Density imaging is a method of inverting the sub-surface density
distribution according to the spectrum of the gravity and gravity
gradient in the wavenumber domain. This method effectively gives full
play to the characteristics of fast calculation in the wavenumber
domain, improves the computation efficiency, and creates an accurate 3D
sub-surface density model. In this paper, the corresponding relation
between the gravity and gravity gradient anomalies and the model, and
their spectral characteristics were analyzed, which according to
preliminary inverse. Then, the 3D density imaging of gravity and gravity
gradient was performed on the theoretical data and its noise-added data
in the wavenumber domain with depth weighing, and a density model
consistent with the theoretical model was obtained. The strong
anti-noise capacity of the density imaging method was proved. Finally,
the method was verified in the Decorah area of the United States, and
the characteristics of gravity and gravity gradient anomalies measured
in this area were analyzed, and the 3D density imaging of gravity and
gravity gradient was performed in the wavenumber domain. The location of
the siliceous intrusive rocks with the relatively low-density and the
Decorah complex with the relatively high-density, and the intrusive rock
mass with the relatively highdensity distributed in the surrounding rock
were obtained through inversion. A clear understanding of the intrusive
pathways to the rock mass was obtained, and the effectiveness of the
density imaging method has been verified. This provides support for
further understanding of the structural division and geological
evolution in this area.