| 其他摘要 | The Bainiuchang super-large deposit, located in Mengzi county, Yunnan Province, China, is one of the biggest polymetallic deposits at Southeastern Yunnan, which is characterized by large scale Ag, Pb, Zn, Sn reserves with lots of dispersed elements (In, Cd, Ga,Ge, etc). It occurred geologically in the Middle Cambrian fine clastic-rock formations at the northwestern terminal of the Caledonian fold system in South China. Since the Bainiuchang deposit was found in late 1980’s, many prospecting and scientific research have been performed and rich economic benefit and scientific achievements were obtained, but it is debatable on the genesis and the relations between the deposit and the granite rocks, and further ore-prospecting work was restricted. Detailed studies on the regional geology, geochemistry and chronology of the Bozhushan granite and the Bainiuchang deposit have been carried out in this study, and ore-forming genesis was discussed, and a metallogenic model was proposed. The main conclusions are listed as follows: 1. Geology and geochemistry of the Bozhushan granite. The Bozhushan granite, dominated by biotite monzogranite, has a characteristic of silicon and alkaline enrichment, high-K, and low-Na content and belongs to peraluminous and calc-alkaline S-type granite. It enriched in Rb, Th, U, Ce and depleted in Sr, Ba, Nb, Hf and Y. Trace elements compositions and REE chondrite-normalized patterns of each unit have the same characteristics, which is suggested to be the same magmatic origin and evolution process. 2. U-Pb and Lu-Hf chronology of zircons from the Bozhushan granite U-Pb zircon dating of the Chenjiazhai sequence, Bozhushan sequence and Dashanjiao separate unit are (84.22±0.74) Ma-(88.1±0.66) Ma, (85.09±0.46) Ma- (87.42±0.64) Ma and (85.27±0.84) Ma, respectively. All consistent ages belong to Late Cretaceous and exclude the Himalayan period of magmatism |
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