Etching Characteristics of Fission Tracks in Minerals, and Fission Track Dating and Calibration of Zircon

Laboratory techniques for fission track dating of zircon, apatite and sphene were discussed in detail through the experiments based on sample selection, mineral separation, etching, irradiation and counting. Etching characteristics of spontaneous tracks on internal and external surfaces of zircons, apatites and sphenes, and induced tracks on an external detector were observed to discuss the variation of track densities during etching, and to measure the anisotropic etching efficiency. The zircons from the Fish Canyon Tuff, one of the universally studied age standards, were analyzed for their fission track ages and uranium concentrations using the external detector method. The combined fission track age of the zircon is 29.85±4.77 (1s) Ma which is well consistent with other fission track and K-Ar ages. The Zeta-values for standard glass dosimeters were preliminarily measured for age calibration using the Fish Canyon Tuff zircons. The values of ξ-factors are 348 for SRM 612, 360 for SRM 962a, 123 for CN 1 and 133 for CN 2.