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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bataleva, Yu. V., Palyanov, Yu. N., Sokol A. G., Borzdov, Yu. M., Bayukov O. A.
Заглавие : The role of rocks saturated with metallic iron in the formation of ferric carbonate-silicate melts: experimental modeling under PT-conditions of lithospheric mantle
Коллективы : Siberian Branch of the Russian Academy of Sciences [31], Russian Foundation for Basic Research [12-05-00740]
Место публикации : Russ. Geol. Geophys.: Elsevier Science, 2015. - Vol. 56, Is. 1-2. - P.143-154. - ISSN 1068, DOI 10.1016/j.rgg.2015.01.008. - ISSN 1878030X(eISSN)
Примечания : Cited References:68. - This work was supported by Integration project 31 from the Siberian Branch of the Russian Academy of Sciences and by grant 12-05-00740 from the Russian Foundation for Basic Research.
Предметные рубрики: OXYGEN FUGACITY
DIAMOND FORMATION
OXIDATION-STATE
EARTHS MANTLE
Ключевые слова (''Своб.индексиров.''): carbonate-silicate melt--graphite--co2 fluid--iron carbide--garnet--redox gradient--high-pressure experiment
Аннотация: Experimental modeling of the processes of formation of ferric carbonate-silicate melts through the carbonate-oxide-metal interaction is performed in the (Mg,Ca)CO3-SiO2-Al2O3-Fe0 system at 6.3 and 7.5 GPa and within 1150-1650 °C, using a multianvil high-pressure apparatus of “split-sphere” type (BARS). Two parallel reactions run in the subsolidus region (1150-1450 °C): decarbonation, producing pyrope-almandine (Fe# = 0.40-0.75) and CO2 fluid, and redox interaction between carbonate and Fe0, resulting in the crystallization of iron carbide in assemblage with magnesiowustite (Fe# = 0.75-0.85). It is shown that the reduction of carbonate or CO2 fluid by iron carbide and parallel redox interaction of magnesiowustite with CO2 produce graphite in assemblage with Fe3 + -containing magnesiowustite. In the temperature range of 1450-1650 °C, generation of carbonate-silicate melts coexisting with pyrope-almandine, magnesiowustite, magnetite, ferrospinel, and graphite takes place. The composition of the produced melts is as follows: SiO2 - 10-15 wt.%, X(FeO + Fe2O3) = 36-43 wt.%, and Fe3+/XFe - 0.18-0.23. These Fe3 + -enriched carbonate-silicate melts/fluids are saturated with carbon and are the medium of graphite crystallization. Oxide and silicate phases (almandine, ferrospinel, and magnetite) coexisting with graphite are also characterized by high Fe3+/XFe values. It has been established that Fe3 + -enriched carbonate-silicate melts can result from the interaction of Fe0-containing rocks with carbonated rocks. In the reduced mantle (with the presence of iron carbides or oxides), melts of this composition can be the source of carbon and the medium of graphite crystallization at once. After separation and ascent, these ferric carbonate-silicate melts can favor oxidizing metasomatism in the lithospheric mantle.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bataleva Yu. V., Palyanov Y .N., Sokol A. G., Borzdov Y. M., Bayukov O. A.
Заглавие : Wüstite stability in the presence of a CO2-fluid and a carbonate-silicate melt: Implications for the graphite/diamond formation and generation of Fe-rich mantle metasomatic agents
Место публикации : Lithos: Elsevier, 2016. - Vol. 244. - P.20-29. - ISSN 00244937 (ISSN), DOI 10.1016/j.lithos.2015.12.001
Примечания : Cited References: 68. - This work was supported by the Russian Science Foundation under grant no. 14-27-00054. The authors thank A. Moskalev for his assistance in the work preparation, A. Khokhryakov for useful suggestions throughout the study, and S. Ovchinnikov for his assistance in implementation of Mössbauer spectroscopy measurements. The authors thank editor M. Scambelluri, and two anonymous reviewers for their useful comments, which helped to profoundly improve the manuscript.
Предметные рубрики: EARTHS LOWER MANTLE
FERRIC IRON CONTENT
DIAMOND FORMATION
MINERAL INCLUSIONS
NATURAL DIAMOND
OXIDATION-STATE
DEEP MANTLECRUST
LITHOSPHERIC MANTLE
OXYGEN FUGACITY
OCEANIC-CRUST
Ключевые слова (''Своб.индексиров.''): 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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