Metallogenic Regularity, Exploration And Evaluation Of Porphyry Copper Deposits In Zhongdian Area, Yunnan

"Sanjinag"metallogenic belt is famous of its unique geological landscape and abundant mineral resources. Zhongdian area (27°41'-28°32'N, 99°40'-100°15'E), located in the southern of Yidun island arc, is a ore deposit concentration area. The island arc had undergone the evolution of subduction orogeny, collision orogeny, post-orogenic extensional, tectonic evolution of strike-slip shear transformation orogeny and so on. Zhongdian area is a Indosinian intermediate-acid porphyry (porphyrite) concentrated area. In recent years, we have found a lot of porphyry copper deposits in this ore deposit concentration area.In this text, we point that a proposed regional metallogenic system is composed of island arc (structural) evolution, island arc volcanic-sedimentary construction and intermediate-acid magmatic activity thought a systemic study of geology background of intermediate-acid porphyry (porphyrite), petromineralogy and geochemistry. The Indosinian high-level intermediate-acid magma is the closed with metallogenesis of porphyry copper, which can form different types of porphyry copper deposits series in different conditions and different parts. Based on the study of regional metallogenic regularity and the typical deposit, we point the mineralization process of porphyry copper deposits is intermediate→intermediate-acid→acid→slight alkaline of comagmatic evolution. The mineralization model is deep fault→comagmatic evolution→magma+structure+hydrothermal alteration→cosed condition of surrounding rocks. And then, a new position and forecast of mineralized porphyry body and effective combination of technology and methods for prospecting can be studied in this text. These methods are applied to practice in prospecting in Zhongdian area and a series of results have been got in Lannitang, Langdu, Chundu, Gaochiping.The following aspects are the innovative results of this paper obtained:1. In the study area, we find anhydrite and magnetite in V1-3 ore body and drill core of ZK3-5 of Lannitang porphyry copper deposit (other deposits have not yet found or reported in this area). The content of anhydrite has a strong correlation with copper grade. We prove intuitively the original magma of porphyry copper deposits are oxidized, which is conducive to the formation of porphyry copper deposits. We propose that Lannitang porphyry copper deposit is a gold-rich porphyry copper deposit formed in high oxygen fugacity conditions.2. Stream sediment geochemical anomalies analysis showed that Indosinian porphyry mineralization system can form Cu-Ag-Sn-Bi mantle derived elements and Yanshanian granite molybdenum mineralization system can produce W-Mo-U crustal derived anomalies elements.3. Porphyry copper system will produce significant magnetic anomalies. Aerospace precision magnetic survey results is the most important evidence for forecasting the constituency of metal deposits.4. Clear the function and status of interdisciplinary approach on evaluation of mineral resources in Zhongdian Area, and then comprehensively analyze, delineate prospecting targets and organize resources exploration and evaluation.