Instability of the southern Canadian Shield during the late Proterozoic

• Published in: Earth and planetary science letters 2018-05, Vol.490, p.100-109
• Main Authors: McDannell, Kalin T., Zeitler, Peter K., Schneider, David A.
• Format: Article
• Language: English
• Subjects: 40Ar/39Ar; craton; stability; Superior Province; thermochronology; underplating
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2018.03.012

Cratons are generally considered to comprise lithosphere that has remained tectonically quiescent for billions of years. Direct evidence for stability is mainly founded in the Phanerozoic sedimentary record and low-temperature thermochronology, but for extensive parts of Canada, earlier stability has been inferred due to the lack of an extensive rock record in both time and space. We used 40Ar/39Ar multi-diffusion domain (MDD) analysis of K-feldspar to constrain cratonic thermal histories across an intermediate (∼150–350 °C) temperature range in an attempt to link published high-temperature geochronology that resolves the timing of orogenesis and metamorphism with lower-temperature data suited for upper-crustal burial and unroofing histories. This work is focused on understanding the transition from Archean–Paleoproterozoic crustal growth to later intervals of stability, and how uninterrupted that record is throughout Earth's Proterozoic “Middle Age.” Intermediate-temperature thermal histories of cratonic rocks at well-constrained localities within the southern Canadian Shield of North America challenge the stability worldview because our data indicate that these rocks were at elevated temperatures in the Proterozoic. Feldspars from granitic rocks collected at the surface cooled at rates of