The oxidized granitoids facilitated the formation of Early Cretaceous molybdenum mineralization in the Jiaodong region, China

Abstract

Oxygen fugacity is a key factor in controlling the formation of porphyry molybdenum deposits. We present new data on Lengjia monzogranite and compile the Mesozoic magmatism data of the Jiaodong Peninsula to elucidate the correlation between magma oxygen fugacity and porphyry Mo mineralization. Zircon U-Pb geochronology indicates that the formation of the Lengjia monzogranite occurred at 113.7 Ma, while molybdenite Re-Os geochronology shows that the Lengjia Mo deposit was formed at 113.5 ± 3.0 Ma. The Lengjia monzogranite, characterized by low Sr/Y ratios (12.28 ∼ 20.16), low Sr, and high Yb and Y concentrations, can be classified as a non-adakite I-type granite. It had low zircon εHf (t) values (–23.8 ∼ -13.8) and ancient TDM2 (Hf) (2047–2680 Ma) with variable zircon O isotopic compositions (5.82 ‰ ∼ 7.38 ‰). The Lengjia monzogranite was formed by partial melting of the Paleoproterozoic crustal source and mantle components metasomatized by slab-derived melt. The zircon trace element calculation revealed that the Weideshan suite had higher ΔFMQ values (0.32 ∼ 4.47, average is 2.27) compared to the Guojialing suite (-0.91 ∼ 2.88, average is 0.82) and Linglong suite (-1.81 ∼ 2.76, average is 0.37). The oxidized Weideshan suite resulted from the increased involvement of mantle metasomatized by slab-derived melt. The elevated oxygen fugacity promoted the porphyry Mo-metallogenic potential of the Weidshanian suite. We propose that the Linglong suite was related to the northwestward flat-slab (subhorizontal) subduction of the Izanagi plate (Paleo-Pacific plate), the Guojialing suite was formed by low-angle northwestward subduction of the Izanagi plate, and the Weideshan suite was related to the northwestward subduction and major slab rollback of the Pacific plate.