Experimental Investigations on the Role of H20 in Magmatic Processes

提出的实验将对水对地幔熔融和地壳分异过程的影响提供约束。这些研究将提供有关熔化和分馏结晶的温度、挥发性含量和压力的信息。水在地球内部的循环对于理解地球在地质时期的化学演化具有根本的重要性。固-液分异过程（地壳形成、地幔分异和地核分离）、海洋和地球上生命的起源都与地球深层内部的水循环有关。提出了三个项目。1)系统研究了H2O对天然玄武岩熔体液相的影响。这些实验将提供定量信息，可用于模拟在不同数量的水存在下硅酸盐的水不饱和熔融，并应有助于解决关于少量水对熔融影响的相当大的不确定性。2)水、压力和地幔成分对橄榄岩熔融作用的研究。这些实验将定量估计水和整体组成（主要是碱元素Na2O和K2O）对俯冲带和次大陆地幔环境中岩浆生成的作用。3)水和压力对地壳玄武岩熔体分晶作用的实验研究。在弧岩浆系统中，分异弧岩浆的组成特征及其矿物组合可为火山爆发前的水含量、温度和深度分异史提供依据。对于前面的所有研究，我们将开发基于热力学的分析模型，以预测熔化/结晶的条件以及涉及H2O时产生的熔体成分。这些研究将对水对地壳和地幔化学演化的影响进行定量限制。这些关于水的信息将引起地球动力学和矿物物理学界的广泛兴趣，并最终与地球海洋和地球上生命的起源有关。本项目将培养研究生和本科生的实验岩石学/地球化学研究方法。本研究结果的实验数据将与社区共享，并将开发和分发预测温度，水含量和熔化/结晶压力的模型。

The proposed experiments will provide constraints on the influence of water on mantle melting and on crustal differentiation processes. The studies will provide information on the temperature, volatile content and pressure of melting and fractional crystallization. The cycling of water through the Earth's interior is of fundamental importance for understanding the chemical evolution of the Earth over geologic time. Processes of solid - liquid differentiation (crust formation, mantle differentiation and core segregation), of the origin of the oceans and of life on Earth are tied to the cycling of H2O through our planet's deep interior. Three projects are proposed. 1) A systematic investigation of the influence of H2O on the liquidus of natural basaltic melts. These experiments will provide quantitative information that can be used to model the H2O-undersaturated melting of silicates in the presence of variable amounts of H2O, and should help resolve the considerable uncertainty on the influence of small amounts of H2O on melting. 2) Investigation of the role of H2O, pressure and mantle composition on peridotite melting. These experiments will provide quantitative estimates of the role played by H2O and bulk composition (primarily the alkali elements Na2O and K2O) on the generation of magmas in subduction zone and sub continental mantle environments. 3) Experimental studies of the role of H2O and pressure on fractional crystallization of basaltic melts in the crust. In arc magmatic systems the compositional characteristics of differentiated arc magmas and their mineral assemblages can provide evidence of the pre-eruptive H2O content, temperature and depth history of differentiation. For all of the preceding studies we will develop thermodynamically based analytic models that allow prediction of conditions of melting/crystallization and compositions of melts generated when H2O is involved. These studies will place quantitative constraints on the influence of H2O on the chemical evolution of the Earth's crust and mantle. This information on H2O will be of broad interest in the geodynamics and mineral physics community and ultimately has relevance for the origin of the Earth's oceans and life on Earth. This project will train graduate and undergraduate students in research methods of experimental petrology/geochemistry. The experimental data that results from this study will be shared with the community and models for predicting temperature, H2O content and pressure of melting/crystallization will be developed and distributed.