川滇黔地区铅锌矿床稳定同位素地球化学研究现状综合分析

A comprehensive analysis of present situation of geochemical researches on stable isotopes of lead-zinc deposits in Sichuan-Yunnan-Guizhou area

川滇黔接壤区是中国重要的铅锌多金属成矿区,目前已经发现了会泽、天宝山、大梁子等超大型-大型铅锌矿床。文章通过系统总结分析区域内铅锌矿床稳定同位素(C、H、O、S同位素)数据,结合区域构造控矿特征,表明成矿热液的碳、氧主要来源于碳酸盐岩围岩,个别矿床可能有有机碳或幔源碳参与成矿作用。黔西北地区从靠SE侧威宁-水城构造带上的铅锌矿床至NW侧垭都-蟒硐构造带上的铅锌矿床,方解石的δ^(13)CV-PDB值从0.6‰~2.5‰转变为-5.3‰~1.5‰,δ18OV-SMOW值从23.3‰~25.5‰转变为11.3‰~20.9‰,均显示出逐渐变小的趋势;SN向小江断裂带内各矿床表现出线性关系,并且具有向δ^(13)CV-PDB、δ^(18)OV-SMOW都亏损的方向偏移趋势,NE向断裂带内的各矿床C、O同位素则表现为集中一致的分布特征。H、O同位素显示成矿流体具有建造水(热卤水和油田卤水)特征,部分可能有大气降水、变质水和岩浆水参与成矿作用。矿床硫源主要为同时代海水硫酸盐的热化学还原(TRS)形成的还原硫,个别矿床细菌还原硫酸盐(BSR)形成的富含轻硫的油气藏中的H2S可能为成矿过程提供了部分硫来源。黔西北地区铅锌矿床S同位素组成具有从SE侧至NW侧向轻硫方向偏移的趋势,SN向小江断裂带内铅锌矿床S同位素组成较为集中一致,NE方向断裂带内铅锌矿床S同位素则具有从SW侧至NE侧向轻硫方向偏移的趋势,TSR的反应强度和反应速率降低可能是导致向轻硫方向偏移的重要原因之一。

The Sichuan-Yunnan-Guizhou border area is an important lead-zinc polymetallic mineralization area in China.Many superlarge and large lead-zinc deposits such as Huize,Tianbaoshan and Daliangzi have been found.It is considered that the C-O isotopes of lead-zinc deposits in the area indicate that the metallogenic hydrothermal fluids were mainly from the carbonate host rock,and some may came from organic carbon or mantle carbon.The δ-（13）CV-PDB and δ-（18）OV-SMOWvalues of the calcite of lead-zinc deposits in Weining-Shuicheng fault zones are 0.6‰ - 2.5‰ and23.3‰ - 25.5‰,the δ-（13）CV-PDBand δ-（18）OV-SMOWvalues of lead-zinc deposits in Yadu-Mangdong fault zone are-5.3‰ - 1.5‰ and 11.3‰ - 20.9‰,the δ-（13）CV-PDBand δ-（18）OV-SMOWvalues tend to decrease from southeast to northwest; the δ-（13）CV-PDBand δ-（18）OV-SMOWvalues of lead-zinc deposits in NS-trending Xiaojiang fault zone show a linear relationship,and tend to decrease.The δ-（13）CV-PDBand δ-（18）OV-SMOWvalues of lead-zinc deposits in NE-trending fault zones show the characteristics of concentrated consistent distribution.The δD and δ-（18）O_（H_2O） values show that oreforming fluids were mainly the formation water（ hot brine and oil field brine）.Part of meteoric water and metamorphic water might have taken part in the ore deposition process.Sulfur sources of ore deposits were mainly from Thermochemical Sulfate Reduction（ TSR） of contemporary seawater,whereas H_2S of reservoir from Bacterial Sulfate Reduction（ BSR） which had a rich light-sulfur and might have provided part of the sulfur source for the oreforming process.The lead-{ inc deposits in northwest Guizhou area tend to evolve toward light sulfur from southeast to northwest.The lead-zinc deposits in the NE-trending Xiaojiang fault zone were concentrated,but the sulfur isotope of the lead-zinc deposits in the NE-trending fault zones from SW to NE tends to evolve toward light sulfur,The reaction intensity and reaction rate of TSR may be one of the main reasons for the tendency to evolve toward light sulfur.