Results of applying Euler deconvolution and finite-difference Euler deconvolution with a window size of 12 000 m and a window step of 2400 m to the aeromagnetic data from Rio de Janeiro, Brazil. (a–c) Euler deconvolution results with structural index |$\eta =1$|⁠, |$\eta =2$| and |$\eta =3$|⁠, respectively. (d) Finite-difference Euler deconvolution results. The structural index of the solutions are represented by pentagons (⁠|$\eta =-1$|⁠), diamonds (⁠|$\eta =0$|⁠), triangles (⁠|$\eta =1$|⁠), squares (⁠|$\eta =2$|⁠) and circles (⁠|$\eta =3$|⁠). For finite-difference Euler deconvolution, the structural index symbol is that of the closest integer to the estimated value. The colour of each symbol represents the estimated depth below the surface of the Earth (topography). Also shown are the total-field anomaly flight-line data, the contours of the post-collisional magmatism and alkaline intrusions (solid black lines) and dykes (dashed lines).