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Balakrishnan, S.
- Are Patna and Bisanattam Granites (Adjoining the Kolar Schist Belt) cogenetic?
Authors
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, IN
2 Department of Earth and Space Sciences, Slate University of New York, Stony Brook, New York 11794, US
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 30, No 2 (1987), Pagination: 98-105Abstract
Structural and geochemical evidence including major and trace elements, and Pb-isotopic data on K-feldspars, froin the granitoid rocks adjoining the Kolar Schist Belt are presented to show (1) that the Patna Granite an the NW of the belt is dissimilar to any granitoid rock E of the belt and (2) that the main granitoid gneiss immediately E of the belt, the Karnbha Gneiss, is nearly identical to the Bisanattam Granite of Narayanaswamy er al (1960).- Geochemistry and Petrogenesis of Dolerite Dykes In and Around Kolar Schist Belt, South India
Authors
1 Department of Earth Sciences, University of Roorkee, Roorkee 247667, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 43, No 5 (1994), Pagination: 511-528Abstract
The Kolar Schist Belt and adjoining areas of Dharwar Craton are considered to be accreted terranes. Two distinct sets of dolerite (diabase) dykes, trending E-W and N-S are found in the area. The major minerals in the dykes are plagioclase feldspars (50-65 mol. % anorthite) and c1inopyroxenes (augite, sub-calcic augite and magnesian pigeonite).
The Kolar dyke samples are essentially tholeiitic except for one sample which resembles a basaltic komatiite. Mineral, as well as, whole rock chemistry of the dyke samples indicate an iron enrichment trend. The modelling of major and trace elements of Kolar dykes suggest that their parental magmas must have been derived from Fe- enriched sources with higher Fe/Mg ratios than primitive mantle. Source for parental magma to the basaltic komatiite dyke has been inferred as garnet lherzolite, whereas, for all others it could be komatiite with variable Fe/Mg ratios.
The Kolar dyke samples are enriched in light rare earth elements (LREE) and have variable abundances of heavy rare earth elements (HREE) relative to chondrites. The modelling of major, trace, and rare earth element data indicate that the generation of parental magmas took place from sources similar to komatiites, by low percentages (<30%) of partial melting, within the lithosphere at pressures less than 3GPa. Magmas representing the dyke samples could have undergone small extents of fractional crystallisation and assimilation of granitoids. It is suggested that the partial melting of lithospheric sources is related to its stretching and elevation of geothermal gradient, possibly, as a result of intrusion of picrite/kornatiite melts into the lithosphere.
Keywords
Dolerite-Dyke, Geochemistry, REE, Igneous Petrology, Kolar Schist Belt, Dharwar Craton, Karnataka.- Geochemistry of Sphene from Granodiorites Surrounding the Hutti-Maski Schist Belt: Significance to Rare Earth Element (REE) Modeling
Authors
1 Department of Earth Sciences, University of Roorkee, Roorkee - 247 667, IN
2 Department of Earth Sciences, Pondicherry University, Pondicherry - 605 014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 2 (1999), Pagination: 107-119Abstract
A study of the distribution of REE in sphene from three granodiorite samples around NNW-SSE trending Hutti-Maski schist belt has been described here. Two distinct sets of sphene-melt Kd, values for REE have been observed among the three sphene-whole rock pairs studied. The chondrite normalized REE pattern of sphene from east (Gajalagatta) and northeast (Uti) granodiorites show LREE enriched and HREE depleted patterns with slight or no negative Eu anomaly. These REE patterns are parallel to the respective whole rock samples. But the chondrite normalized REE pattern of sphene from the sample to west of the schist belt (Ankasdoddi) has markedly depleted Ce and Nd with slight or no negative Eu anomaly and steeply fractionated HREE, resulting in a convex-up pattern. The variation of REE Kd, values of sphenes is not due to differences in the composition of host magmas (because they are all granodiorites with identical major element abundances), but could be a function of temperature of crystallization. Small degrees of fractional crystallization of sphene from granodiorite magmas would result in residual magmas having lower REE abundances either with parallel REE patterns or HREE depleted fan shaped REE patterns, depending on the Kdvalues.Partial melting of granitoid rocks, leaving minor amounts of sphene in the residue gives rise to melts with lower REE abundances than the source. The REE patterns of the melts are parallel to the source if one set of REE Kd sphene-melt values are considered. If the other set of Kd, values are used, the partial melts have (fan shaped) REE patterns with more depletion for heavy REEs.
Keywords
Geochemistry, Granodiorite, Sphene (Titanite), Hutti-Maski Schist Belt, Dharwar Craton, Karnataka.- Petrological and PGE Mineralization Study of the Channagiri Mafic-Ultramafic Complex, Shimoga Supracrustal Belt, Karnataka
Authors
1 Geological Survey of India, Bangalore - 560 078, IN
2 Geological Survey of India, Bangalore - 560078, IN
3 Petrology Division, GSI, Hyderabad - 500 078, IN
4 'Rajamangala', Saptapur, Haliyal Road, Dharwad - 580001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 5 (2008), Pagination: 746-748Abstract
No Abstract.- Hydrochemical Characteristics of Groundwater in the Nainital Lake Basin: Implication on the Landslide Hazards
Authors
1 National Institute of Hydrology, Roorkee - 247 667, IN
2 Institute Instrumentation Centre, Indian Institute of Technology, Roorkee - 247 667, IN
3 Department of Earth Sciences, Pondicherry University, Pondicherry - 605 014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 64, No 2 (2004), Pagination: 139-145Abstract
Hydrochemical characteristics of the groundwater occuring in and around the Nainital lake basin indicate that Ca2+/Mg2+ ratios are less than one. Statistical analyses reveal that the variation in Ca2+/Mg2+ ratios is mainly due to variation in Ca2+. The groundwater is geochemically undersaturated with respect to calcite and dolomite and has a tendency to dissolve the calcareous rocks more readily than it is expected in ideal dolomite terrain. The higher infiltration rates and lower surface runoff indicate that the groundwater will play a major role in the hillside stability. Further, the groundwater movement will enhance dissolution of carbonate rocks and lead to enlargement of fractures. Hence, the quantum of groundwater seepage and their hydrochemical character seem to play a crucial role in the landslide hazards as experienced by the lake basin frequently.Keywords
Hydrochemistry, Dolomite, Landslide Hazard, Groundwater, Nainital, Uttaranchal.- Petrogenesis of Amphibolites from the Banded Gneissic Complex around Masuda, Rajasthan: Significance to Precambrian Crustal Evolution of the Aravalli Craton
Authors
1 Department of Earth Sciences, IIT Roorkee, Roorkee - 247 667, IN
2 Department of Earth Sciences, Pondicherry University, Pondicherry- 605 014, IN
3 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi - 110067, IN