Experimental constraints on melting of sediment-metasomatized peridotite at sub-arc pressures
Abstract
During subduction, the overlying recycled sediments, predicted to ascend as diapirs transfer their compositional signatures to the source region of arc magmas, are important for the mantle heterogeneity and the formation of magmas. The role of recycled sediments from the subducting slab, have been discussed during the last decade in different ways, whereas they are still in debate. Here, we undertake a series of experiments in homogeneous hybrid system to investigate the partial melting behavior of peridotite metasomatized by recycled sediment in mantle at 900-1300 °C and 2.5-4.5 GPa. The starting materials are using powder mixtures of natural marine sediment (S314) and synthesized mantle peridotite. Partial melting experiments were performed in a 1000-ton Walker type multi-anvil press at China University of Geosciences (Wuhan). And, we studied the recovered samples microstructure, composition and melt trace elements. The residual phases of run products were mainly composed by orthopyroxene, clinopyroxene, garnet, phlogopite , rutile and spinel. The melts were mainly trachy-basaltic and trachy-andesitic in all supersolidus mixed experiments. The total alkali (Na2O+K2O) concentrations and Na2O/K2O ratios in quench melt are ~ 4.7-10.3 wt% and ~ 0.3-0.8, respectively. We discussed the importance of the stability of phlogopite for potassium-rich magmas thereafter. And, the similarity of trace element patterns between sediment-derived melts from this study and Arc lavas from the Ryukyu arc-Okinawa Trough, indicating that bulk sediment diapirs should be an important transfer mechanism of slab materials from subducting plate to the upper lithospheric mantle.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V31D0164G
- Keywords:
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- 1031 Subduction zone processes;
- GEOCHEMISTRY;
- 1037 Magma genesis and partial melting;
- GEOCHEMISTRY;
- 1115 Radioisotope geochronology;
- GEOCHRONOLOGY;
- 8104 Continental margins: convergent;
- TECTONOPHYSICS