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Effects of sediment addition on magma generation from oceanic crust in a post-collisional extensional setting: TEXT SIZE: A A A
Constraints from partial melting experiments on mudstone-amphibolite/basalt at 1.0 and 1.5 GPa
To assess the effects of sediment addition on magma generation from oceanic crust during post-collisional extension, we conducted partial melting experiments on amphibolite-mudstone (90 and 10 wt%, respectively) and basalt-mudstone (90 and 10 wt%, respectively) mixtures at 850-1000 degrees C and 1.0 and 1.5 GPa. In the experimental products, partial melt coexists with Amp +/- Pl +/- Grt +/- Cpx at 1.0 GPa and Grt +/- Cpx +/- Amp at 1.5 GPa. Given the high water content of the sediment (> 5 wt%), the partial melts are hydrous even without the addition of water. Compared with previous partial melting experiments on (meta)basalts, our experiments yield similar phase assemblages (Amp +/- Pl +/- Grt +/- Cpx) but different P-T conditions for mineral stabilities. Sediment addition makes the residual minerals (Amp, Pl, and Cpx) more fusible and the crystallization of new minerals (Grt and Cpx) more difficult, thereby producing a high proportion of melt (> 50 vol%) at > 900 degrees C. In the case of high-degree partial melting, the melt is enriched in Al2O3 and depleted in SiO2. Sediment addition enriches the partial melts in Rb, Th, U, and light rare earth elements, and results in high Y contents, low Sr/Y and very low La-N/Yb-N ratios. These effects are apparent in a natural example from east Junggar in northwest China, where -granitoids have major and trace element features comparable with those of partial melts from the amphibolite-sediment mixture at 1.5 GPa. This indicates that sediment addition has a significant effect on magma generation from oceanic crust in a post-collisional extensional setting.
 

Publication name

 JOURNAL OF ASIAN EARTH SCIENCES Volume: 188 Article Number: 104111 DOI: 10.1016/j.jseaes.2019.104111 Published: FEB 2020

Author(s)

 Zang, Chunjuan; Tang, Hongfeng; Wang, Mingliang

Corresponding author(s) 

 TANG Hongfeng 
 tanghongfeng@vip.gyig.ac.cn   
 Chinese Acad Sci, Inst Geochem, Key Lab High Temp & High Pressure Study Earths In, Guiyang 550081, Peoples R China.

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