Uncovering the Iceland Hot Spot Track Beneath Greenland

Abstract

During the past 120 Ma, the Greenland craton drifted over the Iceland hot spot; however, uncertainties in geodynamic modeling and a lack of geophysical evidence prevent an accurate reconstruction of the hot spot track. I image the Greenland lithosphere down to 200‐km depth with both group and phase velocity seismic noise tomography. The 3‐D shear wave velocity model obtained using 4–5 years of continuous seismic records from the Greenland Ice Sheet Monitoring Network is well resolved for most of the Greenland main island. The crustal part of the model clearly shows different tectonic units. The hot spot track is observed as a linear high‐velocity anomaly in the middle and lower crust associated with magmatic intrusions. In the upper mantle, a pronounced low‐velocity anomaly below the east coast might be due to the remnant effect of the Iceland hot spot when it was at its maximum intensity. Thermomechanical modeling suggests that this area has higher temperature and lower viscosity than the surrounding cratonic areas and experiences a higher than average surface heat flow. This new detailed picture of the Greenland lithosphere will drive more accurate geodynamic reconstructions of tectonic plate motions and help to better understand the North Atlantic tectonic history. Models of Greenland glacial isostatic adjustment will benefit from the 3‐D upper‐mantle viscosity model, which in turn will enable more precise estimations of the Greenland ice sheet mass balance.

Lithospheric Structure of Greenland From Ambient Noise and Earthquake Surface Wave Tomography

“…From this region, relatively thick crust extends southward and eastward and coincides with part of the South Archean Block, Eastern Archean Block, and Nagssugtoqidian orogen. In northern Greenland, our model does not indicate crustal thinning as suggested by gravity‐based models (Braun et al, ; Petrov et al, ; Schiffer et al, ; Steffen et al, ) but is relatively consistent with surface wave‐based crustal thickness models (Darbyshire et al, ; Mordret, ). The high degree of heterogeneity in crustal thickness estimates in northern Greenland may be the result of the limited sensitivity of surface waves.…”

“…In that study, the low‐velocity anomaly is more centrally located and of smaller magnitude. The location of the NELVZ is in better agreement with the ANT model of Mordret () at 10‐km depth, but discrepancies in magnitude and in the spatial extent of the anomaly at 25‐km depth exist. The low‐velocity anomaly imaged in that study is reduced in amplitude and more spread out in the mid‐to‐lower crust.…”

“…However, the latter model only extends to a depth of 90 km and has limited ray coverage and resolution at these depths. A similar feature is contained in the global models SL2013sv and SV2013NA of Schaeffer and Lebedev (, ) and the regional model of Mordret (). This low‐velocity corridor is especially interesting because it appears to connect the western and eastern Tertiary basalt provinces.…”

“…Constraints on crustal velocity structure are limited, and general agreement on crustal structure remains a goal. Regional crustal shear wave tomography models from earthquake or ambient noise data suggest the presence of a low‐velocity anomaly in northeastern and central eastern Greenland, but the amplitude and location of this anomaly differ between studies (Darbyshire et al, ; Levshin et al, ; Mordret, ).…”

ArcCRUST: Arctic Crustal Thickness From 3‐D Gravity Inversion

“…In the past 2 years the crustal and upper mantle of the Greenland region were presented by a number of new models; therefore, we scrutinized in more detail our results versus the state‐of‐art models for this area. Crustal thickness and depth to Moho have been computed for Greenland and adjacent regions by using (1) gravity data (Steffen et al, ) and (2) seismological data (Darbyshire et al, ; Mordret, and Pourpoint et al, ). Our depth to Moho (Figure a) is comparable with the model of Darbyshire et al () who used Rayleigh wave anisotropic group velocity tomography to map the 3‐D crustal structure of Greenland and NW Atlantic Ocean.…”