Geochronology and geochemistry of mafic rocks in the Wutai area, North China: Constraints on the latest Neoarchean–Paleoproterozoic tectonic setting of the Trans-North China Orogen and the onset of plate tectonics

Researchers have conducted an integrated geochronological and geochemical study of mafic rocks in the Wutai Complex, North China Craton, revealing key insights into the Neoarchean–Paleoproterozoic tectonic evolution of the Trans-North China Orogen. The ~2.54 Ga Nb-enriched gabbros originated from a depleted mantle wedge metasomatized by slab-derived melts, while the ~2.08 Ga amphibolites formed from partial melting of a spinel-garnet lherzolite source influenced by both slab-derived fluids and sediment melts. These results indicate a tectonic transition from Late Archean subduction to Paleoproterozoic lithospheric extension, providing compelling evidence that plate tectonics likely initiated at least partly during the latest Neoarchean. (Reference: Asim et al., 2025, Cont. Life Evol., https://doi.org/10.55092/cle20250001)

The North China Craton (NCC) represents one of the oldest and most tectonically complex continental blocks, offering critical insights into the geodynamic transition from the Archean to the Proterozoic Eon. Among its key tectonic domains, the Wutai Complex situated within the Trans-North China Orogen (TNCO) preserves a well-exposed and temporally constrained record of Neoarchean to Paleoproterozoic evolution. While numerous studies have focused on the felsic components of the complex, particularly tonalite–trondhjemite–granodiorite (TTG) suites and granitoids, the mafic lithologies have received comparatively limited attention. These mafic rocks, however, play a fundamental role in constraining mantle processes, crust-mantle interactions, and subduction-related geochemical signatures that are essential for reconstructing early plate tectonic regimes.

To address this, Dr. Zubair Raja Asim and colleagues conducted a comprehensive study combining U-Pb zircon geochronology, whole-rock geochemistry, and Sr-Nd isotope analysis of mafic rocks in the Wutai Complex. Their research aimed to constrain the tectonic setting and petrogenesis of these rocks to better understand the Neoarchean to Paleoproterozoic tectonic evolution of the NCC.

The team identified two major magmatic episodes. The first, ~2.54 Ga Nb-enriched gabbros, were derived from a depleted mantle wedge metasomatized by slab-derived melts. These rocks display arc-like geochemical features, including enriched large-ion lithophile elements (LILEs) and depleted high field strength elements (HFSEs), along with high εNd(t) values (+4.9 to +6.1), suggesting a subduction-modified mantle source. The second suite, ~2.08 Ga amphibolites, show signatures of back-arc basin magmatism, with geochemical evidence for partial melting of spinel-garnet lherzolite and metasomatism from slab-derived fluids and sediment melts. These amphibolites display lower εNd(t) values (+0.9 to +1.2) and geochemical traits typical of subduction-modified MORB sources.

This research uncovers a significant tectonic transition from subduction-related magmatism in the Neoarchean to extensional back-arc basin magmatism in the Paleoproterozoic within the Wutai Complex. The integration of petrological, geochemical, and isotopic data strongly supports the hypothesis that plate tectonics began to operate, at least partially, by the latest Neoarchean (~2.54 Ga). These findings challenge traditional views of stagnant-lid tectonics during this time and align the NCC's evolution with global geodynamic trends toward modern-style plate tectonics.

The study also proposes that the distinct Nb-enriched signatures in the gabbros are linked to mantle source metasomatism by siliceous slab melts, while the amphibolites' chemical features reflect a stronger influence of aqueous fluids, sediment melts, and crustal contamination, consistent with their emplacement in a back-arc extensional setting. The contrasting geochemical behaviors of these suites reinforce the multi-phase, subduction-influenced tectonic evolution of the TNCO.

Ultimately, this work contributes a crucial piece to the puzzle of early plate tectonics, showing that subduction, mantle metasomatism, and lithospheric extension coexisted during the Neoarchean–Paleoproterozoic transition in North China.

This paper, “Geochronology and geochemistry of mafic rocks in the Wutai area, North China: constraints on the latest Neoarchean–Paleoproterozoic tectonic setting of the Trans-North China Orogen and the onset of plate tectonics,” was published in Continent & Life and Evolution.

Asim ZR, Wang J, Wu B, Lan C, Long X. Geochronology and geochemistry of mafic rocks in the Wutai area, North China: constraints on the latest Neoarchean–Paleoproterozoic tectonic setting of the Trans-North China Orogen and the onset of plate tectonics. Cont. Life Evol. 2025(1):0001, https://doi.org/10.55092/cle20250001.