Objective
This research project deals with the study of various high-pressure minerals that are found in rock formations at meteorite impact craters in Russia and western Europe. In particular, impact-derived diamonds, which form from graphite that is present in the target rocks, will be studied using a variety of methods. The craters to be studied include the Popigai crater in Siberia, the Kara and Puchez-Katunki craters in Russia, and the Ries crater in Germany. During the hypervelocity impact of a comet nucleus or an asteroid on the Earth, a supersonic shock wave is generated that is propagated into the target rock, leading to a stress wave that will become shock wave moving at supersonic speed. The shock wave leads to compression of the target rocks at pressures far above a material property called the Hugoniot elastic limit (HEL). The HEL can generally be desribed as the maximum stress that a material can be subjected to, while above this limit plastic, or irreversible, distortions occur in the solid medium through which the compressive wave travels. The value of the HEL is about 5-10 GPa for most minerals and whole rocks. The only known process that produces shock pressures exceeding the HELs in nature is impact cratering. Such pressures are enough to cause irreversible changes in the crystal structure of rock-forming and accessory minerals, and to introduce phase changes (i.e. the formation of high pressure phases). While the formation of various form of quartz and feldspar is reasonably well understood, little research has been done on high-pressure carbon phases, i.e. diamond.
Impact diamonds are thought to be formed from crystallised or amorphous carbon such as graphite or coal, that is present in target-rocks, such as graphite-bearing gneisses, during the shock compression. Little is known about the mineralogical, crystallographic, chemical, and isotopic parameters of the various forms of impact diamond. In the current research, trace elements studies, by neutron activation analysis, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and isotope studies, by mass spectrometry, will be used to gain a better understanding of these rare phases. The optical and x-ray studies will enable data to be obtained on the crystal structure of the impact diamonds and the relationship with the crystal structure of the precursor minerals to be assessed, while infrared spectrometry will provide data on possible gaseous inclusions such as carbon dioxide or nitrogen. Chemical studies, by neutron activation analysis, and isotopic analyses, for carbon and nitrogen isotopic composition, will allow comparisons with the composition of the target rocks and precursor minerals and provide some information on possible chemical fractionations during the impact level.
Results will be presented at international scientific meetings and published in international peer review journals.
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1090 Wien
Austria