OBSERVATIONS ON THE MICRO-TEXTURE AND ESR-SPECTRA OF QUARTZ FROM FAULT GOUGE

We have investigated fault gouge samples from a variety of sites in ea stern China with ESR, optical and scanning electron microscopy (SEM), X-ray diffraction and cathodoluminescence. The results reveal two diff erent types of quartz, a macrocrystalline and a microcrystalline varie ty. The macrocrystalline samples show increasing ESR intensities of th e E' centre with increasing grain size whilst the microcrystalline sam ples show the opposite trend. We also found that the dissolution of qu artz grains and secondary quartz precipitation on the surface of the g rains is significant in some samples, indicating active chemical weath ering in these fault zones. The occurrence of secondary quartz has ser ious implications for the reliability of any dating attempt. (C) 1997 Elsevier Science Ltd.