Surface heat flow and lithosphere thermal structure of the Rhenohercynian Zone in the greater Luxembourg region

Abstract

Comprehensive knowledge of surface heat flow and subsurface temperature distribution is indispensable for the interpretation and quantification of crustal/mantle processes as well as for the evaluation of the geothermal potential of an area. In cases where subsurface temperature data are sparse, thermal modeling may be used as a tool for inferring the geothermal resource at depth but requires profound structural, geological, and petrophysical input data. The study area encompasses the Trier–Luxembourg Basin and the western realm of the Rhenish Massif, itself subdivided into the Ardennes region in the west as well as the Eifel and Hunsrück regions in the east. For the study area, 2-D steady-state and conductive thermal models were established based on geological models of lithosphere-scale which were parameterized using thermal rock properties including thermal conductivity, radiogenic heat production, and density. The thermal models are constrained by surface heat flow (qs) and the geophysically-estimated depth of the lithosphere–asthenosphere boundary (LAB). A qs of 75±7 (2σ)mWm−2 was determined in the area. A LAB depth of 100km, as seismically derived for the Ardennes, provides the best fit with the measured qs. Modeled temperatures are in the range of 120–125°C at 5km depth and of 600–650°C at the Moho, respectively. The mantle heat flow amounts to ∼40mWm−2. Possible thermal consequences of the 10–20Ma old Eifel plume, which caused elevation of the LAB to 50–60km depth, were modeled in a steady-state thermal scenario resulting in a qs of 91mWm−2 in the Eifel region. Available qs values (65–80mWm−2) are significantly lower and do indicate that the plume-related heating has not yet reached the surface in its entirety.