Rhenium in molybdenite from Mo (-Cu) deposits in northeastern China

Abstract

Rhenium (Re) is a strategic metal that has wide applications in the field of aerospace, materials science, chemistry, and medicine, and plays an indispensable role in the manufacturing of aircraft engines. It mostly occurs in and is extracted from molybdenite from porphyry deposits. Northeastern China is one of the most Mo-rich regions in the world and contains >90 Mo deposits with a total tonnage of >10 Mt. Mo metal. Previous studies have been mainly focusing on the Mo mineralization, but little is known about the associated Re resources and their enrichment mechanisms. In this study, 73 Mo (-Cu) deposits from NE China with available Re-Os dating ages and molybdenite Re contents have been compiled, with the aims of exploring the factors controlling the Re variations in these different deposits and evaluating their Re recovery potentials. The results show that the majority of the Re-bearing deposits in NE China have Mesozoic ages (i.e., <250 Ma), with only three forming in the Paleozoic. Five of the deposits (i.e., Wunugetu, Chalukou, Duobaoshan, Diyanqin'amu and Daheishan) contain Re reaching large sizes (>50 t Re), and 13 have medium sizes (5–50 t Re). A total of >700 t Re metal has been estimated to be included in these Mo (-Cu) deposits. Generally, the Re contents in molybdenite decrease from porphyry Cu-Mo (100–400 ppm), through porphyry Mo-Cu (20–70 ppm), to porphyry Mo (8–30 ppm) deposits. Skarn and greisen-type deposits are less common in NE China, and the former has molybdenite Re contents ranging mainly from 1 to 30 ppm, while the latter contains Re contents between 5 and 10 ppm. Geochronologically, the older, Paleozoic deposits contain higher-Re molybdenite, while the low-Re molybdenite is more abundant in these younger deposits with Early Cretaceous ages. In the porphyry Cu-Mo deposits, the average molybdenite Re content shows a negative correlation with the Mo grade, demonstrating higher-Re molybdenite in lower Mo grade systems. But this relationship is not observed in the Mo-dominated deposits. The causative intrusions with higher whole-rock ε_Nd(t) and zircon ε_Hf(t) values are generally related to higher molybdenite Re contents, indicating more mantle or juvenile crust contributions to the Re enrichment. In an individual deposit, the Re-rich molybdenite commonly occurs in veins with sericite alteration, likely due to the favorable precipitation of Re at lower fluid temperature and pH conditions. This study reveals that the variations in molybdenite Re contents in NE China are controlled by a combined effect of several factors, including the deposit types and ages, magmas sources, Mo grades, and deposition conditions.