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

Abstract

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 fi ne-grained crystalline clear and milky quartz were formed from hydrothermal fl uids in three stages, namely stages I, II and III. Fluid inclusion microthermometry was carried out on stage I milky quartz, stage II fi negrained alteration quartz and stage III milky quartz ± barite veins and veinlets. Homogenization temperatures (T H ) are >248°C in stage I, 214 -232°C in stage II and 186 -239°C in stage III. These fl uid inclusions have salinity between 1 and 2 wt% 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 fl uids.

About the Special Issue: Collection of Achievements on Earth Resources from AUN/SEED‐Net, Part II

“…Epithermal systems in the Philippine archipelago are described in two papers. Jimenez et al (2007) document fluid inclusion microthermometry and its implications for the mechanisms for ore‐grade gold mineralization, the Lalab orebody of the Sibutad deposit in Mindanao. Payot et al (2007) demonstrate the behavior of major and trace elements during ore deposition at the Pantingan low‐sulfidation gold system in Mount Mariveles, Bataan, Luzon.…”

“…Most papers were presented at the AUN/SEED-Net eighth Fieldwise Seminar on Geological Engineering Field and the third International Symposium and Exhibition entitled "Contribution of Science and Engineering for Geo-Hazard and Geo-Resources Management Toward Sustainable Development" held on 3 -4 August 2006 at Yogyakarta, Indonesia. Three papers describe magmatic and hydrothermal systems of porphyry-type mineralization ( Idrus et al , 2007;Imai et al , 2007;Suerte et al , 2007 ), while seven papers including one short communication report on hydrothermal systems associated with gold mineralization ( Ariffi n & Hewson, 2007;Crisostomo et al , 2007;Harijoko et al , 2007;Jimenez et al , 2007;Syafrizal et al, 2007;Warmada et al , 2007 ). In addition, one paper discusses temporal evolution of island arc magmatism ( Polve et al , 2007 ).…”