Characteristics of the central uplift zone in Qiangtang Basin and its tectonic implications:Evidences from airborne gravity and magnetic data

Academia still has different opinions on whether there is a consecutive central uplift belt in the Qiangtang Basin.The latest high-precision airborne gravity and aeromagnetic data provided in this article verify the existence of the central uplift belt,which is controlled by two faults,traversing the Qiangtang Basin from east to west.A set of near-north-south left-lateral slip fault systems divide this uplift belt into several parts.The uplift belt,gradually converged from west to east,has obviously different characteristics between the east and west sides of Shuanghu County.The west section shows large-scale uplift of the basement,and the bedrock depth is generally within 3~5 km,which is much shallower than those in the North and South Qiangtang depression with the basement depth of 7~15 km.However,the uplift amplitude of the eastern segment decreases significantly,mainly manifested as a low base uplift.In addition,the central uplift belt shows obvious“multi-segments”and“step-like”decreasing trend from west to east,controlled by near-north-south faults.The basement depth of the Shuanghu-Yaqu section is between 5 and 7 km,and that of the Yaqu-Gonney section is between 7 and 9km.According to the structural stratification comparison,it is reveraled that the North Qiangtang Block has a smaller uplift amplitude and better stability than the South Qiangtang Block.The differences in geophysical properties of the basement between the North and South Qiangtang depression indicate that there is not an unified Precambrian metamorphic basement in the Qiangtang Basin,and the formation of the central uplift zone may be related to the melange zone formed during the closure of the Paleo-Tethys Ocean.