Source of Lake Vostok Cations Constrained with Strontium Isotopes

W Berry Lyons,Martyn Tranter,Kathleen A Welch,John C Priscu,George Royston-Bishop

doi:10.3389/feart.2016.00078

Abstract

Lake Vostok is the largest sub-glacial lake in Antarctica. The primary source of our current knowledge regarding the geochemistry and biology of the lake comes from the analysis of refrozen lake water associated with ice core drilling. Several sources of dissolved ions and particulate matter to the lake have been proposed, including materials from the melted glacier ice, the weathering of underlying geological materials, hydrothermal activity and underlying, ancient evaporitic deposits. A sample of Lake Vostok Type 1 accretion ice has been analyzed for its 87Sr/86Sr signature as well as its major cation and anion and Sr concentrations. The strontium isotope ratio of 0.71655 and the Ca/Sr ratio in the sample strongly indicate that the major source of the Sr is from aluminosilicate minerals from the continental crust. These data imply that at least a portion of the other cations in the Type 1 ice also are derived from continental crustal materials and not hydrothermal activity, the melted glacier ice, or evaporitic sources.

Highlights

Close to 400 individual lakes have been documented under the Antarctic ice sheets, with both “static” and hydrologically active, flow-through, lake types having been defined (Smith et al, 2009; Wright and Siegert, 2012)
De Angelis et al (2004) argued that the Type 1 ice formed from lake water in a shallow embayment with erodible lake sediments, while the Type 2 ice was produced in deeper portions of the lake where sediment access was minimal
We present strontium isotope data from a sample of Type 1 accretion ice in order to provide new insight into the source of the solutes in the lake waters, and better constrain the processes controlling the geochemistry/mineralogy of the system

Summary

Introduction

Close to 400 individual lakes have been documented under the Antarctic ice sheets, with both “static” and hydrologically active, flow-through, lake types having been defined (Smith et al, 2009; Wright and Siegert, 2012). Christner et al (2006) predicted from the analysis of the accretion ice, a range of total dissolved major ions (TDS) in the lake water, ranging from ∼50 mM in the shallow embayment to as little as ∼2 mM for the deeper portions of the lake.

Results

Conclusion