Raman Spectrum Study on Quartz Exsolution in Omphacite from Eclogite and Its Tectonic Significances
WANG Lu1, JIN Zhen-min2, HE Mou-chun3 (1.Graduate School, China University of Geosciences, Wuhan430074, China; 2.Faculty of Earth Sciences, China University of Geosciences, Wuhan430074, China; 3.Faculty of Earth Resources, China University of Geosciences, Wuhan430074, China)
The studies on ultra-microstructure characteristic of quartz exsolution in eclogite and coesite in UHP eclogite of several localities are done with the appliance of laser Raman spectroscopy and U-stage. Research results show that the phase transformation of coesite-quartz in garnet and/or omphacite is a continuous process. Topological relationships are present between quartz exsolution in omphacite and its host mineral which shows orientations of two long axes of quartz exsolution parallel to (100) and (-101) of omphacite. At present, some of scholars suggest that the quartz exsolution in omphacite of eclogite is the evidence of UHP metamorphism. However, temperature and pressure condition and the exsolution mechanism of oriented needlelike quartz in omphacite still remain unclear. Therefore further study should be enhanced on experimental study on exsolution mechanism of super-silicate clinopyroxene, which could provide experimental quantitative constraint on quartz exsolution as UHP indicator.