Geochemical Characteristics And Genesis Of Magmatic Rocks For Duolong Ore Concentrated Area In Tibet

Bangong Lake- Nujiang belt is newly discovered copper polymetallic metallogenic belt in northern Tibet in recent years.Duolong ore concentration area is located in this metallogenic belt.The deposit received a matter of great concern of many geologists for the large metallogenic scale and the complex formation of porphyry-epithermal deposits. Based on the comparative study of geological features of the ore deposits in the ore concentration area and the geological characteristics of the deposit, geochemical characteristics of rocks, the diagenetic and metallogenic chronology, the structural background and related problems of diagenetic and mineralization, and combined with field survey, laboratory-test and comprehensive collection of previous research data, this thesis has new understanding of the geological features, the geochemical characteristics of magmatic rocks, the genesis of magmatic rocks of Duolong ore concentration area. Finally, I finished this thesis.The main ore bearing strata are the lower jurassic Quse formation and the lower-middle jurassic Sewa formation in Duolong ore concentration area. mainly magmatite related mineralization is intermediate acidic intrusive rocks, such as granodiorite-porphyry, quartz-diorite-porphyry and granite-porphyry and so on. Geochemistry and petrochemistry of magmatic rocks in the study area with high-k-shoshonite series, Quasi-peraluminous aluminum, Alkaline-calc-alkaline magma characteristics, enrichment of light rare earth and rocks, has a weak Eu negative anomaly, enrichment of LILE element, losses of HFSE element, Displays the characteristics of arc magmas. Different index show that it is happened more fully magmatic crystallization differentiationIn the process of the formation rock.Sr-Nd-Pb-Hf isotopic data shows that the magma is mainly formed in the juvenile crust, and is mixed with mantle derived magma. The average age is 116.15±0.98Ma(MSWD=0.53,n=21)of ZK0701 granite porphyry zircon U-Pb using the LA-ICP-MS method in the thesis. it represent the formation age of the granite porphyry body.The U-Pb ages ranged from 112.5 to 128.67 Ma in ore concentrated area, magmatic activity is more concentrated. That may be the product of one period of magmatic activity. The zircon Ti thermometer calculation showed that crystallization temperature of zircon is between 671.1and 756.6?, The average temperature is 708.9?.It is showed that the porphyry magma in the study area is the origin of the medium temperature. Metal sulfide S-Pb isotope displayed minerals with a mixture of crust and mantle source characteristics; Re element in molybdenite display the minerogenic material originates from mantle. It is possible that some mantle derived ore-forming materials in the process of fluid replacement of mantle wedge are brought into mineralization along with the rising of magma. which also includes crust-derived metallogenic material.Comprehensive study shows that a variety of geochemical data reveal that the acidic magma is mainly formed in the juvenile crust, at the same time, with the addition of mantle derived magma. metallogenic background from the perspective of rocktrace elements, zircon trace elements showed that the formation of rocks and mineralization occurs in the continental margin arc environment, Eventually the diagenetic model was structured.