Shock effects in quartz: Compression versus shear deformation — An example from the Rochechouart impact structure, France

Trepmann, Claudia A.

doi:10.1016/j.epsl.2007.11.035

Cited by 50 publications

(58 citation statements)

References 30 publications

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“… Trepmann and Spray [2006] analyzed samples from the Charlevoix impact structure and observed that the occurrence of basal PDFs, deformation bands, and other shear‐induced features in quartz start at a distance of ∼4–9 km from the center of the structure, while samples lacking sheared elements but containing rhombohedral PDFs occur at <4 km. Trepmann [2008] obtained similar results from the Rochechouart impact structure and concluded that high shock pressures (>20 GPa) are not accompanied by high differential stresses. For lower shock pressures (<15 GPa), differential stresses begin to become effective, thus indicating that as the shock wave propagates through the target, mean stresses decrease while deviatoric stress components increase.…”

Section: Discussionmentioning

confidence: 55%

Feather features: A low-shock-pressure indicator in quartz

2011

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Feather features are a recently discovered type of microstructure in shocked quartz. They occur as short, parallel to subparallel lamellae with spacing similar to that of planar deformation features (PDFs). These lamellae are always found in combination with a planar fracture (PF). Feather features are crystallographically controlled; (0001), {101}, and {112} orientations are common, while {103} and {102} orientations are lacking. Samples from the Nördlinger Ries and the Matt Wilson impact structures are compared with plane wave shock recovery experiments <16 GPa. Microscopic analysis of quartz grains with feather features show that their formation is linked to shearing along the associated PFs during shock deformation. The generation of shear fractures with feather features in plane wave shock recovery experiments suggests a pressure range of ∼7–10 GPa, although further constraints are needed for an upper and lower pressure limit. The orientation of feather features in rock samples is suggested to be controlled by the direction of the principal axis of stress, with sheared PFs at ∼45° angles to the axis and most feather feature lamellae aligned parallel to the axis ±20°. The majority of feather feature lamellae emanate from the PFs in the same direction and in experiments point in the direction from which the shock wave came. On the basis of their appearance in shocked quartz grains from 26 impact craters and the current lack of reports of these features in endogenically deformed crustal rocks, their uniqueness as a new type of impact‐induced planar microstructure alongside PDFs and PFs is proposed.

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Section: Discussionmentioning

confidence: 55%

Feather features: A low-shock-pressure indicator in quartz

2011

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“…1996), but their exact mechanisms of formation are still a topic of research (Goltrant et al. 1992; Trepmann 2008).…”

Section: Resultsmentioning

confidence: 99%

Melt‐bearing impactites (suevite and impact melt rock) within the Gardnos structure, Norway

Kalleson

Dypvik

Nilsen

2010

Meteorit & Planetary Scien

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Abstract-Melt-bearing impactites dominated by suevite, and with a minor content of clastrich impact melt rock, are found within the central part of the Gardnos structure. They are preserved as the eroded remnants in the relatively small complex impact structure with a present diameter of 5 km. These rocks have been mapped in the field and in the Branden drill core, and described according to mineralogy ⁄ petrology, including matrix, litho clast, and melt content, as well as geochemistry. Based on our extensive field mapping, a simple 3-D model of the original crater was constructed to estimate tentative volumes for the meltbearing impactites. The variations in lithic and melt fragment content and chemistry of suevite matrix can mostly be explained by incorporation of mafic rocks into a dominant mixture of granitic, gneissic, and quartzitic target rocks, reflecting mixing of material from different parts of the crater. Melt fragments within suevite occur with a variety of shapes and textures, probably related to different original target rock composition, to the various temperatures the individual fragments were subjected to during the impact event and deposition processes. This study discusses the impact-related deposits based on a sedimentological approach. Their overall composition and structures indicate dominating gravity flow processes in the final transportation and deposition of the suevite.

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“…Basal PDFs (involving Brazil twins) appear at the lowest pressures of 3–10 GPa, followed by ω{103} at about >7–10 GPa, whereas π{102} should be formed at pressures of >20 GPa (French 1998; Blenkinsop 2000). According to Trepmann and Spray (2006) and Trepmann (2008) no amorphous phase is to be expected along basal PDFs, as they represent mechanical Brazil twins, and the rhombohedral PDFs might by annealed. Crystallization of the amorphous phase initially produced by shock is common and efficient, as the amorphous phase is metastable.…”

Section: Discussionmentioning

confidence: 99%

“…Mechanical Brazil twins have therefore not only been found in shocked quartz but also in experimentally deformed quartz. But in nature, they have only been recorded from impact craters (Trepmann and Spray 2006; Trepmann 2008).…”

Section: Discussionmentioning

confidence: 99%

MicroRaman spectroscopy of anomalous planar microstructures in quartz from Mt. Oikeyama: Discovery of a probable impact crater in Japan

Sakamoto¹,

Gucsik²,

Nishido³

et al. 2010

Meteoritics and Planetary Science

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Abstract-Planar deformation features (PDFs) and planar fractures (PFs) have been found and confirmed by optical microscope observations and microRaman spectroscopy in quartz grains from Mt. Oikeyama (Akaishi Mountains, Central Japan), for which the semicircular topographic feature of the ridge suggests a crater formed by an impact event. According to the optical microscope observations, a low shock pressure (8-10 GPa) is estimated by the occurrence of basal or x PDFs leading to lack of multiple sets of PDFs. In addition, a new type of planar microstructure was found in several quartz grains. The microRaman characteristics of PDFs in quartz from Mt. Oikeyama show the amorphous state indicating the presence of weak broad bands at 400 and 800 cm )1 peak positions. These characteristics are indicative of PDFs that are limited to shocked quartz. This indicates an impact origin for distinct planar microstructures in quartz from Mt. Oikeyama.

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Shock effects in quartz: Compression versus shear deformation — An example from the Rochechouart impact structure, France

Cited by 50 publications

References 30 publications

Feather features: A low-shock-pressure indicator in quartz

Feather features: A low-shock-pressure indicator in quartz

Melt‐bearing impactites (suevite and impact melt rock) within the Gardnos structure, Norway

MicroRaman spectroscopy of anomalous planar microstructures in quartz from Mt. Oikeyama: Discovery of a probable impact crater in Japan

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