Image 2:


Caption:

The subject is a reaction zone in a high-pressure (ca. 15 kbar) - high-temperature(>1000 deg. C) garnet-pyroxenite from the Snowbird tectonic zone, northern Saskatchewan, Canada. The age of metamorphism predates 2.6 Ga.

At the top of the field of view is an area of sodian clinopyroxene with locally extensive development of plagioclase (Ab-66) in a vermiform intergrowth. At the bottom of the view is a mass of micron-scale symplectite of corundum and nearly pure anorthite. This region is interpreted to have been where a crystal of kyanite resided within sodian clinopyroxene, and has since been consumed in reaction, and some of the reaction products consumed to make still other products. From the bottom up: corundum+anorthite symplectite, sapphirine+anorthite symplectite, plagioclase zoned from anorthitic to much more albitic compositions, orthopyroxene(black)+plagioclase, clinopyroxene+plagioclase symplectite, and finally locally pristine sodian clinopyroxene.

For more information about this image contact: Michael L. Williams