Jurassic high heat production granites associated with the Weddell Sea rift system, Antarctica.

The distribution of heat flow in Antarctic continental crust is critical to understanding continental tectonics, ice sheet growth and subglacial hydrology. We identify a group of High Heat Production granites, intruded into upper crustal Palaeozoic metasedimentary sequences, which may contribute to locally high heat flow beneath the West Antarctic Ice Sheet. Four of the granite plutons are exposed above ice sheet level at Pagano Nunatak, Pirrit Hills, Nash Hills and Whitmore Mountains. A new Usingle bondPb zircon age from Pirrit Hills of 178.0 ± 3.5 Ma confirms earlier Rbsingle bondSr and Usingle bondPb dating and that the granites were emplaced approximately coincident with the first stage of Gondwana break-up and the developing Weddell rift, and ~ 5 m.y. after eruption of the Karoo-Ferrar large igneous province. Aerogeophysical data indicate that the plutons are distributed unevenly over 40,000 km2 with one intruded into the transtensional Pagano Shear Zone, while the others were emplaced within the more stable Ellsworth-Whitmore mountains continental block. The granites are weakly peraluminous A-types and have Th and U abundances up to 60.7 and 28.6 ppm respectively. Measured heat production of the granite samples is 2.96–9.06 μW/m3 (mean 5.35 W/m3), significantly higher than average upper continental crust and contemporaneous silicic rocks in the Antarctic Peninsula. Heat flow associated with the granite intrusions is predicted to be in the range 70–95 mW/m2 depending on the thickness of the high heat production granite layer and the regional heat flow value. Analysis of detrital zircon compositions and ages indicates that the high Th and U abundances are related to enrichment of the lower-mid crust that dates back to 200–299 Ma at the time of the formation of the Gondwanide fold belt and its post-orogenic collapse and extension.

Details

Publication status:
Published
Author(s):
Authors: Leat, Philip T., Jordan, Tom A. ORCIDORCID record for Tom A. Jordan, Flowerdew, Michael J., Riley, Teal R. ORCIDORCID record for Teal R. Riley, Ferraccioli, Fausto ORCIDORCID record for Fausto Ferraccioli, Whitehouse, Martin J.

On this site: Fausto Ferraccioli, Philip Leat, Tom Jordan, Teal Riley
Date:
2 January, 2018
Journal/Source:
Tectonophysics / 722
Page(s):
249-264
Link to published article:
https://doi.org/10.1016/j.tecto.2017.11.011