Recent field survey in the eastern Dabieshan Mountains has revealed extensive occurrences of pseudotachylite. The pseudotachylite tends to occur as simple veins and injected networks along the NE-SW-trending fracture ...Recent field survey in the eastern Dabieshan Mountains has revealed extensive occurrences of pseudotachylite. The pseudotachylite tends to occur as simple veins and injected networks along the NE-SW-trending fracture zones or shear zones, which are parallel to the Tanlu fault zone and cut all the pre-Cretaceous geological bodies. The characteristics of both the microstructures gained by the optical microscope and SEM imaging and the geochemistry between the pseudotachylites and their host rocks show that the pseudotachylites were formed mainly by ultracataclasis of their wall rocks in which they occur. The bulk K-Ar ages of the pseudotachylites yielded a narrow range of 81 -93 Ma, and moreover the laser-probe 40Ar/39Ar dating of phengite overprinting on the pseudotachylite gave a weighted mean age of 78.9 Ma. These results show that the pseudotachylites from the eastern Dabieshan Mountains formed along the NE-SW-trending fault zone during the uplifting of the orogenic belt at 80-90 Ma, which places important constrains on the cooling and exhumation history of the Dabieshan Mountains during and after the late Cretaceous.展开更多
Pseudotachylite was found in the Yagan detachment fault in the Sino-Mongolian boundary area but so many generations that occurred have seldom been reported in literature.Although Wagliughlin and Spray (1992) have full...Pseudotachylite was found in the Yagan detachment fault in the Sino-Mongolian boundary area but so many generations that occurred have seldom been reported in literature.Although Wagliughlin and Spray (1992) have fully reviewed its origin, there展开更多
The article describes the characteristics of the Yagan metamorphic core complex, especially the associated detachment fault and various extensional structures in its footwall. The age of the complex is discussed in so...The article describes the characteristics of the Yagan metamorphic core complex, especially the associated detachment fault and various extensional structures in its footwall. The age of the complex is discussed in some detail as well. The basic features of the Yagan metamorphic complex (Jurassic in age) are similar to those of the metamorphic core complex (Tertiary in age) in the Cordilleran area; they are as follows: (a) mylonitic gneisses in the footwall, (b) chloritized sheared mylonitic rocks, (c) pseudotachylites and flinty cataclasites or microbreccias, (d) unmetamorphosed or epimetamorphic rocks in the hanging wall with a layer of fault gouges or incohesive fault breccia next to the detachment fault. In contrast to its Cordilleran counterpart, however, there are many extensional faults with different styles (from dactile low-angle normal faults through brittle-ductile to brittle high-angle normal faults)in the footwall.展开更多
The glasses already found in nature fall into three categories: (1) volcanic glass related to volcanic eruptions, (2) diaplectic glass related to meteoritic impactions or nuclear explosions, and (3) pseudotachylite re...The glasses already found in nature fall into three categories: (1) volcanic glass related to volcanic eruptions, (2) diaplectic glass related to meteoritic impactions or nuclear explosions, and (3) pseudotachylite related to high-speed faulting movements. The volcanic glass, resulting from rapid cooling of high-temperature magma, is closely connected to volcanic rocks and does not contain any water. The diaplectic glass,展开更多
基金the National Natural Scicnce Foundation Grant 40172077 the Regional Geological Survey,CAGS,DKD2001009.
文摘Recent field survey in the eastern Dabieshan Mountains has revealed extensive occurrences of pseudotachylite. The pseudotachylite tends to occur as simple veins and injected networks along the NE-SW-trending fracture zones or shear zones, which are parallel to the Tanlu fault zone and cut all the pre-Cretaceous geological bodies. The characteristics of both the microstructures gained by the optical microscope and SEM imaging and the geochemistry between the pseudotachylites and their host rocks show that the pseudotachylites were formed mainly by ultracataclasis of their wall rocks in which they occur. The bulk K-Ar ages of the pseudotachylites yielded a narrow range of 81 -93 Ma, and moreover the laser-probe 40Ar/39Ar dating of phengite overprinting on the pseudotachylite gave a weighted mean age of 78.9 Ma. These results show that the pseudotachylites from the eastern Dabieshan Mountains formed along the NE-SW-trending fault zone during the uplifting of the orogenic belt at 80-90 Ma, which places important constrains on the cooling and exhumation history of the Dabieshan Mountains during and after the late Cretaceous.
文摘Pseudotachylite was found in the Yagan detachment fault in the Sino-Mongolian boundary area but so many generations that occurred have seldom been reported in literature.Although Wagliughlin and Spray (1992) have fully reviewed its origin, there
基金Project 49070135 supported by the National Natural Science Foundation of China
文摘The article describes the characteristics of the Yagan metamorphic core complex, especially the associated detachment fault and various extensional structures in its footwall. The age of the complex is discussed in some detail as well. The basic features of the Yagan metamorphic complex (Jurassic in age) are similar to those of the metamorphic core complex (Tertiary in age) in the Cordilleran area; they are as follows: (a) mylonitic gneisses in the footwall, (b) chloritized sheared mylonitic rocks, (c) pseudotachylites and flinty cataclasites or microbreccias, (d) unmetamorphosed or epimetamorphic rocks in the hanging wall with a layer of fault gouges or incohesive fault breccia next to the detachment fault. In contrast to its Cordilleran counterpart, however, there are many extensional faults with different styles (from dactile low-angle normal faults through brittle-ductile to brittle high-angle normal faults)in the footwall.
基金Project supported by the National Natural Science Foundation of China, and this report is one of the results of the NSFC item "Ductile shear zone" (85072)
文摘The glasses already found in nature fall into three categories: (1) volcanic glass related to volcanic eruptions, (2) diaplectic glass related to meteoritic impactions or nuclear explosions, and (3) pseudotachylite related to high-speed faulting movements. The volcanic glass, resulting from rapid cooling of high-temperature magma, is closely connected to volcanic rocks and does not contain any water. The diaplectic glass,
