40Ar/ 39Ar dating of Penninic Front tectonic displacement (W Alps) during the Lower Oligocene (31–34 Ma) - Archive ouverte HAL Access content directly
Journal Articles Terra Nova Year : 2009

40Ar/ 39Ar dating of Penninic Front tectonic displacement (W Alps) during the Lower Oligocene (31–34 Ma)

(1) , (2) , (3) , (3) , (1) , (2) , (2)
1
2
3

Abstract

Direct absolute dating of the Penninic Frontal Thrust tectonic motion is achieved using the 40Ar/39Ar technique in the Pelvoux Crystalline Massif (Western Alps). The dated phengites were formed syn-kinematically in shear zones. They underline the brittle-ductile stretching lineation, pressure-shadow fibres and slickensides consistent with underthrusting of the European continental slab below the propagating Penninic Thrust. Chlorite–phengite thermobarometry yields 10–15 km and T∼280 °C, while 40Ar/39Ar phengite ages mainly range between 34 and 30 Ma, with one younger age at 27 Ma. This Early Oligocene age range matches a major tectonic rearrangement of the Alpine chain. Preservation of prograde 40Ar/39Ar ages is ascribed to passive exhumation of the Pelvoux shear zone network, sandwiched between more external thrusts and the Penninic Front reactivated as an E-dipping detachment fault. Partial resetting in the Low Temperature part of argon spectra below 24 Ma is ascribed to brittle deformation and alteration of phengites.

Dates and versions

insu-00411593 , version 1 (28-08-2009)

Identifiers

Cite

T. Simon-Labric, Yan Rolland, Thierry Dumont, Thomas Heymes, Christine Authemayou, et al.. 40Ar/ 39Ar dating of Penninic Front tectonic displacement (W Alps) during the Lower Oligocene (31–34 Ma). Terra Nova, 2009, 21 (2), pp.127-136. ⟨10.1111/j.1365-3121.2009.00865.x⟩. ⟨insu-00411593⟩
142 View
0 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More