New constraints on the Polish moldavite finds: a separate sub-strewn field of the central European tektite field or re-deposited materials?

Abstract

Rusko and Mielęcin represent the most remote localities from the Ries impact structure with the distance of about 475 km. The previously published data were limited to electron-microprobe analyses of four specimens. Here we provide additional compositional data for a single moldavite from the North Stanisław sandpit near Rusko. Combined data of electron microprobe (EPMA; major elements) and laser-ablation inductively-coupled--plasma mass spectrometry (LA-ICP-MS; minor and trace elements) provide new insights into chemical variability of CET. Electron-microprobe analyses supplemented with back-scattered electron images showed marked chemical heterogeneity of the Polish moldavite on the micrometre scale, confirmed also by LA-ICP-MS. The major-element composition of the volumetrically dominating glass of the specimen is indistinguishable from the majority of c. 5000 available EPMA analyses of moldavites from other regions and, consequently, it does not provide any unambiguous link to any of these sub-strewn fields. Rare schlieren in the sample with unique Ca-Mg-rich composition have counterparts among several South Bohemian moldavites. In general, Polish moldavites are small (less than 0.5 g) irregular fragments or splinters of angular shape with multistage sculpturing. Their morphological character and paleogeography of Central Europe in the last 15 Myr suggest that they were redeposited at time of the Gozdnica Fm. sedimentation from yet unknown sub--strewn field north of the Sudetic Mountains. : moldavites, tektites, Lower Silesia, Poland, Ries impact structure, geochemistry Received: 4 December, 2015; accepted: 3 May, 2016; handling editor: E. Jelínek The online version of this article (doi: 10.3190/jgeosci.214) contains supplementary electronic material. KeywordsCentral European tektites (CET) are called moldavites. They were formed from the uppermost sedimentary rocks layer during the Ries-Steinheim impact event in Miocene. The recent occurrences of CET in several small areas (sub-strewn fields) reflect the paleogeography at the time of impact as well as further geological history of the area.

The fate of moderately volatile elements in impact events—Lithium connection between the Ries sediments and central European tektites

“…The latter is consistent with Li concentration measured by Skála et al. (). Replicate analysis includes new sample dissolution, chemical separation, and mass spectrometry routines.…”

Cathodoluminescence of moldavites

“…Cathodoluminescence imaging revealed differences between the rims of lechatelierite inclusions in direct contact with the surrounding moldavite glass and the core areas of these inclusions (see also Skála et al. ). The visible CL of the rims was brighter than the CL in the cores (Fig.…”

“…; Skála et al. ). Most of them were made using SEM‐CL method, providing the disadvantage that the generated CL pictures under SEM are not real color pictures, but subsequently colored.…”

“…In the study of Skála et al. () cathodoluminescence (CL) analysis on Polish moldavites were made, proving the existence of distinct rim and core areas in lechatelierite inclusions. However, the focus of this study was on the geochemistry of the Polish moldavites.…”

The most distal moldavite findings from Lower Silesia, Poland

“…B. and C. General view of the Gozdnica Formation in the western part of the Nowa Wieś Kącka sandpit. (d'après BRACHANIEC et al, 2014b(d'après BRACHANIEC et al, , 2015(d'après BRACHANIEC et al, , 2016 2012SKÁLA et al, 2016;RODOVSKÁ et al, 2016). BRACHANIEC et al (2014bBRACHANIEC et al ( , 2015BRACHANIEC et al ( , 2016 and SZOPA et al (2017a) recently described moldavite finds in SW Poland.…”