Hornblende and biotite ~(40) Ar /~(39) Ar ages of the Yeniuquan quartz diorite and dacite-porphyry in the East Kunlun orogenic belt,Xinjiang

Ar- 39 Ar dating on of hornblende from the Yeniuquan quartz-diorite and biotite from the Ye-niuquan dacite-porphyry exposed in the diorite-granodiorite belt in the Luoyanshan-Arka Mountain area,East Kunlun Mountains ,Xinjiang,gave a hornblende plateau age of (219±1.4)Ma and an isochron age of (220±11)Ma and a biotite plateau age of (218.59±0.94)Ma and an isochron age of (226±11)Ma ,indicating a Late Triassic age.As they have the petrological and geochemical characteristics of arc intrusions ,the age determination is of great significance for the study of the tectonic evolution of the South Kunlun orogenic belt marked by the occurrence of the Muztag-Jingyuhu ophiolitic melange belt.