Geochemistry and geochronology of the Chatree epithermal gold-silver deposit: Implications for the tectonic setting of the Loei Fold Belt, central Thailand

The Chatree deposit is the largest epithermal Au deposit in mainland SE Asia. Despite its economic significance, the stratigraphy, age, geochemistry and tectonic setting of the host volcanic sequence is poorly documented in the literature. The Chatree deposit is located between Phichit and Phetchabun provinces, central Thailand, and is hosted by Late Permian to Early Triassic volcaniclastic and volcanogenic sedimentary rocks. Detailed field mapping, U-Pb zircon dating, geochemistry and stratigraphy suggest that the volcanic sequence can be subdivided into four stratigraphic units and two volcanic suites. The Late Permian Suite 1 volcanic units are sourced from a more depleted mantle relative to the overlying Early Triassic Suite 2 volcanic units. The Late Permian Suite 1 units probably formed immediately after the beginning of subduction and at the creation of a new island arc. The less depleted Early Triassic Suite 2 units were erupted during ongoing subduction once the system had achieved a steady state. The Chatree Au mineralization appears to have occurred during the switch between the two mantle sources and this switch of magma source is marked by a mixed volcano-plutonic magmatism at the Permo-Triassic boundary (ca. 250 Ma).