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Diverse Magmatic Processes and Eruptive Styles in the Serdán Oriental Basin : Insights from Mafic to Garnet-Bearing Rhyolitic Compositions

Loup Fayolas1, Kevin Gemali Pedroza Aldana2, Marie-Noëlle Guilbaud2, Erwan Martin1, Hélène Balcone-Boissard1, Laura Sofia Ortiz Blanco2

  • Affiliations: 1Sorbonne Université, CY Cergy Paris Université, CNRS INSU, Institut des Sciences de la Terre de Paris, ISTeP, F-75005 Paris 2Departamento de Vulcanología, Instituto de Geofísica, Universidad Nacional Autónoma de México, Coyoacán, México D.F., México

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 10

  • Programme No: 3.7.17

  • Theme 3 > Session 7

Abstract

Continental subduction zones exhibit diverse volcanoes and eruptive behaviors, influenced by complex and poorly understood crustal magmatic processes. The Trans-Mexican Volcanic Belt is an active continental arc dominated by monogenetic fields, but also punctuated by large polygenetic volcanoes. In the eastern region lies the Serdán Oriental Basin, which is characterized by abundant bimodal monogenetic volcanism ranging from the Pliocene to the Quaternary. At the center of the basin is the Las Derrumbadas Volcanic Field (<25 ka B.P.), where two large rhyolitic domes are surrounded by over a dozen monogenetic volcanic structures, distributed within a ~16 km radius. The basin is bordered by polygenetic volcanoes, such as Los Humeros. These volcanoes exhibit a wide range of eruptive styles and compositions, spanning from basalts to rhyolites with a dacitic gap, following a calc-alkaline series. Mafic and intermediate compositions represent small volumes (<1 km³ per volcano), while rhyolitic magmas constitute larger ones (Las Derrumbadas domes >10 km³). Two rhyolite groups distinguish: garnet-free and garnet-bearing. Mafic and intermediate samples show similar trace element spectra (LaN/YbN=5-13.6). Garnet-free rhyolites show relatively flat REE spectra (LaN/YbN=2), low REE concentrations, and a marked negative Eu anomaly (EuN/EuN*=0.08), attributed to plagioclase fractionation. Garnet-bearing rhyolites show slightly higher LREE content than mafic and intermediate compositions, but present a strong HREE depletion (LaN/YbN=49-201). We propose that mafic, intermediate, and garnet-free rhyolites are the result of polybaric fractional crystallization of mantle-derived melts, while the garnet-bearing rhyolites originate from the partial melting of mafic lower crust, followed by rapid ascension that preserves garnets.