Stratigraphy, chemistry, and eruptive dynamics of the 12.4 ka plinian eruption of Apoyeque volcano, Managua, Nicaragua |
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Authors: | Denis Ramón Avellán José Luis Macías Giovanni Sosa-Ceballos Gema Velásquez |
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Institution: | 1. Instituto de Geología y Geofísica, Universidad Nacional Autónoma de Nicaragua (IGG-CIGEO/UNAN-Managua), Managua, Nicaragua 2. Instituto de Geofísica, Unidad Michoacán, Universidad Nacional Autónoma de México, Ex-Hacienda de San José de La Huerta, C.P. 58190, Morelia, Michoacán, México 3. Facultad de Ciencias e Ingeniería, Universidad Nacional Autónoma de Nicaragua, Managua, Nicaragua
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Abstract: | Apoyeque volcano, located 9 km northwest of Managua city, erupted explosively at 12.4 ka. The Plinian eruption deposited a widespread pumice fall deposit known as the Upper Apoyeque Tephra (UAq). The UAq is massive, reversely graded, and consists of white juvenile pumice (~78 vol.%), a variety of cognate lithics and accidental altered lithics. The whole-rock pumice composition is rhyodacitic (SiO2?=?66.9–68.5 wt.%) with a mineral paragenesis of plagioclase, orthopyroxene, clinopyroxene, amphibole, titanomagnetite, and ilmenite in a rhyolitic glass groundmass (SiO2?=?74.4?±?0.6 wt.%). The deposit’s dispersal axis is to the south, with the deposit covering a minimum area of 877 km2 within the 50 cm isopach and has a total volume of 3 km3 (dense rock equivalent, 1.15 km3). The eruption column reached a maximum height of ca.28 km. The eruption ejected a total mass of 3?×?1012 kg at an average rate of 2?×?108 kg/s, and based on available models, we infer duration of almost 4 h. Petrographic and geochemical characteristics suggest that the eruption was triggered by magma mixing. |
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