Search for Fullerenes in Rocks from Ries Impact Crater

Fullerenes have been so far identified in a few rock types with unique geological history. One group of these finds is related to impacts of extraterrestrial bodies on Earth surface, strictly speaking the impact structure of Sudbury (Becker et al., 1994) and to events recorded from Permian/Triassic (Becker et al., 2001) and Cretaceous/Tertiary boundaries (Heymann et al., 1994). Generally two basic hypotheses have been proposed for the origin of fullerenes at these sites. The first one considers formation of fullerenes during the impact, the latter supposes their extraterrestrial origin. To elucidate this problem, we searched for fullerenes in the Ries impact structure, Germany, where the target rocks are carbon-rich and thus could have been the source of carbon in the fullerenes, if they are to be formed during the impact. The Ries impact crater lies in southeastern Germany. It is approximately a circular structure with the inner diameter of 25 km, 15 Ma in age. Impact breccias from the Ries crater, the suevites, can be differentiated to various classes depending on the grade of shock metamorphism, where the highest ranked classes comprise mainly glass. Considering our previous works on fullerenes in rocks, one of the most important factors of fullerene survival till the present is the matrix of rock in which fullerenes could be preserved from weathering, especially from the influence of molecular oxygen and ozone and ultraviolet radiation. Suevites of lower metamorphic class are affected predominantly mechanically, with weak thermal transformation, and show low stability against weathering. On the contrary, impact glasses from the Ries crater are far less weathered, thus they represent almost ideal medium for fullerene conservation. In addition, moldavite tektites, which can be interpreted as condensates of vaporized, surficial sediments (Vonengelhardt et al., 1995), have been chosen as another possible carrier of fullerenes that could originate during the Ries impact event. And as for suevite glasses, moldavites are very stable under air conditions. In the first step, suevites containing larger amounts of glass from Otting (Ries crater, Germany) were sampled and – together with moldavite samples from Habří (Czech Republic) – subjected to demineralization in a mixture of HF and HCl acids (2:1), the residuum in HF only, then repeatedly washed in distilled water. This was followed by a 2-hour ultrasound toluene extraction of the remaining material and HPLC analysis usSearch for Fullerenes in Rocks from Ries Impact Crater