【作者】 李科；

【导师】 顾雪祥；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2009， 硕士

【摘要】 山东沂南矽卡岩-热液型金铜铁矿床位于华北板块东南缘沂沭断裂带(郯庐断裂带的中段)西侧的鲁西地区,辖相距6 km的铜井和金场两个矿区,是沂沭断裂带西侧与中生代次火山作用有关的金铜铁多金属矿床的典型代表。矿床受控于燕山期中酸性杂岩体与围岩的接触带及围岩中的构造薄弱带(不整合面、层间破碎带、滑脱带),矿体围绕岩体呈环带状产出。本文在成矿地质条件分析基础上,系统分析了沂南金矿床的氢、氧、碳、硫、铅同位素以及铷锶同位素的组成特征,探讨了成矿热液类型和成岩成矿物质来源。结合流体包裹体研究,讨论了成矿流体性质及其演化特点。运用同位素地质年代学方法(全岩Rb-Sr等时线法和单颗粒锆石LA-ICPMS法),厘定了矿床的成岩成矿年龄。研究表明,成矿热液早期以岩浆热液为主,后期有部分大气降水的加入,且两者均与围岩发生了同位素交换作用。热液中碳主要为深源岩浆来源,少量来自海相碳酸盐岩的溶解作用。硫化物矿石中的硫同位素组成特征反映了硫源具有深源岩浆硫的特征。矿石铅主要为放射性成因的“J型铅”,其源区年龄(2.37Ga)暗示了矿床的成矿物质来源于结晶基底(新太古代泰山群)。铷锶同位素组成特征表明,含矿中酸性岩体的成岩物质来源为幔壳混合型。研究认为,由早期成矿阶段至晚期成矿阶段,成矿流体的均一温度和盐度依次下降。成矿作用在中低压力的中浅成至浅成条件下进行,主成矿阶段的含矿流体具有中高温、高盐度的特点,流体的沸腾可能是金、铜、铁等成矿物质大量沉淀富集的主要原因。不同方法所测定的成岩年龄基本吻合,集中在113～135 Ma之间,表明沂南金矿床主要侵入岩体形成于早白垩世中晚期。鉴于矽卡岩型矿床成岩-成矿作用在时间上的密切关系,推测沂南金矿床的成矿年龄应略晚于成岩年龄。更多还原

【Abstract】 As a typical Mesozoic subvolcanic-related Au-Cu-Fe deposit in Western Shandong Province, the Yinan skarn-hydrothermal type gold deposit is located on the west side of the Yishu fault zone (the middle segment of the Tanlu fault zone) at the southeastern margin of the North China plate. It includes the Tongjing and Jinchang ore districts which are 6 km away from each other. The ore bodies occur in the contact zones between the Yanshanian intermediate-acidic composite intrusions and their surrounding wall rocks,and the structural weakness zones (unconformity surface, inter-layer fracture zone, slip zone) in the wall rocks. The ore bodies are zonal distribution around the intrusions. Based on the metallogenic settings, this paper has analyzed the composition characters of the H, O, C, S, Pb and Rb-Sr isotopes and the indicative meaning of these isotopes to the chemistry of the ore fluids and the sources of the ore-forming materials and the intrusions. Combining with the fluid inclusion studies, the nature and evolution characteristics of ore-forming fluids are discussed. The diagenetic and metallogenic ages are determined in the use of isotope geochronology method (Rb-Sr whole-rock isochron and single-grain zircon LA-ICPMS method).The composition of H and O isotopes shows that the ore fluids were most likely composed of magmatic water mixed with limited meteoric water at the later mineralization stage. Sulfur and carbon isotopic data suggest that the ore-forming materials were mainly derived from the deep magma and subordinately from the dissolution of wall rocks. The significant Pb isotopic values of the ore might have resulted from the interfusion with a large amount of radioactive anomalous Pb (“J”type Pb), whose calculated age (2.37Ga) implies that the ore-forming materials had close genetic relations with the crystalline basement (Taishan Group). It can be deduced from the composition of Rb-Sr isotopes that the ore-forming stocks might have been the remelting products of high maturity crustal materials or have resulted from the mixture of crustal materials with limited mantle components.Detailed study on fluid inclusions indicated that the homogenization temperature and salinity of the ore-forming fluids declined from the early to late mineralization stage, and the mineralization occurred under the low-medium pressure and epithermal conditions. The ore-bearing fluids were characterized by medium-high temperature and high salinity in the main ore-forming stages. The boiling of ore-forming fluids may have caused the precipitation and concentration of Au, Cu, and Fe.The diagenetic ages measured by different methods are basically consistent and concentrated in 113 ~ 135 Ma, indicating that the main intrusions formed in the middle-late Early Cretaceous. In view of the close time relationship between diagenesis and mineralization of skarn type deposits, the metallogenic age of Yinan gold deposit should be slightly later than the diagenetic age.更多还原