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  • 51.
    Cooper, Mark R.
    et al.
    Geol Survey Northern Ireland, Dundonald House,Upper Newtownards Rd, Belfast BT4 3SB, Antrim, North Ireland.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Lemon, Kirstin
    Geol Survey Northern Ireland, Dundonald House,Upper Newtownards Rd, Belfast BT4 3SB, Antrim, North Ireland.
    The "Clay-with-Flints' deposit in Northern Ireland: reassessment of the evidence for an early Paleocene ignimbrite2018Ingår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 155, nr 8, s. 1811-1820Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reassessment of key geological sections, field relationships and petrographical characteristics of the Northern Ireland Clay-with-Flints' and Donald's Hill Ignimbrite Formation' show they formed dominantly by sedimentary processes. The involvement of a previously postulated pyroclastic flow during early Paleocene time is not recognized and, as such, the Donald's Hill Ignimbrite Formation stratigraphic term is discounted. Instead a multistage model of formation by sedimentary accumulation and remobilization is presented and the term Clay-with-Flints is retained. Regionally, two dominant facies are recognized in most Clay-with-Flints sections. Facies 1 was formed by an initial accumulation of flints on a chalk landscape undergoing karstification, and involved deposition of a clay matrix derived predominantly from contemporaneous erosion of subtropical soil horizons formed mainly on basalt. In Facies 2, evidence is observed for widespread remobilization of Facies 1 deposits by high-density mudflows driven by the advancement of the Antrim Lava Group, which caused the blockage of subsurface and marginalization of surface drainage. A stratigraphical constraint imposed by the presence of a supposed ignimbrite in this part of the North Atlantic Igneous Province has been problematic, but this is resolved by its identification as a diachronous, sedimentary deposit that formed until buried by either the lower or upper formations of the Antrim Lava Group.

  • 52.
    Dahrén, Börje
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Burchardt, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Emeleus, C.H.
    Mattson, T.
    Berg, Sylvia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    3D-model of the Rum central complex2014Konferensbidrag (Refereegranskat)
  • 53.
    Dahrén, Börje
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Barker, Abigail
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Meade, Fiona C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Holm, Paul Martin
    University of Copenhagen, Department of Geosciences and Natural Resource Management, Øster Voldgade 10, Copenhagen DK-1350, Denmark.
    Søager, Nina
    GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany.
    Plagioclase mineral chemistry in the Faroe Islands Basalt Group2015Ingår i: Faroe Islands Exploration Conference: Proceedings of the 4th ConferenceArtikel i tidskrift (Refereegranskat)
  • 54.
    Dahrén, Börje
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Andersson, Ulf B.
    Chadwick, Jane P.
    Gardner, Mairi F.
    Jaxybulatov, Kairly
    Koulakov, Ivan
    Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions2012Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 163, nr 4, s. 631-651Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s), at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km, while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes.

  • 55.
    Dahrén, Börje
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Andersson, Ulf-Bertil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Chadwick, Jane P.
    Dept. of Petrology, Vrieje Universiteit Amsterdam, Amsterdam, The Netherlands.
    Gardner, Máiri F.
    Dept. of Geology, University College Cork, Cork, Ireland.
    Investigating magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions2010Ingår i: 7th EGU General Assembly, Copernicus Publications , 2010Konferensbidrag (Övrigt vetenskapligt)
  • 56.
    Darmawan, Herlan
    et al.
    GFZ German Res Ctr Geosci, Dept Phys Earth, D-14473 Potsdam, Germany;Univ Gadjah Mada, Fac Math & Nat Sci, Dept Phys, Lab Geophys, Yogyakarta 55281, Indonesia.
    Walter, Thomas R.
    GFZ German Res Ctr Geosci, Dept Phys Earth, D-14473 Potsdam, Germany.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Univ Padjajaran, Fac Geol Engn, Bandung 45363, Indonesia.
    Budi-Santoso, Agus
    BPPTKG, Jalan Cendana 15, Yogyakarta 55166, Indonesia.
    Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption2018Ingår i: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 18, nr 12, s. 3267-3281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lava domes are subjected to structural weakening that can lead to gravitational collapse and produce pyroclastic flows that may travel up to several kilometers from a volcano's summit. At Merapi volcano, Indonesia, pyroclastic flows are a major hazard, frequently causing high numbers of casualties. After the Volcanic Explosivity Index 4 eruption in 2010, a new lava dome developed on Merapi volcano and was structurally destabilized by six steam-driven explosions between 2012 and 2014. Previous studies revealed that the explosions produced elongated open fissures and a delineated block in the southern dome sector. Here, we investigated the geomorphology, structures, thermal fingerprint, alteration mapping and hazard potential of the Merapi lava dome by using drone-based geomorphologic data and forward-looking thermal infrared images The block on the southern dome of Merapi is delineated by a horseshoe-shaped structure with a maximum depth of 8 m and it is located on the unbuttressed southern steep flank. We identify intense thermal, fumarole and hydrothermal alteration activities along this horseshoe-shaped structure. We conjecture that hydrothermal alteration may weaken the horseshoe-shaped structure, which then may develop into a failure plane that can lead to gravitational collapse. To test this instability hypothesis, we calculated the factor of safety and ran a numerical model of block-and-ash flow using Titan2D. Results of the factor of safety analysis confirm that intense rainfall events may reduce the internal friction and thus gradually destabilize the dome. The titan2D model suggests that a hypothetical gravitational collapse of the delineated unstable dome sector may travel southward for up to 4 km. This study highlights the relevance of gradual structural weakening of lava domes, which can influence the development fumaroles and hydrothermal alteration activities of cooling lava domes for years after initial emplacement.

  • 57.
    Deegan, Frances M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Barker, Abigail
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Harris, C.
    Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa.
    Chadwick, J.P.
    Science Gallery, Trinity College Dublin, Dublin 2, Ireland.
    Carracedo, J.C.
    Departamento de Física (GEOVOL), Universidad de Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, Spain.
    Delcamp, A.
    Department of Geography, Vrije Universiteit Brussels, Belgium.
    Crustal versus source processes recorded in dykes from the Northeast volcanic rift zone of Tenerife, Canary Islands2012Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 334, s. 324-344Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Miocene–Pliocene Northeast Rift Zone (NERZ) on Tenerife is a well exposed example of a feeder system to a major ocean island volcanic rift. We present elemental and O–Sr–Nd–Pb isotope data for dykes of the NERZ with the aim of unravelling the petrological evolution of the rift and ultimately defining the mantle source contributions. Fractional crystallisation is found to be the principal control on major and trace element variability in the dykes. Differing degrees of low temperature alteration and assimilation of hydrothermally altered island edifice and pre-island siliciclastic sediment elevated the δ18O and the 87Sr/86Sr ratio of many of the dykes, but had little to no discernible effect on Nd and Pb isotopes. Once the data are screened for alteration and shallow level contamination, the underlying source variations of the NERZ essentially reflect derivation from a young High-μ (HIMU, where μ = 238U/204Pb)-type mantle component mixed with depleted mid-ocean ridge-type mantle (DMM). The Pb isotope data of the NERZ rocks (206Pb/204Pb and 207Pb/204Pb range from 19.591 to 19.838 and 15.603 to 15.635, respectively) support a model of initiation and growth of the rift from the Central Shield volcano (Roque del Conde), consistent with latest geochronology results. The similar isotope signature of the NERZ to both the Miocene Central Shield and the Pliocene Las Cañadas central volcano suggests that the central part of Tenerife Island was supplied from a mantle source that remained of similar composition through the Miocene to the Pliocene. This can be explained by the presence of a discrete column of young HIMU-like plume material, ≤ 100 km in vertical extent, occupying the melting zone beneath central Tenerife throughout this period. The most recent central magmatism on Tenerife appears to reflect greater entrainment of DMM material, perhaps due to waning of the HIMU-like “blob” with time.

  • 58.
    Deegan, Frances M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Deyhle, Annette
    Scripps Institutionof Oceanography, University of California San Diego, California, USA.
    Hansteen, Thor H
    Leibniz-Institute of Marine Sciences,IFM-Geomar, Kiel, Germany2639.
    Boron isotopes in feldspar: Tracing magmatic processes on Gran Canaria2010Ingår i: Geophysical Research Abstracts, ISSN 1029-7006, E-ISSN 1607-7962, Vol. 12Artikel i tidskrift (Refereegranskat)
  • 59.
    Deegan, Frances M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Freda, Carmela
    INGV Rome, Italy.
    Misiti, Valeria
    INGV Rome, Italy.
    Chadwick, Jane P
    Vrije Universiteit Amsterdam, the Netherlands.
    Fast and furious; crustal CO2 loss at Merapi volcano, Indonesia.2011Ingår i: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 27, nr 2, s. 63-64Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    New experimental results show that when magma interacts with carbonate-rich crustal rock, such as limestone, it rapidly liberates crustal CO2, with potentially devastating repercussions for explosive volcanic behaviour.

  • 60.
    Deegan, Frances M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Department of Geosciences, Swedish Museum of Natural History, SE-104 05, Stockholm, Sweden.
    Whitehouse, Martin
    Department of Geosciences, Swedish Museum of Natural History, SE-104 05, Stockholm, Sweden.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Budd, David A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Harris, Chris
    Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa.
    Geiger, Harri
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Hålenius, Ulf
    Department of Geosciences, Swedish Museum of Natural History, SE-104 05, Stockholm, Sweden.
    Pyroxene standards for SIMS oxygen isotope analysis and their application to Merapi volcano, Sunda arc, Indonesia2016Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 447, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurement of oxygen isotope ratios in common silicate minerals such as olivine, pyroxene, feldspar, garnet, and quartz is increasingly performed by Secondary Ion Mass Spectrometry (SIMS). However, certain mineral groups exhibit solid solution series, and the large compositional spectrum of these mineral phases will result in matrix effects during SIMS analysis. These matrix effects must be corrected through repeated analysis of compositionally similar standards to ensure accurate results. In order to widen the current applicability of SIMS to solid solution mineral groups in common igneous rocks, we performed SIMS homogeneity tests on new augite (NRM-AG-1) and enstatite (NRM-EN-2) reference materials sourced from Stromboli, Italy and Webster, North Carolina, respectively. Aliquots of the standard minerals were analysed by laser fluorination (LF) to establish their δ18O values. Repeated SIMS measurements were then performed on randomly oriented fragments of the same pyroxene crystals, which yielded a range in δ18O less than ± 0.42 and ± 0.58‰ (2σ) for NRM-AG-1 and NRM-EN-2, respectively. Homogeneity tests verified that NRM-AG-1 and NRM-EN-2 do not show any crystallographic orientation bias and that they are sufficiently homogeneous on the 20 μm scale to be used as routine mineral standards for SIMS δ18O analysis. We subsequently tested our new standard materials on recently erupted pyroxene crystals from Merapi volcano, Indonesia. The δ18O values for Merapi pyroxene obtained by SIMS (n = 204) agree within error with the LF-derived δ18O values for Merapi pyroxene but differ from bulk mineral and whole-rock data obtained by conventional fluorination. The bulk samples are offset to higher δ18O values as a result of incorporation of mineral and glass inclusions that in part reflects crustal contamination processes. The Merapi pyroxene SIMS data, in turn, display a frequency peak at 5.8‰, which allows us to estimate the δ18O value of the primary mafic magma at Merapi to ~ 6.1‰ when assuming closed system differentiation.

  • 61.
    Deegan, Frances
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Uppsala University.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Bédard, Jean
    Evenchick, Carol
    Dewing, Keith
    Grasby, Stephen
    Geiger, Harri
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Freda, Carmela
    Misiti, Valeria
    Mollo, Silvio
    The stiff upper LIP: investigating the High Arctic Large Igneous Province2016Ingår i: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 32, nr 3, s. 92-98Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The Canadian Arctic Islands expose a complex network of dykes and sills that belong to the High Arctic Large Igneous Province (HALIP), which intruded volatile-rich sedimentary rocks of the Sverdrup Basin (shale, limestone, sandstone and evaporite) some 130 to 120 million years ago. There is thus great potential in studying the HALIP to learn how volatile-rich sedimentary rocks respond to magmatic heating events during LIP emplacement. The HALIP remains, however, one of the least well known LIPs on the planet due to its remote location, short field season, and harsh climate. A Canadian–Swedish team of geologists set out in summer 2015 to further explore HALIP sills and their sedimentary host rocks, including the sampling of igneous and meta-sedimentary rocks for subsequent geochemical analysis, and high pressure-temperature petrological experiments to help define the actual processes and time-scales of magma–sediment interaction. The research results will advance our understanding of how climate-active volatiles such as CO2, SO2 and CH4 are mobilised during the magma–sediment interaction related to LIP events, a process which is hypothesised to have drastically affected Earth's carbon and sulphur cycles. In addition, assimilation of sulphate evaporites, for example, is anticipated to trigger sulphide immiscibility in the magma bodies and in so doing could promote the formation of Ni-PGE ore bodies. Here we document the joys and challenges of ‘frontier arctic fieldwork’ and discuss some of our initial observations from the High Arctic Large Igneous Province.

  • 62.
    Deegan, Frances
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Freda, C.
    Misiti, V.
    Chadwick, J.P.
    McLeod, C.
    Davidson, J.P.
    Magma-carbonate interaction processes and associated CO2 release at Merapi volcano, Indonesia: insights from experimental petrology2010Ingår i: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, nr 5, s. 1027-1051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is considerable evidence for continuing, late-stage interaction between the magmatic system at Merapi volcano, Indonesia, and local crustal carbonate (limestone). Calc-silicate xenoliths within Merapi basaltic-andesite eruptive rocks display textures indicative of intense interaction between magma and crustal carbonate, and Merapi feldspar phenocrysts frequently contain crustally contaminated cores and zones. To resolve the interaction processes between magma and limestone in detail we have performed a series of time-variable decarbonation experiments in silicate melt, at magmatic pressure and temperature, using a Merapi basaltic-andesite and local Javanese limestone as starting materials. We have used in situ analytical methods to determine the elemental and strontium isotope composition of the experimental products and to trace the textural, chemical, and isotopic evolution of carbonate assimilation. The major processes of magma-carbonate interaction identified are: (1) rapid decomposition and degassing of carbonate; (2) generation of a Ca-enriched, highly radiogenic strontium contaminant melt, distinct from the starting material composition; (3) intense CO2 vesiculation, particularly within the contaminated zones; (4) physical mingling between the contaminated and unaffected melt domains; (5) chemical mixing between melts. The experiments reproduce many of the features of magma-carbonate interaction observed in the natural Merapi xenoliths and feldspar phenocrysts. The Ca-rich, high 87Sr/86Sr contaminant melt produced in the experiments is considered as a precursor to the Ca-rich (often 'hyper-calcic') phases found in the xenoliths and the contaminated zones in Merapi feldspars.The xenoliths also exhibit micro-vesicular textures that can be linked to the CO2 liberation process seen in the experiments.This study, therefore, provides well-constrained petrological insights into the problem of crustal interaction at Merapi and points toward the substantial impact of such interaction on the volatile budget of the volcano.

  • 63.
    Deegan, Frances
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Freda, Carmela
    Istituto Nazionale Di Geofisica E Vulcanologia, 00143 Rome, Italy.
    Misiti, Valeria
    Istituto Nazionale Di Geofisica E Vulcanologia, 00143 Rome, Italy.
    Chadwick, Jane P.
    Department of Petrology (Falw), Vrije Universiteit, 1081 Hv Amsterdam, The Netherlands.
    McLeod, C.L.
    Department of Earth Sciences, The University of Durham, Durham Dh1 3Le, Uk .
    Davidson, J.P.
    Department of Earth Sciences, The University of Durham, Durham Dh1 3Le, Uk .
    Magma–Carbonate Interaction Processes and Associated CO2 Release at Merapi Volcano, Indonesia: Insights from Experimental Petrology2010Ingår i: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, nr 5, s. 1027-1051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is considerable evidence for continuing, late-stage interaction between the magmatic system at Merapi volcano, Indonesia, and local crustal carbonate (limestone). Calc-silicate xenoliths within Merapi basaltic-andesite eruptive rocks display textures indicative of intense interaction between magma and crustal carbonate, and Merapi feldspar phenocrysts frequently contain crustally contaminated cores and zones. To resolve the interaction processes between magma and limestone in detail we have performed a series of time-variable decarbonation experiments in silicate melt, at magmatic pressure and temperature, using a Merapi basaltic-andesite and local Javanese limestone as starting materials. We have used in situ analytical methods to determine the elemental and strontium isotope composition of the experimental products and to trace the textural, chemical, and isotopic evolution of carbonate assimilation. The major processes of magma–carbonate interaction identified are: (1) rapid decomposition and degassing of carbonate; (2) generation of a Ca-enriched, highly radiogenic strontium contaminant melt, distinct from the starting material composition; (3) intense CO2 vesiculation, particularly within the contaminated zones; (4) physical mingling between the contaminated and unaffected melt domains; (5) chemical mixing between melts. The experiments reproduce many of the features of magma–carbonate interaction observed in the natural Merapi xenoliths and feldspar phenocrysts. The Ca-rich, high 87Sr/86Sr contaminant melt produced in the experiments is considered as a precursor to the Ca-rich (often ‘hyper-calcic’) phases found in the xenoliths and the contaminated zones in Merapi feldspars. The xenoliths also exhibit micro-vesicular textures that can be linked to the CO2 liberation process seen in the experiments. This study, therefore, provides well-constrained petrological insights into the problem of crustal interaction at Merapi and points toward the substantial impact of such interaction on the volatile budget of the volcano.

  • 64.
    Deegan, Frances
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Freda, Carmela
    Istituto Nazionale Di Geofisica E Vulcanologia, 00143 Rome, Italy.
    Misiti, Valeria
    Istituto Nazionale Di Geofisica E Vulcanologia, 00143 Rome, Italy.
    Chadwick, Jane P.
    Department of Petrology (Falw), Vrije Universiteit, 1081 Hv Amsterdam, The Netherlands.
    McLeod, Claire M.
    Department of Earth Sciences, The University of Durham, Durham Dh1 3Le, UK.
    Davidson, Jon P.
    Department of Earth Sciences, The University of Durham, Durham Dh1 3Le, UK.
    Magma–Carbonate Interaction Processes and Associated CO2 Release at Merapi Volcano, Indonesia: Insights from Experimental Petrology2010Ingår i: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, nr 5, s. 1027-1051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is considerable evidence for continuing, late-stage interaction between the magmatic system at Merapi volcano, Indonesia, and local crustal carbonate (limestone). Calc-silicate xenoliths within Merapi basaltic-andesite eruptive rocks display textures indicative of intense interaction between magma and crustal carbonate, and Merapi feldspar phenocrysts frequently contain crustally contaminated cores and zones. To resolve the interaction processes between magma and limestone in detail we have performed a series of time-variable decarbonation experiments in silicate melt, at magmatic pressure and temperature, using a Merapi basaltic-andesite and local Javanese limestone as starting materials. We have used in situ analytical methods to determine the elemental and strontium isotope composition of the experimental products and to trace the textural, chemical, and isotopic evolution of carbonate assimilation. The major processes of magma–carbonate interaction identified are: (1) rapid decomposition and degassing of carbonate; (2) generation of a Ca-enriched, highly radiogenic strontium contaminant melt, distinct from the starting material composition; (3) intense CO2 vesiculation, particularly within the contaminated zones; (4) physical mingling between the contaminated and unaffected melt domains; (5) chemical mixing between melts. The experiments reproduce many of the features of magma–carbonate interaction observed in the natural Merapi xenoliths and feldspar phenocrysts. The Ca-rich, high 87Sr/86Sr contaminant melt produced in the experiments is considered as a precursor to the Ca-rich (often ‘hyper-calcic’) phases found in the xenoliths and the contaminated zones in Merapi feldspars. The xenoliths also exhibit micro-vesicular textures that can be linked to the CO2 liberation process seen in the experiments. This study, therefore, provides well-constrained petrological insights into the problem of crustal interaction at Merapi and points toward the substantial impact of such interaction on the volatile budget of the volcano.

  • 65.
    Deegan, Frances
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Jolis, Ester Muños
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Freda, C.
    Hilton, D.R.
    Budd, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Gertisser, R.
    Blythe, Lara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Chadwick, J.P.
    Schwarzkopf, L.M.
    Zimmer, M
    The role of CO2-rich basement at Merapi; perspectives from petrology, geochemistry, and experiments2014Konferensbidrag (Refereegranskat)
  • 66.
    Deegan, Frances
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Swedish Museum Nat Hist, Dept Geosci, SE-10405 Stockholm, Sweden..
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Istituto Nazionale di Geofisica e Vulcanologia (INGV), I-00143 Rome, Italy..
    Whitehouse, Martin J.
    Swedish Museum Nat Hist, Dept Geosci, SE-10405 Stockholm, Sweden..
    Jolis, Ester M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Freda, Carmela
    Istituto Nazionale di Geofisica e Vulcanologia (INGV), I-00143 Rome, Italy..
    Boron isotope fractionation in magma via crustal carbonate dissolution2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 30774Artikel i tidskrift (Refereegranskat)
    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.

  • 67. Deegan, Frances
    et al.
    Whitehouse, Martin
    Troll, Valentin
    Budd, David
    Harris, Chris
    Geiger, Harri
    Hålenius, Ulf
    New augite and enstatite pyroxene standards for SIMS oxygen isotope analysis and their application to Merapi volcano, Sunda arc, IndonesiaManuskript (preprint) (Övrigt vetenskapligt)
  • 68. Delcamp, A.
    et al.
    Petronis, M.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Discerning magmatic flow patterns in shallow-level basaltic dykes from the North-East Rift Zone of Tenerife, Spain using the Anisotropy of Magnetic Susceptibility (AMS) technique2014Ingår i: The Use of Palaeomagnetism and Rock Magnetism to Understand Volcanic Processes / [ed] Ort M.H., Porreca M. & Geissmann J.W., Geological Society of London, 2014Kapitel i bok, del av antologi (Refereegranskat)
  • 69. Delcamp, A.
    et al.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    van Wyk de Vries, B.
    Laboratoire Magmas et Volcans CNRS-UMR 6524, Université Blaise Pascal, Laboratoire Magmas et Volcans, LMV, CNRS, UMR 6524, IRD R163, Clermont-Ferrand, France.
    Carracedo, J.C.
    GEOVOL, Dpto. Física, Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain.
    Petronis, M.S.
    Environmental Geology Natural Resource Management Department, New Mexico Highlands University, Las Vegas, NM 87 701, USA.
    Pérez-Torrado, F.J.
    GEOVOL, Dpto. Física, Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain.
    Deegan, Frances
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones2012Ingår i: Bulletin of Volcanology, ISSN 0258-8900, E-ISSN 1432-0819, Vol. 74, nr 5, s. 963-980Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many oceanic island rift zones are associated with lateral sector collapses, and several models have been proposed to explain this link. The North–East Rift Zone (NERZ) of Tenerife Island, Spain offers an opportunity to explore this relationship, as three successive collapses are located on both sides of the rift. We have carried out a systematic and detailed mapping campaign on the rift zone, including analysis of about 400 dykes. We recorded dyke morphology, thickness, composition, internal textural features and orientation to provide a catalogue of the characteristics of rift zone dykes. Dykes were intruded along the rift, but also radiate from several nodes along the rift and form en échelon sets along the walls of collapse scars. A striking characteristic of the dykes along the collapse scars is that they dip away from rift or embayment axes and are oblique to the collapse walls. This dyke pattern is consistent with the lateral spreading of the sectors long before the collapse events. The slump sides would create the necessary strike-slip movement to promote en échelon dyke patterns. The spreading flank would probably involve a basal decollement. Lateral flank spreading could have been generated by the intense intrusive activity along the rift but sectorial spreading in turn focused intrusive activity and allowed the development of deep intra-volcanic intrusive complexes. With continued magma supply, spreading caused temporary stabilisation of the rift by reducing slopes and relaxing stress. However, as magmatic intrusion persisted, a critical point was reached, beyond which further intrusion led to large-scale flank failure and sector collapse. During the early stages of growth, the rift could have been influenced by regional stress/strain fields and by pre-existing oceanic structures, but its later and mature development probably depended largely on the local volcanic and magmatic stress/strain fields that are effectively controlled by the rift zone growth, the intrusive complex development, the flank creep, the speed of flank deformation and the associated changes in topography. Using different approaches, a similar rift evolution has been proposed in volcanic oceanic islands elsewhere, showing that this model likely reflects a general and widespread process. This study, however, shows that the idea that dykes orient simply parallel to the rift or to the collapse scar walls is too simple; instead, a dynamic interplay between external factors (e.g. collapse, erosion) and internal forces (e.g. intrusions) is envisaged. This model thus provides a geological framework to understand the evolution of the NERZ and may help to predict developments in similar oceanic volcanoes elsewhere.

  • 70.
    Delcamp, Audray
    et al.
    Department of Geology, Trinity College, Dublin, Dublin 2, Ireland.
    Petronis, M. S.
    Environmental Geology Natural Resource Management Department, New Mexico Highlands University, Las Vegas, New Mexico, 87 701, USA.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Carracedo, Juan Carlos
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    van Wyk de Vries, B.
    Laboratoire Magmas et Volcans CNRS-UMR 6524, Observatoire du Physique du Globe de Clermont Université Blaise Pascal, Clermont-Ferrand, France.
    Pérez-Torrado, Francisco José
    Departamento de Física-Geología, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain.
    Vertical axis rotation of the upper portions of the north-east rift of Tenerife Island inferred from paleomagnetic data2010Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 492, nr 1-4, s. 40-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Paleomagnetic sampling sites were established in 82 dykes along an 8 km long section of the north-east rift-zone (NERZ) of Tenerife, Canary Islands, Spain. Of the 70 interpretable sites, 16 are of normal polarity and 54 of reversed polarity. Four normal polarity sites and fifteen reverse polarity sites were excluded from the grand mean calculation for statistical reasons. After inverting the reverse polarity sites through the origin, the in-situ grand mean yields a declination (D) = 023.8°, an inclination (I) = 42.3°, α95 = 3.2°, ĸ = 39.0, N = 51 that is discordant to the expected late Miocene to Pleistocene field direction (D = 357.6°, I = 38.8°, α95 = 4.7°). This discordance can be explained as either a 26° clockwise vertical axis rotation or a 28° WNW-side-down-tilt about an average 009° horizontal tilt axis. The sampled section is composed of numerous semi-vertical dykes cutting mainly lava flow units that are sub-horizontal and cross-cut by steeply dipping faults (70°–90°). Field evidence is therefore more compatible with a vertical-axis rotation rather than a horizontal axis tilt of the drilled units. We argue that this clockwise vertical-axis rotation is likely related to strike-slip movements that occurred along the edges of the collapse scars and accommodate the emplacement and growth of the underlying intrusive core and associated dykes. Six new 40Ar/39Ar age determinations constrain the main interval of dyke emplacement within the NERZ between 0.99 Ma and 0.56 Ma. The intrusive activity in the sampled section of the rift appears to have been almost continuous, with several intrusion pulses that are probably related to flank destabilisation event(s) during the mid Pleistocene. Our study thus demonstrates a long-lived, multi-faceted history that shaped the NERZ.

  • 71.
    Di Baldassarre, Giuliano
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.;IHE Delft Inst Water Educ, Delft, Netherlands..
    Nohrstedt, Daniel
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Statsvetenskapliga institutionen. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Mård, Johanna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Burchardt, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Albin, Cecilia
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för freds- och konfliktforskning. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Bondesson, Sara
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Statsvetenskapliga institutionen. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.; Swedish Def Univ, Stockholm, Sweden..
    Breinl, Korbinian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Deegan, Frances M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Fuentes, Diana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Lopez, Marc Girons
    Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.;Univ Zurich, Dept Geog, Zurich, Switzerland..
    Granberg, Mikael
    Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.;Karlstad Univ, Ctr Climate & Safety, Karlstad, Switzerland..
    Nyberg, Lars
    Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.;Karlstad Univ, Ctr Climate & Safety, Karlstad, Switzerland..
    Nyman, Monika Rydstedt
    Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.;Karlstad Univ, Ctr Climate & Safety, Karlstad, Switzerland..
    Rhodes, Emma
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    Young, Stephanie
    Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.;Swedish Def Univ, Stockholm, Sweden..
    Walch, Colin
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för freds- och konfliktforskning. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden.; Univ Calif Berkeley, Dept Polit Sci, Berkeley, CA USA..
    Parker, Charles F.
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Statsvetenskapliga institutionen. Ctr Nat Hazards & Disaster Sci CNDS, Uppsala, Sweden..
    An Integrative Research Framework to Unravel the Interplay of Natural Hazards and Vulnerabilities2018Ingår i: Earth's Future, ISSN 1384-5160, E-ISSN 2328-4277, Vol. 6, nr 3, s. 305-310Artikel i tidskrift (Refereegranskat)
    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.

  • 72. Donoghue, Eleanor
    et al.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Harris, Chris
    Fluid-Rock Interaction in the Miocene, Post-Caldera, Tejeda Intrusive Complex, Gran Canaria (Canary Islands): Insights from Mineralogy, and O- and H-Isotope Geochemistry2010Ingår i: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, nr 10, s. 2149-2176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The intra-caldera volcaniclastic deposits of the Miocene Tejeda caldera on Gran Canaria host an similar to 12 km diameter intrusive complex comprising a peralkaline, trachytic to phonolitic cone sheet swarm surrounding a central core of hypabyssal syenite stocks. Both intrusive rock types display textural and mineralogical features indicative of secondary fluid-rock interaction, including (1) deuteric mineral phases (e.g. aegirine, alkali-amphibole, analcime), (2) turbid alkali feldspars, and (3) hydrothermal mineral phases (phyllosilicates, Fe-Ti oxides, Mn-oxides, and quartz). Altered cone sheets have whole-rock delta O-18 values ranging from 0 center dot 1 to 10 center dot 0 parts per thousand (n = 22), and whole-rock delta D values between -62 and -149 parts per thousand (n = 28). Three altered syenite samples have whole-rock delta O-18 values of 2 center dot 5, 1 center dot 5, and 0 center dot 9 parts per thousand, and corresponding delta D values of -91, -99, and -121 parts per thousand. The H2O concentrations of the altered cone sheets range from 0 center dot 4 to 0 center dot 8 wt % (n = 28), and the altered syenites have H2O concentrations of 0 center dot 5, 0 center dot 5, and 0 center dot 6 wt %, respectively. The majority of altered samples are depleted in O-18 relative to the typical delta O-18 range for unaltered trachytes and syenites (delta O-18 = 6-8 parts per thousand), indicative of interaction with local meteoric water (delta O-18 c. -8 parts per thousand) at temperatures epsilon 150 degrees C. Only one cone sheet sample appears petrographically unaltered and has a typical 'igneous' isotopic composition (delta O-18 = 7 center dot 1 parts per thousand, delta D = -48 parts per thousand) and a relatively high H2O concentration (2 center dot 2 wt %). A weak correlation (r = 0 center dot 55) between delta D and H2O is observed in the cone sheets, reflecting the combined effects of magmatic H2O exsolution, and subsequent deuteric and hydrothermal alteration. No systematic variation in delta O-18 or delta D was detected across the cone sheet swarm, most likely reflecting overprinting of isotopic compositions during successive intrusive events. However, the highest delta O-18 values (8 center dot 2-10 center dot 0 parts per thousand) occur in clay-bearing cone sheets from the central part of the intrusive complex, suggesting enhanced infiltration of relatively cool meteoric water in this area. Overall, at least three phases of fluid-rock interaction can be distinguished: (1) deuteric alteration (c. 300-500 degrees C) by late magmatic fluids expelled from a solidifying crystal mush; (2) hydrothermal alteration (epsilon 150-300 degrees C) by meteoric water during the final stages of crystallization and/or immediately following solidification of the intrusive complex; (3) retrograde alteration related to the influx of relatively cool (150 degrees C) meteoric waters.

  • 73.
    Donoghue, Eleanor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. Trinity College Dublin.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Schwarzkopf, Lothar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. GeoDocCon.
    Goodhue, Robbie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. Trinity College Dublin.
    Clayton, Geoff
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. Trinity College Dublin.
    Organic coatings on blocks in block and ash flow deposits form Merapi volcano, Java, Indonesia.2008Ingår i: Geological Magazine, Vol. (in press)Artikel i tidskrift (Refereegranskat)
  • 74. Emeleus, C. H.
    et al.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    The Rum Igneous Centre, Scotland2014Ingår i: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 78, nr 4, s. 805-839Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The publication of the British Geological Survey memoir on Rum and the Small Isles in 1997 was followed by a period of intense petrological and mineralogical research, leading to some 40 papers, books and other publications. The research progress since then is reviewed here and integrated with the information previously available to provide an overview of the current status of understanding of the centre. New data on the acidic and mixed acid/basic magmas of the early Rum caldera demonstrate that frequent mafic replenishments were the main driver for magmatic activity at Rum right from its initial stages. The caldera is bound by the Main Ring Fault, a structure which probably also exercised an influence on the emplacement of the subsequent basic and ultrabasic intrusions. The later emplacement of gabbros and ultrabasic rocks caused only limited thermal metamorphism of the surrounding Torridonian sandstones, contrasting markedly with the crustal isotope signatures of the early intra-caldera ignimbrite magmas and the intense alteration of uplifted masses of Lewisian gneiss within the ring fault. Rare picritic dykes provide an indication of the possible parent magma for the mafic and ultrabasic rocks, but these, as with most other magmatic rocks on Rum, have undergone varying degrees of crustal contamination, involving both Lewisian granulite and amphibolite-type crust but, notably, no Moine metasedimentary compositions as is the case at the nearby Ardnamurchan centre. Detailed textural studies on the gabbroic and ultrabasic rocks allow a distinction between intrusive peridotites and peridotite that forms part of the classic layered cumulate units of Rum and, furthermore, this work and that on the chromite seams and veins in these rocks shows that movement of trapped magma and magma derived from later intrusions, may produce textures regarded previously as of primary cumulate origin. Sulfides in the chromitite seams and ultrabasic rocks, in turn, show possible influences from assimilated Mesozoic sediments. Igneous activity on Rum was short-lived, possibly only between 0.5 and 1 m.y. in duration and commenced at similar to 60.5 Ma. The Rum Central Complex was extinct by the time the main activity at the nearby Skye Central Complex commenced (similar to 59 Ma). From recent apatite fission-track studies it seems probable that Rum, in common with other Palaeogene centres, underwent a brief, but significantly later heating event (similar to 45 Ma).

  • 75. Emeleus, C. Henry
    et al.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Chew, David M.
    Meade, Fiona C.
    Lateral versus vertical emplacement in shallow-level intrusions?: The Slieve Gullion Ring-complex revisited2012Ingår i: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 169, nr 2, s. 157-171Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent studies on shallow-level arcuate intrusions have identified numerous examples of horizontal mineral fabrics. These are commonly interpreted as reflecting considerable lateral flow during magma emplacement, thus querying established 'semi-vertical' ring-dyke models. We question the recent lateral emplacement model proposed for the Palaeocene Slieve Gullion Ring-complex, NE Ireland, where the absence of steep fabrics in parts of the ring-complex has been used to support a shallow, semi-horizontal sheet intrusion mechanism. We argue that such simple flow models cannot be applied to explosive ring-fissure eruptions and that fabric data alone do not warrant rejection of the ring-dyke model. Moreover, the apparent 'absence of steep intrusive contacts' along the intrusion's perimeter is readdressed and we present numerous examples of outcrops (27) with steep-sided geometries. The Camlough Breccias are reinterpreted as the product of gas-driven tuffisites injected along the active ring-fault (rather than of purely tectonic origin). Crucially, the porphyritic microgranite and porphyritic rhyolite ring-dyke rocks exhibit geochemical and petrographic signatures of contamination by the geographically restricted Palaeozoic Newry granodiorite and are best explained through crustal interaction vertically beneath the ring-complex. Subsequently, these silicic magmas rose into ignimbrite feeders along a caldera ring-fault system that was emplaced into near-surface vent-filling breccias.

  • 76.
    Emeleus, C.H.
    et al.
    Department of Earth Sciences, Durham University, Durham DH1 3LE, UK .
    Troll, Valentin R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Recent research developments on the Isle of Rum, NW Scotland2011Ingår i: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 27, nr 5, s. 184-193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The appearance in 1997 of the British Geological Survey's memoir on Rum was followed by a period of intense research, leading to upwards of 35 papers, books and other articles. The scope of these publications, and the research progress over the last 15 years since publication of the memoir, is reviewed here. Igneous activity on Rum was short lived, possibly only ca. 500 ka, and, at about 60.5 Ma. The Rum central complex thus pre-dates the nearby Skye central complex. The earliest, acidic and mixed acidic/basic magmatism on Rum involved both shallow intrusions and ignimbrite eruptions into a collapsing caldera bound by the Main Ring Fault, a structure which probably also exercised a structural influence on subsequent mafic and ultrabasic magmatism. Subsequent emplacement of gabbros and ultrabasic rocks caused only limited thermal metamorphism of the surrounding Torridonian sandstones, contrasting markedly with the intense alteration of uplifted masses of Lewisian gneiss within the ring fault. Detailed textural studies on the gabbroic and ultrabasic rocks allow distinction between intrusive peridotites and peridotite that formed as part of the classic layered units of Rum and, furthermore, this work and that on the chromite seams and veins in these rocks shows that movements of trapped magma and magma derived from later intrusions, may produce textures and structures hitherto regarded as primary features of cumulate rocks. Rare picritic dykes provide an indication of likely parent magma for the mafic and ultrabasic rocks, but these and other magmatic rocks on Rum have all undergone varying degrees of crustal contamination, involving both Lewisian granulite and amphibolite crust but, notably, not Moine rocks as at Ardnamurchan. Sulphides in the chromite seams and ultrabasic rocks show possible influences from assimilated Jurassic sediments. From recent apatite fission track studies it seems likely that Rum, in common with other Palaeogene centres, underwent a brief, but significantly younger (Mesozoic) heating event.

  • 77.
    Emeleus, Henry
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. Durham University.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    The Palaeocene Igneous Rocks of the Isle of Rum, Scotland2008Bok (Refereegranskat)
  • 78. Galland, O.
    et al.
    Burchardt, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Volcanic and Igneous Plumbing Systems: State-of-the-art and future developments2013Ingår i: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 94, nr 18, s. 169-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamics of volcanic and igneous plumbing systems (VIPS) are governed by complex interacting chemical and mechanical processes, which control how magmas stall or propagate through the Earth's crust, the way they are emplaced, and the dynamics of their eruption. In addition, these processes control dramatic volcanotectonic phenomena such as caldera and sector collapse. Traditionally, the study of the dynamics of VIPS is method based, and relatively limited bridges between the distinct methodological approaches exist. Consequently, studies that employ different methods often lead to contradictory conclusions, illustrating a need for integrated multidisciplinary research approaches.

  • 79. Ganerod, M.
    et al.
    Chew, D. M.
    Smethurst, M. A.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Corfu, F.
    Meade, F.
    Prestvik, T.
    Geochronology of the Tardree Rhyolite Complex, Northern Ireland: Implications for zircon fission track studies, the North Atlantic Igneous Province and the age of the Fish Canyon sanidine standard2011Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 286, nr 3-4, s. 222-228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The British-Irish Palaeogene Igneous Province (BIPIP) is part of the larger North Atlantic Igneous Province and includes the lava fields of Antrim, Mull, and Skye. The Tardree Rhyolite Complex (TRC) in Northern Ireland forms an important stratigraphic unit between the Lower and Upper Basalt Formations of the Antrim Lava Group (ALG). Previous zircon age determinations obtained from the TRC have been used as a standard in zircon fission track studies, but contradict several (40)Ar/(39)Ar sanidine and U-Pb zircon results. We provide new (40)Ar/(39)Ar sanidine and U-Pb CA-TIMS zircon ages which resolve this discrepancy. Two sanidine samples from the Sandy Braes vent and the columnar-jointed dome-forming rhyolites of Tardree Forest yield a weighted mean (40)Ar/(39)Ar age of 61.13 +/- 0.42 Ma (2 sigma, internal error). Ten U-Pb CA-TIMS zircon analyses were undertaken, eight of which employed the CA-TIMS approach on both multi-grain fractions and single grains. Six of the CA-TIMS data yield a disequilibrium-corrected weighted mean (206)Pb-(238)U age of 61.32 +/- 0.09 Ma (2 sigma). The consistency of the (40)Ar/(39)Ar ages with the CA-TIMS U-Pb zircon age, points to a closed system of both K and Ar since eruption. We propose that the crystallization age of the TRC be taken as 61.32 +/- 0.09 Ma and that the currently used age of the zircon fission track standard (58.4 +/- 0.7 Ma) be changed accordingly. This also places the eruption of the TRC in magnetochron C26r, which is consistent with the reversed polarity magnetic remanence observed in the ALG, and supports the conclusion of Ganered et al. (2010) that the Lower Basalt Formation is older than the Vaigat Formation in Western Greenland. No resolvable zircon inheritance has been detected by the TIMS analyses, consistent with the fact that the temporal and geographic extent of rhyolitic magmatism within this sector of the BIPIP was very limited, and hence was unlikely to provide inherited magmatic zircons from slightly older magmas (antecrysts). Potentially older zircon xenocrysts would be derived from the underlying Caledonian basement (>400 Ma) or yet older rocks. These should be easily detectable if the Tardree zircon was to be employed as a U-Pb zircon standard. The paired (40)Ar/(39)Ar and (206)Pb-(238)U results from this study indicate an age of 28.393 +/- 0.194 Ma for the widely used Fish Canyon sanidine standard and gives further support to the recent calibrations of Kuiper et al. (2008) and Renne et al. (2010).

  • 80. Gardner, M.
    et al.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Gamble, J.
    Gertisser, R.
    Hart, G.
    Ellam, R.
    Harris, C.
    Wolff, J.
    Crustal differentiation processes at Krakatau volcano, Indonesia2013Ingår i: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 54, nr 1, s. 149-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anak Krakatau is a basaltic andesite cone that has grown following the famous caldera-forming 1883 eruption of Krakatau. It breached sea level in 1927 and since the 1950s has been growing at an average rate of similar to 8 cm a week. We present new major and trace element data combined with whole-rock delta O-18, Sr and Nd isotope data for 1883, 1993 and 2002 Krakatau eruptive products and the surrounding crust. Bombs erupted from Anak Krakatau during 2002 contain frothy metasedimentary and plutonic xenoliths that show variable degrees of thermal metamorphism, plastic deformation and partial melting. Contact-metamorphic minerals such as cordierite and tridymite in metasedimentary xenoliths are consistent with high-temperature metamorphism and incorporation at mid- to upper-crustal depth. Energy-constrained assimilation and fractional crystallization modelling of whole-rock data suggests that the Anak Krakatau magmas have a genetic relationship with the 1883 eruption products. The geochemical impact of crustal contaminants on whole-rock compositions is apparently small, and we conclude that low levels of assimilation of a quartzo-feldspathic sediment are recorded in Anak Krakatau magmas. Plagioclase phenocrysts from the 2002 eruption exhibit disequilibrium textures and complex compositional zoning, however, and are also isotopically variable with a total range in Sr-87/Sr-86 of 0 center dot 7043-0 center dot 7048 as determined by in situ laser ablation inductively coupled plasma mass spectrometry. This suggests that although shallow crustal assimilation appears to have had a limited effect on whole-rock chemistry, a complex late-stage differentiation history is recorded within the magma's cargo of crystals and xenoliths.

  • 81.
    Geiger, Harri
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Barker, Abigail K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Univ Las Palmas Gran Canaria, Dept Phys GEOVOL, La Palmas Gran Canaria, Spain.
    Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 33629Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano’s underlying magma supply system is sparse. To characterize Mt. Cameroon’s magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano’s two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs.

  • 82.
    Geiger, Harri
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Univ Padjajaran UNPAD, Fac Geol Engn, Bandung, Indonesia;Ist Nazl Geofis & Vulcanol, Rome, Italy.
    Jolis, Ester M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Geomar Helmholtz Ctr Ocean Res, Kiel, Germany.
    Deegan, Frances M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ist Nazl Geofis & Vulcanol, Rome, Italy.
    Harris, Chris
    Univ Cape Town, Dept Geol Sci, Cape Town, South Africa.
    Hilton, David R.
    Scripps Inst Oceanog, Geosci Res Div, La Jolla, CA USA.
    Freda, Carmela
    Ist Nazl Geofis & Vulcanol, Rome, Italy.
    Multi-level magma plumbing at Agung and Batur volcanoes increases risk of hazardous eruptions2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 10547Artikel i tidskrift (Refereegranskat)
    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.

  • 83. Gertisser, R.
    et al.
    Charbonnier, S.J.
    Troll, Valentin R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Keller, J.
    Preece, K.
    Chadwick, J.P.
    Barclay, J.
    Herd, R.A.
    Merapi (Java, Indonesia): anatomy of a killer volcano2011Ingår i: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 27, nr 2, s. 57-62Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Merapi is Indonesia's most dangerous volcano with a history of deadly eruptions. Over the past two centuries, the volcanic activity has been dominated by prolonged periods of lava dome growth and intermittent gravitational or explosive dome failures to produce pyroclastic flows every few years. Explosive eruptions, such as in 2010, have occurred occasionally during this period, but were more common in pre-historical time, during which a collapse of the western sector of the volcano occurred at least once. Variations in magma supply from depth, magma ascent rates and the degassing behaviour during ascent are thought to be important factors that control whether Merapi erupts effusively or explosively. A combination of sub-surface processes operating at relatively shallow depth inside the volcano, including complex conduit processes and the release of carbon dioxide into the magmatic system through assimilation of carbonate crustal rocks, may result in unpredictable explosive behaviour during periods of dome growth. Pyroclastic flows generated by gravitational or explosive lava dome collapses and subsequent lahars remain the most likely immediate hazards near the volcano, although the possibility of more violent eruptions that affect areas farther away from the volcano cannot be fully discounted. In order to improve hazard assessment during future volcanic crises at Merapi, we consider it crucial to improve our understanding of the processes operating in the volcano's plumbing system and their surface manifestations, to generate accurate hazard zonation maps that make use of numerical mass flow models on a realistic digital terrain model, and to utilize probabilistic information on eruption recurrence and inundation areas.

  • 84.
    Goodenough, Kathryn
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. BGS edinburgh.
    Emeleus, Henry
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. Durham University.
    Jerram, Dougal
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi. Durham University.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Golden Rum – understanding the ‘Forbidden Isle’2008Ingår i: Geoscientist, Vol. 18, nr 3, s. 22-24Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 85.
    Halldórsson, S.A.
    et al.
    Fluids and Volatiles Laboratory, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244, USA.
    Hilton, D.R.
    Fluids and Volatiles Laboratory, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244, USA.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Fischer, T.P.
    Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131-1116, USA.
    Resolving volatile sources along the western Sunda arc, Indonesia2013Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 339, nr SI, s. 263-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the chemical and isotope (HeCN) characterization of active fumaroles and hydrothermal gases and waters from the summits and flanks of 19 volcanic centers along the western Sunda arc, Indonesia. Samples were collected over two field expeditions (1991 and 2010) and cover 13 volcanic centers in Sumatra, 5 in Java and one in Bali. In addition, we present data from three geothermal sites in Sumatra associated with active fault systems in-between volcanic centers (IBVC). The overall aim is to resolve volatiles associated with the sub-arc mantle (subducting slab and mantle wedge) from inputs derived from the over-riding arc crust. The western Sunda arc is a prime locality to assess controls on volatile provenance at subduction zones due to changes in composition and thickness of over-riding crust and variations in sediment input rates along the strike of the arc.

    The dry gas chemistry of the majority of volcanic samples is dominated by CO2 with inert gas variations (HeArN2) typical of subduction zone gases. However, there is a strong crustal control on the HeCO2 isotope and relative abundance systematics on a number of volcanic centers: this effect is most clearly observed at flank localities and in water phase samples. Filtering the entire database for modifications due to air contamination, degassing-induced fractionation (C-isotopes and CO2/3He ratios) and crustal contamination associated with volatile transport within shallow-level hydrothermal systems allows recognition of the magmatic volatile signature of individual volcanoes along the arc. Helium isotopes at all but two volcanic centers (Talang and Dempo on Sumatra) range from 5.3 RA to 8.1 RA (RA = air 3He/4He) pointing to the mantle wedge as the principal source of He but with a small input of crustal (radiogenic) He at some localities. Samples from Java and Bali span an even more limited range (6.6 to 7.9 RA) implying a relatively smaller input of crustal He. Carbon isotope and CO2/3He ratios vary from − 1.4‰ to − 6.4‰ and 4.38 to 150 (× 109), respectively, with higher and more variable values to the north of Sumatra. This latitudinal effect is not apparent in air-corrected N-isotope values (δ15NC = − 3.91 to + 5.92‰) or various elemental ratios such as N2/Ar and N2/He. The three IBVC sites, all located in Sumatra, have significantly lower 3He/4He ratios (< 3.6 RA) with CO2/3He values both higher and lower than volcanic centers. Their δ13C, δ15NC and gas ratios overlap with the volcanic centers.

    The elemental and isotopic characteristics of carbon and helium have been modified at IBVC sites due to crustal processes. However, based upon relationships between CH4 and 3He as well as co-variations between HeCN isotopes, the over-riding crust and associated sediments add minimal volatiles to volcanic centers throughout the western Sunda arc. In turn, subducted sediment, particularly the Nicobar Fan which supplies Himalayan-derived sediment to the slab off Sumatra, exerts a strong control on the magmatic CO2 characteristics although it is less influential for N2. In spite of large sections of incoming sedimentary material being off-scraped during subduction, our data suggest that a significant fraction must enter the trench, enhancing fluid/melt production in the mantle wedge. We propose that subduction-related source contamination plays the dominant role over thick/old crustal basement in supplying the major volatile output budget of the western Sunda arc.

  • 86. Holohan, E.P.
    et al.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Errington, M.
    Donaldson, C.H.
    Nicoll G.R., G.R.
    Emeleus, C.H.
    The Southern Mountains Zone, Isle of Rum, Scotland: volcanic and sedimentary processes upon an uplifted and subsided magma chamber roof2009Ingår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 146, nr 3, s. 400-418Artikel i tidskrift (Refereegranskat)
  • 87. Holohan, E.P.
    et al.
    Walter, T.R.
    Schöpfer, M.P.J.
    Walsh, J.J.
    van Wyk de Vries, B.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Origins of oblique-slip faulting during caldera subsidence2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 4, s. 1778-1794Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although conventionally described as purely dip-slip, faults at caldera volcanoes may have a strike-slip displacement component. Examples occur in the calderas of Olympus Mons (Mars), Miyakejima (Japan) and Dolomieu (La Reunion). To investigate this phenomenon, we ran numerical and analog simulations of caldera subsidence caused by magma reservoir deflation. The numerical models constrain mechanical causes of oblique-slip faulting from the three-dimensional stress field in the initial elastic phase of subsidence. The analog experiments directly characterize the development of oblique-slip faulting, especially in the later, non-elastic phases of subsidence. The combined results of both approaches can account for the orientation, mode and location of oblique-slip faulting at natural calderas. Kinematically, oblique-slip faulting originates to resolve: (1) horizontal components of displacement that are directed radially toward the caldera centre; and (2) horizontal translation arising from off-centered or ‘asymmetric’ subsidence. We informally call these two origins the “camera iris” and “sliding trapdoor” effects, respectively. Our findings emphasize the fundamentally three-dimensional nature of deformation during caldera subsidence. They hence provide an improved basis for analyzing structural, geodetic and geophysical data from calderas, as well as analogous systems, such as mines and producing hydrocarbon reservoirs.

  • 88.
    Högdahl, Karin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Nilsson, K.P.
    Jonsson, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Structural evolution of the apatite-iron oxide deposit at Grängesberg, Bergslagen, Sweden2013Ingår i: Mineral deposit research for a high-tech world, s. 1650-1553Artikel i tidskrift (Refereegranskat)
  • 89.
    Jamshidi, K.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Ghasemi, H.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Sadeghian, M.
    Dahrén, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Magma storage and plumbing of adakite-type post-ophiolite intrusions in the Sabzevar ophiolitic zone, northeast Iran2015Ingår i: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 6, nr 1, s. 49-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Subduction-related adakite-type intrusive rocks emplaced into the late Cretaceous-Paleocene Sabzevar ophiolite zone, northeast Iran, range from Mg-andesite to rhyodacite in composition. Here we investigate the magma supply system to these subvolcanic intrusive rocks by applying thermobarometric mineral and mineral-melt equilibrium models, including amphibole thermobarometry, plagioclase-melt thermobarometry and clinopyroxene-melt barometry. Based on the results of these thermobarometric models, plagioclase crystallized dominantly at pressures of similar to 350 (130 to 468) MPa, while amphiboles record both low pressures (similar to 300 MPa) and very high pressures (> 700 MPa) of crystallization. The latter is supported by the calculated pressures for clinopyroxene crystallization (550 to 730 MPa). The association of amphibole with clinopyroxene and no plagioclase in the most primitive samples (Mg-andesites) is consistent with amphibole fractionation from very hydrous magmas at deep crustal levels of the plumbing system, which may have been a key process in intensifying adakite-type affinities in this rock suite. Barometry, combined with frequent disequilibrium features such as oscillatory-zoned and sieve-textured plagioclase crystals with An-rich overgrowths in more evolved samples, implies that final magma differentiation occurred in an open upper crustal magma system that developed progressively stronger compositional modifications during high-level magma storage.

  • 90. Jaxybulatov, Kairly
    et al.
    Koulakov, Ivan
    Ibs-von Seht, Malte
    Klinge, Klaus
    Reichert, Christian
    Dahrén, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Evidence for high fluid/melt content beneath Krakatau volcano (Indonesia) from local earthquake tomography2011Ingår i: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 206, nr 3-4, s. 96-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Within the KRAKMON project for multiparameter monitoring of Anak Krakatau volcano (Indonesia), a network of temporary stations was installed on the islands of the Krakatau complex as well as in the surrounding areas of the Sunda Strait, Sumatra and Java. The network was operated from June 2005 until January 2006. More than 700 local events were recorded during this experiment, and travel times from these events were used to perform a tomographic inversion for P and S velocities and for the Vp/Vs ratio. In this study, special attention was paid to the validation of the computed model based on different tests, such as inversion of independent data subsets and synthetic modeling. Although the network configuration and the distribution of the events are not favorable for high-quality tomographic imaging, we have obtained some important and robust features which give information about sources of volcanic activity in the Krakatau complex. The most interesting feature of this study is a zone of high Vp/Vs ratio beneath the Krakatau complex. At depths down to 4 km depth we observe anticorrelation of higher P- and lower S-velocities that leads to Vp/Vs ratio higher than 2. This is a probable indicator of the presence of partially molten and/or with high fluid content material with a composition corresponding to deeper layers. It is important that the anomaly of high Vp/Vs ratio beneath the Krakatau complex appears to be separated in two parts at a depth of 5-6 km. This fits to results of geobarometric analysis that presume the existence of several levels of magma chambers beneath Anak Krakatau.

  • 91.
    Jeffery, Adam J.
    et al.
    School of Physical and Geographical Sciences, Keele University, UK.
    Gertisser, Ralf
    School of Physical and Geographical Sciences, Keele University, UK.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Jolis, Ester M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Dahrén, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Harris, Chris
    University of Cape Town, South Africa.
    Tindle, Andrew G.
    CEPSAR (Centre for Earth, Planetary, Space and Astronomy Research), The Open University, UK.
    Preece, Katie
    University of East Anglia.
    O'Driscoll, Brain
    Humaida, Hanik
    Balai Penyelidikan dan Pengembangan Teknologi, Indonesia.
    Chadwick, Jane P.
    Science Gallery, Trinity College Dublin, Dublin.
    The pre-eruptive magma plumbing system of the 2007–2008 dome-forming eruption of Kelut volcano, East Java, Indonesia2013Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 166, nr 1, s. 275-308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Kelut volcano, East Java, is an active volcanic complex hosting a summit crater lake that has been the source of some of Indonesia’s most destructive lahars. In November 2007, an effusive eruption lasting approximately 7 months led to the formation of a 260-m-high and 400-m-wide lava dome that displaced most of the crater lake. The 2007–2008 Kelut dome comprises crystal-rich basaltic andesite with a texturally complex crystal cargo of strongly zoned and in part resorbed plagioclase (An47–94), orthopyroxene (En64–72, Fs24–32, Wo2–4), clinopyroxene (En40–48, Fs14–19, Wo34–46), Ti-magnetite (Usp16–34) and trace amounts of apatite, as well as ubiquitous glomerocrysts of varying magmatic mineral assemblages. In addition, the notable occurrence of magmatic and crustal xenoliths (meta-basalts, amphibole-bearing cumulates, and skarn-type calc-silicates and meta-volcaniclastic rocks) is a distinct feature of the dome. New petrographical, whole rock major and trace element data, mineral chemistry as well as oxygen isotope data for both whole rocks and minerals indicate a complex regime of magma-mixing, decompression-driven resorption, degassing and crystallisation and crustal assimilation within the Kelut plumbing system prior to extrusion of the dome. Detailed investigation of plagioclase textures alongside crystal size distribution analyses provide evidence for magma mixing as a major pre-eruptive process that blends multiple crystal cargoes together. Distinct magma storage zones are postulated, with a deeper zone at lower crustal levels or near the crust-mantle boundary (>15 km depth), a second zone at mid-crustal levels (~10 km depth) and several magma storage zones distributed throughout the uppermost crust (<10 km depth). Plagioclase-melt and amphibole hygrometry indicate magmatic H2O contents ranging from ~8.1 to 8.6 wt.% in the lower crustal system to ~1.5 to 3.3 wt.% in the mid to upper crust. Pyroxene and plagioclase δ18O values range from 5.4 to 6.7 ‰, and 6.5 to 7.6 ‰, respectively. A single whole rock analysis of the 2007–2008 dome lava gave a δ18O value of 7.6 ‰, whereas meta-basaltic and calc-silicate xenoliths are characterised by δ18O values of 6.2 and 10.3 ‰, respectively. Magmatic δ18O values calculated from individual pyroxene and plagioclase analyses range from 5.7 to 7.0 ‰, and 6.2 to 7.4 ‰, respectively. This range in O-isotopic compositions is explained by crystallisation of pyroxenes in the lower to mid-crust, where crustal contamination is either absent or masked by assimilation of material having similar δ18O values to the ascending melts. This population is mixed with isotopically distinct plagioclase and pyroxenes that crystallised from a more contaminated magma in the upper crustal system. Binary bulk mixing models suggest that shallow-level, recycled volcaniclastic sedimentary rocks together with calc-silicates and/or limestones are the most likely contaminants of the 2007–2008 Kelut magma, with the volcaniclastic sediments being dominant.

  • 92.
    Jerram, Dougal A.
    et al.
    Department of Earth Sciences, University of Durham, South Road, Durham DH1 3LE, UK.
    Goodenough, Kathryn M.
    British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Introduction: from the British Tertiary into the future – modern perspectives on the British Palaeogene and North Atlantic Igneous provinces2009Ingår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 146, nr 3, s. 305-308Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The study of volcanic rocks and igneous centres has long been a classic part of geological research. Despite the lack of active volcanism, the British Isles have been a key centre for the study of igneous rocks ever since ancient lava flows and excavated igneous centres were recognized there in the 18th century (Hutton, 1788). This led to some of the earliest detailed studies of petrology. The starting point for many of these studies was the British Palaeogene Igneous Province (BPIP; formerly known as the ‘British Tertiary’ (Judd, 1889), and still recognized by this name by many geologists around the globe). This collection of lavas, volcanic centres and sill/dyke swarms covers much of the west of Scotland and the Antrim plateau of Northern Ireland, and together with similar rocks in the Faroe Islands, Iceland and Greenland forms a world-class Large Igneous Province. This North Atlantic Igneous Province (NAIP) began to form through continental rifting above a mantle plume at c. 60 Ma, and subsequently evolved as North America separated from Europe, creating the North Atlantic Ocean.

  • 93.
    Jolis, E. M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, V. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Deegan, F. M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Blythe, L. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Harris, C.
    Freda, C.
    Hilton, D.
    Chadwick, J.
    van Helden, M.
    Tracing crustal contamination along the Java segment of the Sunda Arc, Indonesia2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Arc magmas typically display chemical and petrographic characteristics indicative of crustal input. Crustal contamination can take place either in the mantle source region or as magma traverses the upper crust (e.g. [1]). While source contamination is generally considered the dominant process (e.g. [2]), late-stage crustal contamination has been recognised at volcanic arcs too (e.g. [3]). In light of this, we aim to test the extent of upper crustal versus source contamination along the Java segment of the Sunda arc, which, due its variable upper crustal structure, is an exemplary natural laboratory. We present a detailed geochemical study of 7 volcanoes along a traverse from Anak-Krakatau in the Sunda strait through Java and Bali, to characterise the impact of the overlying crust on arc magma composition. Using rock and mineral elemental geochemistry, radiogenic (Sr, Nd and Pb) and, stable (O) isotopes, we show a correlation between upper crustal composition and the degree of upper crustal contamination. We find an increase in 87Sr/86Sr and δ18O values, and a decrease in 143Nd/144Nd values from Krakatau towards Merapi, indicating substantial crustal input from the thick continental basement present. Volcanoes to the east of Merapi and the Progo-Muria fault transition zone, where the upper crust is thinner, in turn, show considerably less crustal input in their isotopic signatures, indicating a stronger influence of the mantle source. Our new data represent a systematic and high-resolution arc-wide sampling effort that allows us to distinguish the effects of the upper crust on the compositional spectrum of individual volcanic systems along the Sunda arc. [1] Davidson, J.P, Hora, J.M, Garrison, J.M & Dungan, M.A 2005. Crustal Forensics in Arc Magmas. J. Geotherm. Res. 140, 157-170; [2] Debaille, V., Doucelance, R., Weis, D., & Schiano, P. 2005. Geochim. Cosmochim. Acta, 70,723-741; [3] Gasparon, M., Hilton, D.R., & Varne, R. 1994. Earth Planet. Sci. Lett., 126, 15-22.

  • 94.
    Jolis, E. M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, V. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Deegan, F. M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Blythe, L. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Harris, C
    Freda, C
    Hilton, D.
    Chadwick, J.
    van Helden, M.
    Tracing crustal contamination along the Java segment of the Sunda Arc, Indonesia2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Arc magmas typically display chemical and petrographic characteristics indicative of crustal input. Crustal contamination can take place either in the mantle source region or as magma traverses the crust (e.g. [1]). While source contamination is generally considered the dominant process (e.g. [2, 3, 4]), crustal contamination in high level magma chambers has also been recognised at volcanic arcs (e.g. [5, 6]). In light of this, we aim to test the extent of upper crustal versus source contamination along the Java segment of the Sunda arc, which, because of its variable upper crustal structure, is ideal for the task.

    We present a detailed geochemical study of 7 volcanoes along a traverse from Anak-Krakatau in the Sunda strait through Java (Gede, Slamet, Merapi, Kelut, Kawah-Ijen) and Bali (Batur). Using rock and mineral elemental geochemistry and radiogenic (Sr, Nd and Pb) and, stable (O) isotopes, we show a correspondence between changes in composition of the upper crust and the apparent degree of upper crustal contamination. There is an increase in 87Sr/86Sr and δ18O, and a decrease in 143Nd/144Nd from Krakatau towards Merapi, indicating substantial input from the thick quasi-continental basement beneath East and Central Java. Volcanoes to the east of Merapi, and the Progo-Muria fault zone, where the upper crust is thinner and increasingly oceanic in nature have lower 87Sr/86Sr and δ18O, and higher 143Nd/144Nd indicating a stronger influence of the mantle source [7]. Our new data represent a systematic and high-resolution arc-wide sampling effort that allows us to distinguish the effects of the upper crust on the compositional spectrum of individual volcanic systems along the Sunda arc.

     

     

    [1] Davidson, J.P, Hora, J.M, Garrison, J.M & Dungan, M.A (2005), J. Geotherm. Res., 140, 157-170.

    [2] Hilton, D.R., Fischer, T.P. & Marty, B. (2002), Rev. Mineral. Geochem., 47, 319-370.

    [3] Gertisser, R. & Keller, J. (2003). J. Petrol., 44, 457-489

    [4] Debaille, V., Doucelance, R., Weis, D., & Schiano, P. (2005), Geochim. Cosmochim. Acta, 70,723-741.

    [5] Gasparon, M., Hilton, D.R., & Varne, R. (1994), Earth Planet. Sci. Lett., 126, 15-22.

    [6] Chadwick, J.P., Troll, V.R., Ginibre, C., Morgan, D., Gertisser, R., Waight, T.E. & Davidson, J.P. (2007), J. Petrol., 48, 1793-1812.

    [7] Whitford, D.J. (1975), Geochim. Cosmochim. Acta, 39, 1287-1302.

  • 95.
    Jolis, Ester M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Freda, Carmela
    Istituto Nazionale di Geofisica e Vulcanologia, INGV, Rome.
    Troll, Valentin R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Deegan, Frances M.
    Dept. of Geoscience, Swedish Museum of Natural History, Stockholm.
    Blythe, Lara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    McLeod, Claire L.
    University of Houston.
    Davidson, Jon P.
    Durham University.
    Experimental simulation of magma-carbonate interaction beneath Mt. Vesuvius, Italy2012Ingår i: Annual Report 2012, HP-HT Laboratory of experimental Volcanology and Geophysics, s. 163-166Artikel i tidskrift (Refereegranskat)
  • 96.
    Jolis, Ester M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik. Ist Nazl Geofis & Vulcanol, I-00143 Rome, Italy..
    Harris, C.
    Univ Cape Town, Dept Geol Sci, ZA-7701 Rondebosch, South Africa..
    Freda, C.
    Ist Nazl Geofis & Vulcanol, I-00143 Rome, Italy..
    Gaeta, M.
    Ist Nazl Geofis & Vulcanol, I-00143 Rome, Italy.;Univ Roma La Sapienza, Dipartimento Sci Terra, I-00185 Rome, Italy..
    Orsi, G.
    Univ Naples Federico II, Dip Sci Terra Ambiente & Risorse, I-80138 Naples, Italy.;Univ Salerno, Dip Fis ER Caianiello, I-84100 Salerno, Italy..
    Siebe, C.
    Univ Nacl Autonoma Mexico, Inst Geofis, Dept Vulcanol, Mexico City 04510, DF, Mexico..
    Skarn xenolith record crustal CO2 liberation during Pompeii and Pollena eruptions, Vesuvius volcanic system, central Italy2015Ingår i: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 415, s. 17-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Limestone assimilation and skarn formation are important processes in magmatic systems emplaced within carbonate-rich crust and can affect the composition of the magma and that of associated volcanic gas. In this study we focus on marble and calc-silicate (skarn) xenoliths from contact reactions between magma and carbonate wall-rock of the Vesuvius volcanic system. We present new elemental and C-O isotope data for marble and skarn xenoliths as well as for igneous rocks collected from the AD 79 (Pompeii) and AD 472 (Pollena) eruptions. The igneous samples have consistently high delta O-18 values (9.3 to 10.8 parts per thousand), but low H2O contents (<= 1.5%), indicating that magma-crust interaction prior to eruption took place. The marble xenoliths, in turn, record initial decarbonation reactions and fluid-mass exchange in their textures and delta C-13 and delta O-18 ranges, while the skarn xenoliths reflect prolonged magma-carbonate interaction and intense contact metamorphism. Skarn-xenoliths record Ca and Mg release from the original carbonate and uptake of Al and Si and span the full delta O-18 data range from unmetamorphosed carbonate (>18 parts per thousand) to values typical for Vesuvius magmatic rocks (similar to 7.5 parts per thousand), which implies that skarn xenoliths comprise carbonate and magmatic components. Textural and chemical evidence suggest that direct carbonate dissolution into the host magmas occurred as well as post-metamorphic skarn recycling, resulting in progressive Ca and Mg liberation from the skarn xenoliths into the magma. Magma-carbonate interaction is an additional source of CO2 during carbonate break-down and assimilation and we calculate the amount of extra volatile components likely liberated by contact metamorphic reactions before and during the investigated eruptions. We find that the extra CO2 added into the volcanic system could have outweighed the magmatic CO2 component by >= factor seven and thus likely increased the intensity of both the Pompeii and the Pollena eruptive events.

  • 97.
    Jolis, Ester Muñoz
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Freda, C.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Deegan, Frances M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Blythe, Lara S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    McLeod, C. L.
    Davidson, J. P.
    Experimental simulation of magma-carbonate interaction beneath Mt. Vesuvius, Italy2013Ingår i: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 166, nr 5, s. 1335-1353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We simulated the process of magma-carbonate interaction beneath Mt. Vesuvius in short duration piston-cylinder experiments under controlled magmatic conditions (from 0 to 300 s at 0.5 GPa and 1,200 A degrees C), using a Vesuvius shoshonite composition and upper crustal limestone and dolostone as starting materials. Backscattered electron images and chemical analysis (major and trace elements and Sr isotopes) of sequential experimental products allow us to identify the textural and chemical evolution of carbonated products during the assimilation process. We demonstrate that melt-carbonate interaction can be extremely fast (minutes), and results in dynamic contamination of the host melt with respect to Ca, Mg and Sr-87/Sr-86, coupled with intense CO2 vesiculation at the melt-carbonate interface. Binary mixing between carbonate and uncontaminated melt cannot explain the geochemical variations of the experimental charges in full and convection and diffusion likely also operated in the charges. Physical mixing and mingling driven by exsolving volatiles seems to be a key process to promote melt homogenisation. Our results reinforce hypotheses that magma-carbonate interaction is a relevant and ongoing process at Mt. Vesuvius and one that may operate not only on a geological, but on a human timescale.

  • 98.
    Jonsson, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Högdahl, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Grön teknik slukar sällsynta metaller2012Ingår i: Forskning & framsteg, nr 7, s. 34-37Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 99.
    Jonsson, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Högdahl, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Harris, Chris
    Weis, Franz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Nilsson, Katarina P.
    Skelton, Alasdair
    Magmatic origin of giant 'Kiruna-type' apatite-iron-oxide ores in Central Sweden2013Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, s. 1644-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iron is the most important metal for modern industry and Sweden is by far the largest iron-producer in Europe, yet the genesis of Sweden's main iron-source, the 'Kiruna-type' apatite-iron-oxide ores, remains enigmatic. We show that magnetites from the largest central Swedish 'Kiruna-type' deposit at Grangesberg have delta O-18 values between -0.4 and +3.7%, while the 1.90-1.88 Ga meta-volcanic host rocks have d18O values between +4.9 and +9%. Over 90% of the magnetite data are consistent with direct precipitation from intermediate to felsic magmas or magmatic fluids at high-temperature (delta O-18(mgt). > +0.9 parts per thousand, i.e. ortho-magmatic). A smaller group of magnetites (delta O-18(mgt) <= +0.9 parts per thousand), in turn, equilibrated with high-delta O-18, likely meteoric, hydrothermal fluids at low temperatures. The central Swedish 'Kiruna-type' ores thus formed dominantly through magmatic iron-oxide precipitation within a larger volcanic superstructure, while local hydrothermal activity resulted from low-temperature fluid circulation in the shallower parts of this system.

  • 100.
    Krumbholz, Michael
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Hieronymus, Christoph
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Burchardt, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Troll, Valentin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Tanner, David
    Leibniz Institute of Applied Geophysics.
    Friese, Nadine
    Wintershall Norge AS.
    Weibull-distributed dyke thickness reflects probabilistic character of host-rock strength2014Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, s. 3272-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magmatic sheet intrusions (dykes) constitute the main form of magma transport in the Earth’s crust. The size distribution of dykes is a crucial parameter that controls volcanic surface deformation and eruption rates and is required to realistically model volcano deformation for eruption forecasting. Here we present statistical analyses of 3,676 dyke thickness measurements from different tectonic settings and show that dyke thickness consistently follows the Weibull distribution. Known from materials science, power law-distributed flaws in brittle materials lead to Weibull-distributed failure stress. We therefore propose a dynamic model in which dyke thickness is determined by variable magma pressure that exploits differently sized host-rock weaknesses. The observed dyke thickness distributions are thus site-specific because rock strength, rather than magma viscosity and composition, exerts the dominant control on dyke emplacement. Fundamentally, the strength of geomaterials is scale-dependent and should be approximated by a probability distribution.

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