Petrogenesis of the Dapingtianshan intrusive complex, South China: Geochemistry, zircon U-Pb geochronology, Sr-Nd-Hf-O isotopes, and implications for geodynamic setting and mineralization

Abstract

The petrogenesis, tectonic setting and associated mineralization of magmatic suites associated with the subduction of the Paleo-Pacific plate have been topics of considerable debate. Hence, we explore the Dapingtianshan intrusive complex in South China, a composite intrusion with granodiorite in the margin and monzonite in the core. Geochemical features indicate typical I-type and high-K calc-alkaline characteristics, including abundant mafic microgranular enclaves (MMEs). Zircon U–Pb ages of 96.9 ± 0.3 Ma and 96.2 ± 2.9 Ma for the monzonite and MMEs suggest coeval magmatism. Biotite from both exhibits similar compositions, crystallizing at 700–750 °C. The monzonite and MMEs are metaluminous (A/CNK = 0.68–1.05), with trace element patterns showing enrichments in Rb, U, and Nd and depletions in Ba, Nb, Sr, P, and Ti. Chondrite-normalized REE distribution patterns reveal LREE enrichment and negative Eu anomalies. Zircon analyses show monzonite εHf(t) values of −2.4 to 0.6 and δ¹⁸O values of 5.6 to 8.6. MMEs exhibit εHf(t) values of −3.0 to 3.6. Sr-Nd isotopes suggest isotopic equilibrium during magma mixing, with (87Sr/86Sr)i of 0.70831 to 0.71426 and εNd(t) of −5.6 to −4.6. Findings suggest magma involvement of partial melts from the Mesoproterozoic metamorphic basement and enriched lithospheric mantle metasomatized by sediment-related melts linked to the subduction of the Pacific plate. Combining these results, we propose that the Dapingtianshan complex potentially hosts magmatic-hydrothermal Au–Ag–Cu–Pb–Zn metallogenic systems. The study hints at the extension of the Cu–Au metallogenic belt from the Dayaoshan area to the Qin-Hang metallogenic belt and South China.