The 3-D Density Structure of the Large Shield Volcanic Structure in the Gardner Region Revealed by a New Gravity Inversion

Abstract

The Gardner region is a well-known shield volcanic complex on the Moon. Its magma origin and formation mechanism are of significant interest but still enigmatic. To reveal the subsurface structure of this volcanic complex, we propose a new 3-D inversion method of the gravity field based on the regularizations of the L1 norm of the model and its gradients. The model test indicates that our proposed method can recover the density structures with high resolution. Subsequently, we apply it to the Bouguer gravity data in the Gardner region. Our result shows a large, dense body with a volume of about 45 × 45 × 13 km3 centered under the topographic bulge of the Gardner Plateau. We infer that this structure is most likely dense basalts trapped at the crust-mantle boundary as a sill and acted as the magma reservoir that has fed the volcanic complex in the Gardner area.