Progressive evolution of paleostress in the Hutti-Maski Greenstone belt, Eastern Dharwar Craton, southern India

This study presents a paleostress reconstruction of the metavolcanic and granitoid rocks of the Hutti-Maski greentone belt, Eastern Dharwar Craton (EDC), southern India, aimed at evaluating progressive changes in the regional stress field at ca. 2.5 Ga. Paleostress was constrained using quartz vein orientations, Anisotropy of Magnetic Susceptibility (AMS) fabrics, and fault–slip data from metavolcanic and granitoid rocks.

Anisotropy of Magnetic Susceptibility (AMS) data from granitoids reveal a dominant NNW–SSE–striking magnetic fabric developed during earlier D1/D2 deformation. Paleostress analysis using vein orientations of dilational quartz veins in the granitoids yields an apparent NE–SW compressional stress field. However, kinematic analysis demonstrates that these veins in the granitoids were formed by dextral simple shear along the pre-existing NNW–SSE–oriented fabric under a regional N–S–directed D3 compression. From previous studies it is already well established that this regional N–S–directed D3 compression was responsible for D3 folds with E–W–striking axial planes found in different parts of EDC. N-S-oriented dilational quartz veins in the metavolcanic rocks of this greenstone belt were also formed due to this N-S oriented D3 compression. This interpretation is further supported by comparable stress ratio values obtained from three-dimensional Mohr circle analyses of vein populations in both lithologies.

Fault–slip analysis of displaced veins in granitoids reveals a late-stage NNE–SSW compressional stress field, indicating localised brittle deformation during the final stages of D3. This late brittle overprint is interpreted as resulting from late-D3 brittle deformation during the cratonization of the Dharwar Craton at approximately 2.5 Ga.

Therefore, this study demonstrates that there are pitfalls in the direct evaluation of paleostress using only vein orientations and that it is crucial to integrate kinematic constraints with vein orientation data during paleostress analysis of dilational veins.