Halogen geochemistry and isotope geochemistry in magmatic systems

岩浆系统中的卤素地球化学和同位素地球化学

• 批准号: 398824902
• 负责人: Privatdozent Dr. Michael Marks
• 金额: --
• 依托单位: IPREM - Institut des Sciences Analytiques
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/398824902?language=en
• 关键词: Halogen; geochemistry; isotope; magmatic; systems

The current project represents a systematic study on halogen distribution, halogen fractionation and halogen isotope fractionation in magmatic systems, focussing on Cl and Br. The study will investigate peralkaline rocks as these are halogen-rich and contain abundant sodalite and eudialyte-group minerals (EGM), the major Cl and Br carriers in peralkaline magmatic systems. Our preliminary data indicate that (i) Cl and Br may be fractionated from each other during magmatic differentiation and (ii) the amount and timing of sodalite fractionation has a major impact on the Cl/Br evolution of residual melts. Therefore, four otherwise well-studied peralkaline complexes that contain (i) abundant orthomagmatic sodalite-EGM assemblages (Ilímaussaq), (ii) minor orthomagmatic but abundant late-magmatic sodalite-EGM assemblages (Khibina), (iii) rare late-magmatic sodalite-EGM assemblages (Tamazeght) and (iv) sodalite-free assemblages with EGM as the only major Cl-rich phase (Norra Kärr), will be investigated and compared with each other with respect to halogen abundances (F, Cl, Br, I) and halogen isotope compositions (δ37Cl and δ81Br) of sodalite and EGM.This project is a first systematic study on the behaviour of Cl (and Br) stable isotopes in magmatic systems and will investigate the suitability of these two isotope systems for deciphering magmatic and hydrothermal processes, including fractional crystallization and fluid exsolution/degassing. The combination of the halogen concentration data and the halogen isotope data from all four localities, combined with mass balance and Rayleigh-type calculations accounting for the relative effects of sodalite and EGM fractionation will also allow for constraining compositional heterogeneities in the respective mantle sources for these rocks with respect to halogen ratios and halogen isotope compositions. This will help to constrain the scales and amplitudes of mantle heterogeneities concerning the halogens, for which already evidence was presented, both with respect to halogen concentrations and Cl-isotope compositions.

当前的项目代表了一项关于卤素分布，卤素分馏和卤素同位素分馏的系统研究，重点是CL和BR。这项研究将研究上碱性岩石，因为这些岩石富含卤素，并包含大量的Sodalite和Edialyte-Group矿物质（EGM），即甲基氨基岩岩浆系统中的主要CL和BR载体。我们的初步数据表明（I）CL和BR在岩浆分化过程中可能会彼此分馏，并且（ii）索达石分馏的数量和时机对残留熔体的Cl/BR演变产生了重大影响。因此，包含（i）丰富的正交sodalite-egm组合（IlímaussAQ）的四个原本良好的上碱性络合物，（ii）次要的原磁性但丰富的后期含量但丰富的杂种sodalite-egm组合（Khibina），（khibina），（iii）稀有的magmagmatic sodalite and sodalite and sodalite and tam and tam and tam-tam and tam-tam-agess（tam angages）（tam angages） - 将研究以EGM为唯一的主要ClICH阶段（NorraKärr）的无硫酸盐组合，并将彼此相对于卤素丰度（F，Cl，Br，I）和卤素同位素组成（Δ37CL和Δ81BR）相互比较。将研究这两个同位素系统对破译岩浆和热液过程的适用性，包括分数结晶和流体溶液/脱气。来自所有四个地方的卤素浓度数据和卤素同位素数据的组合，结合质量平衡和瑞利型计算，这些计算对硫酸盐和EGM分馏的相对影响也将允许这些岩石对卤代含量和Halogen Ispostors的相对构成岩体来源的约束组合异质性。这将有助于限制有关卤素的地幔异质性的量表和放大器，在卤素浓度和CL-异位素组成方面已经提供了证据。