2 CGB 2 – Mactier Exit
Sheila Ballantyne and Phillip Ruscica
GPS Coordinates (45°05’43.8″N , 79°47’06.7″W)
Parking: This site can be accessed on the west side of the road on a wide shoulder.
At the time of writing, this site was no longer accessible. This rock cut is near the exit from Highway 400 to Mactier, Ontario, on the east side of highway 400.
This rock cut is a pink and white finely layered gneiss with black pods of highly deformed mafic dyke. The foliation and orientation of the dyke contacts are highly variable here.
Click here to open the bedrock geology legend on the OGS website
The images in the slides below highlight the foliated gneiss and deformed mafic dyke observed at this outcrop.
Digital Outcrop
Click on the arrows in the image below to view various perspectives of this outcrop. A link at the bottom left will take you to a 3D model of the outcrop in Sketchfab.
Digital Hand Samples
The following rock sample (VLS-21-25) is from one of the black pods of mafic dyke. Click on the image (or here) to view the 3D model of the sample in Sketchfab! Note the fine to medium grained mafic minerals (dominantly hornblende and biotite) peppered with white mineral (mostly plagioclase). Thin sections for this sample are shown below. No close-up rotation videos were made for this thin section. Electron Probe Micro-Analyser (EPMA) results are available upon request for this sample.
This rock (VLS-21-26) is from the finely layered felsic gneiss. Click on the image (or here) to view the 3D model of the sample in Sketchfab! The minerals are dominantly medium to coarse grained pink and white feldspars and quartz, with minor amounts of biotite, hornblende, pyroxene, and fine grained garnet. Small dark unidentified opaque minerals are also observed. Thin sections for this sample are shown below. No close-up rotation videos were made for this thin section. Electron Probe Micro-Analyser (EPMA) results are available upon request for this sample.
Digital Thin Sections
Four thin Sections images are shown below of the mafic dyke sample (VLS-21-25) and the surrounding gneiss (VLS-21-26). No close-up rotation videos were made for this thin section. Electron Probe Micro-Analyser (EPMA) results are available upon request for this sample.
Sample VLS-21-25
Sample VLS-21-26
Additional photographs, detailed descriptions, and high resolution images of thin sections are available to post-secondary instructors. Please email virtual.petrology.network@utoronto.ca
All comments, questions, and concerns are always welcome at this email address.
Go to the next chapter: CGB 3 – Gravenhurst!