| Abstract: | Abstract— Chassigny is a shock-metamorphosed dunite of probable Martian origin. In order to determine its degree of shock metamorphism and to define the starting conditions prior to its ejection from Mars, the shock signature of Chassigny has been carefully examined by optical and electronoptical techniques. Dominant shock effects are the conversion of feldspars to diaplectic glass (maskelynite), the clino-/orthoenstatite inversion, strong mosaicism of olivine, and the activation of numerous planar fractures and c dislocations in olivine. High-resolution transmission electron microscopy (TEM) reveals additionally the coexistance of planar fractures with, so far, unknown discontinuous fractures in olivine. These findings point to a shock pressure of 35 GPa. Chassigny has thus experienced a high and similar degree of shock metamorphism as the shergottites. The results of this study suggest that Chassigny was at a shallow target position, close to the point of impact, when it was ejected. |
