Shatter cones at the Keurusselkä impact structure and their relation to local jointing

2016 ◽  
Vol 51 (8) ◽  
pp. 1534-1552 ◽  
Author(s):  
Maximilian Hasch ◽  
Wolf Uwe Reimold ◽  
Ulli Raschke ◽  
Patrice Tristan Zaag
Keyword(s):  
Impact Structure ◽  
Shatter Cones

scholarly journals Melting and cataclastic features in shatter cones in basalt from the Vista Alegre impact structure, Brazil

2015 ◽  
Vol 50 (7) ◽  
pp. 1228-1243 ◽  
Author(s):  
Lidia Pittarello ◽  
Fabrizio Nestola ◽  
Cecilia Viti ◽  
Alvaro Penteado Crósta ◽  
Christian Koeberl
Keyword(s):  
Impact Structure ◽  
Shatter Cones

Shatter cones and planar deformation features confirm Santa Marta in Piauí State, Brazil, as an impact structure

2014 ◽  
Vol 49 (10) ◽  
pp. 1915-1928 ◽  
Author(s):  
Grace Juliana Gonçalves de Oliveira ◽  
Marcos Alberto Rodrigues Vasconcelos ◽  
Alvaro Penteado Crósta ◽  
Wolf Uwe Reimold ◽  
Ana Maria Góes ◽  
...  
Keyword(s):  
Impact Structure ◽  
Planar Deformation ◽  
Deformation Features ◽  
Shatter Cones ◽  
Planar Deformation Features

Shock deformation microstructures in xenotime from the Spider impact structure, Western Australia

2021 ◽  
Author(s):  
Morgan A. Cox ◽  
Aaron J. Cavosie ◽  
Michael Poelchau ◽  
Thomas Kenkmann ◽  
Phil A. Bland ◽  
...  
Keyword(s):  
Western Australia ◽  
Impact Structure ◽  
High Angle ◽  
Deformation Bands ◽  
Stress Regime ◽  
Shock Deformation ◽  
Deformation Twins ◽  
Formation Conditions ◽  
Shatter Cones ◽  
Micro Structures

ABSTRACT The rare earth element–bearing phosphate xenotime (YPO4) is isostructural with zircon, and therefore it has been predicted that xenotime forms similar shock deformation microstructures. However, systematic characterization of the range of micro structures that form in xenotime has not been conducted previously. Here, we report a study of 25 xenotime grains from 10 shatter cones in silicified sandstone from the Spider impact structure in Western Australia. We used electron backscatter diffrac tion (EBSD) in order to characterize deformation and microstructures within xenotime. The studied grains preserve multiple sets of planar fractures, lamellar {112} deformation twins, high-angle planar deformation bands (PDBs), partially recrystallized domains, and pre-impact polycrystalline grains. Pressure estimates from micro structures in coexisting minerals (quartz and zircon) allow some broad empirical constraints on formation conditions of ~10–20 GPa to be placed on the observed microstructures in xenotime; at present, more precise formation conditions are unavailable due to the absence of experimental constraints. Results from this study indicate that the most promising microstructures in xenotime for recording shock deformation are lamellar {112} twins, polycrystalline grains, and high-angle PDBs. The {112} deformation twins in xenotime are likely to be a diagnostic shock indicator, but they may require a different stress regime than that of {112} twinning in zircon. Likewise, polycrystalline grains are suggestive of impact-induced thermal recrystallization; however, in contrast to zircon, the impact-generated polycrystalline xenotime grains here appear to have formed in the solid state, and, in some cases, they may be difficult to distinguish from diagenetic xenotime with broadly similar textures.

Meteorite traces on a shatter cone surface from the Agoudal impact site, Morocco

2015 ◽  
Vol 152 (4) ◽  
pp. 751-757 ◽  
Author(s):  
M. SCHMIEDER ◽  
H. CHENNAOUI AOUDJEHANE ◽  
E. BUCHNER ◽  
E. TOHVER
Keyword(s):  
Iron Meteorite ◽  
Impact Structure ◽  
Iron Meteorites ◽  
Electron Microscopic ◽  
Impact Site ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Cone Surface ◽  
Shatter Cones ◽  
The Impact

AbstractThe recently discovered Agoudal impact site in Morocco is a small, eroded impact structure with well-developed shatter cones. A scanning electron microscopic study of a shatter cone surface has revealed the presence of schreibersite – a phosphide very rare on Earth but common in iron meteorites – and Fe–Ni oxides. This is the first reported evidence for primary meteoritic matter adherent to shatter cones and suggests that the Agoudal crater was formed by the impact of an iron meteorite, probably the Agoudal IIAB iron. Shatter cones from other terrestrial impact structures might also hold valuable information about the nature of the impacting projectiles.

Shatter cones and shocked rocks in southwestern Montana: The Beaverhead impact structure

Geology ◽  
1990 ◽  
Vol 18 (9) ◽  
pp. 832 ◽  
Author(s):  
R. B. Hargraves ◽  
C. E. Cullicott ◽  
K. S. Deffeyes ◽  
S. Hougen ◽  
P. P. Christiansen ◽  
...  
Keyword(s):  
Impact Structure ◽  
Southwestern Montana ◽  
Shatter Cones

Micro-Shock Deformation adjacent to the Surface of Shatter Cones from the Beaverhead Impact Structure, Montana

1996 ◽  
Vol 104 (2) ◽  
pp. 233-238 ◽  
Author(s):  
R. B. Hargraves ◽  
J. C. White
Keyword(s):  
Impact Structure ◽  
Shock Deformation ◽  
Shatter Cones

scholarly journals Geological investigation of the central portion of the Santa Marta impact structure, Piauí State, Brazil

2017 ◽  
Vol 47 (4) ◽  
pp. 673-692 ◽  
Author(s):  
Grace Juliana Gonçalves de Oliveira ◽  
Marlei Antônio Carrari Chamani ◽  
Ana Maria Góes ◽  
Alvaro Penteado Crósta ◽  
Marcos Alberto Rodrigues Vasconcelos ◽  
...  
Keyword(s):  
Central Area ◽  
Sedimentary Basins ◽  
Northeastern Brazil ◽  
Impact Structure ◽  
Impact Cratering ◽  
Geological Investigation ◽  
Widespread Occurrence ◽  
Deformation Features ◽  
Shatter Cones ◽  
Planar Deformation Features

ABSTRACT: Santa Marta is a 10 km wide, reasonably well preserved, complex impact structure located in southwestern Piauí state, northeastern Brazil, with a central uplift of 3.2 km diameter. The Santa Marta structure was recently recognized as the sixth confirmed impact structure in Brazil, based on widespread occurrence of shatter cones and the presence of shock deformation features in quartz. The latter includes planar deformation features (PDF), planar fractures (PF), and feather features (FF). The structure was formed in sedimentary strata (conglomerates, sandstones, siltstones and shales) accumulated in two distinct sedimentary basins that overlap in this region: the Paleozoic Parnaíba and the Mesozoic Sanfranciscan basins. Here, we provide an overview of the geology and stratigraphy of the sedimentary successions that occur within the structure, focusing especially on the deformation aspects of the strata from the central area. This study is aimed at advancing the knowledge about Brazilian impact structures and contributing to a better comprehension of impact cratering in sedimentary targets. The deformation in the Santa Marta structure is directly related to variations in the thickness of sedimentary strata and to lithologic diversity in the interior of the structure, which determined the complexity of the deformation, including the formation of inner rings.

The Slate Islands: a probable complex meteorite impact structure in Lake Superior

1976 ◽  
Vol 13 (9) ◽  
pp. 1301-1309 ◽  
Author(s):  
H. C. Halls ◽  
R. A. F. Grieve
Keyword(s):  
Country Rock ◽  
Lake Superior ◽  
Impact Structure ◽  
Early Paleozoic ◽  
Meteorite Impact ◽  
Erosion Level ◽  
Igneous Activity ◽  
Shatter Cones ◽  
Host Rocks ◽  
Sedimentary Unit

Shock metamorphic effects in samples from the Slate Islands, Lake Superior (48°40' N, 87°00' W) suggest that the islands are part of a meteorite impact structure. The islands form the central uplift of a complex crater and are ringed by a submerged trough and annular ridge with a diameter of 30 km. Precambrian bedrock units are locally brecciated and cut by allochthonous breccia dikes. These dikes contain clasts of identifiable country rock and also fragments of a sedimentary unit, possibly Upper Keweenawan in age, which is no longer present in outcrop. The orienta tions of shatter-cones present in the breccia host-rocks indicate the interior of the islands as the approximate shock centre. Microscopic planar features, equivalent to those described from other impact sites, occur in quartz and plagioclase and the level of shock deformation increases towards the interior of the islands. The shock event postdates Keweenawan igneous activity (about 1.1 b.y. old) and, on the basis of the erosion level, may be early Paleozoic in age.

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