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

这项探索性研究小额赠款旨在探索镁同位素在了解南极洲干谷土壤中冰的保存方面的应用。由于该地区降水很少，这些冰应该已经完全升华了，尽管如此，在一些地区有地质证据表明存在1000万年的冰。它在干谷土壤中的普遍存在意味着某种形式的补给，似乎与低降水率不相容。本项目研究可溶性盐中发现的镁同位素，并通过关联研究水的运输。镁同位素在挥发和凝结过程中经历质量依赖的分馏，因此提供了限制水源和冰动员的其他过程的可能性。测量需要的高精度，直到最近MC-ICPMS的发展才成为可能。该方法将应用于从存档的南极土壤中提取的镁盐，以及20世纪70年代干谷钻探项目恢复的岩心。就更广泛的影响而言，该项目将支持一名研究生，他们将学习最前沿的地球化学技术，同时将其应用于一个令人兴奋的地球科学问题。这项工作对于了解干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冰记录。这项工作也应用于了解火星上的永久冻土，并解释最近的漫游者观测结果。

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.