EAR-PF: Diffusion of water in clinopyroxene

伊丽莎白·费里斯博士被授予美国国家科学基金会地球科学博士后奖学金，在哥伦比亚大学拉蒙特-多尔蒂地球研究所开展一项研究和教育计划。这项研究将研究水在单斜辉石矿物群中的扩散，特别是铝、钛和铁的影响。该项目的更大目标是开发一种新的工具来确定地球表面附近岩浆的上升速度。准确地量化这一速度很重要，因为物理模型表明，上升速度在很大程度上控制着火山喷发的强度。将进行两组实验。首先，一组天然单斜辉石将被脱水，并将测量它们的扩散轮廓。这种方法允许对广泛的自然系统进行调查，并与以前以类似方式进行的实验建立了重要的联系。其次，合成富含铝和水的单斜辉石，并在高压下与熔体平衡。然后，这个系统将被减压，导致熔体和辉石的脱水。这项实验将需要大量的准备工作，但难度的增加被近距离模拟晶体生长、吸收水和减压时脱水所经历的自然过程的价值所抵消。这项研究将测试一种新的分析技术，用于测量对火山喷发物理模型至关重要的参数，并将提供对研究地幔水平衡非常有用的数据，这在行星到构造的尺度上都很重要。此外，费里斯博士还将联合组织一个地球动力学演讲者系列和一个关于地质系统扩散的研究生研讨会。

Dr. Elizabeth Ferriss has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at the Lamont-Doherty Earth Institute, Columbia University. This study will investigate the diffusion of water in the clinopyroxene mineral group, with particular emphasis on the effects of aluminum, titanium, and iron. The larger goal of the project is to develop a new tool to determine the ascent rate of magma near the surface of the Earth. Accurately quantifying this rate is important because physical models suggest that the ascent rate largely controls the vigor of volcanic eruptions. Two sets of experiments will be conducted. First, a set of natural clinopyroxenes will be dehydrated, and their diffusion profiles will be measured. This approach allows the investigation of a wide range of natural systems and creates an important link with previous experiments that were conducted in a similar way. Second, aluminum- and water-rich clinopyroxene will be synthesized and equilibrated with a melt at high pressure. This system will then be decompressed, resulting in dehydration of both the melt and the pyroxenes. This experiment will require a substantial amount of preparation, but the increase in difficulty is offset by the value of closely simulating the natural processes experienced by crystals as they grow, incorporate water, and dehydrate upon decompression.This study will test a novel analytical technique for measuring a parameter that is central to physical models of volcanic eruptions and will also provide data that will be highly useful for investigating the mantle's water budget, which is important at the planetary to tectonic scale. In addition, Dr. Ferriss will co-organize both a geodynamics speaker series and a graduate seminar on diffusion in geological systems.