TY - JOUR

T1 - Slab-derived melts interacting with peridotite: Toward the origin of diamond-forming melts

AU - Shatskiy, A.

AU - Bekhtenova, A.

AU - Arefiev, A. V.

AU - Podborodnikov, I. V.

AU - Litasov, K. D.

N1 - Funding Information: This work is financially supported by Russian Science Foundation (project No 21-77-10057). We are grateful to A. Abersteiner and anonymous reviewer for constructive reviews; S. Tappe for the revision of an earlier version of the manuscript; V.S. Shatsky and A.L. Ragozin for providing natural peridotite 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. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Publisher Copyright: © 2022 Elsevier B.V.

PY - 2022/3

Y1 - 2022/3

N2 - It was recently shown that partial melting of carbonated metapelites, subducted to a depth of 200 km, yields the formation of two immiscible melts, CO2-bearing phonolitic and K-rich carbonate. These melts resemble silicic and low-Mg carbonatitic melt inclusions in diamonds from kimberlites and placers worldwide. Here we studied the interaction of these melts with natural garnet lherzolite at 6 GPa. We found that the CO2-bearing phonolite melt reacts with peridotite consuming olivine to produce orthopyroxene and garnet, while K2O and CO2 enter carbonate melt. The latter has Ca# 24–29 and appears in equilibrium with garnet lherzolite. The SiO2 content in the carbonate melt varies from 2 to 18 wt% as temperature increases from 1200 to 1500 °C. Our results imply that the slab-derived immiscible silicic and low-Mg carbonatitic melts react with peridotitic mantle producing the high-Mg carbonatitic melt, which makes up the majority of carbonatitic inclusions in diamonds. Thus, the melt entrapped by diamonds may decipher genetic signatures of different mantle lithologies: silicic and low-Mg carbonatitic inclusions correspond to eclogite or recycled pelite, while high-Mg carbonatitic inclusions correspond to peridotite.

AB - It was recently shown that partial melting of carbonated metapelites, subducted to a depth of 200 km, yields the formation of two immiscible melts, CO2-bearing phonolitic and K-rich carbonate. These melts resemble silicic and low-Mg carbonatitic melt inclusions in diamonds from kimberlites and placers worldwide. Here we studied the interaction of these melts with natural garnet lherzolite at 6 GPa. We found that the CO2-bearing phonolite melt reacts with peridotite consuming olivine to produce orthopyroxene and garnet, while K2O and CO2 enter carbonate melt. The latter has Ca# 24–29 and appears in equilibrium with garnet lherzolite. The SiO2 content in the carbonate melt varies from 2 to 18 wt% as temperature increases from 1200 to 1500 °C. Our results imply that the slab-derived immiscible silicic and low-Mg carbonatitic melts react with peridotitic mantle producing the high-Mg carbonatitic melt, which makes up the majority of carbonatitic inclusions in diamonds. Thus, the melt entrapped by diamonds may decipher genetic signatures of different mantle lithologies: silicic and low-Mg carbonatitic inclusions correspond to eclogite or recycled pelite, while high-Mg carbonatitic inclusions correspond to peridotite.

KW - Carbonate-silicate immiscibility

KW - Carbonatite

KW - Diamond forming melts

KW - HDF

KW - High-pressure experiment

UR - http://www.scopus.com/inward/record.url?scp=85124197146&partnerID=8YFLogxK

U2 - 10.1016/j.lithos.2022.106615

DO - 10.1016/j.lithos.2022.106615

M3 - Article

AN - SCOPUS:85124197146

VL - 412-413

JO - Lithos

JF - Lithos

SN - 0024-4937

M1 - 106615

ER -