DIAMONDIFEROUS PERIDOTITES FROM OCEANIC PROTOLITHS: CRUSTAL SIGNATURES FROM YAKUTIAN KIMBERLITES
L.A. Taylor, Z.V. Spetsius*, R. Wiesli**, M. Spicuzza**, and J.W. Valley**
Planetary Geosciences Institute, Department of Earth & Planetary Sciences,
University of Tennessee, Knoxville, TN, 37996, USA
* ALROSA Co. Ltd., 6 ul. Lenina, Mirny, 678170, Russia
** Depaprtment of Geology & Geophysics, University of Wisconsin, Madison, WI, 53706, USA
Keywords: Peridotites, isotopes, protoliths, diamonds
Pages: 1176-1184
Subsection: COMPOSITION AND STRUCTURE OF CONTINENTAL LITHOSPHERE
Abstract
It is now generally agreed that many of the eclogite xenoliths from kimberlites have protoliths that originated as ancient oceanic crust that was subducted beneath the major cratons worldwide. Similar types of evidence, based mainly upon oxygen isotopes, are used to question the paradigm that peridotite xenoliths in kimberlites are of mantle origin. The same general distribution of δ18O values about the mean mantle value is seen for the peridotites as for the eclogites, both with significant numbers of values distinctly outside of mantle range. It is concluded that at least some of these ultramafic xenoliths, including some diamondiferous ones, have their ultimate origin in the ancient oceanic crust. Indeed, some of the diamonds may have had their carbon derived from crustal sources as well.
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