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世界上大部分已探明的黄金源自于一系列石英脉。这些石英脉是在约30亿年前造山运动期间从沿深大地震活动断层流动的大量水中沉淀而成1-3。石英脉是在地震期间6的震荡压力下形成的4,5,但是其压力震荡的幅度以及对矿床形成的影响尚不清楚。在此我们用一个简单的热动力学活塞模型,模拟计算在地震期间充填流体的断层空穴所经历的流体压力下降。模型的几何形态由典型断层割阶的大小限定,如在西澳大利亚的雷文奇(Revenge)金矿床7以及世界其他金矿中的断层割阶。我们发现空穴的扩张会引起割阶中封闭流体压力的急剧下降,从而膨胀为很低浓度的蒸汽。这种流体的瞬态蒸发作用导致了硅和一系列痕量元素同时迅速地沉淀,形成富金石英脉。随着瞬态蒸发作用的继续,更多流体流入新扩张形成的空穴,直至孔隙压力与环境压力一致。多次地震逐渐形成了达到工业品位的金矿。
Most of the world’s proven gold is derived from a series of quartz veins. These quartz veins were precipitated from large volumes of water that flowed along deep, major seismic faults during the orogeny about 3.0 billion years ago. Quartz veins were formed during turbulent pressure periods 6 and 4, 4 but the magnitude of pressure oscillations and their effect on deposit formation was not clear. Here we use a simple thermodynamic piston model to simulate the drop in fluid pressure experienced by fault-filled cavities during an earthquake. The geometry of the model is defined by the size of a typical fault cut, such as the cut-off in the Revenge gold deposit 7 in Western Australia and other gold deposits in the world. We find that the expansion of holes causes a drastic drop in the pressure of the enclosed fluid in the cut stage, thereby expanding into a very low concentration of steam. The transient evaporation of this fluid results in simultaneous rapid precipitation of silicon and a series of trace elements to form gold-rich quartz veins. As the transient evaporation continues, more fluid flows into the newly expanded cavity until the pore pressure is consistent with the ambient pressure. Many earthquakes gradually formed to achieve industrial grade gold mine.