Mineralization controls in island arc settings: Insights from Philippine metallic deposits

A review of the gold-copper, volcanogenic massive sulfide and ultramafic-hosted (i.e., chromitite, nickel sulfide, platinum-group minerals) deposits in the Philippines is presented. it is critical that a thorough understanding of the spatial and temporal relationship among magmatism, structures and mineralization must be gained if the correct evaluation of the economic potential of a particular deposit is to be done. Structural features conducive to precious and base metal mineralizations are associated with shear zones, extensional jogs and collision zones. In Northern Luzon, alkali and adakitic magmatism are considered good markets for gold-copper mineralization. Volcanogenic massive sulfide deposits are hosted by either ophiolites of marginal basin origin or metamorphic terranes. Exploration works on these deposits have been geared in determining the gold content of the massive sulfides. Chromitite deposits arc related with ultramafic rock-hosted deposits. Their occurrence is attributed to crystallization, magma mixing and mantle-melt interaction processes in subduction-related settings. The multiple stages of partial melting responsible for the formation of supra-subduction zone ophiolites result in the generation of second to third stage melts that are enriched in nickel sulfides and platinum group minerals. On the basis of structural, geochemical and tectonic controls, Panay, Mindoro and Central Mindanao and the Sierra Madre, Leyte, and Samar are good exploration targets for precious and base metal deposition in the western and eastern sides of the Philippines, respectively.