平衡热液体系中硫同位素演化的几个图解

根据含硫矿物的同位素组成推断热液矿床成因是很有意义的。 1968年首先由H.Sakai指出热液的温度和pH值可以影响硫化物的同位素组成。接着,1972年H.Ohmoto以及1979年他和R.O.Rye系统讨论了平衡条件下热液的物理化学条件对硫同位素分馏的影响,建立了高温热液系统和低温热液系统的热液流体以及含硫矿物与热液成分和物理化学条件(温度、压力、氧逸度和酸碱度等)之间的数学表达式。

SEVERAL DIAGRAMS OF SULFUR ISOTOPE EVOLUTION IN EQUILIBRIUM WITH HYDROTHERMAL SYSTEM

According to Ohmoto’s theory regarding the evolution of sulfur isotope in equilibrium with hydrothermal system, the high and low temperature lgfo₂-T diagrams of △_i-f as well as the low temperature lgfo₂-pH diagrams of △_H2S-f are computed and constructed. The following diagrams have been prepared in this paper.(1)lgfo₂-T diagrams of sulfur isotopic fractionation between SO2, H₂S, pyrite or su-Ifates and hydrothermal fluid in the high temperature system(400-800℃)in the condition of Pf =500, 800 and 1,000bar;(2)lgfo₂-T diagrams of sulfur isotopic fractionation between H₂S, HS^-, S^2-, pyrite or sulfates and hydrothermal fluid in the low temperature system(150-350℃)in the conditions of pH=neutral value and I=1.0, 2.0 and3.0; and.(3)lgfo₂-pH diagrams of sulfur isotopic fractionation between H₂S and hydrothermal fluid at T=150, 200, 250, 300 and 350℃ and I=1.0, 2.0 and 3.0.Some new data of chemical reaction equilibrium constants and individual ion activity coefficients of sulfur species are adopted in this paper.