Petrogenesis of Early Cretaceous volcanic rocks of the northeastern North China Craton: Constraints from elemental and Sr–Nd–Pb isotope geochemistry

Abstract

This study examines the geochemical and whole-rock Sr–Nd–Pb isotopic compositions of Early Cretaceous volcanic rocks of the southern Jilin Province (Tonghua and Huanren areas) and Liaodong Peninsula (Xiuyan, Dandong, and Guiyunhua areas), northeastern North China Craton (NCC). Two groups of volcanic rocks are recognized in the northeastern NCC. The geochemistry and isotopic compositions of the intermediate-acid volcanic rocks indicate that a systematic decrease in whole-rock εNd(t) is accompanied by an increase of Zr/Nb. Modeling results suggest that those intermediate-acid volcanic rocks experienced the assimilation-fractional crystallization (AFC) process with different lower continental crust (LCC) components, indicating the heterogeneity of LCC in the northeastern NCC. As for basic volcanic rocks, they are characterized by “weakly enriched” isotopic signatures, i.e., moderately radiogenic Sr (0.7062–0.7082), unradiogenic Nd (−5.29 to −1.14), and highly radiogenic Pb compositions. The narrow scope of Sr–Nd–Pb isotopic compositions of whole-rock indicates insignificant crustal assimilation. Instead, the high Th/Yb ratios were largely inherited from source enrichment through the input of subducted sediment. Furthermore, element-isotopic modeling suggests that the “weakly enriched” mantle-derived rocks have resulted from a depleted mantle source metasomatized via the sediment-derived melt. Our results provide powerful petrological and geochemical evidence on the Early Cretaceous subduction of the Paleo-Pacific plate beneath the northeastern NCC and suggest the metasomatic process by subducted sediment-derived melt may play an important role in depleted mantle enrichment.