The Early Jurassic Chang'anbu porphyry Cu–Mo deposit in Northeastern China: Constraints from zircon U–Pb geochronology and H–O–S–Pb stable isotopes

Abstract

Central Jilin is tectonically subordinate to the Lesser Xing'an Range–Zhangguangcai Range polymetallic metallogenic belt, an important region for Cu–Mo prospecting in NE China. Dozens of large‐scale molybdenum deposits, including Fu'anbu, Chang'anbu, Jide, and Dashihe, have been recently discovered in Central Jilin, whereas porphyry Cu or Cu–Mo deposits have not been found to date. One such example of an intracontinental porphyry Cu–Mo deposit is the Chang'anbu Cu–Mo deposit in Shulan, Jilin Province, hosted in early Yanshanian rocks. Here in this contribution, we described detailed geology based on our field observation and conducted a comparative study on the metallogenic epoch and the ore‐forming sources of the Chang'anbu Cu–Mo deposit by using zircon U–Pb dating and H–O–S–Pb stable isotopes. We propose that the Chang'anbu deposit is rare in the Lesser Xing'an Range–Zhangguangcail Range metallogenic belt and differs from other porphyry deposits that consist solely of Mo, indicating a unique mechanism of metallogenesis. Zircon U–Pb ages indicate emplacement of a granite pluton which is the main metallogenetic rock body during the Early Jurassic (182.10 ± 1.20 Ma). The pluton is spatially and temporally associated with Cu–Mo mineralization and led to large‐scale porphyry Cu–Mo mineralization during the early Yanshanian. Sulphur, Pb, H, and O isotope data suggest that magma generated by subduction of the Paleo‐Pacific oceanic crust was the main ore‐forming source of this deposit (206Pb/204Pb = 18.046–18.734; Pb207/Pb204 = 15.502–15.655; δ34S = 0.3–2‰; δDV–SMOW = −102.2–93.4‰; δ18OV–SMOW = 9.1–11.6‰). The Chang'anbu porphyry Cu–Mo deposit is representative of large‐scale polymetallic metallogenic events in Central Jilin that resulted from magmatism related to crust and mantle melting during the early Yanshanian.