Chlorine isotope fractionation in alkaline magmatic systems

碱性岩浆系统中的氯同位素分馏

• 批准号: 450099520
• 负责人: Privatdozent Dr. Michael Marks
• 金额: --
• 依托单位: Arbeitsgruppe Geologie und Geodynamik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/450099520?language=en
• 关键词: Chlorine; isotope; fractionation; alkaline; magmatic

This project represents a systematic study to constrain the behaviour of the Cl isotope system in alkaline magmatic to hydrothermal systems and the Cl isotope heterogeneity in the mantle. Because of their general derivation from lithospheric mantle sources and their halogen-rich nature, alkaline rocks are important to understand halogen transport from the mantle into the crust and halogen budgets during emplacement, differentiation, and fluid exsolution/degassing of magmatic systems. The extensive sample collection to be worked with includes plutonic, volcanic and metamorphosed alkaline rocks from more than 40 localities worldwide.Based on our preliminary data, the following three hypotheses will be tested during this project: (i) Magmatic processes, such as fractional crystallization and fluid exsolution/ degassing cause fractionation of stable Cl isotopes (ii) Heterogeneity of the mantle with respect to Cl isotope compositions is recorded in alkaline magmas (iii) Deformation and fluid-rock interaction during metamorphism of alkaline rocks does not significantly change their Cl isotopic composition. The project will use Cl isotope data (ICP-MS, SIMS), halogen (F, Cl, Br, I) and S concentration data (EPMA, CIC) as well as O and S isotope data on mineral separates. Combined with mass balance and Rayleigh-type calculations, this will allow to (i) develop applications of Cl isotope data for deciphering magmatic to hydrothermal processes and (ii) to constrain global compositional heterogeneities in the (lithospheric) mantle with respect to halogen ratios (e.g., F/Cl, Cl/Br, Cl/I) and Cl isotope compositions, for which already evidence was presented.

该项目代表了一项系统研究，旨在约束碱性岩浆到热液系统中 Cl 同位素系统的行为以及地幔中 Cl 同位素的异质性。由于碱性岩石通常源自岩石圈地幔源及其富含卤素的性质，因此碱性岩石对于了解卤素从地幔到地壳的迁移以及岩浆系统的侵位、分异和流体溶出/脱气过程中的卤素预算非常重要。所收集的大量样本包括来自全球 40 多个地区的深成岩、火山岩和变质碱性岩。根据我们的初步数据，该项目将测试以下三个假设： (i) 岩浆过程，例如分步结晶和流体溶出/脱气导致稳定 Cl 同位素的分馏 (ii) 在碱性岩浆中记录了地幔相对于 Cl 同位素组成的异质性(iii) 碱性岩变质作用过程中的变形和流体-岩石相互作用不会显着改变其 Cl 同位素组成。该项目将使用 Cl 同位素数据（ICP-MS、SIMS）、卤素（F、Cl、Br、I）和 S 浓度数据（EPMA、CIC）以及矿物分离物的 O 和 S 同位素数据。结合质量平衡和瑞利型计算，这将允许（i）开发 Cl 同位素数据的应用，用于破译岩浆到热液过程，以及（ii）限制（岩石圈）地幔中卤素比率的全球成分异质性（例如，F/Cl、Cl/Br、Cl/I) 和 Cl 同位素组成，对此已经提出了证据。