【作者】 薛昊日；

【导师】 孙丰月； 李碧乐；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2010， 硕士

【摘要】 中条山桐木沟、篦子沟铜矿床位于山西省南部的垣曲县境内,因成矿条件相似,与南和沟、老宝滩铜矿床并称为胡-篦型铜矿床。但对矿床成因却存在分歧,早期有火山-沉积变质成因论;混合热液成因论;远火山沉积变质-再造热液成因论;内源沉积再造论等观点,但目前已经趋向于热水喷流成因。矿体呈层状,似层状,严格受地层岩性控制。矿石中的金属矿物以黄铜矿、黄铁矿、磁黄铁矿为主。矿区发育的不纯白云石大理岩、硅质钠长质岩经分析表现出典型的热水喷流岩的特点。本文在分析研究桐木沟、篦子沟铜矿成矿地质背景的基础上,通过野外调研、岩矿综合鉴定、岩石地球化学等方法和手段,详细研究了该矿床的矿床地质特征、含矿岩系的地球化学特征及其形成的大地构造环境,通过对稳定同位素和流体包裹体的研究确定成矿物质以及成矿流体的主要来源,分析成矿作用的机制和过程,确定桐木沟、篦子沟铜矿矿床成因类型并建立成矿模式。更多还原

【Abstract】 Tongmugou and the Bizigou Cu-deposits are located in Yuanqu county, Shanxi province. Tectonically, they occur in the intersection area of the Zhongtiao trigeminal rift on southern margin of the North China craton. Zhongtiaoshan Cu-orefield is one of the most notable ore-concentrated areas in China with various deposit types due to complicated mineralization environment, which together constituting Hu-Bi type deposits, characterized by copper enrichment and paragenesis with Au, Ag, Co and other valuable components.This paper presents tectonic settings, physical and chemical conditions, mineralization patterns and models of these deposits, based on field works and testing analysis including rock ore appraisal, ICP-MS analysis and fluid inclusion analysis. Strata in mining area are dominated by Paleoproterozoic Zhongtiao formation, from lower to upper, including Jiepailiang group (quartzite), Longyu group (slate), Yuyuanxia group (marble), Bizigou group (schist) and Yujiashan group (marble), among which, Yuyuanxia, Bizigou and Yujiashan group are involved with mineralization.The studying area has undergone volatile metamorphism and deformation during Precambrian, forming nearly S-N striking Hujiayu-Shangyupo superimposed fold and fracture system. The core components of the superimposed fold are dominated by metabasic volcanic rocks, mafic intrusive rocks of Jiangxian group and Beiyu granite. Its southeast flank is marked by Zhongtiao group while the northwest flank marked by the lower strata of Zhongtiao group. The axis of the anticline is NNE-trending in middle section, NEE-trending in north section and SW-trending in south section, presenting“S”shape as a whole. The Hubi type Cu-deposits occur in eastern and southern Shangyupo-Hujiayu anticline. Bizigou deposit occurs within the east flank of the anticline and Tongmugou deposit is distributed at the end of southern anticline.Ore mineral assemblage consists of chalcopyrite, pyrite, pyrrhotite and molybdenite. gangue assemblage includes calcite, quartz, biotite, albite, sericite and chlorite. Hydrothermal alteration in Tongmugou Cu-deposit occurs as silicification, sericitization, biotitization and carbonatization, and in the Bizigou Cu-deposit presents as intense biotitization with typical silicification, sericitization, carbonatization and actinolitization.Mineralization in Tongmugou deposit is closely associated with albite siliceous rocks, biotite marble and black carbon mud schist intergrowth with marble in Bizigou group, while orebodies in Bizigou deposit are hosted by Yuyuanxia group (marble) and Longyu group (calcareous biotite schist). These strata exhibit SEDEX features. Study on fluid inclusion was undertaken to constrain physical and chemical conditions of ore-forming fluids.Hydrothermal fluids in Tongmugou deposit is recorded by vapor-liquid two phase type of fluid inclusions with 4～14um in size and 0.94~1.11 g/cm3 in density, trapped under conditions between 6% and 28% wt%NaCl. eqv, between 12 Mpa and 32Mpa with an average of 21 Mpa, in depth of 2.1km, homogenized between 120°C and 210°C, mostly concentrating in 140~150°C and 160~200°C.Two types of fluid inclusions with 4 to 14 um in size are recognized in the Bizigou deposit: vapor-liquid two-phase type and daughter minerals-bearing three- phase type. Fluid inclusions are characterized by 10 - 28 wt. % NaCl equiv in salinity in two-phase type and 28%~32%wt%NaCl in three-phase type, they were trapped under conditions of 0.96~1.16 g/cm3 in density, 10~30Mpa in pressure with an average of 22 Mpa and 2.3km in depth. Vapor-liquid fluid inclusions homogenized between 120°C and 210°C, mostly concentrated in 150~200°C, representing the temperature of mineralization.The components of fluid inclusions are dominated by cation of Na+, K+, Ca+ and Mg+ with minor Li+ and anion of F-, Cl-, SO42- with minor amount of HCO3-.The features of exhalite and high salinity of fluid inclusions indicate the involvement of the hydrothermal fluid, probably brine, enrichment in silicon, sodium, boron, magnesium, carbonate and sulphide.Based on the above analysis, we propose an alternative metallogenic model as follows:In Zhongtiao area, magmatic activity facilitated to form Hu-Bi thermal field, driving the seawater to cycle and heating it to about 200°C. The heating fluid interacted with surroundings, ejected from the submarine and formed the exhalative rock. Under the continuing effect of thermal field, the hydrothermal fluid changed its nature components due to involvement of vast seawater and progressively higher temperature, leading to the decline of PH value, which in favor of leaching copper from the surrounding rock. Copper-bearing hydrothermal fluid ejected from seabed, and the copper precipitated. With the crystallization of magma, fluid temperature dropped associated with reduced leaching capacity due to the gradual decline of thermal field. Biological activity increased in the spout region due to high temperature, carbon-silicon argillite formed by exhalation carbon deposition covered the ore-bearing rock series, indicating the end of the exhalative process.更多还原