Shock-produced mosaicism in plagioclase, Charlevoix structure, Quebec

Walawender, M. J.

doi:10.1139/e77-008

Cited by 4 publications

(4 citation statements)

References 5 publications

(8 reference statements)

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“…However, recent studies have revised the shock pressure estimate for its formation to~30-35 GPa (Trepmann 2008;Hamers 2013). Despite its ubiquitous association with many impact structures, mosaicism has not been listed as a diagnostic shock phenomenon (Walawender 1977;Sharpton and Schuraytz 1989;French and Koeberl 2010), as it can also be produced by endogenous processes (Spry 1969).…”

Section: Diaplectic Glass and Mosaicismmentioning

confidence: 99%

Documentation of shock features in impactites from the Dhala impact structure, India

Pati

Poelchau

Reimold

et al. 2019

Meteorit & Planetary Scien

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The fundamental approach for the confirmation of any terrestrial meteorite impact structure is the identification of diagnostic shock metamorphic features, together with the physical and chemical characterization of impactites and target lithologies. However, for many of the approximately 200 confirmed impact structures known on Earth to date, multiple scale‐independent tell‐tale impact signatures have not been recorded. Especially some of the pre‐Paleozoic impact structures reported so far have yielded limited shock diagnostic evidence. The rocks of the Dhala structure in India, a deeply eroded Paleoproterozoic impact structure, exhibit a range of diagnostic shock features, and there is even evidence for traces of the impactor. This study provides a detailed look at shocked samples from the Dhala structure, and the shock metamorphic evidence recorded within them. It also includes a first report of shatter cones that form in the shock pressure range from ~2 to 30 GPa, data on feather features (FFs), crystallographic indexing of planar deformation features, first‐ever electron backscatter diffraction data for ballen quartz, and further analysis of shocked zircon. The discovery of FFs in quartz from a sample of the MCB‐10 drill core (497.50 m depth) provides a comparatively lower estimate of shock pressure (~7–10 GPa), whereas melting of a basement granitoid infers at least 50–60 GPa shock pressure. Thus, the Dhala impactites register a strongly heterogeneous shock pressure distribution between <2 and >60 GPa. The present comprehensive review of impact effects should lay to rest the nonimpact genesis of the Dhala structure proposed by some earlier workers from India.

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Section: Diaplectic Glass and Mosaicismmentioning

confidence: 99%

Documentation of shock features in impactites from the Dhala impact structure, India

Pati

Poelchau

Reimold

et al. 2019

Meteorit & Planetary Scien

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“…Due to the complex chemical and crystal structure, the presence of solid solution, and the common presence of cleavage, it is more complicated to study shock metamorphism in feldspar than in quartz. Studies of shock features in feldspar were first conducted with optical microscopy using natural samples from terrestrial impact craters and meteorites (e.g., Chao 1968;Engelhardt and Stoffler 1968;Kieffer et al 1976;Walawender 1977;Short and Gold 1996). A range of shock features were reported, including reduced refractive index, offset and bent twins, planar features, PDFs, mosaicism, partial to complete amorphization, and melting.…”

Section: Introductionmentioning

confidence: 99%

Raman study of shock features in plagioclase feldspar from the Mistastin Lake impact structure, Canada

Xie

Osinski

Shieh

2020

Meteorit & Planetary Scien

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Plagioclase feldspar is one of the most abundant minerals on the surface of the Earth, the Moon, and Mars, and is also commonly found in meteorites. Studying shock effects in feldspar thus provides us with fundamental information about impact cratering processes on planetary bodies. In this study, plagioclase from monomict and polymict breccias, impact melt rocks, and shock‐metamorphosed target rocks, from throughout the Mistastin Lake impact structure, Canada, was examined using 514 nm laser Raman spectroscopy. As one of the very few impact structures with anorthosite in the target rocks, the Mistastin Lake impact structure provides a unique opportunity to study shocked plagioclase displaying progressive shock metamorphic features. A series of microscopic features was observed within plagioclase, including twins, needle‐like inclusions, planar features, and alteration. The lack of planar deformation features is notable. Raman spectra of these features suggest that this technique is capable of differentiating and classifying shock features in low to moderately shocked rocks. Caution should be exercised, however, as Raman spectra collected from unshocked plagioclase references with known compositions indicate that peak width and peak ratio of the Raman peaks in lower wave number region (<350 cm−1) and the main signature peaks around 500 cm−1 vary with chemical composition and crystal orientation. Data collected from diaplectic glass suggest that Raman features are efficient in distinguishing crystalline plagioclase and diaplectic glass. We also observed significant variations in the Raman intensities collected from diaplectic glass, which we ascribe to the localized disorder or inhomogeneity of shock pressure and temperature throughout the target.

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“…Furthermore, by using single crystal XRD to measure the length of streaks in the chi direction (i.e., strain-related mosaicity) they could start to quantify the amount of strain recorded by the crystals and use that as a proxy to quantify shock level. A correlation between streak length and shock level was also documented in a single-crystal XRD study of plagioclase from the Charlevoix impact structure (Walawender, 1977). Pickersgill et al (2015a) built upon this work by using in situ µXRD to quantify strain-related mosaicity by measuring the full width at half maximum (FWHM) of the intensity vs. chi angle pattern, and compared those measurements to optical signs of shock in samples of labradorite and andesine from the Mistastin Lake impact structure, and lunar anorthite collected during the Apollo program.…”

Section: X-ray Diffraction (Xrd)mentioning

confidence: 70%

Shock effects in feldspars: An overview

Pickersgill

Jaret

Pittarello

et al. 2021

Large Meteorite Impacts and Planetary Evolution VI

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Feldspars are the dominant mineral in the crust of most terrestrial planetary bodies, including Earth, Earth’s moon, and Mars, as well as in asteroids, and thus in meteorites. These bodies have experienced large numbers of hypervelocity impact events, and so it is important to have a robust understanding of the effects of shock waves exerted on feldspars. However, due to their optical complexity and susceptibility to weathering, feldspars are underutilized as shock barometers and indicators of hypervelocity impact. Here, we provide an overview of the work done on shocked feldspars so far, in an effort to better frame the current strengths and weaknesses of different techniques, and to highlight some gaps in the literature.

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Shock-produced mosaicism in plagioclase, Charlevoix structure, Quebec

Cited by 4 publications

References 5 publications

Documentation of shock features in impactites from the Dhala impact structure, India

Documentation of shock features in impactites from the Dhala impact structure, India

Raman study of shock features in plagioclase feldspar from the Mistastin Lake impact structure, Canada

Shock effects in feldspars: An overview

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