Preliminary Mineral Resource Investigation of Gold and Copper in Yap, FSM

Preliminary Mineral Resource Investigation of Gold and Copper in Yap, FSM (Report). 1988. doi:10.3133/ofr88206. ISSN 0196-1497.

Abstract: The four islands which comprise the state of Yap in the Federated States of Micronesia are part of a series of intra-oceanic arc-trench systems extending from Palau to the Northern Mariana Islands. These arcs separate the Philippine plate from the Pacific plate. The Yap arc is unique among these arc-trench systems in that metamorphic rocks and a melange comprise the dominant rock types with typical arc-volcanic rocks being present in subordinate amounts. The Yap Formation is the oldest unit and consists of upper greenschist to amphibolite-grade metamorphic rocks. The protolith for the metamorphic rocks likely consists of plutonic and volcanic arc rocks as well as possibly ocean-ridge basalts. Metamorphism likely occurred in response to overthrusting of the volcanic arc from west to east in response to the plugging of the trench by a seamount chain (Hawkins and others, 1977). During overthrusting, the melange of the Map Formation occupied the zone of thrusting. After thrusting, mafic MioceneC?)volcanics, termed the Tomil volcanics, were emplaced. These volcanics are typical of intra-oceanic arcs and are the youngest volcanic rocks present in Yap. A large epithermal precious-metal system has been identified in the Tomil volcanic rocks and is exposed on the islands of Maap and Gagil-Tamil. Numerous quartz veins up to 1 m in width and mineralized breccias occur within the volcanic rocks and commonly contain from trace to 3.7 ppm gold. Other trace elements associated with gold include tellurium, copper, and vanadium. Alteration adjacent to the veins consists of an assemblage of quartz, kaolinite, and sericite. The veins and breccias contain comb quartz and open textures typical of epithermal precious-metal systems. A hot spring ironoxide sinter is present at Guroor Hill on Gagil-Tamil Island, after which the gold system is named. The sinter contains anomalous gold contents up to 1 ppm, and copper, vanadium,…

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MAG: 1542097189
OpenAlex: W1542097189