Chlorine in amphibole: intracrystalline diffusion and partitioning between amphibole and silicate melt

角闪石中的氯：角闪石和硅酸盐熔体之间的晶内扩散和分配

• 批准号: 298850205
• 负责人: Professor Dr. Harald Behrens
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/298850205?language=en
• 关键词: Chlorine; amphibole; intracrystalline; diffusion; partitioning; Chlorine; amphibole; intracrystalline; diffusion; partitioning

Chlorine (Cl) is an abundant volatile element in the interior and outer layers of the Earth and other planets (e.g. Mars), which plays important roles in a variety of geological and environmental processes within a wide range of temperature and pressure. In hydrothermal systems, Cl concentrations can be traced using fluid inclusions. However, as a volatile element, Cl is usually partly released (with fluids) from magmatic systems and there are only little phases which can be used as tracer for Cl concentrations in natural magmatic systems. Amphibole is a common halogen-hosting mineral which exists in a large range of rock systems and of geological conditions, and which can serve as an important tracer of Cl evolution. However, because of the complex structure and chemistry of amphiboles and of the large compositional variation of melt which can coexist with amphibole, the partitioning of Cl between amphibole and melt is still poorly understood. Two key issues will be addressed in this proposal with series of experiments aimed at constraining (1) the partitioning of Cl between amphibole and silicate melt (KCl), and (2) the diffusion rate of Cl in amphibole (DCl). The partitioning of Cl between amphibole and silicate melt will be investigated in a large pressure and temperature range within the stability of amphibole (100-700 MPa and 750-1000 °C) for basaltic to rhyodacitic systems. Preliminary studies show that the bulk composition of natural systems may influence strongly the partitioning of Cl. Using 12 different starting materials, we plan to constrain the main compositional parameters controlling the partitioning of Cl (crystal chemistry of amphibole and melt composition). The experiments on Cl partitioning will be complemented by challenging experiments aimed at understanding the diffusivity of this element in amphibole. Large amphibole crystals will be used as starting materials and the experiments will be designed to achieve Cl/OH exchange between amphibole and melt without other cation exchange. The results of this study are of particular interest for volcanic systems, but have the potential to be applied to magmatic processes on Earth and other planets. The partitioning of Cl between amphibole and melt is crucial to estimate accurately Cl contents in magmas based on amphibole composition and to interpret quantitatively processes occurring in magmatic systems. Chlorine diffusivity in amphibole is crucially needed to extract time scales of geological processes in magmatic systems using Cl concentration profiles in amphiboles.

氯（Cl）是地球和其他行星（例如火星）的内部和外层中的丰富挥发性元件，在温度和压力范围广泛的各种地质​​和环境过程中都起着重要作用。在热液系统中，可以使用流体夹杂物来追踪CL浓度。但是，作为一种挥发性元素，CL通常是从岩浆系统中部分释放（带有流体），只有很少的相可以用作天然岩浆系统中CL浓度的示踪剂。闪石是一种常见的卤素托管矿物质，存在于各种岩石系统和地质条件下，可以作为CL进化的重要示踪剂。然而，由于闪石的复杂结构和化学性质以及可以与闪石共存的熔体大量变化的较大组成变化，因此CL在闪石和熔体之间的分配仍然很差。在本提案中，将解决两个关键问题，旨在限制（1）闪比尔和有机硅熔体（KCL）之间CL的分区，以及（2）CL在闪石（DCL）中的扩散速率。在斜长木（100-700 MPa和750-1000°C）的稳定性内，将研究闪石和有机硅熔体之间CL的分区，以用于玄武岩到纹状体系统。初步研究表明，自然系统的整体组成可能会强烈影响CL的分配。使用12种不同的起始材料，我们计划控制控制Cl分配的主要组成参数（闪石和熔体组成的晶体化学）。 CL分配的实验将通过旨在理解闪石该元素的难度的挑战实验完成。大型闪石晶体将用作起始材料，实验将设计为在没有其他阳离子交换的情况下实现闪石和熔体之间的Cl/OH交换。这项研究的结果对于火山系统特别感兴趣，但有可能应用于地球和其他行星上的岩浆过程。 CL之间CL之间的分配对于估计基于闪石组成的岩浆中的CL含量至关重要，并解释了岩浆系统中发生的定量过程。完全需要闪石中的氯扩散率，以使用闪石中的Cl浓度谱提取岩浆系统中地质过程的时间尺度。