Multi-episode fluid boiling in the Shizishan copper-gold deposit at Tongling, Anhui Province: its bearing on ore formation

The Shizishan copper-gold deposit at Tongling, Anhui Province consists of two magmato-hydrothermal mineralization types: the crypto-explosive breccia type and the skarn type. At least four episodes of boiling occurred to the ore-forming fluids in this deposit. The first episode took place in accompany with the formation of the crypto-explosive breccias. The melt-fluid inclusions giving temperatures above 600°C and salinities higher than 42% NaCl equiv represent a residual magma related to this episode. The second episode occurred during skarnization, giving fluid temperatures of 422°C–472°C, averaging 458°C, and salinities of 10.2%–45.1% NaCl equiv. The third episode corresponds to the main mineralization stage, i.e., the quartz-sulphide stage. Fluid temperatures of this episode vary in a range of 337°C–439°C with an average of 390°C, and salinities in a range of 3%–30% NaCl equiv. The forth episode happened at the waning stage of mineralization, giving fluid temperatures below 350°C with an average of 265°C and salinities of 2.1%–40.4% NaCl equiv.