Repeated reactivation of the Gavilgarh-Tan Shear Zone, Central India: Implications for the tectonic survival of deep-seated intra-continental fault zones

摘要

Continental crust accommodates crustal deformation through repeated reactivation of old shear/fault zones that constitute domains of long-term structural weakness. Reactivation is often triggered by mechanical and chemical (fluid-assisted) changes of the host rocks within the fault core region. However, faults can also reactivate in fluid-poor condition if they are oriented favourably with respect to the prevalent stress regime. An example comes from the Gavilgarh-Tan shear/fault zone (GTSZ) in the central Indian craton which shows clear evidences of repeated fault reactivation movements widely separated in time (in Neoproterozoic, Ordovician, Permo-Triassic, Late Cretaceous and Holocene). Presence of pseudotachylyte along some reactivated fault strands indicates seismogenic fault movements in the past. Kinematic signatures of the shear zone with contrasting slip senses indicate repeated 'geometric reactivation' of the GTSZ in the pre-Quaternary as well as one episode of 'kinematic reactivation' in the Quaternary period. Under the present NNE-SSW directed compressive stress regime of the Indian craton, the GTSZ is prone to further seismogenic fault movements.