Sheared peridotite xenolith from the V. Grib kimberlite pipe, Arkhangelsk Diamond Province, Russia: Texture, composition, and origin

• Published in: Geoscience Frontiers
• Main Authors: Alexey Vladimirovich Kargin, Lyudmila Vyacheslavovna Sazonova, Anna Andreevna Nosova, Vladimir Anatolievich Pervov, Elena Vladimirovna Minevrina, Vladimir Anatolievich Khvostikov, Zhanna Petrovna Burmii
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2017
• Subjects: Sheared peridotite; Mantle metasomatism; Kimberlite; Olivine; Garnet; Clinopyroxene; Geology; QE1-996.5; Arkhangelsk
• Online Access: https://doi.org/10.1016/j.gsf.2016.03.001; https://doaj.org/article/cdaa012e9b234a24b8564fe3340be21a

The petrography and mineral composition of a mantle-derived garnet peridotite xenolith from the V. Grib kimberlite pipe (Arkhangelsk Diamond Province, Russia) was studied. Based on petrographic characteristics, the peridotite xenolith reflects a sheared peridotite. The sheared peridotite experienced a complex evolution with formation of three main mineral assemblages: (1) a relict harzburgite assemblage consist of olivine and orthopyroxene porphyroclasts and cores of garnet grains (Gar1) with sinusoidal rare earth elements (REE) chondrite C1 normalized patterns; (2) a neoblastic olivine and orthopyroxene assemblage; (3) the last assemblage associated with the formation of clinopyroxene and garnet marginal zones (Gar2). Major and trace element compositions of olivine, orthopyroxene, clinopyroxene and garnet indicate that both the neoblast and clinopyroxene-Gar2 mineral assemblages were in equilibrium with a high Fe-Ti carbonate-silicate metasomatic agent. The nature of the metasomatic agent was estimated based on high field strength elements (HFSE) composition of olivine neoblasts, the garnet-clinopyroxene equilibrium condition and calculated by REE-composition of Gar2 and clinopyroxene. All these evidences indicate that the agent was a high temperature carbonate-silicate melt that is geochemically linked to the formation of the protokimberlite melt.