Shock stage distribution of 2280 ordinary chondrites—Can bulk chondrites with a shock stage of S6 exist as individual rocks?

The brecciation and shock classification of 2280 ordinary chondrites of the meteorite thin section collection at the Institut für Planetologie (Münster) has been determined. The shock degree of S3 is the most abundant shock stage for the H and LL chondrites (44% and 41%, respectively), while the L chondrites are on average more heavily shocked having more than 40% of rocks of shock stage S4. Among the H and LL chondrites, 40–50% are “unshocked” or “very weakly shocked.” Considering the petrologic types, in general, the shock degree is increasing with petrologic type. This is the case for all meteorite groups. The main criteria to define a rock as an S6 chondrite are the solid‐state recrystallization and staining of olivine and the melting of plagioclase often accompanied by the formation of high‐pressure phases like ringwoodite. These characteristics are typically restricted to local regions of a bulk chondrite in or near melt zones. In the past, the identification of high‐pressure minerals (e.g., ringwoodite) was often taken as an automatic and practical criterion for a S6 classification during chondrite bulk rock studies. The shock stage classification of many significantly shocked chondrites (>S3) revealed that most ringwoodite‐bearing rocks still contain more than 25% plagioclase (74%). Thus, these bulk chondrites do not even fulfill the S5 criterion (e.g., 75% of plagioclase has to be transformed into maskelynite) and have to be classified as S4. Studying chondrites on typically large thin sections (several cm²) and/or using samples from different areas of the meteorites, bulk chondrites of shock stage S6 should be extremely rare. In this respect, the paper will discuss the probability of the existence of bulk rocks of S6.     

Northwest Africa 4797: A strongly shocked ultramafic poikilitic shergottite related to compositionally intermediate Martian meteorites

Abstract– Northwest Africa (NWA) 4797 is an ultramafic Martian meteorite composed of olivine (40.3 vol%), pigeonite (22.2%), augite (11.9%), plagioclase (9.1%), vesicles (1.6%), and a shock vein (10.3%). Minor phases include chromite (3.4%), merrillite (0.8%), and magmatic inclusions (0.4%). Olivine and pyroxene compositions range from Fo_66–72,En_58–74Fs_19–28Wo_6–15, and En_46–60Fs_14–22Wo_34–40, respectively. The rock is texturally similar to “lherzolitic” shergottites. The oxygen fugacity was QFM?2.9 near the liquidus, increasing to QFM?1.7 as crystallization proceeded. Shock effects in olivine and pyroxene include strong mosaicism, grain boundary melting, local recrystallization, and pervasive fracturing. Shock heating has completely melted and vesiculated igneous plagioclase, which upon cooling has quench‐crystallized plagioclase microlites in glass. A mm‐size shock melt vein transects the rock, containing phosphoran olivine (Fo_69–79), pyroxene (En_44–51Fs_14–18Wo_30–42), and chromite in a groundmass of alkali‐rich glass containing iron sulfide spheres. Trace element analysis reveals that (1) REE in plagioclase and the shock melt vein mimics the whole rock pattern; and (2) the reconstructed NWA 4797 whole rock is slightly enriched in LREE relative to other intermediate ultramafic shergottites, attributable to local mobilization of melt by shock. The shock melt vein represents bulk melting of NWA 4797 injected during pressure release. Calculated oxygen fugacity for NWA 4797 indicates that oxygen fugacity is decoupled from incompatible element concentrations. This is attributed to subsolidus re‐equilibration. We propose an alternative nomenclature for “lherzolitic” shergottites that removes genetic connotations. NWA 4797 is classified as an ultramafic poikilitic shergottite with intermediate trace element characteristics.     

Shock metamorphism in plagioclase and selective amorphization

Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood. In particular, constraining the initiation and progression of shock‐induced amorphization in plagioclase (i.e., conversion to diaplectic glass) would improve our knowledge of how shock progressively deforms plagioclase. In turn, this information would enable plagioclase to be used to evaluate the shock stage of meteorites and terrestrial impactites, whenever they lack traditionally used shock indicator minerals, such as olivine and quartz. Here, we report on an electron backscatter diffraction (EBSD) study of shocked plagioclase grains in a metagranite shatter cone from the central uplift of the Manicouagan impact structure, Canada. Our study suggests that, in plagioclase, shock amorphization is initially localized either within pre‐existing twins or along lamellae, with similar characteristics to planar deformation features (PDFs) but that resemble twins in their periodicity. These lamellae likely represent specific crystallographic planes that undergo preferential structural failure under shock conditions. The orientation of preexisting twin sets that are preferentially amorphized and that of amorphous lamellae is likely favorable with respect to scattering of the local shock wave and corresponds to the “weakest” orientation for a specific shock pressure value. This observation supports a universal formation mechanism for PDFs in silicate minerals.     

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

We reevaluate the systematics and geologic setting of terrestrial, lunar, Martian, and asteroidal “impactites” resulting from single or multiple impacts. For impactites derived from silicate rocks and sediments, we propose a unified and updated system of progressive shock metamorphism. “Shock-metamorphosed rocks” occur as lithic clasts or melt particles in proximal impactites at impact craters, and rarely in distal impactites. They represent a wide range of metamorphism, typically ranging from unshocked to shock melted. As the degree of shock metamorphism, at a given shock pressure, depends primarily on the mineralogical composition and the porosity of a rock or sediment sample, different shock classification systems are required for different types of planetary rocks and sediments. We define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments (1) crystalline rocks with classes F, M, A, and U; (2) chondritic rocks (class C); and (3) sedimentary rocks and sediments with classes SR, SE, and RE. The abbreviations stand for felsic (F), mafic (M), anorthositic (A), ultramafic (U), sedimentary rocks (SR), unconsolidated sediments (SE), and regoliths (RE). In each class, the progressive stages of shock metamorphism are denominated S1 to Sx. These progressive shock stages are introduced as: S1–S7 for F , S1–S7 for M, S1–S6 for A , S1–S7 for U , S1–S7 for C , S1–S7 for SR , S1–S5 for SE , and S1–S6 for RE . S1 stands for “unshocked” and Sx (variable between S5 and S7) stands for “whole rock melting.” We propose a sequence of symbols characterizing the degree of shock metamorphism of a sample, i.e., F-S1 to F-S7 with the option to add the tabulated pressure ranges (in GPa) in parentheses.     

Transformation textures,mechanisms of formation of high‐pressure minerals in shock melt veins of L6 chondrites,and pressure‐temperature conditions of the shock events

Abstract— The high‐pressure polymorphs of olivine, pyroxene, and plagioclase in or adjacent to shock melt veins (SMVs) in two L6 chondrites (Sahara 98222 and Yamato 74445) were investigated to clarify the related transformation mechanisms and to estimate the pressure‐temperature conditions of the shock events. Wadsleyite and jadeite were identified in Sahara 98222. Wadsleyite, ringwoodite, majorite, akimotoite, jadeite, and lingunite (NaAlSi₃O₈‐hollandite) were identified in Yamato 74445. Wadsleyite nucleated along the grain boundaries and fractures of original olivine. The nucleation and growth of ringwoodite occurred along the grain boundaries of original olivine, and as intracrystalline ringwoodite lamellae within original olivine. The nucleation and growth of majorite took place along the grain boundaries or fractures in original enstatite. Jadeite‐containing assemblages have complicated textures containing “particle‐like,” “stringer‐like,” and “polycrystalline‐like” phases. Coexistence of lingunite and jadeite‐containing assemblages shows a vein‐like texture. We discuss these transformation mechanisms based on our textural observations and chemical composition analyses. The shock pressure and temperature conditions in the SMVs of these meteorites were also estimated based on the mineral assemblages in the SMVs and in comparison with static high‐pressure experimental results as follows: 13–16 GPa, >1900 °C for Sahara 98222 and 17–24 GPa, >2100 °C for Yamato 74445.     

THE TIMMERSOI†, NIGER,HYPERSTHENE CHONDRITE

The Timmersoi meteorite, a new type L5 hypersthene chondrite from the Niger Republic is described and microprobe analyses of its olivine, orthopyroxene, clinopyroxene, plagioclase, kamacite, taenite, troilite, chromite, whitlockite, chlorapatite and limonite presented. Veins and patches of black “glassy” material are regarded as products of shock melting. In places this material contains immiscible droplets of troilite each with one or more well-formed crystals of taenite. Calculations indicate equilibrium between olivine and orthopyroxene with a temperature of equilibration of about 850 °C.     

Shock and thermal history of Northwest Africa 4859, an annealed impact‐melt breccia of LL chondrite parentage containing unusual igneous features and pentlandite

Abstract– Northwest Africa 4859 (NWA 4859) is a meteorite of LL chondrite parentage that shows unusual igneous features and contains widely distributed pentlandite. The most obvious unusual feature is a high proportion of large (≤3 cm diameter) igneous‐textured enclaves (LITEs), interpreted as shock melts that were intruded into an LL chondrite host. One such LITE appears to have been produced by whole rock melting of LL chondrite, initial rapid partial crystallization, and subsequent slow cooling of the residual melt in the host to produce a differentiated object. Other unusual features include mm‐sized “overgrowth objects,” fine‐grained plagioclase‐rich bands, and coarse troilite (≤7 mm across) grains. All these features are interpreted as having crystallized from melts produced by a single transient shock event, followed by slow cooling. A subsequent shock event of moderate (S3) intensity produced veining and transformed some of the pyroxene into the clinoenstatite polytype. Pentlandite (together with associated troilite) in NWA 4859 probably formed by the breakdown of a monosulfide precursor phase at low temperature (≤230 °C) following the second shock event. NWA 4859 is interpreted to be an unusual impact‐melt breccia that contains shock melt which crystallized in different forms at depth within the parent body.     

Northwest Africa 2526: A partial melt residue of enstatite chondrite parentage

Abstract— NWA 2526 is a coarse‐grained, achondritic rock dominated by equigranular grains of polysynthetically twinned enstatite (?85 vol%) with frequent 120° triple junctions and ?10–15 vol% of kamacite + terrestrial weathering products. All other phases including troilite, daubreelite, schreibersite, and silica‐normative melt areas make up 相似文献   

Toward quantification of strain‐related mosaicity in shocked lunar and terrestrial plagioclase by in situ micro‐X‐ray diffraction

Studies of shock metamorphism of feldspar typically rely on qualitative petrographic observations, which, while providing invaluable information, can be difficult to interpret. Shocked feldspars, therefore, are now being studied in greater detail by various groups using a variety of modern techniques. We apply in situ micro‐X‐ray diffraction (μXRD) to shocked lunar and terrestrial plagioclase feldspar to contribute to the development of a quantitative scale of shock deformation for the feldspar group. Andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada, and anorthite from Earth's Moon, returned during the Apollo program, were examined using optical petrography and assigned to subgroups of the optical shock level classification system of Stöffler (1971). Two‐dimensional μXRD patterns from the same samples revealed increased peak broadening in the chi dimension (χ), due to strain‐related mosaicity, with increased optical signs of deformation. Measurement of the full width at half maximum along χ (FWHMχ) of these peaks provides a quantitative way to measure strain‐related mosaicity in plagioclase feldspar as a proxy for shock level.     

Lunar highland meteorite Dhofar 026 and Apollo sample 15418: Two strongly shocked,partially melted,granulitic breccias

Abstract— Studies of lunar meteorite Dhofar 026, and comparison to Apollo sample 15418, indicate that Dhofar 026 is a strongly shocked granulitic breccia (or a fragmental breccia consisting almost entirely of granulitic breccia clasts) that experienced considerable post‐shock heating, probably as a result of diffusion of heat into the rock from an external, hotter source. The shock converted plagioclase to maskelynite, indicating that the shock pressure was between 30 and 45 GPa. The post‐shock heating raised the rock's temperature to about 1200 °C; as a result, the maskelynite devitrified, and extensive partial melting took place. The melting was concentrated in pyroxene‐rich areas; all pyroxene melted. As the rock cooled, the partial melts crystallized with fine‐grained, subophitic‐poikilitic textures. Sample 15418 is a strongly shocked granulitic breccia that had a similar history, but evidence for this history is better preserved than in Dhofar 026. The fact that Dhofar 026 was previously interpreted as an impact melt breccia underscores the importance of detailed petrographic study in interpretation of lunar rocks that have complex textures. The name “impact melt” has, in past studies, been applied only to rocks in which the melt fraction formed by shock‐induced total fusion. Recently, however, this name has also been applied to rocks containing melt formed by heating of the rocks by conductive heat transfer, assuming that impact is the ultimate source of the heat. We urge that the name “impact melt” be restricted to rocks in which the bulk of the melt formed by shock‐induced fusion to avoid confusion engendered by applying the same name to rocks melted by different processes.     

TIERRA BLANCA: AN UNUSUAL ACHONDRITE FROM WEST TEXAS

Tierra Blanca is an achondrite (sensu stricto) composed chiefly of orthopyroxene, olivine, plagioclase and clinopyroxene. The mineralogy, major element chemistry and texture are similar to Winona and also Mt. Morris, Acapulco and Antarctic meteorite ALHA 77081 to some degree. The designation of this group as “Winonaites,” as suggested by Prinz et al. (1980), seems justified and useful.     

THE RUHOBOBO,RWANDA METEORITE: A NEW L6 CHONDRITE

Ruhobobo is a new meteorite which fell in Rwanda, Africa, in 1976. We found and analyzed olivine (Fa 23.4), opx (Fs 19.7, Wo 1.4), cpx (Fs 7.5, Wo 44.0), plagioclase (An 11.7, Or 5.6), chromite, “whitlockite”, kamacite, taenite and troilite. Based on these analyses and on microscopic observation, Ruhobobo is an unshocked L6 chondrite.     

Spectral properties of plagioclase and pyroxene mixtures and the interpretation of lunar soil spectra

The effects of particle size and mineral proportions on the spectral characteristics of plagioclase and pyroxene mixtures are investigated. Size separates (<25 μm, 25–45 μm, 45–75 μm, 75–125 μm, 125–250 μm, and 250–500 μm) have been prepared for the following labradorite/enstatite compositional mixtures: 100/0%, 95/5%, 85/15%, 50/50%, and 0/100%. Spectrally, the labradorite and enstatite samples are representative of the plagioclase feldspars and the orthopyroxenes: the labradorite exhibits a weak, broadband centered near 1.25 μm and the enstatite exhibits two well-defined bands centered near 0.9 and 1.9 μm. From analysis of the plagioclase bands of the mixtures, it is found that (1) the amount of plagioclase necessary for the plagioclase band to be observed as a discrete absorption band is dependent on particle size and (2) plagioclase can be detected by flattening of the pyroxene reflectance “peak” between the 0.9- and 1.9-μm absorption bands if significant amounts of plagioclase are present. Analogs for immature and mature lunar highland soils have been created to examine the combined effects of particle size and mineral proportions on spectra of plagioclase and pyroxene mixtures. bidirectional reflectance spectra of these soil analogs are used to examine the detectability of plagioclase in soil-like particle size distributions. Plagioclase in significant amounts is detected by the flattening of the pyroxene reflectance “peak” between the 0.9- and 1.9-μm absorption bands, and the plagioclase absorption band itself is observed with 85% plagioclase present. The soil analogs reveal that particle size accounts for only a minor spectral difference between immature and mature lunar highland soils. From comparisons with spectra of returned lunar samples, agglutinates are found to dominate the spectral variations associated with soil maturity. Spectra of the immature soil analogs can be used to estimate the minimum pyroxene abundance for immature regions observed remotely.     

On the mechanism of the “Noisar” phenomenon in magnetic close binary systems

The mechanisms of “Noisar” phenomenon in AM Herculis-type stars are discussed. In an accretion column above the surface of the magnetized degenerate star the instability of some types may be excited, such as axi-symmetrical quasi-periodical penetration of the low-density “bulks” from the column axis to the outer parts; “boiling” with “bulks” moving inside or outside the column; “tornado” with low-density region rapidly rotating around the column axis; “switchings” of the accretion from one half of the “polar cap” to another and vice versa. The oscillations of different plasma clots (“spaghetti”) may interfer causing flux changes as well. Such “Noisar” oscillations appear in different regions of the accretion column (at the upper shock and near the column base, respectively), so hard and soft X-ray fluxes might not have correlation in their variability. The observations are in qualitative agreement with the models.     

The Kirbyville Eucrite

Abstract— The Kirbyville meteorite is an equilibrated monomict eucrite with a mode (calculated in wt.%): plagioclase 37, inverted pigeonite 58, silica 3, ilmenite 1.4 and troilite 0.3. The pyroxene compositional range is Wo 2–42, Fs 27–62, En 30–40 with an average of Wo 7. The plagioclase average mean is An 89. Kirbyville is one of the “main group” eucrites.     

Pervasive shock melting at >65 GPa in a Martian basalt,the shergottite Northwest Africa 14672

Shergottites have provided abundant information on the volcanic and impact history of Mars. Northwest Africa (NWA) 14672 contributes to both of these aspects. It is a vesicular ophitic depleted olivine–phyric shergottite, with average plagioclase An₆₁Ab₃₉Or_0.2. It is highly ferroan, with pigeonite compositions En_49-25Fs_41-61Wo_10-14 like those of basaltic shergottites, for example, NWA 12335. Olivine (Fo_53-15) has discrete ferroan overgrowths, more ferroan when in contact with plagioclase than when enclosed by pyroxene. The pyroxene (a continuum of augite, subcalcic augite, and pigeonite) is patchy, with ragged “cores” enveloped or invaded by ferroan pyroxene. Magma mixing may be responsible for capture of olivine and formation of pyroxene mantles. The plagioclase is maskelynite-like in appearance, but the original laths were (congruently) melted and the melt partly crystallized as fine dendrites. Most of the 14% vesicles occur within plagioclase. Olivine, pyroxene, and ilmenite occur in part as fine aggregates crystallized after congruent melting with limited subsequent liquid mixing. There are two fine-grained melt components, barred plagioclase with interstitial Fe-bearing phases, and glass with olivine dendrites, derived by melting of mainly plagioclase and mainly pyroxene, respectively. Rare silica particles contain coesite and/or quartz, and silica glass. The rock has experienced >50% melting, compatible with peak pressure >~65 GPa. It is the most highly shocked shergottite so far, at shock stage S6/7. It may belong to the group of depleted shergottites ejected at ~1 Myr from Tooting Crater.     

Petrogenesis of lunar highlands meteorites: Dhofar 025, Dhofar 081, Dar al Gani 262, and Dar al Gani 400

Abstract— The petrogenesis of four lunar highlands meteorites, Dhofar 025 (Dho 025), Dhofar 081 (Dho 081), Dar al Gani 262 (DaG 262), and Dar al Gani 400 (DaG 400) were studied. For Dho 025, measured oxygen isotopic values and Fe‐Mn ratios for mafic minerals provide corroboratory evidence that it originated on the Moon. Similarly, Fe‐Mn ratios in the mafic minerals of Dho 081 indicate lunar origin. Lithologies in Dho 025 and Dho 081 include lithic clasts, granulites, and mineral fragments. A large number of lithic clasts have plagioclase AN# and coexisting mafic mineral Mg# that plot within the “gap” separating ferroan anorthosite suite (FAN) and high‐magnesium suite (HMS) rocks. This is consistent with whole rock Ti‐Sm ratios for Dho 025, Dho 081, and DaG 262, which are also intermediate compared to FAN and HMS lithologies. Although ion microprobe analyses performed on Dho 025, Dho 081, DaG 262, and DaG 400 clasts and minerals show far stronger FAN affinities than whole rock data suggest, most clasts indicate admixture of ≤12% HMS component based on geochemical modeling. In addition, coexisting plagioclase‐pyroxene REE concentration ratios in several clasts were compared to experimentally determined plagioclase‐pyroxene REE distribution coefficient ratios. Two Dho 025 clasts have concordant plagioclase‐pyroxene profiles, indicating that equilibrium between these minerals has been sustained despite shock metamorphism. One clast has an intermediate FAN‐HMS composition. These lunar meteorites appear to represent a type of highland terrain that differs substantially from the KREEP‐signatured impact breccias that dominate the lunar database. From remote sensing data, it is inferred that the lunar far side appears to have appropriate geochemical signatures and lithologies to be the source regions for these rocks; although, the near side cannot be completely excluded as a possibility. If these rocks are, indeed, from the far side, their geochemical characteristics may have far‐reaching implications for our current scientific understanding of the Moon.     

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

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 An_50‐57 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 An_50‐57 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 (An_50‐57) 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.     

Northwest Africa 428: Impact‐induced annealing of an L6 chondrite breccia

Abstract— Northwest Africa (NWA) 428 is an L chondrite that was successively thermally metamorphosed to petrologic type‐6, shocked to stage S4–S5, brecciated, and annealed to approximately petrologic type‐4. Its thermal and shock history resembles that of the previously studied LL6 chondrite, Miller Range (MIL) 99301, which formed on a different asteroid. The petrologic type‐6 classification of NWA 428 is based on its highly recrystallized texture, coarse metal (150 ± 150 μm), troilite (100 ± 170 μm), and plagioclase (20–60 μm) grains, and relatively homogeneous olivine (Fa_{24.4 ± 0.6}), low‐Ca pyroxene (Fs_{20.5 ± 0.4}), and plagioclase (Ab_{84.2 ± 0.4}) compositions. The petrographic criteria that indicate shock stage S4–S5 include the presence of chromite veinlets, chromite‐plagioclase assemblages, numerous occurrences of metallic Cu, irregular troilite grains within metallic Fe‐Ni, polycrystalline troilite, duplex plessite, metal and troilite veins, large troilite nodules, and low‐Ca clinopyroxene with polysynthetic twins. If the rock had been shocked before thermal metamorphism, low‐Ca clinopyroxene produced by the shock event would have transformed into orthopyroxene. Post‐shock brecciation is indicated by the presence of recrystallized clasts and highly shocked clasts that form sharp boundaries with the host. Post‐shock annealing is indicated by the sharp optical extinction of the olivine grains; during annealing, the damaged olivine crystal lattices healed. If temperatures exceeded those approximating petrologic type‐4 (?600–700°C) during annealing, the low‐Ca clinopyroxene would have transformed into orthopyroxene. The other shock indicators, likewise, survived the mild annealing. An impact event is the most plausible source of post‐metamorphic, post‐shock annealing because any ²⁶Al that may have been present when the asteroid accreted would have decayed away by the time NWA 428 was annealed. The similar inferred histories of NWA 428 (L6) and MIL 99301 (LL6) indicate that impact heating affected more than 1 ordinary chondrite parent body.     

Partial amorphization of experimentally shocked plagioclase: A spectroscopic study

Shock amorphization of plagioclase, from partial to complete, has been used to evaluate the degree of shock in meteorites. Important information on the shock amplitude can be derived from the measurement of the refractive index in plagioclase, either from mineral separates or in petrographic thin sections. However, this technique is time‐consuming, and associated sample preparations are considered destructive and are not always possible for precious and rare meteorite samples. In addition, plagioclase amorphization is commonly inhomogeneous at the sample scale and a statistically meaningful number of grains must be considered. Here, we apply several nondestructive spectroscopic techniques, such as Raman spectroscopy, photoluminescence, and cathodoluminescence, to plagioclase experimentally shocked at 28 GPa, and thus in the transition regime between crystalline plagioclase and fully amorphous material. Most of the plagioclase was transformed into diaplectic glass at 28 GPa, yet some grains exhibit heterogeneously distributed crystalline domains. This confirms that intrinsic and extrinsic factors lead to local variations in the intensity of the shock pressure within individual plagioclase crystals of homogeneous composition. The amorphization of plagioclase can qualitatively (and potentially also quantitatively) be investigated by spectroscopic techniques, highlighting such local variations in the shock efficiency.