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51.
52.
随着弹道导弹系统技术的不断改进,影响导弹精度的工具类误差已逐渐降低,地球重力场扰动引力已经成为影响导弹命中精度的主要因素。这里从3个方面分析了扰动引力对弹道的影响,模拟结果表明,对于射程为10000 km以上的远程导弹,扰动引力的影响会造成超过1 km的落点偏差;5×10-5m s-2的扰动引力系统性偏差对导弹落点有明显影响。因此,扰动引力对导弹落点的影响不容忽视。 相似文献
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岩石中的渗透率、流体流动及热液成矿作用 总被引:4,自引:0,他引:4
热液成因的固体金属矿床形成过程中都曾拥有一段流动的历史。成矿物质以溶液的形式从矿源地穿过孔隙或断裂达到了现在的栖身之所,在此过程中流体通过的路径决定了它们的走向,而溶液本身也改变了路径的特征。因此,对于此类矿床的研究不能仅仅囿于眼之所见,而应将古流体流动的观念融入其中,并考察它们的跋涉之路。文中总结了近年来国内外在岩石孔隙、断裂介质及与其相关渗透率对热液成矿作用的控制等领域的研究成果和最新进展,对岩石渗透率、渗透率的影响因素、岩石中流体流动的特征等问题进行了阐述,讨论了渗透率对于热液成矿作用深度、成矿规模、矿质沉淀机制等方面的重要影响,藉此在固体金属矿床研究中强化流"体运动"的观念,并促进构造地质学和成矿作用地球化学间一个新研究方向的发展。 相似文献
55.
V.B. Vasilenko A.V. Tolstov V.A. Minin L.G. Kuznetsova N.V. Surkov 《Russian Geology and Geophysics》2008,49(12):894-907
The intensity of postmagmatic processes in the Botuobinskaya pipe kimberlites was estimated from the calculated content of normative secondary quartz (Q). Several simple algorithms are proposed to calculate the Q content from chemical analyses of kimberlites. Ten groups of altered kimberlites have been recognized from the Q contents. The contents of MgO, some trace elements, and LREE in the groups, the contents of Cr and Ca of crimson garnets, the diamond contents of kimberlites, and the average weight of diamonds decrease as the Q content increases. It is shown that the negative SiO2–MgO correlation is the most effective indicator of the postmagmatic alteration of kimberlites. As the degree of their secondary alteration increases, the kimberlites transform into an assemblage of quartz and clay minerals enriched in some trace elements and almost completely lacking REE and diamonds. 相似文献
56.
Angelo Paone 《International Journal of Earth Sciences》2008,97(3):635-650
A compilation of B–Be–Li data on rocks that cover the entire eruptive history of Somma-Vesuvius is presented and interpreted
in the light of evolution models for the Somma-Vesuvius rocks. Using major and trace element data, fractional crystalllization
models are presented for different geochemical units. These data were used to constrain the source mineralogy of the Somma-Vesuvius
rocks (ol-opx-cpx-gar-amp of 0.4-0.3-0.1-0.1-0.1), the amount of sediment added (5–10%) and the melt fraction from batch partial
melting computations (0.05–0.1). From the B–Li data it is inferred that the main process responsible for the B isotopic signature
is sediment recycling. However, the B–Li data show a major variation in Li abundances respect to B which is explained with
Li dehydration before the fluid enriched the mantle wedge that produced the arc magmas. The Somma-Vesuvius B isotope composition
is intermediate between that of the Campi Flegrei and the broad field of the Eolian Island arc. A low Be isotopes in the recent
volcanic rocks can be explained as: (a) the top 1–22 m of the incoming sediment is accreted, (b) large amounts of sediment
erosion, (c) a slow rate of subduction which have provoked a long magmatic history for the Vesuvius magma, (d) the sediment
component takes several Myr longer than the subducting plate to reach the magma source region beneath Italy. 相似文献
57.
58.
There has been increasing concern about the lack of involvement by social scientists and humanists in a global change program,
although many social scientists are already directly involved in various aspects of research on environmental change, and
their research interests are clearly central to a global change research agenda. Based on a historical review, the role of
social science disciplines as well as social science institutes in an emerging multidecadal global change program is discussed.
Both “plan of action” and “plan of inaction” are suggested to avoid potential pitfalls due to the rush development of a social
science program into the existing global climate change problem. 相似文献
59.
在全面分析大雁矿业集团公司雁南煤矿北二采区的水文地质条件及煤层开采矿井充水因素的基础上,计算了开采27^1号煤层时导水裂隙带发育高度.得出了北二采区各煤层工作面开采即不会受到上部砂砾含水层的影响,雁南煤矿铁路涵洞以西的胜利河冲击沟也不会受到北二采区的采动塌陷影响的结论。 相似文献
60.
Characterization of the microseismic activity (M L <2.0) has been performed at Mt. Melbourne since 1990. We recorded a group of low frequency events with common morphological characteristics, i.e., an emerging onset, an unclear second phase and a sharply dropping coda. Spectral analysis of events recorded at more than one station indicates that the seismogram characteristics and spectral content are largely due to source effects. A polarization filter applied to a set of three component data revealed a first phase made up ofP waves followed (after about 0.9–1.4 sec.) by a second phase probably composed ofSH-type waves. Particle motion analysis detected a seismic ray angle direction mainly between N70°E and N110°E and apparent angle of incidence between 35° and 48° for the first phase. The studied seismicity was localized in an area on the eastern slope of Mt. Melbourne Volcano which presents a surface temperature anomaly (Mazzarini andSalvini, 1994). We formulate two hypotheses for the type of earthquakes recorded: 1) long-period events involving active presence of magmatic fluids in the source processes; 2) or the result of fracturing processes (shear?) in a medium characterized by transition between brittle and plastic behaviors. In the latter hypothesis the superficial thermal anomaly may be a symptom of this behavior at depth and is confirmed by the lown values observed for the exponential fit in the codaQ analysis. 相似文献