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Large-scale chemical and thermal division of the Pacific mantle

机译：太平洋地幔的大规模化学和热力部门

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Isotope analyses of mid-ocean-ridge basalts have led to the identification of large-scale geochemical provinces, with a clear distinction between the Pacific and the Atlantic or Indian Ocean basins. It is widely believed that Pacific ridges are formed from a single, fairly well mixed mantle reservoir, extending from the Australian-Antarctic discordance to the Juan de Fuca ridge and representing one of the largest chemically coherent mantle domains on the Earth. However, the evidence for this conception is mostly based on samples from the northern Pacific ridges. Here we report Sr, Nd and Pb isotope data from the Pacific Antarctic ridge that reveal different isotopic signatures north and south of the Easter microplate (25° S). The evidence for two large-scale geochemical domains is further strengthened by the observation of different average depths of the ridge axes north and south of the 25° S boundary. This boundary is located at the southeastern end of the Darwin rise/Pacific Superswell area, which is interpreted as a zone of upwelling from the lower mantle that has persisted since Cretaceous tunes. We propose that this upwelling has led to the separation into two mantle domains with their own convective histories, producing slight differences in their average isotopic signatures and thermal regimes.
机译：海洋中脊玄武岩的同位素分析已导致对大型地球化学省的鉴定，在太平洋和大西洋或印度洋盆地之间有明显的区别。人们普遍认为，太平洋海脊是由一个单一的，混合良好的地幔储层形成的，从澳大利亚-南极不和谐一直延伸到胡安·德富卡海岭，是地球上最大的化学连贯地幔区域之一。但是，这一概念的证据主要基于北太平洋海脊的样本。在这里，我们报告了太平洋南极山脊的Sr，Nd和Pb同位素数据，这些数据揭示了复活节微孔板（25°S）以北和以南的不同同位素特征。通过观察25°S边界以北和以南的脊轴平均深度不同，进一步加强了两个大规模地球化学域的证据。该边界位于达尔文上升/太平洋超高膨胀区的东南端，这被解释为自白垩纪以来一直持续存在的下地幔上升的区域。我们认为这种上升流导致了两个具有各自对流历史的地幔区域的分离，在它们的平均同位素特征和热力状态上产生了细微的差异。

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