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- D. V. Subba Rao
- V. Divakara Rao
- K. Satyanarayana
- S. M. Hussain
- B. L. Narayana
- P. Rama Rao
- S. M. Ahmad
- B. Uday Raj
- T. Gnaneshwar Rao
- R. H. Sawkar
- B. S. Venkatachala
- Manoj Shukla
- B. Kumar
- R. Natarajan
- Mukund Sharma
- V. N. Vasudev
- M. Shukla
- S. N. Charan
- S. L. Ramesh
- R. Srinivasan
- V. Balaram
- S. M. NAQVI
- B. Vasantha Kumar
- P. K. Govil
- R. M. k. Khan
- M. Arora
- S. Nirmal Charan
- R. M. K. Khan
- Rahul Baldota
- S. R. Suresh
- P. T. Sastri
- A. S. Kulageri
- B. R. Nagabhushan
- D. S. Sarma
- D. V. Subbarao
- D. Srinivasa Sarma
- M. Ram Mohan
- J. G. Rana Prathap
- S. Viswanathan
- P. V. Sunder Raju
- E. V. S. S. K. Babu
- C. Manikyamba
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Naqvi, S. M.
- Archaean Komatiites from the Older Schist Belt of Kalyadi in Western Dharwar Craton, Karnataka
Abstract Views :182 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad-500007, A.P., IN
1 National Geophysical Research Institute, Hyderabad-500007, A.P., IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 53, No 3 (1999), Pagination: 347-354Abstract
The cluster of enclaves at Kalyadi, Hassan district includes ultramafic-mafic metavolcanic rocks and minor metasedimentary rocks such as chert, cherty quartzite and pelite. Occurrence of pillow and vesicular structures in the ultramafic rocks is being reported for the first time from this area. The average composition of the ultramafic rocks is : SiO2 46.05%, TiO2 0.18%, MgO 31.81%, K2O 0.15%. Cr 3409 ppm and Ni 1610 ppm with a CaO/Al2O3) ratio close tol. The composition, relict igneous structures and metasedimentary rock association are suggestive of a komatiitic affinity for these rocks, which possibly accumulated under subaqueous conditions.Keywords
Igneous Petrology, Geochemistry, Komatiites, Pillow Structures, Karnataka.
- Geochemistry and Origin of the Peninsular Gneisses of Karnataka, India
Abstract Views :178 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad, IN
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 15, No 3 (1974), Pagination: 270-277Abstract
Major and trace element analyses of gneisses from parts of the Karnataka State, reveal heterogeneity in their chemical, modal and normative compositions. On the basis of chemical differences it is suggested that the parent material for these gneisses was pelitic/arkosic in nature. Heterogeneity in their composition is attributed to their age difference, degree of granitisation and migmatisation to which the pelitic/arkosic parent material was subjected.- Review of the Present Status of the Geochemical Work on the Precambrian Mafic Rocks of India
Abstract Views :162 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad, IN
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 15, No 4 (1974), Pagination: 380-389Abstract
In the Precambrian terrains of India, mafic rocks are found (i) as extrusive patches along the Dharwar schists, their equivalents, and other younger Proterozoic formations; (ii) as xenoliths in the Peninsular gneisses and charnockites; and (iii) as pre and post Dharwar intrusive dikes and sills. The ages of these mafic rocks range from 3.2 to 0.9 b.y. The mafic igneous activities appear to have taken place in five phases, roughly around 3.2, 2.5, 2.1, 1.4, and 0.9 b.y. Only very scanty and random geochemical work has been carried out on these rocks. However, the available data do reflect secular changes in the compositions of mafic rocks with time; those of the 2.5 b.y. and earlier periods are quartz-olivine tholeiites and show very high ferromagnesium trace element contents; alkali olivine basalts appear to have emplaced for the first time over the Indian Shield around 2.1 b.y.
A comparative study of the chemistry of the mafic rocks of the different periods leads to the inference that in the initial stages, the primary fractionation of the earth was incomplete. This inference should be substantiated by detailed studies for a better understanding of the evolution of the Indian Shield and that of the continental crust. As knowledge on the relationship between mafic igneous activity, metallogenic patterns and crustal evolution is economically significant, a collaborative programme of extensive radioactive-palaeomagnetic dating, and major, trace element, and isotope geochemistry of these rocks should be taken up by different organisations having the available technical know-how and equipment.
- Geochemistry of Spinifex-Textured Peridotitic Komatiites from Ghatti Hosahalli, Karnataka, Indi
Abstract Views :195 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad-500 007, IN
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 4 (1980), Pagination: 194-198Abstract
Spinifex-textured peridotitic komatiites (STPK) of Ghatti Hosahalli have low CaO/Al2O3 ratio (< 1), low TiO2, K2O and high MgO. These STPK have comparable Ni and Co contents with those of the Australian and Canadian shields. These characters support the view that the spinifex-texture observed in these rocks is primary and not the result of later metamorphism. The Al2O3/TiO2 ratios are comparable to those of Chondrites indicating that the STPK are products of partial melting of the Archaean mantle. The STPK of Ghatti Hosahalli arc overlain by exhalative chemical precipitates and argillaceous metamorphosed sediments like bedded-barytes, fuchsite-quartzites and kyanite-mica schists. It is suggested that Ghatti Hosahalli band is a relic of an early Archaean greenstone belt.- Geology and Geochemistry of Paragneisses from the Javanahalli Schist Belt, Karnataka, India
Abstract Views :162 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad-500007, IN
1 National Geophysical Research Institute, Hyderabad-500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 12 (1980), Pagination: 577-592Abstract
The lowermost member of the Javanahalli schist belt consists of meta-arkoses/ paragneisses with interbedded epidote-quartzite and calc-silicate bands. These meta-arkoses exhibit relict current-bedding, arkosic texture and grain-to-grain variation in anorthite content within the same sample. Plagioclase is subordinate to K-feldspar and is relatively more weathered and sericitized. Orthoclase predominates over microcline in the total K-feldspar content and the quartz/feldspar ratio is generally very low. The meta-arkoses appear to be first-cycle sediments.
The composition of these paragneisses is unusual for Archaean metasediments. They are enriched in K, Si, Fe, Mg, Th, Rb, Ni, Cr and Co and depleted in Na, AI, Sr and often in Ca. The meta-arkoses of Javanahalli schist belt may be the product of strong and/or rapid chemical disintegration of Archaean tonalitic gneisses and basic and ultrabasic rocks. all of which were prominent components of the continental crust at the time the Javanahalli belt formed. If the meta-arkoses have not undergone major metasomatism, then their high abundance of K and Rb may indicate intense chemical leaching of these tonalitic source areas. Most of the saIt of the primitive oceans might have been derived from this intense leaching of the ancient cratonic tonalite gneisses.
- Geochemistry and Significance of Mafic-Ultramafic Rocks from the Southern Part of the Holenarasipur Schist Belt, Karnataka
Abstract Views :162 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad-500 007, IN
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 1 (1982), Pagination: 19-31Abstract
The ultramafic rocks of Holenarasipur schist belt show micro-spinifex texture, deformed pillow lava-like structures and contain interbedded fuchsite-quartzite. Compositionally the mafic-ultramafic rocks are similar to peridotitic, pyroxenitic and basaltic komatiites. Available data exhibit a gap between 20 and 30% MgO content, which suggests discontinuity in their composition. A two stage melting model is projected to explain this compositional gap. The abundance of komatiitic mafic-ultramafic rocks supports the view that the Holenarasipur schist belt is a true greenstone belt.- Group Discussion on the Chitradurga Schist Belt
Abstract Views :184 |
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Authors
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 6 (1984), Pagination: 399-400Abstract
No Abstract.Full Text
- Chitradurga Schist Belt - An Archaean Suture (?)
Abstract Views :168 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 26, No 8 (1985), Pagination: 511-525Abstract
Chitradurga schist belt is a 450 km long linear feature of Archaean age and composed of several types of volcanic and sedimentary rocks. It has been deformed by 3-phases of folding rendering elucidation of stratigraphic sequence complicated. The volcanic rocks range in composition from Spinifix Textured Peridotitic Komatiite (STPK) to rhyolite. Volcanism appears to have occurred, at least at two diflerent stratigraphic levels in the belt. The STPK, basalt and rhyolite suites are not genetically related with each other, except in Gadag, where basalt-rhyolite may be cogenetic phases of the same suite. Chemogenic sediments have a higher order contribution and enrichment from volcanogenic exhalative component. Graywacke sedimentation is recognized at two stratigraphic levels. The graywackes of the central part of the belt and those from the Gadag part of the belt differ very much from each other in their abundance of rock fragments, plagioclase/K-feldspar and Na2O/K2O ratios, Fe2O3, MgO, Cr, Ni, Zr, Rb and Sr abundances. Detrital mineral content and REE pattern of the graywackes of the central part are similar to those from other areas of the world of the same period and appear to have been derived from mixed, but predominantly tonalitic source. Gadag graywackes, on the other hand, appear to have had a predominantly volcanic source. Folded BIF horizons too are inferred to form a significant part of the source areas. Gadag part of the belt is the youngest as the Bagewadi-Kodkal conglomerate contains porphyritic granite pebbles along with rhyolites. This progressive younging and widening of the belt to the north is governed by the attitude of the axial plane foliation and plunge of the fold axes. It also probably reflects the style of the opening of a rift in the Archaean continental crust. Gravity data support such a rift origin. Horizontal EW compression is an essential feature of the Chitradurga schist pointing to its being a probable late Archaean suture.- The Conglomerates of Holenarasipur Schist Belt and the Nature of Pre-Holenarasipur Crust of Peninsular India
Abstract Views :166 |
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Authors
S. M. Hussain
1,
S. M. Naqvi
1
Affiliations
1 National Geophysical Research Institute, Hyderabad 500 007, IN
1 National Geophysical Research Institute, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 31, No 6 (1988), Pagination: 538-545Abstract
Two types of conglomerates occur in the Holenarasipur schist belt. The Tattekere conglomerate occurring in the older horizon (>3.4 b.y.) ofthe belt is oligomictic and is tectogenic (autoclastic), devoid of pebbles of detrital sedimentary origin. The Gopalapura conglomerate occurring in the younger horizon (3.2 to 3.0 b.y.) of the belt is, on the other hand, polymictic and sedimentogenic. Occurrence of gneiss pebbles in this conglomerate indicates presence of gneissic terrain in the source area and strongly supports the view that considerable sialic crust had evolved before the younger greenschist sequences were deposited in this region. This extensive crust is formed by widespread emplacement of acidic plutons during the time gap between the older and younger sequences of Holenarasipur. It is proposed that older Holenarasipur schists and gneisses which intruded it supplied the debris to the younger belt.- Silicified Cyanobacteria from the Cherts of Archaean Sandur Schist Belt-Karnataka, India
Abstract Views :160 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
2 Birbal Sahni lnstitute of Palaeobotany, Lucknow 226007, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
2 Birbal Sahni lnstitute of Palaeobotany, Lucknow 226007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 29, No 6 (1987), Pagination: 535-539Abstract
Silicified cyanobacterial remains are recorded from the black cherts interbedded in the Donimalai Formation of the Archaean Sandur Schist Belt and amorphous organic matter in the stromatolites underlying Deogiri Formation of the same belt. The presence of elemental carbon at the fringes of the cyanobacteria is confirmed by microprobe analysis. Carbon (δ13C= -1.4 ± 0.5% vs PDB) and oxygen (δ18O= + 10.6±0.5% vs SMOW) isotopic ratios and the presence of cyanobacteria extend the existence of photosynthetic activity into the Archaean.- Stromatolites from the Chert-Dolomites of Archaean Shimoga Schist Belt, Dharwar Craton, India
Abstract Views :203 |
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Authors
Affiliations
1 Department of Mines and Geology, Race Course Road, Bangalore, IN
2 National Geophysical Research Institute, Hyderabad, IN
3 Birbal Sahni Institute of Palaeobotany, Lucknow, IN
1 Department of Mines and Geology, Race Course Road, Bangalore, IN
2 National Geophysical Research Institute, Hyderabad, IN
3 Birbal Sahni Institute of Palaeobotany, Lucknow, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 33, No 3 (1989), Pagination: 201-205Abstract
Stromatolites of stratifera type showing development of pseudocolumnar structures occur both in chert as well as dolomites near the Kumsi Manganese Mines in the Shimoga schist belt. This report ot stromatolites in the Shimoga belt further confirms widespread biogenic activity prior to 2.6 Ga in the Dharwar Craton.- Geology and Geochemistry of Spinifex-Textured Peridotitic Komatiite from Mayasandra Schist Belt, Karnataka
Abstract Views :163 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 32, No 4 (1988), Pagination: 343-350Abstract
Spinifex-textured peridotitic komatiite occurs on the southeastern margin of Mayasandra schist belt near Nagamangala in Karnataka. Preservation of spinifex-texture made up of pseudomorphically altered phenocrysts of olivine and less commonly clinopyroxene set in a groundrnass of skeletal augite and devitrified glass in the komatiite, is essentially perfect in spite of alteration, deformation and metamorphism. Petrography shows dissimilar shapes and dimensions of the crystals, with more than one pattern of crystal arrangement in the texturally layered komatiite, clearly indicating that conditions and rates of crystallization were not uniform throughout the cooling unit. Compositional variations in terms of major and trace elements appear to be broadly consistent with fractionation of olivine followed by clinopyroxene. The high contents of MgO, Ni, Cr and extremely low percentages of TiO2, Na2O, K2O in the spinifex-textured ultramafic komatHte compare favourably with similar rock types reported from Canada, S. Africa and Australia.- Geochemistry of the Archaean Greywackes from the Northwestern Part of the Chitradurga Schist Belt, Dharwar Craton, South India-Evidence for Granitoid Upper Crust in the Archaean
Abstract Views :149 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 34, No 5 (1989), Pagination: 505-516Abstract
Turbidite greywackes of the northwestern part of the Chitradurga Schist Belt constitute a part of >2.6 Ga Cbitradurga Group of Dharwar Supergroup. They consist of a detrital assemblage of mono- and poly-crystalline quartz, microcline and plagioclase feldspar. and volcanic rock fragments. Quartz content and Na2O/K2O ratios show their quartz intermediate character. In this respect and also in their high FeO(t)+ MgO content they are similar to other Archaean greywackes. The TiO2 content. K2O/Na2O, Al2O3/CaO+Na2O and Al2O3/SiO2 ratios plotted against Fe2O3(t)+MgO, although assign an island arc environment for these greywackes, do not unequivocally discriminate between continental and oceanic island arc setting. The Chitradurga greywackes are highly enriched in Zr, Cr and Ni indicating a mixed felsic and mafic source. The contribution from contemporary volcanism in the basin could be significant. The QFL proportions indicate a dissected arc and/or recycled orogenic nature of the provenance. The chemical index of alteration varying from 58 to 63 and Al2O3/Na2O ratio less than 6, indicate relatively unweathered nature of source rock and chemical immaturity of the sediment respectively. The REE patterns show wen-defined negative europium anomalies which reflect granitoid upper crust in the provenance during the Archaean.- Archaean Shelf-Facies and Stromatolite Proliferation in Dharwar Supergroup, North Kanara District, Karnataka
Abstract Views :191 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
2 Department of Mines and Geology, Race Course Road, Bangalore 560001, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
2 Department of Mines and Geology, Race Course Road, Bangalore 560001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 35, No 2 (1990), Pagination: 203-212Abstract
The stromatolitic cherty dolomite of KaIche is a lithostratigraphic equivalent of the carbonate rocks of the Joldhal Formation of Archaean age. Morphotypes suggest development in subtidal to lower intertidal zone of the Dharwar seas. Some of the forms observed near Kalche are comparable to the domical forms observed near Kumsi in the Shimoga schist belt and Vanivilaspura in the Chitradurga schist belt. The morphotypes observed in these regions contrast with the actively and passively branched columnar stromatolites observed near Dodguni and Bhimasamudra in the Chitradurga schist belt where the stromatolites evolved in an intertidal environment. Diversity of morphotypes of stromatolites appears to have occurred in the Archaean itself, although such diversity appears to have attained stratigraphic significance by the middle Proterozoic.Keywords
Archaean, Palaeobiology, Stromatolites, Dharwar Supergroup, North Kanara, Karnataka.- Geochemistry of Trondhjemites from Sigegudda, Hassan District, Karnataka
Abstract Views :187 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 37, No 4 (1991), Pagination: 351-358Abstract
The Sigegudda trondhjemites contain moderate Zr, high Ni and Cr and therefore appear to have formed by partial melting and/or fractional crystallization of Ni- and Cr-rich rocks like amphibolites. Lack of fractionation of Y, Zr and TiO2 and comparatively lower LREE/HREE ratio in these rocks perhaps indicate that garnet was not present in the magma source. The trondhjcmites were probably emplaced during the stabilization of the western Dharwar craton around 3.0 b.y. ago.Keywords
Trondhjemites, Geochemistry, Sigcgudda, Karnataka.- Geochemistry and Genesis of Banded Iron Formation from Kudremukh Schist Belt, Karnataka Nucleus, India
Abstract Views :296 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 40, No 4 (1992), Pagination: 311-328Abstract
The Banded Iron Fonnation is interbedded with 2.9 Ga old mafic and acid volcanics. It mainly consists of magnetite and quartz; calcite is also present in some mesobands. Thin silicate rich layers with abundant actinolite, cummingtonite, grunerite, biotite, riebeckite and aegirine occur between the quartz and magnetite rich rhythmites. Mixed oxide. silicate and carbonate facies (MOSCF) BIFs are found which arc prcmctamorphic cherty and shaly types. The distribution of Al2O3 , CaO, MgO, K2O, Na2O, Ni, Cr, Co, Rb, Sr, Zr, Cr/MgO and REEs indicate a combination of hydrothenna1, volcanogenic and continental sources. The relationship between Cr/Zr, Zr/Cr+Co+Ni, ZeN and Nd/Yb reflect that certain fine silicate-rich bands between the microbands arc made up of volcanic ash, whereas others are made up of shales of continental source or a mixture of both. LA enrichment, depletion in total REE, positive Eu anomalies, Nd/Yb, La/Lu and LREE/HREE ratios in Fe-rhythmites indicate that Fe, Si and REEs of the BIF were supplied by hydrothennal and fumarolic activity accompanying submarine volcanism. The enrichment in total REE and obliteration of La signature is probably a consequence of mixing of non-chemogenic component and ambient sea water with the chemical precipitates. Absence of negative Ce anomalies is consistent with most of the Archaean BIFs of other localities. Deposition of BIF appears to have taken place below wave base and photic zone of the shallow shelf region. It is inferred that oxygen was generated at some other place in the basin. Ocean circulation and upwelling brought FeO and 02 together resulting in precipitation of iron along with fine grained argillites.Keywords
Geochemistry, Banded Iron Formation, Kudremukh Schist Belt, Kamataka.- Geochemistry of Archaean Arenites Formed by Anoxic Exogenic Processes-An Example from Bababudan Schist Belt, India
Abstract Views :158 |
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Authors
M. Arora
1,
S. M. Naqvi
1
Affiliations
1 National Geophysical Research Institute, Hyderabad 500 007, IN
1 National Geophysical Research Institute, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 42, No 3 (1993), Pagination: 247-268Abstract
Sandy matrix of QPC of Archaean Bababudan schist belt is distinguished, by the abundance of well rounded detrital pyrite, uraninite, chromite, zircon, rutile and micas, and clasts of fuchsite quartzite. Presence of detrital pyrite and uraninite in mature arenites deposited during the initial stage of shallow stable basin, indicate the anoxic nature of ambient atmosphere. Compositional characteristics such as the abundance of Al2O3, K2O, MgO, Cr, Ni, Co, Zr, V, Sc, Rb, Sr and ∑REE reveal that only restites could survive intense chemical weathering and strong hydrodynamic action. High to moderately fractionated REE patterns (LaN/LuN-10) with essentially negative Eu anomalies of the matrix of QPC, typically resemble the Archaean arenitic and pelitic rocks. These characlcristics of the QPC indicate removal of mafic-ultramafic and other unstable constituents of provenance to the deeper part of the basin. Silicic and other resistive part of provenance were deposited on the margin of the basin. Geochemical parameters of these rocks show that initial anoxic stage was changed to rhythmically oxidizing environment, in which very thick oxide facies of BIF got precipitated. Stable tectonic condition was changed to active margin setting, in which immature Kaldurga polymictic conglomerate (KCM) with greywacke matrix was deposited. Available data on various rock types of the Bababudan basin, demonstrate that the composition of atmosphere changes in tectonic setting and depositional environment resulted in the deposition of sediments of divergent type in the basin at various stratigraphic levels.Keywords
Geochemistry, Arenites, Banded Iron Formation, Bababudan Belt, Karnataka.- Symplectites in High-Grade Pelitic Gneisses of Usilampatti, Tamil Nadu: P-T Conditions and Geochemistry
Abstract Views :175 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad-500 007, IN
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 1 (1995), Pagination: 37-45Abstract
Occurrence of fine-grained, fingerprint-like symplectic intergrowths of cordierite, K-feldspar and quartz formed due to the retrogressive, garnet breakdown reactions following decompression during uplift, is reported here from metapelites of Usilampatti area. These metapelites consisting of cordierite, garnet, hypersthene, biotite, hercynitic spinel, sillimanite, K-feldspar assemblage were metamorphosed at 6.5-7.5 Kb and 750-800°C. The symplectites were formed at 600-670°C and 5 Kb pressure. The textural and mineralogical evolutions in these metapelites indicate a rapid decompressional P-T evolution. Petrological and geochemica1 data suggest that these metasediments were derived mostly from an evolved basement source of granodiorite-granite composition with a minor basic component.Keywords
Metamorphic Petrology, Gneiss, Tamil Nadu.- Gold Mineralization in the Sulphidic Bifs of Chitradurga Schist Belt, Karnataka - Possibility of New Workable Gold Deposits
Abstract Views :177 |
PDF Views:137
Authors
Affiliations
1 Hutii Gold Mines, Bangalore, IN
2 National Geophysical Research Institute, Hyderabad, IN
1 Hutii Gold Mines, Bangalore, IN
2 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 1 (1995), Pagination: 91-93Abstract
No Abstract.Full Text
- Relicts of Sedimentary Precursors in Archaean Gneisses : Melukote Paragneiss -An Example from Dharwar Craton, India
Abstract Views :198 |
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Authors
B. Uday Raj
1,
S. M. Naqvi
1
Affiliations
1 National Geophysical Research Institute, Uppal Road, Hyderabad 500007, IN
1 National Geophysical Research Institute, Uppal Road, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 5 (1995), Pagination: 497-520Abstract
Relicts of sedimentary precursors in the Peninsular Gneisses around Melukote-Katteri area ofDharwarCraton are recognised on the basis of field, petrological and geochemical data. The Melukote gneiss has interbeds of carbonates, quartzites. iron-formations and para-amphibolites with a concordant planar fabric. These gneisses are devoid of mafic-ultramafic xenoliths which are one of the essential characteristics ofthe orthogneiss component of Peninsular Gneiss (PG), The Melukote paragneiss (MG) contains interstitial calcite, relict arkosic texture, subrounded to round quartz, plagioclase and zircon. Two generations of quartz and plagioclase are conspicuous in the MG. The MG are high SiO2 and low Al2O3 Cr and Ni are significantly enriched - up to 334 ppm and 73 ppm respectively. The Rb and Sr contents are lower than the typical tonalite-trondhjemite gneisses (TTG). The high HREE patterns of MG and very low negative Eu anomalies are distinct from those of TTG in the surrounding areas. These data indicate that MG represent first cycle immature sediment derived from a heterogenous provenance.Keywords
Petrology, Geochemistry, Peninsular Gneiss, Melukote, Dharwar Craton.- Mineral Composition and its Bearing on Depositional History of Banded Iron-Formation of Kudremukh Schist Belt, Karnataka
Abstract Views :206 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad-500007, IN
1 National Geophysical Research Institute, Hyderabad-500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 6 (1995), Pagination: 603-610Abstract
The iron-formations ofKudremukh mainly contain magnetite, recrystallized chert, gruneritecu mmingtonite (XMg 0.21 to 0.33), hornblende, bioti te along with minor amounts of ankerite (XMg O. 30 to 0.52), calcite (XMg 0.06 to 0.22), chamosite and pyri teo Chamosite, a rare relict mineral, was probably formed by reaction between high Al-clay and Fe. Magnetite was formed during metamorphism. Along with the precipitation of alternating layers rich in silica and iron, clayey material in the form of montmorillonite, illite and/or glauconite along with Fe-Mg carbonates were also deposited, which after metamorphism (430-520°C) gave rise to the present mineralogy.Keywords
BIF, Mineral Chemistry, Kudremukh Schist Belt, Karnataka.- Exploration, Mine Development and Pilot Plant Operation at Gadag Gold Field, Karnataka, India
Abstract Views :219 |
PDF Views:140
Authors
R. H. Sawkar
1,
Rahul Baldota
2,
S. R. Suresh
2,
P. T. Sastri
2,
A. S. Kulageri
3,
B. R. Nagabhushan
3,
D. S. Sarma
4,
D. V. Subbarao
4,
S. Nirmal Charan
4,
S. M. Naqvi
4
Affiliations
1 Bangalore, IN
2 MSPL Ltd., Hospet, IN
3 Hutti Gold Mines Co. Ltd., Chitradurga, IN
4 National Geophysical Research Institute, Hyderabad, IN
1 Bangalore, IN
2 MSPL Ltd., Hospet, IN
3 Hutti Gold Mines Co. Ltd., Chitradurga, IN
4 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 3 (1999), Pagination: 322-326Abstract
No Abstract.Full Text
- Corporate News
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PDF Views:116
Authors
Affiliations
1 MSPL, Hospet, Karnataka, IN
2 NGRL, Hyderabad, IN
3 HGML, Bangalore, IN
4 Bangalore, IN
1 MSPL, Hospet, Karnataka, IN
2 NGRL, Hyderabad, IN
3 HGML, Bangalore, IN
4 Bangalore, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 2 (1999), Pagination: 217-218Abstract
No Abstract.Full Text
- Role of Adakitic Magmatism and Subduction in Gold Endowment of Dharwar NEO-Archaean Greenstone Belts
Abstract Views :191 |
PDF Views:158
Authors
S. M. Naqvi
,
D. Srinivasa Sarma
,
R. H. Sawkar
,
M. Ram Mohan
,
J. G. Rana Prathap
,
S. Viswanathan
1
Affiliations
1 Flat B-203, Block-B, United Avenue Apts, South End, 7 1-29, Ameerpet, Hyderabad-500016, IN
1 Flat B-203, Block-B, United Avenue Apts, South End, 7 1-29, Ameerpet, Hyderabad-500016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 72, No 4 (2008), Pagination: 576-577Abstract
No Abstract.Full Text
- Role of Adakitic Magmatism and Subduction in Gold Endowment of Dharwar Neoarchaean Greenstone Belts, India
Abstract Views :210 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 Mineral Sales Private Limited, Hospet - 583 203, IN
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 Mineral Sales Private Limited, Hospet - 583 203, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 6 (2008), Pagination: 875-888Abstract
Acid volcanics found in auriferous greenstone belts of the Dharwar Craton are rhyolites, adakitic rhyohtes and high silica adakites Adakites are compositionally similar to TTG and characterized by high Na^/K^O, depleted MgO, Cr, Ni, Y and Yb. The adakitic melts were most probably generated by the partial melting of the basaltic slab below a mantle wedge LILE and LREE enriched IAB are the dominant volcanic members of the greenstone belts IAB of the greenstone belts were generated from partial melting of the mantle wedge under the influence of slab derived fluids. The wedge derived IAB and slab derived adakites were deformed and metamorphosed to generate fluids responsible for the gold endowment of these belts. Rhyohtes and possibly rhyohtic adakites were generated by the melting of the sialic continental crust forming top of the descending slab. Identification of adakites in auriferous greenstone belts strengthens the genetic link between adakite magmatism, subduction and Neoarchaean gold endowment.Keywords
Adakites, Dharwar Craton, Gold Greenstone Belt, Karnataka.- Nature of Shear-Zone Hosted Epigenetic Gold Mineralisation in BIF of C.S.halli, Chitradurga Schist Belt, Western Dharwar Craton
Abstract Views :227 |
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Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 68, No 4 (2006), Pagination: 577-581Abstract
Gold mineralisation occurs at Chikkasiddavanahalli (C S Hall!) in Archaean volcano-Sedimentary sequence of the Ingaldhal Formation, in Chiradurga Group, Dharwar craton. The C S Hal1i ridges and low mounds are about 1 2 km long and 100 in wide with N-S strike and vertical to steep easterly dips comprising mixed sulphide/oxide facies banded iron formations (MSOBIF) and associated ferruginous phyllites, metavolcanics and minor carbonates. Several horizons of BIF's occur as parallel to subparallel linear brands and extend over a strike length of 20-40 km with widths ranging from 2-25 m. These BIF s are highly sheared, deformed and metamorphosed to upper greenschist facies. The shears in BIF's are occupied by several syn-Tectonic quartz carbonate veins of various dimensions and found to be favourable loci for Gold-Sulphide mineralisation. Petrological studies show major mineral constituents with pyrite, arsenopyrite and subordinate grunerite, hornblende, chlorite, muscovite, ankerite, calcite, magnesian siderite and quartz. Most gold deposits world over are hosted in second order and subsidiary shear zones. The primary gold in BIFs is enriched with intense fracturing controlled by major shear systems extending from Gadag in the north and Doduguni in the south Active convergent margin settings related to accretionary processes and fluid activity are suggested to have led to Epigenetic gold mineralisation in BIFs at C S Halli area with an average gold grade of 2 08 g/t.Keywords
Au Mineralisation, Structural Controls, Shear Zones, C S Halli, Chitradurga Schist Belt, Karnataka.- Chemical Composition of Tourmaline in Metarhyolite near Majjur, Gadag Schist Belt, Karnataka
Abstract Views :186 |
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Authors
Affiliations
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
2 292, 10th Main, Jayanagar, Bangalore - 560 041., IN
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
2 292, 10th Main, Jayanagar, Bangalore - 560 041., IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 63, No 2 (2004), Pagination: 217-221Abstract
No Abstract.Full Text
- REE-HFSE Distribution/Partitioning Between Garnetiferous Restites and TTG from Nademavinapura Area, Western Dharwar Craton
Abstract Views :249 |
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Authors
S. N. Charan
1,
E. V. S. S. K. Babu
1,
S. M. Naqvi
1,
J. G. Rana Prathap
1,
M. Ram Mohan
1,
D. Srinivasa Sarma
1
Affiliations
1 National Geophysical Research Institute (Council of Scientific and Industrial Research), Hyderabad - 500 606, IN
1 National Geophysical Research Institute (Council of Scientific and Industrial Research), Hyderabad - 500 606, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 73, No 3 (2009), Pagination: 371-378Abstract
The major part of the Peninsular Gneiss in Dharwar craton is made up of Trondjhemite-Tonalite-Granodiorite (TTG) emplaced at different periods ranging from 3.60 to 2.50 Ga. The sodic-silicic magma precursors of these rocks have geochemical features characteristic of partial melting of hydrated basalt. In these TTGs, enclaves of amphibolites (± garnet) are abundant. These restites are considered to be the residue of a basaltic crust after its partial melting. A detailed study of these (residue) enclaves reveals textures formed due to the process of partial melting. Major, trace and REE analysis of these residue enclaves and the melt TTGs and microprobe analysis of the coexisting minerals show partitioning of REE and HFSE between the precursor melt of TTGs and the upper amphibolite facies residues. Formation of garnetiferous amphibolites with biotite, Cpx and plagioclase consequent to melting, has squeezed the original MORB type of basaltic crust and given rise to the TTGs, depleted in Y, Yb, K2O, MgO, FeO, TiO2 and enriched in La, Th, U, Zr and Hf. Coevally during the process of melting, the hydrated basalt was depleted in Na2O, Al2O3, LREE, Th, U and enriched in K2O, MgO, Nb, Ti, Yb, Y, Sc, Ni, Cr and Co. Mineral chemistry of co-existing garnet-biotite and amphiboleplagioclase in these amphibolitic (restite) enclaves indicates an average temperature of 700 ± 50 °C and pressure of 5 ± 1 Kbar. These data are inferred to indicate that during the garnet stability field metamorphism, effective fractionation of HREE and HFSE has taken place between the restites having Fe-Mg silicates, ilmenites and the extracted melt generated from the MORB type of hydrated basalt. These results are strongly substantiated by the reported melting experiments on hydrated basalts.Keywords
Fractionation, HFSE, REE, TTG, Restite, Dharwar Craton.References
- BHASKAR RAO, Y.J., GRIFFIN, W.L., KETCHUM, J., PEARSON, N.J., BEYER, E. and REILLY, S.Y. (2008) An outline of juvenile crust formation and recycling history in the Archaean Western Dharwar Craton from Zircon in-situ U-Pb dating and Hf isotopic composition. (Abstract, Goldschmidt Conference, 2008).
- DRUMMOND, M.S., DEFANT, M.J. and KEPEZHINSKAS, P.K. (1996) Petrogenesis of slab-derived trondhjemite-tonalite-dacite/ adakite magmas. Trans. Royal Soc. Edinburgh, Earth Sci., v.87, pp.205-215.
- JAYANANDA, M. and PEUCAT, J.-J. (1996) Geochronological framework of Southern India. In: M. Santosh and M. Yoshida (Eds.), The Archaean and Proterozoic terrains of Southern India within East Gondwana. Gondwana Res. Group Mem., No.3, pp.53-73.
- KEMP, A.I.S. and HAWKESWORTH, C.J. (2003) Granitic perspectives on the generation and secular evolution of the continental crust. In: R.L. Rudnick (Ed.), The Crust: Treatise on Geochemistry. Elsevier-Pergamon, Oxford, v.3, pp.349-410.
- KERRICH, R. and POLAT, A. (2006) Archaean greenstone-tonalite duality: Thermochemical mantle convection models or plate tectonics in the early Earth global dynamics? Tectonophysics, v.415, pp.141-165.
- NAQVI, S.M., SRINIVASA SARMA, D., SAWKAR, R.H., RAM MOHAN, M. and RANA PRATHAP, J.G. (2008) Role of adakitic magmatism and subduction in gold endowment of Dharwar Neoarhaean greenstone belts, India. Jour. Geol. Soc. India, v.71(6), pp.875-888.
- PEUCAT, J-J., MAHABALESWAR, B. and JAYANANDA, M. (1993) Age of younger tonalitic magmatism and granulite metamorphism in the amphibolite-granulite transition zone of Krishnagiri area and comparison with the older gneiss from Gorur-Hassan area. Jour. Met. Geol., v.11 pp.879-888.
- RADHAKRISHNA, T., KRISHNENDU, N.R. and BALASUBRAMANIAN, G. (2007) Mafic dyke magmatism around the Cuddapah Basin: Age constraints, petrological characteristics and geochemical inference for a possible magma chamber on the southwestern margin of the Basin, Jour. Geol.Soc. India, v.70, pp.194-206.
- RAPP, R.P., SHIMIZU, N., NORMAN, M.D. and APPLEGATE, G.S. (1999) Reaction between slab-derived melts and peridotite in the mantle wedge: experimental constraints at 3.8 GPa. Chem. Geol., v.160, pp.335-356.
- RUDNICK, R.L. and GAO, S. (2003) The composition of the continental crust. In: R.L. Rudnick (Ed.),The Crust: Treatise on Geochemistry. Elsevier-Pergamon, Oxford, v.3, pp.1-64.
- SAMSONOV, A.V., BOGINA, M.M., BIBIKOVA, E.V., PETROVA, A.YU. and SHCHIPANSKY, A.A. (2005) The relationship between adakitic, calc-alkaline volcanic rocks and TTGs: implications for the tectonic setting of the Karelian greenstone belts, Baltic Shield. Lithos, v.79, pp.83-106.
- SUN, S.-S. and MCDONOUGH, W.F. (1989) Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: A.D. Saunders and M.J. Norry (Eds.), Magmatism in the ocean basins. Geol. Soc. London Spec. Publ., no.42, pp.313-345.
- TAYLOR, S.R. and MCLENNAN, S.M. (1985) The continental crust: Its composition. Blackwell Scientific Publishers, Oxford, 312p.
- XIONG, X.L., XIA, B., XU, J.F., NIU, H.C. and XIAO, W.S. (2006) Na depletion in modern adakites via melt/rock reaction within the sub-arc mantle. Chem. Geol., v.229, pp.273-292.
- 'The Expanding Earth'
Abstract Views :228 |
PDF Views:163
Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad, IN
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 10 (1984), Pagination: 685-686Abstract
No Abstract.Full Text
- The Oldest Supracrustals of the Dharwar Craton, India
Abstract Views :180 |
PDF Views:4
Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 22, No 10 (1981), Pagination: 458-469Abstract
The metamorphosed supracrustal rocks of Holenarasipur, Nuggihalli, Krishnarajpet, Hadnur and Ghattihosahalli belts appear to represent the oldest (3.5 b.y.) greenstones of the Dharwar Craton. Detailed geological mapping of these belts and surrounding gneisses shows no evidence of a sialic basement for these predominently ultramafic belts. The sediments of these belts are mostly chemogenic-volcanogenic-volcaniclastic and fine-grained argillites. Fuchsite-quartzite, which is found at the top of the succession is the only siliceous rock unit. Its δO 18 value at+ 12.5, suggests that it is a metachert and not of detrital origin. REE pattern of the sediments of HNSB (Holenarasipur Schist Belt) is distinct from the sediments derived from acid plutons. The ultramafic schists of these belts, interbedded with the sediments, are generally komatiitic in composition and although metamorphosed under amphibolite facies conditions, locally exhibit relict pillow-structure and spinifex-texture.
The development of these greenstone belts was followed by at least three episodes of intrusion by sodic plutons. Erosion of these bodies and of the greenstone belts provided the sediment for the younger schist belts. The first evidence of detrital sedimentation derived from acid plutonic rocks is preserved in the form of current-bedded arkoses and quartzites in the younger greenstone belts. An interfingering sequence of the various successive greenstone belts and acid plutons, precursors of the Peninsular gneisses, can be recognised on the basis of available data.
- Geochemical Prospecting for Copper in the Nuggihalli Schist Belt, Karnataka, India
Abstract Views :254 |
PDF Views:139
Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad, IN
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 17, No 3 (1976), Pagination: 395-398Abstract
Geochemical prospecting for copper in the Nuggihalli schist belt, Karnataka has indicated that the serpentinised dunites are moderately enriched in copper. The copper appears to have no structural control and the enrichment is not uniform in the dunite.Full Text
- Reconnaissance Geochemical Exploration for Copper in the Central Part of the Chitradurga Schist Belt, Karnataka, India
Abstract Views :192 |
PDF Views:128
Authors
Affiliations
1 National Geophysical Research Institute, Hyderabad, IN
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 17, No 4 (1976), Pagination: 551-557Abstract
An area of about 115 Sq km was sampled on a 0.4 km spacing grid. The samples, collected from the bed rock, after removing the thin soil cover, were analysed for Cu, Zn, Pb and Co by the emission spectrograph using indium as internal standard. The Cu concentration map of the area shows nine zones of anomalous Cu content, the highest giving a value of 4000ppm. Of these, four zones of highly anomalous Cu content (2000 ppm-4000 ppm) are very promising and are recommended for detailed geochemical exploration.Full Text
- Geochemical and Isotopic Constraints of Neoarchaean Fossil Plume for Evolution of Volcanic Rocks of Sandur Greenstone Belt, India
Abstract Views :195 |
PDF Views:3
Authors
S. M. Naqvi
1,
C. Manikyamba
1,
T. Gnaneshwar Rao
1,
D. V. Subba Rao
1,
M. Ram Mohan
1,
D. Srinivasa Sarma
1
Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 60, No 1 (2002), Pagination: 27-56Abstract
Metavolcanics of 20 km wide Sultanpura volcanic block of the Neoarchaean Sandur (greenstone) schist belt are divided into tholeiitic basalts, high Mg basalts, Al-depleted and Al-undepleted komatiitic ultramatic schists. Metabasalts are metamorphosed to amphibolite facies, but still preserve their pillow structures. Ultramasic komatiitic rocks are transformed to actinolite-tremolitc schists with no recognizable original textures or mineralogy. Mctabasalts and ultramafic komatiitic schists are interbedded with thin layers of sulphidic banded iron formations, argillaceous carbonate rocks and carbon phyllites that are interprcied as metamorphosed pclagic sediments of the deep ocean. No terrigenous sediments are found in Sultanpura block indicating that eruption of these submarine volcanic rocks took place in the deeper part of the ocean, away from the western and eastern shelf parts of the Sandur belt, where terrigenous sediments are abundant. SuItanpura block in its west and east is discordantly boundcd by thrust, subduction complex and shclf lhcies sedimcnts. These observations are interpreted to indicate that Sultanpura block is a telescoped prolo-oceanic part between the two shelves and island arc complexes. MgO of melavolcanic rocks varies from 6 to 30%, with a gap between 16 to 22%. Al2O3/TiO2 shows characteristic variation for tholeiites (10-15), high Mg basalts (13-21), Al-unclepleted ultramafic komatiitic schists (9-23) and Al-depleted ultramafic komatiitic schists (11-20). CaO/Al2O3, of tholciites and high Mg basalts is ∼1, whereas for the ultramafic komatiitic schists, this ratio exhibits a range between 0.5 to 2, as a consequence of CaO mobility.REE, HFSE and 143Nd/144Nda ta from Sultanpura volcanic rocks vary between CHUR (Chondrite Uniform Rcservoir), primitive mantle and depleted manilc, but appear to be derived from primitive mantle and have been probably contaminated by continental crust. Although the abundance of REE varics from 2 to 12 chondrite, the patterns are smooth and flat with small negative or positive Eu anomalies as artifacts of alteration. Generally positive, but in few samples negative Nb anomalies are also found, with (Ce/Sm)N, and (Gd/Yb)N, being near chondritic. Ti/V, Ti/Zr, Zr/Y, Sc/Y, Nb/La, Nb/Th, Nb/U, MgO/TiO2, MgO/FeO and Al2O3/TiO2, also for many samples are ncar chondritic, εNd=+0.8649±0.00024 resembling CHUR. ThMb, NblU and some other ratios are near to those of Ontong Java and Gorgana plateaus (0.80 Ga) and the tholeiite-komatiitic sequence found in 2.7 Ga Southern volcanic zone, Abitibi belt of Canada and 2.1 Ga Birimian belt of West Africa. Collectively, thcsc data indicate that a mantle plume. derived from an enriched mantle, possibly played an important role in the oceanic volcanic sequence of Sultanpura block. Some of the HFSE follow the olivine control line, whereas other elements following the olivine control line define a narrow array tube. Formation of such array tubes on the plots of some HFSE elements and their ratios, and the scatters of HFSE/REE ratios, probably suggest dynamic melting of the plume during ascent. Entrenchment, mixing of Archaean ocean ridge basalts (AORB), crustal contamination and subduction of such a plume-fed slab may have generated the compositional heterogeneities observed in the Sultanpura metavolcanic rocks.