Two stages of gold mineralization at Hutti mine, India

The Hutti gold mine is located in a high-angle, NNW–SSE-trending shear zone system, which hosts nine discrete auriferous shear zones (reefs). On a clockwise, retrograde PT path two separate stages of deformation/metamorphism (D 2 /M 2 and D 3 /M 3 ) occurred synchronous with two distinct stages of gold mineralization, both of which were associated with different fluid types. Stage 1 mineralization developed during D 2 /M 2 , where the amphibolite host rocks were altered by a metamorphic fluid with a of 7.5–10.1 ‰, rich in K, S, As, and Au at pressure and temperature conditions of around 3 kbar and 530 + 20/−30°C, respectively. The stage 1 auriferous shear zones are enveloped by a zoned alteration consisting of a distal biotite–chlorite and proximal biotite–plagioclase assemblage. Subsequently, D 2 /M 2 was overprinted by D 3 /M 3 deformation and metamorphism at 300–400°C and