1995 Vol. 1, No. 1

Display Method:
CRUSTAL MOVEMENT SEEN AS AN ENTIRETY
Gao Qinghua, Ma Zuongjing, Sun Dianqing
1995, 1(1): 1-7.
Abstract (172) PDF (517KB)(26)
Abstract:
After an overview of what have so far been suggested for earth movements, e. g. tectonic systems and global movement field, plate tectonics and rotational spreading,faultblock structure,mosaic structure,geodepression theory and rotation of the earth,as well as a discussion on the directionality of tectionic migration and the movement of the hydrosphere,atmosphere and biosphere,a unified view on geodynamic sysem is put forward in which it is argued that the change in the speed of the rotation of the earth may be the main causes for crustal movement as a result of the geodynamic processes such as gravity,thermal force and centrifugal force,etc.,Furthermore,the en masse movement of the earth and its change is influenced by celestial activety.
It is pointed out in outline that all kinds of geological phenomena and related natural phenomena are an interrelated entirety which is controlled by the earth movement as a whole.
THE RESPONSE OF THE CRUST AS TECTONIC MOVEMENTS TO THE CHANGES OF ECCENTRICITY OF THE EARTH'S ORBIT
Wu Xihao, Jiang Fuchu, Xiao Huaguo
1995, 1(1): 8-14.
Abstract (162) PDF (519KB)(27)
Abstract:
The main tectonic events and climatic changes which occurred in the last 3Ma coincide with the Earth's orbital eccentricity changes having a period of about 0.4Ma. The boundaries of tectonoclimatic cycles determined from the stratigraphic records in the Loess Plateau giving solar calendar ages of 0.07, 0.46, 0.83, 1.32, 1.70, 2.08, 2.47MaBP respectively correspond to the time intervals where there is a decrease of the eccentricity of the Earth's orbit. Also,the basic data concerning the change of speed in the Earth's revolution and its possible effects on the Earth's rotation and on the interaction between the individual geospheres have been analysed. That the changes of eccentricity of the Earth's orbit may have resulted in a driving force for tectonic movemants is discussed. Finally, it is also pointed out that a study of the tectonoclimatic cycles is of importance for further development of the geomechanics theory.
DIRECTIONAL AND EQUIDISTANT DISTRIBUTION OF MID-OCEANIC RIDGES AND THE MECHANISM OF THEIR FORMATION
Wu Zhenghan, Cui Shengqin
1995, 1(1): 15-24.
Abstract (148) PDF (687KB)(26)
Abstract:
The present directional and equidistant distribution of the mid-oceanic ridges on foe earth's surface,the sinusoidal oppositely compensating top and bottom surfaces of the asthenosphere across the ridges,the long development of synchronous tholeiitic rocks symmetrically arranged on either side of the ridge with respect to the crest,as well as the constancy of their positions relative to the oceanic lithosphere,all these have a close relation with earth's rotation and are determined by the dynamic system within the solid earth.
It is considered that the earth is driven by two major force systems-the westward directed force due to earth's rotation and gravity. Under the action of these forces for a considerably long duration of time the different layers of the earth exhibit rheological behaviors to different extents. Using Navier-Stokes equation,we have a solution of the redial and lateral velocities,for the lithosphere and asthenosphere,which may give a satisfactory explanation to the above features.
GEOMAGNETIC REVERSAL FREQUENCY SINCE THE CARBONIFEROUS AND THE GEODYNAMICS
Yang Zhenyu
1995, 1(1): 25-30.
Abstract (203) PDF (415KB)(24)
Abstract:
On the basis of the magnetic time scale and magnetostratigraphic results,the relationship between changes of the magnetic reversal frequency and core/mantle coupling,especially the episodic evolutions of the D" layer since the Carboniferous, was analysed. The episodic geomagnetic reversal friquencies and the true polar wander could correlate with lower/upper mantle convection and lithospheric dynamics. Tentative correlation between the breakup of the Pangea and the Mesozoic lithospheric geodynamic evolution of eastern Asia was discussed.
RECENT PROGRESS OF THE STUDY ON REGIONAL CRUSTAL STABILITY IN CHINA
Wu Shuren, Chen Qingxuan, Sun Ye
1995, 1(1): 31-37.
Abstract (143) PDF (482KB)(28)
Abstract:
The study of regional crustal stability is considered as a branch between engineering geology and the closely allied geomechanics as well as structural geology. Since the last decade,great progress has been achieved with the rapid development of urban construction and large engineering works,resulting in the initiation of engineering geology relating to regional crustal stability. In this paper,a brief introduction of the advancement of this new specific branch of geology mainly from two broad aspects is made.
(1) Establishment and improvement of the basic theories involved, with the emphasis placed on analysis of crustal stability,estimation of major geological hazards risk and assessment of crustal stability.
(2) Continuous modification and improvement of the train of thought and methodologies concerning the study on crustal stability. This involves 3 different approaches to the subject:(a) a systematic multi-channel approach in different scale of areal extents to the problem under study; (b) an evolutionary treatment of the state the part of the crust interested has been in; (c) application of various methods available in the study that can complement and verify the results each obtained.
RESEARCH OF THE SEISMIC FAULT ON THE NORTHEASTERN MARGIN OF THE QINGHAI-TIBETAN PLATE
Dai Huaguang, Jia Yunhong, Liu Hongchun, Su Xiangzhou, Chen Yongming
1995, 1(1): 38-43.
Abstract (158) PDF (439KB)(25)
Abstract:
The northeastern marginal area of the Qinghai-Tibetan plateau is one of the most tectonically and seismically active regions in China since Quaternary, especially late Pleistocene. It is also one of the regions which are of the highest great earthquake (Ms ≥ 7) frequency. A detailed research on the types of the seismic faults,their behaviours,distribu-tion,the features and the relations with the existed and their relation to the pre-existing faults in 19 large historical earthquakes and 10 fossil earthquakes was made in the region with a resulte of the division of 10 seismotectonic zones. This is expected to contribute to long term prediction research on large earthquakes (Ms ≥ 7)in the region and to the crustal stability study as well for damage reduction.
THE LATITUDINAL NAPPE STRUCTURE IN THE SUNITEZUOQI OF INNER MONGOLIA
Li Shujin, Zhang Weijie
1995, 1(1): 44-52.
Abstract (123) PDF (798KB)(20)
Abstract:
Along the line connecting Tuhamohalagan and Jiaoqier, in the central left Sunite Banner of the Inner Mongolia Autonomous Region, the authors have found a latitudinal nappe zone extending for some 60km. Within the belt,the mid-late Proterozoic(epimetamorphic) green-schists were ovethrust from south to north onto the late Paleozoic granitic batholith at a low angle. On the hanging wall of the nappe (thrust),isoclinal folds are developed with the axial planes inclined to the north in association with imbricated thrusts dipping to the south. In the foot wall,there exist rather wide ductile shear zones. Also,a set of structural windows and klippen are distributed along the zone. The distance of the dislpacement is estimated at about more than 20km. This discovery provides strong evidence for the existence of a latitudinal compressed belt, and shows a considerable shortening of the crust in the meridional direction since the end of Paleozoic.
ON THE FORMATION OF YARLUNG ZANGBO RIVER FAULT ZONE
Lao Xiong
1995, 1(1): 53-59.
Abstract (178) PDF (510KB)(39)
Abstract:
The Yarlung Zangbo River fault zone cosists of four arcuate faults bending towards the southwest. The fault zones had become successively subsided from the northwest to the southeast to receive sediments from late Triassic up to the Quaternary,with the adjoining regions uplifted. The crustal movement that brought about the fault zone are characterized by an uplifting on the north and subsidence on the south of the region,the latter becoming subsequently elevated.
A PRELIMINARY NOTE ON DYNAMOMETAMORPHISM DUE TO TECTONIC FORCES
Wang Zhishun, Zhu Dagang
1995, 1(1): 60-66.
Abstract (206) PDF (538KB)(34)
Abstract:
In this article a basic concept on dynamometamorphism as a result of the action of tectonic forces is presented. This means the metamorphism caused by the deformation and factes transformations of rocks and minerals during the tectonic movement in response to the tectonic forces and the resulting rise of temperature. In terms of the texture and structure of the metamorphic rocks,the dynamic recrystallization and the migmatization,as well as the association of stress minerals and their spatial distribution etc.,there can be divided four stages in increasing grade of metamorphism and four corresponding metamorphic rock types as follows:(a)brittle deformation/metamorphism stage; (b)brittle-ductile transition deformation/metamorphic stage; (c)ductile deformation stage and (d) a fourth stage in which significant flow occurs due to local high heat flow stage. A brief description of the main features is here given.
ANALYSIS OF THE FORMATION OF THE “NORTH CHINA SYSTEM”, A CENOZOIC TECTONIC SYSTEM
Yi Mingchu
1995, 1(1): 67-75.
Abstract (145) PDF (593KB)(18)
Abstract:
The "North China system" is a tectonic system that trends NNW and was widely developed in the North China Block in Cenozoic with the Changping-Weichang area as a type locality. It is also called "Luanhe tectonic system" because about 40 percent of their occurrences are concentrated in the Yixunhe-Luanhe tectonic belt. By an analysis of the accompanying structural features and by referring to stress measurements and focal mechanism solutions,the principal compressive stress responsible for the "North China system" was determined to be ENE-WSW oriented. It is believed that the WSW push by the Pacific Block toward the North China Block met with the resistance of the Qinghai-Tibet Block would produce such a regional stress field in the North China Plain.
SIGNIFICANCE OF THE STUDY OF REPEATED MOVEMENT OF FAULTS
Liu Zhigang, Cui Hongqing, Sun Dianqing
1995, 1(1): 76-81.
Abstract (201) PDF (769KB)(25)
Abstract:
During the long geologic times, an area may have experienced repeated crustal movements in different directions and in different manners thus resulting in different stress fields. Most of the pre-existing faults would be reactivated under changing stress fields to be imparted some new mechanical properties and new features of movement. Sometimes,the later faults may develop by adapting to the earlier ones. Therefore,the reactivity of faults is common and can be seen from place to place. The research on the repeated movement of faults can be carried out,either macroscoscopically or microscopically or both. The former includes study of variation of fault shapes,superposition of slickensides,tectonic breccia and side structures,etc. and the latter microstructures and rock fabric analysis,etc.. The study of repeated movement of faults is of important significance in structural geology,mining geology,coalfield geology and endogenetic mineral deposits.
MODELLING OF MINERALIZATION STRESS FIELD AND CONCEALED DEPOSITS PREDICTION IN LIANHUASHAN GOLD-ORE FIELD OF INNER MONGOLIA
Jiang Xirong, Zhao Yinzhen, Xiao jinmin
1995, 1(1): 82-87.
Abstract (146) PDF (452KB)(26)
Abstract:
Mineralization is the process of the movement of ore forming materials. The activation,migration and concentration of ore-forming elements closely correlates with the accumulation of stress and energy when "the syn-metallogenic structural system" became active and with the release of stress and energy when the hast rocks fail. Ore-forming elements would be mobilized in consequence of continued accumulation of stress and energy,increase of temperature and the presence of water. The rise of stress would eventually cause the rock of the crust to be deformed,broken and dislocated,to release the stress and energy accumulated so that mobilized ore-forming elements migrate toward and concentrate in structural zones of reduced stresses. Photoelastic and mathematical modelling will give the distribution of stress and energy quantities in and around the region of ore deposits. The close link of the formation and distribution of ores with syn-metallogenic stress field may provide some hints for the known and blind deposits. A quantitative instead of qualitative ore prediction is thus stepping up.
THE RELATION BETWEEN ALBITIZATION AND GOLD IN THE DUCTILE SHEAR ZONE OF DAGOUGU AREA, NORTHERN GUANGDONG PROVINCE
Zhu Dagang
1995, 1(1): 88-94.
Abstract (227) PDF (541KB)(22)
Abstract:
This is a preliminary summation of the geological features of the cataclastic albitite type gold deposit in Dagougu area,northern Guangdong Province. With a general description of the macroscopic and microscopic features of the ductile-brittle shear zone and its evolution,and also a discussion on the relation between albitization and gold mineralization.The albitization is divided into three stages and five phases. The tectonic condition for albitization,the texture and structure of the albite,its alteration and its content of gold in the different stages are dealt with.