Evaluation of the terrestrial heat flow in Germany: A case study for the reassessment of global continental heat-flow data

This paper presents the results of a revision of the data on terrestrial heat flow in Germany, termed here as heat -flow density (HFD). The heat-flow values are considered as surface heat flow (qs) sensu stricto. The study is part of the ongoing reassessment of the Global Heat Flow Database organized by the International Heat Flow Com-mission (IHFC). The reassessment of data was deemed necessary as the documentation and quality requirements for HFD data have changed according to the advances in heat-flow science over the past 60 years. A quality score for the HFD values was developed that includes different quality categories. The new nationwide database compiles all data collected in Germany until today. Care was taken to identify HFD values, for which basic data such as temperature gradient, thermal conductivity, and metadata are provided in the records. The rigorous application of this strategy resulted in a significant reduction of published data from 595 to 170 data locations. Heat-flow maps generated for the best-quality data (121 locations) were analyzed for long-and shortwave patterns. The average terrestrial heat flow varies between geological provinces from ca. 66 +/- 11 mW/m2 (Saar-Nahe Basin) to ca. 83 +/- 9 mW/m2 (Black Forest) and locally >90 mW/m2 (in the Erzgebirge/Vogtland and the Upper Rhine Graben). For the latter, more data are needed to substantiate rifting/lithosphere thinning as a governing process for the high heat flow. The (area-weighted) average terrestrial heat flow for Germany is 78 +/- 7 mW/(m2), which is significantly higher (ca. +20%) than earlier estimates (ca. 65 mW/m2). High HFD values mostly result from granitoids in the upper crust and associated radiogenic heat production. Only for five regions, the available HFD data are statistically robust (>12 observations). For a more detailed study of long-and shortwave variations in HFD, new, systematic, and reliable measurements of HFD are needed in areas that are devoid of data.

Automated summary

This paper presents the results of a revision of terrestrial heat flow data in Germany, referred to as heat-flow density (HFD). The study is part of the ongoing reassessment of the Global Heat Flow Database organized by the International Heat Flow Commission (IHFC). The new nationwide database compiles all data collected in Germany until today and a quality score for the HFD values was developed. The average terrestrial heat flow for Germany is significantly higher than earlier estimates and is mostly influenced by granitoids in the upper crust.