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41.
我国东部新生代玄武岩中深源岩石包体内的尖晶石类矿物属铬尖晶石和铁尖晶石,金伯利岩及其地幔岩包体和金刚石中的尖晶石类矿物主要为铝铬铁矿。玄武岩中橄榄岩类包体内的尖晶石比其辉石岩类包体中的尖晶石含Cr高,含Al低,这与Cr为相容元素、Al为不相容元素、玄武岩中橄榄岩类包体是上地幔部分熔融出玄武岩浆后的残留物及其上地幔岩石的捕虏体、而辉石岩类是玄武岩浆结晶的产物有关。玄武岩中深源岩石包体中的尖晶石明显地比金伯利岩中的粗晶、地幔岩石包体及金刚石中的尖晶石含Cr低,含Al高,其主要原因是前者比后者形成的压力低 相似文献
42.
研究地球水文变化的日地物理成因和规律的日地水文学(Solar-TerrestrialHydrology),用于水、旱灾害预测多次获得证实.本文从日地水文物理基础、长江淮河22年周期性大洪水、黄河大洪水和太阳活动关系、太阳活动双重衰减期北方大旱、17世纪日地水文异常变化、太阳活动对暴雨洪水中短期影响、台湾海峡两侧大暴雨洪水落区转移、全球最大洪水日地水文研究以及学科发展和应用前景九个方面,对中国近70多年来的主要成果加以回顾和总结.基础科学、高科技和应用紧密结合,促成对国民经济发展直接相关的新学科,是当代科学进步的一个显著标志,这里又是一个例证. 相似文献
43.
44.
分析了2003年洛阳夏季多雨环流特征,探讨了汛期降水偏多的预报因子,并用副高特征量因子建立了汛期降水预测模型。 相似文献
45.
We present the results of a detailed petrological study of a sparsely phyric basalt (MAPCO CH98-DR11) dredged along the Mid-Atlantic Ridge (30°41′N). The sample contains microphenocrysts of olivine that display four different rapid-growth morphologies. Comparison of these morphologies with those obtained in dynamic crystallization experiments allows us to constrain the thermal history of the sample. The dendritic morphology (swallowtail, chain and lattice olivine) is directly related to the final quenching during magma–seawater interaction. In contrast, the three other morphologies, namely the complex polyhedral crystal, the closed hopper and the complex swallowtail morphology result from several cycles of cooling–heating (corresponding to a maximum degree of undercooling of 20–25°C) during crystal growth. These thermal variations occurred before eruption and are interpreted to be the result of turbulent convection in a small magmatic body beneath the ridge. The results suggest that the Mid-Atlantic Ridge is underlain by a mush zone that releases batches of liquid during tectonic segregation. Aphyric basalts are emitted during eruptions controlled by the tectonic activity, whereas phyric basalts correspond to small fractions of magma from the mush zone mobilized by reinjections of primitive magmas. 相似文献
46.
Linda T Elkins-Tanton 《Earth and Planetary Science Letters》2004,222(1):17-27
Large volumes of mare basalts are present on the surface of the moon, located preferentially in large impact basins. Mechanisms relating impact basins and mare basalt eruptions have previously been suggested: lunar impacts removed low-density material that may have inhibited eruption, and created cracks for fluid flow [Icarus 139 (1999) 246], and lunar basins have long been described as catchments for magma (e.g., [Rev. Geophys. Space Phys. 18 (1980) 107] and references therein). We present a new model for melt creation under near side lunar basins that is triggered by the impacts themselves. Magma can be produced in two stages. First, crater excavation depressurizes underlying material such that it may melt in-situ. Second, the cratered lithosphere rises isostatically, warping isotherms at the lithosphere-asthenosphere boundary which may initiate convection, in which adiabatic melting can occur. The first stage produces by far the largest volume of melt, but convective melting can continue for up to 350 Ma. We propose that giant impacts account for a large portion of the volume and longevity of mare basalt volcanism, as well as for several compositional groups, including high alumina, high titanium, KREEP-rich, and picritic magmas. 相似文献
47.
峨嵋玄武岩同生流体包裹体在800℃爆裂后,2.0g/L NH4Cl溶液提取流体中Pt、Pd,C-410树脂富集-电感耦合等离子体质谱测定,方法相对误差小于25%。激光拉曼光谱与四级质谱测定包裹体的气液成分结果表明:流体中存在一定量的有机组分,这对Pt、Pd以有机螯合态形式进入流体提供了可能。 相似文献
48.
Compositional studies on different forms of magnetite, ulvospinel, ilmenite and hematite mineral phases occurring in 37 lava flows and 6 dykes of the Mandla lobe are presented in this paper. Ilmenite (0001) in equilibrium with titanomanetite show high values of temperature of equilibration, ranging from 1172–974°C, for high alumina quartz normative tholeiitic lava flows of Chemical Type - A; 1129–1229°C for low alumina quartz normative tholeiitic lava flows of Chemical Type - B; 1283–1124°C for tholeiitic lava flows of Chemical Type - F and 1243°C and 99O°C for two diopside olivine normative tholeiite flows of Chemical Type D. High olivine normative flows of Chemical Type - G and H show 1095°C and 1092°C respectively. Whereas, high hypersthene normative tholeiite flow of Chemical me C shows temperature of 1187°C. Data plots disposition over iron-titanium oxide equilibration temperature vs – logfo2, diagram for Mandla lava flows and other parts of the Deccan (Igatpuri, Mahabaleshwer, Nagpur and Sagar areas) revealed that tholeiitic (evolved) basalt of the eastern Deccan volcanic province formed at high temperatures whereas, picritic (primitive) lavas of Igatpuri and tholeiitic basalt of Mahabaleshwar areas were formed at low temperatures. Mahabaleshwer basalts follow FMQ (fayalite-magnetite-quartz) buffer curve but, plots of the Mandla basalts lie above this curve indicating higher temperatures of crystallisation of ilmenite-titanomagnetite than that of the lava flows from other parts of Deccan 'Raps. The eastern Deccan Traps are most evolved types of lava as characterised by its low Mg-number and Ni content whereas, Igatpuri lava flows are picritic (primitive), having high Mg-number and Ni contents. Temperature vs FeO + Fe2O3 / FeO + Fe2O3 + MgO ratio data plots for Mandla and other Deccan lava flows and liquidus data for Hawaiian tholeiites, indicated that Igatpuri basalts lie parallel to the liquidus line of Hawaiian tholeiite but at lower temperatures. Large data plots of Mandla lava flows lie along the liquidus line of the Hawaiian lava. The highly vesicular nature of compound lava flows having large amount of volatile is responsible for low temperature values whereas, lava flows represented by high temperatures show high modal values of glass and opaque minerals. 相似文献
49.
A complete dismembered sequence of ophiolite is well exposed in the south Andaman region that mainly comprises ultramafic
cumulates, serpentinite mafic plutonic and dyke rocks, pillow lava, radiolarian chert, and plagiogranite. Pillow lavas of
basaltic composition occupy a major part of the Andaman ophiolite suite (AOS). These basalts are well exposed all along the
east coast of southern part of the south AOS. Although these basalts are altered due to low-grade metamorphism and late hydrothermal
processes, their igneous textures are still preserved. These basalts are mostly either aphyric or phyric in nature. Aphyric
type exhibits intersertal or variolitic textures, whereas phyric variety shows porphyritic or sub-ophitic textures. The content
of alkalies and silica classify these basalts as sub-alkaline basalts and alkaline basalts. A few samples show basaltic andesite,
trachy-basalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt
samples are probably derived from similar parental magmas. Al2O3/TiO2 and CaO/TiO2 ratios classify these basalts as high-Ti type basalt. On the basis of these ratios and many discriminant functions and diagrams,
it is suggested that the studied basalts, associated with Andaman ophiolite suite, were derived from magma similar to N-MORB
and emplaced in the mid-oceanic ridge tectonic setting. 相似文献
50.
Ninad R. Bondre Raymond A. Duraiswami Gauri Dole 《Journal of Earth System Science》2004,113(4):809-817
The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a matter of great interest as well
as considerable controversy in the recent past. However, even a cursory review of published literature reveals that the Columbia
River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note,
however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world. In
this paper, we first present a short overview of important studies pertaining to the emplacement of flood basalt flows. We
then briefly review the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood
basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces,
and even within the same province. It is quite likely that there were more than one way of emplacing the voluminous and extensive
CFB lava flows. We argue that the establishment of general models of emplacement must be based on a comprehensive documentation
of lava flow morphology from all CFB provinces. 相似文献