Talk Description
One of the oldest cratonic nuclei in the Eastern Indian Shield is the Singhbhum Craton, the southern part of which comprises Archean greenschist facies rocks that are separated by the Barakot Shear Zone (BSZ) from Archean amphibolite to granulite facies rocks of the Rengali Province. Further south, lithounits of the Rengali Province are separated from Neoproterozoic granulite facies rocks of the Eastern Ghats Province (EGP) by the Kerajang Shear Zone (KSZ). The kinematics of the BSZ is debated. One school considers the Rengali Province to be a rotated slice of the Bastar Craton that is juxtaposed against the Singhbhum Craton by strike-slip faulting, while the other school believes the Rengali Province is the exhumed root of the Singhbhum Craton, implying that the BSZ is a thrust. Field studies conducted in this region suggest that the BSZ is an ESE-WNW trending contact with no discernible thrust-related signatures, but is actually associated with an extensional component. The KSZ that lies to the south of the BSZ has a similar trend (ESE-WNW) and is a predominantly dextral, strike-slip shear zone. Microtextural studies of the thin sections from lithounits from both the BSZ and KSZ indicate a strong dextral shear sense. The KSZ can be traced further to the west into the interior of the Bastar Craton. Along the northwestern margin of the EGP the sheared contact between the lithounits of the Bastar Craton and the granulite facies lithounits of the EGP, called the Hatibari Shear Zone (HSZ), is mapped to curve into the ESE-WNW trend of the KSZ. This rotation of the HSZ is attributed to shearing along the KSZ, implying that the KSZ postdates the Bastar Craton-EGP contact (HSZ). The continuation of the KSZ into the Bastar Craton, the rotation of the HSZ and the extensional component of the BSZ support the proposition that the Rengali Province is a dilational step-over zone representing a rotated slice of the Bastar Craton, rather than an exhumed root of the Singhbhum Craton. Thus, the much-debated contact between the Singhbhum Craton and the Rengali Province is an intracontinental, strike-slip shear zone.