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首页> 外文期刊>Nature >ARCHAEAN CRATONIC ROOTS, MANTLE SHEAR ZONES AND DEEP ELECTRICAL ANISOTROPY
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ARCHAEAN CRATONIC ROOTS, MANTLE SHEAR ZONES AND DEEP ELECTRICAL ANISOTROPY

机译：古生物的根源，地幔剪切带和深的电气各向异性

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THE extent to which the mantle participated in the growth and stabilization of ancient cratons is central to our understanding of the evolution of the continents(1). The detection of seismic anisotropy beneath Precambrian North America, for example, has been interpreted as showing that strain-induced orientation of mantle minerals in subcontinental lithospheric mantle can preserve a record of ancient episodes of deformation(2). Here we present magnetotelluric measurements from the Superior Province of the Canadian shield, which reveal pronounced electrical anisotropy in the upper 100 km of the underlying mantle. We argue that this anisotropy is best explained by conducting graphite films, oriented within fractures or on grain boundaries, and associated with metasomatism of the mantle roots of major Archaean shear zones which transect the entire Superior Province. The uppermost mantle beneath the Canadian shield has therefore remained fixed to the crust and isolated from significant tectonic reworking since the late Archaean. [References: 33]
机译：地幔在多大程度上参与了古代克拉通的生长和稳定，这是我们对各大洲演化的了解的核心（1）。例如，对北美前寒武纪以下地震各向异性的探测已被解释为表明应变诱发的陆下岩石圈地幔中地幔矿物的取向可以保留古代变形事件的记录（2）。在这里，我们介绍了来自加拿大盾构上级省的大地电磁测量结果，揭示了下地幔上部100 km的明显电磁各向异性。我们认为，这种各向异性最好通过传导石墨膜来解释，该石墨膜定向在裂缝内或晶界上，并与横穿整个上级省的主要古生剪切带的地幔根交代作用有关。因此，自古生代以来，加拿大盾构下的最上层地幔一直固定在地壳上，并且与重大的构造改造无关。 [参考：33]

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