Fluid Inclusion Microthermometry and Implications for the Mechanisms of Ore-Grade Gold Mineralization in Epithermal System, Lalab Orebody, Sibutad, Zamboanga del Norte, Philippines

摘要

The Sibutad gold deposit has gold associated in quartz veins. The most important of these is the Lalab orebody, which contains ore-grade gold, predominantly, in milky quartz veins and veinlets. Here, alteration quartz and fine-grained crystalline clear and milky quartz were formed from hydrothermal fluids in three stages, namely stages I, II and III. Fluid inclusion microthermometry was carried out on stage I milky quartz, stage II finegrained alteration quartz and stage III milky quartz +- barite veins and veinlets. Homogenization temperatures (T_H) are >248 deg C in stage 1,214-232 deg C in stage II and 186-239 deg C in stage III. These fluid inclusions have salinity between 1 and 2 wt percent NaCl equivalent. In terms of gold assay, stage I drill-core samples have gold grades 0.53-0.76 g/ton Au, stage II samples have 1.12-3.70 g/ton Au and stage III samples have 9.06-23.88 g/ton Au. This correlation suggests that gold was precipitated from the stage II and III fluids.