Origin of the slab component in arc lavas from across-arc variation of B and Pb isotopes

Ishikawa, Tsuyoshi; Nakamura, Eizo

doi:10.1038/370205a0

Cited by 338 publications

(209 citation statements)

References 23 publications

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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%

“…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). However, the composition of slab-derived fluids cannot be constant with P (45).…”

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

confidence: 99%

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Slab melting versus slab dehydration in subduction-zone magmatism

Mibe

Kawamoto

Matsukage

et al. 2011

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

159

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

confidence: 99%

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.

159

View full text Add to dashboard Cite

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“…1990; Ishikawa and Nakamura, 1994;Ishikawa and Tera, 1997;Tonarini et al, 2001). Although the isovalent element pairs zirconium-hafnium and niobium-tantalum have very similar ionic radii and generally behave coherently during magmatic processes, the Zr/Hf and Nb/Ta ratios of some mantle-derived igneous rocks deviate substantially from the chondritic values (Xie and Kerrich, 1995;Stolz et al, 1996;Eggins et al, 1997;Niu and Batiza, 1997;Münker, 1998), leading to an increased interest in using these element ratios as tools for studying geochemical processes in the mantle.…”

mentioning

confidence: 99%

“…Seventeen rock reference samples from the Geological Survey of Japan and the U.S. Geological Survey were analyzed, and the determined concentrations showed good agreement with the reported values obtained by isotope dilution method, as well as with the recommended values. This technique is a simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum concentrations, and it has wide potential for geochemical application, particularly for the determination of boron.Keywords: ICP-MS, analytical method, rock reference samples, boron, high field strength elements 1990; Ishikawa and Nakamura, 1994;Ishikawa and Tera, 1997;Tonarini et al, 2001). Although the isovalent element pairs zirconium-hafnium and niobium-tantalum have very similar ionic radii and generally behave coherently during magmatic processes, the Zr/Hf and Nb/Ta ratios of some mantle-derived igneous rocks deviate sub-…”

mentioning

confidence: 99%

“…Keywords: ICP-MS, analytical method, rock reference samples, boron, high field strength elements 1990; Ishikawa and Nakamura, 1994;Ishikawa and Tera, 1997;Tonarini et al, 2001). Although the isovalent element pairs zirconium-hafnium and niobium-tantalum have very similar ionic radii and generally behave coherently during magmatic processes, the Zr/Hf and Nb/Ta ratios of some mantle-derived igneous rocks deviate sub-…”

mentioning

confidence: 99%

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A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples

Nagaishi

Ishikawa

2009

Geochem. J.

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An analytical technique for determining boron, zirconium, niobium, hafnium and tantalum contents in rock samples by inductively coupled plasma mass spectrometry (ICP-MS) is described. The rock samples (<30 mg) were decomposed with mannitol-added HF, and dissolved in a 0.015 M HF/0.12 M HNO 3 acid mixture for ICP-MS analysis. Boron, zirconium, niobium, hafnium and tantalum concentrations were measured by the internal calibration curve method using three internal standard elements, beryllium for boron, indium for zirconium and niobium, and rhenium for hafnium and tantalum. Seventeen rock reference samples from the Geological Survey of Japan and the U.S. Geological Survey were analyzed, and the determined concentrations showed good agreement with the reported values obtained by isotope dilution method, as well as with the recommended values. This technique is a simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum concentrations, and it has wide potential for geochemical application, particularly for the determination of boron.Keywords: ICP-MS, analytical method, rock reference samples, boron, high field strength elements 1990; Ishikawa and Nakamura, 1994;Ishikawa and Tera, 1997;Tonarini et al., 2001). Although the isovalent element pairs zirconium-hafnium and niobium-tantalum have very similar ionic radii and generally behave coherently during magmatic processes, the Zr/Hf and Nb/Ta ratios of some mantle-derived igneous rocks deviate sub-

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Contrasting sediment melt and fluid signatures for magma components in the Aeolian Arc: Implications for numerical modeling of subduction systems

Zamboni

Gazel

Ryan

et al. 2016

Geochem Geophys Geosyst

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The complex geodynamic evolution of Aeolian Arc in the southern Tyrrhenian Sea resulted in melts with some of the most pronounced along the arc geochemical variation in incompatible trace elements and radiogenic isotopes worldwide, likely reflecting variations in arc magma source components. Here we elucidate the effects of subducted components on magma sources along different sections of the Aeolian Arc by evaluating systematics of elements depleted in the upper mantle but enriched in the subducting slab, focusing on a new set of B, Be, As, and Li measurements. Based on our new results, we suggest that both hydrous fluids and silicate melts were involved in element transport from the subducting slab to the mantle wedge. Hydrous fluids strongly influence the chemical composition of lavas in the central arc (Salina) while a melt component from subducted sediments probably plays a key role in metasomatic reactions in the mantle wedge below the peripheral islands (Stromboli). We also noted similarities in subducting components between the Aeolian Archipelago, the Phlegrean Fields, and other volcanic arcs/arc segments around the world (e.g., Sunda, Cascades, Mexican Volcanic Belt). We suggest that the presence of melt components in all these locations resulted from an increase in the mantle wedge temperature by inflow of hot asthenospheric material from tears/windows in the slab or from around the edges of the sinking slab.

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Origin of the slab component in arc lavas from across-arc variation of B and Pb isotopes

Cited by 338 publications

References 23 publications

Slab melting versus slab dehydration in subduction-zone magmatism

Slab melting versus slab dehydration in subduction-zone magmatism

A simple method for the precise determination of boron, zirconium, niobium, hafnium and tantalum using ICP-MS and new results for rock reference samples

Contrasting sediment melt and fluid signatures for magma components in the Aeolian Arc: Implications for numerical modeling of subduction systems

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