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Evolution des microstructures des serpentinites en contexte convergent: effet du degré de métamorphisme et de la déformation.

Abstract : This manuscript presents a petrological, spectroscopic, TEM, pluridisciplinary approach of the evolution of serpentine microstructures as a function of metamorphic grade and deformation in order to constraint their behavior in convergent context. Experimentally, the four main varieties of serpentine minerals are regularly compressing up to 10 GPa at ambient temperature. Pressure increase is mostly adjusted by reducing interfoliar space. No pressure-enhancement of hydrogen bonding is evidenciated in serpentine minerals. Cubean and alpine serpentinite analysis confirmed the high pressure stability of antigorite. Its microstructures vary with metamorphic grade. High grade antigorites do not display intracrystalline polysomatic disorder which characterize low grade antigorites. We propose that a second step in ordering microstructures is reached under eclogitic facies conditions by eliminating most of microstructural defects, but only in exceptionally well-preserved samples. Serpentinites are extremely sensitive to retrogressed deformation. In alpine serpentinites, low-grade deformation is characterized by brittle behavior at the crystal-scale. Under higher metamorphic grade, deformation seems to be accommodated by pressure solution processes, which are likely to persist up to eclogitic conditions. Planar defects observed in antigorite microstructures suggest that (001) gliding of sheets partly contributes to accommodate the deformation.
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  • HAL Id : tel-00825144, version 1

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Anne-Line Auzende. Evolution des microstructures des serpentinites en contexte convergent: effet du degré de métamorphisme et de la déformation.. Sciences de la Terre. Université Blaise Pascal - Clermont-Ferrand II, 2003. Français. ⟨tel-00825144⟩

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