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胶莱盆地东北缘牧牛山杂岩带金矿成矿机制研究

Study on the metallogenic mechanism of gold deposits in the Muniushan complex zone, northeastern Jiaolai Basin

  • 摘要: 牧牛山杂岩带内岩浆岩以同心环状“反环带”增生方式侵入,燕山晚期伟德山序列岩体沿燕山早期玲珑序列岩体外围侵入,并带来了更多的热能和成矿物质,提供了额外的流体驱动力和上升通道,从而更有利于成矿流体的运移和沉淀。通过对林寺山一带构造行迹的野外详细观察和区域资料、地质勘查成果的综合分析研究,在早白垩世时期,西太平洋板块向华北板块以北北西向高速斜向俯冲的挤压构造应力场背景下,牧牛山杂岩带内构造活动以左行走滑挤压为主,并受多期次构造叠加,在浅部形成高角度铲式断裂,在深部主构造面形成较为平缓、规模较大的脆-韧性转换带。随着携带大量碳酸盐熔体的大气降水与含金流体在深部缓倾的脆-韧性转换带处汇合,该部位空间大且有大量的碳酸盐熔体参与作用,形成厚大的黄铁矿碳酸盐脉型金矿(“辽上式”金矿);部分含金流体继续向上运移,在浅部构造裂隙或破碎带等脆性断裂及层间滑动构造等容矿空间较小的构造薄弱部位形成规模较小的构造蚀变岩型金矿(郭城金矿)。牧牛山杂岩带内金矿为同一构造背景下同一来源的成矿流体在不同构造样式和不同成矿环境下形成的不同规模和不同类型的矿体。

     

    Abstract: The magmatic rocks in the Muniushan complex zone intruded via a concentric“ reverse zonation”accretion pattern. During the Late Yanshanian period, the Weideshan magmatic sequence intruded around the outermargins of the earlier Linglong sequence, introducing additional heat and ore‑forming materials. This provided both anenhanced fluid‑driving force and vertical migration pathways, thereby facilitating the transport and precipitation ofore‑forming fluids.Based on detailed field observations of structural features in the Linshisi Mountain area and acomprehensive analysis of regional data and geological exploration results, it is inferred that during the Early Cretaceous,under a compressive stress regime caused by the high‑angle oblique subduction of the West Pacific Plate beneath theNorth China Plate in a NNW direction, left‑lateral strike‑slip compression dominated the tectonic activity in theMuniushan complex zone. Multiple episodes of tectonic superposition led to the formation of high‑angle shovel‑shapedfaults in the shallow subsurface and broad, gently dipping brittle‑ductile transition zones along major deep structures.Atmospheric precipitation carrying abundant carbonate melts and gold‑bearing fluids converged in these deep, gentlydipping brittle‑ductile transition zones. These zones, with ample space and significant carbonate melt involvement,facilitated the formation of thick pyrite-carbonate vein‑type gold deposits (similar to the“Liaoshang‑style”gold deposits).Portions of the gold‑bearing fluids continued to migrate upward, and in shallow brittle faults, structural fractures, andinterlayer slip zones with smaller ore‑hosting space, smaller‑scale structurally altered‑rock type gold deposits (such asthe Guocheng deposit) were formed.Thus, the gold deposits in the Muniushan complex zone are the result of ore‑formingfluids from a common source and structural regime, forming mineral bodies of different scales and types under variedstructural styles and metallogenic environments.

     

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