The application of large and medium scale gravity measurement to the Gaoer Banner half-concealed Ag-Pb-Zn polymetallic deposit,Inner Mongoli

Gravity survey has been carried out in the basalt overburden area of the Gaoer Banner half-concealed Ag-Pb-Zn polymetallic deposit,Inner Mongolia. In residual gravity anomaly map of 1 : 50000,the Gaoer Banner ore deposit is located at the distortions of the negative gravity anomaly contour line in the contact zone of alternate positive and negative anomalies. Results of 1 : 10000 gravity sur-vey,IP and geochemical soil measurement show that orebodies correspond to nearly east-west banded apparent chargeability anomalies, and Ag-Pb-Zn polymetallic anomalies correspond to the variable area of high and low resistivity anomalies. The north of the orebody is characterized by negative residual gravity and low resistance,while the south of the orebody shows positive residual gravity and high re-sistance. Negative residual gravity in the north results from the concealed rock mass(Carboniferous granite)with low density,low re-sistance related to east-west tectonic fracture zone and the stockwork vein in it. Positive residual gravity is associated with Niqiuhe For-mation. Sandstone with high density and high resistance results from fine-grained feldspar quartz sandstone and siltstone of Niqiuhe For-mation. The fine-grained feldspar quartz sandstone and siltstone block and ore fluid migration probably resulted in deposit formation in the structural fracture zone on the northern side.Large scale gravity survey,electrical measurements and geochemical soil survey are not only important geophysical basis for the study of metallogenic environment,but also provide important information for orebody location.