Publication Date:
2013-10-17
Description:
Pressure-Temperature-time (P-T-t) estimates of the syn-kinematic strain at the peak-pressure conditions reached during shallow underthrusting of the Briançonnais Zone in the Alpine subduction zone was made by thermodynamic modeling and 40 Ar/ 39 Ar dating in the Plan-de-Phasy unit (SE of the Pelvoux Massif, Western Alps). The dated phengite minerals crystallized syn-kinematically in a shear zone indicating top-to-the-N motion. By combining X-ray mapping with multi-equilibrium calculations we estimate the phengite crystallization conditions at 270±50°C and 8.1±2 kbar at an age of 45.9±1.1 Ma. Combining this P-T-t estimate with data from the literature allows us to constrain the timing and geometry of Alpine continental subduction. We propose that the Briançonnais units were scalped on top of the slab during ongoing continental subduction and exhumed continuously until collision. This article is protected by copyright. All rights reserved.
Print ISSN:
0954-4879
Electronic ISSN:
1365-3121
Topics:
Geosciences