Diaplectic labradorite glass from the manicouagan impact crater

Arndt, Jörg; Hummel, W.; Gonzalez-Cabeza, I.

doi:10.1007/bf00309482

Cited by 53 publications

(13 citation statements)

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“…Similarly, Stöffler (1971Stöffler ( , 1972 showed that increased shock level corresponds with degradation of the infrared spectra toward an amorphous material (diaplectic glass), which only shows broad absorption bands near 1,000, 720, and 470 cm À1 . This has been shown for natural samples from Manicouagan and Lonar craters (Arndt et al, 1982;Diemann & Arndt, 1984;Jaret et al, 2015), and remnant infrared spectroscopic anisotropy in the diaplectic plagioclase glass was interpreted to indicate that shocked diaplectic glass retains some remnants of its original feldspar crystalline structure (Jaret et al, 2015).…”

Section: Previous Infrared Studiesmentioning

confidence: 73%

“…At moderate and high shock, feldspars are transformed to diaplectic glass, an amorphous material that retains the grain boundaries of the original crystalline feldspar. Impact-induced amorphization of feldspars has been subject to significant study and debate since the 1960s (Arndt et al, 1982;Bunch et al, 1967;Chen & El Goresy, 2000;Diemann & Arndt, 1984;Fritz et al, 2005;Gillet & El Goresy, 2013;Jaret et al, 2015;Kieffer et al, 1976;Milton & Decarli, 1963;Stöffler, 1971). Feldspars can deform under solid-state mechanisms (Arndt et al, 1982;Diemann & Arndt, 1984;Horz & Quaide, 1973;Jaret et al, 2015) or by quenching from a melt (Chen & El Goresy, 2000;Ferrière & Brandstätter, 2015;Gillet & El Goresy, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Microspectroscopic and Petrographic Comparison of Experimentally Shocked Albite, Andesine, and Bytownite

et al. 2018

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Plagioclase feldspars are common on the surfaces of planetary objects in the solar system such as the Moon and Mars, and in meteorites. Understanding their response to shock deformation is important for interpretations of data from remote sensing, returned samples, and naturally shocked samples from impact craters. We used optical petrography, micro‐Raman, and micro–Fourier transform infrared spectroscopy to systematically document vibrational spectral differences related to structural changes in experimentally shocked (0–56 GPa) albite‐, andesine‐, and bytownite‐rich rocks as a function of pressure and composition. Across all techniques, the specific composition of feldspars was confirmed to affect shock deformation, where more Ca‐rich feldspars transform to an amorphous phase at lower shock conditions than more Na‐rich feldspars. Onset of amorphization occurs at ~50 GPa for albite, between 28 and 30 GPa for andesine, and between 25 and 27 GPa for bytownite. Complete amorphization occurred at pressures greater than ~55 GPa for albite, ~47 GPa for andesine, and ~38 GPa for bytownite. Petrographically, these experimentally shocked samples do not exhibit the planar microstructures common in naturally shocked plagioclase, despite showing the expected trends of internal disordering and deformation as seen in the micro‐Raman and infrared spectra. Average spectra of hyperspectral images of these samples mimic macroscale measurements acquired previously. However, we see micro‐scale heterogeneity in the shock response, resulting from variations in either composition, crystal orientation, or the inherent heterogeneity of the shock wave topology. This is an important factor to consider when deducing shock pressures in naturally shocked samples.

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Section: Previous Infrared Studiesmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Microspectroscopic and Petrographic Comparison of Experimentally Shocked Albite, Andesine, and Bytownite

et al. 2018

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“…McIntyre (1968) and French (1998) described similar plumose features as the product of recrystallization of diaplectic glass. A similar origin has been proposed for microcrystalline plagioclase aggregates by Arndt et al (1982) and Ostertag and Stöffl er (1982).…”

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confidence: 67%

Shock pressure distribution in the Vredefort impact structure, South Africa

Gibson¹,

Reimold²

2005

Large Meteorite Impacts III

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A petrographic study of Archean gneisses exposed in the core of the 80-km-wide central uplift of the Vredefort impact structure has revealed widespread evidence of shock-related metamorphic effects in feldspar and ferromagnesian minerals in addition to the already documented quartz microdeformation features. The shock features are variably overprinted by annealing effects, which increase in intensity toward the center of the structure. The shock effects show a general increase in intensity toward the center of the dome but are most characteristically marked by extreme heterogeneity on a small (centimeter to millimeter) scale, indicating highly localized shock pressure heterogeneity. Closest to the center, the pre-impact Archean fabrics and textures have been locally partially destroyed by comprehensive melting and melt mobilization, which has given rise to distinctive granofelses and clast-laden melt breccias. Based on the features observed, background shock pressures in the currently exposed level of the core of the dome range from ~10 GPa at distances of ~20 km from the center to >30-35 GPa within 5 km of the center. Pressures responsible for localized melting and for the formation of the melt breccias in this central zone may have exceeded 45 GPa, although it is diffi cult to constrain this value more precisely owing to uncertainty about the pre-impact temperature of the rocks and the role of local syn-shock frictional heating in raising temperature. Apart from the localized heterogeneity in shock pressures, the background shock pressure gradient appears to increase toward the center of the dome, approaching ~4 GPa/km in the central parts.

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“…Exposing maskelynite to temperatures of more than 1170 K for several hours to days eventually results in recrystallization to plagioclase (Ostertag and St€ offler 1982). The differences between the recrystallization of almost fully isotropic maskelynite and the crystallization of a thermal mineral glass are discussed by Arndt et al (1982), indicating that maskelynite with high RI could retain a "memory" of the original crystal and, thus differs from a quenched glass. The observed annealing behavior documents the gradual transition of plagioclase to maskelynite and thus supports a solid state transformation process.…”

Section: Shock Formation Of Maskelynitementioning

confidence: 99%

On the formation of diaplectic glass: Shock and thermal experiments with plagioclase of different chemical compositions

Fritz¹,

Fernandes

Greshake

et al. 2019

Meteorit & Planetary Scien

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This contribution addresses the role of chemical composition, pressure, temperature, and time during the shock transformation of plagioclase into diaplectic glass—i.e., maskelynite. Plagioclase of An50‐57 and An94 was recovered as almost fully isotropic maskelynite from room temperature shock experiments at 28 and 24 GPa. The refractive index (RI) decreased to values of a quenched mineral glass for An50‐57 plagioclase shocked to 45 GPa and shows a maximum in An94 plagioclase shocked to 41.5 GPa. The An94 plagioclase experiments can serve as shock thermobarometer for lunar highland rocks and howardite, eucrite, and diogenite meteorites. Shock experiments at 28, 32, 36, and 45 GPa and initial temperatures of 77 and 293 K on plagioclase (An50‐57) produced materials with identical optical and Raman spectroscopic properties. In the low temperature (<540 K) region, the formation of maskelynite is entirely controlled by shock pressure. The RI of maskelynite decreased in heating experiments of 5 min at temperatures of >770 K, thus, providing a conservative upper limit for the postshock temperature history of the rock. Although shock recovery experiments and static pressure experiments differ by nine orders of magnitude in typical time scale (microseconds versus hours), the amorphization of plagioclase occurs at similar pressure and temperature conditions with both methods. The experimental shock calibration of plagioclase can, together with other minerals, be used as shock thermobarometer for naturally shocked rocks.

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Diaplectic labradorite glass from the manicouagan impact crater

Cited by 53 publications

References 20 publications

Microspectroscopic and Petrographic Comparison of Experimentally Shocked Albite, Andesine, and Bytownite

Microspectroscopic and Petrographic Comparison of Experimentally Shocked Albite, Andesine, and Bytownite

Shock pressure distribution in the Vredefort impact structure, South Africa

On the formation of diaplectic glass: Shock and thermal experiments with plagioclase of different chemical compositions

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