Fluid-Rock Interaction and Critical Metal Enrichment: Evidence from Mineral Chemistry of V-Epidote and Ti-Chlorite in Dongargarh Metagabbros, Central India

ABSTRACT This study reports, for the first time, the presence of vanadium-bearing epidote and Ti-rich chlorite associated with V-Ti magnetite in metagabbros of the Nandgaon Group, Shurtoli-Kanholi area, Bastar Craton, Central India. Petrographic and Scanning Electron Microscopic (SEM) analyses reveal a complex mineral assemblage including V-Ti magnetite, ilmenite, hematite, goethite, pyrite, chalcopyrite, clinopyroxene, epidote, and chlorite. Magnetite-ilmenite pairs commonly exhibit exsolution textures, whereas epidote and chlorite typically occur as fracture filling phases within magnetite. The V-Ti magnetite and accompanying cumulus Clinopyroxene (Cpx) formed by fractional crystallization of a Fe-V-Ti-rich parental magma. Later, low-temperature hydrothermal fluids migrated along fractures, forming V-epidote (clinozoisite) due to reduction and a change in the oxidation state of vanadium. Electron Microprobe (EPMA) analyses indicate epidote contains elevated V2O3, ranging from 1.07–6.59 wt%, while chlorite records TiO2 contents of up to 2.82 wt%. The epidote, identified as V-clinozoisite (mukhinite), formed through late-stage hydrothermal fluid activity, and its composition offers important insights into redox and fluid conditions. Chlorite geothermometry suggests formation temperatures of 200–300 °C, consistent with hydrothermal metasomatic processes in a fluid-enriched environment. These findings demonstrate that V-epidote serves as a valuable geochemical tracer of hydrothermal systems and offers a framework for recognising critical metal enrichment processes in similar ore systems regionally within the Bastar Craton and other comparable geological settings.