Petrogenesis of the Paleoproterozoic Liuying hornblendite arc cumulates and implications for the tectonic evolution of the northern North China Craton

Understanding the Paleoproterozoic configuration of the northern North China Craton (NCC) is crucial for reconstructing its Precambrian tectonic history. This study integrates geological field observations, petrological data, U-Pb geochronology, and Lu-Hf isotopic analysis of zircons, alongside mineral and whole-rock geochemistry, including Sr-Nd isotopes from the Liuying ultramafic complex in Hebei Province. Our goal is to enhance the understanding of the tectonic history of the craton’s northern margin. The complex is composed of hornblendite and plagioclase hornblendite, showing igneous cumulate texture. Zircon U-Pb data from the ultramafic complex define three distinct groups of ages: 2211–2343 Ma, 1761–1999 Ma, and 246–310 Ma, corresponding to magma crystallization and metamorphism resulted from crustal thermal events. The major elements of rocks align with the differentiation trend of hydrous arc magmas. They display characteristics of enrichment in large ion lithophile elements and depletion in high field strength elements. Fractional crystallization of arc magmas with H₂O of 7.3–8.1 wt% at middle-lower crust depths (18–23 km) and 966–996 °C formed amphibole-enrichment arc cumulates. The zircon ε_Hf(t) values (–5.96 to + 9.05) are decoupled from enriched Sr-Nd isotopic compositions ((⁸⁷Sr/⁸⁶Sr)_i = 0.704185–0.705932, ε_Nd(t) = −14.6 to −5.68, (⁸⁷Sr/⁸⁶Sr)_amp = 0.705110–0.705846), suggesting a subduction-modified mantle source, incorporating 5–10 % subduction slab-derived melts and fluids. The northern part of the NCC was a continental arc above a paleo-subduction zone on a scale similar to the modern Andes at ca. 2.2 Ga. The oceanic slab subduction between the craton and the Siberian segment resulted in partial melting of metasomatized mantle wedge to form Paleoproterozoic hornblendite arc cumulates.