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Tapas Bhattacharyya

Bio: Tapas Bhattacharyya is an academic researcher from University of Calcutta. The author has contributed to research in topics: Gneiss & Volcanic rock. The author has an hindex of 5, co-authored 10 publications receiving 147 citations.
Topics: Gneiss, Volcanic rock, Simple shear, Craton, Archean

Papers
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Journal ArticleDOI
TL;DR: A review of the state of the art of structural and geochronological knowledge of cratonic rocks in part of central Rajasthan, India, and contributions new observations and isotopic data on the structural features and age of granitic rocks in the area are presented in this paper.

98 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present geochemical and Sm-Nd isotopic data from the Dhanjori and Chaibasa Formations for the first time and combine previous sedimentological data with the goal to expand the framework for understanding the depositional and tectonic setting of these two formations.

30 citations

Journal ArticleDOI
TL;DR: The structural geometry of the Anasagar gneiss dome in the axial zone of the South Delhi Fold Belt is controlled by polyphase folding as mentioned in this paper, and it is classified as a thrust-related gniiss dome and not as a metamorphic core complex.
Abstract: The structural geometry of the Anasagar gneiss dome in the axial zone of the South Delhi Fold Belt is controlled by polyphase folding. It is classified as a thrust-related gneiss dome and not as a metamorphic core complex. Four phases of deformation have affected both the gneiss and the enveloping supracrustal rocks. D 2 and D 3 deformations probably represent early and late stages of a progressive deformation episode in a simple shear regime combined with compression. The contact between the gneiss and the supracrustal rocks is a dislocation plane (thrust) with top-to-east sense of movement which is consistent with the vergence of the D 2 folds. The thrust had a ramp-and-flat geometry at depth. At the present level of exposure it is a footwall flat (that is, parallel to the gneissosity in the footwall), but it truncates the bedding of the hanging wall at some places and is parallel at others. The thrusting was probably broadly coeval with the D 2 folds and the thrust plane is locally folded by D 2 . D 2 and D 3 folds have similar style and orientation as the first and second phases respectively of major folds in the Delhi Supergroup of the South Delhi Fold Belt and these are mutually correlatable. It is suggested that D 1 may be Pre-Delhi in age. Available geochronological data indicate that the emplacement of the Anasagar gneiss predated the formation of volcanic rocks in the Delhi Supergroup and also predated the main crust forming event in the fold belt. The Anasagar gneiss and its enveloping supracrustal rocks are probably older than the Delhi Supergroup.

17 citations

Journal ArticleDOI
TL;DR: The structural geometry in the Barr conglomerate and the neighboring rocks in the western flank of the Meso- to Neoproterozoic South Delhi Fold Belt indicate superposed deformation, with structures developed by horizontal dextral simple shear deformation superimposed on earlier structures formed during approximately ESE-WNW compression and subvertical maximum elongation.

14 citations

Journal ArticleDOI
TL;DR: In the Bundelkhand Craton of central India, mafic dykes intruded when granitoids was partly crystallized as mentioned in this paper, and textural evidence of mingling is represented by acicular apatite morphologies, titanite-plagioclase ocelli and ophitic-subophitic texture.
Abstract: In Bundelkhand Craton of central India, mafic dykes intruded when granitoids was partly crystallized. Cuspate–lobate boundary along the contact of granitoids and mafic magma indicates magma mingling in outcrop scale while textural evidence of mingling is represented by acicular apatite morphologies, titanite–plagioclase ocelli and ophitic–subophitic texture, mafic clots, resorbed plagioclase, and hornblende–zircon associations. Mingling also caused thermal exchange and fluid activity along the boundary between two coeval magmas. Crystal size distribution analyses for hornblende in the mafic rocks yield concave up curves which is also consistent with interaction of felsic and mafic magmas.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: The end-Paleozoic Pangea appears to have contained three continents that had grown in the Precambrian and remained intact until Mesozoic rifting: Ur, formed at 3 Ga and accreted to most of East Antarctica in the middle Proterozoic to form East Gondwana; Arctica, an approximately 2.5-2 Ga continent that contained Archean terranes of the Canadian and Siberian shields and Greenland; and Atlantica formed at 2 Ga of cratons of ~2 Ga age that now occur in West Africa and
Abstract: The end-Paleozoic Pangea appears to have contained three continents that had grown in the Precambrian and remained intact until Mesozoic rifting: Ur, formed at ~3 Ga and accreted to most of East Antarctica in the middle Proterozoic to form East Gondwana; Arctica, an approximately 2.5-2 Ga continent that contained Archean terranes of the Canadian and Siberian shields and Greenland; and Atlantica, formed at ~2 Ga of cratons of ~2 Ga age that now occur in West Africa and eastern South America. Arctica grew at ~1.5 Ga by accretion of most of East Antarctica plus Baltica to form the continent of Nena. Collision of Nena, Ur, and Atlantica, plus minor plates, formed the supercontinent of Rodina at ~1 Ga. Rifting of Rodinia between 1 and 0.5 Ga formed three continents: East Gondwana; Atlantica (which became the nucleus for West Gondwana); and Laurasia (which contained North America, Greenland, Baltica, and Siberia). Gondwana formed at ~0.5 Ga by amalgamation of its eastern and western parts. Various plates accret...

530 citations

Journal ArticleDOI
01 Jan 1940-Nature
TL;DR: The Geology of India by D. N. Wadia as discussed by the authors has been brought up to date by the addition of recent advances in Indian geology and a new geological map is an added attraction.
Abstract: THIS book, which from its first appearance has been the standard text-book of Indian students, has now been brought up to date by the addition of recent advances in Indian geology. The new geological map is an added attraction. Geology of India By D. N. Wadia. Second edition. Pp. xx + 460 + 20 plates. (London: Macmillan and Co., Ltd., 1939.) 24s. net.

200 citations

Journal ArticleDOI
TL;DR: In this article, an ion microprobe was used to measure the ages of zircons from six samples collected from the southern Aravalli Mountains, and the results indicated that the southern segment of the Aravali Craton had broadly stabilized by ∼ 2.5 Ga.

191 citations

Journal ArticleDOI
TL;DR: The Seychelles islands consist of undeformed and unmetamorphosed basaltic magmas derived from metaluminous monzogranites and granodiorites of Neoproterozoic depleted mantle, variably contaminated by Archaean age (> 750 Ma.
Abstract: compositions ( Nd 750 = +5·46 to −0·87; ISr 750 = 0·7021– The Seychelles islands consist of undeformed and unmetamorphosed, 0·7061) that can be modelled as basaltic magmas derived from metaluminous monzogranites and granodiorites of Neoproterozoic depleted mantle, variably contaminated (0–15%) by Archaean age (>750 Ma). Subsolvus, and lesser hypersolvus granitoids are silicic crust. All petrologic, petrographic, geochemical, isotopic and crosscut by coeval dolerite dykes, dominantly of olivine tholeiite chronologic data for Neoproterozoic magmatic rocks of the Seychelles, composition. Field relations suggest that mixing between granitoid coupled with palaeomagnetic data indicating its position at the and doleritic magmas generated a variety of minor intermediate margin of the Rodinia supercontinent at >750 Ma, are at least rocks that occur as irregular masses and enclaves; their compositions consistent with, if not suggestive of, a continental or Andean-type plot as linear arrays between those of dolerites and granitoids. Two arc setting. We argue, therefore, that the conventionally accepted groups of granitoids can be distinguished based on colour, chemistry notion of an extensional (i.e. rift or plume) setting for Seychelles and isotopic signature. Mahe Group granitoids are grey, with magmatism is vulnerable. relatively low incompatible element concentrations and primitive isotopic signatures that cluster at Nd 750 = +2·85 ± 0·17 and ISr 750 = 0·7031 ± 0·0008 (some samples with impossibly low ISr 180 ppm,

182 citations

Journal ArticleDOI
TL;DR: In this article, single grain 207Pb/206Pb zircon ages were determined for granitoids and gneisses which constitute the Archaean basement rocks of the Aravalli craton of Rajasthan.
Abstract: Single grain 207Pb/206Pb zircon ages were determined for granitoids and gneisses which constitute the Archaean basement rocks of the Aravalli craton of Rajasthan, northwestern Indian Shield. The protolith ages for two gneisses, collected from east of Udaipur, are ˜3230 Ma and 2887 Ma respectively. The granitoids display an intrusive relationship with the gneisses and yielded ages ranging between 2666 Ma and 2620 Ma. These ages provide the basis for a geochronological model of evolution of the oldest basement of the Aravalli craton.

181 citations