Abstract
The Fankou giant deposit (with exceeding 10 Mt Zn + Pb metals, grading at 15 wt%) is a carbonate-hosted, stratabound Zn-Pb deposit in the northern Quren Basin, South China. Lenticular, stratiform and wedge-shaped orebodies are strictly hosted in specific layers of Upper Devonian to Lower Carboniferous carbonate sequences along a series of NE and NNE trending faults. Previous ore geological and geochemical studies proposed that the Fankou can be analogous to a Mississippi Valley-type (MVT) deposit, but how the evolution of complex fault system controls ore-forming fluids migration, metals accumulation and orebodies localization remains unclear. To address this question, we conducted a deposit-scale structural analysis based on the geological mapping, underground works, and diamond drills logging. We identified three-order structures gradually growing in the Fankou deposit, including: 1) The first-order fault represented by F203 is a NW-striking thrust fault penetrating basement and acts as a major conduit for ultimate hydrothermal fluids migrations from depth; 2) The second-order faults include a spectrum of NNW-striking faults F2, F3, F4, F4, F5, F6, F7, F8 and F9. They are intersected with F203 in depth, and soon before and synchronous activities with Zn-Pb mineralization; 3) The third-order faults contain a series of NNE-striking F100, F101 and F102 with limited scale, which is subordinate to second-order faults and control the terminal localization of Zn-Pb orebodies. Collectively, we conclude that the evolutionary three groups of deposit-scale faults, derived from the regional NE-striking Wuchuan-Sihui Fault, jointly control the ore-forming fluids migrations from deep to shallow and from SE to NW in space. It is noteworthy that the second- to third-order faults act as the direct metal precipitation space when the upwards metalliferous fluids replaced with the favorable lithological layers. Therefore, we highlight that the southeast part of the mining area, where the metalliferous fluids came from, is a promising exploration target area in future.
Published Version
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