Peridotite and Pyroxenite xenoliths from the Muskox kimberlite, northern Slave craton, Canada

• Main Authors: Newton, David Edward, Kopylova, Maya G, Burgess, Jennifer, Strand, Pamela
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2015
• Subjects: Canada; Wall Rocks; muskox
• Online Access: http://hdl.handle.net/1807/70737; http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2015-0083

Abstract We present petrography, mineralogy and thermobarometry for 53 mantle-derived xenoliths from the Muskox kimberlite pipe in the northern Slave craton. The xenolith suite includes 23% coarse peridotite, 9% porphyroclastic peridotite, 60% websterite and 8% orthopyroxenite. Samples primarily comprise forsteritic olivine (Fo 89-94), enstatite (En 89-94), Cr-diopside, Cr-pyrope garnet and chromite spinel. Coarse peridotites, porphyroclastic peridotites, and pyroxenites equilibrated at 650-1220 °C and 23-63 kbar, 1200-1350 °C and 57-70 kbar, and 1030-1230 °C and 50-63 kbar, respectively. The Muskox xenoliths differ from the neighboring and contemporaneous Jericho kimberlite by their higher levels of depletion, the presence of a shallow zone of metasomatism in the spinel stability field, a higher proportion of pyroxenites at the base of the mantle column, higher Cr2O3 in all pyroxenite minerals, and weaker deformation in the Muskox mantle. We interpret these contrasts as representing small scale heterogeneities in the bulk composition of the mantle, as well as the local effects of interaction between metasomatizing fluids and mantle wall rocks. We suggest that asthenosphere-derived pre-kimberlitic melts and fluids percolated less effectively through the less permeable Muskox mantle resulting in lower degrees of hydrous weakening, strain and fertilization of the peridotitic mantle. The fluids tended to concentrate and pool in the deep mantle causing partial melting and formation of abundant pyroxenites. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.