Hydroxyl in continental deep subduction zone: Evidence from UHP eclogites of the Dabie Mountains

Origin of retrograde fluid in ultrahigh-pressure metamorphic rocks: Constraints from mineral hydrogen isotope and water content changes in eclogite–gneiss transitions in the Sulu orogen

“…These bands are similar to those found in Bixiling garnets (Xia et al, 2005). The position of group III bands is out of the previous investigated natural and synthesized garnets (Aines and Rossman, 1984a,b;Rossman and Aines, 1991;Rossman et al, 1989;Bell and Rossman, 1992b;Beran et al, 1993;Langer et al, 1993;Snyder et al, 1995;Lu and Keppler, 1997;Matsyuk et al, 1998;Withers et al, 1998;Zhang et al, 2001;Su et al, 2002). These bands are generally much broader than group I and II bands, with FWHH often larger than 180.…”

“…Fu et al (2003a) distinguished different generations of fluid inclusions in the UHP rocks: pre-to syn-peak metamorphic fluids, consisting of N 2 , CH 4 and high salinity brines, and post-peak metamorphic fluids rich in CO 2 and low-salinity water. More interesting is the observation that considerable amounts of water were measured in nominally anhydrous minerals such as garnet and omphacite in the Dabie-Sulu UHP rocks (Zhang et al, 2001Su et al, 2002Su et al, , 2004Xia et al, 2005;Sheng et al, 2007). The occurrence of the fluids indicates that the UHP metamorphism proceeded with variable degrees of fluid-rock interaction but with limited mobility of aqueous fluids during subduction and exhumation.…”

Water contents and deformation mechanism in ductile shear zone of middle crust along the Red River fault in southwestern China

“…Studies on content of trace amount of water in quartz and feldspars [36,37] in granitic shear zones and that in NAM [22,23] in deformed low metamorphic grade felsic rocks show that trace amount of water in minerals played an important role. Trace amount of water in eclogite [57][58][59][60] has also been found to enhance dislocation climb, recrystallization and grain size reduction, which are believed to be the major deformation mechanisms associated with shear zone development. In these cases, trace amount of water in the minerals enhanced rock deformation and promoted the development of ductile shear zones.…”

Exsolution microstructures in ultrahigh-pressure rocks: Progress, controversies and challenges

“…(3) It has been shown by recent studies that trace amounts of 'water' may exist in nominally anhydrous minerals of ultrahigh pressure rocks in the form of hydroxyl (OH) and coupled isomorphic substitution with some elements similar to these found in mantle-derived rocks [80][81][82][83][84][85][86][87] . This type of 'water' is possibly the dominant water reservoir in the deep subduction zones with the absence of hydrous minerals.…”