New Zircon U-Pb Ages of the Shirenshan Gneiss, North Qinling and Their Geological Implications

The Qinling Orogenic Belt(QOB)is a composite continental orogenic belt that has experienced many tectonic events.The QOB is subdivided into the following three litho-tectonic units:the North Qinling terrane,the Middle Qinling microplate and the South Qinling terrane.The North Qinling Terrane(NQT)underwent destruction and lithospheric thinning during the late Mesozoic,accompanied by extensive magmatic activity and increased surface heat flux,led to large-scale tectonic extension(e.g.,Ren Shenglian et al.,2016).The Shirenshan gneiss is located along the contact between the NQT and the North China Block(Fig.1).Previous studies suggested that it was produced as a result of the northward subduction of the NQT beneath the North China Block(e.g.,Wang Jingya et al.,2017).Therefore,it is significant to study its structural geology,petrology,geochemistry and chronology in order to understand the tectonic settings and the interaction between the Middle Qinling microplate and the North China Block.