Origin and evolution of the Oligocene rhyolitic magmas in the Mesa Central of Mexico: geochemical, petrological and geochronological evidence from the Guanamé Ignimbrite Article uri icon

abstract

  • Oligocene explosive volcanism is widespread in the central and eastern portion of the Mesa Central (MC), but the origin of the rhyolitic magmas is still under discussion. The Guanamé Ignimbrite is located in the northern portion of the Salinas-Villa de Ramos volcanic field (SVRVF) and a typical rhyolitic and porphyric Oligocene ignimbrite in the central and eastern portion of the MC. U–Pb zircon single grain age determination reveals a crystallization between 30.61 ± 0.73 Ma and 30.73 ± 0.39 Ma and an eruption at 30.12 ± 0.45 Ma (K–Ar whole rock). 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 features and mineral chemistry show that the rhyolitic magmas generated in an intra-plate and extensional setting from partial melting of the lower crust. During the ascent and storage in a shallow magma chamber, fractional crystallization of mainly plagioclase and oxides was the major process taking place in the evolution of the magma. Rhyolite-MELTS models reveal that these rhyolitic magmas were generated by partial melting of the well-studied lower crust in the MC. The models result in a similar mineral assemblage as observed in the samples. The mineral composition and crystallization temperatures of feldspars analyzed in this study are similar to the models confirming the lower crustal origin. © 2021, Geologische Vereinigung e.V. (GV).

publication date

  • 2021-01-01