ABSENCE OR HIATUS OF POST IMPACT VOLCANISM WITHIN THE LARGEST IMPACT CRATERS

The hypothesis that large impacts initiate post impact volcanism is hotly debated. This is a presentation of observations of post impact volcanism within the presumed crater rims of the largest known and some suspected impact craters on continental crust.

Since 2007, I researched MAPCIS, a large impact crater in Australia of a presumed age between ~550Ma – 535Ma. It is surrounded by Kalkarindji LIP ~510Ma and Mooracoochie volcanics ~517Ma. Upon review of 1:250,000 geology maps and the literature, I found no evidence of volcanism in an area of over 300,000 km² within MAPCIS crater rim younger than the presumed impact event. A review of the known largest confirmed impacts of Vredefort 2023Ma, Sudbury 1850Ma, Chicxulub 65Ma, and Acraman 590Ma as well as others such as Chesapeake Bay 35Ma and Beaverhead 600Ma show an absence or significant hiatus of volcanism post impact within the presumed crater rims. Beaverhead impact in Idaho is interesting as it surrounded by volcanic events of the Northwest USA including the Yellowstone hotspot. Gravity images suggest that hotspot volcanism may have been deflected around the area of Beaverhead impact.

If these observations hold true, it could have implications in our understanding of the formation of stable buoyant continental crust. Are large impacts part of the process necessary to form continental crustal cores or cratons and what could be the impact physics underlying it? This opens this question to worldwide research to combine many disciplines of geology.