Integrated Provenance of the Upper Wang River Placer Gold Deposit, Northern Thailand: Constraints from Placer Gold Characteristics and Rutile–Zircon–Magnetite Geochemistry

Reconstructing placer-gold provenance requires mineral-specific interpretation because detrital minerals may record different source rocks and geological processes. This study investigates the Upper Wang River placer gold deposit, northern Thailand, by integrating placer gold morphology and chemistry with rutile, zircon, and magnetite geochemistry. Placer sediments were analyzed using optical microscopy, scanning electron microscopy, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry. Most gold grains display irregular morphologies and limited rounding, indicating relatively short fluvial transport. Gold fineness ranges from 737 to 998‰, and quality-screened core–margin EPMA data show no consistent fineness trend, whereas Hg is a reproducible compositional feature of most analyzed gold grains. Rutile records high-temperature formation conditions (~600–900 °C) and mainly crustal affinities, with a possible metamorphic contribution, whereas zircon geochemistry provides the strongest evidence for a felsic calc-alkaline granitoid source. Magnetite provides local supporting evidence but is restricted to one sampling site. Integrated interpretation suggests that the placer gold was most plausibly derived from hydrothermal quartz-vein and/or sulfide mineralization associated with a granitoid-dominated source terrane, although a specific primary bedrock gold source has not been identified. This mineral-specific approach provides a robust framework for provenance reconstruction in tropical fluvial placer systems.