LARGE EARTH IMPACTS: ACTIVATING PLATE TECTONICS AND CONSTRAINING VOLCANISM?

The interplay between impacts, tectonism and volcanism is a lot for one presentation. I show one impact MAPCIS ~542Ma, is the Eular point for rotation of the South Australia Element/Cratons from the North Australia Element/Cratons. Rift initiation coeval to the Petermann orogeny ~550-535Ma is well dated through divided matching mafic provinces north and south of the Tasman Line as well as drill cores which map the extent of Acraman impact ~590Ma missing ejecta layer and the existence of Mooracoochie volcanics ~517ma within the rift. The rifting appears to have ended with the Delamarian orogeny ~514-490Ma collision of the South Australia Element with Antarctica.

Post impact volcanism is hotly debated. The Kalkarindji LIP ~510Ma and Mooracoochie volcanics ~517Ma dated after MAPCIS, form an almost complete ring around the crater. Besides defining MAPCIS structure and constraining age, the lack of Kalkarindji volcanics as well as no known volcanism within the 300,000 km² crater for the last 542 million years raises questions. Is volcanism suppressed in other large impacts? A review of the known largest confirmed impacts of Vredefort 2023Ma, Chicxulub 65Ma, and Acraman 590Ma as well as others such as Chesapeake Bay 35Ma and Beaverhead 600Ma suggest an absence or significant hiatus of volcanism post impact within the presumed crater rims. Beaverhead impact in Idaho is particularly 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.

These falsifiable observations shed light on post impact effects on tectonism and volcanism. Are large impacts part of the process of formation of stable buoyant continental crustal core? Do large impacts play an active part in plate tectonics? More questions than answers, but there are now places to look.