Metamorphic Rocks Lecture Part 2
Veronica McCann・2 minutes read
Igneous intrusions lead to different mineral grades, with economic star minerals found in mines like Ducktown, Tennessee. Metamorphic rocks form through heat, pressure, and fluid interactions, showcasing varied textures and foliation patterns.
Insights
- Igneous intrusions are crucial in the formation of economically significant star minerals, found in mines like those in Ducktown, Tennessee.
- The sequence of metamorphic rocks from shale to slate to phylite to schist to nice showcases a transformation in mineral composition and grain size, reflecting different levels of metamorphic grade and processes.
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Recent questions
How are economically important star minerals formed?
Star minerals are formed in big zones through the interaction of hot sources like igneous intrusions with rock fractures. These minerals are economically important and can be found in mines such as those in Ducktown, Tennessee.
What causes regional metamorphism in rocks?
Regional metamorphism in rocks is caused by plate motion, which creates friction, pressure, and temperature changes. Convergent margins, such as subduction zones, are common locations where regional metamorphism occurs.
What is the difference between foliated and non-foliated metamorphic rocks?
Foliated metamorphic rocks exhibit layered or stacked minerals due to non-uniform pressure, while non-foliated rocks have a solid appearance from uniform stress. Foliation is a result of mineral alignment caused by pressure.
How do metamorphic rocks demonstrate different types of stress?
Metamorphic rocks demonstrate different types of stress through their textures. Tensional stress creates stretching, compressional stress shortens materials, and shear stress is shown by sliding objects. These stresses affect the alignment of minerals in rocks.
What are the characteristics of nice rocks in metamorphism?
Nice rocks in metamorphism include feldspar, quartz, and coarse grains, with easily visible minerals indicating a high metamorphic grade. These rocks showcase banded foliation with alternating light and dark bands, revealing the intense metamorphic processes they have undergone.
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Summary
00:00
Metamorphic Rocks: Earth's History Revealed
- Igneous intrusion is the hot source, with higher grades closer to it and lower grades further away.
- Fluid from the intrusion or water interacting with rock fractures can recrystallize the rock.
- Star minerals formed in big zones are economically important, found in mines like those in Ducktown, Tennessee.
- The largest iron deposit east of Lake Superior was in Pennsylvania, mined for iron and copper during the Revolutionary War.
- The Pennsylvania mine operated for 234 years, now inactive, with scarring deposits from the Triassic era.
- Unusual minerals formed due to heat, pressure, and fluids in regions with scarred minerals.
- Regional metamorphism involves plate motion, creating friction, pressure, and temperature changes.
- Convergent margins, like subduction zones, lead to regional metamorphism.
- Green schist and blue schist are named after their colors, formed due to heat, pressure, and mineral alignment.
- Mountain building events create high-grade metamorphic rocks, revealing Earth's history through rock characteristics.
21:11
Metamorphic Rocks: Textures and Mineral Transitions
- Migmatite resembles melting but doesn't fully melt, showcasing metamorphic textures.
- The sequence from shale to slate to phylite to schist to nice involves changing minerals and grain size.
- Shale transitions to slate with laminated layers and fine grains, then to phylite with micas and possible garnets.
- Schist features mica resembling fish scales, garnets, and medium grain size with a wrinkled appearance.
- Nice includes feldspar, quartz, and coarse grains, easily visible minerals indicating high metamorphic grade.
- Metamorphic rocks exhibit foliated textures with layered or stacked minerals and non-foliated textures with a solid appearance.
- Foliation signifies non-uniform pressure, while non-foliated rocks result from uniform stress.
- Uniform stress compresses rocks uniformly, reducing their size, as seen in a styrofoam cup example.
- Non-uniform stress, like shearing, aligns minerals in foliated rocks, demonstrated with play-doh balls.
- Play-doh or silly putty can illustrate how pressure aligns minerals in metamorphic rocks, creating parallel lines.
46:11
Stress and Pressure Shape Rock Foliation
- Tensional stress creates stretching, while compressional stress shortens materials.
- Shear stress is demonstrated by sliding objects like cards or paper.
- Mineral alignment in rocks mirrors the rolling of play-doh, leading to foliation.
- Equal pressure results in non-foliated rocks, while directional pressure causes foliation.
- Metamorphic rocks like conglomerate show flattened and stretched pebbles.
- Slate exhibits laminated cleavage, resembling stacked library books.
- Phylite displays a wavy foliation due to larger grains.
- Schistose foliation appears flaky and reflective due to growing mica grains.
- Nice rocks showcase banded foliation, with alternating light and dark bands.
