【作者】 李学军；

【导师】 邓军；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2006， 博士

【摘要】 铜陵地区是中国重要的铜金矿集区,论文以典型复杂矿床——新桥矿床为例,探讨了铜陵地区大规模成矿作用发生的控矿因素、成矿过程及成矿-找矿模式。 铜陵地区石炭纪沉积环境的分析表明,受泥盆系/石炭系层位控制的层状块状硫化物矿床的形成与石炭纪沉积作用关系不大。铜陵地区石炭纪只有规模小、局部分布的沉积赤铁矿层、锰土层以及沉积间断风化剥蚀面存在,没有形成大规模层状块状硫化物矿床的物质基础。 根据区域相对浓集系数（K’）值特点,将地层中元素分成富集元素（K’>1）、贫化元素（K’<1）、不稳定元素（K’>1和K’<1）、稳定元素（K’≈1）四类。铜陵地区志留系—三叠系地层中金属矿质元素含量研究表明,地层中大部分元素属于富集元素或不稳定元素,反映地层受外来热液影响接受矿质沉淀,使矿质元素在地层中呈富集状态,这一特点在地层界面和岩性界面反映更明显。同时,受热（液）影响,地层中元素变得活跃,在地层内活动呈现局部的富集和贫化。地层中元素整体贫化的现象很少,说明铜陵地区的层状矿床或层控矿床的物质来源主要不是来自地层。 深部硅碱质流体对岩浆岩的改造对成矿起了重要作用。它使岩浆岩发生钾化、钠化、硅化及夕卡岩化,并导致岩浆岩中Fe、Cu、Au、Ag、Pb、zn等矿质发生活化、迁移,造成流体更富矿质元素,最终在有利部位沉淀成矿。这种流体的活动具多次性,从而导致成矿作用多次发生以及矿床具一定的韵律性。 铜陵地区容矿构造研究表明北东向褶皱和断层产生的虚脱空间是区内最重要的容矿构造,大型层状矿床均产在这些虚脱空间内。对铜陵地区地层产状及接触关系分析得出铜陵地区北东向构造格架雏形形成于T₂—J₁,属印支期构造运动产物。 新桥矿床胶黄铁矿研究表明胶黄铁矿层（脉）为热液充填、交代成因,胶黄铁矿和地层中结核状黄铁矿的铅同位素组成及硫同位素组成特征均反映其物质成分来自地壳深部或地幔。形成胶黄铁矿的热液活动具多期性,胶黄铁矿形成后还受到了后期热液的影响。新桥矿床铁硅质岩由微细晶的石英和赤铁矿（褐铁矿）组成,为硅质流体充填、交代块状硫化物矿层而形成。铁硅质岩化学成分分析显示Si与Fe的含量呈负相关关系,呈现典型的充填、交代作用特点。对新桥矿床菱铁矿矿石结构、构造进行研究后发现,菱铁矿也是热液充填、交代成因。菱铁矿交代地层岩石并呈环带状、肠状充填在地层空隙中或包裹岩石中球粒,形成菱铁矿层。地层中孔隙大处,菱铁矿颗粒变大,孔隙小处菱铁矿颗粒小。层状菱铁矿的碳同位素组成特征反映其为岩浆碳源或深部碳源,表明层状菱铁矿是岩浆热液活动晚期碳酸盐化阶段热液作用的产物。新桥矿床各类产状石英流体包裹体液氢氧同位素组成特征均反映成矿流体以岩浆热液为主,但有少量天水加入,说明新桥矿床的形成与岩浆热液关系更密切,而与其他热液作用关系不大。 综合铜陵地区各种地质现象和研究成果,提出了铜陵地区矿床形成的两阶段热液作用成矿模式,即早期深部岩浆气-液流体活动形成层状块状黄铁矿矿体,后期富含挥发份的硅碱质流体作用形成各类矿石;同时提出了铜陵地区构造-岩浆岩二元找矿模式,即围绕构造虚脱空间与有后期硅碱质流体活动岩体的复合部位开展找矿工作。模式的建立对进一步探讨铜陵地区的成矿规律及指导铜陵地区今后的找矿工作有一定意义。更多还原

【Abstract】 Tongling area is one of the important Cu-Au deposit cluster areas in China. This paper focuses on ore formation conditions, ore deposit models, and prospecting targets in Tongling area. As a case study, the author analyses the forming process of the Xinqiao Cu-Au-Fe-S deposit—a typical and complex ore deposit in this area.The research on sedimentary environments in the Late Carboniferous shows that the layered ore deposits occurring in the Upper Carboniferous limestones are not formed by sedimentation. In this period, there developed a lot of small-sized hematite beds and manganese wad beds in Tongling area, but there were not advantage depositional conditions for forming the layered ore deposits, especially the large-sized ones.According to values of element concentration factor（K’）, the author divides the elements in sedimentary strata into four kinds: （1）rich elements（K’>1）, （2）impoverish elements（K’<1）, （3）stable elements（K’≈ 1）, and （4）astable elements（K’>1 and K’<1）. Most elements in Silurian-Triassic strata in Tongling area belong to rich elements and astable elements. It is thermal fluid’s activity that leads to this result. Thermal fluid precipitates its compositions in strata and enriches these elements;and it also makes strata elements active and causes a local enrichment and impoverishment of elements in strata. Generally, the elements in strata do not show a whole impoverishment, so the strata do not provide any material to form the layered ore deposits in Tongling area.The alkali-silicic fluid with a high temperature is an important ore fluid. It can act with igneous rocks and make potash-alteration, sodium-alteration, silicatization and skarnization happen in the rocks. By these actions, the elements （Fe, Cu, Au, Ag, Pb, Zn etc.） in igneous rocks can enter the fluid, causing the fluid rich in mineral elements. With decrease of temperature, the fluid precipitates these elements and forms pyrite, chalcopyrite, native gold, native silver, galenite, sphalerite etc. in advantage spaces that make up many different ores. This fluid can act many times, and the mineralization can happen many times, that makes the ore deposits in Tongling area being of certain cyclicity and rhythmicity.The NE-orientation folds and faults are the main ore deposit-hosted structures in Tongling area. All the large-sized ore deposits in this area occur in them. The study of the strata demonstrates that these structures are formed in T₂-J₁ and are the results of the Indo-China movement.The microscopic observations of the melnikovites in the Xinqiao deposit show that they are formed by hydrothermal activities. The Pb and S isotopic compositions of the melnikovites andthe pyrite nodules in strata imply a lower crust or mantle material source. The melnikovites are also affected by later fluid. The siderites in the Xinqiao deposit also show a hydrothermal genesis. They occur in strata pores in comb and ptygma shapes. The pore larger, the grain of siderite bigger. The C-isotopic composition suggests that the siderites are of a magmatic carbon source. So the siderites may be formed by the magmatic fluid. The Fe-Si rock in the Xinqiao deposit are composed of fine-grained quartzs and hematites. The Fe content in the rock has a negative correlation with the Si content, indicating that a silicic fluid acts with orebodies to form the Fe-Si rock. The H-0 isotopic compositions of inclusion water in different quartzs in the Xinqiao deposit suggest that the ore fluid mainly comes from magma. All studies of the Xinqiao deposit demonstrate that this ore deposit is mainly formed by the magmatic fluids.On the basis of research in Tongling area, the author establishes an ore deposit model of two-stage fluid activities: the early ore fluid related to basaltic magma forms the pyrite sheets;the later alkali- silicic fluid forms the Cu and Au ore bodies in the former pyrite sheets. The author also establishes an ore prospecting model of two elements （structure and pluton）: taking the coupling place of large space caused by tectogenetic movement and pluton affected by alkali-silicic fluid as the prospecting target. According to this model, four prospecting targets are proposed for future geological study in Tongling area: （l）the West Longjishan district, （2）the North Baocun district, （3）the South Yaojiawan district, and （4）the Mingshan district.更多还原