Abstract
Achankovil shear-zone, a major crustal discontinuity in South India, which extends for about 120km in a NW-SE direction, separates the khondalite belt from the terrain of massive charnockites in the north. Progressive mylonitisation and shear fabrics, corresponding to a progression in strain as displayed by grain size reduction, flattening, elongation and dimensional preferred orientation of constituent minerals, characterize the shear-zone. The present work incorporates the results of petrofabric and magnetic susceptibility analyses with a view to interpret the kinematic and microstructural evolution of the shear-zone. EBSD derived LPO suggests plastic deformation through the activation of intracrystalline slip systems and modifications in the fabric due to the reactivation. Magnetic fabric data show significant correlation with the field and LPO fabrics reflecting the regional strain/kinematics and fabric development. The fabrics and kinematic indicators on meso- and microscopic scales reveal dominant dextral shear sense with a minor component of sinistral shearing in micro domains due to strain partitioning and/or reactivation of the shear-zone.
Published Version
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