Trace elements and isotopic variation along Java Island, Sunda Arc: an evaluation of slab-derived fluid contribution to arc magmas
Abstract
A compilation of geochemical dataset of lavas from Java island is presented, with the purpose of estimating slab-derived fluid contribution to arc magmas along Java island. Based on volcano distribution and tectonics, we grouped the island into western, central and eastern sections. Along-arc variation of subduction slab influence including both sediment (SED) and altered oceanic crust (AOC) is evaluated by ratios of fluid-mobile elements to high field strength elements/HFSE (e.g. B/Nb, B/Zr, Ba/La). In addition, Sr-Nd-Pb isotopes were determined to estimate contribution of SED and AOC to the source mantle along the island. Typical lava from Java island is characterized by elevated LILE and LREE values, as well as negative anomalies of Nb and Ti. The ratios of Nb/HFSE (e.g. Nb/Ta, Nb/Zr) imply Nb depletion along the island, a characteristic of arc magmas. These Nb/HFSE ratios are uniformly low at volcanic front all along the island. However, they increase from volcanic front toward back arc in central and eastern sections, and evenly low across the western section. The decreasing ratios of B/HFSE and Ba/HFSE from volcanic front toward back arc are observed in the central and eastern sections. However, these ratios only subtly decrease in the western section. The comparison among different sections of the island shows the highest ratios of these trace elements observed in central section. Isotopic ratios of lavas from all sections generally shifted from Indian Ocean MORB field toward higher 87 Sr/86 Sr and lower 143 Nd/144 Nd ratios. The lowest 87 Sr/86 Sr ratios along the island are shown by back-arc lavas from central section, which overlap with mantle array. In contrast, the volcanic front samples of this section overlap with composition of Indian Ocean sediment. Pb isotope ratios show that lavas from all sections are plotted within the Indian Ocean sediment and OIB fields, except Muria samples of central section. The collected lavas from this island indicate typical Indian Ocean MORB mantle characteristics. However, the increasing trend of Nb/HFSE from volcanic front toward back arc in central and eastern sections implies more enriched mantle source in the back arc. On the contrary, lavas from the western sections show a nearly flat trend of Nb/HFSE ratios which signifies similar mantle source across this section. The evidence from Sr-Nd-Pb isotopic ratios corroborates mantle source enrichment towards the back arc, in central and eastern sections. The ratio of fluid mobile elements against HFSE suggests subducted slab influence along this island. The decreasing trends of B/HFSE and Ba/HFSE in central and eastern sections signify a reduced slab-fluid influence in the back arc. The western section is less pronounced in terms of subduction components enrichment. In contrast, the central section shows the greatest enrichment of subduction components, which implies strongest slab fluid imprint in this section. The Sr-Nd-Pb isotopic patterns also confirm the strongest subducted sediment-fluid contribution in volcanic front of the central section.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.V11A2738H
- Keywords:
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- 1031 GEOCHEMISTRY / Subduction zone processes