Compositional variability in mafic arc magmas over short spatial and temporal scales: evidence for the signature of mantle reactive melt channels
Compositional variability in mafic arc magmas over short spatial and temporal scales: evidence for the signature of mantle reactive melt channels
Understanding arc magma genesis is critical to deciphering the construction of continental crust, understanding the relationship between plutonic and volcanic rocks, and for assessing volcanic hazards. Arc magma genesis is complex. Interpreting the underlying causes of major and trace element diversity in erupted magmas is challenging and often non-unique. To navigate this complexity mafic magma diversity is investigated using sample suites that span short temporal and spatial scales. These constraints allow us to evaluate models of arc magma genesis and their geochemical implications based on physical arguments and recent model results. Young volcanic deposits (≲18 kyr) are analysed from the Southern Volcanic Zone (SVZ), Chile, in particular suites of scoria cones on the flanks of arc stratovolcanoes that have erupted relatively primitive magmas of diverse compositions. Our study is centred on the high-resolution post-glacial tephrochronological record for Mocho-Choshuenco volcano where tight age constraints and a high density of scoria cones provide a spatially well-resolved mafic magma dataset. Two compositional trends emerge from the data. Firstly, magmas from cones on the flanks of the main edifice become more mafic with distance from the central vent. This is attributed to fractional crystallisation processes within the crust, with distal cones sampling less differentiated magmas. Secondly, there is a set of cones with distinct major and trace element compositions that are more primitive but enriched in incompatible elements relative to the central system and other ‘normal SVZ’ magmas. This distinct signature – termed the ‘Kangechi’ signature – is observed at three further clusters of cones within the SVZ. This is attributed to greater preservation of the enriched melt signature arising from reactive melt transport within the mantle wedge. Our model has important implications for arc magma genesis in general, and in particular for the spatial and temporal scales over which compositional variations are preserved in erupted magmas.
66-77
Rawson, Harriet
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Keller, Tobias
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Fontijn, Karen
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Pyle, David M.
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Mather, Tamsin A.
fb84c181-8e26-47ac-9f7e-a4bd2d72bc8b
Smith, Victoria C.
38da622d-ce8d-4182-ba0a-26a2a8f6b80c
Naranjo, José A.
949541f2-6b5b-4197-94f3-f464a040e26a
31 October 2016
Rawson, Harriet
56e4aedd-1bfc-46be-8924-bd9a579cd0dd
Keller, Tobias
d8dfcfa5-89d1-4203-aa2d-8c142c00a169
Fontijn, Karen
61ba0400-a2b5-4363-be9d-633d55a23acb
Pyle, David M.
ce901611-520f-4b83-8da1-3de165cd8a7a
Mather, Tamsin A.
fb84c181-8e26-47ac-9f7e-a4bd2d72bc8b
Smith, Victoria C.
38da622d-ce8d-4182-ba0a-26a2a8f6b80c
Naranjo, José A.
949541f2-6b5b-4197-94f3-f464a040e26a
Rawson, Harriet, Keller, Tobias, Fontijn, Karen, Pyle, David M., Mather, Tamsin A., Smith, Victoria C. and Naranjo, José A.
(2016)
Compositional variability in mafic arc magmas over short spatial and temporal scales: evidence for the signature of mantle reactive melt channels.
Earth and Planetary Science Letters, 456, .
(doi:10.1016/j.epsl.2016.09.056).
Abstract
Understanding arc magma genesis is critical to deciphering the construction of continental crust, understanding the relationship between plutonic and volcanic rocks, and for assessing volcanic hazards. Arc magma genesis is complex. Interpreting the underlying causes of major and trace element diversity in erupted magmas is challenging and often non-unique. To navigate this complexity mafic magma diversity is investigated using sample suites that span short temporal and spatial scales. These constraints allow us to evaluate models of arc magma genesis and their geochemical implications based on physical arguments and recent model results. Young volcanic deposits (≲18 kyr) are analysed from the Southern Volcanic Zone (SVZ), Chile, in particular suites of scoria cones on the flanks of arc stratovolcanoes that have erupted relatively primitive magmas of diverse compositions. Our study is centred on the high-resolution post-glacial tephrochronological record for Mocho-Choshuenco volcano where tight age constraints and a high density of scoria cones provide a spatially well-resolved mafic magma dataset. Two compositional trends emerge from the data. Firstly, magmas from cones on the flanks of the main edifice become more mafic with distance from the central vent. This is attributed to fractional crystallisation processes within the crust, with distal cones sampling less differentiated magmas. Secondly, there is a set of cones with distinct major and trace element compositions that are more primitive but enriched in incompatible elements relative to the central system and other ‘normal SVZ’ magmas. This distinct signature – termed the ‘Kangechi’ signature – is observed at three further clusters of cones within the SVZ. This is attributed to greater preservation of the enriched melt signature arising from reactive melt transport within the mantle wedge. Our model has important implications for arc magma genesis in general, and in particular for the spatial and temporal scales over which compositional variations are preserved in erupted magmas.
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Accepted/In Press date: 30 September 2016
e-pub ahead of print date: 31 October 2016
Published date: 31 October 2016
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Local EPrints ID: 488353
URI: http://eprints.soton.ac.uk/id/eprint/488353
ISSN: 0012-821X
PURE UUID: d8526fad-f956-4255-9e76-f0059c3293e1
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Date deposited: 20 Mar 2024 18:12
Last modified: 21 Mar 2024 03:16
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Contributors
Author:
Harriet Rawson
Author:
Tobias Keller
Author:
Karen Fontijn
Author:
David M. Pyle
Author:
Tamsin A. Mather
Author:
Victoria C. Smith
Author:
José A. Naranjo
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