Experimental investigation into the thermodynamic properties of halogens

最近的研究表明，地球在30-40英里之间增长和分化，随着时间的推移，生态化更多地被氧化。然后相对较快地建立了稳定的陆壳。这些过程导致亲铁(爱铁)元素分离到地核，不相容的亲石元素(爱岩石)分离到地壳。行星科学面临的最耐人寻味的问题之一是，不断增长的地球所经历的过程是否代表着发生在其他类地行星甚至系外行星上的过程。答案在于地球最近的邻居：火星。火星探测车(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，包括大量测量卤素，包括氯和溴。此外，火星奥德赛伽马射线光谱仪(GRS)绘制了火星近表面元素氯丰度的赤道和中纬度分布(赵和McLennan，2012)。这些数据集显示，与火星陨石相比，火星上方几十厘米处的氯含量显著丰富，并估计了该行星的整体组成。然而，它并不是均匀分布的。对火星富氯矿物学的大部分关注来自对纳赫利特陨石和雀斑陨石的研究，每一块陨石都含有广泛的岩浆挥发性矿物，包括富氯元素(Filiberto和Treiman，2009；Filberto，等人，2014)。根据McCubbin等人(2009年)的说法，查萨蒂和米勒03346富氯热液UID与岩浆活动之间存在明显的联系，但目前尚不清楚富氯UID是岩浆系统的外源还是内源。M‘dard和Grove(2008)发现，在抑制玄武岩的液线方面，按摩尔计算，氯的效果是水的两倍。尽管这确实表明，在火星地幔中添加氯可能会降低岩浆的形成温度，并可能有助于火星岩浆的成岩，但目前的实验只探索了一种含氯浓度固定的玄武岩成分；因此，将他们的结果应用于陆地和火星岩浆中的氯浓度范围是有问题的。其他实验评估了溶解氯对富含氯化物的流纹岩流体中Fe3+/PFe和磁铁矿溶解度的内在影响，并表明在熔体中加入氯对铁有两个显著的影响：(1)溶解的氯扰乱了磁铁矿-熔体的平衡，使得在含氯熔体中支持磁铁矿饱和所需的FeO总量比在同等体积成分的无氯熔体中更大；(2)随着fO2的增加，测量的Fe3+/PFe值有系统地递减。因此，这两个密切相关的效应对富氯弧岩中发生的氧化还原过程都具有重要的意义。然而，众所周知，火星上的熔体比流纹质熔体富铁得多。因此，应测试较低的Al_2O_3和较高的FeO含量的块体成分，以进一步限制其对氯对近液相线结晶的影响。仅对如上所述的长英质岩浆进行了氯的溶解度研究，对火星岩浆成分的实验很少，因为火星岩浆成分与地球上的岩浆成分有很大的不同。因此，对火星富集型FeO岩浆对氯等卤素溶解度的影响还知之甚少。由于目前尚不清楚是什么影响了氯的溶解，破译火星地幔的分配行为将是理解火星岩浆活动的关键。因此，我建议通过实验方法来研究火星地幔内的氯的溶解，创造化学相似的成分来评估铁对溶解度的影响、是否以及影响的程度，这将有助于揭示火星的岩浆作用和演化。

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.