This report condenses the field research notes conducted during the ERS225 field course during the 2023 summer.
Mikael Syed
Dr. Ashwell
December 2023
Peninsula Road (Near Woodington Road):
Location: Peninsula Road, Near Woodington Road
Date: 29 August, 2023
Time: 3:30pm
Weather: Cloudy
Structure & Texture:
The outcrop is about 4 meters tall with compositional banding of black, white and grey. The banding has 5-10cm of thickness. A majority of the outcrop contains coarse-grained minerals and occasionally mega-crystic quartz crystals (2). The minerals tend to be euhedral and subhedral with garnets being euhedral.
Mineral Composition:
35% Calcite, 10% Garnet, 40% Pyroxene or Amphibole, 15% Quartz.
Protolith & History:
The protolith is most likely a limestone or other sedimentary rock. Since limestone is mainly composed of calcite, however, dolostone could also be a likely protolith. The result of the mineral composition that we see of garnet, pyroxene, amphibole, and quartz, could also aid in the fact the protolith could be a shale. This is backed up by the fact that there is foliation present in the rock. There is a high probability that varying lithologies in this outcrop have led to this mixture.
Peninsula Road (Near Henry Road):
Location: Peninsula Road, Near Henry Road
Date: 29 August, 2023
Time: 4:37pm
Weather: Cloudy
Structure & Texture:
This outcrop is dark and weathered and stands 15-18 meters tall. Compositional banding is
present but is faint from the weathered surface. Shearing of micas can be seen near the
bottom of the outcrop all across. Has a medium to coarse-grained mineralogy present throughout the outcrop.
Mineral Composition:
20% Garnet, 5% Biotite, 10% Amphibole, 10% Quartz, 5% Alkali Feldspar, 30% Pyroxene.
Protolith & History:
The presence of garnet, biotite, amphibole, quartz, K-spar, and pyroxene indicates a
complex mineralogy, and the metamorphic rock likely originated from a shale or granitic
protolith.
The mineralogical composition, along with the shearing of micas and compositional banding, suggests a high-grade metamorphic rock, most likely a gneiss from the compositional banding. Gneisses often show compositional layering or banding due to the segregation of different minerals during metamorphism. The specific protolith might have been a pelitic sedimentary rock (shale) or a felsic igneous rock (granite).
The shearing of micas is the result of ductile deformation, which is common in the higher
grades of metamorphism. The wide range of mineralogy suggests that the original rock had
a varying composition, and the metamorphic process led to the development of these
minerals under high-pressure and temperature conditions. An amphibolite facies are the
likely facies that this rock is due to the mineral composition, as well as the higher
temperature and pressure needed.
Gravenhurst Waterfront:
Location: Highway 169, Gravenhurst, Farmers Market Car Park
Date: 29th August 2023
Time: 1:30 PM
Weather: Sunny, Slightly Cloudy
Structure & Texture:
The outcrop is approximately 10.8 meters tall and most of the lithology is a black to dark grey colour with pegmatite intrusions. These pegmatite intrusions are approximately 0.65 meters thick. Weak to moderate schistosity of micas are present in the outcrop, along with weak gneissic banding.
The pegmatites have coarse-grained mineralogy while the darker lithology of the outcrop has fine-grained mineralogy. Additionally, pegmatites contain (for the most part) euhedral crystal habit with their mineralogy. The darker lithology contains mostly anhedral crystals.
Mineral Composition:
Pegmatite: 60% Alkali Feldspar, 35% Quartz, 5% Biotite.
Darker Lithology: 35% Quartz, 35% Dark Mineral, 15% Garnet, 15% Biotite
Protolith & History:
The protolith for the darker lithology was most likely a shale protolith, due to the
abundance of micas, and garnets. Additionally, this can be attributed to the wavy and
straight foliation with the outcrop itself. The pegmatite was most likely formed through
molten rock crystallizing through the darker lithology.
Ragged Rapids Road and Highway 38
Location: Ragged Rapids Rd, Highway 169
Date: 31st August 2023
Time: 12:40 PM
Weather: Sunny, Clear Skies
Structure & Texture:
About 3 meters tall, has a dark to light grey colour that varies from foliation (quartz, alkali feldspar, Plagioclase). Strong gneissic banding is present throughout the outcrop. There are no sedimentary structures present. The outcrop as well as 0.5cm to 5cm thickness of bands. Veins of quartz are apparent throughout the rock as well. These veins are accompanied by schistosity of biotite and other micas.
Coarse-grained minerals are common in this outcrop with finer-grained dark minerals. Porphyroclastic texture is present with quartz with polygonal amphibole and biotite. Subhedral quartz, garnet, amphibole and biotite are present as well.
Mineral Composition:
Quartz: 60% Alkali Feldspar, 35% Quartz, 5% Biotite.
Darker Lithology: 35% Quartz, 35% Dark Mineral, 15% Garnet, 15% Biotite
Protolith & History:
The protolith for the darker lithology was most likely a shale protolith, due to the abundance of micas, and garnets. Additionally, this can be attributed to the wavy and straight foliation with the outcrop itself. The pegmatite was most likely formed through molten rock crystallizing through the darker lithology.
Near Oastler Lake Provincial Park
Location: Oastler Lake Provincial Park
Date: 31st August 2023
Time: 8:40 AM
Weather: Sunny, Clear Skies
Structure & Texture:
About 2-4 Meters Tall, mostly dark to light grey lithology with pinkish and white veins. Compositional banding is present as well. Schistosity of micas and wavy banding are present.
Gneissis banding, porphyroblasts of quartz, and wavy foliation of biotite make up a lot of the outcrop.
Mineral Composition:
10% Quartz, 15% K-Spar, 5% Muscovite, 30% Biotite, 30% Darker Mineral, 10% Plagioclase.
Protolith & History:
The protolith for the darker lithology was most likely a shale protolith, due to the abundance of micas, and garnets. Additionally, this can be attributed to the wavy and straight foliation with the outcrop itself (possibly a migmatite). The pegmatite was most likely formed through molten rock crystallizing through the darker lithology. Overall, high-grade metamorphism with intense heat and pressure occurred. Most likely an Amphibolite or Granulite facies due to mineral assemblages and the high-grade metamorphism.
Additional References Used
https://files.ontario.ca/ndmnrf-geotours-parry-sound-en-2021-12-13.pdf
https://geology.com/rocks/pegmatite.shtml
https://pubs.geoscienceworld.org/canmin/article-abstract/38/2/471/126237/GRENVILLIAN-METAMORPHISM-OF-MONOCYCLIC-ROCKS
https://turnstone.ca/2143peg.htm
Charts + Tables Utilized For Analysis or Reasoning
Protolith Table #1
Protolith Table #2
Protolith Table #3
Mineral Decision Table
| Mineral | Properties |
|---|---|
| Quartz | Translucent Grey, Foggy White, No Cleavage (Fractures), Hardness > 7 |
| Plagioclase | Cloudy, White Colour, Hard, 2 Cleavages @ 90 degrees |
| Amphibole | Black Colour, 60/120-degree cleavage, Very Hard |
| Biotite | Black Colour, Basal Cleavage, Soft < 3 |
| Muscovite | Shiny luster, Soft, White Colour |
| Alkali Feldspar | Pink Colour, Opaque. 2 Cleavages @ 90 degrees |
| Pyroxene | Dark green to black colour, 90 degree cleavage |
| Garnet | Red Color, No Cleavage, Hardness > 7 |