Crustal thermal state and origin of silicic magma in Iceland: The case of Torfajökull, Ljósufjöll and Snæfellsjökull volcanoes

E. Martin; O. Sigmarsson

doi:10.1007/s00410-006-0165-5

Crustal thermal state and origin of silicic magma in Iceland: The case of Torfajökull, Ljósufjöll and Snæfellsjökull volcanoes

E. Martin, O. Sigmarsson

Science Institute

University of Iceland

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

Abstract

Pleistocene and Holocene peralkaline rhyolites from Torfajökull (South Iceland Volcanic Zone) and Ljósufjöll central volcanoes and trachytes from Snæfellsjökull (Snæfellsnes Volcanic Zone) allow the assessment of the mechanism for silicic magma genesis as a function of geographical location and crustal geothermal gradient. The low δ¹⁸O (2.4‰) and low Sr concentration (12.2 ppm) measured in Torfajökull rhyolites are best explained by partial melting of hydrated metabasaltic crust followed by major fractionation of feldspar. In contrast, very high ⁸⁷Sr/⁸⁶Sr (0.70473) and low Ba (8.7 ppm) and Sr (1.2 ppm) concentrations measured in Ljósufjöll silicic lavas are best explained by fractional crystallisation and subsequent ⁸⁷Rb decay. Snæfellsjökull trachytes are also generated by fractional crystallisation, with less than 10% crustal assimilation, as inferred from their δ¹⁸O. The fact that silicic magmas within, or close to, the rift zone are principally generated by crustal melting whereas those from off-rift zones are better explained by fractional crystallisation clearly illustrates the controlling influence of the thermal state of the crust on silicic magma genesis in Iceland.

Original language	English
Pages (from-to)	593-605
Number of pages	13
Journal	Contributions to Mineralogy and Petrology
Volume	153
Issue number	5
DOIs	https://doi.org/10.1007/s00410-006-0165-5
Publication status	Published - May 2007

Bibliographical note

Funding Information: Acknowledgement We greatly appreciate the guidance and help from Serge Fourcade at ‘‘Géosciences Rennes’’ during the O-isotope analysis, in addition to his pertinent remarks on an earlier version of this manuscript. Analytical assistance from Delphine Auclair, Chantal Bosq, Karine David and Mhammed Benbakkar is also gratefully acknowledged. Fruitful discussions on trace element modelling with Hervé Martin were very useful. We could not have had better company than Gudrun Larsen and Bergrun A. Oladottir during the fieldwork at Hrafntinnusker. Efficient English corrections by Fran Van Wyk de Vries were much appreciated. Constructive comments from two anonymous reviewers improved the manuscript. Finally, a grant from the Icelandic Science Foundation and the French-Icelandic Jules Verne collaboration program is acknowledged.

Other keywords

Assimilation
Fractional crystallisation
Geothermal gradient
Iceland
Partial melting
Silicic magma

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10.1007/s00410-006-0165-5

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@article{cc7f8b4ada574254a57d6ea781b6ff2c,

title = "Crustal thermal state and origin of silicic magma in Iceland: The case of Torfaj{\"o}kull, Lj{\'o}sufj{\"o}ll and Sn{\ae}fellsj{\"o}kull volcanoes",

abstract = "Pleistocene and Holocene peralkaline rhyolites from Torfaj{\"o}kull (South Iceland Volcanic Zone) and Lj{\'o}sufj{\"o}ll central volcanoes and trachytes from Sn{\ae}fellsj{\"o}kull (Sn{\ae}fellsnes Volcanic Zone) allow the assessment of the mechanism for silicic magma genesis as a function of geographical location and crustal geothermal gradient. The low δ18O (2.4‰) and low Sr concentration (12.2 ppm) measured in Torfaj{\"o}kull rhyolites are best explained by partial melting of hydrated metabasaltic crust followed by major fractionation of feldspar. In contrast, very high 87Sr/86Sr (0.70473) and low Ba (8.7 ppm) and Sr (1.2 ppm) concentrations measured in Lj{\'o}sufj{\"o}ll silicic lavas are best explained by fractional crystallisation and subsequent 87Rb decay. Sn{\ae}fellsj{\"o}kull trachytes are also generated by fractional crystallisation, with less than 10\% crustal assimilation, as inferred from their δ18O. The fact that silicic magmas within, or close to, the rift zone are principally generated by crustal melting whereas those from off-rift zones are better explained by fractional crystallisation clearly illustrates the controlling influence of the thermal state of the crust on silicic magma genesis in Iceland.",

keywords = "Assimilation, Fractional crystallisation, Geothermal gradient, Iceland, Partial melting, Silicic magma",

author = "E. Martin and O. Sigmarsson",

note = "Funding Information: Acknowledgement We greatly appreciate the guidance and help from Serge Fourcade at {\textquoteleft}{\textquoteleft}G{\'e}osciences Rennes{\textquoteright}{\textquoteright} during the O-isotope analysis, in addition to his pertinent remarks on an earlier version of this manuscript. Analytical assistance from Delphine Auclair, Chantal Bosq, Karine David and Mhammed Benbakkar is also gratefully acknowledged. Fruitful discussions on trace element modelling with Herv{\'e} Martin were very useful. We could not have had better company than Gudrun Larsen and Bergrun A. Oladottir during the fieldwork at Hrafntinnusker. Efficient English corrections by Fran Van Wyk de Vries were much appreciated. Constructive comments from two anonymous reviewers improved the manuscript. Finally, a grant from the Icelandic Science Foundation and the French-Icelandic Jules Verne collaboration program is acknowledged.",

year = "2007",

month = may,

doi = "10.1007/s00410-006-0165-5",

language = "English",

volume = "153",

pages = "593--605",

journal = "Contributions to Mineralogy and Petrology",

issn = "0010-7999",

publisher = "Springer Verlag",

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TY - JOUR

T1 - Crustal thermal state and origin of silicic magma in Iceland

T2 - The case of Torfajökull, Ljósufjöll and Snæfellsjökull volcanoes

AU - Martin, E.

AU - Sigmarsson, O.

N1 - Funding Information: Acknowledgement We greatly appreciate the guidance and help from Serge Fourcade at ‘‘Géosciences Rennes’’ during the O-isotope analysis, in addition to his pertinent remarks on an earlier version of this manuscript. Analytical assistance from Delphine Auclair, Chantal Bosq, Karine David and Mhammed Benbakkar is also gratefully acknowledged. Fruitful discussions on trace element modelling with Hervé Martin were very useful. We could not have had better company than Gudrun Larsen and Bergrun A. Oladottir during the fieldwork at Hrafntinnusker. Efficient English corrections by Fran Van Wyk de Vries were much appreciated. Constructive comments from two anonymous reviewers improved the manuscript. Finally, a grant from the Icelandic Science Foundation and the French-Icelandic Jules Verne collaboration program is acknowledged.

PY - 2007/5

Y1 - 2007/5

N2 - Pleistocene and Holocene peralkaline rhyolites from Torfajökull (South Iceland Volcanic Zone) and Ljósufjöll central volcanoes and trachytes from Snæfellsjökull (Snæfellsnes Volcanic Zone) allow the assessment of the mechanism for silicic magma genesis as a function of geographical location and crustal geothermal gradient. The low δ18O (2.4‰) and low Sr concentration (12.2 ppm) measured in Torfajökull rhyolites are best explained by partial melting of hydrated metabasaltic crust followed by major fractionation of feldspar. In contrast, very high 87Sr/86Sr (0.70473) and low Ba (8.7 ppm) and Sr (1.2 ppm) concentrations measured in Ljósufjöll silicic lavas are best explained by fractional crystallisation and subsequent 87Rb decay. Snæfellsjökull trachytes are also generated by fractional crystallisation, with less than 10% crustal assimilation, as inferred from their δ18O. The fact that silicic magmas within, or close to, the rift zone are principally generated by crustal melting whereas those from off-rift zones are better explained by fractional crystallisation clearly illustrates the controlling influence of the thermal state of the crust on silicic magma genesis in Iceland.

AB - Pleistocene and Holocene peralkaline rhyolites from Torfajökull (South Iceland Volcanic Zone) and Ljósufjöll central volcanoes and trachytes from Snæfellsjökull (Snæfellsnes Volcanic Zone) allow the assessment of the mechanism for silicic magma genesis as a function of geographical location and crustal geothermal gradient. The low δ18O (2.4‰) and low Sr concentration (12.2 ppm) measured in Torfajökull rhyolites are best explained by partial melting of hydrated metabasaltic crust followed by major fractionation of feldspar. In contrast, very high 87Sr/86Sr (0.70473) and low Ba (8.7 ppm) and Sr (1.2 ppm) concentrations measured in Ljósufjöll silicic lavas are best explained by fractional crystallisation and subsequent 87Rb decay. Snæfellsjökull trachytes are also generated by fractional crystallisation, with less than 10% crustal assimilation, as inferred from their δ18O. The fact that silicic magmas within, or close to, the rift zone are principally generated by crustal melting whereas those from off-rift zones are better explained by fractional crystallisation clearly illustrates the controlling influence of the thermal state of the crust on silicic magma genesis in Iceland.

KW - Assimilation

KW - Fractional crystallisation

KW - Geothermal gradient

KW - Iceland

KW - Partial melting

KW - Silicic magma

UR - https://www.scopus.com/pages/publications/33947717574

U2 - 10.1007/s00410-006-0165-5

DO - 10.1007/s00410-006-0165-5

M3 - Article

SN - 0010-7999

VL - 153

SP - 593

EP - 605

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

IS - 5

ER -

Crustal thermal state and origin of silicic magma in Iceland: The case of Torfajökull, Ljósufjöll and Snæfellsjökull volcanoes

Abstract

Bibliographical note

Other keywords

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