Fluid-inclusion. O-and S-isotope Study of Selected Barite and Enargite Samples from Chinkuashih Cu-Au Deposit

摘要

The Chinkuashih copper-gold deposit, North Taiwan, is the product of a Pleistocene hydrothermal system. We report here our studies of fluid inclusions microthermometry and O-and S-isotope composition of some barite samples of the deposit. The ranges of homogenization temperature and salinity of the fluid inclusions in the barite samples are from 160 to 270°C and 11 to 29per thousand wt. NaCl eq., respectively, while δ~(18)O_(smow) and δ~(34)S~(CDT) values of the samples range from + 8.2 to + 11.3 per thousand and + 24.8 to + 31.4 per thousand, respectively. δ~(18)O_(smow) values of water in isotopic equilibrium with these barites are estimated to range from + 2.6 to + 7.4 per thousand. We therefore conclude that the hydrothermal fluid is likely derived from seawater, that the salinity of the fluid generally decreases during evolution of water / rock interaction and that water/rock ratio of the system is moderate.