Complementary insights from orogenic and xenolithic eclogites as recorders of mass transfer in subduction zones: A unique case study from the Farallon plate

造山带和捕猎榴辉岩作为俯冲带物质传递记录者的补充见解：来自法拉隆板块的独特案例研究

• 批准号: 467699541
• 负责人: Dr. Sonja Aulbach
• 金额: --
• 依托单位: Abteilung Petrologie und Geochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/467699541?language=en
• 关键词: Complementary; insights; orogenic; xenolithic; eclogites

Oceanic subduction zones arguably constitute the single most important interface on Earth where significant crust-mantle interaction, with transfer of volatiles and other elements, occurs - processes that are fundamental to planetary evolution. Some mass transfer is mediated by fluids and melts as a function of composition, pressure, temperature and oxygen fugacity. The effects of these parameters on element mobility in this complex environment remain fuzzy, also owing to the incomplete geological record available for any single subduction zone. Due to a unique geological happenstance, the oceanic crust of the Cretaceous Farallon plate has been sampled over an exceptionally large pressure interval (~2.0-4.7 GPa), by tectonically exhumed eclogites in the Franciscan Complex (western United States), and by eclogite xenoliths occurring in the Navajo Volcanic Field, 700 km to the east. Using a representative sample suite, this study aims to fingerprint the sources of the fluids that interacted with the eclogites during deep mass transfer processes in the Farallon plate with bulk-rock Li-B-Mg-Fe isotopes, and detect short-lived fluid flow events with in situ Li-Mg-Fe isotopes. A pressure-temperature-time-oxygen fugacity path will be delineated by combining geothermo-oxybarometry with a novel garnet U-Pb dating tool. Coupled bulk carbon and sulphur concentrations, speciations and isotopic compositions, enhanced by sulphide δ34S, garnet Fe3+/ΣFe and garnet δ56Fe, will be used to assess the interplay between the redox-sensitive elements Fe, C and S, and identify the reactions by which they are mobilised or retained in the slab. Combined, these data will allow to trace the physicochemical controls on mass transfer processes and volatile cycling from forearc to subarc depth, in a single slab, with unprecedented detail.

海洋俯冲区域在地球上最大的界面中，有明显的地壳相互作用图块和其他元素，是基本的制作，这些构成，温度和氧气的影响。任何细分区的记录样品套件，本研究的目的是旨在用散装岩石li-b-mg-fe同位素在法拉隆板上更深过程中的eclogites的来源，并检测出具有原位li-mg--的短寿命流体流动事件。 Fe同位素。实验室的硫代化学控制，具有未经预言的细节。