Table1_Effect of Terrigenous Sediment Addition on the Generation of Arc Silicic Magma: Constraints From the Comparative Partial Melting Experiment at 1.5 GPa.XLSX

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.

为评估沉积物添加对俯冲洋壳部分熔融及弧型酸性岩浆形成的影响，本研究在850~1000℃、1.5 GPa条件下，采用活塞圆筒压机（Piston-cylinder apparatus）对石榴斜长角闪岩（garnet plagioamphibolite）以及由90 wt%石榴斜长角闪岩与10 wt%斜长板岩（plagioclase slate）组成的混合样品开展了系列对比部分熔融实验。实验产物显示，在850~950℃区间内，部分熔融熔体与角闪石（amphibole）、斜长石（plagioclase）、石榴子石（garnet）及单斜辉石（clinopyroxene）共存；在1000℃时，熔体则与斜长石、石榴子石及单斜辉石共存。与纯石榴斜长角闪岩样品相比，混合样品的部分熔融率更高，且在950℃以上时可形成具备下述地球化学特征的酸性熔体：主量元素层面表现为更高的Na₂O/K₂O比值与更低的Al₂O₃含量，微量元素层面则具有更高的铷（Rb）丰度。本研究结果表明，弧型酸性岩浆可由赋存沉积物的变质俯冲洋壳部分熔融形成，沉积物添加对其化学成分及形成动力学过程均具有重要贡献。