Sunda arc mantle source delta O-18 value revealed by intracrystal isotope analysis

Deegan, Frances M.; Whitehouse, Martin J.; Troll, Valentin R.; Geiger, Harri; Jeon, Heejin; le Roux, Petrus; Harris, Chris; van Helden, Marcel; Gonzalez-Maurel, Osvaldo


Magma plumbing systems underlying subduction zone volcanoes extend from the mantle through the overlying crust and facilitate protracted fractional crystallisation, assimilation, and mixing, which frequently obscures a clear view of mantle source compositions. In order to see through this crustal noise, we present intracrystal Secondary Ion Mass Spectrometry (SIMS) delta O-18 values in clinopyroxene from Merapi, Kelut, Batur, and Agung volcanoes in the Sunda arc, Indonesia, under which the thickness of the crust decreases from ca. 30km at Merapi to = 20km at Agung. Here we show that mean clinopyroxene delta O-18 values decrease concomitantly with crustal thickness and that lavas from Agung possess mantle-like He-Sr-Nd-Pb isotope ratios and clinopyroxene mean equilibrium melt delta O-18 values of 5.7 (+/- 0.2 1SD) indistinguishable from the delta O-18 range for Mid Ocean Ridge Basalt (MORB). The oxygen isotope composition of the mantle underlying the East Sunda Arc is therefore largely unaffected by subduction-driven metasomatism and may thus represent a sediment-poor arc end-member. Subduction zone volcanoes are underlain by extensive magma plumbing systems, which can obscure original mantle source signals. Here, the authors show that intra-crystal oxygen isotope analysis of clinopyroxenes from the Sunda arc (Indonesia) reveal the delta 18 O value of the sub-arc mantle.

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Título según WOS: ID WOS:000669487700007 Not found in local WOS DB
Volumen: 12
Número: 1
Editorial: Nature Publishing Group
Fecha de publicación: 2021


Notas: ISI