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

Abstract

The timing of continental emergence has been a longstanding debate in the geoscience community with proponents of gradual emergence of subaerial landmasses since Mesoarchean downward to Neoarchean

Whole-rock geochemistry and zircon O-Hf isotope compositions of ca. 2.35 Ga strongly peraluminous granites: Implications for increase in zircon δ18O values during the Paleoproterozoic

“…Synmagmatic zircon in our samples have negative ε Hf (t) values of −6.4 to −0.9, consistent with the previously published results (Cui et al, 2019(Cui et al, , 2020Lu et al, 2021).…”

“…7), which are interpreted as the crystallization ages of these granites. The results are consistent with previously published ages of Cuoke SPGs (2340-2363 Ma; Cui et al, 2019Cui et al, , 2020Lu et al 2021). Other than SPG samples (CK19-51~57) collected from the same location as CK19-52 (see Fig.…”

“…1B). These granites were emplaced at 2340-2363 Ma, 2336 Ma, and 2218 Ma, respectively (Cui et al, 2019(Cui et al, , 2020Lu et al, 2021). Synmagmatic zircon grains from the six SPG samples dated here commonly show oscillatory zoning in CL images and yield weighted mean 207 Pb/ 206 Pb ages ranging from 2347 to 2352 Ma (Fig.…”

“…Magmatic zircon from these samples displayed sample average δ 18 O values of 6.9 ± 0.2‰, 9.3 ± 0.2‰, 8.9 ± 0.3‰, respectively. Lu et al (2021) interpreted this data in conjunction with existing igneous and detrital zircon data sets to indicate that continental emergence occurred between ~2.43 to 2.36 Ga. However, SPG data existing from this key locality is still limited to three samples that display variable O and Hf isotopic compositions.…”

“…These SPGs represent ideal targets to constrain the magmatic zircon δ 18 O values in the earliest Paleoproterozoic and to track the isotopic and chemical characteristics of their (meta-)sedimentary sources. Lu et al (2021) studied three SPG samples from the Cuoke area of the Yangtze Block (South China Craton) for zircon U-Pb ages and O-Hf isotopes. The three dated granites yielded zircon U-Pb ages of 2359 ± 6 Ma, 2362 ± 5 Ma, and 2340±5 Ma.…”