Another interesting dilemma (at least for an igneous petrologist!).
Associating contact metamorphism with "hornfels facies" seems to be a bit misleading because the term "hornfels" is (at least sometimes) defined as a textural term describing very fine-grained (not counting porphyroblasts), non-foliated rocks produced mainly by recrystallization due to heating. But lots of modern studies of the contact zones around intermediate to deep intrusions show rocks metamorphosed under strong temperature gradients but also with obvious foliated textures.
These ideas about contact metamorphism only generating changes associated with recrystallization from heat in the absence of directed stress abound in intro. textbooks (first place that students develop misconceptions) and continue to a degree in some petrology textbooks...
I was also wondering if, even at relatively low absolute pressures, rocks experienced with contact metamorphism couldn't develop minerals with preferred orientations if the pressure was strongly non-uniform. If they can, texturally those rocks aren't really hornfels, and putting them into a hornfels facies seems kind of confusing...
Dept of Geology
Grand Valley State University
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Allendale, MI 49401-9403