Separation of supercritical slab-fluids to form aqueous fluid and melt components in subduction zone magmatism

• DOI: 10.1073/pnas.1207687109
• Publication Date: 2012-10-30T05:46:22Z
• Authors: Tatsuhiko Kawamoto; Masami Kanzaki; Kenji Mibe; Kyoko N. Matsukage; Shigeaki Ono
• Keywords: Slab

Subduction-zone magmatism is triggered by the addition of H 2 O-rich slab-derived components: aqueous fluid, hydrous partial melts, or supercritical fluids from subducting slab. Geochemical analyses island arc basalts suggest two signatures a melt and fluid. These liquids unite to fluid under pressure temperature conditions beyond critical endpoint. We ascertain endpoints between sediment high-Mg andesite (HMA) melts located, respectively, at 83-km 92-km depths using an in situ observation technique. are within mantle wedge underlying volcanic fronts, which formed 90 200 km above slabs. data that sediment-derived fluids, fed slab, react with peridotite form HMA fluids. Such separate into 92 depth during ascent. The fluxed asthenospheric basalts, locally associated HMAs hot subduction zones. separated retain their composition limited equilibrium surrounding mantle. Alternatively, they equilibrate change major element chemistry basaltic composition. However, trace remain more melt-derived magma than fluid-induced magma, inherits only fluid-mobile elements Separation can elucidate components observed zone chemistry.