Diatreme Breccia-hosted Epithermal Gold Deposit at Ridge Mountain, Eastern Mindanao, Philippines

摘要

Low-sulfidation epithermal gold mineralisation at Ridge Mountain occurs within the Oligocene to Miocene volcanic rocks comprising andesite, porphyritic dacite and diatreme breccia. A diatreme breccia complex with a NE-SW elongated orientation covers an area of 3.0 * 1.7 km. Four main stages of mineralisation were identified, comprising:1. E-W- to NW-SE-trending quartz-chalcedony veins with disseminated pyrite, chalcopyrite and gold.2. N-S- to NNE-SSW-trending breccia veins with quartz matrix and disseminated pyrite and accessory sphalerite, galena, chalcopyrite and gold.3. NE-SW-trending quartz and calcite veins with disseminated pyrite and accessory sphalerite, galena, chalcopyrite and gold.4. ESE-WNW- to ENE-WSW-trending quartz veins with disseminated pyrite. This stage is only mineralisation that is hosted by diatreme breccia and clearly postdates.Quartz veins of the first, third and fourth stage are less than 2 m wide. Only breccia veins of the second stage are up to 10 m wide. Gold is present in all stages as microscopic inclusions in quartz and sporadically in pyrite. Macroscopic gold can be seen in the first and second mineralisation stages. Gold commonly occurs in association with sphalerite, galena and chalcopyrite in the second and third mineralisation stages.