TY - JOUR

T1 - Solidus and melting of carbonated phlogopite peridotite at 3–6.5 GPa: Implications for mantle metasomatism

AU - Shatskiy, Anton

AU - Bekhtenova, Altyna

AU - Arefiev, Anton V.

AU - Podborodnikov, Ivan V.

AU - Vinogradova, Yulia G.

AU - Rezvukhin, Dmitriy I.

AU - Litasov, Konstantin D.

N1 - Funding Information: This work is financially supported by Russian Science Foundation (project No 21-17-00024). We are grateful to two anonymous reviewers for detailed reviews; N.V. Sobolev, L.N. Pokhilenko, E.I. Nikolenko, A.V. Golovin for discussion and useful suggestions; V.S. Shatsky and A.L. Ragozin for providing natural lherzolite and discussion. The SEM and EDS studies of experimental samples were performed in the Analytical Center for multi-elemental and isotope research SB RAS. We thank N.S. Karmanov and A.T. Titov for their assistance in the analytical works. Publisher Copyright: © 2021 International Association for Gondwana Research

PY - 2022/1

Y1 - 2022/1

N2 - It is well known that water significantly lowers mantle solidi. But it turns out this paradigm is not always true. Here, we studied the interaction of K-rich carbonate melts with the natural garnet lherzolite from the Udachnaya kimberlite (Russia) in the presence of water at 3.0–6.5 GPa, corresponding to depths of 100–200 km. We found that at ≤ 1100 °C, the metasomatic interaction consumes garnet, orthopyroxene, and melt to produce phlogopite ± K-richterite + magnesite ± dolomite. Besides, primary clinopyroxene is replaced by one with a lower amount of jadeite component. Thus, the addition of water to the K-rich carbonate melt, infiltrating the subcontinental lithospheric mantle, should yield its partial or complete disappearance accompanied by phlogopitization and carbonation. The studied systems have H2O/K2O = 2, like that in phlogopite, and therefore correspond to carbonated phlogopite peridotite under fluid-absent conditions. At 4.0–6.5 GPa, the solidus of carbonated phlogopite peridotite is controlled by the following reaction: phlogopite + clinopyroxene + magnesite = garnet + orthopyroxene + olivine + hydrous K-carbonatite melt, which is bracketed between 1100 and 1200 °C. At 3 GPa, the solidus temperature decreases to about 1050 °C presumably owing to the Ca-Mg exchange reaction, clinopyroxene + magnesite = orthopyroxene + dolomite, which stabilizes dolomite reacting with phlogopite at a lower temperature than magnesite. Our results suggest that the phlogopite- and carbonate-rich metasomatic vein networks, weakening rigid lithosphere and promoting continental rifting, could be formed as a result of infiltration of hydrous K-carbonatite melt at the base of subcontinental lithospheric mantle. Stretching and thinning of the cratonic lithosphere make geotherms warmer and shifts their intersections with the solidus of carbonated phlogopite peridotite to shallower depths. Consequently, the successive erosion of the continental lithosphere and ascent of the lithosphere-asthenosphere boundary during continental rifting should be accompanied by remelting of phlogopite-carbonate metasomes, upward percolation of K-rich melt, and its solidification at the front of the magmatic-metasomatic mantle system.

AB - It is well known that water significantly lowers mantle solidi. But it turns out this paradigm is not always true. Here, we studied the interaction of K-rich carbonate melts with the natural garnet lherzolite from the Udachnaya kimberlite (Russia) in the presence of water at 3.0–6.5 GPa, corresponding to depths of 100–200 km. We found that at ≤ 1100 °C, the metasomatic interaction consumes garnet, orthopyroxene, and melt to produce phlogopite ± K-richterite + magnesite ± dolomite. Besides, primary clinopyroxene is replaced by one with a lower amount of jadeite component. Thus, the addition of water to the K-rich carbonate melt, infiltrating the subcontinental lithospheric mantle, should yield its partial or complete disappearance accompanied by phlogopitization and carbonation. The studied systems have H2O/K2O = 2, like that in phlogopite, and therefore correspond to carbonated phlogopite peridotite under fluid-absent conditions. At 4.0–6.5 GPa, the solidus of carbonated phlogopite peridotite is controlled by the following reaction: phlogopite + clinopyroxene + magnesite = garnet + orthopyroxene + olivine + hydrous K-carbonatite melt, which is bracketed between 1100 and 1200 °C. At 3 GPa, the solidus temperature decreases to about 1050 °C presumably owing to the Ca-Mg exchange reaction, clinopyroxene + magnesite = orthopyroxene + dolomite, which stabilizes dolomite reacting with phlogopite at a lower temperature than magnesite. Our results suggest that the phlogopite- and carbonate-rich metasomatic vein networks, weakening rigid lithosphere and promoting continental rifting, could be formed as a result of infiltration of hydrous K-carbonatite melt at the base of subcontinental lithospheric mantle. Stretching and thinning of the cratonic lithosphere make geotherms warmer and shifts their intersections with the solidus of carbonated phlogopite peridotite to shallower depths. Consequently, the successive erosion of the continental lithosphere and ascent of the lithosphere-asthenosphere boundary during continental rifting should be accompanied by remelting of phlogopite-carbonate metasomes, upward percolation of K-rich melt, and its solidification at the front of the magmatic-metasomatic mantle system.

KW - Earth's mantle

KW - High-pressure experiment

KW - K-richterite

KW - Magnesite

KW - Mantle metasomatism

KW - Mantle partial melting

KW - Peridotite-CO-HO

KW - Phlogopite

KW - Solidus carbonated phlogopite peridotite

UR - http://www.scopus.com/inward/record.url?scp=85113332883&partnerID=8YFLogxK

U2 - 10.1016/j.gr.2021.07.023

DO - 10.1016/j.gr.2021.07.023

M3 - Article

AN - SCOPUS:85113332883

VL - 101

SP - 156

EP - 174

JO - Gondwana Research

JF - Gondwana Research

SN - 1342-937X

ER -