Lesson 1 - Intro to Ore Deposits Flashcards
What is the relationship between production volume and price in the mining industry?
There is an inverse relationship—materials used in bulk (like iron and coal) have lower prices due to abundance, while rare materials (like diamonds and gold) are highly priced due to scarcity.
What is an ore body?
An accumulation of solid and fairly continuous mass of ore, distinguishable from enclosing rocks.
What are isometric ore bodies?
Ore accumulations that are approximately equal in all dimensions.
What are flat ore bodies, and what are their types?
Ore bodies with two long dimensions and one short dimension. Types:
- Sheets: Tabular bodies separated by bedding planes.
- Veins: Formed when minerals fill fractures or replace rock along cracks.
- Lenses: Lenticular bodies tapering in all directions.
What are ore pipes or pipes?
Elongated, oval-shaped ore bodies formed when ore concentrates from magmatic melts or hydrothermal solutions.
What are the four basic geological requirements for mineral deposit formation?
- Source – Metals and ligands must originate from a source.
- Transport & Concentration – Mechanism to move and concentrate ore components.
- Deposition – Fixes ore components in place.
- Preservation – Geological setting must allow deposit to remain intact.
What is the role of ligands in ore transport?
Ligands form stable metal-ligand complexes that dissolve and transport metals like gold, copper, and lead in hydrothermal fluids.
What physical controls affect ore deposition?
- Temperature decrease – Causes metal precipitation.
- Pressure drop – Reduces metal solubility, triggering deposition.
- Fluid flow & mixing – Causes chemical changes leading to precipitation.
- Structural traps – Faults, fractures, folds, and porous rocks accumulate fluids.
What chemical controls affect ore deposition?
- pH changes – Alters metal solubility.
- Redox reactions – Affects metal mobility (e.g., Fe²⁺ → Fe³⁺).
- Ligand concentration decrease – Leads to metal precipitation.
- Reaction with host rocks – Can form new minerals.
- Fluid saturation – Causes crystallization of excess minerals.
What is mineral zoning, and why is it important in exploration?
Mineral zoning is the spatial distribution of different minerals due to temperature, pressure, and chemistry changes. It helps geologists locate high-grade ore zones.
What are the sources of metallic elements in ore formation?
- Partial melting & fluid-related leaching from the mantle or crust.
- Ligands from geological, atmospheric, and biological sources.
What are the main mechanisms for metal transport?
- Mechanical transport – Gravity settling, magmatic differentiation.
- Fluid transport – Hydrothermal fluids containing water, gases, salts, and metal complexes.
What are common sources of ore-forming fluids?
- Magmatic fluids from cooling silicate melts.
- Circulated waters (seawater, connate water, meteoric water).
- Metamorphic and diagenetic fluids from rock formation and burial.
What geological factors influence ore localization?
- Lithological units.
- Sedimentary structures.
- Crystallization in mafic and ultramafic rocks.
- Fractures acting as fluid pathways.
How is ore deposit classification determined?
- Composition – Metalliferous, industrial, or energy resources.
- Form – Veins, replacements, disseminations.
- Host Rocks/Geological Setting – Surrounding rock characteristics.
- Interpreted Genesis – Geological processes forming the deposit.
What are the main sources of ore fluids in mineral deposit formation?
- Magmatic sources – Derived from magmas and lavas due to partial melting of the mantle or crust.
- Meteoric, marine, and connate waters – Surface or groundwater percolating through rocks.
- Diagenesis, metamorphism, and deformation – Release of fluids during rock changes.
How do magmatic deposits form?
Direct crystallization from magma. Can form layered intrusions, pegmatites, or kimberlites. Common minerals: Chromite, magnetite, sulfides (Ni-Cu-PGE), diamonds.
What are hydrothermal deposits, and how do they form?
Form from hot, mineral-rich fluids that circulate through fractures and porous rocks. Deposits precipitate as temperature and pressure change. Common types: Vein, porphyry, epithermal, and skarn deposits. Common minerals: Gold, silver, copper, lead, zinc.
What are exhalative deposits, and where do they form?
Form in submarine volcanic or sedimentary environments. Minerals precipitate directly from hydrothermal vents into seawater. Example: Volcanogenic Massive Sulfide (VMS) deposits. Common minerals: Copper, lead, zinc, barite.
What are residual and supergene deposits, and how do they form?
Residual deposits – Concentration of minerals left after intense weathering and leaching. Example: Bauxite (aluminum ore). Supergene deposits – Enrichment of metals due to chemical weathering and groundwater movement. Example: Supergene copper deposits.
What are placer deposits, and how do they form?
Form by mechanical concentration of heavy minerals in riverbeds, beaches, or deserts. Caused by weathering, erosion, and sediment transport. Common minerals: Gold, platinum, tin, diamonds.
How do marine and sedimentary deposits form?
Form by chemical and biological precipitation in ocean basins, lakes, and sedimentary basins. Common types: Evaporite deposits – Salt and gypsum from evaporating water. Phosphorite deposits – Accumulation of phosphorus minerals. Banded Iron Formations (BIFs) – Iron-rich layers from oxygenation of seawater.
What is the difference between syngenetic and epigenetic deposits?
Syngenetic deposits – Form at the same time as the host rock (e.g., BIFs, VMS deposits). Epigenetic deposits – Form after the host rock has been deposited (e.g., hydrothermal veins).
How do diagenesis, metamorphism, and deformation affect ore deposits?
**Diagenesis – Alters minerals during sedimentary rock formation (e.g., formation of phosphorite). Metamorphism – Can remobilize and concentrate minerals, forming deposits like skarn or orogenic gold. Deformation – Creates fractures and faults, allowing for fluid flow and mineral deposition.
What role do ore fluids play in mineral deposit formation?
Ore fluids transport, dissolve, and precipitate minerals under different temperature, pressure, and chemical conditions. Sources of ore fluids: Magmatic (intrusive bodies), Metamorphic (dehydration reactions), Meteoric and marine waters (percolating surface fluids). They are crucial in hydrothermal, exhalative, and sedimentary mineralization.
What are the specific targets of chemical and physical controls of ore deposition?
- Geological conditions where one possible physical-chemical process of deposition could be effective.
- Several concomitant processes may cause deposition simultaneously.
Why is zoning data important in ore exploration?
Depositional processes often cause two- or three-dimensional mineral zoning, which is crucial for exploration.
What are the essential requirements for chemical and physical controls of ore deposition?
Energy, partial melting, fluid-related leaching of the mantle/crust, mechanical or mass transfer mechanisms, and biological processes.
What are the main sources of hydrothermal fluids?
Water with varying amounts of CO₂, H₂S, SO₂, CH₄, N₂, NaCl, and dissolved metal complexes.
What are McQueen’s (2009) sources of ore-forming fluids?
- Water-rich silicate melts
- Circulated sea, connate, and meteoric waters
- Formational, diagenetic, and metamorphic fluids.
How do physicochemical parameter changes result in ore mineral deposition?
Changes in temperature, pressure, pH, redox state, and ligand concentration lead to ore deposition.
What are the main geological factors in ore localization?
The interaction of geological controls determines ore localization and provides a basis for exploration.
How is mineral localization related to lithology?
Ore commonly occurs in specific lithounits, sedimentary structures, mafic/ultramafic rocks, and fractured zones.
What are the main bases for ore deposit classification?
- Composition of deposit
- Form of deposit
- Host rocks/geological setting
- Genesis of deposit.
What are the four main types of mineral deposits based on composition?
- Metalliferous deposits
- Industrial/nonmetallic deposits
- Coal
- Petroleum and natural gas.
What are syngenetic deposits?
Deposits formed contemporaneously with their host rock, either igneous (magmatic intrusion) or sedimentary (e.g., Sedex, VMS).
What are epigenetic deposits?
Deposits formed after their host rock, via migration of metal-bearing fluids (e.g., porphyry, skarn, vein-type deposits).
What are the key features of geochemical signatures in ore formation?
Composition, size, geometry, dispersion pattern, and wall rock alteration.
What are metallogenic provinces?
Large regions (1000+ km) with deposits of one or more minerals, influenced by mantle differences, element concentration, and ore-forming processes.
What are the key metallogenic epochs?
- Archean – Chromite, PGM, Cu-Fe-Ni, Au, some VMS
- Proterozoic – Placer Au, U, PGM, BIF, base metals
- Phanerozoic – Phosphorites, chromite, coal, PCDs.
