40Ar/39Ar age of muscovite from the Galale skarn type copper-gold deposit in Tibet and its geological significance

Located in Gegya County of Ngari Prefecture, Tibet, and lying in the mid-north Lhasa terrane, the Galale skarn-type copper-gold deposit contains medium-size copper resources and large-size gold resources. Based on a systematic field geological survey, the authors obtained a 91.48Ma±0.68Ma 40Ar-39Ar age of muscovite from skarn in this deposit, which presents its metallogenic age and suggests a late Yanshanian product. Combined with regional geological data, the authors have concluded that skarn-porphyry type deposits in mid-north Lhasa terrane, whose metallogenic age is about 90Ma, are mainly concentrated in the Coqen-Xainza magmatic arc. After the closure of Bangong -Nujiang Ocean in the Early Cretaceous, these back-arc basins and inter-arc basins, represented now by the Slainajap belt, evolved into some small oceans, and the evolution of these small oceans seemed to be the main factor for the formation of these 90Ma deposits. The authors hold that more work should be done on the exploration of 90Ma skarn-porphyry type deposits along Coqen-Xainza magmatic arc.