Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (2): 232-253.DOI: 10.13745/j.esf.sf.2020.3.18

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The geophysical exploration of Mesozoic ironcopper mineral system in the Middle and Lower Reaches of the Yangtze River Metallogenic Belt: a synthesis

Lu Qingtian,MENG Guixiang,YAN Jiayong,ZHANG Kun,GONG Xuejing,GAO Fengxia   

  1. 1. Chinese Academy of Geological Sciences, Beijing 100037, China
    2. SinoProbe Center, Chinese Academy of Geological Sciences, Beijing 100037, China
  • Received:2019-12-10 Revised:2020-01-30 Online:2020-03-25 Published:2020-03-25

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.

Key words:  Middle and Lower Reaches of Yangtze River Metallogenic Belt, lithosphere architecture, deep processes, mineral system, geophysical exploration

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