Рубрики:
EARTHS LOWER MANTLE
FERRIC IRON CONTENT
DIAMOND FORMATION
MINERAL INCLUSIONS
NATURAL DIAMOND
OXIDATION-STATE
DEEP MANTLECRUST
LITHOSPHERIC MANTLE
OXYGEN FUGACITY
OCEANIC-CRUST
Кл.слова (ненормированные):
Wustite -- CO2-fluid -- Carbonate-silicate melt -- Decarbonation -- Graphite formation -- HPHT experiment
EARTHS LOWER MANTLE
FERRIC IRON CONTENT
DIAMOND FORMATION
MINERAL INCLUSIONS
NATURAL DIAMOND
OXIDATION-STATE
DEEP MANTLECRUST
LITHOSPHERIC MANTLE
OXYGEN FUGACITY
OCEANIC-CRUST
Кл.слова (ненормированные):
Wustite -- CO2-fluid -- Carbonate-silicate melt -- Decarbonation -- Graphite formation -- HPHT experiment
Аннотация: Experimental simulation of the interaction of wüstite with a CO2-rich fluid and a carbonate-silicate melt was performed using a multianvil high-pressure split-sphere apparatus in the FeO-MgO-CaO-SiO2-Al2O3-CO2 system at a pressure of 6.3GPa and temperatures in the range of 1150°C-1650°C and with run time of 20h. At relatively low temperatures, decarbonation reactions occur in the system to form iron-rich garnet (Alm75Prp17Grs8), magnesiowüstite (Mg#≤0.13), and CO2-rich fluid. Under these conditions, magnesiowüstite was found to be capable of partial reducing CO2 to C0 that leads to the formation of Fe3+-bearing magnesiowüstite, crystallization of magnetite and metastable graphite, and initial growth of diamond seeds. At T≥1450°C, an iron-rich carbonate-silicate melt (FeO~56wt.%, SiO2~12wt.%) forms in the system. Interaction between (Fe,Mg)O, SiO2, fluid and melt leads to oxidation of magnesiowüstite and crystallization of fayalite-magnetite spinel solid solution (1450°C) as well as to complete dissolution of magnesiowüstite in the carbonate-silicate melt (1550°C-1650°C). In the presence of both carbonate-silicate melt and CO2-rich fluid, dissolution (oxidation) of diamond and metastable graphite was found to occur. The study results demonstrate that under pressures of the lithospheric mantle in the presence of a CO2-rich fluid, wüstite/magnesiowüstite is stable only at relatively low temperatures when it is in the absolute excess relative to CO2-rich fluid. In this case, the redox reactions, which produce metastable graphite and diamond with concomitant partial oxidation of wüstite to magnetite, occur. Wüstite is unstable under high concentrations of a CO2-rich fluid as well as in the presence of a carbonate-silicate melt: it is either completely oxidized or dissolves in the melt or fluid phase, leading to the formation of Fe2+- and Fe3+-enriched carbonate-silicate melts, which are potential metasomatic agents in the lithospheric mantle. © 2015 Elsevier B.V.
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Держатели документа:
Sobolev Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences, Koptyug ave 3, Novosibirsk, Russian Federation
Novosibirsk State University, Pirogova str 2, Novosibirsk, Russian Federation
Kirensky Institute of Physics, Siberian Branch of Russian Academy of Sciences, Akademgorodok 50, bld. 38, Krasnoyarsk, Russian Federation
Доп.точки доступа:
Bataleva, Yu. V.; Palyanov, Y .N.; Sokol, A. G.; Borzdov, Y. M.; Bayukov, O. A.; Баюков, Олег Артемьевич