Sm-Nd and zircon U-Pb isotopic constraints on the age of formation of the precambrian crust in Southeast China

Abstract

Nd model ages (T DM) of the Pre-Mesozoic crustal rock samples from Southeast China range from 1.2 to 3.2 Ga. Two age peaks of 1.4 Ga and 1.8 Ga are observed in the histogram ofT DM model ages. Available U-Pb zircon inheritance ages are concentrated around 1.2–1.4 Ga, 1.8 Ga and 2.5 Ga, respectively. The combined use of Sm-Nd and U-Pb zircon inheritance ages suggests that the formation of the Precambrian crust is of episodic character. The oldest crustal nucleus may have been formed during the Late Archean (2.5 Ga or older?). A rapid production of the crust took place 1.8 Ga ago, consistent with the global crust formation event at 1.7–1.9 Ga. Another important episode of the addition of juvenile crustal material from the mantle in Southeast China took place 1.2–1.4 Ga ago, during which the pre-existing crust was strongly reworked and/or remelted.