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

Abstract

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.

Evolution of the northwestern margin of the Basin and Range: The geology and extensional history of the Warner Range and environs, northeastern California

“…The evolution of the ABS models includes a prototype (Kimura and Yoshida, 2006), followed by thoroughly realized models ABS1 (Sendjaja et al, 2009), ABS2 , ABS3 (Kimura et al, 2010), and ABS4 ). The first model in the public domain was ABS2, which considered only aqueous slab fluids and mantle melting with fluid fluxing.…”

Geochemical variation in Tertiary-Quaternary lavas of the West Java arc, Indonesia: Steady-state subduction over the past 10 million years

“…The contrast in the Nd isotope composition originates from the different flux rates of the slab fluid relative to the mantle partial melts; these rates are higher in the RA and lower in the VF. The total fluid addition to the mantle mass is greater in the VF; however, a greater degree of melting in the VF dilutes the contribution of radiogenic Nd from the sediment fluid (Sendjaja et al, 2009). The across -arc geochemical variation between the Tertiary and Quaternary lavas does not differ.…”

“…1). However, the VF -RA classification of the Quaternary lavas based on topography and geochemistry (Sendjaja et al, 2009) correlates spatially with the southnorth tectonic environments in the Tertiary. We thus apply the VF (south) -RA (north) classification to the Tertiary lavas for convenience (thick solid boundary in Fig.…”

“…2b). Data pertaining to the major element, trace elements, and the Sr -Nd isotope for the Quaternary lavas were obtained from a companion paper (Sendjaja et al, 2009); to this data, we have added newly acquired Pb isotope data. Analyses of the major and trace elements and the Sr -Nd -Pb isotope of the Tertiary lavas were carried out for the first time.…”

Geochemical and Sr–Nd isotopic variations in a deep-sea sediment core from Eastern Indian Ocean: Constraints on dust provenances, paleoclimate and volcanic eruption history in the last 300,000years

“…Although Western Australian deserts consist mainly of sand dunes, they are not considered to be a major atmospheric source for long-transport dusts (Prospero et al, 2002) since they are characterised by low dust entrainment, great geomorphic stability and enrichment in larger particles with very high settling velocity (Prospero et al, 2002;Hesse and McTainsh, 2003 (Fig.4). The published isotopic data are summarized in Figure 4 and compiled in Supplementary (Whitford et al, 1981;Ben Othman et al, 1989;Gasparon and Varne, 1998;Turner and Foden, 2001;Gertisser and Keller, 2003;Handley et al, 2008;Sendjaja et al, 2009 The published Sr and Nd isotope data of volcanic ashes from nearby volcanoes, aeolian dusts from Australian continent are used to identify the potential-sediment source of the samples from Core G6-4 (Fig.4) Sr>0.708).…”