Two billion years of mantle evolution in sync with global tectonic cycles

• Published in: Earth and planetary science letters 2019-12, Vol.528, p.115820, Article 115820
• Main Authors: Cutts, Jamie A., Smit, Matthijs A., Spengler, Dirk, Kooijman, Ellen, van Roermund, Herman L.M.
• Format: Article
• Language: English
• Subjects: Archean craton; garnet geochronology; orogenic peridotite; sub-continental lithospheric mantle; Wilson cycle
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2019.115820

The continental crust and sub-continental lithospheric mantle (SCLM) are co-dependent reservoirs in terms of their geochemistry, tectonics, and long-term evolution. Obtaining insight into the mechanisms of lithosphere formation and differentiation requires robust constraint on the complex petrological history of mantle rocks. This has proven difficult as samples from the deep mantle are rare and, although many may have formed in the Archean, no such age has been obtained directly from mantle-derived silicate minerals. Lutetium-hafnium geochronology of garnet has the potential of overcoming this limitation. In this study, this technique was applied on fragments of the SCLM exposed in the Norwegian Caledonides. The chronologic record of these rocks is rich and extensive, yet it is difficult to interpret and is, in part, inconsistent. Our Lu–Hf results from supersilicic pyrope in dunite provide the first Archean internal isochron ages for mantle rocks. These ages are consistent with a period of juvenile crust formation worldwide and provide a record of deeply sourced mantle upwellings from >350 km depth. Results from fertile rock types indicate that melting and isotope re-equilibration occurred in sync with two Proterozoic supercontinent break-up events that are recorded in the Laurentian and Baltic lithospheres. Together, the results indicate that since its extraction during a period of rapid Archean crustal growth, the SCLM appears to have largely been at petro-physical and chemical stasis, with the exception of major episodes of continental break-up. The evolution of the SCLM is thus, highly punctuated and ultimately controlled by the Wilson cycle. •First Archean internal Lu–Hf isochrons for subcontinental lithospheric mantle.•Re-equilibration of Lu–Hf systematics is inhibited in the absence of metasomatism.•Post-majoritic pyrope records ascent of deep (>350 km) Archean mantle upwellings.•Pulsed Proterozoic mantle melting in sync with supercontinent break-up cycles.