Transformations of Crystalline Rocks of the Central Uplift and Its Deep-Seated Zones

Impact-induced transformations of crystalline rocks of the central uplift and their lateral and vertical gradients are studied in detail due to extensive drilling, particularly in VDW cores down to about 5 km deep. The crystalline rock underwent shock metamorphism, crushing and displacement, injections of impact melt, local post-shock heating and superposed hydrothermal alteration. Based on shock effects in minerals (including appearance of diaplectic minerals and glasses, coesite and impact diamond), the attenuation of shock pressure is established from 40–45 GPa at near-surface zone of the central uplift to 15–20 GPa at a depth of 5 km. Within some linear zones of intense cataclasis, shocked rocks underwent a thermal recrystallization under temperatures up to 900–1100 °C exceeding significantly residual post-shock temperature. This resulted in formation of specific lithologies—coptoblastoliths, which are similar by fabric features to “lunar granulites”, and in emergence of a high-amplitude central magnetic anomaly. At last, hydrothermal alteration caused by the appearance of the fluid circulation in the heated rocks is widespread. Based on petrographic evidences, the thermal evolution of the impact crater has been simulated.