Grain-scale anatomy of the Bundelkhand granite: Implications for the interplay of magmatic to sub-magmatic deformation mechanisms

Abstract

Grain-scale structures of the granitoid rocks from the north-western part of the Bundelkhand craton, central India are analysed with the aid of an optical microscope and electron probe micro analyser. Although field-based studies and quick microscopic observations suggest an overall porphyritic texture of the Bundelkhand granitoid, detailed microstructural observations reveal a significant deviation from the first-order igneous porphyritic texture. Here, we show that the Bundelkhand granitoid has three distinct grain-scale structures: (i) original pristine igneous structures, (ii) ductile deformation-related structures, and (iii) brittle fracturing-related structures. Based on microstructural evidences, we argue that the deformation-induced structures (both brittle and ductile) are not restricted to solid state, rather these structures initiated in the sub-magmatic stage and nucleated in partially crystallised magma during the magmatic to sub-magmatic event of the crystallisation history.

The origin and localization of “vermiculite” along the intra‐terrane shear zones in the Bundelkhand Craton, India: Mechanism and implication

“…Chips of infill material occurring in and along the strike of the ductile shear zones were also acquired to identify the precise mineralogy of the infill material (by XRD analysis). A range of microstructural features exhibited by the Bundelkhand granitoids is already described by Sarkar et al (2019). However, the present microstructural investigation is largely focused on the recognition of vermiculite along the precursor brittle fractures, which host the ductile shear zones.…”