Browsing by Author "Sarkar D.P."
Now showing 1 - 1 of 1
Results Per Page
Sort Options
Item Fluid-assisted viscous deformation of pseudotachylyte veins near the frictional-viscous transition of the crust: Insights from the Gavilgarh�Tan Shear Zone, Central India(Springer, 2024) Sarkar A.; Chattopadhyay A.; Sarkar D.P.; Das K.; Ando J.-I.In the repeatedly reactivated Gavilgarh�Tan Shear Zone of central India, sheared and foliated pseudotachylyte (Pt�M) veins, with characteristic signatures of viscous deformation, occur as discrete layers within granitic mylonite. Deformation history and age constraints described by earlier workers suggest that semi-brittle reactivation of the shear zone possibly occurred near the frictional-viscous transition at an intermediate depth of the crust that formed these pseudotachylyte layers. Detailed microstructural study and electron back-scattered diffraction (EBSD) analyses of the mylonite and the Pt�M layers were carried out in the present study, which suggest that the mylonite deformed at a high temperature (>500��600�C) with dominance of Regime 3 Grain Boundary Migration (GBM) recrystallization. Quartz grains in the mylonite deformed dominantly by prism and rhomb slip. In the Pt�M, significant grain size reduction occurred by initial cataclasis and later recrystallization processes. Deformation of quartz grains by a combination of basal and (subordinate) rhomb slip suggests relatively lower temperatures for Pt�M deformation. Grain boundary misorientation distribution (MAD) shows the dominance of low-angle subgrain boundaries in neighbour-pair grains, suggesting the dominance of subgrain rotation (SGR) recrystallization in the Pt�M matrix. Extensive development of chlorite, sericite, and epidote in Pt�M veins suggest hydration during shearing. Prism slip was possibly activated at a lower temperature (<400�C) due to the hydrolytic weakening of quartz. The Pt�M veins developed an interconnected weak layer of biotite, chlorite, and/or epidote during shearing and retrogression that helped in concentrating viscous deformation in these layers. � Indian Academy of Sciences 2024.
