现代海底超镁铁质岩系热液系统与地质意义

现代海底热液循环与洋中脊地质过程一直是国际洋中脊计划研究的热点.海底热液系统多数都与海底玄武岩及其水-岩反应直接相关,而一类与深海橄榄岩的产出及其蛇纹石化作用有关的海底热液系统——超镁铁质岩系热液系统,以具有高浓度H2和CH4异常而低SiO2浓度为显著特征,主要分布在慢速扩张大西洋中脊和超慢速扩张北冰洋Gakkel洋脊和西南印度洋中脊.超镁铁质岩系热液系统在流体组成、构造背景和硫化物成矿方面与玄武岩热液系统有很大差异,主要表现在地幔来源超镁铁质岩石的普遍出露、喷口流体高的H2和CH4异常以及硫化物中高Co/Ni比值.超镁铁质岩系热液系统的发现丰富了全球洋中脊热液系统的研究内容,对洋中脊地质过程、海底热液活动及其成矿作用研究具有重要意义.

CHARACTERISTICS OF SEAFLOOR ULTRAMAFIC HOSTED HYDROTHERMAL SYSTEMS AND THE IMPLICATIONS

The research of submarine hydrothermal circulation and geological processes at mid-ocean ridges is a hotspot of international mid-ocean ridge research.Most of seafloor hydrothermal systems are directly related to submarine basalt and sub-seabed water-rock reaction.And,a new hydrothermal system is characterized by the ultramafic hosted hydrothermal systems with high concentration of H2 and CH4,and low concentration of SiO2,which is located at slow-spreading Mid-Atlantic Ridge and ultraslow-spreading Gakkel Ridge in Arctic Ocean and Southwest Indian Ridge.Hydrothermal fluid composition,structure setting and sulfide mineralization of ultramafic hosted hydrothermal systems are different from basalt hosted hydrothermal systems.Ultramafic rock is generally exposed in slow-ultraslow spreading ridge,and high concentration of H2 and CH4 in vent fluid and high Co/Ni ratio in sulfide are the significant characteristics of ultramafic hosted hydrothermal systems.The discovery of ultramafic hosted hydrothermal systems has enriched the research contents of seafloor hydrothermal systems at the global mid-ocean ridge system,which is significantly important to the study of the international mid-ocean ridge geological process,submarine hydrothermal activity and mineralization.