2000 Vol. 6, No. 1

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2000, 6(1): 1-3.
Abstract (98) PDF (87KB)(5)
Abstract:
ASTHENOSPHERIC STATIC PUSH AND ITS IMPLICATIONS TO PLATE DYNAMICS
WEI Dong-ping
2000, 6(1): 4-14.
Abstract (184) PDF (566KB)(6)
Abstract:
Lithospheric plates are exerted by a fluid pressure,since they immediately overlie the asthenosphere. We define this fluid pressure as Asthenospheric Static Push (ASP). For a oceanic plate,there is no difference of ASP and the traditional ridge push force. Assuming a decoupling of horizontal components and vertical component of the intraplate stresses,we have the two horizontal components of the intraplate stresses due to the ASP and other forces using the 2-D spherical finite element modeling,and the vertical component by isostasy. A differential stress field is obtained by subtracting the vertical component of stresses from the horizontal components.
By introducing the concept of ASP,it is convenient to use the observed stress regimes as constraints to study the problems of plate dynamics and to explain the observed complex stress patterns in the transition regions between the sea and the continent and those in the anomalous gravity regions.
A DYNAMICAL MODEL FOR CONTINENTAL DRIFT AND EXPERIMENTAL SIMULATED RESULTS
QIAN Wei-hong
2000, 6(1): 15-21.
Abstract (203) PDF (251KB)(12)
Abstract:
In this paper, a simple dynamical model for simulating continental drift is formulated based on the angular momentum exchange between inner solid core and outer liquid core during the early stage of the Earth formation. The drift of ideal continental plate as well as the formation of mountains and islands are simulated by applying the model. The results of experimental simulation can explain to some extent the distribution of earth's surface features.
PHYSICAL EXPERIMENTS ON MANTLE UPLIFTING AND CONTINENT EXTENSION
ZHOU Yong-sheng, LI Jian-guo, WANG Sheng-zu
2000, 6(1): 22-32.
Abstract (136) PDF (495KB)(5)
Abstract:
In the present paper,an experiment of the mantle uplifting and lateral extension is conducted under three different boundary conditions using a ductile/brittle double-layer physical model. The experiment results show that when the model is fixed on two sides,uplifting could cause stretch and faults with very small lateral flow. When the model are half or completely open,uplifting could cause very large extension,mainly in the direction of the faults early produced. Evidently the faults early formed in uplifting would create a favourable condition for the subsequent extension and the uplifting would accelerate the flow of ductile layer towards the direction of open boundary to promote further extension. In addition,some passive updoming of lower ductile layer is found where faults occurin the upper brittle layer in our models. It is therefore clear that no large extension should arise from mantle uplifting without favourable boundary conditions.
ON THE METHOD OF TECTONIC SIEVING
QIU Yuan-xi
2000, 6(1): 33-43.
Abstract (85) PDF (409KB)(10)
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The method of tectonic sieving was developed by J.S. Lee(LI Si-guang) in 1942.It is to sort out tectonic structures of different phases from a complex of tectonic features of all phases,including formational and deformational ones.
The first and foremost step is to decide the time sequence of each phase of the structures.This paper systemetically gives the traditional geological methods and other lately developed methods(e.g. isotopic dating method,paleomagnetism method,remote sensing geology method,geochemical and geophycal methods,as well as the method of regional correlation) in determining the time sequence of the deformations.
In this paper the principles,methods and steps to discriminate the different phases of orsuperlarge compound deformations (e.g.compound orogenic belts,compound tectonic systems,compound blocks,compound tectonic domains,and the global compound tectonics) are also outlined.
THREE DIFFERENT TYPES OF PHANEROZOIC OROGENESIS OF NORTHERN BORDER AREA OF NORTH CHINA CRATON
WU Zhen-han
2000, 6(1): 44-51.
Abstract (167) PDF (367KB)(10)
Abstract:
Three different types of Phanerozoic orogenesis are identified in the northern border area of North China Craton.In the Paleozoic era,the northern border area of North China Craton belonged to the tectonic domain of south peri-Paleozoic ocean and is characterized by subduction-collision orogenesis,leading to the formation of EW-to ENE-trending folds,thrust faults,nappes and ductile shear zones etc.In the Mesozoic era,it was located in the interior of east Eurasia continent and belonged to west peri-Pacific tectonic domain and underwent intracontinental compression orogenesis separated by 6 periods of regional unconformity,more than 5 periods of regional volcanic eruption and plutonism,and strong compressional deformation,producing E-W-,NE-, and NNE-trending folds,thrust faults,nappes,ductile shear zones in the whole area,and structural systems of solid state plastic flow and ring structures in some local areas due to northwestward to westward increasing compression arising mainly from the subduction of the Pacific plate.In the Cenozoic era,it experienced intracontinental extensional orogenesis marked by widespread rifting and extensional faulting with weak folding,giving rise eventually to the present-day tectonogeomorphic features of basins and ranges.This regional extension is believed to be caused by the westward motion of Eurasia plate from the subduction zone.
The transfer of these orogenesis types occurred respectively in the early-middle Triassic and late Cretaceous.
THE CHARACTERISTIC FEATURES OF LATE HERCYNIAN-INDOSINIAN TECTONIC ACTIVITIES OF THE LEFT SONID BANNER AREA,INNER MONGOL AUTONOMOUS REGION
GAO De-zhen
2000, 6(1): 52-58.
Abstract (121) PDF (247KB)(7)
Abstract:
The region of Left Sonid Banner of Inner Mongolia is located in the Xing-Meng fold zone of the northern rim of the North China Plate.A comparative study of the shapes of the ENE-trending folds,the causative axial loading and the resulting shortening as well as the geometry of the faults and ductile shear zone has been made.And the strain sequence is thereby established.As a result there has been distinguished Indosinian tectonic features produced on the foundation of the late Hercynian strucures by progressive deformation under the same ensueing stress field.
AN ANALYSIS OF THE ACTIVITY OF THE SHENZHEN FAULT ZONE IN THE TUNNEL ENGINEERING IN SHENZHEN MUNICIPALITY
SUN Ye, ZHAO Xian, XU Xiang-ying, LIU Ting, TAN Cheng-xuan, YANG Geng, YAN Quan-ren, YE Wei-guo, YANG Shi-ping, HE Guang-hai, LI Shu-fen, SUN Dong-xun
2000, 6(1): 59-68.
Abstract (153) PDF (349KB)(9)
Abstract:
After an analysis of the evolution of the activity of the Shenzhen fault zone numerical simulations of both plane-and 3-D present tectonic stress fields are made to calculate quantitatively the angle enclosed between the maximum horizontal principal compressive stress direction and the tunnel axis at different sections of the Shenzhen water diversion tunnel.The displacements of the faults at the intersections between them and the tunnel and the possible stress states of four deep buried sectors of the tunnel are also obtained by the modeling.The results will provide data for the design of the planned tunnel construction.
ON THE FORMATION OF THE BANGONG-CO-NUJIANG FAULT ZONE
LAO Xiong
2000, 6(1): 69-76.
Abstract (253) PDF (276KB)(10)
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The Bangong-Co-Nujiang fault zone consists of four arcuate faults.The zone was subsided successively from north to south to receive sediments derived from the two immediately adjoining uplifted flanks in the late Triassic to the Cretaceous.It was the results of undulated earth's movement.
FINITE STRAIN STUDY ON PALEOZOIC STRUCTURES IN CHENGDAO REGION
DAI Jun-sheng, MENG Zhao-ping
2000, 6(1): 77-83.
Abstract (96) PDF (248KB)(5)
Abstract:
This paper applies the theory of finite strain to the study of Paleozoic structures in Chengdao region.A displacement function is established by resolving the straining processes based on the analysis of the basic tectonic features and their evolution.The E-W,N-S and vertical components of the displacement vectors of points on the bottom surface of the Paleozoic are calculated so as to give a quantitative description of the deformations.The correlation between the displacement components and the periods of tectonic activities is analyzed.
STUDIES ON THE FEATURES OF THE HOLBAOJINAO QUARTERNARY SALT LAKE IN MID-NORTH ERDOS BASIN
TIAN Xiao-xian
2000, 6(1): 84-89,94.
Abstract (131) PDF (232KB)(5)
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The present paper discusses the characteristics of the Holcene Holbojinao salt lake deposits in Mid-north Erodos Basin with a full description of the chemical composition,salinity,type of water chemistry and pH value of the surface brine.A study of the sedimentary regime salinity variation,and the composition of the lake deposits as well as the mineralization conditions has been made.
GRANITE HOODOOS(ARSIHATY)——A NEW GEOMORPHIC LANDSCAPE
QIAN Fang, HE Pei-yuan, HAO Zhi
2000, 6(1): 90-94,99.
Abstract (248) PDF (389KB)(11)
Abstract:
A landscape of granite hoodoos can be seen well developed in Beidashan of the Daixingainling mountain range in Keshiketeng county,Inner Mongol Autonomous Region.Granite hoodoos are formed by freezing,weathering,aeolation of the jointss and crackes developed in the granite.There can be distinguished four stages in their formation:glaciation,freezing weathering,aeolation and planation.It is a new type of the granite landforms,often occurring in an expense of land several hundred metres long,decades of metres wide 5~20 m high,with some individual pillars standing as high as over 20 m.They are very specular,grotesque,sometimes one linked with another to form a fantastic screen.It is forming an attractive item of tourism geology.
2000, 6(1): 95-96.
Abstract (116) PDF (31KB)(7)
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