| 长江中下游成矿带铁-铜成矿系统结构的地球物理探测: 综合分析 |
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| 引用本文： | 吕庆田,孟贵祥,严加永,张昆,龚雪婧,高凤霞.长江中下游成矿带铁-铜成矿系统结构的地球物理探测: 综合分析[J].地学前缘,2020,27(2):232-253. |
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| 作者姓名： | 吕庆田 孟贵祥 严加永 张昆 龚雪婧 高凤霞 |
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| 作者单位： | 1.中国地质科学院, 北京 1000372.中国地质科学院 地球深部探测中心, 北京 100037 |
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| 基金项目： | 国家自然科学基金重点项目(41630320);国家重点研发计划项目(2016YFC0600200) |
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| 摘 要： | 成矿系统是在深部过程驱动下形成的、具有自组织的能量及物质迁移-汇聚系统。系统在形成和演化过程中,在岩石圈不同尺度上留下“痕迹”,这种“痕迹”可以通过地球物理、地球化学和遥感等方法进行探测或观测。文章尝试在成矿系统理论框架下,对近10多年来在长江中下游成矿带进行的多尺度地球物理、地球化学探测结果进行分析,识别典型陆内成矿系统“源区”“通道”“场所”的地球物理、地球化学“痕迹”,尝试构建陆内成矿系统的空间结构模型。主要结论有:(1)长江中下游晚中生代的大规模铁、铜多金属成矿作用是一个完整的成矿系统。该系统包括3个子系统,分别为与高钾钙碱性岩浆岩有关的夕卡岩-斑岩成矿子系统、与橄榄安粗岩有关的陆相火山岩铁(硫)成矿子系统和与碱性岩有关的铜-金(铀)成矿子系统。(2)成矿系统的“源区”来自富集地幔的熔融、底侵,并在壳/幔边界与下地壳物质的混合,具有多级分布特点。幔源岩浆与地壳物质混合的比例决定了成矿金属的类型。(3)成矿带发育的“鳄鱼嘴”构造是铁铜成矿系统的主干“通道”。成矿系统“末端”矿质沉淀的“场所”主要受近地表褶皱、断裂、层间滑脱断层,以及由它们形成的断裂(裂隙)网络控制。(4)区域磁异常、放射性和地球化学异常是成矿系统残留“痕迹”的响应和“标识”。通过分析不同尺度的“标识”特征,可以深入认识成矿系统的空间结构,并可用于深部成矿预测。
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| 关 键 词： | 长江中下游成矿带 岩石圈结构 深部过程 成矿系统 地球物理探测 |
| 收稿时间： | 2019-12-10 |
The geophysical exploration of Mesozoic iron-copper mineral system in the Middle and Lower Reaches of the Yangtze River Metallogenic Belt: a synthesis |
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| LÜ,Qingtian,MENG Guixiang,YAN Jiayong,ZHANG Kun,GONG Xuejing,GAO Fengxia.The geophysical exploration of Mesozoic iron-copper mineral system in the Middle and Lower Reaches of the Yangtze River Metallogenic Belt: a synthesis[J].Earth Science Frontiers,2020,27(2):232-253. |
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| Authors: | LÜ Qingtian MENG Guixiang YAN Jiayong ZHANG Kun GONG Xuejing GAO Fengxia |
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| Institution: | 1. Chinese Academy of Geological Sciences, Beijing 100037, China2. SinoProbe Center, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | Mineral systems driven by deep Earth processes are self-organized critical systems involving the transfer and accumulation of mass and energy. During the formation and evolution of such a system, “fingerprints” are left at different scales across the lithosphere, which can be detected or observed through geophysical, geochemical, and remote sensing methods. In this study, we first analysed multi-scale geophysical and geochemical data over the last decade from the Middle and Lower Yangtze River Metallogenic Belt. Based on the theoretical framework of a deep-seated mineral system, we then attempted to identify the geophysical and geochemical “fingerprints” for the source, channel, and site of a typical intracontinental mineral system. Finally, we attempt to establish a structural model of the mineral system. We concluded that the Late Mesozoic large-scale Fe-Cu polymetallic mineralization in the Middle and Lower Yangtze River Metallogenic Belt may be considered a holistic mineral system, consisting of three subsystems: (1)a skarn-porphyry subsystem related to high-K calc-alkaline magmatic rocks,(2) a terrestrial volcanic iron (sulphur) subsystem related to shoshonite formation, and (3) a Cu-Au (uranium) subsystem related to alkaline rocks. The source area of the mineral system was derived from the melting and underplating of an enriched mantle and subsequent multi-level mixing with lower crustal materials at the crust/mantle boundary. The type of metal formed depended upon the mixing ratio of the mantle-derived magma and crust materials. Moreover, the “crocodile” structure developed in the Middle and Lower Yangtze River Metallogenic Belt is the main channel of the Fe-Cu mineral system. The site of ore precipitation (“termination” of the mineral system)was predominantly controlled by near-surface folds, faults, interlayer detachment faults, and their resultant fracture network. Regional magnetic, radioactive, and geochemical data are the signatures (or “fingerprints”) of a mineral system; by analysing these multi-scale signatures, we can deepen our understanding of the spatial structures of mineral systems and effectively predict deep targets. |
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| Keywords: | Middle and Lower Reaches of Yangtze River Metallogenic Belt lithosphere architecture deep processes mineral system geophysical exploration |
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