Speciation in carbonatitic brine-melts and fluids from molecular simulations

通过分子模拟研究碳酸盐卤水熔体和流体中的形态

• 批准号: 521731223
• 负责人: Professor Dr. Sandro Jahn
• 金额: --
• 依托单位: Institut für Geologie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/521731223?language=en
• 关键词: Speciation; carbonatitic; brine; melts; fluids

Carbonatites are among the most important rocks that contain economically important ore minerals. Their formation is usually assumed to arise from mantle sources. Despite intensive research, primary mantle melt compositions and ultimate carbonatite genesis are still controversial. Fluid and melt inclusions hosted in different carbonatite minerals provide unique information about fluid and melt compositions during entrapment but their interpretation is complicated due to post-entrapment modifications and insufficient knowledge of the thermodynamic phase relations of the usually complex multicomponent chemical systems. In this project, we will use molecular simulation methods to study the molecular structure and thermodynamic properties of evolved carbonatitic brine-melts and related hydrothermal fluids at relevant pressure and temperature conditions. Based on existing reactive force fields, the particle interaction potential will be parameterized for the model system H2O-CO2-Na2CO3-NaCl, which allows simulation in a composition range from high-salinity, high-density, alkali carbonatite fluids to low density, aqueous CO2-rich fluids, which are observed in associated fluid inclusions. The speciation will be derived directly from molecular dynamics simulations and/or from advanced free energy sampling methods such as thermodynamic integration. Results will be benchmarked by reference to observations and ab initio simulations. To connect to results from the ongoing project of the first funding period of the DOME program, we will add the rare earth elements (REE) La and Y to the carbonatitic system to investigate possible REE speciation with carbonate ligands. With this project, we expect to shed new light on the evolution of late-stage carbonatitic melts, during which significant enrichment of incompatible and economically important elements such as the REEs is expected.

碳酸盐岩是最重要的岩石之一，含有重要的经济矿物。它们的形成通常被认为来自地幔源。尽管有深入的研究，原始地幔熔体成分和最终的碳酸盐岩成因仍然存在争议。流体和熔体包裹体托管在不同的碳酸盐岩矿物提供了独特的信息，流体和熔体的组合物在捕获，但他们的解释是复杂的，由于后捕获的修改和知识不足的热力学相关系的通常复杂的多组分化学体系。在本项目中，我们将使用分子模拟方法研究在相关压力和温度条件下演化的碳酸盐岩盐水熔体和相关热液流体的分子结构和热力学性质。基于现有的反应力场，粒子相互作用的潜力将参数化的模型系统H2O-CO2-Na 2CO 3-NaCl，它允许模拟的组成范围从高盐度，高密度，碱性碳酸盐岩流体低密度，含水CO2丰富的流体，这是在相关的流体包裹体中观察到的。物种形成将直接来自分子动力学模拟和/或先进的自由能采样方法，如热力学积分。将通过参考观察结果和从头算模拟对结果进行基准测试。为了与DOME计划第一个资助期正在进行的项目的结果相联系，我们将向碳酸岩系统中添加稀土元素（REE）La和Y，以研究碳酸盐配体可能的REE形态。有了这个项目，我们希望揭示新的光后期碳酸盐熔体的演变，在此期间，不相容的和经济上重要的元素，如稀土元素的显着富集预计。