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

LÜ 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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