Following the Water: H2O in Subducting Slabs and Mantle Wedges

在俯冲板块和地幔楔中寻找水（H2O）对地球上的许多过程都有很大的影响。它是决定火山爆发是否会爆发的最重要因素。在构成地幔的矿物质中存在少量的水可以削弱通常坚硬的矿物质，从而使地幔以地质上的高速流动。在这个项目中，我们将在高温高压下进行实验，以确定哪些含水矿物（如果有的话）可以存在于俯冲的海洋地壳中，以及这些矿物在什么深度脱水。这种脱水最终导致了富含水的岩浆的形成，这些岩浆经常以爆发性的方式喷发。我们还将做实验，以确定多少水可以溶解在地球上地幔中不含水的特定结构部位的常见矿物（橄榄石、辉石、石榴石）的晶体结构中。这些矿物中即使含有少量的水也很重要，因为这些矿物在地幔中是如此丰富，以至于它们所含的总水量可能相当于世界海洋总水量的一倍或几倍。此外，这些矿物中溶解的水的影响会导致它们的强度（或粘度）和地震波穿过地幔的速度发生剧烈变化。我们将使用各种现代超高压设备和先进的化学分析技术来完成这个项目的目标。

Following the Water: H2O in Subducting Slabs and Mantle WedgesEAR-0208456PI: HollowayH2O (water) greatly influences many processes in the Earth. It is the most important factor in determining if a volcanic eruption will be explosive or not. The presence of small amounts of water in the minerals making up the Earth's mantle can weaken normally rigid minerals allowing the mantle to flow at geologically high velocities.In this project, we will conduct experiments at high temperatures and pressures to determine which hydrous minerals, if any, can be present in subducting oceanic crust, and at what depths those minerals dehydrate. Such dehydration ultimately results in the formation of water-rich magmas that often erupt very explosively.We also will do experiments to determine how much water can dissolve in the crystal structure of the common minerals (olivine, pyroxene, garnet) in the Earth's upper mantle that do not contain specific structural sites for H2O. The presence of even small amounts of water in such minerals is important because the minerals are so abundant in the Earth's mantle that the aggregate water contained in them may equal one or more times the total volume contained in the world's oceans. Additionally, the effect of dissolved water in those minerals causes drastic changes in their strength (or viscosity) and the velocity of seismic waves travelling through the mantle. We will use a variety of modern very high-pressure devices and advanced techniques for chemical analysis to complete the objectives of this project.