Experimental Petrology of Planetary Materials

这个项目的总体目标是通过火成岩过程来了解行星的分异。实验室实验用来模拟这些过程。行星分异的主要表现是地核和地幔的分离。Pt族的高亲铁性元素是了解地核形成和演化的关键元素。由于在与岩心形成过程相关的低pO2条件下，在实验硅酸盐中发现的与金属平衡的分散金属块在解释中存在技术问题，因此对硅酸盐和金属之间的地球化学分配知之甚少。新的实验表明，对于Pt，金块不是人为污染物，而是在不完全淬火过程中从溶液中回收的Pt。这一初步结果使地幔中铂含量高的许多谜团变得不那么令人费解了。铂在硅酸盐中的可溶性比通常认为的要高几个数量级。我们将继续通过时间和温度系列研究来探索这一结果。如果得到验证，我们将把对核块形成的研究扩展到Re和Ir，这两种元素在实验工作中也知道它们的地球化学行为受到核块形成的影响。其他项目包括完成在同时高p和高T条件下，通过同步加速器x射线衍射（XRD）完成固溶体系列grossulal -pyrope中石榴石体积的研究。与传统测量方法相比，这项研究显示了一些有趣的异常现象。研究结果与地幔橄榄岩中石榴石的混合和熔融特性有关。石榴石是深橄榄岩部分熔融释放玄武岩的可熔组分的重要储藏库之一。一项相关研究将使用NaCl-KCl体系来模拟高p，T二元溶液中的溶液行为。我们还将测量B1和B2 RbCl的熔点至~ 30kbar，以研究似乎发生在相转化为更高密度、更高配位数的多晶时的键削弱。这项研究与地球上预期的跨相变边界的对流方式变化有关。最后，我们希望完成P对热电偶电动势影响的超热中子共振热测量的数据缩减。本课题是关于在高压下广泛使用的热电偶高温计的校准。

WalkerEAR-0207546The general aim of this project is to understand planetary differentiation by igneous processes. Laboratory experiments are used to simulate those processes. The major expression of planetary differentiation is the separation of core and mantle. The highly siderophile elements of the Pt group are a key suite of elements for understanding the formation and evolution of Earth's core. Their geochemical partitioning between silicate and metal has been poorly understood because of technical problems in the interpretation of the dispersed metal nuggets found in experimental silicates equilibrated with metal at the low pO2 relevant to the core formation process. New experiments show that for Pt the nuggets are not artificial contaminants but are Pt recovered from solution during the incomplete quenching process. This preliminary result makes many of the enigmas of the high abundance of Pt in the Earth's mantle less perplexing. Pt is orders of magnitude more soluble in silicate than conventionally thought. We will continue to explore this result with time and temperature series studies. If verified, we will extend the study of nugget formation to Re and Ir, two elements of the group also known to also have their geochemical behavior clouded by nugget formation in experimental work. Additional projects to be undertaken include the completion of studies of the volumes of garnets across the solid solution series grossular-pyrope at simultaneous high-P and T by synchrotron XRD. This study has shown some interesting anomalies compared to conventional practices used to make these measurements. The results are relevant to the mixing and melting properties of garnets in mantle peridotite. Garnet is one of the important repositories of fusible components that liberate basalt upon deep peridotite partial melting. A related study will use the NaCl-KCl system to model the behavior of a solvus in a binary solution at high-P,T. We will also measure the melting points of B1 and B2 RbCl to ~30 kbar to investigate the bond weakening which seems to take place on conversion of phases to higher density, higher coordination number polymorphs. This study is relevant to expected convective style changes across phase change boundaries in the Earth. Finally, we hope to complete the data reduction of epithermal neutron resonance pyrometry measurements of the effect of P on thermocouple emf. This subproject is relevant to the calibration of widely used thermocouple pyrometry in use at high pressure.