【作者】 郭春影；

【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， 2009， 博士

【摘要】 胶东地区是我国重要的金矿床集中区和黄金工业基地,区内金矿床形成时代集中于早白垩世,严格受区内断裂构造控制。胶东地区地质研究程度较高,但对金矿床形成的大地构造背景、成矿动力学体制、成矿流体来源等存在多种认识。本文以成矿系统理论为指导,通过中生代花岗岩大地构造环境系统判别、三山岛-仓上断裂带成矿流体地球化学、热液蚀变地球化学、断层泥成分及粒度分析,试图重建胶东中生代岩浆活动-板块相互作用过程,解析典型成矿带热液蚀变-矿化作用,初步探讨胶东中生代金成矿系统动力学过程及矿化网络结构。研究认为,胶东地区晚三叠世(230～200Ma)、晚侏罗世(160～140Ma)、早白垩世中期(130～125Ma)、早白垩世晚期(120～100Ma)花岗质岩石可以与扬子板块、华北板块、太平洋板块相互作用的不同阶段相对应。区域成矿事件在时间上与太平洋板块与华北板块俯冲及华北克拉通岩石圈大规模减薄一致,处于弧后拉张环境。流体包裹体测温及成分研究显示成矿流体为中-低温,低盐度NaCl-H2O-CO2体系,呈低氧逸度,弱酸性-弱碱性pH值;黄铁矿较石英能更好的保存成矿流体信息。流体包裹体稳定同位素研究指示成矿流体源于中生代大气降水,CO2源于地幔;成矿流体具有富集重稀土元素,亏损轻稀土元素的特征;成矿流体减压沸腾作用使流体pH由弱酸性过渡到弱碱性导致以Au-S络合物搬运的成矿物质沉淀成矿。热液蚀变前后除Ba、Sr外微量元素带入,轻稀土元素带入,重稀土元素带出;成矿元素具有分形特征,可能与热液成矿期次及元素赋存形式有关。断层泥组成包括石英、长石,伊利石、伊/蒙混层矿物、高岭石以及少量碳酸盐矿物和次生风化矿物。断层泥粒度曲线分为单峰、宽缓单峰、双峰三种类型,分维值普遍大于2.70,显示断层运动方式已经发展到蠕滑阶段而不是粘滑阶段。以成矿系统理论分析区域金成矿系统,成矿物质源于胶东群低温部分熔融后残留铁镁质矿物高温熔融形成的中基性岩浆,经大气降水深循环与幔源CO2构成的成矿流体通过郯庐断裂带次级构造系统搬运至上地壳成矿。成矿能量源于地幔对减薄的地壳稳定热能供给和太平洋板块对华北板块的快速俯冲。矿床、矿点、蚀变带构成了区域上金矿床矿化网络结构。更多还原

【Abstract】 The Jiaodong peninsula is the most important gold camp and gold industrial base of China. Gold deposits were formed in early Cretaceous and strictly controlled by regional faults. Though intensively studied, there are controversies on gold tectonic settings, dynamic systems, source of ore forming fluid, etc. In the direction of metallogenic system theory, analysis were done to tectonic settings of regional Mesozoic granitoid, geochemistry of ore forming fluid, geochemistry of hydrothermal alteration, and mineral composition and particle size distribution of fault gouge from the Sanshandao-Cangshang fault. Based on these, I try to reconstruct the time sequence of regional magmatic-tectonic evolution, decipher hydrothermal alteration and mineralization process, and re-appear the dynamics of regional gold metallogenic system and the resultant mineralization networks.Studies show that regional granitoid of late Triassic, late Jurassic, middle period of early Cretaceous and late period of early Cretaceous were formed successively in different stages of interactions of the Yangtze Plate (YP), the North China Craton (NCC) and the Pacific plate. The gold deposits were formed in regional extension settings, and in consistent with the Pacific plate subduction to the NCC and the great lithospheric thinning of the NCC. Fluid inclusion thermometric and composition determinations indicate a low salinity, low to medium temperature, NaCl-H2O-CO2 fluid with low fO2 and slightly acidic to slightly basic pH. Pyrite contains more reliable ore forming fluid than quartz. Stable isotopic data indicate a Mesozoic meteoric origin of water and mantle source of CO2. The ore forming fluid is rich in HREE and barren in LREE, with anomalous rich in Eu and Sm. The fluid pH transition from slightly acidic to slightly basic due to decompression boiling is responsible for gold precipitation from Au-S complex in fluid. After hydrothermal alteration, trace elements were imported except for Ba and Sr; LREE were imported, while the HREE were exported. Metallic elements show fractal distributions, which may be caused by the multiple hydrothermal events and related element occurrences.Fault gouges are composed of quartz, feldspar, illite, illite/semctite formation, kaolinite, minor carbonate, etc. Particle size distributions (PSDs) show single, broad single or double peaks in log-volume plots. Most of PSD fractal dimensions are above 2.70, which indicate the fault movement is in creep rather than in stick.Analyzed by metallogenic system theory, ore materials were sourced from neutral-basic magma derived from high temperature melting of mafic minerals of the Jiaodong group after low temperature partial melting and separation of felsic minerals. Ore elements were transported by fluid composed of deep cycled Mesozoic meteoric water and mantle CO2 from lower crust to the upper crust to form gold deposits. The hot mantle provided heat to the thinned crust of NCC, and the rapid subduction of Pacific plate to the NCC provided the tectonic dynamics. The gold deposits, mineral occurrences and hydrothermal alteration zones compose the whole structure of regional gold mineralization network.更多还原