会泽超大型铅锌矿床“矿石—接触带—围岩”白云石微区原位地球化学特征及其指示意义  

Geochemical characteristics of in-situ micro-analyzed dolomites in "ore-contact zone-wall rock" of the Huize super-large lead-zinc deposit and their indicative significances

作　　者：谭茂 吴鹏[1,2] 韩润生[1,2] 张艳[1,2] 黄智龙[3] 杨航 TAN Mao;WU Peng;HAN Run-sheng;ZHANG Yan;HUANG Zhi-long;YANG Hang(Faculty of Land Resources Engineering,Kunming University of Science and Technology,Kunming 650093,China;Southwest Institute of Geological Survey,Geological Survey Center for Non-ferrous Metals Resources,Kunming 650093,China;State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093 [2]有色金属矿产地质调查中心西南地质调查所,云南昆明650093 [3]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550081

出　　处：《矿物学报》2022年第3期315-328,共14页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(批准号:41102049);云南省矿产资源预测评价工程实验室(2010);云南省地质过程与矿产资源创新团队(2012)。

摘　　要：会泽铅锌矿床位于扬子地块西南缘,是川滇黔碳酸盐岩型铅锌成矿域规模最大的铅锌矿床。利用扫描电镜、电子探针和LA-ICP-MS原位分析技术,分别对“矿石-接触带-围岩”3个带中的白云石进行主量、微量元素对比分析。结果显示,矿石→接触带→围岩,白云石中的CaO和MgO含量逐渐升高而FeO和MnO含量逐渐降低。同时,Mn、Fe、Ga、Sr、In、Sn、V等微量元素含量依次降低,指示流体演化过程中与白云石发生水/岩相互作用,并且越靠近矿体,水/岩相互作用越强烈,流体中的Mn、Fe、Ga、Sr、In、Sn、V等元素替代白云石中的Ca^(2+)和Mg^(2+),迁入粗晶白云石中参与沉淀。矿石中的白云石Cu、Zn、Ag、Cd等成矿元素含量远高于接触带和围岩中的白云石,表明靠近矿体的白云岩发生强烈的水/岩相互作用,成矿元素迅速进入矿石中的白云石而富集。矿石→接触带→围岩中白云石的稀土元素含量逐渐升高,并且3个带中均表现出Eu、Ce负异常,异常程度逐渐减弱,与白云石CaO含量呈现规律一致,指示水/岩相互作用过程中,稀土元素随白云石中Ca含量的变化而变化。综合研究表明,成矿流体的相对演化方向为矿石→接触带→围岩,流体性质从碱性向中性、弱酸性演化,水/岩相互作用强度从矿石→接触带→围岩逐渐减弱,导致3个带中的白云石主量、微量和稀土元素呈现规律性变化,成为重要的找矿指示标志,白云石的主、微量元素不仅能反映矿床形成的物理化学条件,还可以反映水/岩相互作用过程。The Huize Pb-Zn deposit, located in the southwest margin of the Yangtze block, is the largest Pb-Zn deposit in the Sichuan-Yunnan-Guizhou carbonate-hosted Pb-Zn metallogenic domain. By using scanning electron microscope,electron probe and LA-ICP-MS in-situ analytical methods, the major and trace elements of dolomites in the three zones of "ore-contact zone-wall rock" have been comparatively analyzed. The results show that the contents of CaO and MgO of dolomites in respective zones varying from the ore to contact zone and then to wall rocks increased gradually, while their contents of FeO and MnO decreased gradually. Similarly, their contents of trace elements such as Mn, Fe, Ga, Sr, In, Sn,and V subsequently decreased. These indicate that the water-rock interaction occurred between fluid and dolomite in the process of fluid evolution, and the closer to ore body, the stronger the water-rock interaction in form of substitution of Ca^(2+)and Mg^(2+) in original dolomite by ions of trace elements including Mn, Fe, Ga, Sr, In, Sn, and V in the fluid, to have formed the coarse-grained dolomites for precipitation in zones close to the orebody. The contents of Cu, Zn, Ag, Cd and other ore-forming elements in dolomites of ores are much higher than those in dolomites of the contact zone and wall rock,indicating that dolomites near to the ore body were strongly interacted by the hydrothermal fluid, resulting in the enrichment of ore-forming elements in the interacted dolomite in ores due to the quick ion substitution of Ca and Mg by ore-forming elements. The REE contents of dolomites in various zones varying from the ore to contact zone, then to wall rock are gradually increased, with all negative anomalies of Eu and Ce, and their anomaly degrees are gradually weakened.These are consistent with the variation of CaO contents of dolomites. Thus, it is indicated that the REE contents of dolomites are correspondingly changed with the change of Ca contents in dolomites in the process of water/rock interaction. The comprehensive

关 键 词：白云石 电子探针 LA-ICP-MS原位微量 会泽铅锌矿床 

分 类 号：P574[天文地球—矿物学] P595[天文地球—地质学]