Cretaceous magmatism in the Antarctic Peninsula and its tectonic implications

Bastias, Joaquin; Spikings, Richard; Riley, Teal ORCID: https://orcid.org/0000-0002-3333-5021; Chew, David; Grunow, Anne; Ulianov, Alexey; Chiaradia, Massimo; Burton-Johnson, Alex ORCID: https://orcid.org/0000-0003-2208-0075. 2023 Cretaceous magmatism in the Antarctic Peninsula and its tectonic implications. Journal of the Geological Society, 180 (1), jgs2022-067. 18, pp. 10.1144/jgs2022-067

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Abstract/Summary

Periods of cessation, resumption and enhanced arc activity are recorded in the Cretaceous igneous rocks of the Antarctic Peninsula. We present new geochronological (LA-ICP-MS zircon U-Pb) analyses of 36 intrusive and volcanic Cretaceous rocks, along with LA-ICP-MS apatite U-Pb analyses (a medium-temperature thermochronometer) of 28 Triassic–Cretaceous igneous rocks of the Antarctic Peninsula. These are complemented by new zircon Hf isotope data along with whole-rock geochemistry and isotope (Nd, Sr and Pb) data. Our results indicate that the Cretaceous igneous rocks of the Antarctic Peninsula have geochemical signatures consistent with a continental arc setting and were formed during the interval ∼140–79 Ma, while the main peak of magmatism occurred during ∼118–110 Ma. Trends in εHft (zircon) combined with elevated heat flow that remagnetised rocks and reset apatite U-Pb ages suggests that Cretaceous magmatism formed within a prevailing extensional setting that was punctuated by periods of compression. A noteworthy compressive period probably occurred during ∼147–128 Ma, triggered by the westward migration of South America during opening of the South Atlantic Ocean. Cretaceous arc rocks that crystallised during ∼140–100 Ma define a belt that extends from southeastern Palmer Land to the west coast of Graham Land. This geographic distribution could be explained by (i) a flat slab with east-dipping subduction of the Phoenix Plate, or (ii) west-dipping subduction of the lithosphere of the Weddell Sea, or (iii) an allochthonous origin for the rocks of Alexander Island. A better understanding of the geological history of the pre-Cretaceous rocks of Alexander Island and the inaccessible area of the southern Weddell Sea is required.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1144/jgs2022-067
ISSN:	0016-7649
Date made live:	25 Jul 2022 09:34 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/532407

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