Voluminous Paleogene volcanism in the southern Mesa Central, Mexico: Unravelling the fissure-fed origin of rhyolitic ignimbrites of the Villa Garcia-Loreto Volcanic Complex

Autor: Pascal Sieck, Randall Guevara, Rubén López-Doncel, Alfredo Aguillón-Robles, Klaus Wemmer, Pablo Dávila-Harris, Joselin Almaguer
Rok vydání: 2021
Předmět:
Zdroj: Journal of Volcanology and Geothermal Research. 415:107252
ISSN: 0377-0273
Popis: The southern portion of the Mesa Central (MC) physiographic province is covered by numerous Oligocene to Miocene volcanic successions that are part of the Sierra Madre Occidental silicic large igneous province. The MC merges with the Sierra Madre Occidental and the southern Basin and Range extensional province. The voluminous Villa Garcia-Loreto Volcanic Complex (VGLVC) is located in the southern portion of the MC and consists of predominantly rhyolitic lava flows, and voluminous products of explosive rhyolitic volcanism, mainly as lava-like to rheomorphic ignimbrite sheets. The volcanism in the area appears in two events, first, at 60.4 ± 0.3 Ma (K–Ar whole-rock age) with the fissure-fed eruption of an andesitic lava and second, with the fissure-fed eruption of two densely-welded, crystal-poor ignimbrites at 31.59 ± 0.14 Ma and 28.66 ± 0.07 Ma (40Ar–39Ar sanidine ages). Chondrite-normalized rare earth element patterns and primitive mantle normalized multi-element patterns show enrichment in light rare earth elements (LREE) and high field strength elements (HFSE). Geochemical analysis and mineral chemistry show that the andesitic magmas were generated by partial melting of the uppermost mantle in a subduction-related setting and ascended directly through the brittle crust and erupted along N-S trending faults. Rhyolitic magmas were generated by partial melting of the lower crust in an intra-plate and extensional setting, associated with an intense phase of the southern Basin and Range extension. During the ascent and storage in a shallow magma chamber fractional crystallization of mainly feldspars and pyroxene was the major process taking place in the evolution of the magma. Geophysical results suggest that the volcanic rocks of the VGLVC were originated by fissure-fed eruptions associated with the Loreto Graben fault. The major Basin and Range faults locally reach a depth of 7 km and trending in NNW-SSE direction. The combined results show that the Basin and Range extension favored the formation, ascent, and eruption of rhyolitic and andesitic magmas in the southern MC.
Databáze: OpenAIRE
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