North Qinling Luohansi Rock Group SHRIMP U-Pb Zircon Age and Its Tectonic Significance

The paper presents SHRIMP U-Pb dating results of zircon from south Luohansi group(the sedimentous wedge of forearc basin),cropping out from the north Qinling to Heihe River Xiaowangjian Huangcaoping.The age of crystal tuff obtained was 491±5 Ma.The obtained age indicates that this group is through Ordovician.Combined to granite belt of Caledonian stage widely grown in northern side of Shangdan belt,and the newest age information measured by predecessors in other places,the important evidence of isotopes chronology was offered to subduction of northern Qinling Paleozoic Oceanic basin and plate convergence.At the same time,the powerful evidence was provided to research subduction collision age of ophiolitic mixtite belt.