玄武质熔体水扩散系数测定与地月岩浆海的水迁移和演化

项目名称： 玄武质熔体水扩散系数测定与地月岩浆海的水迁移和演化

项目编号： No.41473058

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 天文学、地球科学

项目作者： 倪怀玮

作者单位： 中国科学技术大学

项目金额： 97万元

中文摘要： 地球和月球内部水的分布、迁移和演化是认识地-月系统早期演化历史的重要线索。根据得到广泛认可的大碰撞假说，约45亿年前的大碰撞形成了大规模的地球岩浆海和月球岩浆海。地球表层大气中的水蒸气可能溶解进入地球岩浆海；与此同时，岩浆海的分离结晶导致水在岩浆中富集，甚至引发岩浆去气。水在超镁铁质/镁铁质熔体中的扩散系数是控制岩浆海中水迁移和演化过程的关键参数。本项目计划在活塞圆筒压机中1500-2000 K和0.5-4 GPa条件下开展玄武质熔体水扩散实验，并通过对实验产物进行红外/拉曼光谱分析获得水扩散系数。在厘定水扩散机制与掌握水扩散系数随温度、压力、水含量和熔体成分变化规律的基础上，建立适用于超镁铁质/镁铁质熔体的水扩散系数模型。水扩散系数模型将被应用于模拟岩浆海结晶过程中水的迁移和演化，评估地、月内部的水含量分布，进而制约地-月系统的早期演化历史。

中文关键词： 水扩散系数；玄武质熔体；岩浆海；地球；月球

英文摘要： The distribution, transport and evolution of water in Earth's interior and lunar interior provide important insights into the early evolution of the Earth-Moon system. Based on the widely accepted giant impact hypothesis, a giant impact at c.a. 4.5 Ga led to the formation of planet-scale terrestrial magma ocean (TMO) and lunar magma ocean (LMO). While the steam in Earth's protoatmosphere could dissolve into the TMO, fractional crystallization of the TMO and the LMO would cause water enrichment and even outgassing of magma oceans. Water diffusivity in ultramafic/mafic siliate melts is a crucial parameter in controlling the transport and evolution of water in the TMO and the LMO. This project proposes to perform water diffusion experiments in basaltic melts at 1500-2000 K and 0.5-4 GPa in a piston cylinder apparatus. Water diffusivity will be extracted from FTIR and Raman analyses of the quenched experimental products. After understanding the mechanism for water diffusion and the variation of water diffusivity with temperature, pressure, water content, and melt composition, universal water diffusivity models applicable to ultramafic/mafic melts will be developed. The water diffusivity models will be applied to simulate the transport and evolution of water in the TMO and the LMO, to evaluate the distribution of water in Earth's interior and lunar interior, so as to constrain the early evolution of the Earth-Moon system.

英文关键词： water diffusivity;basaltic melt;magma ocean;Earth;Moon