【作者】 李永峰；

【导师】 毛景文； 王志光；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2005， 博士

【摘要】 本研究通过较为详细的野外地质工作,采用区域矿床调查和典型矿床解剖的系统研究方法,利用锆石SHRIMP U-Pb法厘定熊耳山地区花岗岩类岩体的年龄,采用ICP-MS法直接测定南泥湖等钼矿床辉钼矿的Re-Os同位素年龄;在准确厘定成矿年龄的基础上,结合花岗岩和钼(金)矿床的地质地球化学特征研究,探讨了花岗岩类的时空演化规律、钼(金)矿大规模成矿作用特征、岩浆演化与钼金矿床的成生关系及其形成的地球动力学过程。阐述了区内中生代花岗岩的时空分布特征、类型及其岩石学、矿物学、岩石化学、微量元素、稀土元素、同位素等特征,并对花岗岩类进行构造环境判别,分析了其形成的大地构造背景。利用SHRIMP 锆石微区U-Pb 测年技术确定五丈山岩体的结晶年龄或侵位时间为156.8±1.2Ma,花山岩体为130.7±1.4Ma,合峪岩体为127.2±1.4Ma,南泥湖岩体为157.1±2.9Ma,上房沟岩体为157.6±2.7Ma,雷门沟岩体为136.2±1.5Ma。总结了本区钼矿床的地质特征、时空分布特征、矿化类型,探讨了钼(金)矿床成矿流体作用和演化特征。采用ICP-MS 法测定了各钼矿床的辉钼矿Re-Os 同位素模式年龄:南泥湖为141.8±2.1Ma;三道庄为144.5±2.2～145.0±2.2Ma,平均为145.0±2.2Ma;上房沟为143.8±2.1～145.8±2.1Ma,平均为144.8±2.1Ma;雷门沟为131.6±2.0Ma～133.1±1.9Ma,平均为132.4±2.0Ma。系统研究了公峪金矿床的地质地球化学特征:公峪金矿床硫化物的δ34S 值变化于-1.7‰～2.2‰之间,与陨石硫的δ34S 值接近,反映为深源;主成矿期Ⅰ阶段流体的δD 值为-68‰～-86‰,δ18OH2O为-0.6‰～+4.9‰,Ⅱ阶段流体的δD 值为-67‰～-84‰,δ18OH2O为-0.6‰～-8.9‰,反映成矿流体Ⅰ阶段以深源水为主,Ⅱ阶段有大量大气降水混入。黄铁矿流体包裹体的3He/4He比值为1.05～3.17R/Ra,高于地壳的3He/4He 比值100 余倍,但明显低于地幔流体的3He/4H e比值;40Ar/36Ar=298～391,略高于大气氩的同位素组成;40Ar /4He 比值0.08～0.35,平均为0.20,与地壳40Ar/4He 比值一致。He、Ar 同位素组成特征显示了公峪金矿床成矿流体以大气降水为主,但同时有地幔流体成分。熊耳山地区钼金矿床大规模成矿与区域地球动力学事件关系密切。钼(钨)矿床在成因上与花岗斑岩体密切相关,而金矿的形成则比较复杂,花岗岩侵位提供了热能,驱动地幔流体与地壳流体混合、对流循环,并从周围前寒武纪岩石萃取成矿物质,在适宜构造带卸载成矿。东秦岭钼矿主要出现在221.5±0.3Ma 左右和144.8±2.1-132.4±2.0Ma 等时限之间,其对应的地球动力学背景分别为华北与扬子克拉通的碰撞造山晚期和中国东部构造体制大转换后期及期后的岩石圈大减薄。更多还原

【Abstract】 Based on the detailed field investigation and previous researches, samples from granitoids , associated with molybdenum (gold) mineralization in Xiong’ershan area, have dated using the zircon SHRIMP(Sensitive High Resolution Ion Microprobe) U-Pb method. Meanwhile, we also dated the molybdenite from the molybdenum deposits by Inductively Coupled Plasma Mass Sperctrometry (ICP-MS), with analytical errors of Re and Os between 0.2-0.3% (2σ). On the basis of the accurately age dating, combined with data on the geology and geochemistry achieved before,the genesis of these granitoids and molybdenum (gold) deposits, and their temporal and spatial relationships have been evaluated. This study provides the first highly precise dating ages of the molybdenum mineralization and rock-forming in Xiong’ershan area. The age of zircon from Wuzhangshan granite stock determined by SHRIMP is156.8±1.2Ma and 130.7±1.4Ma for Huashan stock, and 127.2±1.4Ma for Heyu stock, 157.1±2.9Ma for Nannihu porphyry, and 157.6±2.7Ma for Shangfanggou porphyry and 136.2±1.5Ma for Leimengou granitic porphyry. The results obtained show that the Re-Os model ages are141.8±2.1Ma for Nannihu molybdenum deposit,144.5±2.2 ～145.0±2.2Ma(averaging 145.0±2.2Ma) for the Sandaozhuang deposit, and 143.8±2.1～145.8±2.1Ma(averaging 144.8±2.1Ma) for the Shangfanggou deposit, and a range of 133.1±1.9～131.6±2.0Ma (averaging 132.4±2.0Ma ) for Leimengou deposit. The homogenization temperatures and salinity of the fluid inclusions as well as their He-Ar and S-H-O isotopic components were systematically measured based on 13 samples from the main phase of gold mineralization in the Gongyu gold deposit. The fluid inclusions in the Gongyu mine can be divided into four types, i.e. vapor, vapor-aqueous, aqueous, and CO2-bearing inclusions. The fluid inclusion bubbles are 2-20μm in diameter, mostly in a range of 2-4μm. The homogenization temperatures of the fluid inclusions ranges from 120℃～440℃, mainly in ranges of 150℃～250℃, with three distribution from 150℃～190℃、210℃～250℃and 290 ～350℃. The gold mineralization temperatures vary from 210℃～250℃. Their ice-melting temperatures varies from -2.5℃～-13.5℃, corresponding to a ranges of salinities 4.65wt%～17.26wt% NaCl equivalent. The S-H-O isotopic analytical results show that δ34S values of sulfide are in the range of -1.7‰～2.2‰and close to the value of meteorolite, indicating that the ore-forming substance was probably derived from the upper mantle or some depth. The δD and the δ18OH2O values of the first stage of the main phase of gold mineralization are -68‰～-86‰and -0.6‰～+4.9‰respectively, implying that the ore-forming fluids were derived mainly from the depth. The δD and the δ18OH2O values of the second stage of the main phase gold mineralization are -67‰～-84‰and -0.6‰～-8.9‰respectively, suggesting that the ore-forming fluids probably came from both of the depth and the meteoric water. The Ar-He analytical results show that 3He/4He ratios of fluid inclusions in pyrite are 1.05～3.17R/Ra, 100 times higher than that of the crust and markedly lower than that of the mantle. 40Ar/36Ar ratios are 298～391, slightly higher than that of atmosphere. 40Ar /4He ratios of their corresponding metallogenic fluids are 0.08～0.35 with a mean of 0.20, which are consistent with the value of the crust (0.156). Helium and argon isotope composition of fluid inclusions suggest that the source of ore-forming fluids is mainly meteoric water , and also have some mantle fluids. Therefore, the data above demonstrate that the Gongyu gold deposit is geneticlly related to mantle fluids. In the Qiyugou orefield, although Qiyugou gold deposit (cryptoexplosive breccia type) and Gongyu gold deposit (altered tectonite-type) developed in different types, their fluid inclusions and He-Ar-S-H-O isotopic data show that they originated from the same source and deposited in the same period but at different position, and probably formed in the same metallogenic system which is related to the Yanshanian hydrothermal fluid in Qiyugou orefield. The large-scale Mo(Au) mineralization is a conquerce of the Mesozoic regional tectonic in East China continental. The porphyry Mo and Mo-W deposits are spatial-temporally and genetically related to Mesozoic granite porphyries, Whereas the ore-forming of the gold deposits is more complicated. The emplaced granite intrusions acted as “engines”which drive the mixed hydrothermal solution of the meteorite and mantle fluids to form a conductive circulation system. The hydrothermal solution leached the substance from the Pre-cambrian strata which is proposed the gold source and descharged the gold in some suitable fractures, such as sheer zone to form the gold更多还原