Episodic Archean crustal accretion in the North China Craton: Insights from integrated zircon U-Pb-Hf-O isotopes of the Southern Jilin Complex, northeast China

Abstract

Recent advances in high-precision in-situ analysis of zircon U-Pb-Hf-O isotopes have significantly improved our approach to studying the origin and evolution of Archean crust. This study presents high-precision in-situ zircon U-Pb-Hf-O isotopes for the Southern Jilin Complex (SJC) on the northeastern margin of the North China Craton (NCC) and explores the potential of such an integrated approach in understanding the Archean crust evolution and its tectonic implications. The SJC consists mainly of Archean granitoid gneisses hosting minor supracrustal rock xenoliths. Zircon U-Pb data from representative lithologies reveal three episodes of magmatism at ~2.78, ~2.69 and ~2.55 Ga, respectively. The former two granitoid magmatic events are recognized for the first time in NE NCC, while the latest one is widespread over the NCC. All metamorphic zircon domains document similar metamorphic ages of 2.51–2.48 Ga, consistent with the widespread metamorphism of ~2.50 Ga in the NCC. Most concordant magmatic zircons preserve “mantle-like” O isotopic signatures, indicating the magma sources were not contaminated by large amounts of high δ18O supracrustal sediments. Hf depleted mantle model ages of magmatic zircons display one predominant peak at 2.9–2.8 Ga and two subordinate peaks at 3.3–3.2 Ga and 2.7–2.6 Ga, indicating possible episodic crust-mantle differentiation in Southern Jilin. Integrated zircon U-Pb-O-Hf data from the SJC suggest that magma sources were mainly derived from multiple episodes of reworking of juvenile or ancient crust with mantle component addition, while recycling of sediments was trivial during the Neoarchean in this region. The spatial–temporal relations of magmatism, lack of supracrustal addition to magma sources, and other geological evidence from the NCC are in favor of a bottom-up geodynamic regime possibly related to plume activities, arguing against a widespread top-down mechanism involving modern-style subduction in the NCC during the Neoarchean.