The middle Qilian orogenic belt and Lajishan orogenic belt, both of which were formed in the Caledonian, strike NW-SE direction across southeast Qilian Mountains and their basement consists of pre-Caledonian metamorph...The middle Qilian orogenic belt and Lajishan orogenic belt, both of which were formed in the Caledonian, strike NW-SE direction across southeast Qilian Mountains and their basement consists of pre-Caledonian metamorphic rocks with lozenge-shaped ductile shear zones in the crystalline basement. The blunt angle between the conjugated ductile shear zones ranges from 104° to 114°, indicating approximate 210° of the maximum principal stress. The plateau ages of muscovite ^40Ar/^39Ar obtained from the mylonitized rocks in the ductile shear zones of Jinshaxia-Hualong-Keque massif within the middle Qilian massif are （405.1±2.4） Ma and （418.3±2.8） Ma, respectively. The chronology data confirm the formation of ductile shear zones in the Caledonian basement metamorphic rocks during the Caledonian orogeny. Furthermore, on the basis of basement rock study, precise timing for the closing of the Late Paleozoic volcanic basin （or island-arc basin） and Lajishan ocean basin is determined. This provides us a new insight into the closing of ocean basin in the structural evolution of orogenic belt.展开更多
There is a more consanguineous relation be-tween nano-scale deformation of coal structure and meta-morphic-deformed environment. In different metamor-phic-deformed environments, deformation in the coal struc-ture can ...There is a more consanguineous relation be-tween nano-scale deformation of coal structure and meta-morphic-deformed environment. In different metamor-phic-deformed environments, deformation in the coal struc-ture can occur not only at micro-scale, but also at nano-scale, and even leads to the change of molecular structure and nano-scale pore (<100 nm) structure. The latter is the main space absorbing coalbed methane. Through X-ray diffraction (XRD) and liquid–nitrogen absorption methods, the charac-teristics of macromolecular and nano-scale pore structures of coals in different metamorphic-deformed environments and deformational series of coals have been studied. By combin-ing with high-resolution transmission electron microcopy (HRTEM), the macromolecular and nano-scale pore struc-tures are also directly observed. These results demonstrate that the stacking Lc of the macromolecular BSU in tectonic coals increases quickly from the metamorphic-deformed environment of low rank coals to that of high rank coals. For different deformed tectonic coals, in the same metamor-phic-deformed environment, the difference of Lc is obvious. These changes reflect chiefly the difference of different tem-perature and stress effect of nano-scale deformation in tec-tonic coals. The factor of temperature plays a greater role in the increase of macromolecular structure parameters Lc, the influence of stress factor is also important. With the stress strengthening, Lc shows an increasing trend, and La /Lc shows a decreasing trend. Therefore, Lc and La /Lc can be used as the indicator of nano-scale deformation degree of tectonic coals. With increasing temperature and pressure, especially oriented stress, the orientation of molecular structure be-comes stronger, and ordering degree of C-nets and the ar-rangement of BSU are obviously enhanced. For the deforma-tion of nano-scale pore structure, in the same metamor-phic-deformed environment, along with the strengthening of stress, the ratio of mesopores to its total pores volume of tec-toni展开更多
基金This paper is financially supported by the projects of 1:250 000 Scale Regional Geological Survey of Linxia, and Dingxi (No. 200413000007) from Ministry of Land and Resources of China.
文摘The middle Qilian orogenic belt and Lajishan orogenic belt, both of which were formed in the Caledonian, strike NW-SE direction across southeast Qilian Mountains and their basement consists of pre-Caledonian metamorphic rocks with lozenge-shaped ductile shear zones in the crystalline basement. The blunt angle between the conjugated ductile shear zones ranges from 104° to 114°, indicating approximate 210° of the maximum principal stress. The plateau ages of muscovite ^40Ar/^39Ar obtained from the mylonitized rocks in the ductile shear zones of Jinshaxia-Hualong-Keque massif within the middle Qilian massif are （405.1±2.4） Ma and （418.3±2.8） Ma, respectively. The chronology data confirm the formation of ductile shear zones in the Caledonian basement metamorphic rocks during the Caledonian orogeny. Furthermore, on the basis of basement rock study, precise timing for the closing of the Late Paleozoic volcanic basin （or island-arc basin） and Lajishan ocean basin is determined. This provides us a new insight into the closing of ocean basin in the structural evolution of orogenic belt.
基金This work was supported by the National Key Development Plan Project of Basic Research(973 Plan)(Grant No.2002CB211704)the National N atural Science Foundation of China(Grant No.40172058)+1 种基金China Postdoctoral Science Foundation(Grant No.200403508)Kuancheng Wang Post-doctoral Research Award Fund of Chinese Academy of Sciences.
文摘There is a more consanguineous relation be-tween nano-scale deformation of coal structure and meta-morphic-deformed environment. In different metamor-phic-deformed environments, deformation in the coal struc-ture can occur not only at micro-scale, but also at nano-scale, and even leads to the change of molecular structure and nano-scale pore (<100 nm) structure. The latter is the main space absorbing coalbed methane. Through X-ray diffraction (XRD) and liquid–nitrogen absorption methods, the charac-teristics of macromolecular and nano-scale pore structures of coals in different metamorphic-deformed environments and deformational series of coals have been studied. By combin-ing with high-resolution transmission electron microcopy (HRTEM), the macromolecular and nano-scale pore struc-tures are also directly observed. These results demonstrate that the stacking Lc of the macromolecular BSU in tectonic coals increases quickly from the metamorphic-deformed environment of low rank coals to that of high rank coals. For different deformed tectonic coals, in the same metamor-phic-deformed environment, the difference of Lc is obvious. These changes reflect chiefly the difference of different tem-perature and stress effect of nano-scale deformation in tec-tonic coals. The factor of temperature plays a greater role in the increase of macromolecular structure parameters Lc, the influence of stress factor is also important. With the stress strengthening, Lc shows an increasing trend, and La /Lc shows a decreasing trend. Therefore, Lc and La /Lc can be used as the indicator of nano-scale deformation degree of tectonic coals. With increasing temperature and pressure, especially oriented stress, the orientation of molecular structure be-comes stronger, and ordering degree of C-nets and the ar-rangement of BSU are obviously enhanced. For the deforma-tion of nano-scale pore structure, in the same metamor-phic-deformed environment, along with the strengthening of stress, the ratio of mesopores to its total pores volume of tec-toni
