Kelyphitic rims are present on garnets from xenoliths of various parageneses: peridotites (enriched and depleted), eclogites, pyrpoxenites, and polymictic breccias. Xenoliths of the mantle section under the Udachnaya-East and Noyabrskaya kimberlite pipes (Yakutia, Russia) were studied. Five types of rims are identified: Rim1 develops between garnet and olivine/pyroxene (or rim2) and is composed of high-alumina pyroxenes, spinel, phlogopite; rim2, the coarse grain part of rim1, is located between rim1 and olivine/ pyroxene, and mainly consists of phlogopite and less aluminous larger pyroxenes and spinel; rim3 develops between garnet and kimberlite, and presents with phlogopite and Fe-Ti spinel; rim4 sometimes presents instead of rim1/ rim2 and consists of zoned high-Cr phlogopite with rare fine grains of chromium spinel; rim5, a “pocket” between garnet and rim1, is represented by microcrystalline aggregates of clinopyroxene, mica, spinel, calcite, and feldspar in different variations. Rim formation occurs due to tectonic movements causing rock cracking and system decompression. Metasomatic melts enriched with water, alkalis, chlorine etc., penetrating microcracks, interact with garnet and form kelyphite Rim1/2. Various variants of the reactions depend on the chemical composition of initial garnet and acting fluid/melt. The transformation of the primary rims to form Rim3 occurs when xenoliths interact with the kimberlite melt. Rims 1, 2 are typical for garnets of all studied parageneses. Rim3 is not observed on garnets from pyroxenite and polymictic breccia. Rims 4 and 5 develop on high-Cr subcalcic garnets of the most depleted peridotites. Each type of kelyphite demonstrates a clear enrichment with a certain component: Rim1—MgO and alkalis; rim2—TiO2; rim3—FeO and TiO2; rim4—Cr2O3; and rim5—СаО, suggesting the multistage injection of different components by mantle fluid.
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