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.

本项目是对碱性岩浆-热液体系中Cl同位素体系行为和地幔Cl同位素不均一性的系统研究。由于碱性岩一般来源于岩石圈地幔源和富含卤素的性质，碱性岩对于了解岩浆系统的侵位、分异和流体出溶/脱气过程中卤素从地幔向地壳的迁移和卤素收支是很重要的。我们将从全球40多个地点收集大量的样品，包括深成岩、火山岩和变质碱性岩。根据我们的初步数据，在本项目期间将检验以下三个假设：㈠岩浆过程，如分馏结晶和流体出溶/脱气导致稳定Cl同位素分馏（ii）地幔Cl同位素组成的异质性记录在碱性岩浆（iii）变形和流体-岩石相互作用在碱性岩石变质过程中不会显着改变其Cl同位素组成。该项目将使用氯同位素数据（ICP-MS、西姆斯）、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，用于解释岩浆到热液过程，以及（ii）限制（岩石圈）地幔中相对于卤素比率的全球成分不均匀性（例如，F/Cl、Cl/Br、Cl/I）和Cl同位素组成，这些都已经有了证据。