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Multi-stage arc magma evolution recorded by apatite in volcanic rocks

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Title: Multi-stage arc magma evolution recorded by apatite in volcanic rocks
Authors: Nathwani, C
Loader, M
Wilkinson, J
Buret, Y
Sievwright, R
Hollings, P
Item Type: Journal Article
Abstract: Protracted magma storage in the deep crust is a key stage in the formation of evolved, hydrous arc magmas that can result in explosive volcanism and the formation of economically valuable magmatic13 hydrothermal ore deposits. High magmatic water content in the deep crust results in extensive amphibole ± garnet fractionation and the suppression of plagioclase crystallization as recorded by elevated Sr/Y ratios and high Eu (high Eu/Eu*) in the melt. Here, we use a novel approach to track the petrogenesis of arc magmas using apatite trace element chemistry in volcanic formations from the Cenozoic arc of Central Chile. These rocks formed in a magmatic cycle that culminated in high Sr/Y magmatism and porphyry ore deposit formation in the Miocene. We use Sr/Y, Eu/Eu* and Mg in apatite to track discrete stages of arc magma evolution. We apply fractional crystallization modeling to show that early crystallizing apatite inherits a high Sr/Y and Eu/Eu* melt chemistry signature that is predetermined by amphibole-dominated fractional crystallization in the lower crust. Our modeling shows that crystallization of the in-situ host rock mineral assemblage in the shallow crust causes competition for trace elements in the melt that leads to apatite compositions diverging from bulk magma chemistry. Understanding this decoupling behavior is important for the use of apatite as an indicator of metallogenic fertility in arcs and for interpretation of provenance in detrital studies.
Issue Date: 17-Jan-2020
Date of Acceptance: 5-Dec-2019
URI: http://hdl.handle.net/10044/1/75448
DOI: 10.1130/G46998.1
ISSN: 0091-7613
Publisher: Geological Society of America
Start Page: 323
End Page: 327
Journal / Book Title: Geology (Boulder)
Volume: 48
Issue: 4
Copyright Statement: © 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license (https://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Natural Environment Research Council (NERC)
Funder's Grant Number: NE/P017444/1
Keywords: Geochemistry & Geophysics
04 Earth Sciences
Publication Status: Published
Open Access location: https://doi.org/10.1130/G46998.1
Online Publication Date: 2020-01-17
Appears in Collections:Faculty of Engineering
Earth Science and Engineering