Seismic evidence for global basalt accumulation in the mantle transition zone

被引:14
作者
Yu, Chunquan [1 ,2 ]
Goes, Saskia [3 ]
Day, Elizabeth A. [3 ]
van der Hilst, Robert D. [4 ]
机构
[1] Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen 518055, Peoples R China
[2] Southern Univ Sci & Technol, Guangdong Prov Key Lab Geophys High Resolut Imagin, Shenzhen 518055, Peoples R China
[3] Imperial Coll London, Dept Earth Sci & Engn, London SW7 2BP, England
[4] MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA
关键词
PHASE-TRANSITIONS; BULK COMPOSITION; EARTHS MANTLE; TEMPERATURE; COMPUTATION; TOPOGRAPHY; MINERALS; THERMODYNAMICS; DISCONTINUITY; CONSTRAINTS;
D O I
10.1126/sciadv.adg0095
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The mantle's compositional structure reflects the thermochemical evolution of Earth. Yet, even the radial average composition of the mantle remains debated. Here, we analyze a global dataset of shear and compressional waves reflecting off the 410- and 660-km discontinuities that is 10 times larger than any previous studies. Our array analysis retrieves globally averaged amplitude-distance trends in SS and PP precursor reflectivity from which we infer relative wavespeed and density contrasts and associated mantle composition. Our results are best matched by a basalt-enriched mantle transition zone, with higher basalt fractions near 660 (similar to 40%) than 410 (similar to 18-31%). These are consistent with mantle-convection/plate-recycling simulations, which predict that basaltic crust accumulates in the mantle transition zone, with basalt fractions peaking near the 660. Basalt segregation in the mantle transition zone also implies that the overall mantle is more silica enriched than the often-assumed pyrolitic mantle reference composition.
引用
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页数:14
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