Three-dimensional density structure and geological significance of uppermost mantle beneath the southwestern South China Block
The South China Block has experienced various stages of tectonic-magmatic activity since the Neoproterozoic collision.The lithosphere and deep structure appear to be relatively complex.The location of the suture zone at the southwestern margin between the Yangtze and Cathaysia blocks remains controversial.The density structure of the uppermost mantle can improve our understanding of the lithosphere transformation after the collision of the Yangtze and Cathaysia blocks.Furthermore,it is crucial to locate the suture zone in Guangxi area.We conduct an inversion of the residual gravity anomalies of the lithosphere and uppermost mantle derived from the satellite Bouguer gravity anomaly.The upper mantle density reference model that serves as a constraint for inversion is created by employing the seismic wave velocity-density conversion relationship.We obtain a three-dimensional density structure of the uppermost mantle from the lithosphere to a depth of 300 km.The density structure reveals the undulation of the lithosphere-asthenosphere boundary according to the distribution of density anomalies in the southwestern part of the South China Block.Our results suggest that the high-density lithospheric material is removed in the central area of Guangxi and the low-density asthenospheric material upwells in the south,replacing the delaminated lithospheric roots and penetrating them upwards into the crust,and consequently forming the granite exposed at the surface.With the characteristics of the basement and the terrestrial margin source of detrital zircons,we infer that the suture zone of the Yangtze and Cathaysian blocks in the southwestern South China block(Guangxi section)is along the Fuchuan-Wuxuan-Long'an-Pingxiang line.
Southwestern South China BlockUppermost mantleDensity structureThree-dimensional inversion of gravity anomaly
万方数据
维普
