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A High PT Carbon Impactite from Shock Coalification/Carbonization of Impact Target Vegetation K

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A High PT Carbon Impactite from Shock Coalification/Carbonization of Impact Target Vegetation K X. Минералогия астроблем и метеоритов Chiemite — a high PT carbon impactite from shock coalification/carbonization of impact target vegetation K. Ernstson1, T. G. Shumilova2 1University of Würzburg, Würzburg, Germany; [email protected] 2IG FRC Komi SC UB RAS, Syktyvkar, Russia; [email protected] Introduction Material Unusual carbonaceous matter in the form of Typical chiemite samples from the field are mostly centimeter­sized lumps and cobbles has shown in Fig. 3 as pure chiemite matter, where been sampled in the southeast Bavarian Alpine the pseudomorphosis after wood sticks out, and in Foreland, in the Czech Republic near Pardubice compound with rock and organic matter. Under the and in the Saarland region near the French SEM the typical strongly porous texture is evident. border (Fig. 1). It is a highly porous blackish Physical properties are a low density mostly material with a glassy luster on freshly crushed <1 g/cm3, a significant electrical conductivity and in surfaces (Fig. 2). The material is unknown from some cases a moderate magnetic susceptibility and any industrial or other anthropogenic processes remnant magnetization. and thus appears to have a natural origin. Here we report on results of a detailed analysis of this strange matter pointing to a process of formation Methods (with a focus in proposed meteorite impact events. From its on the Chiemgau impact chiemite): first discovery in the Bavarian Chiemgau impact Optical and atomic force microscopy, X­ray flu­ crater strewn field [1] the name chiemite gained orescence spectroscopy, scanning and transmission currency, and in particular these finds have electron microscopy (SEM, TEM), high­resolution already been addressed earlier (references in [1]) Raman spectroscopy, X­ray diffraction and differen­ before a more general occurrence in impact sites tial thermal analysis, as well as δ13C and 14C radio­ became obvious [2, 3]. carbon isotopic data analysis. Results The most significant observations described in [4] are tabulated in short as follows. Fig. 1. Location map for the three chiemite sources in the Chiemgau, Saarland and Czech impact strewn fields Fig. 3. Chiemite samples from the field. A: various shapes. B, C: chiemite fragments pseudomorphic after pieces of branches. D: chiemite breccia­like intermeshed with a limestone cobble. E: chiemite crust Fig. 2. Freshly broken chiemite sample. Photo on a sandstone cobble. F: relatively fresh wood particle embedded in width 6 cm chiemite [4] 363 Юшкинские чтения — 2020 Fig. 4. Chiemite under the SEM. Chiemgau impact (A, B) [3], Saarland impact (C, D), Czech impact (E). Fossilized wooden structure in C XRF: about 90 % carbon, remaining Si, Al and The chiemite components show similarities to Fe, subordinately S; traces of other elements. after­coal meteorite impacts [5]. — We propose the SEM, microprobe: almost pure glass­like carbon chiemite was formed by meteorite impact shock matrix contains finely dispersed micrometer­ and having affected vegetation like wood and peat in submicrometer­sized inclusions with a complex the impact target area, hence establishing a new composition not known mineralogically. kind of impactite that originated from immediate XRD, XR synchrotron diffraction: Evidence of shock transformation of organic matter to high­ nanocrystalline diamond and graphite. rank carbon. — The impactite nature is underlined TEM: Glass­like carbon structural features. by the occurrence of chiemite samples in three Crystalline carbyne and diamond matter with established or proposed young impact strewn fields different order level. (Fig. 1). The finds closely resembling each other up TEM and Raman: Polycrystalline fine grained to the enigmatic absence of 14C despite their evident aggregates to polynanocrystalline diamond young ages, and a so far unknown isotope separation aggregates and amorphous diamond­like carbon in the impact process has to be assumed. — In all exists. — α­carbyne and β­carbyne but not any three impact cases there is much evidence of big graphite were observed. airbursts, which initiated extreme­temperature gas Raman spectroscopy: Submicrometer­sized jets impinging on the ground. — The surviving of optically transparent substances are carbyne­like fresh organic matter in the impactite under these carbon or diamond­like carbon. extreme conditions is important for astrobiological 13 Carbon isotopes: Carbon δ CPDB data show aspects. — The prediction [5, 6] of more impact values between –22.6 and –24.6 ‰ near to data of diamonds from organic matter than hitherto C3 plants. assumed is likewise underlined. Radiocarbon data for two chiemite samples The authors thank Isaenko S. I., Ulyashev V. V., are void of 14C corresponding to an age of > 48,000 Makeev B. A., Rappenglück M. A., Veligzhanin A. A. for years BP not compatible with the chiemite find help in the analytical studies and discussion. situation. References Discussion and conclusions 1. Rappenglück, M. A., Rappenglück, B. & Ernstson. The fully amorphous chiemite matrix contains K. Cosmic collision in prehistory. — The Chiemgau diamond, amorphous diamond­like carbon and Impact: research in a Bavarian meteorite crater strewn monocrystalline carbyne inclusions. The strongly field // Zeitschrift für Anomalistik. 2017. V 17. P. 235— porous texture requires an intense gas phase during 260. formation. — Carbyne formation needed very high 2. Ernstson, K., Müller, W., Neumair, A. The proposed PT conditions of about 4—6 GPa and 2,500— Nalbach (Saarland, Germany) impact site: is it a compan­ 4,000 K. Probable carbon glass was formed at ion to the Chiemgau (Southeast Bavaria, Germany) im­ temperatures as high as 3,800—4,000 K. — Organic pact strewn field? // 2013. 76th Annual Meteoritical matter was involved in the formation process. — Society Meeting, 5058. The lack of 14C requires an age > 48,000 years 3. Molnár, M., Ventura, K., Švanda, P., Štaffen, Z., (less probable) or isotope separation. — Chiemite Rappenglück, M. A., Ernstson, K. Chrudim — Pardubice: does not correspond to any known natural earth Evidence for a Young Meteorite Impact Strewn Field material. An industrial formation and an occurrence in the Czech Republic // Lunar and Planetary Science from e.g. wildfires can reasonably be excluded. — Conference XLVIII. 2017. 1920. 364 X. Минералогия астроблем и метеоритов 4. Shumilova, T. G., Isaenko, S. I., Ulyashev, V. V., Makeev, enigmatic type of impact diamonds // Eur. J. Min. 2018. B. A., Rappenglück, M. A., Veligzhanin, A. A., Ernstson, V. 30. P. 61—76. K. Enigmatic Glass­Like Carbon from the Alpine Foreland, 6. Shumilova, T. G., Ulyashev, V. V., Kazakov, V. A., Southeast Germany: A Natural Carbonization Process// Isaenko, S. I., Vasil`ev, E. A., Svetov, S. A., Chazhengina, Y., Acta Geologica Sinica. 2018. V. 92, P. 2179—2200. Kovalchuk, N. S. Karite — diamond fossil: a new type of 5. Shumilova, T. G., Isaenko, S. I., Ulyashev, V. V., natural diamond // Geoscience Frontiers, 2019. https:// Kazakov, V. A., and Makeev, B. A. After­coal diamonds: an doi.org/10.1016/j.gsf.2019.09.011 Artifact-in-impactite: a new kind of impact rock. Evidence from the Chiemgau meteorite impact in southeast Germany B. Rappenglück1, M. Hiltl2, K. Ernstson3 1Institute for Interdisciplinary Studies, D­82205 Gilching, Germany; [email protected] 2Carl Zeiss Microscopy GmbH, D­73447 Oberkochen; [email protected] 3University of Würzburg, 97074 Würzburg, Germany; [email protected] Introduction tastrophe layer was excavated sandwiched be­ The Chiemgau impact (Fig. 1) as a meanwhile tween settlement layers of the Stone Age/Bronze established Holocene impact event has featured Age and the Roman Period (Fig. 1, 2) [2]. Among quite a few exceptional observations in the last 15 the finds of ceramics, stone tools, bones and metal years, which are summarized in [1, and referenc­ artefacts also featured externally rather unsight­ es therein]. From the beginning of research it was ly lumps, which were found by use of metal de­ clear that a huge catastrophe in the Bronze Age or tectors and were addressed as «slag» by the ex­ Celtic era must have already affected densely pop­ cavator. Here we report on specifically conducted ulated regions, and in a routine archeological ex­ mineralogical­geochemical investigations on 16 cavation at Lake Chiemsee the worldwide unique «slag» samples which have led to very remarkable constellation was encountered that an impact ca­ results. Fig. 1. Location map for the Stöttham archeological excavation (B) in the Chiemgau impact crater strewn field Fig. 2. Inventory of the Stöttham archeological site (from left to right): diamictite of the catastrophic layer; archeological finds; carbon, metallic and glass spherules; strongly corroded and fractured cobbles, metal­rich «slag» 365.
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