Neoarchean to Palaeoproterozoic tectonic evolution of the Trans-North China Orogen, North China Craton: Evidence from zircon U-Pb geochronology, Lu-Hf isotopes, and geochemistry of the Zanhuang Complex

Research on the Zanhuang Complex has been one of the hotspots in the Neoarchean-Palaeoproterozoic tectonic evolution of the Trans-North China Orogen (TNCO) in the North China Craton (NCC). Here, we present data from petrology, geochemistry, zircon U-Pb geochronology, and Lu-Hf isotopes on a suite of granite, diorite, TTG gneiss, and amphibolite in the Zanhuang Complex to characterize these rocks and understand their genesis. Zircon U-Pb data yield magmatic ages of 2,607 Ma for granite, 2,599 Ma for diorite and 2,561 Ma for TTG gneiss, with subsequent thermal event ages of 2,530 and 2,471 Ma. Lu-Hf isotopes show epsilon(Hf)(t) values ranging from 0.04 to 7.11 and crustal model ages of 2,700-3,100 Ma for the diorite, indicating a Meso- to Neoarchean mantle source with minor input of crustal components. The granite and TTG gneiss have the characteristics of volcanic-arc granite, with low Sr/Y and (La/Yb)(N), high Cr and Ni contents, positive Pb and K anomalies and negative Nb, Ta, P, and Ti anomalies. The amphibolite and diorite are similar to island arc basalt, with low K2O, Sr/Y, (La/Yb)(N), and high FeOT, positive Pb anomaly, negative Nb, Ta, and Ti anomalies and absence of obvious Ce anomaly. These signatures indicate that these rocks were likely formed in a subduction setting. We have proposed a model of subduction-collision process in the TNCO, including subduction at ca. 2.70-2.55 Ga, arc-continent collision at ca. 2.55-2.45 Ga, extension and rifting at ca. 2.30-2.05 Ga, and continent-continent collision at ca. 1.90-1.75 Ga. Our results are consistent with the previous models on the tectonic evolution in the NCC and provide further insights into the Neoarchean-Palaeoproterozoic tectonic history of the craton.