Petrogenesis of the crystalline basement along the western Gulf of Mexico: Postcollisional magmatism during the formation of Pangea

Abstract

The supercontinent of Pangaea formed through the diachronic collision of Laurussia and Gondwana during the Late Paleozoic. Whilst magmatism associated with its formation is well documented in the Variscan orogeny of Europe and Alleghanian orogeny of the USA, little is known about the Sonora orogeny of Northern Mexico. This paper reports geochronology (U-Pb zircon), whole rock geochemistry and Lu-Hf zircon isotope data on basement cores from the Western Gulf of Mexico, that are used to develop a tectonomagmatic model for pre-to post-Pangaea amalgamation. Our results suggest the existence of three distinct phases of magmatism, produced during different stages of continental assembly and disassembly. The first phase consists of Early Permian (294-274 Ma; n= 3) granitoids with geochemical signatures indicative of a continental arc tectonic setting. This phase formed on the margins of Gondwana during the closure of the Rheic Ocean, prior to the final amalgamation of Pangaea. It likely represents a lateral analogue of Late Carboniferous-Early Permian granitoids that intrude the Acatlán and Oaxacan Complexes. The second phase of magmatism includes Late Permian-Early Triassic (263-243 Ma; n= 13) granitoids with suprasubduction geochemical affinities. However, Lu-Hf isotope data indicate that these granitoids formed from crustal anatexis, with ɛHf values and two-step TDM(Hf) model ages comparable to the Oaxaquia continental crust that they intrude. This phase of magmatism is likely to be related to coeval granitoids in the Oaxaca area and Chiapas Massif. We interpret it to reflect late-to post-collisional magmatism along the margin of Gondwana following the assembly of Pangaea. Finally, the third phase of magmatism includes Early-Middle Jurassic (189-164 Ma; n= 2) mafic porphyries that could be related to the synchronous supra-subduction magmatism associated with the Nazas arc. Overall, our results are consistent with Pangaea assembly through diachronous collision of Laurussia and Gondwana during subduction of the Rheic Ocean. They suggest that post-orogenic magmatism in the western termination of the Rheic suture occurred under the influence of a Panthalassan subduction zone, before opening of the Gulf of Mexico.

Evidence of Carboniferous arc magmatism preserved in the Chicxulub impact structure

“…1A). Ediacaran rift-related mafic dyke swarms emplacement and metasedimentary units deposition occurred in the NE Mexico and Chiapas as the final fragmentation of Rodinia occurred and formed the Iapetus Ocean (González-Guzman et al, 2016;Weber et al, 2019Weber et al, , 2020. Ordovician (~480-450 Ma) magmatism and related crustal anatexis, as recorded in Chiapas, Altos Cuchumatanes, and Rabinal, suggest that these terranes are the northern continuation of the Famatinian arc along western Gondwana (Estrada-Carmona et al, 2012;Weber et al, 2018;Alemán-Gallardo et al, 2019;Ortega-Obregón et al, 2008, 2009Juárez-Zúñiga et al, 2019).…”

“…There are only a few exposures of the late Mesoproterozoic Oaxaquian basement including the Novillo Gneiss (Fig. 1; Keppie et al, 2003;Cameron et al, 2004;Trainor et al, 2012;Weber et al, 2019), the Huiznopala Gneiss (Lawlor et al, 1999;Weber et al, 2014), the Oaxacan Complex Solari et al, 2003;2004a;2004b), and the Guichicovi Complex (Weber and Köhler, 1999;Weber and Hecht, 2003). Pre-Mesozoic rocks of the Guichicovi complex are characterized by 1.2 Ga igneous arc-related protoliths and ~1.02-1.01 Ga anorthosite-mangerite-charnockite granites that were metamorphosed under granulite facies conditions between 990-975 Ma (Weber and Köhler, 1999;Ruiz et al, 1999;Weber et al, 2010).…”

Provenance and tectonic setting of the Paleozoic Tamatán Group, NE Mexico: Implications for the closure of the Rheic Ocean

“…Most of the Guacamaya Formation samples plot within the oceanic island arc field in these diagrams. In contrast, the current Permian paleogeographic models for the Mexican peri-Gondwanan terranes correspond to a constantly diachronous closure of the Rheic Ocean and the collision of Gondwana against Laurentia (e.g., Coombs et al, 2020).…”

“…The petrography and geochemical signatures indicate felsitic and mafic sources, which can be derived from the Permian arc. Coombs et al (2020) pointed out that the Permian magmatism developed in three magmatic phases, each of which formed in different stages from the oceanic plate in the same tectonic setting, such as (1) Early Permian (294-274 Ma) granitoids associated with a continental arc formed on the margin of Gondwana during the closure of the Rheic Ocean, prior to the final amalgamation of Pangea; (2) Late Permian-Early Triassic (263-243 Ma) granitoids with supra-subduction affinity formed by crustal anatexis, related to coeval granitoids in southernmost Oaxaquia and Chiapas Massif; and (3) Early-Middle Jurassic (189-164 Ma) mafic porphyries related to synchronous supra-subduction magmatism for the Nazas arc (post-orogenic magmatism). The Guacamaya Formation shows evidences of a 280 Ma magmatism similar to the first phase, which is suggestive of the arc system from mantle-derived melts mixing with continental crust, whereas younger pulses were not observed.…”

“…6, Casas-Peña et al, 2021). Concurrently, the volcanism was continuously active until the Triassic prior to the Pangea breakup (e.g., Coombs et al, 2020), and a cordilleran magmatism in the Permian-Triassic occurred from the Sonora (Sierra Pinta; Arvizu et al, 2009) to central (Gulf Coast Plain;Coombs et al, 2020) and southern Mexico (Chiapas Massif, Maya block; Weber et al, 2007) and the northwestern Andes (e.g., Cochrane et al, 2014). Plutonic rocks with similar ages were reported from the Gulf of Mexico coast drill cores of Tamaulipas (294-274 Ma, Coombs et al, 2020), from the Chiapas Massif Complex (orthogneiss protolith, 272 ± 3 Ma, Weber et al, 2007) and from the Mixteco terrane (Totoltepec pluton, 306-287 Ma;Yañez et al, 1991;Keppie, 2004;Kirsch et al, 2012).…”