Abstract

Oscillating temperature dramatically speeds up recrystallization of a magma analog consisting of ammonium thiocyanate and ammonium chloride crystals in liquid. Linear growth rates increase by a factor of 10 if temperature is oscillated up and down a few degrees (e.g., 47 ± 3 °C) relative to nominally static conditions. Crystals pulse in size during thermal cycling; over the course of hundreds of cycles larger crystals grow and smaller crystals shrink, dramatically skewing the crystal size distribution. Crystal dissolution and growth in a pulsing thermal gradient produces a pronounced fabric, with crystals of ammonium thiocyanate aligned subparallel to the direction of heat flow. Alignment occurs via selective dissolution and growth of crystals of diverse orientations inherited from the starting material. These results have important implications for understanding how crystals grow and for interpreting texture in igneous rocks. Temperature cycling is likely common in magmatic systems and needs to be considered when analyzing chemical zoning of igneous crystals and rock textures.

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