The Whitecourt meteorite impact crater, Alberta, Canada

Abstract-The 45 m in diameter Kamil impact crater was formed <5000 yr ago in the eastern Sahara, close to the southern border of modern Egypt. The original features of this structure, including thousands of fragments of the meteorite impactor, are extremely well preserved. With the exception of a single 83 kg regmaglypted individual, all specimens of Gebel Kamil (the iron meteorite that formed the Kamil crater) are explosion fragments weighing from <1 g to 34 kg. Gebel Kamil is an ungrouped Ni-rich (about 20 wt% Ni) ataxite characterized by high Ge and Ga contents (approximately 120 lg g)1 and approximately 50 lg g)1 , respectively) and by a very fine-grained duplex plessite metal matrix. Accessory mineral phases in Gebel Kamil are schreibersite, troilite, daubre´elite, and native copper. Meteorite fragments are cross-cut by curvilinear shear bands formed during the explosive terrestrial impact. A systematic search around the crater revealed that meteorite fragments have a highly asymmetric distribution, with greater concentrations in the southeast sector and a broad maximum in meteorite concentration in the 125-160°N sector at about 200 m from the crater rim. The total mass of shrapnel specimens >10 g, inferred from the density map compiled in this study is 3400 kg. Field data indicate that the iron bolide approached the Earth's crust from the northwest (305-340°N), travelling along a moderately oblique trajectory. Upon hypervelocity impact, the projectile was disrupted into thousands of fragments. Shattering was accompanied by some melting of the projectile and of the quartzarenite target rocks, which also suffered shock metamorphism.

Section: Resultsmentioning

confidence: 60%

“…2009). Similarly, the shrapnel field of the iron meteorite that generated the Whitecourt impact crater extends downrange, northeast of the crater (e.g., Kofman et al. 2010).…”

Section: Discussionmentioning

confidence: 99%

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Gebel Kamil: The iron meteorite that formed the Kamil crater (Egypt)

D’Orazio

Folco

Zeoli

et al. 2011

“…(); (4) Miura and Kato (); (5) Kofman et al. (); (6) This work; (7) Dietz (); (8) Smith and Hodge (); (9) Bunch and Cohen (); (10) Chao et al. (); (11) Hörz et al.…”

Section: Discussionmentioning

confidence: 94%

Shock metamorphism and impact melting in small impact craters on Earth: Evidence from Kamil crater, Egypt

Fazio

Folco

D’Orazio

et al. 2014

Kamil is a 45 m diameter impact crater identified in 2008 in southern Egypt. It was generated by the hypervelocity impact of the Gebel Kamil iron meteorite on a sedimentary target, namely layered sandstones with subhorizontal bedding. We have carried out a petrographic study of samples from the crater wall and ejecta deposits collected during our first geophysical campaign (February 2010) in order to investigate shock effects recorded in these rocks. Ejecta samples reveal a wide range of shock features common in quartz‐rich target rocks. They have been divided into two categories, as a function of their abundance at thin section scale: (1) pervasive shock features (the most abundant), including fracturing, planar deformation features, and impact melt lapilli and bombs, and (2) localized shock features (the least abundant) including high‐pressure phases and localized impact melting in the form of intergranular melt, melt veins, and melt films in shatter cones. In particular, Kamil crater is the smallest impact crater where shatter cones, coesite, stishovite, diamond, and melt veins have been reported. Based on experimental calibrations reported in the literature, pervasive shock features suggest that the maximum shock pressure was between 30 and 60 GPa. Using the planar impact approximation, we calculate a vertical component of the impact velocity of at least 3.5 km s−1. The wide range of shock features and their freshness make Kamil a natural laboratory for studying impact cratering and shock deformation processes in small impact structures.

“…Projectile fragment distribution around craters can also be asymmetric depending mainly on impact angle and target surface inclination (Kofman et al. ; D'Orazio et al. ; Folco et al.…”

Section: Introductionmentioning

confidence: 99%

Formation of a small impact structure discovered within the Agoudal meteorite strewn field, Morocco

Lorenz

Ivanova

Artemieva

et al. 2014

A relic impact structure was recognized within the strewn field of the Agoudal iron meteorite. The heavily eroded structure has preserved shatter cones in a limestone basement, and remnants of autochthonous and allochthonous breccias. Fragments of iron incorporated into the allochthonous breccia have a chemical composition (Ni = 5.16 wt%, Ir = 0.019 ppm) similar to that of the Agoudal meteorite, supporting a syngenetic origin of the strewn field and the impact structure. The total recovered mass of Agoudal meteorite fragments is estimated at approximately 500 kg. The estimated size of the SE–NW‐oriented strewn field is 6 × 2 km. Model calculations with minimal preatmospheric size show that a similar meteorite strewn field plus one small crater with observed shock effects could be formed by fragmentation of a meteoroid approximately 1.4 m in diameter with an impact angle of approximately 60° from the horizontal. However, the most probable is an impact of a larger, 3–4 m diameter meteoroid, resulting a strewn field with approximately 10 craters, 10–30 m in diameter each, plus numerous meteorite fragments. The calculated scattering area of meteorite shrapnel ejected from these impact craters could completely cover the observed strewn field of the Agoudal meteorite.