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  • 1.
    Barker, Abigail
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Centre of Natural Hazards and Disaster Sciences (CNDS), Uppsala, Sweden.
    Magnusson, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development. Centre of Natural Hazards and Disaster Sciences (CNDS), Uppsala, Sweden;Instituto de Estudios Ambientales y Recursos Naturales (iUNAT), Universidad de Las Palmas de Gran Canaria (ULPGC), Las Palmas de Gran Canaria 35017, Spain.
    Harris, C.
    Mattsson, Hannes B.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Institute for Mineralogy and Petrology, ETH Zürich, Switzerland.
    Holm, P.M.
    Perez-Torrado, F.J.
    Carracedo, J.C.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development. Centre of Natural Hazards and Disaster Sciences (CNDS), Uppsala, Sweden.
    Disequilibrium in historic volcanic rocks from Fogo, Cape Verde traces carbonatite metasomatism of recycled ocean crust2023In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, p. 107328-107328, article id 107328Article in journal (Refereed)
    Abstract [en]

    Fogo, Cape Verde, located upon thick oceanic lithosphere, provides a window into processes occurring in the mantle where recycled ocean crust in an upwelling mantle plume interacts with ambient mantle. Our objective is to investigate the nature of the lithologies of the mantle sources involved in the petrogenesis of historic volcanic rocks from Fogo. We observe enclaves and mingling textures in the lavas combined with oxygen isotope disequilibrium between olivine and clinopyroxene phenocrysts. Olivine δ18O values display positive correlations with Zr/Hf and Zr/Y and a negative correlation with U/Th, whereas clinopyroxene δ 18O values correlate positively with Ba/Nb. Heterogeneity between crystal populations and within the groundmass indicates that multiple magma batches are mixed beneath Fogo. In terms of mantle endmembers and source lithologies, a HIMU endmember was generated by melting of carbonated eclogite as indicated by low δ 18O values, Zr/Hf, Ba/Nb and high U/Th ratios. In contrast, we show the EM1 endmember has high δ 18O, Zr/Hf, Ba/Nb and low U/Th ratios, derived from melting of variably carbonated peridotite. Additionally, Ba/Th ratio are high, indicating that carbonatite melts have contributed to alkaline magma compositions at Fogo.

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  • 2.
    Bejgarn, Therese
    et al.
    Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Söderlund, Ulf
    Lunds universitet.
    Weihed, Pär
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Luleå tekniska universitet.
    Årebäck, Hans
    Boliden Mineral AB.
    Ernst, Richard E.
    Carleton University, Ottawa.
    Palaeoproterozoic porphyry Cu-Au, intrusion-hosted Au and ultramafic Cu-Ni deposits in the Fennoscandian Shield: temporal constraints using U-Pb geochronology2013In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 174, p. 236-254Article in journal (Refereed)
    Abstract [en]

    The Skellefte district, northern Sweden, is known for the occurrence of 1.89 Ga Palaeoproterozoic volcanogenic massive sulphide (VMS) deposits. The deposits are hosted by the older part of a volcanosedimentary succession, which was intruded at 1.88-1.86 Ga by multiple phases of the syn-volcanic, early orogenic Jörn intrusive complex (JIC). The oldest phase of the JIC hosts different styles of mineralisation, among them porphyry Cu-Mo-Au, intrusion-related Au, and mafic-hosted Fe and Cu-Ni deposits. To discriminate between the different intrusive and ore related events, U-Pb ages of zircons have been obtained for nine intrusive phases and from Na-Ca alteration spatially related to mineralisation, while U-Pb ages of baddeleyite (ZrO2) have been used to constrain intrusive ages of three mineralised and barren mafic-ultramafic intrusive rocks.The two main JIC intrusive phases of a granodioritic-tonalitic composition in the southern study area intruded at 1887 ± 3 Ma and 1886 ± 3 Ma, respectively, and were succeeded by the intrusion of layered mafic-ultramafic intrusive rocks in the northern and southern study area at 1879 ± 1 Ma and 1884 ± 2 Ma, respectively. Emplacement of porphyry dykes took place at ca. 1877 Ma in the southern, western and northern JIC. The dykes are spatially and temporally associated with formation of porphyry style mineralisation, alteration and Au-mineralisation, as inferred from 1879 ± 5 Ma zircons in adjacent Na-Ca alteration zones. High SiO2 and Al2O3 content together with high Sr/Y ratios, mingling structures, mafic xenoliths and hornblende phenocrysts in the porphyry dykes suggest that the magma originated from hydrated partial melts, possibly from the base of the crust at a mature stage of subduction. Local extension resulted in intrusion of mafic-ultramafic rocks around 1.88 Ga prior to and after, the porphyry dykes and associated mineralisation, approximately 10 Ma after the formation of the spatially related 1.89 Ga VMS deposits in the Skellefte district. This 1.88 Ga event correlates with other 1.88 Ga mafic-ultramafic units widespread around the world, and could possibly be interpreted as a large scale response to supercontinent formation.

  • 3. Broska, Igor
    et al.
    Petrik, Igor
    Be'eri-Shlevin, Yaron
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Bezak, Vladimir
    Devonian/Mississippian I-type granitoids in the Western Carpathians: A subduction-related hybrid magmatism2013In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 162, p. 27-36Article in journal (Refereed)
    Abstract [en]

    SIMS zircon U-Pb dating of I-type granitoids from four Variscan crystalline basement outcrops in the Western Carpathians (Tribec, Nizke Tatry, Cierna Hora and Slovenske Rudohorie Mts.) implies that they originated between 367 and 353 Ma. Therefore, they belong to the earliest Variscan I-type granitoids. The oldest Devonian age at ca. 367-364 Ma is obtained from an enclave-bearing tonalite and associated dikes of the Tribe Mts. Several granodiorites from the Nizke Tatry, Vepor and Cierna Hora Mts. (353-357 Ma) show younger, Early Carboniferous ages. These data require a re-assessment of older models that explained the genesis of I-type granitoids in the Western Carpathians based on the assumption of younger, Middle to Upper Carboniferous ages. The I-type granite massifs of the Western Carpathians most probably originated in an arc-related environment within the Galatian superterrane, an assemblage of Gondwana derived fragments. The early age of I-type magmatism in the Western Carpathians marks the beginning of a north-dipping subduction of the Paleotethys ocean under Ibero-Ligerian and intra-Alpine terranes. We suggest a term "Proto-Tatricum" for that part of the Galatian superterrane where Devonian/Mississippian I-type granitoids were emplaced. Now the granitoids are incorporated as a part of crystalline basement into the Alpine Tatric and Veporic units within present West-Carpathian mountain chain.

  • 4.
    Godoy, Benigno
    et al.
    Univ Chile, Fac Ciencias Fis & Matemat, Dept Geol, Ctr Excelencia Geotermia Andes CEGA, Plaza Ercilla 803, Santiago, Chile..
    Deegan, Frances M.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    González-Maurel, Osvaldo
    Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa..
    le Roux, Petrus
    Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa..
    Garbe-Schönberg, Dieter
    Univ Kiel, Inst Geosci, D-24118 Kiel, Germany.;Jacobs Univ Bremen, Dept Phys & Earth Sci, D-28759 Bremen, Germany..
    Rodríguez, Inés
    Univ Catolica Temuco, Fac Ingn, Dept Obras Civiles & Geol, Rudecindo Ortega 02950, Temuco, Chile.;Univ Catolica Temuco, Fac Ingn, Ctr Invest Evaluac Riesgos & Mitigac Peligros Geo, Geokimun, Rudecindo Ortega 02950, Temuco, Chile..
    Guzmán-Marusic, Gabriela
    Univ Catolica Temuco, Fac Ingn, Ctr Invest Evaluac Riesgos & Mitigac Peligros Geo, Geokimun, Rudecindo Ortega 02950, Temuco, Chile..
    Marín, Carolina
    Teck Resources Chile Limitada, Alonso Cordova 4580,Piso 10, Santiago, Chile..
    Boron isotope variations in a single monogenetic cone: La Poruña (21°53′S, 68°30′W), Central Andes, Chile2023In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 440, article id 107030Article in journal (Refereed)
    Abstract [en]

    La Poruña is a monogenetic volcano located within the Altiplano-Puna Volcanic Complex (21°-24°S) in the Central Andean subduction zone. Since crustal contamination of Andean magmas is ubiquitous, and because extensive geochemical data exist for La Poruña, we employ this volcano as a case study to examine the behavior of boron isotopes during crustal assimilation. We present whole-rock boron concentration and 11B/10B ratios (as δ11B values) for La Poruña lava samples that were prepared as nano-particulate pressed pellets. La Poruña B contents range from 14 to 20 μg/g and δ11B values range from −1.39 ± 0.54 ‰ (2σ) to +0.94 ± 0.30 ‰ (2σ), which overlap with the range of available whole-rock data for Central Andean lavas. Moreover, La Poruña δ11B values correlate negatively with 87Sr/86Sr ratios from the same samples. Since 87Sr/86Sr is a proxy for crustal contamination at La Poruña, the data lead us to suggest that La Poruña magmas assimilated a low-δ11B, high 87Sr/86Sr component such as Andean continental crust. Mixing models based on B and Sr isotopes support a broadly two-step magma evolution for La Poruña. In step 1, mantle-derived primary melts interacted with boron-rich slab-derived fluids with high δ11B values, which yielded subduction-modified parental magmas with ca. 3 μg/g B and relatively high δ11B values. In step 2, the high δ11B parental magmas ascended through the crust where they assimilated up to 20% crustal material, which further modified their δ11B values and 87Sr/86Sr ratios. In comparison to available regional values for B and δ11B, it appears that La Poruña and nearby volcanic centers shared a similar source and magmatic history, whereas volcanoes south of 23°S differ. We stress, however, that deconvolving the roles of various subduction and crustal inputs in the Central Andes would require further studies on individual volcanoes along the arc.

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  • 5.
    Gonzalez-Maurel, Osvaldo
    et al.
    Univ Catolica Norte, Dept Ciencias Geol, Ave Angamos 0610, Antofagasta, Chile;Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa.
    le Roux, Petrus
    Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa.
    Godoy, Benigno
    Univ Chile, CEGA, Plaza Ercilla 803, Santiago, Chile;Univ Chile, Fac Ciencias Fis & Matemat, Dept Geol, Plaza Ercilla 803, Santiago, Chile.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Uppsala Univ, Dept Earth Sci Nat Resources & Sustainable Dev, SE-75236 Uppsala, Sweden.
    Deegan, Frances
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Menzies, Andrew
    Bruker Nano GmbH, Studio 2D, D-12489 Berlin, Germany.
    The great escape: Petrogenesis of low-silica volcanism of Pliocene to Quaternary age associated with the Altiplano-Puna Volcanic Complex of northern Chile (21 degrees 10 '-22 degrees 50 ' S)2019In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 346/347, article id UNSP 105162Article in journal (Refereed)
    Abstract [en]

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

  • 6. Högdahl, Karin
    et al.
    Sjöström, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Andersson, Ulf B.
    Ahl, Martin
    Continental margin magmatism and migmatisation in the west-central Fennoscandian Shield2008In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 102, no 3-4, p. 435-459Article in journal (Refereed)
    Abstract [en]

    The Ljusdal Batholith (LjB) is a major component of the central Svecofennian Domain in Sweden. It is separated from the Bothnian Basin to the north by the 1.82-1.80 Cia crustal-scale Hassela Shear Zone (HSZ). The LjB has emplacement ages of 1.86-1.84 Cia, is mainly alkali-calcic, metaluminous, has epsilon(Nd) values between -0.3 and + 1.2 and was formed in a magmatic arc setting.

    During the Svecokarelian orogeny the LjB was affected by at least three fold episodes. Large-scale folded screens of migmatised metasedimentary rocks occur in the eastern part of the batholith, and to the north of the HSZ, there is a 50 km wide diatexite belt. The Transition Belt (TrB), consisting of 1.88-1.85 Ga granitoids, is located at the northwestern extension of this belt. A calc-alkaline and peraluminous composition combined with negative epsilon(Nd) values (- 1.7 to -0.8) indicates a large proportion of metasediments in the source for these granitoids.

    U-Pb SIMS data on zircon rims from migmatites and leucogranites to the north and east of LjB yield ages of 1.87-1.86 Ga, i.e. coeval with the granitoids of the LjB and the TrB. There is thus a close relationship between the LjB, the TrB and the migmatites in both space and time. Syn-migmatitic shearing along the HSZ indicates that a proto-HSZ was initiated already at c. 1.86 Ga, and the location of the proto-HSZ is inferred to be controlled by two older nuclei present in the lower parts of the crust. As crustal-scale shear zone systems are known to act as ascent pathways for sheet-like flow in active orogenies the TrB may represents accumulations of melts that were attracted and extracted by the proto-HSZ and intruded in a block that was not pervasively affected by subsequent shear along the HSZ.

    An active continental margin setting for the LjB implies subduction at c. 1.86 Ga, and provides a heat source for both the migmatites and the TrB.

    A later migmatisation at 1.82 Ga has been recorded to the south of the HSZ. Within the LjB the 1.82 Ga stromatic migmatites are folded by F-2 folds, and the fabric is truncated by 1.80 Cia pegmatites.

  • 7.
    Jastrzebski, Miroslaw
    et al.
    Polish Acad Sci, Res Ctr Wroclaw, Inst Geol Sci, Wroclaw, Poland.
    Machowiak, Katarzyna
    Poznan Univ Tech, Inst Civil Engn, Poznan, Poland.
    Krzeminska, Ewa
    Natl Res Inst, Polish Geol Inst, Warsaw, Poland.
    Farmer, G. Lang
    Univ Colorado, CIRES, Boulder, CO USA; Univ Colorado, Dept Geol Sci, Boulder, CO USA.
    Larionov, Alexander N.
    All Russian Geol Res Inst, Ctr Isotop Res, St Petersburg, Russia.
    Murtezi, Mentor
    Polish Acad Sci, Res Ctr Wroclaw, Inst Geol Sci, Wroclaw, 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.
    Sergeev, Sergey
    All Russian Geol Res Inst, Ctr Isotop Res, St Petersburg, Russia;St Petersburg State Univ, Inst Earth Sci, St Petersburg, Russia.
    Ripley, Edward M.
    Indiana Univ, Dept Geol Sci, Bloomington, IN USA.
    Whitehouse, Martin
    Swedish Museum Nat Hist, Lab Isotope Geol, Stockholm, Sweden.
    Geochronology, petrogenesis and geodynamic significance of the Visean igneous rocks in the Central Sudetes, northeastern Bohemian Massif2018In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 316, p. 385-405Article in journal (Refereed)
    Abstract [en]

    New sensitive high-resolution ion microprobe (SHRIMP) UPb zircon geochronologic data, whole-rock geochemical and Sr-Nd-Pb isotopic data, and zircon and quartz δ18O isotopic data from the Staré Město granitoids (SMG), Jawornik granitoids (JG), and Kłodzko-Złoty Stok granitoids (KZSG) and associated mafic and ultramafic rocks are examined. This study provides new insights into the processes of magma generation, transport and emplacement during the Variscan development of the contact zone of the Saxothuringia, Teplá-Barrandia and Brunovistulia in the Central European portion of the Variscan belt. The results of this study, combined with existing geochemical and isotopic data, imply that the parental magmas of these intrusions share a close affinity and suggest that these intrusions formed in a subduction-related tectonic setting. The SMG, JG and KZSG magmas represent hybrids that formed from the contamination of partial melts from the lower crust and/or subducted sediments with various proportions of enriched mantle-derived melts. These mainly sheeted plutons intruded along the main geological boundaries during the Visean and recorded the vertical and lateral displacements between the major tectono-stratigraphic units (microplates) in the NE Bohemian Massif. In the Central Sudetes, these granitoid magmas were first emplaced along the northern continuation of the Moldanubian Zone. The SHRIMP UPb dating of zircons indicates that the SMG intruded the reactivated suture zone between the Brunovistulia and Saxothuringia at 344–341 Ma. Sills of the JG were emplaced between c. 347 and c. 334 Ma. The composite Kłodzko-Złoty Stok Pluton, which includes the KZSG and accompanying mafic enclaves and pyroxenite and lamprophyre dykes, was mainly emplaced at 340–333 Ma. The magmas of the KZSG possibly facilitated the final amalgamation of the Sudetic counterparts of the Teplá-Barrandia and Saxothuringia microplates during the orogenic uplift of the latter. Petrologic and oxygen isotopic data further indicate partial post-magmatic hydrothermal and/or alteration processes. Our new data further stress the connection of magma transfer and active shear zones, which could manifest as crustal-scale magma-ascent conduits.

  • 8. Jastrzebski, Miroslaw
    et al.
    Zelazniewicz, Andrzej
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Murtezi, Mentor
    Bazarnik, Jakub
    Kapitonov, Igor
    Constraints on the Devonian-Carboniferous closure of the Rheic Ocean from a multi-method geochronology study of the Staré Město Belt in the Sudetes (Poland and the Czech Republic)2013In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 170-171, p. 54-72Article in journal (Refereed)
    Abstract [en]

    This paper attempts to clarify the complex nature of how and when the Rheic Ocean closed in what is now Central Europe and, with respect to the various terranes that were involved, offer a regional chronology for the associated structural, metamorphic and igneous processes that accompanied and followed this closure. The Variscan orogen in Europe originated from the multiple collisions of Gondwana-derived terranes (the Armorican Terrane Assemblage) with Laurussia: however, many important structural details on the timing of these collision-related events remain obscure. In the Sudetes, the Stare Mesto Belt represents a WNW-dipping part of the Rheic suture that developed from the continental collision of the eastern terranes of the Armorican Terrane Assemblage (now in the Bohemian Massif) with the Brunovistulian Terrane (a part of Laurussia/Old Red Continent). In this study, the results of monazite Th-U-total Pb, garnet Lu-Hf and zircon U-Pb geochronology were integrated into a newly established D1-D3 tectonometamorphic sequence. A Th-U-total Pb age of similar to 368 Ma from a monazite that grew concurrently with D2 metasedimentary garnet, as well as Lu-Hf ages of similar to 361 Ma and similar to 355 Ma obtained from D2 metasedimentaly garnets, implies that the regional contractional deformation and progressive metamorphism of D2 took place mainly during the Famennian (Late Devonian) and extended into the Visean (Middle Mississippian of the Early Carboniferous). The ion probe U-Pb zircon ages of similar to 355 Ma and similar to 359 Ma obtained from leucocratic neosomes in migmatized amphibolites confirmed a lag in the peak temperature that followed crustal thickening during D1-D2. Metamorphic monazites dated at similar to 340 Ma provide a time for the subsequent D3 dextral transpressional regime. The closure of the Stare Mesto Belt segment of the Rheic Ocean probably resulted from a head-on hard collision between the westerly subducting Brunovistulian promontory of Laurussia and the eastern members of the Armorican Terrane Assemblage. Thus, the Rheic Ocean closed during the Late Devonian at similar to 370-360 Ma and preceded the collision of the Armorican Terrane Assemblage with East Avalonia at the western margin of what is now the Bohemian Massif. Following ocean closure, the Rheic slab may have broken off, resulting in the suture zone becoming dominated by lateral "tectonic escape" movements of the colliding terranes at similar to 340-330 Ma (Visean). Syntectonic D3 intrusions of granodiorite/tonalite magma acted as a hot lubricant and stitched the suture zone together. 

  • 9.
    Jiang, Qiang
    et al.
    Curtin Univ, Western Australian Argon Isotope Facil, Perth, WA 6845, Australia; Curtin Univ, John de Laeter Ctr, Perth, WA 6845, Australia.;Curtin Univ, Sch Earth & Planetary Sci, Perth, WA 6845, Australia.
    Merle, Renaud E.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development. Swedish Museum Nat Hist, Dept Geosci, S-10405 Stockholm, Sweden.
    Jourdan, Fred
    Curtin Univ, Western Australian Argon Isotope Facil, Perth, WA 6845, Australia; Curtin Univ, John de Laeter Ctr, Perth, WA 6845, Australia.;Curtin Univ, Sch Earth & Planetary Sci, Perth, WA 6845, Australia.
    Olierook, Hugo K. H.
    Curtin Univ, John de Laeter Ctr, Perth, WA 6845, Australia; Curtin Univ, Sch Earth & Planetary Sci, Perth, WA 6845, Australia; Curtin Univ, Ctr Explorat Targeting Curtin Node, Sch Earth & Planetary Sci, Timescales Mineral Syst, Perth, WA 6845, Australia.
    Chiaradia, Massimo
    Univ Geneva, Dept Earth Sci, Rue Maraichers 13, CH-1205 Geneva, Switzerland.
    Evans, Katy A.
    Curtin Univ, Sch Earth & Planetary Sci, Perth, WA 6845, Australia.
    Wang, Xuan-Ce
    Yunnan Univ, Res Ctr Earth Syst Sci, Yunnan Key Lab Earth Syst Sci, Kunming 650500, Yunnan, Peoples R China; Changan Univ, Sch Earth Sci & Resources, Xian 710054, Peoples R China; Univ Queensland, Sch Earth & Environm Sci, Brisbane, Qld 4072, Australia.
    Conway, Chris E.
    AIST, Inst Earthquake & Volcano Geol, Geol Survey Japan, 1-1-1 Higashi, Tsukuba, Ibaraki 3058567, Japan.
    Bostock, Helen C.
    Univ Queensland, Sch Earth & Environm Sci, Brisbane, Qld 4072, Australia; Natl Inst Water & Atmospher Res, Private Bag 14-901, Wellington 6241, New Zealand.
    Wysoczanski, Richard J.
    Natl Inst Water & Atmospher Res, Private Bag 14-901, Wellington 6241, New Zealand.
    Origin of geochemically heterogeneous mid-ocean ridge basalts from the Macquarie Ridge Complex, SW Pacific2021In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 380-381, article id 105893Article in journal (Refereed)
    Abstract [en]

    The Macquarie Ridge Complex (MRC), located at the Australian–Pacific plate boundary south of New Zealand, is a rugged bathymetric ridge comprising a series of submarine seamounts and Macquarie Island, the only subaerial portion of the complex. Mid-ocean ridge basalts (MORBs) from Macquarie Island show various enrichments in incompatible elements with compositions ranging from typical normal MORB to enriched MORB. However, these basalts have isotopic compositions trending towards a high μ-like (μ = 238U/204Pb; HIMU) mantle component, which is unusual for MORB-type rocks. The origin of this mantle signature is not understood, and it is unclear whether this isotopic signature is characteristic of the entire MRC or unique to Macquarie Island. Here we report new major and trace element abundances, and Sr, Nd, and Pb isotopes for samples from the MRC seamounts and from new sampling sites on Macquarie Island. The geochemical and isotopic data show that the entire MRC comprises normal to enriched MORB. Mixing modelling indicates that the heterogeneous isotopic signatures of the MRC basalts are not derived from contamination of the nearby Balleny mantle plume but have affinities with that of the Cenozoic Zealandia intraplate HIMU-like basalts. We propose that the heterogeneous geochemical signatures of the MRC basalts are derived from amphibole-bearing garnet pyroxenite veins, which is supported by the rare earth element partial melting modelling and strong correlations between Nd and Pb isotopic ratios vs La/Sm. We posit that the pyroxenite veins were generated in the oceanic lithospheric mantle, which was metasomatised by hydrous and carbonatitic fluids/melts derived either from delaminated, metasomatised Zealandia subcontinental lithosphere mantle, or from subducted material in the asthenosphere. The subducted material could be derived from ancient and/or recent subduction along the former east Gondwana margin.

  • 10.
    Klonowska, Iwona
    et al.
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al 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 Mickiewicza 30, PL-30059 Krakow, Poland..
    Janak, Marian
    Slovak Acad Sci, Earth Sci Inst, Dubravska Cesta 9, Bratislava 84005, Slovakia..
    Petrik, Igor
    Slovak Acad Sci, Earth Sci Inst, Dubravska Cesta 9, Bratislava 84005, Slovakia..
    Froitzheim, Nikolaus
    Univ Bonn, Inst Geosci, Meckenheimer Allee 169, D-53115 Bonn, Germany..
    Gee, David G.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Cuthbert, Simon
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Comment on the paper: "Evolution of a gneiss in the Seve nappe complex of central Sweden - Hints at an early Caledonian, medium-pressure metamorphism" by Li et al. (2020)2021In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 400, article id 106067Article in journal (Other academic)
  • 11.
    Majka, Jaroslaw
    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, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Kosminska, Karolina
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Bazarnik, Jakub
    Natl Res Inst, Polish Geol Inst, Carpathian Branch, Ul Skrzatow 1, PL-31560 Krakow, Poland..
    McClelland, William C.
    Univ Iowa, Dept Earth & Environm Sci, Iowa City, IA 52242 USA..
    The Ordovician Thores volcanic island arc of the Pearya Terrane from northern Ellesmere Island formed on Precambrian continental crust2021In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 386-387, article id 105999Article in journal (Refereed)
    Abstract [en]

    Ion microprobe U & ndash;Pb zircon dating of intermediate to felsic rocks coupled with bulk-rock geochemistry analyses and compared to previously published data shows that the Thores Suite of the Pearya Terrane of northern Ellesmere Island (Arctic Canada) represents an Early Ordovician (c. 490 & ndash;470 Ma) suite formed in an island arc setting. Interestingly, three out of five dated samples contain abundant xenocrystic zircon that have ages spanning from c. 2690 Ma to c. 520 Ma. The vast majority of xenocrystic zircon are Precambrian in age and typical of Laurentia. The youngest well-pronounced age cluster around 580 & ndash;570 Ma is inferred to be an expression of the Timanide Orogen, traditionally ascribed to Baltica. This geochronological dataset provides new insight on the origin of the Thores Suite of the Pearya Terrane, which was traditionally thought to be formed due to the M'Clintock orogenic event and commonly treated as independent from Caledonian tectonism. We suggest that the Thores island arc formed on a sliver of continental crust within the Iapetus Ocean. The timing of igneous activity recorded by the Thores Suite is consistent with other island arcs and subduction-related metamorphic units that occur within the Caledonides of northern Scandinavia and Svalbard. Hence, we suggest that the Thores volcanic island arc was closely associated with age equivalent arcs developed within the northern Iapetus Ocean. Its juxtaposition with the other successions of the Pearya Terrane is explained by a large-scale, left lateral, strike-slip system operating along the northeastern margins of Baltica and Laurentia, coeval with the main collision between the two continents. This strike-slip system was responsible for the juxtaposition of multiple terranes with contrasting Precambrian histories that can be traced in the present day High Arctic, e.g. in southwest Svalbard and the Pearya Terrane.

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  • 12.
    Mattsson, Hannes B.
    et al.
    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. Geology and Mineralogy, Åbo Akademi University, Akatemiankatu 1, 20500 Turku, Finland.
    Carlsson, Matias
    Åbo Akademi University.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    The role of mafic dykes in the petrogenesis of the Archean Siilinjärvi carbonatite complex, east-Central Finland2019In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 342-343, p. 468-479Article in journal (Refereed)
    Abstract [en]

    The Archean (~2.6 Ga) Siilinjärvi carbonatite complex in east-central Finland is crosscut by a few ultramafic lamprophyre dykes, together with a broad array of more evolved mafic dykes that range in composition from foidites to various types of alkali basalts. A possible genetic link between the primitive lamprophyres and the carbonatite complex has previously been hypothesised, but their exact relations have been unclear due to the regional metamorphic overprint (i.e., greenschist facies). Here we focus on the petrology and petrography of the mafic dykes, and integrate the data to present a coherent model that can explain the genesis of the Siilinjärvi carbonatite complex. Field-relations, in combination with petrography and geochemistry, indicate that there are at least three generations of mafic dykes present. The oldest dykes (Generation I) are strongly deformed, and inferred to have been emplaced shortly after the formation of the complex itself. These dykes can be divided into two groups (i.e., ultramafic lamprophyres and Group A), where Group A comprises foidites characterised by low SiO2 (41.4–51.5 wt%) and high alkali (>10 wt% K2O) content. We interpret the foiditic magmas to have evolved from primitive ultramafic lamprophyres by fractionating a clinopyroxene-olivine dominated mineral assemblage that was devoid of feldspar. This fractionation path forced alkali-enrichment in the magmas belonging to Group A, which pushed them into the miscibility gap, and resulted in liquid immiscibility that produced moderately alkaline conjugate carbonatite(s). Subsequent fractionation of the conjugate carbonatite by predominantly calcite and apatite produced the mineralogically homogeneous carbonatite cumulate that is exposed at Siilinjärvi. Younger, less deformed, mafic dykes (belonging to Generations II and III) exhibit trace element characteristics, broadly similar to basaltic dyke swarms in the region. The younger dykes are characterised by the presence of large plagioclase crystals in thin sections. Crystallisation of a feldspar-bearing mineral assemblage resulted in only moderate enrichment of alkalis with increased fractionation, which caused the younger dykes to evolve along the more common basalt-to-trachyte series. Thus, the magmas belonging to Generations II and III at Siilinjärvi never fulfilled the conditions required to produce carbonatites by liquid immiscibility.

  • 13. Mattsson, Hannes B.
    et al.
    Nandedkar, Rohit H.
    Ulmer, Peter
    Petrogenesis of the melilititic and nephelinitic rock suites in the Lake Natron-Engaruka monogenetic volcanic field, northern Tanzania2013In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 179, p. 175-192Article in journal (Refereed)
    Abstract [en]

    The Lake Natron-Engaruka Monogenetic Volcanic Field (LNE-MVF) in northern Tanzania consists of more than 150 vents of Upper Pleistocene to Holocene age that are scattered over an area of 2500 km(2). Here we describe the petrological characteristics of these eruptions in detail and link the magma chemistry to eruptive behavior when the magmas reach the surface. Erupted magmas are predominantly of melilititic or nephelinitic compositions (70 and 25%, respectively), together with minor amounts of basanites (5%). The melilititic magmas form by small degrees (1-2%) of partial melting of a metasomatized upper-mantle source (containing 1-4% gamet together with both amphibole and phlogopite). The melilitites ascend very rapidly through the lithosphere prior to eruption minimizing the effect of fractional crystallization and/or crustal contamination. These eruptions also frequently carry relatively large amounts of mantle debris to the surface which is also reflected in their bulk-rock compositions. The nephelinitic rock suite, on the other hand, forms by larger degrees of melting (2-4%) at higher levels of the sub-continental lithosphere containing less garnet (<< 1%). The scarcity of mantle debris in the nephelinitic eruption deposits, combined with the more evolved magma chemistry, indicates ponding in crustal reservoirs en-route to the surface. For many of the nephelinitic magmas this ponding resulted in fractional crystallization of predominantly olivine, which is also one of the principal phenocryst phases in these rocks. However, these periods of residence in the crust must have been short as none of the investigated rocks show any clear evidence of being affected by crustal contamination. Within the LNE-MVF a rough correlation between magma chemistry and resulting volcanic landforms is recognized. Large maar volcanoes and tuff cones/rings are predominantly of melilititic composition, whereas the nephelinites typically form scoria cones. This is attributed to the fact that melilititic magmas can hold more CO2 dissolved in the liquid compared to nephelinites, in combination with a rapid ascent from the upper mantle to the surface for the melilitites (<1-2 days). We interpret the violent exsolution of CO2 (in response to rapid decompression) to be responsible for the higher explosivity of the melilititic eruptions compared to the nephelinitic magmas within the LNE-MVF. (C) 2013 Elsevier B.V. All rights reserved.

  • 14.
    Mattsson, Hannes
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Högdahl, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Malehmir, Alireza
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    The role of mafic dykes in the petrogenesis of the Archean Siilinjärvi carbonatite complex, eastern Finland2019In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 342-343, p. 468-479Article in journal (Refereed)
  • 15.
    Peate, David
    et al.
    University of Iowa.
    Barker, Abigail
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Rishuus, Morten
    University of Iceland.
    Andreasen, Rasmus
    Temporal variations in crustal assimilation of magma suites in the East Greenland flood basalt province: tracking the evolution of magmatic systems2008In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 102, no 1-2, p. 179-197Article in journal (Refereed)
    Abstract [en]

    We review published radiogenic isotope data (> 350 samples in total) on various suites of magmatic rocks within the Palaeogene central East Greenland flood basalt province to evaluate the types of crustal assimilants and the extent of crustal assimilation involved in each suite. We use these observations to build a regional picture of how magmatic plumbing systems changed with time and location during the sequential development of the province as magmatism responded to the development of a volcanic rifted margin and eventual plate separation. The earliest phase of magmatic activity (c. 62–57 Ma) is characterised by highly contaminated magmas that show a temporal change in assimilant type from amphibolite to granulite. This transition has been linked to the effects of an increasing magma supply rate which allows the more refractory granulite lithologies to be melted. The voluminous break-up phase of magmatism (c. 56–54 Ma) saw a significant decrease in the extent of assimilation because of the decreasing availability of assimilant material in the mature feeder systems, and many samples have Sr–Nd–Pb isotope compositions that overlap with those of asthenospheric melts (as represented by recent Icelandic basalts and North Atlantic MORB). Detailed study has allowed us to recognise packets of lavas that ponded at different levels in the crust and assimilated material of different compositions. The later stages of break-up magmatism show more diverse and more contaminated compositions that indicate a shift from a few large robust feeder systems to numerous small new conduits as the rifting continued. The post-break-up magmatism (c. 54–13 Ma) is characterised by a return to more highly contaminated magmas, which reflects a change in the style of magmatism: the eruption of small-volume alkalic lava flows from newly established conduits through the thicker inland crust, and the intrusion of mafic and silicic alkalic magmas at shallow levels in the Archaean basement along the present coast.

  • 16.
    Peillod, Alexandre
    et al.
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    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..
    Ring, Uwe
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    Drüppel, Kirsten
    Karlsruhe Inst Technol, Dept Petr, Karlsruhe, Germany..
    Patten, Clifford
    Karlsruhe Inst Technol, Dept Ore Geol, Karlsruhe, Germany..
    Karlsson, Andreas
    Swedish Museum Nat Hist, Dept Geosci, Stockholm, Sweden..
    Wlodek, Adam
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland..
    Tehler, Elof
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    Differences in decompression of a high-pressure unit: A case study from the Cycladic Blueschist Unit on Naxos Island, Greece2021In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 386-387, article id 106043Article in journal (Refereed)
    Abstract [en]

    Determining the tectonic evolution and thermal structure of a tectonic unit that experiences a subduction-related pressure temperature (P-T) loop is challenging. Within a single unit, P-T conditions can vary from top to bottom which can only be revealed by detailed petrological work. We present micropetrological data from the middle section of the Cycladic Blueschist Unit (CBU) in Naxos, Greece, which indicates a different P-T loop than that for the top of the sequence. Using Zr-in-rutile and Ti-in-biotite thermometry coupled with quartz-in-garnet elastic barometry and phase equilibrium thermodynamic modeling, we identify a prograde path from 15.4 +/- 0.8 kbar to 19.9 = 0.6 kbar and from 496 +/- 16 degrees C to 572 +/- 7 degrees C (2a uncertainty), equilibration during decompression at 8.3 +/- 15 kbar and 519 +/- 12 degrees C followed by near-isobaric heating to 92 +/- 0.8 kbar and 550 +/- 10 degrees C (or even 584 +/- 19 degrees C), and a final greenschist-facies equilibration stage at 3.8 +/- 0.3 kbar and 520 +/- 4 degrees C. We compare these P-T estimates with published data from the top and also the bottom of the CBU section and find that the bottom half of the CBU on Naxos records higher peak high-pressure (HP) of about 4 kbar than the top of the unit, defining the thickness of the CBU section on Naxos to about 15 km in the Eocene. We determine that crustal thickening of up to similar to 15% occurs in the upper half of the CBU section during exhumation of the HP rocks in an extrusion wedge in a convergence setting. At about 30 Ma, the bottom half of the CBU was finally thrust onto the radiogenic Cycladic basement. Subsequently this bottom half of the CBU section underwent isobaric heating of 9-96 degrees C between c. 32-28 and 23-21 Ma. Isobaric heating occurred below the upper CBU section that thickened during decompression and commenced when HP metamorphism in the Cyclades ended. This suggests that thermal relaxation following tectonic accretion in the Cyclades controlled heating of the evolving Cycladic orogen during a tectonically quiescent period before lithospheric extension commenced by 23-20.5 Ma.

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  • 17. Reichardt, H.
    et al.
    Weinberg, R.F.
    Andersson, U.B.
    Fanning, M.C.
    Hybridization of granitic magmas in the source: The origin of the Karakoram Batholith, Ladakh, NW India2010In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 116, p. 249-272Article in journal (Refereed)
  • 18.
    Waight, Tod E.
    et al.
    Univ Copenhagen, Geol Sect, Dept Geosci & Nat Resource Management, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark..
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Gamble, John A.
    Victoria Univ Wellington, Sch Geog Environm & Earth Sci, POB 600, Wellington, New Zealand.;Univ Coll Cork, Sch Biol Earth & Environm Sci, Cork, Ireland..
    Price, Richard C.
    Univ Waikato, Fac Sci & Engn, Private Bag 3105, Hamilton, New Zealand..
    Chadwick, Jane P.
    Trinity Coll Dublin, Sci Gallery, Pearse St, Dublin 2, Ireland..
    Hf isotope evidence for variable slab input and crustal addition in basalts and andesites of the Taupo Volcanic Zone, New Zealand2017In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 284-285, p. 222-236Article in journal (Refereed)
    Abstract [en]

    Crustal contamination complicates the identification of primary mantle-derived magma compositions in continental arcs. However, when crustal processes and components are well characterised, it is possible to extrapolate through continental arc magma compositional arrays towards the Hf and Nd isotope compositions of uncontaminated primary magmas. This is because of the similar behaviour of Hf and Nd during fractional crystallisation and mantle melting, and the subsequent limited variation in Hf/Nd in mantle-derived magmas and in many crustal lithologies, resulting in linear contamination trends for Hf-Nd isotopes. Here we present new Hf isotope data for a selection of volcanic rocks and crustal lithologies from the Taupo Volcanic Zone (TVZ), New Zealand and propose that the scatter in Hf-Nd isotopes indicates heterogeneity in the parental magmas prior to interactions with crustal lithologies. The observed variations likely represent variability in primary magma compositions as a result of different degrees of sediment addition at the slab-wedge interface. Coupled variations in isotopic composition, LILE/HFSE ratios (e.g. Rb/Zr and Ba/La) and SiO2 also clearly indicate that shallower level crustal interactions have occurred. Andesites from Ruapehu Volcano have more consistent parental magma compositions, and require greater amounts of a source sediment contribution. Notably, the compositions of older Ruapehu lavas can be modelled by interactions between mantle-derived magmas and lower crustal granulites, whereas younger lavas have probably interacted more with mid- to shallow crustal meta-sedimentary greywacke-argillite lithologies of the Permian to Cretaceous composite Torlesse Terrane. Hf-Nd isotopic compositions of meta-igneous granulite xenoliths from Mt. Ruapehu are consistent with previous interpretations that they are derived from oceanic crust that underlies the Torlesse meta-sediments. The results indicate that interactions with sediments at both the slab-wedge interface and in the lithosphere must be considered when evaluating trace element and isotopic variations in continental arcs.

  • 19.
    Walczak, Katarzyna
    et al.
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Ziemniak, Grzegorz
    Univ Wroclaw, Inst Geol Sci, Pl M Borna 9, PL-50204 Wroclaw, Poland..
    Barnes, Christopher
    Polish Acad Sci, Inst Geol Sci, Krakow Res Ctr, PL-31002 Krakow, Poland..
    Callegari, Riccardo
    AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Bukala, Michal
    Polish Acad Sci, Inst Geol Sci, Krakow Res Ctr, PL-31002 Krakow, Poland..
    Kielman-Schmitt, Melanie
    Swedish Museum Nat Hist, Dept Geosci, Stockholm, Sweden..
    Zagorska, Anna
    Polish Acad Sci, Inst Geol Sci, Krakow Res Ctr, PL-31002 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 Mickiewicza 30, PL-30059 Krakow, Poland..
    Late Neoproterozoic extended continental margin development recorded by the Seve Nappe Complex of the northern Scandinavian Caledonides2022In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 416, article id 106640Article in journal (Refereed)
    Abstract [en]

    The Scandinavian Caledonides comprise nappe stacks of far-travelled allochthons that record the opening and closure of the Iapetus Ocean, culminating with the collision of Baltica and Laurentia. The Seve Nappe Complex (SNC) of the Scandinavian Caledonides comprises relics of the outermost Baltoscandian passive margin that were subducted to mantle depths during ocean closure. Subduction of these rocks overprinted much of the Neoproterozoic record for Iapetus Ocean formation, and as a result, much of the work conducted in the SNC has focused solely on the Caledonian orogenic history.& nbsp;In this study, we combined petrological and geochronological work to expand the knowledge about the Neoproterozoic metamorphic history of the Baltoscandian margin in the understudied Vaivancohkka-Salmmecohkat region of the northern Scandinavian Caledonides. The work focused on rocks that belong to the upper gneiss unit, which constitutes part of SNC in the region. The unit comprises migmatitic paragneisses and garnet-mica schist containing metamafic bodies. U-Pb zircon and Th-U-total Pb monazite dating of the migmatitic paragneiss yielded consistent age of metamorphism in 602 +/- 5 Ma and 599 +/- 3 Ma, respectively. A similar U-Pb age of 604 +/- 8 Ma was obtained for the zircon from the leucocratic vein transecting the amphibolite within the studied gneiss. Interestingly, no Caledonian ages were identified. Likewise, no evidence for high or ultra-high pressure conditions was found, neither in the gneisses/schists nor in the metamafic rocks. Petrographic observations and calculated metamorphic P-T conditions indicate that rocks belonging to upper gneiss unit underwent upper-amphibolite facies metamorphism in a melt stability field; 8.0-10.5 kbar at 750-790 degrees C.& nbsp;Since the studied rocks underwent high-grade metamorphism in the Ediacaran and lack obvious evidence for Caledonian high-pressure metamorphism, the studied part of the SNC offers an extraordinary insight into the Late Neoproterozoic history of the hot, extended Baltoscandian margin.

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