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671.
本文基于上海及其邻区活动断裂构造及有关地区潜在地质灾害特点的研究,论证了上海及其邻区潜在地质灾害的三种基本类型及其构造背景与成因机理;指出:上海及其邻区楔形断裂系统的存在与活动是诱发有关地区潜在地质灾害的主导因素。文中明确指出了上海及其邻区楔形断裂系统的研究在相关地区进行潜在地质灾害评价与预测方面的应用前景与发展方向。 相似文献
672.
Our metallogenic studies of the Dachang ore field show that the country-rock media have great influence on the process of
mineralization. They can not only contribute part of the ore-forming material, but also have influence on the geochemical
evolution of granitic magma and ore fluids. The Dachang ore field can be taken as a typical example to show the influence
of country-rock media on mineralization. Geological field investigations indicate that where granites intruded weakly alkalic
country rocks (e.g. middle Devonian limestones and silicorites of platform facies in the Dachang), instead of carbonaceous
shales of reducing basin facies, Sn would be able to enter rock-forming minerals in large quantities to form cassiterite-sulfide
ore deposits of commercial value. So, it may be concluded that the process of magmatic differentiation-evolution, mineralization
and tectonic settings of ore deposits are, more or less, controlled by their country-rock media. 相似文献
673.
674.
675.
我国部份地区雷暴活动、大气电场等与太阳活动的关系 总被引:1,自引:0,他引:1
本文用时序迭加法统计分析了1976—1985年太阳黑子一个完整周期内太阳活动与雷暴活动及地面大气电场之间的可能相关性。结果表明:高纬度地区有较好的相关性,耀斑爆发以后雷暴指数有明显增大趋势,最大关联日在+5日以后。中、低纬度地区几乎不存在相关性。随着耀斑强度增强,相关性也增大,且影响区域从高纬度向中、低纬度移动。在耀斑爆发后2天左右,地面电场强度增大,其关联日比雷暴指数提前。太阳黑子数和雷暴活动之间的相关性很微弱。本文又从全球电路概念出发,简单地解释了形成上述相关性的可能原因。 相似文献
676.
1987年6月19日新疆富蕴县可可托海镇西北发生了Ms=5.8级地震,震中位于喀依尔提河与阿拉散河交汇处,震中烈度为Ⅶ度,等震线长轴方向与可可托海——二台断裂基本一致。震中区人员无伤亡,仅有山石滚落;Ⅵ、Ⅴ度区内的土平房、有不同程度的损坏个别砖平房,楼房出现裂缝。这次地震属于孤立型地震,震前有中短期异常。 相似文献
677.
ON THE MECHANISM OF TELECONNECTIONS BETWEEN EL NINO AND EAST ASIAN ATMOSPHERIC CIRCULATION
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Based on the linear planetary wave theory and observed data,the teleconnections between El Nino andatmospheric circulation in the Northern Hemisphere(NH)are studied.It is shown that the zonal groupvelocity for stationary Rossby waves in the atmosphere is always positive.Thus,the energy of thesedisturbances can not propagate westward.In certain conditions,however,the westward propagation ofnonstationary waves is possible.Going further into this question,we prove that the low-frequency distur-bances over the eastern equatorial Pacific,which are closely related to the large-scale air-sea interactionin low-latitudes,can influence the extratropical atmospheric circulation in the NH along two typical energypaths;i.e.,the waves with wavenumber one(n=1)propagate through the western North Pacific into EastAsia and form the“East Asian Path”,which plays an important part in the teleconnections between ElNino and atmospheric anomalies over East Asia,besides,the waves with n≥2 propagate along the“PNAPath”into the middle and eastern North Pacific as well as North America,leading to the relevant atmos-pheric anomalies to be excited over there. 相似文献
678.
679.
Rui Feng Jun Wang Shuzhen Zheng Guifang Huang Huifen Yan Hainan Zhou Ruoshui Zhang 《地震学报(英文版)》1988,1(4):73-84
Following Airy and Pratt principles, five kinds of local-compensation models are analysed and a rapid 3-D gravity formula
is utilized to calculate isostatic anomalies for 66 models with different parameters. It is noted that isostatic gravity maps
appear nearly identical in their main patterns and features. The optimum compensation model in North China is one of modified
Airy models in which the different density distribution in the surface, upper crust and lower crust is taken into account
and the standard crustal thickness is about 50km. The position of the complete compensation interface is located in the upper
mantle. The North China platform as a whole is under sub-isostatic equilibrium status with an isostatic anomaly of about 18·10−5 m/s2 on an average. The distribution of isostatic gravity anomaly shows an obvious blockwise pattern. Most positive anomaly areas
occur over the eastern part, the Jiao-Liao Block, Mt. Yan block and northern margin of the Hebei-Shandong block, whereas a
negative area occurs in the Shanxi graben. The comparison of models indicates that the Moho discontinuity is not suitable
to be taken as a compensation interface, and the compensation effects in Airy model are better than that in Pratt model, which
is consistent with the feature of dominant layered structure and less lateral inhomogeneity in crust. Some results about composite
compensation, the basic characteristics of isostatic anomaly and deep stucture will be published later in the second part
of this paper.
Wang Bowen took part in some work in this paper. 相似文献
680.
怀安蔓菁沟早前寒武纪高压麻粒岩混杂岩带地质特征、岩石学和同位素年代学 总被引:11,自引:19,他引:11
华北克拉通北缘中段怀安蔓菁沟高压麻粒岩混杂岩带产在太古宙怀安杂岩南缘与花岗岩带交界处,由高压基性麻粒岩、辉长质麻粒岩、英云闪长质麻粒岩和少量夕线石榴片麻岩相间排列的席状岩层构成,岩层间被高应变带或剪切带分隔。高压基性麻粒岩是石榴辉石麻粒岩。据石榴石斑晶内包裹的早期矿物(Cpx+Q)估算的早期高压变质作用条件:T=800℃,P>1.4GPa。环绕斑晶的后成合晶反应边矿物组合(P1+Opx+Hb+Cpx)的变质条件为:T=820℃,P为0.7~0.9GPa。全岩Sm-Nd等时线年龄2.65Ga,矿物Sm-Nd等时线年龄1.82Ga,锆石U-Pb一致线年龄1.83Ga。高压基性麻粒岩的原岩代表晚太古代陆壳的最下部,大约在2.7Ga从上地幔分异出来,可能经壳下垫托作用加在早期陆壳底部,随后经历高压变质作用。早元古代晚期,由于地壳规模的大型逆冲作用,使其上升,并经受褶皱形变、剪切推覆和退变质等作用的改造,形成高压麻粒岩混杂岩带。 相似文献