班公湖-怒江缝合带中段拉弄蛇绿岩地球动力学成因及对新特提斯构造演化的指示

班公湖-怒江缝合中段是研究班公湖-怒江特提斯洋俯冲消减、碰撞造山过程的关键区域。该区蛇绿岩呈“面状”展布，该区的蛇绿岩形成构造环境是弧后盆地、弧前盆地还是洋中脊，一直存在争议。前人在该区域研究的蛇绿岩主要表现为MORB、OIB型的地化特征，而本项目申请发现的靠近班公湖-怒江缝合带南缘的拉弄蛇绿岩具有典型SSZ型特征。本项目拟在前期工作基础之上，选择班怒带南缘的拉弄蛇绿岩典型剖面开展综合研究，借助于野外地质、岩石学、地球化学、同位素年代学等多种手段，重点查明拉弄蛇绿岩的岩石组合类型、接触关系、时空展布特征，利用精细的年代学数据和系统的地球化学数据分析，研究拉弄蛇绿岩地幔源区特征、岩石成因、构造环境及地球动力学机制，为认识班公湖-怒江缝合带中段所代表的特提斯洋盆俯冲、闭合等构造拼接演化过程提供详实可靠资料。

The middle segment of Bangong-Nujiang Suture Zone (BNSZ) is pivotal area to study the Bangong-Nujiang Tethys ocean subduction and collisional orogenesis. With the further comprehensive study of the “planar” distribution ophiolite, the forming tectonic environment (back-arc basin, forearc basin or mid oceanic ridge) has been controversial. The ophiolite mainly showed the MORB-type and OIB-type geochemical characteristics with the previous research, but the applicant find the Lanong ophiolite has the SSZ-type geochemical characteristics at the southern BNSZ through the preliminary investigation. Based on the preliminary investigation and the reported literature, this project will choose the Lanong ophiolite as the main object, and document new field, geochronological, geochemical, Sr-Nd-Pb, Re-Os and zircon Hf-O isotopic data for the ophiolite. The aim for this project is to (1) find out the rock assemblage type, contact relationship and spatio-temporal evolutionary characteristics of Lanong ophiolite; (2) obtain the elaborate chronology and systematic geochemical data; (3) study the mantle source region characteristics and deep geodynamic mechanism. These always provide the detailed and reliable data to recognize the Bangong - Nujiang Tethys ocean subduction, closure and other tectonic envolution.