• Volume 64,Issue 1,1990 Table of Contents
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    • Apparent Polar Wander Path from the Tarim Block in China

      1990, 64(1).

      Abstract (1826) HTML (0) PDF 0.00 Byte (91) Comment (0) Favorites

      Abstract:The apparent polar wander (APW) path from the Tarim block consists of palaeo-magnetic poles ofDevonian (λ=16°N, ψ= 165° E. A_(95)=4°). Late Carboniferous (λ=41° N, ψ=160° E, A_(95)=4°).Permian (λ=61°N, ψ=177° E. A_(95)=9°). Early Triassic (λ=69° N. ψ=183° E. A_(95)=11°) andJurassic/Cretaceous (λ=65° N, ψ=214° E. A_(95)=6°) times. On the basis of this APW path, it is con-cluded that the Tarim block was subducted beneath the Kazakstan plate between Devonian and Permiantimes. The Tarim, North China and South China blocks were sutured between the Early Triassic and EarlyCretaceous. Tarim had moved eastward some 2000 km relative to Siberia since the Cretaceous.

    • The Nadanhada Terrane in Relation to Mesozoic Tectonics on Continental Margins of East Asia

      1990, 64(1).

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      Abstract:The Nadanhada terrane, a Jurassic disrupted terrane in Heilongjiang Province of China, is principallycomposed of Permo-Carboniferous limestone and greenstone, Triassic bedded chert and middle Jurassicsiliceous shale, all enclosed within younger (presumably Late Jurassic-Early Cretaceous) clastics. Palaeon-tological and lithological characteristics and structural features of these formations are entirely identical tothose of the Mino terrane of the Japanese Islands. Prior to opening of the Sea of Japan, these terranesformed a single superterrane together with the Western Sikhote-Alin terrane. Tectono-stratigraphic terranesvery similar to the Nadanhada and Mino terranes are also found in the Ryukyu arc, the Philippines andprobably in Borneo. All these terranes constituted a belt of accretionary complexes during Late Jurassicand / or Early Cretaceous time along the eastern continental margin of Asia after completion of the Triassiccollage of the Chinese continent.

    • Minerogenic Model of Chrysotile Deposits in Ultramafic Rocks

      1990, 64(1).

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      Abstract:Most chrysotile deposits occur in ultramafic rocks of the ophiolite suite. The chrysotile deposits dis-cussed in the present paper were formed through metasomatism and infilling-crystallization in a continentalserpentinization environment after plate convergence, where ultramafic rocks were replaced byhydrothermal solutions consisting mainly of deep-circulating heated water derived from atmospheric precip-itation. The critical state for the formation of asbestos in ultramafic rock bodies might be reached bysuperposition of multiple stages of serpentinization. Favourable fracture systems and relatively stable geo-logical environment are important conditions for forming chrysotile deposits. Three subtypes of chrysotiledeposits could be formed in different tectonic settings and under different minerogenic geochemical condi-tions.

    • Sr, Nd and O Isotopic Studies on the Genesis of the Huashan Granite Complex

      1990, 64(1).

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      Abstract:Systematical Sr, Nd and O isotopic studies were made on the Huashan granite complex in Guangxi. Incombination with the studies of geological, petrological and geochemical data, it is believed that the complexconsists of granites of three stages. with different geneses and different source materials. They are not the prod-ucts of differentiation and evolution of one single consanguineous magma. Granites of the 1st stage are of theIndosinian syntectic type or I type, also derived from a mixed mantle-crustal source. Those of the 2nd stage areof the early Yanshanian syntectic type or I type. also derived from a mixed mantle-crustal source, and those ofthe 3rd stage are of the late Yanshanian transformed type or S type. derived from a crustal source.

    • Geochemical Characteristics of Granitoids in the Eastern Sector of the Northern Tianshan Mountains in Xinjiang

      1990, 64(1).

      Abstract (1883) HTML (0) PDF 0.00 Byte (61) Comment (0) Favorites

      Abstract:The granitioids in question are located in the geosynclinal fold belt of the Northern Tianshan Mountains.The magmas are intruded into a Carboniferous marine volcanic-sedimentary rock series. forming a contempo-raneous. intermediate-basic to acid. composite intrusion. With a whole-rock Rb-Sr isochron age of 315.7 Ma. itis considered to be of middle Heicynian age. The granitoids have a SiO_2 content of 48-78%, a calc-alkali indexof 60 and silica-alkali indices ρ=2.2-2.4 and σ=1.5-2. From basic to acid compositions, the total REE con-tent increases from 38 to 143 ppm. δEu ranges from 0.47 to 0.86 and the Eu anomalies are negative. Thenormalized curves of REE of various rock types are very similar. These coupled with the characteristics of traceelement geochemistry show that the intrusion is an island arc-continental margin, calc-alkaline one. Theδ~(18)O values range from 5.8 to 8.9‰ and the ~(87)Sr/~(86)Sr initial ratio is 0.705. The materials of the intrusion arecomposed of a mixture of the magmas at the top of the upper mantle and in the lower crust, This indicates thatthe rocks might be consanguineous. differentiated and evolved products and possess the characteristics of Ⅰtype granites.

    • A Comprehensive Evaluation on the Devonian-Carboniferous Boundary Stratotype Candidate Section in Nanbiancun, Guilin, Guangxi

      1990, 64(1).

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      Abstract:This paper presents a comprehensive evaluation on the Devonian-Carboniferous Boundary (DCB) sectionin Nanbiancun. Guilin. Guangxi on the basis of Palaeontological, biostratigraphical and sedimentarypetrological studies as well as microfacies analysis. REE and trace element analysis and isotopic dating. The DCB at this section conforms to the definition of this boundary and essentially measure up the criteriaand conditions for selection of the boundary stratotype. Up to 14 fossil groups are contained in the section. Thesection presents a general biostratigraphical framework with multispecies fossils zones, assemblage zones andmultiple groups of fossils and has latent preponderant conditions for magnetostratigraphic andchronostratigraphic studies. The boundary and point occur in a persistent and continuous monofacialcarbonate succession. and the section is located in a tourist city with convenient communication, where variousfacies of DCB sections are developed. allowing the correlation within a small area. So it is an ideal candidateboundary stratotype.

    • Boundary Element Analysis (Laplace Transform Solution) of Groundwater Unsteady Flow to a Multiple Well System in a Confined Aquifer

      1990, 64(1).

      Abstract (1698) HTML (0) PDF 0.00 Byte (72) Comment (0) Favorites

      Abstract:The calculations of unsteady flow to a multiple well system with the application of boundary elementmethod (BEM) are discussed. The mathematical model of unsteady well flow is a boundary value problem ofparabolic differential equation. It is changed into an elliptic one by Laplace transform to eliminate time varia-ble. The image function of water head H can be solved by BEM. We derived the boundary integral equation ofthe transformed variable H and the discretization form of it, so that there is no need to discretize the bounda-ries of well walls and it becomes easier to solve the groundwater head H by numerical inversion.

    • Ordovician-Silurian Boundary Extinction and Its Relationship to Iridium and carbon Isotope Anomalies

      1990, 64(1).

      Abstract (1723) HTML (0) PDF 0.00 Byte (64) Comment (0) Favorites

      Abstract:The abundance distributions of more than 40 elements in the No. 502 Ordovician-Silurian (O/S) bounda-ry section at Fenxiang, Yichang have been studied by RNAA and INAA. The results show that in the bounda-ry bed, there is a distinctive Ir anomaly because the Ir concentration abruptly increases to 0.64 ppb.Furthermore, the Ir is positively correlated in abundance variation with some siderophile and sulphophile ele-ments. In the same bed of the O/S boundary section at Huanghuachang, Yichang, there is also a δ~(13)C excur-sion. These geochemical signs support the hypothesis that the terminal Ordovician mass extinction was proba-bly related to extraterrestrial event, and provide new evidence for defining the O/S boundary between theHirnantia-Kinnella and G. persculptus Zones.

    • The General Characteristics and Distribution of the Glaucophane-Schist Belts of China

      1990, 64(1).

      Abstract (1809) HTML (0) PDF 0.00 Byte (61) Comment (0) Favorites

      Abstract:On the basis of the temperature variation, the glaucophane-schist facies Gan be classified into two faciesgroups, the glaucophane-lawsonite facies group and the glaucophane-greenschist facies group, and forms vari-ous facies series with other metamorphic facies. Glaucophane-schist belts of China are of different types withregard to their average T-P gradients and tectonic environments. They are: (1) Proterozoic intracratonicglaucophane-schist belts, (2) Caledonian intracratonic glaucophane-schist belts, (3) Palaeozoic pericratonicglaucophane-schist belts along the northern margin of the Chinese Platform, and (4) Meso-Cenozoicglaucophane-schist belts related to subduction. The initiation and evolution of glaucophane-schist metamorphism are related to their tectonic environ-ments. Most glaucophane-schist belts of China were formed in sialic environments. First the crust began tobreak up and eventually oceanic crust was formed. It seems that a non-uniformitarian mechanism may be in-volved as this evolution is related to the change of the configuration of the heat flow within the crust.

Chief Editor:HOU Zengqian

Governing Body:China Association for Science and Technology

Organizer:Geological Society of China

start publication :1922

ISSN:ISSN 1000-9515

CN:CN 11-2001/P

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