Two distinct types of migmatite occur in this area. One comprises stromatic migmatite and is most common near the sillimanite-K-feldspar isograd and consists of paired leucosome and melanosome. The other forms a vein network of leucocratic material containing large garnets set in an aluminous gneiss host. Both types are interpreted as the result of anatexis at the peak of the Acadian (Devonian) regional metamorphism, but by different mechanisms. The stromatic migmatites are thought to be due to fluid-present melting at 625o-675oC through a dehydration-melting reaction involving mainly felsic minerals, whereas the vein types appear to have formed by a fluid-absent reaction combining biotite dehydration with melting, probably at >675oC. -R.A.H.
|Number of pages||11|
|Publication status||Published - 1983|