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Izvestiya, Atmospheric and Oceanic Physics - A stable analytical solution is obtained for wave fields of seismic waves in a planetary-sized sphere using the new asymptotic behavior of the Bessel... 相似文献
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This paper reports the calculation data on wave fields for the Earth’s model including the mantle and external and internal core with real parameters. The investigation has made it possible to identify physical phenomenon unknown previously such as the formation of the wave field focusing region in the Earth, emerging to the day surface before the first PKP-wave. This is due to the fact that spherical bodies (in this case, the low-velocity core of the Earth) are characterized by the collecting lens properties.
相似文献3.
Large ore-placer districts in the southern and eastern framing of the North Asian Craton (Bodaibo, Upper Selemdzha, South Verkhoyansk, and Ten’ka) are characterized by some common features such as the confinement to the areas of the decreased crustal thickness and gravity gradient zones traced by deep-seated faults; the fold-thrust structure of the terrigenous-black-shale sequences; the phyllitic, greenschist, and sometimes epidote-amphibolite metamorphism of the ore-bearing rocks; and the complex and long history of the Au accumulation, which involved the subsequent stepwise change from the ore-preparatory to the ore-generating stages. The latter stage is spatially and temporally related with manifestations of orogenic (volcanoplutonic) magmatism, which produced mineralization of the gold-quartz, gold-sulfidequartz, gold-black shale, gold-rare metal, and gold-silver formations. The peculiarities of their spatial relations (juxtaposition-superposition or lateral zoning) determine the scales of the noble metal concentration, the economic significance of the deposits, and the metallogenic potential of the regions. The revealed similarity in the evolution and structure of the compared districts should be taken into account in choosing new promising areas and estimating the potential gold-bearing territories in the framing of the North-Asian and other cratons. 相似文献
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以地质和成矿学论点为依据,内岛弧、大陆边缘及内大陆构造域的火山深成岩带的形成作用具有其共同性;矿石-岩浆系可划分数个级别.金-银矿化的矿物-地球化学特点与局部或整体矿石-岩浆系中含矿岩浆岩岩石化学特点之间存在有可比性.通过含矿脉体-交代岩带的形态、构造、结构特点、物质组成变化的研究表明,产出在单独的矿石-岩浆系,特别是高等温线部位的矿床,其垂向成矿规模最大.在地球物理、地质学、岩石学、物理化学和实验研究的基础上建立同火山作用的金-银成矿系模型是可行的. 相似文献
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The aim of the investigation is to reveal possible causes of isolation and co-occurrence of the economically significant concentrations of gold and tin. Comparative analysis of the different-rank factors that influenced migration and concentration of these elements show that different geochemical properties of Au and Sn are responsible for isolation of their big concentrations giving rise to independent metallogenic provinces, zones, and ore nodes. These differences resulted in individualization of the element migration ways to the level of ore concentration within the fluid-magmatic columns. Three main factors influenced the Au and Sn migration activity: different patterns of metal connection with the melt structure, different relation with oxygen, and different relation with other strong oxidizers. By the moment when ore-bearing fluid became isolated from magmas, the metallogenic signature of the melts, contrasting in redox-potential, had already been defined that was confirmed by the fact that tin ores associate predominantly with the granitoids of ilmenite series and gold ores with those of magnetite series. The fluid-magmatic systemswith an intermediate degree of the melt reduction-oxidation may be considered the potential producers of the combined metal concentrations. In these cases, the combined concentrating of tin and gold is plagued by an opposite direction of the oxidation-reduction reactions when their most common minerals are formed: the main migration form of Sn+2 must be oxidized (with cassiterite portioning) , and the forms of Au+ or Au+3 must be reduced (with native gold portioning) . Probably, because of this the combined tin and gold concentrations are dominated by one of the metals with a tendency of accumulation in different-stage mineral complexes. 相似文献
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A wave method for suppression of multiple waves that does not require knowledge of a depth— velocity medium model is developed.
The method is constructed so as to completely suppress multiple waves in the case of a layer in a half-space. The efficiency
of the method for arbitrary 3D plane-layered media is demonstrated both theoretically and numerically. Examples of the method
application for real media showing a substantial decrease in the multiple wave amplitudes without distortion of the dynamics
of useful reflections are given. 相似文献
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The aim of the investigation is to reveal possible causes of isolation and co-occurrence of the economically significant concentrations of gold and tin. Comparative analysis of the different-rank factors that influenced migration and concentration of these elements show that different geochemical properties of Au and Sn are responsible for isolation of their big concentrations giving rise to independent metallogenic provinces, zones, and ore nodes. These differences resulted in individualization of the elem... 相似文献
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Doklady Earth Sciences - It is generally accepted that PKP precursor waves arriving ahead of PKP-waves observed in real data are explained by scattering on small-scale inhomogeneities in the lower... 相似文献
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