Minimizing Detritus Zircon Grain Contamination in Fission Track Dating Based on Statistical Analysis and Crystal Morphology

Abstract

In the present paper we discuss a method for estimation of contamination of detritus grains in fission track measurement and present a statistical treatment for overcoming these contaminant affects. Fission Track data were obtained from the two zircon sample from different horizons in an acidic tuff outcrop belonging to the Hanazono Formation (HZ0) in southwest Japan. The x²-test of fission track data suggest that non-Poisson's distribution exist in the sample (HZ0-1) from the lower most HZ0.This result indicate that HZ0-1 contains detritus grains in the data set. Result from another sample (HZ0-2) which is 1.7m above the HZ0-1 does not indicate the existence of a non-Poisson's distribution. In further analysis the raw fission track data set of HZ0-1 was divided into two groups based on the zircon morphology. Next, the x² test to the each separated sample were carried out. it is observed that one set of samples show non-Poisson's distribution whereas the other set does not. This result indicates that the detritus zircon show characteristic crystal form and can be identified and separated based on their mor-phology. It was also showed that the population of HZ0-1 sample showing Poisson's distribution is almost the same population of the zircon crystals derived from the sample HZ0-2. Based on above result, the utility of zircon crystal morphology and the use of statistical techniques for minimizing contaminant affects are highlighted.