polymetamorphic diaphthoresis

polymetamorphic diaphthoresis

[¦päl·i‚med·ə′mȯr·fik dī‚af·thə′rē·səs]
(geology)
Retrograde changes during a second phase of metamorphism that is clearly separated from a previous, higher-grade metamorphic period.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.