Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9522657 | Earth and Planetary Science Letters | 2005 | 9 Pages |
Abstract
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.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Earth and Planetary Sciences (General)
Authors
Frank E. Brenker, Laszlo Vincze, Bart Vekemans, Lutz Nasdala, Thomas Stachel, Christian Vollmer, Michael Kersten, Andrea Somogyi, Freddy Adams, Werner Joswig, Jeff W. Harris,