| Инд. авторы: | Bascou J., Doucet L.S., Saumet S., Ionov D.A., Ashchepkov I.V., Golovin A.V. |
| Заглавие: | Seismic velocities, anisotropy and deformation in Siberian cratonic mantle: EBSD data on xenoliths from the Udachnaya kimberlite |
| Библ. ссылка: | Bascou J., Doucet L.S., Saumet S., Ionov D.A., Ashchepkov I.V., Golovin A.V. Seismic velocities, anisotropy and deformation in Siberian cratonic mantle: EBSD data on xenoliths from the Udachnaya kimberlite // Earth and Planetary Science Letters. - 2011. - Vol.304. - Iss. 1-2. - P.71-84. - ISSN 0012-821X. - EISSN 1385-013X. |
| Внешние системы: | DOI: 10.1016/j.epsl.2011.01.016; SCOPUS: 2-s2.0-79952624458; |
| Реферат: | eng: The study presents microstructures and crystallographic preferred orientations (CPO) of minerals obtained by electron back-scattered diffraction (EBSD) in a suite of 23 fresh mantle xenoliths (20 peridotites, 2 eclogites and 1 pyroxenite) from the Udachnaya kimberlite in central Siberian craton. The suite includes coarse spinel- and garnet-facies peridotites equilibrated at 760-1000°C from the upper part of the mantle lithosphere (45-160km) and porphyroclastic garnet peridotites from the base of the lithosphere (160-210km; 1200-1320°C). The data indicate that dislocation creep is the main deformation mechanism in the peridotites and eclogites. The CPO patterns of olivine suggest a dominant activation of the (010) [100] slip system. Within this general pattern, coarse peridotites show a better alignment of [100]-olivine while porphyroclastic rocks have a better alignment of [010]-olivine. Recrystallization in the porphyroclastic peridotites reduces olivine grain size and facilitates the development of a mosaic matrix that leads to a decrease in the CPO strength. Orthopyroxene in peridotites slips parallel to (100) [001]; clinopyroxene shows a clear slip direction on [001] in both peridotites and eclogites. Seismic properties estimated from the CPO data and modal abundances of major minerals show significant differences between peridotites, eclogites and pyroxenites; some differences also exist between peridotite types. Importantly, coarse peridotites have much higher anisotropy than eclogites and may yield higher P-wave velocities in the fast direction (Vp≥8.8km/s). Thus, the extremely high sub-Moho velocities (Vp>8.7km/s) reported from some seismic profiles in the Siberian craton can be better explained by strong anisotropy of coarse peridotites in a horizontally foliated mantle rather than by the presence of abundant eclogites. © 2010 Elsevier B.V.
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| Ключевые слова: | Cratonic mantle; Crystal preferred orientation; Deformation; Microstructure; Clinopyroxenes; Cratonic mantle; Crystal preferred orientation; Crystallographic preferred orientations; Deformation mechanism; Dislocation creep; Eclogites; Electron back-scattered diffraction; Garnet peridotite; General patterns; Grain size; Mantle lithosphere; Mantle xenoliths; matrix; Orthopyroxene; P-wave velocity; Recrystallizations; Seismic profiles; Seismic properties; Seismic velocities; Siberian Craton; Russian Federation; xenolith; seismic velocity; preferred orientation; peridotite; microstructure; mantle; kimberlite; eclogite; deformation mechanism; craton; anisotropy; Crystal orientation; X ray powder diffraction; Single crystals; Silicate minerals; Seismology; Seismic waves; Olivine; Garnets; Dislocations (crystals); Crystallography; Crystal microstructure; Creep; Anisotropy; Alignment; Strong anisotropy; Slip system; Anisotropy; Slip direction; |
| Издано: | 2011 |
| Физ. характеристика: | с.71-84 |