The fractionation of Highly Siderophile Elements (HSE) during partial melting, and its implication for the HSE composition of the Primitive Upper Mantle

高亲铁元素（Pt, Pd, Rh, Ru, Ir, Os， Re和Au - HSE）在地核/地幔分化后（即所谓的“晚覆层”）被添加到地幔中，这是一个被广泛接受的假设，可以解释与金属/硅酸盐-熔体平衡所期望的相比，地幔中过量的HSE。尽管大多数地幔橄榄岩显示出广泛的球粒质HSE模式，但最近的研究表明，存在非球粒质HSE模式的橄榄岩（例如Pd/Ir）。另一个困难是，一些作者认为橄榄岩套被广泛地再成矿，其HSE含量的变化可能是不同程度的再成矿和硫化物再活化的结果。由于我们对地幔相之间HSE的高温分配(即硫化物熔体（这里称为matte）和硅酸盐熔体（）之间的分配行为缺乏了解，经验数据中的不一致性进一步加剧。大多数先前的实验研究给出的数值范围很窄，大约在103-104之间，这表明这些元素在地幔部分熔融期间不应该相互分离，这与经验观测结果直接不同。这些看似恒定的值使一些作者对“晚贴面”模型的有效性产生了怀疑，并提出了其他假设，如地核-地幔相互作用或地幔中添加了不同的非球粒质物质。然而，从基本的热力学考虑，8种HSE的预测结果有很大不同，并且很大程度上取决于氧和硫的逸度（分别为O2和S2）。该项目的目的是使用一种新的方法来测量大范围条件下的实验值，并使用这些值来确定在地幔部分熔融和再利用过程中HSE分馏的机制，并模拟原始上地幔（PUM）的HSE组成。

The addition of chondritic amounts of Highly Siderophile Elements (Pt, Pd, Rh, Ru, Ir, Os, Re and Au - the HSE) into the Earth's mantle after core/mantle differentiation in what is called the "late veneer", is a widely accepted hypothesis to explain the excess of HSE in the mantle compared to what is expected from metal/silicate-melt equilibrium. Although most mantle peridotites display broadly chondritic HSE patterns, recent studies have shown the existence of peridotites with non-chondritic HSE patterns (e.g. Pd/Ir). An added difficulty is that some authors argue that peridotite suites are extensively refertilized and that variations in their HSE contents may be the result of different degrees of refertilization and sulphide remobilization. The inconsistencies found within the empirical data are aggravated by our poor knowledge of the high-temperature partitioning of the HSE between mantle phases namely their partitioning behaviour between sulphide-melt (here called matte) and silicate melt ( ). Most previous experimental studies give a narrow range of values for ca 103-104, indicating that these elements should not fractionate between each other during partial melting of the mantle, in direct disagreement with empirical observations. These seemingly constant values for have led some authors to cast doubt on the validity of the "late veneer" model and suggest alternate hypotheses, such as core-mantle interaction or the addition of different non-chondritic material to the Earth's mantle. However, from basic thermodynamic considerations, is predicted to be substantially different for the eight HSE, and depends greatly on both oxygen and sulphur fugacity (O2 and S2 respectively). It is the aim of this project to use a novel way of measuring experimentally values of , over a large range of conditions, and to use these values to ascertain the mechanisms for the fractionation of HSE throughout partial melting and refertilization of the mantle and model the HSE composition of the primitive upper mantle (PUM).