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951.
In marine strata from Sinian to Middle Triassic in South China, there develop four sets of regional and six sets of local
source rocks, and ten sets of reservoir rocks. The occurrence of four main formation periods in association with five main
reconstruction periods, results in a secondary origin for the most marine gas pools in South China. To improve the understanding
of marine gas pools in South China with severely deformed geological background, the dominant control factors are discussed
in this paper. The fluid sources, including the gas cracked from crude oil, the gas dissolved in water, the gas of inorganic
origin, hydrocarbons generated during the second phase, and the mixed pool fluid source, were the most significant control
factors of the types and the development stage of pools. The period of the pool formation and the reconstruction controlled
the pool evolution and the distribution on a regional scale. Owing to the multiple periods of the pool formation and the reconstruction,
the distribution of marine gas pools was complex both in space and in time, and the gas in the pools is heterogeneous. Pool
elements, such as preservation conditions, traps and migration paths, and reservoir rocks and facies, also served as important
control factors to marine gas pools in South China. Especially, the preservation conditions played a key role in maintaining
marine oil and gas accumulations on a regional or local scale. According to several dominant control factors of a pool, the
pool-controlling model can be constructed. As an example, the pool-controlling model of Sinian gas pool in Weiyuan gas field
in Sichuan basin was summed up. 相似文献
952.
通过对低纬高原地区多个冰雹和暴雨个例的多方面的对比分析,发现冰雹和暴雨的发生在大气环境背景、大气层结、大气不稳定性及云图特征上既有一些相似之处,也存在一些明显的区别.研究发现,发生冰雹时,中纬度低槽较偏南,受北方天气系统影响明显;发生暴雨时,受热带系统影响明显,中纬度低槽稍偏北.在冰雹发生前,大气中层较干、低层较湿,但层结仍为较稳定的状态;在暴雨发生前,大气中、低层均较湿,层结为弱稳定状态.冰雹的发生要求下层大气气温相对较低,以使雹粒在溶化之前可到达地面,而暴雨的发生要求大气富含水汽.冰雹以冬春多见,夏季较少;暴雨以夏季较多,而冬春较少.与此对应,产生暴雨的强对流其对流强度要强于产生冰雹的,但对于同一季节发生的冰雹和暴雨,两者的对流强度是相近的. 相似文献
953.
Young Hong Shin Houze Xu Carla Braitenberg Jian Fang Yong Wang 《Geophysical Journal International》2007,170(3):971-985
954.
955.
Twenty broadband seismographs were deployed along Hongyuan, Sichuan to Wuwei, Gansu. 81 teleseismic events were recorded in one year. We computed receiver functions from teleseismic waveform data and obtained S wave velocity structure beneath each station along the profile by using receiver function inversion method. The results revealed that the crustal structure is very complex and crustal average S wave velocity is to be on the low side. Low velocity structure generally exists in the depth range of 10~40 km in the crust between Aba arc fault and northern edge fault of Qinling earth's axis and it is a tectonic feature of complex geological process such as ancient A'nyemaqen Tethys ocean from closing and side colliding to subducted plate exhumed or thrust rock slice lifted. The Moho is about 50 km depth along the profile and is slightly deeper in the south than in the north. 相似文献
956.
Dong YunPeng Zhang GuoWei Zhou DingWu Luo JinHai Zhang ChengLi Xia LinQi Xu XueYi Li XiangMin 《中国科学D辑(英文版)》2007,50(1):17-24
The properties and tectonic significance of the fault bound zone on the northern margin of the Central Tianshan belt are key
issues to understand the tectonic framework and evolutionary history of the Tianshan Orogenic Belt. Based on the geological
and geochemical studies in the Tianshan orogenic belt, it is suggested that the ophiolitic slices found in the Bingdaban area
represent the remaining oceanic crust of the Early Paleozoic ocean between the Hazakstan and Zhungaer blocks. Mainly composed
of basalts, gabbros and diabases, the ophiolites were overthrust onto the boundary fault between the Northern Tianshan and
Central Tianshan belts. The major element geochemistry is characterized by high TiO2 (1.50%–2.25%) and MgO (6.64%–9.35%), low K2O (0.06%–0.41%) and P2O5 (0.1%–0.2%), and Na2O>K2O as well. Low ΣREE and depletion in LREE indicate that the original magma was derived from a depleted mantle source. Compared
with a primitive mantle, the geochemistry of the basalts from the Bingdaban area is featureded by depletion in Th, U, Nb,
La, Ce and Pr, and unfractionated in HFS elements. The ratios of Zr/Nb, Nb/La, Hf/Ta, Th/Yb and Hf/Th are similar to those
of the typical N-MORB. It can be interpreted that the basalts in the Bingdaban area were derived from a depleted mantle source,
and formed in a matured mid-oceanic ridge setting during the matured evolutionary stage of the Northern Tianshan ocean. In
comparison with the basalts, the diabases from the Bingdaban area show higher contents of Al2O3, ΣREE and HFS elements as well as unfractionated incompatible elements except Cs, Rb and Ba, and about 10 times the values
of the primitive mantle. Thus, the diabases are thought to be derived from a primitive mantle and similar to the typical E-MORB.
The diabases also have slight Nb depletion accompanying no apparent Th enrichment compared with N-MORB. From studies of the
regional geology and all above evidence, it can be suggested that the diabases from the Bingdaban area were formed in the
mid-oceanic ridge of the Northern Tianshan ocean during the initial spreading stage.
Supported by the Major State Research Program of PRC (Grant No. 2001CB409801), the National Natural Science Foundation of
China (Grant Nos. 40472115 and 40234041) and the State Research Program of China Geological Survey (Grant No. 2001130000-22) 相似文献
957.
Xu ZhaoKai Li AnChun Jiang FuQing Li TieGang Meng QingYong Jin Ning 《中国科学D辑(英文版)》2007,50(8):1179-1188
From systemic research of microstructure, geochemistry, uranium-series and 10Be isotope dating on a new-type deepwater ferromanganese crust from the East Philippine Sea, the paleoenvironment evolu-tion of the target area since the terminal Late Miocene was recovered. The vertical section changes of microstructure and chemical composition are consistent in the studied crust, which indicate three major accretion periods and corresponding paleoenvironment evolution of the crust. The bottom crust zone was formed in the terminal Late Miocene (5.6 Ma) with loose microstructure, high detritus content and high growth rate. Reductions of mineral element content, accretion rate and positive Ce-anomaly degree at 4.6 Ma indicate temporal warming, which went against the crust accretion and finally formed an accretion gap in the terminal Middle Pliocene (2.8―2.7 Ma). The more active Antarctic bottom sea-waters in the Late Pliocene (2.7 Ma) facilitated the fast transfer to the top pure crust zone. Hereafter, with the further apart of volcanic source and the keeping increase of eolian material (1.0 Ma), although surrounding conditions were still favorable, mineral element content still shows an obvious reducing trend. It thereby offers new carrier and data for the unclear paleoceanographic research of the target area since the terminal Late Miocene. 相似文献
958.
959.
960.
MM5中尺度非静力模式对云南省降水预报检验 总被引:7,自引:3,他引:7
根据MM5/V3中尺度非静力模式数值预报结果,检验了该模式在云南2001年汛期(6-10月)的降水预报效果。结果表明,MM5模式降水预报对云南大部分地区的小雨有较高的TS评分,对于全省性大雨过程,MM5模式24小时降水预报的TS评分高于同期预报员的主观预报,但对暴雨及以上量级的降水预报,模式结果不太理想。 相似文献