闽东南及邻区重力异常特征及其对地壳深部热背景的启示OA北大核心CSTPCD

The crustal structure of Southeast Fujian has been strongly modified by the collision and subduction of the paleo⁃Pacific Plate on the Eurasian continent since the Mesozoic era,and the development of fractures and extensive magmatic activities in the region have resulted in the rich geothermal resources in the region nowadays.To better study the crustal structure and deep thermal background characteristics of Southeast Fujian,based on the newly published global high⁃resolution earth gravity field model V32.1,the bouguer gravity anomalies of Southeast Fujian and the neighboring areas are calculated by using the gravity forwarding method.Then,the seismic data is used as constraints to obtain the optimal average depth for Moho surface inversion in this region.Finally,the Moho surface depth distribution in the study area is obtained by means of gravity field separation and interface inversion.The results show that the depth of the Moho surface in the study area ranges from 25 km to 32.5 km,and the continental and oceanic regions are roughly bounded by 28 km,with an increasing trend from the southeast to the northwest,which is basically consistent with the previous results,but the Moho surface shows localized uplift in some local areas(e.g.,Zhangzhou Basin).The short⁃wavelength part(20～100 km)of the Bouguer gravity anomaly shows good correspondence with the fracture zones in the region,and under the control of a series of NE and NW⁃trending fracture zones,it displays block⁃like features consistent with the tectonic of"east⁃west zoning,north⁃south blocking".Further linear identification reveals that the linear features in the deep crust are mainly NE⁃oriented,and the Fuan⁃Nanjing fracture zone cuts deeper into the crust than the Zhenghe⁃Dapu rupture,probably reaching the deep middle and lower crust.The local high values of geothermal heat flow mainly appear near the Moho uplift and the deep fracture zone indicated by gravity anomalies,which indicates that the abundant geothermal resources in Southeast Fujian are closely related to the crustal structure of the region,and that the relatively thin crustal thickness(Moho uplift)forms a locally high geothermal temperature field,whereas the deep fracture zone overlying the Moho uplift provides a good channel for the upward transport of the deep heat source.