During the implementation of the multi-element urban geological survey of Wuhan City,a shallow flesh red fine-grained biotite monzogranite was found to have intruded into the metamorphic rocks of Shuangtai Formation of Nan-hua System in a borehole in the northern part of Changjiang New Town.By studying its isotopic chronology and elemental balloon chemistry,the early Cretaceous tectonic background in the area north of the Changjiang New Town was explored.The rock mass has high SiO2,Sr and Sr/Y ratios,low CaO,MgO,Fe2O3,Y and Yb,and Eu positive anomalies,making it a typical adakite rock.No large-scale basic magmatic rocks coexisting with them during the same period were found in field investigations and surrounding boreholes,enriched in light rare earth elements and large ion lithophile elements,and depleted in high field strength elements(Nb,Ta,P,Ti),which may have been formed by partial melting of thickened lower crustal materials.The zircon U-Pb age of the rock mass is(128.3±0.6)Ma,indicating that it was formed in the Early Cretaceous.The rock mass has similar geochemical properties to the Qijianfeng rock mass in northern Hubei,indi-cating that the area north of the Changjiang New Town on the southern edge of the Dabie orogenic belt underwent a tran-sition from a collision compression tectonic system to a post collision extension tectonic system during the Early Creta-ceous(approximately 128 Ma).
adakitic granitezircon U-Pb agemulti factor urban geological surveyChangjiang New Town
万方数据
维普
