Multi-stage mixing in subduction zones: Application to Merapi volcano (Java island, Sunda arc)

The Sunda Arc of Indonesia developed along the convergent margin between the Eurasian and the Australian Plates. More than 100 Quaternary volcanic centers occur along the arc. The West Java Arc is a segment of the Sunda Arc in which more than 10 volcanic centers are located, corresponding to the 120 to 200 km depth contours of the Wadati-Benioff zone. The geochemistry of 207 Quaternary lavas from six centers across the arc was investigated. The lavas range from basalt to dacite. Incompatible element abundances increase from the volcanic front to the rear-arc in response to a change from low-K to high-K suites. Nd-Sr isotope compositions of the basalts scatter between midocean ridge basalt (MORB) source mantle and Indian Ocean sediment (SED) compositions, with volcanic front low-K basalts having more radiogenic Nd than the rear-arc basalts. It is suggested that mixing between slab-derived fluids mainly from the SED and melt from MORB source mantle played a significant role in determining the geochemistry of the West Java basalts. Incompatible element patterns in primitive mantle normalized multi-element plots are almost identical across the arc, except for greater inclination and weaker positive Sr spikes in the rear-arc basalts. This suggests a lower degree of partial melting in the rear-arc mantle, accompanied by change in SED fluid composition between the volcanic front and the rear-arc. The latter is confirmed by fluid-fluxed melting model calculations using multiple trace elements and Nd and Sr isotopes. All the West Java Arc lavas require deficit of Sr from the slab SED. This may occur due to selective breakdown of Sr-rich hydrous silicate minerals, such as zoisite, at shallower depths before the SED component reaches the depth of dehydration effective for magma genesis. The rear-arc basalts need further Sr deficits along with lesser fluid. These features are commonly observed in many arc basalts, and are likely attributable to the same mechanism.

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“…1991; Turner & Foden 2001; Elburg et al. 2002; Gertisser & Keller 2003; Debaille et al. 2006; Handley et al.…”

Section: Discussionunclassified

“…To investigate the source variability, we applied a three‐component model (DMM, AOC, SED) as suggested by many studies of Sunda lavas (Turner & Foden 2001; Gertisser & Keller 2003; Debaille et al. 2006; Handley et al.…”

Section: Discussionmentioning

confidence: 99%

Across‐arc geochemical variation of Quaternary lavas in West Java, Indonesia: Mass‐balance elucidation using arc basalt simulator model

2009

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“…The involvement of at least 4 components in the NE Atlantic mantle can be reconciled with the observation of binary correlations by applying the systematics of ''pseudo-binary mixing" Schilling et al, 1992;Douglass and Schilling, 2000;Debaille et al, 2006a). The two main (final) end-members can be generated by progressively reducing the number of initial components by successive mixing steps likely separated in space and time.…”

Section: Components Existing In the Iceland Mantle Plumementioning

confidence: 98%

Primitive off-rift basalts from Iceland and Jan Mayen: Os-isotopic evidence for a mantle source containing enriched subcontinental lithosphere

Debaille

Trønnes

Brandon

et al. 2009

Geochimica et Cosmochimica Acta

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“…Arc magmas characteristically show petrographic and chemical traits that indicate addition of various amounts of crustal material during petrogenesis [ Hildreth and Moorbath , 1988; Davidson et al , 1990; Thirlwall et al , 1996]. Generally, two fundamental models are considered: crustal material is mixed into the mantle source of arc magma (source contamination), i.e., it is derived from the subducted slab [ Hildreth and Moorbath , 1988; Gertisser and Keller , 2003a; Debaille et al , 2006], or it may be assimilated in the crust of the overriding plate when magma ascends to the surface (crustal contamination) [e.g., Davidson , 1985; Thirlwall et al , 1996; Chadwick et al , 2007]. On the basis of radiogenic isotope systems in continental arcs (ocean‐continent subduction), both contamination scenarios appear significant [ Hildreth and Moorbath , 1988; Davidson et al , 1990].…”

Section: Introductionmentioning

confidence: 99%

“…On the basis of radiogenic isotope systems in continental arcs (ocean‐continent subduction), both contamination scenarios appear significant [ Hildreth and Moorbath , 1988; Davidson et al , 1990]. For island arcs (ocean‐ocean subduction), the former model is generally assumed to dominate [ Plank and Langmuir , 1998; Gertisser and Keller , 2003a; Debaille et al, 2006], although crustal contamination has also been invoked in certain circumstances [ Arculus and Johnson , 1981; Davidson , 1985; Thirlwall et al , 1996].…”

Section: Introductionmentioning

confidence: 99%

Crustal CO₂ liberation during the 2006 eruption and earthquake events at Merapi volcano, Indonesia

Troll¹,

Hilton²,

Jolis³

et al. 2012

Geophysical Research Letters

109

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High‐temperature volcanic gas is widely considered to originate from ascending, mantle‐derived magma. In volcanic arc systems, crustal inputs to magmatic gases mainly occur via subducted sediments in the mantle source region. Our data from Merapi volcano, Indonesia imply, however, that during the April‐October 2006 eruption significant quantities of CO2 were added from shallow crustal sources. We show that prior to the 2006 events, summit fumarole gas δ13C(CO2) is virtually constant (δ13C1994–2005 = −4.1 ± 0.3‰), but during the 2006 eruption and after the shallow Yogyakarta earthquake of late May, 2006 (M6.4; hypocentres at 10–15 km depth), carbon isotope ratios increased to −2.4 ± 0.2‰. This rise in δ13C is consistent with considerable addition of crustal CO2and coincided with an increase in eruptive intensity by a factor of ∼3 to 5. We postulate that this shallow crustal volatile input supplemented the mantle‐derived volatile flux at Merapi, intensifying and sustaining the 2006 eruption. Late‐stage volatile additions from crustal contamination may thus provide a trigger for explosive eruptions independently of conventional magmatic processes.

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Multi-stage mixing in subduction zones: Application to Merapi volcano (Java island, Sunda arc)

Cited by 18 publications

References 83 publications

Across‐arc geochemical variation of Quaternary lavas in West Java, Indonesia: Mass‐balance elucidation using arc basalt simulator model

Across‐arc geochemical variation of Quaternary lavas in West Java, Indonesia: Mass‐balance elucidation using arc basalt simulator model

Primitive off-rift basalts from Iceland and Jan Mayen: Os-isotopic evidence for a mantle source containing enriched subcontinental lithosphere

Crustal CO₂ liberation during the 2006 eruption and earthquake events at Merapi volcano, Indonesia

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Multi-stage mixing in subduction zones: Application to Merapi volcano (Java island, Sunda arc)

Cited by 18 publications

References 83 publications

Across‐arc geochemical variation of Quaternary lavas in West Java, Indonesia: Mass‐balance elucidation using arc basalt simulator model

Across‐arc geochemical variation of Quaternary lavas in West Java, Indonesia: Mass‐balance elucidation using arc basalt simulator model

Primitive off-rift basalts from Iceland and Jan Mayen: Os-isotopic evidence for a mantle source containing enriched subcontinental lithosphere

Crustal CO2 liberation during the 2006 eruption and earthquake events at Merapi volcano, Indonesia

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Crustal CO₂ liberation during the 2006 eruption and earthquake events at Merapi volcano, Indonesia