Geometry and kinematic model of a Neoarchaean auriferous shear zone in the Dharwar Craton, India

The detailed geometry and deformational kinematics of a shear zone at the Hutti Gold Field provides information on the structural evolution of a gold-bearing shear zone in a Neoarchean greenstone belt of southern India. Fluid flow along planar discontinuities in the 2.58 Ga Hutti greenstone belt of Karnataka hydrothermally altered the pillow metabasalt to chlorite- and biotite-phyllite, and silica released during alteration precipitated as quartz veins. Rheological weakening resulting from such alteration turned these zones to foci for high ductile strain during late-stage D 2 deformation, which produced auriferous quartz-mylonites and chlorite- and biotite-phyllonites. The geometry of structures and finite strain suggest that movement on the shear zones was of transpressional type with a dextral strike-slip component and an updip thrust component. We have tried to estimate the finite strain parameters in terms of a kinematic model of simple shear combined with shortening normal to the shear zone. The mean kinematic vorticity number and the average relative proportion of simple shear and pure shear have been determined.