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This pyroxenization would occur in various proportions along the fluid pathways, e. If such rocks were subducted and dehydrated, the slab-derived fluid would become enriched in Ni and silica, enhancing the possibility of producing a high-Ni melt. In addition, a quantitative inversion model of incompatible trace elements has indicated that the Detroit Seamount, as a source of slab-derived fluid, explains the EC lava compositions better compared with cases using the composition of Pacific Plate AOC 31 , These examples of geochemical evidence support the suggestion that a subducted seamount contributed to the generation of the EC magmas and that it probably had an influence on all the lavas along the entire northern Kamchatka traverse, as was suggested earlier 6 — 8.

The Sr—Nd isotopic compositions of the Detroit Seamount exhibit the most depleted characteristics within the Emperor Seamount Chain, reflecting a refractory component of the plume that was sampled only at high degrees of melting. The subducted seamount that contributed to the formation of the EC magmas is expected to have had the same geochemical nature as the Detroit Seamount.

It is emphasized that the EC lavas are not hotspot magmas, but are arc magmas affected by the subducted seamount, which is supposed of hotspot origin, via slab-derived fluids, as discussed above.

A model for the heating of the slab by asthenospheric injection around the slab edge is not supported for the following reasons. Because the mantle beneath the forearc area constitutes a narrow wedge intercalated between the arc crust and the subducting slab, it is difficult for asthenospheric injection to intrude and heat the slab surface beneath the forearc region, including the EC area 3.

This is unlike the Shiveluch Volcano located on the slab edge, where slab melting is considered attributable to hot asthenospheric flow 3 , These thermal structures and fluid processes associated with a warm slab but a relatively low-temperature mantle wedge could explain the petrological variability of the EC lavas and the mineralogical heterogeneity of the HMA Fig.

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Generally, an Ol liquidus field expands as a primary melt ascends from the region of mantle melting. In turn, simultaneous crystallization of Cpx and Ol from the primary magma requires a condition close to the melting condition, under which compositions evolve with lower CaO, SiO 2 , and MnO and higher FeO and NiO 20 compared with those derived by Ol-only fractionation. This is consistent with observations, e. Efficient cooling of magma close to the melting condition is needed for the fractionation of Cpx during the initial stage, as illustrated in Fig.

Pargasite crystallized during the early cooling stage, possibly within a melt pocket or along the vein wall, and it was later mixed with magmas from other melt pockets with different zoning types of Ol. Once melting had occurred and the HMA magma was extracted, the pyroxenite source became exhausted. Subsequently, the residual fluid that had already precipitated silica would have caused flux melting of the peridotite to produce the primitive basalt. This source mantle evolution is supported by the temporal evolution in terms of the major and trace element compositions Supplementary Fig.

The fluid network would have developed upward, assisting the smooth ascent of the melt, which would have crystallized mostly Ol without developing isolated melt pockets. Such temporal evolution suggests a limited supply of slab-derived fluid, which is consistent with a local subducted seamount as the source of the fluid.


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Therefore, the HMA, including the ultra-high-Ni Ol, and subsequent magmatism are considered to reflect a series of products that originated from varying degrees and types of interaction between the mantle wedge and slab-derived fluid supplied from a subducted seamount over limited time and space Fig. Such a suite of local and temporal magmatism triggered by seamount subduction could occur in other subduction zones. For example, the Galapagos track on the Cocos Plate is subducting beneath central Costa Rica, where geochemical contribution from the subducted seamount is suggested based on isotopic signatures of the volcanic rocks and Ol-hosted melt inclusions in central Costa Rica 57 , On the other hand, the northwestern part of the Cocos Plate has no apparent seamount edifices, and it is subducting beneath the Quaternary central Mexican Volcanic Belt MVB located to the northwest of Costa Rica.

Reference 60 argued that these high-Ni Ols were derived from pyroxenites formed by infiltration of multiple silicic components from the subducting slab. Although the MVB could have been affected to some extent by the subducted seamount, the simultaneous occurrence of the HMA with high-Ni Ol and other types of primitive lava might not uniquely indicate seamount subduction; therefore, other components and models need to be examined.

However, seamount subduction is at least one of the important factors that we should examine for constraining past tectonic environments under unclear settings where such volcanic assemblages occur. Weathered parts were removed for the bulk analyses of major elements, trace elements, and isotope ratios. Samples were then crushed by hand into finer grains using a tungsten mill. Finally, these fine-grained samples were powdered using a quartz ball mill Fritsch; Planetary mill pulversette 5. Major elements were analyzed by an X-ray fluorescence spectrometer Rigaku; RIX using the glass bead method with a sample:flux ratio of Both were weighed accurately with an electronic balance and mixed together with agate mortar.

Dots-and-Lines Approach to Subduction Volcanism and Tectonics

The mixture was then made into a glass bead using a fuse-sampler machine Rigaku; sample pretreatment device. The abundance of trace elements was determined using the acid digestion method The decomposed sample was evaporated stepwise until dry. The residue was dissolved with HNO 3 and the solution diluted to times by mass. The analytical procedure used for chemical separation and mass spectrometry for the Sr, Nd, and Pb isotope determinations is outlined in refs 63 — Mass fractionation factors for Pb were corrected using Tl as an external standard.

Additional mass-dependent interelement fractions were also corrected by applying a standard bracketing method using NIST SRM as a standard. Olivine phenocrysts were set in resin Technovit No. The ZAF correction was then applied. The crushed samples were rinsed with DIW in an ultrasonic bath. For potassium analysis, the 3—5-g subsamples used for the argon isotope analysis were pulverized further using an agate mortar. Argon isotopic ratios were determined by a conventional isotope dilution method using an 38 Ar spike. Argon extraction from a sample was performed using a stainless steel ultra-high vacuum extraction line.

Samples of 0. The 38 Ar spike was removed from the reservoir tank using a pipette valve and mixed with sample gas during fusion of the sample. Argon isotopes of an air standard were analyzed once or twice daily for mass discrimination correction.

Potassium contents were determined for mg samples by flame emission spectrometry, using peak integration and the lithium internal standard method Error for the potassium analysis was estimated at 0. The inversion model for estimating the melting condition of the EC lavas 31 consisted of a dehydration process from the slab and a melting process in the mantle wedge. The original mantle lithology was assumed peridotite or pyroxenite and its bulk composition was DMM However, the Ni contents considered the variations estimated from the peridotite xenoliths in Kamchatka After generating the melt, it ascended quickly while maintaining non-equilibrium conditions with the wall rock and retaining the initial composition of the eruption.

We would like to thank Evgeny Gordeev and Muravyev Yarosrav for coordination in Kamchatka, Masashi Ushioda for suggestions regarding analytical techniques, Akihiko Ikemoto for providing part of the program of the inversion model, DSEG analytical members for their assistance in analyses of isotopic element compositions. All authors participated in the discussion and review of the manuscript.

Electronic supplementary material. Supplementary information accompanies this paper at doi Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. National Center for Biotechnology Information , U. Sci Rep. Published online Sep Author information Article notes Copyright and License information Disclaimer.

Tatsuji Nishizawa, Email: pj. Corresponding author. Received Mar 14; Accepted Jul 3. This article has been cited by other articles in PMC. Associated Data Supplementary Materials Supplementary information. Abstract The Kamchatka Peninsula is a prominent and wide volcanic arc located near the northern edge of the Pacific Plate. Introduction The Kamchatka Peninsula is one of the largest volcanic arcs in the world.

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Open in a separate window. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Metasomatism by Si-rich fluid from subducted seamount When such fluid is supplied to an overlying mantle wedge, pyroxenite veins are formed locally along fluid pathways and its melting would generate a high-Ni melt 23 , Compositional variability and evolution of source mantle These thermal structures and fluid processes associated with a warm slab but a relatively low-temperature mantle wedge could explain the petrological variability of the EC lavas and the mineralogical heterogeneity of the HMA Fig.

Method Whole-rock geochemical analyses Weathered parts were removed for the bulk analyses of major elements, trace elements, and isotope ratios. Whole-rock major elements analyses Major elements were analyzed by an X-ray fluorescence spectrometer Rigaku; RIX using the glass bead method with a sample:flux ratio of Whole-rock trace element analyses The abundance of trace elements was determined using the acid digestion method EC-magma generation modeling The inversion model for estimating the melting condition of the EC lavas 31 consisted of a dehydration process from the slab and a melting process in the mantle wedge.

Electronic supplementary material Supplementary information K, pdf. Acknowledgements We would like to thank Evgeny Gordeev and Muravyev Yarosrav for coordination in Kamchatka, Masashi Ushioda for suggestions regarding analytical techniques, Akihiko Ikemoto for providing part of the program of the inversion model, DSEG analytical members for their assistance in analyses of isotopic element compositions.

Author Contributions T. Notes Competing Interests The authors declare that they have no competing interests. Footnotes Electronic supplementary material Supplementary information accompanies this paper at doi References 1. Ponomareva, V. Seismicity and structure of the Kamchatka subduction zone.

This article has been cited by other articles in PMC. Associated Data Supplementary Materials Supplementary information.


  1. Genesis of ultra-high-Ni olivine in high-Mg andesite lava triggered by seamount subduction!
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  5. Abstract The Kamchatka Peninsula is a prominent and wide volcanic arc located near the northern edge of the Pacific Plate. Introduction The Kamchatka Peninsula is one of the largest volcanic arcs in the world. Open in a separate window. Figure 1. Figure 2. Figure 3. Figure 4.

    Genesis of ultra-high-Ni olivine in high-Mg andesite lava triggered by seamount subduction

    Figure 5. Figure 6. Figure 7. Metasomatism by Si-rich fluid from subducted seamount When such fluid is supplied to an overlying mantle wedge, pyroxenite veins are formed locally along fluid pathways and its melting would generate a high-Ni melt 23 , Compositional variability and evolution of source mantle These thermal structures and fluid processes associated with a warm slab but a relatively low-temperature mantle wedge could explain the petrological variability of the EC lavas and the mineralogical heterogeneity of the HMA Fig.

    Method Whole-rock geochemical analyses Weathered parts were removed for the bulk analyses of major elements, trace elements, and isotope ratios. Whole-rock major elements analyses Major elements were analyzed by an X-ray fluorescence spectrometer Rigaku; RIX using the glass bead method with a sample:flux ratio of Whole-rock trace element analyses The abundance of trace elements was determined using the acid digestion method EC-magma generation modeling The inversion model for estimating the melting condition of the EC lavas 31 consisted of a dehydration process from the slab and a melting process in the mantle wedge.