Petrology, Geochemistry, and Sr-Nd-S Isotopic Compositions of the Ore-Hosting Biotite Monzodiorite in the Luanjiahe Gold Deposit, Jiaodong Peninsula, China

The Jiaodong Peninsula is one of the most important Au ore provinces in China. There is an ongoing debate on the correlation between ore formation and magmatism in this province, because few intrusive rocks exhibit a clear association with ore deposits. A mineralized biotite monzodiorite（BM） stock, with disseminated ore, pervasive phyllic alteration, and no deformation, was found in a borehole in the footwall of the Zhaoping fault within the Luanjiahe Au deposit, which may shed light on this debate. The biotite monzodiorite contains explosion breccias, miarolitic cavities, skeletal and dendritic quartz, and late-stage evolved aplite dikes, and the in-situ δ34S values of the disseminated pyrite which is associated with Au mineralization are-1.7‰ to 7.3‰（mean=3.5‰）, indicative of a magmatichydrothermal system. These findings, combined with the reported age of 123 Ma, show that the intrusion has close spatial, temporal, and geochemical relationships with Au mineralization in the area. The biotite monzodiorite is metaluminous, high-K calc-alkaline and shoshonitic, with enrichment in light rare earth elements（REEs） and large-ion lithophile elements（LILEs）, depletion in high-field-strength elements（HFSEs）, and enriched Sr-Nd isotopic compositions. The intrusion may be the product of partial melting of enriched lithospheric mantle with a small lower crustal component. The hydrous, Au-bearing, enriched mantle source, and the strongly oxidized magma that was generated, created favorable conditions for Au mineralization.