贵州纳雍枝铅锌矿床地质、地球化学及矿床成因

发布时间：2018-05-01 06:29

  本文选题：矿床地质 + 硫和铅同位素　； 参考：《地质学报》2017年06期

【摘要】：纳雍枝铅锌矿床位于扬子陆块西南缘,是黔西北地区五指山背斜内近年来取得勘查突破的大型铅锌矿床(1.30Mt),也是川滇黔矿集区贵州境内目前发现的最大规模的铅锌矿床。矿体受层位和构造控制明显,呈似层状、脉状及透镜状产于五指山背斜南东翼穿层和顺层构造带内,赋矿围岩为下寒武统清虚洞组和上震旦统灯影组白云岩。无论是缓倾斜的似层状矿体,还是陡倾斜的脉状矿体,矿石中普遍发育角砾状、脉状、网脉状和浸染状构造,金属矿物主要为闪锌矿,次为方铅矿和黄铁矿,脉石矿物以白云石、方解石为主,次为石英和重晶石。研究结果显示,该矿床硫化物δ~(34)SV-CDT值变化范围较宽,介于4.7‰~22.8‰之间,平均16.68‰,多数集中在18‰~22.5‰之间,远高于赋矿白云岩的δ~(34)S_(V-CDT)值(7.3‰)。硫化物总体呈现δ~(34)S_(闪锌矿)δ~(34)S_(方铅矿)δ~(34)S_(黄铁矿),暗示S同位素分馏未达到平衡,成矿流体的δ~(34)S_(∑S)值应高于硫化物的平均δ~(34)S值(16.68‰)。因此,成矿流体中的硫主要来源于赋矿海相碳酸盐岩中的蒸发膏岩,是蒸发硫酸盐矿物热化学还原(TSR)作用的产物。硫化物具有正常Pb的组成特征,~(206)Pb/~(204)Pb、~(207)Pb/~(204)Pb及~(208)Pb/~(204)Pb变化范围分别为17.8240~17.9701、15.6364~15.7651和37.8956~38.3230,与赋矿白云岩Pb同位素组成略有不同,但壳源特征明显,很可能来源于区域基底岩石。综上认为,纳雍枝铅锌矿床兼具层控和断控成矿特征,成矿物质主要由壳源岩石提供,硫化物沉淀受控于富金属流体与富还原硫流体的混合作用,其形成是区域构造与大规模成矿流体耦合作用的结果,属于MVT矿床。
[Abstract]:Nayongzhi Pb-Zn deposit is located in the southwest margin of Yangzi block. It is a large Pb-Zn deposit in Wuzhishan anticline, northwest of Guizhou, which has made a breakthrough in recent years. It is also the largest Pb-Zn deposit found in Sichuan and Guizhou. The orebody is obviously controlled by strata and tectonics. It is stratiform, vein-like and lenticular, and occurs in the southeastern wing of Wuzhishan anticline and the bedding structural belt. The ore-bearing surrounding rock is dolomite of the lower Cambrian Qingxuidong formation and the Dengying formation of the Upper Sinian. Breccia, vein, net vein and disseminated structure are generally developed in ore, whether it is a gently inclined stratiform orebody or a steeply inclined vein orebody. The main metallic minerals are sphalerite, followed by galena and pyrite. The gangue minerals are dolomite, calcite, quartz and barite. The results show that there is a wide range of SV-CDT values of sulphides in the deposit, ranging from 4.7 鈥，

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