40Ar-39Ar isotopic age study of phlogopite from Kafang altered basalt in Gejiu of Yunnan Province and its significance

Abstract：The Gejiu polymetallic tin ore district in Yunnan Province is the largest tin deposit in the world, and the Kafang copper (tin) deposit is a component part of this ore district. The stratoid ore body of the Kafang copper (tin) deposit, closely related to meta-basalt, is characterized by enriched copper. The basalt has been altered and the alteration intensity is related to the copper mineralization. This paper presents a new 40Ar-39Ar phlogopite age for the meta-basalt in the Kafang tin-copper deposit in order to constrain the timing and duration of the alteration of basalt and the mineralization. Phlogopite yielded 40Ar-39Ar plateau age of 85.49±0.63 Ma, isochronal age of 85.62±0.42 Ma, and inverse isochronal age of 85.59±0.81 Ma. These ages are substantially consistent with each other, pointing to late Cretaceous. These results are coincident with the data obtained from the Gejiu polymetallic tin-copper deposit.