Abstract:

In order to study the source of sediments from Lancang River and the crustal growth history of adjacent block，Lancang River’s detrital zircons were measured for U-Pb ages and Hf isotopic composition by LA-MC-ICP-MS. The detrital zircon U-Pb ages show 5 populations including＜177 Ma，201-418 Ma，428-544 Ma，581-1,189 Ma and 1,406-2,533 Ma.The peak ages are 260 Ma，788 Ma，1,827 Ma and 2,474Ma.The detrital zircon U-Pb age distribution of sediments from the Lancang River is consistent with those of the North Qiangtang Block，which indicates dominant contribution of material from the North Qiangtang Block to the Lancang River. The detrital zircon U-Pb ages and Hf isotopic composition of the Lancang River’s sediments may reflect the formation and evolution history of the North Qiangtang Block. The period from Neoarchean to Mesoproterozoic is the continuous stage of crustal growth from the depleted mantle in the North Qiangtang Block，which accounts for more than 78% of the whole crust; until 0.64 Ga，the crustal growth of North Qiangtang block have mainly completed.

Key words: Lancang River, detrital zircon, U-Pb, Hf isotope, North Qiangtang Block, formation and evolution of crust