湖北徐家山锑矿床地球化学和成矿机理研究

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	湖北徐家山锑矿床地球化学和成矿机理研究
其他题名	Geochemistry and metallogenic mechanism of the Xujiashan antimony deposit in Hubei Province, China
	沈能平
	2008-05-27
学位授予单位	中国科学院地球化学研究所
学位授予地点	地球化学研究所
学位名称	博士
关键词	徐家山锑矿床成矿流体成矿物质成矿时代矿床成因鄂南
摘要	The Xujiashan antimony deposit is located at the Tongshan County, Hubei Province, South China, and its antimony mineralization occurs in the marine carbonates of the Upper Sinian Doushantuo and Dengying Formations. This deposit is the most economic significant antimony deposit in Hubei Province, and also is one of typical antimony deposits in the South China Sb ore belt. Based on previous studies, systematic field investigation and sampling, this doctoral dissertation placed emphasis on fluid inclusion geochemistry, trace element geochemistry (including REE) and isotope geochemistry (C, O, Sr, S, Pb, Sm-Nd) of the Xujiashan deposit. The sources of ore-forming fluid and materials, the mineralization epoch, the ore genesis, as well as the mineralization mechanism of this deposit had been systematically discussed. Finally, the potential of the Sb mineral resources in the Upper Sinian in the South China Sb ore belt had been preliminarily evaluated. Some important conclusions are obtained in this dissertation as follows: 1) The microscopic observation, microthermometry and laser Raman spectroscopy of fluid inclusions in different gangue minerals (including quartz, barite and calcite) from the Xujiashan deposit indicated that, this deposit formed under the low-moderate temperature condition (150 ~ 200℃), and its ore-forming fluid was characterized by NaCl + H2O + CO2 ± N2 type, low salinity (3 ~ 6 wt% NaCl) and moderate density (0.90 ~ 0.96 g/cm3). Combined with H, O, Sr and Pb isotopic results, this fluid was further thought to be of deep circulating meteoric origin, rather than of magmatic hydrothermal origin. 2) The carbon, oxygen isotopic compositions of the pre- and syn-mineralization calcites from this deposit revealed that the ore-forming fluid is characterized by H2CO3 as the dominant dissolved carbon species. The fluid-rock interaction between the ore-forming fluid and host rocks was responsible for the precipitation of stibnite and the syn-mineralization calcite in the Xujiashan mining district. Combined with the REEs data of these calcites, it was concluded that the pre- and syn-mineralization calcites formed during different stages, but they shared the same source. 3) The trace element, carbon, oxygen and sulfur isotopic results indicated that the ore-forming materials of the Xujiashan deposit were closely associated with the host rocks in the mining district. The sulfur isotopic values of stibnite (+11.2‰ ~ +14.4‰) were relatively higher compared with other stibnite from the South China Sb ore belt, these sulfur isotope data were quite uniform, and displayed obvious tower effect in the histogram, which revealed the sulfur source in this deposit was unique, only derived from the host marine strata. 4) The method using Sr and Pb isotopes to trace ore-forming materials was first employed in the Xujiashan antimony deposit. Lead isotope of ores revealed that there existed two source beds in this deposit, one was the host Sinian rocks, and the other was the underlying Mesoproterozoic basement. This conclusion was conflicted with the traditional opinion that the ore-forming materials were only derived from the host strata. Sr isotopic data further provided support for the underlying Mesoproterozoic Lengjiaxi Group basement as an important source bed. 5) The Sm-Nd isotopic compositions of the syn-mineralization calcite from the Xujiashan deposit were determined for the first time. Three isochron ages of 323Ma, 348Ma and 402Ma were obtained. Combined with the Pb model age for stibnite from this deposit and regional metallogenic setting, it was concluded that antimony mineralization in the Xujiashan deposit took place during Caledonian Period, rather than Yanshanian Period as previously expected. This conclusion would be favorable of further understanding the ore genesis and mechanism of this deposit. 6) The mineralization epoch of the Xujiashan antimony deposit is consistent with other antimony (and/or gold) deposits hosted by the Pre-Cambrian strata in Jiangnan Old Land. The ore-forming fluid in the Xujiashan deposit was similar to those of other typical antimony deposits in the South China Sb ore belt. Thus there existed certain common character among antimony deposits occurring in different places and strata in this ore belt, which is helpful for revealing the intrinsic relationship of different antimony deposits and large-scale antimony mineralization mechanism throughout the South China Sb ore belt. 7) Based on the author’s and previous studies, the genetic type of the Xujiashan antimony deposit had been re-determined, that is, the antimony was of sedimentary– reworked stratabound origin. 8) The potential of Sb mineral resources of the Upper Sinian in the South China Sb ore belt had been preliminarily evaluated. The Upper Sinian strata show great potential of mineral resources in the Sb ore belt, especially in the Southern Hubei, Northwestern Jiangxi and Western Hunan, the strata probably became one of the most promising strata for stibnite prospecting in the future.; 　　湖北省通山县的徐家山锑矿床赋存于上震旦统灯影组和陡山沱组的海相碳酸盐岩中，该矿床是华南锑矿带内典型代表性锑矿之一，也是湖北最具经济价值的锑矿床。本论文以该矿床为研究对象，在系统整理前人工作的基础上，进行了深入细致的野外地质考察和系统采样，选取有代表性的样品，运用流体地球化学、元素地球化学、同位素地球化学（C、O、Sr、S、Pb、Sm-Nd）等方法手段，对其成矿流体来源、成矿物质来源、成矿时代、矿床成因等主要矿床学问题进行了系统研究，探讨了该矿床的成矿机理，并对华南锑矿带内上震旦统锑资源潜力进行了初步评价。本论文主要取得以下几点认识： 1）通过对该矿床成矿期脉石矿物（石英、重晶石和方解石）中包裹体镜下观察、显微测温和激光拉曼探针分析，表明该矿床为典型的中低温（150～200℃）热液锑矿床，其热液属NaCl + H2O + CO2 ± N2型，具低盐度（3～6% NaCl）和中等密度（0.90～0.96 g/cm3）特征。结合氢、氧、锶、铅同位素等研究结果，进一步推断这种成矿流体主要来源于经深部循环演化的大气降水，不支持其主要来源于岩浆期后热液的观点。 2）该矿床成矿前和成矿期方解石碳、氧同位素研究结果，表明成矿流体中的溶解碳以H2CO3为主，该流体与围岩发生水－岩相互作用是导致成矿期方解石和辉锑矿沉淀的主要机制。结合方解石的稀土元素地球化学研究，可推断该矿床的两期方解石为同源不同期的产物。 3）微量元素、碳、氧、硫同位素研究结果，表明徐家山矿床的成矿物质与赋矿围岩具有亲缘性；其中最主要的矿石矿物—辉锑矿，其硫同位素组成（+11.2‰～+14.4‰）相对较高（平均值可能在华南锑矿带内最高）、极其均一，且塔式效应明显等为特征，指示该矿的赋矿围岩—震旦纪海相地层是硫的唯一来源。 4）对徐家山锑矿床首次利用锶、铅同位素示踪其成矿物质来源。利用铅同位素示踪手段，首次明确提出该锑矿床存在两个矿源层，部分成矿物质来自赋矿围岩，部分成矿物质来自下伏基底地层，突破了前人对成矿物质仅来源于赋矿围岩的传统认识；并从锶同位素角度，进一步论证了下伏的中元古界冷家溪群基底是成矿元素锑的重要提供者。 5）首次对徐家山矿区成矿期方解石的Sm-Nd同位素组成进行了测定，并初步获得三条等时线年龄（323Ma、348Ma和402Ma）。结合该矿辉锑矿的正常铅模式年龄及成矿地质背景，可推断出该矿床应形成于加里东期。该结论否定了前人燕山期成矿的观点，为重新认识该矿的矿床成因和成矿机理提供新的契机。 6）徐家山锑矿床的成矿时代与那些江南古陆中赋存于前寒武系的锑（和/或金）矿床一致，其成矿流体特征与华南锑矿带其它典型锑矿床相似，揭示出华南锑矿带内不同地段、不同层位产出的锑矿床存在某种共性，这有助于揭示我国华南锑矿带不同锑矿床之间的内在联系以及该矿带锑大规模成矿的机制。 7）根据前人和本文的研究成果，重新厘定了徐家山锑矿床的成因类型，明确提出该锑矿为沉积－改造型矿床，层控特征非常明显。 8）初步评估华南地区上震旦统中锑矿的找矿潜力。认为华南锑矿床带中上震旦统，尤其是鄂南、赣西北、湘西等地的该套地层，锑资源潜力巨大。华南锑矿带中的上震旦统有可能成为我国将来找锑矿取得突破的重要层位之一。
页数	112
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3408
专题	研究生_研究生_学位论文矿床地球化学国家重点实验室
推荐引用方式 GB/T 7714	沈能平. 湖北徐家山锑矿床地球化学和成矿机理研究[D]. 地球化学研究所. 中国科学院地球化学研究所,2008.

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