Zhamanshin Crater Research Articles

On the nature of the Zhamanshin crater (Northern Cis-Aralian Region)

Research subject. The Zhamanshin structure is located in the northern Aral Sea region and represents the outcrops of pre-Mesozoic rocks among Paleogene deposits. This structure has been known in the literature as a young meteorite crater for more than half a century. Aim. To consider all available geological and geophysical information on the structure and material composition of rocks and explain the development features of the Zhamanshin structure in relation to its position within the Late Paleozoic suture-collision zone of the Eastern-Uralian fold system. Materials and methods. The materials of geological surveys of various scales, as well as the interpretation of geophysical data, satellite images, data on the material composition of rock samples and paleotectonic reconstructions were analysed. In addition, the published literature on the meteorite origin of the Zhamanshin structure was analysed. Results. The main structural features of the Zhamanshin structure are rather associated with the accretion-subduction processes in the Paleozoic and strike-slip movements, especially active in the Pliocene, than with an impact event. The young age of glasses (from 10 thousand to 50 Ma) remains unproven due to unreliable methods used. The composition of the glasses allows them to be attributed to Paleozoic volcanic rocks, while some samples of slags and glasses may be of technogenic origin. Conclusions. Almost all arguments in favour of the meteorite origin of the Zhamanshin structure are questioned. A more realistic conclusion is that it has formed by deep tectonic and geological processes. The Zhamanshin structure is a dissected rounded upland with a ring of Paleozoic rocks along the edges and a hollow in the middle, which is associated with an eroded Carboniferous caldera. After the collision in the middle of the Carboniferous, the entire Northern Aral Sea remained an area of denudation until the beginning of the Cretaceous. After that, terrigenous lacustrine-alluvial strata up to 300 m thick had accumulated. During the Paleogene and Miocene, this upland with the remnants located along a circular rampart tens of meters high was covered by marine and continental sediments. In the Pliocene, the area was subjected to active strikeslip movements with the formation of the Tasaran mega-anticline with the Zhamanshin, North-Zhamanshin and Tasaran uplifts. The Irgiz-Tobolsk shear-thrust had limited and uplifted the western flank of the Zhamanshin structure, while feathering faults resulted in the formation and subsidence of a rounded depression around the Paleozoic caldera in the centre of Zhamanshin.

МОРФОЛОГИЯ И СОСТАВ ИМПАКТНЫХ ПРОДУКТОВ

The object of study is the products of the Zhamanshin crater: tektites – irgisites, subtektites, zhamanshinites. The features of morphology and the compositions of products were determined. In the distribution of rare earth elements of irgisites Eu and Ce anomalies appeared. The crystallized components of jamanshinite consist of phayalite, ferrosilite, magnetite. Large inclusions of zhamanshinite are represented by a solid solution of copper and boron, small ones by galenite with impurities of iron and tungsten. Among the accessor minerals of subtektites, xenotime, iocyte, coesite were found. The proximity of the mineral compositions of subtektites and a number of comets was confirmed.

NMR Spectral Characteristics of Ultrahigh Pressure High Temperature Impact Glasses of the Giant Kara Crater (Pay-Khoy, Russia)

In this study, we carried out the analysis of the impact melt vein glasses from the Kara impact crater (Russia) in comparison to low-pressure impact melt glasses (tektites) of the Zhamanshin crater (Kazakhstan). 27Al, 23Na, and 29Si MAS NMR spectra of the samples of these glasses were analyzed. The samples of the natural glass contained inclusions of crystalline phases, paramagnetic elements that greatly complicate and distort the NMR signals from the glass phase itself. Taking into account the Mossbauer distribution of Fe in these glasses, the analysis of the spectra of MAS NMR of glass network-former (Si, Al) and potential network-modifiers (Na) of nuclei leads to the conclusion that the Kara impact melt vein glasses are characterized by complete polymerization of (Si,Al)O4 tetrahedral structural units. The NMR features of the glasses are consistent with the vein hypothesis of their formation under conditions of high pressures and temperatures resulting in their fluidity, relatively slow solidification with partial melt differentiation, polymerization, and precipitation of mineral phases as the impact melt cools. The 70 Ma stability of the Kara impact vein glass can be explained by the stabilization of the glass network with primary fine-dispersed pyroxene and coesite precipitates and by the high polymerization level of the impact glass.

Suevites and Tagamites of Zhamanshin Astrobleme: Distribution in the Crater and Petrographic Features

The study of impact glasses from the Zhamanshin meteorite crater has a long history extending back to early 1970ies. Most attention is paid to unique impact-related rocks known as zhamanshinites (bombs) and irghizites (lapilli). But, as first shown by V.L. Masaitis, other, more common types of impactites, suevites and massive melts (tagamites), are also present in Zhamanshin. We study the distribution in the crater, structure and composition of these particular rocks using powder X-ray diffraction and scanning electron microscopy. It is shown that all impact glasses from the Zhamanshin crater are genetically related and derive from the impact event, while the observed petrographic differences between them reflect the conditions of their formation. Individual varieties of studied impactites (suevites and tagamites) are spatially separated and, as a rule, do not intersect. This points to the absence of global mixing of the target material as a result of the impact event, as well as to the complex nature of the impactor.

A High-Temperature Impact Condensate of the Lonar Crater (India)

A high-calcium high-temperature condensate is detected in the Earth’s impact Lonar crater for the first time. Its finding confirms in practice the theoretical conclusions made earlier from the experimental results. The high-silica condensate found in the Lonar crater, which is similar to those ones in the Zhamanshin crater and in the lunar regolith, confirms the absence of a correlation between the compositions of the target and the impact condensates. The presence of high-temperature condensate glasses in ring structures may be one of the diagnostic criteria to differentiate between volcanogenic and impact formations.

Comparison of the compositions and microstructures of Terrestrial and Lunar impact glasses: samples from The Zhamanshin Crater and Luna 16, 20, and 24 missionse

The paper presents pioneering data on the comparative study of impact glasses from the Zhamanshin crater and lunar regolith (delivered by the Luna 16, 20, and 24 probes). The data were acquired using analytical techniques of ultrahigh spatial resolution. Many of the melt and condensate impact glasses, both terrestrial and lunar, are similar in inner structure and composition, which were controlled primarily by the physics of the impacts and similar compositions of the targets.

Iron oxidation state of impact glasses from the Zhamanshin crater studied by X-ray absorption spectroscopy

X-ray absorption spectroscopy (XAS) has been used to analyze the change in iron oxidation state and coordination numbers of impact glasses from the Zhamanshin crater. Series of samples, specifically aerodynamically shaped small glassy bodies – irghizites, and silica-rich and silica-poor glasses – zhamanshinites, have been investigated. The Fe2.2+ oxidation state was determined for the irghizites and the highest value Fe2.8+ for the silica-poor zhamanshinite. These values agree with the trend of oxidation processes upon high speed interaction of meteorite parent body and target rocks. The obtained data can be used for future establishment of the formation parameters (P, T, fO2 conditions) of these impact glasses as well as relationships between the rocks.

Cosmogenic Substances in the Zhamanshin Crater

Using high-resolution analytical electron microscopy, heterogeneous fragments of cosmogenic substances, such as nickelphosphide Ni3P and the unnamed intermetallide ZnAl2, are detected for the first time for a large meteorite crater, the Zhamanshin circular structure. Due to the impossibility of simultaneous finding these phases in the same meteorite, an assumption is made on the cometary nature of the impactor of the Zhamanshin crater.

Impactor Type and Model of the Origin of the Zhamanshin Astrobleme, Kazakhstan

Fragments of heterogeneous cosmonegic substance (nickelphosphide Ni3P and ZnAl2) were found using high resolution analytical electron microscopic techniques, for the first time in samples from a large meteorite crater: the Zhamanshin astrobleme in Kazakstan. Inasmuch as such fragments cannot simultaneously occur in meteorite of any one type, we suggest that the impactor of the Zhamanshin crater was of comet nature.

The natural high-pressure phase of cubic CdSe in impact glass from Zhamanshin crater

A CdSe high-pressure polymorph of the NaCl structural type of a0 = 0.549 nm and Fm–3m space group was discovered in nature for the first time. Its composition is within range of CdSe–CdSe1–х where x = 0.2 apfu. The phase was discovered as abundant nanosize inclusions in irgizite-type condensate glass separated from the sample of impact rock of the Zhamanshin crater (Central Kazakhstan). The treated mineral was presumably formed within a gas–plasma cloud at the moment of impact.

Condensate glasses from the Zhamanshin crater. I. Irghizites

The presence of condensate glass was established for the first time in natural terrestrial impact glasses. Its existence was previously predicted on the basis of shock evaporation experiments. Condensate glass was found in the irghizites of the Zhamanshin crater. Its characteristic features were described, including a combination of high silica content with the presence of nanoscale crystalline nuclei and typical globular morphology under TEM.

Condensate constituent in impact glasses of the Zhamanshin crater

The presence of condensate glass, which had been forecasted exclusively based on experiments on shock evaporation, was first discovered in natural terrestrial impact glasses. The condensate glass was found in irghizites and zhamanshinites of the Zhamanshin crater. The glass characteristics, a combination of a high silica content and the occurrence of nanosize crystalline nuclei, as well as the typical globular morphology, were determined by means of transmission electron microscopy.

Geochemical characterization of impact glasses from the Zhamanshin crater by various modes of activation analysis. Remarks on genesis of irghizites

A large set of impact glasses from the Zhamanshin crater in Kazakhstan was analyzed by various modes of instrumental neutron activation analysis, supplemented by instrumental photon activation analysis and prompt gamma-ray activation analysis. Results of the determination of more than forty major and trace elements have shown that the analyzed set of homogeneous, tektite-like impact glasses with size of several centimeters and of various forms could be divided into two geochemically different groups. The lustrous, silica rich (acidic) glasses with high Ni content have been classified conventionally as irghizites. The dull, silica poor (basic) glasses with very low Ni content should not be confused with the large, heterogeneous impactite forms—zhamanshinites, but considered as a separate type of impact glass. Within both primary groups, further division has been suggested based on lower contents of Ni in an irghizite subgroup, and evidence of mixing of source materials for both primary groups in a part of the basic glasses. Based on the contents of Ni, Cr, Mn, Fe and Co, an ordinary chondrite impactor has been suggested with its contribution to the irghizite matter ranging between 4 and 21%. Possible source materials and impact processes leading to irghizite formation have been outlined.

Lithium in tektites and impact glasses: Implications for sources, histories and large impacts

Lithium (Li) abundances and isotope compositions were determined in a representative suite of tektites (moldavites, Muong Nong-type tektites and an australite, Ivory Coast tektites and bediasites), impact-related glasses (Libyan Desert Glass, zhamanshinites and irghizites), a glass fragment embedded in the suevite from the Ries impact crater and sedimentary materials in order to test a possible susceptibility of Li to fractionation during hypervelocity impact events and to de-convolve links to their potential parental sources. The overall data show a large spread in Li abundance (4.7–58 ppm Li) and δ 7Li values (−3.2‰ to 26.0‰) but individual groups of tektites and impact glasses have distinctive Li compositions. Most importantly, any significant high-temperature Li isotope fractionation can be excluded by comparing sedimentary lithologies from central Europe with moldavites. Instead, we suggest that Li isotope compositions in tektites and impact-related glasses are probably diagnostic of the precursor materials and their pre-impact geological histories. The Muong Nong-type tektites and australite specimen are identical in terms of Li concentrations and δ 7Li and we tentatively endorse their common origin in a single impact event. Evidence for low-temperature Rayleigh fractionation, which must have operated prior to impact-induced melting and solidification, is provided for a subset of Muong Nong-type tektites. Although Li isotope variations in most tektites are broadly similar to those of the upper continental crust, Libyan Desert Glass carries high δ 7Li ⩾24.7‰, which appears to mirror the previous fluvial history of parental material that was perhaps deposited in lacustrine environment or coastal seawater. Lithium isotopes in impact-related glasses from the Zhamanshin crater define a group distinct from all other samples and point to melting of chemically less evolved mafic lithologies, which is also consistent with their major and trace element patterns. Extreme shock pressures and the related extreme post-shock temperatures alone appear not to have any effect on the Li isotope systematics; therefore, useful information on parental lithologies and magmatic processes may be retrieved from analyses of Martian and lunar meteorites. Moreover, lack of significant Li depletion in tektites provides further constraints on the loss of moderately volatile elements during the Moon-forming impact.

Electron microprobe analysis (WDS EPMA) of Zhamanshin glass reveals the impactor and a common role of accretion in the origin of splash-form impact glass

Impact glass samples collected during expeditions to the Zhamashin and Lonar craters were subjected to a morphology survey and compared to Wabar, Henbury and Darwin impact glasses to reveal that the accretion of fibres and spherules is not exclusive for irghizites but occurs in other splash form glasses over the world. WDS EPMA and LA-ICP-MS assays of Zhamanshin and Lonar glasses enabled the definition of akmurynites as Zhamanshin glass of specific morphology, chemistry and absence of extraterrestrial contamination. However, extraterrestrial contamination in irghizites was verified and further WDS EPMA analyses led to the conclusion that the Zhamanshin crater had been formed by the impact of a primitive achondrite of Lodran chemistry.

Why are blue zhamanshinites blue? Liquid immiscibility in an impact melt

We report here a study of the cause of the coloration of blue zhamanshinites, which are glassy impact melt rocks from the Zhamanshin crater in the USSR. We find that the blue color results from Rayleigh scattering from spherical, 100 nm-diameter inclusions of a separate Ca-Fe-Mg-P-rich silicate glass. These observations can best be explained by the operation of liquid immiscibility in the zhamanshinite melt, and suggest that liquid immiscibility may have a more general role in impactite evolution.

Blue glass: A new impactite variety from Zhamanshin crater, U.S.S.R.

A new variety of impact glass has been discovered at Zhamanshin impact crater (U.S.S.R.). The crater has been known as the source of different impact glasses such as irghizites and Si-rich zhamanshinites (Si-rich varieties) and Si-poor (andesitic) zhamanshinites. The newly discovered impact glass is of distinct blue color and shows a layered structure with numerous small vesicles. The blue color ranges between the layers from opaque turquoise to very dark blue. The layers of blue glass are usually connected with layers of greyish or brownish color showing normal Si-rich zhamanshimte composition. The major and trace element chemistry of the blue glass differs from the chemistry of other Si-rich impact glasses from the Zhamanshin crater in several ways. One of the most distinct features is the high CaO content (up to about 7 wt.%), and the different CaO/MgO ratios. Volatile trace elements are generally intermediate between irghizites and Si-rich zhamanshinites, or even higher than in Si-rich zhamanshinites, reflecting the inhomogeneity of the blue glass. REE abundances are slightly larger than in Si-rich zhamanshinites and irghizites and show a less pronounced Eu anomaly. Impact mixing of country rocks present at the crater seems capable of explaining the chemistry of the blue glass.

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

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.

Comments on “The evidence of ‘CH01’ in sediment core samples of Pacific Ocean collected among FGGE” by Peng Han‐Chang, Zhao Kui‐Huan, and Chen Sui‐Tian

Journal of Geophysical Research: Solid EarthVolume 89, Issue B7 p. 6351-6352 CommentariesFree Access Comments on “The evidence of ‘CH01’ in sediment core samples of Pacific Ocean collected among FGGE” by Peng Han-Chang, Zhao Kui-Huan, and Chen Sui-Tian B. P. Glass, B. P. GlassSearch for more papers by this author B. P. Glass, B. P. GlassSearch for more papers by this author First published: 10 July 1984 https://doi.org/10.1029/JB089iB07p06351Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References Chao, E. C. T., The petrographic and chemical characteristics of tektites, Tektites J. A. O'Keefe, 51– 94, University of Chicago Press, Chicago, Ill., 1963. Chao, E. C. T., E. J. Dwornik, J. Littler, New data on the nickel-iron spherules from Southeast Asian tektites and their implications, Geochim. Cosmochim. Acta, 28, 971– 980, 1964. Eldridge, J. S., G. D. O'Kelley, K. J. Northcutt, Radionuclide concentrations in Apollo 16 lunar samples determined by nondestructive gamma-ray spectrometry, Proc. Lunar Sci. Conf., 4th, 2115– 2122, 1973. Glass, B. P., Microtektite surface sculpturing, Geol. Soc. Am. Bull., 85, 1305– 1314, 1974. Glass, B. P., High-silica (> 60%) lunar glasses in an Apollo 14 soil sample: Evidence for silicic lunar volcanism?, Earth Planet. Sci. Lett., 33, 79– 85, 1976. Glass, B. P., Zhamanshin crater, a possible source of Australasian tektites ?, Geology, 7, 351– 353, 1979. Glass, B. P., R. A. Barlow, Mineral inclusions in Muong Nong-type indochinites: Implications concerning parent material and process of formation, Meteoritics, 14, 55– 67, 1979. Glass, B. P., M. B. Swincki, P. A. Zwart, Australasian, Ivory Coast and North American tektite strewn fields: Size, mass and correlation with geomagnetic reversals and other earth events, Proc. Lunar Planet. Sci. Conf., l0th, 2535– 2545, 1979. Peng, H., K. Zhao, S. Chen, The evidence for ‘CH01’ in sediment core samples of Pacific Ocean collected among FGGE, J. Geophys. Res., 87, 5563– 5565, 1982. Taylor, H. P., S. Epstein, O18/O16 ratios of Apollo 11 lunar rocks and minerals, Proc. Lunar Sci. Conf., 1st, 1613– 1626, 1970. Taylor, S. R., The chemical composition of australites, Geochim. Cosmochim. Acta, 26, 685– 722, 1962. Taylor, S. R., Tektites: A post-Apollo view, Earth Sci. Rev., 9, 101– 123, 1973. Tilton, G. R., Isotopic composition of lead from tektites, Geochim. Cosmochim. Acta, 14, 323– 330, 1958. Citing Literature Volume89, IssueB710 July 1984Pages 6351-6352 ReferencesRelatedInformation

Microirghizites recovered from a sediment sample from the Zhamanshin Impact Structure

Microscopic glass spherules, called microirghizites, have been recovered from a stream deposit in the Zhamanshin crater. The microirghizites partly overlap the irghizites (tektites) and SiO2‐rich zhamanshinites (impactites) in composition, but exhibit greater variations in composition and have lower average SiO2 contents. A similar relationship has been observed between microtektites and tektites in the Australasian, Ivory Coast, and North American strewn fields. The compositions and oxide trends observed for the microirghizites, SiO2‐rich zhamanshinites and irghizites are rather similar to those observed for the Australasian microtektites and tektites. The major differences are the Al2O3 and FeO versus SiO2 trends, which could be explained by differences in amount of meteoritic contamination. The irghizites and microirghizites contain higher nickel contents (up to 0.41%) than the SiO2‐rich zhamanshinites and Australasian tektites and microtektites. The major oxides versus silica trends for the microirghizites support a previous conclusion that the impacting body was a chondrite meteorite and the bulk parent material was terrestrial. Although the irghizites may have been more contaminated by the impacting body than were the SiO2‐rich zhamanshinites, we find that the major differences in composition between the irghizites and SiO2‐rich zhamanshinites may be due to different parent materials rather than meteoritic contamination.