Olivine in the udachnaya-east kimberlite (Yakutia, Russia): Types, compositions and origins

• Published in: Journal of Petrology
• Main Authors: Kamenetsky, Vadim S., Kamenetsky, Maya B., Sobolev, Alexander V., Golovin, Alexander V., Demouchy, Sylvie, Faure, Kévin, Sharygin, Victor V., Kuzmin, Dmitry V.
• Other Authors: ARC Centre of Excellence in Ore Deposits (CODES), University of Tasmania Hobart, Australia (UTAS), School of Earth Sciences Hobart, Max Planck Institute for Chemistry (MPIC), Max-Planck-Gesellschaft, Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKHI), Russian Academy of Sciences Moscow (RAS), Sobolev Institute of Geology and Mineralogy Novosibirsk, Siberian Branch of the Russian Academy of Sciences (SB RAS), University of Minnesota Twin Cities (UMN), University of Minnesota System, GNS Science Lower Hutt, GNS Science
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2008
• Subjects: H2O; oxygen isotopes; partial melting; carbonatitic melt; kimberlite; olivine; [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography; Yakutia; Siberia
• Online Access: https://hal.archives-ouvertes.fr/hal-00411866; https://doi.org/10.1093/petrology/egm033

Olivine is the principal mineral of kimberlite magmas, and is the main contributor to the ultramafic composition of kimberlite rocks. Olivine is partly or completely altered in common kimberlites, and thus unavailable for studies of the origin and evolution of kimberlite magmas. The masking effects of alteration, common in kimberlites worldwide, are overcome in this study of the exceptionally fresh diamondiferous kimberlites of the Udachnaya-East pipe from the DaldynAlakit province, Yakutia, northern Siberia. These serpentine-free kimberlites contain large amounts of olivine (similar to 50 vol.%) in a chloridecarbonate groundmass. Olivine is represented by two populations (olivine-I and groundmass olivine-II) differing in morphology, colour and grain size, and trapped mineral and melt inclusions. The large fragmental olivine-I is compositionally variable in terms of major (Fo(8594)) and trace element concentrations, including H2O content (10-136 ppm). Multiple sources of olivine-I, such as convecting and lithospheric mantle, are suggested. The groundmass olivine-II is recognized by smaller grain sizes and perfect crystallographic shapes that indicate crystallization during magma ascent and emplacement. However, a simple crystallization history for olivine-II is complicated by complex zoning in terms of Fo values and trace element contents. The cores of olivine-II are compositionally similar to olivine-I, which suggests a genetic link between these two types of olivine. Olivine-I and olivine-II have oxygen isotope values ( +5.6+/- 0.1 parts per thousand VSMOW, 1 SD) that are indistinguishable from one another, but higher than values (+5.18 +/- 0.28 parts per thousand) in typical mantle olivine. These elevated values probably reflect equilibrium with the Udachnaya carbonate melt at low temperatures and O-18-enriched mantle source. The volumetrically significant rims of olivine-II have constant Fo values (89.0 +/- 0.2 mol%), but variable trace element compositions. The uniform Fo compositions of the rims imply an ...