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Abstract

The aim of this research is to analyze the variations of the shallow thermal field across two volcanic continental passive margins contrasting in the breakup age; the Southwest (SW) African margin and the Norwegian margin. The SW African passive margin is significantly (around 75 Ma) older than the Norwegian. By comparing these two differently aged passive volcanic margins, we test the hypothesis if the present-day thermal field is different for the two settings. In this regard, we consider two previously published 3D lithospheric-scale and conductive thermal models for the SW African and the Norwegian passive margins. To compare these thermal models, we respect the surface of the upper thermal boundary as a reference surface for the both models and subsequently extract the temperature-depth distribution in a certain depth (1 km) interval down to 6 km below the upper thermal boundary surface. Finally, we calculate the geothermal gradient for the two settings at 1, 2, 3, 4, 5 and 6 km below the surface of the upper thermal boundary. We interpret the geothermal gradient variations concerning the 3D geological structural models to show how radiogenic heat production, sediment thermal blanketing, and the Lithosphere-Asthenosphere Boundary (LAB) depth play the major roles in the shallow thermal field pattern. Our results indicate that the shallow thermal field con-siderably differs comparing the two margins. In the Nor-wegian margin, the thermal field is mostly dominated by the lithosphere age. In contrast, over the SW African passive margin, the crustal configuration is dominating the pattern of the equilibrated shallow thermal field.