[S-CG48] Petrology, Mineralogy & Resource Geology

[SCG48-P03] Geochemical Insights into the Chatree epithermal Au-Ag Deposit, Thailand: Exploration and Environmental Significance

*Sirawit Kaewpaluk¹, Assawincharoenkij Thitiphan^2,1, Christoph Hauzenberger³, Abhisit Salam¹ (1.Chulalongkorn Univ., 2.AMP STAR, Chulalongkorn Univ., 3.NAWI Geocenter, Univ. of Graz)

Keywords:epithermal gold-silver deposit, low sulfidation, ore-vectoring element, hydrothermal alteration

Geochemical zoning plays a crucial role in both mineral exploration and the identification of hazardous metal zones. Therefore, this research focuses on the geochemical features of alteration and ore zone of the Chatree deposit, the largest low-sulfidation (LS) epithermal Au–Ag deposit in Thailand, to assess both its exploration potential and environmental impact. The study categorizes the alteration phases into silicic, phyllic, and propylitic alteration zones, and groups the sources of metal and metalloid into three categories: major components in ore minerals (e.g., As, Cu, Fe, Pb, Sb, and Zn), trace elements in ore minerals (e.g., As, Cd, Hg, and Mn), and trace elements in gangue minerals (e.g., Mn). Geochemically, the enrichment of K₂O and depletion of Na₂O and CaO in the silicic and phyllic zones are caused by hydrothermal alteration. Besides major oxides, some low-field strength elements (e.g., Rb, and Ba) show the same behavior as K₂O, and Sr is similar to CaO. REE patterns and positive Eu anomalies observed in all alteration zones significantly suggest that ore-hosted rocks are dominated by hydrothermal alteration under mildly acidic conditions or contamination of epithermal veins. The study also highlights the importance of As as a vectoring element to the ore, which is associated with the occurrence of electrum and increases towards the ore zone. Other elements such as Mn, Pb, and Cd are abundant in the ore zone, while Ti, Al, Cr, and Ni decrease towards the ore zone as a result of dilution during silicification. The study also suggests that some metals and metalloids in the host rocks and ore zone (e.g., As, Cr, Mn, and Pb) may have environmental impacts, compared to soil standards.