Qiyugou auriferous breccia pipes:A low-sulphidation epithermal system linked with transition of tectonic regime from collisional compression to extension,Xiong'ershan,Henan,China |
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| Authors: | ZHANG Yuanhou ZHANG Shihong Pirajno Franco |
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| Abstract: | The Xiong'ershan area, as a part of a metallogenic province in cetral China, contains substantial Leimengou porphyry molybdenite deposit, Qiyugou breccia gold deposits and vein gold deposit occurred in fault zone, as well as previously refer to as orogenic gold deposit. Around or nearby the Mesozoic porphyry granite, the typical porphyry deposit, much more breccia pipes and breccia gold deposit are developed in the area. In this paper we focus on reporting preliminary results obtained from field, petrographic work on the Leimengou porphyry molybdenite and the Qiyugou breccia gold deposit, as well as laser Raman microspectroscopy and microprobe analyses carried out on samples from the Au-bearing Qiyugou breccia pipes. An adularia-calcite assemblage is reported in these breccia gold deposits. Two stages of hydrothermal alteration, pervasive and vein, are identified. The first stage consists of the alteration of the breccia clasts and rock flour by actinolite, green biotite, epidote, chlorite and minor sericite. This hydrothermal activity is likely to relate to the molybdenite mineralisation episode. The second stage is characterised by quartz veining and adularia and calcite filling open-spaces. Vein ores associated with quartz, sericite, and minor calcite alteration occur in NE-trending fault that cut the first stage of alteration. The adularia-calcite alteration is genetically associated with gold mineralization. The adularia-calcite assemblage in the area suggest that the Qiyugou pipes are of low-sulphidation epithermal in nature. The Qiyugou breccia pipes are coeval and spatially associated with the nearby Leimengou porphyry Mo deposit, which together conform to an alkalic mineralising system. We propose a model for the development and evolution of the breccia pipes in conjunction with a model that describes the genesis of the porphyry Mo and auriferous breccia pipes as a unified magmatic-hydrothermal system, which is linked with transition from collisional compressional to extensional geodynamic regime. |
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| Keywords: | breccia pipe low-sulfidation porphyry Mo magmatic-hydrothermal system Qiyugou |
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