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| Titel |
High-pressure behaviour of Cr-Fe-Mg-Al spinels: applications to diamond geobarometry |
| VerfasserIn |
Benedetta Periotto, Enrico Bruschini, Fabrizio Nestola, Davide Lenaz, Francesco Princivalle, Giovanni B. Andreozzi, Ferdinando Bosi |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090112
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| Publikation (Nr.) |
 EGU/EGU2014-4328.pdf |
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| Zusammenfassung |
| Spinels belonging to the chromite – magnesiochromite – hercynite (FeCr2O4-MgCr2O4-FeAl2O4) system are among the most common inclusions found in diamonds (Stachel and Harris 2008). In particular, although FeCr2O4 and MgCr2O4 components sum to between 85 and 88% of spinels found in diamonds, hercynite FeAl2O4 plays a not negligible role in determining their thermo-elastic properties with concentrations reaching 7-9 % (other minor end-members like MgAl2O4, MgFe2O4 and Fe2O3 rarely reach 2-3% in total, see Lenaz et al. 2009). Recent studies were focused on the determination of the diamond formation pressure by the so-called “elastic method” (see for example Nestola et al. 2011 and references therein). It was demonstrated that accurate and precise thermo-elastic parameters are fundamental to minimize the uncertainty of formation pressure.
In this work we have determined the equations of state at room temperature of three synthetic spinel end-members chromite – magnesiochromite – hercynite and one natural spinel crystal extracted from a diamond (from Udachnaya mine, Siberia, Russia) by single-crystal X-ray diffraction in situ at high-pressure. A diamond-anvil cell was mounted on a STADI IV diffractometer equipped with a point detector and motorized by SINGLE software (Angel and Finger 2011). The natural crystal was investigated to test (and possibly validate) the “empirical prediction model”, capable to provide bulk modulus and its first pressure derivative only knowing the composition of the spinels found in diamonds. Such prediction model could be used to obtain pressure of formation for the diamond-spinel pair through the elastic method. Details and results will be discussed.
The research was funded by the ERC Starting Grant to FN (grant agreement n° 307322).
References
Angel R.J., Finger L.W. (2011) SINGLE A program to control single-crystal diffractometers. Journal of Applied Crystallography, 44, 247-251.
Lenaz D., Logvinova A.M., Princivalle F., Sobolev N. (2009) Structural parameters of chromite included in diamond and kimberlites from Siberia: a new tool for discriminating source. American Mineralogist, 94, 1067-1070.
Nestola F., Nimis P., Ziberna L., Longo M., Marzoli A., Harris J.W., Manghnani M.H., Fedortchouk Y. (2011) First crystal-structure determination of olivine in diamond: composition and implications for provenance in the Earth’s mantle. Earth and Planetary Science Letters, 305, 249-255.
Stachel, T., and Harris, J.W. (2008) The origin of cratonic diamonds – constraints from mineral inclusions. Ore Geology Reviews, 34, 5–32. |
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