Long-Lived Source Heterogeneities in the Galapagos Mantle Plume
Long-Lived Source Heterogeneities in the Galapagos Mantle Plume
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DOI：
10.1029/2017gc007338
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发表时间：
2018-08-01
影响因子：
3.5
通讯作者：
Jicha, Brian
中科院分区：
文献类型：
--
作者：
Gazel, Esteban;Trela, Jarek;Jicha, Brian
地幔柱衍生的熔体提供了一个独特的一瞥深地幔的化学不均匀性。然而，下地幔不均匀性的形成和取样的确切过程仍然没有得到解决，因此，需要进一步的研究，以了解导致其形成的行星分化，地壳再循环和地幔混合的累积效应。加拉帕戈斯地幔柱的特殊之处在于它的熔岩样品中含有四种不同的同位素地幔成分。然而，这些最终成员的起源仍然存在争议。在这项研究中，我们调查的空间和时间的外观和演变，这四个同位素的端成员，包括今天的群岛通过检查古加拉帕戈斯熔岩流保存在增生的火山在哥斯达黎加和巴拿马。我们发现，每个经典定义的加拉帕戈斯域之间的空间关系一直保持相对恒定的整个烟羽的演变。我们的新研究结果延长了时间尺度的独特的同位素异质性的源柱至少70马的南部域和90马的中央，北方域，这表明地球化学异质性的地幔柱上升，通过保持独特的同位素异质性的时间尺度上千万年。此外，微量元素系统学的橄榄石晶体从加拉帕戈斯有关的克波斯和Azuero的火山（50 - 70马）表明衍生的来源，包括回收的成分。总的来说，这些结果表明，地幔柱不仅采样大规模的非均质性在深地幔，但这些源的非均质性可以保持采样的整个生命周期的一个羽。
Mantle plume-derived melts provide a unique glimpse into the chemical heterogeneity of the deep mantle. However, the exact processes involved in forming and sampling lower mantle heterogeneities remain unresolved and thus, require further investigation to understand the cumulative effects of planetary differentiation, crustal recycling, and mantle mixing that lead to their formation. The Galapagos Plume is exceptional in that its lavas sample four distinct isotopic mantle components. However, the origin of each of these end-members remains debated. In this study, we investigate the spatial and temporal appearance and evolution of these four isotopic end-members that comprise the present-day Archipelago by examining ancient Galapagos lava flows preserved in the accreted terranes in Costa Rica and Panama. We discovered that the spatial relationship between each of the classically defined Galapagos Domains has remained relatively constant throughout the evolution of the plume. Our new results extend the time scale of distinct isotopic heterogeneity in the source of the plume to at least 70 Ma for the Southern Domain and 90 Ma for the Central, and Northern Domains, suggesting that geochemically heterogeneous plumes rising through the mantle preserve distinct isotopic heterogeneity on the time scale of tens of millions of years. Additionally, trace element systematics of olivine crystals from the Galapagos-related Quepos and Azuero terranes (50-70 ma) suggest derivation from sources that included recycled components. Collectively, these results suggest that mantle plumes not only sample large-scale heterogeneities within the deep mantle, but that these source heterogeneities can remain sampled throughout the lifetime of a plume.