西南天山洋壳高压-超高压变质岩石的俯冲隧道折返机制

发布时间：2018-04-20 22:25

本文选题：榴辉岩 + 高压变质　；参考：《中国科学:地球科学》2017年01期

【摘要】：出露于造山带的高压-超高压榴辉岩记录了地壳俯冲到地幔深度而后又折返回地表的过程,其俯冲过程与折返机制的研究对理解俯冲带性质、演化、地球动力学过程乃至板块构造理论都有着非常重要的作用.相对于较轻的陆壳长英质高压-超高压岩石,基性洋壳榴辉岩密度大,其折返难度大且过程复杂.折返过程除了受内在浮力的影响,还受外在构造力(如隧道流)的制约,另外板片构造环境(如板片后撤和板片断离)的作用也不可忽视.中国西南天山高压-超高压变质带是典型的经历过深俯冲变质作用的增生混杂岩带,主要由高压-超高压变质沉积岩及夹杂其中的变基性岩透镜体组成,但长期以来其折返模式一直不太清楚.根据其野外产状、岩相学特征、峰期变质温压条件和峰期变质年龄等多方面的综合分析,可以采用沉积岩型"俯冲隧道折返模式"来概括西南天山高压-超高压变质带的形成和演化.部分经历多期变质作用的榴辉岩岩块记录了多期俯冲-折返循环,反映了俯冲隧道内的上下环流运动,有力证明了俯冲隧道的存在.最后,本文对目前研究存在的问题和未来的探索方向进行了展望.
[Abstract]:The high-pressure and ultra-high pressure eclogites exposed to the orogenic belt record the process of crust subduction to mantle depth and then fold back to the surface. The study of subduction process and exhumation mechanism of eclogite has contributed to understanding the nature and evolution of the subduction zone. Geodynamic processes and plate tectonic theory play a very important role. Compared with the relatively light continental feldspathic high-pressure ultrahigh pressure rocks, the basic oceanic eclogite has a high density, and its return is difficult and the process is complicated. In addition to the influence of internal buoyancy, the reentry process is also restricted by external tectonic forces (such as tunnel flow), and the role of plate tectonic environment (such as plate retreat and plate fragment separation) should not be ignored. The Tianshan high-pressure ultrahigh pressure metamorphic zone in southwest China is a typical accretive melange belt with overdeep subduction metamorphism, which is mainly composed of high-pressure ultrahigh pressure metamorphic sedimentary rocks and the lens bodies of the metamorphic rocks. But its return model has long been unclear. According to the field occurrence, lithofacies characteristics, temperature and pressure conditions of peak metamorphic period and metamorphic age of peak period, etc. The sedimentary rock type "subduction tunnel exhumation model" can be used to generalize the formation and evolution of the southwest Tianshan high-pressure and ultra-high pressure metamorphic belt. Some eclogite blocks which experienced multiple metamorphism recorded multiple subduction-reentrant cycles which reflected the upper and lower circulation movement in the subduction tunnel and proved the existence of the subduction tunnel by force. At last, the paper looks forward to the existing problems and future exploration directions.
【作者单位】：中国科学院地质与地球物理研究所矿产资源研究重点实验室;
【基金】：国家自然科学基金项目(批准号:41390445,41502053,41025008) 中国博士后科学基金项目(编号:2015T80135)资助
【分类号】：P588.3

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