Bulletin du Service Géologique de l'Algérie
Volume 5, Numéro 2, Pages 151-165
1994-12-01
Préalpine And Alpine Metamorphisms And Kinematics In The Petite Kabylie Massif (eastern Algeria)
Auteurs : Mahdjoub Yamina .
Résumé
In Petite Kabylie Massif of eastern Algeria, two superposed high grade tcctono-mclamorphic(D1-Ml)cvcas have been recognized and investigated in two distincts crystallines units: upper crystalline units and lower crystallse units -named Beni Fergucne units. The first one event studied in upper units is associated with high temperature (HT) and Low pressure (LP> metamorphism (P=4kb,T=725°C) and issynchroncousof graniteemplacement dated at 27416 Ma (U-Pbon zircon).The east shearing is associated with granite emplacement developed during decompression. Final retrograde evolution corresponding to dccomprcssional cooling following this granite emplacement is associated with extensions shear zones. The second high grade dcformational (D2-M2) event (P=9- 10 Kb, T= 550-650°C) affects mainly lower crystalline units and corresponds to the northward shearing. Previous assemblages (Ml ) arc transformed as andalousitc by kyanitr in metapclites and muscovite by secondary white mica and kyanitc in metagraniles (High pressure assemblages (M2)). In these lower units, the HP event clearly involved 270 - 280 Ma old granites. Field observations, petrological, structural and radiometric data led to suggest that (D2-M2) tcctono-mclamorphic event overprinted LP variscan basement before upper Eocene deformation. Thus, late hcrcynian or coalpin ages for this HP event is debated in this study.
Mots clés
Kinematic -Shearcriteria- Deformation- Metamorphism- Geochronology - Alpin belt - Variscan belt - Petite Kabylie -Algeria
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