Magma assembly and evolution of the Early Cretaceous Sanguliu pluton in the Liaodong Peninsula, NE China

Abstract

• Influx of two magmas from the ancient crust constructed the zoned Sanguliu pluton . • Mafic magma provided primarily heat but little material for the Sanguliu granites . • Magma mingling occurred during the magma ascent and emplacement processes. Zoned granitic plutons and mafic microgranular enclaves (MMEs) contain important information on magma assembly, mixing, and evolution. The Sanguliu pluton in the northeastern North China Craton (NCC) consists of fine-/medium-grained monzogranite in the outer zone and coarse-grained syenogranite-monzogranite in the inner zone, with MMEs being found in both zones. These rocks have similar zircon U-Pb ages of ∼ 130 Ma. The granites in both the outer and inner zones display variably enriched isotopic compositions of ( 87 Sr/ 86 Sr) i (0.7147–0.7163), εNd(t) (−18.6 to −20.8), and zircon εHf(t) (−18.0 to −24.3), indicating that they were mainly sourced from the ancient lower crust with minor depleted mantle contributions. Zircons in the outer-zone MMEs are subhedral-anhedral with patchy zoning in the CL images and have a narrow εHf(t) range (−16.2 to −20.9) similar to zircons from the host granites. In contrast, zircons in the inner-zone MMEs are mainly euhedral with core-rim structure, and have a wider εHf(t) range (−0.3 to −20.8). The complex morphology and internal structure of these zircons are ascribed to the metasomatism and growth during magma mingling processes. The varying zircon εHf(t) values indicate that these MMEs were derived from the depleted mantle and had been isotopically modified by the host granitic magma.