Gardea, et al., suggest that a 100 km-scale, circular region in the Archaean North Atlantic Craton centered at 65.15 N, 51.50 W near Maniitsoq town in West Greenland comprises a set of highly unusual geological features that were created during a single event involving intense crushing and heating and are incompatible with crustal orogenic processes. The presently exposed features of the Maniitsoq structure were buried 20 to 25 km below the surface when this event occurred at around 3 Ga, during a waning convergent orogeny.
These features include a large aeromagnetic anomaly, a central 35 to 50 sq.km. large area of comminuted quartzo-feldspathic material, regional-scale circular deformation, etc.
The diagnostic tools employed to identify impacting in the upper crust are currently inadequate for structures preserved deep within the continental crust. Nevertheless, the inferred scale, strain rates and temperatures necessary to create the Maniitsoq structure rule out a terrestrial origin of the structure....indicating an asteroid or comet impact site.
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