Experimental Petrology of Garnet Lherzolite Melting

本程序使用八面体多砧仪研究3 - 5.5 GPa范围内名义无水石榴石橄榄岩的熔融情况。实验的目标是确定1)P-T空间的高压凝固，2)近固相熔体和晶体的组成，3)熔化反应的细节，以及4)确定熔体生产率所需的温度和熔体分数之间的函数关系。我们正在对一系列不同斜辉石比例的石榴石和辉沸石组成进行实验。这些成分扩展了典型MORB地幔橄榄岩熔融的观测基础，为柱状地幔提供了可能的类似物。实验采用微交换技术表征低于0.1的熔体组分，并采用更经典的方法表征较高熔体组分。在我们的实验室中，详尽的P-T校准工作高于3 GPa，确保了多砧装置中样品环境的可重复性和控制水平，类似于在较低压力下活塞缸装置中常规实现的水平。本研究获得的高压下基本相平衡数据将有助于建立非常有限的石榴石橄榄岩熔融实验数据库。这些数据对于在海洋扩张脊、海洋岩石圈和大陆下地幔上涌熔融橄榄岩的定量模拟是必不可少的。

LesherEAR-0001245This program investigates melting of nominally anhydrous garnet peridotite between 3 and 5.5 GPa using the octahedral multianvil apparatus. The goals of the experiments are determination of 1) high pressure solidii in P-T space, 2) the compositions of near-solidus melts and crystals, 3) the specifics of the melting reaction, and 4) the functional relationships between temperature and melt fraction required to determine melt productivity. We are performing experiments on a range of garnet lherzolite compositions that differ in the proportion of clinopyroxene. These compositions extend the observational basis for peridotite melting of typical MORB mantle to possible analogs for plume mantle. The experiemts employ micro-exchange techniques to characterize the compositions of melt fractions below 0.1, and more classical approaches at higher melt fractions. Exhaustive P-T calibration work in our laboratory above 3 GPa ensures a level of reproducibility and control of sample environment in the multianvil apparatus similar to that routinely achieved in the piston-cylinder apparatus at lower pressures. The fundamental phase equilibrium data at high pressures obtained in this study will contribution to the very limited experimental database for garnet peridotite melting. Such data are essential for quantitative modeling of melting of peridotite by mantle upwelling beneath ocean spreading ridges, oceanic lithosphere, and continents.