云南省太平铅锌矿床地质地球化学特征与成矿机制

发布时间：2018-04-04 04:06

  本文选题：元古界基底地层　切入点：成因矿物学　出处：《中国地质大学(北京)》2016年博士论文

【摘要】：太平铅锌矿床是川滇黔Cu-Au-Pb-Zn-Ag多金属成矿带中的一个典型铅锌矿床,以矿体产于元古界基底地层,且发育有中元古代火山岩为特征。目前对该类型铅锌矿床的研究基础相对薄弱。本文通过对太平铅锌矿床及区域内的中-基性火山岩开展矿物学、岩石学、矿床学的综合研究,探讨了元古界中铅锌矿床的成岩、成矿动力学背景,分析了矿床成因与成矿机制,初步建立了成矿模式并总结其控矿因素与找矿标志。中元古界通安组四段中粗安岩形成年龄约为1470Ma,限定了该地层形成时代下限。元素地球化学特征表明,粗安岩与区域内的左所(~1596Ma)及河尾(~1688Ma)基性岩均为岩浆结晶分离的产物且形成于陆内裂谷构造背景。太平铅锌矿床矿体产于中元古界通安组(Pt2t)中,受北东向张性断裂控制。围岩蚀变主要为硅化、碳酸盐化。热液成矿期可大致划分为硫化物-石英-白云石(Ⅰ阶段)、多金属硫化物-自然金-白云石-石英(Ⅱ阶段)、少量硫化物-方解石(Ⅲ阶段)。成因矿物学研究表明,太平铅锌矿床中闪锌矿Fe含量为0.86%~4.42%,Mn含量仅为44.3ppm~51.6ppm;Zn/Cd比值介于305.77~338.47之间,Ga/In比值远大于1,黄铁矿亏S亏Fe,毒砂富S亏As,表现为层控或沉积-改造型矿床特征。区内黄铁矿-闪锌矿-黄铜矿-辉砷镍矿-方铅矿矿物序列及其化学成分标型指示矿床形成于中低温-中浅成,其矿物组合类似于Viburnum Trend MVT型铅锌矿床。成矿流体以低温(112.6~188.7℃),中盐度(10.61%~19.68%NaCl),中-低压力(32.909~49.889MPa)为特征,成分以Na+、Ca2+、Mg2+、Cl-为主。成矿流体来自于地层中建造水,运移过程中有大气降水的加入。碳主要来源于海相沉积碳酸盐岩的溶解作用,硫(δ34S为10.4‰~12.3‰)主要来源于地层中海相硫酸盐。铅同位素表现为正常铅特征,指示来源于基底地层并受变质作用影响。粗安岩87Sr/86Sr值为0.77~0.87,指示混染了壳源物质;闪锌矿中(87Sr/86Sr)i(t=714Ma)=0.72064~0.72135,指示成矿物质主要来源于基底地层。Zn、Pb、Cu、Ag、As、Co、Ni等成矿元素的富集主要伴随着碳酸盐化和硅化。通过闪锌矿Rb-Sr同位素测年(714±11Ma)获得川滇地区铅锌矿床新的成矿年龄,暗示基底地层中铅锌矿床可能为新元古代成矿,进一步表明澄江期也是区内值得重视的Cu、Zn、Pb多金属成矿期。初步总结了同类型铅锌矿床的综合找矿标志主要包括南北向和北东向断裂、中元古界浅变质岩系、化探异常及硅化、碳酸盐化等围岩蚀变。
[Abstract]:Taiping Pb-Zn deposit is a typical Pb-Zn deposit in the Cu-Au-Pb-Zn-Ag polymetallic metallogenic belt of Sichuan, Yunnan and Guizhou. It is characterized by the occurrence of orebody in the Proterozoic basement strata and the development of Mesoproterozoic volcanic rocks.At present, the research foundation of this type of lead-zinc deposit is relatively weak.Based on the comprehensive study of mineralogy, petrology and mineralogy of the Taiping lead-zinc deposit and the intermediate-basic volcanic rocks in the region, the diagenetic and metallogenic dynamic background of the Proterozoic lead-zinc deposit has been discussed in this paper.The genesis and metallogenic mechanism of the deposit are analyzed and the metallogenic model is preliminarily established and the ore-controlling factors and ore-prospecting indicators are summarized.The age of formation of middle trachyandite in the fourth member of Tongan formation of Middle Proterozoic is about 1470 Ma, which limits the lower limit of formation age.The elemental geochemical characteristics indicate that the basic rocks of the trachyandesand the Zaosuoxiao 1596 Maand the Heweiguanzhang 1688 Maare are the product of magmatic crystallization and formed in the tectonic setting of the intracontinental rift valley.The Taiping Pb-Zn deposit occurs in the Tongan formation of the Middle Proterozoic and is controlled by the NNE extensional fault.The main alteration of surrounding rock is silicification and carbonization.The hydrothermal metallogenic period can be roughly divided into sulfide-quartz-dolomite (stage 鈪，

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