Barium isotope compositions of altered oceanic crust from the IODP Site 1256 at the East Pacific rise

Nan, Xiao-Yun; Wu, Fei; Yu, Hui-Min; Kang, Jin-Ting; Gao, Yong-Jun; Huang, Fang

doi:10.1016/j.chemgeo.2023.121778

Cited by 5 publications

(2 citation statements)

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“…In recent years, barium (Ba) isotopes have been used to trace the fluids dehydrated from subducted AOC (e.g., Hao et al., 2022; Nielsen et al., 2020; Wu et al., 2020). The Ba isotope ratios of AOC show a large variation (δ 138/134 Ba = −0.11‰ to +0.40‰; Figure 1) (Nan et al., 2023; Nielsen et al., 2018) but are overall heavier than that of the depleted mantle beneath the mid‐ocean ridges (DMM) (δ 138/134 Ba = +0.03‰ to +0.05‰) (Wu et al., 2023) and fluids released from AOC dehydration are expected to have even heavier Ba isotopes (Gu et al., 2021; Xu et al., 2023). In contrast, seafloor sediments generally have lighter Ba isotope ratios (δ 138/134 Ba = −0.11‰ to +0.10‰; Figure 1) (Bridgestock et al., 2018; Nielsen et al., 2018, 2020).…”

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“…The contours represent the depth of the descending slab according to Slab2 model(Hayes et al, 2018). (b) Ba isotopic compositions of the Mariana lavas in this study, altered oceanic crust(Nan et al, 2023;Nielsen et al, 2018), and sediment(Bridgestock et al, 2018;Nielsen et al, 2018Nielsen et al, , 2020. The data of the DMM(Wu et al, 2023) is presented for comparison.…”

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Deciphering Contribution of Recycled Altered Oceanic Crust to Arc Magmas Using Ba‐Sr‐Nd Isotopes

Zhang,

Shu,

Turner

et al. 2024

JGR Solid Earth

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Altered oceanic crust (AOC) plays a critical role in geochemical recycling in subduction zones. However, identifying contributions of subducted AOC to arc magmas remains a conundrum due to the lack of effective tracers. Here, we investigate the Ba‐Sr‐Nd isotopic compositions of lavas from the Mariana arc and back‐arc. Based on a statistical analysis of the Sr‐Nd isotopes for global arc volcanoes, we confirm that AOC‐derived fluid (or hydrous melt), rather than sediment‐derived melt or fluid, is responsible for the Sr‐Nd isotope decoupling (i.e., 87Sr/86Sr is “excessively” enriched relative to 143Nd/144Nd when compared to the “normal” mantle derivates) observed in island arc lavas. We show that the arc lavas with increasingly decoupled Sr‐Nd isotopes generally have heavier Ba isotope ratios, which is also a characteristic feature of AOC‐derived fluids. Thus, these results establish an intimate link between subducted AOC, heavy Ba isotope compositions, and Sr‐Nd isotope decoupling signature in island arcs, which provides a powerful tool to trace the AOC recycling in subduction zones. Furthermore, a similar correlation is observed between Sr‐Nd isotope decoupling and heavy B isotope ratios for global arc lavas, implying that the recycling of AOC component is generally linked to serpentinite dehydration in subduction zones.

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