Experimental Petrology of Garnet Lherzolite Melting

Lesherkan-0001245该程序使用八面体多砧装置研究了3 - 5.5 GPa之间名义上无水石榴石橄榄岩的熔融。实验的目的是确定1）P-T空间中的高压凝固，2）近固相线熔体和晶体的组成，3）熔化反应的细节，和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。我们正在对一系列石榴石二辉橄榄岩成分进行实验，这些成分在单斜辉石的比例上不同。这些组成扩展了典型MORB地幔橄榄岩熔融的观测基础，可能类似于地幔柱。实验采用微交换技术来表征低于0.1的熔体分数的组成，并在较高的熔体分数下采用更经典的方法。我们实验室在3GPa以上的详尽P-T校准工作确保了多砧装置中样品环境的再现性和控制水平，类似于在较低压力下活塞-气缸装置中常规实现的水平。本研究所获得的高压下的基本相平衡数据，将有助于丰富石榴橄榄岩熔融的有限实验数据。这些数据是必不可少的定量模拟地幔上涌下洋展脊，大洋岩石圈和大陆的橄榄岩熔融。

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.