Eocene seismogenic reactivation of a Jurassic ductile shear zone at Cap de Creus, Pyrenees, NE Spain

0Citations
Citations of this article
5Readers
Mendeley users who have this article in their library.

Abstract

The Cap de Creus peninsula in NE Spain exposes Variscan amphibolite-facies rocks, transected by greenschist-facies mylonitic shear zones accommodating displacements of up to 1 km. One of these shear zones contains pseudotachylytes with 1–4 mm thick fault veins and cm-scale high-angle injection veins and breccias. The pseudotachylyte matrix encloses mm-to μm-scale wallrock fragments and consists of ultrafine biotite and feldspar, often with a microporphyritic structure suggesting crystallization from a melt. Recent dating of the host shear zone yielded a Jurassic (170-160 Ma) age. Here we present 40Ar/39Ar dating of the pseudotachylytes yielding Early Eocene ages between 52.76 ± 1.64 Ma and 44.55 ± 0.77 Ma, indicating Alpine brittle faulting at times that Jurassic low-angle ductile shears had been tilted to their present vertical position following Alpine thrusting in the Pyrenees. The kinematics of the pseudotachylytes suggest strike-slip reactivation along the host shear zone, consistent with plate-kinematic analyses indicating coeval Iberia - Europe motion dominated by strike-slip. The dimensions of the pseudotachylyte-bearing zone and estimated brittle displacements suggest a moment magnitude of ~4.7–4.9. The average thicknesses of the fault veins indicate deformation at ≥4 km depth, an energy density of ~9.106 J/m2 and a frictional resistance of ~23 MPa.

Cite

CITATION STYLE

APA

Vissers, R. L. M., Ganerød, M., Pennock, G. M., & van Hinsbergen, D. J. J. (2020). Eocene seismogenic reactivation of a Jurassic ductile shear zone at Cap de Creus, Pyrenees, NE Spain. Journal of Structural Geology, 134. https://doi.org/10.1016/j.jsg.2020.103994

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free