Magnetic properties of tidal flat sediments of the Yangtze Estuary and its relationship with particle size   总被引：6，自引：0，他引：6  

张卫国  俞立中 《中国科学D辑(英文版)》2003,46(9):954-966

Since the 1970s, environmental magnetism has found extensive applications in diverse research areas of geoscience[1]. In China, a lot of environmental magnetic studies have been carried out on loess, lake and marine sediments for the purpose of paleoclima…  相似文献   

Denudation rates of crystalline rock in the Huangling anticline of the Three Gorges of the Yangtze River in China since the Eocene     

张丽萍  杨达源  朱大奎 《中国科学D辑(英文版)》2003,46(9):928-940

The processes and rates of the weathering denudation of the bare crystalline rock are important problems in the field of geosciences[1—6]. Essentially, the weathering denudation process is the process of rock destruction and transportation. In different …  相似文献   

The <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar geochronology constraint and geological significance of mylonites in Shangyi-Chicheng fault belt on the north of North China Craton     

Ling?HuEmail author  Honglin?Song  Danping?Yan  Daogong?Hu 《中国科学D辑(英文版)》2003,46(11):1134-1141

A dating of two biotite samples taken from the meso- and low-temperature mylonites within the Shangyi-Chicheng fault belt on the north of the North China Craton yields ⁴⁰Ar/³⁹Ar isotopic ages of (399 ± 1) Ma and (263 ± 2) Ma, respectively. These data reflect an Early Devonian deformation and a Late Carboniferous retrograde metamorphism event along the fault, suggesting that the tectonic activities of the North China Craton in Paleozoic should be reconsidered.  相似文献   

<Emphasis Type="Italic">In-situ</Emphasis> trace element analyses and Pb-Pb dating of zircons in granulite from Huangtuling,Dabieshan by LAM-ICP-MS     

Yuanbao?WuEmail author  Daogong?Chen  Qunke?Xia  Xianglin?Tu  Hao?Cheng  Xiaozhi?Yang 《中国科学D辑(英文版)》2003,46(11):1161-1170

It is revealed by CL images that there are multi-stage growth internal structures of zircons in the Huangtuling granulite, including the inherited zircons, protolith zircons, sector and planar zone zircons and retrograde zircons. In-situ trace element compositions and Pb-Pb ages have been analyzed by LAM-ICP-MS. The sector and the planar zone domains show typical trace element characteristics of granulite zircon (low Th, U, Th/U, total REEs, clear negative Eu anomalies, relatively depleted HREE and small differential degree between MREE and HREE, etc.), indicating that they formed during granulite-facies metamorphism. The protolith zircons have trace element characteristics of crustal zircon (high Th, U, Th/U, total REEs and enriched HREEs, etc.). 12 analyzed spots on granulite-facies domains give a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of (2154±26) Ma (MSWD = 3.8), which is the best estimated age of granulite-facies metamorphism of this sample. The weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 5 analyzed spots on protolith zircon domains is (2714 ± 22) Ma (MSWD = 1.4), which represents the protolith forming time. The discovery of ca. 3.4 Ga inherited zircon indicates that there are Palaeoarchean continental materials in this area. The interpretation of formation conditions and the ages of zircons can be constrained by simultaneous in-situ analysis of trace elements and ages.  相似文献   

Monsoonal precipitation variation in the East Asia since A.D. 1840     

Yu?LiuEmail author  Park?Won-Kyu  Qiufang?Cai  Seo?Jung-Wook  Jung?Hyun-Sook 《中国科学D辑(英文版)》2003,46(10):1031-1039

Three tree-ring rainfall reconstructions from China and Korea are used in this paper to investigate the East Asian summer monsoon-related precipitation variation over the past 160 years. Statistically, there is no linear correlation on a year-by-year basis between Chinese and Korean monsoon rainfall, but region-wide synchronous variation on a decadal-scale was observed. More rainfall intervals were 1860–1890, 1910–1925, and 1940–1960, and dry or even drought periods were 1890–1910, 1925–1940, and 1960–present. Reconstructions also display that the East Asian summer monsoon precipitation suddenly changed from more into less around mid-1920. These tree-ring precipitation records were also confirmed by Chinese historical dryness/wetness index and Korean historical rain gauge data.  相似文献   

Distribution of ionospheric O<Superscript>+</Superscript> ion in synchronous altitude region     

Jiankui?Shi?Email author  Zhenxing?Liu  Zhang?T.?L.  Jianshan?Guo  Manlian?Zhang  Sheping?Shang  Xigui?Luo 《中国科学D辑(英文版)》2003,46(10):986-993

Based on satellite observation data, using dynamics equation, the ionospheric O⁺ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK _p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O⁺ ion’s density and flux versus longitude in the synchronous altitude region for differentK _p are given. The main results show that in the synchronous altitude region: (i) The O⁺ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic activity indexK _p is, the higher the O⁺ ion’s density and flux, and their variation amplitude will be. The O⁺ ion’s density and flux whenK _{p ≥} 6 will be about ten times as great as that whenK _p = 0. (iii) WhenK _p = 0 orK _{p ≥} 6, the O⁺ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK _p = 3−5, the O⁺ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O⁺ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK _p value.  相似文献   

Oxygen isotope compositions of quartz grains (4–16 μm) from Chinese eolian deposits and their implications for provenance     

Shengshan?HouEmail author  Shiling?Yang  Jimin?Sun  Zhongli?Ding 《中国科学D辑(英文版)》2003,46(10):1003-1011

Oxygen isotope compositions were measured in quartz grains extracted from a 7.0 Ma red clay-loess sequence at Lingtai and six late Pleistocene loess sediments (Malan loess). Results show that the changes in oxygen isotope compositions of Malan loess are basically controlled by the geochemical characteristics of the source materials, while the effect of weathering process after dust deposition could be minor. The oxygen isotope distribution of quartz grains from red clay at Lingtai is similar to that of the overlying loess-paleosol sequence, thus indicating that the red clay at Lingtai has the same eolian origin as the loess-paleosol deposits. Furthermore, the oscillations of the isotope compositions in 4–16 μm-sized quartz grains may reflect the changes, to some extent, of the climatic systems of the source region.  相似文献   

Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean   总被引：9，自引：0，他引：9  

卞林根  高志球  陆龙骅  张雅宾  C.Roger  X.D.Zhang 《中国科学D辑(英文版)》2003,46(6):580-591

It is of major scientific interests to determine the parameters of momentum, heat and vapor exchange in the planetary boundary layer in order to study the effects of ocean-ice-atmosphere interactions and their feedback mechanisms on global climate[1]. Lin…  相似文献   

Characteristics of melt inclusions in skarn minerals from Fe,Cu(Au) and Au(Cu) ore deposits in the region from Daye to Jiujiang   总被引：5，自引：0，他引：5  

赵斌  赵劲松  李兆麟  张重泽  彭卓伦 《中国科学D辑(英文版)》2003,46(5):481-497

The skarns and skarn deposits are widely distributed at home and abroad. The skarn deposits include many kinds of ores and higher ore grade. Some of them are broad in scale. Scientists of ore deposits from different countries have paid and are paying grea…  相似文献   

Late Mesozoic crust-mantle interaction and lower crust components in South China: A geochemical study of mafic granulite xenoliths from Cenozoic basalts   总被引：4，自引：1，他引：3  

于津海  徐夕生  周新民 《中国科学D辑(英文版)》2003,46(5):447-460

Mafic granulite xenoliths have been discovered in many volcanoes (especially alkali basalt and kimberlite) all over the world. They formed generally in lower crust, and recorded lots of in- formation on the lithosphere formation and crust-mantle interacti…  相似文献