Long-lived Paleoproterozoic eclogitic lower crust


Buntin S., Artemieva I. M. , Malehmir A., Thybo H., Malinowski M., Hoegdahl K., ...More

NATURE COMMUNICATIONS, vol.12, no.1, 2021 (Peer-Reviewed Journal) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 12 Issue: 1
  • Publication Date: 2021
  • Doi Number: 10.1038/s41467-021-26878-5
  • Journal Name: NATURE COMMUNICATIONS
  • Journal Indexes: Science Citation Index Expanded, Scopus, BIOSIS, CAB Abstracts, Chemical Abstracts Core, EMBASE, Geobase, INSPEC, MEDLINE, Veterinary Science Database, Directory of Open Access Journals

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 similar to 8.5-8.6 km/s) and high density (>3.4 g/cm(3)) immediately beneath equally thinned high-velocity (Vp similar to 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.