Abstract

Four periods and kinds of Precambrian metamorphism are recognized in a single small map area astride the Grenville Front north of Georgian Bay, Ontario. They are, from oldest to youngest: (1) low-grade Hudsonian (Penokean) regional metamorphism of Huronian sedimentary rocks and later, Nipissing? intrusive rocks; (2) moderately low-grade (northwest of the Grenville Front) to high-grade regional metamorphism and generation of granites of Killarnean age associated with development of the Grenville Front and related slip planes; (3) slightly later contact metamorphism about intrusive Killarnean granites, resulting in porphyroblastic growth of andalusite, cordierite, chlorite, muscovite, and perhaps garnet; and (4) nonpervasive post-Keweenawan? retrogressive metamorphism and cataclasis, resulting most commonly in cataclasites derived from the Killarnean granites.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

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