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34 Cards in this Set
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Protolith |
Original rock prior to metamorphism. Can be igneous, sedimentary, metamorphic
Types of metamorphism acronym:
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Contact Metamorphism |
Hot igneous rock intrudes into a pre-existing rock. Little or no increase in pressure |
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Regional Metamorphism |
Increased temperature and/or pressure on a regional scale
Gneiss is most common high grade metamorphic rock (regional) formed from igneous or sedimentary rocks |
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Hydrothermal Metamorphism |
Percolation hydrothermal fluids change chemical makeup of a rock by removing or depositing new elements
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Shock Metamorphism |
Meteorite or lava from a volcanic eruption collides with an existing rock. Characterized by high pressure and high temperature in a short period of time |
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Dynamic Metamorphism |
Associated with zones of high to moderate strain such as a fault. Pressures and mechanical deformation rush rocks into angular fragments
Can form breccia |
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Breccia |
Pieces of rock fragments in a fine matrix |
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Summary:
Heat + pressure =
Heat =
Pressure + faulting = |
Regional metamorphism
Contact metamorphism
Dynamic metamorphism |
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Metamorphic grade |
Level of metamorphism is measured by grade & each grade is called a facies
Grade can be determined by minerals present and grain size. Coarse grain = high grade; fine grain = low grade
Low-grade metamorphic rocks form under low pressure and temperature facies
High-grade metamorphic rocks form under high pressure and temperature facies |
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Fabric |
Metamorphic textures
Relict fabric = fabric of original rock
Either planar or linear |
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Folitation |
Planar metamorphic fabric |
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Lineation |
Linear metamorphic fabric |
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Slaty |
Examples: Slate, phylite Examples:
Sedimentary protoliths
Breaks into sheets |
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Schistose |
Examples: Shist
Sedimentary and igneous protoliths
Mica minerals align in bands |
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Gneissose |
Examples: Gniess
Sedimentary (paragniess) and igneous (orthogneiss) protoliths
Virtually all minerals align in bands |
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Granoblastic |
Metamorphic rock (protolith): Granulite (intrusive igneous), marble (limestone), quartzite (sandstone)
Massive with no foliation
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Hornfelsic |
Examples: Hornfels
Fine grained sedimentary protoliths
Hard, original banding |
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Skarn |
All rock types which have experienced metamorphism and exposure to hydrothermal fluids |
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Metamorphic ore deposits: Cu skarns |
Contact metamorphism (low grade)
Mafic or ultramafic rocks overlain by sedimentary rocks or Ca-rich rocks (carbonate or limestone)
Cu leached from mafic rocks by hydrothermal fluids and transported towards Earth's surface. Fluids encounter organic/carbonate layer & Cu precipitates |
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Metamorphic ore deposits: Archean quartz-carbonate Au |
Form along highly-deformed, steeply-dipping shear zones, generally near contact between metamorphic sedimentary volcanic rock sequences |
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Metamorphic ore deposits: Diamonds |
Host rock: kimberlites (ultramafic, at least 35% olivine). Kimberlites develop through igneous processes but diamonds through metamorphic
To form: require pressure >4 GPa and temperatures 950 - 1350 C. Otherwise graphite will form instead of diamond |
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Kimberlite pipes |
Conditions to form diamonds are found ~200 km below surface. Diamonds are brought to surface by kimberlite pipes. These intrude into the crust explosively and rock crystallizes too quickly for diamonds to revert into graphite. |
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Coal |
Organic sediment consisting of a complex mixture of substances. Most abundant fossil fuel.
70% of world's coal production -> 40% of world's electricity
12% of world's coal production is used to make coke -> 70% of world's steel
22 coal mines in Canada |
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Rank |
Higher rank = coal was buried deeper Black coals: High rank: anthracite Medium rank: bituminous. Coking coal is med. rank. Brown coals: Low rank: sub-bituminous, lignite, peat
Higher rank = increasing carbon, calorific value, cost of extraction Lower rank: increasing moisture, volatile content |
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Biochemical degradation & physico-chemical degradation |
Biochemical = chemical decomposition of botanical matter assisted by organisms
Physico-chemical = caused by conditions of burial (pressure and heat change chemistry and structure of altered organic matter) |
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Macerals |
Smallest microscopically recognizable entities in coal. Analogous to minerals in rocks (but do not have homogeneous chemistry and orderly internal structure) |
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Vitrinite maceral group |
Woody plant material
Gray |
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Inertinite maceral group |
Material that has been oxidized prior to coalification. high carbon content
White |
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Liptinite maceral group |
More resistant parts of plants like spores, cuticles, and resin. Enriched in hydrogen
Dark gray |
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Vitrinite Reflectance |
Most commonly used rank parameter for bituminous or black coals.
Vitrinite reflectance increases as rank of coaol increases |
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Clay minerals |
Most abundant minerals in coal -kaolinite, illite, montmorillonite
Clay minerals with swelling properties expand in contact with water: reduces strength and can be hazardous during mining
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Other minerals in coal |
Carbonates, oxides, sulphides
Pyrite (FeS2) causes acid rain |
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Gross Calorific Value |
Heat liberated by the coal's complete combustion with oxygen |
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Proximate Analysis |
Indicates degree of physico-chemical coalification
FC+M+VM+A = 100%
FC = fixed carbon M = moisture VM = volatile matter A = ash |