Abstract:

The Majiawa AuMo deposit discovered in recent years is located in the north margin of the Xiaoqinling gold area. The orebodies, the AuMobearing quartz veins, are controlled by eastwesttrending brittleductile fault belts. Precise ReOs dating of molybdenite from the Majiawa AuMo deposit has been carried out in this study, and the results show that the ReOs model ages range from 2325 Ma to 2684 Ma with a ReOs isochron age of (231±11) Ma, indicating the molybdenum mineralization occurred in the Triassic. The rhenium contents of molybdenite samples range from 0.474×10-6  to 0.791×10-6, and the initial 187Os/188Os is of 2.4±6.4, which indicate that oreforming materials were derived from the crust. The Majiawa quartz vein type of AuMo deposit was a product of tectonicfluid metallogenic event in the regional extensional regime. It is a new prospective to explore the Indosinian and Yanshanian quartz vein type of AuMo and Mo deposits within brittleductile fault belts developed in Archean basement at the south margin of the North China plate.

Key words: Re-Os age, Triassic, quartz vein, oreforming material, Majiawa Au-Mo deposit, Xiaoqinling