俯冲带是全球最重要的物质再循环场所也是重要的成矿带。研究表明俯冲带岩浆往往具有高氧逸度，但是由于板块俯冲的复杂性，有关俯冲带岩浆高氧逸度的成因问题目前仍存在广泛争议。本项目拟在预研究基础上，选取Lau弧后盆离俯冲带不同距离的基性火山岩玻璃来研究板块俯冲析出的流体对氧逸度的影响；选取Manus弧后盆演化程度不同（涵盖从基性到酸性）的火山岩玻璃，研究岩浆演化对氧逸度的影响。通过参加IODP 351航次，系统采集Amami Sankaku弧后盆代表该岛弧形成、演化的火山岩玻璃，重点研究俯冲带氧逸度随俯冲历史的变化。在此基础上，结合其地球化学组分特征，分析俯冲带氧逸度变化规律和影响因素，以揭示俯冲带高氧逸度的形成机制。氧逸度的测定将利用国内先进的同步辐射X射线吸收近边结构谱微区分析技术，准确测定火山岩玻璃Fe3+/∑Fe和 S6+/∑S比值，计算氧逸度，以期揭示俯冲带高氧逸度及其变化的控制因素。

Subduction zone is the most important place for material recycling and also an important metallogenic belt. Many ore deposits have close relationship with high oxygen fugacity. Previous studies show that arc magma in subduction zone usually has higher oxygen fugacity than Mid-ocean ridge basalt, and it is also found that fluid released from the subducted oceanic plate has high oxygen fugacity. It is, however, still controversial as regards to causal mechanism of the high oxygen fugacity in arc magmas, due to the complexity of subduction process. There have been three major models,subducted material addition, melting of subduction slab and magmatic evolution. In this project, we plan to analyse basic volcanic glass with diffenrent distance from subduction zone from the Lau back-arc basin, volcanic glass (ranging from basic to acidic) of different evolution degree from the Manus back-arc basin, and volcanic glass representing evolution of arc magmas from the primary arc magmas formed during the initiation of the subduction zone to well developed backarc extension in Amami Sankaku basin. The Fe3+/∑Fe and S6+/∑S ratios of volcanic glass will be determined using new synchrotron radiation micro X-ray absorption near edge structure spectra (XANES) technique, to get reliable oxygen fugacity information. Combining with other geochemical and petrological studies, e.g., major and trace elements, the project aims at firmer constraints on the formation of high oxygen fugacity in subduction zones.