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51.
中国东部中一新生代活动大陆边缘构造—岩浆作用演化和发展 总被引:31,自引:5,他引:31
本文论述中国东部中-新生代由科迪勒拉型转变为西太平洋活动大陆边缘过程中的构造-岩浆作用及其演化。在印支旋回(250~185Ma),初始欧亚板块与古太平洋板块强烈挤压俯冲,并伴随大范围改造型花岗岩类的发育。在燕山早期(185~140Ma),继续俯冲,改造型花岗岩进一步发育,并开始有同熔型花岗岩类的形成。在约140Ma两类花岗岩的形成达到高潮。在140~100Ma广泛发育安山-流纹岩系。燕山晚期(100~70Ma)由于弧后扩张,配合红色盆地的广泛形成,发育碱性火山岩和碱性花岗岩带.新生代中国东部大陆花岗岩和中-酸性火山岩活动消失,代之以玄武岩活动;边缘海和岛弧逐渐形成,钙碱性火山岩系转入岛弧地带。 相似文献
52.
A reasonable warmer winter index (IWWI) in the framework of the three equiprobability categories (i.e. warmer, normal and colder categories) is proposed based on the winter temperature data observed at 565 stations in China during 1956-2005, where IWWI is defined as the ratio of the station number of warmer category over the total number of stations. The results suggest that the trend of IWWI was consistent with that of the winter temperature on decadal time scale, and their rates of change were 10%/10 a and 0.4 ℃/10 a, respectively. It is found that only 13 warmer winter events in total were detected by IWWI over the past 50 years, and 85% of them occurred after 1986. 相似文献
53.
Based on thermal simulation experiment, interactions between volcanic fluids and source rocks were studied. Gas generations in the dry system and fluid system under different temperatures were analyzed. The results showed that the various types of source rocks are similar in composition, containing gaseous C1-C5 hydrocarbons, H2 and CO2 whose gas yields increase with increasing temperature. The gas yield of source rocks of type I is the high- est, followed by type II, and that of source rocks of type III is the lowest, indicating that the yield of hydrocarbon gases is related to their hydrocarbon generating potential. Although the generating potential of type III is the lowest, it can still be regarded as a useful gas source when it is buried deeply enough. The basic volcanic fluid restrains the generation of gaseous hydrocarbons in different types of source rocks, but promotes the generation of inorganic gases. 相似文献
54.
黑龙江东部依兰珠山变辉长岩的年代学、地球化学及其构造意义 总被引:1,自引:0,他引:1
对黑龙江东部依兰珠山变辉长岩进行了锆石年代学和地球化学研究,以确定其形成时代、成因及构造背景。变辉长岩锆石均呈自形-半自形晶,具典型的条痕状吸收特征和较高的Th/U比值(0.20~0.86),暗示其岩浆成因。LA-ICP-MS U-Pb测年结果为(256±3)Ma,表明珠山变辉长岩形成于晚二叠世。地球化学特征显示变辉长岩具有贫硅,富镁、铁、铝、钙的特征;其轻稀土元素(LREEs)和大离子亲石元素(Rb、Ba)富集,重稀土元素(HREEs)和高场强元素(Nb、Ta、Zr、Hf和Ti)亏损。结合区域地质资料,认为珠山变辉长岩为俯冲流体交代地幔楔的产物,其形成可能与古大洋板块的俯冲作用有关,暗示佳木斯地块与松嫩地块在晚二叠世之前尚未碰撞拼合。 相似文献
55.
Yu. M. Smirnov 《Astronomy Reports》2003,47(3):240-247
We have experimentally studied the excitation of the rhenium atom by collisions with slow monoenergetic electrons and measured 47 excitational cross sections for lines of ReI at an electron energy of 50 eV. Previously published information about the probabilities of radiative transitions of ReI is analyzed. The data for two experimental studies of the ratios Iλ/gA for transitions with a common upper level differ by three orders of magnitude. 相似文献
56.
57.
58.
High pressure experiments have been made on the stability of richterite50-tremolite50 solid solution by the piston-cylinder type high pressure apparatus in the pressure range from 15 to 40 kb, at temperatures from 700 to 1150°C. This amphibole is stable up to 40 kb at 700°C, and the breakdown pressure gradually decreases with increasing temperatures. It is suggested that this amphibole, on the basis of high pressure experiments, may occur in the upper mantle. 相似文献
59.
A series of enclosed ecosystem experiments were conducted in a land-based tank near the seaside of West Xiamen Harbor. The
results of experiments conducted in different seasons and years showed a repeatable phytoplankton succession. In this relatively
stable ecosystem with added nutrients and trace metals, diatoms dominated initially, dinoflagellates dominated in the later
stage, and dinoflagellate red tides eventually occurred. Vitamin B12 enrichment may speed up this succession process. Stirring the water column could stop this process. Soluble Mn at a level
of 3–4 μg/L in seawater, which also is the existing concentration of soluble Mn in Xiamen Harbor seawater, is sufficient for
the multiplication of algae and occurrence of red tide. The present study showed that excessive soluble Mn in Xiamen Harbor
cannot cause red tide, and that Fe was one of the important factors causing diatiom red tide in this present study.
Project 39570145 supported by NSFC. 相似文献
60.
A series of experiments were done to reveal the overtopping breaching process of non-cohesive and cohesive levees in a U-bend flume. The flood hydrograph and breaching geometry were measured and analyzed in detail. The results show that the levee breaching processes can be briefly divided into four stages: slope erosion, longitudinal headward gully-cutting, lateral erosion, and relative stabilization. For non-cohesive levees, non-symmetrical lateral development of the breach occurs throughout the four stages, and the final non-symmetrical coefficient is approximately 2.2–2.6. Larger flow discharge or higher water level can accelerate the breaching process, while coarser sands tend to accelerate the process initially but depress the process at the end. The fluvial erosion rate of a non-cohesive breach shows a power-function relation with the excess wall shear stress. For cohesive levees, a plateau forms in the breach partially blocking the flow in the first two stages. The breach flow is approximately perpendicular to the levee body, and, thus, the erosion rates of the two breach sides are almost the same. Non-symmetrical lateral development mainly occurs in the third stage when the deep gully forms. The final non-symmetrical coefficient is approximately 2.7–3.3. It is expected that these findings can provide a valuable experimental dataset and a theoretical basis for breach closure and flood alleviation. 相似文献