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28 Cards in this Set
- Front
- Back
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What three basic requirements does an ore deposit need? |
1. Source 2. Transport mechanism 3. Trap |
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What two factors control element behaviour? |
1. Ionic charge 2. Ionic radius
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How do magmatic ore deposits work in relation to the magma? |
They are related to the solidification and and cooling of magmas. Economic commodities generally depend on magma (rock) type (ultramafic, mafic, intermediate, felsic, alkaline)
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How does tectonic environment effect magma? |
Different tectonic environments = different magmas = different metal association |
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What types of metal would you expect with mafic magma? |
Siderophile elements PGEs, Au, Ni, Co... |
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What types of metal would you expect with felsic magma? |
W, U, Zi, Li, REE.... |
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What is involved in magma formation? |
Partial melting- source rocks rarely 100% melted Conditions of melting : - protolith - pressure -temperature - volatile content
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What two methods are there for partial melting? |
- Batch melting: melt stays in equilibrium with solid - Fractional melting: melt removed immediately |
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What are the conditions of partial melting? |
- protolith - pressure -temperature - volatile content |
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What kind of mineralization mechanisms in magmatic deposits are there? |
1. Fractional crystallization 2. magma mixing 3. wall-rock contamination 4. liquid immiscibility |
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Why do layered mafic intrusions form? |
Debated unknown but: 1. plume magmatism 2. rifting magmatism |
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Why are layered mafic intrusions important economically? |
Cr, PGEs, Co, V?, Ti?, plagioclase? |
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How do the reefs in LMI work? |
They are usually thin, they are generally continuous throughout the LMI, a huge tonnage with relatively predictable geometry.
May contain economic mineralization |
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Explain layered mafic intrusion geometry |
- Not as simple as one phase of crystallization after another creating layers - Can have multiple layers, non lithified. Eruption of magma can happen and create "slurries" of crystal and magma - density differences can affect these - similar to diapirism in some ways - can cause disruptions of geatures such as chromite seams/ reefs |
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Define "Ore" |
any naturally occuring material from which a mineral or aggregate of value can be extracted at a profit. |
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Define "Syngenetic" |
refers to ore deposits that form at the same time as their host rocks. |
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Define "epigenetic" |
refers to ore deposits that form after their host rock |
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Define "hypogene" |
refers to mineralization caused by ascending hydrothermal solutions |
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Define "Supergene" |
refers to mineralization caused by descending solutions. Generally refers to the enrichment processes accompanying the weathering and oxidation of sulphide and oxide ores at or near the surface. |
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Define "Metallogeny" |
the study of the genesis of mineral deposits, with emphasis on their relationships in space and time to geological features of the Earth's crust |
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Define "Metallotect" |
any geological, tectonic, lithological, or geological feature that has played a role in the concentration of one or more elements in the Earth's crust |
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Define "Metallogenic Epoch" |
a unit of geologic time facorabole for the deposition of ores or characterized by a particular assemblage of deposit types |
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Define "Metallogenic Province" |
a region characterized by a particular assemblage of deposit types |
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Define "Epithermal" |
Hydrothermal ore deopsits formed at shallow depths (less than 1500 m) and fairly low temperatures (50-200 degrees C) |
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Define "Mesothermal" |
Hydrothermal ore deposits formed at intermediate depths (1500-4500 m) and temperatures (200-400 degrees C) |
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Define "Hypothermal" |
Hydrothermal ore deposits formed at substatial depths (greater than 4500 m) and elevated temperatures (400-600 degrees C) |
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How old is Sudbury Igneous Complex? What is it? |
1.8 Ga impact sheet |
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What type of magma would you expect siderophile elements in? |
Mafic |
