Tectonic setting of porphyry Cu–Au, Mo and related mineralization associated with contrasted Neogene magmatism in the Western Sulawesi Arc

The Neogene Western Sulawesi Arc, from the south going northwards, can be divided into three magmatic provinces of K alkaline–shoshonitic (AK-SH), high-K calc-alkaline (KCA), and low-K–normal calc-alkaline (TH-CA) affinity, referred to, respectively, as South, Central and North Sulawesi. The origin of this magmatism in terms of subduction and collision processes is contentious. Four widely spaced Cu–Au porphyry, and one Mo porphyry district(s) occur along the Western Sulawesi Arc, with the North Sulawesi province being the most mineralized. This porphyry mineralization is part of a regional belt that extends north into the Philippines and possibly south to the Sunda Arc. In western Sulawesi, common features that define the porphyry belt are obscure because the porphyry districts cannot be simply related, either in terms of their magmatic affinity, nature of basement, or tectonic setting. Nevertheless, it can be suggested that the generation of porphyry Mo systems requires involvement of continental crust in terms of magma source, while Au-rich porphyry systems are independent of the nature of the crust, and are derived from a mantle source.