Greenland’s lithospheric structure from integrated modelling of potential field data

Greenland’s tectonic history is complex, and the resulting lithospheric structure is, although extensively studied, not well constrained. Most models agree regarding the location of the North Atlantic Craton in South Greenland, and the most recent surface heat flow model also predicts a cold lithosphere for that area. However, the velocity anomaly from the regional tomography NAT2021 shows two additional cratonic blocks in North Greenland that are not included in geological maps and previous lithospheric models.  

To resolve these differences, we built a lithospheric model for Greenland that is compatible with multiple observables and focuses on data integration. In the first step, a background model is set up that uses petrological information of the mantle to model coherent seismic velocities, densities, and temperatures down to a depth of 400 km. The lithospheric model is then adjusted to reproduce the seismic velocities from NAT2021, the gravity field from satellite data and the isostatic elevation. In a second step, we jointly inverted the residual gravity field data from the lithospheric background model together with airborne magnetic data to estimate the crustal density and susceptibility structure. Both rock properties are coupled with a variation of information coupling constraint that establishes a distinct parameter relationship. To assess the compatibility of the thermal structure of our model with the most recent geothermal heat flow model for Greenland, we perform a grid search for the crustal radiogenic heat production, which would be necessary to reproduce this recent geothermal heat flow map. Finally, the results from the different steps are combined by cluster analysis and compared with petrophysical data from a newly established database of Greenland.

The iterative workflow provides novel insights into the sub-ice geology of Greenland. We can model three cratonic blocks with LAB depths greater than 200 km and simultaneously fit the gravity, magnetic and elevation data in Greenland and the most recent geothermal heat flow model.