萨摩亚单斜辉石中极端的同位素非均质性限制了沉积物的再循环。
Extreme isotopic heterogeneity in Samoan clinopyroxenes constrains sediment recycling.
作者信息
Adams Jenna V, Jackson Matthew G, Spera Frank J, Price Allison A, Byerly Benjamin L, Seward Gareth, Cottle John M
机构信息
Department of Earth Science, University of California Santa Barbara, Santa Barbara, CA, USA.
Isotope Geochemistry Facility - Center for Mantle Zoology, University of California Santa Barbara, Department of Earth Science, Santa Barbara, CA, USA.
出版信息
Nat Commun. 2021 Feb 23;12(1):1234. doi: 10.1038/s41467-021-21416-9.
Lavas erupted at hotspot volcanoes provide evidence of mantle heterogeneity. Samoan Island lavas with high Sr/Sr (>0.706) typify a mantle source incorporating ancient subducted sediments. To further characterize this source, we target a single high Sr/Sr lava from Savai'i Island, Samoa for detailed analyses of Sr/Sr and Nd/Nd isotopes and major and trace elements on individual magmatic clinopyroxenes. We show the clinopyroxenes exhibit a remarkable range of Sr/Sr-including the highest observed in an oceanic hotspot lava-encompassing ~30% of the oceanic mantle's total variability. These new isotopic data, data from other Samoan lavas, and magma mixing calculations are consistent with clinopyroxene Sr/Sr variability resulting from magma mixing between a high silica, high Sr/Sr (up to 0.7316) magma, and a low silica, low Sr/Sr magma. Results provide insight into the composition of magmas derived from a sediment-infiltrated mantle source and document the fate of sediment recycled into Earth's mantle.
热点火山喷发的熔岩提供了地幔不均一性的证据。具有高锶同位素比值（(^{87}Sr/^{86}Sr>0.706)）的萨摩亚群岛熔岩代表了一种包含古老俯冲沉积物的地幔源。为了进一步表征这种地幔源，我们选取了来自萨摩亚萨瓦伊岛的一块高(^{87}Sr/^{86}Sr)熔岩，对单个岩浆单斜辉石进行了(^{87}Sr/^{86}Sr)和(^{143}Nd/^{144}Nd)同位素以及主量和微量元素的详细分析。我们发现单斜辉石显示出显著的(^{87}Sr/^{86}Sr)变化范围——包括在大洋热点熔岩中观测到的最高值——涵盖了大洋地幔总变化范围的约30%。这些新的同位素数据、来自其他萨摩亚熔岩的数据以及岩浆混合计算结果表明，单斜辉石的(^{87}Sr/^{86}Sr)变化是由高硅、高(^{87}Sr/^{86}Sr)（高达0.7316）岩浆与低硅、低(^{87}Sr/^{86}Sr)岩浆之间的岩浆混合导致的。研究结果为源自沉积物渗透地幔源的岩浆成分提供了见解，并记录了再循环到地球地幔中的沉积物的去向。
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