Cu-Au Mineralization of Adakite Belt in the Eastern Section of the North Qilian

The adakite belt in the eastern section of the North Qilian Mountains was derived from the partial melting of the northwards subducted oceanic crust of the Laohushan back-arc basin.The melting process had the features of high temperature,high pressure,abundant fluids,abundant oxygen and rapidly ascending rate,which were beneficial for copper and gold to concent rate in adakitic magma.Many Cu-Au ore deposits found in Mijiashan,Bianqianggou,Yindongliang adakite body and Precam brian strata in Xihuashan indicate that the Cu-Au ore deposits could be formed in the adakite belt.Not only porphyry and hydrothermal alteration Cu-Au ore deposits but also sandstone-type Cu-Au ore deposits are in the belt.Four-box model can be used to describe the formation processes and types of the deposits.The adakite body and the wall rock should be the main prospecting targets.Meanwhile,the Devonian sedimentary should be prospected firstly for sandst one-type Cu-Au ore deposits.