Why do mafic arc magmas contain ∼4wt% water on average?

Plank, Terry; Kelley, K. A.; Zimmer, Mindy M.; Hauri, E. H.; Wallace, Paul

doi:10.1016/j.epsl.2012.11.044

Cited by 416 publications

(250 citation statements)

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“…With a worldwide average of 3 to 5 wt.% H 2 O, island arc magmas are characterized by higher volatile concentrations than magmas erupting from other tectonic settings with <1 wt.% H 2 O (e.g., Stern 2002;Plank et al 2013). At generally ≥90 mol%, H 2 O is the most abundant volatile component dissolved in island arc magmas (Shinohara 2008), with the occasional exception of CO 2 -rich magmas (e.g., Sisson and Bronto 1998).…”

Section: Introductionmentioning

confidence: 99%

Polybaric crystallization differentiation of H2O-saturated island arc low-K tholeiite magmas: a case study of the Izu-Oshima volcano in the Izu arc

et al. 2014

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Island arc low-K tholeiites are basaltic magmas erupting from frontal arc volcanoes of juvenile arcs associated with the subduction of old and cold plates. We investigated the origins of geochemical variation in volcanic rocks having multiple phase saturated liquid compositions from the Izu-Oshima volcano in the northern Izu arc. The geochemical variations in the liquids fall between two endmember trends, namely higher-and lower-Al/Si trends. Polybaric differentiation of H 2 O-saturated melts between a 4-km-deep magma chamber and degassed melts near the surface should be responsible for the observed variation in the liquids.

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Section: Introductionmentioning

confidence: 99%

Polybaric crystallization differentiation of H2O-saturated island arc low-K tholeiite magmas: a case study of the Izu-Oshima volcano in the Izu arc

et al. 2014

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“…As outlined by Plank et al (2013), the H 2 O content of melt inclusions in arc magmas may either be controlled through the melting process or by equilibration of magmas within crustal storage regions if ponding depths are relatively invariable. On the other hand, there is some data that support the notion of volatile control on magma ponding depth.…”

Section: Effect Of Volatiles On Magma Differentiation and Ascentmentioning

confidence: 99%

Volatiles in subduction zone magmatism

Zellmer

Edmonds

Straub

2014

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Abstract:The volatile cycle at subduction zones is key to the petrogenesis, transport, storage and eruption of arc magmas. Volatiles control the flux of slab components into the mantle wedge, are responsible for melt generation through lowering the solidi of mantle materials, and influence the crystallizing phase assemblages in the overriding crust. Globally, magma ponding depths may be partially controlled by melt volatile contents. Volatiles also affect the rate and extent of degassing during magma storage and decompression, influence magma rheology and therefore control eruption style. The style of eruptions in turn determines the injection height of environmentally sensitive gases into the atmosphere and the impact of explosive arc volcanism. In this overview we summarize recent advances regarding the role of volatiles during slab dehydration, melt generation in the mantle wedge, magmatic evolution in the overriding crust, eruption triggering, and the release of some magmatic volatiles from volcanic edifices into the Earth's atmosphere.In contrast to mid-ocean ridge magmatism, where upwelling and adiabatic decompression of the mantle is the primary cause of melt generation, subduction zone magmatism is triggered by the depression of the mantle solidus due to influx of volatiles (dominantly There is ongoing debate about the processes that form extractable melts of the hydrated mantle wedge. One model suggests that efficient melt extraction requires a degree of melting of the wedge so large that melts are generally extracted at or above the 1300 8C isotherm, that is, close to the anhydrous solidus (Kushiro 1987;Schmidt & Poli 1998). The advective flux of heat carried by this melt then perturbs the location of the anhydrous solidus upwards (England & Katz 2010b), and melts eventually penetrate the lithosphere and enter the crust by hydrofracture and dyking. Alternatively, melting is dominated by decompression in slab and mantle diapirs that may rise upwards through the wedge (Behn et al. 2011).Here, we address volatile cycling from the dehydration of the subducting slab to arc volcanic degassing into the atmosphere (Fig. 1). A product of subduction is the output of volatiles as volcanic gases; another is the sinking of the slab containing 'residual' volatiles into the deep mantle. Volcanic gases in arcs are rich in H 2 O, chlorine, bromine and iodine compared to gases at rift and ocean island settings, which directly reflects the influence of slab-derived fluids on primary melt compositions by guest on May 10, 2018 http://sp.lyellcollection.org/ Downloaded from (Pyle & Mather 2009;Kutterolf et al. 2013; Kendrick et al. 2014a, b). Arc magmas are in general far richer in sulphur than their oceanic counterparts, reflecting the higher oxygen fugacity characteristic of arc melts and their enhanced capacity to carry dissolved sulphate (Wallace & Edmonds 2011). There is little direct evidence that primary arc melts are inherently richer in CO 2 than ocean island basalts, although it has been suggested that deep and pe...

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“…There need be no expectation that the maximum volatile contents of multiple aliquots of magma erupted over 15 years should be identical; melt inclusion datasets from volcanoes globally commonly show variable H 2 O contents (e.g. Zimmer et al 2010;Plank et al 2013). However, the fact that the highest H 2 O contents were found in samples erupted in January 2007 by Humphreys et al (2010), and also in samples erupted in August 1997 by Mann et al (2013) suggests that maximum volatile contents have probably not changed substantially over the course of the eruption.…”

Section: Volatile Contents Of Melt Inclusions and Matrix Glassesmentioning

confidence: 99%