Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

S. R. Chatterjee ¹, D. K. Sen Gupta ²

Affiliations
1 M.I.T., Muzaffarpur, Bihar, IN
2 I.I.T., Kharagpur, W. Bengal, IN

Abstract

The polyrnetamorphic sequence includes quartzites, mica-schists, calc-silicates, ortho-amphibolites, migmatites and granite gneisses with pegmatites, aplites and quartz veins. Diastrophic structures in the rocks indicate the presence of a series of buckled and flattened modified parallel or near similar folds of diverging trend and plunge. Structural analyses reveal a complex monoclinic squeezing along NW-SE initiating overturned isoclinal high plunging folds (F₁) with southerly dipping NE-SW axial plane (S₂), superposed with a probable time gap by steeply plunging disharmonic folds of second generation (F₂) with subvertical axial plane (S₃). Conjugate folds and kink bands with kink planes (S₄) striking NW-SE are related to F₃ fold of restricted nature.

The regional metamorphism (sillimanite-muscovite subfacies of almandine-amphibolite facies) is followed by syn- to late-kinematic (with reference to F₁ fold) in situ granitization, Geochemical changes in different rock types leading to in situ granitization have been traced on the basis of (a) petromineralogical study of representative samples, (b) systematic modal analyses, supported by analyses showing Na-K and trace element variations. Morphological and statistical analyses of zircon and authigenic tourmaline occurring in the area confirm a sedimentary parentage of the metamorphites. Stratigraphic position is fixed up above Kolhans.

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D. K. Sen Gupta ¹, S. R. Chatterjee ²

Affiliations
1 Department of Geology and Geophysics, I.I.T., Kharagpur, IN
2 M.I.T., Muzaffarpur, IN

Abstract

No Abstract.

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Syed H. Akhter ¹, A. K. Bhattacharya ¹, D. K. Sen Gupta ¹, I. K. Kaul ¹

Affiliations
1 Department of Geology and Geophysics, I. I. T., Kharagpur 721 302, IN

Abstract

Thermoluminescence (TL) studies on the metasediments of Jabar, lying in the northwestern part of Purulia district of West Bengal, show natural thermoluminescence (NTL). These metasediments of Precambrian age, predominantly consist of marble, calc-silicates and granite gneiss. Each of the representative rock sample exhibits distinct TL glow-curves which can be successfully utilised in a number of geological applications. On the basis of natural as well as artificial thermoluminescence glow-curves, two distinct types of marble sequence have been identified.

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