Backscattered electron image of amphibole grain in AT-1610 with a thick reaction rim surrounding it. Amphibole is a volcanic mineral that crystallizes in magma that contains some amount of water. As magma moves up toward the surface, it loses water and the amphibole reacts, forming a rim containing plagioclase, pyroxene, and oxide minerals. At Mt Redoubt, this process probably happens when the magma reached depths of about 4 km or less. This particular amphibole has a rim that is very well developed, which could indicate it was in a batch of magma that resided beneath Redoubt at somewhat shallow depths for a while. More work will help us figure out timescales and magma depths. Image collected using the Advanced Instrumentation Laboratory (UAF) Cameca SX-50 electron microprobe.

Date:	March 31, 2009 12:00 AM
Volcano(es):	Redoubt
Photographer/Creator:	Larsen, J. F.
URL:	http://www.avo.alaska.edu/images/image.php?id=17572