Kinetics and detectability of the bridgmanite to post-perovskite transformation in the Earth's D″ layer.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31831735.
- Also identified by DOI 10.1038/s41467-019-13482-x and PMC identifier 6908603.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Bridgmanite, the dominant mineral in the Earth's lower mantle, crystallizes in the perovskite structure and transforms into post-perovskite at conditions relevant for the D[Formula: see text] layer. This transformation affects the dynamics of the Earth's lowermost mantle and can explain a range of seismic observations. The thickness over which the two phases coexist, however, can extend over 100 km, casting doubt on the assignment of the observed seismic boundaries. Here, experiments show that the bridgmanite to post-perovskite transition in (Mg[Formula: see text],Fe[Formula: see text])SiO[Formula: see text] is fast on geological timescales. The transformation kinetics, however, affects reflection coefficients of [Formula: see text] and [Formula: see text] waves by more than one order of magnitude. Thick layers of coexisting bridgmanite and post-perovskite can hence be detected using seismic reflections. Morever, the detection and wave period dependence of D[Formula: see text] reflections can be used to constrain significant features of the Earth's lowermost mantle, such as the thickness of the coexistence layer, and obtain information on temperature and grain sizes.