Table of Content

20 December 1997, Volume 3 Issue 4

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Article

STUDY OF THE FALLENICE IN MEICHUN, XISHAN CITY

Hu Zhong-wei1, LI Zhao-lin2, LI Ru-liang1, Jiang Hao-shen1, Wang Er-kang1 Tian Li-qing1, Jiang Yan-hao1, Xu Xi-yuan3, Tian Wei-zhi4, Zheng Su-hue5

1997, 3(4):  361-369. 

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On November 17, 1984, a piece of ice fell down from sky onto the wheat field near Chenshanfang village of Meichun, Xishan city in eastern China. By investigating the scene, eye-witnesses and related departments of meteorology and aviation, the possibilities that the ice originated from artificial, meteorological or airplane events can be excluded. A few samples of the ice were submitted to serious experimental analyses, and the preliminary results show not only some differences between the ice and terrestria1 matters but also similarities between the ice and extraterrestrial matters. This is in favour of the viewpoint that the ice originated from extraterrestrial space, probably from a small comet. Further research on the fallen ice might be of great significance for understanding the nature of comets and water resource on the Earth, as well as relevant problems of meteorology, geology and astronomy.

EXPLORATION OF MOTIONS OF CELESTIAL BODIES AND THE DRIVING FORCE FOR THE PLATE-TECTONIC MOVEMENT-- EXPLANATION OF THE ORIGIN OF PREHISTORIC TECTONIC (MOVEMENT) CYCLE PERIODS

Wang Zheng-dong

1997, 3(4):  370-378. 

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In this paper, formation of primitive celestial bodies from nebular material with independent revolution angular momentum is studied first and discussion is stressed on following problems: the theory of material convective motion produced by heterogeneous distribution of force source in the interior of celestial body；the features and responses of the gravitational field around the earth; the relative movement features of earth’s crust to the core, which rotates around the galactic center; the relationship between the large-scale meridian horizontal movement of terrestrial crust and the galactic year, as well as their comparison to prehistoric tectonic cycle periods. It is thus confirmed that the behaviors of relative movement of the interna1 material in celestial bodies, i.e. the terrestria1 crust large scale meridian movement, is a reflection of revolution angular momentum conservation of the celestia1 body.

Rb-Sr CHRONOLOGICAL STUDY OF METAMORPHIC ROCKS IN DANBA AREA, WESTERN SICHUAN PROVINCE

Shen Wei-zhou1, Xu Shi-jin1, Wang Ru-cheng1, Zhong Hong1, Lin Yu-ping1, Luo Yao-nan2, Hou Li-wei2

1997, 3(4):  379-383. 

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Danba area has undergone multiperiod deformation, metamorphism and magmatism since Mesozoic time. Six belts of metamorphic facies have been established, i.e., the sillimanite, kyanite, staurolite, garnet, biotite and sericite-chlorite belts. Rb-Sr isochron ages for staurolite schist in kyanitc belt and plagio-amphibolite and metabasalt in garnet belt are 149.0±7.1 Ma, 160.0±13.0 Ma and 150.2± 2.4 Ma respectively. They are considered to represent the most principal ages of reginal dynamothermal metamorphic event in Danba area. With reference to available Re0chr0n0i0gical data, the metamorphic history in Danba area is also discussed.

STUDY ON TRACE ELEMENT AND Nd-Sr ISOTOPIC GEOCHEMISTRY OF MESOZOIC POTASH-RICH VOLCANIC ROCKS AND LAMPROPHURES IN WESTERN SHANDONG PROVINCE

Qiu jian-sheng1;2, Wang De-zi1, Zeng Jia-hu1, Brent I. A. McInnes2

1997, 3(4):  384-395. 

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The Mesozoic potash-rich volcanic rocks in western Shangdong occurred mainly in terriestrial depression volcanic basins. Their distribution were controlled obviously by deep faults, and the typical localities of them are Zouping volcanic basin, Linqu volcanic basins, and mainly distributed in two areas, one is in the vicinity of Zaozhuang, such as Xuecheng, Shagou, Tengxian etc., the other is in Xinzhuang. Both potash-rich volcanic rocks and lamprophyres were formed in early Cretaceous (Rb-Sr isochron age of potash-rich volcanic rocks in Mengyin is 119.6±3.7 Ma and K-Ar ages of lamprophyres in Zaozhuang and Xinzhuang are 125～126Ma and 113Ma respectively ). According to their mineral constitutions and chemical compositions, the lithological association of potash-rich volcanic rocks in western Shangdong belongs to a set of trachybasalt-basaltic trachyandesite-reachyandesite-latite-trachyte, of which the latite is the predominant rock type. Lamprophyres in Zaozhuang are of alkaline-rich ultramafic categories, such as cascadite, olivine and pyroxene-bearing kersantite etc., and those in xinzhuang belong to a set of alkaling-rich intermediate to basic types, such as leucite-bearing lamprophyres, kersantite and spessartite etc. Geochemical investigation shows that both potash-rich volcanic rocks and lamprophyres have similar characteristics on major elements, trace elements and Nd-Sr isotopic compositions, i.e., they are all rich in alkali, potassium, LREE and LILE, but poor in HFSE and siderophile elements, and have quit low εNd values and obviously higher Isr rations. The 87Sr/88Sr rations andεNd values of potash-rich volcanic rocks and lamprophyres are 0.71103～0.71322, -11.02～-17.54 and 0.70953～0.71109, -11.57～19.54 respectively, similar to the carbonatite in this district. Based on detailed geochemical investigations and comprehensive studies of their tectonic setting, it is concluded that both potash-rich volcanic rocks and lamprophyre in western Shangdong were originated mainly from the partial melting of enriched mantle.

THE NEPHRITE FIRST FOUND IN FUJIAN, CHINA

Tang De-ping1, Lin Guo-xin2, Jiang Ai-gen1, Yu Jian-chang1, Chen Wen-bin1

1997, 3(4):  396-399. 

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The nephrite was first found in Nanping, Fujian recently. The primary studies show that Nanping nephrites have white to light green color, RI of 1.61-1.62, density of 2.979- 2.989 and hardness of 6.0- 6.1. The nephrites consist simply of tremolite, but sometimes some diopsides. The chemical compositions of the nephrites are close to the theoretical value of tremolite, with low content of FeO. Comparing to XinJiang nephrites they have a stronger 3671cm-1 hand in their IR spectra, which might indicate their lower content of F. Nanping nephrite occurred in Precambrian metamorphic rocks, marble and diopside marble, and was formed through the regional metamorphism.

STUDY ON THE DEFLUORIDATION BY ATTAPULGITE

Sun Chen-yuan, JI Jun-feng, Zhao Mei-fang

1997, 3(4):  400-404. 

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Attapulgite is a fibrous clay mineral containing ribbons of a 2:1 phyllosilicate structure, and has special adsorptive and colloidal properties which are the basis for environmental applications. Defluoridation by attapulgite in laboratory samples of aqueous fluoride solutions has been investigated which shows a greater defluoridation at acidic F-solution than at neutral and alkaline. As the pH increases from 2 to 6, there is a decrease in the percentage of defluoridation, and further increase of pH has negligible effect on fluoride remova1. The F adsorbing property described makes attapulgite highly suitable for environmental protections.

SUBACUTE TOXICITY TEST ON THE COMBINED EFFECT OF STRONTIUM, BORON AND FLUORINE

Zhang Min1, Zhang Jing-rong2, Zhu Fa-hua2, Fan Xiao-ying1

1997, 3(4):  405-410. 

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Subacute toxicity of combined effect of strontium (Sr), boron(B) and fluorine(F) was tested on mice by drinking water containing Sr2+, B3+ and F-. The results showed that F content in bones and activity of alkaline phoshatase (Al, P)in kidney increased significantly(p＜0.01)after the test of water containing 200 ppm F- for six months. ALP activity in serum also Increased sharply (P< 0.01)after 4.5 months, Sr and B added to the water with final concentration of 80 ppm and 100ppm respectively could induce the decrease of F content in bones and activity of Al P in kidney and serum. This indicates that Sr and B are both antidotes to F.

TWO TYPES OF BASIC MODELS FOR CONTINENTAL CRUST ACCRETION AND THEIR COMPARISON

Zhu Guo-qiang, Cheng Xiao-gan, Yang Shu-feng, Chen Han-lin

1997, 3(4):  411-418. 

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Continental Crust is the inevitable product of formation and evolution of the Earth. The Continental Crust is accreted by merging of terranes of different ages, types and scales, and wanes by dividing and separating of prior Continental Crust along new fault system. Hence the formation of Continental Crust is a synthetic result of terrane accretion and separation. The initial Continental Crust was formed during the early Archaean. Since then, the Continental Crust was accreted by two types of basic models, i.e. the Circum-Pacific type and the Tianshan type. The Circum - Pacific type model of continental Crust accretion occurs on continental margins. It is an one-way accreting from old continent to ocean, which the ages of accretion are getting younger along this direction. Generally, the accreted terranees has traveled for a long distance. The accretion is closely related to plate subduction. The Tianshan type of Continental Crust accretion model is developed between continents. Its formation is related to open-closing process of continental crust and may or may not accompany with subduction. When old continent was divided and separated along the faults with certain directions, new trough was formed between separated continents and carbonate rock, normal terrigenous elastic sediment and volcanic material from deep part of Crust Mantle were precipitated. Due to changing of stress condition under Crust, two separated old Continental Crusts moved in opposite direction, the material in trough collided to form fold-orogenic zones, and thus the welding of old Continental Crust from two sides form a new Continental Crust of larger scale.

The Thrust Tectonics and It’s Transpressive Geodynamics in Southern Dabashan Mountains

He Jian-kun, Lu Hua-fu, Zhang Qing-long, Zhu Bin

1997, 3(4):  419-428. 

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The deformation belt of Southern Dabashan mountains, 1ocated between the northeast border of Sichuan craton of Yangtze plate and the Qinling collisional orogenic belt, is of a southward verging thin - skinned thrust wedge which is characterized by superimposition of dextral transpressive deformation. The thrust wedge is mainly composed of the stepped-thrust sheets, the fault-related folds and duplex in the cover strata. Kinetically, the propagation of stepped thrusts is in the piggy- back style from the root zone named the Chengkou- zhongbao thrust which is the northern boundary fault of southern Dabashan mountains where the largest depth of detachment layer is about 8- 10km to the frontal zone of Wenquanjing thrust which is the southern boundary fault of southern Dabashan mountains where the largest depth of detachment layer is less than 1.5km, at the end of Triassic, the thrust deformation was first initiated in the root zone near the Chengkou- zhongbao thrust. Since then the thrusting had propagated southwestward in the form of piggy-back and in the beginning of Cretaceous the deformation had extended to the southmost front of southern Dabashan mountains. Thus the total time span of deformation is about 50Ma. By mapping of balanced-cross sections and restoration of structures, the crustal shortening, the shortening rate and the thrusting velocity are estimated about 64km, 49.3 and 1.28mm/y respectively. Furthermore the geodynamics to develop the deformation belt is dominantly related to the Qinling collisional orogenic processes. In the Mesozoic, the continent- continent collision between North China plate and Yangtze plate resulted in the formation of Qinling collisional orogenic belt and the A-type subduction of Yangtze plate beneath the middle Qinling volcanic arc through the southern Qinling and northern Dabashan tectonic belts. As a result, the A- type subduction led to the horizontal tectonic stress which caused the southwestward propagation of the thrusting toward southern Dabashan mountain deformation bait. Besides, with the existence of Michang mountain uplifting Proterozoic metamorphic complex in the southwest of Dabashan mountains, the morphology of northern margin of Yangtze plate is in the form of northward convex. Under the controlling of this boundary condition, the northward A- type subduction deduced the dextral transpression to the east of Michang mountains uplifting Proterozoic metamorphic complex along the Chengkou-Zhongbao thrust and northern Dabashan mountains extruded eastward. It is this geodynamics that had caused the dextra1 transpression thin- skinned thrusting deformation in southern Dabashan mountains.

SHEARING ANATECTIC MECHANISM OF GNEISSIC GRANITIC ROCKS IN THE HUANGLING FORMATION, WESTERN GUANGDONG

Yang Kun-guang1, Peng Shao-mei2, Zheng JianPing1

1997, 3(4):  429-437. 

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Gneissic granitic rocks of the Huangling formation in western Guangdong are the basement metamorphic series (2600Ma～1700 Ma). Three different structural styles are developed in these rocks: penetrating shear zone in the lower part, regular affine deformation zone in the middle part, and corrugation deformation zone in the upper part. Strain analysis shows that different structural styles are produced by the approximate horizonta1 shearing and its continuous upward migration. Chemical analysis reveals that gneissic granitic rocks possess the characteristics of crustal reformed S-type granite. In fact, these gneissic granitic rocks are resulted groin autochthonous or near autochthonous shearing anatexis, whose protoliths arc neritic- hypoabyssal clasolites. The depth of shearing anatexis is above l3km～ 15km, and the peak of shear deformation occurred on 2000Ma～ 1700Ma.

CORE-MANTLE INTERACTION AND ITS GEODYNAMICAL IMPLICATION

Liu Liang-ming, Peng Sheng-lin

1997, 3(4):  438-444. 

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The core-mantle boundary (CMB) is the greatest contrasting and the most important boundary in the interior of Earth, where core-mantle interactions have been playing an important role in earth’s geodynamics system. On the basis of outlining the basic features of CMB, this paper presents systematica1 summaries of the research results and related problems on the following aspects: the material chemical reactions and forming of D″1ayer, mass transfer between core and mantle; heat transfer from core to mantle and their contribution to mantle convection; and core-mantle coupling and angular momentum transferring.

REFLECTIVE SPECTRAL PROPERTIES OF TWO GRANITES IN GUANGDONG PROVINCE AND THEIR SIGNIFICANCE OF REMOTE SENSING

Liu Hua-gen, Yang Shu-feng, Chen Han-lin, Zhang Deng-rong

1997, 3(4):  445-450. 

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Spectral information of surface object is the base of multispectral remote sensing. Characteristics of spectral information reflect the existence, change and difference of the objects. As a part of the research of physical properties of granite, we analyze the reflective spectral features of two types of Early paleozoic granite in Guangdong province. The samples of the I-type granite are from longtang rock mass in central Guangdong and the S-type granite from Yunkai mountain in western Guangdong province. Through PIS-B high accurate instantaneous spectrometer, the reflecive spectral properties of two granites were obtained. The brightness difference between the two granites is very high. Spectral reflectance of S-type granite is greater than that of I-type granite. Furthermore, the differences of field reflective spectral properties between two granites and between the granites and surrounding rocks are analyzed, which provided a theoretical basis on which different type of rocks can be discriminated in the remote sensing images. In consequence, the techniques and methods to dispose the remote sensing images are also designed on the basis of known differences of spectral properties. Among the several possible designs, an ideal one is to composite the images of TM4(R), TM4/3(G) and TM2/1(B). On the composite images, two granites and the surrounding rocks can be easily discriminated.

A NEW INDOOR MODEL TEST OF SOIL--THE HYDRAULIC GRADIENT SIMILITUDE M0DEL TEST F0R PILED F0UNDATION

Fang Lei1, Li Guang-xin2, Huang Feng2,

1997, 3(4):  451-457. 

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Similitude model test is very important in geotechnics research．But conventional gravity field of lg model test fails to reach the prototype stress leve1, because the stress-strain behavior of soil depends on its level of effective stress. Centrifugal model can provide high body force, so it is used widely in geotechnics, although it has some drawbacks. In this paper, a new model test of soil, the hydraulic gradient similitude (seepage force) model, is introduced through a pile’s seepage force model test. The seepage force model employs a high body forces, hence the high stress levers approaching field conditions can be reproduced. It overcomes some failing in conventional model and centrifugal model of geotechnics. So it is very useful in studying the piled foundation and other practice in geoteehnical engineering.

SEISMOSTRATIGRAPHY AT ITS GERMINATION STAGE -- A BRIEF HISTORY OF RESEARCH ON SEISMITE AND ITS PROSPECT

Liang Ding-yi, Nie Ze-tong, Song Zhi-min, Wan Xiao-qiao

1997, 3(4):  458-461. 

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Earthquake occurs frequently, it is a reflection of the earth’s rhythm. Seismite, a term first proposed by A. Scilacher(1969), was subsequently used at a high tide of its research by European and American geologists. Mutti et a1.(1984) regarded megaturbidite as seismoturbidite which may be used as an element of event stratigraphy for mapping and bedtracing. In China, Song Tianrui is the first geologist who proposed in 1985 the seismo-tsunami sequence as the marker to subdivide and correlate the Wumishan Formation in Yanshan area. Qiao Xiufu et a1.(1994, 1995) established “Seismic sequence in carbonate rocks by vibrational liquefaction” and the “sabkha seismite sequence” in the Upper Sinian-Lower Cambrian Series, and they also made a correlation and genetic stratigraphic study on strata of the same age in the eastern part of North China. The present authors (1991, 1994)pointed out that the Permian seismite in the west margin of the Yangtze massif is composed of two parts: the seismo-disturbed beds of autochthonous facies and the sliding seismite of allochthonous facies; and these two are separated by a seismounconformity which formed instantaneously under water. The sliding seismitcs arc composed of a multicyclic seismitic sequences, in which the beds which mixed fossils show a normal and ordered arrangement and are related apparently to the repealed normal faultings along the basin margin. Hence a new recognition of the Dongwu extension movement along the west margin of the Yangtze massif is proposed, and the study of seismite is geared to the tectono-catastrophe event and event stratigraphy. In the geologic history China was a multiseismic country, hence it is quite possible that there may exist certain favourable sites for the establishment, research and development of a new branch of modern stratigraphy-Seismostratigraphy.

A DISCUSSION ON “PONDERING OVER SOME PROBLEMS IN THE STUDY OF CONTINENTAL GEOLOGY”

Wei Chun-jing

1997, 3(4):  462-463. 

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KEY TOPICS ON PHYSICS AND EVOLUTION OF THE EARTH’S INTERIOR: Ⅱ. GEODYNAMIC SYSTEMS

Chen Sheng-zao

1997, 3(4):  464-480. 

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The continental/lithospheric root formed at the bottom of the lithosphere is associated with depletion of the mantle plumes generated in the core-mantle boundary layer (CMB). It is mainly evidenced from three-dimensional seismic tomography and experimental and numerical simulations. The upwellings and downwellings represent, respectively, the high and numerical simulations. The upwellings and downwellings respectively, the high temperature/low velocity and the low temperature/high velocity zones. The long-wavelength mantle structure bears relations to tectonic features of the Earth’s surface. The boundary layers, either thermal (TBL) or chemical ones (CBL), will bring about direct of indirect effects on the global dynamic systems, and therefore, further study of the boundary layers on its structure, topography, thermodynamics, and physicochemical properties will be of crucial significance in solving those conflicting problems between the whole-mantle convection an the layered convection systems. Global seismic imaging and deep source seismic data have revealed that some formerly subducted fragments (slabs) seem to have continuously or intermittently sunk to the CMB and returned into the mantle plumes originated from the boundary. At present time, the most important task is how to establish an unified model between the whole-mantle convecting and the layered convection systems, rather than arguing whether the whole-mantle convection or the layered convection dominates independently the dynamic system. An integrated study, in terms of theoretical, experimental and numerical simulations on the whole-mantle convection system which is undoubtedly accompanied by the layered convection, locally small-scale of secondary convection during its spatial and temporal evolutionary history, consitues a main direction of today’s geodymamics.