Pressure effect on cathodoluminescence emission intensity recorded in metamorphosed detrital zircons of the Sanbagawa schists

Abstract

The cathodoluminescence (CL) emission and spectra analyses were conducted on detrital zircons in the Cretaceous Sanbagawa schists to describe changes in CL properties of zircons associated with metamorphism. In addition, high-pressure (HP) and high-temperature (HT) experiments were conducted on the non-metamorphosed Miocene Ashizuri igneous zircons, and the CL emission intensities obtained from them were compared with those of the Sanbagawa zircons. As a result, as compared to low-grade Sanbagawa zircons, the emission intensities of the high-grade Sanbagawa zircons reduced. The emission intensities produced from the HP-treated Ashizuri zircons, on the other hand, were twice as high as those generated from untreated zircons, but less than half of those generated from HT-treated zircons. Combining our results with previous studies on the temperature influence on zircon CL properties, it indicates that increasing metamorphic pressure decreases the increase in the CL emission intensity of metamorphosed detrital zircons resulting from the increasing temperature. The pressure effect on the emission intensity of zircon during metamorphism might be larger than the temperature effect.