共查询到20条相似文献，搜索用时 218 毫秒
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Enrico Bonatti 《Earth and Planetary Science Letters》1976,32(2):107-113
Serpentinite may be a significant component of the oceanic crust, not as a continuous layer, but as vertical tectonic protrusions and sills emplaced from the upper mantle into fault zones parallel to the axis of spreading ridges. The diapiric emplacement of serpentinite bodies occurs within 100–200 km of ridge axis, with a rate of ascent on the order of 1 mm/year. Serpentinite protrusions may cause small-scale linear magnetic anomalies parallel to ridge axis. Serpentinites are distributed in the oceanic crust according to an orthogonal pattern, with large serpentinite protrusions aligned along major fracture zones, and smaller serpentinite bodies emplaced in bands parallel to ridge axis. 相似文献
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Abstract Serpentinite bodies in the Kurosegawa Belt are mapped along fault boundaries between the Cretaceous Sanchu Group (forearc basin-fill sediments) and the rocks of the Southern Chichibu Belt (Jurassic to Early Cretaceous accretionary prism) in the northwestern Kanto Mountains, central Japan. The serpentinites were divided into three types based on microtextures and combinations of serpentine minerals: massive, antigorite and chrysotile serpentinites. Massive serpentinite retains initial pseudomorphic textures without any deformation after serpentinization. Antigorite serpentinite exhibits shape-preferred orientation of antigorite replacing the original lizardite and/or chrysotile to form pseudomorphs. It has porphyroclasts of chromian spinel, and is characterized by ductile deformation under relatively high-pressure–temperature conditions. Chrysotile serpentinite shows evidence for overprinting of pre-existing serpentinite features under shallow, low-temperature conditions. It exhibits unidirectional development of chrysotile fibers. Foliations in antigorite and chrysotile serpentinites strike parallel to the elongate direction of the serpentinite bodies, suggesting a continuous deformation during solid-state intrusion along the fault zones after undergoing complete serpentinization at deeper levels (lower crust and upper mantle). 相似文献
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The plotting of the time rate of change in discharge dQ/dt versus discharge Q has become a widely used tool for analyzing recession data since Brutseart and Nieber [Water Resour Res 13 (1977) 637–643] proposed the method. Typically the time increment Δt over which the recession slope dQ/dt is approximated is held constant. It is shown here this that leads to upper and lower envelopes in graphs of log(−dQ/dt) versus log(Q) that have been observed in previous studies but are artifacts. The use of constant time increments also limits accurate representation of the recession relationship to the portion of the hydrograph for which the chosen time increment is appropriate. Where dQ/dt varies by orders of magnitude during recession, this may exclude much of the hydrograph from analysis. In response, a new method is proposed in which Δt for each observation in time is properly scaled to the observed drop in discharge ΔQ. It is shown, with examples, how the new method can succeed in exposing the underlying relationship between dQ/dt and Q where the standard method fails. 相似文献
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D. J. Unwin 《地球表面变化过程与地形》1989,14(5):454-455
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