Effects of temperature, pressure, and ionization of the formation and stability of fission tracks in minerals and glasses

In view of the demonstrated usefulness of the fission-fragment-track technique in geochronology, the effect of various geophysical variables on track formation and stability has been studied. Track fading in tektite glass, zircon, olivine, muscovite, phlogopite, and biotite was studied as a function of temperature, pressure, plastic deformation, and highly ionizing radiation. Temperature was found to be the most important parameter, and track-annealing data are given for each material. Hydrostatic pressures up to 80 kb have practically no effect on annealing curves of zircon and olivine. Track annealing in tektites can be accelerated only upon application of an hydrostatic pressure much larger than would ever be encountered by even a well-buried tektite. Purely hydrostatic pressures do not accelerate track annealing in micas, but shear deformations can shorten, distort, or erase tracks. Large doses of ionizing radiation (other than extremely massive nuclear particles) have no effect on track stability in any of the materials. Tracks formed at 77°K have the same appearance as tracks formed at room temperature or higher.