Based on the currently available zircon Hf and bulk-rock 142Nd isotope data of > 3.6 Ga global ancient terranes, only a few of them are derived from pre-existing Hadean crust (e.g., the review of Carlson et al., 2019). These include the Acasta Gneiss complex, the Nuvvuagittuq greenstone belt, and a few outcrops in the Napier complex. These terranes share a common feature that their geographic locations are not easily reachable. Here we report a newly identified, Hadean crustal derived, Eoarchean terrane in central China named the Muzidian Gneiss complex. The Eoarchean rocks in the Muzidian Gneiss complex were first reported by Qiu et al. (2021) and then Wang et al. (2023). Unlike those terranes in remote areas of Canada or Antarctica, the Muzidian Gneiss complex is near a town and connected with several highways and freeways. We believe that the convenient location of the Muzidian Gneiss complex will provide new opportunities for the early Earth community to further explore the nature of the first crust on Earth in this new decade. Our preliminary studies showed that the oldest TTGs in the Muzidian Gneiss complex are in ages ranging from ~3.9 to 3.5 Ga, whose zircon Hf isotope compositions are generally negative and could be projected back to a ~4.3 Ga mafic crustal source. The negative bulk-rock 142Nd anomalies of these TTGs further confirm that these rocks are most likely reworked pre-existing >4.3 Ga Hadean mafic crust. We also investigated 2.5 – 2.4 Ga rocks in the same complex to explore their genetic relation to the Eoarchean units and the ultimate Hadean crustal source. These Neoarchean rocks yielded negative µ142Nd values and very negative zircon εHf(t) values projectable from the neaby Eoarchean TTGs, which makes it the youngest felsic rocks on Earth with deficits in 142Nd. This highlights the long-lived nature of the initial Hadean crustal components represented by the Muzidian gneisses that served as the initial nucleus, and the Archean continent was possibly built around it.

Reference(s)

Carlson, R.W., Garçon, M., O’Neil, J., Reimink, J., Rizo, H., 2019. The nature of Earth’s first crust. Chemical Geology 530, 119321. Qiu, X.-F., Tong, X.-R., Jiang, T., Khattak, N.U., 2021. Reworking of Hadean continental crust in the Dabie orogen: Evidence from the Muzidian granitic gneisses. Gondwana Research 89, 119–130. 

Wang, D., Qiu, X.-F., Carlson, R.W., 2023. The Eoarchean Muzidian gneiss complex: Long-lived Hadean crustal components in the building of Archean continents. Earth and Planetary Science Letters 605, 118037.