New insights through LA-ICP-MS and sulphur isotope investigations into the occurrence of gold in the Sepon gold deposits, Laos

Abstract

The Sepon sedimentary-rock hosted gold deposits (SHGD) in Laos contain micro-disseminated gold associated with sulphide minerals. New insights into the nature of gold occurrence in the Sepon SHGD through Laser Ablation Inductively Couple Plasma Mass Spectrometer (LA-ICP-MS) investigations have detected gold mostly occurring in overgrowth rims on disseminated pyrite (main-gold stage) containing: (1) high gold grades along the pyrite rims, ranging from >2 to 187 ppm Au with associated high concentrations of Ag, As, Cu, Sb, Tl, Zn, and; (2) and gold poor cores with inclusions of Co, Ni and Pb and very low levels of As, Cu, Sb and Tl. Sulphur isotope values from the Sepon SHGD main-gold stage pyrite are similar to the light d34S values reported for the late gold-ore stage pyrite occurring in the Nevada Carlin-like gold deposits.