2002 Vol. 8, No. 1

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REGIONAL NORTH-SOUTH TRENDING TECTONIC BELT AND GLOBAL LONGITUDE TECTONIC SYSTEM
QIU Yuan-xi
2002, 8(1): 1-14.
Abstract (158) PDF (450KB)(9)
Abstract:
In this paper,following contents are expaunded:① distribution and features of the regional north-south tending tectonic belts in China and its adjacent area;② characters and genesis's types of them which are metioned above;③ genesis connection between the regional north-south trending tectonic belt and the global longitude tectonic system.
THE TRANSFORMATION PROCESS OF MESOZOIC-CENOZOIC TECTONIC REGIME IN THE NORTH OF NORTH CHINA
MA Yin-sheng, CUI Sheng-qin, ZAO Yue, ZENG Qing-li, WU Man-lu
2002, 8(1): 15-25.
Abstract (265) PDF (361KB)(19)
Abstract:
The north of North China is situated in the overlapping area of Paleo-asian ocean tectonic system and Pacific ocean tectonic system.The geological facts of the regional unconformity,the evolution of Mesozoic-Cenozoic fault and basin in the area show that there are five compression deformations in Mesozoic-Cenozoic period.They are the compressions in the end of Middle Triassic (the compression deformation before Laohugou Formation or Xingshikou Formation, ≥ 215Ma),Early Jurassic (that before Haifanggou Formation or Jiulongshan Formation ≥ 178Ma),Late Jurassic (that before Yixian Formation or Donglingtai Formation, ≥ 135Ma),Cretaceous (that before Paleogene,65Ma) and Paleogene(that before Neogene,25Ma).The five compressions are short in time.There are six periods of sedimentary basin formation occurring among the five time compressions,that is longer in time,more gently and extensional in tectonic activity.The six periods of sedimentary basin formation are Early and Middle Triassic,Late Triassic and Early Jurassic,Middle and Late Jurassic,Cretaceous,Paleogene,Neogene and Quaternary.There are obvious extensional characteristics in Middle and Late Jurassic,Cretaceous,Paleogene,Neogene and Quaternary.That is,the Mesozoic-Cenozoic tectonic evolution process in the north of North China is an alternatively developing process of intracontinental (or intraplate) basin sedimentation and compression deformation in the basement of North China Craton.Both of compression and extension are all important,the compression from strong to weak,the extension from weak to strong in the process,and extension stays longer than the compression in time.The compression and extension occurred alternatively,compression structures and extension structures developed alternatively in the structrure evoltion. The tectonic regime transformation process in the north of North China records the continental dynamic process of tectonic regime transformation from the convergent tectonic regime of Paleo-asian ocean tectonic system to the subducting tectonic regime of Pacific ocean tectonic system.
MANY CHANGEMENTS OF REGIONAL TECTONIC STRESS FIELDS OF MESOZOIC ERA IN SOUTH-EAST INNER MONGOLIA
FANG Shu, JU Wen-xin, ZHANG Ya-dun
2002, 8(1): 26-34.
Abstract (152) PDF (273KB)(7)
Abstract:
On the basis of a synthetical study of geological structural features in Mesozoic Era in Shuangjing area,Kalaaqin area and Wolitu area,Inner Mongolia,regional tectonic stress events are divided into seven times.Compressive tectonic stress and tensile tectonic stress fields took place alternately,showing that in the Earth occurred elastic movement.The history of the Earth is the course that its elastic movement is situated in the state of continual accommodation and the balance.During the course a variety of formations and structures was formed.Their dynamics is the ground-stress change caused by the Earth rotation.
THE PROPERTY AND EVOLUTION OF BOUNDARY FAULTS OF YITONG GRABEN
TONG Heng-mao
2002, 8(1): 35-42.
Abstract (165) PDF (259KB)(11)
Abstract:
Basins related to strike-slip faults are relatively complex,and mainly controlled by the property and evolution of boundary faults.In this paper,with application of structural analysis technology,the property and evolution of boundary faults are analyzed with geological,3D seismic,remote sensing,gravity and drilling data.The result shows that there are great differences between the two boundary faults on the property and the influence on basin formation and evolution.The northwest boundary fault is a strike-slip fault,controlling the basin formation and evolution,and experienced right-lateral transtension and tranpression in Eocene and Oligocene respectively,while the property of southeast boundary fault is different in different section and there is accommodation effect on basin subsidence.Both two boundary faults experienced compression in NWW-SEE direction in Neogene.
AGE AND SIGNIFICANCE OF VOLCANIC ROCK OF EARLY CRETACEOUS IN THE BAN GE-QIELICUO AREAA IN TIBET
CHEN Yu-lu, JIANG Yuan-sheng
2002, 8(1): 43-49.
Abstract (122) PDF (210KB)(7)
Abstract:
Our research results show that volcanic rock of Qushenla Formation is angular unconformity with Shamuluo Formation(J3-K1s),and it is covered in angular unconformity by Jingzhuoshang Formation(K1-2j),and its age of Rb-Sr radisotope is 126Ma.All evidence above show that volcanic rock of Qushenla Formation is syntectonic volcanic rock.As time is determined for volcanic rock of Qushenla Formation, it should separate out from Dongqiao ophiolite,it will put out new data for going deep into the research of the ophiolite,and it also should provide the evidence for orogenic event of Early Cretaceous in the Bangongcuo-Nujiang combine zone.
ENGINEERING ACTIVE FAULT INVESTIGATION AND ITS ASSESSMENT IN MAJOR ENGINEERING SELECTED SITE AND AREA
WU Yun-sheng, YI Ming-chu
2002, 8(1): 50-56.
Abstract (137) PDF (208KB)(13)
Abstract:
The "Engineering active fault" is paid a special attention to in study of active fault of major engineering selected site and area,and 3 criteria for the determination of engineering active fault are given:age of fault activity; earthquake activity of fault; current active rate of fault.The key gists on field investigation of engineering active fault and how to assess active fault are stated in the paper.
SHEAR VEIN SYSTEM IN JIAPIGOU GOLD BELT OF EASTERN SEGMENT OF NORTHERN MARGIN OF NORTH CHINA BLOCK
LIU Hong-tao, KE Xue-jin, WANG An-ping, AN Chun-tian, ZHANG Wan-jin
2002, 8(1): 57-70.
Abstract (236) PDF (556KB)(11)
Abstract:
The auriferous veins occurring in the Jiapigou Gold Belt are almost within shear zones of varied orientations and scales.Our study indicates that the regional NS-trending major shear zone had experienced a long-term right-lateral shearing,which resulted in the formation and progressive straining of the secondary shear folding and vein systems along the major shear zone.It is suggested that regional right-lateral shearing controls the general shapes and orientations of the veins,and progressive straining controls their internal structural details of vein systems.Based on these criterions,different vein types,such as R,R',D,T defined by Riedel shear shstem,could be identified within in the Jiapigou shear zone,which may have practical usefulness in mineral prediction and exploration.
GEOLOGICAL FEATURES OF THE LAPEIQUAN CUPPER DEPOSIT IN THE ALTYN TAGH, XINJIANG AND ITS ORE-GENESIS
CHEN Zheng-le, CHEN Xuan-hua, WANG Xiao feng, CHEN Bai-lin, YANG Feng, LI Xue-zhi, YANG Yi
2002, 8(1): 71-78.
Abstract (254) PDF (264KB)(23)
Abstract:
The Lapeiquan cupper deposit was newly found during our field investigation from 1997 to 1999 in Altyn Tagh, financely supported by national key project. This paper mainly focused on the discovery history and geological features of this deposit. Studies on the features of the ore bodies and the ore-controlling structures, combined with the analysis of the ore-forming elements, suggested that the formation of this deposit probably tightly related not only with the the volcanism in ocean bottom in early stage followed with hot water sedimentation, resulting in original cupper concentrating, but also with the re-activation of the Northern Altyn Tagh fault and Lapeiquan fault in second stage, leading to the migration and enrichment of the ore-forming elementws in favorable areas.
A THEORETICAL STUDY ON DUCTILE SHEARING BANDS BASED UPON STRAIN GRADIENT PLASTICITY THEORY
WANG Xue-bin, PAN Yi-shan, MA jin
2002, 8(1): 79-86.
Abstract (208) PDF (250KB)(8)
Abstract:
Many usual phenomena in the realm of geology can be seen as strain localization. Ductile shearing bands are shearing strain localization bands. In the first time, a theoretical study on ductile shearing bands based upon strain gradient plasticity theory is conducted in this paper. The regularities of the shear strain and the ratio of shear strain in the shearing bands are got. The theoretical formulas about the displacement of the shearing bands in the two perpendicular directions are obtained. Besides, the regularities of the volumetric strain and the ratio of volumetric strain in the shearing bands are also got. The strain localization causes volumetric strain localization and the localization of porosity factor. If the strain softening intensifies, the shear strain and the volumetric strain localization intensify. Along with the increase of absolute ratio of shear stress, the intensive extent of ratio of shear strain and volumetric strain intensifies.
ENVIRONMENTAL SIGNIFICANCE OF MAGNETIC SUSCEPTIBILITY AND GRAIN SIZE IN JINGERWA CORE, YANGYUAN BASIN
CHI Zhen-qing, MIN Long-rui, WANG Zhi-ming, LI Kai-qing
2002, 8(1): 87-96.
Abstract (137) PDF (293KB)(7)
Abstract:
Based on the characteristic of grain size, the evolution of Yangyuan lake was divided into swamp, shallow lake, shallow-coastal lake and coastal lake, including eight high-low cycles, during the past 200ka. The 50~100μm grain size, >50μm grain size and median are the valid indicators of environmental change in coastal lake. The fine particle, <5μm and 2~50μm grain size, is good porxy in shallow lake. The values of magnetic susceptibility in Yanyuan lake are controlled by the amount of chemical deposit, grain size and sedimentary facies. They have positive correlation with the content of coarse particles in shallow-coastal lake, and with the content of fine particles in shallow lake. They have no clear correlation in coastal salt lake.