Morgado, E, Morgan, DJ orcid.org/0000-0002-7292-2536, Harvey, J orcid.org/0000-0002-0390-3438 et al. (6 more authors) (2022) The Magmatic Evolution and the Regional Context of the 1835 AD Osorno Volcano Products (41°06’S, Southern Chile). Journal of Petrology, 63 (11). egac105. ISSN 0022-3530
Abstract
Osorno volcano (41°06’S, 72°20’W) is a composite stratovolcano of the Central Southern Volcanic Zone of the Chilean Andes. It is the southernmost member of a NE–SW trending alignment of volcanic edifices including La Picada and Puntiagudo volcanoes and the Cordón Cenizos chain. According to contemporary descriptions recorded by Charles Darwin in 1835, two eruptive events occurred: the first during January–February, and the second during November–December 1835 and January 1836. The volcano erupted basaltic andesite lavas and tephra fall deposits (52.4 to 52.9 SiO2 wt. %), which contain phenocrysts of olivine, plagioclase, clinopyroxene, and spinel. The compositions of these phenocryst phases, together with those of olivine-hosted melt inclusions, allowed us to constrain intensive parameters for the pre-eruptive magmas. These varied from 1060°C to 1140°C, with an oxygen fugacity buffer of ~ΔQFM +1.1, dissolved water concentrations of up to 5.6 wt. % (average of ~4.2 wt. %) and maximum pressures equivalent to ~7-km depth. Textural relations, such as crystal accumulations and clots, zoning in crystals and other indications of disequilibrium, lead us to infer the involvement of a crystal mush, rich in individual crystals and clots of crystals, which underwent a degree of disaggregation and entrainment into the transiting magma prior to eruption. Comparison of trace element abundances, including rare earth elements, fluid-mobile elements, and relatively fluid-immobile elements, combined with 87Sr/86Sr and 143Nd/144Nd isotope ratios, allows us to consider variations in slab-derived fluid input and the minor role of crustal contamination on the Osorno eruptive products and those from neighboring volcanic systems. Our results suggest both a greater contribution from slab-derived fluid and a higher degree of partial melting in the systems supplying stratovolcanoes (Osorno, Calbuco, and La Picada) relative to those supplying small eruptive centers built over the major regional Liquiñe-Ofqui Fault Zone.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2022. This is an author produced version of an article published in Journal of Petrology. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Andean Southern; crystal mush; geothermobarometry; Osorno volcano; oxygen fugacity; Volcanic Zone |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 12 Jan 2023 17:41 |
Last Modified: | 23 Oct 2023 00:13 |
Status: | Published |
Publisher: | Oxford University Press |
Identification Number: | 10.1093/petrology/egac105 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:194896 |