Interplay of small-scale exhumed faults with crustal-scale shear zones and associated paleostress condition in Neoarchean Granite

Abstract

We investigate the brittle tectonic history of the Neoarchean Closepet Granite (2.56–2.51 Ga), in the Eastern Dharwar Craton, India, using paleostress analysis of small-scale fault-slip data. The analysis reveals a strike-slip stress regime driven by a regional NE-SW to E–W maximum horizontal far-field compressive stress. The study area is subdivided into three zones: Zone 1, Zone 2, and Zone 3 based on changes in the pluton boundary orientation. All three zones are characterised by both dextral and sinistral strike-slip to oblique-slip faults. These fault patterns are consistent with a large-scale Riedel shear system, which developed due to regional-scale shearing along the pluton boundary. The faults developed in Zones 1 and 2 are the consequence of sinistral shearing along the NW-SE-oriented shear zone and the pluton boundary, respectively. In contrast, the faults in Zone 3 are the result of dextral shearing along the N-S-oriented pluton boundary. We interpret that these variations in the sense of shear within the shear zones resulted from the angular relationship between E-W far-field compression and both the orientation of the pluton boundary and the internal tectonic fabric of the pluton. We conclude that regional-scale shearing along the pluton boundary, active during and after its emplacement, controlled the localization of strain and produced the intra-pluton fault pattern.