Magmatic-hydrothermal evolution of the Late Permian-Early Triassic Southeast Asian metallogenic system: Insights from the Chatree epithermal gold deposit, Thailand

• Au mineralization in the Loei metallogenic belt occurred in Late Permian-Early Triassic. • Widespread vein-type mineralization occurs in Permian volcanic-volcaniclastic rocks. • 87 Sr/ 86 Sr ratios of gold veins indicates magmatic fluid interacted with the sedimentary basement. The Loei mineral belt is the significant for the Cu-Au-Fe province in magmatic arc-related terranes in mainland Southeast Asia, hosting epithermal Au and porphyry Cu-Au deposits. However, the relationship between magmatic activity and low-sulfidation epithermal mineralization remains unclear. Geochronological and stable isotope studies suggest that hydrothermal fluids played a dominant role in ore formation. This study focuses on petrography, geochemistry, geochronology and strontium isotopes to investigate the linkages between magmatic and gold mineralization. The deposit is hosted by Carboniferous to Triassic volcanic and sedimentary sequences, mainly in andesitic and rhyolitic breccias; andesitic volcanic rocks dominate the lower succession, yielding U-Pb zircon ages of 262–250 Ma while andesitic and basaltic dikes yield 244–238 Ma. Adularia 40 Ar/ 39 Ar dating constrains mineralization to 262–244 Ma, coinciding with the Late Permian to Early Triassic age. The geochronological analysis suggests at least two episodes of magmatism occurred: Late Permian (262–250 Ma), and Early Triassic (250–238 Ma). Insight into intense gold veins with the highest Sr isotope ratios (0.708765–0.717607) indicates that hydrothermal fluid interactions with the underlying sedimentary basement affected the ore fluid.