Polyphase microbreccia injectites in the Maniitsoq structure, West Greenland

In large impacts, the short-lived modification from transient cavity to final crater requires temporary strength degradation of the host rocks. Whereas the process of strength degradation is not well understood, it has been possible to model the crater reorganization observed in large impact structures by employing acoustic fluidization of 100 m-scale individual blocks. Evidence of the repeated compression and dilation that is inherent in such modeling of impact crater modification is found in a regional network of polyphase microbreccia dykes with internal dyke-in-dyke and fold structures in Archean orthogneisses in the Maniitsoq region of West Greenland (interpreted as agiant, deeply eroded Archean impact structure).