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Y. J. Bhaskar Rao ¹, S. A. Drury ²

Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN
2 Department of Earth Sciences, The Open University, Milton Keynes, GB

Abstract

Data on the incompatible trace elements Ti, Rb, Sr, Ba, Zr, Nb, Y, rare-earth elements, Sc, Hf, Ta and Th are presented for basalts, andesites and rhyodacites from the Archaean Bababudan greenstone belt. All samples are genetically related and show general calc-alkaline affinities. The parent magma is proposed to have been formed by about 15 per cent partial melting of mantle at shallow depths. The source mantle is shown to have been enriched in light REE and Zr relative to primitive mantle with 2-3 times chondritic abundances. The parent magma evolved by progressive fractionation of, first olivine and pyroxene to produce incompatible element-enriched alld Cr, Ni and Co depleted tholeiites, which were then accompanied by plagioclase feldspar and possibly magnetite to generate the andesites and rhyodacites. Standard tectonic characterization parameters do not give consistent results for this suite, and until more is known about overall structure, stratigraphy and relative ages within the South Indian Archaean craton, a precise setting cannot be ascribed.

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T. Rajesham ¹, Y. J. Bhaskar Rao ², K. S. Murti ¹

Affiliations
1 Geological Survey of India, S. R., Hyderabad 500 660, IN
2 National Geophysical Research Institute, Hyderabad 500 007, IN

Abstract

A new terrane of granulite facies rocks-the Karimnagar granulite terrane (KGT) is identified. The KGT is ∼ 150 km x 20 km extending along NW-SE in the Karimnagar, Warangal and Khammam districts of Andhra Pradesh along the southern flank of the Godavari graben which separates the Dharwar and Bastar Cratons. The KGT is interesting because of its location far outside the known charnockitic region of south India. The important rock types in the KGT include : hypersthene granite (charnockite), two pyroxene granulite, calc-granulite and sapphirine bearing pelitic rocks. The association of sapphirine with orthopyroxene and cordierite in the pelitic rocks indicates metamorphism at pressures of ∼ 7 Kbar and temperatures of ∼ 750°C.

It is suggested that the KGT is a remnant of an Archaean supracrustal-granite association which underwent granulite grade metamorphism at ∼ 2.5 Ga ago. This ancient orogenic belt appears to have been exhumed during the early Proterozoic.

Keywords

Precambrian Granulites, Sapphirine Granulites, Dbarwar Craton, Godavari Graben, Andhra Pradesh.

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A. F. Trendall ¹, J. R. de Laeter ¹, D. R. Nelson ², Y. J. Bhaskar Rao ³

Affiliations
1 School of Physical Sciences, Curtin University of Technology, GPO Box 1987, Perth 6000, Western Australia, AU
2 Geological Survey of Western Australia, Mineral House, I Plain Street, East Perth 6004, Western Australia, AU
3 National Geophysical Research Institute, Hyderabad 500 007, IN

Abstract

SHRIMP U-Pb analyses of zircons from a rhyolite sample collected from the Daginkatte Formation of the Chitradurga Group (Dharwar Supergroup), close to the type locality, give an age of 2601 ± 6 Ma (1σ 23 of 24 analysed grains). This is within error of the 2614 ± 8 Ma (2σ 11 grains) recently reported by A.P. Nutman and his colleagues in 1996 from a sample of acid volcanic schist of the same formation, about 25 km along strike. Combining Nutman et aI's (1996) published data with the new analyses reported here gives a pooled age of 2606 ± 6 Ma (n = 34, 1σ, χ² = 1.31), within error of both of the separately determined ages. Having regard to the reported uniform lithology of the Daginkatte Fonnation, the pooled age is probably that of a short magmatic event during which it was formed, and provides a firm constraint relevant to this stratigraphic level of the Chitradurga Group; however. it is now important to determine whether the rhyolitic rocks of the Daginkatte Formation are intrusive or extrusive.

Keywords

Geochronology, Zircon U-Ph Age, Rhyolite, Dharwar Supergroup, Karnataka.

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T. R. K. Chetty ¹, Y. J. Bhaskar Rao ¹

Affiliations
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN

Abstract

A rare occurrence of both steep and shallow plunging stretching lineations within a single outcrop, has been described from the Salem-Attur shear belt, and the regional variations in the orientation of stretching lineations are discussed in terms of transpressional tectonics in the Cauvery shear system, southern granulite terrane, South India.

Keywords

Structural Geology, Granulite Terrane, Stretching Lineation, Shear Zone, Transpression, Tamil Nadu.

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Y. J. Bhaskar Rao ¹, S. Das Sarma ¹, B. Sreenivas ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

No Abstract.

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Y. J. Bhaskar Rao ¹, Shakeel Ahmed ¹, Vineet Gahalaut ¹, Anil Kumar ¹, M. Ravi Kumar ¹

Affiliations
1 CSIR–National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN

Abstract

The National Geophysical Research Institute, Hyderabad, under the aegis of the Council of Scientific and Industrial Research, New Delhi, continued its scientific pursuit in many important areas of basic and applied earth sciences research encompassing geophysics, geology, geochemistry, geochronology and geodesy during the year 2014. The Institute is credited with 167 research publications and has accomplished several national and international projects. We give in this article an overview of three select scientific achievements.

Keywords

Aquifer Systems, Earth Sciences Research, Mafic Magmatism, Seismic Hazard.

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Y. J. Bhaskar Rao ¹, V. Balaram ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

No Abstract.

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Y. J. Bhaskar Rao ¹, T. R. K. Chetty ¹, Kusumita Arora ¹

Affiliations
1 NGRI, Hyderabad - 500 007, IN

Abstract

No Abstract.

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Harsh Gupta , Shailesh Nayak , Y. J. Bhaskar Rao , R. K. Chadha , B. K. Bansal , D. Srinagesh , N. Purnachandra Rao , Sukanta Roy

Abstract

No Abstract.

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Y. J. Bhaskar Rao ¹

Affiliations
1 CSIR-NGRI, Hyderabad - 500 007, IN

Abstract

Scientific knowledge of the Earth – its structure, dynamics, evolution, resources and natural hazards – assumes great importance because the survival and progress of mankind almost entirely depend on this pursuit. The establishment of the National Geophysical Research Institute (NGRI) under the Council of Scientific and Industrial Research (CSIR), Ministry of Science and Technology, Govt. of India, in 1961, is an acknowledgement of the importance ascribed to geophysics and allied disciplines. On October 11, 2011, the CSIR-NGRI celebrated its Golden jubilee, a day that marked the culmination of yearlong commemorative events, thematic conferences and lectures (see Journal of Geological Society of India, v.77, p.393- 394). The Golden Jubilee provides a befitting opportunity to reminisce the 50 glorious years of the institute’s journey from a modest beginning to a world class geoscientific centre of excellence, which was possible through the able stewardship of Drs. M.S. Krishnan, Hari Narain, A. Roy, S. Balakrishna, V.K. Gaur, D. Guptasarma, Harsh K. Gupta, S.M. Naqvi, D.C. Mishra and V.P. Dimri. This note highlights the achievements during this eventful sojourn, the present capabilities, aspirations and goals for the future.

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Y. J. Bhaskar Rao ¹

Affiliations
1 CSIR-NGRI, Hyderabad - 500 007, IN

Abstract

As part of the Golden Jubilee celebrations of CSIR-NGRI, distinguished geoscientists from India and abroad delivered popular lectures on a wide range of themes. The lectures brought to fore the global challenges confronting human civilization, presented a glimpse of advanced research on some basic geoscience problems as well as the state-of-the-art in multi-disciplinary Earth science research today. About 700 students from schools and science colleges in Hyderabad and hundreds of geoscientists from various Earth science organizations and universities formed a lively audience.

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