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  • 151.
    Dahrén, Börje
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Barker, Abigail
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Meade, Fiona C.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 Group2015In: Faroe Islands Exploration Conference: Proceedings of the 4th ConferenceArticle in journal (Refereed)
  • 152.
    Dahrén, Börje
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 regions2012In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 163, no 4, p. 631-651Article in journal (Refereed)
    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.

  • 153.
    Dahrén, Börje
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Andersson, Ulf-Bertil
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 regions2010In: 7th EGU General Assembly, Copernicus Publications , 2010Conference paper (Other academic)
  • 154. Dalton, D A
    et al.
    Wong, M
    Goncharov, A F
    Ojwang, J
    Struzhkin, V V
    Konopkova, Zuzana
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Thermal Emission Determination of Argon under Extreme Pressure and Temperature2011Conference paper (Refereed)
    Abstract [en]

    Argon is a common pressure-transmitting medium in diamond anvil cell (DAC) experiments, and is often used as thermal insulation in the laser heated DAC. A more thorough understanding of the thermal properties of argon under extreme conditions is essential for measuring thermal properties of materials under similar conditions. A transient heating technique was applied to a symmetric DAC up to 50 GPa and 2500 K. A 1 μm thick iridium foil positioned within a recessed gasket hole filled with argon served as a laser absorber to pump thermal energy into the sample. Pump pulses of 6 μs temporal width were provided from an electronically modulated Yb-based fiber laser. We determined the temperature of the coupler with 500 ns time resolution by applying a Planckian fit to the thermal emission spectrum. Finite element calculations were also used to simulate thermal diffusion in the DAC cavity. The experimental results show slightly larger thermal conductivity with theory, but the results converge in the limit of high temperature. This work is supported by NSF EAR 1015239, NSF-REU, Carnegie Institution of Washington, and DOE-NNSA (CDAC).

  • 155.
    Deegan, Frances M
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Processes of Magma-crust Interaction: Insights from Geochemistry and Experimental Petrology2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This work focuses on crustal interaction in magmatic systems, drawing on experimental petrology and elemental and isotope geochemistry. Various magma-chamber processes such as magma-mixing, fractional crystallisation and magma-crust interaction are explored throughout the papers comprising the thesis. Emphasis is placed on gaining insights into the extent of crustal contamination in ocean island magmas from the Canary Islands and the processes of magma-crust interaction observed both in nature and in experiments. This research underscores that the compositions of ocean island magmas, even primitive types which are classically used as probes of the mantle, are susceptible to modification by crustal contamination. The principal mechanisms of contamination identified from work on both Tenerife and Gran Canaria (Canary Islands) are assimilation and partial melting of the pre-existing island edifice and intercalated sediments by newly arriving magma (i.e. “island recycling”). The information that we can gain from studying solidified magma and entrained crustal xenoliths concerning the rates and mechanisms of crustal assimilation is, however, limited. To address this shortcoming, a series of time-variable crustal carbonate assimilation experiments were carried out at magmatic pressure and temperature using natural materials from Merapi volcano, Indonesia. A temporally constrained reaction series of carbonate assimilation in magma has hence been constructed. The experiments were analysed using in-situ techniques to observe the progressive textural, elemental, and isotopic evolution of magma-carbonate interaction. Crucially, carbonate assimilation was found to liberate voluminous crustally-derived CO2 on a timescale of only seconds to minutes in the experiments. This points to the role of rapid crustal degassing in volcanic volatile budgets, and, pertinently, in magnifying hazardous volcanic behaviour. This thesis, therefore, delivers detailed insights into the processes of magma-crust interaction from experiments and geochemistry. The outcomes confirm that crustal processes are significant factors in both, i) ocean island magma genesis, and ii) magma differentiation towards compositions with greater explosive potential which can, in turn, manifest as hazardous volcanism.

     

    List of papers
    1. Magma mixing in the 1100 AD Montaña Reventada composite lava flow, Tenerife, Canary Islands: Interaction between rift zone and central volcano plumbing systems
    Open this publication in new window or tab >>Magma mixing in the 1100 AD Montaña Reventada composite lava flow, Tenerife, Canary Islands: Interaction between rift zone and central volcano plumbing systems
    Show others...
    2011 (English)In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 162, no 3, p. 651-669Article in journal (Refereed) Published
    Abstract [en]

    Zoned eruption deposits commonly show a lower felsic and an upper mafic member, thought to reflect eruption from large, stratified magma chambers. In contrast, the Montaña Reventada composite flow (Tenerife) consists of a lower basanite and a much thicker upper phonolite. A sharp interface separates basanite and phonolite, and chilled margins at this contact indicate the basanite was still hot upon emplacement of the phonolite, i.e. the two magmas erupted in quick succession. Four types of mafic to intermediate inclusions are found in the phonolite. Inclusion textures comprise foamy quenched ones, others with chilled margins and yet others that are physically mingled, reflecting progressive mixing with a decreasing temperature contrast between the end-members. Analysis of basanite, phonolite and inclusions for majors, traces and Sr, Nd and Pb isotopes show the inclusions to be derived from binary mixing of basanite and phonolite end-members in ratios of 2:1 to 4:1. Although, basanite and phonolite magmas were in direct contact, contrasting 206Pb/204Pb ratios show that they are genetically distinct (19.7193(21)–19.7418(31) vs. 19.7671(18)–19.7807(23), respectively). We argue that the Montaña Reventada basanite and phonolite first met just prior to eruption and had limited interaction time only. Montaña Reventada erupted from the transition zone between two plumbing systems, the phonolitic Teide-Pico Viejo complex and the basanitic Northwest rift zone. A rift zone basanite dyke most likely intersected the previously emplaced phonolite magma chamber. This led to eruption of geochemically and texturally unaffected basanite, with the inclusion-rich phonolite subsequently following into the established conduit.

    Place, publisher, year, edition, pages
    Springer, 2011
    Keywords
    Magma mixing, basanite, phonolite, Tenerife, Canary Islands, Reventada
    National Category
    Earth and Related Environmental Sciences
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-132696 (URN)10.1007/s00410-010-0596-x (DOI)000294216500013 ()
    Note

    Erratum in: Contributions to Mineralogy and Petrology, 2011, vol. 162, pp 671-673, doi: 10.1007/s00410-011-0668-6

    Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2017-12-12Bibliographically approved
    2. Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones
    Open this publication in new window or tab >>Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones
    Show others...
    2012 (English)In: Bulletin of Volcanology, ISSN 0258-8900, E-ISSN 1432-0819, Vol. 74, no 5, p. 963-980Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    Springer, 2012
    Keywords
    Oceanic island rift zones, Lateral collapses, Intrusive complex, Dykes, Lateral flank spreading, Tenerife
    National Category
    Earth and Related Environmental Sciences
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-188384 (URN)10.1007/s00445-012-0577-1 (DOI)
    Available from: 2012-12-17 Created: 2012-12-17 Last updated: 2017-12-06Bibliographically approved
    3. Crustal versus source processes recorded on the North East volcanic rift zone of Tenerife, Canary Islands
    Open this publication in new window or tab >>Crustal versus source processes recorded on the North East volcanic rift zone of Tenerife, Canary Islands
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Keywords
    Tenerife, volcanic rift zones, ocean islands, isotopes, crustal contamination, mantle source
    National Category
    Earth and Related Environmental Sciences
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-132698 (URN)
    Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2011-01-13
    4. Boron isotopes in feldspar: Tracing magmatic processes on Gran Canaria
    Open this publication in new window or tab >>Boron isotopes in feldspar: Tracing magmatic processes on Gran Canaria
    2010 (English)In: Geophysical Research Abstracts, ISSN 1029-7006, E-ISSN 1607-7962, Vol. 12Article in journal (Refereed) Published
    Keywords
    Boron isotopes, feldspar, Gran Canaria, contamination, ocean islands.
    National Category
    Geology
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-132699 (URN)
    Conference
    EGU2010-4590, General Assembly 2010
    Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2017-12-12Bibliographically approved
    5. Magma-carbonate interaction processes and associated CO2 release at Merapi volcano, Indonesia: insights from experimental petrology
    Open this publication in new window or tab >>Magma-carbonate interaction processes and associated CO2 release at Merapi volcano, Indonesia: insights from experimental petrology
    Show others...
    2010 (English)In: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, no 5, p. 1027-1051Article in journal (Refereed) Published
    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.

    Keywords
    Carbon dioxide, Experimental petrology, Magma-carbonate interaction, Merapi, Strontium isotopes
    National Category
    Earth and Related Environmental Sciences
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-119479 (URN)10.1093/petrology/egq010 (DOI)000277995400003 ()
    Available from: 2010-02-25 Created: 2010-02-25 Last updated: 2017-12-12
    6. Fast and furious; crustal CO2 loss at Merapi volcano, Indonesia.
    Open this publication in new window or tab >>Fast and furious; crustal CO2 loss at Merapi volcano, Indonesia.
    Show others...
    2011 (English)In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 27, no 2, p. 63-64Article in journal (Other (popular science, discussion, etc.)) Published
    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.

    National Category
    Geology
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-132704 (URN)10.1111/j.1365-2451.2011.00785.x (DOI)
    Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2017-12-12
  • 156.
    Deegan, Frances M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Barker, Abigail
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 Islands2012In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 334, p. 324-344Article in journal (Refereed)
    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.

  • 157.
    Deegan, Frances M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin R
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Barker, Abigail K
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Chadwick, Jane P
    Vrije Universiteit Amsterdam, Netherlands.
    Harris, Chris
    University of Cape Town, South Africa.
    Delcamp, Audray
    Geological Survey of Japan.
    Carracedo, Juan Carlos
    IPNA-CSIC, Tenerife, Spain.
    Crustal versus source processes recorded on the North East volcanic rift zone of Tenerife, Canary IslandsManuscript (preprint) (Other academic)
  • 158.
    Deegan, Frances M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin R
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 Canaria2010In: Geophysical Research Abstracts, ISSN 1029-7006, E-ISSN 1607-7962, Vol. 12Article in journal (Refereed)
  • 159.
    Deegan, Frances M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin R
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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.2011In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 27, no 2, p. 63-64Article in journal (Other (popular science, discussion, etc.))
    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.

  • 160.
    Deegan, Frances
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 petrology2010In: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, no 5, p. 1027-1051Article in journal (Refereed)
    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.

  • 161.
    Deegan, Frances
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Jolis, Ester Muños
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Freda, C.
    Hilton, D.R.
    Budd, David
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Gertisser, R.
    Blythe, Lara
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Chadwick, J.P.
    Schwarzkopf, L.M.
    Zimmer, M
    The role of CO2-rich basement at Merapi; perspectives from petrology, geochemistry, and experiments2014Conference paper (Refereed)
  • 162. Delcamp, A.
    et al.
    Petronis, M. S.
    Troll, Valentine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Carracedo, J. C.
    de Vries, B. van Wyk
    Perez-Torrado, F. J.
    Vertical axis rotation of the upper portions of the north-east rift of Tenerife Island inferred from paleomagnetic data2010In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 492, no 1-4, p. 40-59Article in journal (Refereed)
    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 degrees, an inclination (I) = 42.3 degrees, alpha(95) = 3.2 degrees, kappa = 39.0, N = 51 that is discordant to the expected late Miocene to Pleistocene field direction (D = 357.6 degrees, I = 38.8 degrees, alpha(95) = 4.7 degrees). This discordance can be explained as either a 26 degrees clockwise vertical axis rotation or a 28 degrees WNW-side-down-tilt about an average 009 degrees 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 degrees-90 degrees). 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 Ar-40/Ar-39 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.

  • 163. Delcamp, A.
    et al.
    Petronis, M.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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) technique2014In: The Use of Palaeomagnetism and Rock Magnetism to Understand Volcanic Processes / [ed] Ort M.H., Porreca M. & Geissmann J.W., Geological Society of London, 2014Chapter in book (Refereed)
  • 164. Delcamp, A.
    et al.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones2012In: Bulletin of Volcanology, ISSN 0258-8900, E-ISSN 1432-0819, Vol. 74, no 5, p. 963-980Article in journal (Refereed)
    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.

  • 165.
    Deng, Hongling
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Superimposition of Contractional Structures in Models and Nature2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Superimposition of contractional structures is widely observed in different scales in the world. Superimposed structures form due to different processes: change in strain accommodation from one type of structure to another during a single progressive shortening; successive coaxial shortening phases separated by an unconformity; superimposition of different non-coaxial shortening phases. Using results of a series of systematic analogue models and detailed field structural mapping, this thesis focuses on the geometry and kinematics of such superimposed structures that are formed by these three processes. During a single progressive folding, thrusts develop within a fold to accommodate stain variations in different regime of the fold. Limited displacement along these thrusts does not significantly modify the geometry of the fold. However, during multiple shortening phases (coaxial or non-coaxial), early formed structures are modified by the later phase ones. The later thrusts can cut and displace the pre-existing structures. The early folds are tightened or interfered by the later folding phase. Pre-existing thrusts may be reactivated either in dip direction and/or along strike during the later shortening. The pre-existing structures in turn influence development of the later structures, which results in change in structure spacing. An angular unconformity between two shortening phases clearly truncates the early phase structures and separates structures of different levels. Unlike in the post-erosional layers, in the layers below the unconformity, complicated superimposed structures are visible. This thesis shows that geometry and sequence of structures formed during one progressive shortening or multiple shortening phases strongly depend on the mode of the superimposition (coaxial, orthogonal or oblique) and the orientation of pre-existing structures.

    List of papers
    1. Identifying the characteristic signatures of fold-accommodation faults
    Open this publication in new window or tab >>Identifying the characteristic signatures of fold-accommodation faults
    2013 (English)In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 56, p. 1-19Article in journal (Refereed) Published
    Abstract [en]

    Hand-specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold-accommodation faults. We describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold, the displacement distribution along the faults by applying separation-distance plots for the outcrop scale examples, and the change of cut-off angle when the fault cut across folded layers. A comparison between fold-accommodation faults and fault related folds based on their separation-distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold-accommodation faults from the reverse faults geometrically and kinematically similar to them. The analysis results show that fold-accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement. The out-of-syncline thrust has a diagnostically negative slope (separation value decreasing away from the upper fault tip) in the separation-distance graph. The change of cut-off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold. Our analyses show that fold-accommodation faults are kinematically consistent with the flexural slip of the fold. The interbedded strata with competence contrast facilitate formation of fold-accommodation faults. These characteristic signatures are concluded as a set of primary identification criteria for fold-accommodation faults.

    Keywords
    Fold-accommodation faults; Hand-specimen; Outcrop scale; Separation–distance plot; Characteristic signatures
    National Category
    Geology
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-190089 (URN)10.1016/j.jsg.2013.08.006 (DOI)000327922200001 ()
    Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2017-12-06Bibliographically approved
    2. Modeling two sequential coaxial phases of shortening in a foreland thrust belt
    Open this publication in new window or tab >>Modeling two sequential coaxial phases of shortening in a foreland thrust belt
    2014 (English)In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 66, p. 400-415Article in journal (Refereed) Published
    Abstract [en]

    Analog sandbox models are used to simulate two sequential coaxial phases of shortening in a foreland thrust belt. A sufficient hiatus is considered so that erosion and sedimentation after the first phase create an angular unconformity that is subsequently deformed. The effect of variation in thickness of post-erosional sediment package and presence of a weak layer at the unconformity level are analyzed. During the second phase, some first phase thrusts are reactivated and new thrusts are also initiated. Thrust reactivation results in a structure spacing that is smaller than the expected spacing for a thicker sediment package. Reactivation of pre-existing structures prevents the weak layer from acting as an intermediate decollement. An increase in thickness ratio tends to weaken reactivation of pre-existing thrusts. Model results also show that total displacement along individual reactivated thrusts generally increases downwards across the unconformity, which could be used to distinguish thrust reactivation in the field. Two regional examples from the northern Eastern Cordillera in Colombia and from the Variscan frontal zone in Western Europe, respectively, where multiphase coaxial shortening occurred, are compared with model results. Both natural cases show features, such as partially eroded first-generation folds and truncated first-generation thrusts that are indicators for two sequential phases of deformation as observed in the models.

    Keywords
    Coaxial multiple shortening, Deformed unconformity, Sandbox modeling, Thrust reactivation
    National Category
    Geology
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-232585 (URN)10.1016/j.jsg.2014.06.006 (DOI)000340978000026 ()
    Available from: 2014-09-24 Created: 2014-09-22 Last updated: 2017-12-05Bibliographically approved
    3. Mega arrowhead interference pattern in the Central part of the Yanshan Orogenic Belt, North China
    Open this publication in new window or tab >>Mega arrowhead interference pattern in the Central part of the Yanshan Orogenic Belt, North China
    2014 (English)In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 80, p. 25-37Article in journal (Refereed) Published
    Abstract [en]

    The Chengde-Pingquan region is located in the central part of the Yanshan Orogenic Belt (YOB). At Daheishan and Pingquan in the central YOB, thrusts and folds of variable trends are displayed in 2 km-scale fold interference patterns. Detailed field mapping was conducted to decipher the geometry of these two superimposed structures. Map-view geometry and stereonet plots for outcrop-scale folds indicate that the superimposed structures form arrowhead interference pattern where NW-SE-trending F1 folds are refolded by later ENE-WSW F2 folding. After remove the effects of later faulting, restored map-views of the superimposed structures show that when the F1 folds have inclined axial surfaces but with no an overturned limb, an arrowhead interference pattern (here called modified type-2 pattern) can form. Our field data and reinterpretation of the findings of previous studies suggest that five major shortening phases have occurred in the Chengde-Pingquan region. The first two phases, which formed the superimposed folds, occurred earlier than the Late Triassic (D1) and during the Late Triassic to Early Jurassic (D2). These two phases were followed by three deformation phases that are mainly characterized by thrusting and strike-slip faulting, which strongly modified the large-scale fold interference patterns.

    Keywords
    Fold interference patterns; Arrowhead; The Yanshan Orogenic Belt; Kilometer scale
    National Category
    Geology Geosciences, Multidisciplinary
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-240390 (URN)10.1016/j.jsg.2015.06.004 (DOI)000364245100004 ()
    Funder
    Swedish Research Council
    Available from: 2015-01-07 Created: 2015-01-07 Last updated: 2017-12-05Bibliographically approved
    4. Superimposed folding and thrusting by two phases of mutually orthogonal or oblique shortening in analogue models
    Open this publication in new window or tab >>Superimposed folding and thrusting by two phases of mutually orthogonal or oblique shortening in analogue models
    2016 (English)In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 83, p. 28-45Article in journal (Refereed) Published
    Abstract [en]

    Orogens may suffer more than one phase shortening resulting in superposition of structures of different generations. Superimposition of orthogonal or oblique shortening is studied using sandbox and centrifuge modelling. Results of sand models show that in orthogonal superimposition, the two resulting structural trends are approximately orthogonal to each other. In oblique superimposition, structures trend obliquely to each other in the relatively thin areas of the model (foreland), and mutually orthogonal in areas where the model is thickened during the first phase of shortening (i.e. the hinterland). Thrusts formed during the first shortening phase may be reactivated during the later shortening phase. Spacing of the later phase structures is not as wide as expected, considering they across the pre-existing thickened wedge. Superposition of structures results in formation of type 1 fold interference pattern. Bedding is curved outwards both in the dome and basin structures. Folded layers are dipping and plunging outwards in a dome, while they are dipping and plunging inwards in a basin. In the areas between two adjacent domes or basins (i.e. where an anticline is superimposed by a syncline or a syncline is superimposed by an anticline), bedding is curved inwards, and the anticlines plunge inwards and the synclines outwards. The latter feature could be helpful to determine the age relationship for type 2 fold interference pattern. In tectonic regions where multiple phases of shortening have occurred, the orogenic-scale dome-and-basin and arrowhead-shaped interference patterns are commonly formed, as in the models. However, in some areas, the fold interference pattern might be modified by a later phase of thrusting. Similar to models results, superimposition of two and/or even more deformation phases may not be recorded by structures all over the tectonic area.

    Keywords
    multiple orthogonal/oblique shortening; superimposed deformation; structure spacing; fold interference patterns
    National Category
    Geology
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-242960 (URN)10.1016/j.jsg.2015.08.005 (DOI)000371842600003 ()
    Available from: 2015-02-03 Created: 2015-02-03 Last updated: 2020-01-28Bibliographically approved
  • 166.
    Deng, Hongling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Mega arrowhead interference pattern in the Central part of the Yanshan Orogenic Belt, North China2014In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 80, p. 25-37Article in journal (Refereed)
    Abstract [en]

    The Chengde-Pingquan region is located in the central part of the Yanshan Orogenic Belt (YOB). At Daheishan and Pingquan in the central YOB, thrusts and folds of variable trends are displayed in 2 km-scale fold interference patterns. Detailed field mapping was conducted to decipher the geometry of these two superimposed structures. Map-view geometry and stereonet plots for outcrop-scale folds indicate that the superimposed structures form arrowhead interference pattern where NW-SE-trending F1 folds are refolded by later ENE-WSW F2 folding. After remove the effects of later faulting, restored map-views of the superimposed structures show that when the F1 folds have inclined axial surfaces but with no an overturned limb, an arrowhead interference pattern (here called modified type-2 pattern) can form. Our field data and reinterpretation of the findings of previous studies suggest that five major shortening phases have occurred in the Chengde-Pingquan region. The first two phases, which formed the superimposed folds, occurred earlier than the Late Triassic (D1) and during the Late Triassic to Early Jurassic (D2). These two phases were followed by three deformation phases that are mainly characterized by thrusting and strike-slip faulting, which strongly modified the large-scale fold interference patterns.

  • 167.
    Deng, Hongling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Koyi, Hemin A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Froitzheim, Nikolaus
    Modeling two sequential coaxial phases of shortening in a foreland thrust belt2014In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 66, p. 400-415Article in journal (Refereed)
    Abstract [en]

    Analog sandbox models are used to simulate two sequential coaxial phases of shortening in a foreland thrust belt. A sufficient hiatus is considered so that erosion and sedimentation after the first phase create an angular unconformity that is subsequently deformed. The effect of variation in thickness of post-erosional sediment package and presence of a weak layer at the unconformity level are analyzed. During the second phase, some first phase thrusts are reactivated and new thrusts are also initiated. Thrust reactivation results in a structure spacing that is smaller than the expected spacing for a thicker sediment package. Reactivation of pre-existing structures prevents the weak layer from acting as an intermediate decollement. An increase in thickness ratio tends to weaken reactivation of pre-existing thrusts. Model results also show that total displacement along individual reactivated thrusts generally increases downwards across the unconformity, which could be used to distinguish thrust reactivation in the field. Two regional examples from the northern Eastern Cordillera in Colombia and from the Variscan frontal zone in Western Europe, respectively, where multiphase coaxial shortening occurred, are compared with model results. Both natural cases show features, such as partially eroded first-generation folds and truncated first-generation thrusts that are indicators for two sequential phases of deformation as observed in the models.

  • 168.
    Deng, Hongling
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Zhang, Changhou
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Identifying the characteristic signatures of fold-accommodation faults2013In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 56, p. 1-19Article in journal (Refereed)
    Abstract [en]

    Hand-specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold-accommodation faults. We describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold, the displacement distribution along the faults by applying separation-distance plots for the outcrop scale examples, and the change of cut-off angle when the fault cut across folded layers. A comparison between fold-accommodation faults and fault related folds based on their separation-distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold-accommodation faults from the reverse faults geometrically and kinematically similar to them. The analysis results show that fold-accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement. The out-of-syncline thrust has a diagnostically negative slope (separation value decreasing away from the upper fault tip) in the separation-distance graph. The change of cut-off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold. Our analyses show that fold-accommodation faults are kinematically consistent with the flexural slip of the fold. The interbedded strata with competence contrast facilitate formation of fold-accommodation faults. These characteristic signatures are concluded as a set of primary identification criteria for fold-accommodation faults.

  • 169. Dietl, C.
    et al.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Dikes in diapirs – a centrifuge study2010Conference paper (Refereed)
  • 170. Dietl, C.
    et al.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Sheets within diapirs - Results of a centrifuge experiment2011In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 33, no 1, p. 32-37Article in journal (Refereed)
    Abstract [en]

    We carried out a centrifuge experiment to model the diapiric rise of a stratified PDMS layer from three perturbations through a non-Newtonian, ductile overburden. The experiment carried out at 700 g resulted in three composite diapirs fed by different PDMS layers. The three resulting diapirs represent two different stages of diapirism. One of the diapirs (diapir 1), which reached its level of neutral buoyancy and extruded at the surface of the model, was tabular in profile and copied by an internal intrusive body. The other two diapirs (diapirs 2 and 3) were still in the ascending stage when centrifuging was stopped and thus did not extrude at the surface. They displayed a typical balloon-on-string geometry, which develops at a high viscosity contrast between a highly viscous overburden and a less viscous buoyant material. The internal geometry of these last two diapirs, fed by the lower impure PDMS, however, did not copy the shape of their precursors. Instead, they had a finger-like shape. The finger geometry of the internal part of the diapirs might be the result of the higher viscosity of the impure lower PDMS intruding a less viscous clean PDMS. Compared to nature, diapir 1 represents a fully developed concentrically expanded pluton or nested diapir, while diapirs 2 and 3 resemble composite plutons which host magma batches of dyke-like geometry. Based on the results of our experiment we suggest that truly concentrically expanded plutons develop from the latter.

  • 171.
    Dietl, Carlo
    et al.
    Geology and Geochemistry Department, Stockholm University, Sweden .
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Emplacement of nested diapirs: Results of centrifuge modelling.2002In: Journal of the Virtual Explorer, Vol. 7, p. 79-86Article in journal (Refereed)
    Abstract [en]

    Concentrically expanded plutons (CEPs) are a common igneous feature. They are characterized by compositional zoning, mainly concentric magmatic fabric inside the pluton and ductile fabric in the contact aureole which are concordant with the pluton / host rock contact. Two intrusion mechanisms have been proposed for CEPs: dyking + ballooning and diapirism. Here, we present results of a centrifuge model to study the kinematics and dynamics of CEPs. The model consisted of three layers from bottom to the top; a 5 mm thick buoyant lower layer of Rhodorsil Gomme simulating a partially molten magma, a 50 mm thick non-Newtonian Rhodorsil Gomme + Plastilina overburden simulating a natural silicic overburden and a 10 mm thick layer of PDMS simulating a less dense overburden. The model was centrifuged twice with two differently stained buoyant layers attached. After the first stage of the experiment two mushroom-shaped diapirs had intruded and deformed the overburden to spread below the less-dense PDMS layer. The second-stage intrusion occurred along the stem of the preexisting diapirs using them as a mechanically weak pathway. This intrusion was not diapiric, but the buoyant material rose passively similar to a dike. Once reaching the level of neutral buoyancy, the intrusive material spread laterally resulting in extensive spreading and expansion of the overhang of the preexisting diapirs. Model results show that CEPs can be the result of combined initial diapirism and subsequent dyking. Multiple diapirs can form only when the overburden units deform ductiley during the different stages of diapirism.

  • 172. Dietl, Carlo
    et al.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Formation of tabular plutons: results and implications of centrifuge modelling2008In: Journal of geosciences, ISSN 1802-6222, Vol. 53, no 3-4, p. 253-261Article in journal (Refereed)
    Abstract [en]

    Geophysical investigations reveal that many granitoid plutons possess a tabular shape: either laccolithic, lopolithic or phacolithic. In this study, the results of a centrifuge experiment are used to understand the formation mechanisms of these features. The model was build of a sequence of 14 differently coloured plasticine layers. Two buoyant layers - with a volume of c. 40 cm(3) each - were incorporated into the model stratigraphy at different depths to investigate, whether the rise and emplacement of buoyant material at different levels results in different intrusion structures. After centrifuging for 30 min at 700 G, both the buoyant layers had formed two lenticular sills (phacoliths) with aspect ratios (length/thickness) of 6 and 3.4 for the upper and lower phacoliths, respectively, directly above both pre-existing perturbations in the buoyant layers. During their movement, the buoyant phacoliths had pushed their roof plasticine upward. Simultaneously, their floor plasticine had subsided (bottom sinking). Subsidence of the floor material had choked the inflow of further buoyant material into the feeder channel of the developing sills and inhibited their further lateral growth. The observed forced downward movement of the plasticine floor of the forming PDMS (polydimethylsiloxane) phacoliths resembles the so-called "floor depression" of host rock material around an emplacing tabular pluton. Floor depression is supposed to be a very important vertical material transfer process, which provides space for the construction of lopo- and phacoliths. The subsidence of host material made space for the developing buoyant phacoliths, but also restricted their growth to a certain time slot before the influx of new buoyant material into the feeder dyke of the tabular intrusive body was shut off. Similarly, in nature, the growth of a tabular pluton might be limited not only by the rate of magma ascent and its physical properties, but also by the emplacement processes of the evolving pluton.

  • 173. Dietl, Carlo
    et al.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    de Wall, Helga
    Gössmann, Mark
    Centrifuge modelling of plutons intruding shear zones: application to the Fürstenstein Intrusive Complex (Bavarian Forest, Germany)2006In: Geodinamica Acta, ISSN 0985-3111, E-ISSN 1778-3593, Vol. 19, no 3-4, p. 165-184Article in journal (Refereed)
    Abstract [en]

    Models consisting of a thick overburden resting on a buoyant layer were sheared and centrifruged in order to study the relationship between strike-slip shear zones and intrusions of buoyant material. Three experiments were carried out: In model 1, where the overburden consisted of a viscous material, no diapirs formed even after shearing for 40 mm (gamma = - 1.07) and 27 min centrifuging. In models 2 and 3, where the overburden was semi-brittle, prescribed cuts at two different orientations (model 2: parallel to sigma 1; model 3: perpendicular to sigma 1) were initiated in the overburden in order to see whether such cuts acted as pathways for intrusion. In model 2 the prescribed cuts were used by the buoyant material as pathways when the cuts opened during shearing. Continued shearing widened the cuts and allowed the buoyant material to extrude on the surface of the model forming a coalesced elliptical sheet. In model 3. the cuts were closed during shearing and prevented the intrusion of the buoyant material. During further shearing, the Cuts rotated and activated as strike-slip faults bounding pull-apart basins. Such pull-apart basins were not deep enough to tap the buoyant material. Nevertheless, the results of the experiments suggest that magma ascends in shear zones not as diapirs, but rises along preexisting pathways as dykes. Model results were used to evaluate emplacement of the Furstenstein Intrusive Complex (FIC) in the Bavarian Forest, whose magnetic and structural inventory have been investigated in detail. The pluton consists of 5 magma batches, each with distinct magnetic fabrics. which are interpreted as the result of magma intrusion along opening and rotating tension gashes within the BPSZ stress field. Shear failure of the crust in the FIC area due to thermomechanical weakening provided the space for the emplacement of the last and biggest granite magma batch. Overall, the emplacement history of the FIC fits perfectly with the observations made during experiment 2 and indicates that magma ascent in shear zones is bound to tension gashes.

  • 174. Donoghue, E.
    et al.
    Troll, V.R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Harris, C.
    OHalloran, A.
    Perez-Torado, J.F.
    Walter, T.R.
    Low-temperature hydrothermal alteration of intra-caldera tuffs, Tejeda caldera, Gran Canaria: mineralogical and isotopic changes.2008In: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 176, p. 551-564Article in journal (Refereed)
  • 175. Donoghue, E.
    et al.
    Troll, V.R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Schwarzkopf, L.M.
    Goodhue, R.
    Clayton, G.
    Organic block coatings in block and ash flow deposits at Merapi volcano, Java, Indonesia2009In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 146, p. 113-120Article in journal (Refereed)
  • 176. Donoghue, Eleanor
    et al.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    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 Geochemistry2010In: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 51, no 10, p. 2149-2176Article in journal (Refereed)
    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.

  • 177.
    Donoghue, Eleanor
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Trinity College Dublin.
    Troll, Valentin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Schwarzkopf, Lothar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. GeoDocCon.
    Goodhue, Robbie
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Trinity College Dublin.
    Clayton, Geoff
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Trinity College Dublin.
    Organic coatings on blocks in block and ash flow deposits form Merapi volcano, Java, Indonesia.2008In: Geological Magazine, Vol. (in press)Article in journal (Refereed)
  • 178. Drake, Henrik
    et al.
    Tullborg, Eva-Lena
    Annersten, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Red-staining of the wall rock and its influence on the reducing capacity around water conducting fractures2008In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 23, no 7, p. 1898-1920Article in journal (Refereed)
    Abstract [en]

    Red-staining and alteration of wall rock is common around water conducting fractures in the Laxemar-Simpevarp area (SE Sweden), which is currently being investigated by the Swedish Nuclear Fuel and Waste Management Co. (SKB) in common with many other places. Red-staining is often interpreted as a clear sign of oxidation but relevant analyses are seldom performed. The area is dominated by Palaeoproterozoic crystalline rocks ranging in composition from quartz monzodiorite to granite. In this study wall rock samples have been compared with reference samples from within 0.1 to 1 m of the red-stained rock, in order to describe mineralogical and geochemical changes but also changes in redox conditions. A methodology for tracing changes in mineralogy, mineral and whole rock chemistry and Fe3+/Fe-tot ratio in silicates and oxides in the red-stained wall rock and the reference rock is reported. The results show that the red-stained rock adjacent to the fractures displays major changes in mineralogy, biotite, plagioclase and magnetite have been altered and chlorite, K-feldspar, albite, sericite, prehnite, epidote and hematite have been formed. The changes in chemistry are however moderate, K-enrichment, Ca-depletion and constant Fe-tot are documented. The Fe3+/Fe-tot ratio in the oxide phase is higher in the red-stained samples whereas the Fe3+/Fe-tot ratio in the silicate phase is largely similar in the wall rock and the reference samples. Because most of the Fe is hosted in the silicate phase the decrease in reducing capacity (Fe2+), if any, in the red-stained wall rock is very small and not as high as macroscopic observations might suggest. Instead, the mineralogical changes in combination with the modest oxidation and formation of minute hematite grains in porous secondary minerals in pseudomorphs after plagioclase have produced the red-staining. Increased porosity is also characteristic for the red-stained rock. Moderate alteration in the macroscopically fresh reference rock shows that the hydrothermal alteration reaches further from the fracture than the red-staining. The extent of the red-staining can therefore not be used in the same way as the extent of the alteration adjacent to a fracture. The increase in porosity in the red-stained rock may result in enhanced retention of radio-nuclides due to an increased sorptivity and diffusion close to the fracture. The hydrothermal alteration causing the red-staining is thought to have occurred at temperatures of about 250-400 degrees C, based on the secondary mineralogy. The major part of this alteration in the area is assumed to be related to fluid circulation associated with the intrusion of the Mesoproterozoic Gotemar and Uthammar granites nearby.

  • 179. Drury, S.A
    et al.
    Ghebreab, W
    Andrews Dellar, M. E
    Talbot, C.J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Berhe, S.M
    A comment on “Geomorphic development of the Ereitrean margim, southern Red Sea from combined apatite fission track and (U-Th)/He thermochronometry”2006In: Earth. Plant. Sci. Letters, Vol. 242, p. 428-432Article in journal (Refereed)
  • 180.
    Dubrovinsky, LS
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lazor, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Saxena, SK
    Haggkvist, P
    Weber, HP
    Le, Bihan T
    Hausermann, D
    Study of laser heated iron using third generation synchrotron X-ray radiation facility with imaging plate at high pressures1999In: PHYSICS AND CHEMISTRY OF MINERALS, ISSN 0342-1791, Vol. 26, no 7, p. 539-545Article in journal (Refereed)
  • 181.
    Dubrovinsky, LS
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Saxena, SK
    Lazor, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    High-pressure and high-temperature in situ X-ray diffraction study of iron and corundum to 68 GPa using an internally heated diamond anvil cell1998In: PHYSICS AND CHEMISTRY OF MINERALS, ISSN 0342-1791, Vol. 25, no 6, p. 434-441Article in journal (Refereed)
  • 182. Dubrovinsky, LS
    et al.
    Saxena, SK
    Lazor, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Stability of beta-iron: A new synchrotron X-ray study of heated iron at high pressure1998In: EUROPEAN JOURNAL OF MINERALOGY, ISSN 0935-1221, Vol. 10, no 1, p. 43-47Article in journal (Refereed)
    Abstract [en]

    We have conducted a new study on the stability of the beta-iron phase at high pressure and temperature. With the X-ray study of the electrically heated iron wire at pressures between 35 and 68 GPa, we are able to demonstrate the reversibility of transform

  • 183.
    Dubrovinsky, LS
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Saxena, SK
    Lazor, P
    X-ray study of iron with in-situ heating at ultra high pressures1997In: GEOPHYSICAL RESEARCH LETTERS, ISSN 0094-8276, Vol. 24, no 14, p. 1835-1838Article in journal (Refereed)
    Abstract [en]

    We provide experimental evidence concerning the structure and the pressure-temperature stability of a new polymorph of iron with the double hexagonal close-packed (DHCP) structure. This experiment was performed by an in-situ electrical heating of an iron-

  • 184.
    Eddahaoui, K.
    et al.
    LCPGM, Laboratoire de Chimie-Physique Générale des Matériaux, Département de Chimie, Université Hassan II-Mohammedia, Faculté des Sciences Ben M’Sik, Casablanca, Morocco.
    Benmokhtar, S.
    LCPGM, Laboratoire de Chimie-Physique Générale des Matériaux, Département de Chimie, Université Hassan II-Mohammedia, Faculté des Sciences Ben M’Sik, Casablanca, Morocco.
    Manoun, B.
    Equipe Matériaux et Environnement, Laboratoire des Procédés de Valorisation des Ressources Naturelles, des Matériaux et Environnement, Université Hassan 1er Morocco, Morocco.
    Belaaouad, S.
    LCPGM, Laboratoire de Chimie-Physique Générale des Matériaux, Département de Chimie, Université Hassan II-Mohammedia, Faculté des Sciences Ben M’Sik, Casablanca, Morocco.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Vibrational Spectra and Factor Group Analysis of M0.50TiOPO4 Oxyphosphates (M = Mg, Zn, Ni, Co, Fe and Cu)2012In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 99, p. 81-89Article in journal (Refereed)
    Abstract [en]

    Raman spectra of a series of orthophosphates M0.50TiO(PO4) (M = Mg, Zn, Ni, Co, Fe, and Cu) have been recorded in crystalline state. Factor group analysis has been performed for space group P21/c and assignments of the internal modes of the [PO4] tetrahedra and [TiO6] octahedra have been made.

    Graphical abstract

  • 185. Edén, M
    et al.
    Annersten, H
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Zassi, Å
    Pulse asssisted homonuclear dipolar recoupling of half integer quadrupolar spins in magic angle spinning NMR2005In: Chem. Phys. Let., Vol. 410, no 24-30Article in journal (Refereed)
  • 186. Eklund, O