Structural and textural development in Singhbhum shear zone, eastern India

Mukhopadhyay, Dhruba ; Deb, Gautam Kumar (1995) Structural and textural development in Singhbhum shear zone, eastern India Proceedings of the Indian Academy of Sciences - Earth and Planetary Sciences, 104 (3). pp. 385-405. ISSN 0253-4126

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The rocks within the Singhbhum shear zone in the North Singhbhum fold belt, eastern India, form a tectonic melange comprising granitic mylonite, quartz-mica phyllonite, quartz-tourmaline rock and deformed volcanic and volcaniclastic rocks. The granitic rocks show a textural gradation from the least-deformed variety having coarse-to medium-grained granitoid texture through augen-bearing protomylonite and mylonite to ultramylonite. Both type I and type II S-C mylonites are present. The most intensely deformed varieties include ultramylonite. The phyllosilicate-bearing supracrustal rocks are converted to phyllonites. The different minerals exhibit a variety of crystal plastic deformation features. Generation of successive sets of mylonitic foliation, folding of the earlier sets and their truncation by the later ones results from the progressive shearing movement. The shear sense indicators suggest a thrust-type deformation. The microstructural and textural evolution of the rocks took place in an environment of relatively low temperature, dislocation creep accompanied by dynamic recovery and dynamic recrystallization being the principal deformation mechanisms. Palaeostress estimation suggests a flow stress within the range of 50-190 MPa during mylonitization.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Singhbhum Shear Zone; Mylonites; Texture; Shear Sense Indicators
ID Code:21601
Deposited On:22 Nov 2010 11:13
Last Modified:17 May 2016 05:47

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