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121.
Sm/Nd isotopic age determination showed that Xiongshan dike swarm was at 585.7 Ma ± 30 Ma. The trace element geochemistry
and Sr/Nd/Pb isotope gemhemistry studies indicate that the dike swarm was products of back-arc basin spreading ridge and the
magma originated from the depleted mantle region which was metasomatized by LILE-rich liquids/melts derived from subduction
slab.
Project supported by the National Natural Science Foundation of China. 相似文献
122.
By means of barotropic model, the characteristic and initial value problems are investigated to reveal the local two-dimensional
barotropic instability of the nonuniform current to the dynamic mechanism of the formation of the Yangtze-Huaihe River severe
storm in July 1991. Analytical theory and numerical experiment show that (i) the unstable developing modes are chiefly the
two periods of about 44 d and 10 d, which are fundamentally consistent with that of the precipitation change of the Yangtze-Huaihe
River. (ii) The growth rate of the local perturbation is dominated by the meridional wave numbern = 1–5 and zonal wave numberk = 1–12, i.e. the severe storm over the Yangtze-Huaihe River results from the interaction of the systems at different latitudes
and waves of different scales, (iii) The perturbation over the Yangtze-Huaihe River possesses the property of local intensification,
which slowly migrates westward over the lower and middle reaches of the Yangtze-Huaihe River. (iv) The growth rate of the
instability, especially the propagation velocity of the perturbation, is sensitive to the external parameters ū and α.
Project supported by the National Natural Science Foundation of China. 相似文献
123.
Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau 总被引:5,自引:0,他引:5
Two Red Clay profiles near Xi’an and Xifeng were investigated in an attempt to determine magnetostratigraphic and palaeoclimatic
records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma,
and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic
history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5–2.5 Ma. Stepwise
increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the
Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global
ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences
from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan
Plateau, solar radiation, global ice volume, etc.
Project supported by the National Natural Science Foundation of China and the Foundation of Xi’an Laboratory of Loess and
Quaternary Geology, Chinese Academy of Sciences. 相似文献
124.
Evolution of Quaternary groundwater system in North China Plain 总被引:4,自引:0,他引:4
Zonghu Zhang Dehong Shi Fuhong Ren Zhengzhou Yin Jichao Sun Cuiyun Zhang 《中国科学D辑(英文版)》1997,40(3):276-283
The Quaternary groundwater system in the North China Plain is formed mainly through the terrestrial water flow action on the
united geological and tectonic backgrounds. The analysis of groundwater dynamic field, simulation of groundwater geochemistry,
and the14C dating and extraction of isotope information have provided more evidence for recognizing and assessing the evolution of
groundwater circulation system and studying the past global changes. The exploitation and utilization of groundwater on a
large scale and overexploitation have given rise to the decline of regional groundwater level, change of flow field, decrease
of water resources and downward movement of saline water body. The water environment has entered a new evolution stage in
which it is intensely disturbed by the mankind’s activities.
Project supported by the National Natural Science Foundation of China. 相似文献
125.
通过对1992年河南登封4.7级地震的资料分析,表明拐河老井地下水位变化是区域应力场的变化效应。在时间上有连续性,在空间上和构造体系上有一定的相关性 相似文献
126.
滇西北金沙江带蛇绿岩,蛇绿混杂岩形成环境及时代 总被引:22,自引:2,他引:22
本文对滇西北金沙江带蛇绿岩及其混杂岩的产状、规模,岩石学及岩石化学特征等进行系统的综合研究,并根据大量的化石资料,将该区蛇绿岩的形成时代厘定为晚石炭世至二叠纪,蛇绿要岩的形成时代厘定为早、中三叠世,论证了本区蛇绿岩产于规模较小的洋盆环境之中,由于金沙江洋盆发育阶段较短暂,不具有隔离冈瓦纳及扬子两大古生物地理区系的作用,因此,金沙江缝合带不能构成古特提斯域的主缝合带。 相似文献
127.
孙玉壮 《中国地球化学学报》2004,23(2):101-111
Thirty-seven Kupferschiefer samples from southwestern Poland were analyzed by microscopy, Rock-Eval approach and instrumental neutron activation analysis to understand the geochemical and morphological characteristics of kerogen present in the samples. The analytical results indicate that there are two different types of kerogens. One type was only subjected to thermal alteration processes, and the other was further oxidized after deposition of the sediment.In the oxidized samples migrabitumen was transformed into pyrobitumen. Rock-Eval analyses show a significant decrease in HI values in the oxidized samples and an increase in OI values in relation to the samples that were not influenced by oxidation. Variations in S2 versus Corg contents indicate a change in kerogen from Type II to Type III with progressing oxidation. The presence of pyrobitumen and the depletion of hydrogen in the altered kerogen allow one to conclude that the kerogen was used as hydrogen donor for thermochemical sulfate reduction(TSR). 相似文献
128.
129.
The Sanchazi mafic-ultramafic complex in Mianlue tectonic zone, South Qinling can be subdivided into two blocks, i.e. Sanchazi paleo-magmatic arc and Zhuangkegou paleo-oceanic crust fragment (ophiolite). The Sanchazi paleo-magmatic arc is mainly composed of andesite, basaltic and basalt-andesitic gabbro (or diorite), andesitic dyke, plagiogranite and minor ultramafic rocks, which have typical geochemical features of island arc volcanic rocks, such as high field strength element (e.g. Nb, Ti) depletions and lower Cr, Ni contents. The Light rare earth element (LREE) and K enrichments of these rocks and zircon xenocrystals of 900 Ma from plagiogranite suggest that this magmatic arc was developed on the South active continental margin of the South Qinling micro-continent. The U-Pb age of (300 ± 61)Ma for zircons from plagiogranite indicates that the Mianlue paleo-oceanic crust was probably subducted underneath the South Qinling micro-continent in Carboniferous. This is consistent with the formation time (309Ma) of the Huwan eclogite originating from oceanic subduction in Dabie Mountains, suggesting that the Mianlue paleo-ocean probably extended eastward to the Dabie Mountains in Carboniferous. The high-Mg adakitic rocks in Sanchazi paleo-magmatic arc suggest that the subducted oceanic crust was relatively young (<25Ma) and hot. 相似文献
130.
Kela 2 Gas Field, with high formation pressure (74.35MPa), high pressure coefficient (2.022) and difficulty of potential test and evaluation, is the largest integrated proved dry gas reservoir in China so far and the principal source for West-East Gas Development Project. In order to correctly evaluate the elastic-plastic deformation of rocks caused by the pressure decline during production, some researches, as the experiment on reservoir sensitivity to stress of gas filed with abnormal high pressure, are made. By testing the rock mechanic properties, porosities and permeabilities at different temperature and pressure of 342 core samples from 5 wells in this area, the variations of petro-physical properties at changing pressure are analyzed, and the applicable inspection relationship is concluded. The average productivity curve with the reservoir sensitivity to stress is plotted on the basis of the research, integrated with the field-wide productivity equation. The knowledge lays a foundation for the gas well productivity evaluation in the field and the gas field development plan, and provides effective techniques and measures for basic research on the development of similar gas fields. 相似文献