【作者】 汪海；

【导师】 杨晓勇； 段留安；

【作者基本信息】 中国科学技术大学 ， 地质学， 2020， 硕士

【摘要】 安庆-贵池矿集区位于长江中下游成矿带,该区矿产资源丰富,发现了众多的铜金钼矿床。区内广泛发育燕山期岩浆岩,并与铜金等矿化密切相关。宝树尖铜多金属矿床作为区内新发现的矽卡岩型矿床,研究基础相对薄弱,尚未进行地球化学研究。马石铜矿床作为区内典型的斑岩型矿床,近年来在找矿方面有着较大突破,但其深部及外围仍具有很大的找矿潜力。本文以宝树尖铜多金属矿床和马石铜矿床为研究对象,进行全岩主微量元素分析、锆石LA-ICP-MS U-Pb定年、锆石Hf同位素组成分析、全岩Sr-Nd-Pb同位素分析和矿石硫化物硫同位素组成分析,探讨岩石成因及矿床的形成机制,并为寻找类似矿床提供指导性意见。两个矿区的含矿岩体属于高钾钙碱性、钙碱性系列,具有高Sr/Y、(La/Yb)N比值以及低Y、Yb含量。从地球化学特征上来看,两个矿区的侵入岩属于埃达克质岩和岛弧岩浆岩。马石含矿岩体显示出不同于宝树尖含矿岩体的Eu负异常,可能是埃达克质岩浆与亏损的新元古代下地壳混染的结果。锆石U-Pb年代学研究表明,宝树尖成矿相关岩体形成于148.6±3.2Ma,马石成矿相关岩体形成145.2±2.4Ma,是长江中下游燕山早期岩浆活动的产物。继承锆石的U-Pb年龄暗示古老地壳物质曾参与岩石的形成。全岩Sr-Nd-Pb同位素和锆石Hf同位素组成显示,岩石起源于俯冲洋壳及上其覆沉积物的部分熔融。矿石硫化物硫同位素特征则说明了成矿物质不止来源岩浆,还有部分来源地层。锆石Eu异常特征和Ce4+/Ce3+比值表明形成岩石的岩浆具有高氧逸度,这有利于Cu、Au、Zn等成矿物质的迁移。结合区域地质背景,本文认为两个矿床的大致形成过程为:在中生代时期,古太平洋板块向西俯冲到安庆-贵池矿集区的大陆岩石圈之下,形成富集地幔。大约在145Ma时候,残留洋壳部分熔融产生的熔体与富集地幔产生的熔体混合产生埃达克质岩浆,岩浆到达地壳浅部形成含矿侵入岩,并为矿床的形成提供主要成矿物质。更多还原

【Abstract】 The Anqing-Guichi ore-cluster area is located in the Lower Yangtze river Metallogenic Belt,which is rich in mineral resources.Numerous Cu-Au-Mo deposits have been discovered.Yanshanian magmatic rocks are widely developed in this area and are closely related to copper-gold mineralization.As a newly discovered skarn-type deposit in the area,the Baoshujian copper polymetallic deposit had not been taken research before.As a typical porphyry deposit,great breakthroughs in ore prospecting have been made in the Mashi copper deposit,however its deep and peripheral areas still have great prospecting potential.In this paper,the Baoshujian copper polymetallic deposit and the Mashi copper deposit are used as objects.We carried out whole-rock major and trace elements,zircon U-Pb geochronology,whole-rock Sr-Nd-Pb isotopes,in-situ zircon Lu-Hf isotopes on intrusive rocks and the δ34S values in ore,to explore the genesis of rocks and the formation mechanism of the ore deposits.It will provide guidance for finding the similar deposits.Igneous rocks related to mineralization belong to the high-potassium calc-alkaline and calc-alkali series,with high Sr/Y,La/Yb ratios and low Y and Yb contents.The geochemical characteristics are shown as arc magmatic rocks and adakitic rocks.The rocks in Mashi show a different Eu negative anomaly than the Baoshujian,which may be the result of mixing of the adakitic magma and the depleted Neoproterozoic lower crust.Zircon U-Pb gechronological data show that the Baoshujian magmatic rocks were formed at ca.148.6 ±3.2Ma,and the Mashi magmatic rocks were formed at ca.145.2±2.4Ma,both of which are the early Yanshanian Magmatism in the Lower Yangtze River Metallogenic Belt.The ancient crustal materials were involved in the rock formation.The whole rock Sr-Nd-Pb isotopes and in-situ zircon Lu-Hf isotopes indicate that partial melting of the subducted oceanic slab and sediments was the first stage of the rock formation.The δ34S values in ore indicate the ore-forming materials are derived from magmatic hydrothermal fluids mixed with strata.The Eu anomaly characteristics and Ce4+/Ce3+ratios of zircon indicate that the magma forming rock had high oxygen fugacity,which was beneficial to the migration of ore-forming materials such as Cu,Au and Zn,and eventually form the deposit.Based on the regional geological background,we propose a model about the two deposits.During the Mesozoic,the ancient Pacific plate subducted beneath the continental lithosphere in Anqing-Guich ore-cluster area,forming an enriched mantle.At about 145Ma,the melt generated by the partial melting of the subducted oceanic slab and sediments was mixed with the melt generated from the enriched mantle,producing the adakitic magma.The magma reached the shallow crust,forming ore-bearing intrusive rocks,and providing the ore-forming materials for the deposit.更多还原