The Eocene magmatism and mineralization of Xiariduo rocks in the northern Yulong porphyry copper belt, Tibet: Evidence from zircon U-Pb geochronology and geochemistry

In this study, the authors identified the Eocene biotite monzonitic granite porphyry and quartz diorite porphyrite in the Xiariduo mining area, and obtained their crystallization ages of 41.6±0.3~41.7±0.3Ma and 41.1±0.2~41.2±0.2Ma respectively, thus determining the Eocene magmatic events in the Xiariduo mining area for the first time, with the Cu-Mo mineralization related to the structural-magmatic events. Rock geochemistry shows that biotite monzonitic granite porphyry and quartz diorite porphyrite have the same geochemical characteristics, with slightly higher SiO₂, rich K₂O and Na₂O, higher K₂O/Na₂O ratio and lower TFeO content, thus belonging to the weakly peraluminous and high potassium calc alkali-shoshonite series; in addition, they are relatively depleted in K, Ba, Nb, P, Ti and enriched in Th, U, Sr, Hf, thus having the characteristics of highly differentiated Ⅰ-typed granite with high Zr/Hf, Rb/Sr ratios and low Ti/Eu ratio. The formation of Xiariduo porphyry was related to the mixing of shell and mantle material, which was caused by the collision between Indian plate and Asian plate inducing a large-scale sliding system, which caused the sinking of the lower crust, the swelling of the soft-flow ring material, the partial melting of the enriched mantle, and the increasing accumulation of mantle magma.