• Contrasting kinematics of brittle-shears within the Salem–Attur and Bhavani shear zone, south India: Tectonic implications

    • Fulltext

       

        Click here to view fulltext PDF


      Permanent link:
      https://www.ias.ac.in/article/fulltext/jess/129/0062

    • Keywords

       

      Strain marker; rheology; EBSD analysis; Salem–Attur shear zone; Southern Granulite Terrain

    • Abstract

       

      We document kinematics and rheological behaviour of brittle shears ($\sim$50 cm wide) postdating solid-state tectonic fabric in the Salem–Attur (SASZ) and Bhavani (BSZ) shear zone that constitute a Paleoproterozoic ($\sim$2500 Ma) suture juxtaposing disparate granulite blocks in south India. We constrain brittle deformation mechanisms from established relationship between changing orientation of deflected strain marker (quartz vein) and foliation within the shear band with respect to their orientation outside the shear band. Quartz c-axis orientation in charnockite (host lithology) and phyllonite (reworked charnockite) from the SASZ show presence of mixed basal $\langle a \rangle$ (low-T) and prism $\langle a \rangle$ (high-T) slip, and single basal $\langle a \rangle$ slip mechanism, respectively. This suggests considerable cooling of the granulite block prior to the onset of brittle shearing. Distribution of strain parameters – effective shear strain ($\it{\Gamma}$), shear strain ($\it{\gamma}$), stretch $K_{2}$ along intermediate strain axis Y – from margin to the centre of the shear band, show peaked distribution with a single maximum at the shear zone centre. This implies rheological-weakening/ strain-softening induced localizing shear zone character. Kinematically heterogeneous strain distribution during brittle shearing varies from transpression dominated for the BSZ to transpression-to-transtension switchover for the SASZ. Demonstrably, contrasting cooling-exhumation, hitherto unexplored, characterizes post-accretionary tectonics along the paleo-suture zone.

    • Author Affiliations

       

      C ANANTH1 SUBHADIP BHADRA1 ABHISHIKTA GOSWAMI2

      1. Department of Earth Sciences, Pondicherry University, Kalapet, Puducherry 605 014, India.
      2. Department of Applied Geology, Indian Institute of Technology, Dhanbad 826 004, India.
    • Dates

       
    • Supplementary Material

       
  • Journal of Earth System Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2021-2022 Indian Academy of Sciences, Bengaluru.