Mineralization characteristics and ore fluid of Huai Kham on gold deposit, Northern Thailand

Abstract

© World Scientific Publishing Company. Huai Kham On gold deposit is located within the Lampang-Phrae volcanic belt of the Sukhothai Fold Belt in northern Thailand. The gold deposit is hosted by Triassic andesitic tuff and intercalated rhyolitic welded tuff. The host sequence is overlain by sedimentary sequences including Triassic calcareous sandstone of the Wang Chin Formation and Middle Triassic limestone of the Kang Pla Formation Gold nuggets and electrum were found in quartz-rich veins with associated pyrite, chalcopyrite, galena and bournonite cutting across the andesitic tuff and underlying rhyolitic tuff.Sulfur isotope analyses indicate that the gold-ore forming fluids vary in sulfur isotopic values from —5.3 to —3.5 per mil.Fluidinclusion studies indicate that the ore-forming fluids were typically enriched in CO2 which is evidenced by the occurrence of carbonic (CO2 (L)— H2O(L)—CO2(V)) inclusions in quartz adjacent to the gold-bearing sulfide minerals. Three types of fluid inclusions including Type I (L-V) aqueous inclusions, Type II (L-L-V) aqueous—carbonic inclusions, and Type III (V) vapor rich inclusions, were classified in vein quartz. Results from a preliminary microthermometry study of fluid inclusions in ore-bearing vein quartz indicate that the melting temperature of CO2 solid varies from —56.8°C to —56.6°Cand that the homogenization of the carbonic phase varies from 28° C to 31° C suggesting that the carbonic phase contains pure CO2. This interpretation is supported by Laser Raman Spectroscopy analyses. The homogenization temperatures of the carbonic inclusions in quartz vary from 280° C to 300° C Salinities of ore fluids range from 1 to 7 wt.% NaCl equiv.On the basis of available data such as vein texture, alteration, and fluid inclusion data, the Huai Kham On gold deposit is comparable to orogenic gold deposits.