Mass Change Calculations as Applied to the Search for Volcanogenic Massive Sulfide Deposits: An Example from Malusok, Siocon, Zamboanga del Norte, Mindanao, Philippines

Abstract

Abstract:The Malusok volcanogenic massive sulfide (VMS) deposits comprise two adjacent ore bodies, the Main Malusok and the Malusok Southeast ore bodies, hosted within Cretaceous metamorphic rocks. Owing to the structural and metamorphic overprinting combined with intense hydrothermal alteration, primary textures of the Malusok volcanic rocks have been obliterated. The stratigraphic correlation of the Main Malusok and the Malusok Southeast ore bodies show that both deposits are essentially confined within a single stratigraphic interval. The lithogeochemical analysis of the Malusok samples shows that constituent lithologies have precursor compositions ranging from sub-alkaline basalts to rhyodacites. Field and mass flux data suggest that the Main Malusok VMS deposits were derived as a consequence of axial hydrothermal activity. The Malusok Southeast ore bodies represent satellite deposits generated by off-axis hydrothermal activities from vents aligned along a NW-SE trend with the Main Malusok zone. This alignment represents an ancient fissure that served as a pathway for the upwelling metalliferous hydrothermal fluids. In searching for lateral extensions of these VMS deposits, this NW-SE alignment should serve as a possible exploration guide.

Behavior of Major and Trace Elements during Ore Deposition: Example from the Low‐Sulfidation Pantingan Gold System, Mount Mariveles, Bataan, Philippines

“…The largest gains in SiO 2 and Fe 2 O 3 + MgO may be attributed to silica inundation coupled with the occurrence of sulfi de owing to the abundance of pyrite. Gains in Fe 2 O 3 + MgO are normally accompanied by losses in CaO + Na 2 O, indicating breakdown of plagioclase ( Querubin & Yumul, 2005 ). However, in the present analysis signifi cant gains in CaO + Na 2 O are observed along with increased amounts of Fe 2 O 3 + MgO.…”

“…Signifi cant changes in SiO 2 in the samples can be attributed to silica inundation or silica leaching. Gains in Fe 2 O 3 + MgO accompanied by loss in CaO + Na 2 O are being attributed to the breakdown of plagioclase ( Helba et al , 2001;Querubin & Yumul, 2005 ). In contrast, the increase in CaO + Na 2 O suggests the possible occurrence of calcite.…”