1995 Vol. 1, No. 3

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AN ANALYSIS OF PRESENT-DAY REGIONAL TECTONIC STRESS FIELD AND CRUSTAL MOVEMENT TREND IN CHINA
Sun Ye, Tan Chengxuan
1995, 1(3): 1-12.
Abstract (304) PDF (884KB)(41)
Abstract:
Tectonic stress field is here extended to cover, in addition, crustal defromation field, fault displacement field, deep crustal structures, as well as the factors that may have some influence on the stress field such as structural conditions, geophysical and geochemical conditions and properties of the crustal materials.All these are so closely interrelated that they form a system giving different responses to a crustal movement. Only an integrated, systematic analysis of the tectonic stress field can the trend of the present-day crustal movement be brought to light.Otherwise, what we may have achieved will be only partial expression of the movement.This paper approaches the problem in two steps:a respective analysis and zonation of the various fields mentioned above is first made which is followed by a discussion of the crustal movement trend in China.The results add some new data and knowledge to the present-day crustal movement in China, which may prove useful for the planning and construction of national economy and for disaster reduction and prevention.
MESOZOIC TECTONIC STRESS FIELD IN THE YANSHAN MOUNTAIN REGION, WEST OF BEIJING
Shen Shumin, Feng Xiangyany
1995, 1(3): 13-22.
Abstract (186) PDF (773KB)(30)
Abstract:
The present landscape of the Yanshan mountainous region was sculptured from rocks that had been formed and deformed during the past long geologic period of time.The region, as characterized by the sedimentary formations and structures had undergone rather weak tectonic movement from middle-late Proterozic to Paleozoic, represented by the dominating role of the basement faults. The major orogeny occurred here in the Mesozoic and Cenozoic, during which the rocks were strongly compressed to form linear folds and nappes.In this paper, emphasis is placed on the reconstruction of the Mesozoic stress field and deflection field of the region so as to restore the mechanics process and the movement leading to the deformation in Mesozoic and Cenozoic times.
A NOTE ON THE COMPILATION OF MAP OF CRUSTAL STABILITY ZONATION IN CHINA
Li Xiao, Yi Mingchu, Wang Lianqing, Qiao Zijing
1995, 1(3): 23-29.
Abstract (152) PDF (486KB)(29)
Abstract:
Following the idea of "Safety Island" the crustal stability zonation map of China (1:5000000)is first compiled on a grid basis in different steps using fuzzy synthetic judgement, image recognition and an expert appraisal system.
A strong earthquake and another moderately strong shock have recently been reported to occur in Menglian county of Yunnan province and Yongdeng county of Gansu province indicated as unstable and fairly unstable regions on the map. It is therefore emphasized that a tentative quantification of the evaluation of regional crustal stability proves significant in practical applications.
COUNTERCLOCKWISE ROTATION OF SOUTH CHINA BLOCK EAST OF THE TAN-LU FAULT ZONE
Xing Lisheng, Li Zhongjian, Wang Xiaofeng, Chen Bailin, Zhang Qing, Chen Xuanhua
1995, 1(3): 31-37.
Abstract (198) PDF (481KB)(17)
Abstract:
A paleomagnetic study of the tectonic deformation undergone by the middle Triassic to early Cretaceous rocks from Laiyang, Liuan, Lujiang-Zongyang and Huaining basins, on both sides of the Tan-Lu fault zone since Mesozoic was carried out.Most of the directions of isolated characteristic magnetization passed fold or reversal tests.From areas mentioned above, ten reliable paleomagnetic poles for early Cretaceous to middle Triassic were obtained.
Comparison of the results with the APWP for South China Block suggests no considerably great relative horizontal displacement since at least middle Jurassic between the two sides of Tan-Lu fault zone but a counterclockwise (CCW) rotation of 15°-25° on the part of South China Block to the east of the Tan-Lu fault zone.The rotation mainly occurred in late Jurassic and may be attributed to the collision between the North and South China Block andthe compression by the Pacific Plate.
A NEW VIEWPOINT ON THE EVOLUTION STAGES OF QINLING OROGENIC BELT
Yang Zhihua, Su Shengrui
1995, 1(3): 38-45.
Abstract (240) PDF (619KB)(31)
Abstract:
The development and evolution of Qinling-Dabie orogenic belt is quite similar to the formation and splitting of the Pangea since Phanerozoic eon.The China paleo-plates splitted into North China and Yangtze paleo-plates and Qinling limited ocean basin in middleOrdovician Epoch.The North China and Yangtze paleo-plates coalesced to form China plate and middle Qinling orogenic belt in Carboniferous-Permian times. Since the Mosozoic the newly-formed China plate has once more become splitted.The granites in Qinling-Dabie orogenic belt formed since Mesozoic are the result of splitting rather than the sysmbol of plate convergence and collision.The eclogites containing coesite and diamond and the ultrabasic rocks were brought to eatrh's surface by deep sheets moving upward along the strike of the orogenic belt.
NEW EVIDENCE FOR CORRELATION BETWEEN GLOBAL TECTONIC MOVEMENT AND EARTH'S ROTATION
Wu Zhenhan
1995, 1(3): 46-54.
Abstract (115) PDF (620KB)(30)
Abstract:
In the last 20 years, scientists in different fields have observed and studied the horizontal motion of the diffferent layers of the earth, including the hydrosphere, lithosphere, asthenosphere, lower mantle, core-mantle boundarylayer and outer core resorting to different means and methds.The velocity maps produced for the horizontal motion of each layer from the data accumulated show some new evidence for the correlation between the global tectonic movement and the earth's rotation.
A comparison of the horizontal velocity fields of each layer indicates high similarities;there is a marked westward movement of each layer at middle-low latitudes and some eastward back flow at high latitudes.The horizontal velocity of each layer is statistically related to latitude(φ), the nearer to the equator, the greater the velocity.The steady horizontal velocity for the lithosphere reaches the maximum at φ=0° and φ=35°.These results suggest a close relation between the horizontal motion of the earth and its rotation.
KINEMATIC VORTICITY, POLAR MOHR CIRCLE AND THIER APPLICATION IN QUANTITATIVE ANALYSIS OF GENERAL SHEAR ZONES
Zhang Jinjiang, Zheng Yadong
1995, 1(3): 55-64.
Abstract (164) PDF (605KB)(34)
Abstract:
Most of shear zones in nature are results of co-actions of simple and pure shears and called general shear zones.A general shear zone can be narrowed or broadened. The relationship between simple and pure shears, and the change of shear zones in thickness can be analysed quantitatively by the method of kinematic vorticity (WK) and polar Mohr circle. The kinematic vorticity is a measure of the non-coaxiality in progressive deformation history and, therefore, is the ratio of the pure shear to simple shear of a general shear zone.
WK=cos (v), where v is the angle between the two eigenvectors in a shear zone. For a pure shear, v=90°, WK=0;for a simple shear, v=0°, WK=1;and for a general shear, 0° < v < 90°, 0 < WK < 1. A polar Mohr circle, which can be constructed with some more practical methods presented by this paper f provides a convenient and feasible method for measuring v.
Once a polar Mohr circle is constructed, the angle (v), kinematic vorticity (WK), ratio of the strain-rates (ε/γ)and the change of thickness of a shear zone can be obtained.
NOTE ON SHUIYU COMPOUNDING VORTEX STRUCTURE IN WEST MOUNTAINS, BEIJING
Du Zitu, Li Dongxu, Gao Dezhen
1995, 1(3): 65-71.
Abstract (159) PDF (488KB)(22)
Abstract:
There are three arcuate faults that surround Shuiyu in the form of a turbine in the West Mountains, Beijing, forming a vortex structure. These faults are characteristic of compresso-shear structural planes, and their arrangement indicates a counterclockwise rotation of the outer side relative to the inner side of the structure. By an analysis of the compounding relation of the structural elemonts present in the area, we find that the vortical surfaces of the vortex structure were produced by trailing the preexisting structural planes of other systems. So we come to the conclusion that it was derived from a N-S shearing responsible for the Neocathaysian structural system during the Yanshanian movement.
ON FEATURES OF THE MAJOR TECTONIC BELTS OF THE SHANCHENG POLYMETALLIC ORE-FORMING AREA, JIANGXI PROVINCE AND THEIR CONTROL OF ROCKS AND MINERALS
Zhu Dagang, Liu Xun
1995, 1(3): 72-81.
Abstract (224) PDF (700KB)(14)
Abstract:
A study of the major tectonic belts in the Shancheng polymetallic ore-forming area has been made mainly by an analysis of the structural features, the tectonite, the deformation and phase changes of the minerals and rocks, the tectonogeochemistry, the X-ray petrofabrics and the dynamics.The basic features of these zones, the change of their mechanical properties and their control of rocks and minerals are discussed.As a result, an ore prognosis is attempted.The authors point out that the lambda-type structure composed of the Shafangyuan fault and the Nanguashan-Lengshuikeng fault is the major ore-controlling structure and that the west-northwest structure is an important host structure in the area along which the presently explored ore bodies are distributed.
EVOLUTION OF THE ORE-CONTROLLING STRUCTURES OF ERDAODIANZI GOLD-DEPOSIT IN JILIN PROVINCE
Wang Yiqing, Lu Jiansheng, Yang Yanchen, Li Bile, Gao You
1995, 1(3): 82-88.
Abstract (309) PDF (509KB)(30)
Abstract:
In this paper, a further study of the structures controlling the Erdaodianzi Golddeposit was conducted.The three arcuaete structural belts that compose the Erdaodianzi brush structure are considered as the major structures that controlled the gold-deposits.The general distribution of the gold deposits was restricted to the early compresso-shear faults and the single ore bodies controlled by the tenso-shear brush structure.
THE ORIGIN AND DEVELOPMENT OF THOUGHT OF BIOMIGRATION
Xu Bingchuan
1995, 1(3): 89-96.
Abstract (200) PDF (646KB)(20)
Abstract:
The idea of biomigration was first proposed by Darwin (1859).He considered that any one species of organisms had only a single center of creation.So far as the environment allows it would migrate from the center to areas as far as possible. Adams' concept of center of dispersal (1902), Matthew's theory of new center-old margin (1915), Willis' age-area hypothesis (1922) represented discussions on the idea of biomigration in those days. But after Buckman's plane of migration came out (1922), the point of view that migration was unknowable cast a shadow on the field of science. From then on the study of biomigration had been almost at a standstill for nearly fifty years. During the date shrouded in Buckman's mist, J.S. Lee (1927, 1928) was one of few men who still held Darwin's idea of migration. More and more facts showed the vitality of Darwin's idea. Frequent occurrences of fossil diachronism and a wealth of new biogeographical materials made people throw gradually off the shackle of the unknowabilitism of biomigration. Especially since the eighties a new upsurge of investigation into biomigration has been started owing to new requirements of the studies of the crustal movement, continental drift, marine transgression and regression theories.The feasible ways to explore biomigration can be provided by ① geographical tracing of the lowest horizons;② geographical tracing of the evolutionary sequences;③tracing of the corresponding habitats.Migration, as evolution, keeps going at all times under all pervading action of the Darwin's constraint.It is better to look upon migration as a kind of chance given by habitat than as a kind of ability of biota itself. Migration has created and is maintaining natural ecosystem.The studies of migration will grow into.a new branch of palaeobiogeograplly-biomigratology. Geomechanics has emerged and gone on all along with the thought of bioa migration.Its founder J. S. Lee (1927, 1928)had noted the migration of biota following the regular movement of the seawater toward and away from the equator.There must be some connection between the biota migration and the seawater movement, and this was hinted as changes of climate by J. S. Lee (1962). They may originate from a common cause-change of the rate of the earth's rotation.