Petrogenesis and magmatic evolution of the intermediate–felsic Early Cretaceous Shizhuzi magmatic complex on Liaodong Peninsula, NE China

Abstract

The destruction of the North China Craton (NCC) culminated during the Early Cretaceous, inducing widespread magmatism and related mineralization in the eastern China. The Shizhuzi magmatic complex (SMC) from the Liaodong Peninsula is typical products of this event, thus could provide important insights on the destruction process. Here, we present petrological, geochronological, and elemental and isotopic geochemical data for the SMC rocks in order to reveal their magma sources, petrogenesis and the possible geodynamic process. The complex comprises quartz diorite, granodiorite, and granite, accompanied with Au, Cu and Mo mineral deposits. Zircon UPb dating shows that the different rocks were coeval with the formation ages of 129–126 Ma, coincident with the associated mineralization. However, field relations, whole-rock major and trace element contents and isotopic compositions indicate different origin for the quartz diorites and the coeval granodiorites and granites. The quartz diorites are calc-alkaline rocks with high MgO, Mg# and low SiO2. They are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs) with significant negative Nb, Ta and Ti anomalies. These geochemical data and the highly enriched zircon Hf isotopes suggest that they were derived from partial melting of enriched subcontinental lithospheric mantle. The granodiorites and granites from the SMC have high SiO2 and low MgO contents, suggesting that they were derived from crustal sources. These rocks are I-type rocks with high-K calc-alkaline features. Their primary magma originated from the partial melting of basaltic lower crust and experienced fractional crystallization. The ascending mantle-derived magma provided heat for the melting of the crustal rocks. Based on regional geology, the SMC was generated in the extensional setting related to the roll-back of the subducted Paleo-Pacific plate. The concurrent mantle and crustal melting in the formation of the SMC revealed the loss of stability of the cratonic lithosphere, related to the destruction of the NCC during Early Cretaceous. Besides, the emplacement of SMC might also contribute to the formation of contemporaneous Au, Mo, and Cu deposits.