During an excavation survey to the Daijiayuan vestige of the Western Zhou Dynasty-Late Spring and Autumn Period at Huoshan in Western Anhui,a ground crack related to tectonic movement and filled with silty fine sand w...During an excavation survey to the Daijiayuan vestige of the Western Zhou Dynasty-Late Spring and Autumn Period at Huoshan in Western Anhui,a ground crack related to tectonic movement and filled with silty fine sand was found. This phenomenon was initially confirmed to be due to seismic liquefaction. Many microscopic seismic relics,such as load structure,flow structure,cutoff plane and flotation of organic matter were found in the directional microscopic analysis of deformation. These discoveries and cognitions prove that there were two earthquake events taking place in the Western Zhou Dynasty-Late Spring and Autumn Period in this area. Above-mentioned works enrich and develop the research methods to identify prehistoric earthquake event in eastern China area to a certain extent.展开更多
The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlo...The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlou gold deposits and the E-W and NE-striking ductile shear zones were formed during each event.The E-W-striking ductile shear zone,accompanied by compressional and dextral shear slip,was shear-cut by the NE-striking shear zones,accompanied by compressional-sinistral shear slip and sinistral-normal shear slip,successively.An E-W-striking ductile shear zone developed at a deeper tectonic level and at middle- to high-temperatures,accompanied by abundant microstructures,including microlayering between a polycrystal quartz belt and mica,and quartz deformation was depended on cylinder(10-10) or <c> glide.The development of an E-W-striking shear zone can be seen as a tectonic pattern in the region of the Paishanlou gold deposits of the collision between the Mongolian tectonic belt and the North Archean Craton from Suolun to the Linxi suture zone during the Indosinian.The NE-striking ductile shear zone developed approximately 160 Ma during the early Yianshanian at middle to shallow tectonic levels and at middle- to low-temperatures,accompanied by typical microstructures,including polycrystal quartz aggregation and quartz subgrain rotation recrystallization,etc.,and quartz deformation was depended on prismatic(1011) glide.The last ductile shear event around the NE-striking shear zone developed at low temperatures and shallow tectonic levels,yielding to a pre-existing NE-striking shear zone,accompanied by abundant microstructures,including low-temperature quartz grain boundary migration and bulging recrystallization.The last ductile shear movement may be related to lithosphere thinning and the destruction of the North China Craton from approximately 130-120 Ma,and this shear event resulted directly in the mineralization in the Paishanlou region.展开更多
基金This paper is a contribution to Scientific Research Special Project of the Earthquake Calling (200808064)Science and Technology Tackle Key Problem Plan Project of Anhui Province(08010302204)Natural Science Fund of Anhui Province(070415222),China
文摘During an excavation survey to the Daijiayuan vestige of the Western Zhou Dynasty-Late Spring and Autumn Period at Huoshan in Western Anhui,a ground crack related to tectonic movement and filled with silty fine sand was found. This phenomenon was initially confirmed to be due to seismic liquefaction. Many microscopic seismic relics,such as load structure,flow structure,cutoff plane and flotation of organic matter were found in the directional microscopic analysis of deformation. These discoveries and cognitions prove that there were two earthquake events taking place in the Western Zhou Dynasty-Late Spring and Autumn Period in this area. Above-mentioned works enrich and develop the research methods to identify prehistoric earthquake event in eastern China area to a certain extent.
基金supported by National Crisis Mine Program(Grant No.20089931)National Natural Science Foundation of China(Grant Nos.90814006,91214301,41172089)Foundation of Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Minerals(Grant No.DMSM201005)
文摘The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlou gold deposits and the E-W and NE-striking ductile shear zones were formed during each event.The E-W-striking ductile shear zone,accompanied by compressional and dextral shear slip,was shear-cut by the NE-striking shear zones,accompanied by compressional-sinistral shear slip and sinistral-normal shear slip,successively.An E-W-striking ductile shear zone developed at a deeper tectonic level and at middle- to high-temperatures,accompanied by abundant microstructures,including microlayering between a polycrystal quartz belt and mica,and quartz deformation was depended on cylinder(10-10) or <c> glide.The development of an E-W-striking shear zone can be seen as a tectonic pattern in the region of the Paishanlou gold deposits of the collision between the Mongolian tectonic belt and the North Archean Craton from Suolun to the Linxi suture zone during the Indosinian.The NE-striking ductile shear zone developed approximately 160 Ma during the early Yianshanian at middle to shallow tectonic levels and at middle- to low-temperatures,accompanied by typical microstructures,including polycrystal quartz aggregation and quartz subgrain rotation recrystallization,etc.,and quartz deformation was depended on prismatic(1011) glide.The last ductile shear event around the NE-striking shear zone developed at low temperatures and shallow tectonic levels,yielding to a pre-existing NE-striking shear zone,accompanied by abundant microstructures,including low-temperature quartz grain boundary migration and bulging recrystallization.The last ductile shear movement may be related to lithosphere thinning and the destruction of the North China Craton from approximately 130-120 Ma,and this shear event resulted directly in the mineralization in the Paishanlou region.
