Ancient heat flow, crustal thickness, and lithospheric mantle rheology in the Amenthes region, Mars

Abstract

Surface heat flow calculations for the Amenthes region of Mars can be independently performed using the depth to the brittle–ductile transition and the effective elastic thickness of the lithosphere estimated for the Late Noachian/Early Hesperian (equivalent to an estimated absolute age of ~3.6–3.8 Ga). This, along with crustal heat production rates estimated from heat-producing elements abundances, permits us to put constraints, for that particular place and time, on both the thermal and mechanical properties of the lithosphere and the crustal thickness. The depth to the brittle– ductile transition deduced from modeling of the topography of Amenthes Rupes is 27–35 km, and the associated surface heat flow is 26–37 mWm−2. On the other hand, the effective elastic thickness in this region is between 19 and 35 km: the surface heat flow deduced by considering crustal and lithospheric mantle contributions to the total lithospheric strength, as well as wet or dry olivine for lithospheric mantle rheology, is 31–49mWm−2. The relatively limited overlap among Te- andzBDT-based heat flowvalues implies a surface heat flowof 31–36mWm−2 (with a high fraction originated from crustal heat sources) and awet mantle rheology. The so obtained local crustal thickness is 43–74 km,which suggests an average thickness of~40–75 km for the Martian crust; for the frequently used crustal density of 2900 kgm−3, our results suggest a crustal thickness of 50–63km for theAmenthes region, and an average crustal thickness of ~45–65 km for Mars.