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.
Image courtesy of the AVO/UAF-GI.
Please cite the photographer and the Alaska Volcano Observatory / University of Alaska Fairbanks, Geophysical Institute when using this image.
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