ZIRCON UPb AGE OF THE NIUJIAOSHAN GRANITOID GNEISSES IN THE QINLING COMPLEX OF THE QINLING OROGENIC BELT—WITH A DISCUSSION OF ITS GEOLOGICAL SIGNIFICANCE

Geological characteristics of the Niujiaoshan granitoid gneisses in the Qinling core complex indicate that they are the oldest granitoid plutons recognized in the complex and can be viewd as pre or syntectonic plutons in the Jinning movement. Six groups of zircons with a good crystal form and little magnetism have been selected and dated as 959±3.6 Ma by UPb dating. This age has important implications for understanding the granitic magmatism in the Jinning movement, tectonic setting and age of regional deformations.