P-T-t estimation of deformation in low-grade quartz-feldspar-bearing rocks using thermodynamic modelling and 40Ar/39Ar dating techniques: example of the Plan-de-Phasy shear zone unit (Briançonnais Zone, Western Alps) - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles Terra Nova Year : 2013

P-T-t estimation of deformation in low-grade quartz-feldspar-bearing rocks using thermodynamic modelling and 40Ar/39Ar dating techniques: example of the Plan-de-Phasy shear zone unit (Briançonnais Zone, Western Alps)

Yann Rolland
Olivier Vidal
Stephane Guillot
Thierry Dumont

Abstract

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 modelling and 40Ar/39Ar 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.

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Geomorphology

Dates and versions

insu-00910176 , version 1 (27-11-2013)

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Pierre Lanari, Yann Rolland, Stéphane Schwartz, Olivier Vidal, Stephane Guillot, et al.. P-T-t estimation of deformation in low-grade quartz-feldspar-bearing rocks using thermodynamic modelling and 40Ar/39Ar dating techniques: example of the Plan-de-Phasy shear zone unit (Briançonnais Zone, Western Alps). Terra Nova, 2013, p.114. ⟨10.1111/ter.12079⟩. ⟨insu-00910176⟩
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