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  • 1
    Electronic Resource
    Electronic Resource
    Early Cambrian oceanic plagiogranite in the Silvretta Nappe, eastern Alps: geochemical, zircon U-Pb and Rb-Sr data from garnet-hornblende-plagioclase gneisses (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 822-831 
    Details
    ISSN: 1437-3262
    Keywords: Austro-Alpine ; Eastern Alps ; Oceanic rocks ; Rb-Sr ; Zircon ; U-Pb ; Magmatism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Garnet-hornblende-plagioclase gneisses rich in incompatible elements occur in the crystalline basement of the Austro-Alpine Silvretta nappe and are associated with clinopyroxene norites and harzburgite cumulates. It is proposed here that the gneisses were formerly oceanic plagiogranites. An εNd(530) value of +5.6 for the gneisses as well as initial87Sr/86Sr values of 0.7036–0.7037 for the gabbroic rocks and 0.7026–0.7027 for the ultramafic rocks suggest a mantle source for this rock association. The geochemical characteristics of the garnet-hornblende-plagioclase gneisses indicate that their precursors were derived by fractional crystallization from a basaltic parent magma, by the same process which produced the adjacent clinopyroxene norites and ultramafic cumulates as well. The combined U-Pb upper intercept ages of zircons from two gneiss samples yield an igneous crystallization age of 532 ± 30 Ma, similar to previously dated (mostly calcalkaline) orthogneisses in the same area. High-quality transparent zircons showed the least degree of discordance, but contain extremely low U and Pb levels. The rock suite, including this plagiogranite, was emplaced within oceanic crust which formed in the latest Precambrian-early Palaeozoic off the northern continental margin of Gondwana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02440113
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The evolution of the polymetamorphic basement in the Central Alps unravelled by precise U−Pb zircon dating (1993)
    Springer
    Contributions to mineralogy and petrology 113 (1993), S. 466-478 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The U−Pb age determinations of zircon and rutile from the Aar massif reveal a complex evolution of the Central Alpine basement. The oldest components are found in zircons of metasediments, which bear cores of Archean age; the U−Pb age of discordant prismatic zircons of the same rocks ranges between 580 and 680 Ma, an age that is typical for Pan-African metamorphism. The zircons are interpreted as Pan-African detritus with Archean inheritance. The provenance region of the Pan-African zircons is assumed to be a terrane of Gondwana-affinity, i.e. the W. African craton or the Pentevrian microplate. The Caledonian metamorphism left a pervasive structural imprint in amphibolite facies on the rocks of the Aar massif; it is dated at 456±2 and 445 Ma by zircons of a layered migmatitic gneiss and a migmatitic leucosome, respectively, both occurring in the northernmost zones of the massif. Hercynian metamorphism never exceeded greenschist-facies conditions and is recorded by zircon in a garnet-amphibolite and by rutile in a meta-psammite that yield an age of 330 Ma. Both zircon and rutile are considered to be products of retrograde mineral reactions and therefore do not date the peak conditions of Hercynian metamorphism. The Gastern granite at the western end of the Aar massif is a contaminated granite that intruded at 303±4 Ma, contemporaneously with the wide-spread late Hercynian post-collisional I-type magmatism. The study demonstrates the potential of isotope dilution U−Pb dating of single grains and microfractions in deciphering complex evolutionary histories of polymetamorphic terrains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698316
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  • 3
    Electronic Resource
    Electronic Resource
    The age and source of late Hercynian magmatism in the central Alps: evidence from precise U−Pb ages and initial Hf isotopes (1992)
    Springer
    Contributions to mineralogy and petrology 111 (1992), S. 329-344 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract This study presents U−Pb ages for zircon, titanite, allanite and epidote, and initial Hf isotopic compositions for zircon of Upper Carboniferous granites, diorites and syenites from the Aar massif, central Alps. The rocks were emplaced during three magmatic pulses after Hercynian collisional tectonics: (A) a shoshonitic-ultrapotassic series at 334±2.5 Ma; (B) scattered diorites and granites at 308–310 Ma; and (C) a high-K cale-alkaline granite batholith at 298±2 Ma. Inheritance of old zircons is negligible among all three groups. The Southern Aar granite, in contrast, is a syn-tectonic, probably ca. 350 Ma old granite that contains large amounts of inherited Precambrian zircons. Alpine metamorphism caused weak lead loss in many analyzed zircon fractions, but left the titanite U−Pb system undisturbed: thorites were almost completely reset by Alpine and recent lead loss. Mineral isochrons defined by titanite, allanite, epidote and apatite yield initial Pb isotopic compositions that are in agreement with the model values of Stacey and Kramers. Initial Hf isotopic compositions range from ɛHf=−8 to +3.5. The data follow a trend of increasing ɛHf with decreasing age. The ɛHf versus element concentration relationships suggest mixing between a mantle and a crustal component. These relationships can be explained in terms of generation of the melts from a subcontinental mantle that had been enriched during subduction events at about 1 Ga and by 300 Ma had developed an isotopic signature distinct from that of MORB-type mantle. Further contamination of the melts occurred during ascent and differentiation in the crust. This late Hercynian magmatism can be related to post-collisional strike-slip tectonics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311195
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  • 4
    Electronic Resource
    Electronic Resource
    Post-granulite facies monazite growth and rejuvenation during Permian to Lower Jurassic thermal and fluid events in the Ivrea Zone (Southern Alps) (1999)
    Springer
    Contributions to mineralogy and petrology 134 (1999), S. 405-414 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract U-Pb analyses of single monazite grains from two granulite facies metapelites in the Ivrea Zone (Southern Alps) reveal the presence, in both samples, of at least three different ages and prove that earlier interpretations of supposedly concordant monazite data as cooling ages are unwarranted. One group of monazite data defines a subconcordant discordia line with an upper intercept age of 293.4 ± 5.8 Ma and a lower intercept age of 210 ± 14 Ma. The upper intercept is interpreted as the real cooling age of the monazites. The lower intercept is interpreted as an episode of fluid-driven Pb-loss, indicated by the presence of internal and external corrosion structures not only of the monazites but also of the zircons in the same samples that are also rejuvenated at 210 ± 12 Ma. Another group of monazite data lies above the concordia. The presence of excess 206Pb indicates that these crystals have grown below the monazite blocking temperature, thus after the granulite facies metamorphism. The age of growth of the new monazite crystals is approached by their 207Pb/235U ages that range between 273 and 244 Ma. The two groups of post-cooling age (post-293.4 ± 5.8 Ma) monazite data correspond to two distinct late- and post-Variscan geotectonic regimes that affected the Southern Alps, (1) Permian transtension with decompression and anatectic melting; (2) Upper Triassic to Lower Jurassic rifting with geographically dispersed hydrothermal activity and alkaline magmatism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050493
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  • 5
    Electronic Resource
    Electronic Resource
    Early Cambrian oceanic plagiogranite in the Silvretta Nappe, eastern Alps: geochemical, zircon U–Pb and Rb–Sr data from garnet–hornblende–plagioclase gneisses (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 822-831 
    Details
    ISSN: 0016-7835
    Keywords: Key words Austro-Alpine ; Eastern Alps ; Oceanic rocks ; Rb ; Sr ; Zircon ; U ; Pb ; Magmatism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Garnet–hornblende–plagioclase gneisses rich in incompatible elements occur in the crystalline basement of the Austro-Alpine Silvretta nappe and are associated with clinopyroxene norites and harzburgite cumulates. It is proposed here that the gneisses were formerly oceanic plagiogranites. An εNd( 530 ) value of +5.6 for the gneisses as well as initial 87Sr/86Sr values of 0.7036–0.7037 for the gabbroic rocks and 0.7026–0.7027 for the ultramafic rocks suggest a mantle source for this rock association. The geochemical characteristics of the garnet–hornblende–plagioclase gneisses indicate that their precursors were derived by fractional crystallization from a basaltic parent magma, by the same process which produced the adjacent clinopyroxene norites and ultramafic cumulates as well. The combined U–Pb upper intercept ages of zircons from two gneiss samples yield an igneous crystallization age of 532±30 Ma, similar to previously dated (mostly calc-alkaline) orthogneisses in the same area. High-quality transparent zircons showed the least degree of discordance, but contain extremely low U and Pb levels. The rock suite, including this plagiogranite, was emplaced within oceanic crust which formed in the latest Precambrian–early Palaeozoic off the northern continental margin of Gondwana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050114
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  • 6
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    Miocene syn-rift evolution of the North Croatian Basin (Carpathian–Pannonian Region): new constraints from Mts. Kalnik and Požeška gora volcaniclastic record with regional implications (2020)
    Springer
    Details
    Publication Date: 2023-02-08
    Description: Mts. Kalnik and Požeška gora volcaniclastic sequences hold valuable information concerning the Miocene syn-rift evolution of the North Croatian Basin, and the evolution of the Carpathian–Pannonian Region and the Central Paratethys. We present volcanological, high-precision geochronological, and compositional data of volcanic glass to constrain their tephrochronology, magmatic provenance, and timing of the initial Central Paratethys flooding of the North Croatian Basin. Based on CA-ID-TIMS U–Pb zircon ages (18.060 ± 0.023 Ma for Mt. Kalnik and 15.345 ± 0.020 Ma for Mt. Požeška gora) and coeval 40Ar/39Ar sanidine ages (18.14 ± 0.38 Ma and 18.25 ± 0.38 Ma for Mt. Kalnik and 15.34 ± 0.32 Ma and 15.43 ± 0.32 Ma for Mt. Požeška gora), Mt. Kalnik rhyolitic massive ignimbrites and Mt. Požeška gora rhyolitic primary volcaniclastic turbidites are coeval with Carpathian–Pannonian Region Miocene post-collisional silicic volcanism, which was caused by lithospheric thinning of the Pannonian Basin. Their affiliation to Carpathian–Pannonian Region magmatic activity is supported by their subduction-related geochemical signatures. Although Mts. Kalnik and Požeška gora volcaniclastics are coeval with the Bükkalja Volcanic Field Csv-2 rhyolitic ignimbrites, North Alpine Foreland Basin, Styrian Basin, Vienna Basin, and Dinaride Lake System bentonites and volcaniclastic deposits, reliable tephrochronological interpretations based on comparison of volcanic glass geochemical composition are not possible due to a lack of data and/or methodological discrepancies. Our new high-precision geochronology data prove that the initial Middle Miocene (Badenian) marine flooding of parts of the North Croatian Basin occurred at least ~ 0.35 Ma (during the NN4 Zone) before the generally accepted ~ 15 Ma maximum flooding age at the basin scale, calibrating the timing of the onset of the widespread “mid-Langhian” Central Paratethys flooding.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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