Normalized Full Gradient of Gravity Anomaly Method and Its Application to the Mobrun Sulfide Body, Canada

Abstract

Abstract: Gravity anomalies are sensitive to variations in size, depth and composition of anomalous sources. A suitable approach to detect and estimate spatial locations and depth is the Normalized Full Gradient (NFG) method. The NFG in cross-section or maps manifest clearly the depth of the centers or top of the anomalous bodies at certain harmonic numbers. The obtained results from synthetic data, with and without random noise, show closed maxima on an NFG map that indicate the spatial locations of the centers and depth of the causative bodies. Modeling studies show that the estimated depth largely depends on the harmonic number used to calculate the NFG, which are closely related to the profile lengths and gravity griding intervals. In this study, the NFG method is applied to Mobrun sulfide body in Canada for estimating the depth to the top of it. The NFG closed maxima alongside the borehole data, shows that the Mobrun ore body is located in shallow depths, about 17 meters and extended to 175 meters, approximately. Key words: Gravity • Analytical downward continuation • Normalized full gradient (NFG) • Synthetic gravity model • Mobrun sulfide body