Geological evolution and metallogenesis of the Geza copper polymetallic mineral concentration district,Shangri-La,Southwest Yunnan

The Geza mineral concentration district, which is of more than 50 polymetallic Cu-Mo-Au-W deposits, is located at the junctional areas of the southern Yidun-Shaluli arc-basin of Gantze-Litang tectonic system and the Lijiang continental marginal rift basin in Shangri-La area, southwest Yunnan. In this paper, the relationship between the regional geological evolution and the metallization of polymetallic deposits, especially the relationship between the tectonic evolution and the stratigraphic texture, magmatism, metamorphism, and mineralization, is discussed in detail. The mineralization in study area is characterized by multi-phases, related to the subduction and the closure of the Paleo-Tethys from Permian to Late Triassic and the long term orogenesis from the end of Triassic to Paleogene, i.e. the ocean-continent transition period (P-T₃) and the intracontinental evolution period (J-K-E). The geological evolution in study areas could be further divided into four stages: (1) the evolution stage of the Gantze-Litang oceanic basin (P-T₂), (2) the subduction and collisional orogeny stage of the Gantze-Litang oceanic basin (T₃), (3) the Cretaceous intracontinental extension stage (K), and (4) the Paleogene intracontinental extension and strike-slip stage (N-Q). Three magmatic events, which are the Late Indosinian (221~199 Ma), the Late Yanshanian (88~77 Ma), and the Early Himalayan (50~28 Ma), are closely related to the metallogenesis in study area, respectively. It is suggested that the deeper and outer sections of the ore-forming intrusions are potential for ore prospecting in Geza area in the future.