TY - JOUR

T1 - The Nature of Heterogeneity of High-Chromium Garnets in Xenolite of Deformed Lherzolite from Udachnaya Kimberlite Pipe (Yakutia)

AU - Shatsky, V. S.

AU - Ragozin, A. L.

AU - Sitnikova, E. S.

N1 - Funding Information: The study was conducted within the framework of State Assignments of the Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences and the Vinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences, with the support of the Russian Foundation for Basic Research, project no. 19-05-00394. Publisher Copyright: © 2021, Pleiades Publishing, Ltd.

PY - 2021/12

Y1 - 2021/12

N2 - Significant variations in the composition of garnets, both within individual grains and in the rock, are found in the xenolith of deformed garnet lherzolite from the Udachnaya kimberlite pipe. The central parts of the grains, corresponding in composition to the garnets of the lherzolite paragenesis, demonstrate a sinusoidal distribution of rare earth elements (REEs). At the same time, the edge portions have a distribution characteristic of garnet mega-crystals from kimberlites. Despite being depleted in Y and HREE, the cores are enriched in light rare earth elements, Nb, Ta, Th, and U relative to garnet from primitive garnet peridotite. In terms of the REE distribution, the model melts, which are in equilibrium with the edge parts of garnet, are close to kimberlite but are significantly enriched in comparison with kimberlite in Nb, Ta, and Hf and depleted in Sr. Melts in equilibrium with the central parts of garnet are characterized by a steeper negative slope in the region of heavy and medium REEs and approach kimberlite in the region of light REEs. Based on the data obtained, several stages in the evolution of deformed garnet lherzolite are distinguished. The first stage involves the interaction of depleted peridotite with a melt similar in composition to carbonatite melts. This stage is associated with the formation of garnet with a sinusoidal REE distribution. At the next stage, which was preceded by the dissolution of garnet grains, garnet rims with increased Ti, Zr, and Y contents were formed and clinopyroxene appeared. At the final stage, garnet melted, caused by the inflow of a water–carbon dioxide fluid with a high potassium content, leading to polymineral inclusions and kelyphite rims.

AB - Significant variations in the composition of garnets, both within individual grains and in the rock, are found in the xenolith of deformed garnet lherzolite from the Udachnaya kimberlite pipe. The central parts of the grains, corresponding in composition to the garnets of the lherzolite paragenesis, demonstrate a sinusoidal distribution of rare earth elements (REEs). At the same time, the edge portions have a distribution characteristic of garnet mega-crystals from kimberlites. Despite being depleted in Y and HREE, the cores are enriched in light rare earth elements, Nb, Ta, Th, and U relative to garnet from primitive garnet peridotite. In terms of the REE distribution, the model melts, which are in equilibrium with the edge parts of garnet, are close to kimberlite but are significantly enriched in comparison with kimberlite in Nb, Ta, and Hf and depleted in Sr. Melts in equilibrium with the central parts of garnet are characterized by a steeper negative slope in the region of heavy and medium REEs and approach kimberlite in the region of light REEs. Based on the data obtained, several stages in the evolution of deformed garnet lherzolite are distinguished. The first stage involves the interaction of depleted peridotite with a melt similar in composition to carbonatite melts. This stage is associated with the formation of garnet with a sinusoidal REE distribution. At the next stage, which was preceded by the dissolution of garnet grains, garnet rims with increased Ti, Zr, and Y contents were formed and clinopyroxene appeared. At the final stage, garnet melted, caused by the inflow of a water–carbon dioxide fluid with a high potassium content, leading to polymineral inclusions and kelyphite rims.

KW - mantle metasomatism

KW - peridotite

KW - upper mantle

UR - http://www.scopus.com/inward/record.url?scp=85122092725&partnerID=8YFLogxK

UR - https://www.elibrary.ru/item.asp?id=47551960

UR - https://www.mendeley.com/catalogue/4e64e741-afc8-3366-b529-071bef9ce8c1/

U2 - 10.1134/S1028334X21120102

DO - 10.1134/S1028334X21120102

M3 - Article

AN - SCOPUS:85122092725

VL - 501

SP - 1029

EP - 1037

JO - Doklady Earth Sciences

JF - Doklady Earth Sciences

SN - 1028-334X

IS - 2

M1 - 6

ER -