Zircon U-Pb Geochronology of Baoyintu Group in the Northwestern Margin of the North China Craton and Its Geological Significance

The Baoyintu uplift is located at the northwestern margin of the North China Craton(NCC). The affiliation and evolution history of the uplift have been unresolved until now. Here we present LA-ICP-MS and SHRIMP U-Pb data for zircons extracted from samples of monzogranitic orthogneiss and the Baoyintu Group in the uplift. The 1 679 ± 13 Ma date for the orthogneiss demonstrates that Late Palaeoproterozoic rocks do exist in the uplift. The ca. 1 413 Ma minimum age of detrital zircons in metasedimentary rocks shows that the maximum age of the Baoyintu Group is Mesoproterozoic. The age distribution of detrital zircons in the first unit of the Group form clusters at ca. 2 680, 2 450, 1 800 and 1 560 Ma, which partly correspond to tectonic-magmatic-metamorphic events previously recognised in the NCC, and show that the metasedimentary rocks are largely sourced from different parts of the NCC. These confirm that the Baoyintu uplift is part of the NCC. Amphibolite with a dolerite protolith from the third unit of Baoyintu Group shows evidence for metamorphism during ca. 877–851 Ma. This combined with published geochronological data indicate the presence of Neoproterozoic magmatic and metamorphic events in the NCC, which significantly increases our understanding of the Proterozoic tectonic evolution of the region and its possible correlation with the Rodinian Supercontinent.