Dating of fault zone activity by apatite fission track and apatite (U-Th)/He thermochronometry: A case study from the Lavanttal fault system (Eastern Alps)

摘要

Fission track and (U-Th)/He thermochronology are useful tools to reconstruct distinct thermal events along fault zones, provided that heat advection brings about substantial track annealing and resetting. In a case study, apatite fission track and (U-Th)/He ages from drill cores transecting the Lavanttal fault system (Eastern Alps) revealed rejuvenation of ages in fault-related rocks. Heat transfer via hydrothermal fluids was sufficient to partly reset apatite fission track ages producing a younger age population, reduce track lengths slightly and rejuvenate (U-Th)/He ages in fault cores. Hydrothermal fluid activity can be bracketed between the age of the slightly reset fission tracks and the (U-Th)/He ages, between Late Miocene and Early Pliocene times. Additional thermal history modelling of two host rock samples suggests that the young apatite fission track population slightly coincides with a last exhumation pulse of the adjacent Koralm Complex during Late Miocene times.