【作者】 陆三明；

【导师】 徐晓春；

【作者基本信息】 合肥工业大学 ， 矿物学、岩石学、矿床学， 2007， 博士

【摘要】 铜陵狮子山矿田是长江中下游成矿带内具有代表性和典型性的大型铜、金矿田。矿田内构造活动、岩浆作用及成矿作用复杂。大地构造演化经历了活动（基底形成阶段）-稳定（盖层）-再活动（板内变形）三个发展演化阶段。尤其是中三叠世以后，板内变形阶段引发大规模的中酸性岩浆侵入活动，形成了与中酸性岩浆侵入有关的所谓“三位一体”和“多层楼”的矿床分布格局。铜陵矿集区狮子山矿田地质研究程度较高。根据目前研究现状，论文工作拟在以往工作基础上，主要采用SHRIMP同位素精确定年、矿物流体包裹体成分ICP-MS分析以及包裹体中δ¹³C_CO2、δ^C_CH4质谱分析等现代测试技术，着重分析岩浆岩的成岩时代、流体包裹体气液相成分和微量元素成分、流体成矿的物理化学条件和C、H、O同位素组成等在时间和空间上的变化，旨在结合区域成矿背景的研究，运用现代成岩成矿地质地球化学理论，探索矿田岩浆作用及岩浆演化、成岩与成矿关系、成矿流体的时空演化、成矿物理化学场与矿床矿体定位的时空耦合。论文取得了以下主要成果和创新性认识：1、狮子山矿田侵入岩的岩石类型主要为辉石二长闪长岩、石英二长闪长岩和花岗闪长岩3类。根据岩石化学和地球化学的研究，侵入岩以富钾钙碱性系列岩石为主。岩石低Cr、Ni，高Rb、Th、Ba、K以及Sr富集，表明其属于以幔源物质为主的壳幔混源型岩石。结合Nd、Sr同位素地球化学研究，认为本区岩浆岩是上地幔和下地壳物质部分熔融的产物，岩浆作用发生在由挤压向拉张过渡的地球化学背景。区内岩浆岩的主量元素和稀土元素地球化学研究表明，其具有相同的来源，是同源岩浆演化的结果，成岩过程中镁铁矿物的结晶分离起着重要的作用。综合研究认为，狮子山矿田岩浆岩的形成应是起源于上地幔或下地壳的原生岩浆，当聚集到深部岩浆房中以后，在滞留的过程中发生了一定程度的分离结晶作用，但尚未固结，成分上显示了一定的带状分布，在区域构造应力的松弛及构造事件的诱发下，随机地沿发育的构造裂隙先后上升侵位，冷凝结晶。2、锆石SHRIMP的同位素精确定年表明，岩浆的侵位年龄为133.3Ma～142.9Ma．即晚侏罗世-早白垩世。同位素年龄的相似性和差异性表明矿田侵入岩体是在同期岩浆活动中多次定位形成的。岩浆侵入活动可以划分为分别起始于140Ma±和134Ma～136Ma的早晚两次脉动。从岩浆上升侵位到冷却结晶的时间间隔均较短，但其中的白芒山辉石二长闪长岩冷却史相对较长，且经历了早期深部岩浆房中的分离结晶作用和后期构造脉动、岩浆上升侵位、减压受热、早期晶体再熔蚀及冷却结晶的过程。3、矿田内多种不同类型的矿床沿狮子山铜金矿带和鸡冠石多（贵）金属矿带2个成矿带分布，深部为斑岩型矿床和层控-矽卡岩型矿床，中部为层间矽卡岩型矿床及浅部为角砾岩筒式或接触式矽卡岩型矿床。矿床矿物流体包裹体岩相学研究表明。成矿流体包裹体类型多样。但以富液相包裹体和气相包裹体为主。包裹体均—温度测定显示，矽卡岩阶段为411～600℃，石英-硫化物阶段为173～440℃，碳酸盐阶段为117～280℃，成矿温度变化具有连续性和相对集中的特点。成矿流体的盐度测定表明，在矽卡岩阶段和石英-硫化物阶段显示出高盐度和低盐度的两个端元，而且同一成矿阶段高盐度和低盐度等不同类型包裹体均一温度基本一致，反映成矿过程与流体沸腾作用有关。矿田内各矿床成矿流体在时间上从早阶段向晚阶段演化，p、pH、Eh、f_O2值降低；空间上从深部矿床向浅部矿床p、Eh、f_O2降低，而pH升高。4、矿田内各矿床气相成分以H₂O、CO₂为主，还原性气体CH₄、C₂H₆、N₂、H₂S、Ar为次。还原参数R及H₂S浓度在空间上的不同深度矿床石英-硫化物阶段由深向浅变小。CO₂/H₂O比值在空间上指示成矿流体减压空间为-500m～-550m和-730m～-830m中段，流体减压沸腾是矿石沉淀的主导机制。液相成分中阴离子以Cl^-、SO₄^2-和F^-为主，阳离子以K⁺、Na⁺、Ca²⁺、Mg²⁺为主，K⁺/Na⁺、F^-/Cl^-及相关图解显示，成矿溶液是岩浆热液和地下水热液的混合，成矿溶液中阴、阳离子摩尔浓度显示岩浆热液在成矿过程中起主导作用。空间上K⁺/Na⁺、F^-/Cl^-随深度变浅总体呈降低趋势，但在-500m～-550m左右和-730m～-830m中段显著降低，反映成矿过程中流体混合作用增强，是矿石减压沸腾的空间，也与矿田内矿床的富集部位一致。因而探索了矿床流体成分演化、成矿流体物理化学场与矿床矿体的时空定位的密切关系。5、首次系统的石英包裹体微量元素特征研究表明，成矿流体的微量元素特征决定矿石的微量元素的特征，不同矿床的流体具同源演化的特征，石英包裹体中成矿元素丰度指示了。富铜流体”的存在。相对而言矽卡岩阶段成矿作用较弱，而主成矿阶段石英-硫化物阶段Cu、Sr、Ba等有强烈富集的趋势，成矿作用较强。根据矿床矿石分带和流体成分分析，Cu品位较高的含铜黄铁矿石+磁黄铁矿矿石带，可能是含Cu流体汇聚和活动的异常带。空间上不同矿床反映了由深部向浅部总体上Cu富集系数降低，而Pb、Zn则富集系数增加。特征元素及其比值指示成矿热液具深源流体的特征。6、流体包裹体稀土元素与岩浆岩及矿床石英、石榴子石等单矿物具有较好的一致性，但与矿石存在不同，反映了矿床成矿环境对矿石沉淀的影响。铜金矿床矿石和蚀变岩石稀土元素球粒陨石配分模式呈右倾斜型，LREE界于岩浆岩和大理岩之间。但金矿床矿石蚀变岩石δEu呈弱异常，而铜矿床具弱负δEu和弱正δEu异常，反映了成矿环境的复杂性。系统的石英流体包裹体稀土元素和矿石及其单矿物稀土元素的对比分析表明，石英包裹体的稀土元素特征在刻划流体方面比矿床矿石及其单矿物更具有代表性。金矿床流体包裹体稀土元素配分模式为右倾型，轻重稀土分异弱，且δEu具弱异常；铜矿床流体包裹体总体为LREE富集型，轻重稀土分异弱，其显示了深源流体的特征。空间上，深部和中部矿床流体为负δEu异常，而浅部铜矿床均显示δEu正异常，可能与环境改变和F^-、Cl^-、CO₃^2-离子的络合作用有关。7、方解石碳氧同位素组成表明。成矿的碳质可能主要为深部岩浆来源，水-岩相互作用是热液方解石沉淀的主要因素。石英包裹体的δ¹³C_CO2值总体在岩浆岩系统范围，但部分碳来源于围岩，反映了成矿流体起源于岩浆作用，但成矿晚期有外来地层成分和大气降水的加入。δ¹³C_CH4特征显示有机碳和无机碳的混合，也显示成矿有围岩碳酸盐和有机质的参与，而且空间上由深部矿床向浅部矿床降低。矿田铜矿床和金矿床CH₄含量及其同位素组成的差异，可能显示CH₄是矿床铜金分离和金沉淀的主要因素。8、成矿流体氢氧同位素表明，成矿热液以岩浆水为主，晚期有地层水和大气降水的加入。成矿流体在空间上具有以岩浆岩体为中心，由内向外、由下向上氢氧同位素组成有规律的变化特征；在时间上成矿流体由早阶段至晚阶段岩浆水逐渐减少而大气降水逐渐增多，反映成矿作用以岩浆作用为主导。9、对矿田内2类不同矿石类型中的辉钼矿Re-Os年龄测定，得到成矿年龄为139.1Ma和139.4Ma。显示成岩与成矿密切的成因联系。铅同位素研究表明，矿石铅与岩浆岩的岩石铅一致，均具有深源铅的特征。而与沉积围岩的铅同位素组成不同，也显示成矿物质主要是深部来源的。10、综合矿床地质地球化学的研究认为，区内岩浆作用经历了幔源玄武岩岩浆底侵、下地壳岩石的部分熔融、分凝上升至不同深度的岩浆房、不同性质的岩浆的混合以及分离结晶作用和熔-流分配作用。使成矿元素Cu、Pb、Zn、Mo发生多次富集，形成了“富Cu流体”。这种“富Cu流体”沿构造有利部位主要以渗透的方式扩散，因物理化学条件的改变以及围岩和构造条件的不同，形成了矿田内一些减压区间和流体成分富集带状异常区，在不同的空间引发了流体成分的改变并沉淀，从而形成了矿田成矿金属元素表现为上金下铜、内铜外铅锌分布格局以及矿床成因类型上斑岩型-层控矽卡岩型-层间矽卡岩型-接触交代型复合的、具“多层楼”的矿床分布格局。更多还原

【Abstract】 Shizishan ore-field of Tongling is a huge representative and typical Cu-Au ore-field in the metallogenic belt of the middle and lower reaches of Yangtze River. The tectonic activity and magmatism as well as mineralization in the ore-field are complicated. The tectonic evolution went through three stages from the active stage （the basement forming） to the stable stage （the cover forming） and to the re-active stage （the within-plateform deformation）. Especially after middle Triassic period, the within-plateform deformation led to take place the cosmical middle-acid magmatic intrusion and volcano, sub-volcano movement, and formed so called "multiplayer floor" deposit distributing pattern.Based on the modern analysis technique such as the SHRIMP isotopic precision age determination, the ICP-MS composition analysis of fluid inclusions for minerals and the MS analysis ofδ¹³C_CO2 andδ¹³C_CH4 of fluid inclusion and so on, it is gained for the diagenetic era of magma, the gas and liquid composition of fluid inclusion, the composition of metallogenic elements and trace elements in mineralization fluids, as well as the isotopic compositions of C, H, O and Pb of ore deposits. According to these results and the studies of the setting of the region mineralization, using the modern theory of the diagenetic and metallgenic geology and geochemistry, it is discussed for the magmatism and magmatic evolution, the relation between mineralization and diagenesis, the space-time evolution of mineralizing fluid, the space-time coupling of mineralization physico-chemical field and the location of deposit ore-body. The following main results and innovative views are obtained in this paper:1. Magmatic rock bodies in Shizishan ore-field present as dyke and stock, which are grano-diorite, quartze-monzo-diorite, and pyroxene-monzo-diorite three main petrological types. According to the study of chemistry and geochemistry of intrusive rocks in Shizishan ore-field, they are mainly calc-alkalic series enriching K. The characters of low Cr, Ni and high Rb, Th, Ba, K and enriching Sr indicate that the magma derived from mantle and the magmatic rocks are formed by mantle-crust contamination. Connecting with the study of isotopic geochemistry of Nd and Sr, it is concluded that the magmatic rocks of this region originated from partial melting within upper mantle and lower crust. The magmatism took place in the geological setting from extrusion to spread. The geochemical study of main elements and rare earth elements of magmatic rocks indicates that they have same magmatic source and evolution, and the fractionation crystallization of femic minerals play an important role in diagenetic process. The primary magma originated from magma of upper mantle or lower crust, went up to middle and upper crust and come to magmatic chamber and then took place some extent fractional crystallization. The magma took place some zonal distributing in the composition randomly ascending, emplacing along the tectonic crack and then crystallizing.2. Zircon SHRIMP of precise isotopic age determination shows that the ages of the magmatic emplacement in the ore-field are 133.3Ma～142.9Ma, that is late-Jurassic period to early Cretaceous period. The similarity and difference of isotopic ages indicate that the intrusive rocks are formed by many emplacements in the same magmatic movement. There are two magmatic intrusive activities began from 140Ma and 136Ma respectively. The time for the magmas ascending and emplacing to cooling and crystallizing is generally rather short. But the cooling history of pyroxene monzo-diorite of Baimangshan is longer, the latter went through the fractional crystallization in deep magma chamber, magma ascending and emplacement with tectonic pulsation, heated due to pressure reducing, the re-dissolution of early crystals as well as cooling and crystallizing process.3. Many kinds of mineral deposits distribute in the ore-field, mainly including porphyry deposit in the deep and stratabound skam deposit, interstratified skarn deposit in the middle and breccia pipe or contact skarn deposit in the shallow. The geochemistry study of fluid inclusion shows that there are many kinds of fluid inclusions, but the main types are rich-liquid inclusions and rich-gas inclusions. The homogenization temperature measured reveals that the mineralization temperature is 411℃～600℃in the skarn stage, 173℃～440℃in the quartz-sulfide stage, and 117℃～280℃in the carbonate stage. The changes of mineralizing temperature have characters of continuity and relatively concentration. The salinity of mineralizing fluid has two ends of high salinity and low salinity on the skarn stage and the quartz sulfide stage. Moreover the homogenization temperatures of the inclusions of different types containing high salinity and low salinity are basically identical, which reflects that mineralizing process is related to fluid boiling. In addition, for the mineralizing fluid of every deposits the values of p, pH, Eh, f_O2 reduced with mineralization evolution from early stage to late stage, but the values of p, Eh, f_O2 reduced and the value of pH increased from deep deposit to low deposit in space.4. Gas component of all deposits are mainly H₂O and CO₂, secondly are reduction gases such as CH₄, C₂H₆, N₂, H₂S, Ar. Reduction parameter and H₂S concentration reduces from the deep to the shallow in the same quartz-sulfide stage of different deposit The ratio of CO₂/H₂O denotes that the depressurization space of mineralizing fluid is from -520m to -730m in the middle part And the boiling of fluid caused by depressurization is the dominant mechanism of ore precipitation. In the fluid inclusions, the anions in liquid are mainly Cl^-, SO₄^2- and F, and the cations mainly K⁺, Na⁺, Ca²⁺, Mg²⁺, K⁺/Na⁺, F^-/Cl^- and other relative figures show that the mineralizing solution mainly came from the magmatism. The stratigraphic component and the meteoric water may mix in ore-forming fluids in the later mineralization stages. In space, K⁺/Na⁺, F^-/Cl^- totally submits reducing trend with the depth declining, but the ratios of K⁺/Na⁺, F^-/Cl^- changed obviously from -500m to -730m in the middle part of the section, which reveals that the ore-forming fluids mixed strongly, and this space is according to the mineral enriching position in ore-field.5. The minor element characteristics of fluid inclusions in quartz indicate that the minor element characteristics of the ores are determined by the characteristics of the minor element in mineralizing fluid. The metallogenic element abundance in the fluid instructs that the mineralizing fluids are copper-rich fluids. Comparing with skarn stage and carbonate stage in ore-forming process, Cu, Sr, Ba intensely enriched in quartz-sulphide stage, the main mineralization stage. thus ore-forming processes are more intense. According to the zonal distribution of ore and the characteristics of fluid component of deposits, the zone containing Cu pyrite and pyrrhotite ore belt which have high Cu contents perhaps is the zone of mineralization fluid confluence and unloading mineralization material. Generally, the enrichment coefficients of Cu decrease, but the enrichment coefficient of Pb, Zn increase from the deep to the shallow in space for different ore deposits. Characteristic elements and their ratios show that ore-forming hydrothermal solutions have characteristic of deep sources.6. The comparison studies of REE show that REE geochemical characteristics in fluid inclusions, in magmatic rocks, and in minerals such as quartz and garnet are identical, but different from those in ores, which indicates that ore-forming environment of the deposits may have an important effect for ore deposition. The REE geochemical characteristics of the fluid inclusion in quartz are more representative than those in ores and in minerals. The REEs of fluid inclusion in copper and gold deposits have a right-inclination pattern, weak differentiation between LREE and HREE and less 8Eu abnormality, which shows the mineralization fluids come from deep source. The differentiation between LREE and HREE and SEu abnormality indicate that the mineralization is controlled by the evolution of the mangmatic fluid. The fluids of deposits in the deep and the middle have 8Eu negative abnormality, while those in the shallow have 8Eu positive abnormality. These phenomena perhaps are relative to environment changes and the complex action of F^-, Cl^-, CO₃^2-.7. The C, O isotope composition of calcite indicates that C possibly originated from the deep magma, and water-rock reaction is the main factor of hydrothermal depositing. The values ofδ¹³C_CO2 in fluid inclusion in quartz totally are within the range ofδ¹³C in magmatic system, but perhaps parts of carbon root from wall-rocks, andδ¹³C_CH4 values show the mixture of organic carbon and inorganic carbon. All of these reflect that mineralizing material comes from magmatism, but the stratigraphic component and the meteoric water may add to ore-forming fluids in the later mineralization stages. The values ofδ¹³C_CH4 reduce from the deep deposit to the shallow deposit perhaps reveal that CH4 is the main factor for separating copper and gold in mineralization process.8. Hydrogen and oxygen isotopes of mineralizing fluids show that the ore-forming fluid is mainly magmatic hydrothermal solution, and has the addition of stratum water and the meteoric precipitation in the later mineralization stages. In spatial changes of the composition of hydrogen and oxygen isotopes are regular from the inside to the outside, and from the bottom to the upper, which imply that ore-forming fluids flow from the center of the magmatic body to the outward and the upper. In time, magmatic hydrothermal in the ore-forming fluids reduced gradually and the atmospheric precipitation increased gradually from the early stage to the later stage. These phenomena reveal that magmatism plays the most important role in the mineralization process.9. Re-Os age determination for molybdenite in the two different types of ores in Dongguashan copper deposit shows that the ore-forming ages are 139.1Ma and 139.4Ma. The identity of the diagenetic age and the metallogenic age indicates that the mineralization is closely related to the magmatism. Lead isotope studies show that the lead isotopic compositions of the sulphide in ores are consistent with those of the magmatic rocks, and different from those of the sedimentary rocks, which shows that the mineralization material is also mainly from the deep source.10. Synthesizing above geological and geochemical studies, the magmatism mineralization process can describe as follows: The underplating of the upper mantle-derived basalt magma melted the lower earth crust and formed diorite and monzonite magmas and the metallogenic element enriched firstly. The magma raised, mixed and assimilated the middle or upper earth crust and formed the monzo-diorite magma and the metallogenic element secondly. The magma in chamber took place fractional crystallization of femic minerals and differentiation of melt and solution, and the metallogenic element enriched again. The fluid diffused by the way of infiltration along the favorable structural positions, and the heat of the magmatic bodies cause meteoric precipitation circulated and leached the metallogenic material from the wall-rocks （water-rock reaction）. The metallogenic element enriched many times and formed the rich-Cu fluid. Because of the physical and chemical conditions changed, the wall-rocks and structure changed, and different mineralization fluids mixed, the ores deposited.更多还原