Tertiary Calcareous Nannofossil Biostratigraphy in the North Part of the South China Sea

The marine Tertiary sequence in the north part of the South China Sea may be divided into 18 LateOligocene to Pliocene calcareous nannofossil zones and one unnamed Eocene assemblage based on an analysisof calcareous nannofossils from 40 offshore boreholes. The unnamed Eocene assemblage has been found onlyon the northeast margin of the Zhujiangkou basin. The 18 cakareous nannofossil zones of the Late Oligoceneto Pliocene were deposited in succession, but their development degrees are different. Among the 18 calcareousnannofossil zones, those corresponding to Martini's (1971) NN4- NN5 zones, NN11 zone and NN13-NN15zones are well developed, relatively persistent laterally and also widely distributed. They are the importantmarkers for the stratigraphical subdivision and correlation of the Upper Tertiary between the various basins inthe north part of the South China Sea. Based on the calcareous nannofossils and the sedimentsry features coup-led with the foraminifer zonation in certain basins, the present paper discusses the sedimentary characteristicsof the marine Tertiary and as well as the distribution and development of the sedimentary hiatus in the region.The calcareous nannofossil markers for the Upper / Lower Tertiary and the Quaternary / Tertiary boundaries,and the characteristics and geological significance of the reworked calcareous nannofossils are also discussed inthe paper.     

Arman’ Flora of the magadan region and development of floras in the North Pacific during the Albian-Paleocene

The Arman’ Flora from volcanogenic-sedimentary deposits in the Arman’ River basin and Naraula Formation in the Nel’kandzha-Khasyn interfluve includes 82 species of fossil plants comprising liverworts, horsetails, ferns, caytonealeans, cycadaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms incertae sedis, and angiosperms. The Arman’ Flora appears to be of Turonian-Coniacian age, as it is close to the reliably dated Penzhina and Kaivayam floras from the Northwest Kamchatka and to Tyl’pegyrgynai Flora of the Pekul’nei Ridge. The dating is consistent with isotopic dates (⁴⁰Ar/³⁹Ar and U-Pb SHRIMP) characterizing the age of plant-bearing sequences. Based on the considered position of the Arman’ Flora in the scheme of Cretaceous florogenesis, a leading role in that florogenesis was played by the gradual invasion of floras by new, angiosperm dominated, plant communities. These communities initially populated unstable habitats in the coastal lowlands of Northeast Asia and Alaska, gradually invading with time the Asiatic intracontinental areas. The peculiar combination of Early and Late Cretaceous plants characteristic of the Arman’ Flora is strong evidence that Cenophytic plant communities dominated by angiosperms colonized areas still populated in the Late Cretaceous by Mesophytic communities. Absence of Mesophytic and Cenophytic taxa mixing in the Arman’ Flora burials suggests a replacement of plant communities as whole rather than of separate plants by more advanced taxa.     

Discussing the Oil-Control Effects of the North Latitudinal 38° Belt in Central Part of the Ordos Basin

<正>The Ordos Basin in the western part of the North China Craton is commonly believed to be a multi-controlled oilbearing basin.It is bounded by the Xing’an-Mongolian Orogen to the north,the Qingling Orogen to the south,the Lüliang mountain to the east and the Helanshan-Liupanshan mountain belt to the west.The interpretation of geophysical data reveals a latitudinal(38°)fault belt in the centre of the Ordos Basin,which controls the hydrocarbon generation,migration and accumulation in the basin.This study attempts to     

Characteristics and Formation Mechanism of the Geothermal Field in the North China Downfaulted Basin

The geothermal field is mainly controlled by the regional tectonic framework characterized by alternationsof uplifted and depressed basement. and exhibits a similar zoned distribution of temperatures. In the upliftedarea the geothermal gradient (G) and terrestrial heat flow value(q) of the Cenozoic sedimentary cover are rela-tively high, with G=3.5-5.0℃/100m and q=63-84mW/m~2; whereas in the depressions they are rela-tively low, with G=2.7-3.5℃/100m and q=46-59mW/m~2. In the whole region, G=3.58℃/100m and q=61.5±13.4nW/m~2, indicating a comparatively high geothermal background and the presence of localgeothermal anomalies. A comparison of the results of mathematical simulation of the geothermal field with themeasured values shows a good agrecment between them. The geothermal difference between various tectonicunits is caused chiefly by the lateral and vertical variation of thermal properties of shallow crustal rocks. Thisphenomenon can be regarded as the result of redistribution of relatively uniform heat flows from the deep crustin the surficial part of the crust in the process of their upward conduction.     

Structural Geochemical Study of the Yuxi Fold-Thrust Belt in the Southern North China Plate

The gigantic fold-thrust fracture belt that ex-tends for 900 kmto the NWin the southern NorthChina plate strides across three provinces : Shaanxi ,Henan and Anhui .It is one of the most characteristicstructural deformations in the North China plate .Along this structural belt a series of i mportantcoalfields occur ( e . g. Pingdingshan, Queshan,Huainan) inthe southernmost edge of the North Chi-na coal-concentrating basin. Consequently ,this beltis not only of key value for research onthe…     

The Characteristics of Fluorine in the Groundwater of North China and the Significance of Fluorite-Water Interaction to Fluorine Transportation

This paper approaches the transportation of fluorine in the groundwater ofepigene Quarternary aquifer by calculation and laboratory studies.The conclusionthat the enrichment and saturation abilities of fluorite are related to the transpor-tation of fluorine in groundwater is reached.They would be conducive to findingthe cause of regional fluorine distribution in the groundwater of North China.     

Petrogenetic variability along the North–South Propagating Spreading Center of the North Fiji Basin

Summary Previous studies on propagating rifts suggested that segmentation of a spreading axis could represent the superficial mark of mantle behavior (Sinton et al., 1983; Nicolas, 1989; Gente et al., 1995). The study of North–South Propagating Spreading Center (NS-PSC) from the North Fiji Basin (NFB) brings new insights to this debate. Basalts from the central part of the propagator have more variable incompatible and isotopic ratios then those from its northern tip. A model of dynamic partial melting of a thermally and slightly geochemically and isotopically heterogeneous mantle is proposed. Beneath the central segment, the partial fusion starts deeper (ca. 30km) and reaches a higher rate (ca. 22%). Further open system differentiation occurs within shallow permanent magma reservoirs along most of the central segment. Below the segment closest to the tip of the propagator the partial fusion starts shallower (ca. 25km) and stays at a lower rate (ca. 16%). The maximum of differentiation occurs close to the propagator, in small, periodically disconnected, magma bodies resulting in the production of ferrobasalts close to the tip. In order to explain these variations, the presence of an asthenospheric diapir focused beneath the central part of the NS-PSC is proposed. The petrogenetic processes of propagating spreading centers of mature oceanic basins or back-arc basins are identical.     

Zircon U-Pb Geochronology of the Granites From Xiaoliugou W-Mo Deposit in North Qilian

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The Isotopic Composition of Noble Gases in Gold Deposits and the Source of Ore- Forming Materials in the Region of North Hebei, China

1IntroductionOnthenorthernmarginoftheNorthChinaplatformislocatedoneofthemostimportantAu Ag polymetallicore concentratedzones,wherethereareavarietyoforetypes .Soithasbeenat tractingeverincreasingattentionofmanygeologists (PeiRongfuetal.,1 998;ShenBaofengetal.,1 994 ;LuSongnianetal.,1 997;HuShouxietal.,1 994 ;ChenYuchuan ,1 999;ZhaiYushengetal.,1 999) .Manyscholarspresentedtheirresearchresultsinvariousaspects.How ever ,thesourceofore formingmaterialshaslongbeenafocusofdiscussion .Studieso…     

Three-Dimensional P-Wave Velocity Structure of the Crust of North China

Since the Xingtai (邢台) earthquake in 1966,China Earthquake Administration has carried out a survey campaign along more than thirty deep seismic sounding (DSS) profiles altogether about twenty thousand kilometers long in North China to study the velocity structure of the crust and the upper mantle in this region,and has obtained a great number of research findings. However,these researches have not provided a 3D velocity structure model of the crust of North China and cannot provide seismic evidence for the study of the deep tectonic characteristics of the crust of the whole region. Hence,based on the information from the published data of the DSS profiles,we have chosen 14 profiles to obtain a 3D velocity structure model of North China using the vectorization function of the GIS software (Arc/Info) and the Kriging data gridding method. With this velocity structure model,we have drawn the following conclusions: (1) The P-wave velocity of the uppermost crust of North China changes dramatically,exhibiting a complicated velocity structure in plane view. It can be divided into three velocity zones mainly trending towards north-west. In the research area,the lowest-velocity zones lie in the Haihe (海河) plain and Bohai (渤海) Bay. Although the geological structure of the sedimentary overburden in the study area is somewhat inherited by the upper crust,there are still several differences between them. (2) Generally,the P-wave velocity of the crust increases with depth in the study area,but there still exists local velocity reversion. In the east,low-velocity anomalies of the Haihe plain gradually disappear with increasing depth,and the Shanxi (山西) graben in the west is mainly characterized by relatively low velocity anomalies. Bounded by the Taihang (太行) Mountains,the eastern and western parts differ in structural trend of stratum above the crystalline basement. The structural trend of the Huanghuaihai (黄淮海) block in the east is mainly north-east,while that of the Shanxi block and the eastern edge of the Ordos block is mainly north-west. (3) According to the morphological features of Moho,the crust of the study area can be divided into six blocks. In the Shanxi block,Moho apppears like a nearly south-north trending depression belt with a large crustal thickness. In the southern edge of the Inner Mongolia block and the south of the Yanshan (燕山) block,the Moho exhibits a feature of fold belt,trending nearly towards east-west. In the eastern edge of the Ordos block,the structure of Moho is relatively complex,presenting a pattern of fold trending nearly towards north-west with alternating convexes and concaves. Beneath the Huanghuaihai block,the middle and northern parts of the North China rift zone,the Moho is the shallowest in the entire region,with alternating uplifts and depressions in its shape. For the anteclise zone in the west of Shandong (山东) Province,the Moho is discontinuous for the fault depression extending in the north-west direction along Zaozhuang (枣庄) -Qufu (曲阜).     

Location of the Suture Zone between the South and North China Blocks in Eastern Dabie Orogen

INTRODUCTION TheDabieMountainsareacollisionalorogenbe tweentheSouthandNorthChinablocks.Theageof theultrahighpressuremetamorphism(Hackeretal., 1998;Rowleyetal.,1997;Amesetal.,1993;Liet al.,1993)andthelateststratainvolvedintheforeland fold thrustbelt(Xueta…     

The Role of Evaporatic Rocks in the Formation of the Xishimen Iron Skarn Deposits, Eastern North China Craton

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Occurrence of Bindheimite in North‐West Queensland

Bindheimite has been identified in specimens from the Lvov Lease, N.W. Queensland. Chemical, microscopic and X‐ray data are given for the mineral which was found to possess a cubic lattice with a unit cell dimension of 10–427 A.     

Rb—Sr Isotopic Chronology of the Au—Bearing Quartz Veins in Gold Depostits in the Eastern Part of North China Platform

In the eastern part of Chian there had occurred large-scale gold mineralization during the Mesozoic,resulting in a large number of inprotant gold ore-concentrated areas.In this paper we have selected some isotope data(including four gold deposits previously studied and two gold deposis in this work)of Au-bearing quartz veins of the representative gold deposits in six impor-tant gold ore-concentrated areas in the periphery of the North China Platform and calculated their metallogenic ages using the method of Ludwig(2.90 version).The results show that the repre-sentative gold deposits in the six gold ore-concentrated areas were formed during the Mesozoic.     

Discovery of Coesite in the North Qaidam Caledonian Ultrahigh-High Pressure (UHP-HP) Metamorphic Belt in the NE Qinghai-Tibet Plateau

Coesite was discovered as inclusions in zircon separates from paragneiss associated with a large eclogite body in the North Belt of the Qaidam UHP terrane on the Chinese New Year of 2001 by Laser Raman Spectrometer at Tokyo Institute of Technology. Some graphite inclusions also found. However, extensive search did not reveal the occurrence of microdiamond. This finding confirms our previous suggestion that the North Qaidam UHP terrane was recrystallized at P below the diamond stability…     

Biostratigraphic Study of the Paleocene–Eocene Boundary in Northern Tunisia, North Africa

A new section at Jebel Gorraa,in northern Tunisia,contains the Paleocene-Eocene transition interval.Sample analysis of the section delivers abundant and diverse microfauna of planktonic and benthic foraminifera.Biostratigraphically,the Acarinina sibaiyaensis index-species is identified for the first time in this region,which allows us to specify the location of the Paleocene-Eocene boundary as well as the first E1 biozone of the lower Eocene.Samples from this biozone contain calcitic tests poorly preserved with an enrichment of iron oxide signifying a period of upheaval in local marine environments linked to the global warming of the Paleocene-Eocene Thermal Maximum （PETM）,the marker for the P/E boundary.     

Geochronology and Geochemistry of the Middle Proterozoic Aoyougou Ophiolite in the North Qilian Mountains,Northwestern China

The Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. The diabases and basalts show light rare-earth element enrichment and have relatively high TiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. They are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr-spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proteroz     

Geochronology and Petrology of the Beiligaimiao Magmatic Sulfide Deposit in the Northern Margin of North China Craton, Inner Mongolia

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Subduction of Continental Crust in the Early Palaeozoic North Qaidam Ultrahigh-Pressure Metamorphic Belt, NW China:Evidence from the Discovery of Coesite in the Belt

Coesite was discovered as inclusions in zircon separates from pelitic gneiss associated with a large eclogite body in the North Qaidam ultrahigh-pressure (UHP) terrane. Some graphite inclusions were also found. This finding suggested the occurrence of in-situ UHP metamorphism and that the terrane was most likely recrystallized at pressures below the diamond stability field. It supported other previous indirect UHP evidence, such as polycrystalline quartz inclusions in eclogitic garnet, quartz lamellae in omphacite and P-T estimates for both eclogite and garnet peridotite. The U-Pb and Sm-Nd ages of the North Qaidam eclogite indicated that subduction of continental crust occurred in the Early Palaeozoic, which probably recorded a collision between the Sino-Korean and Yangtze plates.     

Implications of the Precambrian Non-stromatolitic Carbonate Succession Making up the Third Member of Mesoproterozoic Gaoyuzhuang Formation in Yanshan Area of North China

A particular non-stromatolitic carbonate succession making up the third member of the Mesoproterozoic Gaoyuzhuang (高于庄) Formation might demonstrate that a stromatolite decline of the Mesoproterozoic occurring at ca. 1 450 Ma besides other three events of the Proterozoic,respectively,occurred at ca. 2 000 Ma,ca. 1 000 Ma,and ca. 675 Ma. The forming duration of this non-stromatolitic carbonate succession can be generally correlative to that of a similar depositional succession in North America,i.e. a non-stromatolitic carbonate succession made up by the Helena Formation of the Belt Supergroup,which suggests that the stromatolite decline occurring at ca. 1 450 Ma may be a global event. This information endows the non-stromatolitic carbonate succession making up the third member of the Gaoyuzhuang Formation in the Yanshan (燕山) area with important significance for the further understanding of Precambrian sedimentology. The Mesoproterozoic Gaoyuzhuang Formation in Yanshan area is a set of more than 1 000 m thick carbonate strata that can be divided into four members (or subformations). The first member (or the Guandi (官地) subformation) is marked by a set of stromatolitic dolomites overlying a set of transgressive sandstones; the second member (or the Sangshu'an (桑树鞍) subformation) is a set of manganese dolomites with a few stromatolites; the third member (or the Zhangjiayu (张家峪) subformation) is chiefly made up of leiolite and laminite limestones and is characterized by the development of molar-tooth structures in leiolite limestone; the fourth member (or the Huanxiusi (环秀寺) subformation) is composed of a set of dolomites of stromatolitic reefs or lithoherms. Sequence-stratigraphic divisions at two sections,i.e. the Jixian (蓟县) Section in Tianjin (天津) and the Qiangou (千沟) Section of Yanqing (延庆) County in Beijing (北京),demonstrate that a particularly non-stromatolitic succession making up the third member of the Mesoproterozoic Gaoyuzhuang Formation is developed in the Yanshan area of North China,in which lots of grotesque matground structures (wrinkle structures and palimpsest ripples) are developed in beds of leiolite limestone at the Qiangou Section and lots of molar-tooth structures are developed in beds of leiolite limestone at the Jixian Section. The time scale of the Gaoyuzhuang Formation is deduced as 200 Ma (from 1 600 Ma to 1 400 Ma). The duration of an obvious hiatus between the Gaoyuzhuang Formation and the underlying Dahongyu (大红峪) Formation is deduced as 50 Ma to 100 Ma,thus the forming duration of the GaoyuzhuangFormation is thought as 100 Ma (1 500 Ma to 1 400 Ma). Furthermore,the age of the subface of the third member of the Gaoyuzhuang Formation that is just in the mid position of the Gaoyuzhuang Formation can be deduced as about 1 450 Ma,which is the basis to infer a stromatolite decline of the Mesoproterozoic occurring at ca. 1 450 Ma. Importantly,several features of both the molar-tooth structure and the stromatolite,such as the particular forming environment,the important facies-indicative meaning,and the episodic distribution in the earth history,might express the evolutionary periodicity of the surface environment of the earth and can provide meaningful clues for the understanding of the Precambrian world,although their origin and forming mechanism is highly contentious. Therefore,like other three stromatolitic declines,respectively,occurring at ca. 675 Ma,ca. 1 000 Ma,and ca. 2 000 Ma,the identification of the stromatolite decline occurring at ca. 1 450 Ma during the Golden Age of stromatolites (2 800 Ma to 1 000 Ma) has important meaning for the further understanding of the evolving carbonate world of the Precambrian.