Mineralization of the Shangjiazhuang Mo deposit in the Jiaodong peninsula, China: Constraints from S-H-O isotopes and fluid inclusions

The Shangjiazhuang Mo deposit is located in the east of Shandong Peninsula, which is tectonically the eastern extends of the Dabie-Sulu orogenic belt. The ore bodies occur in the Early Cretaceous Yashan porphyritic granodiorite, which are stratiform, vein-like and lentoid. The orebodies are controlled by the fractures with NW direction, and have similar orientations, with strike of 337 degrees-344 degrees and dips of 20 degrees-26 degrees to the northeast. The potassic alteration, biotitization, silicification, sericitization, chloritization, and carbonatization are developed in the country rock. According to the relationship of mineral symbiotic assemblage and the cutting relationship of the hydrothermal veins, the hydrothermal metallogenic period of Shangjiazhuang Mo deposit can be divided into three stages: quartz-molybdenite (early stage), quartz-chalcopyrite and molybdenite (middle stage) and quartz-pyrite (late stage). We studied S-H-O isotopes, fluid inclusions and mineralization age of the Shangjiazhuang Mo deposit, aiming to clarify the genesis mechanism for the Mo deposits in the eastern Jiaodong Peninsula. The delta S-34 value of molybdenite and chalcopyrite in the main metallogenic stage range from 4.5 parts per thousand to 5.0 parts per thousand, which is consistent with magmatic sulfur. The delta O-18(H2O) valve decrease gradually from the early metallogenic stage (4.5 parts per thousand-5.0 parts per thousand) to the late metallogenic stage (0.39 parts per thousand-1.48 parts per thousand), indicating that the ore-forming fluids were mainly magmatic water at the early stage and a mixture of meteoric and magmatic water at the late stage. The oreforming fluids evolved from moderate temperature, CO2-rich and high salinity at the early stage to low temperature, CO2-poor with nearly constant salinity in the late stage. Different types of inclusions with similar temperature and different salinity coexist in the main metallogenic period, indicating that as temperature drops, fluids in the system were either immiscible or boiling, leading to CO2 escape, and finally leads to the precipitation and enrichment of ore-forming elements. Copyright (C) 2021, Guangzhou Institute of Geochemistry. Production and hosting by Elsevier B.V.