Geochemical Evidence for Participation of the Subducted Crust in the Process of Transformation of the Subcontinental Man
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Geochemical Evidence for Participation of the Subducted Crust in the Process of Transformation of the Subcontinental Mantle in the Yakutian Diamondiferous Province Academician V. S. Shatskya,b,c,*, A. L. Ragozina,b, O. A. Kozmenkoa, and A. A. Denisenkob Received April 16, 2020; revised May 4, 2020; accepted May 6, 2020
Abstract—The data available indicate the complex evolution of deformed peridotites of mantle xenoliths, the P–T parameters of which indicate that they are fragments of the metasomatized lower part of the cratonic lithosphere. The zoning established in garnets from xenoliths in kimberlite pipes is interpreted as a result of metasomatism that occurred shortly before xenoliths reached the surface. Metasomatic alterations in xenoliths of deformed harzburgites were manifested not only in the development of zoning of minerals. The study results show that there is a discrepancy between the data calculated based on the contents of incompatible elements in minerals of xenoliths and those obtained due to direct measurements of the bulk composition of xenoliths. To determine the balance of incompatible elements, we have carried out experiments on leaching xenoliths of deformed lherzolites from the Udachnaya kimberlite pipe. It was established that a significant part of LREEs in the studied xenoliths occurs in the intergranular space. The distribution pattern of incompatible elements and, in particular, the presence of a positive Eu anomaly indicate that the appearance of the intergranular component is not associated with contamination of xenoliths by the kimberlite melt. Quite a few xenoliths demonstrate a positive Eu anomaly, which indicates the influence of the subducted crustal component at one of the modification stages of xenoliths. Keywords: upper mantle, crust, subduction, peridotite DOI: 10.1134/S1028334X2007017X
It is generally agreed that deformed mantle peridotite xenoliths are fragments of the metasomatically altered lower part of the cratonic lithosphere [1, 2]. The recognized zoning of garnets from deformed lherzolite xenoliths in kimberlite pipes is interpreted as a consequence of metasomatic processes that occurred shortly before xenoliths reached the surface [3–5]. Agashev et al. [6] concluded that deformed peridotite xenoliths from the Udachnaya kimberlite pipe underwent complex evolution during three stages of metasomatic alterations. According to [6], garnets with a sinusoidal REE distribution pattern were formed at the first stage of metasomatism due to the interaction of harzburgites with the fluid/carbonatite melt. The formation of clinopyroxene and high-Fe garnet with a REE distribution similar to that in garnet aSobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia bNovosibirsk State University, Novosibirsk, 630090 Russia cVinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia *e-mail: [email protected]
xenocrysts from kimberlites is associated with the stage o
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