A CONNECTION BETWEEN THE NORTH CHINA CRATON AND NW LAURENTIA IN THE EARLY TIME OF RODINIA

The Rodinia supercontinent, which assembled during the late Mesoproterozoic to early Neoproterozoic, is hypothesized to have included almost all Proterozoic continental blocks. However, significant uncertainty regarding the configuration of these blocks remains. In particular, the paleogeographic position of the North China Craton (NCC) in Rodinia has been an issue of great contention and demands greater paleomagnetic constraints.

The geochronologic and paleomagnetic studies conducted in recent years do provide crucial constraints for the NCC’s connection with other blocks in Rodinia. Fu et al. (2015) proposed a paleogeographic proximity of the NCC to Laurentia in the early Neoproterozoic time based on an apparent polar wander path comparison between the NCC and Baltica, aided by the“right-way-up” connection between Laurentia and Baltica in Rodinia. The latest geochronologic and paleomagnetic progress in the eastern NCC has strengthened the quality of the pole obtained from the ca. 945–920 Ma mafic sills and acquired several high-quality poles from the late Mesoproterozoic to early Neoproterozoic strata (represented by the Nanfen Formation) (Zhao et al., 2019). The strata are constrained between ca. 1120 and 945 Ma by detrital zircons and the well-dated mafic sills. The new finding reinforce the NCC–NW Laurentia connection and extend it to ca. 1100 Ma, which is based on the well match of the poles from the strata with the ca. 1110–1085 Ma poles from the Midcontinent Rift volcanics in Laurentia.

The NCC–NW Laurentia connection model also makes some testable geological predictions. Detrital zircon age patterns of the late Mesoproterozoic to early Neoproterozoic sedimentary units at the eastern and northern margins of the NCC are similar with those from the Mackenzie and Amundsen basins in NW Laurentia. It is interpreted that the Grenville-age detrital zircons in NW Laurentia were possibly transported from the Grenville Province through a big river system across the Laurentian Craton (Rainbird et al., 2017). Whether the detrital zircons of similar ages in the NCC Precambrian strata also came from the Grenville Province or whether a Grenville-age magmatic belt once existed close to the NW Laurentia and NCC needs more investigations.

References

Fu, X., et al., 2015. Precambrian Res., 269: 90–106.

Rainbird, R.H., et al., 2017. Geol. Soc. Am. Bull., 129: 1408–1423.

Zhao, H., et al., 2019. Geol. Soc. Am. Bull., in press, doi: 10.1130/B35198.1.