TY - JOUR

T1 - Graphite and diamond formation in the carbide–oxide–carbonate interactions (Experimental modeling under mantle P,T-conditions)

AU - Bataleva, Yuliya

AU - Palyanov, Yuri

AU - Borzdov, Yuri

AU - Novoselov, Ivan

AU - Bayukov, Oleg

N1 - Publisher Copyright: © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2018/11/21

Y1 - 2018/11/21

N2 - Experimental modeling of the formation of graphite and diamond as a result of carbide–fluid interactions was performed in the Fe3C–SiO2–Al2O3–(Mg,Ca)CO3 systems at 6.3 and 7.5 GPa and 1100–1650◦C. In the experiments with ƒO2-gradient (7.5 GPa, 1250–1350◦C), graphite + magnesiowüstite + garnet ± cohenite assemblage was formed. Graphite was produced through the redox interactions of carbide with carbonate or CO2 (reducing conditions), and redox reactions of magnesiowüstite and CO2 (oxidizing conditions). At 1450–1650◦C, crystallization of graphite, garnet, magnesiowüstite and ferrospinel, as well as generation of Fe2+,3+-rich carbonate–silicate melt occurred. This melt, saturated with carbon, acted as a medium of graphite crystallization and diamond growth on seeds. In the experiments without ƒO2-gradient (6.3 GPa), decarbonation reactions with the formation of CO2-fluid and Fe,Mg,Ca-silicates, as well as C0-producing redox reactions of CO2-fluid with cohenite were simultaneously realized. As a result, graphite (± diamond growth) was formed in assemblage with Fe2+,Fe3+,Mg-silicates and magnetite (1100–1200◦C), or with Fe3+-rich garnet and orthopyroxene (1300–1500◦C). It has been established that a potential mechanism for the crystallization of graphite or diamond growth is the oxidation of cohenite by CO2-fluid to FeO and Fe3O4, accompanied by the extraction of carbon from Fe3C and the corresponding reduction of CO2 to C0 .

AB - Experimental modeling of the formation of graphite and diamond as a result of carbide–fluid interactions was performed in the Fe3C–SiO2–Al2O3–(Mg,Ca)CO3 systems at 6.3 and 7.5 GPa and 1100–1650◦C. In the experiments with ƒO2-gradient (7.5 GPa, 1250–1350◦C), graphite + magnesiowüstite + garnet ± cohenite assemblage was formed. Graphite was produced through the redox interactions of carbide with carbonate or CO2 (reducing conditions), and redox reactions of magnesiowüstite and CO2 (oxidizing conditions). At 1450–1650◦C, crystallization of graphite, garnet, magnesiowüstite and ferrospinel, as well as generation of Fe2+,3+-rich carbonate–silicate melt occurred. This melt, saturated with carbon, acted as a medium of graphite crystallization and diamond growth on seeds. In the experiments without ƒO2-gradient (6.3 GPa), decarbonation reactions with the formation of CO2-fluid and Fe,Mg,Ca-silicates, as well as C0-producing redox reactions of CO2-fluid with cohenite were simultaneously realized. As a result, graphite (± diamond growth) was formed in assemblage with Fe2+,Fe3+,Mg-silicates and magnetite (1100–1200◦C), or with Fe3+-rich garnet and orthopyroxene (1300–1500◦C). It has been established that a potential mechanism for the crystallization of graphite or diamond growth is the oxidation of cohenite by CO2-fluid to FeO and Fe3O4, accompanied by the extraction of carbon from Fe3C and the corresponding reduction of CO2 to C0 .

KW - Carbonate

KW - CO fluid

KW - Cohenite

KW - Diamond

KW - Experiment

KW - Garnet

KW - Graphite

KW - High pressure

KW - Lithospheric mantle

KW - Metasomatism

KW - lithospheric mantle

KW - INCLUSIONS

KW - IRON CARBIDE

KW - EARTHS MANTLE

KW - STABILITY

KW - garnet

KW - graphite

KW - experiment

KW - CRYSTAL-GROWTH

KW - carbonate

KW - metasomatism

KW - CRYSTALLIZATION

KW - OXIDATION

KW - HIGH-PRESSURE

KW - high pressure

KW - METALLIC IRON

KW - diamond

KW - cohenite

KW - CO2 fluid

KW - NITROGEN

UR - http://www.scopus.com/inward/record.url?scp=85057315914&partnerID=8YFLogxK

U2 - 10.3390/min8110522

DO - 10.3390/min8110522

M3 - Article

AN - SCOPUS:85057315914

VL - 8

JO - Minerals

JF - Minerals

SN - 2075-163X

IS - 11

M1 - 522

ER -