Constraints of zircon U-Pb, molybdenite Re-Os and muscovite 40Ar/39Ar ages on the formation of the Chaobuleng skarn Fe-Zn deposit, NE China

The Chaobuleng skarn Fe-Zn deposit is located in the southern segment of the Great Hinggan Range polymetallic belt, and occurs within the eastern part of the Central Asian Orogenic Belt (CAOB) in NE China. Constraining the exact metallogenic age for ore deposits is critical for understanding the ore-forming process as well as regional exploration. In this study, comprehensive geochronological analyses, including molybdenite Re-Os, zircon U-Pb, and muscovite 40Ar/39Ar dating, have been carried out to constrain the timing and formation of the skarn Fe-Zn mineralization at Chaobuleng. Zircon LA-ICP-MS U-Pb dating of ore-related coarse-grained syenogranite and barren diorite yielded ages of 138.1 +/- 1.1 and 127.8 +/- 1.4 Ma, respectively. A muscovite sample from retrograde skarn stage yielded a plateau age of 136.4 +/- 1.6 Ma, which is consistent with the Re-Os isochron age of 136.1 +/- 4.4 Ma for molybdenite. The obtained age data identify that both the causative intrusive magma and the Fe-Zn mineralization occurred at-136 Ma, and there is a close genetic relation between the felsic magmatism and skarn mineralization. The Chaobuleng deposit is considered to be formed in the early Cretaceous associated with an extensional tectonic setting, which was triggered by the Paleo-Pacific oceanic plate subduction and its sub-sequent slab rollback, lithospheric thinning and crustal extension of the back-arc domain.