Mantle xenoliths from Komsomolskaya kimberlite pipe, Yakutia

Autor(en): Igor V. Ashchepkov, Theodoros Ntaflos, Nikolai S. Medvedev, Nikolai V. Vladykin, Alla M. Logvinova, Denis S. Yudin, Hilary Downes, Igor V. Makovchuk, Ravil F. Salikhov
Abstrakt: Minerals from > 200 mantle xenoliths from Komsomolskaya kimberlite pipe were studied by electron microprobe and LA-ICP-MS. They are metasomatised garnet and spinel peridotites containing phlogopite, amphibole and ilmenite with garnets (up to 12.5 wt% Cr₂O₃) and clinopyroxenes (up to 5 wt% Na₂O) or rarer Fe-pyroxenites and A, B, C eclogites. Thermobarometry indicates that the lithospheric mantle beneath the Komsomolskaya pipe is layered. Heated porphyroclastic, deformed peridotites at the lithosphere base (7–6 GPa) are enriched in Fe. The cold group at 6.0–5.5 GPa (34 mW/m²) are depleted peridotites with sub-Ca garnets. Cpx-fertilized varieties belong to the middle part of the mantle section. Amphiboles range from Cr-hornblendes to edenites (2–6 GPa), showing K-Ti enrichment. Picroilmenites yield two pressure intervals from 6.5 to 5.0 GPa and from 5.0 to 4.0 GPa, forming two differentiation branches. Eclogites mainly occur in the lower part of the section with a peak at pressures of 4–6 GPa. Trace elements of melts that formed harzburgitic garnets-pyroxenes refer to oceanic MORB like melt interaction with peridotites. The sub-calcic S-type garnets are similar to subduction-related melts (S-type REE) with troughs in HFSE. Adakite-like hybrid metasomatism formed Na, Al-rich pyroxenes with peaks in Sr and HFSE. K-bearing pyroxenes and amphiboles refer to shoshonitic metasomatism. Trace elements for Cpx of re-fertilized mantle peridotites reveal high LREE, Nb-Ta troughs and peaks in Zr, Th, Sr, U. They are reacted to carbonatite –alkaline melts. Protokimberlite (essentially carbonatitic) interaction produced HFSE-enrichment. Type B eclogites show more subduction-related features with HFSE troughs while type A eclogites are closer to hybrid and peridotitic signatures. We suggest six types of major metasomatic agents. The ⁴⁰Ar/³⁹Ar ages of phlogopites vary in the 440–690 Ma range, with some at 1.6 Ga, suggesting multistage metasomatism.
Organisation(en): Department für Lithosphärenforschung
Externe Organisation(en): Russian Academy of Sciences, Siberian Branch of the Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry SB RAS, University of London, Alrosa Stock Company
Journal: Geosystems and Geoenvironment
Band: 3
DOI: https://doi.org/10.1016/j.geogeo.2024.100272
Publikationsdatum: 08-2024
Peer-reviewed: Ja
ÖFOS 2012: 105105 Geochemie, 105120 Petrologie
Schlagwörter
ASJC Scopus Sachgebiete: Environmental Science (miscellaneous), Earth and Planetary Sciences (miscellaneous)
Link zum Portal: https://ucrisportal.univie.ac.at/de/publications/5180cd8b-510e-4ce4-86ba-81a9e9c8f062

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