The discovery and significance of the Middle Permian adakites along the Huandong River north of the Xijir Ulan Lake,Qinghai

The Middle Permian adakites were recognized during the geological surveys in 2000-2002 along the Huandong River in the western part of the Xijir Ulan-Jinshajiang suture zone in Qinghai. This kind of rocks is represented by diorites,and similar in chemical composition to the type I adakites,which maybe resulted from the melting of the subducted oceanic crust. Tectonically,the adakites in the study area are confined to the Xijir Ulan section of the Xijir Ulan-Jinshajiang suture zone,implying that the Xijir Ulan oceanic slab was once subducted southwards. The adakites are often closely associated with hydrothermal and porphyry ore deposits such as gold,silver,copper and molybdenum deposits. The copper and gold mineral resources also abound in the eastern part of the suture zone. The discovery may provide a theoretical basis for the prospecting and exploration of the above-mentioned mineral resources in the western part of the suture zone.