--> Abstract: Origin of Detrital Shocked Zircons from Different Sedimentary Environments at the Sudbury Impact Structure, Ontario Canada, by Olivia A. Thomson, Aaron J. Cavosie, Henri A. Radovan, and Desmond E. Moser; #90181 (2013)

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Origin of Detrital Shocked Zircons from Different Sedimentary Environments at the Sudbury Impact Structure, Ontario Canada

Olivia A. Thomson1, Aaron J. Cavosie1, Henri A. Radovan1, and Desmond E. Moser2
1University of Puerto Rico, Mayagüez, PR
2University of Western Ontario, Canada

The presence of shock-metamorphosed minerals is a diagnostic feature used to confirm meteorite impacts. Planar fractures are a unique shock deformation feature preserved in zircons, created by the impact. Here we report occurrences of detrital shocked zircon from the Sudbury impact structure.

The 1850 Ma Sudbury impact structure (Ontario, Canada) is one of the oldest and second largest (∼250-300km) known terrestrial impact structures on Earth. Shocked zircons are preserved in the Levack gneiss and the Onaping Formation.

Quaternary glacial deposits (eskers and deltas) occur across the North and East ranges of the structure. Four main tributaries of the Vermilion River flow southward across the North Range, each crossing the Levack gneiss and/or Onaping Formation. Sediment samples from the Vermilion and the four tributaries, as well as Holocene glacial eskers and deltas were collected and examined using secondary, backscattered electron, and cathodoluminescence imaging and energy dispersive spectroscopy and electron backscatter diffraction analysis with a scanning electron microscope for the presence of detrital shocked zircon.

Detrital shocked zircons (3,978 surveyed) were found in all rivers and most Holocene glacial deposits within the basin. The rivers and glacial deposits either cross/begin in the Levack gneiss or the Onaping Formation, suggesting that one/both of these units are the source of these shocked zircons. This is the first report of detrital shocked zircons found in glacial deposits. These results demonstrate that shocked zircons eroded from a Precambrian impact basin can survive post-impact conditions and enter sedimentary systems up to 2 Gyr after an impact event.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013