Zircon O- and Hf-isotope constraints on the genesis and tectonic significance of Permian magmatism in Patagonia
Published on 2017-05-03T10:12:30Z (GMT) by
The genesis of Permian magmatism in southern South America is actively debated, particularly in relation to the origin of Patagonia. U–Pb zircon ages of <i>c</i>. 255 Ma for igneous rocks from the basement of Tierra del Fuego are the first evidence for southerly prolongation of this magmatism. Zircon in these rocks has εHf<sub>t</sub> values <–1 and δ<sup>18</sup>O > 7.4‰, indicating recycling of Cambrian rocks. Permian granites in the north of the North Patagonian Massif record mantle-like δ<sup>18</sup>O magmatic input at <i>c</i>. 280 and 255 Ma, but reworking of upper crust between these two events, paralleling the recognized deformational history. In northwestern Patagonia, Early Permian granitic rocks have zircon with εHf<sub>t</sub> values ranging from +0.1 to –7.2, and δ <sup>18</sup>O > 6.2‰, suggesting continuity of the Permian magmatic belt along the western margin of South America farther north. Comparison with a sample from the Sierra de la Ventana suggests melting of similar crust on both sides of the Patagonia–South American hypothetical suture. These features, together with other geological considerations, are consistent with an autochthonous or parautochthonous origin of northern Patagonia and connection between southern Patagonia and the Antarctic Peninsula in late Palaeozoic time.
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Castillo, Paula; Fanning, C. Mark; Pankhurst, Robert J.; Hervé, Francisco; Rapela, Carlos W. (2017): Zircon O- and Hf-isotope constraints on the genesis and tectonic significance of Permian magmatism in Patagonia. Geological Society of London.