by these reaction isograds:

:amphibole -> pyroxene + H₂O

:biotite -> K-feldspar + garnet + orthopyroxene + H₂O.

Hornblende granulite subfacies is a transitional coexistence region of anhydrous and hydrated ferromagnesian minerals, so the above-mentioned isograds mark the boundary with pyroxene granulite subfacies - facies with completely anhydrous mineral assemblages.

1911 Encyclopædia Britannica definition

Granulite (Latin granulum, "a little grain") is a name used by petrographers to designate two distinct classes of rocks. According to the terminology of the French school it signifies a granite in which both kinds of mica (muscovite and biotite) occur, and corresponds to the German Granit, or to the English muscovite biotite granite. This application has not been accepted generally. [This granitic meaning of granulite is now obsolete.] To the German petrologists granulite means a more or less banded fine-grained metamorphic rock, consisting mainly of quartz and feldspar in very small irregular crystals and usually also containing a fair number of minute, rounded, pale-red garnets. Among English and American geologists the term is generally employed in this sense.

1.Previous
3.Next