Abstract

Thin sections containing a magma-like mixture of three crystalline ammonium compounds and intercrystalline melt can be prepared and observed microscopically during crystallization, melting, and deformation. The aim of such observations is to establish links between active processes in the crystal-melt mixture and the textural signatures of the processes. The hope is to improve the basis for process interpretation of textures in rocks, although the value of the experimental system in this regard is still unknown. Three unexpected processes are seen: creation of growth centers for later blocky grains by isothermal decomposition of early dendritic grains; migration of grain boundaries early in the crystallization history; and growth of porphyroblast-like grains by phase-boundary migration, with abundant melt nearby. Textural metamorphism begins in this material well before its melt-present history is complete.

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