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  • 1.
    Abirifard, Mahmoud
    et al.
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Raeisi, Ezzat
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Zarei, Mehdi
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Zare, Mohammad
    Shiraz Univ, Coll Sci, Dept Earth Sci, Shiraz, Iran..
    Filippi, Michal
    Czech Acad Sci, Inst Geol, Vvi, Rozvojova 269, Prague 6, Czech Republic..
    Bruthans, Jiri
    Charles Univ Prague, Fac Sci, Albertov 6, Prague 12843 2, Czech Republic..
    Talbot, Christopher J.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Jahani Salt Diapir, Iran: hydrogeology, karst features and effect on surroundings environment2017In: International Journal of Speleology, ISSN 0392-6672, E-ISSN 1827-806X, Vol. 46, no 3, p. 445-457Article in journal (Refereed)
    Abstract [en]

    The Jahani Salt Diapir (JSD), with an area of 54 km(2), is an active diapir in the Simply Folded Belt of the Zagros Orogeny, in the south of Iran. Most of the available studies on this diapir are focused on tectonics. The hydrogeology, schematic model of flow direction and hydrochemical effects of the JSD on the adjacent water resources are lacking, and thus, are the focus of this study. The morphology of the JSD was reevaluated by fieldwork and using available maps. The physicochemical characteristics of the springs and hydrometric stations were also measured. The vent of the diapir is located 250 m higher than the surrounding glaciers, and covered by small polygonal sinkholes (dolines). The glacier is covered by cap soils, sparse trees and pastures, and contains large sinkholes, numerous shafts, several caves, and 30 brine springs. Two main groups of caves were distinguished. Sub-horizontal or inclined stream passages following the surface valleys and vertical shafts (with short inlet caves) at the bottoms of nearly circular blind valleys. Salt exposure is limited to steep slopes. The controlling variables of flow route within salt diapirs are the negligible porosity of the salt rocks at depth more than about ten meters below the ground surface and the rapid halite saturation along the flow route. These mechanisms prevent deep cave development and enforce the emergence points of brine springs with low flow rates and small catchment area throughout the JSD and above the local base of erosion. Tectonics do not affect karst development, because the distributions of sinkholes and brine springs show no preferential directions. The type of spring water is sodium chloride, with a TDS of 320 g/l, and saturated with halite, gypsum, calcite and dolomite. The water balance budget of the JSD indicates that the total recharge water is 1.46 MCM (million cubic meter)/a, emerges from 30 brine springs, two springs from the adjacent karstic limestone, and flows into the Firoozabad River (FR) and the adjacent alluvium aquifer. The FR cuts through the northern margin of the salt diapir, dissolving the glacier salts at the contact with JSD, increasing the halite concentration of the 17.7 MCM/a of the FR from 100 mg/l to 12,000 mg/l. This is a permanent process because the active glacier flows rapidly down the steep slopes into the river gorge from the nearby vent. The possible relocation of the FR channel would enhance the FR water quality, but disrupt the natural beauty of the diapir.

  • 2.
    Ahmadi, Omid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Gessner, Klaus
    Geol Survey Western Australia, 100 Plain St, East Perth, WA 6004, Australia.
    Seismic signatures of complex geological structures in the Cue-Weld range area, Murchison domain, Yilgarn Craton, Western Australia2016In: Tectonophysics, Vol. 689, p. 56-66Article in journal (Refereed)
    Abstract [en]

    The Murchison domain forms the northwest part of the Youanmi Terrane, a tectonic unit within the Neoarchean Yilgarn Craton in Western Australia. In the Cue-Weld Range area the Murchison domain has experienced a complex magmatic and deformation history that resulted in a transposed array of greenstone belts that host significant iron, gold, and base metal deposits. In this study, we interpret the upper 2 s (about 6 km) of a deep crustal seismic profile TOGA-YU1, near the town of Cue, and correlate rock units and structures in outcrop with corresponding reflections. We performed 3D constant velocity ray-tracing and calculate the corresponding travel times for the reflectionsfor time domain pre-stack and post-stack seismic data. This allows us to link shallow reflections with mafic volcanic rocks of the Glen Group and basaltic rocks of the Polelle Group in outcrop. Based on our interpretation and published geological maps and data, we propose a model in which the local stratigraphy represents a refolded thrust system. To test our hypothesis, we applied 2D acoustic finite difference forward modeling. The corresponding synthetic data were processed in the same way as the acquired data. Comparisons between the acquired and the synthetic data show that the model is consistent with observations. We propose a new model for the subsurface of the Cue-Weld Range area and argue that some of the lithologies in the area are repeated structurally at different levels. Our approach highlights the benefit of imaging and modeling of deep seismic transects to resolve local structural complexity in Archean granite-greenstone terrains.

  • 3.
    Almqvist, Bjarne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Biedermann, Andrea
    Klonowska, Iwona
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Misra, Santanu
    Petrofabric development during experimental partial melting and recrystallization of a mica-schist analogue2015In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 16, no 10, p. 3472-3483Article in journal (Refereed)
  • 4.
    Almqvist, Bjarne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Björk, Andreas
    Mattsson, Hannes B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Bäckström, Emma
    Marsden, Paul
    Magnetic characterisation of magnetite and hematite from the Blötberget apatite-iron-oxide deposits (Bergslagen), south-central Sweden2019In: Canadian journal of earth sciences (Print), ISSN 0008-4077, E-ISSN 1480-3313Article in journal (Refereed)
    Abstract [en]

    Rock magnetic measurements were carried out on drill core material and hand specimens from the Blötberget apatite-iron oxide deposit in the Bergslagen ore province, south-central Sweden, to characterise their magnetic properties. Measurements included several kinds of magnetic susceptibility and hysteresis parameters. Petrographic and scanning electron microscopy (SEM) were used to independently identify and quantify the amount and type of magnetite and hematite. Two hematite-rich samples were studied with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify the trace element chemistry in hematite and investigate the potential influence of trace elements on magnetic properties. Three aspects of this study are noteworthy. 1) Hematite-rich samples display strong anisotropy of magnetic susceptibility, which is likely to affect the appearance and modelling of magnetic anomalies. 2) The magnitude-drop in susceptibility across Curie and Néel temperature transitions show significant correlation with the respective weight percent (wt%) of magnetite and hematite. Temperature dependent magnetic susceptibility measurements can therefore be used to infer the amounts of both magnetite and hematite. 3) observations of a strongly depressed Morin transition at ca -60 to -70 C (200 to 210 K) are made during low-temperature susceptibility measurements. This anomalous Morin transition is most likely related to trace amounts of V and Ti that substitute for Fe in the hematite. When taken together, these magnetic observations improve the understanding of the magnetic anomaly signature of the Blötberget apatite-iron oxide deposits and may potentially be utilised in a broader context when assessing similar (Paleoproterozoic) apatite-iron oxide systems.

  • 5.
    Almqvist, Bjarne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Bulk strain in orogenic wedges based on insights from magnetic fabrics in sandbox models2018In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 46, no 6, p. 483-486Article in journal (Refereed)
    Abstract [en]

    Anisotropy of magnetic susceptibility (AMS) analysis is used as a petrofabric indicator for a set of four identical-setup sandbox models that were shortened by different amounts and simulate contraction in a fold-and-thrust belt. During model shortening, a progressive reorientation of the initial magnetic fabric occurs due to horizontal compaction of the sand layers. At the early stages of shortening, magnetic lineation (k(1) axis) rotates parallel to the model backstop with subhorizontal orientation, whereas the minimum susceptibility (k(3) axis) is subvertical, which indicates a partial tectonic overprint of the initial fabric. With further shortening, the k(3) axis rotates to subhorizontal orientation, parallel to shortening direction, marking the development of a dominant tectonic magnetic fabric. A near-linear transition in magnetic fabric is observed from the initial bedding to tectonic fabric in all four models, which reflects a progressive transition in deformation from foreland toward hinterland. Model results confirm a long-held hypothesis where the AMS pattern and degree of anisotropy have been suggested to reflect the amount of layer-parallel shortening, based on field observations in many mountain belts. Results furthermore indicate that grain rotation may play a significant role in low-grade compressive tectonic regimes. The combination of analogue models with AMS enables the possibility to predict magnetic fabrics in different tectonic settings and to develop quantitative links between AMS and strain.

  • 6.
    Almqvist, Bjarne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Misra, Santanu
    Klonowska, Iwona
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Mainprice, David
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Ultrasonic velocity drops and anisotropy reduction in mica-schist analogues due to melting with implications for seismic imaging of continental crust2015In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 425, p. 24-33Article in journal (Refereed)
  • 7.
    Andersson, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Almqvist, Bjarne S. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Snowball, Ian
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Kubler, Lutz
    Geol Survey Sweden, Uppsala, Sweden..
    Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 27635Article in journal (Refereed)
    Abstract [en]

    Magma transport through the Earth's crust occurs dominantly via sheet intrusions, such as dykes and cone-sheets, and is fundamental to crustal evolution, volcanic eruptions and geochemical element cycling. However, reliable methods to reconstruct flow direction in solidified sheet intrusions have proved elusive. Anisotropy of magnetic susceptibility (AMS) in magmatic sheets is often interpreted as primary magma flow, but magnetic fabrics can be modified by post-emplacement processes, making interpretation of AMS data ambiguous. Here we present AMS data from cone-sheets in the Alno carbonatite complex, central Sweden. We discuss six scenarios of syn- and post-emplacement processes that can modify AMS fabrics and offer a conceptual framework for systematic interpretation of magma movements in sheet intrusions. The AMS fabrics in the Alno cone-sheets are dominantly oblate with magnetic foliations parallel to sheet orientations. These fabrics may result from primary lateral flow or from sheet closure at the terminal stage of magma transport. As the cone-sheets are discontinuous along their strike direction, sheet closure is the most probable process to explain the observed AMS fabrics. We argue that these fabrics may be common to cone-sheets and an integrated geology, petrology and AMS approach can be used to distinguish them from primary flow fabrics.

  • 8.
    Andersson, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Helsinki, Dept Geosci & Geog, FI-00014 Helsinki, Finland.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Uppsala, Sweden.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Metamorphism and deformation of a Palaeoproterozoic polymetallic sulphide-oxide mineralisation: Hornkullen, Bergslagen, Sweden2016In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, no 3, p. 410-423Article in journal (Refereed)
    Abstract [en]

    The Hornkullen mineralisation is situated in the westernmost part of the Bergslagen ore province, south-central Sweden. Here, polymetallic sulphides and oxides are hosted by an inlier of Svecofennian, c. 1.9Ga skarn-bearing metavolcanic units, enclosed in the c. 1.8Ga Filipstad granite belonging to the Transscandinavian Igneous Belt. The Ag- and Au-bearing mineralisation is dominated by veins and impregnations of magnetite, pyrrhotite, galena, chalcopyrite and arsenopyrite with subordinate pyrite, sphalerite, ilmenite, lollingite, Pb-Fe-Ag-Cu-Sb sulphosalts and rare gudmundite, pentlandite and molybdenite. Overall, a detailed textural and mineralogical study of the ore assemblages suggests significant deformation and remobilisation at high temperature, which is corroborated by sulphide geothermobarometry. The arsenopyrite geothermometer yields an average temperature of c. 525 degrees C, which is likely to be the result of metamorphic re-equilibration. Sphalerite geobarometry gives peak pressures of c. 300-400MPa, albeit with caveats. The combined observations suggest that the present mineralogical and textural nature of the ore assemblages at Hornkullen is primarily related to remobilisation during Svecokarelian regional metamorphism of a pre-existing, most likely syn-volcanic mineralisation. This scenario is likely to be applicable to many other Svecofennian metasupracrustal-hosted deposits in the Bergslagen ore province.

  • 9.
    Andersson, Stefan S.
    et al.
    Univ Helsinki, Dept Geosci & Geog, POB 64,Gustaf Hallstromin Katu 2a, FI-00014 Helsinki, Finland.
    Wagner, Thomas
    Rhein Westfal TH Aachen, Inst Appl Mineral & Econ Geol, Wullnerstr 2, D-52062 Aachen, Germany.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Box 670, SE-75128 Uppsala, Sweden.
    Fusswinkel, Tobias
    Univ Helsinki, Dept Geosci & Geog, POB 64,Gustaf Hallstromin Katu 2a, FI-00014 Helsinki, Finland;Rhein Westfal TH Aachen, Inst Appl Mineral & Econ Geol, Wullnerstr 2, D-52062 Aachen, Germany.
    Leijd, Magnus
    Leading Edge Mat Corp, Skolallen 2B, SE-82141 Bollnas, Sweden.
    Berg, Johan T.
    Chromafom AB, Banvaktsvagen 22, SE-17148 Solna, Sweden.
    Origin of the high-temperature Olserum-Djupedal REE-phosphate mineralisation, SE Sweden: A unique contact metamorphic-hydrothermal system2018In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 101, p. 740-764Article in journal (Refereed)
    Abstract [en]

    The Swedish part of the Fennoscandian Shield hosts a variety of rare earth element (REE) deposits, including magmatic to magmatic-hydrothermal types. This paper focuses on the origin of the Olserum-Djupedal REEphosphate mineralisation located in the sparsely studied Vastervik region, SE Sweden. Here, mineralisation occurs in three main areas, Olserum, Djupedal and Bersummen. Primary hydrothermal REE mineralisation formed at high temperatures (about 600 degrees C), leading to precipitation of monazite-(Ce), xenotime-(Y), fluor apatite and minor (Y,REE,U,Fe)-(Nb,Ta)-oxides in veins and vein zones dominated by biotite, amphibole, magnetite and quartz. The veins are hosted primarily by metasedimentary rocks present close to, or within, the contact aureole of a local 1.8 Ga ferroan alkali feldspar granite pluton, but also occur within in the chemically most primitive granite in the outermost part of that pluton. In the Djupedal area, REE-mineralised metasedimentary bodies are extensively migmatised, with migmatisation post-dating the main stage of mineralisation. In the Olserum and Bersummen areas, the REE-bearing veins are cross-cut by abundant pegmatitic to granitic dykes. The field-relationships demonstrate a-protracted magmatic evolution of the granitic,pluton and a clear spatial and temporal relationship of the REE mineralisation to the granite. The major and trace element chemistry of ore-associated biotite and magnetite support genetic links between all mineralised areas. Biotite mineral chemistry data further demonstrate a distinct chemical trend from meta sediment-hosted ore-associated biotite distal to the major contact of the granite to the biotite in the granite hosted veins. This trend is characterised by a systematic decrease in Mg and Na and a coupled increase in Fe and Ti with proximity to the granite-hosted veins. The halogen compositions of ore-associated biotite indicate elevated contents of HCl and HF in the primary REE mineralising fluid. Calculated log(f(HF)/f(HCL)) values in the Olserum area suggest a constant ratio of about -1 at temperatures of 650-550 degrees C during the evolution of the primary hydrothermal system. In the Djupedal and Bersummen areas, the fluid locally equilibrated at lower log (f(HF)/f(HCl)) values down to -2. High Na contents in ore-associated biotite and amphibole, and the abundance of primary ore-associated biotite indicate a K- and Na-rich character of the primary REE mineralising fluid and suggest initial high-temperature K-Na metasomatism. With subsequent cooling of the system, the fluid evolved locally to more Ca-rich compositions as indicated by the presence of the Ca-rich minerals allanite-(Ce) and uvitic tourmaline and by the significant calcic alteration of monazite-(Ce). The later Ca-rich stages were probably coeval with low to medium-high temperature (200-500 degrees C) Na-Ca metasomatism variably affecting the granite and the wall rocks, producing distinct white quartz-plagioclase rocks. All observations and data lead us to discard the prevailing model that the REE mineralisation in the Olserum-Djupedal district represents assimilated and remobilised former heavy mineral-rich beds. Instead, we propose that the primary REE mineralisation formed by granite-derived fluids enriched in REE and P that were expelled early during the evolution of a local granitic pluton. The REE mineralisation developed primarily in the contact aureole of this granite and represents the product of a high temperature contact metamorphic-hydrothermal mineralising system. The REE mineralisation probably formed synchronously with K-Na and subsequent Na-Ca metasomatism affecting the granite and the wall rocks. The later Na-Ca metasomatic stage is probably related to a regional Na +/- Ca metasomatic and associated U +/- REE mineralising system operating concurrently with granitic magmatism at c. 1.8 Ga in the Vastervik region. This highlights the potential for discovering hitherto unknown REE deposits and for the reappraisal of already known deposits in this part of the Fennoscandian Shield.

  • 10.
    Andersson, Stefan S.
    et al.
    Univ Helsinki, Dept Geosci & Geog, POB 64,Gustaf Hallstromin Katu 2a, FI-00014 Helsinki, Finland.
    Wagner, Thomas
    Rhein Westfal TH Aachen, Inst Appl Mineral & Econ Geol, Wullnerstr 2, D-52062 Aachen, Germany.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden SGU, Dept Mineral Resources, SE-75128 Uppsala, Sweden.
    Fusswinkel, Tobias
    Rhein Westfal TH Aachen, Inst Appl Mineral & Econ Geol, Wullnerstr 2, D-52062 Aachen, Germany.
    Whitehouse, Martin J.
    Swedish Museum Nat Hist, Box 50007, SE-10405 Stockholm, Sweden.
    Apatite as a tracer of the source, chemistry and evolution of ore-forming fluids: The case of the Olserum-Djupedal REE-phosphate mineralisation, SE Sweden2019In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 255, p. 163-187Article in journal (Refereed)
    Abstract [en]

    This study explores the suitability of apatite as a tracer of the source(s), chemistry, and evolution of ore-forming hydrothermal fluids. This is tested by analysing the halogen (F, Cl, Br, and I), stable Cl isotopic, and trace element compositions of fluorapatite from the regional-scale Olserum-Djupedal rare earth element (REE) phosphate mineralisation in SE Sweden, which is dominated by monazite-(Ce), xenotime-(Y), and fluorapatite. The primary hydrothermal fluid flow system is recorded in a sequence from proximal granite-hosted to distal metasediment-hosted fluorapatite. Along this sequence, primary fluorapatite shows a gradual increase of Cl and Br concentrations and in (Gd/Yb)(N), a decrease of F and I concentrations, a decrease in delta Cl-37 values, in (La/Sm)(N), and partly in (La/Yb)(N) and (Y/Ho)(N). Local compositional differences of halogen and trace element concentrations have developed along rims and in domains adjacent to fractures of fluorapatite due to late-stage partial reaction with fracture fluids. These differences are insignificant compared to the larger deposit-scale zoning. This suggests that apatite can retain the primary record of the original ore-forming fluid despite later overprinting fluid events. The agreement between Br/Cl and I/Cl ratios of apatite and those of co-existing fluid inclusions at lower temperatures indicates that only a minor fractionation of Br from I occurs during apatite precipitation. The halogen ratios of apatite can thus be used as a first-order estimate for the composition of the ore-forming fluid. Taking the small fractionation factors for Cl isotopes between apatite and co-existing fluid at high temperatures into account, we propose that the Cl isotopic composition of apatite and the halogen ratios derived from the apatite composition can be used jointly to trace the source(s) of ore-forming fluids. By contrast, most trace elements incorporated in apatite are affected by the host rock environment and by fluid-mineral partitioning due to growth competition between co-crystallising minerals. Collectively, apatite is sensitive to changing fluid compositions, yet it is also able to record the character of primary ore-forming fluids. Thus, apatite is suitable for tracing the origin, chemistry, and evolution of fluids in hydrothermal ore-forming settings.

  • 11.
    Andersson, Stefan S.
    et al.
    Univ Helsinki, Dept Geosci & Geog, POB 64,Gustaf Hallstromin Katu 2a, FI-00014 Helsinki, Finland..
    Wagner, Thomas
    Rhein Westfal TH Aachen, Inst Appl Mineral & Econ Geol, Wullnerstr 2, D-52062 Aachen, Germany..
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Uppsala, Sweden.;Uppsala Univ, Dept Earth Sci, Villavagen 16, SE-75266 Uppsala, Sweden..
    Michallik, Radoslaw M.
    Univ Helsinki, Dept Geosci & Geog,Gustaf Hallstromin Katu 2a, FI-00014 Helsinki, Finland..
    Mineralogy, paragenesis, and mineral chemistry of REEs in the Olserum-Djupedal REE-phosphate mineralization, SE Sweden2018In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 103, no 1, p. 125-142Article in journal (Refereed)
    Abstract [en]

    The rapidly growing use of rare earth elements and yttrium (REE) in modern-day technologies, not least within the fields of green and carbon-free energy applications, requires exploitation of new REE deposits and deposit types. In this perspective, it is vital to develop a fundamental understanding of the behavior of REE in natural hydrothermal systems and the formation of hydrothermal REE deposits. In this study, we establish a mineralogical, textural, and mineral-chemical framework for a new type of deposit, the hydrothermal Olserum-Djupedal REE-phosphate mineralization in SE Sweden. An early, high-temperature REE stage is characterized by abundant monazite-(Ce) and xenotime-(Y) coexisting with fluorapatite and subordinate amounts of (Y,REE,U,Fe)-(Nb,Ta) oxides. During a subsequent stage, allanite-(Ce) and ferriallanite-(Ce) formed locally, partly resulting from the breakdown of primary monazite-(Ce). Alteration of allanite-(Ce) or ferriallanite-(Ce) to bastnasite-(Ce) and minor synchysite-(Ce) at lower temperatures represents the latest stage of REE mineral formation. The paragenetic sequence and mineral chemistry of the allanites record an increase in Ca content in the fluid. We suggest that this local increase in Ca, in conjunction with changes in oxidation state, were the key factors controlling the stability of monazite-(Ce) in the assemblages of the Olserum-Djupedal deposit. We interpret the alteration and replacement of primary monazite-(Ce), xenotime-(Y), fluorapatite, and minor (Y,REE,U,Fe)-(Nb, Ta) oxide phase(s), to be the consequence of coupled dissolution-reprecipitation processes. These processes mobilized REE,Th,U, and Nb-Ta, which caused the formation of secondary monazite-(Ce), xenotime-(Y), fluorapatite, and minor amounts of allanite-(Ce) and ferriallanite-(Ce). In addition, these alteration processes produced uraninite, thorite, columbite-(Fe), and uncharacterized (Th,U,Y,Ca)-silicates. Textural relations show that the dissolution-reprecipitation processes affecting fluorapatite preceded those affecting monazite-(Ce), xenotime-(Y), and the (Y, REE, U, Fe)-(Nb, Ta) oxide phase(s). The mineralogy of the primary ore mineralization and the subsequently formed alteration assemblages demonstrate the combined mobility of REE and HFSE in a natural F-bearing high-temperature hydrothermal system. The observed coprecipitation of monazite-(Ce), xenotime-(Y), and fluorapatite during the primary REE mineralization stage highlights the need for further research on the potentially important role of the phosphate ligand in hydrothermal REE transporting systems.

  • 12.
    Andrén, Margareta
    et al.
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Stockmann, Gabrielle
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Skelton, Alasdair
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Sturkell, Erik
    Univ Gothenburg, Dept Earth Sci, Gothenburg, Sweden.
    Mörth, Carl-Magnus
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Guðrúnardóttir, Helga Rakel
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Keller, Nicole Simone
    Univ Iceland, Inst Earth Sci, Reykjavik, Iceland.
    Odling, Nic
    Univ Edinburgh, Sch Geosci, Edinburgh, Midlothian, Scotland.
    Dahrén, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Broman, Curt
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Balic-Zunic, Tonci
    Univ Copenhagen, Nat Hist Museum, Copenhagen, Denmark.
    Hjartarsson, Hreinn
    Landsvirkjun, Reykjavik, Iceland.
    Siegmund, Heike
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Freund, Friedemann
    NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA.
    Kockum, Ingrid
    NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA.
    Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland2016In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 121, no 4, p. 2315-2337Article in journal (Refereed)
    Abstract [en]

    Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northernIceland, from October 2008 to June 2015 revealed (1) a long-term decrease in concentration of Si and Naand (2) an abrupt increase in concentration of Na before each of two consecutive M > 5 earthquakes whichoccurred in 2012 and 2013, both 76 km from Hafralækur. Based on a geochemical (major elements and stableisotopes), petrological, and mineralogical study of drill cuttings taken from an adjacent borehole, we areable to show that (1) the long-term decrease in concentration of Si and Na was caused by constant volumereplacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fracturesand (2) the abrupt increase of Na concentration before the first earthquake records a switchover tononstoichiometric dissolution of analcime with preferential release of Na into groundwater. We attributedecay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fracturedor porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are anincrease of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixingbetween groundwater components. Both could have been triggered by preseismic dilation, which was alsoinferred in a previous study by Skelton et al. (2014). The mechanism behind preseismic dilation so far from thefocus of an earthquake remains unknown.

  • 13.
    Barker, Abigail
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Ctr Nat Hazards & Disaster Sci CNDS, Villavagen 16, SE-75236 Uppsala, Sweden.
    Hansteen, Thor H.
    GEOMAR Helmholtz Ctr Ocean Res Kiel, Wischhofstr 1-3, D-24148 Kiel, Germany.
    Nilsson, David
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Unravelling the Crustal Architecture of Cape Verde from the Seamount Xenolith Record2019In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 9, no 2, article id 90Article in journal (Refereed)
    Abstract [en]

    The Cape Verde oceanic plateau hosts 10 islands and 11 seamounts and provides an extensive suite of alkaline lavas and pyroclastic rocks. The volcanic rocks host a range of crustal and mantle xenoliths. These xenoliths provide a spectrum of lithologies available to interact with magma during transport through the lithospheric mantle and crust. We explore the origin and depth of formation of crustal xenoliths to develop a framework of magma-crust interaction and a model for the crustal architecture beneath the Cape Verde oceanic plateau. The host lavas are phononephelinites to phonolites and the crustal xenoliths are mostly mafic plutonic assemblages with one sedimentary xenolith. REE profiles of clinopyroxene in the host lavas are light rare-earth element (LREE) enriched whereas clinopyoxene from the plutonic xenoliths are LREE depleted. Modelling of REE melt compositions indicates the plutonic xenoliths are derived from mid-ocean ridge basalt (MORB)-type ocean crust. Thermobarometry indicates that clinopyroxene in the host lavas formed at depths of 17 to 46 km, whereas those in the xenoliths formed at 5 to 20 km. This places the depth of origin of the plutonic xenoliths in the oceanic crust. Therefore, the xenoliths trace magma-crust interaction to the MORB oceanic crust and overlying sediments located beneath the Cape Verde oceanic plateau.

  • 14.
    Barker, Abigail
    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. Univ Las Palmas, GEOVOL, La Palmas Gran Canaria 35017, Spain.
    Carracedo, Juan Carlos
    Univ Las Palmas, GEOVOL, La Palmas Gran Canaria 35017, Spain.
    Nicholls, Peter A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    The magma plumbing system for the 1971 Teneguía eruption on La Palma, Canary Islands2015In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 170, no 5-6, article id 54Article in journal (Refereed)
    Abstract [en]

    The 1971 Teneguía eruption is the most recent volcanic event of the Cumbre Vieja rift zone on La Palma. The eruption produced basanite lavas that host xenoliths, which we investigate to provide insight into the processes of differentiation, assimilation and magma storage beneath La Palma. We compare our results to the older volcanomagmatic systems of the island with the aim to reconstruct the temporal development of the magma plumbing system beneath La Palma.

    The 1971 lavas are clinopyroxene-olivine-phyric basanites that contain augite, sodic-augite and Aluminium augite. Kaersutite cumulate xenoliths host olivine, clinopyroxene including sodic-diopside, and calcic-amphibole, whereas an analysed leucogabbro xenolith hosts plagioclase, sodic-augite-diopside, calcic-amphibole and hauyne. Mineral and mineral-melt thermobarometry indicate that clinopyroxene and plagioclase in the 1971 Teneguía lavas crystallised at 20 to 45 km depth, coinciding with clinopyroxene and calcic-amphibole crystallisation in the kaersutite cumulate xenoliths at 25 to 45 km and clinopyroxene, calcic-amphibole and plagioclase crystallisation in the leucogabbro xenolith at 30 to 50 km.

    Combined mineral chemistry and thermobarometry suggest that the magmas had already crystallised, differentiated and formed multiple crystal populations in the oceanic lithospheric mantle. Notably, the magmas that supplied the 1949 and 1971 events appear to have crystallised deeper than the earlier Cumbre Vieja magmas, which suggests progressive underplating beneath the Cumbre Vieja rift zone. In addition, the lavas and xenoliths of the 1971 event crystallised at a common depth, indicating a reused plumbing system and progressive recycling of Ocean Island plutonic complexes during subsequent magmatic activity. 

  • 15.
    Barnes, Christopher
    et al.
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Schneider, David
    Univ Ottawa, Dept Earth & Environm Sci, Ottawa, ON, Canada.
    Walczak, Katarzyna
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Bukala, Michal
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Kosminska, Karolina
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Tokarski, Tomasz
    AGH Univ Sci & Technol, Acad Ctr Mat & Nanotechnol, Krakow, Poland.
    Karlsson, Andreas
    Swedish Museum Nat Hist, Dept Geosci, Stockholm, Sweden.
    High-spatial resolution dating of monazite and zircon revealsthe timing of subduction-exhumation of the Vaimok Lens in the Seve Nappe Complex (Scandinavian Caledonides)2019In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 174, no 1, article id 5Article in journal (Refereed)
    Abstract [en]

    In-situ monazite Th-U-total Pb dating and zircon LA-ICP-MS depth-profiling was applied to metasedimentary rocks from the Vaimok Lens in the Seve Nappe Complex (SNC), Scandinavian Caledonides. Results of monazite Th-U-total Pb dating, coupled with major and trace element mapping of monazite, revealed 603 +/- 16 Ma Neoproterozoic cores surrounded by rims that formed at 498 +/- 10 Ma. Monazite rim formation was facilitated via dissolution-reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y2O3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. Multiple zircon grains also exhibit rims formed by dissolution-reprecipitation that are defined by enrichment of light rare earth elements, U, Th, P, +/- Y, and +/- Sr. Rims also have subdued Eu anomalies ( Eu/Eu* approximate to 0.6-1.2) with respect to the cores. The age of zircon rim formation was calculated from three metasedimentary rocks: 480 +/- 22 Ma; 475 +/- 26 Ma; and 479 +/- 38 Ma. These results show that both monazite and zircon experienced dissolution-reprecipitation under high-pressure conditions. Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation.

  • 16.
    Berg, Sylvia E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Las Palmas Gran Canaria, GEOVOL, Las Palmas Gran Canaria, Spain.
    Deegan, Frances M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Krumbholz, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Georg August Univ Gottingen, Geosci Ctr, Goldschmidtstr 1-3, D-37077 Gottingen, Germany.
    Mancini, Lucia
    SCpA, Elettra Sincrotrone Trieste, SS 14 Km 163,5 AREA Sci Pk, I-34149 Trieste, Italy.
    Polacci, Margherita
    Univ Manchester, Sch Earth & Environm Sci, Williamson Bldg,Oxford Rd, Manchester M13 9PL, Lancs, England.
    Carracedo, Juan Carlos
    Univ Las Palmas Gran Canaria, GEOVOL, Las Palmas Gran Canaria, Spain.
    Soler, Vicente
    CSIC, Estn Vulcanol Canarias, Avda Astr Fco Sanchez 3, Tenerife 38206, Spain.
    Arzilli, Fabio
    SCpA, Elettra Sincrotrone Trieste, SS 14 Km 163,5 AREA Sci Pk, I-34149 Trieste, Italy.; Univ Manchester, Sch Earth & Environm Sci, Williamson Bldg,Oxford Rd, Manchester M13 9PL, Lancs, England.
    Brun, Francesco
    SCpA, Elettra Sincrotrone Trieste, SS 14 Km 163,5 AREA Sci Pk, I-34149 Trieste, Italy.; Univ Trieste, Dept Engn & Architecture, Via A Valerio 10, I-34127 Trieste, Italy.
    Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by X-ray computed microtomography2016In: Bulletin of Volcanology, ISSN 0258-8900, E-ISSN 1432-0819, Vol. 78, no 12, article id 85Article in journal (Refereed)
    Abstract [en]

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

  • 17.
    Berg, Sylvia
    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.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Riishuus, Morten S.
    Nordic Volcanological Center. Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavik.
    Whitehouse, Martin J.
    Dept. of Geosciences, Swedish Museum of Natural History, SE-104 05, Stockholm, Sweden.
    Harris, Chris
    Dept. of Geological Sciences, University of Cape Town, Rondebosch, South Africa,.
    Freda, Carmela
    Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.
    Ellis, Ben S.
    Inst. f. Geochemie und Petrologie, ETH, Clausiusstrasse 25, 8092, Zurich, Switzerland.
    Krumbholz, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Gústafsson, Ludvik E.
    Samband Islenskra Sveitarfélag, Borgartúni 30, pósthólf 8100, 128 Reykjavik, Iceland.
    Rapid high-silica magma generation in basalt-dominated rift settings2015Conference paper (Other academic)
  • 18.
    Berg, Sylvia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Iceland, Nord Volcanol Ctr, Inst Earth Sci, Sturlugata 7, IS-101 Reykjavik, Iceland.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Harris, Chris
    Univ Cape Town, Dept Geol Sci, ZA-7701 Rondebosch, South Africa.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Riishuus, Morten S.
    Univ Iceland, Nord Volcanol Ctr, Inst Earth Sci, Sturlugata 7, IS-101 Reykjavik, Iceland.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Krumbholz, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Exceptionally high whole-rock delta O-18 values in intra-caldera rhyolites from Northeast Iceland2018In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 82, no 5, p. 1147-1168Article in journal (Refereed)
    Abstract [en]

    The Icelandic crust is characterized by low delta O-18 values that originate from pervasive high-temperature hydrothermal alteration by O-18-depleted meteoric waters. Igneous rocks in Iceland with delta O-18 values significantly higher than unaltered oceanic crust (similar to 5.7 parts per thousand) are therefore rare. Here we report on rhyolitic intra-caldera samples from a cluster of Neogene central volcanoes in Borgarfjorour Eystri, Northeast Iceland, that show whole-rock delta O-18 values between +2.9 and +17.6 parts per thousand (n = 6), placing them among the highest delta O-18 values thus far recorded for Iceland. Extra-caldera rhyolite samples from the region, in turn, show delta O-18 whole-rock values between +3.7 and +7.8 parts per thousand (n = 6), consistent with the range of previously reported Icelandic rhyolites. Feldspar in the intra-caldera samples (n = 4) show delta O-18 values between +4.9 and +18.7 parts per thousand, whereas pyroxene (n = 4) shows overall low delta O-18 values of +4.0 to +4.2 parts per thousand, consistent with regional rhyolite values. In combination with the evidence from mineralogy and rock H2O contents, the high whole-rock delta O-18 values of the intra-caldera rhyolites appear to be the result of pervasive isotopic exchange during subsolidus hydrothermal alteration with O-18-enriched water. This alteration conceivably occurred in a near-surface hot spring environment at the distal end of an intra-caldera hydrothermal system. and was probably fed by waters that had already undergone significant isotope exchange with the country rock. Alternatively, O-18-enriched alteration fluids may have been produced during evaporation and boiling of standing water in former caldera lakes, which then interacted with the intra-caldera rock suites. Irrespective of the exact exchange processes involved, a previously unrecognized and highly localized delta O-18-enriched rock composition exists on Iceland and thus probably within the Icelandic crust too.

  • 19. Bih, H
    et al.
    Sinouh, H
    H Es-soufi, H
    Bih, L
    Haddad, M
    Bejjit, L
    Manoun, B
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Thermal and structural studies of Li2O-Na2O-SrO-TiO2-B2O3-P2O5 glasses by DTA, IR and EPR spectroscopy2017In: Journal of Applied Surfaces and Interfaces, Vol. 1, no 1-3, p. 57-63Article in journal (Refereed)
  • 20.
    Blythe, Lara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology. School of Physical and Geographical Science, Keele University, Keele, UK.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Department of Geological Sciences, Stockholm University, Stockholm, Sweden.
    Freda, C
    Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.
    Jolis, Ester Muños
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Masotta, M
    Bayerisches Geoinstitut, Universität Bayreuth, Bayreuth, Germany.
    Misiti, V.
    Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.
    Taddeucci, J.
    Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy.
    CO2 bubble generation and migration during magma–carbonate interaction2015In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 169, no 4, article id 42Article in journal (Refereed)
    Abstract [en]

    We conducted quantitative textural analysis of vesicles in high temperature and pressure carbonate assimilation experiments (1200 °C, 0.5 GPa) to investigate CO2 generation and subsequent bubble migration from carbonate into magma. We employed Mt. Merapi (Indonesia) and Mt. Vesuvius (Italy) compositions as magmatic starting materials and present three experimental series using (1) a dry basaltic-andesite, (2) a hydrous basaltic-andesite (2 wt% H2O), and (3) a hydrous shoshonite (2 wt% H2O). The duration of the experiments was varied from 0 to 300 s, and carbonate assimilation produced a CO2-rich fluid and CaO-enriched melts in all cases. The rate of carbonate assimilation, however, changed as a function of melt viscosity, which affected the 2D vesicle number, vesicle volume, and vesicle size distribution within each experiment. Relatively low-viscosity melts (i.e. Vesuvius experiments) facilitated efficient removal of bubbles from the reaction site. This allowed carbonate assimilation to continue unhindered and large volumes of CO2 to be liberated, a scenario thought to fuel sustained CO2-driven eruptions at the surface. Conversely, at higher viscosity (i.e. Merapi experiments), bubble migration became progressively inhibited and bubble concentration at the reaction site caused localised volatile over-pressure that can eventually trigger short-lived explosive outbursts. Melt viscosity therefore exerts a fundamental control on carbonate assimilation rates and, by consequence, the style of CO2-fuelled eruptions.

  • 21. Bosi, Ferdinando
    et al.
    Skogby, Henrik
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Reznitskii, Leonid
    Atomic arrangements around the O3 site in Al- and Cr-rich oxytourmalines: a combined EMP, SREF, FTIR and Raman study2015In: Physics and chemistry of minerals, ISSN 0342-1791, E-ISSN 1432-2021, Vol. 42, no 6, p. 441-453Article in journal (Refereed)
  • 22.
    Boskabadi, Arman
    et al.
    Univ Texas Dallas, Dept Geosci, ROC 21,800 West Campbell Rd, Richardson, TX 75080 USA.;Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    Pitcairn, Iain K.
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    Broman, Curt
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    Boyce, Adrian
    Scottish Univ Environm Res Ctr, E Kilbride, Lanark, Scotland..
    Teagle, Damon A. H.
    Univ Southampton, Natl Oceanog Ctr Southampton, Southampton, Hants, England..
    Cooper, Matthew J.
    Univ Southampton, Natl Oceanog Ctr Southampton, Southampton, Hants, England..
    Azer, Mokhles K.
    Natl Res Ctr, Dept Geol, Cairo, Egypt..
    Stern, Robert J.
    Univ Texas Dallas, Dept Geosci, ROC 21,800 West Campbell Rd, Richardson, TX 75080 USA..
    Mohamed, Fathy H.
    Univ Alexandria, Dept Geol, Fac Sci, Alexandria, Egypt..
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland..
    Carbonate alteration of ophiolitic rocks in the Arabian-Nubian Shield of Egypt: sources and compositions of the carbonating fluid and implications for the formation of Au deposits2017In: International Geology Review, ISSN 0020-6814, E-ISSN 1938-2839, Vol. 59, no 4, p. 391-419Article, review/survey (Refereed)
    Abstract [en]

    Ultramafic portions of ophiolitic fragments in the Arabian-Nubian Shield (ANS) show pervasive carbonate alteration forming various degrees of carbonated serpentinites and listvenitic rocks. Notwithstanding the extent of the alteration, little is known about the processes that caused it, the source of the CO2 or the conditions of alteration. This study investigates the mineralogy, stable (O, C) and radiogenic (Sr) isotope composition, and geochemistry of suites of variably carbonate altered ultramafics from the Meatiq area of the Central Eastern Desert (CED) of Egypt. The samples investigated include least-altered lizardite (Lz) serpentinites, antigorite (Atg) serpentinites and listvenitic rocks with associated carbonate and quartz veins. The C, O and Sr isotopes of the vein samples cluster between -8.1 parts per thousand and -6.8 parts per thousand for delta C-13, +6.4 parts per thousand and +10.5 parts per thousand for delta O-18, and Sr-87/Sr-86 of 0.7028-0.70344, and plot within the depleted mantle compositional field. The serpentinites isotopic compositions plot on a mixing trend between the depleted-mantle and sedimentary carbonate fields. The carbonate veins contain abundant carbonic (CO2 +/- CH4 +/- N-2) and aqueous-carbonic (H2O-NaCl-CO2 +/- CH4 +/- N-2) low salinity fluid, with trapping conditions of 270-300 degrees C and 0.7-1.1kbar. The serpentinites are enriched in Au, As, S and other fluid-mobile elements relative to primitive and depleted mantle. The extensively carbonated Atg-serpentinites contain significantly lower concentrations of these elements than the Lz-serpentinites suggesting that they were depleted during carbonate alteration. Fluid inclusion and stable isotope compositions of Au deposits in the CED are similar to those from the carbonate veins investigated in the study and we suggest that carbonation of ANS ophiolitic rocks due to influx of mantle-derived CO2-bearing fluids caused break down of Au-bearing minerals such as pentlandite, releasing Au and S to the hydrothermal fluids that later formed the Au-deposits. This is the first time that gold has been observed to be remobilized from rocks during the lizardite-antigorite transition.

  • 23.
    Bowles, John F. W.
    et al.
    Univ Manchester, Sch Earth & Environm Sci, Manchester, Lancs, England.
    Cook, Nigel J.
    Univ Adelaide, Sch Chem Engn, Adelaide, Australia.
    Sundblad, Krister
    Univ Turku, Dept Geog & Geol, Turku, Finland; St Petersburg State Univ, Inst Earth Sci, St Petersburg, Russia.
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Uppsala, Sweden.
    Deady, Eimear
    Lyell Ctr, British Geol Survey, Res Ave South, Edinburgh, Midlothian, Scotland; Univ Exeter, Camborne Sch Mines, Penryn Campus, Penryn, England.
    Hughes, Hannah S. R.
    Univ Exeter, Camborne Sch Mines, Penryn Campus, Penryn, England.
    Critical-metal mineralogy and ore genesis: contributions from the European Mineralogical Conference held in Rimini, September 20162018In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 82, p. S1-S4Article in journal (Other academic)
  • 24.
    Budd, David A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Characterising volcanic magma plumbing systems: A tool to improve eruption forecasting at hazardous volcanoes2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis attempts to develop our understanding of volcanic magma plumbing systems and the magmatic processes that operate within them, such as fractional crystallisation, crustal partial melting, assimilation, and magma mixing. I utilise petrology, rock and mineral geochemistry, and isotope systematics to seek to improve our ability to forecast the eruptive frequency and style of active volcanoes, an aspect often lacking in current volcano monitoring efforts. In particular, magma reservoir dynamics are investigated from a mineral scale at Katla volcano in Iceland, to a sub-mineral scale at Merapi, Kelud, and Toba volcanoes in Indonesia.

    The magma plumbing architecture of Katla volcano on Iceland is explored in the first part of this thesis. Crystalline components within tephra and volcanic rock preserve a record of the physical and chemical evolution of a magma, and are analysed through oxygen isotopic and thermobarometric techniques to temporally constrain changes in reservoir depth and decode the petrogenesis of the lavas. We find both prolonged upper crustal magma storage and shallow level assimilation to be occurring at Katla. The results generated from combining these analytical strands reveal the potential for unpredictable explosive volcanism at this lively Icelandic volcano.

    The second part of this thesis examines the magma plumbing systems of Merapi, Kelud and Toba volcanoes of the Sunda arc in Indonesia at higher temporal and petrological resolution than possible for Katla (e.g., due to the crystal poor character of the rocks). For this part of the thesis, minerals were analysed in-situ to take advantage of sub-crystal scale isotopic variations in order to investigate processes of shallow-level assimilation in the build-up to particular eruptions. We find that intra-crystal analyses reveal an otherwise hidden differentiation history at these volcanoes, and establish a better understanding as to how they may have rapidly achieved a critical explosive state.

    The outcomes of this thesis therefore deepen our knowledge of evolutionary trends in magma plumbing system dynamics, and highlight the importance of understanding the geochemical processes that can prime a volcano for eruption. Lastly, I emphasise the vital contribution petrology can make in current volcano monitoring efforts. 

    List of papers
    1. Persistent multitiered magma plumbing beneath Katla volcano, Iceland
    Open this publication in new window or tab >>Persistent multitiered magma plumbing beneath Katla volcano, Iceland
    2016 (English)In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 17, no 3, p. 966-980Article in journal (Refereed) Published
    Abstract [en]

    Recent seismic unrest and a persistent Holocene eruption record at Katla volcano, Iceland indicate that a near-future eruption is possible. Previous petrological investigations suggest that Katla is supplied by a simple plumbing system that delivers magma directly from depth, while seismic and geodetic data also point toward the existence of upper-crustal magma storage. To characterize Katla's recent plumbing system, we established mineral-melt equilibrium crystallization pressures from four age-constrained Katla tephras spanning from 8 kyr BP to 1918. The results point to persistent shallow- (≤8 km depth) as well as deep-crustal (ca. 10 – 25 km depth) magma storage beneath Katla throughout the last 8 kyr. The presence of multiple magma storage regions implies that mafic magma from the deeper reservoir system may become gas-rich during ascent and storage in the shallow crust and erupt explosively. Alternatively, it might intersect evolved magma pockets in the shallow-level storage region, and so increase the potential for explosive mixed-magma ash eruptions.

    Place, publisher, year, edition, pages
    American Geophysical Union (AGU), 2016
    Keywords
    Katla volcano; mineral-melt equilibrium thermobarometry; persistent multi-tiered magma plumbing system
    National Category
    Geology
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-267448 (URN)10.1002/2015GC006118 (DOI)000375144700019 ()
    Funder
    Swedish Research CouncilThe Royal Swedish Academy of Sciences
    Note

    Title in thesis list of papers: Persistent two-tiered magma plumbing beneath Katla volcano, Iceland

    Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2019-09-27Bibliographically approved
    2. Petrogenetic constraints on the Katla rhyolites, South Iceland
    Open this publication in new window or tab >>Petrogenetic constraints on the Katla rhyolites, South Iceland
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Geology
    Identifiers
    urn:nbn:se:uu:diva-267451 (URN)
    Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2016-01-13
    3. New augite and enstatite pyroxene standards for SIMS oxygen isotope analysis and their application to Merapi volcano, Sunda arc, Indonesia
    Open this publication in new window or tab >>New augite and enstatite pyroxene standards for SIMS oxygen isotope analysis and their application to Merapi volcano, Sunda arc, Indonesia
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Geosciences, Multidisciplinary
    Identifiers
    urn:nbn:se:uu:diva-267452 (URN)
    Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2016-04-27
    4. Sudden Plinian eruption of remnant magmas at Kelud volcano, Java, Indonesia
    Open this publication in new window or tab >>Sudden Plinian eruption of remnant magmas at Kelud volcano, Java, Indonesia
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Geology
    Identifiers
    urn:nbn:se:uu:diva-267472 (URN)
    Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2016-01-13
    5. Magma reservoir dynamics recorded by oxygen isotope zoning in quartz
    Open this publication in new window or tab >>Magma reservoir dynamics recorded by oxygen isotope zoning in quartz
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Geology
    Identifiers
    urn:nbn:se:uu:diva-267454 (URN)
    Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2016-01-13
    6. Ancient oral tradition describes volcano-earthquake interaction at Merapi volcano, Indonesia.
    Open this publication in new window or tab >>Ancient oral tradition describes volcano-earthquake interaction at Merapi volcano, Indonesia.
    Show others...
    2015 (English)In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 97, no 1, p. 137-166Article in journal (Refereed) Published
    National Category
    Geosciences, Multidisciplinary
    Research subject
    Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
    Identifiers
    urn:nbn:se:uu:diva-240752 (URN)10.1111/geoa.12099 (DOI)000350500400010 ()
    Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2019-09-25Bibliographically approved
    7. Traversing nature's danger zone: getting up close with Sumatra's volcanoes
    Open this publication in new window or tab >>Traversing nature's danger zone: getting up close with Sumatra's volcanoes
    Show others...
    2012 (English)In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 28, no 2, p. 64-70Article in journal (Refereed) Published
    Abstract [en]

    The Indonesian island of Sumatra, located in one of the most active zones of the Pacific Ring of Fire, is characterized by a chain of subduction-zone volcanoes which extend the entire length of the island. As a group of volcanic geochemists, we embarked upon a five-week sampling expedition to these exotic, remote, and in part explosive volcanoes (SAGE 2010; Sumatran Arc Geochemical Expedition). We set out to collect rock and gas samples from 17 volcanic centres from the Sumatran segment of the Sunda arc system, with the aim of obtaining a regionally significant sample set that will allow quantification of the respective roles of mantle versus crustal sources to magma genesis along the strike of the arc. Here we document our geological journey through Sumatra's unpredictable terrain, including the many challenges faced when working on active volcanoes in pristine tropical climes.

    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-188509 (URN)10.1111/j.1365-2451.2012.00828.x (DOI)
    Available from: 2012-12-17 Created: 2012-12-17 Last updated: 2017-12-06Bibliographically approved
  • 25.
    Budd, David A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Ist Nazl Geofis & Vulcanol, Rome, Italy.
    Deegan, Frances M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Swedish Museum Nat Hist, Dept Geosci, Stockholm, Sweden.
    Jolis, Ester
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Smith, Victoria
    Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford, UK.
    Whitehouse, Martin
    Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden.
    Harris, Chris
    Department of Geological Sciences, University of Cape Town, South Africa.
    Freda, Carmela
    Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy.
    Hilton, David
    Scripps Institution of Oceanography, University of California, San Diego, USA.
    Halldórsson, Sæmundur
    Scripps Institution of Oceanography, University of California, San Diego, USA; Univ Iceland, Inst Earth Sci, Reykjavik, Iceland.
    Bindeman, Ilya
    Department of Geological Sciences, University of Oregon, Oregon, USA.
    Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 40624Article in journal (Refereed)
    Abstract [en]

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

  • 26.
    Budd, David
    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.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Jolis, Ester
    Smith, Victoria
    Whitehouse, Martin
    Harris, Chris
    Freda, Carmela
    Hilton, David
    Halldórsson, Sæmundur
    Bindeman, Ilya
    Magma reservoir dynamics recorded by oxygen isotope zoning in quartzManuscript (preprint) (Other academic)
  • 27.
    Budd, David
    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.
    Harris, Chris
    Meyer, Romain
    Deegan, Frances
    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.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Petrogenetic constraints on the Katla rhyolites, South IcelandManuscript (preprint) (Other academic)
  • 28.
    Budd, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Dahrén, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Persistent multitiered magma plumbing beneath Katla volcano, Iceland2016In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 17, no 3, p. 966-980Article in journal (Refereed)
    Abstract [en]

    Recent seismic unrest and a persistent Holocene eruption record at Katla volcano, Iceland indicate that a near-future eruption is possible. Previous petrological investigations suggest that Katla is supplied by a simple plumbing system that delivers magma directly from depth, while seismic and geodetic data also point toward the existence of upper-crustal magma storage. To characterize Katla's recent plumbing system, we established mineral-melt equilibrium crystallization pressures from four age-constrained Katla tephras spanning from 8 kyr BP to 1918. The results point to persistent shallow- (≤8 km depth) as well as deep-crustal (ca. 10 – 25 km depth) magma storage beneath Katla throughout the last 8 kyr. The presence of multiple magma storage regions implies that mafic magma from the deeper reservoir system may become gas-rich during ascent and storage in the shallow crust and erupt explosively. Alternatively, it might intersect evolved magma pockets in the shallow-level storage region, and so increase the potential for explosive mixed-magma ash eruptions.

  • 29.
    Budzyn, Bartosz
    et al.
    Polish Acad Sci, Res Ctr Krakow ING PAN, Inst Geol Sci, Senacka 1, PL-31002 Krakow, Poland..
    Harlov, Daniel E.
    Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany.;Univ Johannesburg, Dept Geol, POB 524, ZA-2006 Auckland Pk, South Africa..
    Kozub-Budzyn, Gabriela A.
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al A Mickiewicza 30, PL-30059 Krakow, Poland..
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al A Mickiewicza 30, PL-30059 Krakow, Poland..
    Experimental constraints on the relative stabilities of the two systems monazite-(Ce) - allanite-(Ce) - fluorapatite and xenotime-(Y) - (Y,HREE)-rich epidote - (Y,HREE)-rich fluorapatite, in high Ca and Na-Ca environments under P-T conditions of 200-1000 MPa and 450-750 A degrees C2017In: Mineralogy and Petrology, ISSN 0930-0708, E-ISSN 1438-1168, Vol. 111, no 2, p. 183-217Article in journal (Refereed)
    Abstract [en]

    The relative stabilities of phases within the two systems monazite-(Ce) - fluorapatite - allanite-(Ce) and xenotime-(Y) - (Y,HREE)-rich fluorapatite - (Y,HREE)-rich epidote have been tested experimentally as a function of pressure and temperature in systems roughly replicating granitic to pelitic composition with high and moderate bulk CaO/Na2O ratios over a wide range of P-T conditions from 200 to 1000 MPa and 450 to 750 A degrees C via four sets of experiments. These included (1) monazite-(Ce), labradorite, sanidine, biotite, muscovite, SiO2, CaF2, and 2 M Ca(OH)(2); (2) monazite-(Ce), albite, sanidine, biotite, muscovite, SiO2, CaF2, Na2Si2O5, and H2O; (3) xenotime-(Y), labradorite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, and 2 M Ca(OH)(2); and (4) xenotime-(Y), albite, sanidine, biotite, muscovite, garnet, SiO2, CaF2, Na2Si2O5, and H2O. Monazite-(Ce) breakdown was documented in experimental sets (1) and (2). In experimental set (1), the Ca high activity (estimated bulk CaO/Na2O ratio of 13.3) promoted the formation of REE-rich epidote, allanite-(Ce), REE-rich fluorapatite, and fluorcalciobritholite at the expense of monazite-(Ce). In contrast, a bulk CaO/Na2O ratio of similar to 1.0 in runs in set (2) prevented the formation of REE-rich epidote and allanite-(Ce). The reacted monazite-(Ce) was partially replaced by REE-rich fluorapatite-fluorcalciobritholite in all runs, REE-rich steacyite in experiments at 450 A degrees C, 200-1000 MPa, and 550 A degrees C, 200-600 MPa, and minor cheralite in runs at 650-750 A degrees C, 200-1000 MPa. The experimental results support previous natural observations and thermodynamic modeling of phase equilibria, which demonstrate that an increased CaO bulk content expands the stability field of allanite-(Ce) relative to monazite-(Ce) at higher temperatures indicating that the relative stabilities of monazite-(Ce) and allanite-(Ce) depend on the bulk CaO/Na2O ratio. The experiments also provide new insights into the re-equilibration of monazite-(Ce) via fluid-aided coupled dissolution-reprecipitation, which affects the Th-U-Pb system in runs at 450 A degrees C, 200-1000 MPa, and 550 A degrees C, 200-600 MPa. A lack of compositional alteration in the Th, U, and Pb in monazite-(Ce) at 550 A degrees C, 800-1000 MPa, and in experiments at 650-750 A degrees C, 200-1000 MPa indicates the limited influence of fluid-mediated alteration on volume diffusion under high P-T conditions. Experimental sets (3) and (4) resulted in xenotime-(Y) breakdown and partial replacement by (Y,REE)-rich fluorapatite to Y-rich fluorcalciobritholite. Additionally, (Y,HREE)-rich epidote formed at the expense of xenotime-(Y) in three runs with 2 M Ca(OH)(2) fluid, at 550 A degrees C, 800 MPa; 650 A degrees C, 800 MPa; and 650 A degrees C, 1000 MPa similar to the experiments involving monazite-(Ce). These results confirm that replacement of xenotime-(Y) by (Y,HREE)-rich epidote is induced by a high Ca bulk content with a high CaO/Na2O ratio. These experiments demonstrate also that the relative stabilities of xenotime-(Y) and (Y,HREE)-rich epidote are strongly controlled by pressure.

  • 30.
    Bukała, Michał
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Klonowska, Iwona
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Barnes, Christopher
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Kośmińska, Karolina
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.
    Janák, Marian
    Slovak Acad Sci, Earth Sci Inst, Bratislava, Slovakia.
    Broman, Curt
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden.
    Luptáková, Jarmila
    Slovak Acad Sci, Earth Sci Inst, Banska Bystrica, Slovakia.
    UHP metamorphism recorded by phengite eclogite from the Caledonides of northern Sweden: P-T path and tectonic implications2018In: Journal of Metamorphic Geology, ISSN 0263-4929, E-ISSN 1525-1314, Vol. 36, no 5, p. 547-566Article in journal (Refereed)
    Abstract [en]

    The Seve Nappe Complex (SNC) of the Scandinavian Caledonides records a well‐documented history of high pressure (HP) and ultra‐high pressure (UHP) metamorphism. Eclogites of the SNC occur in two areas in Sweden, namely Jämtland and Norrbotten. The Jämtland eclogites and associated rocks are well‐studied and provide evidence for late Ordovician UHP metamorphism, whereas the Norrbotten eclogites, formed during the late Cambrian (Furongian)/Early Ordovician, have not been studied in such detail, especially in terms of the P–T conditions of their formation. Within the studied eclogite, clinopyroxene contains a high‐Na core and two rims: inner, medium‐Na and outer, low‐Na. Garnet consists of a high‐Ca euhedral core, low‐Ca inner rim and medium‐Ca outer rim. A similar pattern occurs within phengite, where high‐Si cores are enveloped by medium and low‐Si rims. The compositions of the mineral cores, inner rims and outer rims reflect three stages in the metamorphic evolution of the eclogite. Applied Quartz‐in‐Garnet geobarometry, coupled with Zr‐in‐rutile geothermometry reveal that garnet nucleation (E0 stage) took place at 1.5–1.6 GPa and 620–660°C. The eclogite peak‐pressure assemblage developed during the E1 stage, it consists of garnet+omphacite+phengite+rutile+coesite? and yields P–T conditions of 2.8–3.1 GPa and 660–780°C as constrained by conventional geothermobarometry and thermodynamic modelling in the NCKFMMnASHT system. Later, lower‐pressure stages E2 and E3 record conditions of 2.2–2.8 GPa, 680–780°C and 2.1 GPa, 735°C, respectively. The prograde metamorphic evolution of the eclogite is inferred from inclusions of epidote, amphibole and clinopyroxene within garnet. The presence of amphibole–quartz–plagioclase symplectites, secondary epidote/zoisite and titanite replacing rutile record the later retrograde changes taking place at <1.5 GPa (referred as E4 stage). The obtained P–T conditions indicate that the Norrbotten eclogites underwent a metamorphic evolution characterized by a clockwise P–T path with peak metamorphism reaching up to coesite stability field within a relatively cold subduction regime (7.8°C/km). The obtained results provide the first evidence for UHP metamorphism in the SNC above the Arctic Circle and document cold subduction regime and multistage exhumation of the deeply subducted Baltican margin at early stage of the Caledonian Orogeny.

  • 31.
    Buntin, Sebastian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Malinowski, Michal
    Polish Acad Sci, Inst Geophys, Warsaw, Poland.
    Larsson, Sven Ake
    Gothenburg Univ, Earth Sci Ctr, Dept Geol, Gothenburg, Sweden.
    Thybo, Hans
    Istanbul Tech Univ, Eurasia Inst Earth Sci, Istanbul, Turkey.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Korja, Annakaisa
    Univ Helsinki, Inst Seismol, Helsinki, Finland.
    Gorszczyk, Andrzej
    Polish Acad Sci, Inst Geophys, Warsaw, Poland.
    Emplacement and 3D geometry of crustal-scale saucer-shaped intrusions in the Fennoscandian Shield2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 10498Article in journal (Refereed)
    Abstract [en]

    Saucer-shaped intrusions of tens of meters to tens of kilometres across have been observed both from surface geological mapping and geophysical observations. However, there is only one location where they have been reported to extend c. 100 km laterally, and emplaced both in a sedimentary basin and the crystalline basement down to 12 km depth. The legacy BABEL offshore seismic data, acquired over the central Fennoscandian Shield in 1989, have been recovered and reprocessed with the main goal of focusing on this series of globally unique crustal-scale saucer-shaped intrusions present onshore and offshore below the Bothnian Sea. The intrusions (c. 1.25 Ga), emplaced in an extensional setting, are observed within both sedimentary rocks (<1.5 Ga) and in the crystalline basement (>1.5 Ga). They have oval shapes with diameters ranging 30-100 km. The reprocessed seismic data provide evidence of up-doming of the lower crust (representing the melt reservoir) below the intrusions that, in turn, are observed at different depths in addition to a steep seismically transparent zone interpreted to be a discordant feeder dyke system. Relative age constraints and correlation with onshore saucer-shaped intrusions of different size suggest that they are internally connected and fed by each other from deeper to shallower levels. We argue for a nested emplacement mechanism and against a controlling role by the overlying sedimentary basin as the saucer-shaped intrusions are emplaced in both the sedimentary rocks as well as in the underlying crystalline basement. The interplay between magma pressure and overburden pressure, as well as the, at the time, ambient stress regime, are responsible for their extensive extent and rather constant thicknesses (c. 100-300 m). Saucer-shaped intrusions may therefore be present elsewhere in the crystalline basement to the same extent as observed in this study some of which are a significant source of raw materials.

  • 32.
    Buntin, Sebastian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Malinowski, Michal
    Polish Academy of Sciences.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Thybo, Hans
    University of Copenhagen, Denmark.
    Buske, Stefan
    TUBAF, Germany.
    Seismic reprocessing of the BABEL lines for improved interpretation of the whole crust – preliminary results2016In: Lithosphere 2016: Ninth Symposium On Structure, Composition And Evolution Of The Lithosphere In Fennoscandia / [ed] Ilmo Kukkonen, Suvi Heinonen, Kati Oinonen, Katriina Arhe, Olav Eklund, Fredrik Karell, Elena Kozlovskaya, Arto Luttinen, Raimo Lahtinen, Juha Lunkka, Vesa Nykänen, Markku Poutanen , Eija Tanskanen and Timo Tiira, Helsinki, Finland: University of Helsinki, Institute of Seismology , 2016, p. 9-12Conference paper (Refereed)
    Abstract [en]

    This ongoing study focuses on the reprocessing of the historical BABEL (Baltic and Bothnian Echoes from the Lithosphere, 1989) seismic lines in the Bay of Bothnia in preparation for the acquisition of a 400 km long onshore reflection and refraction profile in central part of Sweden. The main aim of the project is to increase the understanding of the tectonic evolution of the mineral-rich Bergslagen region both offshore and onshore. The seismic data have been recovered and currently being reprocessed using up-to-date processing methods and preliminary results show promising outcome from this work.

  • 33.
    Burchardt, Steffi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Fuchs, Lukas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Sinking of anhydrite blocks within a Newtonian salt diapir: modelling the influence of block aspect ratio and salt stratification2012In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 188, no 3, p. 763-778Article in journal (Refereed)
    Abstract [en]

    2-D Finite Differences models are used to analyse the strain produced by gravity-driven sinking of dense rectangular inclusions through homogeneous and vertically stratified Newtonian salt. We systematically modelled the descent of dense blocks of different sizes and initial orientations (aspect ratios) representing the Main Anhydrite fragments documented within, for example, the Gorleben salt diapir. Model results demonstrate that size of the blocks is a governing parameter which dictates the amount of strain produced within the block and in the surrounding host salt. Initial block orientation (aspect ratio), on the other hand, causes fundamental differences in block deformation, while the resulting structures produced in the salt are principally the same in all models with homogeneous salt, covering shear zones and folding of passive markers. In models with vertically stratified salt with different viscosities, block descent takes place along complex paths. This results from greater strain accommodation by the salt formation with the lowest viscosity and an asymmetrical distribution of initial vertical shear stresses around the block. Consequently, in these models, block strain is lower compared with the models with homogeneous salt (for the same viscosity as the high-viscosity salt), and sinking is accompanied by block rotation. The latter causes diapir-scale disturbance of the pre-sinking salt stratigraphy and complex sinking paths of the blocks. In particular, vertically oriented blocks sink into high-viscosity salt and drag with them some low-viscosity salt, while horizontal blocks sink in the low-viscosity salt. The resultant sinking velocities vary strongly depending on the sinking path of the block. Based on model results and observed structural configuration within the Gorleben salt diapir, we conclude that the internal complexity of a salt diapir governs its post-ascent deformation. Salt structure and its interaction with dense blocks should hence be considered in the assessment of the long-term stability of storage sites for hazardous waste.

  • 34.
    Burchardt, Steffi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Mattsson, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Palma, J. Octavio
    Y-TEC – CONICET.
    Galland, Olivier
    Physics of Geological Processes, The NJORD Centre, University of Oslo.
    Almqvist, Bjarne
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Mair, Karen
    Physics of Geological Processes, The NJORD Centre, University of Oslo.
    Jerram, Dougal A.
    Dougal Earth Ltd. and CEED, University of Oslo.
    Hammer, Øyvind
    Natural History Museum, University of Oslo.
    Sun, Yang
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Progressive growth of the Cerro Bayo cryptodome, Chachahuén volcano, Argentina – implications for viscous magma emplacement2019In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 124, article id JGRB53599Article in journal (Refereed)
    Abstract [en]

    Cryptodome and dome collapse is associated with volcanic hazards, such as, explosive eruptions, pyroclastic density currents, and volcanic edifice collapse. The study of the growth and evolution of volcanic domes provides vital information on the link between dome growth and the development of weakness zones that may cause collapse. The Cerro Bayo cryptodome is superbly exposed in the eroded Miocene Chachahuén volcano in the Neuquén basin, Argentina. Cerro Bayo is a >0.3 km3 trachyandesitic cryptodome that intruded within the uppermost kilometer of the Chachahuén volcano. Here we investigate the emplacement of the Cerro Bayo cryptodome using structural mapping, photogrammetry, 3D structural modelling and measurement of magma flow indicators, brittle deformation features and magnetic fabrics with anisotropy of magnetic susceptibility (AMS). Magma flow fabrics near the margin are concentric and indicate contact-parallel flow and internal inflation of the body. Magmatic and magnetic fabrics and fracture patterns in the interior of the cryptodome are more complex and outline several structural domains. These domains are separated by magmatic shear zones that accommodated intrusion growth. The shear zones locally overprint the earlier formed concentric fabric. The nature of the structural domains shows that emplacement of Cerro Bayo occurred in three stages that resemble the endogenous to exogenous growth of volcanic domes. The formation of magmatic shear zones during cryptodome formation may have a profound effect on cryptodome stability by creating weakness zones that increase the risk of collapse.

  • 35.
    Burchardt, Steffi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Palma, J. Octavio
    Y-TEC – CONICET. Av. Del Petroleo s/n - (Entre 129 y 143), Berisso (CP 1923), Buenos Aires, Argentina .
    Mattsson, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Galland, Olivier
    Physics of Geological Processes, The NJORD Centre, Department of Geosciences, University of Oslo, Box 1047, Blindern, 0316 Oslo, Norway.
    Almqvist, Bjarne S. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Mair, Karen
    Physics of Geological Processes, The NJORD Centre, Department of Geosciences, University of Oslo, Box 1047, Blindern, 0316 Oslo, Norway.
    Jerram, Dougal A.
    Centre for Earth Evolution and Dynamics (CEED), Department of Geosciences, University of Oslo, P.O. Box 1047, Oslo, Norway.
    Hammer, Øyvind
    Natural History Museum, University of Oslo, Box 1172, 0318 Oslo, Norway.
    Progressive growth of the Cerro Bayo cryptodome, Chachahuén volcano, Argentina – implications for viscous magma emplacementManuscript (preprint) (Other academic)
    Abstract [en]

    Cryptodome and dome collapse is associated with volcanic hazards, such as, explosive eruptions, pyroclastic flows, and volcanic edifice collapse. Study of the growth and evolution of volcanic domes provides vital information on the link between dome growth and the development of weakness zones that may cause collapse. The Cerro Bayo cryptodome is superbly exposed in the eroded Miocene Chachahuén volcano in the Neuquén basin, Argentina. Cerro Bayo is a >0.3 km3 trachyandesitic cryptodome that intruded within the uppermost kilometer of the Chachahuén volcano. Here we investigate the emplacement of the Cerro Bayo cryptodome using structural mapping, photogrammetry, 3D structural modelling and measurement of magma flow indicators, brittle deformation features and magnetic fabrics with anisotropy of magnetic susceptibility (AMS). Magma flow fabrics near the margin are concentric and indicate contact-parallel flow and internal inflation of the body. Magmatic and magnetic fabrics and fracture patters in the interior of the cryptodome are more complex and outline several structural domains. These domains are separated by magmatic shear zones that accommodated intrusion growth. The shear zones locally overprint the earlier formed concentric fabric. The nature of the structural domains shows that emplacement of Cerro Bayo occurred in three stages that resemble the endogenous to exogenous growth of volcanic domes. The formation of magmatic shear zones during cryptodome formation may have a profound effect on cryptodome stability by creating weakness zones that increase the risk of collapse.

  • 36.
    Burchardt, Steffi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Goethe Univ Frankfurt, Fac Earth Sci, Altenhoferallee 1, D-60438 Frankfurt, Germany..
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Blythe, Lara
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Erupted frothy xenoliths may explain lack of country-rock fragments in plutons2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 34566Article in journal (Refereed)
    Abstract [en]

    Magmatic stoping is discussed to be a main mechanism of magma emplacement. As a consequence of stoping, abundant country-rock fragments should occur within, and at the bottom of, magma reservoirs as "xenolith graveyards", or become assimilated. However, the common absence of sufficient amounts of both xenoliths and crustal contamination have led to intense controversy about the efficiency of stoping. Here, we present new evidence that may explain the absence of abundant country-rock fragments in plutons. We report on vesiculated crustal xenoliths in volcanic rocks that experienced devolatilisation during heating and partial melting when entrained in magma. We hypothesise that the consequential inflation and density decrease of the xenoliths allowed them to rise and become erupted instead of being preserved in the plutonic record. Our thermomechanical simulations of this process demonstrate that early-stage xenolith sinking can be followed by the rise of a heated, partially-molten xenolith towards the top of the reservoir. There, remnants may disintegrate and mix with resident magma or erupt. Shallow-crustal plutons emplaced into hydrous country rocks may therefore not necessarily contain evidence of the true amount of magmatic stoping during their emplacement. Further studies are needed to quantify the importance of frothy xenolith in removing stoped material.

  • 37. Busby, CJ
    et al.
    Tamura, Y
    Blum, P
    Guerin, G
    Andrews, GDM
    Barker, Abigail
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Berger, Julien LR
    Bongiolo, EM
    Bordiga, Manuela
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    DeBari, SM
    Gill, JB
    Hamelin, C
    Jia, Jihui
    John, EH
    Jonas, Ann-Sophie
    Jutzeler, Martin
    Kars, Myriam AC
    Kita, Zachary A
    Konrad, Kevin
    Mahony, Susan H
    Martini, Michelangelo
    Miyazaki, Takashi
    Musgrave, Robert J
    Nascimento, Debara B
    Nichols, Alexander R L
    Ribeiro, Julia M
    Sato, Tomoki
    Schindlbeck, Julie C
    Schmitt, Axel K
    Straub, Susanne M
    Mleneck-Vautravers, Maryline J
    Yang, Alexandra Yang
    The missing half of the subduction factory: shipboard results from the Izu rear arc, IODP expedition 3502017In: International Geology Review, ISSN 0020-6814, E-ISSN 1938-2839, Vol. 59, no 13, p. 1677-1708Article in journal (Other academic)
    Abstract [en]

    IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although severalsites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand theevolution of the Izu rear arc, by drilling a deep-water volcaniclastic section with a long temporalrecord (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chainsup to ~100-km long roughly perpendicular to the arc front. Dredge samples from these aregeochemically distinct from arc front rocks, and drilling was undertaken to understand this arcasymmetry. Site U1437 lies in an ~20-km-wide basin between two rear arc seamount chains, ~90-kmwest of the arc front, and was drilled to 1804 m below the sea floor (mbsf) with excellent recovery.We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected(~60%), and the remaining fraction of the section is much finer-grained than predicted from itsposition within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size(clasts <3 cm). Volcanic blocks (>6.4 cm) are only sparsely scattered through the lowermost 25% ofthe section, and only one igneous unit was encountered, a rhyolite peperite intrusion at~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest palaeomagneticdatum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U–Pb zirconconcordia intercept age of (13.6 + 1.6/−1.7) Ma. Both arc front and rear arc sources contributed tothe fine-grained (distal) tephras of the upper 1320 m, but the coarse-grained (proximal) volcani-clastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arcasymmetry is not recorded in rocks older than ~13 Ma.

  • 38. Byrne, P.
    et al.
    Holohan, E
    Kervyn, M
    van Wyk de Vries, B.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Analogue modelling of volcano flank terrace formation on Mars2015In: Volcanism and Tectonism Across the Inner Solar System / [ed] Platz, T., Massironi M., Byrne P.K. and Hisinger H., Geological Society of London, 2015Chapter in book (Refereed)
    Abstract [en]

    Of the features that characterize large shield volcanoes on Mars, flank terraces remain the most enigmatic. Several competing mechanisms have been proposed for these laterally expansive, topographically subtle landforms. Here we test the hypothesis that horizontal contraction of a volcano in response to the down-flexing of its underlying basement leads to flank terracing. We performed a series of analogue models consisting of a conical sand–plaster load emplaced on a basement comprising a layer of brittle sand–plaster atop a reservoir of viscoelastic silicone. Our experiments consistently produced a suite of structures that included a zone of concentric extension distal to the conical load, a flexural trough adjacent to the load base and convexities (terraces) on the cone's flanks. The effects of variations in the thickness of the brittle basal layer, as well as in the volume, slope and planform eccentricity of the cone, were also investigated. For a given cone geometry, we find that terrace formation is enhanced as the brittle basement thickness decreases, but that a sufficiently thick brittle layer can enhance the basement's resistance to loading such that terracing of the cone is reduced or even inhibited altogether. For a given brittle basement thickness, terracing is reduced with decreasing cone slope and/or volume. Our experimental results compare well morphologically to observations of terraced edifices on Mars, and so provide a framework with which to understand the developmental history of large shield volcanoes on the Red Planet.

  • 39.
    Carracedo, Juan Carlos
    et al.
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    Pérez-Torrado, Francisco José
    Departamento de Física-Geología, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain.
    Rodríguez González, Alejandro
    Grupo de Investigación GEOVOL, Dpto. de Física, Universidad de Las Palmas de Gran Canaria, Spain .
    Soler, Vicente
    Estación Volcanológica de Canarias, IPNA‐CSIC, La Laguna, Tenerife, Spain.
    Fernández Turiel, José Luis
    Instituto de Ciencias de la Tierra Jaume Almera, CSIC, Barcelona, Spain.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Wiesmaier, Sebastian
    Department of Earth and Environmental Sciences, Ludwig-Maximilians Universität (LMU), Munich, Germany.
    The 2011 submarine volcanic eruption in El Hierro (Canary Islands)2012In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 28, no 2, p. 53-58Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Forty years after the Teneguía Volcano (La Palma, 1971), a submarine eruption took place off the town of La Restinga, south of El Hierro, the smallest and youngest island of the Canarian Archipelago. Precursors allowed an early detection of the event and its approximate location, suggesting it was submarine. Uncertainties derived from insufficient scientific information available to the authorities during the eruption, leading to disproportionate civil protection measures, which had an impact on the island's economy—based primarily on tourism—while residents experienced extra fear and distress.

  • 40.
    Carracedo, Juan Carlos
    et al.
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    Troll, ValentinUppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Teide Volcano: Geology and Eruptions of a Highly Differentiated Oceanic Stratovolcano2013Collection (editor) (Other academic)
    Abstract [en]

    Teide Volcano has many different meanings: For the Guanche aborigines, who endured several of its eruptions, it was Echeide (Hell). Early navigators had in Teide, a lifesaving widely visible landmark that was towering over the clouds. For the first explorers, Teide was a challenging and dangerous climb, since it was thought that Teide's peak was so high that from its summit the sun was too close and far too hot to survive. Teide was considered the highest mountain in the world at that time and measuring its height precisely was a great undertaking and at the time of global scientific significance. For von Buch, von Humboldt, Lyell and other great 18th and19th century naturalists, Teide helped to shape a new and now increasingly 'volcanic' picture, where the origin of volcanic rocks (from solidified magma) slowly casted aside Neptunism and removed some of the last barriers for the development of modern Geology and Volcanology as the sciences we know today. For the present day population of Tenerife, living on top of the world's third tallest volcanic structure on the planet, Teide has actually become "Padre Teide", a fatherly protector and an emblematic icon of Tenerife, not to say of the Canaries as a whole. The UNESCO acknowledged this iconic and complex volcano, as "of global importance in providing evidence of the geological processes that underpin the evolution of oceanic islands". Today, 'Teide National Park' boasts 4 Million annual visitors including many 'volcano spotters' and is a spectacular natural environment which most keep as an impression to treasure and to never forget. For us, the editors of this book, Teide is all of the above; a 'hell of a job', a navigation point on cloudy days, a challenge beyond imagination, a breakthrough in our understanding of oceanic volcanism that has shaped our way of thinking about volcanoes, and lastly, Teide provides us with a reference point from where to start exploring other oceanic volcanoes in the Canaries and beyond. Here we have compiled the different aspects and the current understanding of this natural wonder.

  • 41.
    Carracedo, Juan Carlos
    et al.
    Estación Volcanológica de Canarias, IPNA-Consejo Superior de Investigaciones Científicas (CSIC), La Laguna, 38206, Tenerife, Spain.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    The Geology of the Canary Islands2016Book (Other academic)
  • 42. Carracedo, Juan Carlos
    et al.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Zaczek, Kirsten
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Rodriguez-Gonzales, Alejandro
    Soler, Vincente
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    The 2011-2012 submarine eruption off El Hierro, Canary Islands: New lessons in oceanic island growth and volcanic crisis management2015In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 150, p. 168-200Article in journal (Refereed)
    Abstract [en]

    Forty years after the eruption of the Teneguía volcano on La Palma, 1971, the last volcanic event in the Canary Islands, a submarine eruption took place in 2011 off-shore El Hierro, the smallest and youngest island of the archipelago. In this paper, we review the periods of seismic unrest leading up to the 2011–2012 El Hierro eruption, the timeline of eruptive events, the erupted products, the wider societal impacts, and the insights garnered for our understanding of ocean island growth mechanisms and hazard management. Seismic precursors allowed early detection of magmatic activity and prediction of the approximate location of the eruption. White coloured “floating stones” (“xeno-pumice”) were described within the first few days of the events, the origin of which were hotly debated because of their potential implications for the character of the eruption. Due to epistemic uncertainty derived from delayed flow of scientific information and equivocal interpretations of the “floating stones”, the El Hierro 2011–2012 events were characterised by cautious civil protection measures, which greatly impacted on the residents' lives and on the island's economy. We therefore summarise the scientific lessons learned from this most recent Canary Island eruption and discuss how emergency managers might cope with similar situations of uncertainty during future eruptive events in the region.

  • 43.
    Carracedo, Juan-Carlos
    et al.
    University of Las Palmas de Gran Canaria, Dept. of Physics, Las Palmas de Gran Canaria, Spain.
    Perez-Torrado, Francisco J.
    University of Las Palmas de Gran Canaria, Dept. of Physics, Las Palmas de Gran Canaria, Spain.
    Rodriguez-Gonzalez, Alejandro
    University of Las Palmas de Gran Canaria, Dept. of Physics, Las Palmas de Gran Canaria, Spain.
    Paris, Raphael
    Université Blaise Pascal Clermont-Ferrand II, France.
    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.
    Volcanic and structural evolution of Pico do Fogo, Cape Verde2015In: Geology Today, ISSN 0266-6979, E-ISSN 1365-2451, Vol. 31, no 4, p. 146-152Article in journal (Refereed)
    Abstract [en]

    In recent months the media have drawn attention to the Cape Verde archipelago, with particular focus on the island of Fogo, the only island presently active and with an eruption that began on 23 November 2014, finally ceasing on 7 February 2015. The Monte Amarelo conical shield forms most of the 476 km2 almost circular island of Fogo. After attaining a critical elevation of about 3500 m, the Monte Amarelo shield volcano was decapitated by a giant landslide that formed a caldera-like depression (Cha das Caldeiras), which was subsequently partially filled by basaltic nested volcanism. This younger eruptive activity culminated in the construction of the 2829 m-high Pico do Fogo stratocone, apparently entirely made of layers of basaltic lapilli. Continued growth of the Pico do Fogo summit eruptions was interrupted in 1750, most likely after the stratocone reached a critical height. Since then, at least eight eruptions have taken place inside the landslide depression at the periphery of the Pico do Fogo cone, including the 2014–2015 eruptive event. Strong geological similarities with the Canary Islands, 1400 km to the north, have been frequently noted, probably as a consequence of a common process of origin and evolution associated with a mantle hot-spot. These similarities are particularly evident when comparing Fogo with the Teide Volcanic Complex on Tenerife, where a lateral collapse of the Las Cañadas stratovolcano also formed a large depression (the Caldera de Las Cañadas), now partially filled with the 3718 m-high Teide stratocone. However, important geological differences also exist and probably relate to the contrasting evolutionary stages of both islands. The Las Cañadas volcano on Tenerife formed at a late post-erosional stage, with predominantly evolved (trachyte and phonolite) magmas, while at Fogo basaltic volcanism is still dominant.

  • 44.
    Carrillo, Emilio
    et al.
    Univ Barcelona, Dept Geoquim Petr & Prospeccio Geol, C Marti & Franques S-N, E-08028 Barcelona, Spain.;Yachay Tech Univ, Sch Geol Sci & Engn, Hacienda San Jose S-N, San Miguel De Urcuqui, Ecuador..
    Koyi, Hemin A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Nilforoushan, Faramarz
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Gavle, Dept Ind Dev IT & Land Management, Gavle, Sweden.;Lantmateriet, Gavle, Sweden..
    Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain)2017In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 86, p. 1310-1326Article in journal (Refereed)
    Abstract [en]

    We run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin-skinned deformation of the Southeastern Pyrenean Basin (SPB; NE Spain). This basin is characterized by the existence of evaporites, deposited during the Early-Middle Eocene with lateral variations in thickness and lithological composition. These evaporites are distributed in three lithostratigraphic units, known as Serrat Evaporites, Vallfogona and Beuda Gypsum formations and acted as decollement levels, during compressional deformation in the Lutetian. In addition to analogue modeling, we have used field data, detailed geological mapping and key cross-sections supported by seismic and well data to build a new structural interpretation for the SPB. In this interpretation, it is recognized that the basal and upper parts of the Serrat Evaporites acted as the main decollement levels of the so-called Cadi thrust sheet and Serrat unit. A balanced restoration of the basin indicates that thrust faults nucleated at the stratigraphic transition of the Serrat Evaporites (zone with lateral variations of thickness and lithological composition), characterized by a wedge of anhydrite and shale. The analogue models were setup based on information extracted from cross-sections, built in two sectors with different lithology and stratigraphy of the evaporites, and the restored section of the SPB. In these models, deformation preferentially concentrated in areas where thickness change, defined by wedges of the ductile materials, was inbuilt. Based on the structural interpretation and model results, a kinematic evolution of the SPB is proposed. The kinematic model is characterized by the generation of out-of-sequence structures developed due to lateral stratigraphic variations of the Serrat Evaporites. The present work shows a good example of the role of stratigraphic heterogeneities of an evaporite formation which acts as decollement level on structural deformation in a fold-thrust belt. The results of this work have implications for hydrocarbon exploration and are relevant for studying structural geometry and mechanics in shortened evaporite basins. (C) 2017 Elsevier Ltd. All rights reserved.

  • 45.
    Cassidy, Mike
    et al.
    Institute of Geosciences, University of Mainz, D-55122 Mainz, Germany.
    Castro, Jonathan
    Institute of Geosciences, University of Mainz, D-55122 Mainz, Germany .
    Helo, Christoph
    Institute of Geosciences, University of Mainz, D-55122 Mainz, Germany .
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Deegan, Frances M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Muir, Duncan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Neave, David
    Institute of Mineralogy, Leibniz University of Hannover, 30167 Hannover, Germany.
    Mueller, Sebastian
    Institute of Geosciences, University of Mainz, D-55122 Mainz, Germany .
    Volatile dilution during magma injections and implications for volcano explosivity2016In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 44, no 12, p. 1027-1030Article in journal (Refereed)
    Abstract [en]

    Magma reservoirs underneath volcanoes grow through episodic emplacement of magma batches. These pulsed magma injections can substantially alter the physical state of the resident magma by changing its temperature, pressure, composition, and volatile content. Here we examine plagioclase phenocrysts in pumice from the 2014 Plinian eruption of Kelud (Indonesia) that record the progressive capture of small melt inclusions within concentric growth zones during crystallization inside a magma reservoir. High-spatial-resolution Raman spectroscopic measurements reveal the concentration of dissolved H2O within the melt inclusions, and provide insights into melt-volatile behavior at the single crystal scale. H2O contents within melt inclusions range from ∼0.45 to 2.27 wt% and do not correlate with melt inclusion size or distance from the crystal rim, suggesting that minimal H2O was lost via diffusion. Instead, inclusion H2O contents vary systematically with anorthite content of the host plagioclase (R2 = 0.51), whereby high anorthite content zones are associated with low H2O contents and vice versa. This relationship suggests that injections of hot and H2O-poor magma can increase the reservoir temperature, leading to the dilution of melt H2O contents. In addition to recording hot and H2O-poor conditions after these injections, plagioclase crystals also record relatively cold and H2O-rich conditions such as prior to the explosive 2014 eruption. In this case, the elevated H2O content and increased viscosity may have contributed to the high explosivity of the eruption. The point at which an eruption occurs within such repeating hot and cool cycles may therefore have important implications for explaining alternating eruptive styles.

  • 46.
    Charalampidis, Charalampos
    et al.
    Bavarian Acad Sci & Humanities, Munich, Germany..
    Fischer, Andrea
    Austrian Acad Sci, Inst Interdisciplinary Mt Res, Innsbruck, Austria..
    Kuhn, Michael
    Univ Innsbruck, Inst Atmospher & Cryospher Sci, Innsbruck, Austria..
    Lambrecht, Astrid
    Bavarian Acad Sci & Humanities, Munich, Germany..
    Mayer, Christoph
    Bavarian Acad Sci & Humanities, Munich, Germany..
    Thomaidis, Konstantinos
    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, LUVAL.
    Weber, Markus
    Tech Univ Munich, Chair Photogrammetry & Remote Sensing, Munich, Germany..
    Mass-Budget Anomalies and Geometry Signals of Three Austrian Glaciers2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, article id UNSP 218Article in journal (Refereed)
    Abstract [en]

    Glacier mass-budget monitoring documents climate fluctuations, provides context for observed glacier-geometry changes, and can provide information on the glaciers' states. We examine the mass-budget series and available geometries of three well-documented glaciers located in the same catchment area less than 10 km from one another in the Austrian Otztal Alps. The altitudinal profiles of the 1981-2010 average specific mass budgets of each glacier serve as climatic reference. We apply these reference mass-budget profiles on all available glacier geometries, thereby retrieving for each glacier reference-climate mass budgets that reveal in a discrete way each glacier's geometric adjustment over time and its impact on mass loss; interpolation of the reference-climate mass budgets over the 1981-2010 period provides the glaciers' geometry signals. The geometric mass-budget anomalies derived with respect to these geometry signals indicate decreasing mass budgets over the 1981-2010 period by 0.020 m water equivalent (w.e.) a(-2), or 31% additional mass loss compared to the centered anomalies derived with respect to the 1981-2010 averages of the conventional mass-budget series. Reference-climate mass budgets with respect to 1981-2010 of older geometries highlight Hintereisferner's adapting geometry by almost continuous retreat since 1850. Further retreat is inevitable as Hintereisferner is the furthest from a steady state amongst the three glaciers. The relatively small Kesselwandferner has been also mostly retreating, while briefly advancing in response to short-term climatic trends. In a stable 1981-2010 climate, Kesselwandferner would relatively quickly reach a steady state. Vernagtferner's geometry since 1979 favors mass loss by thinning, primarily due to extended surge-related mass losses since 1845; this inability to retreat has led to - and will further - Vernagtferner's disintegration.

  • 47.
    Chew, David M.
    et al.
    Department of Geology, Trinity College Dublin, Dublin 2, Ireland .
    Ganerød, Morgan
    Geological Survey of Norway (NGU), Norway.
    Troll, Valentin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Corfu, Fernando
    Department of Geosciences, Un iversity of Oslo, Norway.
    Meade, Fiona
    Department of Geology, Trinity College Dublin, Ireland.
    U-Pb TIMS zircon age constraints on the Tardree Rhyolite zircon fission track standard2008In: On Track Forum, Vol. 16, no 1Article in journal (Other academic)
  • 48.
    Chinnasamy, Sakthi Saravanan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Uken, Ron
    Reinhardt, Juergen
    Selby, David
    Johnson, Spencer
    Pressure, temperature, and timing of mineralization of the sedimentary rock-hosted orogenic gold deposit at Klipwal, southeastern Kaapvaal Craton, South Africa2015In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 50, no 6, p. 739-766Article in journal (Refereed)
    Abstract [en]

    Gold mineralization in the Klipwal Shear Zone (KSZ) at the Klipwal Gold Mine is confined to laminated quartz-carbonate lodes, stringers, and associated alteration in sandstone and siltstone of the Delfkom Formation in the upper Mozaan Group of the Mesoarchaean Pongola Supergroup. The moderately dipping brittle-ductile KSZ strikes N-S with an oblique-reverse, sinistral sense of shear. The deformational events that are recognized include an early compressional phase that produced anastomosing shears defined by shear fabrics with numerous shear-parallel laminated quartz-carbonate fault-fill veins and, in places, extensional quartz vein stockworks, and a late brittle reactivation phase that produced fault breccias, displacing earlier extensional veins. Three closely spaced economic reefs (lodes) are developed: the main R-reef constitutes the KSZ, while the J- and H-reefs represent footwall splays. Alteration comprises chlorite, muscovite, epidote, feldspar, and carbonates along with pyrite, arsenopyrite, and chalcopyrite +/- pyrrhotite. An inner alteration zone is dominated by laminated quartz-carbonate veins with alternating quartz-carbonate-rich and muscovite-chlorite-rich laminae, whereas the proximal zone is characterized by alteration halos of K-feldspar, albite, epidote, chlorite, and muscovite along with carbonates and associated quartz veins. Chlorite thermometry from the inner and proximal zones yielded temperatures of 267 to 312 A degrees C. Arsenopyrite compositions provide temperatures in the same range, 255 to 318 A degrees C. Fluid inclusion microthermometry and Raman spectrometry of quartz veins in the mineralized reefs reveal the presence of metamorphogenic aqueous-gaseous fluid with an average salinity of 6.5 wt% NaCl equiv. Fluid compositions and estimated pressure-temperature (P-T) range (1.1 to 2.5 kbar at 255 to 318 A degrees C) are typical of orogenic gold deposits. Devolatilization during the regional facies metamorphism of the Pongola Supergroup is considered the likely fluid-forming event with fluid flow focused into a "compressional jog" of the KSZ. Shear-induced pressure fluctuations generated a phase separation of the initial aqueous-gaseous fluid, producing a gaseous and low-salinity aqueous fluid. This, together with fluid-rock interaction, and a decrease in fO(2) lead to sulfide and gold precipitation at Klipwal. Re-Os data from six sulfide samples constrain the age of sulfide precipitation and, by inference, gold mineralization, to 2563 A +/- 84 Ma, with an initial Os-187/Os-188 = 0.29 A +/- 0.08 (MSWD = 0.38). This age is distinctly younger than the post-Pongola granites (2863-2721 Ma), ruling out the association of granite emplacement with mineralization. This would suggest that mineralization is linked to the regional D-3 folding event which reactivated the KSZ after emplacement of the post-Pongola granites and that final brittle, post-mineralization reactivation is related to Karoo age faulting. Low initial Os values suggest that ore fluid interacted with mafic rocks, leaching non-radiogenic Os, the likely source being the deeper seated Nsuze Group volcanics and/or the greenstone belts that underlie the Pongola Supergroup.

  • 49.
    Chukanov, Nikita V.
    et al.
    Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Moscow Region, Russia..
    Jonsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Geol Survey Sweden, Dept Mineral Resources, Box 670, S-75128 Uppsala, Sweden.
    Aksenov, Sergey M.
    Russian Acad Sci, Inst Crystallog, 59 Leninskiy Prospekt, Moscow 117333, Russia.;St Petersburg State Univ, Dept Crystallog, Univ Skaya Nab 7-9, St Petersburg 199034, Russia.;Russian Acad Sci, Nesmeyanov Inst Organoelement Cpds, GSP-1,Vavilova St 28,V-334, Moscow 119991, Russia..
    Britvin, Sergey N.
    St Petersburg State Univ, Dept Crystallog, Univ Skaya Nab 7-9, St Petersburg 199034, Russia..
    Rastsvetaeva, Ramiza K.
    Russian Acad Sci, Inst Crystallog, 59 Leninskiy Prospekt, Moscow 117333, Russia..
    Belakovskiy, Dmitriy I.
    Russian Acad Sci, Fersman Mineral Museum, Leninskiy Prospekt 18-2, Moscow 119071, Russia..
    Van, Konstantin V.
    Russian Acad Sci, Inst Expt Mineral, Chernogolovka 142432, Moscow Region, Russia..
    Roymillerite, Pb24Mg9(Si9AlO28)(SiO4)(BO3)(CO3)10(OH)14O4, a new mineral: mineralogical characterization and crystal chemistry2017In: Physics and chemistry of minerals, ISSN 0342-1791, E-ISSN 1432-2021, Vol. 44, no 10, p. 685-699Article in journal (Refereed)
    Abstract [en]

    The new mineral roymillerite Pb24Mg9(Si9AlO28)(SiO4)(BO3)(CO3)(10)(OH)(14)O-4, related to britvinite and molybdophyllite, was discovered in a Pb-rich assemblage from the Kombat Mine, Grootfontein district, Otjozondjupa region, Namibia, which includes also jacobsite, cerussite, hausmannite, sahlinite, rhodochrosite, barite, grootfonteinite, Mn-Fe oxides, and melanotekite. Roymillerite forms platy single-crystal grains up to 1.5 mm across and up to 0.3 mm thick. The new mineral is transparent, colorless to light pink, with a strong vitreous lustre. Cleavage is perfect on (001). Density calculated using the empirical formula is equal to 5.973 g/cm(3). Roymillerite is optically biaxial, negative, alpha = 1.86(1), beta ae gamma = 1.94(1), 2V (meas.) = 5(5)A degrees. The IR spectrum shows the presence of britvinite-type tetrahedral sheets, , , and OH- groups. The chemical composition is (wt%; electron microprobe, H2O and CO2 determined by gas chromatography, the content of B2O3 derived from structural data): MgO 4.93, MnO 1.24, FeO 0.95, PbO 75.38, B2O3 0.50, Al2O3 0.74, CO2 5.83, SiO2 7.90, H2O 1.8, total 99.27. The empirical formula based on 83 O atoms pfu (i.e. Z = 1) is Pb24.12Mg8.74Mn1.25Fe0.94B1.03Al1.04C9.46Si9.39H14.27O83. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is triclinic, space group P , with a = 9.315(1), b = 9.316(1), c = 26.463(4) , alpha = 83.295(3)A degrees, beta = 83.308(3)A degrees, gamma = 60.023(2)A degrees, V = 1971.2(6) (3). The crystal structure of roymillerite is based built by alternating pyrophyllite-type TOT-modules Mg-9(OH)(8)[(Si,Al)(10)O-28] and I-blocks Pb-24(OH)(6)O-4(CO3)(10)(BO3,SiO4). The strongest lines of the powder X-ray diffraction pattern [d, (I, %) (hkl)] are: 25.9 (100) (001), 13.1 (11) (002), 3.480 (12) (017, 107, -115, 1-15), 3.378 (14) (126, 216), 3.282 (16) (-2-15, -1-25), 3.185 (12) (-116, 1-16), 2.684 (16) (031, 301, 030, 300, 332, -109, 0-19, 1-18), 2.382 (11) (0.0.-11). Roymillerite is named to honor Dr. Roy McG. Miller for his important contributions to the knowledge of the geology of Namibia.

  • 50. Ciesielczuk, J.
    et al.
    Kruszewski, L.
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Comparative mineralogical study of thermally-altered coal-dump waste, natural rocks and the products of laboratory heating experiments2015In: International Journal of Coal Geology, ISSN 0166-5162, E-ISSN 1872-7840, Vol. 139, no SI, p. 114-141Article in journal (Refereed)
    Abstract [en]

    Research on rocks formed due to pyrometamorphism of waste in burning coal-mine dumps (BCMD) mainly in the Upper Silesian Coal Basin has enabled identification of a large number of different mineral species. These species are usually well-known minerals, e.g., olivines, plagioclases and clinopyroxenes. However, their crystal chemistry is often unique. Mineralogical- and chemical similarities between the BCMD and non-anthropogenic geological environments are outlined here. To better understand the crystallization processes of the minerals occurring in the BCMD, three types of heating experiments were performed. For these, ten protolith (thermally-unchanged) dump samples, mostly shales and carbonate rocks, were heated alone and mixed together and with a CaF2 flux. Quantitative chemical analyses of the synthesized mixtures have shown that they are mineralogically similar to the rocks found in the BCMD. They are also similar in terms of their crystal chemistry, e.g., synthesized clinopyroxenes are rich in diopside and esseneite components and may capture phosphorus, plagioclase is rich in anorthite and contains iron and magnesium, and wüstite exists as a solid solution with periclase and is doped with calcium and other elements. Highly variable amounts of indialite–ferroindialite were formed in some samples due to solid-phase transformations or melt crystallization, depending on the experimental conditions and the protolith used.

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