GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    Geochemistry of the oldest MORB and OIB in the Isua Supracrustal Belt, southern West Greenland: Implications for the composition and temperature of early Archean upper mantle (2004)
    Melbourne, Australia : Blackwell Science Pty
    The @island arc 13 (2004), S. 0 
    Details
    ISSN: 1440-1738
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract  Recent geological investigations of the Isua Supracrustal Belt (3.8 Ga), southern West Greenland, have suggested that it is the oldest accretionary complex on earth, defined by an oceanic plate-type stratigraphy and a duplex structure. Plate history from mid-oceanic ridge through plume magmatism to subduction zone has been postulated from analysis of the reconstructed oceanic plate stratigraphy in the accretionary complex. Comparison between field occurrence of greenstones in modern and ancient accretionary complexes reveals that two types of tholeiitic basalt from different tectonic settings, mid-oceanic ridge basalt (MORB) and oceanic island basalt (OIB), occur. This work presents major, trace and rare earth element (REE) compositions of greenstones derived from Isua MORB and OIB, and of extremely rare relict igneous clinopyroxene in Isua MORB. The Isua clinopyroxenes (Cpx) have compositional variations equivalent to those of Cpx in modern MORB; in particular, low TiO2 and Na2O contents. The Isua Cpx show slightly light (L)REE-depleted REE patterns, and the calculated REE pattern of the host magma is in agreement with that of Isua MORB. Analyses of 49 least-altered greenstones carefully selected from approximately 1200 samples indicate that Isua MORB are enriched in Al2O3, and depleted in TiO2, FeO*, Y and Zr at the given MgO content, compared with Isua OIB. In addition, Isua MORB show an LREE-depleted pattern, whereas Isua OIB forms a flat REE pattern. Such differences suggest that the Early Archean mantle had already become heterogeneous, depending on the tectonic environment. Isua MORB are enriched in FeO compared with modern MORB. Comparison of Isua MORB with recent melting experiments shows that the source mantle had 85–87 in Mg♯ and was enriched in FeO. Potential mantle temperature is estimated to be approximately 1480°C, indicating that the Early Archean mantle was hotter by at most approximately 150°C than the modern mantle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1738.2003.00416.x
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    The chemical structure of the Hawaiian mantle plume (2005)
    [s.l.] : Nature Publishing Group
    Nature 436 (2005), S. 837-840 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Hawaiian–Emperor volcanic island and seamount chain is usually attributed to a hot mantle plume, located beneath the Pacific lithosphere, that delivers material sourced from deep in the mantle to the surface. The shield volcanoes of the Hawaiian islands are distributed in two ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03907
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    facet.materialart.
    Unknown
    Petit-spot volcanoes on the oldest portion of the Pacific plate (2019)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 154 (103142).
    Details
    Publication Date: 2022-01-31
    Description: The formation of a petit-spot volcano involves the ascent of an asthenospheric melt to the outboard part of a plate subduction zone where flexure of the plate has taken place in the outer trench swell. On the Pacific Plate, the only previously known examples of such volcanoes were in the vicinity of the Japan Trench. We describe here a newly discovered petit-spot submarine volcano that formed in one of the oldest parts of the Pacific Plate among a cluster of small conical knolls to the southeast of Minamitorishima (Marcus) Island. Geochronological data indicate that this petit-spot volcanic eruption occurred less than 3 million years ago. The volcano erupted on the eastern slope of the outer rise, and it is at an unusually large distance from the Mariana trench axis (~800 km) because this rise, near the older part of the Pacific Plate, is wider than those of other subduction systems.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr.2019.103142
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
    facet.materialart.
    Unknown
    COPPER ISOTOPE CHARACTERISTICS OF COPPER-RICH MINERALS FROM BESSHI-TYPE VOLCANOGENIC MASSIVE SULFIDE DEPOSITS, JAPAN, DETERMINED USING A FEMTOSECOND LA-MC-ICP-MS (2011)
    Society of Economic Geologists (SEG)
    Details
    Publication Date: 2011-03-01
    Description: The copper isotope ratios of chalcopyrite, secondary malachite, and native copper of metamorphosed Besshi-type volcanogenic massive sulfide (VMS) deposits from two different mines, Japan, were measured by femtosecond-pulsed laser ablation-multiple collector-inductively coupled plasma-mass spectrometry (fs-LA-MC-ICP-MS). The{delta} 65Cu (where{delta} 65Cu = [{(65Cu/63Cu)sample/(65Cu/63Cu)NIST-SRM976} - 1] x 1,000) values of chalcopyrite samples of both mines are relatively narrow (-0.34 to +0.29{per thousand}) compared to those of previously reported chalcopyrite from modern submarine hydrothermal deposits at mid-oceanic ridge settings (-0.98 to +3.14{per thousand}). However, the{delta} 65Cu values of chalcopyrite are slightly different between the two mines. This suggests that, although metamorphic reequilibration may have reduced the original range of copper isotopes, premetamorphic{delta} 65Cu characteristics of both mines are generally preserved. The chalcopyrite samples of one deposit might be significantly affected by dissolution during reworking processes after precipitation on the sea floor. Secondary malachite ({delta}65Cu = 2.63-2.97{per thousand}) and native copper ({delta}65Cu = 1.43-1.71{per thousand}) have higher{delta} 65Cu values than chalcopyrite from the same deposit. This variation is most reasonably explained in terms of a redox-controlled isotope fractionation at low-temperature conditions during secondary (weathering) processes involving the preferential incorporation of 65Cu in secondary Cu(II) solutions. It is also suggested that significant negative isotopic fractionations accompanying the reduction of Cu (II) solutions to native copper [Cu (0)] occurred.
    Print ISSN: 0361-0128
    Topics: Geosciences
    Published by Society of Economic Geologists (SEG)
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...