Deriving Antarctic crustal heat production using gamma ray spectrometry

Martin Hand1, Jacqueline Halpin2, Derrick Hasterok1, Sandra McLaren3, Tom Raimondo4

1University of Adelaide, Adelaide, Australia, 2Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia, 3University of Melbourne, Melbourne, Australia, 4University of South Australia, Adelaide, Australia

Current Antarctic geothermal heat flux (GHF) models employ simple representations of lithospheric composition that do not yet capture the significant heterogeneity known from geological studies. Radiogenic heating within the crust from decay of naturally occurring radioactive elements, which varies as a function of the geological evolution of a terrane, is particularly poorly resolved, and yet this component can dominate the total surface GHF.

 

Heat production estimates are derived from the main heat producing element (HPE) content (i.e. U-Th-K) of a rock. Generally these HPE concentrations are determined using geochemical methods, and while fairly routine, these techniques are both expensive (~AUD $200/sample) and destructive.

 

We aim to augment the current Antarctic heat production inventory based on compiled geochemical analyses, with a new dataset of heat production estimates using a novel non-destructive method. The U-Th-K content of samples will be determined using a calibrated gamma ray spectrometer containing a high-density bismuth germanate detector in a lead-lined analytical cavity. This system is already in operation at the universities of Adelaide and South Australia and we are establishing a further facility at the University of Tasmania. Using this technique, we will analyse the heat production of legacy rock samples that reside in collections across Australia, encompassing a very high proportion of the entire basement evolution of East Antarctica, at a fraction of the cost of conventional geochemical methods.

 

Using this technique we expect to generate an unprecedented volume of heat production data, which will represent a major advance in characterising the natural variability of radiogenic heat production in Antarctic crust for use in future GHF models.

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