Impact glasses from Zhamanshin crater (U.S.S.R.): chemical composition and discussion of origin

doi:10.1016/0012-821X(86)90174-3

Earth and Planetary Science Letters

Volume 78, Issue 1, May 1986, Pages 80-88

https://doi.org/10.1016/0012-821X(86)90174-3 Get rights and content

Three silica-rich zhamanshinites and one irghizite from the Zhamanshin impact crater (northern Aral area, U.S.S.R.) have been analyzed for up to 40 major, minor, and trace elements. All data point to a clear distinction between these impact glasses and other tektites or impact glasses. e.g. from the Australasian strewn field. Halogens are generally enriched in the irghizites and zhamanshinites when compared to normal splash for tektites. with zhamanshinites enriched more than irghizites. The same holds also for the alkali metals and a number of other volatile elements like Sb and As. Nickel and cobalt are enriched in the irghizite sample to a considerable degree, suggesting meteoritic contamination. This view is also supported by gold and selenium data, but for quantifications other siderophile elements need to be considered. Chromium is not a valid indicator of meteoritic contamination, because smallamounts of ultra-basic igneous material may completely alter the picture. The rare earth elements do show a sedimentary pattern, consistent with two or three different source materials and a variation which is probably mostly due to dilution with silica-rich materials. The peak pressure and temperature experienced by the irghizites was lower than for australites or other splash-form tektites, and even lower for zhamanshinites, which is revealed by the content of volatile elements and lesser homogeneity.

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Cited by (26)

Mechanical properties of natural ultra-high-pressure high-temperature impact glasses at the nanoscale by PeakForce QNM
2022, Journal of Non-Crystalline Solids
Citation Excerpt :
To study the topography and nanomechanical properties six samples of natural impact glasses were selected (Table 1). The samples EG-GLIRG and EG-LDG are homogeneous in phase composition [16,17], where the measurements of topography and properties were carried out on the flattest areas. For these samples, the Young's modulus equal to 70–80 GPa was previously determined by the traditional indentation method [18,19].
Ultra-high-pressure high-temperature (UHPHT) glass from astroblems is a very promising natural material from the point of view of the fundamental problem of the structure and properties of a substance formed under extreme PT-conditions. Such glasses consist of disordered aluminosilicate and silicate micro-sized phases with a heterogeneous structure with domain from units to tens of nanometers in size. We used AFM to evaluation the mechanical properties distribution at nanoscale in UHPHT glasses from the Kara astrobleme. The results of AFM were supplemented with optical and electron microscopy data. It is shown in the work that the nanomechanical properties of glasses measured using by PeakForce QNM generally correspond to the macroscopic properties of a bulk sample. We measured the Young's modulus for the first time for aluminosilicate and silicate phases of UHPHT glasses. AFM can be an effective tool for studying at the micro- and nanoscale mechanical properties of such rigid materials.
The Zhamanshin impact structure, Kazakhstan: A comparative geochemical study of target rocks and impact glasses
2020, Geochimica et Cosmochimica Acta
Citation Excerpt :
This makes our analysis a comprehensive study of target rocks that supplements other recent chemical investigations that were performed mainly on impactites and target rocks from the crater rim (e.g., Jonášová et al., 2016). In addition to the target rocks we analyzed ten impactites, including six zhamanshinite samples (ZH-30a, ZH-6014, ZH-62/3b, ZH-57/2b, and two different lithologies from sample ZH-67/15), and four irghizites (IR-8801, IR-6200, IR-2 and IR-2015/1); see Koeberl and Fredriksson (1986) and Koeberl and Storzer (1987) for some sample information. Sample ZH-67/15 is an inhomogeneous zhamanshinite (see Fig. A1).
The Zhamanshin impact structure, which is about 1 Myr old, has a diameter of 14 km and is situated in the semi-arid region of Kazakhstan (48°24′N, 60°58′E). It has a heterogeneous suite of target rocks, including predominantly crustal lithologies (e.g., clays and siltstones) with minor ultramafics.
Zhamanshin is known for its unique association of impact glasses, including basic and acidic varieties of zhamanshinites and (tektite-like and a few aerodynamically-shaped) irghizites. The origin of both of these impact glasses has long been debated, which is complicated by incomplete sampling of target lithologies at the Zhamanshin site and a limited number of isotopic analyses. However, such studies are a prerequisite for a comprehensive discussion of the mechanisms that formed the unique association of different impact glasses in one impact event.
We present major and trace element contents, as well as combined Sr-Nd isotope data for target rocks and impact glasses from the Zhamanshin impact structure. These data, for the first time, include Paleogene clays and siltstones from a core drilled in the vicinity of the crater and cutting through all major target lithologies. The core samples contain important source lithologies for the impactites from the Zhamanshin area.
Mixing calculations, based on geochemical data and Sr-Nd isotope signatures, indicate that irghizites and Si-rich zhamanshinites can be produced from variously homogenized mixtures of mainly clays and siltstones with minor additions of ultrabasic rocks. Based on highly siderophile element (HSE) and Os isotope data (including the first analyses of the clay and siltstone lithologies) we calculated a hypothetical Os composition of the irghizite precursor, allowing us to approximate a chondritic admixture to the irghizites of roughly 1% of a chondritic component. This confirms previous suggestions about the amount of extraterrestrial components. A new HSE and Os isotope dataset for five zhamanshinites reveals, on average, crust-like HSE concentrations and Os isotope compositions, confirming earlier suggestions of a lack of meteoritic admixtures to these impact glasses.
Mid-infrared bi-directional reflectance spectroscopy of impact melt glasses and tektites
2016, Icarus
Citation Excerpt :
Inclusions of quartz, magnetite, and ilmenite were observed by Gurov and Koeberl (2004). The Irghizite impact glass has a brown color, and shows abundant (Koeberl and Fredriksson, 1986) empty vesicles in the optical and SEM images, but no larger inclusions (Figs. 1 and 2). Popigai melt glass also shows a brown color in the optical images, with abundant vesicles and also some mineral inclusions in the glassy matrix (Fig. 1).
We have analyzed 14 impact melt glass samples, covering the compositional range from highly felsic to mafic/basaltic, as part of our effort to provide mid-infrared spectra (7–14 µm) for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo mission.
Since Mercury was exposed to many impacts in its history, and impact glasses are also common on other bodies, powders of tektites (Irghizite, Libyan Desert Glass, Moldavite, Muong Nong, Thailandite) and impact glasses (from the Dellen, El'gygytgyn, Lonar, Mien, Mistastin, and Popigai impact structures) were analyzed in four size fractions of (0–25, 25–63, 93–125 and 125–250 µm) from 2.5 to 19 µm in bi-directional reflectance. The characteristic Christiansen Feature (CF) is identified between 7.3 µm (Libyan Desert Glass) and 8.2 µm (Dellen). Most samples show mid-infrared spectra typical of highly amorphous material, dominated by a strong Reststrahlen Band (RB) between 8.9 µm (Libyan Desert Glass) and 10.3 µm (Dellen). Even substantial amounts of mineral fragments hardly affect this general band shape.
Comparisons of the SiO₂ content representing the felsic/mafic composition of the samples with the CF shows felsic/intermediate glass and tektites forming a big group, and comparatively mafic samples a second one. An additional sign of a highly amorphous state is the lack of features at wavelengths longer than ∼15 µm. The tektites and two impact glasses, Irghizite and El'gygytgyn respectively, have much weaker water features than most of the other impact glasses.
For the application in remote sensing, spectral features have to be correlated with compositional characteristics of the materials. The dominating RB in the 7–14 µm range correlates well with the SiO₂ content, the Christiansen Feature shows similar dependencies. To distinguish between glass and crystalline phases of the same chemical composition, a comparison between CF the SCFM index (SiO₂/(SiO₂ + CaO + FeO + MgO)) (Walter and Salisbury [1989] J. Geophys. Res., 94, 9203–9213) is useful, if chemical compositional data are also available.
Geochemistry of impact glasses and target rocks from the Zhamanshin impact structure, Kazakhstan: Implications for mixing of target and impactor matter
2016, Geochimica et Cosmochimica Acta
Citation Excerpt :
The original shapes of droplets forming larger splash-form bodies appear to have been modified by glass flow, molding and element diffusion or they disappeared completely. As pointed out in previous studies (e.g., Taylor and McLennan, 1979; Bouška et al., 1981; Koeberl and Fredriksson, 1986; Vetvicka et al., 2010; Mizera et al., 2012), the irghizites exhibit exceptionally high levels of enrichment in Ni, Co and Cr, confirmed by new in-situ analyses on individual glass droplets (Table 3a). Furthermore, irghizites display much higher MgO contents at given SiO2 in comparison to the target lithologies dominated by sand, sandy clay and clay (Fig. 4).
Internal structure and element chemistry including contents of highly siderophile elements (HSE) and Os isotope ratios have been studied in target rocks and several groups of impact glasses of the Zhamanshin impact structure, Kazakhstan. These include larger irregularly-shaped fragments and blocks of impact glass (zhamanshinites), and three types of tektite-like splash-form glasses, part of fallback ejecta. These glassy objects typically are up to 30 mm large and are shaped as teardrops, irregularly bent and curved glass rods and fibers. They can be subdivided into acidic types (irghizites; typically 69–76 wt.% SiO₂), basic splash-forms (typically 53–56 wt.% SiO₂), and rarely occurring highly inhomogeneous composites with abundant mineral inclusions. A comparison with the target rocks shows that zhamanshinites and basic splash-forms usually have no detectable admixture of the projectile matter, indicated by major and trace elements as well as highly siderophile element contents, with the exception of one sample containing Fe-, Cr-, Ni- and Ti-enriched particles and elevated HSE contents. In contrast, irghizites exhibit clear admixture of the projectile matter, which was incorporated by complex processes accompanied by strong element fractionations. Microscopic investigations confirm that irghizites were formed mainly by coalescence of smaller molten glass droplets sized typically below 1 mm. Irghizites exhibit significant enrichments in Ni, Co and Cr, whose concentrations are locally elevated in the rims of the original small droplets. A portion of these elements and also part of Fe and Mn and other elements were derived from the impactor, most likely a Ni-rich carbonaceous chondrite. The contents of HSE are low and strongly fractionated, with moderate depletions of Pt and Pd and strong depletions of other HSE with respect to chondritic element ratios. Osmium shows the strongest depletion, likely related to the presence of oxygen in the post-impact atmosphere causing strong Os loss through volatilization. One composite splash-form contains Fe–Ni–S inclusions and exhibits a less fractionated HSE pattern suggesting the lowest degree of melting, volatilization and condensation. The observed structural and microchemical features of irghizites are interpreted to reflect variable proportions of the uppermost target sediments and the projectile matter, with HSE element ratios influenced by evaporation and condensation processes, and differences in volatility of individual HSE elements and/or their compounds. Two possible pathways of incorporation of the projectile matter into the irghizites include either re-condensation of evaporated projectile matter on the surface of glass droplets, or incorporation of less chemically fractionated microparticles dispersed by the explosion.
The use of heavy mineral correlation for determining the source of impact ejecta: A Manicouagan distal ejecta case study
2009, Earth and Planetary Science Letters
Due to the nature of distal impact ejecta layers on Earth, preserved deposits are rare and are commonly altered by diagenetic/weathering processes. To establish the source of ejecta, trace element signatures of impact glasses have typically been used to establish the source crater of a deposit. However, in many cases, impact glasses in ejecta deposits are devitrified and altered to clays resulting in loss of original melt and original trace element composition. This is the case for the Late Triassic ejecta deposit of SW Britain where impact melt spherules have been completely altered to clay. This Late Triassic ejecta deposit was originally believed to be derived from two possible sources, the Rochechouart or Manicouagan impact structures. To accurately establish the source of this ejecta deposit an alternative correlation technique was developed using garnet major oxide data and radiometric whole grain fusion Ar–Ar dating of shocked biotite (U–Pb dating of zircon was also used but proved inconclusive). Radiogenic dating of shocked biotites (observed exclusively in the ejecta deposit) yielded ages consistent with the Grenvillian target rocks at Manicouagan and excluded Rochechouart as a potential source. Garnet major oxide compositions of garnets in the ejecta deposit were directly compared to garnets from the Manicouagan target rocks and impactite rocks. A strong garnet composition signature correlation between the samples from Manicouagan and the ejecta deposit provides convincing evidence that Manicouagan is the source of the SW Britain ejecta deposit. Furthermore, we suggest that heavy mineral correlation techniques should be considered in future studies as a correlation tool for establishing the source of ejecta.
Comment on "Geochemistry and origin of Muong Nong-type tektites" by C. Koeberl
1993, Geochimica et Cosmochimica Acta

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Impact glasses from Zhamanshin crater (U.S.S.R.): chemical composition and discussion of origin

Geochim. Cosmochim. Acta

Earth Planet. Sci. Len.

J. Non-Cryst. Solids

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

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Der Meteoritenkrater Zhamanshin (nordliches Aralgebiet, UdSSR) und seine Tektite und Impaktite

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Geologo-geofizicheskaja kharakteristika meteoritnogo kratera Zhamanshin

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Zhamanshin impact crater (Western Kazakhstan): Additional geological data

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Micro-irghizites from a sediment sample from the Zhamanshin impact structure

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The Zhamanshin structure: chemical and physical properties of selected samples

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