Abstract

The Chiwaukum Schist, in the Washington Cascade Mountains, has undergone two distinct episodes of metamorphism: (1) Regional Barrovian-type metamorphism and (2) subsequent “contact” metamorphism, associated with the Late Cretaceous intrusion of the Mount Stuart batholith, comparable to part of the Buchan-type progression.

The later metamorphic event is unusual because the effects are predominantly dynamothermal, although in contact with and genetically related to plutonic intrusion. Some indications that penetrative deformation accompanied recrystallization during “contact” metamorphism are (1) preferred orientation of minerals such as cordierite, andalusite and sillimanite; (2) alignment of mafic minerals within granitic rocks near contacts; (3) granitic contacts being generally parallel to the predominant s-plane of the schist; (4) biotite within the schists showing more pronounced alignment the closer it is to granitic contacts; and (5) minerals in the schists near contacts commonly being microboudinaged and showing evidence for rotation during and subsequent to crystallization.

First Page Preview

First page PDF preview
You do not currently have access to this article.