新疆霍什布拉克铅锌矿床微量元素地球化学

Trace element geochemistry of the Huoshibulake zinc-lead deposit, Xinjiang

霍什布拉克铅锌矿床是新疆西南天山地区晚古生代碳酸盐岩容矿的重要矿床。本文采用高精度电感耦合等离子质谱(ICP-MS)对主要矿石矿物(黄铁矿、方铅矿、闪锌矿)和热液脉石矿物方解石进行了微量元素地球化学研究。研究表明,黄铁矿、方铅矿、闪锌矿、方解石具有较为相似的稀土元素特征,Eu正异常明显,弱负或弱正Ce异常指示成矿流体最初由相对氧化的条件演化为还原条件。与霍什布拉克岩体、容矿围岩的稀土元素组成进行对比后发现,硫化物及热液方解石稀土元素配分曲线部分与重结晶泥晶灰岩重合,结合前人同位素地球化学研究,认为容矿坦盖塔尔组碳酸盐岩为成矿提供了必要的成矿物质及成矿流体组分。Ga/In值显示闪锌矿为低温成矿;硫化物明显富集LREE,Hf/Sm、Nb/La和Th/La值小于1,显示铅锌成矿过程中成矿流体主体以富Cl为特征;Y/Ho、Zr/Hf和Nb/Ta值变化范围相对较小,表明成矿期流体性质相对较为稳定,基本未混入外来流体。

The Huoshibulake deposit,hosted in the late Paleozoic carbonate rocks,is an important Zn-Pb deposit in southwestern Tianshan Mountains,Xinjiang.The trace elements of main ore minerals （pyrite,galena and sphalerite） and hydrothermal calcite were analyzed by ICP-MS in this study.The results show that pyrite,galena,sphalerite and calcite have similar REE characteristics,positive Eu anomalies and faint Ce anomalies,indicating that the ore-forming fluids evolved from a relatively oxidizing environment to a reduction environment.The authors compared the REE patterns of sulfides,calcite,Huoshibulake granite and ore-bearing wall rocks,and found that they are partly coincident with recrystallized micritic limestone.In combination with previous researches on isotope geochemistry,the authors have reached the conclusion that the Tangaitaer carbonate supplied essential metallogenic materials and ore-forming fluids.The Ga/In ratios indicate that the ore-forming temperature was low.Sulfides have light REE enrichment characteristics,with the Th/La and Nb/La ratios less than 1,suggesting Cl-richness of the ore-forming fluids.Ratios of Y/Ho,Zr/Hf and Nb/Ta varying in narrow ranges indicate that the source of the ore-forming fluid at the main metallogenic stage was simple and stable,with no addition of other fluids.