CENOZOIC VOLCANIC ROCK SERIES IN SOUTHEASTERN CHINA——PETROCHEMISTRY

In this paper, the age, spatial distribution and petrochemistry of Cenozoic volcanic rocks of southeastern China are discussed. They are subalkalic and alkalic. Except for the Pleistocene calc-alkalic volcanic rocks of northern Taiwan and the Late Tertiary tholeiitic rocks of Eastern Coastal Range of Taiwan, the alkalic basaltic rocks form the majority. Only alkalic and strongly alkalic basaltic and ultrabasic volcanic rocks occur in the inland to the west of the Haifeng-Zhenghe-Shangyu fracture zone. It follows that the petrochemical nature of the Cenozoic volcanics studied exhibits a marked trend of variation with time and space, implying that their formation was obviously controlled by the geotectonic setting.     

THREE-COMPONENT MIXING AND FOUR-SYSTEM RECYCLING MODELS FOR EXPLAINING Nd-Sr-Pb ISOTOPIC CORRELATIONS OF SUBOCEANIC AND SUBCONTINENTAL MANTLES

The Pb-Sr-Nd isotopic data of Cenozoic volcanic rocks from the continent of China show that there exist three main end members of the mantle, which are the enriched mantle of Wudalianchi in Northeast China, the depleted mantle in South China and the recycling mantle of Yunnan in southwestern China. A11 the data can well fit a curved surface of three-component mixing in Pb-Sr-Nd isotopic space. Seven major end members in the global mantle can be identified. Based on the intersection line between two curved surfaces of three-component mixing in the continent of China and the ocean, the Pb-Sr-Nd isotopic ratios in the primatire mantle can be calculated. In order to explain the genesis of seven end members of the mantle, four-and three-system recycling models were used. The theoretical results are well comparative with the isotopic distribution observed in global Cenozoic volcahics, and can provide useful constraints on the process of the geochemical evolution in the crust-mantle system.     

AEROMAGNETIC SURVEY AND GEOLOGICAL STRUCTURE OF OFFSHORE CHINA

This paper discusses the characteristics of the regional geological structure of the Bohai Sea, the Huanghai Sea, the East China Sea and the South China Sea on the basis of the data achieved by aeromagnetic surveys over the past years.The Huanghai Sea is an intercontinental sea which is tectenically similar, and can be connected, to the adjacent continental parts. It is a submerged part of the continent. Aeromagnetic survey shows that the deep structures in this area strike E-W, belonging to the Pal-Asiatic Tectonic Domain. The South China Sea is a typical marginal sea of the Western Pacific Ocean, resulting from the fracturing of the continental margin and the sea floor spreading from the Mid-Oligocene to the Miocene.     

GEOCHEMISTRY OF SEDIMENTS AND ENVIRONMENT IN XIHU LAKE OF GREAT WALL STATION OF CHINA, ANTARCTICA

The determined results in this paper, which were obtained by the multielement analysis of the 260 cm-deep core sediments under the water of Xihu Lake in the Great Wall Station area, are as follows: The Cenozoic volcanic rocks around Xihu Lake are the main source of sediments in the lake. The chemical differentiation in very fine particles is still detectable. From the variation of ratios of the Cs/Rb, Br/CI and La/Yb in the clay fraction with depth and from the variation or CaCO_3 contained in the sediments, cation replacing amount in the clay grains and the sediment grain sizes in time, it can be seen that since 3600 a. B. P., there has existed the climatic variation of warm-cold-warm, which embodies the advance and retreat history of the ice sheet in this area.     

TECTONIC FRAMEWORK OF THE CONTINENTAL BASEMENT OF SOUTHEAST CHINA

The chronology and tectonic evolution model of the continental basement in southeast China margin is an important debatable geological subject. The Cathaysia is shown in this paper to be in accordance with many geological facts and also with the age data obtained by multi-dating method. Its age has been determined to range from 900 to 2000 Ma. The age of the unconformity plane in the Cathaysia is 1400 Ma. The collision and suture between the Jiangnan oldland and the Cathaysia took place during the early Jinning Period. Toward Jiangxi, Hunan, Guangdong and Guangxi, these two continents gradually opened to form a residual oceanic basin. The sedimentation centre of the basin continuously migrated southwestward from the Jinning through the Caledonian Period, and finally closed in the Guangxi Movement and Dongwu Movement. The drift-rotation of the Cathaysia after the Jinning Period has been inferred.     

GEOCHEMISTRY OF IGNEOUS ROCK IN PANXI RIFT

In this paper the petrogenesis and magmatism of igneous rocks in the Panxi Rift are discussed based on the major element, transition metallic element, REE and other trace element analysis data of more than 40 samples.According to major element data, a feature of bimodal distribution is displayed. The transition metal patterns show that Cr and Ni are highly depleted and Ti is highly concentrated, reflecting a rather complex history of crystallization differentiation.The distribution patterns of hygromagmatophile element abundance of basalts normalized with primary mantle values are shown to be intermediate between those of alkali basalts and continental tholeiites. This provides evidence suggesting that the basalts were generated in a rift tectonic environment, and that the primary magma came deeply from the primary mantle as a result of partial melting of garnet lherzolite.     

3D S-Wave Velocity Structure of the Crust and Upper Mantle

In this paper, 238 Rayleigh wave path data are selected and processed by the matched-filtering frequency-time analysis technique and the grid dispersion inversion method to obtain the 3D S-wave velocity structure of China mainland and its adjacent sea regions. The results show that the velocity structure relates to geotectonic division, Bouguer gravity anomaly is basically controlled by the relief of Moho discontinuity, the buried depth of LVL in upper mantle concerns the surface heat flow deeply. In this paper, authors indicate the main characteristics of the velocity structure in tectonic active and stable regions.     

The Discovery and Geological Feature of Kyanite-Topazite in High-Pressure Belt From Central China

For the first time, we find kyanite-topazite which is similar to the white schist from abroad, in Jiangsu, Anhui, Henan of China. Because of intercontinental obduction and collision, the kyanite-topazite is formed from the superhigh-pressure metamorphism of sedimentary rock in continental crust, at the depth of mantle. Kyanite-topazite runs parallel to blue schist, eclogite and constitutes the high-pressure metamorphic belt in Central China. Its original rocks are a set of sedimentary rock series which is mainly composed of marginal shallow marine facies to continental facies pelitic to magnesium carbonatite, both rocks exist in Precambrian Middle-Upper Proterozoic metamorphic strata.     

LINEAR ISOSTATIC GRAVITY ANOMALIES IN THE SOUTH CHINA SEA

In this paper a model of linear isostatic gravity has been shown in the South China Sea. By means of resolving a stochastic integral equation, a compensating density, which is corresponding to the topographic masses of unit volume, has been established. By calculation, the average depth of the mantle bottom under the South China Sea is 450 km and the depth of one of the interfaces within the layer B is 250 km. The depression areas of the South China Sea are caused by the surplus of the compensation in the depth between 450 and 560 km. The compensating and isostatic gravity anomalies have been resolved, and a geological interpretation has been made.     

WAVE CHARACTERISTICS OF CRUSTAL TECTONICS IN CONTINENTAL MARGINS

Continental margins are the transitional zone between continents and oceans. The tectonic deformation of crust in continental margins is very complex. This paper deals with the complex crust tectonics of continental margins in terms of the basic principle that elastic waves travel through semi-infinlte medium and the wave theory of crust. The continental margin off the North American coasts of the Atlantic used to be the active Pacifictype margin. At present, the crust movement in this margin tends to be stable; therefore it becomes the Atlantic type.     

A STUDY ON THE ORDERING PATH OF ALKALINE FELDSPAR IN VOLCANIC ROCKS

In this paper, the study on the ordering path of alkaline feldspar from some volcanic areas by X-ray powder method is presented. The published data by mathematical statistics is treated, a series of formulas and figures to determine chemical composition and degree of Al site occupancy of alkaline feldspar are reset-up, and the simulated function Y=Z~(?) with Thompson's coefficients Y, Z and κ as the indexes of ordering path is suggested. Based on the difference between ordering paths distinguished by κ of alkaline feldspar from volcanic basins, the petrological characters of volcanic basins and the petrological characters of volcanic rocks, some preliminary conclusions of the origin are also summarized.     

REE AND Sr, Nd, Pb ISOTOPIC GEOCHEMISTRY OF HUANGYISHAN BASALT, KUANDIAN, LIAONING, NORTHEAST CHINA

In the light of major element geochemistry, mineral chemistry and REE and isotopic data, the small but apparent isotopic differences between the Cenozoic volcanic rocks east and west of the Tancheng-Lujiang fault are believed to be caused by the mixing and metasomatism of crustal and mantle material in tho mantle source region in response to Pacific plate subduction. The presence of phlogopite and pargasite in mantle xenoliths lends strong support to mantle metasomatism.     

ALGAL, SPORES AND POLLEN ASSEMBLAGES FROM LATE PLEISTOCENE IN THE EAST PART OF THE CHINA SEA AND THEIR PALEOENVIRONMENTS

The paper deals with fossil spores, pollen and algae from the sediments of 70,00-12,000a B. P. in the eastern sea area of China, distinguishing three spores, pollen and algal zones. Zone Ⅰ indicates that the climate was cold, the sea level was lower, the continental shelf of theDonghai Sea (the East China Sea)was exposed as the plain with various grasses thickened and manylakes andswamps dotted in which lived abundant freshwater algae of Pediastrum, Zygnema, etc.The hills in the continental margin were covered by the dark coniferous forests of Abies, Piceaand Pinus. The climate of Zone Ⅱ was warm, resulting in the sea level rising and the con-tinental shelf submerged as neritic environment with a variety of diatoms, dinoflagllate andDictyocha. The vegetation of the hills in the continental margin became mixed forests ofconiferous and broad-leaf trees mainly composed of Pinus and Quercus. Zone Ⅲ indicatesthat the climate became cold again and the continental shelf was exposed as plain with thesame lan     

THE DISTRIBUTION OF P ELEMENTS IN D. melanogaster ALONG THE COAST OF CHINA STUDIED BY DNA HYBRIDIZATION METHOD

The distribution of the P-M system in four local Drosophila melanogaster populations obtained insouthern China has been examined by mating tests. There was no P strain. A HindⅢfragnment ofthe P element has been cloned, named as pPH 0.86, and used as probe in this study. The distribu-tion of the P element itself in thirteen local D. melanogaster populations along the eastern coast ofChina has been studied by the method of DNA hybridization. It is found that all the populations ob-tained from the north of Shanghai carry P elements but few populations from the south of Shanghai carry Pelements. In comparison with the mating test, the method of DNA hybridization is more direct andreliable.The origin and trends of distribution of P elements in China are discussed in this paper.     

SUBVOLCANIC GRANITOIDS IN SOUTHEASTERN CHINA AND THEIR METALLOGENESIS

Mesozoic volcanic rocks are widely distributed in southeastern China. There exist various kinds of subvolcanic granitoids associated with the volcanic rocks. This paper deals with the geological setting, the characteristics and the metallogenesis of these subvolcanic granitoids.     

TRACE ELEMENTS GEOCHEMISTRY OF GRANITOID IN PANXI AREA

A lot of granitoid rocks occur in Panxi area, SW China, which were formed during Jinningnian-Chengjiangnian, Hercynian-Indosinian and Yenshanian. According to their trace elements geochemical and petrochemical characteristics, they can be divided into calc-alkaline and alkaline granites. The petrogenesis and magma sources of these granitoid rocks are different. The Jinningnian-Chengjiangnian granitoid rocks include Mopanshan granite body, Moshaying granite body and Lugu granite body. The Mopanshan body might be formed by partial melting of the lower crust and due to refusion of basic volcanic rocks. The magma source of the Moshaying and the Lugu bodies might be formed by partial melting of the upper crust. The Hongge-Ailanghe granites belonging to the Hercynian-Indosinian may be products of complex melting from the crust-mantle materials caused by the increase of temperature during rifting stage in the area. The Cida and Taihe alkaline granites belonging to the Hercynian-Indosinian might be derived from     

DISTINGUISHING OF TWO VOLCANIC ROCK SERIES IN THE LANCANG GROUP, YUNNAN PROVINCE, SW CHINA AND ITS GEOLOGICAL IMPLICATION

The detailed study on petrochemistry and geochemistry shows that meta-volcanics from Huimin and meta-basalts from Suyi belong, respectively, to different volcanic series. The former is of non-alkalic volcanic series and the latter is of straddle A-type alkslic series. Based on their geochemical characteristics of REE, LIL, HFS and Nd, Sr isotope elements, we suggest that Huimin volcanics were formed in an island arc setting and Suyi basalts were formed in a back-continental arc extensive setting. These two volcanic series have not petrogenic relationship.     

GEOCHEMICAL PRINCIPLES OF ALKALINE METASOMATISM

Studies made in the last twenty years and more have shown that alkaline metasomatism (AM) is far more exstensive and important in metallogenesis and rock-forming processes than what have been recognized up to date. In this paper geochemical essential of the AM, which is closely related to the ore formation of a series of oxygenfile and chalcofile elements, and their dozens of mineralization types are discussed. In fact, the so-called hydrothermal process is mainly represented by the AM. The AM is also a fundamental mechanism of formation of the rocks such as granite, migmatite, agpaite, carbonatite, spilitekeratophyre, etc., which are intimately connected with the degassing, dewatering, dealkalinizing from the mantle,     

GENETIC CHARACTERISTICS OF KAOLIN DEPOSITS IN CHINA

This paper gives an outline of the geological environments and geochemical characteristicsof the kaolin deposits of various geneses occurring in China. The author proposes that theenrichment of kaolin is derived from continuous leach-alteration of parent rocks by variousacidic solutions. takes a new view on the genesis that the primary sedimentary kaolin depositsare formed by autochthonous reconstruction of aluminosilicates after their sedimentation, andnames them the "false sedimentary layers". The author studies in detail the developing pro-cess and evolutional regularities of kaolin minerals, and finally summarizes a series of theirformation and genesis-characteristic mineral-indicators in the pay zones of different geneses.     

CONDUCTIVE LAYER IN THE CRUST IN NORTH CHINA AND ITS RELATION TO CRUSTAL TECTONISM

Since 1976 observations of more than forty magnetotelluric (MT) sites have been carriedout in North China, and the conductive layer at the depths of 15-25 km with the longitudinaleonduetances of several hundreds to more than one thousand siemens have been found beneathmost of the MT sites. In this region, tho depth of the conductive layer is very close to thatof the minimum velocity layer determined by DSS. Most earthquakes have occurred above thislayer, and a lot of normal faults have vanished above this layer, too. The area, where thedepth and longitudinal conductance of the conductive layer are shallow and high, has a higherheat flow and stronger tectonism during the Cenozoic time. The authors suggest that the con-duetive layer in the crust boneath the plain might result from partial melting of the felsieminerals, while that beneath the surrounding areas from dehydration of the minerals withcrystal water.