Characterization of shocked quartz grains from Chicxulub peak ring granites and shock pressure estimates. (2nd October 2020)

• Record Type: Journal Article
• Authors: Feignon, Jean‐Guillaume; FerriÈre, Ludovic; Leroux, Hugues; Koeberl, Christian
• Is Part Of: Meteoritics & planetary science. Volume 55:Number 10(2020)
• Page Start: 2206
• Page End: 2223
• Publication Date: 2020-10-02
• Subjects: Meteorites -- Periodicals; Planetology -- Periodicals; 523.4
• DOI: 10.1111/maps.13570
• Languages: English
• ISSNs: 1086-9379

Abstract

Abstract: Planar deformation features (PDFs) in quartz are a commonly used and well‐documented indicator of shock metamorphism in terrestrial rocks. The measurement of PDF orientations provides constraints on the shock pressure experienced by a rock sample. A total of 963 PDF sets were measured in 352 quartz grains in 11 granite samples from the basement of the Chicxulub impact structure's peak ring (IODP‐ICDP Expedition 364 drill core), with the aim to quantify the shock pressure distribution and a possible decay of the recorded shock pressure with depth, in the attempt to better constrain shock wave propagation and attenuation within a peak ring. The investigated quartz grains are highly shocked (99.8% are shocked), with an average of 2.8 PDF sets per grain; this is significantly higher than in all previously investigated drill cores recovered from Chicxulub and also for most K‐Pg boundary samples (for which shocked quartz data are available). PDF orientations are roughly homogenous from a sample to another sample and mainly parallel to {10 1 - 3} and {10 1 - 4} orientations (these two orientations representing on average 68.6% of the total), then to {10 1 - 2} orientation, known to form at higher shock pressure. Our shock pressure estimates are within a narrow range, between ~16 and 18 GPa, with a slight shock attenuation with increasing depth in the drill core. The relatively high shock pressure estimates, coupled with the rare occurrence of basal PDFs, i.e., parallel to the (0001) orientation, suggest that the granite basement in the peak ring could be one of the sources of the shocked quartz grains found in the most distal K‐Pg boundary sites.