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971.
英国工业旅游发展的基本特征与经验启示 总被引:30,自引:1,他引:30
本文从英国工业旅游兴起发展的社会-经济-市场条件,政府的主导作用,开发主体的经营管理理念的分析入手,剖析了英国工业旅游兴起与发展的天时,地利,人和的背景条件,归纳总结了英国工业旅游发展的基本特征。指出了英国工业旅游发展中的一些有益的经验启示。 相似文献
972.
The Late Ordovician Solund-Stavfjord ophiolite in western Norway represents a remnant of the Iapetus oceanic lithosphere that developed in a Caledonian marginal basin. The ophiolite contains three structural domains that display distinctively different crustal architecture that reflects the mode and nature of magmatic and tectonic processes operated during the multi-stage seafloor spreading evolution of this marginal basin. Domain I includes, from top to bottom, an extensive extrusive sequence, a transition zone consisting of dike swarms with screens of pillow breccias, a sheeted dike complex, and plutonic rocks composed mainly of isotropic gabbro and microgabbro. Extrusive rocks include pillow lavas, pillow breccias, and massive sheet flows and are locally sheared and mineralized, containing epidosites, sulfide-sulfate deposits, Fe-oxides, and anhydrite veins, reminiscent of hydrothermal alteration zones on the seafloor along modern mid-ocean ridges. A fossil lava lake in the northern part of the ophiolite consists of a >65-m-thick volcanic sequence composed of a number of separate massive lava units interlayered with pillow lavas and pillow breccia horizons. The NE-trending sheeted dike complex contains multiple intrusions of metabasaltic dikes with one- and two-sided chilled margins and displays a network of both dike-parallel normal and dike-perpendicular oblique-slip faults of oceanic origin. The dike-gabbro boundary is mutually intrusive and represents the root zone of the sheeted dike complex. The internal architecture and rock types of Domain I are analogous to those of intermediate-spreading oceanic crust at modern mid-ocean ridge environments. The ophiolitic units in Domain II include mainly sheeted dikes and plutonic rocks with a general NW structural grain and are commonly faulted against each other, although primary intrusive relations between the sheeted dikes and the gabbros are locally well preserved. The exposures of this domain occur only in the northern and southern parts of the ophiolite complex and are separated by the ENE-trending Domain III, in which isotropic to pegmatitic gabbros and dike swarms are plastically deformed along ENE-striking sinistral shear zones. These shear zones, which locally include fault slivers of serpentinite intrusions, are crosscut by N20°E-striking undeformed basaltic dike swarms that contain xenoliths of gabbroic material. The NW-trending sheeted dike complex in the northern part of Domain II curves into an ENE orientation approaching Domain III in the south. The anomalous nature of deformed crust in Domain III is interpreted to have developed within an oceanic fracture zone or transform fault boundary.REE chemistry of representative extrusive and dike rocks from all three domains indicates N- to E-MORB affinities of their magmas with high Th/Ta ratios that are characteristic of subduction zone environments. The magmatic evolution of Domain I encompasses closed-system fractional crystallization of high-Mg basaltic magmas in small ephemeral chambers, which gradually interconnected to form large chambers in which mixing of primary magmas with more evolved and fractionated magma caused resetting of magma compositions through time. The compositional range from high-Mg basalts to ferrobasalts within Domain I is reminiscent of modern propagating rift basalts. We interpret the NE-trending Domain I as a remnant of an intermediate-spread rift system that propagated northeastwards (in present coordinate system) into a pre-existing oceanic crust, which was developed along the NW-trending doomed rift (Domain II) in the marginal basin. The N20°E dikes laterally intruding into the anomalous oceanic crust in Domain III represent the tip of the rift propagator. The inferred propagating rift tectonics of the Solund-Stavfjord ophiolite is similar to the evolutionary history of the modern Lau back-arc basin in the SW Pacific and suggests a complex magmatic evolution of the Caledonian marginal basin via multi-stage seafloor spreading tectonics. 相似文献
973.
湘西北镍钼多金属矿床的元素组合及微量元素地球化学 总被引:4,自引:0,他引:4
湘西北镍钼多金属矿床富集了多种元素,形成一个以Ni、Mo、Cu、Zn、Pd、Pt、As、Se、Ba、V、P为主的特殊元素组合;微量元素As、Se、Ba等成10^1 ̄10^3倍富集,它们的地球化学特征表明,这类矿床属海底喷气沉积矿床,这组特殊元素来源和富集,与海底喷流作用有关。 相似文献
974.
分析了1996年3月19日新疆阿图什MS6.9地震前几种地震波参数的异常特征。该次地震前初动符号、振幅比、尾波衰减系数、尾波持续时间比均有不同程度的异常,地震活动空间图象、时序曲线也存在一定的异常。根据上述异常作者对该次地震作出了短临预报,预报三要素与实际地震相符。介绍了预报思路和方法,并对异常机理进行了初步分析 相似文献
975.
主要从区域系统是开放系统的角度,结合国内外开发实例,分析了开发是开放性的,以此为根据,对开发西北的对策进行了探讨,旨在推动西北的发展。 相似文献
976.
When marine magnetic-anomaly data are used to construct geomagnetic polarity timescales, the usual assumption of a smooth spreading-rate function at one seafloor spreading ridge forces much more erratic rate functions at other ridges. To eliminate this problem, we propose a formalism for the timescale problem that penalizes non-smooth spreading behaviour equally for all ridges. Specifically, we establish a non-linear Lagrange multiplier optimization problem for finding the timescale that (1) agrees with known chron ages and with anomaly-interval distance data from multiple ridges and (2) allows the rate functions for each ridge to be as nearly constant as possible, according to a cumulative penalty function. The method is applied to a synthetic data set reconstructed from the timescale and rate functions for seven ridges, derived by Cande & Kent (1992) under the assumption of smooth spreading in the South Atlantic. We find that only modest changes in the timescale (less than 5 per cent for each reversal) are needed if no one ridge is singled out for the preferential assumption of smoothness. Future implementation of this non-prejudicial treatment of spreading-rate data from multiple ridges to large anomaly-distance data sets should lead to the next incremental improvement to the pre-Quaternary geomagnetic polarity timescale, as well as allow a more accurate assessment of global and local changes in seafloor spreading rates over time. 相似文献
977.
大同-阳高2次中强地震前,长治电感地应力曾出现明显的趋势异常和短临异常。本文就长治地应力的观测条件以及地震前后的异常特征进行了分析研究,认为对于山西地震带北部地区的地震监测预报有参考价值。 相似文献
978.
通过对永善地震台8年的水氡资料进行了数学处理,发现水氡异常与地震对应率较高。并对水氡异常特征及其机理作了分析.从而讨论了利用水氡资料对本地区短临地震监测的预测意义。 相似文献
979.
980.
根据1911~1994年地震资料,详细讨论了西藏地区强震活动分期、特征及其趋势,并应用统计方法分析研究了该区强震的时间分布规律和发震概率。结果表明,本世纪以来西藏地区经历了3个强震轮回,目前正处于第Ⅳ轮回平静幕结束、新的活跃幕即将开始之际,未来活跃幕内将出现数组地震丛集现象,1995~1996年发生MS≥6地震的累计概率为80%~87%,发生MS≥6.5强震的累计概率达60%~76%。 相似文献