Mysterious long-living ultrahigh-pressure or secondary impact crisis

Abstract

High-pressure glass has attracted interest in terms of both its fundamental state under extreme conditions and its possible applications as an advanced material. in this context, natural impact glasses are of considerable interest because they are formed under ultrahigh-pressure and high-temperature (UHpHt) conditions in larger volumes than laboratory fabrication can produce. Studying the UHpHt glasses of the unique giant Kara astrobleme (Russia), we found that the specific geological position of the UHpHt melt glass veins points to an origin from a secondary ultrahigh-pressure (UHp) melt according to the characteristics of the host suevites, which suggest later bottom flow. Here, we propose a fundamentally novel model involving an upward-injected UHp melt complex with complicated multilevel and multi-process differentiation based on observations of the UHP silica glass, single-crystal coesite and related UHp smectite that crystallized from an impact-generated hydrous melt. this model proposes a secondary UHP crisis during the modification stage of the Kara crater formation. The results are very important for addressing fundamental problems in fields as diverse as condensed matter states under extreme pressure and temperature (pt) conditions, material and geological reconstructions of impact structures, water conditions in mineral substances under UHp conditions in the deep earth, and the duration and magnitude of the catastrophic effects of large asteroid impacts. The structure and properties of disordered substances have been studied for a long time and used in a wide range of applications. The behaviour of such substances under extreme conditions, including intense compression, is particularly interesting and is actively studied both theoretically and experimentally 1-7. High-pressure glasses have drawn interest both fundamentally as a material formed under extreme conditions and as a novel compound that could be used in new applications 8,9. The behaviour of disordered and weakly ordered systems under compression has been studied in microvolumes via diamond anvil. Typically, the compression process is performed at pressures of up to 100 GPa and sometimes higher. Furthermore, the experiments are typically performed at room temperature 1,4-6,9. Only a few experiments combining both high pressures and high temperatures have been carried out. However, such studies are intriguing because the simultaneous effects of temperature and pressure can produce profound internal changes in a substance. For example, SiO 2 glass has a significantly higher density and strength at a pressure of approximately 8 GPa and a temperature of 1100 °C than under cold compression 10. The most important properties expected from these glasses are the heat capacity, hardness, unusual optical properties and other physical properties, which can be used in high-tech materials and technologies, including high-energy lasers, microelectronics and innovative optics. Glasses with microstructural features at a nanoscale are potential basic matrices ...

X-ray computed microtomography of diamondiferous impact suevitic breccia and clast-poor melt rock from the Kara astrobleme (Pay-Khoy, Russia)

“…Within the impact melt occurrences at the studied region of the Kara astrobleme, hydrothermal alteration generated smectite within their pore space, as observed by SEM (Shumilova et al, 2020). This smectite may not be related to autometasomatic alteration, but to general melt rock solidification with minerals formation during impact melt cooling -crystallization (Osinski et al, 2013).…”

“…This smectite may not be related to autometasomatic alteration, but to general melt rock solidification with minerals formation during impact melt cooling -crystallization (Osinski et al, 2013). Shumilova et al (2020) proposed that the smectite that has been found within the ultrahigh-pressure high temperature impact melt vein glasses containing melt-crystallized singlecrystalline coesite (Shumilova et al, 2020). Origin of the smectite is beyond the scope of this paper.…”

NMR Spectral Characteristics of Ultrahigh Pressure High Temperature Impact Glasses of the Giant Kara Crater (Pay-Khoy, Russia)

“…UHPHT melt impact glasses were sampled in 2015 and 2017 from impactites of the southern sector of the Kara crater from vein bodies cutting suevite massif (Figure 1) at the Kara River (Pay-Khoy, Russia) and these are samples KP15-12-115 and KP15-12-118. A preliminary analysis of the structural state of these glasses was carried out using a set of standard mineralogical research methods [13,14,16]. The main feature distinguishing UHPHT melts from clast type glasses and massive melt impactites was found to be the multilevel differentiation of impact melt, including liquation of silicate and aluminosilicate melts and partial silica melt crystallization to UHP SiO 2 variety-monocrystalline coesite [13,14].…”

“…The discovery of a high concentration of non-bridging oxygen atoms was highly unexpected based on the results [17] used for the interpretation of Raman spectra. In addition, electron microscopic images presented in [13,16] showed the presence of widespread pyroxene (Q 2 ) microcrystallites in the glass matrix. These observations call for further investigation of the polymerization of the UHPHT impact Kara glasses.…”

“…The synthesis of materials under the influence of both high pressures and high temperatures with the formation of UHP melts and their solidification products is interesting both in terms of the fundamental state of the substance and in anticipation of the specific properties of materials [12]. From this point of view, the discovered natural ultrahighpressure high-temperature (UHPHT) melt impact glasses with monocrystalline coesite [13] formed at pressures of more than 60 GPa and temperature of about 2800 K in the giant Kara impact crater (Pay-Khoy, Russia) [14] are of great interest. Using 57 Fe Mössbauer spectroscopy, a small portion of ferrous iron ions in 8-fold coordination (4%), similar to the structural positions of ions in garnets, was revealed in Kara glasses [14,15].…”