扬子克拉通黄陵穹隆古元古代混杂岩成因及深俯冲动力学意义

Early Precambrian tectonic ophiolitic mélange, as a symbolic record of plate subduction and collision sutures in the early earth, is a critical research object to unravel significant frontier problems in Geoscience, such as start timing of plate tectonics and dynamic mechanism of tectonic evolution, etc. As for a big geological frontier issue of interaction between slab and mantle boundary in subduction channels within Precambrian subduction-collision orogens, this study focuses on a newly recognized Paleoproterozoic Shuiyuesi ophiolitic mélange in the northern Huangling Dome within the Yangtze craton. By applying multi-disciplinary study methods including detailed structural-petrological mapping of key geological profiles and typical outcrops, tectonics, microstructure, petrology, geochemistry and isotopic geochronology, etc., we will concentrate on studying genesis, deformation fabrics (foliations, lineations, etc.), metamorphic microstructure P-T-t paths and formation age of representative tecto-lithostratigraphic units in the mélange (e.g., high-pressure metamorphic rocks, meta-mafic/ultramafic rocks etc.), in order to determine genesis and tectonic-metamorphic evolution, subduction polarity, tectonic exhumation mechanisms of deep subduction . Conclusively, we will try to illuminate tectonodynamic significance of the Paleoproterozoic deep subduction and collision orogenic evolution. This study will provide critical geological insights into unraveling several great geological problems, such as assembly and breakup of the Paleoproterozoic Columbia supercontinent, etc.

早前寒武纪蛇绿混杂岩（混杂岩）是地球早期板块俯冲-碰撞缝合带的标志性记录和板块构造体制启动时间、大地构造演化动力学机制等重大地学前沿问题关键研究对象。研究针对早前寒武纪板块俯冲-碰撞造山俯冲隧道板片-地幔边界相互作用前沿研究课题，以扬子克拉通黄陵穹隆基底新发现的古元古代水月寺蛇绿混杂岩为研究对象，运用关键剖面和典型露头精细构造岩石填图解析、大地构造相、显微构造学、岩石学、地球化学及同位素年代学等研究方法，重点研究蛇绿混杂岩内代表性构造单元（高压变质岩、变镁铁-超镁铁岩等）成因、变形组构（面理、线理等）、变质显微构造P-T-t轨迹及形成时代特征，厘定扬子克拉通古元古代蛇绿混杂岩带及标志性构造岩石单元成因、构造变质演化、俯冲极性、深俯冲构造折返机制，揭示古元古代深俯冲-碰撞造山成因演化的构造动力学意义，为古元古代哥伦比亚超大陆聚合与裂解等重大地质问题研究提供关键地质依据。

早前寒武纪蛇绿混杂岩（混杂岩）是地球早期板块俯冲-碰撞缝合带标志性记录和板块构造体制启动时间及机制等重大地学前沿问题关键研究对象。华南扬子克拉通黄陵穹隆基底北部古元古代水月寺蛇绿混杂岩变沉积岩及构造岩块（高压变沉积岩、变镁铁-超镁铁岩）成因、变形组构、变质显微构造P-T-t轨迹及年代学特征的综合研究，主要获得以下重要新成果：.（1）首次在古元古代水月寺蛇绿混杂岩带内发现华南最古老（～2.00Ga）冷俯冲低温高压榴辉岩相（571～576℃, 19.2～21.8kbar）变泥质岩，为现代板块构造体制古元古代启动提供了关键变质地质证据。.（2）古元古代水月寺蛇绿混杂岩带内发现冷俯冲典型低温高压-高温低压双变质带岩石组合（1.99～2.02Ga），为古元古代水月寺蛇绿混杂岩带形成的俯冲极性提供了重要地质证据。.（3）古元古代水月寺蛇绿混杂岩带及东部微陆块中发现识别两期分别与俯冲板片回转和板片断离作用有关的高镁中性岩浆岩（2.15～2.12Ga）、富铌基性岩脉（2.05～2.03Ga），为古元古代碰撞造山结束时间提供了重要制约。.（4）古元古代水月寺蛇绿混杂岩带中发现识别古元古代两类不同时代和成因特征的花岗岩（2.00～1.85Ga），为古元古代俯冲-碰撞造山形成演化提供了岩浆岩的重要证据。.（5）确定了古元古代水月寺蛇绿混杂岩带内韧性变形橄榄辉石岩、辉石岩（大洋岩石圈）与东缘变形蛇纹石化方辉橄榄岩（大陆地幔楔）岩片具有不同时代和成因特征，但均卷入了古元古代（～2.00Ga）深俯冲-碰撞造山及折返作用，证明深俯冲隧道不仅携带有大洋岩石圈物质，也可卷入大陆地幔楔物质。