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  • 601.
    Wang, Z
    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, S.K
    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.
    O'Neill, H.S.C
    An in situ Raman spectroscopic study of pressure-induced dissociation of spinel NiCr2O4.2003In: J. Phys. Chem. Solids, Vol. 64, no 3, p. 425-431Article in journal (Refereed)
  • 602. Wang, Z
    et al.
    Zhao, Y
    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.
    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.
    Saxena, S.K
    In situ pressure Raman spectroscopy and mechanical stability of superhard boron suboxide2005In: Applied Physics Letters, Vol. 86, p. 041911:1-3Article in journal (Refereed)
  • 603.
    Wang, ZW
    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
    A new empirical method for estimating the high-pressure melting temperatures of solids: NaCl as an example2001In: HIGH TEMPERATURES-HIGH PRESSURES, ISSN 0018-1544, Vol. 33, no 3, p. 357-363Article in journal (Refereed)
    Abstract [en]

    Thermal pressure along with its temperature dependence has been used to calculate the melting temperatures of solids under high pressures. Compared with the reference volume (300 K), a critical melting volume corresponding to the melting point is determin

  • 604.
    Wang, ZW
    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
    A simple model for assessing the high pressure melting of metals: nickel, aluminum and platinum2001In: PHYSICA B, ISSN 0921-4526, Vol. 293, no 3-4, p. 408-416Article in journal (Refereed)
    Abstract [en]

    High-pressure melting has been of general interest for our understanding of solid-liquid phase transition due to the importance in high-pressure physics and material science, and here a simple model was developed to address the high-pressure melting of me

  • 605.
    Wang, ZW
    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
    The analysis on high pressure melting temperature dependence of the thermodynamic parameters of solids2001In: MATERIALS LETTERS, ISSN 0167-577X, Vol. 49, no 5, p. 287-293Article in journal (Refereed)
    Abstract [en]

    Based on the relation between thermodynamic properties and temperature, one simple model has been developed to predict the melting of solids under high pressures. For this model, a critical temperature representing the melting temperature is defined, comp

  • 606.
    Wang, Z.W
    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, S.K
    Artioli, G.
    High pressure Raman spectroscopic study of spinel ZnCr2O42002In: J. Solid State Chem., Vol. 16, p. 165-170Article in journal (Refereed)
  • 607.
    Wang, ZW
    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.
    Schott, B
    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
    Improved equations for addressing the high pressure melting of metastable silicate perovskites2001In: JOURNAL OF ALLOYS AND COMPOUNDS, ISSN 0925-8388, Vol. 315, no 1-2, p. 51-58Article in journal (Refereed)
    Abstract [en]

    Based on our previous thermodynamic model ol high pressure melting of any solid that is stable under ambient pressure (Wang et al., J. Alloys Comp. 299 (1000) 287-291), we have derived a few equations to calculate the melting temperatures of the metastabl

  • 608.
    Weis, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Oxygen and iron isotope systematics of the Grängesberg Mining District (GMD), Central Sweden2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Iron is the most important metal for modern industry and Sweden is the number one iron producer in Europe. The main sources for iron ore in Sweden are the apatite-iron oxide deposits of the "Kiruna-type", named after the iconic Kiruna ore deposit in Northern Sweden. The genesis of this ore type is, however, not fully understood and various schools of thought exist, being broadly divided into "ortho-magmatic" versus the "hydrothermal replacement" approaches. This study focuses on the origin of apatite-iron oxide ore of the Grängesberg Mining District (GMD) in Central Sweden, one of the largest iron reserves in Sweden, employing oxygen and iron isotope analyses on massive, vein and disseminated GMD magnetite, quartz and meta-volcanic host rocks. As a reference, oxygen and iron isotopes of magnetites from other Swedish and international iron ores as well as from various international volcanic materials were also analysed. These additional samples included both "ortho-magmatic" and "hydrothermal" magnetites and thus represent a basis for a comparative analysis with the GMD ore. The combined data and the derived temperatures support a scenario that is consistent with the GMD apatite-iron oxides having originated dominantly (ca. 87 %) through ortho-magmatic processes with magnetite crystallisation from oxide-rich intermediate magmas and magmatic fluids at temperatures of 600 °C to 900 °C. A minor portion of the GMD magnetites (ca. 13 %), exclusively made up of vein and disseminated ore types, is in equilibrium with a high-δ18O and low-δ56Fe hydrothermal fluid at temperatures below 400 °C, indicating the existence of a hydrothermal system associated with the GMD volcano.

  • 609.
    Weis, Franz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Hålensius, U.
    Norrskogen – en centralafrikansk fosfatpegmatit I Upplandsskogarna2013Other (Other (popular science, discussion, etc.))
  • 610.
    Weis, Franz
    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.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Högdahl, Karin
    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.
    Millet, M.-A.
    Nilsson, K.P.
    Iron and oxygen isotope characteristics of apatite-iron-oxide ores from central Sweden2013In: Mineral deposit research for a high-tech world, p. 1675-1678Article in journal (Refereed)
  • 611. Wiesmaier, S.
    et al.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Carracedo, J. C.
    Ellam, R. M.
    Bindeman, I.
    Wolff, J. A.
    Bimodality of lavas in the teide-pico viejo succession in tenerife-the role of crustal melting in the origin of recent phonolites2012In: Journal of Petrology, ISSN 0022-3530, E-ISSN 1460-2415, Vol. 53, no 12, p. 2465-2495Article in journal (Refereed)
    Abstract [en]

    In Tenerife, lavas of the recent Teide-Pico Viejo central complex show a marked bimodality in composition from initially mafic lavas (200-30 ka) to highly differentiated phonolites (30-0 ka). After this abrupt change, the bimodality of the lavas continued to manifest itself between the now felsic Teide-Pico Viejo central complex and the adjacent, but exclusively mafic, rift zones. Whole-rock trace element fingerprinting distinguishes three compositional groups (mafic, transitional, felsic). Groundmass Sr-Nd-Pb-O and feldspar δ. 18O data demonstrate open-system behaviour for the petrogenesis of the Teide-Pico Viejo felsic lavas by high. 87Sr/. 86Sr ratios of up to 0·7049, uniform. 206Pb/. 204Pb (19·75-19·78), variable. 207Pb/. 204Pb (15·53-15·62) and heterogeneous δ. 18O values (5·43-6·80‰). However, ocean sediment contamination can be excluded because of the low. 206Pb/. 204Pb ratios of North Atlantic sediments. Isotope mixing hyperbolae reproduce the entire Teide-Pico Viejo succession and require an assimilant of predominantly felsic composition. Unsystematic and heterogeneous variation of δ. 18O in fresh and unaltered feldspars across the Teide-Pico Viejo succession indicates magmatic addition of diverse δ. 18O assimilants, altered near surface at high and low temperatures. The best fit for these requirements is provided by nepheline syenite that occurs as fresh or altered lithic blocks in voluminous pre-Teide ignimbrite deposits and is similarly heterogeneous in oxygen isotope composition. Nepheline syenite blocks are considered to represent deep remnants of associated earlier eruptions and were thus available for assimilation at depth. Rare earth element modelling indicates that nepheline syenite needs to be melted in bulk to form a suitable end-member composition. Using this assimilant, energy-constrained assimilation fractional crystallization (EC-AFC) modelling reproduces the bulk of the succession, which leads us to suggest that Teide-Pico Viejo petrogenesis is governed by assimilation and fractional crystallization. Both mixing hyperbolae and EC-AFC models indicate that assimilation is more pronounced for the more felsic lavas. The maximum assimilation is evident in the most strongly differentiated (and the most radiogenic in Sr) lava and computes to >97·8% of the assimilant. This most evolved eruption probably represents nepheline syenite bulk melts that formed spatially decoupled from juvenile material. This study therefore recognizes a wider variability of magmatic differentiation processes at Teide-Pico Viejo than previously thought.

  • 612.
    Wiesmaier, Sebastian
    et al.
    Department of Geology, Trinity College Dublin, 2 College Green, Dublin 2, Ireland.
    Deegan, Frances M
    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.
    Carracedo, Juan Carlos
    Estación Volcanológica de Canarias, IPNA-CSIC, Av. Astrofísica Francisco Sanchez 3, 38206 La Laguna, Tenerife, Spain.
    Chadwick, Jane P
    Department of Petrology (FALW), Vrjie Universiteit, 1081 HV Amsterdam, The Netherlands.
    Chew, David M
    Department of Geology, Trinity College Dublin, 2 College Green, Dublin 2, Ireland.
    Magma mixing in the 1100 AD Montaña Reventada composite lava flow, Tenerife, Canary Islands: Interaction between rift zone and central volcano plumbing systems2011In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 162, no 3, p. 651-669Article in journal (Refereed)
    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.

  • 613.
    Wiesmaier, Sebastian
    et al.
    Department of Earth and Environmental Sciences, Ludwig-Maximilians Universität (LMU), Munich, Germany.
    Deegan, Frances
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Carracedo, Juan Carlos
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    Chadwick, Jane P.
    Department of Petrology (Falw), Vrije Universiteit, 1081 Hv Amsterdam, The Netherlands.
    Magma Mixing in the 1100 AD Montaña Reventada Composite Lava Flow: Interaction of Rift Zone and Central Complex Magmatism2013In: Teide Volcano: Geology and eruptions of a highly differentiated oceanic stratovolcano, Springer Berlin/Heidelberg, 2013, p. 191-211Chapter in book (Refereed)
    Abstract [en]

    Zoned eruption deposits frequently show a lower felsic and an upper maficmember, thought to reflect eruption from a large, stratified magmachambers. In contrast, however, the Montaña Reventada composite flow inTenerife consists of a lower basanite and a much thicker upper phonolite. Asharp interface separates the basanite and phonolite, and a chilled margin atthis contact indicates the basanite was still hot upon emplacement of thephonolite, i.e. the two magmas erupted in very quick succession. Threetypes of mafic to intermediate inclusions are found in the phonolite, whichcomprise foamy quenched ones, inclusions with chilled margins and thosethat are physically mingled, reflecting progressive mixing with adecreasing temperature contrast between the end-member magmasinvolved. Analysis of basanite, phonolite and inclusions for majors, tracesand Sr, Nd and Pb isotopes show the inclusions to be derived from binarymixing of basanite and phonolite end-members in ratios of 2:1–4:1.Although basanite and phonolite magmas were erupted in quick succession, contrasting206Pb/204Pb ratios show them to be geneticallydistinct. The Montaña Reventada basanite and phonolite first came intocontact just prior to eruption and had seemingly limited interaction time.Montaña Reventada erupted from the transition zone between twoplumbing systems, the phonolitic Teide-Pico Viejo complex and thebasanitic Northwest rift zone. A rift zone basanite dyke most likelyintersected a previously emplaced phonolite magma pocket, leading toeruption of geochemically and texturally unaffected basanite, followed byinclusion-rich phonolite that exploited the already established conduit.

  • 614.
    Wiesmaier, Sebastian
    et al.
    Department of Earth and Environmental Sciences, Ludwig-Maximilians Universität (LMU), Munich, Germany.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Carracedo, Juan Carlos
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    Ellam, Robert M.
    Scottish Universities Environmental Research Centre (SUERC), East Kilbride, Scotland, UK.
    Bindemann, Ilya
    Department of Geological Sciences, University of Oregon, Eugene, OR, USA.
    Wolff, John A.
    Department of Geology, Washington State University, Pullman, WA, USA.
    Deegan, Frances
    Magmatic Differentiation in the Teide–Pico Viejo Succession: Isotope Analysis as a Key to Deciphering the Origin of Phonolite Magma2013In: Teide Volcano: Geology and eruptions of a highly differentiated oceanic stratovolcano, Springer Berlin/Heidelberg, 2013, p. 173-190Chapter in book (Refereed)
    Abstract [en]

    In Tenerife, lavas of the recent Teide–Pico Viejo central complex show a marked bimodality in composition from initially mafic lava (200–30 ka) to highly differentiated phonolite (30–0 ka). Groundmass Sr–Nd–Pb–O and feldspar 18O data demonstrate open system behaviour for the petrogenesis of Teide–Pico Viejo felsic lavas, but contamination by ocean sediment can be excluded due to the low 206Pb/204Pb ratios of North Atlantic sediment. Isotope mixing hyperbolae require an assimilant of predominantly felsic composition for the Teide–Pico Viejo succession. Unsystematic and heterogeneous variation of 18O in fresh and unaltered feldspars across the Teide–Pico Viejo succession indicates magmatic addition of diverse 18O assimilants, best matched by nepheline syenites that occur as fresh and altered lithic blocks in voluminous pre-Teide ignimbrite deposits. Rare earth element modelling indicates that nepheline syenite needs to be melted in bulk to form a suitable end-member composition. Energy-Constrained Assimilation Fractional Crystallisation (EC-AFC) modelling reproduces the bulk of the succession, which implies that the petrogenesis of Teide–Pico Viejo lavas is governed by the coupled assimilation of nepheline syenite during fractional crystallisation. The most differentiated (and most radiogenic) lava computes to >97.8 % assimilant, likely represented by a nepheline syenite bulk melt that formed by underplating with juvenile mafic material. These recent research developments therefore recognise a wider variability of magmatic differentiation processes at Teide–Pico Viejo than previously considered.

  • 615. Wiesmaier, Sebastian
    et al.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Wolff, John A.
    Carlos Carracedo, Juan
    Open-system processes in the differentiation of mafic magma in the Teide-Pico Viejo succession, Tenerife2013In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 170, no 3, p. 557-570Article in journal (Refereed)
    Abstract [en]

    Oceanic island basalts are commonly thought to differentiate by fractional crystallization, yet closed-system fractionation models have so far failed to reproduce major and trace element variations observed in mafic lavas from the Teide-Pico Viejo stratovolcano complex on Tenerife. Here, new high-precision plagioclase trace element data are fed into such a fractionation model. The results confirm that fractionation of phenocrysts found in the lavas does not reproduce trace element variations, in particular enrichment of Sr and Zr observed in the Teide-Pico Viejo mafic suite. This enrichment of Sr and Zr is tested by an energy-constrained recharge, assimilation and fractional crystallization (EC-RAFC) model at high T and low Lambda T intervals, consistent with previously determined magma storage beneath Tenerife at sub-Moho depths. Published mineral-melt equilibrium relations using the plagioclase anorthite content (0.4 < X-An < 0.8) constrain the temperature during differentiation. Gabbroic xenoliths found in Tenerife lavas are assumed as contaminant. Enrichment of Sr and Zr in the Teide mafic suite is reproduced by this combined assimilation and fractional crystallization model, as assimilation causes higher degrees of enrichment in incompatible trace elements than is possible by crystal fractionation alone. Recycling of plutonic roots may thus have significantly enriched trace elements in the primitive lavas of the Teide-Pico Viejo succession.

  • 616.
    Wiesmaier, Sebastian
    et al.
    Department of Earth and Environmental Sciences, Ludwig-Maximilians Universität (LMU), Munich, Germany.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Rodríguez-Badiola, Eduardo
    Museo Nacional de Ciencias Naturales del CSIC, Madrid, Spain.
    Carracedo, Juan Carlos
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    Timing, Distribution and Petrological Evolution of the Teide-Pico Viejo Volcanic Complex2013In: Teide Volcano: Geology and eruptions of a highly differentiated oceanic stratovolcano, Springer Berlin/Heidelberg, 2013, p. 155-172Chapter in book (Refereed)
    Abstract [en]

    Several cycles of initially mafic to progressively felsic activity have given rise to large volume felsic deposits on Tenerife that serve as prime examples of pronounced magmatic differentiation in an ocean island setting. The Teide–Pico Viejo succession is the most recent of these cycles to show a systematic evolution from initially basanitic to phonolitic eruptions. Basanite lava flows bear olivine, pyroxene and occasionally plagioclase, while phonolites mainly display alkali feldspar with subordinate pyroxene, amphibole, biotite and oxides. Three groups of eruptives can be discerned based on their trace element composition: (1) Mafic lavas that show typical OIB signatures, (2) Transitional lavas, which are enriched in incompatible trace elements but may be depleted in Ba and Sr and (3) Phonolites, which are more enriched in incompatible trace elements, but show the strongest negative Ba and Sr anomalies. Linking the spatio-chronological distribution of eruptions with these compositional groups shows a progressive migration of mafic activity from the outskirts of the rift zones towards the central complex over the last 30 ka. The arrival of mafic activity at the central complex coincided with the onset of more evolved eruptions at Teide, thought to be triggered by mafic underplating. The distribution of mafic activity at the surface may thus be related to the volume of mafic underplating beneath the volcanic edifice at a given time.

  • 617. Wikström, A
    et al.
    Andersson, U.B
    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.
    Geological features of the Småland-Värmland Belt along the Svecofennian margin. Part I, from the Loftahammar to the Tiveden-Askersund areas2004In: The Transscandinavian Igneous Belt (TIB) in Sweden; a review of its character and evolution, 2004, p. 22-39Chapter in book (Refereed)
  • 618.
    Winell, S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Annersten, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Prekapenko, V.
    The high pressure transformation of magnesiumferrite MgFe2O42006In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 91, no 4, p. 560-567Article in journal (Refereed)
  • 619.
    Winell, Sofia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Amcoff, Örjan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III.
    Cation ordering in NiFe2-xCrxO4-spinels studied by Mössbauer spectroscopy in external fields2008In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 245, no 8, p. 1635-1640Article in journal (Refereed)
    Abstract [en]

    NiFe2-xCrxO4, 0 < ;= x < ;= 1.8, produced from appropriate oxides, has been studied using Mossbauer spectroscopy (MS) at low and ambient temperatures and in external fields up to 7 Tesla. X-ray diffraction (XRD) shows all samples to be single phase cubic spinels, where a(0) change in x, as a concave curve, with a minimum at around x=1. Analyses, based on Mossbauer spectra, show NiFe2-xCrxO4 to be a nearly perfect inverted spinel for x < ;= 0.6. However, for higher x-values the ordering is more complicated. It is shown that iron also populates the octahedral positions for x > ;= 0.8.

  • 620.
    Winell, Sofia
    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. Berg.
    Annersten, Hans
    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. Berg.
    Prakapenka, Vitali
    The high-pressure phase transformation and breakdown of MgFe2O42006In: American Mineralogist, Vol. 91, p. 560-567Article in journal (Refereed)
    Abstract [en]

    The high-pressure transformation of MgFe2O4 was studied by Mössbauer and Raman spectroscopy and synchrotron X-ray diffraction using the DAC technique and laser annealing at temperatures of 1500-2000 K. The high-pressure phase of MgFe2O4 was observed from in situ Mössbauer spectra

    at 17 ± 1 GPa after laser annealing by the appearance of two quadrupole doublets. This indicates a disordered distribution of Mg and Fe in an early stage. The displacive nature of the transformation of the spinel into its high-pressure polymorph was shown at increasing pressure by the redistribution of iron into only one site. After decompression Mössbauer spectroscopy revealed the presence of Fe2O3 in the sample. This was further confirmed by Raman spectroscopy at ambient conditions and by in situ high-pressure XRD, indicating a partial breakdown of the spinel into its constituent oxides MgO and Fe2O3. The XRD pattern of the high-pressure phase of MgFe2O4 can be indexed in agreement with the

    CaMn2O4-type structure, with cell parameters a = 2.775(2), b = 9.283(16), and c = 9.446(5)

  • 621. Wong, M L
    et al.
    Goncharov, A F
    Dalton, D A
    Ojwang, J
    Struzhkin, V
    Konopkova, Z
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Thermal Conductivity of Argon at High Pressures and High Temperatures2010Conference paper (Refereed)
    Abstract [en]

    Accurate data on the thermal conductivity of argon at high pressures and high temperatures is essential to unraveling the nature of the Earth’s interior. Argon is a common pressure-transmitting medium in diamond anvil cell (DAC) experiments, which is commonly used for studying the properties of minerals at pressures and temperatures native to the mantel and core. We used a transient heating technique (Beck et al., 2007) in a symmetric DAC up to 50 GPa and 2500 K. A thin iridium foil (1 μm thick) positioned in a recessed gasket hole filled with argon served as a heat absorber (coupler) to pump thermal energy into the sample. We used 6 μs width pulses from electronically modulated Yb-based fiber laser. We determined the temperature of the coupler with 500 ns time resolution by applying the Planck function to its thermal emission spectrum, and doing this over time yields temperature verses time for the coupler. Using finite element (FE) calculation methods we simulated the heat flux transfer in the DAC cavity using the experimentally determined geometric and laser heating parameters. The thermochemical parameters of Ir and Ar were determined by scaling the ambient pressure data using the available equations of state. The temperature dependent thermal conductivity of Ar was determined by fitting the results of FE calculations to the experimentally determined time dependent coupler temperature. We used the results of the theoretical calculations (Tretiakov & Scandolo, 2004) as the initial input. The results for the pressure and temperature dependent thermal conductivity of Ar will be reported at the meeting. This work is supported by NSF EAR 0711358, NSF-REU, Carnegie Institution of Washington, and DOE-NNSA (CDAC). Beck, P; Goncharov, A.F., Struzhkin, V.V., Militzer, B, Mao, H.K, Hemley, R.J. (2007). Measurement of thermal diffusivity at high pressure using a transient heating technique, Appl Phys. Lett. 91, 181914-(1-3). Tretiakov, K. V. & S. Scandolo (2004). Thermal conductivity of solid argon at high pressure and high temperature: A molecular dynamics study. J. Chem. Phys. 121, 11177-11182.

  • 622.
    Wärnå, John
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Banerjee, Amitava
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III.
    Reaction Coordinate Mapping of Hydrogen Evolution Mechanism on Mg3N2MonolayerManuscript (preprint) (Other academic)
  • 623.
    Zaczek, Kirsten
    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.
    Cachao, Mario
    Ferreira, Jorge
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Carracedo, Juan-Carlos
    University of Las Palmas de Gran Canaria, Dept. of Physics, Las Palmas de Gran Canaria, Spain.
    Soler, Vincente
    Meade, Fiona C.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Nannofossils in 2011 El Hierro eruptive products reinstate plume model for Canary Islands2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, p. 7945-Article in journal (Refereed)
    Abstract [en]

    The origin and life cycle of ocean islands have been debated since the early days of Geology. In the case of the Canary archipelago, its proximity to the Atlas orogen led to initial fracture-controlled models for island genesis, while later workers cited a Miocene-Quaternary east-west age-progression to support an underlying mantle-plume. The recent discovery of submarine Cretaceous volcanic rocks near the westernmost island of El Hierro now questions this systematic age-progression within the archipelago. If a mantle-plume is indeed responsible for the Canaries, the onshore volcanic age-progression should be complemented by progressively younger pre-island sedimentary strata towards the west, however, direct age constraints for the westernmost pre-island sediments are lacking. Here we report on new age data obtained from calcareous nannofossils in sedimentary xenoliths erupted during the 2011 El Hierro events, which date the sub-island sedimentary rocks to between late Cretaceous and Pliocene in age. This age-range includes substantially younger pre-volcanic sedimentary rocks than the Jurassic to Miocene strata known from the older eastern islands and now reinstate the mantle-plume hypothesis as the most plausible explanation for Canary volcanism. The recently discovered Cretaceous submarine volcanic rocks in the region are, in turn, part of an older, fracture-related tectonic episode.

  • 624. Zarei, M.
    et al.
    Raeisi, E.
    Talbot, Christopher J.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Karst development on a mobile substrate: Konarsiah salt extrusion, Iran2012In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 149, no 3, p. 412-422Article in journal (Refereed)
    Abstract [en]

    Most karst terranes develop slowly on static limestone substrates as part of the global hydrological cycle. Here we introduce the novel concept of a karst morphology developing very rapidly on a more soluble substrate of salt (NaCl) that is moving through its own global cycle. We open with a reminder of karst features and processes in limestone. We then illustrate the global salt cycle using the 180 or so extrusions of Hormoz salt in the Zagros Mountains of Iran. After describing the geology of an example, we consider how it fits into the evolution of salt extrusions. This example, Konarsiah, was chosen for its simple hydrology. Konarsiah is covered by residual soils of the insoluble components that remain in place as the Hormoz salt is dissolved. Dolines in the surface of these soils enlarge and the soils thicken as the moving salt dissolves. The long-term rate of salt dissolution and soil production on Konarsiah are estimated using traditional methods. The calculated age of the thickest, most distal soil is used to constrain the average rate at which the underlying salt flows downslope after extruding from two vents. The average velocities constrained for salt flow are lower than rates of displacement of markers near the summit of Konarsiah measured at irregular intervals over five years. Salt extruding from recently truncated diapirs near the arid south coast of Iran exhibit all the features seen in classical karst terranes. In the more humid mountains inland, vegetated soils protect salt extrusions like Konarsiah from erosion and limit their salt karst features. Soil covers also probably even out salt flow velocities. Salt extrusions advance when such protective covers grow and thicken in humid conditions. They retreat when such protection is lost to erosion in drier conditions. These external signs complement internal recumbent folds in extruded salt that signal intervals of faster salt flow when wet than dry. They also add to the features that render salt extrusions records of climate change.

  • 625.
    Zarifi, Zoya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Nilfouroushan, Faramarz
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Raeesi, Mohammad
    Department of Earth Science, University of Bergen, Allegaten 41, 5007 Bergen, Norway.
    Crustal stress Map of Iran: Insight from seismic and geodetic computations2014In: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 171, no 17, p. 1219-1236Article in journal (Refereed)
    Abstract [en]

    We used the focal mechanisms of crustal earthquakes (depth <40 km) in the period 1909-2012 and the available GPS velocities, estimated from the data collected between 1999 to 2011, to estimate the magnitude and directions of maximum principal stress and strain rates in Iran. The Pearson product moment correlation was used to find the correlation between the stress field obtained from the focal mechanism stress inversion and that obtained using the seismic and geodetic strain rates. Our assumption is that stresses in a continuum are produced by tectonic forces and the consequent deformation on the crustal scale. Therefore, the direction of the stress and strain (or strain rate) are ideally be the same. Our results show a strong correlation between the directions of the principal components of stress and strain (rate) obtained using the different data/methods.  Using  weighted average analysis, we present a new stress map for Iran.

  • 626. Zazzi, Åsa
    et al.
    Hirsch, Tomas K.
    Kaikikonen, Andrei
    Grins, Jekabs
    Annersten, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Edén, Mattias
    Structural investigations of natural and synthetic chlorite minerals by X-ray diffraction, mössbauer spectroscopy and solid-state nuclear magnetic resonance2006In: Clays and clay minerals, ISSN 0009-8604, E-ISSN 1552-8367, Vol. 54, no 2, p. 252-265Article in journal (Refereed)
    Abstract [en]

    The structures of one synthetic and two natural chlorites of the chlinochlore type were explored using X-ray diffraction, magic-angle spinning nuclear magnetic resonance (NMR) and Mössbauer spectroscopy. Rietveld refinements indicated that all structures are of the trioctahedral ordered IIb polytype. Mössbauer spectra provided the ratio IIFe/IIIFe but gave no evidence for the presence of IIIFe in the brucite-like sheet. We also report unit-cell parameters, Mössbauer isomeric shifts, 29Si NMR chemical shifts as well as27 Al isotropic shifts and quadrupolar coupling parameters. Very broad 29Si NMR peaks from the natural samples prevented us from obtaining accurate information on the Si-Al ordering in the tetrahedral sheets; the limitations of 29Si NMR as applied to natural chlorites are discussed. High-resolution 3QMAS NMR resolved the 27Al signal of the M4 octahedral site in the brucite-like sheet from the other three Al signals of crystallographically inequivalent octahedral positions.

  • 627.
    Zhuk, Yuliya
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Structural analysis of a recent rockslide in Southern Stockholm2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The present Bachelor thesis is written about a rock slide which took place in the southern part of Stockholm in the early 2000s. The studied area is located relatively close to a steeply-dipping fault with NW-SE orientation. The field work was carried out by four students, with me and other student focussing on the rock slide slope and two scan lines N and E of the rock slide. The geological structures, which were assumed to be responsible for the rock slide, have been studied carefully during surface mapping. The data was analysed using two rock mass classifications and stereographic projection. Additionally, a digital elevation map of the area was analysed in terms of slope angle distributions using GIS. It was shown that the orientation of discontinuities at the site coincides with the direction of the cutting work. Thus, the rock slide was unavoidable since the cutting work was carried out subparallel to the fractures main orientation. 

10111213 601 - 627 of 627
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