Abstract

The ores from Cu Jut Sb deposit (Dak Nong Province) were collected to study on mineralogical characteristics and mode of occurrence of gold. Mineral assemblage of the Cu Ju Sb deposit consists of large amount of stibnite, lesser amounts of arsenopyrite, pyrite, chalcopyrite, and small amounts of magnetite and ilmenite. Based on the cutting relationship among the minerals, mineralization sequence in the Cu Jut Sb deposit was thought to start from magnetite and ilmenite, through chalcopyrite, arsenopyrite, and pyrite, to stibnite. Native gold had not been observed, although, there are significant amounts of Au in the chemical compositions of the Cu Jut pyrite and arsenopyrite. Almost results of quantitative analysis for Au in the Cu Jut pyrite and arsenopyrite using an electron probe micro-analyzer (EPMA) higher than detection limit (500 ppm). The Au contents in the Cu Jut pyrite and arsenopyrite reach to 900 and 1,200 ppm, respectively. Distribution of Au in the Cu Jut pyrite and arsenopyrite had been confirmed by using scanning electron microscopy (SEM). Results show that Au distribute heterogeneously, even in a single grain of pyrite and arsenopyrite. This suggests that, in the Cu Jut deposit, gold occur as invisible grains disseminating in the pyrite and arsenopyrite grains. On the other hand, Au show positive correlation with As and Fe in the ores. The gold mineralization in the Cu Jut Sb deposit is thought to similar with gold mineralization in the reported Han Han deposit (Bac Kan) and Nam Quang deposit (Cao Bang) and other Carlin-type gold deposits.