Two fluid systems in the Lanping basin, Yunnan, China — Their interaction and implications for mineralization
文摘
The Lanping basin in SW China is a Late Triassic to Eocene basin filled with terrestrial sediments. The basin is located between the Tibet–Yunnan and Yangtze plates, controlled by deep-seated faults, and contains a number of metallic deposits, including the world-class Jinding Zn–Pb deposit. Based on fluid inclusion and noble gases, Pb, and S isotope data, we proposes that there were two fluid systems operating in the basin: one was derived from the mantle, characterized by high CO2 content and relatively low salinities, and the other was from within the basin, having relatively high salinities and low temperature. The former was probably a major carrier of metals, whereas the latter provided reduced sulfur through reduction of sulfates. The formation of major base metal deposits requires geologic conditions that favor interaction of the two fluid systems, which lead to precipitation of sulfides in a localized volume.