Mobilisation of rare earth elements in shear zones: Insights from the Tabouchent granodioritic pluton (Jebilet massif, Variscan Belt, Morocco)
Résumé
In the Jebilet massif (Variscan belt, Morocco), two peraluminous granodioritic plutons (the Eastern and Central Jebilet plutons) are spatially associated with a regional shear zone. The Central Jebilet pluton includes the Tabouchent, Bramram and Bamega intrusions, which represent variably eroded portions of an arcuate apical part of the pluton. The intrusions are composed of biotite ± cordieritebearing granodiorite that is crosscut by tourmaline-bearing leucogranite, which is greisenized in the Bramram cupola. Fluorine, Sn-W (Au) mineralization is present in the pluton while Cu-Au and Pb-Zn-Ag-Au mineralizations are present in the contact metamorphic aureole around the intrusion. Deformation is more homogeneous in the Bramram and Bamega than in the Tabouchent granodioritic intrusion where deformation is very heterogeneous and concentrated within conjugate subvertical meter-scale ductile shear zones that crosscut the intrusion. In the shear zones the breakdown of feldspar and biotite resulted in the transformation of the granodiorite to phyllonites composed of quartz
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