LA-ICP-MS U-Pb ages of detrital zircons from clastics of the undated fore-arc sedimentary unit (FAS) along the Shangdan Suture and the Middle-Upper Devonian Liuling Group in the South Qinling belt are used to establish the maximum depositional age and provenance of these tectonic units which were deposited on both sides of the Shangdan suture zone between the North China Block (NCB) and South China Block (SCB).The new data and geological evidence show that the FAS was deposited in a fore-arc basin with an exclusive source of the clastics in the North Qinling Belt (NQB).