【作者】 王玉婷；

【导师】 何明友；

【作者基本信息】 成都理工大学 ， 地球化学， 2011， 博士

【摘要】 四川石棉大水沟碲矿床位于扬子地台西缘槽台结合部，松潘-甘孜造山带东缘，龙门山-大雪山-锦屏山的推覆构造中段。区域构造活动强烈，形成有西油房、宾多两条滑脱-推覆韧性剪切带以及蟹螺岩片带、大水沟岩片带和洪坝岩片带。岩浆作用强烈，火成岩发育，出露有晋宁期花岗岩、石英闪长岩。印支、燕山－喜山期的花岗岩、二长花岗岩、闪长岩、石英闪长岩，以及规模较小的海西期基性岩、超基性岩脉等。碲矿床主要产出于中、下三叠世块状粗-中晶白云质大理岩、含炭泥质白云质大理岩夹钙质变基性火山岩中。矿区内热液活动强烈，围岩蚀变发育，主要有白云石化、次为钠长石化、角闪石-黑云母-绿泥石化、绢云母/白云母化、硅化、黄铁矿化。最重要的矿物共生组合为：白云石-方解石-磁黄铁矿-黄铁矿-石英-绢云母-辉碲铋矿、楚碲铋矿、辉铋矿、碲铋矿、自然碲等。本文在研究区域地质构造背景、矿床地质地球化学特征基础上，系统研究了碲矿床成矿的源→运→聚地球化学过程。研究内容包括：成矿物质来源；成矿流体的物理化学热力学条件；碲元素的迁移形式；碲元素沉淀富集的地球化学机理。并探讨了碲矿床成矿模式。通过以上研究，得出如下认识：（1）大水沟碲矿床区域地质构造背景十分复杂，既有区域性深大断裂的继承性活动，也有深部岩浆的多期次活动，还有十分重要的强烈的热事件作用。该矿床的形成与区域性深大断裂活动、深部岩浆的多期次活动、强烈热事件作用这三者的作用密切相关。（2）稀土元素配分模型为右倾型。碲矿床具有明显的Eu正异常、Ce负异常、轻稀土元素亏损和重稀土元素富集的特征。这与赋矿围岩的岩石具有轻稀土元素富集、重稀土元素亏损，以及Eu、Ce略显亏损的特点相反。同时，还对大水沟碲矿床花岗岩稀土元素、微量元素与其它地区产矿花岗岩的稀土元素、微量元素进行对比研究。结果表明，大水沟花岗岩具有深度亏损稀土元素铕（Eu）、贫微量元素U、Th，低Ba、Nb、Sr的特点。这预示碲矿床的形成与深部地质过程有关。（3）铅同位素证据证明，矿床铅具有壳幔混源的异常铅特征。矿床矿物、岩石和矿石铅的△β-△γ变化范围成因分类图投影结果也显示出矿床形成与岩浆活动作用密切相关。矿床硫同位素组成δ34S值几乎都为较小的正值，且变化范围较小。碲矿床成矿物质明显具有来源于壳幔物质的特点。CO₂的碳同位素组成也明显表现出岩浆来源碳特征。这些同位素证据一致证明，碲与矿化剂硫、碳很可能同源，均来自深部。（4）成矿流体不同阶段水的氢氧同位素组成的特点表明，原始或成矿早期流体具有岩浆水的氢氧同位素组成特征。成矿期流体则以岩浆水为主，但有大气降水混入。这表明成矿流体主要为深源流体，而非大气降水。（5）成矿热流体物理化学条件的地球化学热力学研究表明：成矿热流体为中低盐度、中低密度的流体；包裹体测温结果显示，碲矿床为中－高温热液矿床；成矿热流体性质，早期高温阶段为碱性流体，成矿期中温阶段为弱碱性流体，成矿晚期低温阶段为弱酸性流体。这表明碲的成矿过程是碱性降低，酸性增强的过程。氧化还原电位的变化则随着含矿热流体温度的降低，氧化还原电位逐渐增高，早期高温阶段氧化还原电位相对较低，成矿期中温阶段到成矿晚期低温阶段氧化还原电位相对增高。表明含矿热液过程是一个氧化还原电位增高的过程。同时表明，早期高温阶段成矿热流体的还原能力较强，但是氧化能力较弱，成矿期中温阶段到成矿晚期低温阶段氧化还原电位增高，说明热热流体的还原能力较弱，但是氧化能力较强。其次，氧逸度和硫逸度的变化，则表现为：随着热流体温度和压力的降低，氧逸度和硫逸度则不断降低。由此推测，碲矿床中的碲元素很可能是在相对还原的环境中迁移，而在相对氧化的环境中被还原。（6）成矿热流体中，碲元素主要以碲氯配合物、碲硫配合物和碲氢配合物三类形式迁移。随着成矿热流体物理化学条件的改变，碲氯配合物、碲硫配合物和碲氢配合物发生化学解析过程，碲被还原，沉淀富集成矿。更多还原

【Abstract】 Dashuigou tellurium deposit of Shimian, Sichuan province is located in the connecting part of Geosyncline and Western Yangtze platform, eastern Songpan-Garze orogenic belt and middle part of nappe structure of Mt. LongMen-Mt. DaXue-Mt. JingPing. Regional tectonic activities are very strong here. There are two nappe decollement ductile shear zones namely XiYoufang and Binduo and other slice belts such as crab and snail slice belt, Dashuigou slice belt and Hongba slice belt are formed. The magmatism is intensive. The igneous rock is grown. The exposed rocks include Jinningian granite and quartz diorite, Indosinian, Yanshanian-Xishanian granite, monzogranite, diorite, quartz diorite and small scaled Hercynian basic rock and ultrabasic rock dike. Tellurium deposits have occurred mainly in nubby coarse grained dolomitic marbles of the Middle and lower Triassic, belted carbon bearing muddy dolomitic marbles that contained calcareous metamorphic basic volcanic rocks. There are strong hydrothermal fluid activities in mining area. Wall rock alteration is developed. Dolmitization is the main trend followed by albitization, amphibole rock-biotite-chloritized alteration, sericitization or muscovitizatio, siliconization and pyritization. The most important mineral assemblages are dolomite-calcite-pyrrhotite-pyrite-quartz-sericite-daphyllite, Tsumoite, bismuthinite, tellurobismuthite, sylvan and so on.Based on the study of background of regional tectonics and geochemical characteristics of deposit, this paper systemically studies the geochemical process of origin, movement and assembles of ore forming of tellurium deposit. The study includes the origin of ore-forming material resources, The main research contents include:the source of deposit, physical; chemical and thermodynamic conditions of ore-forming fluid; migrating form of tellurium element and geochemical mechanism of precipitation preconcentration of tellurium element. And it discusses the metallogenic model of tellurium deposit. Through the above study, reached the following understanding:Firstly, the regional geologic tectonics of Dashuigou tellurium deposit is very complicated. There are not only successive activities of regional discordogenic fault but also activities of hypomagma in many times. There are still effects of very important and strong tectonic-thermal events. The formation of this deposit is closely tied with activities of regional discordogenic fault, activities of hypomagma in many times and strong tectonic-thermal events.Secondly, the lanthanon proportion model is right deviation. Tellurium deposit has obvious characteristics of positive Eu anomaly, negative Ce nomaly, light rare earth elements loss and heavy rare earth elements enrichment. It is contrary to the characteristics of host rock, namely light rare earth elements enrichment, heavy rare earth elements loss and slightly losses of Eu and Ce. Also Dashuigou Te deposit on granite REE, trace elements and other parts of granite mine production of rare earth elements, trace elements were compared. The results show that the loss of a large ditch with deep granite REE Eu (Eu), depleted trace elements U, Th, low Ba, Nb, Sr characteristics. It predicts that the forming of tellurium deposit is related with the deep geological process. It predicts that the forming of tellurium deposit is related with the deep geological process.Thirdly, the lead isotope evidences prove that ore-forming materials of tellurium deposit came obviously from the crust and mantle materials. Deposit minerals, rocks and ores of lead△β-βγ causes, map projection range also showed that the deposit formation is closely related with the magmatic activity. Sulfur isotopic composition of deposits δ34S value comes almost to a smaller and smaller range. Tellurium deposit forming material with obvious from the characteristics of crust and mantle. The carbon isotopic composition of CO2is also evident in the characteristics of the magma source of carbon. The isotopic evidence proves consistent, tellurium and sulfur mineralization agent, carbon is likely homologous, both from the deep.Fourthly, the features of hydrogen and oxygen isotopes composition of ore-forming fluids in different stages show that the fluid in the initial or early ore-forming stage has the characteristics of hydrogen and oxygen isotopes composition of magmatic water. The fluid in the stage of ore-forming is mainly composed of magmatic water. But there was wet precipitation mixed into it. It indicates that ore- forming fluid is mainly not wet precipitation but deep fluid.Fifthly, chemical and thermodynamic conditions of ore-forming fluid of Geochemistry and Thermodynamics show that ore-forming thermal fluid is middle-low salinity and density fluid. The results of temperature test of inclusions show that tellurium deposit is mesothermal or hyperthermal deposit. In the early hyperthermal stage, ore-forming thermal fluid was alkaline fluid. In the mesothermal stage of ore forming, it was alkalescence fluid. In the late stage of ore-forming, it was subacidity fluid. It shows that the ore forming of tellurium is a process of decreasing of alkalescence but increasing of acidity. Oxidation-reduction potential is gradually increasing with the lowering temperature of ore-bearing thermal fluid. In the early hyperthermal stage, oxidation-reduction potential is relatively low. It increases relatively in the middle and late hyperthermal stage. It indicates that the process of ore-bearing thermal fluid is a process that oxidation-reduction potential increasing. It also shows that the ability of deoxidization of ore-forming fluid is high in the early hyperthermal stage. Ansd its oxidation capacity is low. The increasing of oxidation-reduction potential in the middle and late hyperthermal stage shows that the capacity of deoxidization of thermal fluid is weak relatively. But its oxidation capacity is strong. Next, the changes of oxygen fugacity and sulfur fugacity are as follows:with the lowering of temperature and pressure of thermal fluid, the oxygen fugacity and sulfur fugacity are coming down. It can be deducted that the tellurium element in the deposit are likely to transport in the relative reduction environment and be reduced in relative oxidation environment.Sixthly, in the ore-forming thermal fluid, tellurium element transports in three forms includes tellurium-chlorine complex, tellurium-sulfur complex and tellurium-hydrogen complex. With the changing of chemical and thermodynamic conditions of ore-forming fluid, tellurium-chlorine complex, tellurium-sulfur complex and tellurium-hydrogen complex go through a chemical resolving process. Tellurium is deduced and concentrated into ores.更多还原