Abstract
A new classification of kelyphitic rims on garnets from xenoliths of peridotitic and eclogitic parageneses of the mantle section under the Udachnaya-East kimberlite pipe (Yakutia) is presented. 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. Rims 1, 2, and 3 are typical for garnets of all studied parageneses. Rims 4 and 5 develop on high-Cr subcalcic garnets of the most depleted peridotites. Reactions of the formation of all types of rims are given in the article. 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—CaO, suggesting the multistage injection of different components by mantle fluid.
Highlights
The first mentions of peridotite garnet rims appeared in the mid-19th century [1,2,3]
Kelyphite rims were observed on several minerals, but most often this term is applied to fine-grained aggregates forming around the garnet, which is relevant in the context of this article
It is obvious that the formation of rim2 was accompanied by an inflow of titanium, which was distributed depending on the initial conditions of the system
Summary
The first mentions of peridotite garnet rims appeared in the mid-19th century [1,2,3]. Using data on a representative collection of samples from the kimberlite regions of the central and marginal parts of the Siberian Platform, Kharkiv and Vishnevsky [16] concluded that the isochemical formation of the rims surround peridotite garnets They emphasized the presence of significant differences between the features of kelyphitization of garnets from xenoliths and kimberlite cement (dominance of clino- and orthopyroxenes and chromium spinel in the rim composition in the first case, and the predominance of hydrous phases (phlogopite) in the second), confirming the conclusion of Ilupin and his co-authors [21] on the different origins of such rims. The cross-scattering region may exceed the size of the analyzed phase (here, the mineral grains of the kelyphite rim surrounding the garnet) In this case, values of some components may be overestimated or underestimated. CMIO—Unnamed Calcium Magnesium Iron Oxide (Ca,Mn)Mg(Fe,Al,Si)6O11 (according to [41])
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
