Zinc Isotopes of the Mariana and Ryukyu Arc‐Related Lavas Reveal Recycling of Forearc Serpentinites Into the Subarc Mantle

Abstract

Mantle heterogeneity in subduction zones is largely controlled by the involvement of slab-derived components and the state of the relative depletion of the mantle (e.g.,

Heavy Copper Isotopes in Arc‐Related Lavas From Cold Subduction Zones Uncover a Sub‐Arc Mantle Metasomatized by Serpentinite‐Derived Sulfate‐Rich Fluids

“…The elemental contents and Sr‐Nd isotopic compositions of the samples collected from the Mariana and Ryukyu subduction zones were reported by Chen, Chen, et al. (2021). Detailed sample descriptions are presented in Table S1 in Supporting Information S1.…”

“…Accordingly, the involvement of isotopically heavy Cu 2+ ‐bearing fluids via oxidizing sulfate $$\left({\mathrm{S}\mathrm{O}}_{4}^{2-}\right)$$ species related to serpentinite dehydration produced the observed heavy S and Cu isotopic compositions of the arc‐related lavas (Figure 9). Beyond sub‐arc depths, antigorite breaks down entirely (Alt et al., 2012; Ulmer & Trommsdorff, 1995); therefore, sulfate‐rich fluids are absent (Chen, Chen, et al., 2021). Accordingly, back‐arc lavas have MORB‐like S and Cu isotopic signatures (Figure 9).…”

“…The middle Mariana Trough (at ∼18°N) is an actively spreading back‐arc basin that erupts lava compositionally similar to MORB (Alt et al., 1993; Gribble et al., 1996, 1998; Stern, 2002; Stern et al., 1990; Volpe et al., 1987). Comparatively, various subduction components contribute to lavas from the Mariana Arc (Chen, Chen, et al., 2021; Elliott et al., 1997; Li et al., 2021; Straub et al., 2015; Woodhead, 1989). The southernmost magmatic arc is weakly developed and completely submarine (Figure 1 and Figure S1 in Supporting Information S1; Ribeiro et al., 2013; Stern et al., 2013).…”

“…The Okinawa Trough is a continental back‐arc basin (Sibuet et al., 1987) formed by the northwestward subduction of the Philippine Sea Plate along the Ryukyu trench beneath the Eurasian plate (Figure 1a). Lavas from the southern Okinawa Trough are influenced by more subducted components owing to their geographic proximity to the Ryukyu arc (Chen, Chen, et al., 2021; Shu et al., 2017). The eastern Manus Basin is located adjacent to the New Britain island arc (Figure 1a).…”

Tracing Sediment Melt Activity in the Sub‐Continental Lithosphere: Insights From Zn‐Fe Stable Isotopes

“… Zinc‐Fe isotopic compositions of bulk‐rock and mineral separates of the clinopyroxenites and sample DMP528. Data for volcanic arc rocks (Z. Chen et al., 2021; Foden et al., 2018; Huang et al., 2018; Nebel et al., 2015), ocean island basalts (Beunon et al., 2020; H. Chen et al., 2013; Konter et al., 2016; Teng et al., 2013; Wang et al., 2017), and mid‐ocean ridge basalts (Huang et al., 2018; Teng et al., 2013; Wang et al., 2017) are plotted for comparison. The light blue and light green bars represent the estimated δ 66 Zn value (0.20‰ ± 0.03‰) and δ 56 Fe value (0.03‰ ± 0.03‰) of Bulk Silicate Earth (Doucet et al., 2020).…”