Lithospheric Structure of Venusian Crustal Plateaus

TL;DR

This study investigates the lithospheric structure of Venusian crustal plateaus using gravity and topography data, revealing that most are supported by crustal thickening with low elastic thickness, and providing insights into their formation and heat flow conditions.

Contribution

It offers the first comprehensive analysis of Venusian crustal plateaus' lithospheric support mechanisms using admittance modeling and compares different isostatic and flexural scenarios.

Findings

Most plateaus are supported by crustal thickening.

Elastic thickness is less than 35 km, averaging around 15 km.

Global Venus crustal thickness estimated at about 20 km.

Abstract

Crustal plateaus are Venusian highlands characterized by tectonized terrains. It is commonly interpreted that their topography is isostatically supported and that they represent fossils of an extinct tectonic regime. Using gravity and topography we perform a comprehensive investigation of the lithospheric structure of six crustal plateaus. We computed the admittance (gravity to topography wavelength-dependent ratio) for each region and compared them to modeled admittances. Three compensation scenarios were tested: Airy isostasy, a surface-loading flexural model, and a flexural model with surface and subsurface loads. Our results show that the topography of most plateaus is supported by crustal thickening and that the addition of a mantle support component is not necessary at the investigated wavelengths. The elastic thickness was constrained to be less than 35 km with a best-fitting average of 15 km, confirming that these regions are consistent with an isostatic regime. The average crustal thickness of the plateaus ranges from 15 to 34 km, and if they are in Airy isostasy, this implies that the global average crustal thickness of Venus is about 20 km. Phoebe Regio is the sole exception of our analysis in that crustal thicknesses that are compatible with the other plateaus are obtained only when a buoyant layer is included. Heat flow estimations computed from the elastic thickness indicate that the plateaus formed under higher heat flow conditions compared to the current global average and could have caused localized melting. Present-day heat flow predictions suggest that eclogitization could occur where the crust is thickest.