The origin of a hypogene sarabauite-calcite mineralization at the Lucky Hill AuSb mine Sarawak, Malaysia

Abstract

A gold-bearing hypogene mineralization from the Lucky Mill Mine in the Bau mining district, Sarawak, containing sarabauite and calcite as major constituents was investigated using a combination of optical microscopy, XRD and SEM + EDX. Sarabauite is the only Sb mineral of hypogene origin that is amenable to fluid inclusion studies in thin section under normal light. The ore mineralization may be subdivided into two different stages. During stage I at temperatures somewhat higher than 400°C, wollastonite, diopside and epidote evolved in the Bau Limestone that forms the wall rocks of the AuSb mineralization under study. In stage II, sarabauite developed together with gold at temperatures above 377°C, followed by calcite, stibnite and senarmontite, which formed in the T interval 377-194°C. The AuSb mineralization is of high temperature origin and characterized by Fe and S limitations. Both the temperature of formation and the chemical composition of the mineralizing fluids were responsible for the peculiar Sb-sulphide-oxides.