40Ar/39Ar geochronology of Volcan Tepetiltic, western Mexico: Implications for the origin of zoned rhyodacite-rhyolite liquid erupted explosively from an andesite stratovolcano after a prolonged hiatus

Abstract

40Ar/ 39 Ar geochronology is used to determine the eruptive history of Volcán Tepetiltic, a predominantly andesitic stratovolcano that underwent caldera collapse during explosive eruption of zoned rhyodacite-rhyolite. The main edifi ce was largely constructed between 560 and 450 ka, but it was not complete until ca. 416 ka, during which time ~42 km 3 of phenocryst-rich (25-40 vol%) lavas ranging from 57 to 69 wt% SiO 2 were erupted. After a hiatus of ~180 k.y., there was a climactic Plinian eruption of ~4-8 km 3 of zoned magma (68-75 wt% SiO 2 ). Afterward, a small rhyodacite dome (69 wt% SiO 2 ; 190 ± 22 ka) and an andesite dome were emplaced on the caldera fl oor. There has been no subsequent volcanic activity. The crystal-poor (0-5 vol%) Plinian pumice could not be dated directly, owing to the hydration of glass and the absence of a K-rich mineral phase. Instead, the age of the climactic eruption was bracketed to be ca. 236 ± 52 ka from 40 Ar/ 39 Ar dates (±2σ) on peripherally erupted basaltic andesite fl ows, which are found underneath (241 ± 47 ka) and overlying (220 ± 36 ka) the associated fallout deposits. A volume of ~9 km 3 of basaltic andesite was erupted from three peripheral vents surrounding Volcán Tepetiltic, most of it from a shield volcano that was active before, during, and after the Plinian event. Thermal models indicate that the magma chamber beneath Volcán Tepetiltic would have cooled below its solidus within 36 k.y. in the absence of new injections of magma. Given the long hiatus (~180 k.y.) between the cone-building episode that built the andesite stratovolcano and the explosive eruption of rhyodacite-rhyolite, it is proposed that the infl ux of voluminous basaltic andesite into the upper crust drove partial melting of the subsolidus magma chamber beneath Volcán Tepetiltic, which explains the synchronicity of the basaltic andesite volcanism with the Plinian eruption of zoned, crystal-poor rhyolitic melt.

Combined magnetotelluric and petrologic constrains for the nature of the magma storage system beneath the Late Pleistocene Ciomadul volcano (SE Carpathians)

“…However, there are signs that volcanoes can be reactivated even after several 10s ka quiescence (Clynne and Muffler, 2010;Escobar-Wolf et al, 2010;Frey et al, 2013).…”

Episodes of dormancy and eruption of the Late Pleistocene Ciomadul volcanic complex (Eastern Carpathians, Romania) constrained by zircon geochronology

“…Understanding the frequency of eruptions in long-lived volcanic complexes is important to evaluate their potential hazards especially when these systems remained dormant for protracted periods. Many intermediate (andesitic-dacitic) volcanic systems in continental arc or collision zones are characterized by long (>100 kyr) dormancy peri ods after which volcanism is rejuvenated (Hildreth and Lanphere, 1994;Hoshizumi et al, 1999;Gamble et al, 2003;Hora et al, 2007;Bablon et al, 2018;Molnár et al, 2018), often with explosive eruptions (Frey et al, 2014). Thus, protracted quiescence since the last volcanic eruption may be misleading in estimating eruptive recurrence and the potential for volcanic reawakening.…”

The Volcanic-Plutonic Connection

“…Others, going back at least a century, proposed that silicic magmas form by separation of liquids from crystallizing magmas. The experimental work of Tuttle and Bowen (1958) is generally viewed as evidence that fractional crystallization can produce granites and rhyolites, but other experimental work and geochemical datasets point to partial melting as an alternative (Peterson and Roberts 1963;Taylor et al 1968;Sisson et al 2005;Frey et al 2014).…”