dc.date.accessioned2021-08-23T22:57:27Z
dc.date.accessioned2022-10-19T00:28:10Z
dc.date.available2021-08-23T22:57:27Z
dc.date.available2022-10-19T00:28:10Z
dc.date.created2021-08-23T22:57:27Z
dc.date.issued2018
dc.identifierhttp://hdl.handle.net/10533/252057
dc.identifier1151469
dc.identifierWOS:000449900900009
dc.identifier.urihttps://repositorioslatinoamericanos.uchile.cl/handle/2250/4483320
dc.description.abstractWe describe the stratigraphy, age, constituent geochemistry and phenocryst thermobarometry of a closely spaced Holocene tephra couplet from Volcan Melimoyu (VMm), located in the Northern Patagonian Andes. The lower tephra unit (La Junta Tephra, Mm-1) is distinctly banded comprising a dominant lower layer of rhyodacitic (similar to 70% SiO2) pumiceous ash and lapilli (Mm-1p) that abruptly transitions to a subordinate upper scoriaceous layer (Mm-1s) of basaltic andesite composition (similar to 53% SiO2). This bimodality within Mm-1 contrasts significantly with the closely overlying Santa Ana Tephra (Mm-2) that has a homogeneous trachyte-dacite (similar to 63% SiO2) composition and is intermediate between the two magmatic end members of Mm-1. We propose a genetic affiliation between Mm-1 and Mm-2, and that the latter event likely represents a hybridised-remnant of those discrete magmas involved in the earlier Mm-1 eruption. To test this hypothesis we applied whole rock elemental mixing and fractional crystallisation model to reproduce the composition and crystallinity of Mm-2. Results indicate that Mm-2 can be reproduced by mixing similar to 70% Mm-1p with-30% Mm-1s, with subsequent similar to 13% fractional crystallisation of plagioclase, and minor amphibole, orthopyroxene, magnetite and biotite. Equilibrium P-T conditions calculated from Mm-1p phenocrysts point towards magma residency at moderately shallow depths (200-290 MPa, similar to 7-10-km depth, 850-1000 degrees C), whereas Mm-1s phenocrysts indicate higher overall P-T conditions (240-480 MPa, similar to 8.5-17-km depth, 1080-1150 degrees C). P-T conditions determined for Mm-2 (similar to 290 MPa, similar to 10-km depth, 930-1000 degrees C) are similar to those of Mm-1p. There is no physical and/or geochemical evidence of mafic magma involvement in the Mm-2 eruption. Similar compositionally bimodal tephra are known from other Northern Patagonian Andean centres (i.e. Playas Blanca-Negra Tephra, Antillanca; Lepue Tephra, Michimahuida; Ho and H3 eruptions of Hudson) suggests that the intrusion of mafic magma into more silicic magma bodies is a common occurrence throughout this Andean sector. These widely dispersed, compositionally bimodal tephra not only provide key insights into pre-eruptive magmatic conditions and triggering processes, but can also be readily identified geochemically, and thereby be more fully utilised within future hazard- and paleoenvironmental-related studies. (C) 2018 Elsevier Ltd. All rights reserved.
dc.languageeng
dc.relationhttps://doi.org/10.1016/j.quascirev.2018.09.034
dc.relationhandle/10533/111557
dc.relation10.1016/j.quascirev.2018.09.034
dc.relationhandle/10533/111541
dc.relationhandle/10533/108045
dc.rightsinfo:eu-repo/semantics/article
dc.rightsinfo:eu-repo/semantics/openAccess
dc.rightsAtribución-NoComercial-SinDerivadas 3.0 Chile
dc.rightshttp://creativecommons.org/licenses/by-nc-nd/3.0/cl/
dc.titleA widespread compositionally bimodal tephra sourced from Volcan Melimoyu (44 degrees S, Northern Patagonian Andes): Insights into magmatic reservoir processes and opportunities for regional correlation
dc.typeArticulo


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