uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Berg, Sylvia
Alternative names
Publications (10 of 17) Show all publications
Berg, S., Troll, V. R., Harris, C., Deegan, F., Riishuus, M. S., Burchardt, S. & Krumbholz, M. (2018). Exceptionally high whole-rock delta O-18 values in intra-caldera rhyolites from Northeast Iceland. Mineralogical magazine, 82(5), 1147-1168
Open this publication in new window or tab >>Exceptionally high whole-rock delta O-18 values in intra-caldera rhyolites from Northeast Iceland
Show others...
2018 (English)In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 82, no 5, p. 1147-1168Article in journal (Refereed) Published
Abstract [en]

The Icelandic crust is characterized by low delta O-18 values that originate from pervasive high-temperature hydrothermal alteration by O-18-depleted meteoric waters. Igneous rocks in Iceland with delta O-18 values significantly higher than unaltered oceanic crust (similar to 5.7 parts per thousand) are therefore rare. Here we report on rhyolitic intra-caldera samples from a cluster of Neogene central volcanoes in Borgarfjorour Eystri, Northeast Iceland, that show whole-rock delta O-18 values between +2.9 and +17.6 parts per thousand (n = 6), placing them among the highest delta O-18 values thus far recorded for Iceland. Extra-caldera rhyolite samples from the region, in turn, show delta O-18 whole-rock values between +3.7 and +7.8 parts per thousand (n = 6), consistent with the range of previously reported Icelandic rhyolites. Feldspar in the intra-caldera samples (n = 4) show delta O-18 values between +4.9 and +18.7 parts per thousand, whereas pyroxene (n = 4) shows overall low delta O-18 values of +4.0 to +4.2 parts per thousand, consistent with regional rhyolite values. In combination with the evidence from mineralogy and rock H2O contents, the high whole-rock delta O-18 values of the intra-caldera rhyolites appear to be the result of pervasive isotopic exchange during subsolidus hydrothermal alteration with O-18-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, O-18-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 delta O-18-enriched rock composition exists on Iceland and thus probably within the Icelandic crust too.

Place, publisher, year, edition, pages
MINERALOGICAL SOC, 2018
Keywords
Northeast Iceland, high(18)O values, hydrothermal alteration, intra-caldera lakes
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-372902 (URN)10.1180/mgm.2018.114 (DOI)000452016700011 ()
Funder
Swedish Research CouncilThe Royal Swedish Academy of Sciences
Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-11Bibliographically approved
Berg, S. E., Troll, V. R., Deegan, F. M., Burchardt, S., Krumbholz, M., Mancini, L., . . . Brun, F. (2016). Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by X-ray computed microtomography. Bulletin of Volcanology, 78(12), Article ID 85.
Open this publication in new window or tab >>Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by X-ray computed microtomography
Show others...
2016 (English)In: Bulletin of Volcanology, ISSN 0258-8900, E-ISSN 1432-0819, Vol. 78, no 12, article id 85Article in journal (Refereed) Published
Abstract [en]

During the first week of the 2011 El Hierro submarine eruption, abundant light-coloured pumiceous, high-silica volcanic bombs coated in dark basanite were found floating on the sea. The composition of the light-coloured frothy material ('xeno-pumice') is akin to that of sedimentary rocks from the region, but the textures resemble felsic magmatic pumice, leaving their exact mode of formation unclear. To help decipher their origin, we investigated representative El Hierro xeno-pumice samples using X-ray computed microtomography for their internal vesicle shapes, volumes, and bulk porosity, as well as for the spatial arrangement and size distributions of vesicles in three dimensions (3D). We find a wide range of vesicle morphologies, which are especially variable around small fragments of rock contained in the xeno-pumice samples. Notably, these rock fragments are almost exclusively of sedimentary origin, and we therefore interpret them as relicts an the original sedimentary ocean crust protolith(s). The irregular vesiculation textures observed probably resulted from pulsatory release of volatiles from multiple sources during xeno-pumice formation, most likely by successive release of pore water and mineral water during incremental heating and decompression of the sedimentary protoliths.

Keywords
El Hierro, Xeno-pumice, X-CT imaging, Vesicle morphologies, Vesicle size distribution, Heterogeneous vesiculation, Sedimentary ocean crust
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-272316 (URN)10.1007/s00445-016-1080-x (DOI)000394130700001 ()
Funder
The Royal Swedish Academy of SciencesSwedish Research Council
Note

The manuscript version of this article was used under the name "Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by synchrotron μ-CT" in the following thesis: Silicic Magma Genesis in Basalt-dominated Oceanic Settings: Examples from Iceland and the Canary Islands http://uu.diva-portal.org/smash/record.jsf?pid=diva2:893923

Available from: 2016-01-13 Created: 2016-01-13 Last updated: 2017-11-30Bibliographically approved
Berg, S. E. (2016). Silicic Magma Genesis in Basalt-dominated Oceanic Settings: Examples from Iceland and the Canary Islands. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Silicic Magma Genesis in Basalt-dominated Oceanic Settings: Examples from Iceland and the Canary Islands
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The origin of silicic magma in basalt-dominated oceanic settings is fundamental to our understanding of magmatic processes and formation of the earliest continental crust. Particularly significant is magma-crust interaction that can modify the composition of magma and the dynamics of volcanism. This thesis investigates silicic magma genesis on different scales in two ocean island settings. First, volcanic products from a series of voluminous Neogene silicic centres in northeast Iceland are investigated using rock and mineral geochemistry, U-Pb geochronology, and oxygen isotope analysis. Second, interfacial processes of magma-crust interaction are investigated using geochemistry and 3D X-ray computed microtomography on crustal xenoliths from the 2011-12 El Hierro eruption, Canary Islands.

The results from northeast Iceland constrain a rapid outburst of silicic magmatism driven by a flare of the Iceland plume and/or by formation of a new rift zone, causing large volume injection of basaltic magma into hydrated basaltic crust. This promoted crustal recycling by partial melting of the hydrothermally altered Icelandic crust, thereby producing mixed-origin silicic melt pockets that reflect the heterogeneous nature of the crustal protolith with respect to oxygen isotopes. In particular, a previously unrecognised high-δ18O end-member on Iceland was documented, which implies potentially complex multi-component assimilation histories for magmas ascending through the Icelandic crust. Common geochemical traits between Icelandic and Hadean zircon populations strengthen the concept of Iceland as an analogue for early Earth, implying that crustal recycling in emergent rifts was pivotal in generating Earth’s earliest continental silicic crust.

Crustal xenoliths from the El Hierro 2011-2012 eruption underline the role of partial melting and assimilation of pre-island sedimentary layers in the early shield-building phase of ocean islands. This phenomenon may contribute to the formation of evolved magmas, and importantly, the release of volatiles from the xenoliths may be sufficient to increase the volatile load of the magma and temporarily alter the character and intensity of an eruption.

This thesis sheds new light on the generation of silicic magma in basalt-dominated oceanic settings and emphasises the relevance of magma-crust interaction for magma evolution, silicic crust formation, and eruption style from early Earth to present.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. p. 54
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1338
Keywords
Silicic magmatism, Iceland, magma-crust interaction, proto-continental crust, early Earth, zircon geochronology and geochemistry, oxygen isotopes, 2011-2012 El Hierro eruption, crustal xenoliths, 3D X-ray μ-CT, volatiles
National Category
Geochemistry Geology
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-272318 (URN)978-91-554-9454-4 (ISBN)
Public defence
2016-03-03, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2016-02-11 Created: 2016-01-13 Last updated: 2016-02-19
Berg, S., Troll, V., Burchardt, S., Deegan, F., Riishuus, M. S., Whitehouse, M. J., . . . Gústafsson, L. E. (2015). Rapid high-silica magma generation in basalt-dominated rift settings. In: : . Paper presented at EGU General Assembly 2015 (pp. 13103). , 17
Open this publication in new window or tab >>Rapid high-silica magma generation in basalt-dominated rift settings
Show others...
2015 (English)Conference paper, Oral presentation with published abstract (Other academic)
National Category
Geosciences, Multidisciplinary Geochemistry
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-270976 (URN)
Conference
EGU General Assembly 2015
Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2016-01-05
Dahrén, B., Burchardt, S., Troll, V., Emeleus, C., Mattson, T. & Berg, S. (2014). 3D-model of the Rum central complex. In: : . Paper presented at Volcanic and Magmatic Studies Group Annual Meeting.
Open this publication in new window or tab >>3D-model of the Rum central complex
Show others...
2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Geology Geosciences, Multidisciplinary
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-240938 (URN)
Conference
Volcanic and Magmatic Studies Group Annual Meeting
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2015-01-08
Berg, S., Troll, V., Burchardt, S., Riishuus, M., Krumbholz, M. & Gústafsson, L. (2014). Iceland's best kept secret. Geology Today, 30(2), 54-60
Open this publication in new window or tab >>Iceland's best kept secret
Show others...
2014 (English)In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 30, no 2, p. 54-60Article in journal (Refereed) Published
Abstract [en]

The ‘forgotten fjords’ and ‘deserted inlets’ of NE-Iceland, in the region between Borgarfjörður Eystri and Loðmundarfjörður, are not only prominent because of their pristine landscape, their alleged elfin settlements, and the puffins that breed in the harbour, but also for their magnificent geology. From a geological point of view, the area may hold Iceland's best kept geological secret. The greater Borgarfjörður Eystri area hosts mountain chains that consist of voluminous and colourful silicic rocks that are concentrated within a surprisingly small area (Fig. 1), and that represent the second-most voluminous occurrence of silicic rocks in the whole of Iceland. In particular, the presence of unusually large volumes of ignimbrite sheets documents extremely violent eruptions during the Neogene, which is atypical for this geotectonic setting. As a group of geoscientists from Uppsala University (Sweden) and the Nordic Volcanological Center (NordVulk, Iceland) we set out to explore this remote place, with the aim of collecting material that may allow us to unravel the petrogenesis of these large volumes of silicic rocks. This effort could provide an answer to a long-standing petrological dilemma; the question of how silicic continental crust is initially created. Here we document on our geological journey, our field strategy, and describe our field work in the remote valleys of NE-Iceland.

National Category
Geosciences, Multidisciplinary
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-213020 (URN)DOI: 10.1111/gto.12042 (DOI)
Available from: 2013-12-17 Created: 2013-12-17 Last updated: 2017-12-06
Troll, V., Deegan, F., Jolis, E. M., Dahrén, B., Blythe, L., Harris, C., . . . Freda, C. (2014). Magma storage at Krakatau volcanic complex. In: : . Paper presented at City On volcanoes.
Open this publication in new window or tab >>Magma storage at Krakatau volcanic complex
Show others...
2014 (English)Conference paper, Oral presentation only (Refereed)
National Category
Geology Geosciences, Multidisciplinary
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-240897 (URN)
Conference
City On volcanoes
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2015-01-08
Berg, S., Troll, V., Burchardt, S., Riishuus, M., Deegan, F., Harris, C., . . . Gustafsson, L. (2014). Making Earth’s earliest continental crust: an analogue from voluminous Neogene silicic volcanism in NE-Iceland. In: : . Paper presented at EGU General Assembly 2014, Vienna, Austria.
Open this publication in new window or tab >>Making Earth’s earliest continental crust: an analogue from voluminous Neogene silicic volcanism in NE-Iceland
Show others...
2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Borgarfjörður Eystri in NE-Iceland represents the second-most voluminous exposure of silicic eruptive rocksin Iceland and is a superb example of bimodal volcanism (Bunsen-Daly gap), which represents a long-standingcontroversy that touches on the problem of crustal growth in early Earth. The silicic rocks in NE-Iceland approach25 % of the exposed rock mass in the region (Gústafsson et al., 1989), thus they significantly exceed the usual≤ 12 % in Iceland as a whole (e.g. Walker, 1966; Jonasson, 2007). The origin, significance, and duration of thevoluminous (> 300 km3) and dominantly explosive silicic activity in Borgarfjörður Eystri is not yet constrained(c.f. Gústafsson, 1992), leaving us unclear as to what causes silicic volcanism in otherwise basaltic provinces.Here we report SIMS zircon U-Pb ages and δ18O values from the region, which record the commencement ofsilicic igneous activity with rhyolite lavas at 13.5 to 12.8 Ma, closely followed by large caldera-forming ignimbriteeruptions from the Breiðavik and Dyrfjöll central volcanoes (12.4 Ma). Silicic activity ended abruptly with dacitelava at 12.1 Ma, defining a ≤ 1 Myr long window of silicic volcanism. Magma δ18O values estimated fromzircon range from 3.1 to 5.5 (± 0.3; n = 170) and indicate up to 45 % assimilation of a low-δ18O component (e.g.typically δ18O = 0 h Bindeman et al., 2012). A Neogene rift relocation (Martin et al., 2011) or the birth of anoff-rift zone to the east of the mature rift associated with a thermal/chemical pulse in the Iceland plume (Óskarsson& Riishuus, 2013), likely brought mantle-derived magma into contact with fertile hydrothermally-altered basalticcrust. The resulting interaction triggered large-scale crustal melting and generated mixed-origin silicic melts. Suchrapid formation of silicic magmas from sustained basaltic volcanism may serve as an analogue for generatingcontinental crust in a subduction–free early Earth (e.g. ≥ 3 Ga, Kamber et al., 2005).

REFERENCES:Bindeman, I.N., et al., 2012. Terra Nova 24, 227–232.Gústafsson, L.E., et al., 1989. Jökull, v. 39, 75–89.Gústafsson, L.E., 1992. PhD dissertation, Freie Universität Berlin.Jonasson, K., 2007. Journal of Geodynamics, 43, 101–117.Kamber, B.S., et al., 2005. Earth Planet. Sci. Lett., Vol. 240 (2), 276-290.Martin, E., et al., 2011. Earth Planet. Sc. Lett., 311, 28–38.Óskarsson, B.V., & Riishuus, M.S., 2013. J. Volcanol. Geoth.Res., 267, 92–118.Walker, G.P.L., 1966. Bull. Volcanol., 29 (1), 375-402.

National Category
Geosciences, Multidisciplinary
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-240747 (URN)
Conference
EGU General Assembly 2014, Vienna, Austria
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2015-01-08
Pedroza, K., Troll, V., Deegan, F., Meade, F. C., Burchardt, S., Carracedo, J., . . . Barker, A. (2014). Origin and significance of the 2011 El Hierro xeno-pumice. In: : . Paper presented at EGU General Assembly, 2014, Vienna.
Open this publication in new window or tab >>Origin and significance of the 2011 El Hierro xeno-pumice
Show others...
2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Geology Geosciences, Multidisciplinary
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-240939 (URN)
Conference
EGU General Assembly, 2014, Vienna
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2015-01-08
Troll, V., Dahrén, B., Deegan, F., Jolis, E. M., Blythe, L., Harris, C., . . . Freda, C. (2014). Reconstructing the plumbing system of Krakatau volcano. In: : . Paper presented at EGU General Assembly, 2014, Vienna.
Open this publication in new window or tab >>Reconstructing the plumbing system of Krakatau volcano
Show others...
2014 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Geosciences, Multidisciplinary Geology
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-240945 (URN)
Conference
EGU General Assembly, 2014, Vienna
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2015-01-08
Organisations

Search in DiVA

Show all publications