句中有一些专有词汇。如果抛开文章不说,单看这一个句子,则句首的layered mantle thesis就难以理解。但是如果读者能够读懂句子的大致意思,看到layered mantle thesisr最有力证据就是其材料fundamentally different from the upper mantle,这应该可以推测出,既然不同于上层地幔,则这个理论一定是在说地幔有不同的层面。
意群训练:The best evidence for the layered-mantle thesis is the well-established fact that volcanic rocks found on oceanic islands,islands believed to result from mantle plumes arising from the lower mantle,are composed of material fundamentally different from that of the mid-ocean ridge system, whose source,most geologists contend,is the upper mantle.
2. Some geologists,however,on the basis of observations concerning mantle xenoliths, argue that the mantle is not layered,but that heterogeneity is created by fluids rich in incompatible elements percolating upward and transforming portions of the upper mantle irregularly,according to the vagaries of the fluids pathways.
但是,某些地质学家,以对地幔捕虏岩体所作的观察为依据,指出地幔并非是分层排列的,相反,地幔的异质性是由那些富含不相容成分的流质构成的,这些成分趋向于流体而非固体的状态,自下而上渗透扩散,并依照这些流质流向的任意性,不规则地将上部地幔的某些部分予以改变。
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