TY - JOUR

T1 - CO2-bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

AU - Mikhno, Anastasia O.

AU - Musiyachenko, Kira A.

AU - Shchepetova, Olga V.

AU - Korsakov, Andrey V.

AU - Rashchenko, Sergey V.

N1 - Publisher Copyright: Copyright © 2017 John Wiley & Sons, Ltd.

PY - 2017/11/1

Y1 - 2017/11/1

N2 - CO2-bearing fluid inclusions coexisting with diamonds were identified in zircons from diamondiferous gneiss in the Kokchetav Massif. This discovery provides evidence for the presence of CO2 in UHP fluids and diamond formation in moderately oxidized conditions in the Kokchetav gneiss. Fluid and multiphase solid inclusions coexisting in zircons represent immiscible melt and fluid captured close to the peak metamorphic conditions for the Kokchetav UHP gneiss. Most of CO2-bearing inclusions are CO2+H2O mixtures except for some cases when they also contain daughter phases (e.g. muscovite, calcite and quartz) tracing the presence of aqueous and solute-rich fluids at different phases of UHP metamorphism. Decrease of pressure and temperature may have been responsible for the reduction of solutes in the CO2-bearing fluid. The lack of CO2-bearing inclusions in garnet porphyroblasts from diamond-bearing gneiss, as well as the common coexistence of aqueous CO2-bearing inclusions with calcite, testify that most likely all CO2 in fluid was consumed by the calcite-forming reaction and hydrous melt was the only remaining growth medium during retrograde metamorphism of the Kokchetav UHPM gneisses. Neither K-cymrite nor kokchetavite was identified among daughter phases in the hydrous melt inclusions in garnet, which indicates that they hardly could originate in a metapelitic system.

AB - CO2-bearing fluid inclusions coexisting with diamonds were identified in zircons from diamondiferous gneiss in the Kokchetav Massif. This discovery provides evidence for the presence of CO2 in UHP fluids and diamond formation in moderately oxidized conditions in the Kokchetav gneiss. Fluid and multiphase solid inclusions coexisting in zircons represent immiscible melt and fluid captured close to the peak metamorphic conditions for the Kokchetav UHP gneiss. Most of CO2-bearing inclusions are CO2+H2O mixtures except for some cases when they also contain daughter phases (e.g. muscovite, calcite and quartz) tracing the presence of aqueous and solute-rich fluids at different phases of UHP metamorphism. Decrease of pressure and temperature may have been responsible for the reduction of solutes in the CO2-bearing fluid. The lack of CO2-bearing inclusions in garnet porphyroblasts from diamond-bearing gneiss, as well as the common coexistence of aqueous CO2-bearing inclusions with calcite, testify that most likely all CO2 in fluid was consumed by the calcite-forming reaction and hydrous melt was the only remaining growth medium during retrograde metamorphism of the Kokchetav UHPM gneisses. Neither K-cymrite nor kokchetavite was identified among daughter phases in the hydrous melt inclusions in garnet, which indicates that they hardly could originate in a metapelitic system.

KW - CO-bearing fluid

KW - diamond

KW - Kokchetav

KW - Raman spectroscopy

KW - UHP metamorphism

KW - BOHEMIAN MASSIF

KW - EXPERIMENTAL CONSTRAINTS

KW - RAMAN-SPECTROSCOPY

KW - NORTHERN-KAZAKSTAN

KW - METAMORPHIC ROCKS

KW - SUBDUCTED CONTINENTAL-CRUST

KW - ULTRAHIGH-PRESSURE GNEISS

KW - MELT INCLUSIONS

KW - K-CYMRITE

KW - POTASSIUM-FELDSPAR

KW - CO2-bearing fluid

UR - http://www.scopus.com/inward/record.url?scp=85018381310&partnerID=8YFLogxK

U2 - 10.1002/jrs.5139

DO - 10.1002/jrs.5139

M3 - Article

AN - SCOPUS:85018381310

VL - 48

SP - 1566

EP - 1573

JO - Journal of Raman Spectroscopy

JF - Journal of Raman Spectroscopy

SN - 0377-0486

IS - 11

ER -