Water contents of mantle xenoliths from Sytykanskaya kimberlite pipe (Yakutian diamondiferous province, Russia)

Water plays a key role in evolution and dynamic of the Earth. It can change physical and chemical properties of mantle minerals, or the part of the mantle, for instance, the effect on mineral deformation and its impact on mantle rheology (Miller et al., 1987). Mantle xenoliths from kimberlites are one of direct source of information on the petrology and geochemistry of the deep mantle rocks.

Sytykanskaya pipe located in the central part of Yakutian diamondiferous province is characterized by a large amount of deep-seated xenoliths which contain relics of fresh minerals, e.g. clinopyroxenes, garnets, olivines, phlogopites, amphiboles, chromites, ilmenites and some other rare phases (Ashchepkov et al., 2015). Moreover it is known that there are several processes which can affect the mantle xenoliths, including metasomatism. Five peridotite xenoliths have been studied in order to indentify water enrichment. Using calibration coefficients (Bell et al., 2003) we calculated water content in the olivines. Water contents in olivine range from 12 to 92 ppm. In previous research (Kolesnichenko et al., 2017) we have studied peridotites from Udachnaya kimberlite pipe and found similar water content in olivines (2-95 ppm). So, the variably low water contents suggest a heterogeneous distribution of water beneath the mantle, which can be connected with metasomatism of essentially dry diamondiferous cratonic roots by hydrous and carbonatitic agents, and its related hydration and carbonation of peridotite accompanied by oxidation and dissolution of diamonds.

This work was supported by the Russian Science Foundation under Grant No 16-17-10067.

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