Significant Increase of Continental Freeboard During the Early Paleoproterozoic: Insights From Metasediment-Derived Granites

Subaerial continental crust plays a fundamental role in modulating the composition of the ocean, atmosphere, and biosphere, but the timing and rate of continental emergence above sea level remain unclear. Here, we use the zircon oxygen isotopic compositions of early Paleoproterozoic metasediment-derived granitoids from the southwestern Yangtze Block to constrain the rapidity of continental emergence. Statistical analyses of compiled igneous and detrital zircon oxygen isotopic database show a rapid increase in zircon delta O-18 at similar to 2.36 Ga. We suggest that this isotopic shift is best explained by a significant increase of continental freeboard between similar to 2.43 and similar to 2.36 Ga due to the increasing strength of the continental lithosphere since the late Archean, concomitantly yielding a high-delta O-18 sedimentary reservoir. Subsequent melting of these high-delta O-18 sediments in a variety of tectonic regimes results in high zircon delta O-18.

Automated summary

This study utilized zircon oxygen isotopic compositions to show a rapid continental emergence around 2.36 billion years ago, possibly due to an increase in continental freeboard from the strengthening of continental lithosphere, resulting in high-delta O-18 sedimentary reservoirs. Subsequent melting of these sediments in various tectonic regimes led to high zircon delta O-18 values.