Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We use 36Cl surface exposure dating to determine the slip release pattern over the last ~ 15 kyr for the Velino-Magnola fault, a major active normal fault in Central Italy. We sampled the fault at five well-separated sites along its length, and modeled the 36Cl concentrations measured in the 376 samples. We find that the fault broke in at least 9 large earthquakes that occurred in two 5-6 ka-long supercycles. Each cycle included a 4-5 ka-long phase of relative quiescence, followed by a cluster of at least 3 large earthquakes or earthquake sequences that released most of the accumulated strain in ~ 1 ka. All 9 identified events broke the entire fault and produced maximum surface slips of 2-3 m. Though the Velino-Magnola fault seems presently in a stage of relative quiescence, it may re-enter a phase of paroxysmal seismic activity in a few hundred of years
ISSN: 0012-821X

hal-00667280
https://hal.archives-ouvertes.fr/hal-00667280
DOI : 10.1016/j.epsl.2011.05.022

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Field study, thermochronology and geochemistry of the east Lungmu Co (LMC) range highlight some of the geological events that shaped western Tibet. The LMC fault zone has long been interpreted as the boundary between the Tianshuihai terrane of Laurasian affinity and the Qiangtang block of Gondwanian affinity. In the LMC range, the Paleozoic series is intruded by the Mangtsa leucogranite whose zircon have a U/Pb age of 116.9 ± 1 Ma and by mafic rocks with U/Pb zircon ages ranging from 116.9 ± 1 to 95.1 ± 1.7 Ma. Geochemistry of the mafic rocks indicates that they have been emplaced in a supra-subduction zone setting, probably the north dipping Nujiang suture zone. 40Ar/39Ar micas ages of the granite indicate that cooling below ~ 350 °C occurred between 105 and 85 Ma. 40Ar/39Ar K-feldspar data suggest a fast cooling event at 60-55 Ma, which we relate to the reactivation of the LMC suture zone as a thrust at the onset of the India-Eurasia collision. The last, and still active, deformation event corresponds to left-lateral strike-slip faulting along the ENE-WSW LMC fault.
ISSN: 1342-937X

hal-00660491
https://hal.archives-ouvertes.fr/hal-00660491
DOI : 10.1016/j.gr.2011.07.026