Subduction zones are unique to Earth and fundamental in its evolution, yet we still know little about the causes and mechanisms of their initiation. A new study, co-authored by PCIGR researcher Matthijs Smit and published this week in Nature Geoscience, investigates a fossil system, the archetypal Semail Ophiolite of Oman, which exposes both lower and upper plate relics of incipient subduction stages.
Lu–Hf and U–Pb geochronology of the lower and upper plate material indicate that initial burial of the lower plate occurred before 104 million years ago, predating upper plate extension and the formation of Semail oceanic crust by at least 8 Myr. Such a time lag reveals far-field forced subduction initiation and provides unequivocal, direct evidence for a subduction initiation mechanism in the geological record.
Guilmette C., Smit M.A., van Hinsbergen D.J.J., Gürer D., Corfu F., Charette B., Maffione M., Rabeau O., and Savard D. 2018. Forced subduction initiation recorded in the sole and crust of the Semail Ophiolite of Oman. Nature Geoscience, 11, 688–695.
Nature Geoscience article: Forced subduction initiation recorded in the sole and crust of the Semail Ophiolite of Oman
UBC Science story: New theory on how Earth’s subduction zones formed