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Deegan, Frances
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Publications (10 of 54) Show all publications
Whitley, S., Gertisser, R., Halama, R., Preece, K., Troll, V. R. & Deegan, F. (2019). Crustal CO2 contribution to subduction zone degassing recorded through calc-silicate xenoliths in arc lavas. Scientific Reports, 9, Article ID 8803.
Open this publication in new window or tab >>Crustal CO2 contribution to subduction zone degassing recorded through calc-silicate xenoliths in arc lavas
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 8803Article in journal (Refereed) Published
Abstract [en]

Interaction between magma and crustal carbonate at active arc volcanoes has recently been proposed as a source of atmospheric CO2, in addition to CO2 released from the mantle and subducted oceanic crust. However, quantitative constraints on efficiency and timing of these processes are poorly established. Here, we present the first in situ carbon and oxygen isotope data of texturally distinct calcite in calc-silicate xenoliths from arc volcanics in a case study from Merapi volcano (Indonesia). Textures and C-O isotopic data provide unique evidence for decarbonation, magma-fluid interaction, and the generation of carbonate melts. We report extremely light delta C-13(PDB) values down to -29.3%o which are among the lowest reported in magmatic systems so far. Combined with the general paucity of relict calcite, these extremely low values demonstrate highly efficient remobilisation of crustal CO2 over geologically short timescales of thousands of years or less. This rapid release of large volumes of crustal CO2 may impact global carbon cycling.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
National Category
Geochemistry
Identifiers
urn:nbn:se:uu:diva-390198 (URN)10.1038/s41598-019-44929-2 (DOI)000472030000036 ()31217464 (PubMedID)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-08-08Bibliographically approved
Heap, M. J., Troll, V. R., Kushnir, A. R. L., Gilg, H. A., Collinson, A. S. D., Deegan, F. M., . . . Walter, T. R. (2019). Hydrothermal alteration of andesitic lava domes can lead to explosive volcanic behaviour. Nature Communications, 10, Article ID 5063.
Open this publication in new window or tab >>Hydrothermal alteration of andesitic lava domes can lead to explosive volcanic behaviour
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 5063Article in journal (Refereed) Published
Abstract [en]

Dome-forming volcanoes are among the most hazardous volcanoes on Earth. Magmatic outgassing can be hindered if the permeability of a lava dome is reduced, promoting pore pressure augmentation and explosive behaviour. Laboratory data show that acid-sulphate alteration, common to volcanoes worldwide, can reduce the permeability on the sample lengthscale by up to four orders of magnitude and is the result of pore- and microfracture-filling mineral precipitation. Calculations using these data demonstrate that intense alteration can reduce the equivalent permeability of a dome by two orders of magnitude, which we show using numerical modelling to be sufficient to increase pore pressure. The fragmentation criterion shows that the predicted pore pressure increase is capable of fragmenting the majority of dome-forming materials, thus promoting explosive volcanism. It is crucial that hydrothermal alteration, which develops over months to years, is monitored at dome-forming volcanoes and is incorporated into real-time hazard assessments.

National Category
Geology
Identifiers
urn:nbn:se:uu:diva-397637 (URN)10.1038/s41467-019-13102-8 (DOI)000494938500001 ()31700076 (PubMedID)
Funder
EU, Horizon 2020
Available from: 2019-11-22 Created: 2019-11-22 Last updated: 2019-11-22Bibliographically approved
Troll, V. R., Rodriguez-Gonzalez, A., Deegan, F., Perez-Torrado, F. J., Carracedo, J. C., Thomaidis, K., . . . Meade, F. C. (2019). Sacred ground; the Maipés necropolis of north-west Gran Canaria: the Maipés necropolis of north-west Gran Canaria. Geology Today, 35(2), 55-62
Open this publication in new window or tab >>Sacred ground; the Maipés necropolis of north-west Gran Canaria: the Maipés necropolis of north-west Gran Canaria
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2019 (English)In: Geology Today, Vol. 35, no 2, p. 55-62Article in journal (Refereed) Published
Abstract [en]

Gran Canaria, like most of the Canary Islands, shows evidence for young basaltic volcanism in the form of cinder cones and valley-hugging lava flows. These landforms were of no particular use to the aboriginal population, nor to the subsequent Spanish settlers, and young lava flows and lava fields are still referred to as ‘malpaís’ (badlands) in the Canary Islands. In north-west Gran Canaria, one such lava flow fills the bottom of a steep-sided valley, which reaches the sea at the present day village of Agaete. The lava flow erupted c. 3030 ± 90 yr bp and displays a total length of ∌ 11 km. At its distal end, just outside Agaete, it hosts one of Europe’s largest and most important pre-historic burial sites constructed of volcanic rock: the Maipés necropolis. Over 700 pre-historic tombs (or tumuli) constructed from the aa-type clinker materials have been identified on top of the valley-filling lava flow. The up to soccer-ball sized vesicular clinker fragments are sufficiently low in density to provide abundant, workable basalt blocks for the construction of the tumuli, allowing the pre-hispanic aboriginal population to create a large and magnificent ‘sacred ground’ in an otherwise barren landscape.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-383080 (URN)10.1111/gto.12262 (DOI)
Available from: 2019-05-09 Created: 2019-05-09 Last updated: 2020-02-20Bibliographically approved
Gonzalez-Maurel, O., le Roux, P., Godoy, B., Troll, V. R., Deegan, F. & Menzies, A. (2019). The great escape: Petrogenesis of low-silica volcanism of Pliocene to Quaternary age associated with the Altiplano-Puna Volcanic Complex of northern Chile (21 degrees 10 '-22 degrees 50 ' S). Lithos, 346/347, Article ID UNSP 105162.
Open this publication in new window or tab >>The great escape: Petrogenesis of low-silica volcanism of Pliocene to Quaternary age associated with the Altiplano-Puna Volcanic Complex of northern Chile (21 degrees 10 '-22 degrees 50 ' S)
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2019 (English)In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 346/347, article id UNSP 105162Article in journal (Refereed) Published
Abstract [en]

The Pliocene to Quaternary volcanic arc of the Central Andes formed on 70-74 km thick continental crust. Physical interaction between mafic and acid magmas for this arc are therefore difficult to recognize due to the differentiation of mantle-derived magma during ascent through the thickened crust and a corresponding lack of erupted primitive lavas. However, a rare concentration of less evolved rocks is located marginal to the partially molten Altiplano-Puna Magma Body (APMB) in the Altiplano-Puna Volcanic Complex of northern Chile, between 21 degrees 10'S and 22 degrees 50'S. To unravel the relationship between this less evolved magmatism and the APMB, we present major and trace element data, and Sr and Nd isotope ratios of fourteen volcanoes. Whole-rock compositional and Sr and Nd isotope data reveal a large degree for compositional heterogeneity, e.g., SiO2 = 53.2 to 63.2 wt%, MgO = 1.74 to 6.08 wt%, Cr = 2 to 382 ppm, Sr = 304 to 885 ppm, (87)sr/(86)sr = 0.7055 to 0.7088, and Nd-143/Nd-144 = 0.5122 to 0.5125. The combined dataset points to magma spatial compositional changes resulting from magma mixing, fractional crystallization and crustal assimilation. The least evolved products erupted along the periphery of the APMB and are likely equivalent to the replenishing magmas that thermally sustain the large APMB system. We suggest that the mafic to intermediate eruptives we have investigated reflect mafic melt injections that underplate the APMB and escape along the side of the large felsic body to avoid significant compositional modifications during ascent, which helps to assess the evolution of the APMB through space and time. (C) 2019 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
Low-silica volcanism, Altiplano-Puna Volcanic Complex, Altiplano-Puna Magma Body, Sr and Nd radiogenic isotopes
National Category
Geochemistry
Identifiers
urn:nbn:se:uu:diva-395713 (URN)10.1016/j.lithos.2019.105162 (DOI)000488335600019 ()
Funder
Swedish Research Council
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved
Di Baldassarre, G., Nohrstedt, D., Mård, J., Burchardt, S., Albin, C., Bondesson, S., . . . Parker, C. F. (2018). An Integrative Research Framework to Unravel the Interplay of Natural Hazards and Vulnerabilities. Earth's Future, 6(3), 305-310
Open this publication in new window or tab >>An Integrative Research Framework to Unravel the Interplay of Natural Hazards and Vulnerabilities
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2018 (English)In: Earth's Future, ISSN 1384-5160, E-ISSN 2328-4277, Vol. 6, no 3, p. 305-310Article in journal (Refereed) Published
Abstract [en]

Climate change, globalization, urbanization, social isolation, and increased interconnectedness between physical, human, and technological systems pose major challenges to disaster risk reduction (DRR). Subsequently, economic losses caused by natural hazards are increasing in many regions of the world, despite scientific progress, persistent policy action, and international cooperation. We argue that these dramatic figures call for novel scientific approaches and new types of data collection to integrate the two main approaches that still dominate the science underpinning DRR: the hazard paradigm and the vulnerability paradigm. Building from these two approaches, here we propose a research framework that specifies the scope of enquiry, concepts, and general relations among phenomena. We then discuss the essential steps to advance systematic empirical research and evidence-based DRR policy action. Plain Language Summary The recent deadly earthquake in Iran-Iraq has been yet another reminder of the topicality of natural hazards, and it has come just after an unprecedented series of catastrophic events, including the extensive flooding in South Asia and the string of devastating hurricanes in the Americas. He we identify three main puzzles in the nexus of natural hazards and vulnerabilities, and demonstrate how novel approaches are needed to solve them with reference to a flood risk example. Specifically, we show how a new research framework can guide systematic data collections to advance the fundamental understanding of socionatural interactions, which is an essential step to improve the development of policies for disaster risk reduction.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
Disaster risk reduction, Natural hazards, Vulnerability, Flood risk, Socio-hydrology
National Category
Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-350188 (URN)10.1002/2017EF000764 (DOI)000430171600002 ()
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-18Bibliographically approved
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
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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
Geiger, H., Troll, V. R., Jolis, E. M., Deegan, F. M., Harris, C., Hilton, D. R. & Freda, C. (2018). Multi-level magma plumbing at Agung and Batur volcanoes increases risk of hazardous eruptions. Scientific Reports, 8, Article ID 10547.
Open this publication in new window or tab >>Multi-level magma plumbing at Agung and Batur volcanoes increases risk of hazardous eruptions
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 10547Article in journal (Refereed) Published
Abstract [en]

The island of Bali in Indonesia is home to two active stratovolcanoes, Agung and Batur, but relatively little is known of their underlying magma plumbing systems. Here we define magma storage depths and isotopic evolution of the 1963 and 1974 eruptions using mineral-melt equilibrium thermobarometry and oxygen and helium isotopes in mineral separates. Olivine crystallised from a primitive magma and has average delta O-18 values of 4.8%. Clinopyroxene records magma storage at the crust-mantle boundary, and displays mantle-like isotope values for Helium (8.62 R-A) and delta O-18 (5.0-5.8%). Plagioclase reveals crystallisation in upper crustal storage reservoirs and shows delta O-18 values of 5.5-6.4%. Our new thermobarometry and isotope data thus corroborate earlier seismic and InSAR studies that inferred upper crustal magma storage in the region. This type of multi-level plumbing architecture could drive replenishing magma to rapid volatile saturation, thus increasing the likelihood of explosive eruptions and the consequent hazard potential for the population of Bali.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Geochemistry Geology
Identifiers
urn:nbn:se:uu:diva-361269 (URN)10.1038/s41598-018-28125-2 (DOI)000438343600057 ()30002471 (PubMedID)
Funder
Swedish Research CouncilThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT), SA2015-6212
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2019-05-09Bibliographically approved
Budd, D. A., Troll, V. R., Deegan, F. M., Jolis, E., Smith, V., Whitehouse, M., . . . Bindeman, I. (2017). Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz. Scientific Reports, 7, Article ID 40624.
Open this publication in new window or tab >>Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 40624Article in journal (Refereed) Published
Abstract [en]

Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core−rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

National Category
Geochemistry
Identifiers
urn:nbn:se:uu:diva-316065 (URN)10.1038/srep40624 (DOI)000392659100001 ()28120860 (PubMedID)
Funder
Swedish Research CouncilThe Royal Swedish Academy of Sciences
Available from: 2017-02-24 Created: 2017-02-24 Last updated: 2019-09-26Bibliographically approved
Troll, V. R., Carracedo, J. C., Jägerup, B., Streng, M., Barker, A., Deegan, F., . . . Geiger, H. (2017). Volcanic particles in agriculture and gardening. Geology Today, 33(4), 148-154
Open this publication in new window or tab >>Volcanic particles in agriculture and gardening
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2017 (English)In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 33, no 4, p. 148-154Article in journal (Refereed) Published
Abstract [en]

Volcanic pyroclasts of small size, such as lapilli and small pumice stones, are widely used in agriculture, gardening, and for pot plants as natural inorganic mulch. The technique of using pyroclasts to enhance topsoil stems from the eighteenth century, and specifically from the ad 1730–1736 eruption on Lanzarote. Critical observations on plant development during and after the eruption showed that the vegetation died when buried under a thick layer of lapilli, but grew vigorously when covered thinly. While the agriculture of Lanzarote was restricted to cereals before the eruption, it diversified to many kinds of fruit and vegetables afterwards, including the production of the famous Malvasía wines in the Canaries. The population of Lanzarote doubled in the years after the eruption, from about 5000 in 1730 to near 10 000 in 1768, predominantly as a result of the higher agricultural productivity. This outcome led to widespread use of lapilli and pumice fragments throughout the islands and eventually the rest of the globe. Lapilli and pumice provide vesicle space for moisture to be retained longer within the planting soil, which can create an environment for micro-bacteria to thrive in. Through this route, nutrients from volcanic matter are transported into the surrounding soil where they become available to plant life. The detailed processes that operate within the pyroclasts are less well understood, such as the breakdown of nutrients from the rock matrix and transport into the soil by biological action. Further studies promise significant potential to optimize future agricultural efforts, particularly in otherwise arid areas of the globe.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-383079 (URN)10.1111/gto.12193 (DOI)
Available from: 2019-05-09 Created: 2019-05-09 Last updated: 2019-09-03Bibliographically approved
Deegan, F., Troll, V. R., Whitehouse, M. J., Jolis, E. M. & Freda, C. (2016). Boron isotope fractionation in magma via crustal carbonate dissolution. Scientific Reports, 6, Article ID 30774.
Open this publication in new window or tab >>Boron isotope fractionation in magma via crustal carbonate dissolution
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2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 30774Article in journal (Refereed) Published
Abstract [en]

Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low delta B-11 values down to -41.5%, reflecting preferential partitioning of B-10 into the assimilating melt. Loss of B-11 from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports B-11 away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low delta B-11 melt values in arc magmas could flag shallow-level additions to the subduction cycle.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-302679 (URN)10.1038/srep30774 (DOI)000380873400001 ()27488228 (PubMedID)
Funder
Swedish Research CouncilThe Royal Swedish Academy of SciencesNatural‐Disaster Science
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2017-11-21Bibliographically approved
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