2002 Vol. 8, No. 2

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ACTIVE TECTONICS AND GEOLOGICAL HAZARDS OF THE XIDATAN-LAHSA SECTION ALONG QINGHAI-TIBET RAILWAY AND THE ASSESSMENT ON ITS ENGINEERING GEOLOGY
WU Yun-sheng, YI Ming-chu
2002, 8(2): 97-135.
Abstract (210) PDF (1385KB)(10)
Abstract:
Based on the field survey for hydrogeology and engineering geology along the Qinghai-Tibet Railway made in 1975~1977,consulting the results obtained recently by the other people,the active tectonics,geological hazards and the engineering assessment on the Qinghai-Tibet Railway are expounded in the paper.The relationship between active tectonics and modern and fossil earthquakes,the relationship between active structural belt and earthquakes structural belt,dating of active faults and their active rate,the relationship between active fault and earthquake surface rupture,the earthquake period in the main earthquake structural belts are placed emphasis on. According to above mentioned active faults and earthquakes,in consideration of the geological hazards,the 4 types of section of engineering geology of the Xidatan-Lahsa Section along Qinghai-Tibet Railway are given in the paper.They are ①good;②general;③bad;④extremely bad.
COMPARISON OF GEOSTRESS MEASUREMENT BETWEEN AE METHOD WITH STRESS RELIEF BY OVERCORING IN SILIN POWER STATION,GUIZHOU PROVINCE
WANG Xi-hai
2002, 8(2): 136-140.
Abstract (216) PDF (168KB)(6)
Abstract:
In order to study the stress condition of the underground area at Silin power station,Guizhou Province,which will be constructed,the geostress measurements by acoustic emission(AE) and stress relief methods are carried out here.The results show that the magnitude of maximum principal stress by AE is 15.9MPa,and the direction of the maximum principal stress is NE 70.9° and its magnitude 16.03 MPa by overcoring,suggesting that at the same position the results obtained by two methods are very similar and believable.
PHYSICAL EXPERIMENTS ON CONTINENT EXTENSIONAL STRUCTURES
ZHOU Yong-sheng, LI Jian-guo, WANG Sheng-zu, ZHANG Liu
2002, 8(2): 141-148.
Abstract (139) PDF (302KB)(9)
Abstract:
According to the theory that plastic flow of the lower layer (including lower crust and upper mantle lithosphere) controls upper layer (upper crust) deformation in the multi-layer lithosphere, the paper studies the physical experiments of extensional structures adopted ductile/brittle double-layers model. The experiment results show that the lower ductile layer whose flow speed is larger than that of upper brittle layer. Controlled by compressed and free flow, the areas of model deformation can be divided into three parts:extensional region, transition region and compressive region. Among all, the main part is extensional region where "graben-horst" is characterized by major extensional structures. The displacements of mark points on upper face of models show that the deformation quantities of upper brittle layer are focus on the parts of faults. In addition, the passive uplifting of lower ductile layer is found at faults region of upper brittle layer in our models.
FABRIC FEATURES OF QUARTZ AND STRAIN ANALYSIS ON GNEISSIC GRANITE PLUTON IN SHUANGHE, DABIE
LIU Qiang, YANG Kun-guang
2002, 8(2): 149-155.
Abstract (195) PDF (272KB)(8)
Abstract:
Systematic measurements are made respectively on the quartz C-axis fabric, biotite (001) cleavage fabric and 3-D strain analysis by quartz for gneissic granite in Shuanghe, Dabie. The results show that Shuanghe gneissic granite pluton is characterized by compression during its emplacement and the subsequent evolution, and it has been compressed along NW-SE and NE-SW orientation, with the NW-SE orientation more strongly compressed. which develops the fundamental structure pattern of the pluton. Combining with the regional stress fields, the Shuanghe pluton recorded the Early Triassic and Early Jurassic NW-SE compression, Middle Jurassic and later NE-SW compression. Stress fields show a clockwise change of compression directions.
STABLE ISOTOPE CHARACTERISTICS OF THE JIN CHANG GOU LIAN GOLD DEPOSIT IN INNER MONGOLIA AND ITS ORIGIN
ZHANG Chang-chun, WANG Shi-qi, ZHANG Tao
2002, 8(2): 156-164.
Abstract (219) PDF (328KB)(17)
Abstract:
The research on stable isotope is very important and useful for analyzing the origin of deposits.The H,O,C and S isotope of quartz mineral vein in gold deposit of Jinchanggouliang in Inner Mongolia inherits the characteristics of metamorphic rocks and magmatic rocks in the area.Their compositions of hydrogen,oxygen,carbon and sulphur isotope have the similar traits and the changeable range of δ18OH2O and δD isotopic value is also similar.These features indicate that the Archean metamorphic rock in this area is the source of ore material of gold deposit,and the magmatized hydrothermal made the source of the ore material active many times and the ore materials gradually gathered in the suitable tectonic fractures and eventually formed the gold deposit in the late Yanshanian stage.So the gold deposit is a magma-hydrothermal-type ore deposit associated with multiple mineralization.
THE ANALYSIS ON THE DEVELOPMENT OF ALLUVIAL AND LAKE LANDFORM IN FEN RIVER DRAINAGE BASINS
HU Xiao-meng, FU Jian-li, LI You-li, MA Zhi-zheng, YANG Jing-chun
2002, 8(2): 165-172.
Abstract (194) PDF (243KB)(11)
Abstract:
It has been unclear how the landform in Fen River drainage developed in Quaternary until now.This paper reveals that there exist three alluvial or lake terraces in the edges of Fen River drainage basins since the middle-late Pleistocene.There are a succession of loess-paleosol unites accumulated on these terraces.The ages of these terraces can be inferred by studying the stratigraphy of the overlying loess/paleosol,particularly the superjacent loess/paleosol on it.The facts acquired in the fieldwork show that three terraces formed when paleosols began to develop,whereas the paleoclimate became warm and wet.Using paleomagnetism,loess/paleosol series,thermoluminescene to date the terraces,we find that these terraces emerged in consistent with the formation of S8,S5 and S1 in time,while the basins were experiencing three low-stands of lake-level.The ages of three terraces in Fen River drainage basins are about 0.76MaB.P.,0.55MaB.P.and 0.13MaB.P.respectively.Taking all the facts into account,we draw the conclusions:1) It is three teconic uplifts that results in the formation of three alluvial of lake terraces,or three low-stands of lake-level in the drainage.2) It seems reasonable that the thee uplifts of Tibet plateau caused the changes of Fe River drainage basins.
PILOT STUDY ON THE COLLAPSES AND LANDSLIDES OF THE THREE GROGE RESERVIOR OF THE CHANGJIANG RIVER
YANG Dy-yuan, LI Xu-sheng, FENG Li-mei, JIANG Hong-tao
2002, 8(2): 173-178.
Abstract (124) PDF (180KB)(7)
Abstract:
There are 134 large-scale accumulations of the collapsed ladnslide along the bank slope of the Three-Gorge reservoir.Their formation related to the depp-dissection of the mainstream of the Changjiang River in the Three-Gorge area.The steep bank-slopes cracked and the fissured rocks collapsed.The collapsing and landslide lead to power release and make the bank-slope tend to be stable.After the Three-Gorge reservoir will have completed,the vermicular fissure rocks would be most dangerous.So we should pay attention to the concretion of some slippage-surface and clear up unstable rocks on the bank-slope.
DESTROY CHARACTER AND COULOMB CRITERION OF ROCK SPECIMEN IN PSEUDO-TRIAXIAL COMPRESSION
YOU Ming-qing
2002, 8(2): 179-185.
Abstract (177) PDF (298KB)(12)
Abstract:
The relation is linear between axial supporting capacity of specimen and confining pressure,but the crack angle of specimen can not be given by Coulomb criterion.The axial supporting capacity of sections with angle around 45°+φ/2 is nearly the same based on the concept of cohesion and internal friction.So the real crack face usually resulted from the bedding and defect in the specimen.The failure of specimen for sandstone that is made of clearly particles is usually diagonal crack with part cone,but one for coal and limestone which is made of tiny particles is plane crack.For specimen with the ratio 2 of length to diameter,the plane with angle 45°+φ/2 will connect the upper and lower face of the specimen,not the surround face when the internal friction angle is larger than 36.87° or the influencing coefficient of confining pressure on the strength is larger than 4.And it is difficult to analyze the supporting character of specimen with Coulomb criterion.
RETROSPECT AND PROSPECT OF FIFTY YEARS MINERAL DEPOSIT IN CHINA
ZHANG Hui-xu, LU Chun-rong
2002, 8(2): 186-192.
Abstract (140) PDF (185KB)(8)
Abstract:
This paper is a brief summary of the development of the mineral deposits in China. Since the foundation of the People's Republic of China, much progress has been achieved in the mineral exploration and exploitation, regional geological mapping, and geological science researches. The authors suggest that more studies should be done on the metallogenic theories, exploration methods, and regional and global metallogenic regularities in future, and more attention should be paid to the researches on mineral deposits in middle and western China, new types of mineral deposits, and mineral deposits in ocean.