论文部分内容阅读
许多太古代绿岩金矿、维特瓦特斯兰德金矿、板岩带金矿及浅成热液金矿的形成与低盐度、高温(>200℃)还原流体有关。这种含金流体出现在不同时空、岩石序列及构造背景中,是镁铁质岩和/或杂砂岩变质去挥发分作用的产物。绿泥石-钠长石-方解石-石英组合(如镁铁质岩或杂砂岩),在绿片岩-角闪岩相边界发生的变质作用(约480℃±20°,3～5kbar)产生大量低盐度H_2O-CO_2流体,其成分与许多金矿床已查明的流体相似。流体含还原硫(由黄铁矿溶解提供),具备Au呈Au-S络合分子搬运的理想条件。金的沉淀可以因温度、硫活度降低及氧活度变化实现。变质去挥发分流体模式解释了主要金省之共性(如高地热梯度、低盐度以及与变质作用大致同时),也说明了容矿岩石与构造、具体时序关系、蚀交组合以及不同矿床地质年龄之多变性。相似性是由深部过程产生,而差异性则是由沉淀位置或其附近的作用造成。
Many of the Archean Greenstone Gold, Witterwatlander Gold, Slate Gold and Epithermal gold formations are associated with low salinity, high temperature (> 200 ° C) reduction fluids. The gold-bearing fluid, which appears in different time and space, rock sequences and tectonic settings, is the product of metamorphism and devolatilization of mafic rocks and / or miscellaneous sandstones. Chlorite-albite-calcite-quartz assemblage (such as mafic rocks or miscellaneous sandstones) produce a large amount of metamorphism (about 480 ℃ ± 20 °, 3-5kbar) at the metamorphite-amphibolite facies Low-salinity H_2O-CO_2 fluids have compositions similar to those found in many gold deposits. The fluid contains reduced sulfur (provided by the dissolution of pyrite), with Au being the ideal condition for Au-S complexation. Gold precipitation can be due to temperature, sulfur activity and oxygen activity changes to achieve. The metamorphic to volatile fluid model explains the commonalities of the major gold provinces (eg, high geothermal gradients, low salinities, and metamorphism), as well as the rock and structure of ore-hosting, the specific timing relationships, eclogite assemblages, Variability of age. Similarity is generated by deep processes and differences are caused by the role of the sedimentation site or its vicinity.