Detection of a Ca-rich lithology in the Earth's deep (> 300 km) convecting mantle
Earth and planetary science letters. Bd. 236. H. 3/4. Amsterdam u.a.: Elsevier 2005 S. 579 - 587
Erscheinungsjahr: 2005
ISBN/ISSN: 0012-821X
Publikationstyp: Zeitschriftenaufsatz
Sprache: Englisch
Doi/URN: 10.1016/j.epsl.2005.05.021
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Inhaltszusammenfassung
Earth%27s deep convecting upper mantle is believed to represent a rather homogenous geochemical reservoir of spinel or garnet lherzolite with primitive major element and moderately depleted trace element composition. Only where subduction occurs is this homogeneity disrupted by a suite of rocks ranging from eclogites/garnet pyroxenites (former oceanic crust) to residual harzburgites. In addition to these well documented peridotitic and metabasaltic rocks we have now discovered the presence of...Earth%27s deep convecting upper mantle is believed to represent a rather homogenous geochemical reservoir of spinel or garnet lherzolite with primitive major element and moderately depleted trace element composition. Only where subduction occurs is this homogeneity disrupted by a suite of rocks ranging from eclogites/garnet pyroxenites (former oceanic crust) to residual harzburgites. In addition to these well documented peridotitic and metabasaltic rocks we have now discovered the presence of a chemically distinct reservoir in the deep convecting upper mantle. In situ structural analyses (micro X-ray diffraction and micro Raman spectroscopy) and three-dimensional trace element mapping (confocal micro X-ray fluorescence imaging) of polyphase inclusions in a diamond from Guinea that formed at about 300-360 km depth reveal the existence of a deep Ca-rich source, in the absence of several common mantle minerals, like olivine, garnet and low-Ca pyroxene. This reservoir may represent metasomatized oceanic lithosphere (rodingites, ophicarbonates) or metamorphosed carbonaceous sediments. (c) 2005 Elsevier B.V. All rights reserved.» weiterlesen» einklappen
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