Small Grant Exploratory Research: The Application of Mg Isotopes as an Indictor for Water and Brine Migration into Dry Valley Permafrost

这项探索性研究的小额赠款探索了镁同位素在了解南极洲干燥山谷土壤中冰的保存方面的应用。在该地区降雨量如此之少的情况下，这些冰应该已经完全升华掉了，尽管在一些地区有1000万年前的冰的地质证据。它在干旱山谷的土壤中无处不在，意味着某种形式的补给，似乎与低降雨率不相容。该项目研究了在可溶盐中发现的镁同位素，并通过缔合作用研究了水的运输。镁同位素在挥发和冷凝过程中经历与质量相关的分馏，从而提供了限制水源和其他动员冰的过程的可能性。测量需要高精度，直到最近MC-ICPMS的开发才成为可能。该方法将应用于从南极存档土壤中提取的镁盐，以及1970年代干谷钻探项目回收的岩心。在更广泛的影响方面，这个项目将支持一名研究生，他将学习尖端的地球化学技术，同时将它们应用于一个令人兴奋的地球科学问题。这项工作对于理解干燥山谷提供的环境记录至关重要，包括可能提供700万年前地球大气样本的深层冰记录。这项工作还应用于了解火星上的永久冻土，并解释最近火星车的观测结果。

This Small Grant for Exploratory Research explores the use of magnesium isotopes in understanding the preservation of ice in soils from the Dry Valleys of Antarctica. With such little precipitation in the region, this ice should have completely sublimed away, nonetheless there is geologic evidence of ten-million-year-old ice in some areas. Its ubiquitous presence in Dry Valley's soils implies some form of recharge, seemingly incompatible with the low precipitation rates. This project studies the Mg-isotopes found in soluble salts and, by association, water transport. Magnesium isotopes undergo mass dependent fractionation during the volatilization and condensation, and thus offer the possibility to constrain both the water source and other processes by which ice is mobilized. The measurements require the high precision made possible only recently by development of the MC-ICPMS. The method will be applied to Mg-salts extracted from archived Antarctic soils, as well as cores recovered by the 1970s Dry Valley Drilling Project. In terms of broader impacts, this project would support a graduate student, who would learn cutting edge geochemical techniques while applying them to an exciting earth science question. This work is critical to understanding the environmental record offered by the Dry Valleys, including the deep ice records that may give seven-million year old samples of the earth's atmosphere. The work also has applications to understanding permafrost on Mars and interpreting recent rover observations.