【作者】 房海波；

【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， 2009， 硕士

【摘要】 狮子山矿田是安徽铜陵矿集区内最具代表性的大型铜、金矿田。矿田内成矿作用十分复杂,发育多种类型的铜矿床和金矿床。铜和金或各自独立产出,或相互共生或伴生产出。矿田内铜矿床和金矿床的矿床地质特征、流体作用和演化及成矿作用机制一直是人们关注的问题。本文在系统收集和全面了解狮子山矿田成矿地质背景的基础上,通过细致的野外地质观察,并采集样品进行室内鉴定、实验室分析测定,对狮子山矿田中的典型铜矿床和金矿床的地质特征和流体包裹体地球化学特征进行了系统的分析和对比,获得了以下认识:铜矿床和金矿床的地质特征既相似又不同:铜矿床和金矿床产于相似的宏观地质背景,受相似的矿田构造、赋矿地层及岩浆岩的控制,但空间上铜矿床主要在产于矿田深部,金矿床主要产于浅部;时间上铜矿床成矿时间相对较早,而金矿床相对较晚;成因类型上铜矿床主要为层间或层控矽卡岩型、斑岩型和隐爆角砾岩筒型,而金矿床主要为接触交代矽卡岩型和中低温热液型;铜矿床的赋矿围岩主要为上石炭统黄龙组和船山组、上二叠统大隆组、下三叠统和龙山组、殷坑组和南陵湖组地层,而金矿床主要赋存于下三叠统和龙山组和南陵湖和中三叠统东马鞍山组地层中;铜矿床的控矿构造主要为顺层滑脱构造、层间裂隙及隐爆角砾岩筒等构造部位,而金矿床主要受侵入岩体与围岩的接触带及断裂破碎带和裂隙控制;铜矿床主要与花岗闪长岩、石英二长闪长岩及二长闪长岩类侵入体有关,而金矿床主要与辉石二长闪长岩侵入体有关。铜矿床和金矿床主成矿阶段的流体包裹体地球化学特征显示其成矿流体特征及其演化也具有既相似又不同的特征:铜矿床的流体包裹体均一温度范围较大,成矿温度相对较高,金矿床的均一温度相对较低,显示铜矿床的成矿热液开始活动时的温度较高,持续时间较长;铜矿床的流体包裹体盐度峰值仅出现在低盐度区间,而金矿床盐度峰值出现了高盐度和低盐度两个区间;铜矿床相对于金矿床成矿流体的密度较小,压力较高,pH值较低呈弱酸性,Eh值较低,fO₂较低,反映铜矿床的成矿流体为弱酸性及弱还原性,而金矿床的成矿流体为偏中性及弱氧化性;流体包裹体气液相成分特征上,铜矿床的CO₂含量比金矿床成矿流体中的稍低,表明搬运金的成矿热液更富含CO₂;铜矿床中H₂S、Cl^-和SO₂^4-的含量相对于金矿床低,说明这些离子有利于金的迁移和富集。同时,铜矿床和金矿床成矿热液流体中的稀土元素配分模型和微量元素蛛网图具有相似的特征,反映其成矿热液流体均具有对岩浆岩的继承性,为岩浆分异的热液流体;流体包裹体氢、氧和碳同位素组成特征显示铜矿床和金矿床的成矿流体均来源于岩浆水与大气降水（地层水）的混合。综上所述,导致铜和金分离和沉淀的原因可能主要是成矿温度、流体盐度以及成矿流体中气液相成分的变化。成矿流体在较深部位活动时,流体温度较高、盐度较低、H₂S、Cl^-和SO₂^4-的浓度也相对较低,流体处于弱酸性和还原条件下,铜富集达到饱和并开始沉淀成矿;而随着流体运移上升,流体不断萃取和淋滤围岩地层组分,温度逐渐降低,但盐度升高,H₂S、Cl^-和SO₂^4-的浓度也相对升高,此时流体处于弱氧化和偏中性的环境下,金在成矿热液流体中达到饱和并沉淀成矿。更多还原

【Abstract】 Shizishan ore field is the most representative copper-gold ore-field in the Tongling Mineralization Cluster Area, Anhui Province. This ore-field contains many types of copper deposits and gold deposits. Copper and gold exist separately, or in paragenetic and associated. The matallogenetic processes are very complex. Geologisits always focus on the geological characteristics and the evolution process of ore-forming fluids.Basing on the detail field geological studies and systematical laboratory analysis, it is carried out for the comparativation of the ore geological characteristics and geochemical characteristics of fluid inclusions of copper deposits and gold deposits in Shizishan ore-field. The main conclusions are drawn as follows:In the geology, the copper deposits and gold deposits in Shizishan ore-field have both similarities and differences. The metallogenic geological setting, ore-field structure and host strata of the copper deposits and gold deposits are similar. But in the spacial distribution, the copper deposits are seat in deep relatively. In the forming time, the copper deposits are earlier than the gold deposits. The genetic types of copper deposits are mainly interformational skarn type, strata-bound skarn type, porphyry type and crypto-explosive breccia pipe-type, those of the gold deposits are contact-metasomatic skarn type, moderate- low temperature hydrothermal type. The host strata of copper deposits are mainly Huanglong and Chuanshan Formation of upper Carboniferous, Dalong Formation of upper Permian, Helongshan, Yinkeng and Nanlinghu Formationin of lower Triassic; those of the gold deposits are mainly the Helongshan and Nanlinghu Formationin of lower Triassic, East-Ma’anshan Formation of middle Triassic. The main ore-controlling structures of the copper deposits are bedding decollement structure, interstratified crack and crypto- explosive breccia pipe, and those of the gold deposits are contact zone between magmatic body and wall-rock, fault fracture zone and fissure structure. The copper deposits are associated with granodiorite, quartz monzodiorite and monzodiorite intrusions, and the gold deposits with the pyroxene-monzodiorite intrusions.The formation of the copper deposits and gold deposits progresses through the skarn stage, quartz-sulfide stage and carbonate stage. The analysis and comparative study of fluid inclusions of the major mineralization stages shows that the characteristics and evolution of ore-forming fluids also exist similarities and differences between the copper deposits and gold deposit. The homogenized temperatures of copper deposits have a wide range and are higher than those of the gold deposits, which indicated the copper deposits had a higher ore-forming temperature and longer duration of fluid evolution. The salinity peak values of copper deposist occurre in a lower value range, and the gold deposits have a lower and a higher salinity range. The pH and Eh indicated that the fluids of copper deposits are weak acid and weak reduction environment, and the gold deposits formed in neutrality and weak oxidation environment. Analytical data of gas and liquid phases of fluid inclusions demonstrated that the content of CO₂, H₂S, Cl^- and SO₂^4- of quartz-sulfide stage of copper deposits are lower than those of the gold deposit. Otherwise the copper and gold deposits have the similar chorndrite- normalized REE distribution patterns and Chinese continental crust-normalized trace element spider diagram, which indicated that the hydrothermal fluid of copper deposits and gold deposits were all derived from the magmatic differentiation. Hydrogen, oxygen and carbon isotopic compositions imply that the ore-forming fluid is likely to be mixed with meteoric waters.Based on the above geological and geochemical studies, it is concluded that the copper and gold seprated deposition may be mainly caused by the changes of temprature, salinity and the gas-liquid contents of the ore-forming fluid. At the earlier ore-forming stage and the deep part, the hydrothermal solutions had a high temprature, low salinity, and low contents of H₂S, Cl^- and SO₂^4- , copper began deposition in weak acid and weak reduction environment. With the fluid ascend, the temprature decreases, the gold-bearing fluid eluviated more strata components, and the contents of H₂S, Cl^- and SO₂^4- increases, which brought about favorable conditions for migration and enrichment of gold, when the salinity of ore-forming fluid increace to be saturated, the gold began deposition in weak oxidation and neutrality environment and favourable places, and further forms gold ore deposits.更多还原