Academic Journal
Origin of felsic granulite microstructure by heterogeneous decomposition of alkali feldspar and extreme weakening of orogenic lower crust during the Variscan orogeny
| العنوان: | Origin of felsic granulite microstructure by heterogeneous decomposition of alkali feldspar and extreme weakening of orogenic lower crust during the Variscan orogeny |
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| المؤلفون: | Franek, J., Schulmann, Karel, Lexa, O., Ulrich, Stanislav, Štípska, P., Haloda, J., Tycova, P. |
| المساهمون: | Czech Geological Survey Praha, Dynamique de la lithosphère et des bassins sédimentaires (IPGS) (IPGS-Dylbas), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Petrology and Structural geology, Charles University Prague (CU), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Geophysics of the Czech Academy of Sciences (IG / CAS), Czech Academy of Sciences Prague (CAS), ANR-06-BLAN-0352,LFO in orogens,Laterally-forced overturns (LFO) enhanced by melt induced softening (MIS) in orogens: new model for continental tectonics(2006) |
| المصدر: | Hyper Article en Ligne - Sciences de l'Homme et de la Société ; ISSN: 0263-4929 ; EISSN: 1525-1314 ; Journal of Metamorphic Geology ; Journal of Metamorphic Geology, Wiley-Blackwell, 2011, 29 (1), pp.103-130. ⟨10.1111/j.1525-1314.2010.00911.x⟩ |
| بيانات النشر: | HAL CCSD Wiley-Blackwell |
| سنة النشر: | 2011 |
| مصطلحات موضوعية: | Variscan belt, quartz and feldspar rheology, felsic granulites, Moldanubian domain, quantitative microstructural analysis, geo, art |
| الوصف: | International audience This study answers the question of origin and evolution of a granulitic microstructure typically developed in felsic granulites of the European Variscan belt. It shows that the precursor of the Variscan felsic granulites was a high-pressure alkali feldspar-rich coarse-grained layered orthogneiss. Its S1 subhorizontal layering is defined by the alignment of alkali feldspar porphyroclasts alternating with monomineralic bands of quartz and bands rich in plagioclase and garnet. The alkali feldspar porphyroclasts contain inclusions of quartz, garnet, kyanite, biotite and rutile, reflecting peak P-T conditions of 1.6-1.8 GPa and 850 degrees C during S1 formation. Superimposed steep folds and steep cleavage, S2, are associated with recrystallization of alkali feldspar, plagioclase and quartz, and garnet chemistry modifications that correspond to 0.9-1.0 GPa and 800 degrees C. During exhumation, involving 0.8 GPa decompression and cooling, the probably perthitic alkali feldspar underwent an unusual process of heterogeneous decomposition along irregular reaction fronts forming a fine-grained matrix composed of plagioclase and K-feldspar grains. Regular grain distributions in the matrix, nucleation-dominated crystal size distribution and preservation of lattice orientation of the parental perthite crystals are all explained by a discontinuous precipitation process. This heterogeneous decomposition of alkali feldspar solid solution is controlled by chemically and strain induced grain-boundary migration. During exhumation and decompression, the fine-grained matrix underwent viscous deformation, forming the typical microstructure of the Variscan granulites. Random phase distributions, minor coarsening and feldspar textures are interpreted as a result of strain softening due to diffusion creep-accommodated grain-boundary sliding. Subordinate large quartz ribbons were rheologically stronger than the feldspar-dominated matrix due to the activity of different deformational mechanisms. Finally, in ... |
| نوع الوثيقة: | article in journal/newspaper |
| اللغة: | English |
| Relation: | hal-00738028; 10670/1.n6td33; https://hal.archives-ouvertes.fr/hal-00738028 |
| DOI: | 10.1111/j.1525-1314.2010.00911.x |
| الاتاحة: | https://doi.org/10.1111/j.1525-1314.2010.00911.x https://hal.archives-ouvertes.fr/hal-00738028 |
| Rights: | undefined |
| رقم الانضمام: | edsbas.E33ED331 |
| قاعدة البيانات: | BASE |
| DOI: | 10.1111/j.1525-1314.2010.00911.x |
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