Combined with field studies, microscopic observations, and EBSD fabric analysis, we defined a possible Early Cretaceous metamorphic core complex （MCC） in the Wulian area along the Sulu orogenic belt in eastern China...Combined with field studies, microscopic observations, and EBSD fabric analysis, we defined a possible Early Cretaceous metamorphic core complex （MCC） in the Wulian area along the Sulu orogenic belt in eastern China. The MCC is of typical Cordilleran type with five elements： （1） a master detachment fault and sheared rocks beneath it, a lower plate of crystalline rockswith （2） middle crust metamorphic rocks, （3） syn-kinematic plutons, （4） an upper plate of weakly deformed Proterozoic metamorphic rocks, and （5） Cretaceous volcanic-sedimentary rocks in the supradetachment basin. Some postkinematic incursions cut across the master detachment fault zone and two plates. In the upper plate, Zhucheng （诸城） Basin basement consists of the Proterozoic Fenzishan （粉子山） Group, Jinning period granite （762–834 Ma）. The s u pr a de tac hme nt ba sin a bo ve the Proterozoic rocks is filled with the Early Cretaceous Laiyang （莱阳） （~135–125 Ma） and Qingshan （青山） groups （120–105 Ma）, as wellas the Late Cretaceous Wangshi （王氏） Group （85–65 Ma）. The detachment fault zone is developed at the base and margin of the superposed basin. Pseudotachylite and micro breccia layers located at the top of the detachment fault. Stretching lineation and foliation are well developed in the ductile shear belt in the detachment faults. The stretching lineation indicates a transport direction of nearly east to west on the whole, while the foliations trend WNW, WSW, and SE. Protomylonite, mylonite, and ultramylonite are universally developed in the faults, transitioning to mylonitic gneiss, and finally to gneiss downward. Microstructure and quartz preferred orientation show that the mylonites formed at high greenschist facies to low greenschist facies as a whole. The footwall metamorphic rock series of the Wulian MCC are chiefly UHP （ultrahigh pressure） metamorphic rocks. Syntectonic rocks developed simultaneously with the Wulian MCC detachment and extension. Geo展开更多
As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure （UHP） metamorphism together with its host eclogites. Thus, it could play some role in trans- porting water into the deep ear...As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure （UHP） metamorphism together with its host eclogites. Thus, it could play some role in trans- porting water into the deep earth. Here we present a detailed investigation of water concentrations of kyanite, and for reference, of garnet and omphacite from four Maobei eclogites in the Sulu orogenic belt, eastern China. Fourier transform infrared （FTIR） measurements show that kyanites, garnets, and omphacites all have distinct hydroxyl absorption bands due to OH groups bound in their crystal struc- ture. The FTIR profile analyses on ten grains from different samples reveal a homogeneous distribution of water across kyanite, suggesting insignificant water loss during exhumation. The calculated water concentrations in kyanite （21 wt ppm-41 wt ppm） are comparable to those reported previously for kyanite from various geological occurrences when using the most recent calibration. They are however much lower compared with those in garnet （46 wt ppm-83 wt ppm） and omphacite （302 wt ppm-548 wt ppm） from the Maobei eclogites. This implies that kyanite is not a major water carrier in eclogites con- sidering its low volume fraction and contributes negligibly to transport water into the deep mantle ac- companying subducted oceanic crust until its possible transformation to AISiO3OH.展开更多
基金supported by the National Natural Science Foundation of China(Nos.90814006,91214301)the Natural Science Foundation of Shandong Province(No.ZR2009EQ002)+1 种基金the Foundation of the Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Minerals(No.DMSM201005)the National Key Basic Research Development Program (973Program) of China(No.2012CB723104)
文摘Combined with field studies, microscopic observations, and EBSD fabric analysis, we defined a possible Early Cretaceous metamorphic core complex （MCC） in the Wulian area along the Sulu orogenic belt in eastern China. The MCC is of typical Cordilleran type with five elements： （1） a master detachment fault and sheared rocks beneath it, a lower plate of crystalline rockswith （2） middle crust metamorphic rocks, （3） syn-kinematic plutons, （4） an upper plate of weakly deformed Proterozoic metamorphic rocks, and （5） Cretaceous volcanic-sedimentary rocks in the supradetachment basin. Some postkinematic incursions cut across the master detachment fault zone and two plates. In the upper plate, Zhucheng （诸城） Basin basement consists of the Proterozoic Fenzishan （粉子山） Group, Jinning period granite （762–834 Ma）. The s u pr a de tac hme nt ba sin a bo ve the Proterozoic rocks is filled with the Early Cretaceous Laiyang （莱阳） （~135–125 Ma） and Qingshan （青山） groups （120–105 Ma）, as wellas the Late Cretaceous Wangshi （王氏） Group （85–65 Ma）. The detachment fault zone is developed at the base and margin of the superposed basin. Pseudotachylite and micro breccia layers located at the top of the detachment fault. Stretching lineation and foliation are well developed in the ductile shear belt in the detachment faults. The stretching lineation indicates a transport direction of nearly east to west on the whole, while the foliations trend WNW, WSW, and SE. Protomylonite, mylonite, and ultramylonite are universally developed in the faults, transitioning to mylonitic gneiss, and finally to gneiss downward. Microstructure and quartz preferred orientation show that the mylonites formed at high greenschist facies to low greenschist facies as a whole. The footwall metamorphic rock series of the Wulian MCC are chiefly UHP （ultrahigh pressure） metamorphic rocks. Syntectonic rocks developed simultaneously with the Wulian MCC detachment and extension. Geo
基金supported by the National Natural Science Foundation of China (Nos. 41372224 and 41590623)
文摘As a minor phase, kyanite has been repeatedly shown to have experienced ultrahigh pressure （UHP） metamorphism together with its host eclogites. Thus, it could play some role in trans- porting water into the deep earth. Here we present a detailed investigation of water concentrations of kyanite, and for reference, of garnet and omphacite from four Maobei eclogites in the Sulu orogenic belt, eastern China. Fourier transform infrared （FTIR） measurements show that kyanites, garnets, and omphacites all have distinct hydroxyl absorption bands due to OH groups bound in their crystal struc- ture. The FTIR profile analyses on ten grains from different samples reveal a homogeneous distribution of water across kyanite, suggesting insignificant water loss during exhumation. The calculated water concentrations in kyanite （21 wt ppm-41 wt ppm） are comparable to those reported previously for kyanite from various geological occurrences when using the most recent calibration. They are however much lower compared with those in garnet （46 wt ppm-83 wt ppm） and omphacite （302 wt ppm-548 wt ppm） from the Maobei eclogites. This implies that kyanite is not a major water carrier in eclogites con- sidering its low volume fraction and contributes negligibly to transport water into the deep mantle ac- companying subducted oceanic crust until its possible transformation to AISiO3OH.
