Sieve-textured plagioclase in volcanic rocks produced by rapid decompression

A study was conducted on sieve-textured plagioclase found in orogenic volcanic rocks formed by rapid decompression. The plagioclasetexture was previously interpreted as a result of magma mixing but may occur via rapid decompression. High-pressure piston-cylinder experiments on an andesite showed that the presence of sieve-textured plagioclase should not onlybe attributed to magma mixing but to rapid decompression as well. Further experimentation also revealed that rapid decompression may occur in conjunctionwith magma mixing.