STRUCTURALLY-CONTROLLED GOLD OCCURRENCES IN THE SOUTHERN BRASÍLIA FOLD-THRUST BELT OF CENTRAL AND SE-GOIÁS

Abstract

The study of occurrences of hydrothermal alteration products (tin, emerald, barite, and gold), in an area of approximately 28,7000 km 2 in the Southern Brasília fold-belt of Goiás, Central Brazil, reveals a strong structural control for these occurrences. Despite the lack of major deposits in the study area, gold has been the main ore mined both in primary lodes and placer deposit, since the 17 th century. E-W-trending intermediate-angle (30°-60° dip angle) thrust-sense shear-zone and NW-and NE-trending high-angle (>60° dip angle) strike-slip shear-zone veins are the main Brasíliano host structures of gold deposits. We propose that gold mineralizations were generated as primary deposits mostly in pegmatite and quartz veins associated with the emplacement of pre-Brasíliano Sand early-Brasíliano A-type granitoids. Pervasive Brasíliano deformation dispersed and relocated gold in preferential EW-trending shear zones associated with lateral ramps of E-verging thrusts, frontal ramps of S-SE-verging thrusts, and with NW-and NE-trending shear zones, associated with late-Brasíliano high-angle strike-slip-sense shear zones. These structural controls may indicate targets for further gold exploration in the study area.