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

Abstract

a clay mineral of economic importance, is reported for the first time from the Bundelkhand Craton. The locales of the vermiculite occurrence are mapped within the Bundelkhand granitoids at several places. The identification of the fracture system and the zones of strain localization within Bundelkhand granitoids are critical for targeting the occurrences of vermiculite. A range of studies including meso-, micro-, and sub-microscopic analyses were used to delineate the characteristic features of vermiculite along the brittle/ductile shear zones in the Bundelkhand Craton. SEM-based EDS, EPMA, and XRD analyses confirm the ubiquitous dominance of vermiculite as fracture infills and/or channel infill materials along the zones of nucleation of ductile shear zones. It is postulated here that the occurrence of vermiculite is a result of supergene alteration of biotite present in the vein material. The parent material of the fracture infills from which the veins crystallized is genetically derived from the host rock (Bundelkhand granitoid), which later healed the fractures and prompted the nucleation of ductile shear zones in the Bundelkhand Craton.

Contextual relationship between mechanical heterogeneity and dyking: constraints from magma emplacement dynamics of the ca. 2.21 Ga Anantapur–Kunigal mafic dyke swarm, Dharwar Craton, India

“…The former involves primary hydraulic fracturing in the undeformed country rock, whereas the latter takes advantage of the pre-existing inhomogeneities in the crust (Jourdan et al 2006), i.e. change in lithology, fractures, foliations, faults and intra-terrane shear zones (Banerjee et al 2022). Giant radiating dyke swarms are generally related to mantle plume-related tectonics (e.g., Ernst et al 2001; Hou, 2012; Ernst, 2014).…”