ABSTRACT
The Hutti Gold Mine is located in the Archean Dharwar Craton of south Indian peninsular. It is currently producing 1.5 t of gold a year at an average grade of 6.5 g/t gold from 7 reefs in an underground operation. These reefs form part of a high-angle strike-slip shear zone system cutting amphibolites from the strata of the Hutti-Maski Greenstone Belt. The schist belt was subjected to a polyphase tectonometamorphic history. The first recognizable event is marked by greenschist/amphibolite facies metamorphism and regional folding. On the retrograde path 2 episodes of deformation and related fluid infiltration restricted to the mineralized reefs occurred in the greenschist facies. Due to the later overprint, the first alteration assemblage of biotite, plagioclase, ilmenite, quartz, arsenopyrite, pyrite, and gold has a static fabric. The second episode is characterized by an oblique dextral strike-slip reactivation of the reefs as well as intense quartz veining. The second alteration paragenesis comprises of chlorite, quartz, calcite, tourmaline, titanite, epidote/zoisite, sericite, pyrrhotite, chalcopyrite, sphalerite, and gold. Highest gold grades are found in the quartz veins, however the mined ore is defined by the lateral extent of alteration. The orientation of the intersection lineation from the 2 reef structures controls the location of ore shoots. Later, regional scale deformation events have not affected the distribution of gold mineralisation at Hutti.
