The Bikou volcanic terrane is predominated by subalkaline tholeiitic lavas. Rock samples display lower initial ratios of Sr and Nd, 0.701248-0.704413 and 0.511080-0.512341 respectively. 207Pb and 208Pb are significant...The Bikou volcanic terrane is predominated by subalkaline tholeiitic lavas. Rock samples display lower initial ratios of Sr and Nd, 0.701248-0.704413 and 0.511080-0.512341 respectively. 207Pb and 208Pb are significantly enriched in the lavas. Most samples have positive εNd, which indicates that the magma was derived from EM-type mantle source, while a few samples with negative εNd indicate that there was contamination in the magma evolution. Magma differentiation is demonstrated by variations of LREE and LILE from depletion to enrichment. Additionally, normalized REE patterns and trace elements showed that lavas from the Bikou volcanic terrane have similar characteristics to those of basalts in arc settings caused by subduction and collision. Analyses showed that the Bikou volcanic terrane is a volcanic arc. New evidence proved that the Hengdan Group, north of the Bikou arc, is a turbidite terrane filling a forearc basin. Consequently, the Bikou volcanic terrane and the Hengdan turbidite terrane construct an arc-basin system. New SHRIMP ages showed that this arc-basin system developed on the northern margin of the Yangtze craton in the Neoproterozoic (846-776 Ma), and this arc-basin system is in agreement with the tectonic processes of Rodinia in the Neoproterzoic.展开更多
The process and result of fractal research of natural fault gouge collected from the active fault zone at northern edge of Western Qinling Mt. by using optical and electronic microscope technics were introduced in thi...The process and result of fractal research of natural fault gouge collected from the active fault zone at northern edge of Western Qinling Mt. by using optical and electronic microscope technics were introduced in this paper. The fractal dimension of this fault gouge is D =2.594±0.122 (2 D plane D =1.594±0.122), and its upper limit of fractal dimension occurs at grain size at 9.6～19.2 mm. The study result shows that this gouge is fractal, and its characteristic displacement parameter of stick slip friction can be determined by upper limit of fractal dimension. The feature of protolith which affect fractality and the significance of gouge fractal to seismic fault changes are also disscussed in the paper.展开更多
基金supports from the National Natural Science Foundation of China(grants 40172071 and 40211120151 to Yan Quanren)the Ministry of Science and Technology of the People’s Republic of China(grant 2202CB412608 to Wang Zongqi)+2 种基金the China Geological Survey(grant DKD2001002 to Wang Zongqi)the University of Nevada Las Vegas(to Hanson)and the Geological Society of America(to Druschke)are gratefully appreciated.
文摘The Bikou volcanic terrane is predominated by subalkaline tholeiitic lavas. Rock samples display lower initial ratios of Sr and Nd, 0.701248-0.704413 and 0.511080-0.512341 respectively. 207Pb and 208Pb are significantly enriched in the lavas. Most samples have positive εNd, which indicates that the magma was derived from EM-type mantle source, while a few samples with negative εNd indicate that there was contamination in the magma evolution. Magma differentiation is demonstrated by variations of LREE and LILE from depletion to enrichment. Additionally, normalized REE patterns and trace elements showed that lavas from the Bikou volcanic terrane have similar characteristics to those of basalts in arc settings caused by subduction and collision. Analyses showed that the Bikou volcanic terrane is a volcanic arc. New evidence proved that the Hengdan Group, north of the Bikou arc, is a turbidite terrane filling a forearc basin. Consequently, the Bikou volcanic terrane and the Hengdan turbidite terrane construct an arc-basin system. New SHRIMP ages showed that this arc-basin system developed on the northern margin of the Yangtze craton in the Neoproterozoic (846-776 Ma), and this arc-basin system is in agreement with the tectonic processes of Rodinia in the Neoproterzoic.
文摘The process and result of fractal research of natural fault gouge collected from the active fault zone at northern edge of Western Qinling Mt. by using optical and electronic microscope technics were introduced in this paper. The fractal dimension of this fault gouge is D =2.594±0.122 (2 D plane D =1.594±0.122), and its upper limit of fractal dimension occurs at grain size at 9.6～19.2 mm. The study result shows that this gouge is fractal, and its characteristic displacement parameter of stick slip friction can be determined by upper limit of fractal dimension. The feature of protolith which affect fractality and the significance of gouge fractal to seismic fault changes are also disscussed in the paper.
