Geochemical Effects of Deep Subduction of Oceanic Crust: An Experimental Study of 4-20 GPa

[9706517] Rapp海洋地壳深俯冲地球化学效应的实验研究分为两部分。第一个方面是对闪长岩-闪长岩花岗闪长岩成矿作用与克拉通化联系过程进行实验约束。在900-1200oC、4- 8gpa压力范围内对含水天然玄武岩进行一系列多砧试验，以补充现有1- 3gpa的实验数据。目的包括确定该范围内湿玄武岩固相，确定含水熔融-榴辉岩岩组合的物相组成，估算微量元素矿物-熔体分配系数，以约束部分熔融榴辉岩残留物的地球化学特征。第二个方面的建议旨在通过在多砧装置中对含水玄武岩进行相平衡实验，研究海洋地壳在超越岛弧状态进入过渡带时所经历的地球化学变化。这方面将通过定义P-T范围4- 20gpa和900-1300oC的含水玄武岩的一般相关系来解决，然后重点研究石榴石、斜辉石及其在天然玄武岩组成中的固溶体中微量元素的系统分布及其与压力的关系。

9706517 Rapp This experimental study on the geochemical effects of deep subduction of the oceanic crust has two parts. The first aspect is to place experimental constraints on the linked processes of tonalite-trondhjemite granodiorite plutonism and cratonization. A series of multi-anvil experiments on hydrous natural basalts will be conducted in the pressure range 4-8 GPa at 900-1200oC, to complement existing experimental data at 1-3 GPa. Objectives include defining the wet basalt solidus in this range, determining the compositions of the phases in the hydrous melt-eclogite restite assemblage, and estimating the trace element mineral-melt partition coefficients in order to constrain the geochemical characteristics of eclogite residues of partial melting. The second aspect of the proposal aims to examine the geochemical changes oceanic crust undergoes as it subducts beyond the island arc regime into the transition zone, again by conducting phase equilibria experiments on hydrous basalt in the multi-anvil apparatus. This aspect will be addressed by defining the general phase relations for hydrous basalt in the P-T range 4-20 GPa and 900-1300oC, and then focusing on trace element systematics in garnet, clinopyroxene, and their solid solutions in natural basalt compositions as a function of pressure.