LATE TRIASSIC ORE-CONTROLLING STRUCTURES OF PULANG PORPHYRY COPPER DEPOSIT IN YUNNAN PROVINCE

Pulang copper deposit is of a super-large porphyry type in the eastern Yidun island arc polymetallic ore belt with frequent tectonic magmatic activities and significant superposition of fissure structure and ore forming-ore controlling conditions. However, the research degree is weak. Based on the comprehensive study of tectonic petrography of tunnels in Pulang copper orefield, combined with the regional metallogenic tectonic setting, the paper determines the macroscopic characteristics of folds and faults, and analyzes the joints/fissures in the typical levels. The results show that the mineralization of porphyry copper deposit during the closure of Paleo-Tethys Ocean is closely related to the Late Triassic tectonic evolution and magmatic activity, with Pulang copper deposit formed in subduction orogeny stage. The regional deep faults control the sedimentary formation and magmatite distribution in the orefield. The depositis is generally occurred in the core of Pulang antiform. The secondary NEE- and NE-trending faults control the development of ore-bearing porphyry and joints/fissures, while the ore/mineralized bodies occur at the junction of two groups of faults. The tension joint-dominated compound joint system provides passage and storage space for ore-bearing hydrothermal fluid migration, diffusion and enrichment. The development degree of fissures is positively correlated with copper mineralization. By studying the characteristics of magmatic intrusion-tectonic fissure system and ore-controlling rule in the orefield, it is considered that the hydrothermal vein ore/mineralized bodies are strictly controlled by the reformation and enrichment of tectonic and fissure system, and the site where fissure structure is well-developed is favorable target for vein ore prospecting.