TITANIAN CLINOHUMITE AND TITANOCHONDRODITE EXSOLUTION IN CLINOPYROXENE FROM GARNET PERIDOTITES IN CCSD-PP1, SU-LU TERRANE, CHINA

Subduction zone probably is the most important place where the continental materials recycled into the mantle, which is essential for Earth dynamics (Ernst, 2001). Exsolution textures found in UHP rocks provide excellent chance to understand the exhumation histories of the continental materials in subduction zones (e.g., Liou et al., 1998). Some H2O-bearing mineral phases such as phlogopite (Zhu and Ogasawara, 2002) and amphibole (Xu et al., in prep.) exsolved from clinopyroxene in UHP rocks suggested that H2O could recycled into deep mantle (>250 km) through subduction zone. Garnet peridotite samples studied here collected from the CCSD-PP1, located in Donghai district, southeast of Su-Lu UHP terrane. Garnet contains abundant clinopyroxene inclusions. Titanian clinohumite and Titanochondrodite exsolution texture is found in such clinopyroxene (Figure). These exsolution phases (50-80µm in length, 0.2µm in width) occur as flake or rod in clinopyroxene. Theremobarometer calculation resulted T=716 - 914ºCp=48-51 Kbar, which are interpreted as the equilibrtrium temperature and pressure during exsolution. No flourine is detected in titanian clinohumite (FOH=1XF=0XFe=0.074 - 0.094 with an average of 0.082XTi=0.41 - 0.74 with an average of 0.56). The composition of this mineral phase suggested its forming pressure of >35 Kba (>850ºC) and therefore inplies that titanian clinohumite exsolution happened at UHP conditions during exhumation of the garnet peridotite.