| 湖南黄沙坪多金属矿床含矿斑岩锆石U-Pb年龄、Hf同位素组成及其地质意义 |
| 艾昊
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| 导师 | 李晓峰
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| 2013
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| 学位授予单位 | 中国科学院研究生院
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| 学位授予地点 | 北京
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| 学位名称 | 硕士
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| 学位专业 | 地球化学
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| 关键词 | 黄沙坪
含矿斑岩
锆石u-pb年龄
Hf同位素
壳幔相互作用
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| 摘要 | 湖南省黄沙坪是一个以Pb、Zn为主，伴生W、Mo、Cu、Ag等多种有益元素的多金属矿床，位于湖南千里山-骑田岭矿集区的西部，在大地构造位置上位于南岭构造带中段北缘，处于郴州-蓝山北东向基底构造岩浆岩带与郴州-邵阳北西向基底构造岩浆带的交汇部位，耒阳-临武南北向构造带的中段，具有优越的成矿地质条件，是南岭多金属成矿带的重要组成部分。 本论文在深入细致的总结前人资料的基础上，统计了黄沙坪含矿斑岩的地球化学组成，并与区域内有关的成矿花岗岩体进行对比研究；对黄沙坪矿区进行了详细的野外地质工作，系统的采集了与成矿有关的花岗斑岩、花斑岩和石英斑岩及其相关的矿石样品，通过手标本及光薄片镜下鉴定，分析了岩浆岩及矿石的矿物组成、结构构造等；通过对岩浆锆石进行U-Pb同位素年代学以及锆石原位Hf同位素组成的研究，重新精确的厘定了黄沙坪多金属矿床含矿斑岩的成岩时代及成岩物质来源，结合矿区所在的大地构造位置以及区域内成矿规律，讨论该矿床形成的地球动力学背景，另外，尝试从岩浆物质来源及其与矿区成矿作用关系入手，对矿床成因及成矿过程进行重新归纳。该论文取得的主要认识如下： 黄沙坪多金属矿床与成矿有关的岩浆岩主要为石英斑岩、花岗斑岩和花斑岩，根据锆石的晶体形态特征、CL图像和Th/U比值，表明锆石为岩浆锆石，但可能受到了热液蚀变作用的影响；岩浆锆石U-Pb年代学表明含矿斑岩成岩年龄在150~155Ma之间，形成于晚侏罗世，其中，石英斑岩为155.3±0.7Ma、花斑岩为150.1±0.4Ma、花岗斑岩为150.2±0.4Ma；锆石原位Hf同位素数据表明，含矿斑岩的成岩物质来源主要为中晚元古代古老基底的重熔，其中石英斑岩成岩物质主要来源于地壳，地幔物质参与较少，花斑岩和花岗斑岩的形成有少量地幔物质的参与；在本文数据的基础上，结合矿床所在的区域地质背景和岩浆岩及其与之有关矿床的时空分布规律，认为该矿床成岩成矿地球动力学背景主要与中-晚侏罗世活动的Farallon-Izanagi洋岭/转换断层俯冲作用有关。另外在总结区内成矿地质条件、成矿规律、地球化学特征的基础上，结合本文锆石U-Pb年龄及Hf同位素数据，将矿床的形成过程与壳幔相互作用相联系，重新归纳该矿床的成矿过程。 |
| 其他摘要 | The Huangshaping Pb-Zn polymetallic deposit in Hunan Province is located in the west part of the famous Qianlishan-Qitianling mineralization zone and the northern section of Nanling Moutain granites zone. It is also distributed in the intersection part of Chenzhou-Lanshan NE-trending base tectonic magmatic rocks belt and Chenzhou-Shaoyang NE-trending base tectonic magmatic rocks belt with superior metallogenic geological conditions and it is an important part of Nanling Mountain Metallogenic belt. In this paper, on the basis of the summary of predecessors’ study, the geochemistry characteristics of ore-related granites were summarized and were compared with other ore-related granites in southeast Hunan province. Besides, we carried on detailed field geological work and systematically collected granite porphyry, granophyre, quartz porphyry and related ore samples. Combined with hand specimen and microscopic research, the mineral composition, structure and so on were analyzed. Meanwhile, the radioactive age by LA-ICP-Ms U-Pb dating method and Hf isotope composition of zircons by LA-MC-ICP-Ms method have been systematically reported for granophyre, granite porphyry, and quartz-porphyry which are important for mineralization. Based on this study and combing with the tectonic background, the sources and the geodynamic of the ore-related granites have been discussed and finally the formation process of Huangshaping polymetallic deposit was proposed. The main conclusions are listed as follows. The Huangshaping Pb-Zn polymetallic deposit is mainly associated to quartz porphyry, granite porphyry and granophyre. According to the crystals form, CL images and the Th/U ratios of zircons, these zircons from ore-related rocks belong to igneous zircons which are influenced by hydrothermal alteration. The LA -ICP-MS zircon U-Pb dating shows that the ages of granophyre, granite porphyry and quartz porphyry are 150.1±0.4Ma, 150.2±0.4Ma, 155.3±0.7Ma distinctively, which suggest an middle Yanshanian emplacement. The in situ Hf isotope analysis reveals that these three kinds of ore-related porphyries were derived from the melt of the ancient basement of Mesoproterozoic. Among these three ore-related porphyries, the quartz-porphyry was mainly derived from the lower crust without mantle material, meanwhile, granophyre and granite porphyry were derived from the mixed sources of the lower crust and mantle as a product of crust-mantle interactions. Based on this study and combing with the tectonic background and the metallogenic regularity in Nanling Mountain, we suggest that the formation process of Huangshaping ore-related porphyries should be related to some mantle material and they formed under an extensional regime related to middle Later Jurassic Farallon-Izanagi triple ridge subduction and transform faults subduction. Meanwhile, on the basis of the summary of predecessors’ study and combine with the data in this paper, a possible genetic mechanism of the ore field is proposed which is combined with mantle-crust interaction. |
| 学科领域 | 矿床地球化学
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/5841
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| 专题 | 研究生_研究生_学位论文
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推荐引用方式
GB/T 7714 |
艾昊. 湖南黄沙坪多金属矿床含矿斑岩锆石U-Pb年龄、Hf同位素组成及其地质意义[D]. 北京. 中国科学院研究生院,2013.
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