云南会泽超大型铅锌矿田热液白云岩的成因及地质意义  

The Origin of Hydrothermal Dolomite in the Huize Giant Pb-Zn Ore-field in the Yunnan Province and its Geological Implications

作　　者：崔广申 包志伟[1,3] 李群 CUI Guangshen;BAO Zhiwei;LI Qun(Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China)

机构地区：[1]中国科学院,广州地球化学研究所,矿物学与成矿学重点实验室,广东广州510640 [2]中国科学院大学地球与行星科学学院,北京100049 [3]中国科学院深地科学卓越创新中心,广东广州510640

出　　处：《大地构造与成矿学》2023年第2期361-375,共15页Geotectonica et Metallogenia

基　　金：国家自然科学基金面上项目(41972078、41672075)资助。

摘　　要：川滇黔铅锌矿集区会泽超大型铅锌矿田赋矿地层石炭系摆佐组碳酸盐岩广泛发育热液白云岩化。本文通过岩相学、主量和微量元素分析讨论了热液白云岩的成因、成矿流体来源及演化。热液白云岩包括热液流体交代早期微‒细晶白云岩形成的细‒中晶白云岩和交代灰岩形成的粗晶白云岩。细‒中晶白云岩中的部分白云石在阴极发光下显示核边和环带结构特征,与早期成岩阶段形成的微‒细晶白云岩具有相似的稀土元素含量和分布模式,继承了原岩稀土元素组成特征。粗晶白云岩呈厚层状和团块状产出,ΣREE含量相对较低,并且相对亏损轻稀土,表明稀土元素主要源于灰岩,热液流体(盆地卤水)活化迁移了部分轻稀土元素。近矿粗晶白云岩受MVT铅锌成矿流体交代,具有较高的Fe和Mn含量,白云石在阴极发光下呈亮红色,可能为矿化过程中与盆地流体有关的粗晶白云岩溶解再沉淀的产物。脉石方解石的Fe、Mn、ΣREE和Y含量相对较高,并显示轻‒中稀土元素富集、Ce异常不显著的特征,暗示成矿流体(深循环酸性卤水)可能萃取了基底岩石中的稀土元素和成矿金属。脉石方解石的Y/Ho值与近矿粗晶白云岩相似,指示成矿流体与碳酸盐岩围岩也发生了反应。结合前人的研究,我们认为热液白云岩化与铅锌矿化为盆地流体和深循环含矿热液连续作用的产物,热液白云岩化贯穿MVT铅锌矿成矿前及成矿阶段。因此,热液白云岩可以作为MVT矿床找矿勘查的重要线索。Hydrothermal dolomitization was pervasively developed in the Lower Carboniferous Baizuo Formation,which is the major ore-bearing strata of the Huize giant lead-zinc ore deposit in the Sichuan-Yunnan-Guizhou lead-zinc ore province.Based on detailed petrographic observation and major and trace element analyses,the paragenetic sequence is delineated and the origin and evolution of hydrothermal dolomitizing fluid and ore-forming fluid as well are discussed.There are two types of hydrothermal dolomite,including fine-to medium-grained dolomite and coarsely crystalline dolomite.Fine-to medium-grained dolomite shows dull to dark red luminescent zones and core-rim structures under cathodoluminescence and has total rare earth element(REE)contents and patterns similar to those of the micritic and fine crystalline dolomite formed in the early burial stage,which suggests the fine-to medium-grained dolomite inherited the REE signatures of the parent rock.The coarsely crystalline dolomite occurs in massive and crumby shapes.It has total REE contents lower than that of the limestone and shows light REE depletion,which indicates the limestone was leached by the hydrothermal dolomitizing fluid(basin brine),and the REEs in the dolomite were likely derived from the limestone.The coarsely crystalline dolomite near the ore shows bright red luminescence under cathodoluminescence and has higher Fe and Mn contents,indicating the interaction between ore-forming fluid and the coarsely crystalline dolomite might have promoted the precipitation of the sulfides.Gangue calcite is enriched in Fe,Mn,REE,and Y and shows light and middle REE enrichment without Ce anomaly,implying ore-forming fluid was deep-derived acid brine that extracted the REEs and ore metals in the basement rocks.The hydrothermal coarsely crystalline dolomite near the ore and gangue calcite have similar Y/Ho values,suggestive of precipitation from a common hydrothermal fluid system albeit during different stages.This study emphasizes that the hydrothermal dolomitization occur

关 键 词：会泽铅锌矿田 热液白云岩 稀土元素 Y/Ho值 找矿线索 

分 类 号：P612[天文地球—矿床学] P595[天文地球—地质学]