俯冲带高压/超高压硬玉石英岩形成过程中流体作用和元素行为

Jadeite quartzite is a rare metamorphic rock, usually occurring as tectonic blocks of high-pressure (HP) to ultrahigh-pressure (UHP) metamorphic zones in continental and oceanic subduction zone. Although previous studies consistently suggest the formation of jadeite quartzite is the product of fluid precipitation or fluid metasomatism in HP to UHP metamorphism, it is still in hot debate concerning the protolith of jadeite quartzite, the origin of the fluid and it's composition, the exact timing of fluid-rock interaction, the spatial extents that affected by the fluid and transport mechanism for such fluid in the subduction zone. To address these questions, in this project, my study is focused on jadeite quartzite and its associated rock from Dabie orogenic belt in China (continetal subduction zone) and the Rio San Juan Complex (RSJC) in Dominican Republic (oceanic subduction zone). Based on the detailed petrological studies, we carry out modern petrological studies and geochemical analysis. By Mg-O isotope analysis of minerals and whole-rocks, zircon in situ U-Pb dating and Hf-O isotope analysis, combined with the systematic petrographic observations, mineral microanalysis of major and trace elements and isotopes, we expect to give new tight constraints for the protolith of jadeite quartzite, reveal the origin and composition of the fluids, elucidate the exact timing of fluid metasomatism and its influence on the elements and isotopes of accessory minerals. On these bases, we will further explore the mechanism for fluid-rock interaction in the root of continental and oceanic subducted zones, as well as the consequences of the fluid-rock interaction for the evolution of the orogen.

硬玉石英岩是一种稀少的高级变质岩，却同时出露于洋壳和陆壳俯冲带中。尽管前人研究认为部分硬玉石英岩是俯冲带深部流体作用的产物，但对硬玉石英岩的原岩属性、形成过程中的流体来源和特征、流体作用的时限及运移机制的认识仍很不清楚。针对这些问题，本项目选取中国大别造山带超高压硬玉石英岩(大陆俯冲带)和多米尼加瑞三环地体中的高压硬玉石英岩(大洋俯冲带)及其围岩进行研究。通过对全岩主微量元素、矿物Mg-O同位素分析和锆石学研究，结合系统的岩相学观察、矿物微区原位元素和同位素分析，进而查明硬玉石英岩的原岩属性，明确硬玉石英岩形成过程中流体的来源和性质，限定流体作用的时限，深化元素迁移的行为和机制，进而探讨大洋和大陆俯冲带深部流体-岩石相互作用的方式及其与构造演化的关系，以期为俯冲带流体来源和性质、元素迁移及壳幔相互作用提供新的制约。

本项目根据项目申请时的研究计划执行，以中国大别造山带超高压硬玉石英岩(大陆俯冲带)和多米尼加瑞三环地体中的高压硬玉石英岩(大洋俯冲带)及其围岩进行系统岩石地化研究。通过对全岩主微量元素、锆石学以及传统/非传统稳定同位素分析相结合，同时结合系统的岩相学观察、矿物微区原位元素和同位素分析。四年来在项目组全体努力下，我们查明了大陆俯冲带大别造山带广泛出露的硬玉石英岩的原岩属性及其岩石成因，同时明确了硬玉石英岩形成过程中流体的来源和性质，限定流体作用的时限，深化元素迁移的行为和机制，进而探讨大洋和大陆俯冲带深部流体-岩石相互作用的方式及其与构造演化的关系，为俯冲带流体来源和性质、元素迁移及壳幔相互作用提供新的制约。其相关研究成果共发表7篇论文，其中有5篇发表在高影响因子国际地质学主流SCI学术期刊上：1篇Geochimica et Cosmochimica Acta，1篇Chemical Geology，1篇Journal of Metamorphic Geology，1篇Lithos和1篇Journal of Asian Earth Sciences。以及两篇国内核心期刊论文：1篇地球科学，1篇矿物岩石地球化学通报。值得一提的是，以上7篇论文均是本人为第一作者或通讯作者论文。此外，项目执行期间，培养一名优青（基金委优秀青年科学基金）高晓英，2名博士李万财和张龙，2名硕士张强强和周琨。