Field and textural relationship in pelitic schists and gneisses from the area around Mangpu, Darjeeling district, West Bengal |
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| Authors: | D Prakash S Tewari |
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| Institution: | 160. Centre of Advanced study in Geology, Banaras Hindu University, Varanasi, 221 005, India
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| Abstract: | The metasedimentary rocks of the area around Mangpu constitute a portion of the hinge zone of the northern limb of the major synform of Lower Darjeeling Himalaya. The rocks display evidences of multiple deformation and at least three major phases of deformation have been recognized. The time relations between the phases of deformation (D1, D2, D3) and metamorphic crystallization reveal a single major prograde metamorphic event that initiated with the D1 deformation and finally outlasted it. The earlier phase of this metamorphism is essentially regional syn-tectonic lowgrade (greenschist facies) which may be designated (M1, early). This was followed by regional static metamorphism (M1, late) in the post-tectonic phase between D1 and D2 deformations (upper green schist and amphibolite facies). This M1 metamorphism is superposed by later retrogressive metamorphism (M2) during the D2 and D3 deformations (lower greenschist facies). Within the study area four isograds have been delineated by the first appearance of index minerals in the pelitic schists and gneiss which display Barrovian type of metamorphism. |
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