台湾龟山岛热液流体扩散及其对元素分布的影响

Although it has been revealed that the elements in the Kueishan Tao hydrothermal fluids are from ambient seawater and host andesite, the impact on the ambient by the output and diffusion of the fluids are still not yet clear. Thus, the hydrothermal fluid diffusion and its influence on the element distribution in Kueishan Tao hydrothermal field off northeastern Taiwan will be carried out. The trace element (Fe, Cu, Co, V, Mn, As and Hg) and rare earth element distribution in the hydrothermal fluids, ambient water, normal seawater and hydrothermal sulfur particles will be studied systematically, combining the density and flow of the fluid, the temperature difference between the seawater and fluid, the pH, Eh and Fe/Mn ratio of the water samples, the size and density of the particles and the specific heat capacity and flow viscosity of seawater, to estimate the hydrothermal flux (heat flux and matter flux), obtain the structure and scale of the hydrothermal fluid diffusion and reveal the influence on the element distribution by seawater dilution, redox and the sedimentation and adsorption of the sulfur particles. Based upon, we will understand the factors controlling the element composition variation during the hydrothermal fluid diffusion, enrich the knowledge of geochemical behavior of elements in the hydrothermal environment that help to understand the influence on the ambient by hydrothermal activity and develop the theory of submarine hydrothermal activity and mineralization.

虽然前期工作揭示出龟山岛热液流体中的元素来源于周围海水和基底安山岩，但热液流体的输出与扩散对周围海水环境的影响机制还尚不明晰。因此，将开展龟山岛热液流体扩散及其对元素分布的影响研究，综合分析龟山岛热液流体、热液喷口附近水体、正常海水和热液S颗粒物中的微量元素（Fe、Cu、Co、V、Mn、As和Hg）和REE特征，结合热液流体的密度、流速、流量、其与海水之间的温度差、水体样品的pH值、Eh值、Fe/Mn比值、颗粒物样品的粒径和密度以及海水的比热容和流动粘度等参数，评估龟山岛热液流体输出的热通量和物质通量、获得龟山岛热液流体扩散的结构和规模、揭示海水稀释作用、氧化还原作用和热液S颗粒物的沉降与吸附作用对元素分布的影响。从而深入认识热液流体扩散过程中元素变化的控制因素及机理，丰富对热液环境中元素地球化学行为的认识，有助于热液活动对海水环境影响机制问题的解决，丰富和发展海底热液活动及其成矿理论。

龟山岛是沿冲绳海槽扩张轴向西南延伸的最后一个火山中心，正喷发大量热液流体，对周围的海水、沉积和生态环境产生了影响。该项目完成台湾龟山岛热液活动调查，获得热液流体、沉积砂、硫磺颗粒等样品。在此基础上，开展了热液通量研究，明确了龟山岛热液活动的稳定性。开展了热液流体扩散及其对元素分布的影响研究，模拟了龟山岛热液流体与海水混合过程；发现砷是龟山岛热液流体扩散有效指示剂；揭示出龟山岛热液流体Fe、Mn、As和REE在海水中的扩散模式，提出Mn/Fe比值可指示龟山岛喷口附近海水是否受到热液流体的影响，而As（V）/As（III）比值，可有效反映龟山岛热液流体与海水混合后氧化还原性质的变化情况。开展了热液产物中记录的热液活动信息研究，阐明了龟山岛热液柱含硫颗粒物、沉积砂中黄铁矿微形貌与化学组成特征，揭示了黄铁矿微晶成因，揭示了龟山岛热液流体对生物壳体元素分布的影响，阐明热液成因铁氧化物记录的热液流体信息，同时还解释了生物和非生物作用在铁氧化物形成过程中的竞争机制。攻克了自然硫颗粒微量元素和稀土元素测试关键技术。提出一套有效的海底浮岩前处理方法。合作撰写研究论文12篇，其中SCI论文10篇；获授权实用新型专利2项。