Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Unique Amphibole Bearing Mantle Column Beneath the Leningrad Kimberlite Pipe, West Ukukit Field, NE Yakutia

Version 1 : Received: 26 December 2021 / Approved: 28 December 2021 / Online: 28 December 2021 (10:55:15 CET)

How to cite: Ashchepkov, I.V.; Babushkina, S.A.; Mevedev, N.S.; Oleinikov, O.B. Unique Amphibole Bearing Mantle Column Beneath the Leningrad Kimberlite Pipe, West Ukukit Field, NE Yakutia. Preprints 2021, 2021120444 (doi: 10.20944/preprints202112.0444.v1). Ashchepkov, I.V.; Babushkina, S.A.; Mevedev, N.S.; Oleinikov, O.B. Unique Amphibole Bearing Mantle Column Beneath the Leningrad Kimberlite Pipe, West Ukukit Field, NE Yakutia. Preprints 2021, 2021120444 (doi: 10.20944/preprints202112.0444.v1).

Abstract

In the subcratonic mantle beneath Leningrad pipe, West Ukukit field, Yakutia garnet thermoba-rometry give division to 7 horizons (paleosubduction slabs). Cr-bearing amphiboles >500 reveal a broad range changing from Cr- pargasitic hornblendes to pargasites, edinites, kataforites, К-richterites with increasing pressure determined with new amphibole thermobarometer. Cr-hornblendes compiles the high-temperature branch from 3.5 GPa to Moho for basaltic melt. Amphiboles in the middle eddinites and high-pressure interval reveal different PT ranges from 35 to 40 mw/m2. Richterites near the lithosphere base both trace low –T and convective branches. The amphiboles reveal the 9 geochemical groups. The low-temperature varieties reveal Eu minima and U, Ba, Sr peaks high LILE, Sr, Rb and troughs in Nb, Pb. While high –T varieties have no Eu dips and reveal higher HFSE. Clinopyroxenes and garnets show variable trace ele-ment patterns and divisions in groups eth the plume and subduction signs. The contrasting be-haviour of Ta and Nb is regulated by the rutile partition coefficients likely for primary eclogites. Subduction and Na and K (siliceous) types of fluids percolated through the mantle with abun-dant eclogites causing amphibolization at the different levels of the mantle column. The plume melts produced hybridism and more smooth trace element patterns in reacted minerals, clino-pyroxene. monomineral thermobarometry.

Keywords

kimberlite; garnet; amphibole; monomineral thermobarometry; trace elements; lithospheric mantle

Subject

EARTH SCIENCES, Geochemistry & Petrology

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