Detection of a Ca-rich lithology in the Earth's deep (> 300 km) convecting mantle

Frank E. Brenker*, Laszlo Vincze, Bart Vekemans, Lutz Nasdala, Thomas Stachel, Christian Vollmer, Michael Kersten, Andrea Somogyi, Freddy Adams, Werner Joswig, Jeff W. Harris

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)


Earth's 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.

Original languageEnglish
Pages (from-to)579-587
Number of pages9
JournalEarth and Planetary Science Letters
Issue number3-4
Publication statusPublished - 15 Aug 2005
Externally publishedYes


  • Inclusions in diamond
  • Kankan
  • Mantle heterogeneity
  • Raman spectroscopy
  • Synchrotron
  • X-ray fluorescence


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