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331.
梁柱-板柱组合结构(住宅)体系模型振动台试验研究 总被引:2,自引:0,他引:2
梁柱-板柱组合结构(住宅)体系由上部大开间板柱结构和底部框架结构构成,是一种可持续发展的新型结构形式。通过两个12层l:15模型的振动台对比试验,探讨其动力特性、地震反应和破坏情况。试验表明,该体系的抗震性能介于框架结构和板柱结构之间。总层数在12层以下时,不设剪力墙的该体系在7度区基本上满足规范要求,合理设置剪力墙后可用于8度区。 相似文献
332.
温州地区淤泥质潮滩冲淤遥感反演研究 总被引:11,自引:1,他引:11
滩涂围垦、水产养殖、防波堤建设和航道疏浚等往往涉及潮滩冲淤变化的研究。冲淤变化是一种复杂的物理过程,它包括许多自然因素和人类诱发因素。该文使用MSS、TM、ETM及SPOT四类数据源,共计24个时相,时间跨度为1976—2002年,利用多时相卫星遥感图像水边线高程反演技术,确定了温州地区不同部位淤泥质潮滩岸线的变化,计算不同部位潮滩坡度及淤积、侵蚀速度,为温州地区潮滩的开发建设提供了理论依据。 相似文献
333.
Compositional variation and genesis of ferromanganese crusts of the Afanasiy—Nikitin Seamount, Equatorial Indian Ocean 总被引:1,自引:0,他引:1
R. P. Rajani V. K. Banakar G. Parthiban A. V. Mudholkar A. R. Chodankar 《Journal of Earth System Science》2005,114(1):51-61
Eight ferromanganese crusts (Fe-Mn crusts) with igneous and sedimentary substrates collected at different water depths from
the Afanasiy-Nikitin Seamount are studied for their bulk major, minor and rare earth element composition. The Mn/Fe ratios
< 1.5 indicate the hydrogenetic accretion of the Fe-Mn hydroxides. These Fe-Mn crusts are enriched in Co (up to 0.9%, average
∼ 0.5%) and Ce. The Ce-content is the highest reported so far (up to 3763 ppm, average ∼ 2250 ppm) for global ocean seamount
Fe-Mn crusts. In spite of general similarity in the range of major, minor, and strictly trivalent rare earth element composition,
the dissimilarity between the present Fe-Mn crusts and the Pacific seamount Fe-Mn crusts in Co and Ce associations with major
mineral phases indicates inter-oceanic heterogeneity and region-specific conditions responsible for their enrichment. The
decrease in Ce-anomaly (from ∼ 8 to ∼ 1.5) with increasing water depth (from ∼ 1.7 km to ∼ 3.2 km) might suggest that the
modern intermediate depth low oxygen layer was shifted and sustained at a deeper depth for a long period in the past. 相似文献
334.
335.
336.
华北南部晚古生代陆表海的沉积充填、聚煤特征和构造演化 总被引:7,自引:0,他引:7
华北南部晚古生代煤系为海退型剖面,沉积环境演化为由陆表海碳酸盐—碎屑海岸、碎屑潮坪至被河流三角洲充填的半咸水海湾。晚石炭世中期华北南缘与秦岭—大别山区因拉张分离出现了陆表海,陆源碎屑自北向南的充填表明北方蒙古—西伯利亚板块向华北板块北缘的对接俯冲。沉积中心和聚煤作用随之自北向南迁移,因此在华北南部集中了丰富的煤炭资源。聚煤最有利的沉积环境是海退形成的滨海平原和河流注入浅水海湾形成的三角洲平原。煤变质带自本区中部向南递减表明三叠纪沉积中心向北迁移,表明华北南缘与秦岭—大别山地块以及华南板块的对接拼合时间可能发生在煤系形成之后至三叠纪以前,海西末期的可能性较大。 相似文献
337.
From July 2003 to July 2004, samples were collected on Chongming Island east tidal flat every two months. The research showed that the nitrous oxide (N2O) production rate was very low in the water, Chongming east tidal flat (CM) sediment was the N2O source of the water. Sediment N2O natural production rate was between -0.08 and 1.74 μmolN·m-2·h-1. N2O natural production rate was higher in the summer. The difference of the N2O natural production rate in the different tidal flats, the correlation between the N2O natural production rate and the denitrification rate, and those with the temperature and DO indicate that middle tidal flat sediment denitrification was the main process of the N2O production, while in the low tidal flat sediment, the production of the N2O came from several processes of the nitrogen cycling. Tidal flat sediment denitrification reaction was stronger in summer and winter but relatively lower in the late autumn and early spring. Seasonal change of the sediment denitrification rate was wide, from 1.12 to 33.34 μmolN·m-2·h-1. Temperature, DO and the coactions of them had the prominent effect on the tidal flat sediment denitrification. 相似文献
338.
The development of a carbonate reservoir is dominated by its primary sedimentary environment. Generally, a good reservoir
must be the oolite of a bank or bioclastics of an organic reef in a marginal mesa, which must deposit on the slope of the
mesa. Therefore, the analyses of sequence stratigraphy are the key for predicting the presence of carbonate reservoirs. A
typical sequence pattern can be seen in the Puguang gas field. As an independent lithological body, the mechanical property
of a reef flat is very different from the surrounding rock, causing stress to concentrate. Stress centralization will, in
turn, cause a lot of fractures and faults to develop, and ultimately, result in a gas chimney, which is a seismic smear zone
beneath or above the reef flat. Known gas fields, such as the puguang gas field, also possess gas chimneys. Sequence stratigraphy
patterns in the marginal mesa and gas chimney near the reservoir are very obvious in all known fields in southeast and east
Sichuan Province. By analyzing the seismic features of all known gas fields, a model to predict carbonate reservoirs has been
set up. Using this prediction model, we have found that there is a typical reef flat of the marginal mesa in the Malubei structure
of Tongnanba structural belts whose sequence stratigraphy pattern is very much like that of the Puguang gas field; and in
the Cangxi-Jiulongshan structure, there is another reef flat which is symmetrical to the Malubei reef. The Cangxi reef flat
possesses the largest platform edge shallow facies domestically found, and has a typical prograding sequence. Its gas chimney
is very obvious too. Because the Cangxi reef flat is in the very vicinity of the hydrocarbon kitchen and the depression is
much bigger than that of the Puguang gas fields, we predict that there may be a gigascopic gas field in Cangxi County. There
may also be a large gas field in the Malubei structure.
Translated from Oil & Gas Geology, 2006, 27(3): 332–339 [译自: 石油与天然气地质] 相似文献
339.
340.
Mesozoic magmatism is widespread in the eastern South China Block and has a close genetic relationship with intensive polymetallic mineralization. However, proper tectonic driver remains elusive to reconcile the broad intracontinental magmatic province. This study presents integrated zircon U-Pb dating, Hf isotopes and whole-rock geochemistry of the Xiwan dioritic porphyry in the NE Jiangxi ophiolitic mélange. Zircon U-Pb dating by SIMS and LA-ICP-MS methods yielded an emplacement age of ~160 Ma for the Xiwan diorite, confirming its inclusion into the Mesozoic magmatic province in SE China, instead of a component of the Neoproterozoic ophiolitic mélange genetically. The dioritic rocks have low Si02(58.08 wt%-59.15 wt%), and high Na_2 O(5.00 wt%-5.21 wt%) and MgO(4.60 wt%-5.24 wt%) contents with low TFeO/MgO ratios(1.02-1.09). They show an adakitic geochemical affinity but exhibit relatively low Sr/Y ratios(24.8-31.1) and high Y contents(14.6-18.3 ppm) compared to the Dexing adakitic porphyries. In addition, the Xiwan diorites have moderately evolved zircon Hf isotopic compositions(ε_(Hf)(t)=-6.1--0.1; T_(DM2)=1597-1219 Ma). These elemental and isotopic signatures suggest that the Xiwan diorite formed through partial melting of a remnant arc lower crust(i.e., early Neoproterozoic mafic arc-related rocks) in response to the underplating of coeval mafic magmas. In conjunction with the temporal-spatial distribution and complex geochemical characteristics of the Mesozoic magmatism, our case study attests to the feasibility of a flat-slab subduction model in developing the broad intracontinental magmatic province in SE China. The flat-slab delamination tends to trigger an asthenospheric upwelling and thus results in extensive partial melting of the overlying lithospheric mantle and lower crustal materials in an extensional setting during the Mesozoic. 相似文献