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Exceptionally high whole-rock δ18O values in intra-caldera rhyolites from Northeast Iceland

Published online by Cambridge University Press:  29 May 2018

Sylvia E. Berg ,
Valentin R. Troll ,
Chris Harris ,
Frances M. Deegan ,
Morten S. Riishuus ,
Steffi Burchardt  and
Michael Krumbholz
Sylvia E. Berg*
Affiliation:
Department of Earth Sciences, Section for Mineralogy, Petrology and Tectonics, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Sturlugata 7, Askja, 101 Reykjavik, Iceland
Valentin R. Troll
Affiliation:
Department of Earth Sciences, Section for Mineralogy, Petrology and Tectonics, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
Chris Harris
Affiliation:
Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa
Frances M. Deegan
Affiliation:
Department of Earth Sciences, Section for Mineralogy, Petrology and Tectonics, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
Morten S. Riishuus
Affiliation:
Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Sturlugata 7, Askja, 101 Reykjavik, Iceland
Steffi Burchardt
Affiliation:
Department of Earth Sciences, Section for Mineralogy, Petrology and Tectonics, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
Michael Krumbholz
Affiliation:
Department of Earth Sciences, Section for Mineralogy, Petrology and Tectonics, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
*
*E-mail: e.sylviaberg@gmail.com
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Abstract

The Icelandic crust is characterized by low δ18O values that originate from pervasive high-temperature hydrothermal alteration by 18O-depleted meteoric waters. Igneous rocks in Iceland with δ18O values significantly higher than unaltered oceanic crust (~5.7‰) are therefore rare. Here we report on rhyolitic intra-caldera samples from a cluster of Neogene central volcanoes in Borgarfjörður Eystri, Northeast Iceland, that show whole-rock δ18O values between +2.9 and +17.6‰ (n = 6), placing them among the highest δ18O values thus far recorded for Iceland. Extra-caldera rhyolite samples from the region, in turn, show δ18O whole-rock values between +3.7 and +7.8‰ (n = 6), consistent with the range of previously reported Icelandic rhyolites. Feldspar in the intra-caldera samples (n = 4) show δ18O values between +4.9 and +18.7‰, whereas pyroxene (n = 4) shows overall low δ18O values of +4.0 to +4.2‰, consistent with regional rhyolite values. In combination with the evidence from mineralogy and rock H2O contents, the high whole-rock δ18O values of the intra-caldera rhyolites appear to be the result of pervasive isotopic exchange during subsolidus hydrothermal alteration with 18O-enriched water. This alteration conceivably occurred in a near-surface hot spring environment at the distal end of an intra-caldera hydrothermal system, and was probably fed by waters that had already undergone significant isotope exchange with the country rock. Alternatively, 18O-enriched alteration fluids may have been produced during evaporation and boiling of standing water in former caldera lakes, which then interacted with the intra-caldera rock suites. Irrespective of the exact exchange processes involved, a previously unrecognized and highly localized δ18O-enriched rock composition exists on Iceland and thus probably within the Icelandic crust too.

Keywords

Northeast Icelandhigh 18O valueshydrothermal alterationintra-caldera lakes
Type
Article
Information
Mineralogical Magazine , Volume 82 , Issue 5 , October 2018 , pp. 1147 - 1168
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2018 

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Footnotes

Associate Editor: Jason Harvey

References

Árnason, B. (1976) Groundwater Systems in Iceland traced by Deuterium. Societas Scientiarum Islandica, Reykjavik.Google Scholar
Arnórsson, S. (1995) Geothermal systems in Iceland: structure and conceptual models – I. High-temperature areas. Geothermics, 24, 561–602.Google Scholar
Berg, S.E. (2016) Silicic magma genesis in basalt-dominated oceanic settings: examples from Iceland and the Canary Islands. Doctoral dissertation, Acta Universitatis Upsaliensis.Google Scholar
Berg, S.E., Troll, V.R., Burchardt, S., Riishuus, M.S., Krumbholz, M. and Gústafsson, L.E. (2014) Iceland's best kept secret. Geology Today, 30, 54–60.Google Scholar
Bindeman, I. (2008) Oxygen isotopes in mantle and crustal magmas as revealed by single crystal analysis. Reviews in Mineralogy and Geochemistry, 69, 445–478.Google Scholar
Bindeman, I.N., Gurenko, A., Carley, T., Miller, C., Martin, E. and Sigmarsson, O. (2012) Silicic magma petrogenesis in Iceland by remelting of hydrothermally altered crust based on oxygen isotope diversity and disequilibria between zircon and magma with implications for MORB. Terra Nova, 24, 227–232.Google Scholar
Björnsson, A. (1985) Dynamics of crustal rifting in NE Iceland. Journal of Geophysical Research, 90, 10151–10162.Google Scholar
Borthwick, J. and Harmon, R.S. (1982) A note regarding CIF3 as an alternative to BrF5 for oxygen isotope analysis. Geochimica et Cosmochimica Acta, 46, 1665–1668.Google Scholar
Budd, D.A., Troll, V.R., Deegan, F.M., Jolis, E.M., Smith, V.C., Whitehouse, M.J., Harris, C., Freda, C., Hilton, D.R., Halldórsson, S.A. and Bindeman, I.N. (2017) Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz. Scientific Reports, 7, 40624.Google Scholar
Burchardt, S., Tanner, D.C., Troll, V.R., Krumbholz, M. and Gústafsson, L.E. (2011) Three-dimensional geometry of concentric intrusive sheet swarms in the Geitafell and the Dyrfjöll Volcanoes, Eastern Iceland. Geochemistry, Geophysics, Geosystems, 12, Q0AB09.Google Scholar
Carley, T.L., Miller, C.F., Wooden, J.L., Padilla, A.J., Schmitt, A.K., Economos, R.C., Bindeman, I.N. and Jordan, B.T. (2014) Iceland is not a magmatic analog for the Hadean: Evidence from the zircon record. Earth and Planetary Science Letters, 405, 85–97.Google Scholar
Carley, T.L., Miller, C.F., Sigmarsson, O., Coble, M.A., Fisher, C.M., Hanchar, J.M., Schmitt, A.K. and Economos, R.C. (2017) Detrital zircon resolve longevity and evolution of silicic magmatism in extinct volcanic centres: A case study from the East Fjords of Iceland. Geosphere, 13, https://doi.org/10.1130/GES01467.1Google Scholar
Chiba, H., Chacko, T., Clayton, R.N. and Goldsmith, J.R. (1989) Oxygen isotope fractionations involving diopside, forsterite, magnetite, and calcite: Application to geothermometry. Geochimica et Cosmochimica Acta, 53, 2985–2995.Google Scholar
Condomines, M., Grönvold, K., Hooker, P.J., Muehlenbachs, K., O'Nions, R.K., Óskarsson, N. and Oxburgh, E.R. (1983) Helium, oxygen, strontium and neodymium isotopic relationships in Icelandic volcanics. Earth and Planetary Science Letters, 66, 125–136.Google Scholar
Cousens, B.L., Spera, F.J. and Dobson, P.F. (1993) Post-eruptive alteration of silicic ignimbrites and lavas, Gran Canaria, Canary Islands: Strontium, neodymium, lead, and oxygen isotopic evidence. Geochimica et Cosmochimica Acta, 57, 631–640.Google Scholar
Craig, H., Gordon, L.I. and Horibe, Y. (1963) Isotopic exchange effects in the evaporation of water: 1. Low-temperature experimental results. Journal of Geophysical Research, 68, 5079–5087.Google Scholar
Deegan, F.M., Troll, V.R., Barker, A.K., Harris, C., Chadwick, J.P., Carracedo, J.C. and Delcamp, A. (2012) Crustal versus source processes recorded in dykes from the Northeast volcanic rift zone of Tenerife, Canary Islands. Chemical Geology, 34, 324–344.Google Scholar
Donoghue, E., Troll, V.R., Harris, C., O'Halloran, A., Walter, T.R. and Pérez Torrado, F.J. (2008) Low-temperature hydrothermal alteration of intra-caldera tuffs, Miocene Tejeda caldera, Gran Canaria, Canary Islands. Journal of Volcanology and Geothermal Research, 176, 551–564.Google Scholar
Donoghue, E., Troll, V.R. and Harris, C. (2010) Fluid–rock interaction in the Miocene, Post-Caldera, Tejeda intrusive complex, Gran Canaria (Canary Islands): insights from mineralogy, and O-and H-isotope geochemistry. Journal of Petrology, 51, 2149–2176.Google Scholar
Duffield, W.A. and Ruiz, J. (1998) A model that helps explain Sr-isotope disequilibrium between feldspar phenocrysts and melt in large-volume silicic magma systems Journal of Volcanology and Geothermal Research, 87, 7–13.Google Scholar
Eiler, J.M. (2001) Oxygen isotope variations of basaltic lavas and upper mantle rocks. Pp. 319–364 in: Stable Isotope Geochemistry (Valley, J.W. and Cole, D., editors). Reviews in Mineralogy & Geochemistry, 43. Mineralogical Society of America and the Geochemical Society, Washington, DC.Google Scholar
Fagereng, Å., Harris, C., La Grange, M. and Stevens, G. (2008) Stable isotope study of the Archaean rocks of the Vredefort impact structure, central Kaapvaal Craton, South Africa. Contributions to Mineralogy and Petrology, 155, 63–78.Google Scholar
Faure, G. (1986) Principles of Isotope Geology. New York, Wiley, 589 pp.Google Scholar
Feng, X., Faiia, A.M., WoldeGabriel, G., Aronson, J.L., Poage, M.A. and Chamberlain, C.P. (1999) Oxygen isotope studies of illite/smectite and clinoptilolite from Yucca Mountain: implications for paleohydrologic conditions. Earth and Planetary Science Letters, 171, 95–106.Google Scholar
Franzson, H., Thordarson, S., Björnsson, G., Gudlaugsson, S.T., Richter, B., Fridleifsson, G.O. and Thorhallsson, S. (2002) Reykjanes high-temperature field, SW-Iceland. Geology and hydrothermal alteration of well RN-10. Twenty-Seventh Workshop on Geothermal Reservoir Engineering. Stanford University, California, USA, 28–30.Google Scholar
Gautason, B. and Muehlenbachs, K. (1998) Oxygen isotope fluxes associated with high-temperature processes in the rift zones of Iceland. Chemical Geology, 145, 275–286.Google Scholar
Geiger, H., Mattsson, T., Deegan, F.M., Troll, V.R., Burchardt, S., Gudmundsson, O., Tryggvason, A., Krumbholz, M. and Harris, C. (2016) Magma plumbing for the 2014–2015 Holuhraun eruption, Iceland. Geochemistry, Geophysics, Geosystems, 17, 2953–2968.Google Scholar
Giggenbach, W.F. and Stewart, M.K. (1982) Processes controlling the isotopic composition of steam and water discharges from steam vents and steam-heated pools in geothermal areas. Geothermics, 11, 71–80.Google Scholar
Gislason, S.R. and Eugster, H.P. (1987) Meteoric water-basalt interactions. I: A laboratory study. Geochimica et Cosmochimica Acta, 51, 2827–2840.Google Scholar
Götze, J., Tichomirowa, M., Fuchs, H., Pilot, J. and Sharp, Z.D. (2001) Geochemistry of agates: a trace element and stable isotope study. Chemical Geology, 175, 523–541.Google Scholar
Gregory, R.T., Criss, R.E. and Taylor, H.P. (1989) Oxygen isotope exchange kinetics of mineral pairs in closed and open systems: applications to problems of hydrothermal alteration of igneous rocks and Precambrian iron formations. Chemical Geology, 75, 1–42.Google Scholar
Gunnarsson, B., Marsh, B.D. and Taylor, H.P. (1998) Generation of Icelandic rhyolites: silicic lavas from the Torfajökull central volcano. Journal of Volcanology and Geothermal Research, 83, 1–45.Google Scholar
Gurenko, A.A., Bindeman, I.N. and Sigurdsson, I.A. (2015) To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths. Contributions to Mineralogy and Petrology, 169, 1–21.Google Scholar
Gústafsson, L.E. (1992) Geology and Petrology of the Dyrfjöll Central Volcano, Eastern Iceland. PhD dissertation, Freie Universität Berlin.Google Scholar
Gústafsson, L.E., Lapp, B., Thomas, L. and Lapp, M. (1989) Tertiary silicic rocks in the area of the Kækjuskörð rhyolitic volcano, eastern Iceland. Jökull, 39, 75–89.Google Scholar
Hards, V.L., Kempton, P.D., Thompson, R.N. and Greenwood, P.B. (2000) The magmatic evolution of the Snæfell volcanic centre; an example of volcanism during incipient rifting in Iceland. Journal of Volcanology and Geothermal Research, 99, 97–121.Google Scholar
Harris, C. and Ashwal, L.D. (2002) The origin of low δ18O granites and related rocks from the Seychelles. Contributions to Mineralogy and Petrology, 143, 366–376.Google Scholar
Harris, C. and Vogeli, J. (2010) Oxygen isotope composition of garnet in the Peninsula Granite, Cape Granite Suite, South Africa: constraints on melting and emplacement mechanisms. South African Journal of Geology, 113, 401–412.Google Scholar
Harris, C., Pronost, J.J., Ashwal, L.D. and Cawthorn, R.G. (2005) Oxygen and hydrogen isotope stratigraphy of the Rustenburg Layered Suite, Bushveld Complex: constraints on crustal contamination. Journal of Petrology, 46, 579–601.Google Scholar
Hattori, K. and Muehlenbachs, K. (1982) Oxygen isotope ratios of the Icelandic crust. Journal of Geophysical Research, 87, 6559–6565.Google Scholar
Hemond, C., Arndt, N.T., Lichtenstein, U., Hofmann, A.W., Óskarsson, N. and Steinthorsson, S. (1993) The heterogeneous Iceland plume: Nd-Sr-O isotopes and trace element constraints. Journal of Geophysical Research, 98, 15833–15850.Google Scholar
Hoefs, J. (1973) Stable Isotope Geochemistry. Springer Verlag, Berlin, 140 pp.Google Scholar
Jørgensen, K.A. (1980) The Thorsmörk ignimbrite: an unusual comenditic pyroclastic flow in southern Iceland. Journal of Volcanology and Geothermal Research, 8, 7–22.Google Scholar
Kristmannsdóttir, H. (1982) Alteration in the IRDP drill hole compared with other drill holes in Iceland. Journal of Geophysical Research, 87, 6525–6531, https://doi.org/10.1029/JB087iB08p06525Google Scholar
Lacasse, C., Sigurdsson, H., Carey, S.N., Jóhannesson, H., Thomas, L.E. and Rogers, N.W. (2007) Bimodal volcanism at the Katla subglacial caldera, Iceland: insight into the geochemistry and petrogenesis of rhyolitic magmas. Bulletin of Volcanology, 69, 373–399.Google Scholar
Lackey, J.S., Valley, J.W., Chen, J.H. and Stockli, D.F. (2008) Dynamic magma systems, crustal recycling, and alteration in the Central Sierra Nevada Batholith: the oxygen isotope record. Journal of Petrology, 49, 1397–1426.Google Scholar
Le Maitre, R.W., Bateman, O., Dudek, A., Keller, J., Lameyre Le Bas, M.J., Sabine, P.A., Schmid, R., Sorensen, H., Streckeisen, A., Woolley, A.R. and Zanettin, B. (1989) A Classification of Igneous Rocks and Glossary of Terms. Blackwell, Oxford.Google Scholar
Lipman, P.W. (1984) The roots of ash-flow calderas in western North America: Windows into the tops of granitic batholiths. Journal of Geophysical Research, 89, 8801–8841.Google Scholar
Lofgren, G. (1971 a) Spherulitic textures in glassy and crystalline rocks. Journal of Geophysical Research, 76, 5635–5648.Google Scholar
Lofgren, G. (1971 b) Experimentally produced devitrification textures in natural rhyolitic glass. Geological Society of America Bulletin, 82, 111–124.Google Scholar
MacDonald, R., Sparks, R.S.J., Sigurdsson, H., Mattey, D.P., McGarvie, D.W. and Smith, R.L. (1987) The 1875 eruption of Askja volcano, Iceland: combined fractional crystallisation and selective contamination in the generation of rhyolitic magma. Mineralogical Magazine, 51, 183–202.Google Scholar
Macpherson, C.G., Hilton, D.R., Day, J.M., Lowry, D. and Grönvold, K. (2005) High-3He/4He, depleted mantle and low-δ18O, recycled oceanic lithosphere in the source of central Iceland magmatism. Earth and Planetary Science Letters, 233, 411–427.Google Scholar
Martin, E., Paquette, J.L., Bosse, V., Ruffet, G., Tiepolo, M. and Sigmarsson, O. (2011) Geodynamics of rift–plume interaction in Iceland as constrained by new 40Ar/39Ar and in situ U–Pb zircon ages. Earth and Planetary Science Letters, 311, 28–38.Google Scholar
Matsuhisa, Y., Goldsmith, J.R. and Clayton, R.N. (1979) Oxygen isotopic fractionation in the system quartz-albite-anorthite-water. Geochimica et Cosmochimica Acta, 43, 1131–1140.Google Scholar
Muehlenbachs, K., Anderson, A.T. and Sigvaldason, G.E. (1974) Low- δ18O basalts from Iceland. Geochimica et Cosmochimica Acta, 38, 577–588.Google Scholar
Ólafsson, J. and Riley, J.P. (1978) Geochemical studies on the thermal brine from Reykjanes (Iceland) Chemical Geology, 21, 219–237.Google Scholar
O'Neil, J.R., Shaw, S.E. and Flood, R.H. (1977) Oxygen and hydrogen isotope compositions as indicators of granite genesis in the New England Batholith, Australia. Contributions to Mineralogy and Petrology, 62, 313–328.Google Scholar
O'Nions, R.K. and Grönvold, K. (1973) Petrogenetic relationships of acid and basic rocks in Iceland: Sr-isotopes and rare-earth elements in late and postglacial volcanics. Earth and Planetary Science Letters, 19, 397–409.Google Scholar
Óskarsson, B.V. and Riishuus, M.S. (2013) The mode of emplacement of Neogene flood basalts in Eastern Iceland: Facies architecture and structure of the Hólmar and Grjótá olivine basalt groups. Journal of Volcanology and Geothermal Research, 267, 92–118.Google Scholar
Óskarsson, N., Sigvaldason, G. E. and Steinthórsson, S. (1982) A dynamic model of rift zone petrogenesis and the regional petrology of Iceland. Journal of Petrology, 23, 28–74.Google Scholar
Óskarsson, N., Steinthórsson, S. and Sigvaldason, G.E. (1985) Iceland geochemical anomaly: origin, volcanotectonics, chemical fractionation and isotope evolution of the crust. Journal of Geophysical Research, 90, 10011–10025.Google Scholar
Óskarsson, B.V., Riishuus, M.S. and Arnalds, Ó. (2012) Climate-dependent chemical weathering of volcanic soils in Iceland. Geoderma, 189, 635–651.Google Scholar
Owen, J., Tuffen, H. and McGarvie, D.W. (2013) Explosive subglacial rhyolitic eruptions in Iceland are fuelled by high magmatic H2O and closed-system degassing. Geology, 41, 251–254.Google Scholar
Prestvik, T., Goldberg, S., Karlsson, H. and Grönvold, K. (2001) Anomalous strontium and lead isotope signatures in the off-rift Öræfajökull central volcano in south-east Iceland: Evidence for enriched endmember (s) of the Iceland mantle plume? Earth and Planetary Science Letters, 190, 211–220.Google Scholar
Rhodes, A.L. and Oreskes, N. (1999) Oxygen isotope composition of magnetite deposits at El Laco, Chile: Evidence of formation from isotopically heavy fluids. Society of Economic Geology Special Publication, 7, 333–351.Google Scholar
Ross, C.S. and Smith, R.L. (1961) Ash-flow tuffs: Their origin, geologic relations, and identification. United States Geological Survey Professional Paper 366. U.S. Geological Survey, Reston, Virginia, USA.Google Scholar
Rozanski, K., Araguás-Araguás, L. and Gonfiantini, R. (1993) Isotopic patterns in modern global precipitation. Pp. 1–37 in: Climate change in continental isotopic records (Swart, P.K., Lohmann, K.C., McKenzie, J. and Savin, S., editors). Geophysical Monograph Series 78. American Geophysical Union, USA.Google Scholar
Savin, S.M. and Epstein, S. (1970) The oyxgen and hydrogen isotope geochemistry of ocean sediments and shales. Geochimica et Cosmochimica Acta, 34, 43–63.Google Scholar
Schattel, N., Portnyagin, M., Golowin, R., Hoernle, K. and Bindeman, I. (2014) Contrasting conditions of rift and off-rift silicic magma origin on Iceland. Geophysical Research Letters, 41, 5813–5820.Google Scholar
Seligman, A.N., Bindeman, I.N., Watkins, J.M. and Ross, A.M. (2016) Water in volcanic glass: from volcanic degassing to secondary hydration. Geochimica et Cosmochimica Acta, 191, 216–238.Google Scholar
Sharp, Z. (2007) Principles of Stable Isotope Geochemistry. Pearson Education, Upper Saddle River, NJ, USA, pp. 344.Google Scholar
Sheppard, S.M. (1986) Characterization and isotopic variations in natural waters. Pp. 165–184 in: Stable Isotopes in High Temperature Geological Processes (Valley, J.W., Taylor, H.P. Jr. and O'Neil, J.R., editors). Reviews in Mineralogy and Geochemistry, 16. Mineralogical Society of America, Washington, DC.Google Scholar
Sigmarsson, O., Condomines, M. and Fourcade, S. (1992) Mantle and crustal contribution in the genesis of recent basalts from off-rift zones in Iceland: constraints from Th, Sr and O isotopes. Earth and Planetary Science Letters, 110, 149–162.Google Scholar
Sigmundsson, F. (2006) Iceland Geodynamics, Crustal Deformation and Divergent Plate Tectonics. Praxis Publishing/Springer-Verlag, Chichester, 209.Google Scholar
Sigurdsson, H. and Sparks, R.S.J. (1978) Rifting episode in north Iceland in 1874–1875 and the eruptions of Askja and Sveinagja. Bulletin of Volcanology, 41, 149–167.Google Scholar
Sveinbjörnsdóttir, Á.E. and Johnsen, S.J. (1992) Stable isotope study of the Thingvallavatn area. Groundwater origin, age and evaporation models. Oikos, 136–150.Google Scholar
Sveinbjörnsdóttír, Á.E., Ármannsson, H., Ólafsson, M., Óskarsson, F., Markússon, S. and Magnusdottir, S. (2013) The Theistareykir geothermal field, NE Iceland. Isotopic characteristics and origin of circulating fluids. Procedia Earth and Planetary Science, 7, 822–825.Google Scholar
Taylor, H.P. (1968) The oxygen isotope geochemistry of igneous rocks. Contributions to Mineralogy and Petrology, 19, 1–71.Google Scholar
Thordarson, T. and Larsen, G. (2007) Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history. Journal of Geodynamics, 43, 118–152.Google Scholar
Troll, V.R. and Schmincke, H.U. (2002) Magma mixing and crustal recycling recorded in ternary feldspar from compositionally zoned peralkaline ignimbrite ‘A’, Gran Canaria, Canary Islands. Journal of Petrology, 43, 243–270.Google Scholar
Troll, V.R., Walter, T.R. and Schmincke, H.U. (2002) Cyclic caldera collapse: Piston or piecemeal subsidence? Field and experimental evidence. Geology, 30, 135–138.Google Scholar
Valley, J.W., Lackey, J.S., Cavosie, A.J., Clechenko, C.C., Spicuzza, M.J., Basei, M.A.S., Bindeman, I.N., Ferreira, V.P., Sial, A.N., King, E.M., Peck, W.H., Sinha, A.K and Wei, C.S. (2005) 4.4 billion years of crustal maturation: oxygen isotope ratios of magmatic zircon. Contributions to Mineralogy and Petrology, 150, 561–580.Google Scholar
Vennemann, T.W. and Smith, H.S. (1990) The rate and temperature of reaction of CIF3 with silicate minerals, and their relevance to oxygen isotope analysis. Chemical Geology, 86, 83–88.Google Scholar
Walker, G.P.L. (1960) Zeolite zones and dike distribution in relation to the structure of the basalts of eastern Iceland. Journal of Geology, 68, 515–527.Google Scholar
Walker, G.P.L. (1975) A new concept of the evolution of the British Tertiary intrusive centres. Journal of the Geological Society of London, 131, 121–141.Google Scholar
Walker, G.P.L. and Carmichael, I.S.E. (1962) Garronite, a new zeolite from Ireland and Iceland. Mineralogical Magazine, 33, 173–186.Google Scholar
Walter, T.R. and Troll, V.R. (2001) Formation of caldera periphery faults: an experimental study. Bulletin of Volcanology, 63, 191–203.Google Scholar
Wood, D.A. (1978) Major and trace element variations in the Tertiary lavas of eastern Iceland and their significance with respect to the Iceland geochemical anomaly. Journal of Petrology, 19, 393–436.Google Scholar
Zierenberg, R.A., Schiffman, P., Barfod, G.H., Lesher, C.E., Marks, N.E., Lowenstern, J.B., Mortensen, A.K., Pope, E.C., Bird, D.K., Reed, J.B., Friðleifsson, G.Ó. and Elders, W.A. (2013) Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland. Contributions to Mineralogy and Petrology, 165, 327–347.Google Scholar