Heat flow evolution, subsidence and erosion in the Rheno-Hercynian orogenic wedge of central Europe

Abstract

AbstractNumerical, thermal and rheological modelling techniques are applied to unravel the basin-forming processes and the heat flow and burial history of the Rheno-Hercynian fold belt (Rhenish Massif), the adjacent Subvariscan foreland (Ruhr Basin), and the intramontane Saar-Nahe Basin. Thermal history and crustal architecture in the study areas were affected mainly by the Variscan Orogeny during late Palaeozoic times. Calibration of the simulated thermal histories is primarily based on vitrinite reflectance and fission-track data. Mechanical modelling reveals averageβvalues of 1.7, reaching a maximum of 2.4 in the central basin (Mosel Graben) and at the transition to the Giessen Ocean to the south during Early Devonian rifting. This stage was associated with tholeitic magmatism and an elevated heat flow of up to 110 mW m−2, preserved in weakly overprinted syn-rift sediments. Average basal heat flow during maximum burial at the end of the Carboniferous period (i.e. the end of crustal shortening) was between 50 and 70 mW m−2with a slight decrease from the Subvarian foreland basins towards the Rheno-Hercynian in the south. The values suggest average crustal thicknesses of between 32 and 36 km during late Carboniferous time. For the Saar-Nahe Basin, values between 50 and 75 mW/m2represent the thermal regime in the upper crust during the late Stephanian and early Permian time. Estimated eroded thicknesses of Palaeozoic sediments vary between 2500 m in the northern and central Ruhr Basin and more than 6000 m in the Osteifel and the Siegen Anticline within the Rheno-Hercynian, and between 1800 and 3600 m in the Saar-Nahe Basin. Fission-track data provide evidence for significant reheating during the Mesozoic era within the entire study area. This phase of heating, probably linked to North Atlantic rifting, coincides with post-Variscan ore formation and with major tectono-magmatic events in central Europe.