Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

Source: AGU Advances

Plate tectonics is a part of mantle convection. However, planetary evolution includes both thermal and compositional effects. During seafloor spreading, for example, the upper mantle material is fractionated into basaltic crust and a harzburgite layer. Recent seismological studies and geodynamic models suggest that when oceanic plates are recycled back into the mantle, the associated depth-dependent density differences can cause chemical layering around the 660 kilometers phase transition.

Analyzing seismic waveforms from underside reflections, Hao et al. [2024] provide new constraints on associated chemical variations with depth, finding that the basalt fraction decreases below 660 kilometers, creating a harzburgite-rich layer. While questions about the role of volatile variations remain, it is becoming clearer how chemistry significantly influences transition mass transport, reviving debates on mantle composition and evolution.

Citation: Hao, S., Wei, S. S., & Shearer, P. M. (2024). Substantial global radial variations of basalt content near the 660-km discontinuity. AGU Advances, 5, e2024AV001409. https://doi.org/10.1029/2024AV001409

—Thorsten W. Becker, Editor, AGU Advances

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