Processes that form deposits of metalliferous ores
- Created by: Former Member
- Created on: 07-12-18 15:59
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- Processes that form deposits of metalliferous ores
- Hydrothermal Ore Deposits
- heat & water source from: magma in intrusion
- hydrothermal vein: example of deposit
- fracturing of a rock allows hydrothermal solution to deposit ore in open space
- the vein is younger than the rocks that contain it
- first minerals crystallise at the edges and later form towards the centre
- the vein is younger than the rocks that contain it
- fracturing of a rock allows hydrothermal solution to deposit ore in open space
- Magmatic deposits
- syngenetic: ore minerals crystallise from same liquid that produces the silicate minerals
- pegmatite: example
- very coarse-grained igneous rock = usually granitic composition
- fractional crystallisation occurs where rare metals become conc in water-rich residual magma = this magma migrates to form pegmatites
- Gravity settling in ore deposits
- Bushveld Igneous Complex is example
- dense ore minerals form conc layer at base of intrusion to form accumulates
- as magma rises and cools it differentiates
- Porphyry Ore Deposits
- often formed in island arc plate tectonic environments
- magma cools at depth forming large crystals
- if magma escapes, water boils to create fractures in overlying rock
- magma cools & crystallises to give matrix of small crystals around large crystals
- if magma escapes, water boils to create fractures in overlying rock
- Hydrothermal Ore Deposits
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