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| Titel |
Ultrabasic-basic change over primary inclusions in lower-mantle diamonds:
Mineralogical and experimental evidence for crucial role of stishovite
paradox |
| VerfasserIn |
Yuriy Litvin, Anna Spivak |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141289
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| Publikation (Nr.) |
 EGU/EGU2017-4785.pdf |
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| Zusammenfassung |
| Melting relations of the lower-mantle magmatic system MgO – FeO – CaO - SiO2 are
characterized by peritectic reaction of bridgmanite (Mg,Fe)SiO3 and melt with formation of
Fe-rich phases of periclase-wustite solid solutions (MgO•FeO)ss and stishovite SiO2.
The reaction proceeds also in melts-solutions of lower-mantle diamond-parental
system MgO – FeO – CaO - SiO2 – (Mg-Fe-Ca-Na-carbonate) – C. Xenoliths of
lower mantle rocks were never found among the deep mantle derived materials.
Estimation of lower-mantle mineralogy as ferropericlase+ bridgmanite+ Ca-perovskite
association is inferred from high-pressure subsolidus experiments with ultrabasic pyrolite
composition (Akaogi, 2007). The paradoxical in situ paragenesis of stishovite and
ferropericlase as primary inclusions in lower-mantle diamonds (Kaminsky, 2012) takes its
explanation from the bridgmanite peritectic reaction (effect of “stishovite paradox”)
(Litvin et al., 2014). Based on the data for inclusions, physico-chemical study on
syngenesis of diamonds and primary inclusions has experimentally revealed the
ferropericlase-bridgmanite-Ca-perovskite-stishovite-magnesiowustite-(Mg-Fe-Ca-Na-carbonate)-carbon
compositions of the lower-mantle diamond-forming system .(Litvin et al., 2016). The
generalized diagram of diamong-forming media characterizes the variable compositions of
growths melts for diamonds and paragenetic phases and their genetic relationships with lower
mantle matter, and it is the reason for genetic classifying primary inclusions. Fractional
ultrabasic-basic evolution and continuous paragenetic transition from ultrabasic
bridgmanite-ferropericlase to basic stishovite-magnesiowustite assemblages in the of
lower-mantle diamond-parental melts-solutions are providing by the physico-chemical
mechanism of stishovite paradox.
References
Akaogi M. (2007). Phase transformations of minerals in the transition zone and upper part
of the lower mantle. In Advances in High-Pressure Mineralogy (Ohtani E., ed.). Geol. Soc.
Am. Spec. Paper 421, 1-13.
Kaminsky F.V. (2012). Mineralogy of the lower mantle: a review of “supper-deep”
mineral inclusions in diamonds. Earth Sci. Rev. 110, 127-147.
Litvin Yu.A., Spivak A.V., Solopova N.A., Dubrovinsky L.S. (2014). On origin of
lower-mantle diamonds and their primary inclusions. Phys. Earth Planet. Inter. 228,
176-185.
Litvin Yu.A., Spivak A.V., Dubrovinsky L.S. (2016). Magmatic evolution of the
material of the Earth’s lower mantle: stishovite paradox and origin of superdeep
diamonds (experiments at 24-26 GPa). Geochemistry Internat. 54(11, 936-947.) |
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