Zircon U–Pb Geochronology and Hf Isotope, Whole-Rock Geochemistry and Sr–Nd Isotopes of the Late Jurassic–Early Cretaceous Intrusive Rocks From North Shanxi Province: Insight on Petrogenesis and Magmatic Process in the Central North China Craton

The Late Jurassic to Early Cretaceous was a critical transformative period for the North China Craton (NCC), marked by a tectonic shift from compression to extension and the formation of numerous Yanshanian magmatic intrusions across Shanxi Province. This article presents zircon U–Pb geochronology and Hf isotope, whole-rock geochemistry and Sr–Nd isotopic compositions of Late Jurassic to Early Cretaceous intrusive rocks from the Hunyuan area in northern Shanxi Province. The Chakou, Liulengshan and Zhongzhuangpu intrusions yield zircon U–Pb ages of 150.9 ± 1.7 Ma, 137.9 ± 2.0 Ma and 115.4 ± 0.6 Ma, respectively. The Chakou monzogranites exhibit typical features of high-K calc-alkaline I-type granites, and they are enriched in Rb, Ba, K and U, and depleted in Nb and Ta. The Sr and Nd isotopes of these samples show (⁸⁷Sr/⁸⁶Sr)_i values ranging from 0.7062 to 0.7103 and ε _Nd(t) values between −8.8 and −8.7. Additionally, zircon rims show highly variable ε _Hf(t) values, spanning from −12.7 to −8.1. Geochemistry and isotopes suggest that the Chakou monzogranites originated primarily from the partial melting of the lower crust. The Liulengshan quartz syenites exhibit low SiO₂ and high K₂O contents, classifying them as shoshonitic I-type quartz syenites. They are enriched in LREE and LILE, depleted in HFSE with a weak negative Eu anomaly, and display moderate ε _Nd(t) values between −17.1 and −17.0. Zircon Hf isotope composition is relatively uniform, with ε _Hf(t) values ranging from −22.6 to −20.4. We propose that the quartz syenites from Liulengshan were formed by mixed products of mantle-derived and crust-derived magmas, with the latter being dominant. The Zhongzhuangpu biotite monzogranites are petrologically and geochemically uniform, showing enrichment in Pb and Ta, and strong depletion in Sr, Ba and Eu. We consider that they originated from the partial melting of crustal materials. Collectively, our data indicate that continuous crustal extension, thinning and asthenospheric upwelling facilitated partial melting of both lithospheric mantle and crustal materials. These processes were the primary drivers behind the formation of intrusions in the NCC during the Late Jurassic to Early Cretaceous.