Depositional age, provenance and metamorphic timing of metasedimentary rocks from the eastern margin of the Jiaobei terrane, North China Craton: evidence from SHRIMP zircon U-Pb dating

Jingshan Group metasedimentary rocks are widespread east of the Wulian-Yantai fault. Only a few studies focus on the provenance, depositional age, metamorphic timing and tectonic affinity of these rocks. Two Jingshan Group metasedimentary rocks and one associated gneissic trondhjemite were selected for SHRIMP U-Pb dating. Zircons from the metasedimentary rock near Xujiadian town show a major U-Pb age cluster at 2.55-2.45 Ga, with minor clusters at 2.2-2.0 Ga and ~2.72 Ga and a few >3.0 Ga. The sample was metamorphosed at ~1.86 Ga. Detrital zircon cores from the other metasedimentary rock collected at Huxi village likely crystallized at ~2.56 Ga, whereas the rims yield two metamorphic ages of 2.47 Ga and 231 Ma. A gneissic trondhjemite that may have intruded the second metasedimentary rock was emplaced at 2.51 Ga and metamorphosed at 2.47 Ga. According to these results, the depositional ages of the metasedimentary rocks from Xujiadian town and Huxi village can be constrained to 2.1-1.86 Ga and 2.56-2.47 Ga (possibly 2.56-2.51 Ga), respectively. Our studies indicate that small volumes of late Archean to early Paleoproterozoic (~2.5 Ga) supracrustal rocks can be distinguished from the metasedimentary rocks described as belonging to the mid-late Paleoproterozoic Jingshan Group. The two metasedimentary rocks presented in this study were derived from the Jiaobei terrane. Combining our results with published data, basement rocks located east of the Wulian-Yantai fault have a Jiaobei terrane affinity, implying that the suture zone between the Jiaobei terrane and the Sulu orogeny lies east of the Wulian-Yantai fault and is probably represented by the Muping-Jimo fault. The weighted mean age of 230.8 ± 5.5 Ma obtained from zircon metamorphic rims of biotite-muscovite schist (JS02) reported here provides robust evidence that the basement rocks of the Jiaobei terrane were involved in the Triassic subduction of the Yangtze Craton.