【作者】 郭晓东；

【导师】 侯增谦；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2009， 博士

【摘要】 马厂箐铜钼金矿床是“三江”成矿带上与喜马拉雅期富碱斑岩有关的典型矿床之一,产于大陆碰撞造环境。通过研究,查明了矿区岩浆演化序列、蚀变矿化分带规律、流体演化以及控矿因素,揭示了其成矿机理,提出了成矿模型,探讨了矿床的成矿潜力。建立了马厂箐矿区岩浆演化序列,初步将其分为三大岩浆组合,即斑状花岗岩+煌斑岩组合、正长斑岩+二长斑岩+花岗斑岩组合和碱性花岗斑岩+煌斑岩组合。初步查明,斑状花岗岩+煌斑岩组合形成于50Ma左右,构成含矿围岩;正长斑岩+二长斑岩+花岗斑岩组合形成于36Ma左右,成为主要含矿岩系;碱性花岗斑岩+煌斑岩组合侵入最晚,侵入时代32Ma左右。研究发现36Ma的岩浆组合中发育闪长质暗色微粒包体,并出现浸染状黄铁矿化和磁铁矿化,反映这套岩浆组合与铜钼金成矿有关,经历强烈的壳幔岩浆混合作用。通过构造控矿特征研究,确定岩体侵入过程中垂直应力作用形成的岩浆侵入接触构造样式是主要控岩控矿构造,岩体内构造裂隙控制内斑岩型Mo、Cu矿化,接触带构造控制接触交代型Cu、Mo、Au、Fe矿化,近接触带层间滑脱带控制破碎蚀变岩型和石英脉复合型Au、Ag、PbZn矿化,远接触带围岩地层中的引张裂隙带控制浅成低温热液型Au、Ag、PbZn、Sb矿化,反映出岩浆侵入接触构造体系控矿的特征。成矿元素存在以岩体为核心的水平分带;基于矿床地质特征、蚀变矿化类型、成矿元素组合、流体演化、同位素地球化学以及控矿构造等方面研究,提出马厂箐铜钼金矿床和金厂箐金矿属于同一个岩浆-构造-成矿系统产物,成矿作用在时空上紧密共生,蚀变矿化类型空间展布特征清晰地展示出含矿流体从岩浆体结晶分异出来并在向外运移过程中堆积相应金属元素图景,表明马厂箐矿集区成岩成矿作用受控于同一动力学系统。表现出随着热液成矿作用进行和矿化由斑岩体→接触带→近接触带→远接触带推进,从宝兴厂矿段→乱硐山矿段→人头箐-金厂箐矿段成矿温度、盐度和压力逐渐降低,成矿深度逐渐变浅的趋势;富碱岩体起源于壳幔过渡带或加厚下地壳,是一种大陆内部碰撞造山环境下形成的钾质埃达克岩。与成矿有关的正长斑岩+二长斑岩+花岗斑岩组合以脉状为主,其所能够提供成矿的物质、流体和动力条件有限,暗色微粒包体指示其快速的岩浆结晶过程,不利于形成大量有效的成矿流体。A脉、B脉和D脉在空间上相互重叠、分带性不明显以及矿化不强的特征,反映并不存在大规模流体出溶,北接触带存在铜钼金与铅锌矿化空间上重叠的现象也说明并没有大规模的成矿流体存在,这些因素可能制约矿床规模。更多还原

【Abstract】 The Machangqing porphyry-type Cu-Mo-(Au) deposit (or deposit cluster) forms in a continental orogeny and it is one of the typical deposits related to alkaline-rich porphyry of Himalaya epoch in the Sanjiang metallogenic belt. This paper reveals that magmatic evolutionary series, the regulation of alteration-mineralizing zonation, fluid evolution and ore-controlling factors, bringing forward some thoughts of ore -exploring further, and achieving anticipated purpose.Magmatic series mainly include following assemblages: porphyritic granite+ lamprophyre, (quartz) orthophyre (syenite)+(quartz)monzonite (ivernite)+granite porphyry and alkaline granite porphyry + lamprophyre. Among them, the assemblage of porphyritic granite+ lamprophyre intrusive age is 50 Ma±, which is the wall-rock of orebody; whereas the assemblage of (quartz) orthophyre (syenite)+ (quartz) monzonite (ivernite)+granite porphyry, its intrusive age is 36Ma±and some dark particulate enclaves of dioritoid with disseminated pyritization and magnetitization have been found in this assemblage, showing that the assemblage is the product of mixture of two kinds magma: crustal magma and mantle magma. Mantle magma provides the magmatic system with mineralizing elements such as Cu,Au,S, fluid and power. The combination of alkaline granite-porphyry+lamprophyre intrusive is at the latest, aged 32Ma.Studying the characteristics of ore-controlling structures, it is confirmed that intrusive-contact structures ascribing to vertical stress due to the force of magma intrusive during the magma intrusive is main rock- and ore-control structures.Porphyry-type Cu-Mo mineralization is controlled by the fissures intra-porphyry rockbody. The contact-metasomatism-type mineralization of Cu-Mo-Au-Fe is controlled by the contact structures. Interlayer decollement near the contact belt controls the compound mineralization of quartz-vein-type, fractured-alteration-type of Au,Ag, and Pb-Zn. Epithermal Au-Pb-Zn-Ag mineralization is controlled by tensile structures of the surrounding rock far from the contact belt, showing the characteristics of intrusion-contact structures. Mineralizing elements is zoned horizontally at the centre of rockbody.In terms of geological characteristics of the deposit, alteration-mineralization types and mineralizing element combination, fluid evolution, isotope geochemical and ore-controlling features, Machangqing Cu-Mo-(Au) deposit and Jinchangqing Au deposit are thought to be the products of the same magmatic-structural-mineralizing system, which is intimated with the mineralization spatially and temporally. By the spatial distribution of alteration-mineralization types, it is clear to image that the mineralizing fluid exsoluted from the crystalling magma and accumulated mineralizing elements in the course of move outward.It demonstrates that diagenetic-mineralization is controlled by the identical dynamic system in Machangqing deposit cluster. With the outwardness of mineralizing fluid exsolution from the crystalling magma and the physicochemical change of mineralizing conditions, it forms different mineralizing types in different boundary conditions. With the processes of ore-forming, mineralization took place from the intra-intrusive→near the contact→far away the contact, mineralizing temperatures, pressures and salinity are from high to low, the tendency of mineralizing depths is from deep to shallow.Alkaline-rich intrusion derives from the transition belt of crust-mantle or thickened lower crustal layer, and it is a kind of potassic adakite belonging to C-type adakite formed in intra-continental collisional belts. The rock combination of (quartz) orthophyre (syenite)+ (quartz) monzonite (ivernite)+granite porphyry is in the form of veins, which is limit to provide mineralizing materials, fluid and dynamic conditions. The superposition of A-,B- and D-veins spatially, unclear zonation, weak mineralization and overlapped Cu-Mo-Au and Pb-Zn mineralizations in north contact are combined to show no large-scale fluid exsolution. These factors may decide the size of deposit.更多还原