【作者】 涂伟；

【导师】 杜杨松；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2014， 博士

【摘要】 矽卡岩型金矿的成矿作用是近年来矿床学界的研究热点之一。长江中下游地区是我国最重要的金（铜）矽卡岩型矿成矿带。安徽铜陵朝山金矿是该成矿带一典型的矽卡岩型金矿，该矿床矿体埋藏浅、矿石品位高、成矿过程复杂，具有很高的研究价值。笔者在前人研究的基础上，对该矿床的成矿母岩、变质岩、蚀变岩以及矿石开展岩相学、矿物学和地球化学等方面的研究，试图从以上几方面的特征中挖掘该矿床的成因信息。通过本论文的工作，获得了以下主要认识。首先，该矿床的成矿母岩——白芒山辉石闪长岩属于高钾、准铝质的岩浆岩，它形成于碰撞后的构造环境，其母岩浆是来自富集岩石圈地幔的碱性玄武质岩浆，通过底侵作用在下地壳形成深部岩浆房，并与下地壳物质发生同化混染作用，角闪石和辉石斑晶也是在这个深部岩浆房中结晶的。白芒山辉石闪长岩含有较多的磁铁矿，属于氧化型的岩体。再者，朝山金矿形成过程中主要经历了接触热变质阶段、干矽卡岩阶段、湿矽卡岩阶段、石英硫化物阶段、碳酸盐硫化物阶段、硫酸盐阶段以及表生氧化阶段。接触热变质阶段有反应矽卡岩形成。干矽卡岩阶段形成的矿物主要是石榴石，其次是单斜辉石、方柱石、硅灰石。退化蚀变阶段（从湿矽卡岩阶段到硫酸盐阶段）形成的主要矿物有绿帘石、阳起石、符山石、绿泥石、石英、方解石、绢云母、金云母。金成矿和退化蚀变阶段关系密切，尤其是石英硫化物阶段和碳酸盐硫化物阶段。在干矽卡岩中石榴石的含量明显多于单斜辉石，而且石榴石核部多贫铁，但常见富铁的石榴石增生边，单斜辉石铁含量很低。这些特征都表明朝山金矿为氧化型的矽卡岩型金矿。蚀变带矿物组合、矿物成分以及全岩地球化学特征及变化规律表明热液蚀变系统中的硅、铝、铁、镁、钠、钾、水主要来自岩浆而钙主要来自碳酸盐地层。稳定同位素特征表明成矿流体中的水和碳主要来自岩浆而硫则来自于岩浆和膏盐层。另外，成矿流体从早到晚经历了从相对酸性和还原到相对碱性和氧化的转变，这种转变有利于金的沉淀，流体的沸腾可能是导致这种转变的原因之一。金在成矿流体中主要以含硫络合物的形式运移，金的成矿主要发生在相对低温的条件下。更多还原

【Abstract】 The ore-forming processes of gold skarn deposits have been one of the hottest topics in thefield of economic geology. The middle and lower Yangtze River Valley is the most importantmetallogenic belt of gold (copper) skarn deposits in China. The Chaoshan deposit is a typicalgold skarn deposit of this belt. The orebodies of this deposit have been buried in shallow depthand the ores generally have high grades. Because the ore-forming process was relativelycomplex, this deposit is of great value for genetic research. On the basis of the formerresearchers, the author has carried out petrographic, mineralogical and geochemical research onthis deposit. The following achievements have been obtained in this dissertation.The Baimangshan pyroxene diorite, which is the mother rock of the Chaoshan deposit,belongs to high-K and metaluminous igneous rocks and was formed in a postcollisional tectonicenviroment. The mother magma of the Baimangshan pyroxene diorite was alkalic basalticmagma which came from enriched lithospheric mantle. This magma underplated into the lowercrust, which resulted in the material exchange between the magma and the lower crust as well asthe formation of a magma chamber in that depth. Amphibole and clinopyroxene phenocrystswere formed just in this magma chamber. There is a lot of magnetite in the Baimangshanproxene diorite, which means that it is a oxidized pluton.There are seven main mineralization stages, which are contact thermal metamorphism stage,dry skarn stage, wet skarn stage, quartz-sulfide stage, carbonate-sulfide stage, sulfate stage andsupergene oxidization stage, in the formation of the Chaoshan deposit. Reaction skarns wereformed in the contact thermal metamorphism stage. The main mineral formed in the dry skarnstage is garnet, which is accompanied by minor diopside, scapolite and wollastonite. The mainminerals formed in the retrograde alteration stages (from wet skarn stage to sulfate stage) areepidote, actinolite, vesuvianite, chlorite, quartz, calcite, sericite and phlogopite. Goldmineralization had a close relationship with retrograde alteration, especially quartz and calcite.There are more garnet than clinopyroxene in dry skarns. The garnet cores generally have lowiron contents but the garnet rims generally have high iron contents. Clinopyroxene generally hasvery low iron contents. These characteristics all indicate that the Chaoshan deposit is an oxidizedgold skarn deposit.The characteristics and variations of mineral associations, mineral chemistry and whole rock chemistry in the alteration zone indicate that Si, Al, Fe, Mg, Na and K were mainly from themagma and Ca was mainly from the the carbonate in the strata. Stable isotope contents of theores of the Chaoshan deposit indicate that carbon and water of the ore-forming fluid was mainlyfrom the magma and sulfur was from the magma and anhydrock in the strata.The ore-forming fluid of the Chaoshan deposit changed from relatively acidic and reducedto relatively alkalic and oxidized. This change, which was caused partly by the boiling of thefluid, benefited the deposition of gold. Gold was carried in the form of sulfur complex in thefluid and was deposited at relatively low temperatures.更多还原