Tomasz Brachaniec, Krzysztof Szopa and Łukasz Karwowski

Department of Geochemistry, Mineralogy and Petrology, Faculty of Earth Sciences, University of Silesia, Sosnowiec, Poland

We report the first occurrence of moldavites in Poland. This discovery confirms the hypothesis that moldavites could have been distributed up to 500 km from the Ries crater in Germany. The tektites were reworked from Middle Miocene sediments and redeposited in Late Miocene (Pannonian) fluvial deposits of the Gozdnicka Formation in Lower Silesia. The Polish moldavites are represented by nine (<8 mm) fragments with a total of 0.471 g. The lack of the autochthonous tektites indicates that tektites investigated here had to be redeposited in a fluvial environment, probably from the Lusatian area. The chemical composition of the Polish moldavites plots in the same area with those from other localities.

Reference
Brachaniec T, Szopa K and Karwowski Ł  (in press) Discovery of the most distal Ries tektites found in Lower Silesia, southwestern Poland. Meteoritics & Planetary Science
[doi:10.1111/maps.12311]
Published by arrangement with John Wiley & Sons

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Ulli Raschke¹, Patrice Tristan Zaag¹, Ralf Thomas Schmitt¹ and Wolf Uwe Reimold^1,2

¹Museum für Naturkunde Berlin, Berlin, Germany
²Humboldt-Universität zu Berlin, Berlin, Germany

El’gygytgyn is a 3.6 Ma, 18 km diameter, impact crater formed in an approximately 88 Ma old volcanic target in Northeast Siberia. The structure has been the subject of a recent ICDP drilling project. In parallel to those efforts, a Russian-German expedition was undertaken in summer 2011 to investigate the permafrost soil, lake terraces, and the volcanic rocks of the southern and eastern crater rim. This provided the unique opportunity for mapping and sampling of the volcanic target rocks around a large part of this complex impact structure. Samples from 43 outcrops were collected and analyzed petrographically and geochemically. The results were combined with earlier mapping outcomes to create a new geological map of this impact structure and its immediate environs, at the scale of 1:50,000. Compositions of our rock suites are compared with the lithologies of the 2009 ICDP drill core. The ignimbrite described as lower bedrock in the ICDP drill core shows petrographically and chemically strong similarities to the rhyolitic and rhyodacitic ignimbrites observed on surface. The suevite sequence exposed in the ICDP drill core is a mixture of all observed target rocks at their respective proportions in the area. In contrast to previous studies, the calculated average target composition of El’gygytgyn takes the contribution of the basic target rocks into consideration: mafic and intermediate rocks approximately 7.5%, and felsic rocks approximately 92.5%.

Reference
Raschke U, Zaag PT, Schmitt RT and Reimold WU  (in press) The 2011 expedition to the El’gygytgyn impact structure, Northeast Russia: Toward a new geological map for the crater area. Meteoritics & Planetary Science
[doi:10.1111/maps.12306]
Published by arrangement with John Wiley & Sons

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Maitrayee Bose^a, Thomas J. Zega^b and Peter Williams^a

^aArizona State University, Department of Chemistry and Biochemistry, Physical Sciences Building, Room D-57, PO Box 871604, Tempe, AZ 85287, United States
^bLunar and Planetary Laboratory, University of Arizona, 1629 East University Blvd., Tucson, AZ 85721, United States

Insight into the presolar and interstellar grain inventory of the CO3 chondrite Queen Alexandra Range (QUE) 97416 is gained through correlated secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and synchrotron-based X-ray absorption near-edge structure spectroscopy (XANES). Only one presolar silicate grain [; ] that may have formed in a low-mass Red Giant or Asymptotic Giant Branch star occurs in the coarse-grained matrix of QUE 97416. No other presolar grains were identified. Although presolar grains are rare in QUE 97416, numerous (898±259 ppm) ¹⁵N-rich domains ( to +3069‰) occur in the thin section. Based on TEM of an extracted section, two ¹⁵N-rich domains are amorphous, C-bearing, and texturally uniform, and they are embedded in a ferromagnesian silicate matrix with varied grain sizes. The individual ¹⁵N-rich organic regions with high  (+2942±107‰ and +2341±140‰) exhibit diverse carbon functional groups, such as aromatic, vinyl-keto, amidyl, and carboxylic functionality, while the nitrogen XANES reveals traces of nitrile functionality. QUE 97416 appears to have escaped aqueous alteration based on the absence of hydrated minerals but is thermally altered, which could have resulted in the destruction of presolar grains. However, this process at >400 °C metamorphic temperatures was inefficient in destroying the carriers of N isotope anomalies, which may indicate the resistant nature of the organic carriers and/or the limited extent of thermal metamorphism on the QUE 97416 parent body.

Reference
Bose M, Zega TJ and Williams P  (2014) Assessment of alteration processes on circumstellar and interstellar grains in Queen Alexandra Range 97416. Earth and Planetary Science Letters 399:128.
[doi:10.1016/j.epsl.2014.05.007]
Copyright Elsevier

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