Paleotemperature investigation of the Variscan southern external domain: the case of the Montagne Noire (France) - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Article Dans Une Revue Bulletin de la Société Géologique de France Année : 2020

Paleotemperature investigation of the Variscan southern external domain: the case of the Montagne Noire (France)

Résumé

The Montagne Noire located in the southern part of the French Massif Central represents the northern part of the South-Variscan Foreland. It is subdivided into three parts. The granite-migmatite Axial Zone dome is surrounded by non-or weakly metamorphosed Paleozoic sedimentary series. Both northern and southern flanks of the Montagne Noire dome are deformed by km-scale, south to southeast facing recumbent folds and thrusts sheets. The Raman Spectroscopy of Carbonaceous Material (RSCM) method, carried out in the low-grade metamorphic rocks of the southern flank of the Montagne Noire, yielded temperatures comprised between 400°C near the dome, and 230°C in the southern domain. Three Raman geothermometers were used to cover this temperature range. RSCM temperatures comply qualitatively with previous estimates based on illite crystallinity, conodont color alteration, and fluid inclusions carried out in the same area, which document a metamorphic temperature increase towards the dome. The isotherms cut across the different nappe contacts and are oriented parallel to the southern margin of the Axial Zone. This temperature distribution supports the idea that the thermal structure was acquired during the Axial Zone dome emplacement. The thermal structure acquired during the recumbent folds emplacement and burial of the sedimentary series is totally overprinted by the doming event. In addition, in a domain relatively remote from the Axial Zone dome, the RSCM measurements yielded significantly higher temperatures than illite crystallinity. This discrepancy points to a higher sensitivity of RSCM to short-lived thermal events than illite crystallinity, possibly because of more efficient kinetics of the carbonization reaction. On the other hand, high RSCM temperatures analysed far from the Axial Zone, between 300°C and 360°C could be explained by the presence of granitic plutons under the foreland basin.
Fichier principal
Vignette du fichier
bsgf_2020_192_3_200033.pdf (14.96 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

insu-03086940 , version 1 (23-12-2020)
insu-03086940 , version 2 (31-03-2021)

Identifiants

Citer

Clément Montmartin, Michel Faure, Hugues Raimbourg. Paleotemperature investigation of the Variscan southern external domain: the case of the Montagne Noire (France). Bulletin de la Société Géologique de France, 2020, 192, ⟨10.1051/bsgf/2020043⟩. ⟨insu-03086940v2⟩
156 Consultations
55 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More