Fracture Analysis of α-Quartz Crystals Subjected to Shear Stress

Martinelli, Giovanni; Plescia, P.; Tempesta, Emanuela; Paris, Enrico; Gallucci, Francesco

doi:10.3390/min10100870

Cited by 6 publications

(3 citation statements)

References 20 publications

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“…Wilk et al [6] found amorphous silica in experimentally shocked rocks called shatter cones that formed at low shock pressures of 0.5-5 GPa. Laboratory shock experiments by Martinelli et al [79] used quartz crystals with a minimum diameter of 3400 µm, larger than we tested. The reported compression applied was as low as 0.2 GPa; the maximum compression applied is unclear but appears to have been <1 GPa.…”

Section: Previous Studies Of Amorphous Silica In Quartz Grainsmentioning

confidence: 99%

Microstructures in shocked quartz: linking nuclear airbursts and meteorite impacts

Hermes,

Wenk,

Kennett

et al. 2023

Airbursts and Cratering Impacts

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Many studies of hypervelocity impact craters have described the characteristics of quartz grains shock-metamorphosed at high pressures of >10 GPa. In contrast, few studies have investigated shock metamorphism at lower shock pressures. In this study, we test the hypothesis that low-pressure shock metamorphism occurs in near-surface nuclear airbursts and that this process shares essential characteristics with crater-forming impact events. To investigate low-grade shock microstructures, we compared quartz grains from Meteor Crater, a 1.2-km-wide impact crater, to those from near-surface nuclear airbursts at the Alamogordo Bombing Range, New Mexico in 1945 and Kazakhstan in 1949/1953. This investigation utilized a comprehensive analytical suite of high-resolution techniques, including transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). Meteor Crater and the nuclear test sites all exhibit quartz grains with closely spaced, sub-micron-wide fractures that appear to have formed at low shock pressures. Significantly, these micro-fractures are closely associated with Dauphiné twins and are filled with amorphous silica (glass), widely considered a classic indicator of shock metamorphism. Thus, this study confirms that glass-filled shock fractures in quartz form during near-surface nuclear airbursts, as well as crater-forming impact events, and by extension, it suggests that they may form in any near-surface cosmic airbursts in which the shockwave is coupled to Earth’s surface, as has been proposed. The robust characterization of such events is crucial because of their potential catastrophic effects on the Earth’s environmental and biotic systems.

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Section: Previous Studies Of Amorphous Silica In Quartz Grainsmentioning

confidence: 99%

Microstructures in shocked quartz: linking nuclear airbursts and meteorite impacts

Hermes,

Wenk,

Kennett

et al. 2023

Airbursts and Cratering Impacts

View full text Add to dashboard Cite

show abstract

“…Laboratory shock experiments by Martinelli et al [90] produced intragranular fractures in quartz crystals with a minimum diameter of 3400 µm, larger than any we examined. The fracturing process reportedly produced amorphous silica composed of low-temperature nanocrystalline cristobalite, which was not observed in the fractures of our study.…”

mentioning

confidence: 63%

“…In laboratory experiments, Martinelli et al [90] concluded that fractures in quartz form rapidly in <50 ns not by compression but by tensional expansion produced by the reflected shockwave. They found that the fracturing process generates temperatures >1713°C, the melting point of quartz, thus producing amorphous silica along the fractures, as first proposed by Ernstson [33].…”

Section: Potential Formation Mechanismsmentioning

confidence: 99%

Abu Hureyra, Syria, Part 1: Shock-fractured quartz grains support 12,800-year-old cosmic airburst at the Younger Dryas onset

Moore,

Kennett,

LeCompte

et al. 2023

Airbursts and Cratering Impacts

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A previous investigation revealed that shock-fracturing, a form of low-pressure shock metamorphism in quartz grains, can be produced during near-surface atomic airbursts and in cosmic impact structures, most likely at pressures lower than 8 GPa. This discovery implies that similar shock-fracturing may also form in quartz grains exposed to near-surface airbursts by comets and asteroids. Here, we investigate this hypothesis by examining quartz grains in a sedimentary profile from Abu Hureyra, a prehistoric archaeological site in northern Syria. This site was previously proposed to have experienced a nearby, low-altitude cosmic airburst at the onset of the Younger Dryas (~12,800 years ago). The Younger Dryas boundary layer (YDB) at Abu Hureyra has previously been shown to contain a rich assemblage of materials consistent in indicating a cosmic impact. These include anomalously high concentrations of melted micro-spherules displaying increased remanent magnetism; meltglass with low water content indicative of high-temperature melting; nanodiamonds, potentially including lonsdaleite; carbon spherules produced by biomass burning; black carbon or soot; total organic carbon; and abnormally high-temperature melted refractory minerals and elements, including platinum, iridium, chromite, and zircon. To further test this impact hypothesis, we searched for evidence of shocked quartz, a robust, widely accepted indicator of cosmic impacts. We used a comprehensive analytical suite of high-resolution techniques, including transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD), to examine and characterize quartz grains from the YDB layer at Abu Hureyra. Our analyses revealed the presence of quartz grains with sub-planar, sub-parallel, and sub-micron-wide intragranular fractures, most likely produced by mechanical and thermal shock or the combination of both. Furthermore, these fractures are typically filled with amorphous silica (glass), a classic indicator of shock metamorphism. Elemental analyses of the weight percentages of oxygen in the amorphous silica indicate that this could not have formed from the deposition of hydrated silica (e.g., opal and hyalite), which is enhanced in oxygen. Instead, the silica we observed is typically depleted in oxygen, consistent with melting under highly reducing conditions. The shock fractures in quartz grains also display Dauphiné twinning, which sometimes develops during the stress of high temperatures or pressures. This evidence is consistent with the hypothesis that the glass-filled fractures in quartz grains were produced by thermal and mechanical shock during a near-surface cosmic airburst at Abu Hureyra. These glass-filled fractures closely resemble those formed in near-surface atomic airbursts and crater-forming impact events.

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Sands Subjected to Repetitive Loading Cycles and Associated Granular Degradation

Park,

Santamarina

2023

J. Geotech. Geoenviron. Eng.

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Fracture Analysis of α-Quartz Crystals Subjected to Shear Stress

Cited by 6 publications

References 20 publications

Microstructures in shocked quartz: linking nuclear airbursts and meteorite impacts

Microstructures in shocked quartz: linking nuclear airbursts and meteorite impacts

Abu Hureyra, Syria, Part 1: Shock-fractured quartz grains support 12,800-year-old cosmic airburst at the Younger Dryas onset

Sands Subjected to Repetitive Loading Cycles and Associated Granular Degradation

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