Alternating augite‐plagioclase wedges in basement dolerites of Lockne impact structure, Sweden: A new shock wave‐induced deformation feature

Agarwal, Amar; Резник, Б.; Alva‐Valdivia, Luis M.; Srivastava, Deepak C.

doi:10.1111/maps.12806

Cited by 9 publications

(3 citation statements)

References 55 publications

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“…Formation of new magnetite at mechanical heterogeneity such as cleavage or kink planes in biotite and transformation of Fe oxides/hydroxides into magnetite cannot be excluded. Lithological interfaces, for example, due to foliation, may lead to shock pressure excursions, additional accumulated strain, and localized shear displacements as observed at the microscale (Agarwal, Reznik, Alva-Valdivia, & Srivastava, 2016;Agarwal, Reznik, Kontny, et al, 2016) and in the field (Kenkmann & Ivanov, 2006).…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

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

et al. 2019

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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.

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Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

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

et al. 2019

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“…Such microstructures more likely represent the brittle fracture of pyroxene (e.g., see also similar textures in rocks from the terrestrial Lockne impact crater, Sweden; fig. 3 of Agarwal et al 2017).…”

Section: Stem Observationsmentioning

confidence: 98%

Occurrence and implications of secondary olivine veinlets in lunar highland breccia Northwest Africa 11273

Zeng

Joy

et al. 2019

Meteorit & Planetary Scien

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Lunar breccias preserve the records of geologic processes on the Moon. In this study, we report the occurrence, petrography, mineralogy, and geologic significance of the observed secondary olivine veinlets in lunar feldspathic breccia meteorite Northwest Africa (NWA) 11273. Bulk-rock composition measurements show that this meteorite is geochemically similar to other lunar highland meteorites. In NWA 11273, five clasts are observed to host veinlets that are dominated by interconnecting olivine mineral grains. The host clasts are mainly composed of mafic minerals (i.e., pyroxene and olivine) and probably sourced from a basaltic lithology. The studied olivine veinlets (~5 to 30 lm in width) are distributed within the mafic mineral host, but do not extend into the adjacent plagioclase. Chemically, these olivine veinlets are Fe-richer (Fo 41.4-51.9), compared with other olivine grains (Fo 54.3-83.1) in lithic clasts and matrix of NWA 11273. By analogy with the secondary olivine veinlets observed in meteorites from asteroid Vesta (howardite-eucrite-diogenite group samples) and lunar mare samples, our study suggests that the newly observed olivine veinlets in NWA 11273 are likely formed by secondary deposition from a lunar fluid, rather than by crystallization from a high-temperature silicate melt. Such fluid could be sulfur-and phosphorous-poor and likely had an endogenic origin on the Moon. The new occurrence of secondary olivine veinlets in breccia NWA 11273 reveals that the fluid mobility and deposition could be a previously underappreciated geological process on the Moon.

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“…Similar morphologies are observed in terrestrial craters formed in shallow‐marine environments such as Chesapeake Bay (Gohn et al, 2008) or Lockne (Ormö & Lindström, 2000). On a much smaller scale, the shock wave reflects, refracts, and superposes at boundaries of materials with contrasting mechanical properties to cause localized intense shock deformation (e.g., Agarwal et al, 2016; Agarwal et al, 2016; Kenkmann et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Impact Experiment on Gneiss: The Effects of Foliation on Cratering Process

et al. 2019

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Two impact experiments were carried out on blocks of Maggia gneiss to assess the influence of mechanical target anisotropies on the cratering process. The experiments were done within the framework of Multidisciplinary Experimental and Modeling Impact Research Network. In one experiment the metamorphic foliation was vertical, that is, oriented perpendicular to the target surface, and in the other horizontal, that is, parallel to the target surface. This study reveals that due to preferred spallation along the foliation, the cratering efficiency is higher if the foliation is horizontal. The study further presents a comprehensive quantitative strain analysis in the subsurface of these craters. We use biotite kink bands as strain markers. The distribution of strain differs strongly in both experiments. If the foliation is vertical, the area beneath the central crater floor shows a high compressive strain. This is attributed to the ability of biotite to kink more easily when shortened parallel to its basal plane. If the foliation is horizontal, surface kinking is reduced and tensile failure along the foliation deepens the crater during unloading.

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Alternating augite‐plagioclase wedges in basement dolerites of Lockne impact structure, Sweden: A new shock wave‐induced deformation feature

Cited by 9 publications

References 55 publications

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

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

Occurrence and implications of secondary olivine veinlets in lunar highland breccia Northwest Africa 11273

Impact Experiment on Gneiss: The Effects of Foliation on Cratering Process

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