关键词: 台湾造山带, 台北盆地, 火成活动, 冷却收缩

Abstract: The Taipei Basin is located in the northern part of the Taiwan Orogen. Although this extensional basin was developed in an active orogen,it has peculiar formation mechanism different from that of basins resulted from the collapse of orogen in general sense. However,little attention has been paid to this peculiarity in previous studies,so that the problem concerning the formation of the Taipei Basin has evoked much controversy. Recently,bore holes and seismic prospecting data have revealed that the Shanjiao Fault,which has controlled the formation of the basin,consists of 3 segments,rather than a fault. Each segment controlled one center of subsidence,and has not connected with the other segments. The activity of different segments is not uniform,and it becomes stronger with time toward northeast. At present,the strongest activity is concentrated on the middle and northern segments,while the southern segment is no longer active. A series of NW-trending faults in the basin are the secondary structures produced during the subsidence of the different subsidence centers. There are a series of volcanoes that had erupted around the basin,so the formation of the basin should be affected by magmatic activities around the basin. Because the development of the basin treaded on the heels of these volcanic activities,there were essential relationship between the formation of the basin and the volcanic activities around the basin. Geophysical data,the structural characteristics and the migration of depocenter have shown that the development of the Taipei Basin was resulted from the cooling and contraction of the magma body at depth. The magma body beneath the Taipei Basin is connected with the magma body beneath the Tatun volcanic cluster,and the cooling of the magma has migrated from southwest to northeast. Moreover,the Tatun volcanic cluster is currently in its stage of subsidence,so the formation of the Taipei Basin was not an independent phenomenon. Both the Taipei Basin and Tatun volcanic cluster belong to one larger extensional basin.

Key words: Taiwan orogen, Taipei Basin, magma activity, cooling and contraction