Richter Marianne, Nebel Oliver, Maas Roland, Mather Ben, Nebel-Jacobsen Yona, Capitanio Fabio A, Dick Henry J B, Cawood Peter A
Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia.
School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia.
Sci Adv. 2020 Oct 30;6(44). doi: 10.1126/sciadv.abb4340. Print 2020 Oct.
Earth's upper mantle, as sampled by mid-ocean ridge basalts (MORBs) at oceanic spreading centers, has developed chemical and isotopic heterogeneity over billions of years through focused melt extraction and re-enrichment by recycled crustal components. Chemical and isotopic heterogeneity of MORB is dwarfed by the large compositional spectrum of lavas at convergent margins, identifying subduction zones as the major site for crustal recycling into and modification of the mantle. The fate of subduction-modified mantle and if this heterogeneity transmits into MORB chemistry remains elusive. Here, we investigate the origin of upper mantle chemical heterogeneity underneath the Western Gakkel Ridge region in the Arctic Ocean through MORB geochemistry and tectonic plate reconstruction. We find that seafloor lavas from the Western Gakkel Ridge region mirror geochemical signatures of an Early Cretaceous, paleo-subduction zone, and conclude that the upper mantle can preserve a long-lived, stationary geochemical memory of past geodynamic processes.
在大洋中脊扩张中心采集的洋中脊玄武岩（MORB）所代表的地球上地幔，在数十亿年的时间里，通过集中的熔体提取以及被循环地壳组分的再富集，形成了化学和同位素的不均一性。与汇聚边缘熔岩的巨大成分谱相比，MORB的化学和同位素不均一性显得微不足道，这表明俯冲带是地壳再循环进入地幔并使其发生改变的主要场所。俯冲作用改造后的地幔的归宿以及这种不均一性是否会传递到MORB化学组成中仍然难以捉摸。在这里，我们通过MORB地球化学和构造板块重建，研究了北冰洋西部加克尔海岭地区下地幔化学不均一性的起源。我们发现，来自西部加克尔海岭地区的海底熔岩反映了早白垩世古俯冲带的地球化学特征，并得出结论：上地幔可以保留过去地球动力学过程的长期、稳定的地球化学记忆。
