In-situ U-Pb age dating and the oxygen isotopic composition of accessory minerals in jadeitites: investigating the timing of fluid release and fluid-rock interactions in subduction zones

原位 U-Pb 年龄测定和硬玉中副矿物的氧同位素组成：研究俯冲带中流体释放的时间和流体-岩石相互作用

• 批准号: 508778581
• 负责人: Dr. Andreas Hertwig
• 金额: --
• 依托单位: John de Laeter Research Centre
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2022
• 资助国家: 德国
• 起止时间: 2021-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/508778581?language=en
• 关键词: situ; Pb; age; dating; oxygen

When crustal rocks return into Earth’s mantle at subduction zones, fluids released from subducted material initiate melting in the mantle wedge which ultimately leads to the build-up of new continental crust and venting of volcanic gases into the atmosphere. Since fluids act as major agents of mass and energy transfer in such a setting, understanding how and when fluids are released is of paramount importance for constructing a coherent picture of this ongoing global material recycling at subduction zones. Jadeitites – rocks composed mainly of the sodic clinopyroxene jadeite - either directly witnessed such subduction-zone fluids or represent crystallized portions of these fluids themselves. The timing of fluid release(s) could then be constrained by determining the formation ages of jadeitites by dating certain accessory minerals such as zircon. However, zircon has the ability to survive partial melting and high-grade metamorphism which leads to some ambiguity concerning its primary origin in jadeitites. In this study it is therefore proposed to perform in-situ U-Pb dating by secondary ion mass spectrometry (SIMS) of other common accessories in jadeitites including titanite, rutile, and apatite which can often be directly linked to the effect of fluids. In combination with SIMS oxygen isotope analysis of accessory phases, the proposed investigations can provide valuable information about jadeitite formation and, ultimately, fluid production in subduction zones.

当地壳恢复到地球的材料区域时，最终导致将新的大陆地壳堆积到大气中，因为流体ASCT是主要的质量和能量转移，以了解流体的重要性以及何时至关重要。为了构建一个连贯的图片。然而，锆石具有在部分融化和高级变质的能力，这导致了对玉米的主要起源的歧义。钛铁矿，金红石和磷灰石通常可以直接与流体的效果联系起来，与SIMS氧同位素分析HE支撑的研究可以提供有关JadeItite研究的有价值的信息，并最终在屈服区域中产生流体。