The Age and Origin of the Ruwai Polymetallic Skarn Deposit, Indonesia: Evidence of Cretaceous Mineralization in the Central Borneo Metallogenic Belt

Abstract The Ruwai skarn deposit is the largest polymetallic in Borneo and located Schwaner Mountains. skarns massive orebodies are hosted marble of Jurassic Ketapang Complex, which was intruded by Cretaceous Sukadana granitoids. prograde-stage garnet retrograde-stage titanite yielded U-Pb ages 97.0 ± 1.8 to 94.2 10.3 Ma 96.0 2.9 95.0 2.0 Ma, respectively. These similar Re-Os obtained on sulfides (96.0 2.3 Ma) magnetite (99.3 3.6 Ma). zircon reveal that magmatism at occurred three phases, including Early (ca. 145.7 106.7–105.7 Ma; andesite-dacite), Late 99.7–97.1 diorite-granodiorite), late Miocene 10.94–9.51 diorite-dolerite). Based geochemical stable isotopic data (C-O-S) ores interpreted have formed from oxidized fluids ca. 160 670°C. ore-forming metals were mostly magmatic origin but with significant crustal input. mineralization Cretaceous, associated Paleo-Pacific subduction beneath Sundaland after Southwest accretion. first occurrence recognized Central metallogenic belt.