Shock Metamorphism Research Articles

The redox state of iron in the matrix of CI, CM and metamorphosed CM chondrites by XANES spectroscopy

Carbonaceous chondrites record the action of water at some point of their petrological history. These meteorites are usually connected to low albedo asteroid, which present visible/near-IR absorption explained by iron related absorption within phyllosilicates and oxides. In order to obtain quantitative insight into the mineralogy of iron-bearing phases, we have measured X-ray absorption near-edge spectroscopy at the iron K-edge of matrix from carbonaceous chondrites. This method enables to constrain the redox state and environment of iron in these meteorites. For this study, we selected seven CM chondrites and the CI Orgueil, expected to span a range of aqueous alteration degrees. Our analysis of the pre-edge features show that the redox state of Orgueil (CI) is dominated by octahedral Fe and that the Fe3+/(Fe3++Fe2+) atomic ratio is above 80%. Full-inversion of the spectra suggests that the iron budget is dominated by iron oxides, with additional contributions from phyllosilicate. In the case of the CM, the iron speciation appears different that in the case of Orgueil. Cronstedtite is identified from the inversion of the spectra, and suggested by the presence of significant amount of tetrahedral Fe3+. Within the CM chondrites, a trend of aqueous alteration appears presents, and which is roughly correlated to the scheme defined by Rubin et al. (2007). This trend is characterized by an increase in the amount of iron oxides. Two shock metamorphosed CM are present in our dataset (PCA 91008, WIS 91600). If WIS 91600 does not appear distinguishable, from the CM trend, in the case of PCA 91008, shock metamorphism did impact the pre-edge intensity and an increased amount of anhydrous silicates is found. Although the matrix was dehydrated, significant amount of Fe3+ is still present, providing a memory of the aqueous alteration.

Shock and thermal annealing history of the ALH 77005 Martian meteorite: a micro-Raman spectroscopical investigation

Abstract We studied optical microscopic and micro-Raman spectroscopic signatures of shocked olivine from the ALH 77005 Martian meteorite sample. The purpose of this study is to document pressure and temperature-related effects in olivine over the entire sample, which can aid in understanding structural changes due to shock metamorphism and the post-shock thermal annealing processes of lherzolitic Martian meteorites. According to the optical microscope observations, three areas may be discernible in olivine of the ALH 77005 in the vicinity of the melt pocket. The first area is the thermally undisturbed part of a grain, which contains a high density of shock-induced planar microdeformations such as Planar Deformation Features (PDFs) and Planar Fractures (PFs). Compared to the first area, the second area shows less shock-induced microstructures, while the third area is a strongly recrystallized region, but not formed from a melt. A common Raman spectral feature of these olivines is a regular doublet peak cen...

Very high-K KREEP-rich clasts in the impact melt breccia of the lunar meteorite SaU 169: New constraints on the last residue of the Lunar Magma Ocean

In the impact melt breccia (IMB) of Sayh al Uhaymir (SaU) 169, the most KREEP-rich lunar meteorite to date (Gnos et al., 2004), clasts of a new type of lithologies were discovered, consisting of Ca-poor and Ca-rich pyroxenes (60.8vol.%), Ba-rich K-feldspar (27.9vol.%), phosphates (5.6vol.%), Nb-rich ilmenite (4.0vol.%), zircon (1.2vol.%) and minor sulfide (0.6vol.%). These mafic lithic clasts are more enriched in KREEP component (∼1500×CI) than the host meteorite and are highly enriched in potassium. They are referred to as very high-K (VHK) KREEP lithology, and probably most close to the last residual liquid of the Lunar Magma Ocean without significant dilution by other Mg-rich magmas. The fine-grained matrix of the SaU 169 IMB has very similar mineral chemistry to the VHK KREEP lithology, but contains abundant plagioclase with trace K-feldspar. The matrix shows decoupling of K from the REEP-like component; however, it cannot be simply interpreted by mixing the VHK KREEP lithology with anorthosites, which should have diluted the REEP-like component with the same proportion.SIMS Pb–Pb dating was conducted on zircons in various petrographic settings and with different crystal habits. All analyses show a main age peak at 3921±3Ma and a smaller one at 4016±6Ma. The main age peak is identical to the previous Pb–Pb age by Gnos et al. (2006) and U–Pb age by Liu et al. (2009), dating the catastrophic shock event contributed to the formation of SaU 169 IMB. The older ages are consistent with the previous report of an older bulk U–Pb age by Kramers et al. (2007), suggestive of presence of relict crystals in a few large zircon grains. The VHK KREEP clasts predated the fine-grained matrix, but have the same zircon Pb–Pb ages as the latter within the analytical uncertainties. Plagioclase was converted to maskelynite whereas zircon was shocked to diaplectic glass, probably by a second event at ∼2.8Ga. However, the identical zircon Pb–Pb ages of the amorphous parts and the remained crystalline areas indicate no resetting of Pb–Pb isotopes by the later shock metamorphism, or there was another severe impact event postdated solidification of the fine-grained matrix within a few million years.

Talundilly, Western Queensland, Australia: geophysical and petrological evidence for an 84 km-large impact structure and an Early Cretaceous impact cluster

The Talundilly Structure, southwestern Queensland, Australia, is represented on 2D seismic reflection transects as a major seismic anomaly disrupting the consistent ‘C’ seismic–stratigraphic horizon above the early Cretaceous Bulldog Wallumbilla Formation throughout the Eromanga Basin. The seismic anomalous zone, estimated at 84 km in diameter from the maximum extent of horizon disruption, coincides with a prominent aeromagnetic (TMI) high which is centrally located within a near-circular seismic anomaly of the ‘C’ horizon. The structure consists of a raised central area, with radial faults extending from the central high, an annular synform with disrupted seismic elements dipping at low angles towards the central uplift, and an outer faulted rim. Cuttings from the Talundilly-1 well, drilled ∼30 km northwest from the central high, contain quartz grains with planar deformation features (PDF) indicative of shock metamorphism. The age of the structure, as determined from seismic correlation and sparse palynology, post-dates the ‘C’ seismic horizon and is determined as approximately 125 Ma, coinciding with a marine transgression. Correlation of seismic profiles suggest that the Talundilly impact structure is a possible twin of the Tookoonooka impact structure, dated as 125 ± 1 Ma and located 328 km to the south.

Iron deficiency in pyrrhotite of suevites from the Chesapeake Bay impact crater, USA—A consequence of shock metamorphism?

Abstract– Pyrrhotite from suevite of the 35 Ma Chesapeake Bay impact structure (CBIS) shows a shock metamorphism and we report on several mineralogical and magnetic features. Pyrrhotite shows strong brittle deformation with a high density of stacking faults, twinning parallel to the hexagonal (001) planes and average fault distances in the order of 10 nm. Although the determination of a superstructure was not possible due to the lattice defects, the reflections of the NiAs subcell, which is typical of all pyrrhotite modifications, were clearly detected. This phase is ferrimagnetic with a Curie temperature (TC) between 350 and 365 °C, and suevite with this phase does not show the 34 K transition. The most peculiar feature is the low metal/sulfur ratio of 0.81, which indicates a distinctly higher vacancy concentration than for 4C pyrrhotite and a composition close to smythite (Fe9S11). This phase carries a stable natural remanent magnetization and is relatively hard magnetic. Steep inclinations of the natural remanent magnetization vector, however, suggest that this phase has been remagnetized by the drilling process. A possible explanation is the magnetic domain size of faultless areas of about 10 nm in diameter, which is at the lower limit of the single domain size near the threshold, below which superparamagnetic behavior occurs. The low thermal stability of this phase excludes postshock heating above 300 °C for the suevite of the CBIS. Our results imply that the iron‐deficient pyrrhotite is produced by shock metamorphism, although an iron loss due to shock has never been reported before for pyrrhotite.

Uranium-lead age of baddeleyite in shergottite Roberts Massif 04261: Implications for magmatic activity on Mars

[1] The issue of the duration of Martian magmatic activity is one of the controversial debates recently: whether the young radiometric ages of ∼180 Ma for shergottites, a class of Martian meteorites, reflect the timing of crystallization from a magma or rather record later events related to shock metamorphism. In order to address the timescale over which Mars was geologically active, we have undertaken U-Pb isotopic studies on baddeleyite in the Roberts Massif (RBT) 04261 shergottite. Baddeleyite in RBT 04261 is usually associated with ilmenite and shows monoclinic structure, suggesting that the baddeleyite could have formed by crystallization from a residual liquid and not by shock metamorphism. In situ U-Th-Pb isotopic analyses of baddeleyite yield a young238U-206Pb age of ∼200 Ma. Since the U-Pb system of baddeleyite is considered to be more resistant to resetting during reheating events, and olivine in RBT 04261 preserves an igneous calcium zoning, the young age of baddeleyite could be interpreted as a crystallization age of RBT 04261. The present results imply that Martian magma was still forming only 200 Ma ago, and that Mars had been geologically active until the recent past.

Shock-induced changes in density and porosity in shock-metamorphosed crystalline rocks, Haughton impact structure, Canada

Abstract– Shock metamorphism can occur at transient pressures that reach tens of GPa and well over 1000 °C, altering the target material on both megascopic and microscopic scales. This study explores the effects of shock metamorphism on crystalline, quartzofeldspathic basement material from the Haughton impact structure on Devon Island, Arctic Canada. Shock levels were assigned to samples based on petrographic examination of main mineral phases. Conventional shock classification schemes proved to incompletely describe the Haughton samples so a modified shock classification system is presented. Fifty-two crystalline bedrock samples from the clast-rich impact melt rocks in the crater, and one reference site outside of the crater, were classified using this system. The shock levels range from 0 to 7 (according to the new shock stage classification proposed here, i.e., stages 0–IV after the Stoffler classification), indicating shock pressures ranging from 0 to approximately 80 GPa. The second aspect of this study involved measuring bulk physical characteristics of the shocked samples. The bulk density, grain density, and porosity were determined using a water displacement method, a bead displacement method, and a Hepycnometer. Results suggest a nonlinear, negative correlation between density and shock level such that densities of crystalline rocks with original densities of approximately 3 g cm−3 are reduced to <1.0 g cm−3 at high shock levels. The results also show a positive nonlinear correlation between porosity and shock level. These data illustrate the effect of shock on the bulk physical characteristics of crystalline rocks, and has implications for assessing the habitability of shocked rocks.

Rock magnetic and paleomagnetic study of the Keurusselkä impact structure, central Finland

Abstract–There are 31 proven impact structures in Fennoscandia—one of the most densely crater‐populated areas of the Earth. The recently discovered Keurusselkä impact structure (62°08′ N, 24°37′ E) is located within the Central Finland Granitoid Complex, which formed 1890–1860 Ma ago during the Svecofennian orogeny. It is a deeply eroded complex crater that yields in situ shatter cones with evidence of shock metamorphism, e.g., planar deformation features in quartz. New petrophysical and rock magnetic results of shocked and unshocked target rocks of various lithologies combined with paleomagnetic studies are presented. The suggested central uplift with shatter cones is characterized by increased magnetization and susceptibility. The presence of magnetite and pyrrhotite was observed as carriers for the remanent magnetization. Four different remanent magnetization directions were isolated: (1) a characteristic Svecofennian target rock component A with a mean direction ofD = 334.8°,I = 45.6°, α95 = 14.9° yielding a pole (Plat = 51.1°, Plon = 241.9°,A95 = 15.1°), (2) component B,D = 42.4°,I = 64.1°, α95 = 8.4° yielding a pole (Plat = 61.0°, Plon = 129.1°,A95 = 10.6°), (3) component C (D = 159.5°,I= 65.4°, α95 = 10.7°) yielding a pole (Plat = 21.0°, Plon = 39.3°,A95 = 15.6°), and (4) component E (D = 275.5°,I = 62.0°, α95 = 14.4°) yielding a pole (Plat = 39.7°, Plon = 314.3°,A95 = 19.7°). Components C and E are considered much younger, possibly Neoproterozoic overprints, compared with the components A and B. The pole of component B corresponds with the 1120 Ma pole of Salla diabase dyke and is in agreement with the40Ar/39Ar age of 1140 Ma from a pseudotachylitic breccia vein in a central part of the structure. Therefore, component B could be related to the impact, and thus represent the impact age.

Ringwoodite microstructures in L-chondrite NWA 5011: implications for transformation mechanism and source region in L parent body

Ringwoodite, produced by shock metamorphism, is common in and adjacent to melt veins in highly shocked chondrites. Although ringwoodite can be crystallized from the silicate melt in the shock-veins or pockets, a major part of the easily observed ringwoodite in shock veins is formed by the transformation of olivine in host-rock fragments entrained in the melt or olivine along shock-vein margins. In this paper we examine the microstructures and textures of ringwoodites from NWA 5011 L-chondrite in order to better understanding the transformation mechanisms of ringwoodite by optical microscope. Finally, we attempt to locate the source region of L-type chondrites in three different impact scenarios of the L parent body.

The newly confirmed Luizi impact structure, Democratic Republic of Congo—Insights into central uplift formation and post-impact erosion

Rocks exposed within the uplifted central part of meteorite impact structures come from signifi cant stratigraphic depths, in some cases as much as several kilometers. On Earth, cen- tral uplifts are commonly the fi nal and only feature of an impact crater that remains after the rest of the structure is lost to erosion. However, the crater-forming process that results in the formation of intricate features such as central peak and peak rings is poorly understood. Much of our knowledge is based on extraterrestrial observations; as on Earth, there are very few unequivocal examples of impact craters with well-preserved peak and ring morphologies, because of erosion. In this study we describe the ~17-km-diameter Luizi structure (Katanga region, Democratic Republic of Congo), a moderate-sized complex crater, with an intermedi- ate ring (~5.2 km in diameter), and an ~2-km-wide circular central ring around a central depression. For the fi rst time, unique evidence of shock metamorphism, in the form of macro- scopic shatter cones and multiple sets of microscopic planar deformation features in quartz and feldspar grains, is described, confi rming the meteorite impact origin of the structure. Our observations at Luizi provide insights into the formation of mid-sized impact craters on Earth, adding to the evidence that, in the case of sedimentary target lithologies, structural ring struc- tures within the central uplift may form by the collapse of an unstable central peak. Given the preservation state of the Luizi crater, it cannot be excluded that structural rings may be a common feature for mid-size craters developed in layered target rocks.

Laboratory thermal emission spectroscopy of shocked basalt from Lonar Crater, India, and implications for Mars orbital and sample data

Whereas the thermal infrared (TIR) spectra of specific minerals and/or igneous and metamorphic rocks have been compared to data of the Martian surface, TIR data of the impactite products of the shock metamorphism of basalt have not been examined in detail. The effects of shock on the thermal infrared spectrum of Deccan basalt are described here. Sample collection at Lonar Crater, India, yielded four classes of shocked basalt: classes 1, 2, 4, and 5. Spectral features attributed to labradorite in TIR spectrum of unshocked Deccan basalt are absent in the spectrum of class 2 shocked basalt. Petrography confirms that labradorite has been replaced by diaplectic glass (maskelynite). The TIR spectrum of class 2 shocked basalt is nearly identical to that of the Los Angeles shergottite. The addition of experimentally shocked plagioclase feldspars as TIR end‐members improves fits and lowers RMS errors for the deconvolution of the TIR spectrum of the maskelynite‐bearing impactite, and the correct mineralogy is chosen to within 5%. Class 4 shocked basalt contains vesiculated plagioclase glass (due to more heat) and highly fractured augites. Two class 5 spectral types have primary Si‐O stretching vibrations at lower wave numbers than Si and Si‐K glass end‐members commonly used in analyses of TIR data, agreeing with lower SiO2 abundances (∼50%) determined from two techniques. At least three differences in spectral features exist between the two class 5 spectral types that we attribute to incomplete melting in the class 5A samples based on comparison to the class 4 spectrum. These samples and their TIR spectra represent excellent analogs for Martian shocked basalt and new lithologic end‐members for use in spectral libraries used to analyze TIR data from Mars.

ANIE: A mathematical algorithm for automated indexing of planar deformation features in quartz grains

Abstract– Planar deformation features (PDFs) in quartz, one of the most commonly used diagnostic indicators of shock metamorphism, are planes of amorphous material that follow crystallographic orientations, and can thus be distinguished from non‐shock‐induced fractures in quartz. The process of indexing data for PDFs from universal‐stage measurements has traditionally been performed using a manual graphical method, a time‐consuming process in which errors can easily be introduced. A mathematical method and computer algorithm, which we call the Automated Numerical Index Executor (ANIE) program for indexing PDFs, was produced, and is presented here. The ANIE program is more accurate and faster than the manual graphical determination of Miller–Bravais indices, as it allows control of the exact error used in the calculation and removal of human error from the process.

Gebel Kamil: The iron meteorite that formed the Kamil crater (Egypt)

Abstract– The 45 m in diameter Kamil impact crater was formed &lt;5000 yr ago in the eastern Sahara, close to the southern border of modern Egypt. The original features of this structure, including thousands of fragments of the meteorite impactor, are extremely well preserved. With the exception of a single 83 kg regmaglypted individual, all specimens of Gebel Kamil (the iron meteorite that formed the Kamil crater) are explosion fragments weighing from &lt;1 g to 34 kg. Gebel Kamil is an ungrouped Ni‐rich (about 20 wt% Ni) ataxite characterized by high Ge and Ga contents (approximately 120 μg g−1 and approximately 50 μg g−1, respectively) and by a very fine‐grained duplex plessite metal matrix. Accessory mineral phases in Gebel Kamil are schreibersite, troilite, daubréelite, and native copper. Meteorite fragments are cross‐cut by curvilinear shear bands formed during the explosive terrestrial impact. A systematic search around the crater revealed that meteorite fragments have a highly asymmetric distribution, with greater concentrations in the southeast sector and a broad maximum in meteorite concentration in the 125–160° N sector at about 200 m from the crater rim. The total mass of shrapnel specimens &gt;10 g, inferred from the density map compiled in this study is 3400 kg. Field data indicate that the iron bolide approached the Earth’s crust from the northwest (305–340° N), travelling along a moderately oblique trajectory. Upon hypervelocity impact, the projectile was disrupted into thousands of fragments. Shattering was accompanied by some melting of the projectile and of the quartz‐arenite target rocks, which also suffered shock metamorphism.

Shock effects and the classification of H-chondrites from the Grove Mountains, East Antarctica: Implications for the shock history of H-chondrite parent bodies

The shock metamorphism of 47 H group chondrites (H-chondrites) from the Grove Mountains including undulatory extinction, planar fractures, mosaic extinction, shock veins and pockets, and dendritic eutectic metal-sulfide, is observed through optical microscope. The textures and assemblages of shock veins in these H-chondrites are examined by the scanning electron microscope. Based on observations of the above shock effects, the shock stages of the 47 H-chondrites are classified into S1(5), S2(19), S3(14), S4(8) and S5(1). Of these H-chondrites, GRV 022469 has the highest(S5) shock stage. The comparison of shock stages in these H-chondrites with L group chondrites(L-chondrites) indicates that the shock metamorphism of H-chondrites is relatively low (except for GRV 022469, they are all lower than S5). A scenario for the history of the H-chondrite parent body is proposed that suggests the duration of the shock events in the H-chondrite parent bodies was much shorter than those in L-chondrite parent bodies. Also, the pressure may have been released more quickly, and consequently, the high-pressure phases should be easily preserved. However, the parent bodies of the H-chondrites may have been exposed to high temperatures for a longer time after the shock event, so the high-pressure phases formed by solid transformation might have retro-metamorphosed to low-pressure ones; its peak pressure is estimated to be less than 15 GPa. Wadsleyite was found in a shock vein in GRV022469, as confirmed by the Raman spectrometer. Petrological and mineralogical characteristics support the idea that the wadsleyite was formed by solid-state transformation.

Jared R. Morrow (October 8, 1959-October 7, 2010)

Jared R. Morrow (October 8, 1959-October 7, 2010)

(U‐Th)/He dating of terrestrial impact structures: The Manicouagan example

The accurate dating of meteorite impact structures on Earth has proven to be challenging. Melt sheets are amenable to high‐precision dating by the U‐Pb and 40Ar/39Ar methods, but many impact events do not produce them, or they are not preserved. In cases where high‐temperature shock metamorphism of the target materials has occurred without widespread melting, these isotopic chronometers may be partially reset and yield dates that are difficult to interpret unambiguously as the age of impact. However, the (U‐Th)/He chronometer is sensitive to thermal resetting and can provide a powerful new tool for dating impactites. We report (U‐Th)/He dates for accessory minerals from the Manicouagan impact structure in Quebec, Canada. Nine zircons from a melt sheet sample yield a weighted mean age of 213.2 ± 5.4 Ma (2SE), indistinguishable from the published 214 ± 1 Ma (2σ) U‐Pb zircon age for the impact. In contrast, five apatites from this sample yield dates between 205.9 ± 6.5 and 162.0 ± 5.3 Ma (2σ), indicating variable postimpact helium loss due to low‐temperature thermal disturbance. Preimpact titanite crystals from a shocked meta‐anorthosite sample yield two dates consistent with the impact age, at 212 ± 27 and 214 ± 13 Ma (2σ), and two younger dates of 189.6 ± 6.9 and 192.2 ± 9.8 Ma (2σ), suggestive of postimpact helium loss. These results indicate that (U‐Th)/He chronometry is a suitable method for dating impact events, although interpretation of the results requires recognition of possible 4He loss related to reheating subsequent to impact.

Planar deformation features in quartz from impact‐produced polymict breccia of the Xiuyan crater, China

Abstract– The 1.8 km‐diameter Xiuyan crater is an impact structure in northeastern China, exposed in a Proterozoic metamorphic rock complex. The major rocks of the crater are composed of granulite, hornblendite, gneiss, tremolite marble, and marble. The bottom at the center of the crater covers about 100 m thick lacustrine sediments underlain by 188 m thick crater‐fill breccia. A layer of polymict breccia composed of clasts of granulite, gneiss, hornblendite, and fragments of glass as well as clastic matrix, occurs near the base, in the depth interval from 260 to 295 m. An investigation in quartz from the polymict breccia in the crater‐fill units reveals abundant planar deformation features (PDFs). Quartz with multiple sets of PDFs is found in clasts of granulite that consist of mainly quartz and feldspar, and in fine‐grained matrix of the impact‐produced polymict breccia. A universal stage was used to measure the orientation of PDFs in 70 grains of quartz from five thin sections made from the clasts of granulite of polymict breccia recovered at the depth of 290 m. Forty‐four percent of the quartz grains contain three sets of PDFs, and another 40% contain two sets of PDFs. The most abundant PDFs are rhombohedron forms of , , and with frequency of 33.5, 22.3, and 9.6%, respectively. A predominant PDF form of in quartz suggests a shock pressure &gt;20 GPa. The occurrence of PDFs in quartz from the polymict breccia provides crucial evidence for shock metamorphism of target rocks and confirms the impact origin of this crater, which thus appears to be the first confirmed impact crater in China.

Ca‐Al‐Fe‐rich inclusion in the Vigarano CV3 chondrite

Abstract– An anomalous Ca‐Al‐Fe‐rich spherical inclusion (CAFI) was found in the Vigarano CV3 chondrite. The CAFI has an igneous texture and contains large amounts of almost pure and coarse‐grained hercynite grains (approximately 56 vol%) as well as refractory phases such as grossite and perovskite. However, melilite and Mg‐spinel, which are common in ordinary Ca‐Al‐rich inclusions, are very rare (&lt;1 vol%). Another unique characteristic of the CAFI is the presence in its core of dmitryivanovite (CaAl2O4), which was formed by shock metamorphism of a low‐pressure form of CaAl2O4 that was originally crystallized from a molten droplet. The fine‐grained hercynite and unidentified aluminous phase in the rim of the CAFI may have been produced from grossite during aqueous alteration in the Vigarano parent body.

Petrography, mineral chemistry and shock metamorphism of Yamato 984028 lherzolitic shergottite

Y984028 is a new lherzolitic shergottite, consisting of poikilitic and non-poikilitic lithologies. The mafic silicates are FeO-poor, and the chromite is TiO2-poor in the poikilitic lithology compared to the grains in the non-poikilitic lithology. This meteorite shares similar mineral petrography and mineral chemistry with GRV 99027, but is not paired with the latter because of their different shock-induced features. Y984028 was severely shocked and experienced no significant thermal metamorphism after the main impact event. Hence, Y984028 serves as a probe for the study of meteorite impact processes on terrestrial surfaces. The melt veins in Y984028 are characterized by the absence of any high-pressure polymorphs, the presence of abundant small mineral fragments, and the prevailing granulation textures of olivine and chromite. These features are consistent with adiabatic melting during the release of shock-induced high-pressure and quenching at ambient pressure.

Shock metamorphism investigations of quartz grains in clasts from impact breccia of the Eyreville B drill core, Chesapeake Bay impact structure, USA

Abstract– The Chesapeake Bay impact structure, approximately 85 km in diameter, has been drilled in 2005–2006 at Eyreville (Virginia, USA), to a total depth of 1766 m. In the drill cores, the abundance of shock metamorphosed material is very variable with depth. Shocked mineral and lithic clasts, as well as melt particles, are most abundant in suevitic impact breccia section (1397–1451 m depth). Shocked quartz (i.e., quartz grains with planar fractures and/or planar deformation features) and melt particles, although rare, are also dispersed in the Exmore Formation unit (444–867 m depth). Other lithologies in the Eyreville drill cores show no clear evidence of shock metamorphism. Here, we report on the investigations of 40 samples from the impact breccia section. A total of more than 27,000 quartz grains were examined in about 200 clasts. The abundance of highly shocked clasts tends to decrease with increasing depth. Crystalline clasts derived from the crystalline basement are commonly only slightly shocked (contain generally &lt;10 rel% of shocked quartz grains). The clasts of metamorphosed sediments show a low proportion of shocked quartz grains (mostly &lt;10 rel%). Sedimentary clasts show a wide range of proportions of shocked quartz grains, with several of them being highly shocked clasts (most values between 0 and 40 rel%). Conglomerates show the highest proportion of shocked quartz grains of all types of clasts (up to 83 rel%). Polycrystalline quartz clasts are also commonly highly shocked (contain mostly between 10 and 40 rel% of shocked quartz grains). These hard nonporous clasts are possibly more liable to show evidence of shock. The investigations suggest that the intensity of shock metamorphism is the result of several parameters, such as original position in the target (both horizontal and vertical) and the properties of each lithology (e.g., grain size, porosity, and amount of matrix). According to the universal‐stage investigations, the dominant orientations of planar deformation features in quartz are , , and also .