Lithospheric Loading Model for Large Impact Basins Where a Mantle Plug Is Present

Abstract

AbstractCharacterizing the thermophysical properties of the lithosphere is critical for studying its evolution. We determine the elastic thickness of the lithosphere by modeling mass‐related loads and lithospheric deflection and analyzing gravity and topography data. In impact basins region where a mantle plug is present, the correlation between topography and gravity can be low, and the admittance can change quickly, making it difficult to develop accurate models without considering mantle uplift. In this study, we developed a lithospheric loading model for large impact basins that take advantage of a high‐resolution crustal thickness model and does not require the assuming compensation. Since the mantle uplift formed by super‐isostatic adjustment following the impact, the elastic thickness obtained by fitting the observed data reflects the lithospheric temperature at the end of the super‐isostatic process. Sensitivity analysis suggests that modeling the impact‐induced load is critical to reproduce how the mascon is expressed in the correlation and admittance data. Our mantle loading model provides a better fit to the observed admittance spectrum compared to previous research. The larger elastic thicknesses obtained for the Hellas basin indicate a longer duration of mascon formation or a faster cooling of the lithosphere. Models that consider a denser upper crust and an elastic thickness of about 0 km fit the observed admittance of the Utopia basin. The elastic thickness of the Argyre and Isidis basins cannot be precisely inferred without additional constraints on the load ratio.