Petrography of impact glasses and melt breccias from the El'gygytgyn impact structure, Russia
Article first published online: 19 FEB 2013
© The Meteoritical Society, 2013.
Meteoritics & Planetary Science
Special Issue: The 2009 ICDP drilling project at the El'gygytgyn impact structure in Arctic Russia.
Volume 48, Issue 7, pages 1236–1250, July 2013
How to Cite
Pittarello, L. and Koeberl, C. (2013), Petrography of impact glasses and melt breccias from the El'gygytgyn impact structure, Russia. Meteoritics & Planetary Science, 48: 1236–1250. doi: 10.1111/maps.12048
- Issue published online: 8 JUL 2013
- Article first published online: 19 FEB 2013
- Manuscript Accepted: 7 NOV 2012
- Manuscript Received: 14 MAR 2012
- Austrian Science Foundation FWF. Grant Number: P21821-N19
The El'gygytgyn impact structure, 18 km in diameter and 3.6 Ma old, in Arctic Siberia, Russia, is the only impact structure on Earth mostly excavated in acidic volcanic rocks. The Late Cretaceous volcanic target includes lavas, tuffs, and ignimbrites of rhyolitic, dacitic, and andesitic composition, and local occurrence of basalt. Although the ejecta blanket around the crater is nearly completely eroded, bomb-shaped impact glasses, redeposited after the impact event, occur in lacustrine terraces within the crater. Here we present detailed petrographic descriptions of newly collected impact glass-bearing samples. The observed features contribute to constrain the formation of the melt and its cooling history within the framework of the impact process. The collected samples can be grouped into two types, characterized by specific features: (1) “pure” glasses, containing very few clasts or new crystals and which were likely formed during the early stages of cratering and (2) a second type, which represents composite samples with impact melt breccia lenses embedded in silicate glass. These mixed samples probably resulted from inclusion of unmelted impact debris during ejection and deposition. After deposition the glassy portions continued to deform, whereas the impact melt breccia inclusions that probably had already cooled down behaved as rigid bodies in the flow.