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Frozen magma lenses below the oceanic crust

机译:海洋地壳下方的冻岩浆透镜

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The Earth's oceanic crust crystallizes from magmatic systems generated at mid-ocean ridges. Whereas a single magma body residing within the mid-crust is thought to be responsible for the generation of the upper oceanic crust, it remains unclear if the lower crust is formed from the same magma body, or if it mainly crystallizes from magma lenses located at the base of the crust(1-3). Thermal modelling(4-6), tomography(7), compliance(8) and wide-angle seismic studies(9), supported by geological evidence(3,10-18), suggest the presence of gabbroic-melt accumulations within the Moho transition zone in the vicinity of fast- to intermediate-spreading centres. Until now, however, no reflection images have been obtained of such a structure within the Moho transition zone. Here we show images of groups of Moho transition zone reflection events that resulted from the analysis of similar to 1,500 km of multichannel seismic data collected across the intermediate-spreading-rate(19) Juan de Fuca ridge. From our observations we suggest that gabbro lenses and melt accumulations embedded within dunite or residual mantle peridotite are the most probable cause for the observed reflectivity, thus providing support for the hypothesis that the crust is generated from multiple magma bodies.
机译:地球的洋壳是从洋中脊产生的岩浆系统中结晶出来的。认为存在于中地壳内的单个岩浆体是上洋壳的产生的原因,但尚不清楚下地壳是否由相同的岩浆体形成,或者它是否主要是由位于地壳内的岩浆透镜结晶而来的。地壳的底部(1-3)。热建模(4-6),层析成像(7),顺应性(8)和广角地震研究(9),并有地质证据(3,10-18)的支持,表明莫霍面内存在辉长岩融解积聚过渡区到快速扩展中心到中间扩展中心附近。然而,到目前为止,尚未在Moho过渡区内获得这种结构的反射图像。在这里,我们显示了Moho过渡带反射事件组的图像,这些图像是通过分析跨中扩展速率(19)Juan de Fuca脊收集的类似于1,500 km的多通道地震数据而得到的。根据我们的观察结果,我们认为辉长透镜和埋在榴辉岩或残余地幔橄榄岩中的熔体堆积是观察到反射率的最可能原因,从而为地壳是由多个岩浆体生成的假设提供了支持。

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