Hadean detrital zircon in the North China Craton

Abstract

Due to a lack of rock samples from the Hadean Eon, the Hadean zircons have become an important means of understanding the Earth's earliest history. This study reports the occurrence of a Hadean detrital zircon with a concordia U-Pb age of 4081 ± 71 Ma and 207Pb/206Pb age of 4087 ± 31 Ma from the Paleoproterozoic metasedimentary rocks in the Jiao-Liao-Ji Belt (JLJB) in the North China Craton. The analyzed zircon grain exhibits low luminescence and striped absorption and has relatively high Th/U ratio (0.37), all suggesting an igneous origin. It is euhedral with length/width ratios of 3:2, implying a short distance of transportation from its source. The Hadean age is ∼ 570 million years older than the oldest zircon previously identified in the JLJB. This further demonstrates the existence of a Hadean continental crustal remnant in the North China Craton. In addition, to our knowledge, it is the first case of a Hadean zircon being recognized in the Paleoproterozoic sediments on Earth. The documentation of a 4.09 Ga detrital zircon not only provides a geochronological record of the oldest known crustal materials in the JLJB, but also identifies the geological environment for further exploration for the Hadean zircons or even the Hadean rocks.