2.8–1.7 Ga history of the Jiao-Liao-Ji Belt of the North China Craton from the geochronology and geochemistry of mafic Liaohe meta-igneous rocks

Highlights • Lithospheric mantle stabilization under Jiao-Liao-Ji Belt at 2.8Ga (SmNd isochron) • Liaohe mafic meta-igneous rocks formed in active continental margin subduction zone • Emplacement of Liaohe mafic igneous rocks at ~2.2 Ga (LuHf isochron) • Amphibolite retrograde metamorphism from exhumation at 1824 ± 19 Ma (PbPb isochron) • Cooling of terrane to ~500 °C at 1671 ± 58 Ma (RbSr isochron) Abstract The assembly and long-term evolution of the Eastern Block of the North China Craton are poorly constrained. Here we use bulk rock geochronological and geochemical data from mafic meta-igneous rocks (hornblendites, amphibolites and a metagabbro) of the Liaohe Group to reconstruct the Neoarchean to Paleoproterozoic history of the Jiao-Liao-Ji Belt, located between the Longgang and Nangrim blocks that together form the Eastern Block of the North China Craton. The mafic/ultramafic meta-igneous rocks have intrusive or tectonic contacts with the Liaoji granitic rocks (~2.2–2.0 Ga), which form the basement of the Jiao-Liao-Ji Belt. The major and trace element data indicate that the protoliths had calc-alkaline composition and formed along an active continental margin subduction zone. The mafic rocks form a whole-rock 176Lu/177Hf isochron with an age of 2.25 ± 0.31 Ga, overlapping with UPb zircon ages for mafic and granitic rocks from the Jiao-Liao-Ji Belt and consistent with being the emplacement age of the mafic protoliths along the active continental margin. In contrast, the whole-rock 147Sm/144Nd isochron age of 2.83 ± 0.18 Ga is likely to reflect the average age of the lithospheric mantle source from which the mafic/ultramafic protoliths were extracted. Together with geological evidence, we propose that the southwestern portion of the Longgang Block was an active continental margin since at least the early Paleoproteorozic. Literature age data from metamorphic zircons show that peak granulite metamorphism took place at ~1.96–1.88 Ga, resulting from the collisional