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Hong’an area contains three high-pressure (HP) and ultra-high-pressure (UHP) metamorphic zones,including a HP eclogite zone, an UHP/Ky eclogite zone and a greenschist and transitional greenschistblueschist factes zone.HP eclogites show systematical changes in their mineral compositions from south to noyth. The pyropecontent in garnet increases and Kd ofgTt-cpx pair decreases from south to north. Such a change from northto south suggests a north-dipping subduction process.Kyanite eclogite is predominant in the UHP zone. A few of eclogites in this zone contain inclusions ofcoesite and its pseudomorph in garnet and omphacite. The samples in the middle and east of this zone yielda pressure range of 2.56-3.37 GPa and temperature range of 488-774℃ for peak metamorphism.The preliminary structural research shows that the HP and UHP zones may be interpreted as a slice pile,which the UHP slice is on the bottom, and the greenschist and transitional greenschist-blueschist factesslice is on the top. The boundries among these slices probably are shear zones that are ofnomal sense ofshear.
Hong’an area contains three high-pressure (HP) and ultra-high-pressure (UHP) metamorphic zones, including a HP eclogite zone, an UHP / Ky eclogite zone and a greenschist and transitional greenschistblueschist factes zone. HP eclogites show systematical changes in their mineral compositions from south to noyth. The pyropecontent in garnet increases and Kd of Tg-cpx pair decreases from south to north. Such a change from northto south suggests a north-dipping subduction process. Kyanite eclogite is predominant in the UHP zone. A few of eclogites in this zone contain inclusions of coesite and its pseudomorph in garnet and omphacite. The samples in the middle and east of this zone yielda pressure range of 2.56-3.37 GPa and temperature range of 488-774 ° C. for peak metamorphism. The preliminary structural research shows that the HP and UHP zones may be interpreted as a slice pile, which the UHP slice is on the bottom, and the greenschist and transitional greenschist-blueschist factesslice is on the t op. The boundries among these slices probably are shear zones that are of nomal sense ofshear.