高镁安山岩和富Nb玄武岩是显生宙非常少见但对岛弧构造-岩浆演化有指示意义的岩石组合。班公湖-怒江缝合带南侧侏罗纪俯冲型蛇绿岩对应的岛弧火山岩到底在哪里？一直是困扰班怒带构造演化的基础科学问题。申请团队在狮泉河火山岩带中发现了与蛇绿岩伴生的11处中-晚侏罗世喷出岛弧高镁安山岩、富Nb玄武岩，为回答这一问题打开了窗口。拟精选两条剖面，通过野外地质考察，岩相学和矿物学，全岩地球化学、矿物原位微区LA-ICP-MS微量和电子探针主量分析，Li-B-Sr-Nd-Pb-Hf-Os同位素示踪，揭示高镁安山岩和富Nb玄武岩的岩石成因；开展锆石U-Pb定年和Ar-Ar定年查明其形成年代和期次；结合全球对比，恢复其代表岛弧的属性和构造-岩浆演化，为重建整个中特提斯洋构造格局和演化提供基础依据。

The high-Mg andesite and Nb enriched basalt suites are rare on earth's Phanerozoic times, yet they are critical to understanding the tectonic-magmatic evolution of island arcs. Where are the Jurassic island arc volcanics which are associated with the Jurassic supra-subduction zone ophiolite in the south side of Bangong-Nujiang suture zone? This is a key but puzzling scientific issue for tectonic framework and evolution of Bangong-Nujiang Meso-Tethys. Recently, we have discovered 11 outcrops of Middle-Late Jurassic island arc origin extrusive high-Mg andesite and Nb enriched basalt which exposed together with ophiolite in Shiquanhe area. This discovery opens a window for answer the question. In this study, we plan to focus on 2 typical vocanic sections, in an attempt to reveal its petrogenesis, chronology and tectonic affinity. We will perform field survey, petrographical and mineralogical observations as well as comprehensive studies on geochemistry and isotope chronology, including whole-rock geochemistry, in-situ LA-ICP-MS mineral trace-element analysis and EPMA major-element analysis, Li-B-Sr-Nd-Pb-Hf-Os isotope analysis, zircon U-Pb dating, and Ar-Ar dating. We will discuss its tectonic setting, and establish the tectonic evolution model of the Shiquanhe island arc.