![Étude du métamorphisme de moyenne pression - haute température dans la formation des « Schistes X ».](./styles/unilbeau/images/no_image_m2.jpg)
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Titre : | Étude du métamorphisme de moyenne pression - haute température dans la formation des « Schistes X ». : Caractérisation des assemblages minéralogiques. |
Auteurs : | Théophile CHOLET ; Valentin OGE |
Type de document : | Mémoire d'initiation à la recherche |
Année de publication : | 2021 |
Concepts : |
MONTAGNE NOIRE
METAMORPHISME |
Résumé : | The Montagne Noire is the southern termination of the Massif Central in France, corresponding to the northern extremity of the ancient Catalan craton, detached from Gondwana about 470Ma ago. The Montagne Noire is divided into 3 units which are from North to South: the northern side, the Axial Zone composed of a gneissic dome, and the southern side. Both sides are Hercynian nappes, overlapping to the South. The Axial Zone is surrounded by a metasedimentary cortex arranged in clusters, commonly called Schistes X". These Cambro-Ordovician metapelites are affected by high temperature metamorphism due to the rise of the dome, as evidenced by isogrades. A mineralogical and geochemical characterisation of the paragenesis composing the "Schistes X" was carried out on samples between Labastide-Rouairoux and St-Pons-de-Thomières, in the south of the Agoût massif. It allowed thermodynamic modelling, to constraint the pressure-temperature conditions for the formation of the paragenesis observed, and to trace the metamorphic evolution of the " Schistes X ". A decrease in temperature and pressure was demonstrated from the North to the South of the western area of St-Pons-de-Thomières. In the North, temperatures reached 520 - 680 °C and pressures of 0.16 - 1.1 GPa in the Silty Schists. These parameters decrease southward with 460 - 580°C for 0.1 - 0.8 GPa in the Monotone Schists. However, these results do not allow us to propose an evolutionary model for the rise of the Axial Zone dome. A variation in the composition of the paragenesis was nevertheless highlighted in the study area. It is linked to a difference in geochemistry during the genesis of the rocks and to the alteration of the metamorphic facies by retromorphism and fluid circulation." |
Spécialité : | Géologie |
Numéro de promo : | 83 |
numéro MIR : | 032 |