Thermal stability of ESR signals in hydrothermal barites

Thermal stability of the ESR signals from barites in chimneys deposited from hydrothermal vents is investigated using isothermal and isochronal annealing experiments. A combination of first and second order kinetics is required to explain the results. The Arrhenius plots of the decay rate constants give the activation energies of 1.0-1.3 eV. From the estimated decay rate constants at the sea bottom (3 oC), the decay rate of the signal was calculated to be less than 2% for the period of 20 ka, suggesting the applicability of the ESR method for dating barites up to about twenty thousand years.