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

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.

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 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

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

scholarly journals Variations in shock deformation at the Slate Islands Impact Structure, Lake Superior, Canada

1977 ◽  
Vol 61 (1) ◽  
pp. 107-107 ◽  
Author(s):  
R. A. F. Grieve ◽  
P. B. Robertson
Keyword(s):  
Lake Superior ◽  
Impact Structure ◽  
Shock Deformation

Variations in shock deformation at the Slate Islands impact structure, Lake Superior, Canada

1976 ◽  
Vol 58 (1) ◽  
pp. 37-49 ◽  
Author(s):  
Richard A. F. Grieve ◽  
P. Blyth Robertson
Keyword(s):  
Lake Superior ◽  
Impact Structure ◽  
Shock Deformation

scholarly journals Shock deformation in zircon grains from the Mien impact structure, Sweden

2021 ◽  
Vol 56 (2) ◽  
pp. 362-378
Author(s):  
Josefin Martell ◽  
Carl Alwmark ◽  
Sanna Holm‐Alwmark ◽  
Paula Lindgren
Keyword(s):  
Impact Structure ◽  
Shock Deformation

scholarly journals Empirical constraints on progressive shock metamorphism of magnetite from the Siljan impact structure, Sweden

Geology ◽  
2021 ◽  
Author(s):  
Sanna Holm-Alwmark ◽  
Timmons M. Erickson ◽  
Aaron J. Cavosie
Keyword(s):  
Electron Backscatter Diffraction ◽  
Crystallographic Analysis ◽  
Hypervelocity Impact ◽  
Accessory Mineral ◽  
Shear Direction ◽  
Impact Structure ◽  
Shock Deformation ◽  
Deformation Features ◽  
Backscatter Diffraction ◽  
Impact Events

Little is known about the microstructural behavior of magnetite during hypervelocity impact events, even though it is a widespread accessory mineral and an important magnetic carrier in terrestrial and extraterrestrial rocks. We report systematic electron backscatter diffraction crystallographic analysis of shock features in magnetite from a transect across the 52-km-diameter ca. 380 Ma Siljan impact structure in Sweden. Magnetite grains in granitoid samples contain brittle fracturing, crystal-plasticity, and lamellar twins. Deformation twins along {111} with shear direction of <112> are consistent with spinel-law twins. Inferred bulk shock pressures for the investigated samples, as constrained by planar deformation features (PDFs) in quartz and shock twins in zircon, range from 0 to 20 GPa; onset of shock-induced twinning in magnetite is observed at >5 GPa. These results highlight the utility of magnetite to record shock deformation in rocks that experience shock pressures >5 GPa, which may be useful in quartz-poor samples. Despite significant hydrothermal alteration and the variable transformation of host magnetite to hematite, shock effects are preserved, which demonstrates that magnetite is a reliable mineral for preserving shock deformation over geologic time.

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.

Asymmetric shock deformation at the Spider impact structure, Western Australia

2021 ◽  
Author(s):  
Morgan A. Cox ◽  
Aaron J. Cavosie ◽  
Michael H. Poelchau ◽  
Thomas Kenkmann ◽  
Katarina Miljković ◽  
...  
Keyword(s):  
Western Australia ◽  
Impact Structure ◽  
Shock Deformation ◽  
Asymmetric Shock
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