rocks in the Taba Metamorphic Complex (TMC) with sharp contacts and are divided into massive and zoned pegmatites. Massive pegmatites are the most common and form veins, dykes and masses of variable dimensions; strikes range mainly from E-W through NW-SE to N-S. Mineralogically, the massive pegmatites are divided into K-feldspar-rich and albite-rich groups. Zoned pegmatites occur as lenses of variable dimensions, featuring a quartz core, an intermediate zone rich in K-feldspars and an outer finer-grained zone rich in albite. All compositions are highly evolved and display geochemical characteristics of post-collisional A-type granites: high SiO2, Na2O+K2O, FeO*/MgO, Ga/Al, Zr, Nb, Ga and Y alongside low CaO, MgO, Ba and Sr. They are rich in Rare Earth Elements (REE) and have extreme negative Eu anomalies (Eu/Eu*= 0.03–0.09). A genetic linkage between the pegmatites, aplites and alkali granite is confirmed by their common mild alkaline affinity and many other geochemical characteristics. These pegmatites and aplites represent the last small fraction of liquid remaining after extensive crystallization of granitic magma, injected along the foliation and into fractures of the host metamorphic rocks. The extensional tectonic regime and shallow depth of emplacement are consistent with a post-collisional environment. (Author)

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)

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

International Nuclear Information System (INIS)

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

1980-01-01

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

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.

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

Perspectives for Li- and Ta-Mineralization in the Borborema Pegmatite Province, NE-Brazil: A review

Science.gov (United States)

Beurlen, Hartmut; Thomas, Rainer; da Silva, Marcelo R. Rodrigues; Müller, Axel; Rhede, Dieter; Soares, Dwight Rodrigues

2014-12-01

The increasing strategic importance of Li- and Ta-ores during the last decades due to the strong consumption growth for rechargeable batteries and high temperature and corrosion resistant capacitors reactivated the interest of studies in pegmatite fields around the world, because these rocks supply respectively 25% and 100% of the world consumption in these elements. Research on petrogenetic issues and major and accessory mineral chemistry variations in rare element (REL)-pegmatites of the Borborema Pegmatite Province in Northeast Brazil were tested as tools for the diagnosis of the metallogenetic potential of rare metals in individual pegmatites and in the province as a whole along the last dozen of years. The results allowed to establish the nearly isobaric (3.8 kbar) crystallization conditions of the REL-pegmatites between approximately 580 °C (liquidus) and 400 °C (solidus) from a peraluminous melt saturated in an aquo-carbonic medium to low salinity volatile phase and an immiscible peralkaline flux-enriched (H2O, CO2, F, B, Li etc.) melt fraction, based on melt and fluid inclusion studies. Mineral-chemistry data from 30 selected REL-pegmatites in the province allowed to classify three of them as being of the complex-spodumene or -lepidolite subtype in Černý's classification. Both subtypes are supposed to be potentially fertile, (highly fractionated, and with good chances to bear Li- and Ta-ore concentrations). It was also possible to identify several pegmatitic granite intrusions with textural and lithogeochemical characteristics also found in source granites of REL-pegmatite provinces elsewhere. Preliminary chemical Pb/U/Th geochronological determinations in uraninite and xenotyme crystals of these granites indicate an age of 520 ± 10 Ma and match recently published Ar/Ar in mica and U/Pb ages in columbite-group minerals (CGM) of the REL-pegmatites between 509 and 525 Ma. Mineral-chemistry data from grains of the outer zones of the pegmatites do not

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 �

The formation mechanism and prognosis on the prospect of pegmatite type uranium deposit in Eastern Qinling of China

Energy Technology Data Exchange (ETDEWEB)

Mingyue, Feng; Jiashu, Rong; Zhifu, Sun; Ziyang, Xu; Hongjie, Xie [Beijing Research Inst. of Uranium Geology (China); Qifeng, Liu [North-West of Geologic Exploration of Nuclear Industry, Xi` an (China)

1996-12-01

Lithologies of Qinling Group are composed of pelite-felsic metamorphic rocks, basic metamorphic rocks and calcareous metamorphic rocks. The Pelite-felsic metamorphic rocks account for the most part of the sequence and the bulk of the Qinling Group. The Pelite-felsic metamorphic rocks associated with uranium-hosting pegmatite are characterized by high content of SiO{sub 2} and alkali, higher content of potassium than that of sodium, and moderate content of uranium. The granites in Eastern Qinling can be divided into two genetic types, i.e. I-type and S-type. Three types of pegmatites located in the study region can be attributed to one series of unified evolution of remelting magma and are connected with each other, as well as differ from each other. They resulted from partial melting of Qinling Group. Uhosting pegmatite is the new U-hosting body. The pegmatite-type uranium deposit are of new type too. The formation of such deposit is attributed to gaseous transfer differentiation. The plate subduction of recent tectonic regime, the dome-formed granite Massif, the pegmatite vein system that resulted from the metamorphism of Qinling Group occurred in Qinling during Early Paleozoic are the main conditions for the formation of pegmatite-type uranium deposits. (5 refs., 10 tabs.).

The formation mechanism and prognosis on the prospect of pegmatite type uranium deposit in Eastern Qinling of China

International Nuclear Information System (INIS)

Feng Mingyue; Rong Jiashu; Sun Zhifu; Xu Ziyang; Xie Hongjie; Liu Qifeng

1996-12-01

Lithologies of Qinling Group are composed of pelite-felsic metamorphic rocks, basic metamorphic rocks and calcareous metamorphic rocks. The Pelite-felsic metamorphic rocks account for the most part of the sequence and the bulk of the Qinling Group. The Pelite-felsic metamorphic rocks associated with uranium-hosting pegmatite are characterized by high content of SiO 2 and alkali, higher content of potassium than that of sodium, and moderate content of uranium. The granites in Eastern Qinling can be divided into two genetic types, i.e. I-type and S-type. Three types of pegmatites located in the study region can be attributed to one series of unified evolution of remelting magma and are connected with each other, as well as differ from each other. They resulted from partial melting of Qinling Group. Uhosting pegmatite is the new U-hosting body. The pegmatite-type uranium deposit are of new type too. The formation of such deposit is attributed to gaseous transfer differentiation. The plate subduction of recent tectonic regime, the dome-formed granite Massif, the pegmatite vein system that resulted from the metamorphism of Qinling Group occurred in Qinling during Early Paleozoic are the main conditions for the formation of pegmatite-type uranium deposits. (5 refs., 10 tabs.)

Discussion on the genesis of uranium-producing pegmatite in Shangdan area

Energy Technology Data Exchange (ETDEWEB)

Mingyue, Feng [Beijing Research Inst. of Uranium Geology (China)

1996-01-01

This paper describes the characteristics of uranium-producing pematite, gneissic granodiorite metamorphic rocks of the Qinling Group in such aspects as petrochemical compositions, contents of trace elements (Rb and Sr etc.), initial ratio of strontium isotopes and assemblage types of accessory minerals. Through the comparison between U-barren pegmatite within the massif and U-producing pegmatite outside the massif, and the study on Sm and Nd isotope tracers, a viewpoint is presented that the U-producing pegmatite veins resulted from slow crystallization of granitic magma under relatively confined condition produced from the selective melting of the Qinling Group metamorphic rocks rather than residual magmatic crystallization from the late-stage magmatic differentiation of gneissic granodiorite (T{sub DM} is about 10 Ma).

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

International Nuclear Information System (INIS)

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

2007-01-01

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

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

Geophysical interpretation of the gneiss terrane of northern Washington and southern British Columbia, and its implications for uranium exploration

Science.gov (United States)

Cady, John W.; Fox, Kenneth F.

1984-01-01

The Omineca crystalline belt of northeastern Washington and southern British Columbia has a regional Bouguer gravity high, and individual gneiss domes within the terrane are marked by local gravity highs. Models of crustal structure that satisfy the limited available seismic-refraction data and explain the gravity high over the gneiss terrane permit the hypothesis that the core metamorphic complexes are the surface expression of a zone of dense infrastructure that makes up the upper 20 km (kilometers) of the crust within the crystalline belt. The Omineca crystalline belt is characterized regionally by low aeromagnetic relief. The gneiss domes and biotite- and biotite-muscovite granites are generally marked by low magnetic relief, whereas hornblende-biotite granites often cause magnetic highs. Exceptional magnetic highs mark zones of magnetic rock within the biotite- and biotite-muscovite granites and the gneiss domes; these areas are worthy of study, both to determine the origin and disposition of the magnetite and to explore the possible existence of uraniferous magnetite deposits.

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

A NEW INVESTIGATION OF VIETNAM’S BERYL

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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.

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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

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Stowell Harold H.

2008-12-01

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

Genesis of rare-metal pegmatites and alkaline apatite-fluorite rocks of Burpala massi, Northern Baikal folded zone

Science.gov (United States)

Sotnikova, Irina; Vladykin, Nikolai

2015-04-01

Burpalinsky rare metal alkaline massif in the Northern Baikal folded zone in southern margin of Siberian Platform, is a of intrusion central type, created 287 Ma covering area of about 250 km2. It is composed of nepheline syenites and pulaskites grading to quartz syenites in the contacts. Veines and dykes are represented by shonkinites, sodalite syenite, leucocratic granophyres, alkali granites and numerous rare metal alkaline syenite pegmatites and two dykes of carbonatites. All rocks except for granites are cut by a large apatite-fluorite dyke rocks with mica and magnetite, which in turn is cut by alaskite granites dyke. The massif has been studied by A.M. Portnov, A.A. Ganzeev et al. (1992) Burpalinsky massif is highly enriched with trace elements, which are concentrated in pegmatite dykes. About 70 rare-metal minerals we found in massif. Zr-silicates: zircon, eudialyte, lovenite, Ti-lovenite, velerite, burpalite, seidozerite, Ca- seidozerite, Rosenbuschite, vlasovite, katapleite, Ca-katapleite, elpidite. Ti- minerals:- sphene, astrophyllite, ramsaite, Mn-neptunite bafertisite, chevkinite, Mn-ilmenite, pirofanite, Sr-perrerit, landauite, rutile, anatase, brookite; TR- minerals - loparite, metaloparite, britolite, rinkolite, melanocerite, bastnesite, parisite, ankilite, monazite, fluocerite, TR-apatite; Nb- minerals - pyrochlore, loparite. Other rare minerals leucophanite, hambergite, pyrochlore, betafite, torite, thorianite, tayniolite, brewsterite, cryolite and others. We have proposed a new scheme massif: shonkinites - nepheline syenites - alkaline syenite - quartz syenites - veined rocks: mariupolites, rare-metal pegmatites, apatite, fluorite rock alyaskite and alkaline granites and carbonatites (Sotnikova, 2009). Apatite-fluorite rocks are found in the central part of massif. This is a large vein body of 2 km length and a 20 m width cutting prevailing pulaskites. Previously, these rocks were regarded as hydrothermal low-temperature phase. New geological and

Petrochemical Characteristics and Age of Rare Metal (Ta-Nb Mineralization in Precambrian Pegmatites, Komu, Nigeria

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A. OLUGBENGA

2010-06-01

Full Text Available The Precambrian pegmatites of Komu area intrude semi discordantly older rock types, such as biotite gneiss, amphibolites and pelitic schists. The pegmatites occur as near flat lying bodies. This study aims at elucidating the geological setting, petrography, geochemical features and age of mineralization of these pegmatite bodies, with a view to classifying them and knowing their economic potential. The petrographic analysis shows that the pegmatite samples contain mainly quartz (35%, plagioclase (15%, microcline (10% and muscovite (12% with accessories like tourmaline, tantalum, niobium and illmeno-rutiles. Geochemical analysis of the muscovites extracted from pegmatites show that these rocks are enriched in silica (>60% and Al2O3 (>12% and depleted in Fe2O3, MgO and TiO2. Trace element analysis shows that the pegmatites contain rare metals with moderately high Ta, Nb, Sn, Rb, Li and Cs values and depleted in Ti, Ba and Zr. Elemental ratios indicate low ratios of K/Cs, Th/U and K/Rb. Variation plots of Ta/(Ta+Nb versus Mn/ (Mn+Fe show that the pegmatites plot in the complex (beryl subtype field. The Na/K versus Sn, Nb, Rb variation plots show that the pegmatites of Komu area are mineralized and compare favourably with those of other mineralized pegma-tite areas like Egbe and Ijero in southwestern Nigeria. The variation plots of Ta versus K/Cs, and Ta/W versus Cs, also confirm rare metal mineralization of Komu pegmatites, which plot over the mineralized line of Beus and Gordiyenko. The K/Rb versus Rb, Cs and Sn plots indicate low K/Rb ratios indicating moderate differentiation. The Rare Earth Elements (REE show high heavy REE values and lower light REE values with prominent positive Ce anomaly and negative Eu anomaly from normalized chondrite plots. K/Ar dating of the age of mineralization of muscovites extracted from the pegmatite yielded late Pan-African ages between 502.8±13Ma and 514.5±13.2Ma. This period represents the cooling ages of the

Isotope age of the rare metal pegmatite formation in the Kolmozero-Voron'ya greenstone belt (Kola region of the Fennoscandian shield): U-Pb (TIMS) microlite and tourmaline dating

Science.gov (United States)

Kudryashov, Nikolay; Lyalina, Ludmila; Mokrushin, Artem; Zozulya, Dmitry; Groshev, Nikolay; Steshenko, Ekaterina; Kunakkuzin, Evgeniy

2016-04-01

The Kolmozero-Voron'ya greenstone belt is located in the central suture zone, which separates the Murmansk block from the Central-Kola and the Keivy blocks. The belt is represented by volcano-sedimentary rocks of Archaean age of 2.9-2.5 Ga. Rare metal pegmatites (Li, Cs with accessory Nb, Ta, and Be) occur among amphibolite and gabbroid intrusions in the northwestern and southeastern parts of the belt. According to the Rb-Sr data, the age of pegmatites was considered to be 2.7 Ga. Until recently there was no generally accepted point of view on the origin of pegmatites. Now we have isotopic data for a range of rock complexes that could pretend to be parental granites for the rare metal pegmatites. These are granodiorites with the zircon age of 2733±Ma, and microcline and tourmaline granites, which Pb-Pb isochronal age on tourmaline from the tourmaline granite located near the deposit is estimated to be 2520±70 Ma. The pegmatite field of the Vasin Myl'k deposit with the lepidolite--albite--microcline--spodumene--pollucite association is located among amphibolites in the northwestern part of the belt. The deposit is represented by subparallel low-angle zoned veins up to 220 m long and 5 m thick dipping in the southeastern direction at an angle of 10° too 30°. The minerals of the columbite--tonalite group from Vasin Myl'k deposit include microlite, simpsonite, and torolite, and are the oldest among different minerals represented by several generations in pegmatites under consideration. Zircons from the pegmatites are mostly represented by crystals with the structure affected by the action of fluids that put certain restrictions on its use as a geochronometer of the crystallization process. Microlite from the pegmatite taken from the dump of a prospecting drill hole was used for U--Pb (TIMS). The mineral is represented by 0.5--1.0 mm long euhedral octahedral crystals. It is brown in color, and transparent. The microlite crystals were preliminarily cleaned from

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

Alkaline / peralkaline gneisses near the northern margin of the Natal structural and metamorphic province

International Nuclear Information System (INIS)

Scogings, A.J.

1990-01-01

Alkaline / peralkaline gneisses occur within three granitoid complexes at Ngoye, Bull's Run and Wangu, near the northern margin of the Natal Structural and Metamorphic Province. A wide range of rock types is present, from nepheline syenite gneisses through to peralkaline granite gneisses, with minor carbonatite and monzodiorite gneiss intrusive phases noted within two of the bodies. It is suggested that the three alkaline gneiss occurences so far mapped constitute the remnants of a metamorphosed alkaline magmatic province, and that such magmatism occured either in a post-collisional or anorogenic post-D1, pre-D2 tectonic setting. The three complexes are described with respect to mineralogy and chemistry, followed by a brief overview of the possible tectonic setting at the time of their intrusion. 1 tab., 3 refs

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.

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.

Loellingite, uraninite and products of its alteration within pegmatite from Corrego do Urucum (Minas Gerais - Brazil)

International Nuclear Information System (INIS)

Cassedanne, Jacques; Cassedanne, Jeannine; Carvalho, H.F. de.

1986-01-01

The zoned Corrego do Urucum granitic pegmatite lies in Governador Valadares, in Minas Gerais State - Brazil. Opaque minerals are described: loellingite, bismuth, tennantite, covellite, hematite, pyrite and uraninite, like that products proceeding from arsenate and phosphate alteration. The minerals were characterized by X-ray fluorescence analysis and chemical analysis. (Author) [pt

Complex pegmatite - apelitic of Cabecinha - strategies appreciation of geological heritage and economic development of the region

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Nobre, José; Cabral, Tiago; Cabral, João; Gomes, Ana

2014-05-01

The Complex pegmatite - apelitic of Cabecinha corresponds to an isolated ridge that reaches 933 meters, located in the middle zone of transition between the Hesperian massif and the Cova da Beira being located in the NE central part of Portugal, more specifically in the Mountainous region of the province of Beira Alta, council of Sabugal. This complex lies embedded in porphyritic granites with terms of switching to a medium-grained granite rich in sodium feldspars in which they are muscovite granite intrusions. The lodes have pegmatites with NE-SW orientation, presenting phases of predominantly quartz crystallization with multiple parageneses. The inclusions observed are veins filonianian secondary. Some veins have structural discontinuity due to further their training tectonics. The apelitico material is basic in nature engaging in descontinuiddes of pegmatite material, showing no preferred orientation. The petrological characteristics of the area in question provide the appearance of motivating exotic landforms of scientific interest. These landforms, over time, have motivated the popular level the emergence of various myths, thus contributing to the enrichment of the local cultural heritage. This study proceeded to the geological and geomorphological mapping an area of about 6945,350 m2 with a maximum length of 182 m. The huge patent mineralogical, petrological and geomorphological level geodiversity, allied to the structural complexity and associated cultural heritage, allow geoconservation strategies and recovery, using new multimedia technologies including use of QR codes and 3D. All this geological framework and environment becomes an asset for the scientific, educational and economic development of the region. On the other hand, it has the vital Importance in the context of the strategy of forming a geological park, in the point of view of tourism, research and interpretation.

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

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.

P-T path fluid evolution in the Gross Spitzkoppe granite stock, Namibia

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Stephen Frindt

2002-01-01

Full Text Available The Gross Spitzkoppe granite stock (GSS is a zoned 30 km^2 epizonal intrusion that consists of three main granites: 1 medium-grained biotite granite (marginal, 2 a coarse-grained biotite granite, and 3 a central, porphyritic granite. The stock contains pegmatites as banded marginal stockscheiders and isolated pockets composed of large alkali feldspar and quartz, dark mica, interstitial fluorite, and euhedral topaz and beryl crystals. In the porphyritic granite there are local wolframite-bearing greisens and hydrothermal fluorite and topaz-rich veins.Fluid inclusion studies were conducted on: 1 topaz and quartz crystals from the marginal stockscheider; 2 quartz, topaz, fluorite and beryl crystals from isolated pegmatites; 3 topaz from a miarolitic pegmatite; 4 beryl and quartz veins from greisenized porphyritic granite; and 5 fluorite from a late fluorite vein inthe coarse-grained biotite granite. Preliminary data indicate the presence of three compositionally distinct primary and pseudosecondary inclusion types that are of late magmatic-hydrothermal origin.Type 1. Low salinity (0–10 eq. wt% NaCl H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 550˚C. These inclusions are from quartz, topaz and beryl. Inclusions in fluorite from the fluorite vein homogenize at ~170˚C and have a salinity of ca. 1–2 eq. wt% NaCl.Type 2. Saline (25–30 eq. wt% NaCl halite-bearing H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 400˚C. These inclusions are from quartz.Type 3. Low salinity (0–3 eq. wt% NaCl H2O-CO2 inclusions that homogenize to vapor phase in the temperature range of 330 to 550˚C. These inclusions are from quartz and topaz.Hydrothermal fluids from greisen minerals are represented by type 1 and type 2 H2O inclusions. They are predominantly of low salinity (~8 eq. wt% NaCl and homogenize to the liquid phase in the temperature range of 300 to 500�

Petrography, geochemistry, and U-Pb geochronology of pegmatites and aplites associated with the Alvand intrusive complex in the Hamedan region, Sanandaj-Sirjan zone, Zagros orogen (Iran)

Science.gov (United States)

Sepahi, Ali Asghar; Salami, Sedigheh; Lentz, David; McFarlane, Christopher; Maanijou, Mohammad

2018-04-01

The Alvand intrusive complex in the Hamedan area in Iran is in the Sanandaj-Sirjan zone of the Zagros orogen. It consists of a wide range of plutonic rocks, mainly gabbro, diorite, granodiorite, granite, and leucogranites that were intruded by aplitic and pegmatitic dykes. At least three successive magmatic episodes generated an older gabbro-diorite-tonalite assemblage, followed by a voluminous granodiorite-granite association, which was then followed by minor leucocratic granitoids. Aplitic and pegmatitic dykes and bodies have truncated both plutonic rocks of the Alvand intrusive complex and its metamorphic aureole. Chemically they belong to peraluminous LCT (Li-, Cs-, and Ta-bearing) family of pegmatites. Mineralogically, they resemble Muscovite (MS) and Muscovite Rare Element (MSREL) classes of pegmatites. High amounts of some elements, such as Sn (up to 10,000 ppm), Rb (up to 936 ppm), Ba (up to 706 ppm), and LREE (up to 404 ppm) indicate the highly fractionated nature of some of these aplites and pegmatites. U-Pb dating of monazite, zircon, and allanite by LA-ICPMS indicate the following ages: monazite-bearing aplites of Heydareh-e-Poshteshahr and Barfejin areas, southwest of Hamedan, give an age range of 162-172 Ma; zircon in Heydareh-e-Poshteshar gives an average age of 165 Ma and for allanite-bearing pegmatites of Artiman area, north of Tuyserkan, an age of 154.1 ± 3.7 Ma was determined. These overlap with previously reported ages (ca. 167-153 Ma) for the plutonic rocks of the Alvand complex. Therefore, these data reveal that the Jurassic was a period of magmatism in the Hamedan region and adjacent areas in the Sanandaj-Sirjan zone, which was situated at the southern edge of the central Iranian micro-plate (southern Eurasian plate) at this time. Our results also suggest that advective heating in a continental arc setting has caused melting of fertile supracrustal lithologies, such as meta-pelites. These partial melts were then emplaced at much higher

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

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

Alkaline lixiviation of uranium in granitic pegmatite

International Nuclear Information System (INIS)

Jambor, S.

1980-06-01

The work described herein concerns the determination of the experimental optimum conditions for the alkaline lixiviation of uranium based on the following parameters: time, pH, temperature, density and grane size. The samples were obtained from the Supamo complex, near the Currupia river in the Piar District of the Bolivar State in Venezuela. They have a granitic composition and graphitic texture. The uranium was found in them as a secondary oxidized mineral of green-yellow colour localized in fractures fissures, intergranular spaces and also in the mica as. Secondary uranitite. The lixiviation process was carried out using Na 2 CO 3 /NaHCO 3 buffer solution and for 100 gr. samples the best values for an efficient process were found by using 170 mesh grane size and 500 ml of pH buffer at 70 0 C for a 24 hour time period. (author)

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.)

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

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

Structural control on the emplacement of contemporaneous Sn-Ta-Nb mineralized LCT pegmatites and Sn bearing quartz veins: Insights from the Musha and Ntunga deposits of the Karagwe-Ankole Belt, Rwanda

Science.gov (United States)

Hulsbosch, Niels; Van Daele, Johanna; Reinders, Nathan; Dewaele, Stijn; Jacques, Dominique; Muchez, Philippe

2017-10-01

The Nb-Ta-Sn pegmatites and Sn quartz veins of the Rwamagana-Musha-Ntunga area in eastern Rwanda are part of the Mesoproterozoic Karagwe-Ankole Belt. These commodities are on a regional scale spatiotemporally associated to the early Neoproterozoic fertile G4-granite generation. Although a transition from the lithium-cesium-tantalum pegmatites to cassiterite-microcline-quartz veins has been observed in the Rwamagana-Musha-Ntunga area, the structural control and the paragenetic relationship between the mineralized pegmatites and the Sn bearing quartz veins is largely unknown. Consequently, this study investigates the occurrence of pegmatites and quartz veins and the structural and lithological controls on their emplacement. The metasediments in the area are affected by a regional compressional regime with a shortening direction oriented N70E, which resulted in a N20W-oriented fold sequence. The Lake Muhazi granite is present in center of the Karehe anticline. The structural orientations of pegmatites and quartz veins show that two important factors control their emplacement. The first control is the reactivation of pre-existing discontinuities such as the bedding, bedding-parallel joints or strike-slip fault planes. In view of the regional structural grain in the Rwamagana-Musha-Ntunga area, this corresponds with abundant N20W-oriented pegmatites and quartz veins. The reactivation is strongly related to the lithology of the host rocks. The Musha Formation, which mainly consists of decimeter- to meter-scale lithological alternations of metapelite, metasiltstone and metasandstone, represents the most suitable environment for bedding reactivation. This is reflected in the predominance of bedding-parallel pegmatites and quartz veins hosted by the Musha Formation. Strike-parallel joints were mainly observed in the competent lithologies. The second controlling factor is related to the regional post-compressional stress regime. New joints initiated upon emplacement of the

Petrography and petrology of the Hamadan pegmatites

International Nuclear Information System (INIS)

Valizadeh, M.V.; Torkian, A.

2000-01-01

Petrological investigation on the pegmatites of Hamadan area was carried out for their abundance, mineralogical variations and their distribution. They reveal the genesis of Granitoid of Alvand in western parts of Iran in Sanandaj - Sirjan metamorphic belt. Field investigations show that pegmatites are mainly dispersed both on north and south of Alvand mass. They mainly consist of Graphic - pegmatites, Tourmaline Pegmatites, Aluminosilicate - pegmatites and Quartz veins. Muscovite - Aluminosilicate pegmatites are located only in south and outside of granitoid mass, for example near Dehnow Asad - Ol - llah - Khan and Manga villages. Regarding to field investigation, mineralogical characteristics and based on radiometric dating the age of biotites of granitoid is a bout 70-80 M.Y. and the age of Muscovite - pegmatites is about 100 M.Y. Therefore, pegmatites are prior to Alvand emplacement. This is in accordance with pegmatites genesis idea proposed by Winkler and von Platen. So, we suppose that pegmatites of Alvand are metamorphic and their formation do not follow normal magmatic trends. Our petrologic investigation shows that as a result of movement of Arabic plate towards Iranian pa lte (SW - NE), sedimentary rocks composing of metamorphed clays (meta-sediments) in 680-800 d eg C and 2-5 kbar was melted resulting in aplitic melt to come upwards. With the present of thermal dome, transportation of water and mineralizing gas large crystals of Muscovite and Tourmaline were formed slowly and gradually pegmatites were formed. In this condition a melt from sandstone-shale source began to move upward and in different T-P condition it formed aluminosilicate pegmatites. Each of these assemblages present specific conditions of formation

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.)

Characterization lithium mineralized pegmatite

International Nuclear Information System (INIS)

Pereira, E.F.S.; Luz Ferreira, O. da; Cancado, R.Z.L.

1986-01-01

Lithium economic importance has increased in the last years. In Brazil its reserves, generally pegmatites bodies, are found in Itinga-Aracuai-MG. This study of characterization belongs to a global plan of lithium mineralized bodies research of 'Arqueana de Minerios e Metais Ltda', which purpose is to give subsidies for implementation of pegmatite unit, in order to make better use of them. (F.E.) [pt

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.)

Age and Isotopic Studies of Some Pan-African Granite from North-Central Nigeria

International Nuclear Information System (INIS)

Breemen, O. van; Pidgeon, R.T.; Bowden, P.

1977-01-01

Twenty-nine Rb-Sr whole-rock isotopic analyses and three U-Pb zircon analyses on foliated granites and largely unfoliated charnockitic rocks indicate that the central part of the Pan-African belt in west Africa was characterised by intense orogenic plutonism. These data and Rb-Sr analyses on muscovite books from late cross-cutting pegmatites indicate that the peak of magmatic activity occurred 610 +- 10 m.y.ago. Initial 87 Sr/ 86 Sr ratios for the granitic and charnockitic rocks are in the range 0.7065-0.7125, and indicate a significantly older crustal component in the magmas

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

Uranium- and thorium-bearing pegmatites of the United States

International Nuclear Information System (INIS)

Adams, J.W.; Arengi, J.T.; Parrish, I.S.

1980-04-01

This report is part of the National Uranium Resource Evaluation (NURE) Program designed to identify criteria favorable for the occurrence of the world's significant uranium deposits. This project deals specifically with uranium- and thorium-bearing pegmatites in the United States and, in particular, their distribution and origin. From an extensive literature survey and field examination of 44 pegmatite localities in the United States and Canada, the authors have compiled an index to about 300 uranium- and thorium-bearing pegmatites in the United States, maps giving location of these deposits, and an annotated bibliography to some of the most pertinent literature on the geology of pegmatites. Pegmatites form from late-state magma differentiates rich in volatile constituents with an attendant aqueous vapor phase. It is the presence of an aqueous phase which results in the development of the variable grain size which characterizes pegmatites. All pegmatites occur in areas of tectonic mobility involving crustal material usually along plate margins. Those pegmatites containing radioactive mineral species show, essentially, a similar distribution to those without radioactive minerals. Criteria such as tectonic setting, magma composition, host rock, and elemental indicators among others, all serve to help delineate areas more favorable for uranium- and thorium-bearing pegmatites. The most useful guide remains the radioactivity exhibited by uranium- and thorium-bearing pegmatites. Although pegmatites are frequently noted as favorable hosts for radioactive minerals, the general paucity and sporadic distribution of these minerals and inherent mining and milling difficulties negate the resource potential of pegmatites for uranium and thorium

Uranium- and thorium-bearing pegmatites of the United States

Energy Technology Data Exchange (ETDEWEB)

Adams, J.W.; Arengi, J.T.; Parrish, I.S.

1980-04-01

This report is part of the National Uranium Resource Evaluation (NURE) Program designed to identify criteria favorable for the occurrence of the world's significant uranium deposits. This project deals specifically with uranium- and thorium-bearing pegmatites in the United States and, in particular, their distribution and origin. From an extensive literature survey and field examination of 44 pegmatite localities in the United States and Canada, the authors have compiled an index to about 300 uranium- and thorium-bearing pegmatites in the United States, maps giving location of these deposits, and an annotated bibliography to some of the most pertinent literature on the geology of pegmatites. Pegmatites form from late-state magma differentiates rich in volatile constituents with an attendant aqueous vapor phase. It is the presence of an aqueous phase which results in the development of the variable grain size which characterizes pegmatites. All pegmatites occur in areas of tectonic mobility involving crustal material usually along plate margins. Those pegmatites containing radioactive mineral species show, essentially, a similar distribution to those without radioactive minerals. Criteria such as tectonic setting, magma composition, host rock, and elemental indicators among others, all serve to help delineate areas more favorable for uranium- and thorium-bearing pegmatites. The most useful guide remains the radioactivity exhibited by uranium- and thorium-bearing pegmatites. Although pegmatites are frequently noted as favorable hosts for radioactive minerals, the general paucity and sporadic distribution of these minerals and inherent mining and milling difficulties negate the resource potential of pegmatites for uranium and thorium.

Petrography and petrology of the Ayghalesi granite, east of Takab area (northwest of Iran

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Saeed Kamran

2017-03-01

Full Text Available The investigated granite intrusion is located at the north of Ayghalesi village, east of Takab The Ayghalesi granite has been intruded the Eocene sandstone and conglomerate rocks and low grade metamorphic hornfels have been metamorphosed host rocks. The main constituent minerals are K-feldspar, plagioclase, quartz and muscovite.and minor garnet. The main texture is granular but pegmatitic, myrmektitic, graphic and perthitic occur as minor textures. Chemically, the rocks are granite on the various classification diagrams. The Ayghalesi intrusion body is classified as S-type, peraluminous composition, calc-alkaline nature and is calcic-alkali to alkali-calcic on the base of modified alkali lime index (MALI. The investigated body, on the tectonic discrimination diagrams, fall on syn-collisional tectonic setting domain, suggesting that it was originated during collision of Central Iranian and Arabian plates Key words: granite,

The ultimate fate of a synmagmatic shear zone. Interplay between rupturing and ductile flow in a cooling granite pluton

Science.gov (United States)

Zibra, I.; White, J. C.; Menegon, L.; Dering, G.; Gessner, K.

2018-05-01

The Neoarchean Cundimurra Pluton (Yilgarn Craton, Western Australia) was emplaced incrementally along the transpressional Cundimurra Shear Zone. During syndeformational cooling, discrete networks of cataclasites and ultramylonites developed in the narrowest segment of the shear zone, showing the same kinematics as the earlier synmagmatic structures. Lithological boundaries between aplite/pegmatite veins and host granitic gneiss show more intense pre-cataclasite fabrics than homogeneous material, and these boundaries later became the preferred sites of shear rupture and cataclasite nucleation. Transient ductile instabilities established along lithological boundaries culminated in shear rupture at relatively high temperature (∼500-600 °C). Here, tensile fractures at high angles from the fault plane formed asymmetrically on one side of the fault, indicating development during seismic rupture, establishing the oldest documented earthquake on Earth. Tourmaline veins were emplaced during brittle shearing, but fluid pressure probably played a minor role in brittle failure, as cataclasites are in places tourmaline-free. Subsequent ductile deformation localized in the rheologically weak tourmaline-rich aggregates, forming ultramylonites that deformed by grain-size sensitive creep. The shape and width of the pluton/shear zone and the regime of strain partitioning, induced by melt-present deformation and established during pluton emplacement, played a key role in controlling the local distribution of brittle and then ductile subsolidus structures.

Characteristics and its uranium metallogenic potential of the granite belt between Bange and Jiali county, tibet

International Nuclear Information System (INIS)

Zhao Baoguang; Wang Qin; Liu Zhipeng; Chen Yuliang; Xu Wei

2012-01-01

The granite belt between Bange and Jiali county is a composite batholith which intruded at multistage, it con- trolled by several groups of the fault system, the alteration is developed, with the alaskite, aplite, pegmatitic vein intruded, it is type Ⅰ in the beginning of forming, and change to type S in the late time. There is a large of geochemical anomalies of uranium (U>6.8 X 10 -6 ) in Gulu town and Sangba village, of which middle of the granite belt and Bianba county of which east of the granite belt, that anomalies area have 1200 km 2 , 800 km”2 and 1500 km 2 . All the anomalies is considered that its forming relate to batholith and its external contact, so it shows that it has favorite geological conditions for granite type uranium metallogenesis. (authors)

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.

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

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Ahmad Ahmadi Khalaji

2015-10-01

-existing tourmaline with pegmatite garnets and andalusite with schist garnets; zoning in garnets (oscillatory zoning of Al in pegmatite garnet, Mn increasing in the cores of schist garnet contrasted with Mn decreasing in the cores of pegmatite garnets; the decrease of Mg in the cores of pegmatite garnets, contrasted with the increase of this element in the cores of schist garnets; and the linear trends of Al and Ca in hornfels garnets Pyrope garnet composition in schist indicates a closed system for garnet formation condition in schist and a magmatic source for pegmatites. The compositions of garnets from schists change from Alm0.63, Prp0.07, Sps0.24, Grs0.05 in the cores, to Alm0.71, Prp0.09, Sps0.13, Grs0.05 in the rims. Garnets from pegmatites show a change from Alm0.73, Prp0.015, Sps0.24, Grs0.07 in the cores, to Alm0.71, Prp0.011, Sps0.28, Grs0.00 in the rims. Garnets from hornfelses showed changes from Alm 0.79, Prp0.14, Sps 0.06, Grs0.07 in the cores to Alm 0.8, Prp0.13, Sps 0.05, Grs0.01 in the rims. Discussion The percent of almandine and spessartine in the garnets of the schists and pegmatites are higher than that of garnets in the hornfelses. Almandine and spessartine in the pegmatite garnets from core to rim show a completely reversed trend. In the schist garnets from core to rim, the almandine trend is decreasing outward– increasing inward, while the spessartine trend is increasing – decreasing. In the hornfels garnets no specific trend could be determined, there is no zoning. This difference in trend between pegmatite garnets from that in schist garnets and hornfels garnets shows differences in their origin. Texture homogenization, rich in potassium, metaluminous to peraluminous magma of Hamedan granitoid intrusion (Aliani et al., 2012, Peraluminous biotite in this intrusion and lack of garnet zoning show that garnet pegmatites have been formed directly from granitic melt crystallization. References Aliani, F., Maanijou, M., Sabouri, Z. and Sepahi, A.A., 2012

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

Uraniferous alaskitic granites with special reference to the Damara Orogenic Belt

International Nuclear Information System (INIS)

Toens, P.D.; Corner, B.

1980-10-01

The control and patterns of uranium mineralisation in the alaskitic granites of the Damara Orogenic Belt are discussed. The polyphase Damara metamorphism produced high-grade metamorphic assemblages, migmatites and syn-, late-, and post-tectonic anatectic granites through reactivation of the basement and overlying Damara rocks. During anatexis the incompatible elements, particularly the uranium derived from these formations, were incorporated into the melts which then rose, in an attempt to attain gravitational equilibrium, by varying distances depending on the depth of origin of the melts, on their water content and on the availability of tensional environments. Fractional crystallisation during ascent and increased water content concentrated the uranium into residual melts which finally crystallised as alaskitic pegmatitic granite. Structural episodes played an important part in the emplacement of the uraniferous granites and the presence of marble bands was an important factor in not only providing a structural trap for the alaskitic melts and associated uranium-rich volatiles, but also by leading to the boiling of the magma and the subsequent deposition of uranium. The present-day level of erosion is considered to be an important factor contributing to the preservation of many of the uraniferous granite bodies. In addition it is suggested that secondary enrichment occurring above the water-table in the prevailing desert environment is an important criterion in enriching the tenor of mineralisation to ore grades. The exploration techniques necessary for the location of uraniferous granite bodies are briefly outlined [af

Radiometric age of granite from Campo Formoso, BA-Brazil - a minimum age for Jacobina group

International Nuclear Information System (INIS)

Torquato, J.R.; Oliveira, M.A.F.T. de; Bartels, R.L.

1978-01-01

The Campo Formoso granite represents the magmatic phase of the remobilized Pre-Jacobina basement, located within an are defined by the Serra de Jacobina, north of Campo Formoso, Bahia. Intrusive relationships between this granite and the Jacobina Group metasediments, gradational changes in textures and compositions between the granite and basement rocks, and the general structural-topographic expression of this suggest a mantled gneiss dome model for this area. A RB/Sr whole rock isochron age of 1911 +- 13 m.y. for the Campo Formoso granite is established. This date is interpreted as the age of the development of the structure, as well as a minimum age for the Jacobina Group metasediments. K/Ar dates on muscovites from the Campo Formoso granite are concordant with the Rb/Sr isocron. It is suggested that a lower regional thermal gradient in the Campo Formoso area during Transamazonic time is the cause for a more rapid cooling environment. (Author) [pt

Study of fluid inclusions in rodioactive mineralized pegmatites, dara area northern eastern desert, Egypt

International Nuclear Information System (INIS)

Ali, B.H.; Abdel Warith, A.

2003-01-01

Numerous pegmatite pockets of un zoned and zoned types are the most important rock types from the radioactive point of view. They occur at the marginal parts and higher topographic level of G.Dara younger granites. Zoned pegmatites are composed of extremely coarse-grained milky quartz core, intermediate zone and wall zone. The alteration zone is found at the contact between quartz core and intermediate zone. It is recorded the highest radioactive values due to their mineral composition, as a result of alteration processes associated with radioactive minerals. Only two alteration zones (P1 and P2) has been studied in this paper. The late magmatic alteration process (hematization, kaolinization, chloritization and fluortization) of the pegmatite resulted in the formation of chlorite, fluorite, clay minerals and carbonates (calcite) in the alteration zones as mineral assemblage. opaque minerals are found as pyrite, iron oxyhydroxide and garnet. Fluid inclusion studies by microthermometry were carried out on authigenic minerals (such as quartz and fluorite) in alteration zones (primary fluid inclusions). This study revealed that, at least two stages of the post-magmatic hydrothermal alteration are involved. The first stages of high temperature, low saline fluids are involved. The first stage is of high temperature, low saline fluids which characterized with hematization and/or chloritization resulted from fluid-rock interaction with late magmatic fluids that very probably mixed with external low salinity fluids along brittle structure. The second stage is of low temperature the main role in re high saline fluids characterized the fluoritized alteration due to consequent reaction with wall rocks and mixing with meteoric water. Mixing of low salinity meteoric water with hot a sending saline hydrothermal solution leads to ph change and continuous interaction with wall rock

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

International Nuclear Information System (INIS)

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

1988-01-01

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

The natural radioactivity in the Serido Pegmatite Province - Rio Grande do Norte State (Brazil): assessment and monitoring of water's source

International Nuclear Information System (INIS)

Campos, Thomas F.C; Petta, Reinaldo A.; Malanca, Alberto; Guimaraes Guedes, Anderson; Pastura, Valeria F.S.; Sindern, Sven

2008-01-01

Full text: This abstract show the preliminary considerations of a study accomplished on the radioactive minerals, primary and secondary uranium minerals that occur in the pegmatites of the Serido Region, State of Rio Grande do Norte, Brazil and their influence on the several sources of water provision and on population nuclei of the area from the municipal district of Parelhas and Ecuador. In general, the pegmatite from the area of Ecuador-Parelhas present high environmental radioactivity so much due to the dispersed uranium in the crystalline structure of minerals (columbite-tantalite, albite, microcline, quartz, phosphate minerals, tourmaline, lepidolite and apatite), as primary and secondary uranium minerals (uraninite, pitchblende, gummite, autunite, torbernite, and uranium-bearing opal, etc.). These uranium minerals appear associates to the fracture and voids in the pegmatite and in the tourmaline-bearing granite. These minerals were identified by petrography, X-Rays diffraction, ultraviolet fluorescence analysis, infrared spectroscopy, radioactivity (HPGe gamma spectrometry), thermal behavior and chemical analysis (ICP-MS and AAS, Microprobe). Geochemistry and hydrochemistry preliminary environmental studies on the pegmatites bodies from Serido Region show gamma radiation level which between 150 to 30.000 cps; uranium (U 3 O 8 ) and thorium (ThO 2 ) content in Columbite-Tantalite (and/or polycrase) varying between 0,3% - 3,0% and 0,1% - 0,5% respectively, and the coating existent in these minerals show uranium contents varying between 20% to 60%. While the soil samples gathered in Ecuador/Parelhas districts show an average activity of 226 Ra, 232 Th, and 40 K of 27.1/39.1; 33.74/48.5; 260.1/234.8 (Bq.kg -1 , dry-weight), respectively, and the corresponding kerma rate (l) in air are 50 and 67 nGyh -1 ], suggesting that the acid underground waters and others oxidizers attack and dissolve the radioactive minerals from pegmatite, generating solutions rich in U 6

Augen gneisses versus Augen gneisses from the Jaguaribeana Belt, northeastern region from Brazil: stratigraphy, geochemistry and U-Pb ages

International Nuclear Information System (INIS)

Sa, Jaziel Martins; Silva, Elvis Roberto da; Bertrand, Jean Michel; Leterrier, Jacques

1997-01-01

The Jaguaribeana Belt is located at Borborema Province, Ceara State, Brazil and this study aims to present Uranium-Lead (U-Pb) data and the augen gneisses petrographic and geochemical study of the Jaguaribe Belt, and to realize comparisons between these and the augen gneisses from the Oros Belt. It describes the geological characteristics of this region, the augen gneisses petrography and geochemical data and the U-Pb method results for a discussion about the augen gneisses from the Oros and Jaguaribe Belt

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

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

METALLOGENY OF EOCENE SYNCOLLISIONAL GRANITES OF MOTAJICA AND PROSARA MOUNTAINS

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Ivan Jurković

2004-12-01

Full Text Available The geological setting is dominated by Eocene (48.7 Ma syncollisional granitoids in the form of a small pluton in the Motajica Mt. and in the form of numerous sills and dykes in the Prosara Mt. Microelement paragenesis of these magmatites, pegmatites, greisens and quartz veins are distinguished by U, Th, Ce, Y, P, Nb, Ta, B, Li, F, Be, Sn, Mo, W, Fe, Cu, Pb. These elements and 87Sr/86Sr and 18O isotopic values indicate the mantle origin of magma contaminated by relatively sterile lithospheric rocks. The most probable hypothesis of such a hybrid magma formation is the "slab break-off model". Deep erosion of Motajica granitoid pluton opened its acrobatholitic and epibatholitic level with numerous, but small pegmatite deposits (beryllites, tourmalinites, emeraldites and sylexites with piezoelectric quartz. Greisenization marked by strong silicification and muscovitization affected less than 1% of pluton. It is characterized by minor and accessory molybdenite, wolframite, huebnerite, scheelite, fluorite. Hydrothermal occurrences, galena and Fe minerals have only a mineralogical significance. Economically significant are numerous autochthonous kaolin deposits formed in Pliocene-Pleistocene time. Prosara apomagmatic granitoids, exclusively granite dykes are metallogenetically sterile.

Metallogenic aspects of the feldspars and micas geochemistry in pegmatite from Alto-Ligonha (Mocambique)

International Nuclear Information System (INIS)

Neves, J.M.C.

1990-01-01

This paper deals with metallogenic aspects concerning the huge Alto Ligonha pegmatite Province. The geological setting of the pegmatites is briefly reviewed and the metamorphic grade of the country rocks of the pegmatites, ranging from granulitic to greenschist facies, has been considered. The economically most interesting pegmatites are those emplaced within rocks with lighter metamorphism. The available geochronological data allow us to link, the most interesting pegmatites from Alto Ligonha, to the Pan-African granitoid magmatism, about 500 Ma ago. (author)

Site investigation SFR. Rock type coding, overview geological mapping and identification of rock units and possible deformation zones in drill cores from the construction of SFR

Energy Technology Data Exchange (ETDEWEB)

Petersson, Jesper (Vattenfall Power Consultant AB, Stockholm (Sweden)); Curtis, Philip; Bockgaard, Niclas (Golder Associates AB (Sweden)); Mattsson, Haakan (GeoVista AB, Luleaa (Sweden))

2011-01-15

, or a lack of quality in the available data, for example, time and transport have that affected the frequency and condition of fractures. This activity has been performed on all 32 boreholes considered in this report: KFR01, KFR02, KFR03, KFR05, KFR10, KFR11, KFR 12, KFR14, KFR19, KFR20, KFR31, KFR32, KFR34, KFR37, KFR38, KFR51, KFR52, KFR57, KFR61-KFR68, KFR69, KFR70, KFR71, KFR72, KFR89, SFR (Silo 1). The lithology in KFR01 and KFR02 was earlier described in terms of pegmatite, coarse-grained granite, fine-grained biotite gneiss and fine- to medium-grained granite gneiss. Generally, the pegmatite and coarse-grained granite were translated into pegmatitic granite (101061), whereas the gneisses were coded as felsic to intermediate meta volcanic rock (103076) and fine- to medium-grained metagranite-granodiorite (101057). The major lithological components in the eleven drill cores subjected to the overview mapping are fine- to medium-grained metagranite-granodiorite (101057), pegmatitic granite (101061), felsic to intermediate meta volcanic rock (103076), fine- to medium-grained granite (111058) and subordinate occurrences of amphibolite (102017) and aplitic metagranite (101058). A continuous occurrence of cataclastic rock (108003) with a total drill core length of 11.2 m occurs in KFR71. Alteration other than oxidation is typically found in drill cores from boreholes intersecting or in the intimate vicinity of the Singoe deformation zone (i.e. KFR69, KFR71 and KFR72). Up to seven rock units have been identified in a single borehole, with an average of 2-4. Most rock units are dominated by fine- to medium-grained metagranite-granodiorite (101057) or pegmatitic granite (101061). All rock units have been interpreted with a medium or high degree of confidence. The rock units with a lower degree of confidence are restricted to boreholes with existing mappings, which were rock coded during the Forsmark site investigation, when the geological experience from the SFR area was

Site investigation SFR. Rock type coding, overview geological mapping and identification of rock units and possible deformation zones in drill cores from the construction of SFR

International Nuclear Information System (INIS)

Petersson, Jesper; Curtis, Philip; Bockgaard, Niclas; Mattsson, Haakan

2011-01-01

lack of quality in the available data, for example, time and transport have that affected the frequency and condition of fractures. This activity has been performed on all 32 boreholes considered in this report: KFR01, KFR02, KFR03, KFR05, KFR10, KFR11, KFR 12, KFR14, KFR19, KFR20, KFR31, KFR32, KFR34, KFR37, KFR38, KFR51, KFR52, KFR57, KFR61-KFR68, KFR69, KFR70, KFR71, KFR72, KFR89, SFR (Silo 1). The lithology in KFR01 and KFR02 was earlier described in terms of pegmatite, coarse-grained granite, fine-grained biotite gneiss and fine- to medium-grained granite gneiss. Generally, the pegmatite and coarse-grained granite were translated into pegmatitic granite (101061), whereas the gneisses were coded as felsic to intermediate meta volcanic rock (103076) and fine- to medium-grained metagranite-granodiorite (101057). The major lithological components in the eleven drill cores subjected to the overview mapping are fine- to medium-grained metagranite-granodiorite (101057), pegmatitic granite (101061), felsic to intermediate meta volcanic rock (103076), fine- to medium-grained granite (111058) and subordinate occurrences of amphibolite (102017) and aplitic metagranite (101058). A continuous occurrence of cataclastic rock (108003) with a total drill core length of 11.2 m occurs in KFR71. Alteration other than oxidation is typically found in drill cores from boreholes intersecting or in the intimate vicinity of the Singoe deformation zone (i.e. KFR69, KFR71 and KFR72). Up to seven rock units have been identified in a single borehole, with an average of 2-4. Most rock units are dominated by fine- to medium-grained metagranite-granodiorite (101057) or pegmatitic granite (101061). All rock units have been interpreted with a medium or high degree of confidence. The rock units with a lower degree of confidence are restricted to boreholes with existing mappings, which were rock coded during the Forsmark site investigation, when the geological experience from the SFR area was more

A preliminary deposit model for lithium-cesium-tantalum (LCT) pegmatites

Science.gov (United States)

Bradley, Dwight; McCauley, Andrew

2013-01-01

This report is part of an effort by the U.S. Geological Survey to update existing mineral deposit models and to develop new ones. We emphasize practical aspects of pegmatite geology that might directly or indirectly help in exploration for lithium-cesium-tantalum (LCT) pegmatites, or for assessing regions for pegmatite-related mineral resource potential. These deposits are an important link in the world’s supply chain of rare and strategic elements, accounting for about one-third of world lithium production, most of the tantalum, and all of the cesium.

Uranium-lead age determinations on granitic rocks from the eastern Bushveld Complex

International Nuclear Information System (INIS)

Faurie, J.N.

1978-08-01

Uranium-lead age determinations were carried out on four types of granitic rocks from the eastern Bushveld Complex. The oldest rocks in the area are gneisses and felsites - 2604 plus minus 100 m.y. old - which form the centre of the Dennilton dome. The Rooiberg felsites could not be dated directly because of the absence of zircon, however a porphyritic granite sill, which shows intrusive relations with the Rooiberg felsites, was dated at 2090 plus minus 40 m.y., an age which can also be regarded as a minimum age for the Rooiberg felsites. No reliable age could be determined for the granophyres because of the large amount of lead-loss reflected in the zircon. The majority of zircons from these granophyres showed a peculiar hieroglyphic texture, a phenomena which has not yet been recorded in literature. The samples collected from the granites gave an age of 1950 plus minus 80 m.y. and thus form part of the Nebo Granite. Attempts have been made to obtain more concordant zircon ages throughout the present study. Although some success was achieved by analysing different size fractions of a zircon population, the non-magnetic fractions gave the most promising results [af

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

International Nuclear Information System (INIS)

Baidya, Tapan Kumar

2014-01-01

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

Geochemistry, Mineralogy and Economic Potential of a Pan-African Pegmatite from Wadi Huwar, Southwest Jordan

International Nuclear Information System (INIS)

Saffarini, G.; Jarrar, G.

2002-01-01

The Wadi Huwar pegmatite (WHP) is hosted in a two-mice monzogranite (TMG). The host rock is a post-tectonic granitoid intrusion, belongs to the Rahma suite of the Aqaba complex and represents a late stage of the Pan-African orogeny. The emplacement of the pegmatite was controlled by the late Pan-African tectonics. The pegmatites and their host are mainly composed of quartz, alkali feldspar, Na-plagioclase, muscovite and biotite. Garnet and zircon are accessories in the monzogranite, whereas in the hosted pegmatites both minerals are abundant. Major, minor and trace element geochemistries indicate that the pegmatites and their host are peraluminous in nature and were intruded under a syn-collision tectonic regime. The mineralogical simplicity, decrease in abundance of ferromagnesian minerals in pegmatite and the sharp contacts with the host, as well as phase equilibria calculations using muscovite chemistry imply that the studied pegmatites might have crystallized during magma ascent to low crustal levels (2 Kbar and 550 deg C). Based on pegtrographic, geochemical and economic evaluation, the studied pegmatites were found to be unprofitable. (authors) 32., 9 figs., 6 tabs

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

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

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

Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia

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Elena Badanina

2012-11-01

Full Text Available In this paper we show that the pegmatite-forming processes responsible for the formation of the Malkhan pegmatites started at magmatic temperatures around 720 °C. The primary melts or supercritical fluids were very water- and boron-rich (maximum values of about 10% (g/g B2O3 and over the temperature interval from 720 to 600 °C formed a pseudobinary solvus, indicated by the coexistence of two types of primary melt inclusions (type-A and type-B representing a pair of conjugate melts. Due to the high water and boron concentration the pegmatite-forming melts are metastable and can be characterized either as genuine melts or silicate-rich fluids. This statement is underscored by Raman spectroscopic studies. This study suggested that the gel state proposed by some authors cannot represent the main stage of the pegmatite-forming processes in the Malkhan pegmatites, and probably in all others. However there are points in the evolution of the pegmatites where the gel- or gel-like state has left traces in form of real gel inclusions in some mineral in the Malkhan pegmatite, however only in a late, fluid dominated stage.

Hydrothermal mobilization of pegmatite-hosted REE and Zr at Strange Lake, Canada: A reaction path model

Science.gov (United States)

Gysi, Alexander P.; Williams-Jones, Anthony E.

2013-12-01

Petrological and geochemical observations of pegmatites in the Strange Lake pluton, Canada, have been combined with numerical simulations to improve our understanding of fluid-rock interaction in peralkaline granitic systems. In particular, they have made it possible to evaluate reaction paths responsible for hydrothermal mobilization and mineralization of rare earth elements (REE) and Zr. The focus of the study was the B-Zone in the northwest of the pluton, which contains a pegmatite swarm and is the target of exploration for an economically exploitable REE deposit. Many of the pegmatites are mineralogically zoned into a border consisting of variably altered primary K-feldspar, arfvedsonite, quartz, and zirconosilicates, and a core rich in quartz, fluorite and exotic REE minerals. Textural relationships indicate that the primary silicate minerals in the pegmatites were leached and/or replaced during acidic alteration by K-, Fe- and Al-phyllosilicates, aegirine, hematite, fluorite and/or quartz, and that primary zirconosilicates (e.g., elpidite) were replaced by gittinsite and/or zircon. Reaction textures recording coupled dissolution of silicate minerals and crystallization of secondary REE-silicates indicate hydrothermal mobilization of the REE. The mobility of the light (L)REE was limited by the stability of REE-F-(CO2)-minerals (basnäsite-(Ce) and fluocerite-(Ce)), whereas zirconosilicates and secondary gadolinite-group minerals controlled the mobility of Zr and the heavy (H)REE. Hydrothermal fluorite and fluorite-fluocerite-(Ce) solid solutions are interpreted to indicate the former presence of F-bearing saline fluids in the pegmatites. Numerical simulations show that the mobilization of REE and Zr in saline HCl-HF-bearing fluids is controlled by pH, ligand activity and temperature. Mobilization of Zr is significant in both saline HF- and HCl-HF-bearing fluids at low temperature (250 °C). In contrast, the REE are mobilized by saline HCl-bearing fluids

Petrography, mineral chemistry and lithochemistry of the albitite and granite-gneissics rocks of anomaly 35 from Lagoa Real uranium province

International Nuclear Information System (INIS)

Santos, Camila Marques dos

2016-01-01

In the northwestern portion of the Lagoa Real Uranium Province (LRUP), located in south-central Bahia, it is located one of the most promising uranium anomalies Brazil (an35, Gameleira I deposit), the reserves and proximity to the Cachoeira mine. Other anomalies of this sector (eg. 31 AN and AN34), are also considered strategic for the content of radioactive minerals and REE. The objective was to develop a study of a representative drill core of an35, where the main rocks PULR are present. The research focused on the mineralogical and chemical changes observed in the passages of a lithology to another, from the rock to the meta granitic albitites, through gneiss and transitional rocks, and making comparisons with similar lithologies sampled on testimonies of AN31 and 34. The granites are classified as hypersolvus coarse alkali-feldspar granite and are variably deformed. The main mineral assemblage in granites are perthitic orthoclase+hedenbergite+ quartz +hastingsite + biotite, and zircon, apatite, ilmenite and titanite are accessories. The reddening of these rocks are characterized by feldspars sericitization and hematitization and the presence of 'vazios'. The gneisses are mainly gray and reach milonitic to protomilonitics terms. These rocks have characteristics of subsolidus changes as swapped rims and metasomatic perthites. The tardi-magmatic association (amphibole+biotite) indicates final crystallization or late influx by superficial fluids resulting in an increase in water and volatiles, such as F and Cl in the system, which must also have carried rare-earth elementsGranites have geochemical affinity with A-type ferroan granite, A2, reduced and are post-collisional. Their patterns of incompatible elements and rare earths are comparable to Sao Timoteo Granite, but their petrographic features indicate that it is a less common granite facies. Albitites were classified as garnet albitites, magnetite albitites and biotite albitites. Contacts between

Geochemistry and petrogenesis of the proterozoic granites from Jhabua and Dhar districts, Madhya Pradesh, India and their bearing on uranium mineralisation

International Nuclear Information System (INIS)

Pant, P.C.; Goyal, Navin; Rawal, Neeru

2004-01-01

In the western part of Madhya Pradesh a number of small plutonic granites occur as intrusive into the gneisses and Aravalli metasediments. Granites are of grey, pink colour and gneissic varieties. Mineralogically, the granites are two mica bearing. Chemically they are K 2 O rich, calc-alkaline, metaluminous to peraluminous and differentiated in nature. Tectonically they are volcanic arc types with an affinity to syn-collisional setup. Basement reactivation may be the cause of the emplacement of these granites as the area is traversed by a number of basement lineaments. They are enriched in light REE with Ce/Yb ratio ranging from 1.4 to 8.4. Negative Eu anomaly (Eu/Eu* 0.2 to 0.8) suggests that they are fractionated. High Th/U ratio (1-18) indicates that uranium has been leached out. Hence the overlying infratrappeans hold potential for litho/structural controlled uranium mineralisation.(author)

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

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

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)

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.)

A study of the Eocene S-type granites of Chapedony metamorphic core complex (northeast of Yazd province, Central Iran)

International Nuclear Information System (INIS)

Zakipour, A.; Torabi, Gh.

2016-01-01

The Eocene Chapedony metamorphic core complex, is located in western part of the Posht-e-Badam block. This complex is consisting of migmatite, gneiss, amphibolite, marble, micaschist and various types of granitoids. In middle part of this complex (Kalut-e-Chapedony), an Eocene granitic rock unit cross cuts the other rocks. The minerals of this granite are plagioclase (An 9 Ab 8 7O r 4), potassium feldspars (orthoclase), quartz, euhedral garnet (Alm 7 7Sps 1 3Prp 9 Grs 1 ), zircon, apatite, fibrolitic sillimanite and muscovite. Petrology and geochemical studies reveal calc-alkaline, peraluminous and S-type nature of the studied granites. Chondrite-normalized REE patterns represent evident negative anomaly of Eu and low values of the REEs. Continental crust and North American shale composite (NASC) - normalized multi-elements spider diagrams indicate trace elements depletion. These granites are formed by melting of continental crust sedimentary rocks, resulted by emplacement of mantle-derived magma at the bottom of continental crust which formed the Chapedony metamorphic core complex. The source rock of these granites should be a clay-rich sedimentary rock with low amount of plagioclase and CaO/Na 2 O ratio.

Emplacement and deformation of the A-type Madeira granite (Amazonian Craton, Brazil)

Science.gov (United States)

Siachoque, Astrid; Salazar, Carlos Alejandro; Trindade, Ricardo

2017-04-01

The Madeira granite is one of the Paleoproterozoic (1.82 Ga) A-type granite intrusions in the Amazonian Craton. It is elongated in the NE-SW direction and is composed of four facies. Classical structural techniques and the anisotropy of magnetic susceptibility (AMS) method were applied to the study of its internal fabric. Magnetic susceptibility measurements, thermomagnetic curves, remanent coercivity spectra, optical microscopy and SEM (scanning electron microscopy) analyses were carried out on the earlier and later facies of the Madeira granite: the rapakivi granite (RG) and the albite granite (AG) respectively. The last one is subdivided into the border albite granite (BAG) and the core albite granite (CAG) subfacies. AMS fabric pattern is controlled by pure magnetite in all facies, despite significant amounts of hematite in the BAG subfacies. Microstructural observations show that in almost all sites, magnetic fabric correlates to magmatic state fabrics that are defined by a weak NE-SW orientation of mafic and felsic silicates. However, strain mechanisms in both subfacies of AG also exhibit evidence for solid-state deformation at high to moderate temperatures. Pegmatite dyke, strike slip fault (SFA-B-C), hydrothermal vein, normal fault (F1-2) and joint (J) structures were observed and their orientation and kinematics is consistent with the magmatic and solid-state structures. Dykes, SFA-C and F1, are usually orientated along the N70°E/40°N plane, which is nearly parallel to the strike of AMS and magmatic foliations. In contrast, veins, SFB, F2 and some J are oriented perpendicular to the N70°E trend. Kinematic analysis in these structures shows evidence for a dextral sense of movement in the system in the brittle regime. The coherent structural pattern for the three facies of Madeira granite suggests that the different facies form a nested pluton. The coherence in orientation and kinematics from magmatic to high-temperature solid-state, and into the brittle

Evaluation of uranium anomalies in the Hylas zone and northern Richmond basin, east-central Virginia

International Nuclear Information System (INIS)

Baillieul, T.A.; Dexter, J.J.

1982-01-01

Conclusions from this study are: (1) Radon values in ground water from the Hylas Zone and the adjacent Richmomd Basin are anomalous and may indicate nearby uranium-enriched source rocks. (2) Pegmatites, protomylonitic granite, and the Petersburg Granite can be good sources of uranium for ground water. The pegmatites described in this report appear to be the best source rocks because of uranium values ranging from 82 to 235 ppM eU and corresponding low values of Th as well (average Th/U = 0.18). The protomylonitic granite has an average Th/U ratio of 0.5. Ground-water samples (ranging from 70 to 270 ppB uranium) from southwest Richmond are believed to have originated from a major ground-water system at the contact of the Petersburg Granite and overlying coastal plain sediments. Thus, the Petersburg Granite may be considered a possible source of uranium available to ground water entering the Richmond Basin. (3) The Richmond Basin could host uranium deposits of the sandstone class. As mentioned above, there appears to be an adequate supply of uranium in rocks surrounding the basin. The basin environment is presently classified as unevaluated. Further work is warranted on the basis of this study. (4) Pegmatites in the Hylas Zone could be favorable for the occurrence of uranium deposits of the pegmatitic class. However, it is not known how the uranium occurs in the pegmatites, and only pegmatites exposed in the Boscobel quarry were examined. Therefore, this environment remains unevaluated. 3 figures, 4 tables

Geochronology (Rb-Sr, Sm-Nd and Pb-Pb) of the proterozoic granulitic and granitic rocks around Usilampatti, Madurai district, Tamil Nadu: implication on age of various lithounits

International Nuclear Information System (INIS)

Pandey, U.K.; Pandey, B.K.; Krishnamurthy, P.

2005-01-01

Rb-Sr, Sm-Nd and Pb-Pb systematics on mafic granulites, intermediate- charnockites, charnockites, calc-granulites, orthogneisses, leptynites, granites and two (2) mineral samples (microcline and muscovite) from pegmatite have been studied. Sm-Nd model ages (T DM ) for most of the rocks cluster around 2.1 Ga. Calc-granulites gave Rb-Sr whole rock isochron age of 1339 ± 110 Ma with initial 87 Sr/ 86 Sr ratio (I.R.) = 0.709. Mesoproterozoic age for the Metasedimentary Group of rocks (calc-granulites) has been inferred based on their 87 Sr/ 86 Sr ratio also. Granites and leptynites have yielded Rb-Sr whole rock isochron ages of 823± 38 Ma, with I.R. = 0.713 and 894± 82 Ma, with I.R. = 0.708 respectively which are younger than the calc-granulites. Microcline and muscovite from pegmatite gave Rb-Sr model ages as 532 and 491 Ma respectively. Granites, leptynites and calc-granulites are derived from the crustal source as indicated by their high initial 87 Sr/ 86 Sr ratios. Most probably the protolith of the granitic and granulitic rocks is of Palaeoproterozoic age in this part of the Madurai Block. The minimum age of granulite grade of metamorphism has been inferred at c. 850 Ma, indirectly on the basis of Rb-Sr ages of leptynites, which normally form during the evolution of granulite facies assemblages. Both granulite facies metamorphism and granitic magmatism probably took place during Neoproterozoic period correlatable to the early phase of Pan-African orogeny. Later decompression, causing mineral scale resetting of the Rb-Sr and Sm-Nd systematics, around 450-550 Ma, may correspond to the final exhumation, which brought the middle to lower crustal granulites to upper crustal levels, during the last phase of Pan-African activity. As per ages obtained on various lithounits in the present study the Metasedimentary Group of rocks (Mesoproterozoic) are younger than the Charnockite Group of rocks (Palaeoproterozoic) followed by the rocks belonging to the Migmatite Complex

Geochronology (Rb-Sr, Sm-Nd and Pb-Pb) of the proterozoic granulitic and granitic rocks around Usilampatti, Madurai District, Tamil Nadu: implication on age of various lithounits

International Nuclear Information System (INIS)

Pandey, U.K.; Pandey, B.K.; Krishnamurthy, P.

2005-01-01

Rb-Sr, Sm-Nd and Pb-Pb systematics on mafic granulites, intermediate-charnockites, charnockites, calc- granulites, orthogneisses, leptynites, granites and two (2) mineral samples (microcline and muscovite) from pegmatite have been studied. Sm-Nd model ages (T DM ) for most of the rocks cluster around 2.1 Ga. Calc-granulites gave Rb-Sr whole rock isochron age of 1339± 110 Ma with initial 87 Sr/ 86 Sr ratio (IR)= 0.709. Mesoproterozoic age for the metasedimentary group of rocks (calc-granulites) has been inferred based on their 86 Sr/ 86 Sr ratio also. Granites and leptynites have yielded Rb-Sr whole rock isochron ages of 823 ± 38 Ma, with I.R. = 0.713 and 894± 82 Ma, with I.R.= 0.708 respectively which are younger than the calc-granulites. Microcline and muscovite from pegmatite gave Rb-Sr model ages as 532 and 491 Ma respectively. Granites, leptynites and calc-granulites are derived from the crustal source as indicated by their high initial 87 Sr/ 86 Sr ratios. Most probably the protolith of the granitic and granulitic rocks is of Palaeoproterozoic age in this part of the Madurai Block. The minimum age of granulite grade of metamorphism has been inferred at c. 850 Ma, indirectly on the basis of Rb-Sr ages of leptynites, which normally form during the evolution of granulite facies assemblages. Both granulite facies metamorphism and granitic magmatism probably took place during Neoproterozoic period correlatable to the early phase of Pan-African orogeny. Later decompression, causing mineral scale resetting of the Rb-Sr and Sm-Nd systematics, around 450-550 Ma, may correspond to the final exhumation, which brought the middle to lower crustal granulites to upper crustal levels, during the last phase of Pan-African activity. As per ages obtained on various lithounits in the present study the Metasedimentary Group of rocks (Mesoproterozoic) are younger than the Charnockite Group of rocks (Palaeoproterozoic) followed by the rocks belonging to the Migmatite Complex

Trace element mobility in mine waters from granitic pegmatite U–Th–REE deposits, Bancroft area, Ontario

International Nuclear Information System (INIS)

Desbarats, A.J.; Percival, J.B.; Venance, K.E.

2016-01-01

Small, low-grade, granitic pegmatite U–Th–REE deposits are found throughout the Grenville geological province of eastern Canada. Groundwater quality at historical mining properties in the Bancroft area was investigated in order to better understand the mobility of trace elements that may pose health risks if there is renewed development of this class of mineral deposit. Groundwater samples were obtained from diamond drill holes, flowing adits and flooded mine shafts. Uranium occurs almost entirely in the dissolved (<0.45 μm) phase and is found at concentrations reaching 2579 μg/L. The Canadian maximum acceptable concentration for U in drinking water (0.02 mg/L) was exceeded in 70% of samples. Regulatory limits for 226 Ra (0.5 Bq/L) and for 210 Pb (0.2 Bq/L) were generally exceeded in these samples as well. Speciation modeling indicates that over 98% of dissolved U is in the form of highly mobile uranyl-Ca–carbonate complexes known to inhibit U adsorption. Uranium concentrations in groundwater appear to be correlated with the uranothorite content of the deposits rather than with their U grade. Uranothorite may be more soluble than uraninite, the other ore mineral, because of its non-ideal composition and metamict structure. Thorium, released concomitantly with U during the dissolution of uranothorite and thorian uraninite, exhibits median and maximum total concentrations of only 0.1 and 11 μg/L, respectively. Mass balance and stoichiometric considerations indicate that almost all Th is immobilized very close to its source. The sums of total light REE (La–Gd) concentrations have median and maximum values of 6 and 117 μg/L, respectively. The sums of total heavy REE (Tb–Lu) concentrations have median and maximum values of 0.8 and 21 μg/L, respectively. Light REE are derived mainly from the dissolution of metamict allanite whereas the sources of heavy REE are widely dispersed among accessory minerals. Fractionation patterns of REE in the dissolved

Geologic columns for the ICDP-USGS Eyreville B core, Chesapeake Bay impact structure: Impactites and crystalline rocks, 1766 to 1096 m depth

Science.gov (United States)

Horton, J. Wright; Gibson, R.L.; Reimold, W.U.; Wittmann, A.; Gohn, G.S.; Edwards, L.E.

2009-01-01

The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville drill cores from the Chesapeake Bay impact structure provide one of the most complete geologic sections ever obtained from an impact structure. This paper presents a series of geologic columns and descriptive lithologic information for the lower impactite and crystalline-rock sections in the cores. The lowermost cored section (1766-1551 m depth) is a complex assemblage of mica schists that commonly contain graphite and fibrolitic sillimanite, intrusive granite pegmatites that grade into coarse granite, and local zones of mylonitic deformation. This basement-derived section is variably overprinted by brittle cataclastic fabrics and locally cut by dikes of polymict impact breccia, including several suevite dikes. An overlying succession of suevites and lithic impact breccias (1551-1397 m) includes a lower section dominated by polymict lithic impact breccia with blocks (up to 17 m) and boulders of cataclastic gneiss and an upper section (above 1474 m) of suevites and clast-rich impact melt rocks. The uppermost suevite is overlain by 26 m (1397-1371 m) of gravelly quartz sand that contains an amphibolite block and boulders of cataclasite and suevite. Above the sand, a 275-m-thick allochthonous granite slab (1371-1096 m) includes gneissic biotite granite, fine- and medium-to-coarse-grained biotite granites, and red altered granite near the base. The granite slab is overlain by more gravelly sand, and both are attributed to debris-avalanche and/or rockslide deposition that slightly preceded or accompanied seawater-resurge into the collapsing transient crater. ?? 2009 The Geological Society of America.

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)

Geochronological determination of pegmatites from Rio de Janeiro state

International Nuclear Information System (INIS)

Oliveira Menezes, S. de; Cordani, U.G.; Teixeira, W.

1987-01-01

Samples of muscovite and plagioclase were collected from the pegmatites located in the counties of Niteroi and Sao Goncalo, State of Rio de Janeiro. Geochronological Research Center of the University of Sao Paulo has selected some samples for potassium-argon and rubidium-strontion analysis. Three samples of muscovite analysed by K-Ar dating method gave ages between 437±13 and 447±16 m.y and two others, by Rb-Sr dating method, gave 495±15 and 500±13 m.y.. One sample of plagioclase analysed by K-Ar method gave age of 337±16 m.y.. In this paper, the locations of the analysed samples are described and the samples of vicinity are listed in the Appendix. interpretation of the radiometric ages and discussion of results are made. Taking into account the results of Table 1 and the geologic setting of the pegmatites sampled in Niteroi and Sao Goncalo, we way conclude that all cooling ages (440-550 m.y.) are related to the Brasiliano Orogeny. These pegmatites are regard as having same geological history and their ages are supposed 500 m.y [pt

The Keimoes Suite redefined: The geochronological and geochemical characteristics of the ferroan granites of the eastern Namaqua Sector, Mesoproterozoic Namaqua-Natal Metamorphic Province, southern Africa

Science.gov (United States)

Bailie, Russell; Macey, Paul Hugh; Nethenzheni, Sedzani; Frei, Dirk; le Roux, Petrus

2017-10-01

Voluminous granite gneisses and granites straddle the boundary between the Kakamas and Areachap Terranes in the eastern Namaqua Sector (NS) of the Mesoproterozoic Namaqua-Natal Metamorphic Province (NNMP). These rocks have been previously poorly defined and loosely grouped into the Keimoes Suite, but a recent U-Pb age study has suggested the suite be subdivided into syn-tectonic and post-tectonic groups relative to the main phase of the Namaqua Orogeny. This study adds new whole rock geochemical, isotopic and age data for these granites that confirms the subdivision is appropriate. The older group of syn-tectonic granite gneisses, dated between 1175 and 1146 Ma, have penetrative foliations and are largely derived from fractionated, leucogranitic metaluminous to peraluminous magmas with low maficity, low Ti, Mn and Ca. They were derived from mildly depleted sources (εNd(t): -1.47 to 1.78), with Meso-to Paleoproterozoic Nd model ages (1.57-1.91 Ga), and high initial Sr ratios (0.71970-0.75567) suggesting mixing between younger depleted and older, arc-like sources imparting an arc-like signature to the magmas. High initial Sr ratios appear to be an intrinsic character of these granites reflecting those of granites in the region and the highly radiogenic nature of the NS. The weakly to unfoliated late-to post-tectonic megacrystic granodiorites and monzogranites, including charnockites, intruded between 1110 and 1078 Ma and constitute the Keimoes Suite proper. They have I-type characteristics, being strongly metaluminous and locally hornblende- and orthopyroxene-bearing with moderate SiO2 and with arc-type affinities (LILE enrichment relative to the HFSE, Ta-Nb, Ti and P anomalies). However, the granitoids also have high Fe/Mg ratios, along with high HFSE, LILE and REE contents more indicative of A-type granites. They show an increasing maficity, metaluminous character, and general decreasing degree of fractionation with decreasing age. They are similar to the syn

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.)

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.)

Gamma-rays and heat-treatment conversions of point defects in massive rose quartz from the Borborema Pegmatite Province, Northeast Brazil

Science.gov (United States)

Guzzo, Pedro L.; Barreto, Sandra B.; Miranda, Milena R.; Gonzaga, Raysa S. G.; Casals, Sandra A.

2017-11-01

An extensive characterization of trace elements and point defects in rose quartz from the Borborema Pegmatite Province (BPP) in the northeast of Brazil was carried out by complementary spectroscopic methods. The aim here was to document the change in the configuration of point defects into the quartz lattice induced by heat-treatment and ionizing radiation. The samples were extracted from the core of two granitic rare element (REL) pegmatites, Taboa (Carnaúba dos Dantas, RN) and Alto do Feio (Pedra Lavrada, PB). The contents of Al, P, Ti, Ni, Fe, Ge, Li, Be, B and K were measured by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Polished plates were heat-treated at 500 and 1000 °C and then irradiated with 50 kGy of γ rays. Point defects were characterized by optical (UV-Vis), infrared (IR), and electron paramagnetic resonance (EPR) spectroscopies. In the as-received condition, [AlO4/H]0 centers, Li- and B-dependent OH defects were observed. Point defects related to Al and Li species were significantly affected by heat-treatment at 1000 °C and/or γ radiation. Paramagnetic centers such as [AlO4]0, [GeO4/Li]0, [TiO4/Li]0 and [O2 3-/Li]0 were created by the diffusion of Li+ ions from their original diamagnetic centers related to substitutional Al3+ and OH-species. The smoky color developed after irradiation and the signal intensities of the paramagnetic centers were independent from the original rose color grade. The samples from the Taboa (TB) pegmatite showed the highest concentration of Al, Ti, Fe and Li elements as well as the highest signal intensities for [AlO4]0, [AlO4/H]0, [GeO4/Li]0 and [TiO4/Li]0 centers. Although TB also showed the higher concentration of B element, the intensity of the 3597 cm-1 IR band related to [BO4/H]0 centers was higher for Alto do Feio (AF) samples. This result suggests that the uptake of B into the quartz core of each pegmatite took place through different mechanisms. It was concluded that the change in

Geochemistry of the uranium mineralized Achala granitic complex, Argentina: Comparison with Hercynian peraluminous leucogranites of western Europe

International Nuclear Information System (INIS)

Cuney, M.; Leroy, J.; Valdiviezo, P.A.; Daziano, C.; Gamba, M.; Zarco, A.J.; Morello, O.; Ninci, C.; Molina, P.

1989-01-01

The Achala granitic complex belongs to the Sierras Pampeanas Hercynian belt, located west of the city of Cordoba, Argentina. This complex is very large (about 100 km N-S and 40 km E-W) and is composed of biotite, biotite with muscovite and muscovite with tourmaline granites intruded in amphibolite grade metamorphic rocks, along a main N 20 deg. E structural direction. Numerous uranium mineralizations are located within the granitic massif and tungsten mineralizations are present both in the enclosing metamorphic rocks and in the granite. The geochemistry of the granite has been studied in four test areas (Southern, Copina, Median and Don Vincente). Two test areas (Median and Don Vicente) present clear evidence of hydrothermal alteration: albitization and dequartzification similar to the French 'episyenites', silicification and argillic alteration. Potassic alteration is rare and weakly developed. The two test areas with hydrothermal alteration present a high uranium geochemical background (5-30 ppm). High thorium contents (up to 65 ppm) are essentially observed in the less differentiated granites of the Copina and Median areas. Thorium/uranium ratios are highly variable (1-10). Uranium minerals are related to different environments - (1) apatite-biotite enclave mineralized with uraninite and uranothorite, (2) gneiss from the contact metamorphism rim, (3) granite with incipient dequartzification, (4) granite associated with albitic episyenites and (5) silicified granite - but are all located in the two test areas presenting clear evidence of hydrothermal alteration. The three petrogenetic events are clearly related to very different mechanisms, separated from each other by several tens of millions of years in the west European Hercynian chain. In the same period the same succession of events leading to uranium deposits is observed in Argentina. 34 refs, 10 figs, 1 tab

Geology and U-Pb geochronology of the Banabuiu granite, Northeastern Ceara, Brazil; Geologia y geocronologia U-Pb del granito de Banabuiu, Noreste de Ceara, Brasil

Energy Technology Data Exchange (ETDEWEB)

Lima, M. N.; Nogueira Neto, J. A.; Azevedo, M. R.; Valle Aguado,

2010-07-01

The Banabuiu massif crops out in the Central Ceara Domain (DCC) of the Borborema Province (NE Brasil), as an N-S elongate granite intrusion, concordant with the regional structures. It was emplaced into basement rocks of Paleoproterozoic age, extensively transformed into gneisses and migmatites during the Brasilian orogeny ({approx}600 Ma). Using U-Pb zircon dating, the crystallization age of the Banabuiu syn-kinematic two-mica granite was estimated at 578.6 {+-} 6.5 Ma. The granite is strongly peraluminous (A/CNK 1,098 - 1,134) and shows a typical S-type geochemical signature. The {epsilon}Nd{sub 5}80 values are strongly negative ({epsilon}Nd{sub 5}80 = -19 a - 23) and partially overlap with those of the Paleoproterozoic gneissmigmatite complex ({epsilon}Nd{sub 5}80 = -12 to -26), suggesting that the parental magmas of the Banabuiu granite could have been produced by partial melting of similar crustal materials. (Author) 21 refs.

Characterization of Loma Venturilla pegmatites using nuclear techniques

International Nuclear Information System (INIS)

Pena Fortes, B.; Caopte Rodriguez, G.; Toujague La Rosa, R.; Sukar Satraputa, K.

1996-01-01

Neutron Activation Analysis (NAA) and gamma spectrometry Analysis (GEA) were used for the determination of 21 trace elements in geological samples of pegmatites of Loma Venturilla area. Both methods permitted, in general, the determination of K, Cr, Co, Sc, Rb, Cs, Ba, Ta, HF, Th, and U and 10 rare earths elements: La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb, and Lu. The results were obtained with good precision and accuracy The knowledge of such concentrations is of great interest in geosciences. The values of the concentrations obtained can be extensively used in petrogenetic studies of those rocks, since they facilitate the evaluation and estimation of the extent of the main process, involved in the generation and differentiation of the melts from which the pegmatites were derivates

2005 dossier: granite; Dossier 2005: granite

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the geologic disposal of high-level and long-lived radioactive wastes in granite formations. Content: 1 - advantage of granitic formations for the geologic disposal; 2 - containers; 3 - design study of a disposal facility in granitic environment; 4 - understanding and modelling of granite; 5 - description of disposal concepts in granitic environment; 6 - long-term and safety aspects; 7 - conclusion. (J.S.)

Mortimer Hills pegmatite uranium prospect: a Rossing-type uranium deposit in the Gascoyne Province

International Nuclear Information System (INIS)

Carter, J.D.

1984-01-01

A uraninite-bearing pegmatite of large dimensions in the Gascoyne Province is described. The pegmatite is compared with the Rossing uranium ore body of South West Africa and the two are shown to have common characteristics. Exploration recommendations for Rossing-type uranium mineralization in the Gascoyne Province are made

Chevkinite-group minerals from granulite-facies metamorphic rocks and associated pegmatites of East Antarctica and South India

Science.gov (United States)

Belkin, Harvey E.; Macdonald, R.; Grew, E.S.

2009-01-01

Electron microprobe data are presented for chevkinite-group minerals from granulite-facies rocks and associated pegmatites of the Napier Complex and Mawson Station charnockite in East Antarctica and from the Eastern Ghats, South India. Their compositions conform to the general formula for this group, viz. A4BC2D2Si4O22 where, in the analysed specimens A = (rare-earth elements (REE), Ca, Y, Th), B = Fe2+, Mg, C = (Al, Mg, Ti, Fe2+, Fe3+, Zr) and D = Ti and plot within the perrierite field of the total Fe (as FeO) (wt.%) vs. CaO (wt.%) discriminator diagram of Macdonald and Belkin (2002). In contrast to most chevkinite-group minerals, the A site shows unusual enrichment in the MREE and HREE relative to the LREE and Ca. In one sample from the Napier Complex, Y is the dominant cation among the total REE + Y in the A site, the first reported case of Y-dominance in the chevkinite group. The minerals include the most Al-rich yet reported in the chevkinite group (≤9.15 wt.% Al2O3), sufficient to fill the C site in two samples. Conversely, the amount of Ti in these samples does not fill the D site, and, thus, some of the Al could be making up the deficiency at D, a situation not previously reported in the chevkinite group. Fe abundances are low, requiring Mg to occupy up to 45% of the B site. The chevkinite-group minerals analysed originated from three distinct parageneses: (1) pegmatites containing hornblende and orthopyroxene or garnet; (2) orthopyroxene-bearing gneiss and granulite; (3) highly aluminous paragneisses in which the associated minerals are relatively magnesian or aluminous. Chevkinite-group minerals from the first two parageneses have relatively high FeO content and low MgO and Al2O3 contents; their compositions plot in the field for mafic and intermediate igneous rocks. In contrast, chevkinite-group minerals from the third paragenesis are notably more aluminous and have greater Mg/Fe ratios

Contrasting styles of Sn-W mineralisation in peninsular Thailand and SW England

Science.gov (United States)

Manning, D. A. C.

1986-01-01

The Sn-W deposits of SW England and SE Asia are associated with crustally derived granitic rocks with late volatile-enriched (F, Li, B, P) differentiates. In peninsular Thailand, primary ores are principally pegmatitic, and hydrothermal vein systems are only locally important. In SW England, wolframite and cassiterite mainly occur in hydrothermal vein systems, and are associated with greisening and tourmalinisation; mineralised pegmatites are rare. These two styles of mineralisation are thought to arise because of differences in the character of late magmatic processes. In peninsular Thailand, late-stage tourmaline-bearing granitic rocks are enriched in B, but not Li and F, compared to earlier biotite granites. Similar late-stage granitic rocks occur also in SW England, but a later topaz granite, enriched in F, Li and P, also occurs. The Thai pegmatitic Sn-W deposits are thought to have formed by late magmatic crystallisation from an aqueous phase enriched in metals and derived by exsolution from a B and metal-rich magma, whereas the SW England mineralisation involved essentially post-magmatic hydrothermal processes. Complexing agents (especially F) and metals may have been derived from granitic or country rocks during hydrothermal circulation at the current level of emplacement.

Preliminary investigation of pegmatites in Obudu Area, Southeastern ...

African Journals Online (AJOL)

... Southern Obudu show low mineralization potentials of pegmatites of the Obudu Plateau. The elements in Obudu stream sediments show perfect, strong, moderate and weak correlations among themselves, indicative of variations in their mobility. Keywords: Correlation matrix, Major and Trace Elements, Stream sediments, ...

The infrared use on boron characterization from pegmatites ores

International Nuclear Information System (INIS)

Rocha Oliveiros, M.V.R.P. da; Neves, C.; Marques, J.

1987-01-01

The study of minerals of zoned pegmatites outcroping near of Governador Valadares, Minas Gerais State, using infrared absorption spectrometry and X-ray diffraction, allowed the identification of B proxing for Si in the tetrahedral sites of some minerals, such as muscovite, biotite, feldspars, quartz and garnets. The valence balancing was achieved with one monolayer of water in the structure as revealed by infrared absorption too. Infrared absorption is a very important research tool to disclose the proxing of B for Si in geological systems where this element occurs only at traces levels as we found in samples from the Ferreirinha pegmatite quarry. Only the mineral phases collected close to the quartz core show the absorption bands linked to the stretching of the B-O bond and to the H 2 O monolayer. (author) [pt

U-Pb isotopic dating of zircon from damaogou granite stock of Guangshigou uranium deposit in Danfeng area and it's significance

International Nuclear Information System (INIS)

Zuo Wenqian; Sha Yazhou; Chen Bing; Luo Zhongcheng; Zhang Zhanshi

2010-01-01

Danfeng area is an important pegmatite-type uranium production area in China, Guangshigou deposit is one of the biggest and the most important uranium deposit in this areas, Damaogou granite stock has a very close relationship with Guangshigou uranium deposit. Therefore the accurate formation dating and its evolution history of this stock is crucial for understanding the mineralization of this district. LA-ICP-MS U-Pb dating of zircon has been applied and yield the formation age of 418.3 ± 8.8 Ma of Damaogou stock, which is corresponding to the uranium mineralization age in Guangshigou deposit. The age of 1980.5 ± 19.47 Ma revealed by residual zircon might infer that Damaogou stock was derived from Qinling group, while the age of 465 Ma for the inner core of zircon grain E might represent the formation age of Huichizi gneissoid monzonitic granite. There was 30 Ma time gap between the formation of Huichizi pluton and Damaogou stock. (authors)

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

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

Uranium rich granite and uranium productive granite in south China

Energy Technology Data Exchange (ETDEWEB)

Mingyue, Feng; Debao, He [CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology, Beijing Research Institute of Uranium Geology (China)

2012-07-15

The paper briefly introduces the differences between uranium rich granite and uranium productive granite in the 5 provinces of South China, and discusses their main characteristics in 4 aspects, the uranium productive granite is highly developed in fracture, very strong in alteration, often occurred as two-mica granite and regularly developed with intermediate-basic and acid dikes. The above characteristics distinguish the uranium productive granite from the uranium rich granite. (authors)

Uranium rich granite and uranium productive granite in south China

International Nuclear Information System (INIS)

Feng Mingyue; He Debao

2012-01-01

The paper briefly introduces the differences between uranium rich granite and uranium productive granite in the 5 provinces of South China, and discusses their main characteristics in 4 aspects, the uranium productive granite is highly developed in fracture, very strong in alteration, often occurred as two-mica granite and regularly developed with intermediate-basic and acid dikes. The above characteristics distinguish the uranium productive granite from the uranium rich granite. (authors)

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.

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

Science.gov (United States)

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

2018-05-01

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

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)

The Early Jurassic Bokan Mountain peralkaline granitic complex (southeastern Alaska): geochemistry, petrogenesis and rare-metal mineralization

Science.gov (United States)

Dostal, Jaroslav; Kontak, Daniel J.; Karl, Susan M.

2014-01-01

The Early Jurassic (ca. 177 Ma) Bokan Mountain granitic complex, located on southern Prince of Wales Island, southernmost Alaska, cross-cuts Paleozoic igneous and metasedimentary rocks of the Alexander terrane of the North American Cordillera and was emplaced during a rifting event. The complex is a circular body (~3 km in diameter) of peralkaline granitic composition that has a core of arfvedsonite granite surrounded by aegirine granite. All the rock-forming minerals typically record a two-stage growth history and aegirine and arfvedsonite were the last major phases to crystalize from the magma. The Bokan granites and related dikes have SiO2 from 72 to 78 wt. %, high iron (FeO (tot) ~3-4.5 wt. %) and alkali (8-10 wt.%) concentrations with high FeO(tot)/(FeO(tot)+MgO) ratios (typically >0.95) and the molar Al2O3/(Na2O+K2O) ratio Nd values which are indicative of a mantle signature. The parent magma is inferred to be derived from an earlier metasomatized lithospheric mantle by low degrees of partial melting and generated the Bokan granitic melt through extensive fractional crystallization. The Bokan complex hosts significant rare-metal (REE, Y, U, Th, Nb) mineralization that is related to the late-stage crystallization history of the complex which involved the overlap of emplacement of felsic dikes, including pegmatite bodies, and generation of orthomagmatic fluids. The abundances of REE, HFSE, U and Th as well as Pb and Nd isotopic values of the pluton and dikes were modified by orthomagmatic hydrothermal fluids highly enriched in the strongly incompatible trace elements, which also escaped along zones of structural weakness to generate rare-metal mineralization. The latter was deposited in two stages: the first relates to the latest stage of magma emplacement and is associated with felsic dikes that intruded along the faults and shear deformations, whereas the second stage involved ingress of hydrothermal fluids that both remobilized and enriched the initial

Southern complex: geology, geochemistry, mineralogy, and mineral chemistry of selected uranium- and thorium-rich granites

International Nuclear Information System (INIS)

Hoffman, M.A.

1987-01-01

Four major rock groups are defined in the Southern Complex: the Bell Creek Granite (BCG), the Clotted Granitoids (CGR), the Albite Granite (AGR), and the Migmatite Complex. Metatexites of the Migmatite Complex are the oldest rocks and include paleosome of a metasedimentary and metavolcanic protolith represented by Banded Iron Formation, Banded Amphibolite, and Banded Gneisses, and interlayered or crosscutting leucogranites. The CGR span the range from metatexite to diatexite and represent in-situ partial melting of metapelitic layers in the protolith during intrusion of the BCG. The BCG cuts the migmatites, is locally cut by the CGR, and was derived by partial melting of a dominantly metasedimentary protolith at some depth below the presently exposed migmatites during a regional tectonothermal event. The Albite Granite is a 2km diameter, muscovite-fluorite-columbite-bearing intrusive stock that cuts all other major units. The thorium history of the BCG is a function of the history of monazite. The thorium history of the CGR is also dominated by monazite but the thorium content of this unit cannot be entirely accounted for by original restite monazite. The uranium history of the BCG and CGR was dominated by magmatic differentiation and post magmatic, metamorphic and supergene redistributions and is largely independent of the thorium history. The thorium and uranium history of the AGR was dominated by magmatic/deuteric processes unlike the BCG and CGR

Zircon U-Pb ages of Guyana greenstone-gneiss terrane

Energy Technology Data Exchange (ETDEWEB)

Gibbs, A.K. (Cornell Univ., Ithaca, NY (USA)); Olszewski, W.J. Jr. (New Hampshire Univ., Durham (USA))

1982-04-01

Isotopic U-Pb studies of zircons collected from weathered metagreywackes of the Barama-Mazaruni Supergroup of northern Guyana, South America, demonstrate an age of origin of ca. 2250 Ma. This is the best estimate for the age of the associated metavolcanic rocks. Zircons from weathered gneiss of the Bartica complex, adjacent to the volcanic-sedimentary belts, yield a similar age. The contiguous greenstone-gneiss terrane of eastern Venezuela is also of similar age and comparable greenstone-gneiss terranes of eastern Suriname and French Guiana are probably also of this age. Continental crust formation of a style closely comparable to that of the Canadian Archean occurred on a very widespread scale in the Lower Proterozoic of the Guiana shield. The lead losses from the weathered zircons are comparable to those from zircons from fresh rock from the adjacent terrane of Venezuela, and the advantages of field concentration from numerous saprolite exposures warrant use of such material in future geochronological studies of the region.

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.

The economic potential of some pegmatites from the Kenhardt area in relation to the trace-element content of their border zones

International Nuclear Information System (INIS)

Logan, C.

1976-01-01

Forty-one samples collected from the border zones of pegmatites were analysed for their lithium, beryllium, niobium, tantalum, uranium, thorium, bismuth, and tin contents. A technique developed previously was used in an attempt to classify the pegmatites as containing economically significant quantities of these rare elements or as barren. Twenty-one of the samples were collected from pegmatites that were known (from previous attempts to mine them) to be either economically significant or barren, and were used as a control group; 75 per cent of these samples were classified correctly. Of twenty samples from pegmatites of unknown economic potential, two were classified as economically significant. However, in view of the low rate of success of classification of the control group, it is considered that further refinement of the technique is necessary before classification of a pegmatite as containing economically significant amounts of minerals can be considered to be conclusive

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

Sample size clay kaolin of primary in pegmatites regions Junco Serido - PB and Equador - RN

International Nuclear Information System (INIS)

Meyer, M.F.; Sousa, J.B.M.; Sales, L.R.; Silva, P.A.S.; Lima, A.D.D.

2016-01-01

Kaolin is a clay formed mainly of kaolinite resulting from feldspar weathering or hydrothermal. This study aims to investigate the way of occurrence, kaolin particle size of the pegmatites of the Borborema Province Pegmatitic in the regions of Junco do Serido-PB and Ecuador-RN. These variables were analyzed considering granulometric intervals obtained from wet sieving of samples of pegmatite mines in the region. Kaolin was received using sieves of 200, 325, 400 and 500 mesh and the sieve fractions retained by generating statistical parameters histograms. kaolin particles are extremely fine and pass in its entirety through 500 mesh sieve. The characterization of minerals in fine fractions by diffraction of X-rays showed that the relative amount of sericite in fractions retained in sieves 400 and 500 mesh impairing the whiteness and mineralogical texture kaolin production. (author)

tectonic environments and rare metal mineralization in pegmatites of ...

African Journals Online (AJOL)

Admin

The discrimination diagrams: Rb versus Nb +Y and Nb versus Y, and Th/Ta ratio combined with field observations and empirical information from the literature were used to infer the tectonic environments and sources of the rare metal mineralization in the pegmatites of Komu area, southwestern Nigeria. The discrimination ...

Petrography, mineral chemistry and lithochemistry of the albitite and granite-gneissics rocks of anomaly 35 from Lagoa Real uranium province; Petrografia, quimica mineral e litoquimica do albitito e das rochas granito-gnaissicas da anomalia 35, provincia uranifera de Lagoa Real

Energy Technology Data Exchange (ETDEWEB)

Santos, Camila Marques dos

2016-07-01

In the northwestern portion of the Lagoa Real Uranium Province (LRUP), located in south-central Bahia, it is located one of the most promising uranium anomalies Brazil (an35, Gameleira I deposit), the reserves and proximity to the Cachoeira mine. Other anomalies of this sector (eg. 31 AN and AN34), are also considered strategic for the content of radioactive minerals and REE. The objective was to develop a study of a representative drill core of an35, where the main rocks PULR are present. The research focused on the mineralogical and chemical changes observed in the passages of a lithology to another, from the rock to the meta granitic albitites, through gneiss and transitional rocks, and making comparisons with similar lithologies sampled on testimonies of AN31 and 34. The granites are classified as hypersolvus coarse alkali-feldspar granite and are variably deformed. The main mineral assemblage in granites are perthitic orthoclase+hedenbergite+ quartz +hastingsite + biotite, and zircon, apatite, ilmenite and titanite are accessories. The reddening of these rocks are characterized by feldspars sericitization and hematitization and the presence of 'vazios'. The gneisses are mainly gray and reach milonitic to protomilonitics terms. These rocks have characteristics of subsolidus changes as swapped rims and metasomatic perthites. The tardi-magmatic association (amphibole+biotite) indicates final crystallization or late influx by superficial fluids resulting in an increase in water and volatiles, such as F and Cl in the system, which must also have carried rare-earth elementsGranites have geochemical affinity with A-type ferroan granite, A2, reduced and are post-collisional. Their patterns of incompatible elements and rare earths are comparable to Sao Timoteo Granite, but their petrographic features indicate that it is a less common granite facies. Albitites were classified as garnet albitites, magnetite albitites and biotite albitites. Contacts between

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

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

International Nuclear Information System (INIS)

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

1989-05-01

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

[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.

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

Magmatic evolution and controls on rare metal-enrichment of the Strange Lake A-type peralkaline granitic pluton, Québec-Labrador

Science.gov (United States)

Siegel, Karin; Vasyukova, Olga V.; Williams-Jones, Anthony E.

2018-05-01

granite, which contained a higher proportion of LREE-fluoride melt droplets. Further evolution in the magma chamber led to a transition from a miaskitic to an agpaitic composition. The transsolvus granite was intruded in the form of a low viscosity crystal mush of alkali feldspar, quartz, arfvedsonite (after appreciable crystallization of arfvedsonite) and LREE-fluoride melt droplets. Upon emplacement, arfvedsonite (and gagarinite-(Ce)) crystals segregated as cumulates in response to a combination of flow differentiation and gravity settling. The immiscible fluoride melt accumulated in a volatile-rich residual silicate magma, which migrated to the top of the pluton where it formed the F-REE-rich cores of highly mineralized pegmatites.

Origin of pegmatites and fluids at Ponta Negra (RJ, Brazil) during late- to post-collisional stages of the Gondwana Assembly

Science.gov (United States)

Bongiolo, Everton Marques; Renac, Christophe; Piza, Patricia d'Almeida de Toledo; Schmitt, Renata da Silva; Mexias, André Sampaio

2016-01-01

The Ponta Negra Pegmatites (PNP), part of a pegmatitic province in Rio de Janeiro State, Brazil, crop out along an intensely deformed, medium- to high-grade metamorphic area that is proximal to a crustal-scale thrust zone developed during the Brasiliano/Pan-African Orogeny. Fieldwork shows that the pegmatites formed in two distinct stages: (i) syn-collisional leucosome veins (Group I) conformable with the tectonic foliation of the gneissic host rocks and (ii) late- to post-collisional dykes (Group II) that cross-cut the same tectonic foliation at a high angle. In this paper, we use geochemistry of whole-rock and mineral separates (alkali-feldspar and biotite), fluid inclusion microthermometry and stable isotopic (δ18O, δD, δ13C) determinations on minerals (quartz, alkali-feldspar, biotite and magnetite) and fluid inclusions to provide insights into the composition of the pegmatite-forming melts, associated fluids, and their geotectonic significance. U-Pb SHRIMP dating of the Cajú syenogranite was performed to evaluate and compare the timing of magmatic events along the Cabo Frio Tectonic Domain as this is the closest post-collisional pluton to the studied pegmatites. The calculated temperature for the Group I syn-collisional veins (740 °C) is similar to previous estimates for the peak metamorphic conditions in the study area. Variations in the temperature of the Group II pegmatite dykes obtained from stable isotopes (380 to 720 °C), and microthermometric data from primary fluid inclusions with traces of N2 (Th = 280 to 360 °C), may reflect the thermodynamics of the pegmatite crystallization, exsolution textures and isotopic exchange. The composition of fluids in equilibrium within the pegmatite dykes consists of magmatic and metamorphic components. The minimum pressures calculated for the emplacement of the pegmatites are equivalent to a shallow crustal depth between 1.7 and 3.5 km, which corresponds to the exhumation of the orogen since the emplacement of

2005 dossier: granite

International Nuclear Information System (INIS)

2005-01-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the geologic disposal of high-level and long-lived radioactive wastes in granite formations. Content: 1 - advantage of granitic formations for the geologic disposal; 2 - containers; 3 - design study of a disposal facility in granitic environment; 4 - understanding and modelling of granite; 5 - description of disposal concepts in granitic environment; 6 - long-term and safety aspects; 7 - conclusion. (J.S.)

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.

Pb-Pb and U-Pb zircon ages of archean syntetocnic granites of the Carajas metallogenic province, northern Brazil

International Nuclear Information System (INIS)

Barros, Carlos Eduardo de Mesquita; Sardinha, Alex Souza; Barbosa, Jaime dos Passos de Oliveira; Krimski, Robert; Macambira, Moacir Jose Buenano

2001-01-01

The Carajas Metallogenic Province is located in the southeastern Amazonian Craton. It has been divided in two domains, the southernmost comprises the Rio Maria region and the northernmost corresponds to Caraj region (Souza et al. 1996). The former domain is made up of Archean greenstone sequences (2,97 Ga), TTG (2,9 Ga) and calc-alkaline granitoids (2,87 Ga) (Macambira and Lafon 1995, Leite et al. 1999, Althoff et al. 2000). The Carajas block is constituted of minor mafic granulites (3,00 Ga) and quartzofeldspathic gneisses (2,81 Ga), metavolcanosedimentary sequences (2,76 Ga) and granites (2,76 to 2,56 Ga) (Machado et al. 1991; Huhn et al. 1999, Pidgeon et al. 2000). Widespread anorogenic A-type granites are found in both areas (Docegeo 1988; Dall'Agnol et al. 1994). In the last two decades several authors (Lindenamyer et al. 1994, Barros and Barbey 1998, Huhn et al. 1999 and others) have emphasized the role of the Archean granite magmatism in the tectonicthermal evolution in the Carajas Province. In this paper we discuss the tectonic significance of the Pb- Pb and U-Pb ages obtained in some granitoids from the Carajas region. The Estrela Granite Complex and the granitoids located to the north of Parauapebas were dated by Pb- Pb evaporation zircon method (cf. Kober 1987). Data are presented considering 2σ ∼ . The Pb corrections have been done in the basis of the evolution model of Pb in double stage (cf. Stacey and Kramers 1975). U-Pb zircon method (cf. Krogh 1973, Stacey and Kramers 1975, Parrish 1987, Ludwuig 1999), recently put on routine in the Para-Iso laboratories, was employed to date the granite from the Serra do Rabo area. Analyses were carried on the Finnigan Mat 262 spectrometer (au)

Geochemical signature of columbite-tantalite and radiometric survey of radioactive pegmatites in the region of Parelhas, Rio Grande do Norte, Brazil

International Nuclear Information System (INIS)

Moura, Jorge Costa de

2013-01-01

This thesis is the result of geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area, located in the surroundings of the city of Parelhas in the region of the Serra da Borborema, is well known for its thousands of pegmatitic bodies exploited in primitive mines called 'garimpos'. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of the ratio U/Th versus Nb 2 O 5 /Ta 2 O 5 provides geochemical signatures (analytical fingerprints) for the source location of such ore. A test of the new method with coltan samples of commercial batches from the Brazilian states Amapa and Rondonia also generated distinct geochemical signatures. A radiometric survey (CPS) was carried out in several mines and pegmatites to study the environmental impact of gamma radiation. It included in situ measurements of pegmatite walls, host rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and environmental gamma radiation therefore generally is not enhanced to a dangerous level. (author)

Uranium in granites

International Nuclear Information System (INIS)

Maurice, Y.T.

1982-01-01

Recent research activities of the Canadian Uranium in Granites Study are presented in 18 papers and 3 abstracts. 'Granites' is used as a generic term for granitoids, granitic rocks, and plutonic rocks

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Directory of Open Access Journals (Sweden)

L. Dai

2018-03-01

Full Text Available The electrical conductivity of gneiss samples with different chemical compositions (WA = Na2O + K2O + CaO  =  7.12, 7.27 and 7.64 % weight percent was measured using a complex impedance spectroscopic technique at 623–1073 K and 1.5 GPa and a frequency range of 10−1 to 106 Hz. Simultaneously, a pressure effect on the electrical conductivity was also determined for the WA = 7.12 % gneiss. The results indicated that the gneiss conductivities markedly increase with total alkali and calcium ion content. The sample conductivity and temperature conform to an Arrhenius relationship within a certain temperature range. The influence of pressure on gneiss conductivity is weaker than temperature, although conductivity still increases with pressure. According to various ranges of activation enthalpy (0.35–0.52 and 0.76–0.87 eV at 1.5 GPa, two main conduction mechanisms are suggested that dominate the electrical conductivity of gneiss: impurity conduction in the lower-temperature region and ionic conduction (charge carriers are K+, Na+ and Ca2+ in the higher-temperature region. The electrical conductivity of gneiss with various chemical compositions cannot be used to interpret the high conductivity anomalies in the Dabie–Sulu ultrahigh-pressure metamorphic belt. However, the conductivity–depth profiles for gneiss may provide an important constraint on the interpretation of field magnetotelluric conductivity results in the regional metamorphic belt.

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.)

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-15

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

OH-point defects in quartz in B- and Li-bearing systems and their application to pegmatites

Science.gov (United States)

Baron, M. A.; Stalder, R.; Konzett, J.; Hauzenberger, C. A.

2015-01-01

OH incorporation in quartz in Al-, B- and Li-bearing systems (granitic systems containing tourmaline or spodumene) was studied experimentally in order to investigate the effect of pressure, temperature and chemical impurities on the generation of OH-defects. High-pressure experiments were carried out at pressures between 5 and 25 kbar and temperatures between 800 and 900 °C, and OH-contents in quartz were calculated from IR absorption spectra measured on oriented quartz crystals. IR absorption features were assigned to impurity substitutions, such as AlOH (3,420, 3,379 and 3,315 cm-1) and BOH (3,595 cm-1), LiOH (3,483 cm-1), and hydrogarnet substitution (4H)Si defects (3,583 cm-1). Results indicate a negative correlation of incorporated Al-specific OH-defect content versus pressure (630 ± 130 wt ppm H2O at 5 kbar to 102 ± 6 wt ppm H2O at 25 kbar), but no clear correlation of B-specific OH-defects with pressure. In runs initially containing spodumene, virtually OH-free quartzes were observed at pressures ≥10 kbar, where impurity cations compensate each other forming an anhydrous eucryptite-defect component. In contrast, at 5 kbar, both Li- ad Al-specific OH-defects are observed (corresponding to 470 ± 75 wt ppm H2O). Results from this study may therefore be used to monitor formation conditions of quartz in terms of pressure and trace metal saturation of the crystallizing petrological system. IR spectra obtained from natural quartz grains from a tourmaline-bearing pegmatite exhibit B- and Al-related OH-bands. The B-related OH-band is also exhibited in quartz from a tourmaline + spodumene-bearing pegmatite. Li- and Al-related OH-bands, however, are subordinate or not observed at all in the spodumene-bearing system, which suggests that OH-vibrations do not reflect absolute Li-contents in quartz due to efficient coupled substitution involving Al. Data from experimental runs and natural specimens indicate that the B-related OH-band can be used as a rough proxy for

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

Science.gov (United States)

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

2009-01-01

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

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...

Geochemical signature of columbite-tantalite and environmental impact of radioactive pegmatite mining in the Parelhas region, Rio Grande do Norte, Northeast Brazil

International Nuclear Information System (INIS)

Moura, Jorge Costa de; Cruz, Paulo R.; Pereira, Valmir; Ludka, Isabel P.; Mendes, Julio C.

2013-01-01

This article comprises geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area is located in the surroundings of the city of Parelhas, in the geotectonic Province of Borborema. It is well known for its thousands of pegmatitic bodies exploited in primitive mines called garimpos. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of U/Th vs. Nb 2 O 5 /Ta 2 O 5 provides geochemical signatures (analytical fingerprints) for the source location of such ore. The new method was tested with coltan samples of commercial batches from the Brazilian states of Amapa and Rondonia and also generated distinct geochemical signatures. A radiometric survey (CPS) to study the environmental impact of gamma radiation was also carried out in several mines and pegmatites. It included in situ measurements of pegmatite walls, enclosing rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and therefore environmental gamma radiation generally is not enhanced to a dangerous level. (author)

Hydrothermal modification of host rock geochemistry within Mo-Cu porphyry deposits in the Galway Granite, western Ireland

Science.gov (United States)

Tolometti, Gavin; McCarthy, Will

2016-04-01

Hydrothermal alteration of host rock is a process inherent to the formation of porphyry deposits and the required geochemical modification of these rocks is regularly used to indicate proximity to an economic target. The study involves examining the changes in major, minor and trace elements to understand how the quartz vein structures have influenced the chemistry within the Murvey Granite that forms part of the 380-425Ma Galway Granite Complex in western Ireland. Molybdenite mineralisation within the Galway Granite Complex occurred in close association with protracted magmatism at 423Ma, 410Ma, 407Ma, 397Ma and 383Ma and this continues to be of interest to active exploration. The aim of the project is to characterize hydrothermal alteration associated with Mo-Cu mineralisation and identify geochemical indicators that can guide future exploration work. The Murvey Granite intrudes metagabbros and gneiss that form part of the Connemara Metamorphic complex. The intrusion is composed of albite-rich pink granite, garnetiferous granite and phenocrytic orthoclase granite. Minor doleritic dykes post-date the Murvey Granite, found commonly along its margins. Field mapping shows that the granite is truncated to the east by a regional NW-SE fault and that several small subparallel structures host Mo-Cu bearing quartz veins. Petrographic observations show heavily sericitized feldspars and plagioclase and biotite which have undergone kaolinization and chloritisation. Chalcopyrite minerals are fine grained, heavily fractured found crystallized along the margins of the feldspars and 2mm pyrite crystals. Molybdenite are also seen along the margins of the feldspars, crystallized whilst the Murvey Granite cooled. Field and petrographic observations indicate that mineralisation is structurally controlled by NW-SE faults from the selected mineralization zones and conjugate NE-SW cross cutting the Murvey Granite. Both fault orientations exhibit quartz and disseminated molybdenite

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

Science.gov (United States)

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

2009-01-01

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

The Mesoarchean Tiejiashan-Gongchangling potassic granite in the Anshan-Benxi area, North China Craton: Origin by recycling of Paleo- to Eoarchean crust from U-Pb-Nd-Hf-O isotopic studies

Science.gov (United States)

Dong, Chunyan; Wan, Yusheng; Xie, Hangqiang; Nutman, Allen P.; Xie, Shiwen; Liu, Shoujie; Ma, Mingzhu; Liu, Dunyi

2017-10-01

Mesoarchean and older potassic granites are important indicators of recycling of ancient continental crust early in Earth's history. This study of integrated whole rock and zircon geochemistry and geochronology reports the age and identification of the source materials of the > 200 km2 Mesoarchean Tiejiashan-Gongchangling granite in the Anshan-Benxi area, North China Craton, the largest pre-Neoarchean granite domain in the craton. SHRIMP U-Pb zircon dating on 15 samples indicates the magmatic crystallization of the granites between 2.95 and 3.0 Ga and reveals a superimposed tectonothermal event at 2.91 Ga. The granites are characterized by high SiO2 and K2O, low CaO, FeOt, MgO and TiO2 with peraluminuous features. They show large variations in (La/Yb)n and strong negative Eu and Ba anomalies and Nb, P and Ti depletions. Whole rock Nd and magmatic zircon Hf isotopic compositions show large variations, but with most having εNd(t) and εHf(t) values recycling of Paleo- to Eoarchean continental material in an intracontinental environment, with little if any contribution from Mesoarchean mantle sources. The sources could be predominantly unaltered ancient gneisses, together with yet to be identified Paleo- to Eoarchean materials affected by early low temperature alteration (weathered rocks or clastic sediment).

Granites and granitoids of the southern region - Granite molybdenite system

International Nuclear Information System (INIS)

Issler, R.S.

1987-01-01

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

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

Science.gov (United States)

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

2009-01-01

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

Origin and evolution of Gneiss-Charnockite rocks of Dharmapuri District, Tamil Nadu, India

Science.gov (United States)

Rao, D. Rameshwar; Narayana, B. L.

1988-01-01

A low- to high-grade transition area in Dharmapuri district was investigated petrologically and geochemically. The investigation confirmed the presence of a continuous section through a former lower crust, with felsic charnockites predominating the lower part and felsic gneisses the upper part. The structure of original gneisses is preserved in charnockites and the latter show petrographic evidence for prograde metamorphism. The prograde metamorphism is of isochemical nature as revealed by the similarity of compositions of tonalitic gneisses and tonalitic charnockites. However, the depletion of LIL elements particularly Rb, caused variation in K/Rb ratios from low values (345) in the gneisses in upper part to higher values (1775) in the charnockites in the lower crust. This variation in K/Rb ratio in a north to south traverse is related to the progressive break-down of hydrous minerals under decreasing H2O and increasing CO2 fluid conditions. Metasomatism and partial melting has also taken place to a limited extent along shear planes and weak zones. During cooling the H2O circulation affected substantial auto-regression in the transition zone resulting in the formation of second generation biotite.

Geochemical signature of columbite-tantalite and environmental impact of radioactive pegmatite mining in the Parelhas region, Rio Grande do Norte, Northeast Brazil

Energy Technology Data Exchange (ETDEWEB)

Moura, Jorge Costa de; Cruz, Paulo R.; Pereira, Valmir, E-mail: jcmoura@cnen.gov.br, E-mail: pcruz@cnen.gov.br, E-mail: vpereira@cnen.gov.br [Comissao Nacional de Energia Nuclear (CNEN-RJ), Rio de Janeiro, RJ (Brazil); Ludka, Isabel P.; Mendes, Julio C., E-mail: ludka@geologia.ufrj.br, E-mail: julio@geologia.ufrj.br [Universidade Federal de Rio do Janeiro (CCMN/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Ciencias Matematicas e da Natureza. Dept. de Geologia

2013-07-01

This article comprises geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area is located in the surroundings of the city of Parelhas, in the geotectonic Province of Borborema. It is well known for its thousands of pegmatitic bodies exploited in primitive mines called garimpos. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of U/Th vs. Nb{sub 2}O{sub 5}/Ta{sub 2}O{sub 5} provides geochemical signatures (analytical fingerprints) for the source location of such ore. The new method was tested with coltan samples of commercial batches from the Brazilian states of Amapa and Rondonia and also generated distinct geochemical signatures. A radiometric survey (CPS) to study the environmental impact of gamma radiation was also carried out in several mines and pegmatites. It included in situ measurements of pegmatite walls, enclosing rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and therefore environmental gamma radiation generally is not enhanced to a dangerous level. (author)

Characterization of fluid inclusions from mineralized pegmatites of the Damara Belt, Namibia: insight into late-stage fluid evolution and implications for mineralization

Science.gov (United States)

Ashworth, Luisa; Kinnaird, Judith Ann; Nex, Paul Andrew Martin; Erasmus, Rudolph Marthinus; Przybyłowicz, Wojciech Józef

2018-05-01

Mineralized NYF and LCT pegmatites occur throughout the northeast-trending Neoproterozoic Damara Belt, Namibia. Mineralization in the pegmatites varies geographically, from the northeast, where they are enriched in Li-Be, to the southwest, where they also contain notable Sn and U. Similar fluid inclusion populations occur throughout the pegmatites, regardless of their respective metal enrichments, and primary fluid inclusion textures were destroyed by continued fluid activity. Pseudosecondary to secondary inclusions are aqueo-carbonic, carbonic, and aqueous in composition, and have been divided into five types. The earliest populations are saline (>26.3 eq. wt.% NaCl), homogenizing at temperatures in excess of 300 °C. Their carbonic phase is composed of CO2, with minor CH4, and micro-elemental mapping indicates they contain trace metals, including Ca, Fe, Zn, Cu, and K. Type 3 inclusions formed later, homogenize at 325 °C, and are less saline, with a carbonic phase composed of CO2. Type 4 carbonic inclusions are composed of pure CO2, and represent the latest stages of fluid evolution, while Type 5 aqueous inclusions are believed to be unrelated to the crystallization of the pegmatites, and rather the result of regional Cretaceous magmatism, or the ingress of meteoric water. The similarities in fluid inclusion populations observed in the pegmatites suggest that differences in mineralization were driven by magma composition rather than fluid activity alone, however saline fluids facilitated the enrichment and deposition of metals during the late stages of crystallization. Furthermore, the similarities between fluid inclusion populations in different pegmatites suggests they share a similar fluid evolution.

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

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

Geochronological determination of the pegmatites from Rio de Janeiro State

International Nuclear Information System (INIS)

Oliveira Menezes, S. de; Cordani, U.G.; Teixeira, W.

1987-01-01

Samples of muscovite and plagioclase were collected from the pegmatites located in the counties of Niteroi and Sao Goncalo, State of Rio de Janeiro. Geochronological Research Center of the University of Sao Paulo has selected some samples for pottasium-argon and rubidium-strontium analysis. Three samples of muscovite analysed by K-Ar dating method lave ages between 437+-13 and 447+-16 m.y and two others, by Rb-Sr dating method, gave 495+-15 and 500+-13 m.y.. One sample of plagioclase analysed by K-Ar method gave age of 337+-16 m.y.. In this paper, the locations of the analysed samples are described and the samples of vicinity are listed in the Appendix. Interpretation of the radiometrio ages and discussion of results are made. Taking into account the results of Table l and the geologic setting of the pegmatities sample in Niteroi and Sao Goncalo, we way conclude that all cooling ages (440-550 m.y.) are related to the Brasiliano Orogeny. These pegmatites are regard as having same geological history and their ages are supposed 500 m.y.. (author) [pt

Core drilling of drillhole ONK-PVA8 in ONKALO at Olkiluoto 2010

International Nuclear Information System (INIS)

Toropainen, V.

2010-12-01

Suomen Malmi Oy (Smoy) core drilled a drillhole for groundwater monitoring station in ONKALO at Eurajoki, Olkiluoto in July 2010. The groundwater monitoring stations are used for monitoring changes in groundwater conditions. The identification number of the hole is ONK-PVA8, and the length of the drillhole is 17.74 m. The drillhole is 75.7 mm by diameter. The drillhole was drilled in a niche of the access tunnel at chainage 2935. 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. 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 diatexitic gneiss and pegmatitic granite. The average fracture frequency in drill core ONK-PVA8 is 1.7 pcs / m and the average RQD value 96.0 %. (orig.)

ONKALO POSE experiment. Determination of in situ thermal properties of rocks in drillholes ONK-PP340, ONK-PP346, ONK-PP398, ONK-PP399, ONK-PP405, ONK-PP411

International Nuclear Information System (INIS)

Korpisalo, A.; Suppala, I.; Kukkonen, I.; Koskinen, T.

2014-12-01

The thermal drillhole device TERO76 (for diameter 76 mm drillholes) used in this study for determining thermal properties of rocks in situ was developed at the Geological Survey of Finland for Posiva in the early 2000's. The measurement method is based on monitoring the temperature variation of a cylindrical heating source in a drillhole. The measured data can be interpreted with full numerical 3D codes as well as with an analytical infinite line source method, a 'rapid interpretation tool', which makes it possible to calculate the first estimates of thermal properties already in the field. Both methods were applied in this study. Because of the unique measurement geometry, only the thermal conductivities can accurately be estimated using the late times of heating periods (accuracy ± 2%). The cylindrical source method cannot directly give the thermal diffusivity or volumetric heat capacity at a sufficient accuracy. Thermal diffusivities are estimated by using the average specific heat capacities and densities of the rock type at the measurement point, or the laboratory results on the general diffusivity-conductivity relationship for different Olkiluoto rock types. The latter technique was applied in this study. Thermal properties were determined in four shallow drillholes (ONK-PP398, ONK-PP399, ONK-PP405, ONK-PP411) located in the ONKALO investigation niche 3 (ONK-TKU-3620) at the access tunnel chainage of 3620 m. The measurement positions (17) were strictly selected on the grounds that approximately an equal number of in situ results would be available in both veined gneiss (VGN) and pegmatitic granite (PGR). The results from the drillholes ONK-PP340 and ONK-PP346 measured in a previous project are also presented in this report. In veined gneiss, the average conductivity determined with numerical model of the present measurements is 3.49 (2.83) Wm -1 K -1 and diffusivity 1.89 x 10 -6 (1.3 10 -6 ) m 2 s -1 . The laboratory values of Olkiluoto rocks

Uranium occurrences in the Granite Zone

International Nuclear Information System (INIS)

Nyegaard, P.; Armour-Brown, A.

1986-04-01

This report describes the work and results of the South Greenland Exploration Programme (Sydex) during the 1984 field season in the Granite Zone, and discusses the results and conclusions that can be drawn from them. It also contains a structural analysis of the Ivigtut-Julianehaab region, which will help in future exploration by indicating the likely directions of uraniferous faults and fractures. It also includes suggestions for future work with both exploration and scientific aspects. The project was carried out by the Geological Survey Greenland (GGU) in co-operation with Risoe National Laboratory. It was financed by the Danish Ministry of Energy. The structural analysis was carried out using previous geological maps, our own field observations and an analysis of lineament frequencies taken from aerial photographs and satellite images. Major lineaments in the region are due to E-W sinistral wrench faults and NE-SW normal faults. Analysis of the minor lineaments showed that the region could be divided into three blocks which have each reacted differently to the same regional stress field which was active throughout the Gardar period. A northern block which has been influenced by an older system of faults in the Archaean gneiss, a central block dominated by a graben, and a southern block where there is a change to a less intensively faulted area. 2 maps, 27 refs. (EG)

Mineralogical Control on Microbial Diversity in a Weathered Granite?

Science.gov (United States)

Gleeson, D.; Clipson, N.; McDermott, F.

2003-12-01

Mineral transformation reactions and the behaviour of metals in rock and soils are affected not only by physicochemical parameters but also by biological factors, particularly by microbial activity. Microbes inhabit a wide range of niches in surface and subsurface environments, with mineral-microbe interactions being generally poorly understood. The focus of this study is to elucidate the role of microbial activity in the weathering of common silicate minerals in granitic rocks. A site in the Wicklow Mountains (Ireland) has been identified that consists of an outcrop surface of Caledonian (ca. 400 million years old) pegmatitic granite from which large intact crystals of variably weathered muscovite, plagioclase, K-feldspar and quartz were sampled, together with whole-rock granite. Culture-based microbial approaches have been widely used to profile microbial communities, particularly from copiotrophic environments, but it is now well established that for oligotrophic environments such as those that would be expected on weathering faces, perhaps less than 1% of microbial diversity can be profiled by cultural means. A number of culture-independent molecular based approaches have been developed to profile microbial diversity and community structure. These rely on successfully isolating environmental DNA from a given environment, followed by the use of the polymerase chain reaction (PCR) to amplify the typically small quantities of extracted DNA. Amplified DNA can then be analysed using cloning based approaches as well as community fingerprinting systems such as denaturing gradient gel electrophoresis (DGGE), terminal restriction fragment length polymorphism (TRFLP) and ribosomal intergenic spacer analysis (RISA). Community DNA was extracted and the intergenic spacer region (ITS) between small (16S) and large (23S) bacterial subunit rRNA genes was amplified. RISA fragments were then electrophoresed on a non-denaturing polyacrylamide gel. Banding patterns suggest that

New radiometric ages on gneisses of the Oliverian domes in New Hampshire and Massachusetts

International Nuclear Information System (INIS)

Zartman, R.E.; Leo, G.W.

1985-01-01

Gneissic plutons of the Oliverian domes, mantled by Ammonoosuc Volcanics, are located along the axis of the Bronson Hill anticlinorium from New Hampshire to Connecticut. The contacts between the plutonic and volcanic rocks appear to be concordant on a regional scale, but gneiss intrudes the volcanics in several domes. Available radiometric and fossil evidence suggests that the Ammonoosuc Volcanics have a Middle Ordovician age but are somewhat older than the Oliverian gneisses. New U-Pb zircon data from Oliverian gneisses of six domes plot on a concordia diagram as an almost colinear array that yields an upper intercept age of about 444 m.y. The plotted data vary from nearly concordant to moderately discordant, the degree of discordance, correlating with 207 Pb/ 206 Pb ages that range from 459 to 415 m.y. The pattern of discordance does not relate to the uranium contents of the zircons nor to the geographic distribution of the domes. If 207 Pb/ 206 Pb ages are considered individually without an assumed consanguinity of the units, however, they do not find particular support in geologic relationships. Thus, they prefer the concordia intercept age of 444 +/- 8 m.y. for the suite as the best estimate for the time of crystallization of the Oliverian gneisses. Possibly, the Whitefield, Gneiss in the Jefferson dome represents a 10 to 15 m.y. older unit, although they are cautious about claiming such resolution with the present data

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

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.)

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.

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 ...

The late Variscan ferroan granite magmatism of southern Sardinia: inferences from Mo metallogenesis

Science.gov (United States)

Naitza, Stefano; Conte, Aida Maria; Cuccuru, Stefano; Fadda, Sandro; Fiori, Maddalena; Oggiano, Giacomo; Secchi, Francesco

2017-04-01

Metallogeny is a powerful tool to investigate crustal evolution; a good example is offered by the Variscan basement of Sardinia and its Mo deposits. Mo ores are poorly represented in Variscan metallogenic provinces of Europe: however, in Sardinia, numerous small Mo deposits, often associated to Sn, W and F ores, are present, invariably related to an early Permian intrusive peak bracketed at about 290 Ma (Fadda et al., 2015; Naitza et al., 2017). In Sardinia, two main magmatic peaks have been schematized at pre-300 and 290 Ma. In southern Sardinia, the 290 magmatic peak is made up of several intrusive F-bearing rock-suites (Conte et al., 2016), belonging to ilmenite series, showing a slight peraluminous character and mostly classifiable as ferroan granites (sensu Frost and Frost, 2011). Mo-bearing granites form a distinct suite of relatively small plutons, emplaced at very shallow depth (about 1kb) in an exhumed Variscan low-grade basement. Peculiar characters of Mo-bearing granites are the occurrence of greisenized microgranite and granophyre cupolas, with fayalite-bearing pegmatites, and ilmenite, xenotime-(Y), monazite, fluorite, and local topaz as accessory phases. Recently, Conte et al. (2016) interpreted these granites as originated by partial melting of low crustal felsic metaigneous photoliths enriched in granophiles (Mo, Sn, W). Mo ores occur as: a) endo- and exo- quartz-muscovite greisens with molybdenite±Fe-Cu sulphides, and b) quartz-molybdenite±wolframite±Fe-Cu-Zn sulphides±fluorite±topaz hydrothermal veins and stockworks, hosted in granites or in country rocks. Redox state of magmas exerts a strong control on Mo metallogeny, as in Mo districts worldwide ores are usually hosted by high-fO2 magnetite series intrusions (Ishihara, 1981). The close field association of Sardinian Mo mineralization with ferroan, low-fO2 ilmenite-series granites may be explained in terms of Mo-enriched crustal sources of magmas, and very efficient geochemical

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

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

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.

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.)

Reconnaissance Rb-Sr dates for the Himalayan Central Gneiss, Northwest India

International Nuclear Information System (INIS)

Powell, C. McA.; Crawford, A.R.; Armstrong, R.L.; Wynne-Edwards, H.R.; Prakash, R.

1979-01-01

Rb-Sr analysis of whole-rock samples and biotite and biotite - or muscovite - whole rock pairs suggests that the Himalayan Central Gneiss in the crystalline nappes of the Lesser Himalaya and the root zone in the High Himalaya was formed during Oligocene to mid-Miocene times by deformation and metamorphism of older rocks, including Precambrian. Four whole-rock samples from the Almora-Askot thrust sheets define an isochron of 1620 +- 90 Ma with a high initial 87 Sr/ 86 Sr ratio of 0.749 +- 0.007; other single whole-rock samples give dates in the range 268 to 1065 Ma, assuming an initial 87 Sr/ 86 Sr ratio of 0.704. These dates are considered to represent either depositional or early instructive/deformational events. Three biotite-whole rock pairs from the root zone of the Himalayan Central Gneiss in Lahaul give aqes of 16 to 19 Ma and two muscovite-whole rock pairs give similar mid-Cenozoic ages (12 and 26 Ma); two muscovite-whole rock pairs give Paleozoic ages, which suggests incomplete resetting of the muscovite by the Cenozoic metamorphism. The pattern of ages is similar to recent results from adjacent areas, and consistent with models of Himalayan tectonics involving formation of the Central Gneiss from older Indian crust during the mid-Cenozoic. (auth.)

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

Directory of Open Access Journals (Sweden)

Ferreira, J. A.

2014-12-01

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

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

same shear zone. The observation that pst is preferentially sheared indicates that it is weaker than the host rock, although their bulk compositions are about the same, suggesting that the governing factors for localization are the finer grain size and the elongate, nearly planar geometry of the original pst generation zone. The same may be true of the sheared dolerite dykes, which are long, narrow and generally finer grained than the surrounding gneiss or granite. Although quartz-rich pegmatites are not preferred sites of localization, quartzo-feldspathic mylonites are fully recrystallized with a relatively coarse grain size (typically > 50 microns) typical of rather low long-term flow stress. We therefore propose that localization in the lower crust only occurs on long planar layers with a finer grain size that can promote weakening by grain-size sensitive creep. Coarser-grained lithological layers and boundaries are not exploited during the initiation of a shear zone and, in particular, quartz-rich layers are not preferentially sheared.

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

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

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.

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

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

International Nuclear Information System (INIS)

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

1998-01-01

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

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 ...

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

International Nuclear Information System (INIS)

Baidya, Tapan Kumar

2013-01-01

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

Re-Os dating of molybdenites from Southern India: implication for Pan-African metallogeny

International Nuclear Information System (INIS)

Santosh, M.; Suzuki, Katsuhiko; Masuda, Akimasa

1994-01-01

Rhenium-osmium (Re-Os) dating of two molybdenite samples from the alkali granite and pegmatite of Ambalavayal in northern Kerala (S. India) yielded ages of 567 ±28 Ma and 566±77 Ma, respectively. These ages closely compare with the previously determined Rb-Sr whole rock age of 595±20 Ma Rb-Sr for granite, and K-Ar biotite age of 560±30 Ma for the pegmatite. Our study provides the first direct determination of the timing of ore mineralization associated with felsic magmatism in southern India, and reveals the fingerprints of a prominent Pan-African metallogenic event. This timing coincides with the formation of rare metal and gemstone-bearing pegmatites in different parts of southern India, Sri Lanka, Madagascar and East Antarctica. In most cases, the mineralizations are genetically related to felsic magmas emplaced along structural conduits, suggesting that the magmatism and metallogeny are related to deep-seated extension in the cratonized crustal segments of the Gondwana assembly. (author). 20 refs., 3 figs., 1 tab

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.)

Fluid inclusion study of radioactive granite and cherty cataclasite in the Southeastern part of Nanded district, Maharashtra: implications for the uranium mineralisation

International Nuclear Information System (INIS)

Banerjee, Rahul; Shivkumar, K.; Thomas, Tresa; Thomas, Jugina; Pandian, M.S.

2013-01-01

Southeastern part of Nanded district, Maharashtra exposes Palaeoproterozoic granitoids, representing the younger phase of Peninsular Gneissic Complex (PGC), mark the northeastern extension of Eastern Dharwar Craton. These granitoids are predominantly pink/grey granites, which are traversed by younger phosphatic cherty cataclasites close to the Deccan Trap capping. They are also affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations, especially close to fault/shear zones. A number of N-S to NNE-SSW, NE-SW, NW-SE and E-W trending lineaments marked by faults/fractures/shear zones and dykes are delineated in this granitic terrain. Among these, NE-SW and NNE-SSW faults/shear zones affecting granitoids and cherty cataclasites in Shahpur-Sujayatpur and Thadisaoli area have recorded significant uranium anomalies (Granitoids: upto 1% U 3 O 8 and 0.20% ThO 2 ; Cherty cataclasites upto 0.11% U 3 O 8 and <0.005% ThO 2 ) and enrichment in rare metal and rare earth element content (Nb-77ppm, Y-111 ppm, Zr-432ppm; n=9 and total REE-1167ppm; n=3). Presence of discrete uranium/thorium minerals (uraninite, b-uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite are responsible for radioactivity in granitoids while phosphatic material accounts for radioactivity in cherty cataclasites

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

Fission track dating and uranium estimation in pegmatitic minerals of Rajasthan state (India)

Energy Technology Data Exchange (ETDEWEB)

Singh, S; Virk, H S [Punjabi Univ., Patiala (India). Dept. of Physics

1978-12-01

Fission track geochronology of muscovite samples collected from some pegmatitic mines of Bhilwara and Ajmer districts of Rajasthan state (India) has been discussed. The ages obtained suggest the occurrence of Delhi Orogenic Cycle as the last major metamorphic activity in the region. The atomic fraction of uranium in muscovite samples is less than 1 p.p.b.

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 ...

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.)

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.)

Petrology, geochemistry and LA-ICP-MS U-Pb geochronology of Paleoproterozoic basement rocks in Bangladesh: An evaluation of calc-alkaline magmatism and implication for Columbia supercontinent amalgamation

Science.gov (United States)

Hossain, Ismail; Tsunogae, Toshiaki; Tsutsumi, Yukiyasu; Takahashi, Kazuki

2018-05-01

The Paleoproterozoic (1.7 Ga) basement rocks from Maddhapara, Bangladesh show a large range of chemical variations (e.g. SiO2 = 50.7-74.7%) and include diorite, quartz diorite, monzodiorite, quartz monzonite and granite. The pluton overall displays metaluminous, calc-alkaline orogenic suite; mostly I-type suites formed within subduction-related magmatism. The observed major elements show general trends for fractional crystallization. Trace element contents also indicate the possibility of a fractionation or assimilation; explain the entire variation from diorite to monzonite, even granite. The pluton may have evolved the unique chemical features by a process that included partial melting of calc-alkaline lithologies and mixing of mantle-derived magmas, followed by fractional crystallization, and by assimilation of country rocks. The pluton shows evidence of crystal fractionation involving largely plagioclase, amphibole and possibly biotite. Some of the fractionated magmas may have mixed with more potassic melts from distinct parts of the continental lithosphere to produce granites and/or pegmatites. New geochronological results of granitic pegmatite (1722 ± 10 Ma) are indisputably consistent with diorite and tonalite and those data showing credible geochronological sequence (i.e., diorite - tonalite - granitic pegmatite). Identical Paleoproterozoic age (1.7 Ga) with distinctive magmatism of the Maddhapara basement rocks have agreeable relationship with the CITZ, India. The consistent magmatism is also common in the Transamazonian of South America, Trans-Hudson orogeny in North America, Bohemian Massif and the Svecofennian, Poland, have identified the sequential growth of the continent through the amalgamation of juvenile terrains, succeeded by a major collisional orogeny. Such Paleoproterozoic subduction-related orogens in Australia have similar counterparts in Antarctica and other part of the world. These types of Paleoproterozoic magmatism dominantly contributed

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

Science.gov (United States)

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

Different periods of uranium and thorium occurrence in Madagascar (1960)

International Nuclear Information System (INIS)

Moreau, M.

1960-01-01

In Madagascar, the first typical occurrences of thorium and uranium are about 500 million years old. Previously thorium and uranium were rather concentrated in the granitic and charnockitic zones, chiefly in minerals such as monazite, apatite and zircon. At the end of the Precambrian period, metasomatic granites occur especially in the anticlinal series (Andriba orthite granite). The granitization is followed by the formation of the main pegmatitic areas in the Island with Th-U niobotantalates, uraninite and beryl. The pegmatites are well developed in the synclinal series with a poor migmatization or no migmatization at all. In the same time a large uranium and thorium province with uranothorianite deposits appears within the calcomagnesian series of the Southern part of Madagascar. Later, large amounts of monazite were carried down to the detritic Karroo sediments during tile erosion of the metamorphic precambrian rocks. Monazite has been concentrated again by frequent marine incursions, till the present time. In the medium Karroo, near Folakara, uranium minerals occur in direct relation with carbonaceous material. Finally we must note the uranium occurrence in the pleistocene carbonaceous shales of Antsirabe basin, in contact with crystalline rocks. (author) [fr

Heat production in granitic rocks

DEFF Research Database (Denmark)

Artemieva, Irina; Thybo, Hans; Jakobsen, Kiki

2017-01-01

Granitic rocks play special role in the dynamics and evolution of the Earth and its thermal regime. First, their compositional variability, reflected in the distribution of concentrations of radiogenic elements, provides constraints on global differentiation processes and large scale planetary...... evolution, where emplacement of granites is considered a particularly important process for the formation of continental crust. Second, heat production by radioactive decay is among the main heat sources in the Earth. Therefore knowledge of heat production in granitic rocks is pivotal for thermal modelling...... of the continental lithosphere, given that most radiogenic elements are concentrated in granitic rocks of the upper continental crust whereas heat production in rocks of the lower crust and lithospheric mantle is negligible. We present and analyze a new global database GRANITE2017 (with about 500 entries...

Strength and strain anisotropy of olkiluoto mica gneiss

International Nuclear Information System (INIS)

Hakala, M.; Kuula, H.; Hudson, J.

2006-10-01

An anisotropy in the elastic moduli values of intact rock with a ratio of more than 1.3∼1.5 has been reported to have an effect on the calculated magnitudes and orientations of the in situ principal stress components as measured by the overcoring method. Work related to the on-going site investigation for a deep radioactive waste repository at the Olkiluoto site in Western Finland has shown that the migmatic mica gneiss is anisotropic which could therefore affect the interpretation of overcoring stress measurement results. This paper includes a summary of the theory of anisotropy concerning the intact rock moduli via the strain compliance matrix, a description of the core sample testing methods, and interpretation of results for the migmatic mica gneiss from two site investigation boreholes. In this case study, 19 specimens were tested and the results showed a modulus anisotropy of about 1.4. Because such anisotropy is high enough to produce significant errors in the estimation of the in situ principal stresses, it is recommended to take this into account in the interpretation of the stress measurement results, both in the context of the current work in Finland and in other projects where similar anisotropy is encountered. (orig.)

Core drilling of hydco drillholes ONK-PP262 and ONK-PP274 in ONKALO at Olkiluoto 2010

Energy Technology Data Exchange (ETDEWEB)

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

2011-10-15

Suomen Malmi Oy (Smoy) core drilled two drillholes for HYDCO-program in ONKALO at Eurajoki, Olkiluoto in 2010. The drillhole ONK-PP262 was drilled in May 2010 and the drillhole ONK-PP274 in December 2010. The lengths of the drillholes are 25.02 and 23.88 m respectively. The drillholes are 75.7 mm by diameter. The drillholes were drilled in the investigation niche 4 at the access tunnel chainage 3747. 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 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 and pegmatitic granite. The average fracture frequencies in both drill cores are 1.4 pcs/m. The average RQD values in the drillcores are 97.2 % (ONK-PP262) and 98.6 % (ONK-PP274). (orig.)

Core drilling of hydco drillholes ONK-PP262 and ONK-PP274 in ONKALO at Olkiluoto 2010

International Nuclear Information System (INIS)

Toropainen, V.

2011-10-01

Suomen Malmi Oy (Smoy) core drilled two drillholes for HYDCO-program in ONKALO at Eurajoki, Olkiluoto in 2010. The drillhole ONK-PP262 was drilled in May 2010 and the drillhole ONK-PP274 in December 2010. The lengths of the drillholes are 25.02 and 23.88 m respectively. The drillholes are 75.7 mm by diameter. The drillholes were drilled in the investigation niche 4 at the access tunnel chainage 3747. 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 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 and pegmatitic granite. The average fracture frequencies in both drill cores are 1.4 pcs/m. The average RQD values in the drillcores are 97.2 % (ONK-PP262) and 98.6 % (ONK-PP274). (orig.)

Geochemistry of U-Th- REE bearing minerals, in radioactive pegmatite in Um Swassi-Dara area, north eastern desert, Egypt

International Nuclear Information System (INIS)

Ali, B. H.

2007-01-01

Some of the pegmatites in the north Eastern Desert of Egypt have high radioactive values, between them the studied radioactive pegmatites which are clustered just in the western margin of Um Swassi-Dara hosted monzogranites. In zoned pegmatite the alteration zones locate between quartz core and intermediate zone are characterizing with the abundance of rare-earth minerals, anderbergite, cenosite, Y-allanite and uranium, thorium minerals such as euxenite, ferro-columbite and complex titanium-yetrum oxides (Kobbite). This zone is a result of many alteration processes developed from volatile-rich magmatic fluids and/or hydrothermal solution which evolved from late differentiated magmatic fluid and lead to increase of U, Th, Zr, Nb, Ti and REE bearing minerals. Such a distinctive alkaline mineralization suite, possibly related to an alkali fluid phase, is superimposed on a more normal, less alkaline group of minerals such as cassiterite, chalcopyrite, and galena. Nb-Ta-Ti minerals bearing U and Th, define a sequence of oxide, cyclosilicate and silicate minerals, showing the effect of hydrothermal overprinting with extreme REE enrichment of the fluids. It can be concluded that the studied mineralization took place in three overlapping stages

Natural alpha recoil particle radiation and ionizing radiation sensitivities in quartz detected with EPR: implications for geochronometry

International Nuclear Information System (INIS)

Rink, W.J.; Odom, A.L.

1991-01-01

The electron paramagnetic resonance EPR signals in granitic quartz samples of known age are studied. Time-integrated alpha recoil activity and EPR signal intensity are more significantly correlated than sample age and EPR signal intensity. Neutron activation analysis for internal uranium and thorium in quartz are reported. Natural germanium EPR signals are observed in pegmatitic quartz samples and one granitic quartz. Pegmatitic quartz exhibits germanium EPR center growth competing strongly with E' center growth, apparently leading to depleted natural concentrations of E' centers. Calculations of lattice vacancy accumulation associated with alpha recoil damage are presented and compared with concentrations of paramagnetic oxygen vacancies in the quartz. Based on the results reported, the potential and problems associated with dating quartz are discussed, relating both to accumulated lattice damage and the additive dose methods. (author)

Partial melting of UHP calc-gneiss from the Dabie Mountains

Science.gov (United States)

Liu, Penglei; Wu, Yao; Liu, Qiang; Zhang, Junfeng; Zhang, Li; Jin, Zhenmin

2014-04-01

Exhumation melting has been proposed for the ultra-high pressure (UHP) metamorphic rocks in the Dabie Mountains based on melting experiments. We document here the first petrological and mineralogical evidence demonstrating that the UHP calc-gneisses from the Ganjialing area in the Dabie Mountains experienced partial melting during early exhumation. The assemblage of garnet, phengite (Si = 3.65 pfu), coesite, rutile and carbonate preserved in the calc-gneisses indicates a peak metamorphic condition of 692-757 °C and 4.0-4.8 GPa. Partial melting is indicated by several lines of evidence: the melting textures of phengite, the feldspar-dominated films, bands, branches, blebs and veins, the euhedral K-feldspars, the intergrowth film of plagioclase and K-feldspar, the plagioclase + biotite intergrowth after garnet and the epidote poikiloblasts. Polyphase inclusions in garnet are characterized with wedge-like offshoots and serrate outlines whereas those in epidote display negative crystal shapes, which can be best interpreted by entrapment of former melts. We propose a wet melting reaction of Phn + Q ± Na-Cpx + H2O = Bt + Pl + Grt + felsic melts, which likely took place at ca.650-800 °C and ca.1.0-2.0 GPa, to interpret the melting event in the calc-gneisses. Chemical exchanges between garnet and melts produced new garnet domains with higher almandine, spessartine, MREE, HREE and Y but lower grossular, pyrope, P, Sc, Ti, V and Zr contents. Zr-in-rutile thermometer reveals a low temperature of 620-643 °C at 5 GPa, indicating a later reset for Zr in rutile. Healed fractures are suggested to be responsible for the formation of some polyphase inclusions in garnet.

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.

EXPLOITATION OF GRANITE BOULDER

Directory of Open Access Journals (Sweden)

Ivan Cotman

1994-12-01

Full Text Available The processes of forming, petrography, features, properties and exploitation of granite boulders are described. The directional drilling and black powder blasting is the succesful method in exploitation of granite boulders (boulder technology (the paper is published in Croatian.

AMS studies in Portuguese variscan granites

Science.gov (United States)

Sant'Ovaia, Helena; Martins, Helena; Noronha, Fernando

2014-05-01

A large volume of Variscan granitic rocks outcrop in Central Iberian Zone which are well documented concerning geological mapping, petrography and geochemistry but whose magnetic characteristics and fabric remain unknown. In this study we summarize the available AMS data from approximately 644 sampling stations (5152 samples) on different massifs of Variscan Portuguese granites. Despite their different geological, petrographic and geochemical characteristics, magnetic susceptibility (K) values obtained for the majority of the studied granites range from 15 to 300 × 10-6 SI. The dominant paramagnetic behaviour of the granite bodies reflects the presence of ilmenite as the main iron oxide. This feature indicates the reduced conditions involved in the granite melt formation during the Variscan orogeny. The two-mica granites show K values ranging between 15 to 70 × 10-6 SI which are lower than values displayed by the biotite-rich facies scattered within the interval of 70 and 300 × 10-6 SI. The magnetite-bearing granites are scarce but represented in Lavadores, Gerês and Manteigas. Even so, only the Lavadores body could be considered as a true magnetite-type granite (K >3.0 × 10-3 SI) in face of its K, comprised between 1550 and 19303 × 10-6 SI. Magnetic anisotropy can be used as a "marker" for the deformation experienced by granite mushes during their crustal emplacement and further cooling. Magnetic anisotropy can thus be correlated with the finite deformation of a rock, as record by mineral fabrics. Post-tectonic granites, such as those from Vila Pouca de Aguiar, Pedras Salgadas, Caria, Vila da Ponte, Chaves and Lamas de Olo, have a magnetic anisotropy <2.5% which corresponds to a deformation hardly visible to the naked eye. Nevertheless, at microscopic scale, these granites display almost ubiquitous magmatic to submagmatic microstructures (rare wavy extinction in quartz, erratic subgrain boundaries in quartz and, eventually, folded or kinked biotites). For

Granites petrology, structure, geological setting, and metallogeny

CERN Document Server

Nédélec, Anne; Bowden, Peter

2015-01-01

Granites are emblematic rocks developed from a magma that crystallized in the Earth’s crust. They ultimately outcrop at the surface worldwide. This book, translated and updated from the original French edition Pétrologie des Granites (2011) is a modern presentation of granitic rocks from magma genesis to their crystallization at a higher level into the crust. Segregation from the source, magma ascent and shapes of granitic intrusions are also discussed, as well as the eventual formation of hybrid rocks by mingling/mixing processes and the thermomechanical aspects in country rocks around granite plutons. Modern techniques for structural studies of granites are detailed extensively. Granites are considered in their geological spatial and temporal frame, in relation with plate tectonics and Earth history from the Archaean eon. A chapter on granite metallogeny explains how elements of economic interest are concentrated during magma crystallization, and examples of Sn, Cu, F and U ore deposits are presented. Mi...

New progress of the study on uranium-gold association

International Nuclear Information System (INIS)

Feng Mingyue; Sun Zhifu

1992-01-01

Through the study on heavy minerals from the uraniferous granite-pegmatite it is found that nature gold is associated with uraninite, which provides the new information for the study on uranium-gold association and its metallogenesis

New progress of the study on uranium-gold association

Energy Technology Data Exchange (ETDEWEB)

Mingyue, Feng; Zhifu, Sun [Beijing Research Inst. of Uranium Geology (China)

1992-07-01

Through the study on heavy minerals from the uraniferous granite-pegmatite it is found that nature gold is associated with uraninite, which provides the new information for the study on uranium-gold association and its metallogenesis.

Petrogenesis of peralkaline granite dykes of the Straumsvola complex, western Dronning Maud Land, Antarctica

Science.gov (United States)

Harris, Chris; Dreyer, Tanya; le Roux, Petrus

2018-01-01

the granites by assimilation are unfeasible, unless an unexposed high-δ18O contaminant is invoked. Instead, it is proposed that the peralkaline syenite and granite dykes formed by partial melting of alkali-metasomatised gneiss that surrounds the nepheline syenite, followed by fractional crystallization.

Radiocrystallographic study of the triphylite of pegmatite from Bela Vista, Minas Gerais State, in Brazil

International Nuclear Information System (INIS)

Baptista, N.R.; Baptista, A.

1985-01-01

Conclusions through the triphylite mineral monocrystal Li (Fe,Mn)PO4 study from Bela Vista pegmatite, Minas Gerais State were related. Reticular parameters were evaluated and through the reflection levels analysis present in the different reciprocal levels photographyed, a space group mentioned in literature were confirmed. (L.M.J.) [pt

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)

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

Leppikangas granodiorite, 10 km southwest of Sorronmäki, is 1824±5 Ma. Within the limits of experimental error, these ages are identical and maybe associated with a thermal event that accompanied the D3 deformation phase. D3 structures fold D2 structures in a plastic deformation zone situated between the sample locations. Pegmatitic granite dykes intrude this NW-SE trending zone.

Geochemistry of Gneisses from Dabie Complex and Tongbai Complex in Qinling-Tongbai-Dabie Orogenic Belt: Implications for Location of Yangtze-Sino-Korean Suture

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

The Dabie complex (DC) and the Tongbai complex (TBC) are separately distributed in the middle and eastern parts of the Qinling-Tongbai-Dabie orogenic belt. In this study, the Dabie complex can be divided into two units: one is the complex with no high pressure and ultrahigh pressure metamorphic rocks (DC1), and the other is the complex containing coesite-bearing eclogite lenses or boudins (DC2). Gneisses are predominant in the TBC, DC1 and DC2. Major and trace element data of gneisses in the TBC, DC1 and DC2 show them to be the orthogneisses. The gneisses in the DC1 have higher incompatible element contents and higher ratios of w(K2O)/w(Na2O) and w(La)n/w(Yb)n than those in the DC2. However, no obvious differences arise in other element contents and the ratios of w(La)/w( Nb), w(Nb)/w(Th), w(Nb)/w(Hf), w(Ba)/w(La), w(Sm)/w(Nd) and w(Th)/w(U) between the gneisses in the DC2 and those in the DC1. These observations suggest that the protoliths of the gneisses in the DC2 have affinities to those in the DC1. The difference between the DC1 and DC2 gneisses in incompat- ible element contents could reflect the difference in their partial melting extent. The TBC gneisses are geochemically similar to the DC1 gneisses, suggesting that the TBC and DC1 gneisses are the same lithologic unit in the Qinling-Tongbai-Dabie orogenic belt and that they have experienced similar formations and evolution histories. In the Qinling-Tongbai area, the TBC is part of the northern blocks of the Yangtze craton. Given the similarity of geochemical characteristics, the rock assemblage and the ages between the TBC and DC1 gneisses, we can infer that the Dabie complex also belongs to the northern blocks of the Yangtze craton. In terms of the distribution of eciogites and metamorphic facies, we propose that the collisionai suture in the Dabie area is distributed along the Xiaotian-Mozitan fault, at the contact with the Shang-Dan-Tongbai fault to the west.

Natural radionuclide distribution in Brazilian commercial granites

International Nuclear Information System (INIS)

Anjos, R.M.; Veiga, R.; Soares, T.; Santos, A.M.A.; Aguiar, J.G.; Frasca, M.H.B.O.; Brage, J.A.P.; Uzeda, D.; Mangia, L.; Facure, A.; Mosquera, B.; Carvalho, C.; Gomes, P.R.S.

2005-01-01

The dimension stones sector in Brazil produces several varieties of granites, marbles, slates and basalts. More than half of this production corresponds to around 200 different commercial types of granites with specific names, geographical and geological origins and mineral compositions. The well-known natural radioactivity present in rocks, where high radiation levels are associated with igneous rocks such as granite, can be used to determine their general petrologic features. This subject is important in environmental radiological protection, since granites are widely used as building and ornamental stones. In this paper, it is applied to correlate the petrographic characteristics of commercial granites with their corresponding dose rates for natural radioactivity. Amounts of thorium, uranium and potassium concentrations have been reported in several Brazilian commercial granite samples

2005 dossier: granite. Tome: phenomenological evolution of the geologic disposal; Dossier 2005: Granite. Tome evolution phenomenologique du stockage geologique

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the phenomenological aspects of the geologic disposal of high-level and long-lived radioactive wastes (HLLL) in granite formations. Content: 1 - introduction: ANDRA's research program on disposal in granitic formation; 2 - the granitic environment: geologic history, French granites; 3 - HLLL wastes and disposal design concepts; 4 - identification, characterization and modeling of a granitic site: approach, geologic modeling, hydrologic and hydro-geochemical modeling, geomechanical and thermal modeling, long-term geologic evolution of a site; 5 - phenomenological evolution of a disposal: main aspects of the evolution of a repository with time, disposal infrastructures, B-type wastes disposal area, C-type wastes disposal area; spent fuels disposal area, radionuclides transfer and retention in the granitic environment; 6 - conclusions: available knowledge, methods and tools for the understanding and modeling of the phenomenological evolution of a granitic disposal site. (J.S.)

2005 dossier: granite. Tome: phenomenological evolution of the geologic disposal; Dossier 2005: Granite. Tome evolution phenomenologique du stockage geologique

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the phenomenological aspects of the geologic disposal of high-level and long-lived radioactive wastes (HLLL) in granite formations. Content: 1 - introduction: ANDRA's research program on disposal in granitic formation; 2 - the granitic environment: geologic history, French granites; 3 - HLLL wastes and disposal design concepts; 4 - identification, characterization and modeling of a granitic site: approach, geologic modeling, hydrologic and hydro-geochemical modeling, geomechanical and thermal modeling, long-term geologic evolution of a site; 5 - phenomenological evolution of a disposal: main aspects of the evolution of a repository with time, disposal infrastructures, B-type wastes disposal area, C-type wastes disposal area; spent fuels disposal area, radionuclides transfer and retention in the granitic environment; 6 - conclusions: available knowledge, methods and tools for the understanding and modeling of the phenomenological evolution of a granitic disposal site. (J.S.)

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

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

Two-mica granites of northeastern Nevada.

Science.gov (United States)

Lee, D.E.; Kistler, R.W.; Friedman, I.; Van Loenen, R. E.

1981-01-01

The field settings are described and analytical data are presented for six two-mica granites from NE Nevada. High delta 18O and 87Sr/86Sr values indicate that all are S-type granite, derived from continental crust. The major element chemistry and accessory mineral contents of these rocks also are characteristic of S-type granites. Chemical, X ray, and other data are presented for the micas recovered from these granites. The muscovites are notably high in Fe2O3, FeO, and MgO. Except for one hydrobiotite, each of the biotites has an MgO content near 6.0 wt%. Two different types of two-mica granites are recognized in the area of this study. One type is distinguished by the presence of many biotite euhedra within muscovite phenocrysts and by an unusual suite of accessory minerals completely devoid of opaque oxides. This type probably resulted from anatexis of late Precambrian argillites under conditions of relatively low oxygen fugacity, along a line that roughly coincides with the westward disappearance of continental basement. In the other textural type of two-mica granite the micas are equigranular and there is a greater variety of accessory minerals. The magmatic evolution of this type also appears to reflect the influence of late Precambrian argillites; there may be age differences between the two types of two-mica granites.-Author

Late Triassic granites from Bangka, Indonesia: A continuation of the Main Range granite province of the South-East Asian Tin Belt

Science.gov (United States)

Ng, Samuel Wai-Pan; Whitehouse, Martin J.; Roselee, Muhammad H.; Teschner, Claudia; Murtadha, Sayed; Oliver, Grahame J. H.; Ghani, Azman A.; Chang, Su-Chin

2017-05-01

The South-East Asian Tin Belt is one of the most tin-productive regions in the world. It comprises three north-south oriented granite provinces, of which the arc-related Eastern granite province and the collision-related Main Range granite province run across Thailand, Singapore, and Indonesia. These tin-producing granite provinces with different mineral assemblages are separated by Paleo-Tethyan sutures exposed in Thailand and Malaysia. The Eastern Province is usually characterised by granites with biotite ± hornblende. Main Range granites are sometimes characterised by the presence of biotite ± muscovite. However, the physical boundary between the two types of granite is not well-defined on the Indonesian Tin Islands, because the Paleo-Tethyan suture is not exposed on land there. Both hornblende-bearing (previously interpreted as I-type) and hornblende-barren (previously interpreted as S-type) granites are apparently randomly distributed on the Indonesian Tin Islands. Granites exposed on Bangka, the largest and southernmost Tin Island, no matter whether they are hornblende-bearing or hornblende-barren, are geochemically similar to Malaysian Main Range granites. The average ɛNd(t) value obtained from the granites from Bangka (average ɛNd(t) = -8.2) falls within the range of the Main Range Province (-9.6 to -5.4). These granites have SIMS zircon U-Pb ages of ca. 225 Ma and ca. 220 Ma, respectively that are both within the period of Main Range magmatism (∼226-201 Ma) in the Peninsular Malaysia. We suggest that the granites exposed on Bangka represent the continuation of the Main Range Province, and that the Paleo-Tethyan suture lies to the east of the island.

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

Science.gov (United States)

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

2009-04-01

]. Analyses of cores of some zircons from granodiorites of Lupveem batholith indicate Precambrian age of protolith (717, 1070.4 and 1581.5 m.a.) [15]. 40Ar-39Ar age of synmetamorphic biotite varies from 108 to 103 m.a. [15]. Intrusive rocks of Alarmaut dome are represented by wide spectrum of rocks: diorites, Q diorites, Q monzodiorites, granodiorites, tonalites, granites. Granodiorites and granites contain mafic enclaves of monzonites and Q monzonites. SiO2 contents in rocks of Alarmaut dome varies from 58,55% in diorites to 71,3% in granites; in enclaves - from 54,6% in monzonites to 61.89% in Q monzonites. Granitoids are normal and subalkaline rocks according to SiO2 vs K2O+Na2O and belong to high-K calc-alkaline and shoshonite series according to K2O vs SiO2. They are mainly metaluminous rocks (ASI intermediate rocks are characterized by LREE enrichment, HREE depletion and insignificant negative Eu-anomaly (LaN/YbN=8,42-15,69; Eu/Eu*=0,66-0,94). Granodiorites and granites REE patterns are more enriched in LREE, more depleted in HREE and have deeper negative Eu-anomaly (LaN/YbN=11,48-45,6; Eu/Eu*=0,47-0,81). REE patterns of monzonites from enclaves in granites and granodiorites are similar to patterns of host rocks. REE patterns of intermediate rocks and granodiorites are well correlated with those of "mafic root" rocks of K2 Kigluaik pluton from the core part of the same name gneiss dome, Seward Peninsula, Alaska [16], and K1-2 granitoids of Chauna fold zone, West Chukotka [17]. Spidergrams of granitoids and enclaves are similar and characterized by LILE, LREE enrichment and Nb, Sr, P, Ti depletion, typical for supra-subduction magmatites. On F1-F2 diagram [18], separating granitoids by geodynamic settings, granitoids fall in the field of collisional granites; on Rb vs Y+Nb diagram, along the boundary between the fields of syncollisional granites and volcanic arc granites, but within the field of postcollisional [19]. Geochronological and structural data indicate temporal

Mineralogic investigation into occurrence of high uranium well waters in upstate South Carolina, USA

Energy Technology Data Exchange (ETDEWEB)

Warner, Richard, E-mail: wrichar@clemson.edu [Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC 29634-0919 (United States); Meadows, Jason; Sojda, Scott; Price, Van; Temples, Tom [Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC 29634-0919 (United States); Arai, Yuji [Department of Entomology, Soils, and Plant Sciences, Clemson University, Clemson, SC 29634-0315 (United States); Fleisher, Chris [Department of Geology, University of Georgia, Athens, GA 30602-2501 (United States); Crawford, Bruce; Stone, Peter [Bureau of Water, South Carolina Department of Health and Environmental Control, Columbia, SC 29201 (United States)

2011-05-15

Research Highlights: > Oxidative dissolution of uraninite in biotite granite is primary source of uranium in high-U well waters near Simpsonville, SC. > Uranium is chiefly transported as mixed uranyl hydroxyl-carbonate complexes. > Local reduction has resulted in secondary precipitation of uranium along fractures as coffinite. > Dissolution of uraninite and precipitation of coffinite were geologically recent. - Abstract: High levels of U (up to 5570 {mu}g/L) have been discovered in well waters near Simpsonville, South Carolina, USA. In order to characterize the mineralogical source of the U and possible structural controls on its presence, a deep (214 m) well was cored adjacent to one of the enriched wells. The highest gamma-ray emissions in the recovered core occur in coarse biotite granite at a depth just below 52 m. A slickenlined fault plane at 48.6 m and narrow pegmatite layers at depths of 113, 203 and 207 m also yield high gamma-ray counts. Thin sections were made from the above materials and along several subvertical healed fractures. Uraninite and coffinite are the principal U-rich minerals in the core. Other U-bearing minerals include thorite and thorogummite, monazite, zircon and allanite. Primary uraninite occurs in the biotite granite and in pegmatite layers. Secondary coffinite is present as tiny (<5 {mu}m) crystals dispersed along fractures in the granite and pegmatites. Coffinite also occurs along the slickenlined fault plane, where it is associated with calcite and calcic zeolite and also replaces allanite. Coffinite lacks radiogenic Pb, hence is considerably younger than the uraninite. Dissolution of partially oxidized Ca-rich uraninite occurring in the surficial biotite granite (or secondary coffinite in fracture zones) is likely the main source for the current high levels of U in nearby area wells. The high-U well waters have a carbonate signature, consistent with pervasive calcite vein mineralization in the core. Aqueous speciation calculations

Determination of dispersity of crushed granite

International Nuclear Information System (INIS)

Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong

2004-01-01

The experimental crushed granite column breakthrough curves, using 99 Tc as spike tracer and 3 H as invariant tracer, are analyzed by different linear regression techniques. Dispersity of crushed granite and retardation factor of 99 TcO 4 - on the crushed granite are determined simultaneously by one linear regression technique. Dispersity of crushed granite is also obtained with 3 H as invariant tracer by the other linear regression technique. The dispersities found by spike source and invariant source methods are compared. The experimental results show that the dispersity found by spike source method is close to that found by invariant source method. It indicates that dispersity is only the characteristic of dispersion medium

Determination of dispersity of crushed granite

International Nuclear Information System (INIS)

Liu, D.J.; Fan, X.H.

2005-01-01

Experimental crushed granite column breakthrough curves, using 99 Tc as spike tracer and 3 H as invariant tracer, were analyzed by different linear regression techniques. Dispersity of crushed granite and the retardation factor of 99 TcO 4 - on the crushed granite were determined simultaneously by one linear regression. Dispersity of crushed granite was also obtained with 3 H as invariant tracer by the other linear regression. The dispersities found by spike source and invariant source methods are compared. Experimental results show that the dispersity found by the spike source method is close to that found by the invariant source method. This indicates that dispersity is only a characteristic of the dispersion medium. (author)

Uranium-enriched granites in Sweden

International Nuclear Information System (INIS)

Wilson, M.R.; Aakerblom, G.

1980-01-01

Granites with uranium contents higher than normal occur in a variety of geological settings in the Swedish Precambrian, and represent a variety of granite types and ages. They may have been generated by the anatexis of continental crust or processes occurring at a much greater depth. They commonly show enrichment in F, Sn, W and/or Mo. Only in one case is an important uranium mineralization thought to be directly related to a uranium-enriched granite, while the majority of epigenetic uranium mineralizations with economic potential are related to hydrothermal processes in areas where the bedrock is regionally uranium-enhanced. (author)

Uranium enriched granites in Sweden

International Nuclear Information System (INIS)

Wilson, M.R.; Aakerblom, G.

1980-01-01

Granites with uranium contents higher than normal occur in a variety of geological settings in the Swedish Precambrian, and represent a variety of granite types and ages. They may have been generated by (1) the anatexis of continental crust (2) processes occurring at a much greater depth. They commonly show enrichement in F, Sn, W and/or Mo. Only in one case is an important uranium mineralization thought to be directly related to a uranium-enriched granite, while the majority of epigenetic uranium mineralizations with economic potential are related to hydrothermal processes in areas where the bedrock is regionally uranium-enhanced. (Authors)

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.

The research frontier and beyond: granitic terrains

Science.gov (United States)

Twidale, C. R.

1993-07-01

Investigations of granite forms and landscapes over the past two centuries suggest that many features, major and minor, are shaped by fracture-controlled subsurface weathering, and particularly moisture-driven alteration: in other words etch forms are especially well represented in granitic terrains. Commonly referred to as two stage forms, many are in reality multistage in origin, for the structural contrasts exploited by weathering and erosion that are essential to the mechanism originated as magmatic, thermal or tectonic events in the distant geological past. Fracture patterns are critical to landform and landscape development in granitic terrains, but other structural factors also come into play. Location with respect to water table and moisture contact are also important. Once exposed and comparatively dry, granite forms tend to stability; they are developed and diversified, and many are gradually destroyed as new, epigene, forms evolve, but many granite forms persist over long ages. Reinforcement effects frequently play a part in landform development. Several granite forms are convergent, i.e. features of similar morphology evolve under the influence of different processes, frequently in contrasted environments. On the other hand many landforms considered to be typical of granitic terrains are also developed in bedrock that is petrologically different but physically similar to granite; and in particular is subdivided by fractures of similar pattern and density. To date, most of the general statements concerning the evolution of granitic terrains have been based in work in the tropics but other climatic settings, and notably those of cold land, are now yielding significant results. Future research will extend and develop these avenues, but biotic factors, and particularly the role of bacteria, in such areas as weathering, will take on a new importance. Structural variations inherited from the magnetic, thermal and tectonic events to which granite bodies have

Identification of granite varieties from colour spectrum data.

Science.gov (United States)

Araújo, María; Martínez, Javier; Ordóñez, Celestino; Vilán, José Antonio

2010-01-01

The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product stage optimizes the management and control of stocks of granite slabs and tiles and facilitates the operation of traceability systems. We describe a methodology for automatically identifying granite varieties by processing spectral information captured by a spectrophotometer at various stages of processing using functional machine learning techniques.

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

Science.gov (United States)

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

Textures and melt-crystal-gas interactions in granites

Directory of Open Access Journals (Sweden)

Jean-Louis Vigneresse

2015-09-01

Full Text Available Felsic intrusions present ubiquitous structures. They result from the differential interactions between the magma components (crystal, melt, gas phase while it flows or when the flow is perturbed by a new magma injection. The most obvious structure consists in fabrics caused by the interactions of rotating grains in a flowing viscous melt. New magma inputs through dikes affect the buk massif flow, considered as global within each mineral facies. A review of the deformation and flow types developing in a magma chamber identifis the patterns that could be expected. It determines their controlling parameters and summarizes the tools for their quantification. Similarly, a brief review of the rheology of a complex multi-phase magma identifies and suggests interactions between the different components. The specific responses each component presents lead to instability development. In particular, the change in vorticity orientation, associated with the switch between monoclinic to triclinic flow is a cause of many instabilities. Those are preferentially local. Illustrations include fabric development, shear zones and flow banding. They depend of the underlying rheology of interacting magmas. Dikes, enclaves, schlieren and ladder dikes result from the interactions between the magma components and changing boundary conditions. Orbicules, pegmatites, unidirectional solidification textures and miarolitic cavities result from the interaction of the melt with a gaseous phase. The illustrations examine what is relevant to the bulk flow, local structures or boundary conditions. In each case a field observation illustrates the instability. The discussion reformulates instability observations, suggesting new trails for ther description and interpretation in terms of local departure to a bulk flow. A brief look at larger structures and at their evolution tries to relate these instabilities on a broader scale. The helical structures of the Říčany pluton, Czech

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

Mineralización de uranio en la Sierra de Velasco, La Rioja

International Nuclear Information System (INIS)

Morello, O.; Aparicio González, P.

2013-01-01

This contribution describes an uranium mineralization found in the Sierra de Velasco, La Rioja Province, Northwest of Ar¬gentina. In the study area crop out granites, pegmatites and metamorphic rocks. The host rocks of the mineralization are the La Chinchilla Granite (Carboniferous) and the La Cébila metamorphic Complex (Precambrian-Ordovician). The mine¬ralization is perigranitic and occurs disseminated, in fractures and in the contact between the granite and the metamorphic rocks. In the La Chinchilla Granite was identified a U-Nb-Ta oxide, and in the metamorphic rocks U-silicates (uranophane, uranophane-beta), U-phosphates (phurcalite and meta-autunite) and uranium oxides (pitchblende and coffinite) were found. (authors) [es

Etude de la diagraphie neutron du granite de Beauvoir. Effet neutron des altérations et de la matrice du granite. Calibration granite. Porosité totale à l'eau et porosité neutron Analysis of the Beauvoir Granite Neutron Log. Neutron Effect of Alterations and of the Granite Matrix. Granite Calibration. Total Water Porosity and Neutron Porosity

Directory of Open Access Journals (Sweden)

Galle C.

2006-11-01

Full Text Available Cet article rend compte des travaux effectués sur la porosité du granite de Beauvoir (Sondage GPF 1 d'Echassières, Massif Central français. L'objectif de notre étude est de pouvoir obtenir des valeurs représentatives de la saturation en eau (porosité totale à l'eau n du granite de Beauvoir à partir des mesures de porosité neutron PorositéN (diagraphie neutron BRGM sans avoir recours aux mesures sur carottes. Notre démarche est expérimentale et nous avons tenté d'approfondir certains problèmes liés à l'utilisation de la diagraphie neutron dans une roche granitique. Deux facteurs principaux conditionnent la réponse neutron : la concentration en hydrogène de la formation (eau libre et eau de constitution de certains minéraux et la présence d'éléments absorbeurs à forte section de capture comme le gadolinium, le cadmium, le bore, . . . et dans le cas du granite de Beauvoir, le lithium. A partir des mesures de porosité totale à l'eau n sur carottes, des essais de pertes au feu sur poudre qui nous permettent de déterminer la porosité neutron liée à l'eau de constitution PorositéN(OH- et des analyses chimiques avec lesquelles nous évaluons la porosité neutron thermique PorositéN(ox (Programme SNUPAR, Schlumberger liée à la capture neutronique, nous reconstituons la porosité neutron totale PorositéNR du granite de Beauvoir. Pour 7 échantillons caractéristiques du granite de Beauvoir, nous réalisons grâce à ces résultats une nouvelle calibration du taux de comptage neutron initial corrigé du gradient thermique et de l'effet de trou. Grâce à cette opération, il est possible de déterminer, pour les échantillons traités, la porosité neutron du granite avec une calibration granite (PorositéNg et non calcaire (PorositéNc. La connaissance de l'effet neutron de la matrice nous permet enfin d'évaluer la teneur en eau du granite (porosité totale à l'eau et de comparer celle-ci avec la porosité mesurée sur

Hydrothermal alteration of Hercynian granites, its significance to the evolution of geothermal systems in granitic rocks

Energy Technology Data Exchange (ETDEWEB)

Marques, Jose M.; Matias, Maria J.; Basto, Maria J.; Aires-Barros, Luis A. [Instituto Superior Tecnico, Centro de Petrologia e Geoquimica, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Carreira, Paula M. [Instituto Tecnologico e Nuclear, Estrada Nacional n 10, 2686 - 953 Sacavem (Portugal); Goff, Fraser E. [Earth and Planetary Sciences Department, Univ. of New Mexico, Albuquerque, NM 87131 (United States)

2010-06-15

We discuss geochemical and isotopic ({sup 18}O/{sup 16}O, {sup 2}H/{sup 1}H and {sup 87}Sr/{sup 86}Sr) data recording the hydrothermal alteration of northern Portuguese Hercynian granites by Na-HCO{sub 3}-CO{sub 2}-rich mineral waters. Whole-rock samples from drill cores of Vilarelho da Raia granite have {delta}{sup 18}O values in the +11.47 to +10.10 permille range. The lower values correspond to highly fractured granite samples displaying vein and pervasive alteration. In the pervasive alteration stage, which probably results from a convective hydrothermal system set up by the intrusion of the granites, the metamorphic waters are in equilibrium with hydrous minerals. In contrast, the vein alteration of these granitic rocks was caused by water of meteoric origin. The oxygen ratios between water (W) and rock (R), the so-called W/R ratios, obtained for the open system (where the heated water is lost from the system by escape to the surface) range between 0.05 and 0.11, suggesting that the recrystallization of the veins was influenced by a small flux of meteoric water. Stable isotope analyses performed on the cores show that the vein alteration stage relates to post-emplacement tectonic stresses acting on the granite, probably of late Hercynian age. Our results are consistent with the existence of two separate alteration events (pervasive and vein) caused by hydrothermal waters of different isotopic characteristics. The studies presented in this paper should be viewed as a natural analogue that uses the alteration features observed in a fossil geothermal system at Vilarelho da Raia to assess possible water-rock reactions presently occurring at depth in granitic rocks of the nearby Chaves area. (author)

Radiometric analysis of Chinese commercial granites

International Nuclear Information System (INIS)

Xinwei, L.; Lingqing, W.; Xiaodan, J.

2006-01-01

Due to the widespread use of granites as building and ornamental materials, measurements of 226 Ra, 232 Th and 40 K activities in commercial granites have been carried out using a NaI(Tl) γ-ray spectrometer with a matrix-inversion-based spectral stripping technique. The concentrations of 226 Ra, 232 Th and 40 K in Chinese commercial granite range from 14.5 to 204.7 Bq x kg -1 , 16.7 to 186.7 Bq x kg -1 and 185.7 to 1745.6 Bq x kg -1 , respectively. The mean values of the activity concentrations of 226 Ra, 232 Th and 40 K in red and pink commercial granites are all higher than those in black and gray commercial ones. The radium equivalent activity (Ra eq ), the external hazard index (H ex ), the internal hazard index (H in ) and the annual gonadal dose equivalent (AGDE) were also calculated and compared to the international recommended values. Six types of red commercial granites (CBR, MLR, QXR, PBR, JXR, LQR, YDR and TSR) of China do not satisfy the universal standards. (author)

Rn-222 release to the environment: comparison between different granite sources

International Nuclear Information System (INIS)

Mamoon, M.; Kamal, S.M.

2005-01-01

In this work three different types of granites were studied, namely: pure granite, alkali granite and altered (hydrated) alkali granite. General radioactivity of the granites was studied along with the potential for 222 Rn emanation. The study indicated that altered alkali granite releases, relatively, the highest 222 Rn emanation to the surrounding air while alkali granite emits the more intense gamma radiation of the three granites. Hence, altered alkali granite can be used as a laboratory source for 222 Rn.

Posiva microseismic network. Core drilling of drillholes ONK-PP348...351 in ONKALO at Olkiluoto 2012

Energy Technology Data Exchange (ETDEWEB)

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

2014-04-15

Suomen Malmi Oy (Smoy) core drilled four drillholes for the Posiva's ONKALO microseismic network in ONKALO at Eurajoki, 2012. The drillholes are used for geophone instrumentation and geological characterization. The drillholes ONKPP348... 351 were core drilled in February 2012. All the drillholes are ∼ 9.40 m by length. The drillholes are 56.5 mm by diameter. The drillholes were drilled in deep angles to the floors of the access tunnel and three niches near each other at access tunnel chainages 3019 - 3080. 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 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 drillcores are diatexitic gneiss and pegmatitic granite. The average fracture frequency of the drillcores range from 1.2 to 2.4 pc/m and the average RQD value from 96.6 % to 98.6 %. Two fractured zones were intersected. (orig.)

Posiva microseismic network. Core drilling of drillholes ONK-PP348...351 in ONKALO at Olkiluoto 2012

International Nuclear Information System (INIS)

Toropainen, V.

2014-04-01

Suomen Malmi Oy (Smoy) core drilled four drillholes for the Posiva's ONKALO microseismic network in ONKALO at Eurajoki, 2012. The drillholes are used for geophone instrumentation and geological characterization. The drillholes ONKPP348... 351 were core drilled in February 2012. All the drillholes are ∼ 9.40 m by length. The drillholes are 56.5 mm by diameter. The drillholes were drilled in deep angles to the floors of the access tunnel and three niches near each other at access tunnel chainages 3019 - 3080. 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 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 drillcores are diatexitic gneiss and pegmatitic granite. The average fracture frequency of the drillcores range from 1.2 to 2.4 pc/m and the average RQD value from 96.6 % to 98.6 %. Two fractured zones were intersected. (orig.)

Fracture patterns and stresses in granite

International Nuclear Information System (INIS)

Price, N.J.

1979-01-01

If granite bodies are to be used as receptacles for toxic waste materials, the presence or absence of barren fractures and the virgin stresses in the granite are of fundamental importance. Unfortunately, very little is known regarding the incidence of fractures, or stresses, which exist at depths (of about 1 km) in granite bodies. A simple analysis is presented of a hypothetical intrusion which indicates the magnitudes of stresses and the possible fracture development which may be expected in such bodies. (auth)

Chemical characteristics of zircon from A-type granites and comparison to zircon of S-type granites

Czech Academy of Sciences Publication Activity Database

Breiter, Karel; Lamarão, C. N.; Krás Borges, R. M.; Dall'Agnol, R.

1192/195, April (2014), s. 208-225 ISSN 0024-4937 Institutional support: RVO:67985831 Keywords : zircon * A-type granites * S-type granites * Wiborg batholith * Brazil * Krušné hory/Erzgebirge Subject RIV: DD - Geochemistry Impact factor: 4.482, year: 2014

Rare metal granites and related rocks of the Ukrainian shield

Directory of Open Access Journals (Sweden)

Esipchuk, K.Ye.

1993-12-01

Full Text Available Two rare metal leucocratic granites, Perga and Kamennaya complexes, can be distinquished on the Ukrainian shield. The Perga complex consists of medium- and coarse grained, mainly porphyric, biotite, riebeckite and aegirine granites, granite porphyries, microclinites and albitites with rare metal mineralization (genthelvite, phenacite, tantalite, cassiterite and wolframite etc.. Granites from several stocks (up to 30 km2 in the northwestern part of the shield, situated along the fracture zone, restricted the large Korosten pluton of rapakivi granites to the northwest. The age of these granites (Pb-Pb and U-Pb methods on zircon and monazite practically coincide with the age of rapakivi granites being 1750 Ma. Within the Korosten complex of rapakivi granites we consider that zinnwaldite granites, which are characterized by fluorite and topazine mineralization, represent the final phase of pluton. These granites differ from the Perga ones by their low content of rare metals. The Kamennaya Mogila complex lies in the southeastern part of the Ukrainian shield. It consists of biotite and muscovite-biotite, medium- and coarse-grained (also porphyric, and occasionally greisining granites with rare metal mineralization (cassiterite, columbite, molybdenite, wolframite and beryl. Granites form several stocks (5-30 km2 situated 10-30 km to the west-northwest of the South-Kalchik gabbro-syenite-granite pluton. Granitoids in both of these complexes have similar isotopic ages (1800 Ma. Leucocratic subalkaline granites (the Novoyanisol type are known within the pluton itself, occupying an intermediate position between the above mentioned in terms of mineral and geochemical composition. The gabbro-syenite-granite formation of the Nearazov region has a substantial similarity to the anorthosite-rapakivi-granite formation. In this respect the relation of each of them to rare metal granites is rather remarkable. This relation is, most probably, not only spatial, but

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

International Nuclear Information System (INIS)

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

2001-01-01

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

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

, tonalitic-granodioritic- granitic gneiss and pegmatite granite. The average fracture frequency is 1.6 pes/m in borehole OL-KR43 and 1.5 pes/m in borehole OL-KR43B. The average RQD values were 96.2 % and 97.7 %. In borehole OL-KR43 24 fractured zones and in borehole OL-KR43B one fractured zone were penetrated during drilling work. (orig.)

Geology and fracture system at Stripa. Technical information report No. 21

International Nuclear Information System (INIS)

Olkiewicz, A.; Gale, J.E.; Thorpe, R.; Paulsson, B.

1979-02-01

The Stripa test site has been excavated in granitic rock between 338 m and 360 m below the ground surface, and is located under the north limb of an ENE-plunging synclinal structure. The granitic rocks, in the areas mapped, are of Archean age and are dominated by a reddish, medium-grained, massive monzogranite that shows varying degrees of deformation. The granitic rocks have been intruded by diabase (dolerite) and pegmatite dikes. Surface and subsurface mapping shows that the Stripa granite is highly fractured and that there are at least four joint sets in the area of the test excavations. In addition to the joints, the rock mass contains fissures, fracture zones, and small-scale shear zones, representing the complete spectrum of the fracture family. Most of the fractures are lined with chlorite, occasionally with calcite. Many of the small-scale shear fractures are filled or coated with epidote. Offsets of pegmatite dikes formed by these fractures are usually limited to one to two meters. Water seepage is observed only as drops from fractures or moist fracture surfaces. It was found that reconstruction of the local three-dimensional fracture system is the heater-experiment sites was difficult, and in some cases subjective. Such reconstruction is a prerequisite to accurate interpretation of thermal and mechanical data from such sites

Origin of the pegmatite veins within the skarn body at Vevčice near Znojmo (Gfohl Unit, Moldanubian Zone)

Czech Academy of Sciences Publication Activity Database

Buriánek, D.; Houzar, S.; Krmíček, Lukáš; Šmerda, J.

2017-01-01

Roč. 62, č. 1 (2017), s. 1-23 ISSN 1802-6222 Institutional support: RVO:67985831 Keywords : diorite pegmatite * skarn * mineralogy * geochemistry * Moldanubian Zone * Bohemian Massif Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 0.609, year: 2016

Site investigation SFR. Boremap mapping of percussion drilled borehole HFR106

Energy Technology Data Exchange (ETDEWEB)

Winell, Sofia (Geosigma AB (Sweden))

2010-06-15

This report presents the result from the Boremap mapping of the percussion drilled borehole HFR106, which is drilled from an islet located ca 220 m southeast of the pier above SFR. The purpose of the location and orientation of the borehole is to investigate the possible occurrence of gently dipping, water-bearing structures in the area. HFR106 has a length of 190.4 m and oriented 269.4 deg/-60.9 deg. The mapping is based on the borehole image (BIPS), investigation of drill cuttings and generalized, as well as more detailed geophysical logs. The dominating rock type, which occupies 68% of HFR106, is fine- to medium-grained, pinkish grey metagranite-granodiorite (rock code 101057) mapped as foliated with a medium to strong intensity. Pegmatite to pegmatitic granite (rock code 101061) occupies 29% of the borehole. Subordinate rock types are felsic to intermediate meta volcanic rock (rock code 103076) and fine- to medium-grained granite (rock code 111058). Rock occurrences (rock types < 1 m in length) occupy about 16% of the mapped interval, of which half is veins, dykes and unspecified occurrences of pegmatite and pegmatitic granite. Only 5.5% of HFR106 is inferred to be altered, mainly oxidation in two intervals with an increased fracture frequency. A total number of 845 fractures are registered in HFR106. Of these are 64 interpreted as open with a certain aperture, 230 open with a possible aperture, and 551 sealed. This result in the following fracture frequencies: 1.6 open fractures/m and 3.0 sealed fractures/m. Three fracture sets of open and sealed fractures with the orientations 290 deg/70 deg, 150 deg/85 deg and 200 deg/85 deg can be distinguished in HFR106. The fracture frequency is generally higher in the second half of the borehole, and particularly in the interval 176-187.4 m.

Site investigation SFR. Boremap mapping of percussion drilled borehole HFR106

International Nuclear Information System (INIS)

Winell, Sofia

2010-06-01

This report presents the result from the Boremap mapping of the percussion drilled borehole HFR106, which is drilled from an islet located ca 220 m southeast of the pier above SFR. The purpose of the location and orientation of the borehole is to investigate the possible occurrence of gently dipping, water-bearing structures in the area. HFR106 has a length of 190.4 m and oriented 269.4 deg/-60.9 deg. The mapping is based on the borehole image (BIPS), investigation of drill cuttings and generalized, as well as more detailed geophysical logs. The dominating rock type, which occupies 68% of HFR106, is fine- to medium-grained, pinkish grey metagranite-granodiorite (rock code 101057) mapped as foliated with a medium to strong intensity. Pegmatite to pegmatitic granite (rock code 101061) occupies 29% of the borehole. Subordinate rock types are felsic to intermediate meta volcanic rock (rock code 103076) and fine- to medium-grained granite (rock code 111058). Rock occurrences (rock types < 1 m in length) occupy about 16% of the mapped interval, of which half is veins, dykes and unspecified occurrences of pegmatite and pegmatitic granite. Only 5.5% of HFR106 is inferred to be altered, mainly oxidation in two intervals with an increased fracture frequency. A total number of 845 fractures are registered in HFR106. Of these are 64 interpreted as open with a certain aperture, 230 open with a possible aperture, and 551 sealed. This result in the following fracture frequencies: 1.6 open fractures/m and 3.0 sealed fractures/m. Three fracture sets of open and sealed fractures with the orientations 290 deg/70 deg, 150 deg/85 deg and 200 deg/85 deg can be distinguished in HFR106. The fracture frequency is generally higher in the second half of the borehole, and particularly in the interval 176-187.4 m

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

NARCIS (Netherlands)

Zwart, H.J.

1963-01-01

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

Age of Pedra Branca granite (Goias) and possible geotectonic implications

International Nuclear Information System (INIS)

Marini, O.J.; Botelho, N.F.; Macambira, M.J.B.; Provost, A.

1986-01-01

Rb-Sr geochronologic dating of granites from the Pedra Branca Granite Massif (Nova Roma, Goias) shown an age of 1405 ± 21My. and a questionable initial Sr 87 /Sr 86 ratio of 0,7004 ± 0,006. Rhyolite from the base of the Arai Group is probably of the same age as the granitic intrusion. The 475 ± 19 My. age for the granitic intrusion is evidence of the Brasiliano Cycle imprint in Pedra Branca region. The age attributed to the Pedra Branca Granite is lower than known ages of the Goias tin granites giving rise to new geotectonic interpretations. It is possible that the Pedra Branca Granite represents a low-level intrusion emplaced at the beginning of structuration and deposition of the Arai basin. It may be correlated with granitic intrusions related to a rift stage above mantle hot spots, like the Nigerian tin younger granites. (author)

Tasmanian tin and tungsten granites - their radiometric characteristics

International Nuclear Information System (INIS)

Yeates, A.N.

1982-01-01

A radiometric survey of Tasmanian granites has shown, with one exception, that tin and tungsten-bearing granites have high radioactivity, largely owing to increased uranium. Many have a high uranium/thorium ratio as well. Radiometric measurements can also delineate different granite types within composite bodies

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

Portuguese granites associated with Sn-W and Au mineralizations

Directory of Open Access Journals (Sweden)

Ana M.R. Neiva

2002-01-01

Full Text Available In northern and central Portugal, there are different tin-bearing granites. Most of them are of S-type, others have mixed characteristics of I-type and S-type granites and a few are of I-type. Tin-tungsten deposits are commonly associated with Hercynian tin-bearing S-type granites. Some quartz veins with wolframite are associated with an I-type granite, which has a low Sn content. In suites of tin-bearing S-type granitic rocks, Sn content increases as a function of the degree of fractional crystallization. Greisenizations of two-mica S-type granites associated with tin-tungsten mineralizations are accompanied by an increase in SiO2, H2O+, Sn, W, Nb, Ta, Rb, Zn, and Pb and decrease in MgO, Na2O, V, Sc,Zr, and Sr. The granite associated with the Jales gold deposit is of S-type and strongly differentiated like the tin-bearing S-type granites, but it has a very low Sn content. During fractional crystallization, Si, Rb, Sn, Pb, Au, As, Sb, and S increase. During increasing degree of hydrothermal alteration of this granite at the gold-quartz vein walls, there are progressive increases in K2O, H2O+, Sn, Cs, Cu, Pb, Au, Sb, As, and S.

Au-As (lead) vein mineralizations of the Cevennes and Chataigneraie regions (French Massif Central). Isotopic characterization (Pb). Mineralizing role of granites in the setting up of these mineralizations

International Nuclear Information System (INIS)

Havard, M.L.

1997-06-01

This work has been carried out in the Frame of the national program 'Geofrance 3D' jointly organized by the French office for geologic and mining researches (BRGM), and the CNRS-INSU/DSPT3. Its aim is the study of the formation of gold-bearing mineralizations of the Variscan chain in the Cevennes and Chataigneraie regions (French Massif Central). In the Cevennes region, the gold-bearing veins are linked with the intrusion of the late-tectonic granodioritic plutons. The aim of this study is to determine the chronology of the mineralizing episodes and to analyze the relationship between the metal concentrates and the setting up of the granites. In the Chataigneraie region, the granites are intrusive in ortho- and para-gneiss series. The hydrothermal activity associated with the contact metamorphism should be responsible for the deposition of gold-bearing wolfram mineralization. The geochemistry of lead isotopes is used to determine the origin of metals in the sulfide mineralizations. The scanning electron microscopy (SEM) is used for the visualization of the microstructure heterogeneities of the minerals and for the quantitative chemical analysis of their successive para-geneses. The comparison between the results obtained in both regions allows to make a difference between their relative degree of erosion and their gold potentialities. (J.S.)

Adsorption behavior of Am(III) on granite

International Nuclear Information System (INIS)

Zhang Yingjie; Feng Xiaogui; Liang Junfu; Chen Jing; Su Rui; Wang Ju; Liu Chunli

2009-01-01

The adsorption behavior of Am(III) on granite (sampled from drilling well BS01 at Beishan (BS) area--a potential candidate site for China's high-level radioactive waste repository, the granite sample's depth about 300 m) was studied in BS03 well groundwater by a batch technique at (25±1) degree C. The influences of pH, sulphate ion, total carbonate ion, humic acid, and concentration of the Am(III) on the adsorption behavior were also studied, and the possible adsorption mechanism was discussed. Experimental results show that the adsorption distribution rate of Am(III) on granite increases with increasing pH of aqueous phase. The chemical composition of the groundwater is the main factor which influences the species of Am(III) and adsorption behavior. The adsorption mechanism of Am(III) on granite is surface complexation. The adsorption isotherm of Am(III) on granite can be described by Freundlich's equation. (authors)

Portuguese granites associated with Sn-W and Au mineralizations

OpenAIRE

Ana M.R. Neiva

2002-01-01

In northern and central Portugal, there are different tin-bearing granites. Most of them are of S-type, others have mixed characteristics of I-type and S-type granites and a few are of I-type. Tin-tungsten deposits are commonly associated with Hercynian tin-bearing S-type granites. Some quartz veins with wolframite are associated with an I-type granite, which has a low Sn content. In suites of tin-bearing S-type granitic rocks, Sn content increases as a function of the degree of fractional cr...

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

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

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

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 Loma Venturilla pegmatites using nuclear techniques; Caracterizacion de las pegmatitas de Loma Venturilla mediante el uso de tecnicas nucleares

Energy Technology Data Exchange (ETDEWEB)

Pena Fortes, B; Caopte Rodriguez, G; Toujague La Rosa, R [Centro de Estudios Aplicados al Desarrollo Nuclear (CEADEN), La Habana (Cuba); Sukar Satraputa, K [Instituto de Geofisica y Astronomia, La Habana (Cuba)

1996-10-01

Neutron Activation Analysis (NAA) and gamma spectrometry Analysis (GEA) were used for the determination of 21 trace elements in geological samples of pegmatites of Loma Venturilla area. Both methods permitted, in general, the determination of K, Cr, Co, Sc, Rb, Cs, Ba, Ta, HF, Th, and U and 10 rare earths elements: La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb, and Lu. The results were obtained with good precision and accuracy The knowledge of such concentrations is of great interest in geosciences. The values of the concentrations obtained can be extensively used in petrogenetic studies of those rocks, since they facilitate the evaluation and estimation of the extent of the main process, involved in the generation and differentiation of the melts from which the pegmatites were derivates.

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

The Taitao Granites: I-type granites formed by subduction of the Chile Ridge and its implication in growth of continental crusts

Science.gov (United States)

Anma, Ryo

2016-04-01

Late Miocene to Early Pliocene granite plutons are exposed at the tip of the Taitao peninsula, the westernmost promontory of the Chilean coast, together with a contemporaneous ophiolite with a Penrose-type stratigraphy. Namely, the Taitao granites and the Taitao ohiolite, respectively, are located at ~30 km southeast of the Chile triple junction, where a spreading center of the Chile ridge system is subducting underneath the South America plate. This unique tectonic setting provides an excellent opportunity to study the generation processes of granitic magmas at a ridge subduction environment, and the complex magmatic interactions between the subducting ridge, overlying crust and sediments, and mantle. This paper reviews previous studies on the Taitao ophiolite/granite complex and use geochemical data and U-Pb age distributions of zircons separated from igneous and sedimentary rocks from the area to discuss the mechanism that formed juvenile magma of calc-alkaline I-type granites during ridge subduction. Our model implies that the magmas of the Taitao granites formed mainly due to partial melting of hot oceanic crust adjacent to the subducting mid-oceanic ridge that has been under influence of deep crustal contamination and/or metasomatized sub-arc mantle through slab window. The partial melting took place under garnet-free-amphibolite conditions. The juvenile magmas then incorporated a different amount of subducted sediments to form the I-type granites with various compositions. The Taitao granites provide an ideal case study field that shows the processes to develop continental crusts out of oceanic crusts through ridge subduction.

Sources and controls of Arsenic contamination in groundwater of Rajnandgaon and Kanker District, Chattisgarh Central India

Science.gov (United States)

Shukla, Dericks Praise; Dubey, C. S.; Singh, Ningthoujam P.; Tajbakhsh, M.; Chaudhry, M.

2010-12-01

SummaryA high concentration of Arsenic (As) contamination in ground water has been reported in the village of Kaudikasa in Rajnandgaon district, wherein around 10% of the population is suffering from As-borne diseases. The region does not share any demographic or geological similarity with the sedimentary aquifers of the Bengal Delta Plain in Eastern India, but represents an igneous terrain with elevated As concentrations in groundwater. There is limited information about the source of As in groundwater and its mobility constraints. In this area, almost all the wells are located in the granitic terrain with pegmatitic intrusions. Most of these wells are characterized by As concentration above the World Health Organization ( WHO, 1999) and the BIS (Bureau of Indian Standards) standards, with the highest being found in a well with more than 250 μg/L of As. Here we report petrographic studies of the granitic host rock and X-ray diffraction results that indicate that altered realgar (α-As 4S 4), para realgar (AsS), and/or tennantite (Cu 12As 4S 13), are the main mineral that contain As. This element is leached during the weathering and water-rock interactions. Microprobe analysis of the altered realgar grains of in pegmatitic intrusions of the host granite indicate 23-27 wt.% As. Remote sensing is useful to delineate the source of this contaminant, which appears to lie at the intersection of a mineralized NW-SE and N-S lineaments associated with the Kotri rift zone. These lineaments are structurally controlled as rifting followed by thrusting and other types of faulting caused left-lateral displacement of N-S Kotri lineament along a NW-SE fault plane showing sinistral shearing. This process caused water drainage in the areas to flow along these highly mineralized weak zones. Thus, the water becomes highly contaminated due to leaching of minerals at the intersection of these lineaments, clearly visible at two areas of high contamination that lie very near to this

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

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.

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

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 Bacillus subtilis on Granite Weathering: A Laboratory Experiment

Science.gov (United States)

Song, W.; Ogawa, N.; Oguchi, C. T.; Hatta, T.; Matsukura, Y.

2006-12-01

We performed a comparative experiment to investigate how the ubiquitous soil bacterium Bacillus subtilis weathers granite and which granite-forming minerals weather more rapidly via biological processes. Batch type experiments (granite specimen in a 500 ml solution including NaCl, glucose, yeast extract and bacteria Bacillus subtilis at 27°E C) were carried out for 30 days. Granite surfaces were observed by SEM before and after the experiment. Bacillus subtilis had a strong influence on granite weathering by forming pits. There were 2.4 times as many pits and micropores were 2.3 times wider in granite exposed to Bacillus subtilis when compared with bacteria-free samples. Bacillus subtilis appear to preferentially select an optimum place to adhere to the mineral and dissolve essential elements from the mineral to live. Plagioclase was more vulnerable to bacterial weathering than biotite among the granite composing minerals.

Depositional features and stratigraphic sections in granitic plutons: implications for the emplacement and crystallization of granitic magma

Science.gov (United States)

Wiebe, R. A.; Collins, W. J.

1998-09-01

Many granitic plutons contain sheet-like masses of dioritic to gabbroic rocks or swarms of mafic to intermediate enclaves which represent the input of higher temperature, more mafic magma during crystallization of the granitic plutons. Small-scale structures associated with these bodies (e.g. load-cast and compaction features, silicic pipes extending from granitic layers into adjacent gabbroic sheets) indicate that the sheets and enclave swarms were deposited on a floor of the magma chamber (on granitic crystal mush and beneath crystal-poor magma) while the mafic magma was incompletely crystallized. These structures indicate 'way up', typically toward the interior of the intrusions, and appear to indicate that packages of mafic sheets and enclave concentrations in these plutons are a record of sequential deposition. Hence, these plutons preserve a stratigraphic history of events involved in the construction (filling, replenishment) and crystallization of the magma chamber. The distinctive features of these depositional portions of plutons allow them to be distinguished from sheeted intrusions, which usually preserve mutual intrusive contacts and 'dike-sill' relations of different magma types. The considerable thickness of material that can be interpreted as depositional, and the evidence for replenishment, suggest that magma chamber volumes at any one time were probably much less than the final size of the pluton. Thus, magma chambers may be constructed much more slowly than presently envisaged. The present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber (along with the underlying solidified granite and country rock) sank during continuing episodes of magma chamber replenishment. These internal magmatic structures support recent suggestions that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber.

Geochemical signature of columbite-tantalite and radiometric survey of radioactive pegmatites in the region of Parelhas, Rio Grande do Norte, Brazil; Assinatura geoquimica de columbita-tantalita e levantamento radiometrico de pegmatitos radioativos da regiao de Parelhas, RN, Brasil

Energy Technology Data Exchange (ETDEWEB)

Moura, Jorge Costa de

2013-07-01

This thesis is the result of geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area, located in the surroundings of the city of Parelhas in the region of the Serra da Borborema, is well known for its thousands of pegmatitic bodies exploited in primitive mines called 'garimpos'. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of the ratio U/Th versus Nb{sub 2}O{sub 5}/Ta{sub 2}O{sub 5} provides geochemical signatures (analytical fingerprints) for the source location of such ore. A test of the new method with coltan samples of commercial batches from the Brazilian states Amapa and Rondonia also generated distinct geochemical signatures. A radiometric survey (CPS) was carried out in several mines and pegmatites to study the environmental impact of gamma radiation. It included in situ measurements of pegmatite walls, host rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and environmental gamma radiation therefore generally is not enhanced to a dangerous level. (author)

Geochemical signature of columbite-tantalite and radiometric survey of radioactive pegmatites in the region of Parelhas, Rio Grande do Norte, Brazil; Assinatura geoquimica de columbita-tantalita e levantamento radiometrico de pegmatitos radioativos da regiao de Parelhas, RN, Brasil

Energy Technology Data Exchange (ETDEWEB)

Moura, Jorge Costa de

2013-07-01

This thesis is the result of geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area, located in the surroundings of the city of Parelhas in the region of the Serra da Borborema, is well known for its thousands of pegmatitic bodies exploited in primitive mines called 'garimpos'. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of the ratio U/Th versus Nb{sub 2}O{sub 5}/Ta{sub 2}O{sub 5} provides geochemical signatures (analytical fingerprints) for the source location of such ore. A test of the new method with coltan samples of commercial batches from the Brazilian states Amapa and Rondonia also generated distinct geochemical signatures. A radiometric survey (CPS) was carried out in several mines and pegmatites to study the environmental impact of gamma radiation. It included in situ measurements of pegmatite walls, host rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and environmental gamma radiation therefore generally is not enhanced to a dangerous level. (author)

Hydrogeochemical radioactive features and prospecting in granopegmatite type uranium ore district in Danfeng area

International Nuclear Information System (INIS)

Feng Zhangsheng

2011-01-01

Hydrochemical radioactive prospecting plays an important role in the all stages of grano-pegmatite type uranium deposit exploration in Danfeng area dut to its fast, simple, economic and high effective advantage. Radioactive anomalous halo in the shallow underground water has identical distribution scopes with the ore-bearing biotite granite-pegmatite, which can be used to delineate uranium ore-forming prospective area, reconnaissance area and detailed prospecting area. Deep underground water close to the ore is characterized by hydrogeochemical radioactive features with high uranium and radon content. Through prospecting engineering of radioactive hydrogeochemical, the situation of blind ore bodies can be used to guide the layout. (authors)

Granite intrusion in a metamorphic core complex: the example of the Mykonos laccolith (Cyclades, Greece)

Science.gov (United States)

Denèle, Yoann; Lecomte, Emmanuel; Jolivet, Laurent; Huet, Benjamin; Labrousse, Loïc.; Le Pourhiet, Laetitia; Lacombe, Olivier

2010-05-01

Numerical and analogical modelling underlined the importance of a pre-existing anomaly of viscosity-density such as a granite or migmatitic body below the brittle-ductile transition as a primary cause of metamorphic core complex (MCC) developpement. While field studies of MCC show a spatial and temporal link between MCC formation and plutonic activity, thermochronological studies show that there is no link between the intrusion of granites and the velocity of slip on the detachement plane. The Aegean domain is a good natural laboratory for studying the formation of MCC and syn-tectonic granites. In the northern Cyclades, the Mykonos-Delos-Rhenia MCC is characterised by the intrusion of a plurikilometric Late Miocene pluton of I-type granite within a migmatitic gneiss dome. AMS (Anisotropy of magnetic susceptibility) and microstructural studies in the Mykonos granites combined with recent cooling rate data allow us to use the granites as strain marker. The Mykonos granitoïds form a plurikilometric laccolith slightly deeping to the east and presenting an elliptical shape with a N170°E long axis. The laccolith is strongly asymmetrical with an outlying root zone in the SW cropping out on Delos and Rhenia islands and a major body mainly developed to the NE and cropping out on Mykonos Island. The laccolith consists of various petrographic facies presenting straight contacts that demonstrate emplacement by successive pulses of more or less differentiated magmas. The laccolith was developed at the interface between the Cycladic Basement and the Blueschists Unit and within the Blueschist Unit. Two events of deformation have been recorded in the granites. The first event is characterized by submagmatic and high to middle temperature protomylonite microstructures developped during or just after the intrusion. The second event of deformation characterized by low temperature mylonites and cataclasites close to the major detachment fault corresponds to the localization of

Granitic rocks from the southern Gyeongsang basin, southeastern Korea, (1)

International Nuclear Information System (INIS)

Lee, Yoon-Jong

1980-01-01

In southern Gyeongsang basin, southeastern Korea, there are many granitic rock masses. They were divided into 7 groups according to their geological evidences. K-Ar age was determined on 36 samples obtained from the respective groups. Group A: pre-Gyeongsang granitic rock (Pre-Cretaceous), A 1 220 m.y., A 2 166 m.y.; group B: outer zone granitic rock (Cretaceous), 115-72 m.y.; group C: ditto (ditto), 97-70 m.y.; group D: ditto (ditto), 89-68 m.y.; group E: ditto (ditto), 82-68 m.y.; group F: inner zone granitic rock (Cretaceous), 75-74 m.y.; group G: Tertiary granitic rock, 63-41 m.y. The large part of the Cretaceous granitic masses show the double elongated ring form. Most of the Tertiary granitic rocks were probably emplaced in close relation with the Eonyang fault line and Ulsan fault line/or their extension line of the area. (J.P.N.)

2005 dossier: granite. Tome: phenomenological evolution of the geologic disposal

International Nuclear Information System (INIS)

2005-01-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the phenomenological aspects of the geologic disposal of high-level and long-lived radioactive wastes (HLLL) in granite formations. Content: 1 - introduction: ANDRA's research program on disposal in granitic formation; 2 - the granitic environment: geologic history, French granites; 3 - HLLL wastes and disposal design concepts; 4 - identification, characterization and modeling of a granitic site: approach, geologic modeling, hydrologic and hydro-geochemical modeling, geomechanical and thermal modeling, long-term geologic evolution of a site; 5 - phenomenological evolution of a disposal: main aspects of the evolution of a repository with time, disposal infrastructures, B-type wastes disposal area, C-type wastes disposal area; spent fuels disposal area, radionuclides transfer and retention in the granitic environment; 6 - conclusions: available knowledge, methods and tools for the understanding and modeling of the phenomenological evolution of a granitic disposal site. (J.S.)

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

Preliminary study of the uranium favorability of granitic and contact-metamorphic rocks of the Owens Valley area, Inyo and Mono Counties, California, and Esmeralda and Mineral Counties, Nevada

International Nuclear Information System (INIS)

Cupp, G.M.; Mitchell, T.P.

1978-01-01

Granitic and contact-metamorphic rocks of the Owens Valley area were sampled to determine their favorability for uranium. Uranium deposits associated with these rocks were examined to determine the mode of occurrence. Metamorphic rocks near contacts with intrusive rocks include skarns, schists, quartzites, metaconglomerates, hornfels, gneisses, and metavolcanics. The grade of contact metamorphism ranges from slight to intense, depending upon the distance from the intrusive contact. The average U 3 O 8 content of the metamorphic rock samples is 3 ppM. Metamorphic rock samples in a roof pendant at the Claw prospect contain as much as 3 percent U 3 O 8 . Skarn samples from the Birch Creek pluton contain as much as 114 ppM U 3 O 8 ; those from the Santa Rita Flat pluton contain as much as 23 ppM U 3 O 8 . Most of the intrusive rocks are granite, quartz monzonite, or monzonite. Granodiorite and diorite are less common, and gabbro is rare. The average U 3 O 8 content of the crystalline rock samples is 4 ppM. Samples from a quartz-monzonite pluton east of Lone Pine, California, and quartz monzonite in the Santa Rosa Hills had maximum contents of 28 and 13 ppM U 3 O 8 , respectively. Areas of contact metamorphism and metasomatism, such as those at the Claw prospect and Birch Creek pluton, are probably the most favorable sites for uranium deposits. There are many miles of granitic and contact-metamorphic zones in which undiscovered uranium deposits may exist. Although the overall uranium content of granitic rocks appears to be low, the pluton east of Lone Pine and the Hunter Mountain pluton in the area of the Santa Rosa Hills have sufficient uranium to have acted as uranium and detrital source rocks for uranium deposits that may now be buried in Tertiary sediments in the basins around the plutons. The Claw deposit is the only known uranium deposit of a size and grade to be of possible commercial interest

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

Liandratite from Karkonosze pegmatites, Sudetes, Southwestern Poland

Science.gov (United States)

Matyszczak, Witold

2018-06-01

The chemical composition of liandratite, U6+(Nb,Ta)2O8, was determined from material collected in Niobium, Yttrium, Fluorine type (NYF) pegmatites of the Karkonosze intrusion (Sudetes, SW Poland). Liandratite occurs mainly as rims, up to 40 µm thick, and fracture infillings in fergusonite-(Y) and other Nb-Ta-Ti minerals. Its formation was related to the fluid-driven alteration of primary minerals by three potential mechanisms: (i) direct replacement of a primary mineral by liandratite; (ii) breakdown of the primary mineral to liandratite and a product with the composition of minerals of the pyrochlore group; (iii) multistage alteration, which involved: removal of A-site cations (mostly Y + REE with the exception of U4+) and formation of phases with the composition of pyrochlore group minerals; then crystallization of U-, Bi-, Pb-rich pyrochlores and their replacement by liandratite. The chemical compositions of liandratite formed by the breakdown of different primary minerals are also different, mainly in their U, Ti and Nb contents. Excess Ti, relative to the U6+Nb2O8 end-member, is incorporated into the structure together with additional U. The Ti content of liandratite, and partially through this the U content, are dependent on the nature of the precursor mineral.

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

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)

PREVALENCE OF METABOLIC SYNDROME IN GRANITE WORKERS

Directory of Open Access Journals (Sweden)

Srilakshmi

2015-10-01

Full Text Available BACKGROUND: The prevalence of the metabolic syndrome (MS has significantly increased over the last few decades and has become a main health challenge worldwide. Prevalence of MS is quickly rising in developing countries due to changing lifestyle. It was considered worthwhile to study MS and its components in granite workers since granite factories are situated in and around Khammam area. Moreover, no studies of MS in granite workers have been reported in literature. OBJECTIVES: Aim of our study is to assess the prevalence of metabolic syndrome and its components in granite workers. MATERIALS AND METHODS: 210 male workers in the age group of 20 - 50 working in granite industries located in and around the Khammam town of Telangana State are selected for the present study. Blood pressures (BP, waist circumference (WC were measured. Fasting blood samples were collected for the estimation of glucose and lipids. RESULTS: 69 subjects out of 210 were identified as having MS based on updated National cholesterol education programme - Adult Treatment Panel III (NCEP - ATP III guidelines. CONCLUSION: MS should be identified and remedial measures may be suggested, so that the risk of hypertension, cardiovascular risk, diabetes and the resultant morbidity is minimized and can be delayed

Sample size clay kaolin of primary in pegmatites regions Junco Serido - PB and Equador - RN; Granulometria de argila caulim primario dos pegmatitos nas regioes do Junco do Serido - PB e Equador - RN

Energy Technology Data Exchange (ETDEWEB)

Meyer, M.F.; Sousa, J.B.M.; Sales, L.R.; Silva, P.A.S.; Lima, A.D.D., E-mail: mauro.meyer@ifrn.edu.br [Instituto Federal do Rio Grande do Norte (IFRN), RN (Brazil)

2016-07-01

Kaolin is a clay formed mainly of kaolinite resulting from feldspar weathering or hydrothermal. This study aims to investigate the way of occurrence, kaolin particle size of the pegmatites of the Borborema Province Pegmatitic in the regions of Junco do Serido-PB and Ecuador-RN. These variables were analyzed considering granulometric intervals obtained from wet sieving of samples of pegmatite mines in the region. Kaolin was received using sieves of 200, 325, 400 and 500 mesh and the sieve fractions retained by generating statistical parameters histograms. kaolin particles are extremely fine and pass in its entirety through 500 mesh sieve. The characterization of minerals in fine fractions by diffraction of X-rays showed that the relative amount of sericite in fractions retained in sieves 400 and 500 mesh impairing the whiteness and mineralogical texture kaolin production. (author)

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.

The instrumental neutron-activation analysis of granites from the Bushveld Complex

International Nuclear Information System (INIS)

Watterson, J.I.W.

1978-01-01

Three methods of instrumental neutron-activation analysis, 14MeV, reactor thermal, and reactor epithermal, are compared for the analysis of granites form the Bushveld Complex. A total of 34 elements can be determined in the granites by these methods. Samples from the Zaaiplaats area were analysed by thermal neutron activation, and 22 elements were determined in all of them. These elements were used to distinguish between the mineralized Bobbejaankop and Lease granites and the Main granite by the use of multivariate statistics. The Bobbejaankop granite appears as a more-differentaited rock carrying greater amounts of the incompatible elements than does the Main granite [af

Status of LLNL granite projects

International Nuclear Information System (INIS)

Ramspott, L.D.

1980-01-01

The status of LLNL Projects dealing with nuclear waste disposal in granitic rocks is reviewed. This review covers work done subsequent to the June 1979 Workshop on Thermomechanical Modeling for a Hardrock Waste Repository and is prepared for the July 1980 Workshop on Thermomechanical-Hydrochemical Modeling for a Hardrock Waste Repository. Topics reviewed include laboratory determination of thermal, mechanical, and transport properties of rocks at conditions simulating a deep geologic repository, and field testing at the Climax granitic stock at the USDOE Nevada Test Site

Sorption of Np (Ⅴ) on Beishan granite fracture filling materials

International Nuclear Information System (INIS)

Jiang Tao; Wang Bo; Bao Liangjin; Zhou Duo; Long Haoqi; Song Zhixin; Chen Xi

2012-01-01

The sorption behaviors of Np (Ⅴ) on the granite fracture filling materials were studied by batch experiments under anaerobic in Beishan groundwater. The impact of pH of groundwater, CO 3 2- , humic acid and different components of granite fracture filling materials on sorption of Np (Ⅴ) was investigated. The results show that the granite fracture filling materials have strong capacity of Np (Ⅴ) adsorption. The value of K d , for Np (Ⅴ) sorption on the granite fracture filling materials is 843 mL/g. With the increase of pH, the value of K d increases at first and then decreases. K d of Np sorption on granite fracture filling materials in the presence of CO 3 2- and humic acid decreases. The chlorite and feldspar are major contributors to the sorption of Np (Ⅴ) on Beishan granite fracture filling materials. (authors)

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.

Core drilling of drillholes ONK-KR13, ONK-KR14 and ONK-KR15 in ONKALO at Olkiluoto 2010 - 2011

International Nuclear Information System (INIS)

Toropainen, V.

2011-08-01

As a part of the confirming site investigations at Olkiluoto, Suomen Malmi Oy (Smoy) core drilled three drillholes ONK-KR13 (120.45 m), ONK-KR14 (75.27 m) and ONK-KR15 (79.96 m) in ONKALO, at Olkiluoto in June 2010 - March 2011. The diameter of the drillholes is 75.7 mm. Sodium fluorescein was used as a label agent in the drilling water, and the drillholes were washed and flushed after the drilling. The deviations of the drillholes were measured with the deviation measuring instruments EMS and Gyro. The core samples were logged according to Posiva's normal procedure for drillholes. The main rock types are veined and diatexitic gneisses and pegmatitic granite. The average natural fracture frequencies and RQDs of the core samples are 1.6 pcs/m and 97.0 % (ONK-KR13), 0.5 pcs/m and 99.3 % (ONK-KR14) and 1.6 pcs/m and 97.3 % (ONK-KR15). In drillhole ONK-KR13 one, and in drillhole ONK-KR15 three fractured zones were intersected. There was no fractured zones in drillhole ONK-KR14. Rock mechanical tests were performed to core samples. The average uniaxial compressive strength was 143.2 MPa, the average Young's Modulus was 57.3 GPa and the average Poisson's ratio was 0.25. (orig.)

Core drilling of drillholes ONK-PVA9 and ONK-PVA10 in ONKALO at Olkiluoto 2011

Energy Technology Data Exchange (ETDEWEB)

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

2011-10-15

Suomen Malmi Oy (Smoy) core drilled two drillholes for groundwater monitoring stations in ONKALO at Eurajoki, Olkiluoto in 2011. The groundwater monitoring stations are used for monitoring changes in groundwater conditions. The drillhole ONK-PVA9 was drilled in March 2011 and the drillhole ONK-PVA10 in June 2011. The lengths of the drillholes are 15.95 and 20.10 m respectively. The drillholes are 75.7 mm by diameter. The drillhole ONK-PVA9 was drilled in a niche of the access tunnel at chainage 4366 and the ONK-PVA10 in the access tunnel wall at chainage 3851. 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 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 and pegmatitic granite. The average fracture frequencies in drill cores are 2.9 pcs/m (ONK-PVA9) and 2.3 pcs/m (ONK-PVA10) and the average RQD values 81.6 % and 96.2 % respectively. (orig.)

Granite-related hypothermal uranium mineralization in South China

International Nuclear Information System (INIS)

Liu, X.; Wu, J.; Pan, J.; Zhu, M.

2014-01-01

As one of the important geological types, granite-related uranium deposits account for about 29% of the total discovered natural uranium resources in China. Most of the granite-related uranium deposits located in Taoshan - Zhuguang uranium metallogenic belt, South China. In addition to the typical pitchblende vein-type uranium mineralization of epithermal metallogenic system, a new type of granite-related uranium mineralization with characteristics of hypothermal matallogenic system was discovered in South China by current studies. However, hypothermal is contact thermal to epithermal mineralization, and not the conventional intrusive high temperature mineralization. Hypothermal uranium mineralization is presented by disseminated uraninite or pitchblende stockwork in fissures in granites normally with extensive alkaline alteration. The high temperature mineral assemblage of uraninite associate with scheelite and tourmaline was identified in hypothermal uranium mineralization. Fluid inclusion studies on this type mineralization indicated the middle to high temperature (>250℃) mineralization with the mixing evidence of ore forming solution derived from deep level, and the boiling and mixing of ore forming solution are regarded as the dominant mineralization mechanism for the precipitating of uranium. In contrast to the mineralization ages of 67 Ma to 87 Ma for typical pitchblende vein mineralization of epithermal metallogenic system, the mineralization age is older than 100 Ma for hypothermal uranium mineralization in granite. In the Shituling deposit, Xiazhuang uranium ore field, uraninite and pitchblende micro veins with extensive potassic alteration, chloritization and sericitization are hosted in fissures of Indo-Chinese epoch granites with the uranium mineralization age of 130 Ma to 138 Ma with a mineralization temperature of 290℃ to 330℃ indicated. Other examples sharing the similar characters of hypothermal uranium mineralization have been recognized in

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

Directory of Open Access Journals (Sweden)

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.

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.

Geochemistry and petrogenesis of Proterozoic granitic rocks from ...

Indian Academy of Sciences (India)

Geochemistry and petrogenesis of Proterozoic granitic ... This study presents the geochemical characteristics of granitic rocks located on the northern ... Frost and Frost 2013). ...... King P L, White A J R, Chappell B W and Allen C M 1997.

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.

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.

Neobvyklý P-, Li- a Sn-bohatý pegmatit z Vernéřova u Aše, Česká republika

Czech Academy of Sciences Publication Activity Database

Breiter, Karel; Škoda, R.; Veselovský, F.

2009-01-01

Roč. 17, č. 1 (2009), s. 41-59 ISSN 1211-0329 R&D Projects: GA AV ČR IAA300130801 Institutional research plan: CEZ:AV0Z30130516 Keywords : pegmatite * mineralogy * phosphates * montebrasite * sulfides * genesis * Vernéřov near Aš (Western Bohemia) Subject RIV: DB - Geology ; Mineralogy

Homogenization Experiments of Crystal-Rich Inclusions in Spodumene from Jiajika Lithium Deposit, China, under Elevated External Pressures in a Hydrothermal Diamond-Anvil Cell

Directory of Open Access Journals (Sweden)

Jiankang Li

2017-01-01

Full Text Available Extensive studies of the crystal-rich inclusions (CIs hosted in minerals in pegmatite have resulted in substantially different models for the formation mechanism of the pegmatite. In order to evaluate these previously proposed formation mechanisms, the total homogenization processes of CIs hosted in spodumene from the Jiajika pegmatite deposit in Sichuan, China, were observed in situ under external H2O pressures in a new type of hydrothermal diamond-anvil cell (HDAC. The CIs in a spodumene chip were loaded in the sample chamber of HDAC with water, such that the CIs were under preset external H2O pressures during heating to avoid possible decrepitation. Our in situ observations showed that the crystals within the CIs were dissolved in carbonic-rich aqueous fluid during heating and that cristobalite was usually the first mineral being dissolved, followed by zabuyelite and silicate minerals until their total dissolution at temperatures between 500 and 720°C. These observations indicated that the minerals within the CIs were daughter minerals crystallized from an entrapped carbonate- and silica-rich aqueous solution and therefore provided useful information for evaluating the formation models of granitic pegmatites.

The source rock characters of U-rich granite

Energy Technology Data Exchange (ETDEWEB)

Mingyue, Feng; Debao, He [CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology, Beijing Research Institute of Uranium Geology (China)

2012-03-15

This paper discusses the stratum composition, lithological association, uranium content of crust and the activation, migration, concentration of uranium at each tectonic cycle in South China. The authors point out that the source rock of U-rich granite is U-rich continental crust which is rich in Si, Al and K. The lithological association is mainly composed of terrestrial clastic rocks formation of mudstone and sandstone, mingled with intermediate-acidic, mafic pyroclastic rocks and carbonate rocks formation. During tectonic movements, the rocks had undergone regional metamorphism, migmatitization, granitization, and formed U-rich granites finally. (authors)

The source rock characters of U-rich granite

International Nuclear Information System (INIS)

Feng Mingyue; He Debao

2012-01-01

This paper discusses the stratum composition, lithological association, uranium content of crust and the activation, migration, concentration of uranium at each tectonic cycle in South China. The authors point out that the source rock of U-rich granite is U-rich continental crust which is rich in Si, Al and K. The lithological association is mainly composed of terrestrial clastic rocks formation of mudstone and sandstone, mingled with intermediate-acidic, mafic pyroclastic rocks and carbonate rocks formation. During tectonic movements, the rocks had undergone regional metamorphism, migmatitization, granitization, and formed U-rich granites finally. (authors)

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

Radon exhalation from granitic rocks

International Nuclear Information System (INIS)

Del Claro, Flávia; Paschuk, Sergei A.; Corrêa, Janine N.; Mazer, Wellington; Narloch, Danielle Cristine; Martin, Aline Cristina; Denyak, Valeriy

2017-01-01

Naturally occurring radionuclides such as radon ( 222 Rn), its decay products and other elements from the radioactive series of uranium ( 238 U and 235 U) and thorium ( 232 Th) are an important source of human exposure to natural radioactivity. The worldwide evaluation of health radiobiological effects and risks from population exposure to natural radionuclides is a growing concern. About 50% of personal radiation annual dose is related to radionuclides such as radon ( 222 Rn), thoron ( 220 Rn), radium ( 226 Ra), thorium ( 232 Th) and potassium ( 40 K), which are present in modern materials commonly used in construction of dwellings and buildings. The radioactivity of marbles and granites is of big concern since under certain conditions the radioactivity levels of these materials can be hazardous to the population and require the implementation of mitigation procedures. Present survey of the 222 Rn and 220 Rn activity concentration liberated in the air was performed using commercialized Brazilian granite rocks at national market as well as exported to other countries. The 222 Rn and 220 Rn measurements were performed using the AlphaGUARD instant monitor and RAD7 detector, respectively. This study was performed at the Applied Nuclear Physics Laboratory of the Federal University of Technology – Paraná (UTFPR). Obtained results of radon concentration activity in air exhaled studied samples of granites varied from 3±1 Bq/m 3 to 2087±19 Bq/m 3 , which shows that some samples of granitic rocks represent rather elevated health risk the population. (author)

The Serra do Carambei Granite - PR and the uraniferous anomalism

International Nuclear Information System (INIS)

Pinto-Coelho, C.V.

1986-01-01

The Serra do Carambei Granite forms a pluton relatively homogeneous, covering about 33 km 2 , cropping out as an elongate retangular body trending NE-SW, being emplaced in the Cunhaporanga Granitoid Complex. Its characteristics indicates a kind of hololeucocratic granite, equigranular, medium to coarse-grained, consisting predominantly of microperthitic alkali-feldspar, quartz and a small amount of biotite (less than 1%), thus being classified as an alaskite. Chemical data allows a classification in the group of granite with high contents of silica (74-76% Wt. SiO 2 ), dominantly alkaline chemism and hypersolvus character, derived from a parental magma under saturated in water with distinguished features of granitoids from the magnetite series and types I and A granites. The pluton shows important chemical variations due to weathering processes. However detailed chemical studies reveal the presence of anomalous concentrations of trace elements such as U, Sn, Nb, Y, Zr, the Serra do Carambei Granite lacks economically important mineralizations because of the absence of well-developed tardi/pos-magmatic processes that could concentrate them. The SW side of the granite is cut by leucocratic rhyolite dykes that show some radiometric anomalies. These rocks, which are highly diferentiated, were emplaced contemporaneously to the Serra do Carambei Granite. Although petrographic and chronological similarities are found between the uraniferous alaskite of Roessing (Namibia) and the Serra do Carambei Granite anyhow it was not possible to establish any lateral continuity with the uranifeous Pan-African Province. (Author) [pt

2005 dossier: granite. Tome: architecture and management of the geologic disposal; Dossier 2005: granite. Tome architecture et gestion du stockage geologique

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the geologic disposal of high-level and long-lived radioactive wastes in granite formations. Content: 1 - Approach of the study: main steps since the December 30, 1991 law, ANDRA's research program on disposal in granitic formations; 2 - high-level and long-lived (HLLL) wastes: production scenarios, waste categories, inventory model; 3 - disposal facility design in granitic environment: definition of the geologic disposal functions, the granitic material, general facility design options; 4 - general architecture of a disposal facility in granitic environment: surface facilities, underground facilities, disposal process, operational safety; 5 - B-type wastes disposal area: primary containers of B-type wastes, safety options, concrete containers, disposal alveoles, architecture of the B-type wastes disposal area, disposal process and feasibility aspects, functions of disposal components with time; 6 - C-type wastes disposal area: C-type wastes primary containers, safety options, super-containers, disposal alveoles, architecture of the C-type wastes disposal area, disposal process in a reversibility logics, functions of disposal components with time; 7 - spent fuels disposal area: spent fuel assemblies, safety options, spent fuel containers, disposal alveoles, architecture of the spent fuel disposal area, disposal process in a reversibility logics, functions of disposal components with time; 8 - conclusions: suitability of the architecture with various types of French granites, strong design, reversibility taken into consideration. (J.S.)

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

Movement of fossil pore fluids in granite basement, Illinois

International Nuclear Information System (INIS)

Couture, R.A.; Seitz, M.G.

1986-01-01

The compositions of pore fluids in granite cores from the Precambrian basement in northern Illinois were determined. The estimated chloride concentration in the aqueous phase increases from near zero at the upper contact with sandstone to 2.7 M at 624 m below the contact. Traces of aliphatic oil are present in the overlying sandstone and the upper 516 m of granite, and oil occupies most of the pore space in one sample of unaltered granite 176 m below the contact. The oil has a Δ 13 C of -25%, about the same as average petroleum. The high concentrations of salt more than 500 m below the contact imply that little or no fresh water has reached these levels of the granite by flow. Lower concentrations near the contact are consistent with replacement of brine in the sandstone by fresh water at least 11 m.y. ago and subsequent upward diffusion of salt from the granite. Geologic data suggest that the time of replacement was about 130 Ma. The purpose of the investigation is to study the record of movement of intergranular fluids within a granite pluton. The composition and movement of ground waters can determine the extent that hazardous or radioactive wastes disposed in igneous rock will remain isolated

Limit of the radionuclides in granite

International Nuclear Information System (INIS)

Wang Shaling; Jiang Rangrong

2003-01-01

Granite is an important sort of building materials. Their radionuclide contents are limited by the national standard GB6566-2001 just as other building materials. This standard divides them into main materials and decorative materials, and relaxes the limit of the latter obviously. Owing to the consideration of public dose limit and environment protection, this method needs discussion. Otherwise, red granite contains high radionuclide contents relatively, especially the sort of Indian Red, and need be paid more attention

Core drilling of deep drillhole OL-KR48 at Olkiluoto in Eurajoki 2007

International Nuclear Information System (INIS)

Toropainen, V.

2008-01-01

Poisson's ratio (0.36) were measured from the core samples. The main rock types are veined and diatexitic gneisses, pegmatitic granite and tonalitic-granodioritic-granitic gneiss. Average fracture frequency is 1.1 pcs/m. and average RQD value is 98.0 %. In drillhole OL-KR48 seven fractured zones were penetrated during drilling work. (orig.)

Core drilling of deep borehole OL-KR46 at Olkiluoto in Eurajoki 2007

International Nuclear Information System (INIS)

Toropainen, V.

2007-09-01

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 600.10 m and 45.16 m deep boreholes with a diameter of 75.7 mm at Olkiluoto in May - June 2007. The identification numbers of the boreholes are OL-KR46 and OL-KR46B, 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 water, and the volume of drilling 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 466 m 3 and 20 m 3 in boreholes OL-KR46 and OL-KR46B, respectively. Measured volumes of the returning water were 407 m 3 in borehole OL-KR46 and 12 m 3 in borehole OL-KR46B. 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 116.5 MPa, the average Young's Modulus is 31.5 GPa and the average Poisson's ratio is 0.20. The main rock types are veined gneiss, tonalitic-granodioritic-granitic gneiss and pegmatite

Core drilling of deep drillhole OL-KR45 at Olkiluoto in Eurajoki 2007

International Nuclear Information System (INIS)

Toropainen, V.

2007-11-01

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 1023.30 m and 44.75 m deep drillholes with a diameter of 75.7 mm at Olkiluoto in June - September 2007. The identification numbers of the drillholes are OL-KR45 and OL-KR45B, 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 washing water were 1186 m 3 and 19 m 3 in drillholes OL-KR45 and OL-KR45B, respectively. Measured volumes of the returning water were 962 m 3 in drillhole OL-KR45 and 15 m 3 in drillhole OL-KR45B. 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 126.2 MPa, the average Young's Modulus is 42.5 GPa and the average Poisson's ratio is 0.21. The main rock types are veined and diatexitic gneisses, pegmatitic granite and tonalitic-granodioritic-granitic

Crystal chemistry of nephelines from ijolites and nepheline-rich pegmatites: influence of composition and genesis on the crystal structure investigated by X-ray diffraction

DEFF Research Database (Denmark)

Vulić, Predrag; Balić-Žunić, Tonči; Belmonte, Louise Josefine

2011-01-01

Ten nepheline single crystals from five different localities representing rocks from nepheline-syenite pegmatites to urtite, ijolite and cancrinite-ijolite were investigated chemically and structurally. The chemical compositions were determined by electron microprobe, whereas the crystal structur...

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

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)

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

Radon exhalation from granitic rocks

Energy Technology Data Exchange (ETDEWEB)

Del Claro, Flávia; Paschuk, Sergei A.; Corrêa, Janine N.; Mazer, Wellington; Narloch, Danielle Cristine; Martin, Aline Cristina [Universidade Tecnológica Federal do Paraná (UTFPR), Curitiba, PR (Brazil); Denyak, Valeriy, E-mail: flaviadelclaro@gmail.com, E-mail: spaschuk@gmail.com, E-mail: janine_nicolosi@hotmail.com, E-mail: denyak@gmail.com [Instituto de Pesquisa Pelé Pequeno Príncipe (IPPP), Curitiba, PR (Brazil)

2017-07-01

Naturally occurring radionuclides such as radon ({sup 222}Rn), its decay products and other elements from the radioactive series of uranium ({sup 238}U and {sup 235}U) and thorium ({sup 232}Th) are an important source of human exposure to natural radioactivity. The worldwide evaluation of health radiobiological effects and risks from population exposure to natural radionuclides is a growing concern. About 50% of personal radiation annual dose is related to radionuclides such as radon ({sup 222}Rn), thoron ({sup 220}Rn), radium ({sup 226}Ra), thorium ({sup 232}Th) and potassium ({sup 40}K), which are present in modern materials commonly used in construction of dwellings and buildings. The radioactivity of marbles and granites is of big concern since under certain conditions the radioactivity levels of these materials can be hazardous to the population and require the implementation of mitigation procedures. Present survey of the {sup 222}Rn and {sup 220}Rn activity concentration liberated in the air was performed using commercialized Brazilian granite rocks at national market as well as exported to other countries. The {sup 222}Rn and {sup 220}Rn measurements were performed using the AlphaGUARD instant monitor and RAD7 detector, respectively. This study was performed at the Applied Nuclear Physics Laboratory of the Federal University of Technology – Paraná (UTFPR). Obtained results of radon concentration activity in air exhaled studied samples of granites varied from 3±1 Bq/m{sup 3} to 2087±19 Bq/m{sup 3}, which shows that some samples of granitic rocks represent rather elevated health risk the population. (author)

Petrologic Applications of Tourmaline

Science.gov (United States)

London, D.; Morgan, G. B., VI; Wolf, M. B.; Guttery, B. M.

2011-12-01

Compositions of tourmaline reflect its chemical environment of formation. Schorl-dravite is an accessory in metapelites and persists up to the onset of anatexis. Amphibolites and marbles contain uvite, and magnesiofoitite-povandraite is distinctive of base-metal porphyries. In granitic pegmatites, schorl-dravite at the contacts evolves toward foitite and olenite (aluminous) components as Fe is depleted from the melt. Fractionation may bring residual melts to saturation in elbaite, an Li-rich component of tourmaline. Common tourmaline (schorl-dravite-olenite-foitite solid solution) possesses a wide P-T field of stability. Synthesis experiments put the upper thermal limit of common tourmaline at ~ 750°-850°C from 50 MPa to 10 GPa, and dravite has been synthesized as low as 350°C. The boron content of granitic melt or aqueous fluid in equilibrium with common tourmaline alone and with equivalent silicate mineral assemblages varies sharply with temperature according to a relationship of CB2O3melt,vapor ~ 0.0032e0.0087T(C). Common tourmaline is stable over an aSiO2 at and below saturation in Qtz; besides FeMg, its stability hinges principally on the solubility product [aAl2O3]3*[aB2O3]1.5 in vapor or melt. Surprisingly, increasing activities of H2O or fluoride components (both are present in tourmaline) destabilize common tourmaline in granitic melt, as both components form complexes with Al that reduce aAl2O3 in the melt. As a result, common tourmaline may survive anatexis when the aH2O attending melting is low. In contrast to common tourmaline, most attempts to synthesize elbaite have failed. Aluminous tourmaline containing 37 mol% Elb component has been synthesized recently, which is significant for understanding occurrences in pegmatites as well as for the potential appearance of synthetic elbaite on the gem market. Experimental calibration of δ11B between aqueous fluid and dravite at 50-500 MPa and 350°-750°C varies by only 6.1 % over this range of conditions

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

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

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

U(VI) sorption on granite: prediction and experiments

International Nuclear Information System (INIS)

Nebelung, C.; Brendler, V.

2010-01-01

One widely accepted approach - component additivity (CA) - to describe the sorption of contaminants onto complex materials such as rocks or soils is based on the assumption that the surface of a complex mineral assemblage is composed of a mixture of mineral constituents whose surface properties are known from independent studies. An internally consistent SCM (surface complexation model) database can be developed that describes the adsorption reactions of solutes to each phase. Here, the capability of such a methodology was tested, using the code MINTEQA2 including thermodynamic data of the NEA-TDB, and literature data for SCM, namely the DDL model. The sorption characteristics of U(VI) on granite (from Eibenstock, Saxony, Germany, with the main components quartz, albite, orthoclase, and muscovite) was predicted and then compared to batch experiments. Granite plays an important role in the remediation of former uranium ore mining and milling sites, but is also one of the host rocks considered for final disposal of nuclear materials. Safety assessment requires a detailed understanding of this system and its retention potential with regard to hazardous components. Namely the sorption of uranium in this complex rock is not fully understood yet. The experiments thus also provided a better understanding of the far-field behaviour in granitic geological nuclear repositories. The robustness of the prediction was tested by variation of the granite composition and the variation of the specific surface area (SSA) - first all components were predicted with a uniform granite SSA, second with a distinct SSA for each granite component (determined on pure minerals for the same grain size fractions). Changes in compositions yielded only marginal differences in the prediction. Different approaches to SSA showed somewhat larger deviations. In conclusion, the CA methodology is a valid and robust approach to U(VI) sorption onto complex substrates such as granite, provided sufficient

Permian ultrafelsic A-type granite from Besar Islands group, Johor, peninsular Malaysia

Science.gov (United States)

Ghani, Azman A.; Hazad, Fatin Izzani; Jamil, Azmiah; Xiang, Quek Long; Atiqah Wan Ismail, Wan Nur; Chung, Sun-Lin; Lai, Yu-Ming; Roselee, Muhammad Hatta; Islami, Nur; Nyein, Kyaw Kyaw; Amir Hassan, Meor Hakif; Abu Bakar, Mohd Farid; Umor, Mohd Rozi

2014-12-01

The granitic rocks of the peninsula have traditionally been divided into two provinces, i.e., Western and Eastern provinces, corresponding to S- and I-type granite respectively. The Western Province granite is characterised by megacrystic and coarse-grained biotite, tin-mineralised, continental collision granite, whereas, the Eastern Province granite is bimodal I-type dominated by granodiorite and associated gabbroic of arc type granite. This paper reports the occurrence of an A-type granite from peninsular Malaysia. The rocks occur in the Besar, Tengah, and Hujung islands located in the southeastern part of the peninsula. The granite is highly felsic with SiO2 ranging from 75.70% to 77.90% (differentiation index = 94.2-97.04). It is weakly peraluminous (average ACNK =1.02), has normative hypersthene (0.09-2.19%) and high alkali content (8.32-8.60%). The granites have many A-type characteristics, among them are shallow level of emplacement, high Ga, FeT/MgO and low P, Sr, Ti, CaO and Nb. Calculated zircon saturation temperatures for the Besar magma ranging from 793 ∘ to 806 ∘C is consistent with high temperature partial melting of a felsic infracrustal source which is taken as one of the mechanisms to produce A-type magma. The occurrence of the A-type granite can be related to the extensional back arc basin in the Indo-China terrane during the earliest Permian.

Rare-earth elements in granites: concentration and distribution pattern

International Nuclear Information System (INIS)

Galindo, A.C.

1983-01-01

The geochemistry of rare earth elements in granites is studied. The rare earth element (REE) distribution pattern in granites is characterized by a smooth curve with decreasing concentrations from La to Lu, and frequently a marked Eu negative anomaly. It seems to exist relationship between granite genesis and its REE pattern, in that bodies of primary (magmatic differentiation) origin always show this negative Eu anomaly, while those bodies generated by crustal anatexis do not show this anomaly. (E.G.) [pt

U-Pb zircon geochronology of Mesoproterozoic postorogenic rocks and implications for post-Ottawan magmatism and metallogenesis, New Jersey Highlands and contiguous areas, USA

Science.gov (United States)

Volkert, R.A.; Zartman, R.E.; Moore, P.B.

2005-01-01

Postorogenic rocks are widespread in Grenville terranes of the north-central Appalachians where they form small, discordant, largely pegmatitic felsic intrusive bodies, veins, and dikes, and also metasomatic calcic skarns that are unfoliated and postdate the regional 1090 to 1030 Ma upper amphibolite- to granulite-facies metamorphism related to the Grenville (Ottawan) Orogeny. Zircons from magmatic and nonmagmatic rocks from northern New Jersey and southern New York were dated to provide information on the regional tectonomagmatic and metallogenic history following Ottawan orogenesis. We obtained U-Th-Pb zircon ages of 1004 ?? 3 Ma for pegmatite associated with the 1020 ?? 4 Ma Mount Eve Granite near Big Island, New York, 986 ?? 4 Ma for unfoliated, discordant pegmatite that intrudes supracrustal marble at the Buckwheat open cut, Franklin, New Jersey, ???990 Ma for a silicate-borate skarn layer in the Franklin Marble at Rudeville, New Jersey, and 940 ?? 2 Ma for a calc-silicate skarn layer at Lower Twin Lake, New York. This new data, together with previously published ages of 1020 ?? 4 to 965 ?? 10 Ma for postorogenic rocks from New Jersey and southern New York, provide evidence of magmatic activity that lasted for up to 60 Ma past the peak of high-grade metamorphism. Postorogenic magmatism was almost exclusively felsic and involved relatively small volumes of metaluminous to mildly peraluminous melt that fractionated from an A-type granite parent source. Field relationships suggest the melts were emplaced along lithosphere-scale fault zones in the Highlands that were undergoing extension and that emplacement followed orogenic collapse by least 30 Ma. Postorogenic felsic intrusions correspond to the niobium-yttrium-fluorine (NYF) class of pegmatites of C??erny?? (1992a). Geochronologic data provide a temporal constraint on late-stage hydrothermal activity and a metallogenic event in New Jersey at ???990 to 940 Ma that mineralized pegmatites with subeconomic to

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.)

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)

Granite Exfoliation, Cosumnes River Watershed, Somerset, California

Science.gov (United States)

Crockett, I. Q.; Neiss-Cortez, M.

2015-12-01

In the Sierra Nevada foothills of California there are many exposed granite plutons within the greater Sierra Nevada batholith. As with most exposed parts of the batholith, these granite slabs exfoliate. It is important to understand exfoliation for issues of public safety as it can cause rock slides near homes, roads, and recreation areas. Through observation, measuring, and mapping we characterize exfoliation in our Cosumnes River watershed community.

Granite disposal of U.S. high-level radioactive waste.

Energy Technology Data Exchange (ETDEWEB)

Freeze, Geoffrey A.; Mariner, Paul E.; Lee, Joon H.; Hardin, Ernest L.; Goldstein, Barry; Hansen, Francis D.; Price, Ronald H.; Lord, Anna Snider

2011-08-01

This report evaluates the feasibility of disposing U.S. high-level radioactive waste in granite several hundred meters below the surface of the earth. The U.S. has many granite formations with positive attributes for permanent disposal. Similar crystalline formations have been extensively studied by international programs, two of which, in Sweden and Finland, are the host rocks of submitted or imminent repository license applications. This report is enabled by the advanced work of the international community to establish functional and operational requirements for disposal of a range of waste forms in granite media. In this report we develop scoping performance analyses, based on the applicable features, events, and processes (FEPs) identified by international investigators, to support generic conclusions regarding post-closure safety. Unlike the safety analyses for disposal in salt, shale/clay, or deep boreholes, the safety analysis for a mined granite repository depends largely on waste package preservation. In crystalline rock, waste packages are preserved by the high mechanical stability of the excavations, the diffusive barrier of the buffer, and favorable chemical conditions. The buffer is preserved by low groundwater fluxes, favorable chemical conditions, backfill, and the rigid confines of the host rock. An added advantage of a mined granite repository is that waste packages would be fairly easy to retrieve, should retrievability be an important objective. The results of the safety analyses performed in this study are consistent with the results of comprehensive safety assessments performed for sites in Sweden, Finland, and Canada. They indicate that a granite repository would satisfy established safety criteria and suggest that a small number of FEPs would largely control the release and transport of radionuclides. In the event the U.S. decides to pursue a potential repository in granite, a detailed evaluation of these FEPs would be needed to inform site

Composition of coarse-grained magnetite from pegmatite dikes related to plutons of quartz monzonite in the Jabal Lababa area, Kingdom of Saudi Arabia

Science.gov (United States)

Overstreet, William C.; Mousa, Hassan; Matzko, John J.

1985-01-01

Crystals of magnetite as large as 30 mm long and 7 mm thick are locally present in quartz-rich zones of interior and exterior pegmatite dikes related to plutons of quartz monzonite in the Jabal Lababa area. Niobium, tin, and yttrium are strongly enriched in six specimens of magnetite from interior pegmatite dikes in a small pluton where these elements form geochemical anomalies in nonmagnetic heavy-mineral concentrates from wadi sediment. Less abundant anomalous elements in the magnetite are molybdenum, lead, and zirconium, which also tend to be present in anomalous amounts in the nonmagnetic concentrates from the niobium-bearing pluton. The most anomalous trace element in the magnetite is zinc, which is at least 10 times as abundant as it is in the quartz monzonite plutons or in the nonmagnetic concentrates. The capacity of magnetite to scavenge molybdenum, zinc, niobium, lead, tin, yttrium, and zirconium suggests the possible utility of magnetite as a geochemical sample medium.

Weathering-related origin of widespread monazite in S-type granites

Energy Technology Data Exchange (ETDEWEB)

Sawka, W N; Banfield, J F; Chappell, B W

1986-01-01

The S-type granite suites comprising more than a quarter of the extensively developed granites in the Lachlan Fold Belt, Australia, contain monazite which may be related to the chemical weathering of the sedimentary source rocks. We report a process whereby chemical weathering fixes mobile rare-earth elements (REE) in hydrous phosphate phases such as florencite and rhabdophane. This material contains up to 50 wt.% LREE and occurs as very small particles (approx. 3 ..mu..m). Dehydration of these hydrous REE phases during anatexis directly yields monazite. The low solubility of phosphorus in S-type granite melts inhibits dissolution of both monazite and apatite. Refractory monazite may be thus entrained and transported in S-type granites in a manner similar to processes resulting in inherited zircon. Since both Th and the light REE are major components in monazite, materials containing this minute phase may be of widespread geochemical significance in both granites and metamorphic rocks.

Gamma-spectrometric surveys in differentiated granites. II: the Joaquim Murtinho Granite in the Cunhaporanga Granitic Complex, Parana, SE Brazil; Levantamentos gamaespectrometricos em granitos diferenciados. II: O exemplo do Granito Joaquim Murtinho, Complexo Granitico Cunhaporanga, Parana

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Francisco Jose Fonseca [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia. Lab. de Pesquisas em Geofisica Aplicada; Fruchting, Allan [Votorantim Metais, Sao Paulo, SP (Brazil)], e-mail: allan.fruchting@vmetais.com.br; Guimaraes, Gilson Burigo [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil). Dept. de Geociencias], e-mail: gburigo@ig.com.br; Alves, Luizemara Soares [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)], e-mail: luizemara@petrobras.com.br; Martin, Victor Miguel Oliveira; Ulbrich, Horstpeter Herberto Gustavo Jose [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica], e-mail: vicmartin6@ig.com.br, e-mail: hulbrich@usp.br

2009-07-01

Detailed mapping at the NW corner of the large Neo proterozoic Cunhaporanga Granitic Complex (CGC), Parana state, SE Brazil, redefined the Joaquim Murtinho Granite (JMG), a late intrusion in CGC with an exposed area of about 10 km{sup 2}, made up mainly by evolved 'alaskites' (alkali-feldspar leuco granites). This unit is in tectonic contact with the Neoproterozoic-Eocambrian volcano-sedimentary Castro Group, to the W, and is intrusive into other less evolved granitic units of the CGC to the E. Petrographically, JMG shows mainly mesoperthite and quartz, with subordinate amounts of altered micas and some accessory phases, mainly zircon. The equi to inequigranular granites are usually deformed with cataclastic textures, are often brecciated, and may have miarolitic structures. Formation of late albite, sericite, carbonate and hematite was caused by deuteric and hydrothermal alteration. A gamma-ray spectrometric survey at 231 stations which measured total counts (TC), Ueq K%, eU ppm and eTh ppm was used to construct several direct and derived maps. Compared to neighboring units the JMG has significant anomalies, especially in the TC, %K, eTh and eU maps, although the differences are less obvious in some derived maps. These evolved granites are enriched in these three elements. Geochemical behavior of K, Th and U is used to analyse the results observed in maps. Enhanced weathering under a subtropical climate with moderate to high average temperatures and heavy rainfall affects mainly feldspars and biotite, and may also destabilize most U and Th-bearing accessory phases. Th is most likely retained in restite minerals in soils, being relatively immobile, while part of U may migrate as uranyl ion in oxidizing media. K is especially affected by feldspar alteration to K-free clays (mainly kaolinite), and may be completely leached. Gamma-ray spectrometric methods are valid tools to study facies in granitic rocks, especially in those that are enriched in K, Th and U

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)

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.

Phosphates of crandallite type (plumibogummite, goyazite, gorceixcite) results of amblygonite under weathering conditions from Coronel Murta's pegmatites (northeastern Miras Gerais) and your paleoecological meaning

International Nuclear Information System (INIS)

Neves, J.M.C.; Marciano, V.R.P.R.O.; Lena, J.C. de; Soares, A.C.P.

1987-01-01

This paper deals with crandallite type phosphates (plumbogummite, go yazite gorceixcite) originating from amblygonite under weathering conditions active in very recent times in the Coronel Murta are (northeastern Minas Gerais). Amblygonite, the crystallization of which too place about 500 Ma ago within the replacement bodies of pegmatites emplaced in mia-bearing quartzites from the Proterozoic Salinas Group, was the start ing material for the above mentione supergene minerals. The pegmatitic veins, emplaced in the quartzites according to wo perpendicular joint systems, underwent a strong weathering which produced the total kaolinization of the pegmatitic primary feldspars observed at the present time. During the supergene processes, the amblygonite, after acting as a geochemical fence for Ca, Sr, Ba, Pb etc., which provided conditions for the formation of the crandallitic minerals, was transformed into kaolinite. The stability fields these crandallitic minerals, comparared to those of kaolinite and amblygonite, show that they are easily formed under rather high pH values. As the environment becomes more acid and keeping in mind the very low cationic activities in groundwaters, al these phosphates become unstable and, under SiO 2 metasomatism, envolve to kaolinite. This is thermodynamically sound as revealed not only by the calculated stability diagrams but by the identified mineral assemblages as well. These mineral assemblages and their widespread regional scaterring seem to be induced not only by climatic and relief conditions but also by their position within the weathering profile. In the Coronel Murta area the most effective factors seem to have the very recent climatic and relief changes. (author) [pt

Uranium occurrence at Sao Teodosio farm, Currais Novos, Rio Grande do Norte, Brazil

International Nuclear Information System (INIS)

Favali, J.C.; Leal, J.R.L.V.

1974-01-01

The areas of certain radiometric anomalies discovered in Serido geosyncline were selected for intensive study because of the similarity of the geology to that of known uranium deposits in other parts of the world. The uranium mineralization at Sao Teodosio farm, near Currais Novos, RN, on the Serrinha anticline axis, occurs in alaskite similar to that at Rossing in Southwest Africa. The Rossing deposit is the best example of the model proposed by Armstrong (1974) as 'porphyry' uranium deposits. That uranium deposit presents low grade of uranium content, about 0,030% U 3 O 8 and hundred thousands tons of uranium oxide. At Sao Teodosio occurs 550 m.y. alaskitic pegmatitic granite and garnet-quartz-biotite-schists of Serido formation, Upper Precambrian. These older rocks are cut by diabases dykes of Upper Terciary age. Uranium mineralization is associated with pegmatitic granite bodies similar to dykes and sills. The most common uranium minerals are: uraninite, meta-autunite and uranophane. Oligoclase, microline and quartz are the most frequent minerals. Acessory minerals are magnetite, titanite and zircon. Uranium oxide content at Sao Teodosio is 0,023% and average thickness is 2,80 m [pt

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...

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.

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 ...

Rb-Sr geochronolgy of the Jervois Range area in the eastern part of the Arunta Block, NT

International Nuclear Information System (INIS)

Black, L.P.

1980-01-01

New Rb-Sr isotopic data are presented for the Jervois Range area in the eastern part of the Arunta Block. The post-metamorphic Jinka and Jervois Granites yield an age of about 1750 m.y. An alaskitic granite is dated at about 1460 m.y. Pegmatite formation occurred about 1660 m.y. ago. Mineral ages are generally younger than total-rock ages, but no values significantly less than that of the alaskitic granite were found. This means that the Alice Springs Orogeny, which extensively reset large areas of the Arunta Block to the west, did not effect the Jervois area. In this and other geochronological comparisons, the Jervois area seems more akin to the rocks of the Tennant Creek Block, 400 km to the northwest, than to those of the Arunta Block

Geochemistry of biotite granites from the Lamas de Olo Pluton, northern Portugal

Science.gov (United States)

Fernandes, Susana; Gomes, Maria; Teixeira, Rui; Corfu, Fernando

2013-04-01

In the Central Iberian Zone (CIZ) extensive crustal recycling occurred during the post-thickening extension stage of the Variscan orogeny (~330-290 Ma). After the ductile deformation phase D3 (~320-300 Ma), characterized by the intrusion of large volumes of highly peraluminous granitic magmas, rapid and drastic tectonic changes at about 300 Ma gave rise to the brittle phase of deformation D4 that controlled the emplacement of Fe-K subalkaline granites (296-290 Ma; Dias et al. 1998). The Lamas de Olo Pluton (LOP) is controlled by NE-SW and NW-SE fracture systems, probably related to the Régua-Verin fault zone (Pereira, 1989). The LOP is a medium to coarse-grained, porphyritic biotite granite, accompanied by medium- to fine grained, porphyritic biotite granite (Alto dos Cabeços- AC) and a more leucocratic, fine-grained, slightly porphyritic biotite-muscovite granite (Barragens- BA). The contacts between LO and AC are generally diffuse, whereas those to BA are sharp. In fact, the BA granite can occur in dykes and sills cutting LO and AC. Microgranular enclaves and xenoliths are very rare. The LOP intrudes the Douro Group, presumably of Precambrian to Cambrian age, and two-mica granites from the Vila Real composite massif. The LOP granites consist of quartz, microcline, plagioclase, biotite, zircon, titanite, tourmaline apatite, fluorite, ilmenite, magnetite, and rutile, with muscovite in BA granite and rare allanite in the LO and AC granites. The plagioclase composition is of oligoclase (An12) - andesine (An35) for LO granite, albite (An9) - andesine (An30) for CA granite and albite (An5) - oligoclase (An20) for BA granite. There are decreases in: a) anorthite content from phenocryst to matrix plagioclase; b) Ba content from phenocryst to matrix microcline in all granites. The Fe2+ biotite has a composition similar to that of biotite from calc-alkaline to sub-alkaline rock series. The LO and AC granites are meta- to peraluminous with ASI variable between 1.05 and 1

Granites of Zoz area, Baroda district, Gujarat and its economic significance

International Nuclear Information System (INIS)

Maithani, P.B.; Rathaiah, Y.V.; Varughese, Siby K.; Singh, Rajendra

1998-01-01

The granites around Zoz represent a differentiated, calc-alkaline, subaluminous, A-type granite with higher uranium content. The A-type affinity points to the possibility of encountering Sn, Mo, Bi, Nb, Ta and F mineralization in the area. The low Th/U ratio also favours vein type U-deposits within granites or in adjacent metasediments. (author)

Crisp clustering of airborne geophysical data from the Alto Ligonha pegmatite field, northeastern Mozambique, to predict zones of increased rare earth element potential

Science.gov (United States)

Eberle, Detlef G.; Daudi, Elias X. F.; Muiuane, Elônio A.; Nyabeze, Peter; Pontavida, Alfredo M.

2012-01-01

The National Geology Directorate of Mozambique (DNG) and Maputo-based Eduardo-Mondlane University (UEM) entered a joint venture with the South African Council for Geoscience (CGS) to conduct a case study over the meso-Proterozoic Alto Ligonha pegmatite field in the Zambézia Province of northeastern Mozambique to support the local exploration and mining sectors. Rare-metal minerals, i.e. tantalum and niobium, as well as rare-earth minerals have been mined in the Alto Ligonha pegmatite field since decades, but due to the civil war (1977-1992) production nearly ceased. The Government now strives to promote mining in the region as contribution to poverty alleviation. This study was undertaken to facilitate the extraction of geological information from the high resolution airborne magnetic and radiometric data sets recently acquired through a World Bank funded survey and mapping project. The aim was to generate a value-added map from the airborne geophysical data that is easier to read and use by the exploration and mining industries than mere airborne geophysical grid data or maps. As a first step towards clustering, thorium (Th) and potassium (K) concentrations were determined from the airborne geophysical data as well as apparent magnetic susceptibility and first vertical magnetic gradient data. These four datasets were projected onto a 100 m spaced regular grid to assemble 850,000 four-element (multivariate) sample vectors over the study area. Classification of the sample vectors using crisp clustering based upon the Euclidian distance between sample and class centre provided a (pseudo-) geology map or value-added map, respectively, displaying the spatial distribution of six different classes in the study area. To learn the quality of sample allocation, the degree of membership of each sample vector was determined using a-posterior discriminant analysis. Geophysical ground truth control was essential to allocate geology/geophysical attributes to the six classes

Mobility of heavy metals through granitic soils using mini column infiltration test

Science.gov (United States)

Zarime, Nur'Aishah; Yaacob, W. Z. W.

2014-09-01

This study is about the mobility of cadmium through compacted granitic soils. Two granitic soils namely the Broga (BGR) and Kajang (KGR) granitic soils were collected in Selangor, Malaysia. Physical and chemical tests were applied for both granitic soils to determine the physical and chemical properties of soil materials. Physical test results shows granitic soils (BGR and KGR) have high percentage of sand ranging between 54%-63% and 46%-54% respectively, an intermediate and intermediate to high plasticity index as well as high specific gravity ie; 2.50-2.59 and 2.45-2.66 respectively. For chemical test, granitic soils shows acidic pH values ranged from 5.35-5.85 for BGR and pH 5.32-5.54 for KGR. For organic matter, SSA and CEC test, it shows low values ranged from 0.22%-0.34% and 0.39%- 0.50% respectively for organic matter test, 17.96 m2/g-21.93 m2/g and 25.76 m2/g-26.83 m2/g respectively for SSA test and 0.79 meq/100g-1.35 meq/100g and 1.31 meq/100g-1.35 meq/100g respectively for CEC test. Mini column infiltration test was conducted to determine the retention of cadmium while flowing through granite soils. This test conducted based on the falling head permeability concepts. Different G-force ranging from 231G to 1442G was used in this test. The breakthrough curves show the concentration of Cd becomes higher with the increasing of G-force for both granitic samples (BGR and KGR). The selectivity sorption for both granites ranked in the following decreasing order of; 231G>519G>923G>1442G. Results demonstrated that granitic soils also have low buffering capacity due to low resist of pH changes.

Design of a dosimetric evaluation protocol workers granite quarries

International Nuclear Information System (INIS)

Guillen, J.; Tejado, J. J.; Baeza, A.

2011-01-01

The Autonomous Community of Extremadura is one of the major regions of Spain as far as the extraction of granite and further processing of products derived from it are concerned. One of the most industrialized areas of the sector presents a serious problem for non-radiological occupational health of workers, particularly silicosis. Since in this area of activity levels of granites can be classified as medium-high within the precipitates ranges, the question is whether in addition to this occupational disease, there is a radiological impact associated with the activity NORM extraction and manufacturing of granite.

Structural and petrophysical characterisation of granite: intended for radioactive waste stocking

International Nuclear Information System (INIS)

Stanek, Martin

2013-01-01

Structural and petrophysical analysis have been conducted within the Melechov massif with focus on structures controlling the porosity, permeability and thermal conductivity of the rock. The structure of the massif has been constrained based on extensive dataset including AMS and field structural measurements of ductile and brittle structures. The fracture system of the massif has been described by four sets of fractures. The measured petrophysical data have been used to characterize the effect of fracturing and alteration on pore space geometry and in turn on permeability, thermal conductivity and elastic properties of the studied granite. Distinct petrophysical properties have been identified for pristine granite, for fractured fresh granite as well as for fractured granite altered by Fe-oxide, chlorite and clay minerals. A detailed microstructural study combined with multidirectional P-wave velocity measurements at high confining pressure and with AMS analysis has been conducted on a Schlieren bearing sample of Lipnice granite. The granite VP anisotropy at low confining pressure was controlled by intergranular cracks interconnecting Schlieren-sub parallel cleavage cracks in micas and feldspars and by exfoliation fracture-sub parallel intra- or trans-granular cracks in cleavage-free quartz. Major closing of the crack porosity linked to the Schlieren granite below depth of 500 m has been interpreted in terms of crack compliance reflected by rapid increase in VP with confining pressure. (author)

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.

Radiocrystallographic study of Eosphorite found in pegmatites from lavra da Ilha, Itinga, Minas Gerais, Brazil

International Nuclear Information System (INIS)

Zalan, M.S.; Baptista, A.

1982-01-01

The space group and the unit cell constants of Eosphorite, a phosphate of iron and manganese, have been determined. The specimens examined are found in the pegmatites of the Rio Jequitinhonha valley, State of Minas Gerais, Brazil. X-ray diffraction methods (power, Buerger's precession camera, Weissenberg's method), X-ray fluorescence analysis differential thermal analysis and thermal gravimetric analysis are applied to this phosphate. The space group of Eosphorite is determined to be Bbam and the unit cell constants determined by the Buerger's precession method are: a 0 = 10 .423 A; b 0 = 13 .477 A; c 0 = 6 .975 A; Z=8. (Author) [pt

Radiogeologic reconnaissance in Perus region, Sao Paulo, Brazil

International Nuclear Information System (INIS)

Coelho, P.E.F.P.

1980-01-01

The determination of the means and the identification of the radiometric anomalies, and the classification of this anomalies orgin, and it probable correlation with uraniferous secundary minerals from Perus and Taipas were studied. Petrological, stratigraphic, tectonic and geochronological studies in this region were done. The radiometric anomalies was observed in granitic-pegmatic massifs, later Sao Roque group. The radiocitivity of this area was affected by litology, being the pegmatite more radiogenic than granite. The topography is also a influent factor to detected radioactivity. The cinthylometry was efficient to U an Th anomalies detection. Three kinds of radioctive focus were detected by microautoradiography method [pt

Terrestrial gamma ray dose rates on Ryoke granitic rocks in Ikoma Mountains

International Nuclear Information System (INIS)

Ikeda, Tadashi; Ueshima, Masaaki; Shibayama, Motohiko; Hiraoka, Yoshitsugu; Muslim, Dicky

2012-01-01

We measured the γ dose rate of 16 rock bodies in the field, which belonged to Ryoke granitic rocks distributed over Ikoma Mountains. The measurement points were 190 spots, and the mean dose rate was 82.0 ± 21.0 nGy/h. Results of analysis were summarized as follows. (1) The distribution of the dose rate in the Fukihata quartz diorite showed that the rocks crystallization differentiation had progressed from the south to the north. (2) The dose rate of granite tended to arise with the increase of SiO 2 quantity, but in the Iwahashiyama granite, the Takayasuyama granite, the Omichi granite and the Katakami granite, it was revealed that the dose rate was low in spite of high SiO 2 quantity. (3) It became clear that the dose rate of Ryoke granitic rocks from the first stage to the fourth stage was high to be considered as a new rock body. (4) Because the relationship between the dose rate of rocks and the main chemical elements did not show a common characteristic, it may be that those rocks were formed from different Magma. (author)

Isotopic geochronology of granitic rocks from the Central Iberian Zone: comparison of methodologies

Energy Technology Data Exchange (ETDEWEB)

Antunes, I. M. H. R.; Neiva, A. M. R.; Silva, M. M. V. G.

2010-07-01

Five granitic rocks, concentrically disposed from core to rim, were distinguished in the Castelo Branco pluton. U-Pb-Th electron microprobe monazite ages from granitic rocks are similar and ranging between 297-303 Ma. The granitic rocks from Castelo Branco pluton are 310 {+-} 1 Ma old, obtained by U-Pb (ID-TIMS) in separated zircon and monazite crystals, indicating a similar emplacement age for all granitic rocks of the pluton. Initial {sup 8}7Sr/{sup 8}6Sr isotopic ratios and {epsilon}Nd{sub 3}10 and {delta}{sup 1}8O values suggest three distinct pulses of granitic magma and that they are derived from partial melting of heterogeneous metasedimentary materials. The other granitic rocks are related by magmatic differentiation and show small variations in ({sup 8}7Sr/{sup 8}6Sr)310, {epsilon}Nd{sub 3}10 and {delta}{sup 1}8O. The granitic pluton of Castelo Branco shows a rare reverse zoning. (Author) 12 refs.

Experimental analysis on physical and mechanical properties of thermal shock damage of granite

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He Xiao

2017-01-01

Full Text Available The purpose of this study was to explore the changes of mechanical and physical properties of granite under different thermal loading effects. Uniaxial compression experiments studying the rules of the influence of temperature load on mechanical properties of granite were carried out. After high-temperature heating at above 600 °C, granite tended to have stronger ductility and plasticity as well as declined peak stress and compressive strength. Thermogravimetry - differential scanning calorimetry (TG-DSC analysis results showed that, thermal load at different temperatures induced reactions such as water loss, oxidation and crystallization in the microstructure of granite, which led to physical changes of granite. Hence it is concluded that, heating can significantly weaken the mechanical performance of granite, which provides an important support for the optimization of heating assisted processing of granite. It also reveals that, heating assisted cutting technique can effectively lower energy consumption and improve processing efficiency.

On the sources of uranium in some Scottish Caledonian granites

International Nuclear Information System (INIS)

Halliday, A.N.

1982-01-01

The lead isotope systematics, zircon uranium concentrations and whole-rock rubidium concentrations of 11 Scottish Caledonian granites are examined for clues to the origin of their uranium. A positive correlation between U in zircon and initial lead isotope ratios suggests that U and Pb were derived from the same source which, as some of these granites contain their U in inherited zircons, is likely to have been within the crust. It is argued, therefore, that most of the uranium in these granites had a crustal derivation but lead isotope ratios indicate that any Lewisian contribution was minor in comparison with those from postulated Grenville, Morarian or Caledonian metamorphic reservoirs. However, additional data are required before this conclusion can be extended to include uraniferous Caledonian granites such as Cairngorm. (author)

Soil Radon In The Nigerian Younger Granites | Dewu | Nigerian ...

African Journals Online (AJOL)

... not had enough time to attain equilibrium with its daughters. In general, the results suggest that with proper control, soil radon measurements over the Younger Granite can be used for uranium exploration in the region. Keywords: Radon, younger granite, soil uranium, half-lifeand thorium. Nigerian Journal of Physics Vol.

The distribution and uranium content characteristics of Indosinian granite in South China

International Nuclear Information System (INIS)

Sun Wenliang; Zhang Zhuo; Chen Wenwen; Chen Lulu; Xu Wenzheng

2014-01-01

In recent years, more and more Indosinian granite plutons has been found in South China, so some new ideas about the granity were proposed by scholars. The Indosinian granite in South China distributed in lineshape, and is controlled by some regional faults. Its formation was mainly related to geodynamic setting which began in the late Permian (about 256 Ma) by the subduction of the ancient Pacific Plate to the Eurasia. The average uranium content of Indosinian granite is 10.34ppm, much higher than the average value of world's acid rock. There occurs some couplings between the distribution of the Indosinian granite plutons and uranium mineralization belt in South China. So the Indosinian granite in South China may act as important uranium sources for the mineralization. (authors)

Mineralogy, geochemistry and petrophysics of red coloured granite adjacent to fractures

International Nuclear Information System (INIS)

Eliasson, T.

1993-03-01

Mineralogical, geochemical and petrophysical investigations were conducted of red-coloured alteration rims and of the neighbouring unaltered equivalents along fractures within granite from Aespoe. An investigation was made also of a weak to rather strong, red-coloured granite from the Stripa mine, as well as a weak brownish-red colouration, definitely no hydrothermal in origin, of weathered rinds at a glacial polished rock surface in the Bohus granite. When approaching the fracture planes in the Aespoe granite, the most diagnostic alteration features are * the saussuritisation and Fe-oxyhydroxide staining of plagioclase, * the crystallisation chlorite pseudomorphs after biotite and * the hematisation of magnetite. The porosity within the alteration zones increases generally 2 to 3 times compared with the protolith rock, whereas the densities decrease by some 5 to 10%. The oxidation of magnetite gives as much as a tenfold lowering of the magnetic susceptibility. The red colouration of the Stripa granite is caused by hematite ± Fe-oxyhydroxide formation along microfractures, grain boundaries and, subordinately, the main minerals. Oxidation and re-precipitation of iron liberated during a retrograde muscovitisation of principally chlorite is interpreted to be the cause of the formation of the ferric oxides. The rather homogeneous density and porosity values of the grey and of the red-coloured granites reflect the minor change in the mineralogy when going from fresh into altered granite. Weathering and whitening of plagioclase in the bleached, outer zone and precipitation of small quantities of Fe-oxyhydroxides/hydroxides in the brownish-red zone cause the macroscopic colouration of the weathering rind below the glacial polished rock surface of Bohus granite. There is a marked increase in porosity from the interior fresh (c. 0.4-0.5%) towards the exterior bleached zone (c.1.5-2%) of the subaerialy, weathered Bohus granite surface. The incipient decomposition of

[Study on the fine structure of K-feldspar of Qichun granite].

Science.gov (United States)

Du, Deng-Wen; Hong, Han-Lie; Fan, Kan; Wang, Chao-Wen; Yin, Ke

2013-03-01

Fine structure of K-feldspar from the Qichun granite was investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR), and inductively coupled plasma mass spectrometry methods to understand the evolution of the granitic magmatism and its correlation to molybdenite mineralization. The XRD results showed that K-feldspar of the potassic alteration veins has higher ordering index and triclinicity and is namely microcline with triclinic symmetry. K-feldspar of the early cretaceous granite has relatively lower ordering index and has widening [131] peak and is locally triclinic ordering. K-feldspar of the late cretaceous granite has lowest ordering index and sharp [131] peak and is honiogeneously monoclinic. The FTIR results showed that the IR spectra of the Qichun K-feldspar are similar to that of orthoclase reported by Farmer (1974). The 640 cm-1 absorption band increases while the 540 cm-' absorption band decreases with increase in K-feldspar ordering index, also, the 1,010 cm-1 absorption band separates into 1,010 and 1,046 cm-1 absorption bands, with a change in the band shape from widening to sharp outline. The ICP-MS results suggested that K-feldspar of the early cretaceous granite has relatively higher metal elements and rare earth elements, and the granite exhibits better mineralization background, K-feldspar of the potassic alteration veins has markedly lower Sr and Ba, indicating that the alteration fluid originated from the granitic magmatism, and hence, potassic alteration is a good indicator for molybdenite exploration.

The evolution of pegmatite-hosted Sn-W mineralization at Nong Sua, Thailand: Evidence from fluid inclusions and stable isotopes

Science.gov (United States)

Linnen, Robert L.; Williams-Jones, Anthony E.

1994-01-01

The Nong Sua aplite-pergmatite complex contains two dominant styles of Sn-W-Ta-Nb mineralization. Cassiterite ± Nb-Ta-Ti oxide minerals are disseminated in the pegmatite, and cassiterite and wolframite are hosted by quartz-tourmaline veins which are contained solely within aplite. The orthomagmatic fluid at Nong Sua is preserved as primary fluid inclusions in the cores of magmatic garnet crystals that have high tin concentrations (garnet cores without fluid inclusions do not contain elevated tin concentrations). These fluid inclusions have a composition of 3 wt% NaCl eq. The low salinity suggests that, at vapor saturation, tin was partitioned in favour of the melt, which allowed cassiterite to initially crystallize directly from the melt. Primary, pseudosecondary, and secondary fluid inclusions in cassiterite, tourmaline, and quartz record three-component mixing of the orthomagmatic fluid with high salinity aqueous and with CO 2-rich fluids. The orthomagmatic water is interpreted to have had δ 18O value of +8.7 to +9.9 per mil and a δD value of -72 to -78 per mil from δ18O analyses of muscovite and quartz, and δD of muscovite. The δ18O composition of muscovite decreased from 10.1 to 8.0 per mil and δD increased from - 106 to - 85 per mil, from the magmatic to the hydrothermal stages of pegmatite evolution. These changes are consistent with an influx of metamorphic fluids or evolved meteoric waters. We consider that the saturation of the melt with vapor caused the pressure in the pegmatite to rise to approximately 3.8 kbar, at a temperature of 650°C. Fluid overpressure caused the aplite to fracture, and veins to form from fluids which migrated into the fracture-induced low pressure zones. This event can be modeled by an isothermal decompression to 2.7 kbar. Cassiterite deposition was probably controlled by increasing fO 2, whereas wolframite deposition resulted from the mixing of W-rich with Fe-Mn-rich fluids. In both cases decompression, cooling, and

Geology of Muntok area and the potency of menumbang granite as source of Uranium and Thorium

International Nuclear Information System (INIS)

Kurniawan Dwi Saksama; Ngadenin

2013-01-01

In the West Bangka there are some granites namely Menumbing, Pelangas, Tempilang, and Jebus granite. The granites is granite tin belt that stretches from Thailand-Malaysia-Bangka Belitung. Granite tin belt or granite source of tin (cassiterite) can act as a source of U and Th. Aims of the study is to find out the information on the geology of Muntok area and its surrounding and to determine the potency of Menumbing granite as a source of U and Th. The methods used is surface geological mapping in Muntok areas and its surrounding with scale 1 : 25.000, measurement grade of uranium and thorium in Menumbing granite areas and petrographic and grain size analysis of sample of Menumbing granite. Determination of granites a source of U and Th is based on content of radioactive mineral, anomaly of U and Th, megascopic and microscopic observation of granite. Morphology of Muntok areas and its surrounding is denudasional undulating plains to hills with an elevation ranging from 0 to 455 meters. Stratigraphy of research areas from old to young is meta sandstone units, granite intrusion of Menumbing and alluvial. Evolving fault is a fault trending West-East. Based on the presence of radioactive minerals, grade of U and Th as well as the type of granite, it was concluded that the Menumbing granite is a source of Th and not sources of U. (author)

A fractal derivative constitutive model for three stages in granite creep

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R. Wang

Full Text Available In this paper, by replacing the Newtonian dashpot with the fractal dashpot and considering damage effect, a new constitutive model is proposed in terms of time fractal derivative to describe the full creep regions of granite. The analytic solutions of the fractal derivative creep constitutive equation are derived via scaling transform. The conventional triaxial compression creep tests are performed on MTS 815 rock mechanics test system to verify the efficiency of the new model. The granite specimen is taken from Beishan site, the most potential area for the China’s high-level radioactive waste repository. It is shown that the proposed fractal model can characterize the creep behavior of granite especially in accelerating stage which the classical models cannot predict. The parametric sensitivity analysis is also conducted to investigate the effects of model parameters on the creep strain of granite. Keywords: Beishan granite, Fractal derivative, Damage evolution, Scaling transformation

Mechanical properties of Stripa granite

International Nuclear Information System (INIS)

Stephansson, O.; Swan, G.; Leijon, B.

1978-01-01

For the determination of the mechanical properties of Stripa Granite samples were taken from the boreholes in the vicinity of the test site. The granite type taken from these different sources is of variable character. For the purpose of numerical calculations performed in projects related to the waste storage research program the following parameters have been determined: Young's modulus, Poisson's ratio, compressive fracture stress and expansion coefficient as a function of temperature 20< T<200C; Young's modulus and compressive fracture stress as a function of confining pressure; Brazilian tensile fracture stress; residual shear stress as a function of normal stress; anisotropy ratio for Young's modulus and compressive fracture stress; dilatational wave velocity and deduced dynamic Young's modulus. A brief description of the test methods and the results for each test are presented

Mobility of heavy metals through granitic soils using mini column infiltration test

International Nuclear Information System (INIS)

Zarime, Nur 'Aishah; Yaacob, W. Z.W.

2014-01-01

This study is about the mobility of cadmium through compacted granitic soils. Two granitic soils namely the Broga (BGR) and Kajang (KGR) granitic soils were collected in Selangor, Malaysia. Physical and chemical tests were applied for both granitic soils to determine the physical and chemical properties of soil materials. Physical test results shows granitic soils (BGR and KGR) have high percentage of sand ranging between 54%–63% and 46%–54% respectively, an intermediate and intermediate to high plasticity index as well as high specific gravity ie; 2.50–2.59 and 2.45–2.66 respectively. For chemical test, granitic soils shows acidic pH values ranged from 5.35–5.85 for BGR and pH 5.32–5.54 for KGR. For organic matter, SSA and CEC test, it shows low values ranged from 0.22%–0.34% and 0.39%– 0.50% respectively for organic matter test, 17.96 m 2 /g–21.93 m 2 /g and 25.76 m 2 /g–26.83 m 2 /g respectively for SSA test and 0.79 meq/100g–1.35 meq/100g and 1.31 meq/100g–1.35 meq/100g respectively for CEC test. Mini column infiltration test was conducted to determine the retention of cadmium while flowing through granite soils. This test conducted based on the falling head permeability concepts. Different G-force ranging from 231G to 1442G was used in this test. The breakthrough curves show the concentration of Cd becomes higher with the increasing of G-force for both granitic samples (BGR and KGR). The selectivity sorption for both granites ranked in the following decreasing order of; 231G>519G>923G>1442G. Results demonstrated that granitic soils also have low buffering capacity due to low resist of pH changes

Contamination in mafic mineral-rich calc-alkaline granites: a geochemical and Sr-Nd isotope study of the Neoproterozoic Piedade Granite, SE Brazil

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Leite Renato J.

2006-01-01

Full Text Available The Piedade Granite (~600 Ma was emplaced shortly after the main phase of granite magmatism in the Agudos Grandes batholith, Apiaí-Guaxupé Terrane, SE Brazil. Its main units are: mafic mineral-rich porphyritic granites forming the border (peraluminous muscovite-biotite granodiorite-monzogranite MBmg unit and core (metaluminous titanite-bearing biotite monzogranite BmgT unit and felsic pink inequigranular granite (Bmg unit between them. Bmg has high LaN/YbN (up to 100, Th/U (>10 and low Rb, Nb and Ta, and can be a crustal melt derived from deep-seated sources with residual garnet and biotite. The core BmgT unit derived from oxidized magmas with high Mg# (~45, Ba and Sr, fractionated REE patterns (LaN/YbN= 45, 87Sr/86Sr(t~ 0.710, epsilonNd(t ~ -12 to -14, interpreted as being high-K calc-alkaline magmas contaminated with metasedimentary rocks that had upper-crust signature (high U, Cs, Ta. The mafic-rich peraluminous granites show a more evolved isotope signature (87Sr/86Sr(t = 0.713-0.714; epsilonNd(t= -14 to -16, similar to Bmg, and Mg# and incompatible trace-element concentrations intermediate between Bmg and BmgT. A model is presented in whichMBmgis envisaged as the product of contamination between a mafic mineral-rich magma consanguineous with BmgT and pure crustal melts akin to Bmg.

How are the emplacement of rare-element pegmatites, regional metamorphism and magmatism interrelated in the Moldanubian domain of the Variscan Bohemian Massif, Czech Republic?

Czech Academy of Sciences Publication Activity Database

Melleton, J.; Gloaguen, E.; Frei, D.; Novák, M.; Breiter, Karel

2012-01-01

Roč. 50, č. 6 (2012), s. 1751-1773 ISSN 0008-4476 Institutional support: RVO:67985831 Keywords : LCT pegmatite * rare-element-enriched magma * columbite-tantalite * LA-SF-ICP-MS dating * Variscan orogeny * Bohemian Massif * Moldanubian domain * Bohemian Massif (Czech Republic) Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.180, year: 2012

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 ...

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...

Petrographic and mineralogical features of the uraniferous pink granites in the north eastern desert of egypt

International Nuclear Information System (INIS)

Atawiya, M.Y.; Salman, A.B.; El-Bayyomi, R.M.

1998-01-01

The present work is concerned with the petrological, mineralogical and geochemical studies of some uranium bearing younger granites in the north eastern desert of egypt particularly Gebel Gattar area. The area around Gebel Gattar comprises the following rock units (starting from the oldest): meta volcanic, diorite-grano-diorite complex- Dokhan volcanics- Hammamat sediments, younger granites and dykes. The most significant structural features are represented by NNE-ENE dominantly trending faults and joints. Petrographicaly, the pink granites are divided into normal and mineralized (uraniferous) granites. Normal granites are classified into three types; a) leucocratic perthitic granite, b) hornblende- biotite perthitic granite and c) two feldspars perthitic granite. Mineralized granites are sheared, deformed, pinkish brown in colour and strongly altered. A remarkable secondary uranium mineralization has been recorded along fault and fracture zones

The role of granites for the ore mineralization in South German Variscides

International Nuclear Information System (INIS)

Dill, H.G.

1987-01-01

Granites are of widespred occurrence in the South German Variscides (F.R. of Germany), the Black Forest (=BF), and the NE Bavarian Basement (=NEBB). These areas are crossed by the Saxothuringian-Moldanubian plate boundary and were also affected by crustal subdulction and nappe tectonism, both of which are thought to be responsible for granitisation and enrichment of Sn, W,U,Au, Sb,Pb,Zn,F, and Ba in veins of different kind. Heat produced by gliding of plates above each other, by decay of radioctive elements in granites as well as set free by the granites themselves caused the above-mentioned elements to be released from their protores, which formed during Late Proterozoic and Early Paleozoic rifting. These hypogene ore mineralizations may be crudely subdivided into thrustbound, granite-related and granite-induced ore deposites. During Tertiary-Quaternary these granites were exposed the pervasive weathering under subtropical conditions, so that ''U yellow ores'' and china clay deposits came into existence. The whole ore mineralization in that region may be explained by a simple four-step model: preconcentration, fracturation, activation and peneplaination. (author) [pt

Geochemical characteristics and origin of the Lebowa Granite Suite, Bushveld Complex

Science.gov (United States)

Hill, M.; Barker, F.; Hunter, D.; Knight, R.

1996-01-01

The ??? 2052-Ma Lebowa Granite Suite (LGS) represents the culminating phase of an Early Proterozoic magmatic cycle in the Central Transvaal area of the Kaapvaal Province. Following extrusion of at least 200,000 km3 of intermediate to acid volcanics (Rooiberg Felsite), mafic and ultramafic magmas intruded at 2065 Ma to form the Rustenburg Layered Suite (RLS). The LGS includes the Nebo, Makhutso, Bobbejaankop, Lease, and Klipkloof granites. The Nebo Granite intruded the Rooiberg Felsite as sheets up to 4 km thick above the RLS. Smaller stocks of the other granites crosscut the Nebo. We determined major- and trace-element compositions and oxygen, Rb-Sr, and Sm-Nd isotope ratios for samples of: Nebo Granite; Rooiberg Felsite; granophyre and granophyric granite; Makhutso, Bobbejaankop, and Lease granites; and feldspar porphyry from areas throughout the exposed area of the LGS (Dennilton, Verena Balmoral, Enkeldoorn, Sekhukhune Plateau, Zaaiplaats-Potgeitersrus, and Western Transvaal). Coherent floor-to-roof geochemical trends exist in some areas, although it is not possible to model them convincingly. Regional variations in geochemistry exist and likely are related to source variations in the estimated 200,000 km3 of the Nebo Granite sheets. ??18O for the LGS range from +5.9??? to +9.5???; if these are approximate primary magmatic values, pelitic sediments cannot have been an important source for the LGS. The Rb-Sr isotope system has been altered, a finding consistent with previous studies. A mineral isochron for Nebo Granite near Dennilton yields a York regression age of 1995 ?? 99 Ma, with initial 143Nd/144Nd = 0.50978??8 and ???CHUR=-5.12. Samples from the Sekhukhune Plateau have higher 143Nd/144Nd ratios than do Dennilton-area samples, suggesting that the former originated from older or less LREE-enriched sources. We suggest that intrusion of mafic to ultramafic magmas at depth in the continental crust triggered melting of Archean quartzofeldspathic crystalline

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

International Nuclear Information System (INIS)

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

2011-01-01

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

The behavior of major and trace elements of the tourmaline from the Mangavai and Ganjnameh pegmatitic rocks (Hamadan area

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Ahmad Ahmadi khalaji

2016-09-01

Full Text Available The Mangavai and Ganjnameh pegmatitic rocks are part of the Alvand granitoid pluton in the Sanandaj-Sirjan zone. The composition of tourmaline in Mangavi is Schorl and that of the Ganjnameh lies in the Schorl- foitite fields. The amounts of aluminum and X-vacancy in the Ganjnameh tourmalines are more than those of Mangavi. But commonly, the main substitution of both types of tourmaline is proton production and Al increase types that Al increase; X-vacancy and Fe reduce occurred. During these substitutions, olenite and foitite, Al-tourmaline and X-vacancy have been formed, respectively. The absence of dravite and the Fe # value over 0.8 in analyzed samples indicate that the tourmalines in pegmatites are related to magmatic types. In addition, the substitution of X-vacancy and Na+Al (olenite type of tourmaline point to its magmatic nature and so, the required elements (i.e. boron, iron, sodium and aluminum provided by magmatic fluids. The HREE amount of the Mangavi tourmalines due to accompanied garnet are very low but in the absence of garnet, the Ganjnameh tourmaline have high levels of these elements. Although tourmalines have the extensive substitutions but do not have a tendency to absorb all rare earth elements and the greatest impact on the control of these elements in tourmaline related to paragenesis minerals.

Monte Carlo simulations for generic granite repository studies

Energy Technology Data Exchange (ETDEWEB)

Chu, Shaoping [Los Alamos National Laboratory; Lee, Joon H [SNL; Wang, Yifeng [SNL

2010-12-08

In a collaborative study between Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) for the DOE-NE Office of Fuel Cycle Technologies Used Fuel Disposition (UFD) Campaign project, we have conducted preliminary system-level analyses to support the development of a long-term strategy for geologic disposal of high-level radioactive waste. A general modeling framework consisting of a near- and a far-field submodel for a granite GDSE was developed. A representative far-field transport model for a generic granite repository was merged with an integrated systems (GoldSim) near-field model. Integrated Monte Carlo model runs with the combined near- and farfield transport models were performed, and the parameter sensitivities were evaluated for the combined system. In addition, a sub-set of radionuclides that are potentially important to repository performance were identified and evaluated for a series of model runs. The analyses were conducted with different waste inventory scenarios. Analyses were also conducted for different repository radionuelide release scenarios. While the results to date are for a generic granite repository, the work establishes the method to be used in the future to provide guidance on the development of strategy for long-term disposal of high-level radioactive waste in a granite repository.

Extraction of Th and U from Swiss granites

International Nuclear Information System (INIS)

Bajo, C.

1980-12-01

The extraction, at the laboratory level, of U and Th from Swiss granites is discussed. The Mittagfluh, Bergell and Rotondo granites and the Giuv syenite offered a wide range of U and Th concentrations; 7.7 to 20.0 ppm U and 25.5 to 67.0 ppm Th. U and Th were determined in the leach solutions by the fission track method and by spectrophotometry, respectively. Samples containing less than 0.3 μg U and 4 μg Th, could be measured with an accuracy of 10% for U and 5% for Th. Leach tests were performed during which the following parameters were varied: granite-type, grain size, acid-type, acid concentration, temperature and time. There were very great leaching differences between the granites studied. Temperature was the most important parameter. Sharp differences in extraction occurred between 20 0 C, 50 0 C and 80 0 C. At 80 0 C, more than 85% U and Th were extracted. The extraction curve (percent extracted as a function of time) of aliquots sampled after 1, 2, 4, 8, 12 and 24 hours showed a plateau after 8 hours. The half life of the reaction was between one and two hours. As a general rule, Th was better extracted than U. (Auth.)

Granit, Prof. Ragnar Arthur

Indian Academy of Sciences (India)

Home; Fellowship. Fellow Profile. Elected: 1964 Honorary. Granit, Prof. Ragnar Arthur Nobel Laureate (Medicine) - 1967. Date of birth: 30 October 1900. Date of death: 11 March 1991. YouTube; Twitter; Facebook; Blog. Academy News. IAS Logo. 29th Mid-year meeting. Posted on 19 January 2018. The 29th Mid-year ...

Chemical and isotopic studies of granitic Archean rocks, Owl Creek Mountains, Wyoming: Geochronology of an Archean granite, Owl Creek Mountains, Wyoming

International Nuclear Information System (INIS)

Hedge, C.E.; Simmons, K.R.; Stuckless, J.S.

1986-01-01

Rubidium-strontium analyses of whole-rock samples of an Archean granite from the Owl Creek Mountains, Wyo., indicate an intrusive age of 2640 ± 125 Ma. Muscovite-bearing samples give results suggesting that these samples were altered about 2300 Ma. This event may have caused extensive strontium loss from the rocks as potassium feldspar was altered to muscovite. Alteration was highly localized in nature as evidence by unaffected rubidium-strontium mineral ages in the Owl Creek Mountains area. Furthermore, the event probably involved a small volume of fluid relative to the volume of rock because whole-rock δ 18 O values of altered rocks are not distinct from those of unaltered rocks. In contrast to the rubidium-strontium whole-rock system, zircons from the granite have been so severely affected by the alteration event, and possibly by a late-Precambrian uplift event, that the zircon system yields little usable age information. The average initial 87 Sr/ 86 Sr (0.7033 ± 0.0042) calculated from the isochron intercept varies significantly. Calculated initial 87 Sr/ 86 Sr ratios for nine apparently unaltered samples yield a range of 0.7025 to 0.7047. These calculated initial ratios correlate positively with whole-rock δ 18 O values; and, therefore, the granite was probably derived from an isotopically heterogeneous source. The highest initial 87 Sr/ 86 Sr ratio is lower than the lowest reported for the metamorphic rocks intruded by the granite as it would have existed at 2640 Ma. Thus, the metamorphic sequence, at its current level of exposure, can represent no more than a part of the protolith for the granite

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

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

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Syafrizal

2017-07-01

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

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.

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

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

ASSESSING LAND COVER CHANGES CAUSED BY GRANITE QUARRYING USING REMOTE SENSING

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R. S. Moeletsi

2017-11-01

Full Text Available Dimension stone quarrying in the area between Rustenburg and Brits in the North West Province of South Africa has been in existence for over 70 decades. The unique characteristics of the granite deposits in South Africa resulted in making the country a global producer of the granite rocks. This led to intensified quarrying activities between Rustenburg and Brits town. However, this surface mining method, has a potential to impact the environment in a negative way causing loss in vegetation, depletion of natural resources, loss of scenic beauty and contamination of surface water resources. To assess the land cover changes caused by granite quarrying activities, remotely sensed data in the form of Landsat images between 1998 and 2015 were used. Supervised classification was used to create maps. Accuracy assessment using Google EarthTM as a reference data yielded an overall accuracy of 78 %. The post classification change detection method was used to assess land cover changes within the granite quarries. Granite quarries increased by 1174.86 ha while formation of quarry lakes increased to 5.3 ha over the 17-year period. Vegetation cover decreased by 1308 ha in area while 18.3 ha bare land was lost during the same period. This study demonstrated the utility of remote sensing to detect changes in land cover within granite quarries.

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 ...

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 ...

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 ...

Citizen-Scientist Led Quartz Vein Investigation in the McDowell Sonoran Preserve, Scottsdale, Arizona, Resulting in Significant Geologic Discoveries and a Peer-Reviewed Report Coauthored and with Maps by Citizen-Scientists.

Science.gov (United States)

Gruber, D.; Gootee, B.

2016-12-01

Citizen-scientists of the McDowell Sonoran Conservancy Field Institute originated and led this project to study milky quartz deposits. Milky quartz veins of all sizes are visible throughout the McDowell Sonoran Preserve (Scottsdale, Arizona) and are commonly found in Arizona Proterozoic rocks. No research on milky quartz has been done locally and little is known about its formation and emplacement history. Working with Brian Gootee, research geologist with the Arizona Geological Survey (AZGS), a citizen science team identified candidate study sites with large quartz veins and then conducted aerial balloon photography followed by geologic mapping, basic data collection, photo-documentation, and sampling from two sites. Samples were analyzed with a UV lamp, Geiger counter, and x-ray fluorescence spectrometer. Petroscopic analysis and interpretation of the samples were done by Gootee. Daniel Gruber, the citizen-science project leader, and Gootee summarized methodology, sample analyses, and interpretation in a report including detailed geologic maps. Analysis of samples from one site provided evidence of several events of Proterozoic quartz formation. The other site hosted pegmatite, cumulates, graphic granite and orbicular granite in association with milky quartz, all discovered by citizen scientists. The milky quartz and surrounding pegmatites in granite at this site trace the progression of late-stage crystallization at the margin of a fractionated granite batholith, providing an exemplary opportunity for further research into batholith geochemistry and evolution. The project required 1000 hours of citizen-science time for training, field work, data organization and entry, mapping, and writing. The report by Gootee and Gruber was reviewed and published by AZGS as an Open File Report in its online document repository. The citizen scientist team leveraged the time of professional geologists to expand knowledge of an important geologic feature of the McDowell Mountains.

Temporal evolution of mineralization events in the Bohemian Massif inferred from the Re-Os geochronology of molybdenite

Science.gov (United States)

Ackerman, Lukáš; Haluzová, Eva; Creaser, Robert A.; Pašava, Jan; Veselovský, František; Breiter, Karel; Erban, Vojtěch; Drábek, Milan

2017-06-01

Molybdenite is a common mineral accompanying Sn-W, Au, and base metal mineralizations located in different geotectonic units of the Bohemian Massif, but it is also widespread in granitoids and/or related quartz veins/pegmatites forming disseminated Mo mineralization. Thirty Re-Os ages were obtained for molybdenite samples from the Bohemian Massif to provide constraints on the timing and duration of mineralization event(s) within the framework of previously published geochronological data for the host and/or associated rocks. The obtained data for Sn-W-(Li) deposits in the Erzgebirge metallogenetic province indicate the predominance of one and/or multiple short-time mineralization events taking place between ˜319 and 323 Ma, with the exception of the Krupka deposit associated with the Altenberg-Teplice caldera where the data may suggest prolonged activity until ˜315 Ma. The ages of the Pb-Zn-(Au-Mo) Hůrky u Rakovníka and Fe-Cu-As Obří důl mineralizations from the exocontacts of the Čistá pluton and Krkonoše-Jizera Plutonic Complex, respectively, provide evidence for synchronous emplacement of the ore and the associated granitic rocks. In contrast, the Padrť Fe-As-Mo mineralization postdates the age of the associated Padrť granite. Disseminated Mo mineralization in Cadomian and Variscan granitoids and/or related to quartz veins/pegmatites provides Re-Os ages that overlap with the previously published geochronological data for the host rocks, suggesting coeval evolution. Molybdenite samples from the Sázava suite granites of the Central Bohemian Plutonic Complex (CBPC) have resolvable younger ages than their host granites, but similar to the age of spatially related Au mineralization which is associated with the latest evolution of the CBPC.

Geochemistry, geochronology and Nd isotopes of the Gogó da Onça Granite: A new Paleoproterozoic A-type granite of Carajás Province, Brazil

Science.gov (United States)

Teixeira, Mayara Fraeda Barbosa; Dall'Agnol, Roberto; Santos, João Orestes Schneider; de Sousa, Luan Alexandre Martins; Lafon, Jean-Michel

2017-12-01

The Gogó da Onça Granite (GOG) comprise a stock located in the Carajás Province in the southeastern part of Amazonian Craton near its border with the Araguaia Belt. Three facies were identified in the pluton: biotite-amphibole granodiorite, biotite-amphibole monzogranite and amphibole-biotite syenogranite. The GGO crosscut discordantly the Archean country rocks and are not foliated. All Gogó da Onça Granite varieties are metaluminous, ferroan A2-subtype granites with reduced character. The major and trace element behavior suggests that its different facies are related by fractional crystallization. Zircon and titanite U-Pb SHRIMP ages show that the pluton crystallized at ∼1880-1870 Ma and is related to the remarkable Paleoproterozoic magmatic event identified in the Carajás Province. Whole-rock Nd isotope data (TDM ages 2.78 to 2.81, εNd values of -9.07 to -9.48) indicate that the GOG magmas derived from an Archaean source compatible with that of some other Paleoproterozoic suites from Carajás Province. The GOG show significant contrasts with the Jamon and Velho Guilherme Paleoproterozoic suites from Carajás Province and the inclusion of the Gogó da Onça granite in any of these suites is not justified. The GOG is more akin to the Serra dos Carajás Suite and to the Seringa and São João granites of Carajás and to the Mesoproterozoic Sherman granite of USA and the Paleoproterozoic Suomenniemi Batholith of Finland. This study puts in evidence the relevance of precise geochronological data and estimation of magma oxidation state in the characterization and correlation of A-type granites.

Uranium and selected trace elements in granites from the Caledonides of East Greenland

International Nuclear Information System (INIS)

Steenfelt, A.

1982-01-01

The Caledonian fold belt of East Greenland contains calc-alkaline granite (sensu lato) intrusions with ages ranging from c.2000 Ma to c.350 Ma. The Proterozoic granites have low U contents and the pre-Devonian Caledonian granites contents of U corresponding to the clarke value for U in granites. Some aspects of the geochemistry of U are discussed using U-K/Rb, U-Sr, U-Zr, and U-Th diagrams. Secondary enrichment and mineralization occurs in fractured and hydrothermally altered granites and rhyolites situated in or near a major NNE fault zone. The U is associated with iron oxides or hydrocarbons. It is suggested that the source of the mineralization was Devonian acid magma, which also acted as a heat source for circulating hydrothermal fluids. (author)

The rapakivi granite plutons of Bodom and Obbnäs, southern Finland: petrography and geochemistry

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Kosunen, P.

1999-12-01

Full Text Available The Obbnäs and Bodom granite plutons of southernmost Finland show the typical petrographic and geochemical features of the Proterozoic rapakivi granites in Finland and elsewhere: they cut sharply across the 1900 Ma Svecofennian metamorphic bedrock and have the geochemical characteristics of subalkaline A-type granites. The Bodom pluton is composed of porphyritic granites (hornblende-, hornblende-biotite-, and biotite-bearing varieties and an even-grained granite that probably represent two separate intrusive phases. This lithologic variation does not occur in the Obbnäs pluton, which is almost entirely composed of porphyritic hornblende-biotite granite that gradually becomes more mafic to the southwest. Three types of hybrid granitoids resulting from magma mingling and mixing occur on the southwestern tip of the Obbnäs peninsula. The Bodom granites are syenogranites, whereas the composition of the Obbnäs granite varies from syeno- to monzogranite. The main silicates of both the Bodom and Obbnäs granites are quartz, microcline, plagioclase (An1541, biotite (siderophyllite, and generally also amphibole (ferropargasite or hastingsite. Plagioclase-mantled alkali feldspar megacrysts are absent or rare. The accessory minerals are fluorite, allanite, zircon, apatite, and iron-titanium oxides; the Obbnäs granite also contains titanite. The Bodom and Obbnäs granites are metaluminous to weakly peraluminous, with average A/CNK of 1.00 and 1.05, respectively, have high Fe/Mg (average FeOtot/[FeOtot+MgO] is 0.94 for the Bodom and 0.87 for the Obbnäs granites, and high Ga/Al (3.78 to 5.22 in Bodom and 2.46 to 4.18 in Obbnäs. The REE contents are high with LREE-enriched chondrite-normalized patterns and moderate (Obbnäs to relatively strong (Bodom negative Eu-anomalies. The Obbnäs granite is enriched in CaO, TiO2, MgO, and FeO, and depleted in SiO2 and K2O compared to the Bodom granites. Also, there are differences in the Ba, Rb, and Sr contents of

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.

The spatial variation of initial 87Sr/86Sr ratios in the Toki granite, Central Japan. Implications for the intrusion and cooling processes of a granitic pluton

International Nuclear Information System (INIS)

Yuguchi, Takashi; Tsuruta, Tadahiko; Hama, Katsuhiro; Nishiyama, Tadao

2013-01-01

The spatial variation in initial 87 Sr/ 86 Sr ratios (SrI) in the Toki granite, Central Japan, shows heterogeneity ranging from 0.708942 to 0.710069, which provides information on the intrusion and cooling processes of plutons. The Toki granite has three mineralogy-based rock facies: muscovite-biotite granite (MBG), hornblende-biotite granite (HBG) and biotite granite (BG). Large SrI values were found to be distributed at the western margin (west MBG) and the lithologically central region (central BG), while small SrI values were found at the northeast margin (northeast MBG). Regions with high and low Sr concentrations were also found in the Toki granite. In the Sr-rich samples, SrI (0.708942-0.709789) increases with 100/Sr (0.7-1.5). This geochemical trend extends towards the country sedimentary rocks of the Mino Terrane, which can be interpreted to result from assimilation and fractional crystallization (AFC) between the original granitic magma and the Mino sedimentary rocks. The SrI values in the Sr-rich regions show a correlation with the Alumina Saturation Index (ASI). In particular, the west MBG, with large SrI values, is classified as a peraluminous granitoid with large ASI, suggesting that the western margin of the pluton was strongly affected by assimilation during the intrusion process. The Sr-poor samples are present both in the central BG, with large SrI values, and in the northeast MBG, with small SrI values. The Sr-poor samples have small ASI and large differentiation indices, indicating that the central BG and the northeast MBG were generated either by different AFC process with different amounts of contaminants or by the intrusion and fractionation of different source magma with different SrI values. Overall, the geochemical spatial variations found in the Toki granite can be explained by various degrees of assimilation and fractional crystallization in the magma chamber and/or multi-stage intrusions with different degrees of crystallization of

Chemical zoning of muscovite megacrystal from the Brazilian Pegmatite Province

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Rúbia R. Viana

2007-09-01

Full Text Available Macroscopically homogenous muscovite plate from the Cruzeiro pegmatite, located in the Eastern Pegmatite Province in Minas Gerais, may show complex distribution patterns of some trace elements. In geochronological and petrological studies, as for example in the distinction of magmatic and post-magmatic mica, the cause of zoning could be taken into consideration. The complex chemical zoning in the studied mica plate can be best explained by growth in an evolving magma followed by alteration due to percolation of hydrothermal fluids. Enrichment of Rb towards the border is interpreted as resulting from the chemical evolution of the residual magma during crystal growth. The depletion in (IV Al+VI Al as well as the increase in (Fe+Mg and Si along a fracture could be due to the hydrothermal celadonitic substitution of muscovite. This alteration also caused depletion in the contents of Rb, Ga, Y, Nb, Sn, and Zn and residual concentration of Ti. Elements such as Ga, Y, Nb, Sn, and Zn, rarely considered in the discussion of differentiation or alteration processes in micas, have been shown to be as significant as the alkali-elements.Um grande cristal de muscovita, macroscopicamente homogêneo, procedente do Pegmatito Cruzeiro, localizado na Província Pegmatítica Oriental, em Minas Gerais, exibe padrão de distribuição complexa para alguns elementos traços. Em estudos geocronológicos e petrológicos, como, por exemplo, na separação entre micas magmáticas e pós-magmáticas, a causa de zoneamento deve ser levada em consideração. O complexo zoneamento químico no cristal de mica estudado é melhor explicado pelo crescimento em um magma evoluído, seguido pela alteração, proveniente da percolação de fluidos hidrotermais. O enriquecimento de Rb nas bordas é interpretado como resultado da evolução química do magma residual durante o crescimento do cristal. A diminuição em (IV Al+VI Al, bem como o aumento de (Fe+Mg e Si ao longo da fratura �

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

The Swedish Bohus granite - a stone with a fascinating history

Science.gov (United States)

Schouenborg, Björn; Eliasson, Thomas

2015-04-01

One of the most well-known and well spread Swedish stone types used as building stones is the Bonus granite. It outcrops in an area north of Gothenburgh (SW Sweden), along the coastline, approximately 35 km wide and 85 km long. The granite continues into Norway as the Iddefjord granite. The Bohus granite is one of Sweden's youngest granites. Isotopic dating shows that the magma cooled at about 920 M years ago and thus marking the end of the Sveconorwegian orogoney. It is a composite granite massif area with several granitic intrusions but with rather homogeneous mineralogy. However, colour and texture varies quite a lot and the colour ranges from red to reddish grey although some pure grey varieties occur sparsely. The grain size ranges from medium grained to coarse grained and even with some porphyric parts. Quarrying in an industrial scale started 1842. The merchant A C Kullgren opened the first quarry and produced stones for the construction of the 86 km long Trollhättan channel connecting lake Vänern and the Atlantic ocean in the SW Sweden The stone was used for constructing harbors and wharves along the channel. Several quarries opened in the late 1800 around 1870 - 1890 and the export increased steadily with deliveries to Germany, Denmark, Holland, England and even to South America. The stone industries in Bohuslän (Bohus county), at its peak in 1929, engaged around 7 000 employees. During the depression in 1930 almost all of them became unemployed. However, as a curiosity, production and export continued to Germany for construction of Germania, the future World capital city ("Welthauptstadt Germania"), planned by Adolf Hitler and Albert Speer. About 500 stone workers were kept employed for this project during the late thirties. Today several varieties are still produced: Evja/Ävja, Tossene, Brastad, Näsinge, Broberg, Nolby, Allemarken and Skarstad. However, the number of stone workers is far from that of the early 1900. The Swedish production is mainly

Greisen deposits associated to carboniferous post-orogenic granites with mineralization potential, Sierra de Fiambala, Catamarca, Argentina

International Nuclear Information System (INIS)

Fogliata, A. S.; Rubinstein, N. R.; Avila, J. C.; Baez, M.

2008-01-01

The Fiambala range is located in the central south part of the province of Catamarca, Western Sierras Pampeanas, Argentina. It is largely conformed by Precambrian metamorphic rocks, a Cambrian granitic intrusive, Ordovician basic and ultra basic rocks and epi zonal Carboniferous granites (Los Ratones, El Salto and Ayacucho Granites). The Carboniferous granites are sub alkaline, weakly peraluminous, high silica (except for the porphyritic facies of Los Ratones granite) and moderately enriched in K. Contents of trace elements and REE indicate that El S alto and Ayacucho granites and the granular facies of Los Ratones granite have characteristics of evolved and differentiated granite associated with hydrothermal systems. The variations of trace elements, particularly Sn, W, U, Rb, Ba, Zr and Sr suggest that they correspond to granites with mineralization potential. Genetically linked to these granites there are Sn, W, U and minor base metals greisen deposits. The hydrothermal process that yield to these deposits involved two main alteration stages, beginning with alkali metasomatism follow by greissenization. According to the isotopic ages the hydrothermal processes postdate about 1 Ma the magmatic activity. The analyses of the granites and the associated greisen deposits confirm that the post orogenic carboniferous magmatism is the major metallogenetic control of the ore deposits from the studied area. This metallogenetic control could be a useful tool in prospecting similar deposits in the rest of the Western Sierras Pampeanas. (Author)

2005 dossier: granite. Tome: architecture and management of the geologic disposal

International Nuclear Information System (INIS)

2005-01-01

This document makes a status of the researches carried out by the French national agency of radioactive wastes (ANDRA) about the geologic disposal of high-level and long-lived radioactive wastes in granite formations. Content: 1 - Approach of the study: main steps since the December 30, 1991 law, ANDRA's research program on disposal in granitic formations; 2 - high-level and long-lived (HLLL) wastes: production scenarios, waste categories, inventory model; 3 - disposal facility design in granitic environment: definition of the geologic disposal functions, the granitic material, general facility design options; 4 - general architecture of a disposal facility in granitic environment: surface facilities, underground facilities, disposal process, operational safety; 5 - B-type wastes disposal area: primary containers of B-type wastes, safety options, concrete containers, disposal alveoles, architecture of the B-type wastes disposal area, disposal process and feasibility aspects, functions of disposal components with time; 6 - C-type wastes disposal area: C-type wastes primary containers, safety options, super-containers, disposal alveoles, architecture of the C-type wastes disposal area, disposal process in a reversibility logics, functions of disposal components with time; 7 - spent fuels disposal area: spent fuel assemblies, safety options, spent fuel containers, disposal alveoles, architecture of the spent fuel disposal area, disposal process in a reversibility logics, functions of disposal components with time; 8 - conclusions: suitability of the architecture with various types of French granites, strong design, reversibility taken into consideration. (J.S.)

Uranium distribution in Brazilian granitic rocks. Identification of uranium provinces

International Nuclear Information System (INIS)

Tassinari, C.G.G.

1993-01-01

The research characterized and described uranium enriched granitoids in Brazil. They occur in a variety of tectonic environments and are represented by a variety granite types of distinct ages. It may be deduced that in general they have been generated by partial melting process of continental crust. However, some of them, those with tonality composition, indicate a contribution from mantle derived materials, thus suggesting primary uranium enrichment from the upper mantle. Through this study, the identification and characterization of uranium enriched granite or uranium provinces in Brazil can be made. This may also help identify areas with potential for uranium mineralization although it has been note that uranium mineralization in Brazil are not related to the uranium enrichment process. In general the U-anomalous granitoids are composed of granites with alkaline composition and granite ''sensu strictu'' which comprise mainly of syenites, quartz-syenites and biotite-hornblende granites, with ages between 1,800 - 1,300 M.a. The U-anomalous belongings to this period present high Sr initial ratios values, above 0.706, and high Rb contents. Most of the U-enriched granitoids occur within ancient cratonic areas, or within Early to Mid-Proterozoic mobile belts, but after their cratonization. Generally, these granitoids are related to the border zones of the mobile belts or deep crustal discontinuity. Refs, 12 figs, 3 tabs

Distribution of monazite in granite and alluvial of South Bangka

International Nuclear Information System (INIS)

Ngadenin

2011-01-01

Monazite is one source of thorium (Th), which has significant economic value and potential as an alternative fuel of nuclear power plants. The aims of research is to find out the distribution monazite alternative fuel of nuclear power plants. The aims of research is to find out the distribution monazite and its potential as a resource of radioactive minerals on the Bangka Island, then the data will be used and its potential as a resource of radioactive minerals on the Bangka Island, then the data will be used as a reference in the development of radioactive minerals exploration areas in the coming year. The research location is in the Bencah and Gadung villages, South Bangka Regency. The method used is the geological mapping, sampling of rock for petrographic, mineragraphic and autoradiographic analysis and heavy mineral for grains counting analysis. The results showed that lithologic area of Bencah Village composed of clay stone and alluvial deposits, while the Gadung Village composed by granite and alluvial deposits. Granite Gadung is predicted as the ilmenite series granite and tend to be of S type, while the material of Bencah alluvial is predicted come from the Klabat granite groups. In general, distribution of monazite in the alluvial slightly more potent of monazite than in the granite so that the development of radioactive minerals exploration will be prioritized in the alluvial areas. (author)

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 ...

A Rb-Sr isotope study of a young granite sheet at Marble Delta, southern Natal

International Nuclear Information System (INIS)

Naidoo, D.D.; Eglington, B.M.; Harmer, R.E.

1989-01-01

Rb-Sr isotope data are presented for two apophyses of a granite sheet intrusive into marble at Marble Delta, southern Natal. Granite samples collected near the margins of these apophyses contain calcite and are thought to have been contaminated by the marble during intrusion of the granite magma. In contrast, those further away from contacts lack calcite. The 'uncontaminated' granite samples define an isochron date of 899 ± 11 Ma. This data is thought to represent the intrusive age of the granite sheet. 11 refs., 5 figs., 2 tabs

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

Caulins brasileiros: alguns aspectos da geologia e da mineralogia Brazilian kaolins: some aspects of the geology and mineralogy

Directory of Open Access Journals (Sweden)

Ian Richard Wilson

1998-08-01

, kaolin derived from pegmatite, from granitic rocks, from volcanic rocks and kaolin derived from anorthosite. The sedimentary clays are mainly found in the Amazon basin and those adjacent to the Jari River are being exploited commercially for export as a paper coating clay. Amazon kaolin is characterised by high iron and titania (lattice-held with low levels of alkali and exhibiting euhedral kaolinite crystals. The South-eastern pegmatite, when not iron stained, are extremely low in iron and titania and a mixture of kaolinite 7Å/10Å-halloysite occurs in all deposits. The North-eastern pegmatite produces kaolin constituted only by euhedral kaolinites with an absence of halloysite. Kaolin from granites generally has higher iron levels when compared with pegmatite and deposits constituted only by kaolinite are rare, a mixture of kaolinite/7Å-halloysite being common. Both the pegmatite and granite derived kaolin are utilised as a paper filler and in general ceramics. Volcanic rocks on alteration produce a fine siliceous clay with titania levels higher than other types and are generally mixtures of kaolinite-7Å. Volcanic derived clays are utilized locally in ceramics. Kaolins derived from anorthosite are similar in iron and titania levels to those from granitic kaolins. Assemblages of kaolinite and small quantities of 7Å-halloysite are found. These clays are used in both whiteware ceramics and paper filler.

Generation of post-collisional normal calc-alkaline and adakitic granites in the Tongbai orogen, central China

Science.gov (United States)

Zhang, Wen-Xiang; Zhu, Liu-Qin; Wang, Hao; Wu, Yuan-Bao

2018-01-01

Post-collisional granites are generally generated by partial melting of continental crust during orogenic extension. The occurrence of normal calc-alkaline granites following adakitic granites in a collisional orogen is frequently supposed as a sign of tectonic regime transition from compression to extension, which has been debated yet. In this paper, we present a comprehensive study of zircon U-Pb ages, Hf-O isotopes, as well as whole-rock major and trace elements and Sr-Nd isotopes, for Tongbai and Jigongshan post-collisional granitic plutons in the Tongbai orogen. Zircon U-Pb dating yields intrusion ages of ca. 140 and 135 Ma for the Tongbai and Jigongshan plutons, respectively, suggesting they are post-collisional granites. These granites are high-K calc-alkaline series, metaluminous to weakly peraluminous with A/CNK ratios of 0.85-1.08. The Tongbai gneissic granites are normal calc-alkaline granite, having variable SiO2 (61.93-76.74 wt%) and Sr/Y (2.9-38.9) and (La/Yb)N (1.7-30.1) ratios with variably negative Eu anomalies (0.41-0.92). They have relatively high initial Sr isotope ratios of 0.707571 to 0.710317, and low εNd(t) (- 15.74 to - 11.09) and εHf(t) (- 17.6 to - 16.9) values. Their Nd and Hf model ages range from 2.2 to 1.8 Ga and 2.3 to 2.2 Ga. On the contrary, the Jigongshan granites show higher SiO2 (66.56-72.11 wt%) and Sr/Y (30.1-182.0) and (La/Yb)N (27.4-91.4) ratios with insignificant Eu anomalies (0.73-1.00), belonging to adakitic granite. They have Isr = 0.707843-0.708366, εNd(t) = - 19.83 to - 17.59, and εHf(t) = - 26.0 to - 23.5. Their Nd and Hf model ages vary from ca. 2.5 to 2.4 Ga and ca. 2.8 to 2.6 Ga. The Tongbai and Jigongshan granites are characterized by mantle-like zircon δ18O values (5.17-5.46‰). These geochemical features suggest that the Tongbai and Jigongshan granites were derived from partial melting of Paleoproterozoic and Archean continental crust, respectively. Fractional crystallization affected the geochemical

Biofouling of granite-rapakivi in St. Petersburg monuments and in the quarry in Russia and Finland

Science.gov (United States)

Vlasov, Dmitry; Panova, Elena; Alampieva, Elena; Olhovaya, Elena; Popova, Tatyana; Vlasov, Alexey; Zelenskaya, Marina

2013-04-01

Granite-rapakivi was widely used in the architecture of St. Petersburg: the facades of buildings, embankments of rivers and canals, bridges, sculptural monuments, pedestals, facing the metro stations. This stone is rapidly destroyed due to the peculiarities of its structure. Biofouling of granite is insufficiently studied. Cause the destruction of granite can be bacteria, microscopic algae, fungi, mosses, lichens, higher plants, invertebrates and vertebrates. They often form specific lithobiotic communities that contribute to the destruction of granite-rapakivi. The objects of research were monuments of St. Petersburg (granite sculpture, facades, facing embankments) as well as granite-rapakivi quarries in Russia and Finland, where the stone was quarried for use in St. Petersburg. Sampling was carried out from the most typical biofouling sites. Different methods were applied for the study of damaged granite: petrographic analysis, light and scanning electron microscopy, methods for detection and identification of microorganisms, X-ray microprobe analysis. As result the main forms of granite destruction were described: fractures, ovoid weathering, granular disintegration, surface films, crusts and layers, pitting and fouling. Lichens, mosses, herbaceous and micromycetes were dominated on the granite-rapakivi in quarries. For example, in a Monferran quarry (Virolahti region) the complicated lithobiotic community was revealed. It included 30 species of micromycetes, 31 species of lichens, 10 species of moss. Bacteriological analysis showed the dominance of bacteria Bacillus, and actinomycetes in microbial biofilms. More than 100 species of plants were found on the granite embankments in St. Petersburg. They were confined to the cracks, seams of granite blocks. Plants and mosses were common to the granite embankments of rivers and canals in the central (historical) part of the city. Dimensions of mosses depend on the area of the deepening which they occupy. The most

Radiatives elements distribution in Serra do Carambei granite, Parana, Brazil

International Nuclear Information System (INIS)

Pinto-Coelho, C.V.; Siedlecki, K.N.

1988-01-01

In the Serra do Carambei Granite, the uranium present in the rock in anomalous concentration is hosted, preferentially, in accessory mineralogical phases-zircon, xenotime, magnetite and ilmenite, and, in lesser proportion, in the essential minerals of the rock-potassium feldspar and also iron oxydes/hydroxydes and alterated biotite. Optical petrography, autorradiomicrography, scanning electronic microscopy, and the utilization of correlation matrixes and the respective dendrograms revealed a distribution of radioactive elements basically controlled by autometassomatic, tardi/pos-magmatic or supergene processes. Intrusive felsic dikes in the Serra do Carambei Granite have radioelement concentration level approximately four times higher than the enclosing granite, where uranium as well as thorium is preferentially found in metamictized accessory minerals-zircon and allanite. (author) [pt

Figure-Ground Processing: A Reassessment of Gelb and Granit.

Science.gov (United States)

Nelson, Rolf; Hebda, Nicholas

2018-03-01

In 1923, Adhemar Gelb and Ragnar Granit, two prominent researchers in early Gestalt perceptual theory, reported a lower threshold for detection of a target (a small colored dot) on the ground region of an image than on an adjacent figural region. Although their results had a wide influence on the understanding of figure-ground perception, they are at odds with more recent investigations in which figural regions appear to have a processing advantage over ground regions. The two present studies replicated Gelb and Granit's experiment using a similar figure-ground stimulus albeit with a two-alternative forced choice procedure rather than their original method of adjustment. Experiment 1 found that, contrary to Gelb and Granit's findings, a detection advantage was found for the figural over the ground region. Experiment 2 indicated that explicit contours might have played a role in detection.

Review of geomechanics data from French nuclear explosions in the Hoggar granite, with some comparisons to tests in US granite

International Nuclear Information System (INIS)

Heuze, F.E.

1983-05-01

Numerous unclassified reports on the French nuclear explosions in the Hoggar (1961-1966) were reviewed from the standpoint of geomechanics. The following aspects of the tests are summarized: spectral content of the tests compared to U.S. results; shock front positions with time; cavity radius as a function of yield, coupling, density of rock, rock shear strength, and overburden; radial pressure, tangential pressure and peak velocity as a function of distance and yield; pressure vs. time at various distances; mechanical properties of granite; scaling laws for acceleration, velocity and displacement as a function of yield and distance for all Hoggar shots; extent of tunnel damage as a function of distance and yield; time to collapse of chimney as a function of yield, or cavity radius; extent of granite crushing and disking as a function of distance and yield cavity height relation to cavity radius; faulting and jointing on the Taourirt Tan Afella massif; and influence of water content on cavity radius vs. yield. Whenever possible, these French data are compared to corresponding data obtained in the U.S. granite events Hard Hat, Shoal, and Piledriver. The following results emerge from the comparison: (1) agreement is found between the French and U.S. experience for: mechanical properties of the granites, rock damage due to the blast, and yield-scaled peak values of acceleration, velocity and displacement; and (2) lack of agreement exists for: cavity size, chminey height, and time to cavity collapse. Average spacing of rock joints also was about 5 times greater in the Hoggar

High level and long life radioactive wastes. Todays situation and future evolutions. Framework and process of the Granite collegial mission of dialogue. FAQ about the Granite collegial mission of dialogue

International Nuclear Information System (INIS)

2000-03-01

On December 9, 1998, the French government decided the construction of two underground laboratories for the study of the disposal of radioactive wastes in the deep underground. One site will be located in a granitic massif which remains to be determined. This document presents the framework and the different steps of the 'Granite' mission: the situation of radioactive wastes in France, some data about the conditioning, storage and reprocessing of high activity and long life radioactive wastes, the legal framework of the management of radioactive wastes and the related warranties, the disposal in deep underground and the realization of underground research laboratories, the government decision of December 9, 1998, the 'Granite' collegial mission of dialogue and the different steps of the geological surveys about granites. A second part answers some frequently asked questions about the 'Granite' collegial mission of dialogue: decision procedure, planning of the mission, consultation of the geologic survey, role of the mission, public information etc.. (J.S.)

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

Link between the granitic and volcanic rocks of the Bushveld Complex, South Africa

Science.gov (United States)

Schweitzer, J. K.; Hatton, C. J.; De Waal, S. A.

1997-02-01

Until recently, it was proposed that the Bushveld Complex, consisting of the extrusive Rooiberg Group and the intrusive Rashoop Granophyre, Rustenburg Layered and Lebowa Granite Suites, evolved over a long period of time, possibly exceeding 100 Ma. Most workers therefore considered that the various intrusive and extrusive episodes were unrelated. Recent findings suggest that the intrusive, mafic Rustenburg Layered Suite, siliceous Rashoop Granophyre Suite and the volcanic Rooiberg Group were synchronous, implying that the Bushveld igneous event was short-lived. Accepting the short-lived nature of the complex, the hypothesis that the granites are genetically unrelated to the other events of the Bushveld Complex can be reconsidered. Re-examination of the potential Rooiberg Group/Lebowa Granite Suite relationship suggests that the granites form part of the Bushveld event. Rhyolite lava, granite and granophyre melts originated from a source similar in composition to upper crustal rocks. This source is interpreted to have been melted by a thermal input associated with a mantle plume. Granite intruded after extrusion of the last Rooiberg rhyolite, or possibly overlapped in time with the formation of the youngest volcanic flows.

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.

Rare metal granites in the structures of the Russian sector of Pacific ore belt

Directory of Open Access Journals (Sweden)

В. И. Алексеев

2016-08-01

Full Text Available Data are presented on the geology of areas of rare metal granites proliferation in the Russian sector of the Pacific Ore Belt that make one take a fresh look at the East Asian granitoid area to update its metallogeny. History is reviewed of studying rare metal granites of the Russian Far East. As a rule, these are found in the vicinity of major tungsten-stanniferous ore deposits, except much later than discovering the former, at the stages of their assessment and survey. Rare earth granites are usually missed by the geologists during the early stages of regional geological surveys due to their small size, weak eroding and external similarity with earlier granites. Using the examples of the Central Polousny, Badzhal and Kuyviveem-Pyrekakay regions the structural and geological conditions are characterized of localization of rare metal granites. Comparative analysis of geological situations made it possible to formulate the areal character of manifestation of rare metal granites; their confinedness to late Mesozoic orogenic arched uplifts of bogen structures above deep granitoid batholiths; positioning in the areas where longitudinal and transversal deep laying faults cross; gravitation to the environs of pre-Cambrian median masses. Similarity of structural-geological conditions for manifestation of the well-studied ore-containing granites serves to confirm the hypothesis on the joint stage of late Cretaceous rare metal magmatism in the Russian sector of the Pacific Ore Belt and the existence in the region of a magmatic super-province – the Far East belt of rare metal granites that includes the Novosibirsk-Chukotka, the Yana-Kolyma and the Sikhote-Alin rare metal – granite provinces.

Comparative Study on The Geological and Geochemical Characteristics of Some Rare-Metal Granites, Southeastern Desert, Egypt

International Nuclear Information System (INIS)

El Galy, M.M.; Khaleal, F.M.; Bakhit, A.F.

2016-01-01

The Egyptian younger granites are characterized by the presence of more than 14 exposures of rare- metal granites. The studied granites are included into three geological modes of occurrence. The first includes Igla and Abu Dabbab plutons, which occur as small stocks of circular, ovoid, or apophyses and leucocratic outcrops. The second comprises the plugs and dyke-like bodies intruded peralkaline granites of Bir Um Hibal. The third includes Homrit Waggat and Muweilha plutons. vThey cover small areas and exhibit obvious pervasive post magmatic alterations. The petrographic and mineralogical studies are confirmed by the geochemical investigations indicating that the concerned rare-metal granites being broadly distinguished into magmatic and metasomatic associations. The magmatic granite associations are further subdivided into two subgroups; i) peraluminous granites (Li-mica rich) including Igla and Abu Dabbab plutons and ii) peralkaline granites including Um Hibal pluton. The studied peraluminous granites are generally enriched in Nb, Rb, Ta, Li, F, Y, Zr, U and Th elements. The peralkaline granites are enriched in K_,0 oxide as well as Zr, Nb, F, U, Th and Ta elements. On the other hand, the metasomatic granite associations are represented by Homrit Waggat and Muweilha plutons. They are characterized by high contents of Na_2O oxide as well as Nb, Ta, U, Th and Rb elements. Igla pluton has highest average U and Th contents (42 ppm and 58 ppm respectively), while Um Hibal pluton has lowest average U and Th contents (14 ppm and 26 ppm respectively)

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

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

Science.gov (United States)

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

2017-12-01

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

Contribution to the radioactivity of Um Ara granitic pluton, south-eastern desert, Egypt

International Nuclear Information System (INIS)

El Reedy, M.W.; Kamel, A.F.; Mansour, S.E.I.

1988-01-01

Um Ara area lies in the southern part of the eastern desert between latitudes 22 0 30' and 22 0 41'N and longitudes 33 0 46' and 33 0 54'E. Several types of granitic varieties ranging from high silica granite (SiO 2 >75%) to low silica granite (SiO 2 68-70%) occur in Um Ara granitic pluton. Surface samples were collected from the high anomalous locations in the pluton together with trenches samples (about 50cm in depth). The U content in the surface samples ranges from 69 to 7 ppm while in trenches samples, it ranges from 38 to 759 ppm. The thorium content on the other hand ranges from 34 to 402 ppm in surface samples and from 158 to 316 ppm in trenches samples. Some samples show no Th contents. The Th/U ratios ranges from 0.065 to 3.137 in surface samples and from 0.386 to 2.590 in trenches samples. An enrichment of U content is the main feature characterising this granitic pluton, it is mainly connected with the fractured zones. Uranium is mostly present as secondary U mineralization accompanied by Fe, Mn and to some extent by carbonate materials. A hydrothermal origin could be considered for this U mineralization in the pluton. Primary U mineralization (pitchblende) together with secondary mineralization was observed in some locations in the area disseminated in the granite, this reflects the syngenetic origin of this granitic type

The occurrence of rare earth elements in some Finnish mires

Directory of Open Access Journals (Sweden)

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.

Carboniferous granite basement dredged from a site on the southwest margin of the Challenger Plateau, Tasman Sea

International Nuclear Information System (INIS)

Tulloch, A.J.; Kimbrough, D.L.; Wood, R.A.

1991-01-01

Discordant zircon fractions from a granite sample dredged off a basement horst on the western margin of the Challenger Plateau yield a 335 ± 7 Ma lower intercept date interpreted as the crystallisation age of the granite. This age, and the modal composition of the granite, is similar to that of the Karamea Suite of Westland and Nelson, New Zealand, and some Tasmanian granites. The concordia upper intercept date of 1747 ± 300 Ma implies the presence of Proterozoic continental crustal material in the source region of the granite. The Challenger granite is distinct from older S-type granites of southeastern Australia and I-type granites of northern Victoria Land and Marie Byrd Land, Antarctica. Subsequent to emplacement, the granite was brecciated and hydrothermally altered. A K-Ar age of 95 Ma on hydrothermal sericite indicates that this event overlapped with a major crustal extension event recorded in Westland and Nelson, and predates the oldest known sea floor in the Tasman Basin by at least 11 Ma. (author). 23 refs., 3 figs., 2 tabs

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

Analysis of Shield Construction in Spherical Weathered Granite Development Area