Metamorphism in the Wabigoon Subprovince in the vicinity of Vermilion Bay and Sioux Lookout, Ontario
Date of Award
Master of Science (MS)
D. Perkins, III
The Wabigoon-English River subprovince boundary has been proposed by various workers to be either a fault, an unconformity, an intrusive contact or a gradational boundary. North of the Wabigoon Fault, in the Vermilion Bay-Dryden area, migmatization and partial melting of meta sediments have produced a variety of metatexitic and diatexitic migmatites. Because migmatites are not encountered in the Wabigoon subprovince proper and the area north of the Wabigoon fault is so different from the rest of the subprovince, it is thought that the area may constitute the southernmost part of the English River sub province.
The Wabigoon Subprovince is a volcanic-plutonic belt located within the Superior Province of the canadian Shield. The subprovince contains metavolcanic rocks with small amounts of metasedimentary rocks which have been intruded by granitoid rocks. The study area is located along the northernmost edge of the Wabigoon Subprovince extending from vermilion Bay to Sioux Lookout, Ontario.
Three isograds can be mapped in the field: l) an area of medium-grade, andalusite-bearing, metamorphosed pelitic sediments, 2) an area of medium-grade, garnet-bearing, metamorphosed pelitic sediments, and 3) an area of high grade, metamorphosed pelitic sediments containing metastable sillimanite. The isograds are on the average 2 to 4 Km apart.
Results from the application of three geothermometers (biotite-garnet, garnet-cordierite and biotite cordierite) geothermometry indicate there is a gradual temperature increase from 4Sa°C in the southern half of the study area to 6ao0 c in the northern half. Pressures calculated by applying two geobarometers (garnet-cordierite and garnet-plagioclase-sillimanite-quartz) for the northern half of the study area ranged from 3.9 to 4.8 Kb; those in the southern half are less than 3.9 Kb.
The observed changes in mineralogy, geobarometry and geothermometry, are characteristic of a regular progressive increase in metamorphic grade from the Wabigoon fault north to the start of migmitization. There is a gradual increase in temperature and pressure, with no major jumps or breaks, from south to north.
The study area represents either a part of the English River Subprovince or a transitional zone between the Wabigoon and English River Subprovinces.
Roob, Christine K., "Metamorphism in the Wabigoon Subprovince in the vicinity of Vermilion Bay and Sioux Lookout, Ontario" (1987). Theses and Dissertations. 249.