Buoyancy of slabs and plumes enhanced by curved post-garnet phase boundary

During their formation, terrestrial planets underwent a magma ocean phase during which their metallic cores segregated from their silicate mantles and their early atmospheres formed. These planetary formation processes resulted in a redistribution of the abundances of highly volatile elements (HVEs, such as H, C, N, and S) between the planets’ metallic cores, silicate mantles, and atmospheres. This review presents the numerous experimental techniques used to simulate the conditions and identify the parameters that influenced the behavior of HVEs during planetary formation. We also review the analytical techniques used to characterize the different types of experimental samples and quantify the distribution of HVEs between metallic and silicate phases, as well as their solubilities in silicate glasses. This exhaustive review targets students and young researchers beginning their work on the subject, or, more generally, scientists seeking a better understanding of this field of research.

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Basalt Accumulation Fuels Warm Slab’s Subduction into Lower Mantle

Shi,

Shen,

Shi

et al. 2024

Preprint

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How and why oceanic slabs subduct into the lower mantle is crucial in understanding the mantle dynamics and evolution, but remains unclear. Here we present seismic images of the mantle transition zone (MTZ) beneath the Sumatra subduction zone that reveal phase transformations of both the olivine and garnet systems, exhibiting a relatively warm slab in a ~250-km-wide passage from ~350 to ~750 km, then broadening to ~600 km wide at ~780 km depths. The amplitudes of converted waves at the interfaces of the MTZ base and the topmost of the lower mantle suggest up to ~75±25% of basalts in a basalt-harzburgite assemblage and thus intensive enrichment of oceanic crust near the upper-lower mantle boundary, and a gradual reduction of basalt content toward the depthsof ~780 km. Mineral physics modeling shows that such basaltic enrichment provides sufficient positive density contrasts and driving forces for downwelling of the slab assemblage into the lower mantle, and negative density contrasts and thereby buoyancy for the upward concentration of basalts in the uppermost lower mantle. The residual part of the slab assemblage subjected to the basalt reduction is rheologically more weak and conducive to itsflattening and broadening between 750 to 1200 km depths.

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Buoyancy of slabs and plumes enhanced by curved post-garnet phase boundary

Cited by 4 publications

References 54 publications

Alumina solubility in periclase determined to lower mantle conditions and implications for ferropericlase inclusions in diamonds

Alumina solubility in periclase determined to lower mantle conditions and implications for ferropericlase inclusions in diamonds

Review of experimental and analytical techniques to determine H, C, N, and S solubility and metal–silicate partitioning during planetary differentiation

Basalt Accumulation Fuels Warm Slab’s Subduction into Lower Mantle

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