Effect of Terrigenous Sediment Addition on the Generation of Arc Silicic Magma: Constraints From the Comparative Partial Melting Experiment at 1.5 GPa

Chunjuan Zang,Mingliang Wang

doi:10.3389/feart.2022.851236

Abstract

To assess the effects of sediment addition on the partial melting of subducted oceanic crust and generation of arc silicic magma, a series of comparative partial melting experiments on a garnet plagioamphibolite and a 90 wt% garnet plagioamphibolite + 10 wt% plagioclase slate mixture at 850–1,000°C/1.5 GPa were conducted on a Piston-cylinder apparatus. In the experimental products, partial melt coexists with amphibole + plagioclase + garnet + clinopyroxene at 850–950°C and plagioclase + garnet + clinopyroxene at 1000°C. Compared with pure garnet plagioamphibolite, partial melting of mixture get a higher melting percentage and generates the silicic melt with geochemical characteristics of higher Na2O/K2O and lower Al2O3 in major element and high Rb content in trace element at over 950°C. This result indicates that silicic arc magma may generate from partial melting of metamorphic subducted oceanic crust with sediments thereon, sediment addition contributes to their chemical component and generation dynamic process.

Highlights

IntroductionConvergent plate margins are the most active areas on earth
According to plate tectonics, convergent plate margins are the most active areas on earth
A number of previous studies have focussed on the partial melting of basic rocks (Beard and Lofgren, 1991; Rapp et al, 1991; Rushmer, 1991; Sen and Dunn, 1994; Rapp and Watson, 1995; Takahahshi et al, 1998; Yaxley and Green, 1998; Koepke et al, 2004; Sisson et al, 2005; Xiong et al, 2005; Xiong et al, 2006; Qian and Hermann, 2013). These findings have revealed the partial melting behavior of pure basaltic oceanic crust during the subduction process; studies focussing on the partial melting of basic rock and sediment are very limited (Mccarthy and Patiño Douce, 1997; Zang et al, 2020)

Summary

Introduction

Convergent plate margins are the most active areas on earth. These magmas cannot be formed by partial melting of the peridotite mantle wedge, even ~52 wt% SiO2 melt could be generated by a very low degree (~2 wt%) partial melt of peridotite in the upper mantle wedge (Baker et al, 1995), but such a low percentage partial melting cannot generate real magma due to magmatic dynamic characteristics. While the melting percentage increases, the SiO2 content of melts from partial melting of peridotite will decrease rapidly, so partial melting of the mantle cannot generate silicic magma generally

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Discussion

Conclusion