Geochemistry and geochronology of intrusive units in the Suyoc epithermal deposit: Constraints on magma fertility in the Mankayan Mineral District, Philippines

The Mankayan Mineral District in northern Luzon, Philippines is host to world-class Cu-Au hydrothermal deposits such as the Far Southeast porphyry copper deposit and the Lepanto, Victoria, and Teresa epithermal deposits. It also hosts the Suyoc epithermal prospect in the southern portion of the district. This study focuses on the petrography, whole rock geochemistry, mineral chemistry and U-Pb dating of the three massive batholitic intrusive units (gabbro-diabase basement, tonalite-granodiorite, and hornblende quartz diorite) in Suyoc. U-Pb dating results reveal that the tonalite is Late Eocene in age (37.20 ± 4.70 Ma), while the hornblende quartz diorite was dated 3.18 ± 0.77 Ma (Middle Pliocene). The gabbro-diabase exhibits tholeiitic signature while the tonalite-granodiorite and hornblende quartz diorite are calc-alkaline. Trace element plots for the three host rocks indicate formation in a subduction setting. Furthermore, discrimination diagrams point to an adakitic character for the younger hornblende quartz diorite and typical arc rock signatures for the older gabbro and tonalite-granodiorite. The results indicate that hydrothermal mineralization is attributed to the hornblende quartz diorite, which coincides with the Pliocene mineralization recognized in the Mankayan Mineral District.