Cross-Arc Geochemical Variations in the Kurile Arc as a Function of Slab Depth

Ryan, Jeffrey G.; Morris, Julie; Tera, F.; Leeman, William P.; Tsvetkov, A. A.

doi:10.1126/science.270.5236.625

Cited by 233 publications

(132 citation statements)

References 31 publications

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“…The enrichment of EVF and CKD melt inclusions in U, Th, K, Ba, La, Pb and the positive correlation of these elements with B suggests that the B-rich fluid also carries these elements. Our melt inclusion data are in agreement with previously published results (Ryan et al 1995;Ishikawa and Tera 1997;Ishikawa et al 2001; Wörner et al Dy / Yb 2 2001), suggesting that B-rich fluids are contributed in EVF and CKD regions. In detail, however, a significant difference in fluid compositions is observed between EVF-and CKD-fluids.…”

Section: Sulfur Chlorine and Fluid-mobile Elementssupporting

confidence: 83%

“…13b; Ryan et al 1995;Wörner et al 2001;Ishikawa et al 2001) and the role of a Li-rich fluid increases, the Li/B ratio shows a strong cross-arc zonation (Fig. 13c).…”

Section: Li-b Decoupling Across the Kamchatka Arcmentioning

confidence: 99%

“…Therefore back arc Li enrichment is probably also contributed from the fluid phase. Ryan et al (1995) suggested for the Kuril-Kamchatka arc that semi-mobile elements like Be and LREE may move from the subducted slab with fluids liberated at depth >200 km. Churikova et al (2001) showed that about 50% of the Ce must be contributed by fluids in the deep SR source.…”

Section: Li-rich Fluids In Kamchatka Back Arcmentioning

confidence: 99%

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Volatile (S, Cl and F) and fluid mobile trace element compositions in melt inclusions: implications for variable fluid sources across the Kamchatka arc

Churikova

Wörner²,

Mironov

et al. 2007

Contrib Mineral Petrol

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Volatile element, major and trace element compositions were measured in glass inclusions in olivine from samples across the Kamchatka arc. Glasses were analyzed in reheated melt inclusions by electron microprobe for major elements, S and Cl, trace elements and F were determined by SIMS. Volatile element-trace element ratios correlated with fluid-mobile elements (B, Li) suggesting successive changes and three distinct fluid compositions with increasing slab depth. The Eastern Volcanic arc Front (EVF) was dominated by fluid highly enriched in B, Cl and chalcophile elements and also LILE (U, Th, Ba, Pb), F, S and LREE (La, Ce). This arc-front fluid contributed less to magmas from the central volcanic zone and was not involved in back arc magmatism. The Central Kamchatka Depression (CKD) was dominated by a second fluid enriched in S and U, showing the highest S/K 2 O and U/Th ratios. Additionally this fluid was unusually enriched in 87 Sr and 18 O. In the back arc Sredinny Ridge (SR) a third fluid was observed, highly enriched in F, Li, and Be as well as LILE and LREE. We argue from the decoupling of B and Li that dehydration of different water-rich minerals at different depths explains the presence of different fluids across the Kamchatka arc. In the arc front, fluids were derived from amphibole and serpentine dehydration and probably were water-rich, low in silica and high in B, LILE, sulfur and chlorine. Large amounts of water produced high degrees of melting below the EVF and CKD. Fluids below the CKD were released at a depth between 100 and 200 km due to dehydration of lawsonite and phengite and probably were poorer in water and richer in silica. Fluids released at high pressure conditions below the back arc (SR) probably were much denser and dissolved significant amounts of silicate minerals, and potentially carried high amounts of LILE and HFSE.

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Section: Sulfur Chlorine and Fluid-mobile Elementssupporting

confidence: 83%

“…13b; Ryan et al 1995;Wörner et al 2001;Ishikawa et al 2001) and the role of a Li-rich fluid increases, the Li/B ratio shows a strong cross-arc zonation (Fig. 13c).…”

Section: Li-b Decoupling Across the Kamchatka Arcmentioning

confidence: 99%

Section: Li-rich Fluids In Kamchatka Back Arcmentioning

confidence: 99%

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Volatile (S, Cl and F) and fluid mobile trace element compositions in melt inclusions: implications for variable fluid sources across the Kamchatka arc

Churikova

Wörner²,

Mironov

et al. 2007

Contrib Mineral Petrol

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“…It has been reported that the ratio of FME to FIE in volcanic rocks decreases continuously from the volcanic front to the back-arc side (46,47). These across-arc geochemical variations have often been interpreted as a sign that the amount of fluid released from a slab decreases continuously with increasing depth of the Wadati-Benioff zone, assuming that the trace element composition of the fluid remains constant with slab depth (46).…”

Section: Depths Of the Second Critical Endpoints And Their Bearing Onmentioning

confidence: 99%

Slab melting versus slab dehydration in subduction-zone magmatism

Mibe

Kawamoto

Matsukage

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

156

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The second critical endpoint in the basalt-H 2 O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770°C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones.water | island arc | silicate melt | synchrotron X-ray | high-pressure research W ater plays an important role in subduction-zone magmatism because it can reduce the melting temperature of rocks in subduction zones and hence can generate magmas (1-7). There is a long-standing debate about whether the fluids released from a subducting slab are aqueous fluid, hydrous silicate melt, supercritical fluid (SCF), or a combination of these (2,4,(8)(9)(10)(11)(12). Whether the subducting slab melts or dehydrates depends on the thermal structure and the phase relation of slab materials under hydrous conditions. Therefore, this long-standing question cannot be answered until the detailed stability fields of these fluids are clarified.Under high-pressure (P) and high-temperature (T) conditions, it has been shown that the solubility of both water in silicate melt (13-16) and silicate in aqueous fluid (13, 17-25) increases with increasing P. As a result, silicate melt and aqueous fluid in the interior of the Earth are expected to become SCF, and the hydrous solidus of the system can no longer be defined beyond a certain critical condition (26-36). This condition is called the second (or upper) critical endpoint (26) and is the point of intersection between the critical curve and hydrous solidus. Basalt is one of the dominant constituents of a subducting slab and is considered the main carrier of water that triggers the melting of rocks in subduction zones. Therefore, the second critical endpoint in the basalt-H 2 O system has to be determined in order to understand fully the subduction-zone magmatism.In some silicic silicate-H 2 O systems, the location of the second critical endpoint has been reported [e.g., 1.0 GPa, 1,080°C in the SiO 2 -H 2 O system (13); 1.5 GPa, 670°C in the system NaAlSi 3 O 8 -H 2 O (21); 1.5 GPa, 800°C in the system KAlSi 3 O 8 -H 2 O (36)]. In mafic systems, however, the determination of the second critical endpoints is not easy because of the difficulty in identifying phases (aqueous fluid versus hydrous silicate melt) in the recovered samples quenched from high-P and high-T conditio...

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“…High boron abundance in volcanic front lavas decreases across the arc (Ryan et al, 1995;Ishikawa and Tera, 1997;Miyoshi et al, 2008). The continuous depletion of boron reflects the gradual depletion of volatiles and fluid-mobile elements during dehydration of the subducting slab (Ishikawa and Tera, 1997).…”

Section: Along-arc Variations Of Boron and Other Predominately Slab-dmentioning

confidence: 99%

Boron and other trace element constraints on the slab-derived component in Quaternary volcanic rocks from the Southern Volcanic Zone of the Andes

Shinjoe

Orihashi

Naranjo³

et al. 2013

Geochem. J.

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Cross-Arc Geochemical Variations in the Kurile Arc as a Function of Slab Depth

Cited by 233 publications

References 31 publications

Volatile (S, Cl and F) and fluid mobile trace element compositions in melt inclusions: implications for variable fluid sources across the Kamchatka arc

Volatile (S, Cl and F) and fluid mobile trace element compositions in melt inclusions: implications for variable fluid sources across the Kamchatka arc

Slab melting versus slab dehydration in subduction-zone magmatism

Boron and other trace element constraints on the slab-derived component in Quaternary volcanic rocks from the Southern Volcanic Zone of the Andes

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