Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system

Stöffler, D.; Hamann, Christopher; Metzler, K.

doi:10.1111/maps.12912

Cited by 331 publications

(401 citation statements)

References 115 publications

Supporting

Mentioning

359

Contrasting

Unclassified

Order By: Relevance

“…Clast‐poor or clast‐free impact melt rocks with igneous texture/microtexture are often observed in parts of thick melt sheets related to relatively large impact structures, as well as dikes in both large and small craters (e.g., Manicouagan and Sudbury in Canada and Tenoumer in Mauritania; Fudali, ; Grieve et al, ; Pilles et al, ; Simonds et al, ). Models involving melt sheets, pools, and dikes are also applied for clast‐laden or clast‐poor impact melt meteorites (Keil et al, ; Stöffler et al, ). Compared to most impact melt rocks and breccias with the presence of nonstoichiometric glass (e.g.…”

Section: Discussionmentioning

confidence: 99%

Petrogenesis and In Situ U‐Pb Geochronology of a Strongly Shocked L‐Melt Rock Northwest Africa 11042

Hsu

2019

JGR Planets

View full text Add to dashboard Cite

Northwest Africa (NWA) 11042, originally classified as a primitive achondrite with no chondritic relicts, is rather a unique L‐melt rock. It is a severely shocked, igneous‐textured ultramafic rock composed of euhedral to subhedral olivine (Fa25.1 ± 0.5) and pyroxenes (low‐Ca pyroxene Fs20.7 ± 0.8Wo4.2 ± 1.0 and Ca‐rich pyroxene Fs11.5 ± 0.5Wo37.6 ± 1.2) with interstitial albitic plagioclase (Ab80.7 ± 1.7Or5.0 ± 0.7) that has been completely converted to maskelynite. Mineral compositions are similar to those of equilibrated L‐chondrites. Melt pockets are scattered throughout the sample, containing high‐pressure minerals including ringwoodite, wadsleyite, jadeite, and lingunite. Merrillite and apatite in NWA 11042 contain significantly higher REE abundances than those of ordinary chondrites, indicative of igneous fractional crystallization. In situ U‐Pb dating of apatite in NWA 11042 reveals an upper intercept age of 4,479 ± 43 Myr and a lower intercept age of 465 ± 47 Myr on the normal U‐Pb concordia diagram. The upper intercept age recorded the time when NWA 11042 initially crystallized. This age is much younger than when the decay of short‐lived nuclides (e.g., 26Al) would act as a major heat source, suggesting that melting and crystallization of NWA 11042 could be otherwise triggered by an impact event. The lower intercept age represents a reset age due to a later impact event, which is in coincidence with the disruption event of L‐chondrite parent body at ~470 Myr. NWA 11042 is an excellent example to link igneous‐textured meteorites with a chondritic parent body through shock‐induced melting.

show abstract

Section: Discussionmentioning

confidence: 99%

Petrogenesis and In Situ U‐Pb Geochronology of a Strongly Shocked L‐Melt Rock Northwest Africa 11042

Hsu

2019

JGR Planets

View full text Add to dashboard Cite

show abstract

“…AMS of magnetic fabric is already an established technique for understanding impact processes, especially at low peak shock pressures (0.5 to 3 GPa), at which other common shock indicators are rare (e.g., Agarwal et al, ; Agarwal, Kontny, Srivastava, & Greiling, ; Misra et al, ; Stöffler et al, ). The present study concludes that folding and kinking of biotite due to shock deformation may cause a significant reorientation of magnetic fabrics by passively changing the position of magnetite grains with respect to each other.…”

Section: Discussionmentioning

confidence: 99%

Variation in Magnetic Fabrics at Low Shock Pressure Due to Experimental Impact Cratering

et al. 2019

View full text Add to dashboard Cite

Magnetic fabrics provide important clues for understanding impact cratering processes. However, only a few magnetic fabric studies for experimentally shocked material have been reported so far. In the framework of MEMIN (Multidisciplinary Experimental and Modeling Impact Research Network), we conducted two impact experiments on blocks of Maggia gneiss with the foliation oriented perpendicular (A38) and parallel (A37) to the target surface. Maggia gneiss has plenty of biotite bands forming a strong rock foliation. The bulk magnetic susceptibility varies from 0.376 × 10−3 to 1.298 × 10−3 SI in unshocked and from 0.443 × 10−3 to 3.940 × 10−3 SI in shocked gneiss. The thermomagnetic curves reveal a Verwey transition at −147 °C and a Curie temperature between 576 and 579 °C in unshocked and shocked samples, indicating nearly pure magnetite, which carries the magnetic fabrics. In A37 and A38 kinking is prominent from the point source down to a depth of 2 and 4.2 dp (projectile diameter) or 1 and 2.1 cm, respectively. Kinking, folding, and fracturing changed the position of magnetite grains with respect to each other to reorient the magnetic fabrics. Reorientation of magnetic fabrics is conspicuous down to 20 dp (10 cm) in A38, where no other impact‐related deformation is visible. The reorientation of magnetic fabrics may, therefore, aid in identifying impact processes at very low pressures, starting at 0.1 GPa, when other common indicators are absent.

show abstract

“…Collectively, these effects suggest shock pressures from >5 GPa to ~35 GPa (Stöffler ; Stöffler and Langenhorst ; Stöffler et al. ).…”

Section: Microscopic Observationsmentioning

confidence: 99%

Quartz–coesite–stishovite relations in shocked metaquartzites from the Vredefort impact structure, South Africa

Spray

Boonsue

2017

Meteorit & Planetary Scien

View full text Add to dashboard Cite

Abstract-Coesite and stishovite are developed in shock veins within metaquartzites beyond a radius of~30 km from the center of the 2.02 Ga Vredefort impact structure. This work focuses on deploying analytical field emission scanning electron microscopy, electron backscattered diffraction, and Raman spectrometry to better understand the temporal and spatial relations of these silica polymorphs. a-Quartz in the host metaquartzites, away from shock veins, exhibits planar features, Brazil twins, and decorated planar deformation features, indicating a primary (bulk) shock loading of >5 < 35 GPa. Within the shock veins, coesite forms anhedral grains, ranging in size from 0.5 to 4 lm, with an average of 1.25 lm. It occurs in clasts, where it displays a distinct jigsaw texture, indicative of partial reversion to a less dense SiO 2 phase, now represented by microcrystalline quartz. It is also developed in the matrix of the shock veins, where it is typically of smaller size (<1 lm). Stishovite occurs as euhedral acicular crystals, typically <0.5 lm wide and up to 15 lm in length, associated with clast-matrix or shock vein margin-matrix interfaces. In this context, the needles occur as radiating or subparallel clusters, which grow into/over both coesite and what is now microcrystalline quartz. Stishovite also occurs as more blebby, subhedral to anhedral grains in the vein matrix (typically <1 lm). We propose a model for the evolution of the veins (1) precursory frictional melting in a microfault (~1 mm wide) generates a molten matrix containing quartz clasts. This is followed by (2) arrival of the main shock front, which shocks to 35 GPa. This generates coesite in the clasts and in the matrix. (3) On initial shock release, the coesite partly reverts to a less dense SiO 2 phase, which is now represented by microcrystalline quartz. (4) With continued release, stishovite forms euhedral needle clusters at solid-liquid interfaces and as anhedral crystals in the matrix. (5) With decreasing pressure-temperature, the matrix completes crystallization to yield a microcrystalline quasi-igneous texture comprising quartz-coesite-stishovite-kyanite-biotitealkali feldspar and accessory phases. It is possible that the shock vein represents the locus of a thermal spike within the bulk shock, in which case there is no requirement for additional pressure (i.e., the bulk shock was ≃35 GPa). However, if that pressure was not realized from the main shock, then supplementary pressure excursions within the vein would have been required. These could have taken the form of localized reverberations from wave trapping, or implosion processes, including pore collapse, phase change-initiated volume reduction, and melt cavitation.

show abstract

Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system

Cited by 331 publications

References 115 publications

Petrogenesis and In Situ U‐Pb Geochronology of a Strongly Shocked L‐Melt Rock Northwest Africa 11042

Petrogenesis and In Situ U‐Pb Geochronology of a Strongly Shocked L‐Melt Rock Northwest Africa 11042

Variation in Magnetic Fabrics at Low Shock Pressure Due to Experimental Impact Cratering

Quartz–coesite–stishovite relations in shocked metaquartzites from the Vredefort impact structure, South Africa

Contact Info

Product

Resources

About