热液成矿作用地球化学:以金矿为例

Geochemistry of hydrothermal mineralization:Taking gold deposit as an example.

文中以金矿为例总结了热液成矿地球化学特征,包括热液蚀变、金在成矿热液中的地球化学行为、富集-沉淀机制以及在硫化物中的存在形式。热液蚀变过程中形成的矿物组合反映了成矿流体的地球化学特征,蚀变模式具有重要的找矿勘探意义。在热液体系中,金主要以Au-Cl或者Au-S络合物的形式进行运移,体系温度、压力、氧逸度以及硫逸度等条件的变化是导致络合物分解、金沉淀的主要机制。在较高压力条件下,金趋向于在热液蒸汽相中富集。As和Sb是金矿热液体系中常见的伴生元素,在较低硫逸度条件下,形成自然砷/自然锑-自然金组合。金从热液中沉淀后主要以显微包裹体或者固溶体金的形式赋存于黄铜矿、毒砂、磁黄铁矿以及黄铁矿等硫化物中,而硫化物中固溶体金的量主要受热液H_2S活动性的控制。

Hydrothermal alteration,geochemistry of gold in hydrothermal fluid,concentration form and precipitation mechanism of gold and its forms in sulfide are summarized in this paper.Hydrothermal alteration is the reaction between fluid and host rocks.Mineral assemblages formed during alteration reflect the geochemical feature of ore-forming fluids.Gold is always transported as Au-Cl and Au-S complexes in fluids.The change of physicochemical conditions such as temperature,pressure,oxygen fugacity and sulfur fugacity is the effective mechanism for gold precipitation.In fluid with high temperature and pressure,gold tends to concentrate in vapor phase.Au-As and Au-Sb associations are common in gold deposit.In hydrothermal with low sulfur fugacity, native antimony/arsenic-native gold assemblage may precipitate.Gold is probably hosted in sulfide as inclusion or solid solution after precipitated from fluid.