Warm, warmer, hot! Antarctic crustal radiogenic heat production.

Jacqueline Halpin1, Alex Burton-Johnson2, Sally Watson1, Joanne Whittaker1, Tobias Staal1, Anya Reading1, Alessandro Maritati1

1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia, 2British Antarctic Survey, Cambridge, United Kingdom

The geothermal heat flux (GHF) to the base of the Antarctic ice sheet is inherently difficult to measure, yet accurate estimates are necessary to better understand cryosphere dynamics. GHF includes heat supplied to the lithosphere from the convective mantle and radiogenic heat generated within the lithosphere from the decay of heat producing elements (HPEs), mainly Thorium (Th), Uranium (U) and Potassium (K). Through differentiation processes, HPEs are preferentially concentrated into the dominantly felsic rocks of the upper continental crust. The distribution of HPEs is therefore heterogeneous at a range of scales, and fundamentally tied to the geological evolution of the crust in space and time.

 

Current GHF models of the Antarctic continent based on geophysical properties use idealised crustal parameters that do not reflect the inherent geological heterogeneity. For example, recent studies have shown that radiogenic heat production values for Antarctic granites and gneisses can be significantly enriched (>10-15, and up to 65 micro watts per metre cubed) compared to average crustal values that are used across the entire continent in existing Antarctic GHF models (~ 1-2 micro watts per metre cubed). Regional ice sheet models have shown that localised regions of such high HPE-enriched crust can impact the organisation of ice flow, particularly in slow-flowing regions, underscoring the need for improved knowledge of both the magnitude and spatial variability of radiogenic heat production in Antarctic crust.

 

Here we assess the range in heat production values from diverse lithologies across outcrops and moraines in Antarctica using a compilation of previously published and new geochemical analyses. We explore variations with lithology, age and between geological terranes. Our analysis demonstrates significant spatial variability in heat production that will need to be integrated with deeper lithospheric structure and heat flow constraints to improve GHF models of the Antarctic continent.

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