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  • 1
    Electronic Resource
    Electronic Resource
    Cryptic striations in the upper mantle revealed by hafnium isotopes in southeast Indian ridge basalts (2006)
    [s.l.] : Nature Publishing Group
    Nature 440 (2006), S. 199-202 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Earth's mantle is isotopically heterogeneous on length scales ranging from centimetres to more than 104 kilometres. This heterogeneity originates from partial melt extraction and plate tectonic recycling, whereas stirring during mantle convection tends to reduce it. Here ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04582
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A short timescale for terrestrial planet formation from Hf–W chronometry of meteorites (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 418 (2002), S. 949-952 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Determining the chronology for the assembly of planetary bodies in the early Solar System is essential for a complete understanding of star- and planet-formation processes. Various radionuclide chronometers (applied to meteorites) have been used to determine that ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature00995
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The Lu–Hf dating of garnets and the ages of the Alpine high-pressure metamorphism (1997)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 387 (1997), S. 586-589 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It remains controversial whether burial and exhumation in mountain belts represent episodic or continuous processes. Regional patterns of crystallization and closure ages of high-pressure rocks may help to discriminate one mode from the other but, unfortunately, metamorphic geochronology ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/42446
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence from Sardinian basalt geochemistry for recycling of plume heads into the Earth's mantle (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 408 (2000), S. 701-704 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Up to 10 per cent of the ocean floor consists of plateaux—regions of unusually thick oceanic crust thought to be formed by the heads of mantle plumes. Given the ubiquitous presence of recycled oceanic crust in the mantle source of hotspot basalts, it follows that plateau material ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35047049
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Separation of Hf and Lu for high-precision isotope analysis of rock samples by magnetic sector-multiple collector ICP-MS (1997)
    Springer
    Contributions to mineralogy and petrology 127 (1997), S. 248-260 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Potential applications of the Lu-Hf isotope system have long been impeded by the analytical difficulties of obtaining data on a wide variety of geological materials. Many of these limitations will now be eliminated because Hf isotopes can be readily measured with high precision and accuracy on small and/or Hf-poor samples using the newly developed magnetic sector-multiple collector ICP-MS, also known as MC-ICP-MS or the `Plasma 54'. We present here a new method to separate and determine isotopic compositions of both Hf and Lu from various types of geological materials using MC-ICP-MS. The chemical separation of Hf and Lu has been designed to take advantage of the characteristics of this unique instrument. The separation of Hf can be achieved with a straightforward two-step ion-exchange column chemistry, which has a high efficiency (better than 85% recovery) and low blanks (typical total blanks less than 150 pg for the largest samples of 1 g bulk rock). The isolation of Lu is achieved with a single-stage ion-exchange column procedure with near 100% yields and blanks below 20 pg. Hf isotopic compositions can be routinely measured on 50 ng Hf with an internal precision better than 20 ppm in less than 15 min and with an external precision better than 40 ppm. Our value for the 176Hf/177Hf ratio of the JMC 475 Hf standard currently is 0.282163 ± 9 (2s). The Lu isotopic ratio is measured rapidly and precisely without isolating Lu from the bulk of Yb, and a mass fractionation correction increases the accuracy of the results compared with TIMS data. Our current reproducibility of the Lu/Hf ratio is ≈1%. Selected Lu-Hf isotope analyses of some modern and ancient geological samples validate the technique we have described here and illustrate the new opportunities for Lu-Hf isotope geochemistry that have opened up with the advent of magnetic-sector ICP mass spectrometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050278
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  • 6
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    The origin of enriched mantle beneath São Miguel, Azores (2007)
    In:  Geochimica et Cosmochimica Acta
    Details
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/article
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    GFZ OAI
  • 7
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    Understanding melt generation beneath the slow-spreading Kolbeinsey Ridge using 238U, 230Th, and 231Pa excesses (2011)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 75 (21). pp. 6300-6329.
    Details
    Publication Date: 2017-09-27
    Description: To examine the petrogenesis and sources of basalts from the Kolbeinsey Ridge, one of the shallowest locations along the global ridge system, we present new measurements of Nd, Sr, Hf, and Pb isotopes and U-series disequilibria on 32 axial basalts. Young Kolbeinsey basalts (full-spreading rate = 1.8 cm/yr; 67°05′–70°26′N) display (230Th/238U) 〈 1 and (230Th/238U) 〉 1 with (230Th/238U) from 0.95 to 1.30 and have low U (11.3–65.6 ppb) and Th (33.0 ppb–2.40 ppm) concentrations. Except for characteristic isotopic enrichment near the Jan Mayen region, the otherwise depleted Kolbeinsey basalts (e.g. 87Sr/86Sr = 0.70272–0.70301, εNd = 8.4–10.5, εHf = 15.4–19.6 (La/Yb)N = 0.28–0.84) encompass a narrow range of (230Th/232Th) (1.20–1.32) over a large range in (238U/232Th) (0.94–1.32), producing a horizontal array on a (230Th/232Th) vs. (238U/232Th) diagram and a large variation in (230Th/238U). However, the (230Th/238U) of the Kolbeinsey Ridge basalts (0.96–1.30) are inversely correlated with (234U/238U) (1.001–1.031). Samples with low (230Th/238U) and elevated (234U/238U) reflect alteration by seawater or seawater-derived materials. The unaltered Kolbeinsey lavas with equilibrium 234U/238U have high (230Th/238U) values (〉=1.2), which are consistent with melting in the presence of garnet. This is in keeping with the thick crust and anomalously shallow axial depth for the Kolbeinsey Ridge, which is thought to be the product of large degrees of melting in a long melt column. A time-dependent, dynamic melting scenario involving a long, slowly upwelling melting column that initiates well within the garnet peridotite stability zone can, in general, reproduce the (230Th/238U) and (231Pa/235U) ratios in uncontaminated Kolbeinsey lavas, but low (231Pa/235U) ratios in Eggvin Bank samples suggest eclogite involvement in the source for that ridge segment.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.gca.2011.08.020
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    North Atlantic hotspot-ridge interaction near Jan Mayen Island (2016)
    European Association of Geochemistry
    In:  Geochemical Perspectives Letters, 2 (1). pp. 55-67.
    Details
    Publication Date: 2019-09-23
    Description: At slow to ultraslow spreading rates along mid-ocean ridges, thicker lithosphere typically impedes magma generation and tectonic extension can play a more significant role in crustal production (Dick et al., 2003). The source of anomalously high magma supply thus remains unclear along ridges with ultraslow-spreading rates adjacent to Jan Mayen Island in the North Atlantic (Neumann and Schilling, 1984; Mertz et al., 1991; Haase et al., 1996; Schilling et al., 1999; Trønnes et al., 1999; Haase et al., 2003; Mertz et al., 2004; Blichert-Toft et al., 2005; Debaille et al., 2009). Here we show that Jan Mayen volcanism is likely the surface expression of a small mantle plume, which exerts significant influence on nearby mid-ocean ridge tectonics and volcanism. Progressive dilution of Jan Mayen geochemical signatures with distance from the hotspot is observed in lava samples from the immediately adjacent Mohns Ridge, and morphological indicators of enhanced magma supply are observed on both the Mohns Ridge and the nearby Kolbeinsey Ridge, which additionally locally overlies a highly heterogeneous, eclogite-bearing mantle source. These morphological and geochemical influences underscore the importance of heterogeneous mantle sources in modifying melt supply and thus the local expression of tectonic boundaries.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.7185/geochemlet.1606
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Hafnium isotopic variations in East Atlantic intraplate volcanism (2009)
    In:  [Talk] In: EGU General Assembly 2009, 19.-24.04, Vienna, Austria .
    Details
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 10
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    Hafnium isotopic variations in volcanic rocks from the Caribbean Large Igneous Province and Galápagos hotspot tracks (2003)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 422 (7). 2002GC000477.
    Details
    Publication Date: 2018-01-30
    Description: [1] We report Hf isotope compositions of 79 lavas that record the early (∼5–95 Ma) history of the Galápagos plume volcanism. These include lavas from the Caribbean Large Igneous Province (CLIP; ∼95–70 Ma), the accreted Galápagos paleo-hot spot track terranes (54–65 Ma) of Costa Rica (Quepos, Osa and Burica igneous complexes), and the Galápagos hot spot tracks (〈20 Ma) located on the Pacific seafloor (Cocos, Carnegie, Malpelo, and Coiba Ridges and associated seamounts). These samples have previously been well characterized in terms of major and trace elements, Sr-Nd-Pb isotopes and Ar/Ar ages. As a result of the relative immobility of the high field strength and rare earth elements during syn- and post-emplacement hydrothermal activity and low-temperature alteration, combined Lu-Hf and Sm-Nd isotope systematics, when used in conjunction with Pb isotopes, provide a particular powerful tool, for evaluating the source compositions of ancient and submarine lavas. The combined Nd-Hf isotope data suggest that three of the isotopically distinct source components found today in the Galápagos Islands (the Floreana-like southern component, the Fernandina-like central component, and the depleted Genovesa-like eastern component) were present in the CLIP already by 95–70 Ma. The fourth Pinta-like northern component is first recorded at about 83–85 Ma by volcanism taking place during the transition from the plume head/CLIP to plume tail stage and has then been present in the hot spot track continuously thereafter. The identification of the unique northern and southern Galápagos Plume Hf-Nd-Pb isotope source signatures within the CLIP and the oldest hot spot track lavas provides direct evidence that the CLIP represents the plume head stage of the Galápagos hot spot. Hafnium isotopes are consistent with the possibility that two types of sediment components may have contributed to the Hf, Nd and Pb isotope compositions of the Galápagos plume lavas. One component, characterized by Δ207Pb/204Pb ≈ 0 and high positive ΔεHf has an isotope signature indicative of relatively recently recycled pelagic sediment, a signature typical of the southern Galápagos island Floreana. The other component has an EM like isotopic composition resembling modern seafloor sediments with positive Δ207Pb/204Pb and lower ΔεHf, a signature typical of the northern Galápagos island Pinta.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2002GC000477
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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