金在现代海底热液系统中的分布及演化  

The Occurrence and Evolution of Gold in Modern Seafloor Hydrothermal Systems

作　　者：黄威[1,2,3] 陶春辉[3,4] 孙治雷[1,2] 李军[1,2] 崔汝勇 

机构地区：[1]国土资源部海洋油气资源与环境地质重点实验室青岛海洋地质研究所,山东青岛266071 [2]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,山东青岛266071 [3]中国地质大学地球物理与空间信息学院,武汉430074 [4]国家海洋局海底科学重点实验室国家海洋局第二海洋研究所,杭州310012

出　　处：《地质论评》2017年第3期758-769,共12页Geological Review

基　　金：国家自然科学基金资助项目(编号:41506074);国际海域资源调查与开发“十二·五”课题(编号:DY125-22-QY-25);中国地质调查局海域天然气水合物勘查工程(编号:DD20160218)的成果

摘　　要：现代海底热液系统内冷海水的下渗和热液流体的上涌及由此引发的水岩反应驱动着金的循环演化,并可在海底形成极具经济前景的富金矿床。海底下覆基岩深部层位中的金会因为水岩反应而大量溶解迁移到热液流体中,金含量可比海水高千倍的热液流体在向海底表面运移过程中发生的相分离作用会进一步富集金,当遭遇冷海水发生混合作用后引发H_2S浓度和温度的降低,由此导致金因溶解度降低而从热液流体中迁移出来并赋存在一同形成的硫化物矿物中。海底硫化物中金含量的分布受到围岩性质和构造环境的控制,形成在岛弧和弧后环境中的硫化物一般比洋中脊环境中的硫化物的金含量高,而在相似构造环境下形成在长英质围岩系统和超镁铁质围岩系统中的硫化物其金含量比镁铁质围岩系统中的高。相对于高温阶段形成的黄铜矿,低温成因的黄铁矿和闪锌矿普遍更富集金。在分布最广的黄铁矿的晶格内,固溶体态金的溶解度受到砷含量的控制,当超过矿物的溶解度时则会出现纳米到微米级金颗粒聚合体。虽然热液硫化物中的金含量比热液沉积物高的多,但由于受其捕获效率的制约,随热液流体运移到海底表面的金还是有相当一部分最终随着羽状流扩散到了远端沉积物中或被海洋水体所接纳。若要更清晰甚至定量化地厘清金在现代海底热液系统中的迁移演化过程及控制因素,则微区、原位和高精度的实验方法、分析技术和模拟研究将是下一步工作的重点。The cold seawater penetrates down into thepermeable crust and is heated to rise to the seafloor, these processes cause the water—rock interaction and drive the cycling of gold in modern seafloor hydrothermal systems, even the great commercial prospects for the gold rich deposits thus can be accumulated on the seafloor. The significant amounts of gold is leached from deeper levels in the oceanic crust during hydrothermal alteration, and then dissolve in the hydrothermal fluids which may finally enrich about 1000 times with respect to seawater and subsequently rise rapidly to the seafloor. Phase separation may also occur at more than one location during the hydrothermal fluids’ passage through the oceanic crust leads to gold enrichment in the vapour phase. The gold coprecipitates with the sulfide assemblages from the vent fluids as the effect of cooling and the decrease ofH2S concentrations from mixing with the seawater. The host rock compositions and the tectonic setting leave a strong imprint on the gold contents of the associated seafloor hydrothermal sulfides, the abundances of gold in hydrothermal sulfides collected from intra oceanic arcs and back arc systems are higher than from the mid ocean ridge systems,furthermore, the gold has high contents in sulfides hosted by the felsic rocks and ultramafic rocks than mafic rocks in the similar tectonic setting. The sphalerite and pyrite generally have higher contents of gold compared to the chalcopyrite, which is characterized by higher precipitation temperatures. The solid solubility limit of gold in pyrite which is the most common sulfide in the Earth’s crust controlled by the contents of arsenic, the concentrations data points of gold and arsenic above the saturated solubility implies that the nano micro particulates of gold can accumulate in the pyrite structure. Although the gold contents in hydrothermal sulfides are much higher than the hydrothermal metalliferous sediments, the trapping mechanisms of the seafloor hydrothermal sulfides mineralization for

关 键 词：海底 热液系统 金 

分 类 号：P618.51[天文地球—矿床学] P744[天文地球—地质学]