云南会泽铅锌矿床硫同位素问题探讨

Discussion on sulfur isotope of Huize Pb-Zn deposit in Yunnan,China

运用地球化学理论,剖析云南会泽铅锌矿床硫同位素相关认识,重新厘定硫同位素组成,探讨矿床硫源及成矿机理。认为确定矿床硫同位素组成时,样品必须为矿床主要硫化物且样点控制整个矿床。会泽铅锌矿床硫同位素特征为:方铅矿δ34 S=4.8‰～14.5‰,极差为9.7‰;闪锌矿δ34 S=6.9‰～16.0‰,极差为9.1‰。矿床下部硫化矿带的黄铁矿δ34 S=12.1‰～17.4‰,极差为5.3‰;总的δ34S=4.8‰～17.4‰,极差为12.6‰。成矿流体具自上而下流动特点,导致上部早期硫化物富轻硫,向下较晚晶出的硫化物δ34S随深度增加而增高;矿床硫源自容矿层的层间海水硫酸盐。成矿机理为地壳深部高温、贫硫、富金属(包括Fe2+)成矿流体沿导矿断裂上移,至容矿层后转而向下运移,与层间海水硫酸盐相遇并将其不断还原,持续成矿,最终形成超大型铅锌矿床。

By using the geochemical theory the authors of this paper analyzes the related recognition of the sulfur isotope of the Huize Ph-Zn deposit in Yunnan, determine the composition of the sulfur isotope and discuss the sulphur origin and mineralization mechanism of this deposit. After that, the authors indicate that the selected samples must be the main sulphides of this deposit and the distribution of samples must occupy the whole ore deposit when we determine the isotopic compositions of sulfur. The characteristics of sulphur isotope of the Huize Pb-Zn deposit are as follows.δ^34 S of galena is 4.8‰～14.5‰ and the sample limit error is 9.7‰. δ^34 S of sphalerite is 6.9‰～16.0‰ and the sample limit error is 9.1‰. 834 S of the pyrite in the lower part of the sulphide ore belt is 12.1‰～17.4‰, the sample limit error is 5.3‰, the total δ^34S is 4.8‰～17.4‰ and the sample limit error is 12.6‰. The ore-forming fluid flows downward so that the early sulfide in the upper part of the sulphide ore belt is rich in light sulfur, the δ^34 S of the sulfide of the late crystals increases with depth. The source of sulfur of this deposit is from seawater sulfate between the host strata. The metallogenic mechanism is as follows. After intruding upon the host strata, the ore-forming fluid with high temperature, depleted sulfur and rich metal （including Fe^2＋ ） from the deep earth＇s crust flows down along the host strata and meets the seawater sulfate and reduces the seawater sulfate constantly. Then, the mineralization occurs continuously and results in a super giant Pb-Zn deposit at last.