Secondary Ion Mass Spectrometry (SIMS) Analyses of Trace Elements in Seafloor Massive Sulfides

该项目涉及二级离子质谱法（SIMS）的发展，作为一种有效和有用的技术，用于定量特定硫化物矿物相中微量元素的浓度。我们计划利用这项技术，通过在10微米尺度上检测ppm至亚ppm水平的微量元素，来研究现代海底硫化物矿床的形成过程和早期演化。海底热液与海水混合形成富硫化物矿床，记录了海底热液活动的时空反应和变化历史。微量元素（Co, Se, Mo, As, Sb, Pb, Cd, Mn, Ag, Au）存在于硫化物矿物中，可以提供有关沉积条件（如温度），源流体组成方面以及矿床和海底热液喷口矿床中金属再活化和化学分带过程的宝贵信息。实现目标的三个步骤是：1)创建标准并建立使用SIMS测量硫化物颗粒（黄铁矿、黄铜矿、磁黄铁矿、黄铁矿和斑铁矿）中微量元素Co、Se、Mo、As、Sb、Cd、Pb、Ag、Ni、Bi和U浓度的方法。2)考察了矿物沉淀条件较好的海底烟囱原生沉淀中10s微米尺度的微量元素分布。3)研究了黑烟烟囱和富铁块状硫化物中与置换和再结晶有关的微量元素分布。SIMS作为一种测量硫化物矿物中微量元素的技术的发展，不仅有利于海底硫化物矿床的研究，而且将在各种环境中硫化物的研究中有更广泛的应用。

This project involves development of Secondary Ion Mass Spectrometry (SIMS) as a valid and useful technique for quantifying concentrations of trace elements in specific sulfide mineral phases. We plan to use this technique to investigate the processes of formation and early evolution of modern seafloor sulfide deposits through examination of trace elements at the ppm to sub-ppm level on a scale of 10s of microns. Sulfide-rich deposits form on the seafloor from mixtures of hydrothermal fluid and seawater, and record a history of reactions and changes in hydrothermal activity through space and time. Trace elements (Co, Se, Mo, As, Sb, Pb, Cd, Mn, Ag, Au) reside in sulfide minerals and can provide valuable information about depositional conditions (e.g., temperature), aspects of source fluid compositions, and the processes of metal remobilization and chemical zoning in ore deposits and in sea-floor hydrothermal vent deposits. The three steps in achieving our objectives are: 1) To create standards and establish methods using SIMS to measure the concentrations of the trace elements Co, Se, Mo, As, Sb, Cd, Pb, Ag, Ni, Bi, and U in sulfide grains (pyrite, chalcopyrite, pyrrhotite, marcasite, and bornite). 2) To examine the distribution of trace elements on a scale of 10s of microns in primary precipitates in seafloor chimneys where the conditions during mineral precipitation are well characterized. 3) To examine trace element distribution associated with replacement and recrystallization within black smoker chimneys, and within Fe-rich massive sulfides. Development of SIMS as a technique to measure trace elements in sulfide minerals will not only benefit studies of seafloor sulfide deposits, but will have wider application for studies of sulfides from a variety of environments.