P-T-X conditions of hydrothermal fluids and precipitation mechanism of stibnite-gold mineralization at the Wiluna lode-gold deposits, Western Australia: conventional and infrared microthermometric constraints

摘要

The Wiluna lode-gold deposits are located in the Archean Wiluna greenstone belt, in the northern sector of the Norseman-Wiluna belt in the Yilgarn Craton of Western Australia. They are hosted in subgreenschist facies meta-basalts, and controlled by the Wiluna strike-slip fault system and associated shear veins and breccias. The 13 individual lode-gold deposits have produced around 115 t Au from 1901 to 1946 and 1986 to today. Historically, they also produced 38.3 t As and 3.5 t Sb. Gold formed in two stages: stage 1 gold-pyrite-arsenopyrite is finely disseminated in the wallrock and breccia fragments, whereas stage 2 gold-stibnite is located in massive shear veins and breccia matrix, as fracture-fill and in banded-colloform textured veins. Stibnite-gold orebodies only occur in some of the deposits (e.g., Moonlight and northern part of the West Lode) and also display a restricted vertical extent, being preserved only in the uppermost 200 m of stibnite-bearing lodes.