Geochronology and geochemical characteristics of the Guola complex intrusion in the Hongponiuchang Cu-Au mining area of Deqin area, Yunnan Province, and its tectonic and prospecting significance

The Hongponiuchang copper-gold deposit, located in the middle part of the Jiangda-Weixi volcanic arc Fe-Cu-Pb-Zn polymetallic metallogenic belt, is a skarn-hydrothermal polymetallic deposit related to the Guola complex intrusion.Zircon LA-ICP-MS U-Pb geochronology shows that the emplacement ages of the complex are 226.4±2.0 Ma and 36.59±0.22 Ma for the center (quartz monzonite) and the rim (quartz diorite porphyrite), respectively, suggesting that the complex represents the magmatic product of both Indosinian and Himalaya periods.The quartz monzonite as the center of complex has high SiO₂ (65.8%~68.5%) and low MgO (1.40%~2.17%) content and represents high-K calc-alkali series; High Sr and low Yb and Y content indicates its adakitic characteristics.The geochemical characteristics and comparisons indicate that it was probably derived directly from the bottom of the thickened crust, with source material similar to the composition of the eclogite instead of the melting product of subduction oceanic crust.The quartz diorite porphyrite in the rims has low SiO₂ (55.8%~56.6%) and high MgO (6.45%~7.50%), Cr (228×10^-6~353×10^-6), and Ni (72.3×10^-6~90.0×10^-6) values, indicating a typical high-magnesium diorite.Geochemical characteristics show that it is the product of melting of the lower crust at the depth of the mantle.This study has provided new geochronologic constraint for the evolution of the Jinshajiang Paleo-Tethys Ocean, and discovered the Himalayan magmatic activity in the Jiangda-Weixi arc belt, thus being of great significance to the genesis for the Hongponiuchang copper-gold deposit and the summary of the metallogenic regularity as well as the study of prospecting direction.