G. Graup's research while affiliated with Max Planck Institute for Chemistry and other places

Publications (7)

Article
Akaogiite, an ultra-dense polymorph of TiO2 was encountered in heavily shocked garnet-cordierite-sillimanite gneiss in the Suevite breccia of the Ries meteorite impact crater in Germany. The chemical formula of akaogiite is TiO2, containing (wt%) TiO2 97.6–97.7; Nb2O5 0.15–0.20, and FeO 0.11–0.14. The empirical formula is: Ti0.998Fe0.002Nb0.001O2....
Article
We report the discovery of a new cubic, transparent and super-hard polymorph of carbon from the Ries and Popigai craters: This phase will have important implications in understanding high-pressure phase transitions in the carbon system.
Article
We report two new natural shock-induced very dense polymorphs of rutile from suevites of the Ries Crater, Germany. This finding sets entirely new parameters for a robust estimation of peak-shock pressures and post-shock temperatures not accounted for before.

Citations

... In the epitaxial films deposited on c-sapphire at 400-600 1C and on r-sapphire at 350-550 1C, the densities were markedly higher and equaled to 4.370.1 g/cm 3 . The former value was comparable to that of anatase [35] while the latter one was similar to the densities reported for rutile [13] and TiO 2 -II [3,13,30,36]. With the increase of T G from 550 to 600 1C, the densities of films deposited on r-sapphire decreased down to 4.0 g/cm 3 while the decrease was in correlation with the increasing surface roughness (Fig. 4a) and, thus, with decreasing homogeneity of the films. ...
... Still they do not rule out the possibility of localized pressure peaks of 60 to 80 GPa, in agreement with the observation of melt pockets. Sharp et al. (1999) and El Goresy et al. (2000Goresy et al. ( , 2003, from the texture and speciation of silica and other high pressure phases, argue that the pressure in Shergotty exceeded 90 GPa, in agreement with the presence of post-stishovite in a α-PbO 2 structure (Dera et al. 2002). They further argue that the density of maskelynite is not appropriate to indicate the peak pressure. ...
... During hypervelocity impact events into the siliceous continental crust, high-pressure phase transformations of quartz may occur. Coesite and stishovite are known from several impact craters, ranging from small-sized crater pits such as the Wabar craters, Saudi Arabia ) and the kilometer-sized Meteor Crater, USA (Chao et al. 1960), to the 25 km diameter Ries crater, Germany (Shoemaker and Chao 1961;El Goresy et al. 2001;Fazio et al. 2017) and the 100 km sized Popigai crater, Russia (Vishnevsky et al. 1974). The pressure and temperature required for the formation and preservation of high-pressure phases of quartz seem to be different when comparing impact environments with quasi-static conditions (Carl et al. 2017). ...
... 31,32 The lattice structures of most crystalline TiO 2 polymorphs are dominated by TiO 6 octahedra sharing edges and corners. 33 In denser phases stabilized by high pressure, such as the akaogiite (space group P21/c) 34,35 and the cotunnite-type TiO 2 (space group Pnma), 36 the lattice may feature instead seven-coordinated oxygen polyhedra around Ti ions (TiO 7 ). On the other hand, TiO 2 can also be synthesized in lower density, amorphous form when lowtemperature processing is used. ...
... Impactites from the Ries have been studied in great detail and have revealed some basic principles of impact metamorphism (e.g., Hˆrz 1965;Stˆffler 1971aStˆffler , 1974avon Engelhardt et al. 1969von Engelhardt et al. , 1995von Engelhardt 1990von Engelhardt , 1997Newsom et al. 1990). Various ultra-high pressure minerals were found and intensely studied in Ries impactites, e.g., stishovite, coesite (Stˆffler 1971b), diamond (e.g., Hough et al. 1995El Goresy et al. 2001a;Schmitt et al. 2005), a post-diamond carbon polymorph (El Goresy et al. 2003), baddeleyite-structured TiO 2 (El Goresy et al. 2001b), and reidite (Gucsik et al. 2004a(Gucsik et al. , 2004b. ...