Department of Earth Sciences, University of Cambridge, Cambridge, UK.
Institute of Astronomy, University of Cambridge, Cambridge, UK.
Sci Adv. 2023 Mar 10;9(10):eadd5030. doi: 10.1126/sciadv.add5030.
The lavas associated with mantle plumes may sample domains throughout Earth's mantle and probe its dynamics. However, plume studies are often only able to take snapshots in time, usually of the most recent plume activity, leaving the chemical and geodynamic evolution of major convective upwellings in Earth's mantle poorly constrained. Here, we report the geodynamically key information of how the lithology and density of a plume change from plume head phase to tail. We use iron stable isotopes and thermodynamic modeling to show that the Galápagos plume has contained small, nearly constant, amounts of dense recycled crust over its 90-million-year history. Despite a temporal evolution in the amount of recycled crust-derived melt in Galápagos-related lavas, we show that this can be explained by plume cooling alone, without associated changes in the plume's mantle source; results are also consistent with a plume rooted in a lower mantle low-velocity zone also sampling primordial components.
与地幔柱相关的熔岩可能会在整个地幔中取样，并探测其动力学。然而，地幔柱的研究通常只能在时间上进行快照，通常是最近的地幔柱活动，而对地幔中主要对流上升流的化学和地球动力学演化则缺乏严格的限制。在这里，我们报告了在地幔柱的头部到尾部阶段，地幔柱的岩性和密度如何变化的关键地球动力学信息。我们使用铁稳定同位素和热力学模拟表明，加拉帕戈斯地幔柱在其 9000 万年的历史中一直含有少量的、几乎恒定的高密度再生地壳。尽管加拉帕戈斯相关熔岩中源自再生地壳的熔体的数量随时间发生了变化，但我们表明，这可以仅通过地幔柱冷却来解释，而不需要地幔柱源区的相关变化；研究结果也与地幔柱起源于一个采样原始成分的下地幔低速带的观点一致。
