Multi‐stage evolution of frost‐induced microtextures on the surface of quartz grains—An experimental study

Coarse sand‐sized (0.5–1.0 mm) grains of vein quartz were subjected to frost‐induced stress under controlled laboratory conditions. A total of 1,000 freeze–thaw (FT) cycles, simulated under different (low, high) water mineralization conditions in the temperature range from −5°C up to +10°C, were used to test effects on collected samples. Scanning electron microscopic (SEM) microtextural analysis of grain surfaces was performed at 0 (start) and after 50, 100, 300, 700, and 1,000 FT cycles. The results indicate that variable frost‐induced microtextural imprints encountered on quartz grain surfaces prior to and following analysis depend largely on the mineralization (dissolved solute content) of water involved in the weathering process. The higher the water mineralization, the greater the intensity of mechanical weathering. Two predominant outcomes in the course of these micro‐scale frost weathering tests have been identified: a physical (mechanical) aspect manifested by the occurrence of conchoidal fractures and breakage block microtextures dominating up to 300 FT cycles, and a chemical aspect resulting in the occurrence of precipitation crusts and obliteration of grain microrelief. Moreover, three additional stages of microtexture development may be distinguished with the evolution of frost‐induced microrelief on the surface of quartz grains: (i) initial cracks of large‐sized conchoidal fractures, (ii) increasing frost cycles yielding additional small‐sized conchoidal fractures, and (iii) advanced breakage blocks. Frost‐induced exposure of fresh, unweathered grain surfaces leads to refreshing of the grain surface.