DOI: 10.5176/2251-3353_GEOS15.40
Authors: Mrinal Kanti Mukherjee, Kunal Modak and Sohini Das
Abstract: The deformation of Mesoproterozoic sedimentary cover rocks of the Kaladgi basin, southwestern India has been studied with reference to structural geometry, kinematics and associated thermal constraints. The deformation structures of the basin are naturally grouped in a way that defines a northern sector and southern-central sector based on the type, geometry, distribution, and association of structural elements. An association of WNW–ESE trending, both northerly and southerly verging, asymmetric-to-overturned, plane-non-cylindrical, gently plunging folds with axial-planar cleavages and both E–W and N–S trending faults, together, define the contractional deformation zone in the southern-central sector. In the northern sector, the cover rocks are gently dipping (10) towards south and define a homocline that is affected at places by normal faults, tensile and hybrid joints, and torn-apart segments. Together, these define the extensional deformation zone in the northern sector of the basin. Distribution, mode of occurrence, variation and interrelationship of structural elements in the basin, reveal that, the contractional domain and extensional domain are connected throughout in an unbroken sequence from the southern parts of the basin to the northern extremities and are spatially related as a part of a single deformational event. The grade of metamorphim of the deformed Mesoproterozoic cover rocks have been determined using Illite-Crystallinity (IC) Index. IC index values ranging between 0.601°2and 0.259°2in a set of 33 representative samples), indicate deep diagenetic to higher anchizone (very low grade) metamorphic conditions characterized by a temperature range of 150C-300°C.The deformation pattern and the thermal constraints indicate that the deformed cover represented a thin crust and the deformation was due to a southerly-directed gravity gliding of the cover above the basement.
Keywords: Kaladgi basin; Anchizone metamorphism; Illite-crystallinity; gravity gliding; Deformation
Updating...