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Experimental investigation into the thermodynamic properties of halogens

卤素热力学性质的实验研究

基本信息

批准号：
1941721
负责人：
金额：
--
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-1941721
关键词：
Experimental investigation into thermodynamic properties

项目摘要

Recent research has shown that the Earth accreted and differentiated over 30-40 Myr,ecoming more oxidised through time. Stable continental crust was then established relatively quickly. These processes led to the segregation of siderophile (iron-loving) elements to the Earths core and incompatible lithophile (rock-loving) elements to the crust. One of the most intriguing questions facing planetary science is whether the processes experienced by the growing Earth represent those which took place on other terrestrial planets or even exoplanets. The answer lies with Earths nearest neighbour: Mars.The Mars Exploration Rovers (MER) and orbital missions continue to deliver largevolumes of high-quality chemical and mineralogical data from the Martian surface, including bountiful measurements of halogens, including chlorine and bromine. In addition,the Mars Odyssey Gamma Ray Spectrometer (GRS) has mapped the equatorial and midlatitude distribution of elemental Cl abundances at the near-surface of Mars (Zhao and McLennan, 2012). These datasets show the upper few tens of centimetres of Mars is significantly enriched in Cl relative to Martian meteorites and estimates for the bulk composition of the planet. However, it is not homogenously distributed.Much of the focus on the Cl-rich mineralogy of Mars derives from studies of the nakhlite and chassignite meteorites, each containing a broad array of magmatic volatile bearing minerals including Cl-enrichment (Filiberto and Treiman 2009; Filberto, et al., 2014). According to McCubbin et al., (2009), there is a clear link between chlorine-rich hydrothermal uids and magmatic activity in Chassigny and MIL 03346, but it is presently unclear whether the Cl-rich uid was exogenous or endogenous to the magmatic system. M'dard and Grove (2008), found that on a molar basis, Cl is twice as effective as H2O in depressing the liquidus of basalts. Although this does suggest that the addition of Cl to the Martian mantle may lower the magma genesis temperature and potentially aid in the petrogenesis of Martian magmas, current experiments have only explored a basalt composition with a xed Cl concentration; hence, applying their results to the range of Cl concentrations in terrestrial and Martian magmas becomes problematic. Other experiments evaluate the intrinsic effects of dissolved chlorine on Fe3+/PFe and magnetite solubility in hydrous chloride-rich rhyodacitic liquids, and show Cl addition to the melt has two prominent effects on iron: (1) dissolved Cl perturbs the magnetite-melt equilibrium, such that greater FeO total contents are required to support magnetite saturation in Cl-bearing melts than in Cl-free melts of equivalent bulk compositions; and (2) a systematic and progressive decrease of the measured Fe3+/PFe as fO2 is increased. Hence, the two intimately related effects each have important implications for redox processes occurring in Cl-enriched arc magmas. It is, however, well established that the Martian planet is vastly more Fe-rich than rhyodacitic melts. Therefore, bulk composition with lower Al2O3 and higher FeO contents should be tested to further constrain its effect on the influence of chlorine on near-liquidus crystallisation.The solubility of Cl has only been investigated for felsic magmas as above, with few experiments on Martian magmas compositions, which differ significantly from terrestrial. Therefore, the effect of Martian enriched FeO magmas on the solubility of halogens such as Cl is poorly understood. As it is unknown what in infuences Cl solubility, deciphering the partitioning behaviours of the martian mantle will be key to understanding the magmatic activity on Mars.I therefore propose to study Cl solubility within the Martian mantle through experimental methodology, creating chemically similar compositions to assess, if, and the extent at which Fe influences solubility, as this will shed light on the Martia magmatism and evolution.

最近的研究表明，地球吸积和分化了 30-40 迈尔，随着时间的推移，氧化程度越来越高。随后相对较快地建立了稳定的大陆地壳。这些过程导致亲铁（喜铁）元素偏析到地核，而不相容的亲石（喜岩石）元素偏析到地壳。行星科学面临的最有趣的问题之一是，地球不断生长所经历的过程是否代表了其他类地行星甚至系外行星上发生的过程。答案在于地球最近的邻居：火星。火星探索漫游者 (MER) 和轨道任务继续从火星表面提供大量高质量的化学和矿物学数据，包括对氯和溴等卤素的大量测量。此外，火星奥德赛伽玛射线光谱仪（GRS）绘制了火星近地表赤道和中纬度元素Cl丰度分布图（Zhao和McLennan，2012）。这些数据集显示，相对于火星陨石，火星上部几十厘米的 Cl 含量显着丰富，并对火星的总体成分进行了估计。然而，它的分布并不均匀。对火星富含 Cl 的矿物学的关注大部分来自对钠辉石和辉石陨石的研究，每种陨石都含有广泛的岩浆挥发性含矿物，包括富含 Cl（Filiberto 和 Treiman，2009 年；Filberto 等人，2014 年）。根据 McCubbin 等人 (2009) 的说法，Chassigny 和 MIL 03346 中的富氯热液与岩浆活动之间存在明显的联系，但目前尚不清楚富氯热液对于岩浆系统来说是外源的还是内源的。 M'dard 和 Grove (2008) 发现，以摩尔计算，Cl 在抑制玄武岩液相线方面的效果是 H2O 的两倍。尽管这确实表明向火星地幔添加Cl可能会降低岩浆生成温度并可能有助于火星岩浆的岩石生成，但目前的实验仅探索了具有固定Cl浓度的玄武岩成分；因此，将他们的结果应用于陆地和火星岩浆中的 Cl 浓度范围变得有问题。其他实验评估了溶解氯对富水氯化物流英安岩液体中 Fe3+/PFe 和磁铁矿溶解度的内在影响，并表明向熔体中添加 Cl 对铁有两个显着影响：（1）溶解的 Cl 扰乱了磁铁矿-熔体平衡，因此含 Cl 熔体中比无 Cl 熔体中需要更大的 FeO 总含量来支持磁铁矿饱和。等效散装组合物； (2) 随着 fO2 的增加，测得的 Fe3+/PFe 系统性地逐渐减少。因此，这两种密切相关的效应对富氯弧岩浆中发生的氧化还原过程都有重要影响。然而，众所周知，火星行星的铁含量比流英安岩熔体丰富得多。因此，应测试具有较低Al2O3和较高FeO含量的整体成分，以进一步限制其对氯对近液相线结晶影响的影响。如上所述，仅针对长英质岩浆研究了Cl的溶解度，很少对火星岩浆成分进行实验，因为火星岩浆成分与陆地存在显着差异。因此，人们对火星富含 FeO 岩浆对 Cl 等卤素溶解度的影响知之甚少。由于尚不清楚什么因素会影响 Cl 的溶解度，因此破译火星地幔的分配行为将是了解火星岩浆活动的关键。因此，我建议通过实验方法研究火星地幔内 Cl 的溶解度，创造化学上相似的成分来评估 Fe 是否影响溶解度以及影响溶解度的程度，因为这将为火星岩浆活动和演化提供线索。