The discovery of Hadean detrital zircon in Late Devonian strata in Hexi Corridor, Northwest China

Two detrital zircons with the age of 3.9Ga and 4.0Ga have been dated from Late Devonian strata in Hexi Corridor by LA-ICP-MS method. They are both magmatic zircons and the Th/U ratios are 1.01 and 0.58 respectively. Both zircons are enriched in heavy REE (HREE) compared to light REE (LREE) and show a distinctive positive Ce. The 4.0Ga zircon is with negative Eu while the 3.9Ga zircon without negative Eu. Using the geothennometer-Ti-49 content of zircon, we calculated magmatic temperatures that were 792 36 C (3.9Ga) and 967 45 C (4.OGa) respectively. The 3.9Ga zircon was analyzed for Hf-isotope Hf-176/Hf-177(i) = 0.280169, epsilon(Hf)(t) = -3. 6, t(DM) =4139Ma, t(DM)(C) =4319Ma. It is the first report of the >3.9Ga zircons in Northwest China. The trace element characteristics of the zircons prove that the crust may exist on earth in the Hadean. Further, Combined with previous paleontological and paleomagnetic results, these results indicate that the Hexi Corridor might have the affinity with northwestern Australia in the Late Devonian.