Long-lived Paleoproterozoic eclogitic lower crust.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34772954.
- Also identified by DOI 10.1038/s41467-021-26878-5 and PMC identifier 8589968.
- 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
The nature of the lower crust and the crust-mantle transition is fundamental to Earth sciences. Transformation of lower crustal rocks into eclogite facies is usually expected to result in lower crustal delamination. Here we provide compelling evidence for long-lasting presence of lower crustal eclogite below the seismic Moho. Our new wide-angle seismic data from the Paleoproterozoic Fennoscandian Shield identify a 6-8 km thick body with extremely high velocity (Vp ~ 8.5-8.6 km/s) and high density (>3.4 g/cm3) immediately beneath equally thinned high-velocity (Vp ~ 7.3-7.4 km/s) lowermost crust, which extends over >350 km distance. We relate this observed structure to partial (50-70%) transformation of part of the mafic lowermost crustal layer into eclogite facies during Paleoproterozoic orogeny without later delamination. Our findings challenge conventional models for the role of lower crustal eclogitization and delamination in lithosphere evolution and for the long-term stability of cratonic crust.