Neoarchean orogenic belt evolution in the northeast North China Craton: Implications for the reconstruction of early Earth’s microplates

Abstract

Identification and detailed studies of ancient orogens are one of the most important scientific problems for understanding the formation and evolution of early continental crust. However, it is tough to identify the original architecture of ancient orogenic belts due to the strong disturbances of late tectonothermal events, which makes it hard to reconstruct the formation mechanism and evolution process of early microplates. Here we used the spatial–temporal evolution of Neoarchean tectono-magmatism to trace orogenic processes of the Neoarchean continental crust of the North China Craton. Regional investigations in lithological assemblages, structural geology, chronology, geochemistry, and isotopic characteristics suggest that the Archean crystalline basement of the Eastern Liaoning Range in the northeastern North China Craton may be divided into three tectonic zones, each with its independent tectono-thermal evolution. We suggest therefore that these are independent terranes, namely microplates. Anshan-Benxi microplate in the southwest is a ∼ 3.8 to ∼ 2.9 Ga ancient continental nucleus with abundant Neoarchean (2.54–2.49 Ga) crust-derived K₂O-rich granitoids. Waitoushan-Weiziyu-Jiubing microplate in the center is mainly composed of ∼ 2.7 Ga tonalite-trondhjemite-granodiorite suite and 2.6–2.5 Ga diversified granitoids with some remnants of ancient oceanic lithosphere. Liaobei microplate in the northeast contains mainly late Neoarchean (2.57–2.52 Ga) magmatic rocks with minor Mesoarchean (∼3.1 Ga) crustal materials. We summarize the formation mechanism, essential features, and identification marks of the Archean orogenic belt, and conclude that the Eastern Liaoning Range experienced the following four stages of Neoarchean geodynamic evolution. (1) In the early Neoarchean (2.71–2.68 Ga), intra-oceanic subduction generated the ∼ 2.7 Ga island arc belt (proto-Waitoushan-Weiziyu-Jiubing microplate); (2) The 2.60–2.56 Ga warm subduction of oceanic slabs reformed proto-Liaobei microplate, and re-deformed the residual ∼ 2.7 Ga island arc belt; (3) During 2.56–2.54 Ga, the Waitoushan-Weiziyu-Jiubing microplate and Liaobei microplate were amalgamated by an ‘arc-arc’ collision; (4) At the end of Archean (2.54–2.50 Ga), the Waitoushan-Weiziyu-Jiubing microplate + Liaobei microplate and proto-Anshan-Benxi microplate were finally aggregated through the ‘arc-proto-continental’ collision, forming a unified crystalline basement of the Eastern Liaoning Range. Our work suggests that the short-term, small-scale subduction-collision orogenic cycles within pristine plate tectonic regimes played a crucial role in the Neoarchean crustal growth and evolution of the North China Craton.