Mid-paleozoic collision in the north Qinling: Sm-Nd, Rb-Sr and 40Ar/39Ar ages and their tectonic implications

Different isotopic geochronometers have been used to study the nature of the mid-Paleozoic tectonothermal event in the North Qinling arc system at the southern margin of the North China Block. 40Ar/39Ar age of amphibole front sample QH-3 (426 +/- 2 Ma), Rb-Sr mineral isochron age (411 +/- 5 Ma) of sample QSP-10 of the Danfeng Group and Rb-Sr whole rock isochron age (406 +/- 22 Ma) of a greenschist facies pillow lava sample of the Erlangping Group indicate a widespread Late Silurian tectonothermal event in the North Qinling area. The data also suggest a limited uplift in the North Qinling during the Late Silurian tectonothermal event. This event is restricted to the North Qinling area and the southern margin of North China Block, and not observed in the South Qinling belt and the northern margin of the South China Block. Consequently, it is related to the collision between the North China Block and a North Qinling arc system, which resulted in the closure of the North Qinling back-arc basin(s). (C) 2002 Elsevier Science Ltd. All rights reserved.