Experimental Studies of Garnet-Melt Trace Element Partitioning

了解石榴石和共存的硅酸盐熔体的组成如何影响微量元素的分配，对于理解类地行星内部地幔演化至关重要。石榴石与斜辉石是上地幔熔融结晶过程中分选微量元素的两种重要矿物之一。然而，目前还没有模型能够预测在超过4 Gpa的压力下，这些分馏是如何随着压力、温度和成分的变化而演变的，这严重阻碍了通过行星地幔熔融进行大规模分馏过程的成岩模型的发展。该实验程序旨在研究高压下石榴石熔体微量元素分配的关键控制。一些待研究的元素（如Sm、Nd、Lu、Hf、Th）定义了同位素系统的行为，对揭示行星内部的演化具有根本的重要性。该项目建立在最近的实验和理论工作的基础上，这些工作揭示了影响石榴石和无水熔体之间分配的重要因素，包括元素铁和钛的作用以及石榴石的多数石和粗石含量。我们寻求获得所需的数据，以充分了解这些成分控制石榴石熔体分配之间的相互关系。

Understanding how the compositions of garnet and coexisting silicate melt influence partitioning of trace elements is critical for understanding mantle evolution in terrestrial planetary interiors. Garnet is one of the two most important minerals (along with clinopyroxene) for fractionating trace elements during upper mantle melting and crystallization. However, no model exists that predicts how these fractionations evolve as a function of pressure, temperature, and composition at pressures exceeding 4 Gpa, severely hampering development of petrogenetic models of large-scale differentiation processes through melting in planetary mantles. This experimental program is designed to investigate critical controls on garnet-melt trace element partitioning at high pressure. Some of the elements to be studied (e. g. Sm, Nd, Lu, Hf, Th) define the behavior of isotopic systems of fundamental importance in unraveling the evolution of planetary interiors. The project builds on recent experimental and theoretical work that has revealed important factors affecting partitioning between garnet and anhydrous melt, including the roles of the elements iron and titanium and the garnet's majorite and grossular contents. We seek to acquire the data needed to understand fully the interrelationships between these compositional controls on garnet-melt partitioning.