Geology and hydrothermal alteration of Tambulun Cu-Au skarn prospect in Sulit Air area, Solok district, West Sumatra province, Indonesia

Study area is located at Tambulun copper-gold skarn prospect and its vicinity in Sulit Air area, Solok district, West Sumatra, Indonesia. The prospect has been known for a long time, however, detailed study on alteration and ore mineralization characteristics is not done yet. This study, therefore, is dealing with geological framework and characteritics of mineralogy, and geochemistry of the skarn prospect. Surface geological and alteration mapping as well as various laboratory analyses including petrography, ore microscopy, FA-AAS and ICP-MS of selected samples taken were performed. Skarn alteration and mineralization mostly occurs along the contact between Triassic crytalline limestone of Tuhur Formation and Jurassic granodiorite of Sulit Air granitoid suite. Ore mineralization is structurally controlled by WNW-ESE dextral slip-fault and NE-SW, N-S sinistral slip faults. Skarn alteration is zoned upon intrusions from proximal to distal consisting of garnet-pyroxene, pyroxene-garnet and chlorite-epidote zones. Silicified (quartz-clinopyroxene) alteration is also locally observed. Copper bearing sulfides such as bornite and chalcopyrite as well as supergene products such as chalcocite, covellite, chrysocolla, azurite and malachite are intimately associated with proximal garnet-pyroxene zone. Ore mineralization shows elevated grades of 20.9 Cu, 8.02 g/t Au and 573 g/t Ag, respectively, and they show a positive correlation. Those preliminary data exhibit that the skarn prospect seems to be promising to be followed-up for the next-step systematic exploration. © Published under licence by IOP Publishing Ltd.