Reevaluating Archean eclogite-facies metamorphism in the North China Craton

Subduction-driven plate tectonics is one of the most important processes shaping present-day Earth, yet there is no consensus regarding the timing of its onset. A recent study posits that garnet clinopyroxenites hosted in garnet granulites from the Zunhua-Shangying complex (North China Craton) records eclogite-facies metamorphism at ca. 2.47 Ga, which serves as a key argument for subduction-driven tectonics since the end of the Archean. Nevertheless, this interpretation remains uncertain because the garnet clinopyroxenites were not directly dated; zircon U-Pb dates from the host garnet granulites define a discordia from the late Neoarchean to the mid-Paleoproterozoic; no trace element data were presented to link the zircon U-Pb dates to garnet growth. To resolve this age ambiguity, we apply laser ablation−inductively coupled plasma−tandem mass spectrometry garnet Lu-Hf geochronology to directly date the metamorphism. The garnet grains extracted from the garnet clinopyroxenites show no significant major element zoning patterns, except for the outermost rims, and display typical Lu growth zoning, with concentration gradients decreasing from core to rim, confirming minimal postcrystallization diffusion. The analyzed garnet grains yield tightly clustered Lu-Hf ages ranging from 1869 ± 137 Ma to 1423 ± 378 Ma, with no detectable Archean isotopic inheritance. Our findings demonstrate that the so-called eclogite-facies garnet pyroxenites in the Zunhua-Shangying complex were metamorphosed in the mid-Paleoproterozoic as part of a globally distributed suite that records metamorphism during the assembly of Nuna supercontinent by subduction-driven plate tectonics. We propose a global reappraisal of purported ancient eclogite-facies terranes using in situ garnet Lu-Hf geochronology, given that zircon-based timelines may be ambiguous, leading to misinterpretation of the age of events in polyphase metamorphic basements.