Lead isotope composition and constraints on origin of Dafulou ore deposit, Guangxi, China
(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals,Ministry of Education, Central South University, Changsha 410083, China;2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;3. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry,Chinese Academy of Sciences, Guiyang 550002, China)
Abstract: To discuss the material source and tectonic setting, the lead isotope composition was analyzed based on the samples from the latest tunnel of the Dafulou deposit. The lead isotope values are 17.478-18.431, 15.440-15.717, and 37.556-38.839 for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, respectively. The values of Φ, μ, and Th/U are 0.592-0.638, 9.26-9.69 and 3.74-3.97. By comparing the lead isotope composition of the different ore belts, it indicates that the lead source of the west belt may be more single than the other ore belts. The lead isotope value in the middle and east belts are the maximum and minimum, respectively. In the Dachang ore district, the lead sources are comprised of the upper crust lead, the mixed crust and mantle subduction zone lead and the orogenic lead. The tectonic distinguish model suggests that the ore lead derived from both the mantle and crust. And, the upper crust and magmatism played an important role during the mineralization. The orogenesis also supplied a minority of ore lead. The ore deposit should be the result of the crust-mantle interaction and maybe had been formed in the orogenic environment.
Key words: Pb isotope; ore source; tectonic setting; Dafulou; Dachang ore field