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Earth Science India Vol.1 (I), January, 2008, pp. 1-11
e-journal: http://www.earthscienceindia.info/ |
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Basement Rocks of the Kumaun - Garhwal Himalaya: Some Implications for Himalayan Tectonics
A. R. Bhattacharya
Centre of Advanced Study in Geology, University of Lucknow, Lucknow, India |
Abstract: The Himalayan orogenic belt is characterized by the presence of basement rocks. These rocks got involved in the evolution of the mountain belt and, as such, have played a great role in the structural architecture and tectonic framework of the orogen. These rocks have evolved from depth due to concentration of compressive stresses generated by plate collision and rose vertically up because of buoyancy up to the surface and were then pushed southwards over the less- or un-metamorphosed , younger rocks of the sedimentary belt of the Lesser Himalaya. In order to make room for such a vast chunk of the basement, the sedimentary pile had to undergo large scale deformation sympathetically. As such, the present tectonic setting, structural architecture and deformation pattern of the upper crustal rocks of the Himalaya owe much to the rise of the basement rocks during evolutionary stages of the Himalaya. The paper examines some aspects of the tectonics and structural framework of the Himalaya as related to the basement rocks in the Kumaun - Garhwal sectors.
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Earth Science India Vol.1 (I), January, 2008, pp. 12-21
e-journal: http://www.earthscienceindia.info/ |
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Fluvial Palaeohydrological Studies in Western India: A Synthesis
Alpa Sridhar
Department of Geology, Faculty of Science, The M.S.University of Baroda,
Vadodara- 390 002,India |
Abstract: The river basins of India are important repository of the late Quaternary hydrological and climatic changes. The long term (millennial scale) and short term (centennial scale) hydrological changes in these river basins can be reconstructed through the records of platform alterations and sediment deposits that occur during the rare extreme flood events. The status of fluvial palaeohydrological studies in western India and the future prospects are discussed in this synthesis. Almost continuous palaeoflood records spanning two thousand years is available from the bedrock rivers on western India, whereas older events dating back to ~ 5 ka have also been documented from the alluvial reaches. Though bedrock gorges are considered to be ideal sites for the preservation of palaeoflood deposits and related discharge estimations, the alluvial reaches of the rivers in western India owing to their unique geomorphic set up are equally promising. Regime-based palaeodischarge estimations for the average flows in these alluvial reaches would be significant in providing a regional history of the hydrological changes that have occurred in the river basins of western India.
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Earth Science India Vol.1 (I), January, 2008, pp. 22-35
e-journal:http://www.earthscienceindia.info/ |
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Geothermal Energy Resources and Their Potential in India
P.N.Razdan |
Abstract: Geothermal Energy is the vast reservoir of heat energy in the earth's interior, whose surface manifestations are the volcanoes, fumaroles, geysers, steaming grounds and hot springs. Each geothermal system has its own structural setup, hydrological, geochemical and enthalpy characteristics. Based on the studies of structural setup, hydrology, geochemistry, geophysical studies and exploratory drilling, the geothermal systems can be classified for the purpose of energy exploration. On the basis of enthalpy characteristics the geothermal systems in India, are classified into medium (100 0 C--200 0 C)-and low enthalpy (<100 0 C) geothermal energy resources/systems. Medium enthalpy geothermal energy systems are associated with younger intrusive granites as in Himalayas; major tectonic features/lineaments and rifts and grabens. The Low enthalpy geothermal energy systems are associated with Tertiary tectonism and neotectonic activity and Shield areas with localized abnormal heat flow, which is normally very low. The geothermal systems commonly have a magmatic heat source at depths of ~8km. Chemistry of thermal discharges is related to a number of factors that begin with the hydrothermal system (rock leaching, mineral dissolution precipitation exchange reactions gas reactions, boiling of fluids at depth, and mixing of thermal fluids with ground waters. One of the dominant gases discharging in almost all geothermal systems all over the world is CO 2 .The chemical types of thermal discharges, are determined on the basis of molar ratios. Usually concentration of H 2 S is usually much smaller (a few percent or less by volume) than that of CO 2 (50-99% by volume, excluding H 2 O). Oxidation of H 2 S ultimately forms sulfuric acid and is the source of most acid waters in geothermal areas. The primary and most important aspect of geothermal system is to understand the heat source and its capacity for exploitation. On the basis of the reservoir temperatures the actual potential of geothermal fields is determined for further evaluation of the resources. About 300 thermal springs are known to occur in India, falling under orogenic (Himalayan) as well as non-orogenic (Peninsular) province. The temperatures of these springs range from 35 0 C to the boiling point of water. Studies carried out, so far, have clearly pointed that adequate geothermal potential in respect of direct heat utilization and power generation up to the level of some KWe does exist at all the geothermal sites so far explored in the country. Reservoir simulation studies have suggested the possibility of generating over 3 MW electric power in Puga (J&K) field, if deeper levels are probed at least up to the depth of 500 m.Geological Survey of India's data synthesis has been brought out in the form of two publications viz. Geothermal Atlas of India (1989) and Geothermal Energy Resources of India (2002).
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Earth Science India Vol.1 (I), January, 2008, pp. 36-52
e-journal:http://www.earthscienceindia.info/ |
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Synthetic Minerals for Electronic Applications
P. S. Anjana, Sherin Thomas, M. T. Sebastian and J. James*
Materials & Minerals Division, National Institute for Interdisciplinary Science and Technology, (NIIST) Council of Scientific and Industrial Research (CSIR), Thiruvananthapuram - 695019, India
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Abstract: Several of the mineral phases used for our common use are available in nature. However, the purity of the natural mineral phases, their consistency of properties, structure, morphology and availability make them unsuitable for large scale continuous use in electronic and other applications. Therefore, several inorganic minerals are synthesized to tailor their properties for specific applications. These minerals, though similar in their structural characteristics to the naturally occurring minerals, gives flexibility in controlling their purity, and crystallographic characteristics. This in turn helps to develop newer and improved applications like electronic and magnetic devices for communication. This article has concentrated on of some of the major synthetic materials used for electronic applications with special ephasis on their mineralogical aspects, structure, preparation and uses. The minerals covered include: quartz, synthetic Berlinite, synthetic Perovskites, synthetic halites, synthetic pyrites, synthetic rutiles, synthetic pyrochlores, synthetic spinels, synthetic sphalerites, synthetic wurtzites, synthetic corundum.
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Earth Science India Vol.1 (II), April, 2008, pp. 53-69
e-journal:http://www.earthscienceindia.info/ |
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Lateral
Zonation Around Archean Nucleus of the Dharwar Craton (India): Its Deformation, Segmentation
and Subsequent Breakup
O.P. PANDEY
*1
and
P.K. AGRAWAL
2
National Geophysical Research Institute,
Hyderabad- 500 007, India 1
5-82/A, Vivekanand Nagar, Street No.8,
Habsiguda, Hyderabad- 500 007, India 2
Abstract: Regional scale
variation of the nature of geological units across the earliest evolved
regions of the earth may contain fundamental information about continental
evolution. Among the Archean blocks, the Indian shield appears to possess
certain unique geotectonic and geodynamical characteristics which provide an
opportunity to understand its multi-stage crustal evolution both in space
and time. Our study of the south Indian shield reveals segmentation and a
secular and progressive lateral zonation of the continental lithosphere
around Dharwar nucleus since mid-Archean. However, its cratonic nucleus
seems to have ultimately broken due to successive crustal remobilization and
foundering of the rheologically and tectonically weak Archean lithosphere.
Such weakness were caused by (i) episodic plume induced tectonothermal
events since 2.7 Ga, and (ii) asthenospheric convective processes associated
with a new rifting phase triggered by Marion plume activity along the
India's western margin at about 90 Ma. The Antongil block of northeast
Madagascar seems to correspond to the broken segment of the western Dharwar
craton.
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Earth Science India Vol.1 (II), April, 2008, pp. 70-82
e-journal:http://www.earthscienceindia.info/ |
Some Observations on the Thrust Geometry of the Siwalik Rocks of the Outer Himalaya , India
A. R. Bhattacharya* and K. K. Agarwal
Centre of Advanced Study in Geology, University of Lucknow , Lucknow 226007, India Abstract: The rocks of the Siwalik Supergroup of the Outer Himalaya have been found to show a complicated system of thrust geometry in their internal domain. The structures which the lithic layers commonly show include the following: duplex, imbricate fan system, thrust propagation structures, fault propagation folds, pop-up structures, antiformal stack, snakehead anticline, snakehead duplex, overstep thrust system and the related types. Occurrence of these structures suggests, amongst others, the active role, and/or reactivation, of the anisotropy planes of the rocks during deformation, and that the deformation was progressive in nature. Development of most of these structures may have involved addition of mass to the moving thrust complexes. Presence of the above structures possibly indicates that the Siwalik strata, in general, may have undergone structural thickening in their internal domain during the overall deformation of these rocks .
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Brissid echinoid Eupatagus L. Agassiz, 1847 from the Khuiala Formation, Jaisalmer district, Rajasthan, India
D. K. Srivastava 1 * and Hukam Singh 2
Centre of Advanced Study in Geology, University of Lucknow , Lucknow – 226 007, India 1 Birbal Sahni Institute of Palaeobotany, Lucknow – 226 007, India 2
Abstract: The spatangoid genus Eupatagus L. Agassiz, 1847 is recorded, for the first time, from the sediments of the Khuiala Formation (Early Eocene) exposed near Habur, Jaisalmer district, Rajasthan, India. The specimens are placed in a new species characterised by its large, oval test with mild frontal sinus; convex aboral surface; flat oral surface; anteriorly eccentric ethmolytic apical system; anteriorly eccentric kidney- shaped peristome; long, petaloid ambulacral petals; longitudinally oval periproct at the posterior truncation and imperforate, non crenulated tubercles.
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Society of Earth Scientists |
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