Age of the Granitoid Pluton from Nanjiao,Zhoukoudian,Beijing and Its Geological Implication

Magmatic zircons in two samples of quartz monzonite pluton from southern Nanjiao,Zhoukoudian,Beijing,were analysed using LA-ICP-MS technique,yielding206Pb/238U ages of(133.0+2.0/-5.0) Ma and(134.0+1.0/-5.0) Ma,with weighted average age of(134.0+1.0/-2.0) Ma.This provides constraints that the quartz monzonite granitoid is of the late Yanshanian intrusion,and that the slip structure along the parallel unconformity of the Carboniferous on the Ordovician strata should have occurred no later than ~134 Ma.The quartz monzonite plutons in the Najiao area intruded at the peak of lithosphere destruction of the northeastern China.