Deciphering variable mantle sources and hydrous inputs to arc magmas in Kamchatka

Iveson, Alexander A.; Humphreys, Madeleine C. S.; Savov, Ivan P.; Hoog, Jan C. M. De; Turner, Scott S.; Churikova, Tatiana; Macpherson, Colin G.; Mather, Tamsin A.; Gordeychik, Boris; Tomanikova, Lubomira; Agostini, Samuele; Hammond, Keiji; Pyle, David M.; Cooper, George F.

doi:10.1016/j.epsl.2021.116848

Cited by 13 publications

(21 citation statements)

References 60 publications

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“…Indeed, a significant fraction of the Ichinsky lavas display elevated Ce/Tl (on average 1331) and Dy/Yb >2 (Supplementary Fig. 3 ) consistent with the presence of a deep, garnet-rich component in their source 27 , 32 , 48 , 58 , 59 , 70 . Therefore, we disregard samples that likely reflect an OIB-like component, and only rely on samples that have similar Ce/Tl and Dy/Yb to the rest of the Kamchatka arc series.…”

Section: Resultsmentioning

confidence: 67%

“…However, based on relatively high Nb/La, Churikova et al (2001) suggested that some magmas at Ichinsky and other back-arc volcanoes are sourced from a mantle wedge that was enriched by an OIB-type mantle component 24 . Such a mantle signature would be expected to be associated with variably high Ce/Tl 48 , 58 , 59 , and elevated Dy/Yb due to the presence of garnet 27 , 32 , 70 . Indeed, a significant fraction of the Ichinsky lavas display elevated Ce/Tl (on average 1331) and Dy/Yb >2 (Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

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Sources of dehydration fluids underneath the Kamchatka arc

et al. 2022

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Fluids mediate the transport of subducted slab material and play a crucial role in the generation of arc magmas. However, the source of subduction-derived fluids remains debated. The Kamchatka arc is an ideal subduction zone to identify the source of fluids because the arc magmas are comparably mafic, their source appears to be essentially free of subducted sediment-derived components, and subducted Hawaii-Emperor Seamount Chain (HESC) is thought to contribute a substantial fluid flux to the Kamchatka magmas. Here we show that Tl isotope ratios are unique tracers of HESC contribution to Kamchatka arc magma sources. In conjunction with trace element ratios and literature data, we trace the progressive dehydration and melting of subducted HESC across the Kamchatka arc. In succession, serpentine (<100 km depth), lawsonite (100–250 km depth) and phengite (>250 km depth) break down and produce fluids that contribute to arc magmatism at the Eastern Volcanic Front (EVF), Central Kamchatka Depression (CKD), and Sredinny Ridge (SR), respectively. However, given the Tl-poor nature of serpentine and lawsonite fluids, simultaneous melting of subducted HESC is required to explain the HESC-like Tl isotope signatures observed in EVF and CKD lavas. In the absence of eclogitic crust melting processes in this region of the Kamchatka arc, we propose that progressive dehydration and melting of a HESC-dominated mélange offers the most compelling interpretation of the combined isotope and trace element data.

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Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Sources of dehydration fluids underneath the Kamchatka arc

et al. 2022

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“…The test results (Figure 10) show that our tomography can reveal a continuous dipping high‐ V s zone beneath Kamchatka if it exists. The subducting Pacific slab had ever existed in the upper mantle beneath north Kamchatka, because the Sredinny Range was still a volcanic front in the Pliocene (Iveson et al., 2021; Volynets et al., 2010). But slab tearing or detachment may have occurred beneath Kamchatka, inferred from the shut‐down of volcanic activities at the Sredinny Range and the formation of the very active Klyuchevskoy volcano (e.g., Green et al., 2020; Jiang et al., 2009; Koulakov et al., 2020; Levin, Shapiro, et al., 2002).…”

Section: Discussionmentioning

confidence: 99%

Mapping the Pacific Slab Edge and Toroidal Mantle Flow Beneath Kamchatka

et al. 2021

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The Kamchatka subduction zone is located at the northwestern corner of the Pacific Ocean, where the Pacific plate, the Okhotsk plate, and the North American plate strongly interact with each other (Figure 1). The Pacific plate is subducting beneath the Okhotsk plate along the Kamchatka trench (Bird, 2003). Earthquakes take place actively down to a depth of ∼600 km on the south of ∼57°N latitude, whereas there is no deep seismicity on the north (Figure 1b). Volcanoes on Kamchatka can be divided into three trench-parallel volcanic chains (e.g., Tatsumi et al., 1994), which are located in the Sredinny Range, the Central Kamchatka Depression (CKD), and the Eastern Volcanic Front (EVF). The EVF is the active volcanic front, whereas the Sredinny Range generally represents the volcanic front in the Pliocene (Iveson et al., 2021;Volynets et al., 2010). The CKD is an active intra-arc rift zone where very active volcanoes of the Klyuchevskoy Group and Shiveluch exist (Koulakov et al., 2020).

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“…Equilibration of B between residual olivine and clinopyroxene and fluids at sub-arc conditions, for example during serpentine dehydration, could result in the opposite signature of 11 B enrichment in slabs (De Hoog and Savov, 2018). Recent studies also consider the effect of multiple fluid extraction events and B isotopic disequilibria during slab dehydration (Clarke et al, 2020), the extent to which melt inclusions record multiple isotopic signatures of slab-derived material (Iveson et al, 2021), and even the extent to which ocean island basalts record a signature of boron subduction beyond the depths of sub-arc magmatism and into the deep mantle (Walowski et al, 2021). However, interpretation of geochemical data is typically reliant on simple assumptions of the extent of B isotope fractionation, and B coordination environments.…”

Section: Implications For B Isotope Fractionationmentioning

confidence: 99%

Boron Incorporation in Silicate Melt: Pressure-induced Coordination Changes and Implications for B Isotope Fractionation

Drewitt

Bromiley

2022

Front. Earth Sci.

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Ab initio molecular dynamics simulations have been employed to investigate the nature of boron incorporation in a haplobasalt melt at pressures up to 8 GPa. At ambient pressure, boron is predominantly incorporated as trigonal planar BO3 units. With increasing pressure, the proportion of tetrahedral BO4 increases markedly in parallel with increases in the coordination of other cations in silicate liquids. In contrast to studies of high-pressure boron-rich silicate glasses and liquids where boron units are polymerized, simulations of low B-concentration liquid here indicate that boron does not adopt a significant role as a network-forming cation. Marked changes in the proportion of BO4 in silicate melt at even moderate pressures (from 5 to 20%, over the pressure range 0–3 GPa) imply that pressure may significantly affect the extent of melt/fluid and melt/crystal boron isotope fractionation. This pressure-effect should be considered when using boron isotope data to elucidate processes occurring within the mantle.

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Deciphering variable mantle sources and hydrous inputs to arc magmas in Kamchatka

Cited by 13 publications

References 60 publications

Sources of dehydration fluids underneath the Kamchatka arc

Sources of dehydration fluids underneath the Kamchatka arc

Mapping the Pacific Slab Edge and Toroidal Mantle Flow Beneath Kamchatka

Boron Incorporation in Silicate Melt: Pressure-induced Coordination Changes and Implications for B Isotope Fractionation

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