Water Speciation and Viscosity of Hydrous Melts

含水硅酸盐熔体的粘度在气泡生长、岩浆破碎和火山爆发中起着关键作用。 该提案要求资助开发一个新的长期项目，使用我实验室多年来开发的一种新技术进行粘度测量。 它是基于玻璃化转变温度与硅酸盐熔体中水合物种反应的表观平衡温度之间的等效性。 为了使用该方法获得粘度，还必须表征含水物质反应的平衡。 这些数据本身对于理解熔体结构、水溶解度和岩浆中的扩散以及水蒸气和熔体之间的D/H分馏都很重要。 在三年的资助期内，我们将集中研究以下内容：a）含水流纹质熔体在高压下的形态和粘度，压力高达8 GPa; B）含水英安质熔体的形态平衡和这种熔体在高溶解H2O含量（高达8重量%溶解H2O）下的粘度;以及c）开发含水流纹质和英安质熔体更精确的粘度模型。 新的粘度模型将被应用于重新评估以前的气泡生长和岩浆破碎的结果。

ZhangEAR-0125506Viscosity of hydrous silicate melts plays a critical role in bubble growth, magma fragmentation and volcanic eruptions. This proposal requests funding to develop a new and long-term project for viscosity measurement using a novel technique developed over the years in my lab. It is based on the equivalence between glass transition temperature and the apparent equilibrium temperature of the hydrous species reaction in silicate melt. In order to obtain viscosity using this method, the equilibrium of the hydrous species reaction must also be characterized. Such data are important in their own right in understanding melt structure, water solubility and diffusion in magma, and D/H fractionation between water vapor and melt. In the three years of the grant period, we will concentrate on the following: a) speciation and viscosity at high pressures for hydrous rhyolitic melt up to 8 GPa; b) speciation equilibrium in hydrous dacitic melts and the viscosity of such melts to high dissolved H2O content (up to 8 wt% dissolved H2O); and c) development of more accurate viscosity models for hydrous rhyolitic and dacitic melts. The new viscosity model will be applied to re-evaluate previous results of bubble growth and magma fragmentation.