Oxygen isotope evidence for progressively assimilating trans-crustal magma plumbing systems in Iceland

A. Caracciolo; S. A. Halldórsson; E. Bali; E. W. Marshall; H. Jeon; M. J. Whitehouse; J. D. Barnes; G. H. Guðfinnsson; M. Kahl; M. E. Hartley

doi:10.1130/G49874.1

Oxygen isotope evidence for progressively assimilating trans-crustal magma plumbing systems in Iceland

A. Caracciolo, S. A. Halldórsson, E. Bali, E. W. Marshall, H. Jeon, M. J. Whitehouse, J. D. Barnes, G. H. Guðfinnsson, M. Kahl, M. E. Hartley

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

Abstract

The oxygen isotope composition of mantle-derived melts can place important constraints on how magmas are processed as they traverse the crust. Assimilation of crustal material is a crucial aspect of basalt petrogenesis, as it affects the chemical and rheological characteristics of eruptive magmas at active volcanoes. We report oxygen isotope (δ18O) and trace element (TE) data from a suite of well-characterized basaltic melt inclusions and groundmass glasses from the Bárðarbunga volcanic system in Iceland to assess how and where in the plumbing system crustal rocks interact with ascending magmas. While both melt inclusions and groundmass glasses record a large range in δ¹⁸O values (+3.2‰ to +6.4‰ and +2.6‰ to +5.5‰, respectively) groundmass glasses record lower values on average. Relationships between incompatible trace element (e.g., Zr/Nb) and oxygen isotope ratios are best explained with three-component mixing, where primary melts derived from depleted and enriched mantle components with distinct δ¹⁸O values mix and acquire a low-δ¹⁸O character upon progressive contamination with altered Icelandic crust. The majority (60%) of melt inclusions require 10–30% exchange of oxygen with the Icelandic crust. In addition, for the first time, we link the extent of oxygen isotope exchange with melt equilibration depths, showing that most of the contamination occurs at 1–2 kbar (3–7 km depth). We propose that a progressively assimilating, multi-tiered plumbing system is a characteristic feature of the Bárðarbunga volcanic system, whereby chemical modifications resulting from interaction with the crust systematically increase as melts migrate through higher crustal levels. We show that similar processes may also occur across the active rift zone in Iceland.

Original language	English
Pages (from-to)	796-800
Number of pages	5
Journal	Geology
Volume	50
Issue number	7
DOIs	https://doi.org/10.1130/G49874.1
Publication status	Published - 11 Apr 2022

Bibliographical note

Funding Information:
A. Caracciolo was supported by the University of Iceland Research Fund (HI17060092) and by the Nordic Volcanological Center. S.A. Halldórsson and E.W. Marshall acknowledge support from the Icelandic Research Fund (grants 196139–051 and #195638–051). The involvement of S.A. Halldórs-son was partly in relation to Horizon 2020 project EUROVOLC, which is funded by the European Commission (grant 731070). M. Kahl acknowledges funding by the German Research Foundation (grant KA 3532/2-1) The NordSIMS ion microprobe facility acknowledges support by the Swedish Research Council (grant 2017-00671), the Swedish Museum of Natural History, and the University of Iceland; this is NordSIMS publication 705. We thank K. Lindén for laboratory assistance in Stockholm, R. Sohn for help with mathematical equations, and J. Cullen for laser fluorination analyses. We also thank U. Schaltegger for editorial handing and J. Troch and an anonymous reviewer for helpful reviews.

Publisher Copyright:
© 2022. The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license

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10.1130/G49874.1

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title = "Oxygen isotope evidence for progressively assimilating trans-crustal magma plumbing systems in Iceland",

abstract = "The oxygen isotope composition of mantle-derived melts can place important constraints on how magmas are processed as they traverse the crust. Assimilation of crustal material is a crucial aspect of basalt petrogenesis, as it affects the chemical and rheological characteristics of eruptive magmas at active volcanoes. We report oxygen isotope (δ18O) and trace element (TE) data from a suite of well-characterized basaltic melt inclusions and groundmass glasses from the B{\'a}r{\dh}arbunga volcanic system in Iceland to assess how and where in the plumbing system crustal rocks interact with ascending magmas. While both melt inclusions and groundmass glasses record a large range in δ18O values (+3.2‰ to +6.4‰ and +2.6‰ to +5.5‰, respectively) groundmass glasses record lower values on average. Relationships between incompatible trace element (e.g., Zr/Nb) and oxygen isotope ratios are best explained with three-component mixing, where primary melts derived from depleted and enriched mantle components with distinct δ18O values mix and acquire a low-δ18O character upon progressive contamination with altered Icelandic crust. The majority (60%) of melt inclusions require 10–30% exchange of oxygen with the Icelandic crust. In addition, for the first time, we link the extent of oxygen isotope exchange with melt equilibration depths, showing that most of the contamination occurs at 1–2 kbar (3–7 km depth). We propose that a progressively assimilating, multi-tiered plumbing system is a characteristic feature of the B{\'a}r{\dh}arbunga volcanic system, whereby chemical modifications resulting from interaction with the crust systematically increase as melts migrate through higher crustal levels. We show that similar processes may also occur across the active rift zone in Iceland.",

author = "A. Caracciolo and Halld{\'o}rsson, {S. A.} and E. Bali and Marshall, {E. W.} and H. Jeon and Whitehouse, {M. J.} and Barnes, {J. D.} and Gu{\dh}finnsson, {G. H.} and M. Kahl and Hartley, {M. E.}",

note = "Funding Information: A. Caracciolo was supported by the University of Iceland Research Fund (HI17060092) and by the Nordic Volcanological Center. S.A. Halld{\'o}rsson and E.W. Marshall acknowledge support from the Icelandic Research Fund (grants 196139–051 and #195638–051). The involvement of S.A. Halld{\'o}rs-son was partly in relation to Horizon 2020 project EUROVOLC, which is funded by the European Commission (grant 731070). M. Kahl acknowledges funding by the German Research Foundation (grant KA 3532/2-1) The NordSIMS ion microprobe facility acknowledges support by the Swedish Research Council (grant 2017-00671), the Swedish Museum of Natural History, and the University of Iceland; this is NordSIMS publication 705. We thank K. Lind{\'e}n for laboratory assistance in Stockholm, R. Sohn for help with mathematical equations, and J. Cullen for laser fluorination analyses. We also thank U. Schaltegger for editorial handing and J. Troch and an anonymous reviewer for helpful reviews. Publisher Copyright: {\textcopyright} 2022. The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license",

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doi = "10.1130/G49874.1",

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AU - Caracciolo, A.

AU - Halldórsson, S. A.

AU - Bali, E.

AU - Marshall, E. W.

AU - Jeon, H.

AU - Whitehouse, M. J.

AU - Barnes, J. D.

AU - Guðfinnsson, G. H.

AU - Kahl, M.

AU - Hartley, M. E.

N1 - Funding Information: A. Caracciolo was supported by the University of Iceland Research Fund (HI17060092) and by the Nordic Volcanological Center. S.A. Halldórsson and E.W. Marshall acknowledge support from the Icelandic Research Fund (grants 196139–051 and #195638–051). The involvement of S.A. Halldórs-son was partly in relation to Horizon 2020 project EUROVOLC, which is funded by the European Commission (grant 731070). M. Kahl acknowledges funding by the German Research Foundation (grant KA 3532/2-1) The NordSIMS ion microprobe facility acknowledges support by the Swedish Research Council (grant 2017-00671), the Swedish Museum of Natural History, and the University of Iceland; this is NordSIMS publication 705. We thank K. Lindén for laboratory assistance in Stockholm, R. Sohn for help with mathematical equations, and J. Cullen for laser fluorination analyses. We also thank U. Schaltegger for editorial handing and J. Troch and an anonymous reviewer for helpful reviews. Publisher Copyright: © 2022. The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license

PY - 2022/4/11

Y1 - 2022/4/11

N2 - The oxygen isotope composition of mantle-derived melts can place important constraints on how magmas are processed as they traverse the crust. Assimilation of crustal material is a crucial aspect of basalt petrogenesis, as it affects the chemical and rheological characteristics of eruptive magmas at active volcanoes. We report oxygen isotope (δ18O) and trace element (TE) data from a suite of well-characterized basaltic melt inclusions and groundmass glasses from the Bárðarbunga volcanic system in Iceland to assess how and where in the plumbing system crustal rocks interact with ascending magmas. While both melt inclusions and groundmass glasses record a large range in δ18O values (+3.2‰ to +6.4‰ and +2.6‰ to +5.5‰, respectively) groundmass glasses record lower values on average. Relationships between incompatible trace element (e.g., Zr/Nb) and oxygen isotope ratios are best explained with three-component mixing, where primary melts derived from depleted and enriched mantle components with distinct δ18O values mix and acquire a low-δ18O character upon progressive contamination with altered Icelandic crust. The majority (60%) of melt inclusions require 10–30% exchange of oxygen with the Icelandic crust. In addition, for the first time, we link the extent of oxygen isotope exchange with melt equilibration depths, showing that most of the contamination occurs at 1–2 kbar (3–7 km depth). We propose that a progressively assimilating, multi-tiered plumbing system is a characteristic feature of the Bárðarbunga volcanic system, whereby chemical modifications resulting from interaction with the crust systematically increase as melts migrate through higher crustal levels. We show that similar processes may also occur across the active rift zone in Iceland.

AB - The oxygen isotope composition of mantle-derived melts can place important constraints on how magmas are processed as they traverse the crust. Assimilation of crustal material is a crucial aspect of basalt petrogenesis, as it affects the chemical and rheological characteristics of eruptive magmas at active volcanoes. We report oxygen isotope (δ18O) and trace element (TE) data from a suite of well-characterized basaltic melt inclusions and groundmass glasses from the Bárðarbunga volcanic system in Iceland to assess how and where in the plumbing system crustal rocks interact with ascending magmas. While both melt inclusions and groundmass glasses record a large range in δ18O values (+3.2‰ to +6.4‰ and +2.6‰ to +5.5‰, respectively) groundmass glasses record lower values on average. Relationships between incompatible trace element (e.g., Zr/Nb) and oxygen isotope ratios are best explained with three-component mixing, where primary melts derived from depleted and enriched mantle components with distinct δ18O values mix and acquire a low-δ18O character upon progressive contamination with altered Icelandic crust. The majority (60%) of melt inclusions require 10–30% exchange of oxygen with the Icelandic crust. In addition, for the first time, we link the extent of oxygen isotope exchange with melt equilibration depths, showing that most of the contamination occurs at 1–2 kbar (3–7 km depth). We propose that a progressively assimilating, multi-tiered plumbing system is a characteristic feature of the Bárðarbunga volcanic system, whereby chemical modifications resulting from interaction with the crust systematically increase as melts migrate through higher crustal levels. We show that similar processes may also occur across the active rift zone in Iceland.

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ER -

Oxygen isotope evidence for progressively assimilating trans-crustal magma plumbing systems in Iceland

Abstract

Bibliographical note

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