The Yishu fault zone （mid-segment of the Tanlu fault zone） was formed in the Presinian. Periodic tectonic activities and strong seismic events have occurred along the fault zone. During the initial stage of the Cale...The Yishu fault zone （mid-segment of the Tanlu fault zone） was formed in the Presinian. Periodic tectonic activities and strong seismic events have occurred along the fault zone. During the initial stage of the Caledonian Movement, with the proceeding of the marine transgression from the Yishu paleo-channel to the western Shandong, uneven thick sediments, composed mainly of sand, mud and carbonates of littoral, lagoon, and neritic facies, were deposited in the Yishu fault zone and western Shandong, and constructed the bottom part of the Lower Cambrian consisting of the Liguan and Zhushadong formations. Through field observations and the lab-examinations, various paleoseismic records have been discovered in the Liguan Formation and the Zhushadong Formations of the Yishu fault zone and its vicinity, including some layers with syn-sedimentary deformation structures that were triggered by strong earthquakes （i.e. seismite, seismo-olistostrome, and seismo-turbidite）. Paleoseismic records developed in the Zhushadong Formation are mainly seismites with soft-sediment deformation structures, such as liquefied diapir, small liquefied-carbonate lime-mud volcano, liquefied vein, liquefied breccia, convolute deformation （seismic fold）, graded fault, soft siliceous vein, and deformation stromatolite, as well as seismites with brittle deformation structures of semiconsolidated sediments. Paleoseismic records preserved in the Liguan Formation are not only seismo-olistostrome with a slump fold, load structure, and ball-and-pillows, but also seismo-turbidite with convolution bedding, graded bedding and wavy-bedding. However, in the western Shandong area, the closer to the Yishu fault zone, the greater the thickness of the Liguan Formation and the Zhushadong Formation, the greater the number and type of layers with paleoseismic records, and the higher the earthquake intensity reflected by associations of seismic records. This evidence indicates that tectonic taphrogenesis accompanied by strong earthquake events occurred in the Yishu fault zone during the initial stage of the Caledonian Movement, which embodied the break-up of the Sino-Korean Plate along the Paleo-Tanlu fault zone at that time.展开更多
The Longquanzhan gold deposit hosted in granitic cataclasites with mylontization of the foot wall of the main Yishui-Tangtou fault. 3He/4He ratios in fluid inclusions range from 0. 14 to 0. 24 R/Ra,close to those of t...The Longquanzhan gold deposit hosted in granitic cataclasites with mylontization of the foot wall of the main Yishui-Tangtou fault. 3He/4He ratios in fluid inclusions range from 0. 14 to 0. 24 R/Ra,close to those of the crust-source helium. 40Ar/36Ar ratios were measured to be 289-1811, slightly higher than those of atmospheric argon. The results of analysis of helium and argon isotopes suggested that ore-forming fluids were derived chiefly from the crust. The δ18O values of fluid inclusions from vein quartz range from -1.78‰ to 4.07‰, and the δD values of the fluid inclusions vary between -74‰ and -77‰. The hydrogen and oxygen isotope data indicated that the ore-forming fluid for the Longquanzhan gold deposit had mixed with meteoric water in the process of mineralization. This is consistent with the conclusion from the helium and argon isotope data.展开更多
In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock...In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.展开更多
On the basis of comprehensive analyses of fault textures and geometry,the active methods,stress field,mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper.The results sh...On the basis of comprehensive analyses of fault textures and geometry,the active methods,stress field,mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper.The results show that the Yishu Fault Zone is a major mobile belt since the Quaternary.It consists of four major active faults with reverse dextral slip.Their active intensity increases eastwards and southwards.Fault-slip data from many active faults in the fault zone demonstrate that ENE-WSW compression predominated in the neotectonic period.Detailed field investigation shows that formation mechanism of shallow,active faults in the Yishu Fault Zone includes direct boundary fault reactivity,buried fault propagation,and reactivity of antithetic and truncating faults.In most cases,shallow,active faults in the fault zone are developed through direct reactivity or upward propagation of the previous four graben boundary faults.展开更多
Buried faults in Weifang city and surrounding areas are studied with geophysical surveys such as shallow seismic survey and electrical exploration, and verified with engineering drilling. Six main faults are detected ...Buried faults in Weifang city and surrounding areas are studied with geophysical surveys such as shallow seismic survey and electrical exploration, and verified with engineering drilling. Six main faults are detected including the Yishul-Tangtou fault, Tangwu-Gegou fault, Hanting fault and Weixian fault, etc. The latest active age is determined by OSL, TL and ESR dating techniques. No active fault has been found so far in the Weifang urban area. Our results provide a scientific basis for land use and urban planning.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.:41272066)the Scientific Research Key Project of Shandong Province’s Geoscience Forum(LDXHLT-2007-10-001)the China Geological Survey Project(Grant No.:1212010510509)
文摘The Yishu fault zone （mid-segment of the Tanlu fault zone） was formed in the Presinian. Periodic tectonic activities and strong seismic events have occurred along the fault zone. During the initial stage of the Caledonian Movement, with the proceeding of the marine transgression from the Yishu paleo-channel to the western Shandong, uneven thick sediments, composed mainly of sand, mud and carbonates of littoral, lagoon, and neritic facies, were deposited in the Yishu fault zone and western Shandong, and constructed the bottom part of the Lower Cambrian consisting of the Liguan and Zhushadong formations. Through field observations and the lab-examinations, various paleoseismic records have been discovered in the Liguan Formation and the Zhushadong Formations of the Yishu fault zone and its vicinity, including some layers with syn-sedimentary deformation structures that were triggered by strong earthquakes （i.e. seismite, seismo-olistostrome, and seismo-turbidite）. Paleoseismic records developed in the Zhushadong Formation are mainly seismites with soft-sediment deformation structures, such as liquefied diapir, small liquefied-carbonate lime-mud volcano, liquefied vein, liquefied breccia, convolute deformation （seismic fold）, graded fault, soft siliceous vein, and deformation stromatolite, as well as seismites with brittle deformation structures of semiconsolidated sediments. Paleoseismic records preserved in the Liguan Formation are not only seismo-olistostrome with a slump fold, load structure, and ball-and-pillows, but also seismo-turbidite with convolution bedding, graded bedding and wavy-bedding. However, in the western Shandong area, the closer to the Yishu fault zone, the greater the thickness of the Liguan Formation and the Zhushadong Formation, the greater the number and type of layers with paleoseismic records, and the higher the earthquake intensity reflected by associations of seismic records. This evidence indicates that tectonic taphrogenesis accompanied by strong earthquake events occurred in the Yishu fault zone during the initial stage of the Caledonian Movement, which embodied the break-up of the Sino-Korean Plate along the Paleo-Tanlu fault zone at that time.
基金This research is jointly granted by the National Natural Science Foundation of China （Grant No. 40272088）.
文摘The Longquanzhan gold deposit hosted in granitic cataclasites with mylontization of the foot wall of the main Yishui-Tangtou fault. 3He/4He ratios in fluid inclusions range from 0. 14 to 0. 24 R/Ra,close to those of the crust-source helium. 40Ar/36Ar ratios were measured to be 289-1811, slightly higher than those of atmospheric argon. The results of analysis of helium and argon isotopes suggested that ore-forming fluids were derived chiefly from the crust. The δ18O values of fluid inclusions from vein quartz range from -1.78‰ to 4.07‰, and the δD values of the fluid inclusions vary between -74‰ and -77‰. The hydrogen and oxygen isotope data indicated that the ore-forming fluid for the Longquanzhan gold deposit had mixed with meteoric water in the process of mineralization. This is consistent with the conclusion from the helium and argon isotope data.
文摘In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.
基金supported by National Natural Science Foundation of China(Grant No.91214301)Geological Survey of China(Grant No.1212011120104)
文摘On the basis of comprehensive analyses of fault textures and geometry,the active methods,stress field,mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper.The results show that the Yishu Fault Zone is a major mobile belt since the Quaternary.It consists of four major active faults with reverse dextral slip.Their active intensity increases eastwards and southwards.Fault-slip data from many active faults in the fault zone demonstrate that ENE-WSW compression predominated in the neotectonic period.Detailed field investigation shows that formation mechanism of shallow,active faults in the Yishu Fault Zone includes direct boundary fault reactivity,buried fault propagation,and reactivity of antithetic and truncating faults.In most cases,shallow,active faults in the fault zone are developed through direct reactivity or upward propagation of the previous four graben boundary faults.
基金Key Projects of Earthquake Prevention and Disasters Mitigationin the 10th "Five-Year Plan" of Shandong Province (SD10503)
文摘Buried faults in Weifang city and surrounding areas are studied with geophysical surveys such as shallow seismic survey and electrical exploration, and verified with engineering drilling. Six main faults are detected including the Yishul-Tangtou fault, Tangwu-Gegou fault, Hanting fault and Weixian fault, etc. The latest active age is determined by OSL, TL and ESR dating techniques. No active fault has been found so far in the Weifang urban area. Our results provide a scientific basis for land use and urban planning.
