Trace Elements and Li Isotope Compositions Across the Kamchatka Arc: Constraints on Slab‐Derived Fluid Sources

Liu, Haiyang; Xiao, Yilin; Sun, He; Tong, Fengtai; Heuser, Alexander; Churikova, Tatiana

doi:10.1029/2019jb019237

Cited by 16 publications

(19 citation statements)

References 100 publications

(314 reference statements)

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“…Our observations thus suggest that most of the Li in primitive arc magmas come from the mantle wedge with minimal amplification from the slab. Our results are consistent with the absence of slab-derived Li isotopic signatures in most arc magmas 11 , 12 , 38 , 39 . The lack of slab Li in arc magmas indicates that Li is not released from the slab or that the slab is not itself enriched in Li.…”

Section: Discussionsupporting

confidence: 90%

Lithium systematics in global arc magmas and the importance of crustal thickening for lithium enrichment

et al. 2020

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Much of the world’s Li deposits occurs as basinal brines in magmatic orogens, particularly in continental volcanic arcs. However, the exact origin of Li enrichment in arc magmatic systems is not clear. Here, we show that, globally, primitive arc magmas have Li contents and Li/Y ratios similar to mid-ocean ridge basalts, indicating that the subducting slab has limited contribution to Li enrichment in arc magmas. Instead, we find that Li enrichment is enhanced by lower degrees of sub-arc mantle melting and higher extents of intracrustal differentiation. These enrichment effects are favored in arcs with thick crust, which explains why magmatism and differentiation in continental arcs, like the Andes, reach greater Li contents than their island arc counterparts. Weathering of these enriched source rocks mobilizes and transports such Li into the hydrologic system, ultimately developing Li brines with the combination of arid climate and the presence of landlocked extensional basins in thickened orogenic settings.

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Section: Discussionsupporting

confidence: 90%

Lithium systematics in global arc magmas and the importance of crustal thickening for lithium enrichment

et al. 2020

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“…Hence, the heavy Tl isotope compositions in the Kamchatka lavas could be consistent with the addition of variable amounts of pelagic sediment to the melting region. However, previous studies have concluded that sediments are essentially absent in the Kamchatka melting region (Churikova et al., 2001, 2007; Dorendorf, Churikova, et al., 2000; Dorendorf, Wiechert, et al., 2000; Huang et al., 2018; Liu et al., 2020; Münker et al., 2004) and pelagic clays are associated with Ce/Tl ratios as low as 20 (Nielsen et al., 2016; Nielsen, Prytulak, et al., 2017; Shu et al., 2017). Thus, the trend toward heavy isotope compositions with increasing Ce/Tl ratios in the Kamchatka lavas cannot be explained by variable slab inputs.…”

Section: Discussionmentioning

confidence: 97%

“…These observations together suggest that the magma source was relatively uniform. Fluid‐mobile elements, however, show large enrichments and are more variable as expressed in high and variable ratios of B/La, Ba/Nb (Churikova et al., 2007) and As/Ce or Sb/Ce (Liu et al., 2020).…”

Section: Samples and Methodsmentioning

confidence: 99%

“…We also present data for a set of basaltic lavas from the Kamchatka arc to test the potential effects of lava degassing in natural samples. These samples were selected because a significant sediment contribution to their mantle wedge magma source has been excluded in previous studies (Churikova et al, 2001(Churikova et al, , 2007Dorendorf, Churikova, et al, 2000;Dorendorf, Wiechert, et al, 2000;Huang et al, 2018;Liu et al, 2020;Münker et al, 2004). These Kamchatka lavas show Tl concentration and isotope patterns for individual volcanoes that are identical to those produced by the degassing experiments.…”

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confidence: 99%

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Thallium Isotope Fractionation During Magma Degassing: Evidence From Experiments and Kamchatka Arc Lavas

Nielsen

Shu

Wood

et al. 2021

Geochem Geophys Geosyst

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Recycling of oceanic crust and sediments into the mantle at subduction zones is one of the most important processes occurring in the solid Earth. It controls the vast majority of mass transfer between the surface and deep Earth including water and other volatiles as well as radiogenic heat-producing elements like K, Th, and U. Thus, crustal recycling is the primary determinant of the viscosity and heat budget of the Earth's mantle. In addition, these recycled crustal reservoirs are thought to give rise to mantle plumes that are expressed at the Earth's surface as ocean island basalts (OIBs) or large igneous provinces (LIPs) (e.g., Hofmann & White, 1982). Much research has focused on understanding the physical and chemical consequences of crustal recycling, both those occurring during subduction itself and those associated with Abstract Thallium (Tl) isotope ratios are an emerging tool that can be used to trace crustal recycling processes in arc lavas and ocean island basalts (OIBs). Thallium is a highly volatile metal that is enriched in volcanic fumaroles, but it is unknown whether degassing of Tl from subaerial lavas has a significant effect on their residual Tl isotope compositions. Here, we present Tl isotope and concentration data from degassing experiments that are best explained by Rayleigh kinetic isotope fractionation during Tl loss. Our data closely follow predicted isotope fractionation models in which TlCl is the primary degassed species and where Tl loss is controlled by diffusion and natural convection, consistent with the slow gas advection velocity utilized during our experiments. We calculate that degassing into air should be associated with a net Tl isotope fractionation factor of α net = 0.99969 for diffusion and natural gas convection (low gas velocities) and α net = 0.99955 for diffusion and forced gas convection (high gas velocities). We also show that lavas from three volcanoes in the Kamchatka arc exhibit Tl isotope and concentration patterns that plot in between the two different gas convection regimes, implying that degassing played an important role in controlling the observed Tl isotope compositions in these three volcanoes. Literature inspection of Tl isotope data for subaerial lavas reveals that the majority of these appear only minorly affected by degassing, although a few samples from both OIBs and arc volcanoes can be identified that likely experienced some Tl degassing.Plain Language Summary Volcanic degassing is an important process for understanding emissions to the atmosphere of greenhouse gasses and toxic metals. Thallium (Tl) is a toxic metal that is highly volatile, which in recent years has been developed as a stable isotope system that can be applied to understand the transfer of material from the Earth surface to the deep mantle via measurements of volcanic lavas. However, degassing of Tl from volcanic lavas could potentially alter the isotope ratio of the residual lava and, thus, render applications of Tl isotopes in lavas difficult to relate to deep Earth material tran...

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“…These observations together suggest that the magma source was relatively uniform. Fluid-mobile elements, however, show large enrichments and are more variable as expressed in high and variable ratios of B/La, Ba/Nb (Churikova et al, 2007) and As/Ce or Sb/Ce (Liu et al, 2020).…”

Section: Kamchatka Lavasmentioning

confidence: 99%

Thallium isotope fractionation during magma degassing: evidence from experiments and Kamchatka arc lavas

Nielsen¹,

Auro²,

Shu³

et al. 2021

Goldschmidt2021 Abstracts

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Trace Elements and Li Isotope Compositions Across the Kamchatka Arc: Constraints on Slab‐Derived Fluid Sources

Cited by 16 publications

References 100 publications

Lithium systematics in global arc magmas and the importance of crustal thickening for lithium enrichment

Lithium systematics in global arc magmas and the importance of crustal thickening for lithium enrichment

Thallium Isotope Fractionation During Magma Degassing: Evidence From Experiments and Kamchatka Arc Lavas

Thallium isotope fractionation during magma degassing: evidence from experiments and Kamchatka arc lavas

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