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Srinivasa Sarma, D.
- Geochemistry and Petrogenesis of Amphibolites from the Southern Part of Gadag Greenstone Belt, Karnataka
Abstract Views :173 |
PDF Views:2
Authors
M. Ram Mohan
1,
D. Srinivasa Sarma
1,
S. N. Charan
1,
V. Balaram
1,
V. B. Rajasekhar
1,
Talat Ahmad
2
Affiliations
1 National Geophysical Research Institute, Uppal Road, Hyderabad-500007, IN
2 Department of Geology, University of Delhi, Delhi-110007, IN
1 National Geophysical Research Institute, Uppal Road, Hyderabad-500007, IN
2 Department of Geology, University of Delhi, Delhi-110007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 72, No 4 (2008), Pagination: 484-494Abstract
Gadag Greenstone Belt (GGB) is the northern continuation of Chitradurga Greenstone Belt (CGB). It consists of a variety of metavolcanic and metasedimentary rocks. Two types of metavolcanic assemblages are found in this terrane (l) the tholeute-calc-alkaline island arc bimodal assemblage and (u) the tholeute-high-Mg basalt assemblage The tholente-calc-alkaline assemblage is exposed in the central and northern parts, whereas the tholentic-high-Mg basaltic assemblage is found in the southwestern part of the belt. Tholente-high-Mg basalts are represented by the coarse-grained amphibolites formed under lower amphibolite facies conditions REE and HFSE data along with major element compositions confirm that these coarse-grained amphibolites are tholentic basalts derived from an intraoceanic island arc setting. The REE patterns are coherent, flat to slightly LREE depleted (La/Ybn =0.79 to 1.20, La/Smn =0.84-0.97, Gd/Ybn=1.07-1.50) with no Eu anomaly. Relationship between compatible and incompatible elements suggests least effects of alteration and no crustal contamination or fractional crystallization. The mixing calculations indicate that these rocks are derived by partial melting of a depleted mantle source, with source composition in between that of the N-MORB and high-Mg basalts.Keywords
Geochemistry, Petrogenesis, Amphibolites, Gadag Greenstone Belt.
- 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
- Occurrence of Hydrothermal Phosphate Minerals in the Gold Mineralized Zones at Hutti Gold Deposit, Karnataka, South India
Abstract Views :196 |
PDF Views:2
Authors
Affiliations
1 National Geophysical Research lnstitute, Uppal Road, Hyderabad-500007, IN
2 Centre for Microscopy and Microanalysis, University of Western Australia, 35, Stirling Highway, Crawley, 6009, IN
3 Centre for Exploration Targeting, University of Western Australia, 35, Stiriling Highway, Crawley 6009, IN
1 National Geophysical Research lnstitute, Uppal Road, Hyderabad-500007, IN
2 Centre for Microscopy and Microanalysis, University of Western Australia, 35, Stirling Highway, Crawley, 6009, IN
3 Centre for Exploration Targeting, University of Western Australia, 35, Stiriling Highway, Crawley 6009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 2 (2008), Pagination: 223-228Abstract
We report here, for the first time, the occurrence of hydrothermal monazite and xenotime in alteration haloes associated with the gold-Mineralized zones of the Hutti Gold Deposit in Karnataka, India. These minerals were identified by systematic scanning of polished thin sections in an SEM using backscattered electron and energy dispersive X-Ray detectors. Most of the grains are very small (<10 μm), although some larger gram (30-40 μm) have also been identified Hydrothermal monazite and xenotime, though volumetrically minor, have been found to be important components in many orogenic gold deposits in Australia, Canada, Brazil and South Africa,as they form a part of the primary ore mineral assemblage, elther in ore-Bearing veins itself or are intergrown wlth ore minerals in wallrock alteration zones. Both monazite and xenotime are excellent geochronometers, and their importance is that they allow precise ages to be obtained for gold mineralization events. The discovery of these minerals in hydrothermally altered rocks from the Hutti gold deposit Dharwar Craton enables us to estimate the age of gold mineralization event(s).Keywords
Hutti Gold Deposit, Alteration Zones, Hydrothermal Minerals, Monazite, Xenotime, Karnataka.- Role of Adakitic Magmatism and Subduction in Gold Endowment of Dharwar Neoarchaean Greenstone Belts, India
Abstract Views :210 |
PDF Views:2
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.- Chemical Composition of Tourmaline in Metarhyolite near Majjur, Gadag Schist Belt, Karnataka
Abstract Views :186 |
PDF Views:138
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
- Geochemistry of the Unusual Mafic Intrusions in Betul Fold Belt, Central India: Implications for Ni-Cu-Au-PGE Metallogeny
Abstract Views :249 |
PDF Views:119
Authors
D. V. Subba Rao
1,
M. Satyanarayanan
1,
D. Srinivasa Sarma
1,
K. S. V. Subramanyam
1,
K. Venkateswarlu
1,
M. Hanuma Prasad
2
Affiliations
1 CSIR-National Geophysical Research Institute, Hyderabad 500 007, IN
2 Geomysore Services (India) Pvt Ltd, Bengaluru 560 037, IN
1 CSIR-National Geophysical Research Institute, Hyderabad 500 007, IN
2 Geomysore Services (India) Pvt Ltd, Bengaluru 560 037, IN
Source
Current Science, Vol 108, No 4 (2015), Pagination: 713-722Abstract
We report here the recent occurrence of native gold and platinoids, associated with Fe-Ni-Cu-Pb-Zn sulphides and tungsten-bearing phases in the gabbroic intrusions emplaced in the Betul-Chhindwara Belt in the Central Indian Tectonic Zone (CITZ). The ore minerals are represented mainly by native gold, pentlandite, chalcopyrite, pyrite, bowieite and rare phases of tungsten, cadmium and palladium, which were identified by scanning electron microscopy. The whole rock geochemistry shows anomalous Ni-Cu and platinum group elements (PGE) in which palladium is always higher in concentration than in platinum. The inter-element relationships of PGE such as Pd versus Ir and Pt versus Ir indicate their fractionation by a sulphide phase and also suggest that the parental magmas are primitive in nature having high-Mg, low- Ti characteristics, which indicate the boninitic/picritic nature of magmas. A thorough investigation is essential for exploring the Betul mafic-ultramafic intrusions for proving their potential as the host rocks for Au and Ni-Cu-PGE ores.Keywords
Gabbro Intrusions, Geochemistry, Citz, Native Gold, Platinum Group Elements.Full Text
- REE-HFSE Distribution/Partitioning Between Garnetiferous Restites and TTG from Nademavinapura Area, Western Dharwar Craton
Abstract Views :248 |
PDF Views:0
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.
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- 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.
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- Geochemical and Isotopic Constraints of Neoarchaean Fossil Plume for Evolution of Volcanic Rocks of Sandur Greenstone Belt, India
Abstract Views :193 |
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.