U–Pb dating and Hf isotope study of detrital zircons from the Zhifu Group, Jiaobei Terrane, North China Craton: Provenance and implications for Precambrian crustal growth and recycling

Abstract

The Zhifu Group exposed in the northeastern Jiaobei Terrane is subdivided from base to top into the Laoyeshan, Bingying and Dongkou formations, and comprises mainly quartzites and muscovite- and tourmaline-bearing quartz schists. In order to define its provenance and depositional age, and to constrain the crustal growth and recycling of the source regions, we have conducted LA-ICP-MS U–Pb dating and in situ Hf isotopic study of detrital zircons from three quartz schists samples collected from the Zhifu Group. Most of the analyzed zircon grains have oscillatory zoning and Th/U ratios >0.4, suggesting igneous origins. 270 detrital zircons U–Pb analyses yield U–Pb ages of 1709–3679Ma that cluster into three major age populations of 1.7–1.9Ga with a peak at 1844Ma, 1.9–2.0Ga with a peak at 1936Ma and 2.4–2.55Ga with a peak at 2465Ma, and two minor age populations of 2.2–2.35 and 2.6–2.7Ga. The peaking age of 1844Ma for the youngest age population indicates that the Zhifu Group must be deposited after 1844Ma. Detrital zircons with ages of 1.7–2.35Ga can be linked to pre- and post-tectonic polyphase magmatic events along the JLJB, and most of the zircons have negative ɛHf(t) values from +1.76 to −18.02 and two-stage Hf model ages (TDM2) concentrating at ∼2.7–3.0Ga, indicating that source rocks of these zircons were derived from recycling of ancient crusts. Detrital zircons with ages of 2.4–2.9Ga may have been sourced from the Archean granitoid (mainly TTG) gneisses in the Jiaobei Terrane, and these zircons have ɛHf(t) values from +6.4 to −7.53 and TDM2 of 2.6–3.4Ga (peak at ∼2.7–3.0Ga), suggesting that source rocks of these zircons were mainly derived from juvenile crusts associated with a major crustal growth at ∼2.7–3.0Ga, and a limited amount of ancient crustal component. The two detrital zircons with ages of 3631 and 3679Ma have negative ɛHf(t) values of −4.42 and −1.51 and TDM2 of 4137 and 4000Ma, respectively, implying the recycling of ancient continental crust (>3.6Ga) and crustal growth prior to 4.1Ga in the NCC.