Cordierite-Anthophyllite Rock
“Metamorphosed from chemically exotic protoliths”
Cordierite-anthophyllite rock is an unusual metamorphic assemblage that develops from highly magnesian and aluminous protoliths — often hydrothermally altered sea floor rocks. The distinctive combination of cordierite and anthophyllite marks a very specific bulk chemistry and metamorphic grade.
cordierite, anthophyllite, garnet, biotite, quartz, plagioclase, sillimanite
Orijarvi (Finland — type locality), Broken Hill (Australia), Bergslagen (Sweden), Blue Ridge (North Carolina, USA), Limpopo Belt
6-7
These rocks are prized by metamorphic petrologists because their unusual chemistry means that subtle changes in temperature and pressure produce dramatic changes in mineralogy — they're natural experiments in metamorphic reactions.
Test Your Knowledge
What type of protolith (original rock) typically produces cordierite-anthophyllite assemblages during metamorphism?
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