• Volume 64,Issue 4,1990 Table of Contents
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    • Mechanical Research on Biucleus-Type Vortex Structures

      1990, 64(4).

      Abstract (1048) HTML (0) PDF 0.00 Byte (73) Comment (0) Favorites

      Abstract:A new type of vortex structure-binucleus-type vortex structure-is presented in this paper. It is charac-terized by two nuclear columns which distinguish it from uninuclcus-type vorlex structure. The vortical sur-faces of the structure are commonly s-shaped and reversed s-shaped and subordinately of clliptic andhyperbolic shape. and sometimes turbine-like surfaces are observed. On the basis of field structural studies. a mechanical model of rotation around a binuclear column ofcrustal materials is presented in the paper. Burgers viscoelastic solutions of the stress field and deformationfield of this structural type have been obtained using the principle and method of rheology. and simulation ex-periments have been performed. The results of the theoretical calculation and experiments indicate that theproposed mechanical model is applicable.

    • Geophysical and Geological Features of the Meso-Cenozoic Lower Yangtze Rift Zone

      1990, 64(4).

      Abstract (1234) HTML (0) PDF 0.00 Byte (96) Comment (0) Favorites

      Abstract:It is clarified in this paper that the Lower Yangtze depression is a Meso-Cenozoic rift zone formed on thebasement of the Hercynian-Indosinian foreland basins. The rift zone is divided into eastern and western sectorsand is different in northern and southern parts. The rift zone in plane combination comprises parallel.trifurcate or splitting rifts. The North Jiangsu-South Yellow Sea region represents a "drift-type" rift basinwhose deposition center migrates gradually castward. The formation mechanism and dynamic evolution of therift basin are discussed from a viewpoint of the crustal fine-structure, with evidence in geology and geophysicsand analysis results of dynamic forces given.

    • Petrological Study on the Ductile Shear Zones in the Core of the Eastern Qinling Orogenic Belt in Western Henan

      1990, 64(4).

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      Abstract:A series of ductile shear zones of the overthrust and strike-slip-types and related ductile shear metamorphicrocks, including tectonic melange and mylonites. were formed in the core of the Qinling orogenic belt in thecourse of the Caledonian-Indosinian ductilc and brittle-ductile reworking. The study on their petrography. va-riations in composition and conditions of formation is conducive to revealing the metamorphism-deformationhistory of the core of the Qinling orogenic belt and further to understanding the dynamic mechanism of its evo-lution.

    • A Lower Ordovician Carbonate Contourite Drift on the Margin of the South China Paleocontinent at Jiuxi,Northern Hunan

      1990, 64(4).

      Abstract (1056) HTML (0) PDF 0.00 Byte (95) Comment (0) Favorites

      Abstract:Carbonate contourite drift at Jiuxi. Taoyuan, northern Hunan, was developed in a deepwater area ofnorthern Hunan on the margin of the Early Ordovician South China palcocontinent. The Lower Ordoviciansequence in the area is more than 350 m thick and contains well-developed contourites that can be groupedinto the following five types: the calcilutitic, the arenitic, the siltitic. the fine ruditic and the bioclastic. Thefirst three often constitute a complete or incomplete contourite succession. The arenitic contourite is nearlyuniformly distributed as interlayers throughout the succession, creating a monotonously rhythmic texture inthe contourite drift. The pattern of spatial distribution of the succession shows that the contourite drift is ahuge ridge-like sedimentary body extending along the trend of paleoslope. Numerous marks of flow direc-tion have pointed to an eastward paleoflow direction along the slope.

    • Formation Mechanism of the Tongyu Gold Deposit,Shaanxi——A Discussion of a Model for the Formation of Syntectonic Gold Deposits

      1990, 64(4).

      Abstract (1350) HTML (0) PDF 0.00 Byte (95) Comment (0) Favorites

      Abstract:The formation of the Tongyu gold deposit, controlled by regional polyphase deformation-metamorphism.is closely related to the regional composite antiform-shear slip fracture zone. Late-stage reworking of theTaihua Group accounts for the enrichment of ore substances. It is a typical syntectonic gold deposit. The formation and evolution of the deposit involved four stages: (Ⅰ) the state of preparation of ore sub-stances, in which primary source beds originated: (Ⅱ) the stage of remobilization of ore substances, in whichregional progressive metamorphism and migmatization and thermodynamic-chemical differentiation led toremobilization of gold and its initial local concentration: (Ⅲ) the stage of gold deposit formation, in which re-gional folding produced concordant and cross shear-slip fractures and under the dynamic action gold was sepa-rated and migrated in a certain direction and concentrated to form a gold deposit: (Ⅳ) the stage ofsuperpositon, reworking and exposure of orebodies, in which the block uplifted and the deposit againunderwent reworking through faulting and mechanical differentiation.Thermodynamic mineralization played adominant role in the formation of the deposit.

    • Metabasic Dyke Swarms in a High-Grade Metamorphic Terrane——A Case Study in the Taipingzhai-Jinchangyu Area,Eastern Hebei Province

      1990, 64(4).

      Abstract (1180) HTML (0) PDF 0.00 Byte (96) Comment (0) Favorites

      Abstract:Geological and petrological studies indicate that three phases of metabasic dykes are present in theTaipingzhai-Jinchangyu area within the high-grade metamorphic terrane of eastern Hebei. Garnet andhornblende in metabasic dykes of the second and third phases occur separately, forming two mineral aggregateareas gl+cpx+pl±hy and hb+cpx+pl-hy. P_(H_2O) in the rocks appears to be the main factor controlling theformation of the two aggregate areas. Both were formed simultaneously at the same metamorphic temperature. The second-phase basic dykes underwent metamorphism of pyroxene-granulite facies at a temperature ofsome 825C: later the dykes, together with the third-phase basic dykes experienced metamorphism ofamphibole-granulite facies at a temperature of about 750C under pressure of 0.9GPa.

    • A New Fauna——Qinghezhen Fauna——from the Northern Margin of the North China Platform

      1990, 64(4).

      Abstract (1607) HTML (0) PDF 0.00 Byte (73) Comment (0) Favorites

      Abstract:In the Inner Mongolia axis and Jiaoliao anteclise along the northern margin of the North China Platform.it has been found that the strata formerly considered as Archaean and Proterozoic are in fact an ophiolite suitesimilar to the Early Palaeozoic Ondor Sum Group in the Northern Geosyncline region of China. The stratahave been named in northern Liaoning as the Qinghezhen Group. The emphasis of this paper is on the discus-sion of the simall shelly fossils found in the siliceous rocks in the upper part of the Qinghezhen Group. Thisophiolite suite stretches in an E-W direction for about 1000 km along the northern margin of the North ChinaPlatform. in which 15 fossil localities with stable stratigraphic horizons have been discovered. In this paper. 4types. 7 genera (including 5 new ones) and 10 species (including 8 new ones and 1 new subspecies) aredescribed, which are collectively referred to as the Qinghezhen Fauna. The characteristics of these fossils are:shell form simple. the maximum length not exceeding 4 mm. with obvious shell wall and wall ornaments. TheQinghezhen Fauna is comparable in shell structure of some genera and species with the Meishucun Fauna inSouth China, but differs from the latter in having only monotonous fossil groups developed in a distinctly va-ried ecological environment. The two faunas may belong to the same evolutionary stage of the Early Cambrianbut have developed parallelly in different regions. The existence of the Qinghezhen Fauna represents an impor-tant biological event in the Early Cambrian in the Northern Geosyncline region of China. The discovery of theQinghezhen Fauna will bring new knowledge and profound influence to a series of problems on basic geologyand mineral deposit prospecting such as the Cambrian faunas. biogeographical povincialism in China and thegeotectonic features of the northern margin of the North China Platform.

    • ACTA GEOLOGICA SINICA Contents of Vol.3,1990

      1990, 64(4).

      Abstract (1126) HTML (0) PDF 0.00 Byte (84) Comment (0) Favorites

      Abstract:N0.1APp之zrent Pola「W是znder Path from rheT之注rim Bloek一n China 乙iya。刀i,,g咬李燕平).尺。方rrrs力ar那,M,‘子,uez材‘、wizzia,,,万,21,a,,92力er:g大u,,t张正坤).乙zy‘,,,g,al,(李永安).孟, ’Q沁嘴(李强).2力“iY(川g和),(翟永健)and Ga。z加nitt(高振家)TheN“danhad之一Terrane in Relat一on to Mesozoie Tcctonies on Continental Margins ofEastAs一a············-·····一·‘··… 盯i二:Jr‘:。ishi,,户r‘,(水芥伸治郎),51,aojs,u,,(邵济安)andZ),a,,gQII,脚ng(张庆龙)M Inerogen,c …

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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