Evolution of chalcophile elements in the magmas of the Bonin Islands

Valetich, Matthew; Mavrogenes, John; Arculus, R. J.; Umino, Susumu

doi:10.1016/j.chemgeo.2018.07.011

Cited by 15 publications

(13 citation statements)

References 91 publications

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“…The sulfur contents of all but three FAB glasses (the two enriched FAB and the FAB‐related andesite) appear to be controlled by incompatibility during crystal fractionation (Figure 5c, and see S vs. MgO in supplement), indicating that there has not been significant sulfur loss to a volatile phase (Figure 5c). In contrast, the boninite glasses have lower sulfur contents (<200 ppm), similar to those reported in melt inclusions and seafloor glass from the nearby Bonin Islands (Figure 5c, Valetich et al., 2019).…”

Section: Discussionsupporting

confidence: 81%

“…Existing solubility models calibrated using experimental data (e.g., D‐COMPRESS; Burgisser et al., 2015) predict that a silicate melt with H 2 O and CO 2 contents broadly similar to that of the boninite glasses (∼2 wt % H 2 O, ∼50 ppm CO 2 ) will be vapor saturated with ∼1,700 ppm sulfur at ∼760 bars total pressure, and that sulfur concentration is not predicted to decrease below 500 ppm until pressures lower than 50 bars. On the other hand, low sulfur (i.e., <200 ppm) and moderate H 2 O contents (i.e., ≥2 wt%) in silicate glasses have been observed in subduction settings by others (Brounce et al., 2016; Davis et al., 1991; Jenner et al., 2010; Rasmussen et al., 2018) including in boninitic magmas (Cooper et al., 2010; Valetich et al., 2019). These studies produce evidence both for (Cooper et al., 2010; Rasmussen et al., 2018) and against (Brounce et al., 2016; Valetich et al., 2019) high‐pressure sulfur degassing, and in sum, describe significant uncertainty in the factors that control sulfur mobility during low pressure differentiation in subduction settings.…”

Section: Discussionmentioning

confidence: 96%

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Covariation of Slab Tracers, Volatiles, and Oxidation During Subduction Initiation

Brounce

Reagan

Kelley

et al. 2021

Geochem Geophys Geosyst

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Subduction‐related lavas have higher Fe3+/∑Fe than midocean ridge basalts (MORB). Hypotheses for this offset include imprint from subducting slabs and differentiation in thickened crust. These ideas are readily tested through examination of the time‐dependent evolution of slab‐derived signatures, thickening crust of the overriding plate, and evolving redox during subduction initiation. Here, we present Fe3+/ΣFe and volatile element abundances of volcanic glasses recovered from International Ocean Discovery Program (IODP) Expedition 352 to the Izu‐Bonin‐Mariana (IBM) forearc. The samples include forearc basalts (FAB) that are stratigraphically overlain by low‐ and high‐silica boninite lavas. The FAB glasses have 0.18–0.85 wt% H2O, 75–233 ppm CO2, S contents controlled by saturation with a sulfide phase (602–1,386 ppm), Ba/La from 3.9‐10, and Fe3+/ΣFe ratios from 0.136 to 0.177. These compositions are similar to MORB and suggest that decompression melting of dry and reduced mantle dominates the earliest stages of subduction initiation. Low‐ and high‐silica boninite glasses have 1.51–3.19 wt% H2O, CO2 below detection, S contents below those required for sulfide saturation (5–235 ppm), Ba/La from 11 to 29, and Fe3+/∑Fe from 0.181 to 0.225. The compositions are broadly similar to modern arc lavas in the IBM arc. These data demonstrate that the establishment of fluid‐fluxed melting of the mantle, which occurs in just 0.6–1.2 my after subduction initiation, is synchronous with the production of oxidized, mantle‐derived magmas. The coherence of high Fe3+/∑Fe and Ba/La ratios with high H2O contents in Expedition 352 glasses and the modern IBM arc rocks strongly links the production of oxidized arc magmas to signatures of slab dehydration.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 96%

Covariation of Slab Tracers, Volatiles, and Oxidation During Subduction Initiation

Brounce

Reagan

Kelley

et al. 2021

Geochem Geophys Geosyst

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“…Thus, the H 2 O concentrations of boninite series glasses (and the E‐FAB discussed above) reflect some degree of degassing prior to and during eruption on the ocean floor as well as providing evidence that all slab melts involved in boninite genesis were water‐rich. This degassing likely caused magmas also to lose S, although the low S concentrations in boninites may also reflect strong prior depletion of the mantle source (Valetich et al., 2019).…”

Section: Discussionmentioning

confidence: 99%

Magma Source Evolution Following Subduction Initiation: Evidence From the Element Concentrations, Stable Isotope Ratios, and Water Contents of Volcanic Glasses From the Bonin Forearc (IODP Expedition 352)

Coulthard

Reagan

Shimizu

et al. 2021

Geochem Geophys Geosyst

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International Ocean Discovery Program Expedition 352 to the Bonin forearc drilled the sequence of volcanic rocks erupted in the immediate aftermath of subduction initiation along the western margin of the Pacific Plate. Pristine volcanic glasses collected during this expedition were analyzed for major and trace elements, halogens, sulfur, and H and O isotopes with goals of characterizing the fluids and melts of subducted materials that were involved in generating the nascent upper plate crust. Incompatible trace element compositions of the oldest lavas (forearc basalts [FAB]) are similar to those of the most depleted mid‐ocean ridge basalts globally. Most FAB were generated by decompression melting during seafloor spreading in a near‐trench, supra‐subduction zone environment with only minor involvement of diverse and generally dilute water‐rich fluids from the subducting plate. Boninite series glasses are enriched in incompatible trace elements mobilized from the subducting plate, but strongly depleted in other elements, such as the middle‐heavy rare‐earth elements. These traits are attributed to generation of boninites largely by flux melting involving water‐rich melts first derived from the leading edge of subducted basaltic crust and then from both subducted crust and sediment. These melts were generated at low pressures as the shallow, embryonic slab extracted heat from hot asthenosphere near the trench. The progressive depletion of the mantle source for the FAB‐through‐boninite sequence suggests that the asthenospheric mantle remained trapped above the nascent subducting plate for the first several million years of subduction beneath the Philippine Sea Plate.

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“…Given the compositional zonation of the crystalline phases, and the uncertainty of establishing polyphase, heterogeneous equilibria, detailed thermobarometry (via a relevant reaction that includes 56 , boninite 20,67,68 , FAB of Izu-Bonin-Mariana 11,54,55 and literature cited in ref. 19 .…”

Section: Discussionmentioning

confidence: 99%

Basalt derived from highly refractory mantle sources during early Izu-Bonin-Mariana arc development

Arculus

Ishizuka

et al. 2021

Nat Commun

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The magmatic character of early subduction zone and arc development is unlike mature systems. Low-Ti-K tholeiitic basalts and boninites dominate the early Izu-Bonin-Mariana (IBM) system. Basalts recovered from the Amami Sankaku Basin (ASB), underlying and located west of the IBM’s oldest remnant arc, erupted at ~49 Ma. This was 3 million years after subduction inception (51-52 Ma) represented by forearc basalt (FAB), at the tipping point between FAB-boninite and typical arc magmatism. We show ASB basalts are low-Ti-K, aluminous spinel-bearing tholeiites, distinct compared to mid-ocean ridge (MOR), backarc basin, island arc or ocean island basalts. Their upper mantle source was hot, reduced, refractory peridotite, indicating prior melt extraction. ASB basalts transferred rapidly from pressures (~0.7-2 GPa) at the plagioclase-spinel peridotite facies boundary to the surface. Vestiges of a polybaric-polythermal mineralogy are preserved in this basalt, and were not obliterated during persistent recharge-mix-tap-fractionate regimes typical of MOR or mature arcs.

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Evolution of chalcophile elements in the magmas of the Bonin Islands

Cited by 15 publications

References 91 publications

Covariation of Slab Tracers, Volatiles, and Oxidation During Subduction Initiation

Covariation of Slab Tracers, Volatiles, and Oxidation During Subduction Initiation

Magma Source Evolution Following Subduction Initiation: Evidence From the Element Concentrations, Stable Isotope Ratios, and Water Contents of Volcanic Glasses From the Bonin Forearc (IODP Expedition 352)

Basalt derived from highly refractory mantle sources during early Izu-Bonin-Mariana arc development

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