ARE LEAD SULPHIDES AND ZINC SULPHIDES OF LEAD-ZINC ORE DEPOSITS PRECIPITATED FROM ACIDIC SOLUTIONS?A DISCUSSION ON THE ORE-FORMING FLUID OF HUIZE LEAD-ZINC ORE DEPOSIT,YUNNAN PROVINCE

Whether the fluid is acidic does not depend on whether its pH value is higher than 7,but depends on whether its pH value is higher than the pure water's pH value at its temperature.This paper studied the variation of pH value of ore-forming fluid with temperatures under the condition of equilibrium among minerals crystallized at different ore-forming stages in the Huize lead-zinc ore deposit. It is shown that the metallic minerals including metallic sulfides were precipitated from neutral to slightly alkalic solutions rather than from acidic solution.This conclusion differs from that of Zhou Chaoxian(1997) and Zhu Laimin et al.(1995).