Stable Isotope and Geochemical Observations in the Kago Low-sulfidation Au/Ag Deposit, Southern Kyushu, Japan

The Kago low-sulfidation Au/Ag deposit was an extensively excavated mine, primarily in the Edo-period (1684), reaching as far as 1943. Au grades ranged from 4.1-13.3 g/t, while Ag ranges from 2.6-6.6 g/t. The higher grades of gold made this deposit more favourable to mine, in comparison to other operating mines such as Serigano towards the north. The deposit is located approximately 5 km from both the Kasuga and Iwato high-sulfidation deposits located towards the south. In this study, surficial quartz veins were measured for 18O in quartz and 34S in pyrite hosted in the veins. Where available, fluid inclusion microthermometry was carried out to establish the likely temperature of the mineralising fluids. Fluid 18O compositions were estimated using microthermometry results. Host rocks surrounding the veins were analysed for their alteration mineralogy. Within the Central Vein Group (CVT), veins typically exhibit low temperature argillic alteration grading out into a regional propylitic zone.