Zircon U-Pb ages and Lu-Hf isotopes of Paleoproterozoic metasedimentary rocks in the North China Craton: Implications for its crust and evolution

Abstract

The northern margin of the North China Craton is an important tectonic zone, bordered by the globe’s largest Phanerozoic accretionary orogen, the Central Asian Orogenic Belt. The Paleoproterozoic strata on the northern margin of the North China Craton (NCC) comprise a relatively intact low-grade (meta-)sedimentary sequence, but whether there are breaks in the sequence and the tectonic setting in which the sequence was deposited are uncertain. In this work, Lu–Hf isotopic, and zircon U–Pb geochronological analyses were performed on (meta-)sedimentary rocks from the Paleoproterozoic strata, to investigate the potential provenance, depositional age, and depositional environment, and discuss the likely tectonic setting of sedimentation on the northern margin of the NCC during the Paleoproterozoic. The distribution of detrital zircon ages shows that the lower meta-feldspathic sandstone unit of the Paleoproterozoic sequence was deposited after ca. 2.2 Ga, whereas the maximum depositional age of (meta-)quartz siltstone and quartzites were around 1.89 Ga and at from ca. 1.86 to 1.81 Ga, respectively. Integration of our U–Pb and Hf isotope data with data from the other regions of the NCC, indicate that the Paleoproterozoic strata have experienced a depositional environment between ca. 2.2–1.81 Ga in an extensional basin system. We further proposed that the northern margin of the NCC evolved from an extensional tectonic setting, possibly related to slab rollback. Subsequently, the Paleoproterozoic sequence was affected by a ~1.8 Ga metamorphic event to form these (meta-)sedimentary rocks in the region.