Mineral Resources Flashcards
What are earth resources?
All materials used by modern society are either derived directly or are manufactured from Earth:
- Water
- Wood
- Food
- Metals
- Glass
- Cement
- Etc.
The availability and cost of mineral and rock products influence:
a country’s standard of living, economy, and position in the world.
Most people do not know where minerals occur naturally or how they are mined and processed
To survive, we need food, water, and shelter. Today, we also “need”:
phones, airplanes, cars, and computers
- Use more resources per individual
- Use a greater variety of resources from more sources
- Synthesized new materials from raw resources
Basic need: food
- Technology has allow food production to keep pace with growing population (irrigation, tractors, fossil fuels, fertilizers)
- The more the population grows, the more land is diverted away from agriculture
Resources are either renewable or non-renewable
Renewable resources:
- Replenished over short time scales (months or years)
- Trees, light, water, animals, etc.
Non-renewable resources:
- Exist on Earth in a fixed quantity
- Replenished over thousands to millions of years
- Minerals, soils, etc.
Mineral Resources
Natural concentrations that result from physical and chemical processes active in Earth’s crust
There are two main types of mineral resources:
- Metallic
2. Non-metallic
Which physical property of minerals does the term metallic describe?
Lustre
Non-Metallic Mineral Uses
- Sulfur: matches, tires, bug spray
- Halite: salt, rock salt
- Diamond: rings, blades
- Gypsum: cement, construction
Agricultural Minerals (fertilizer)
Nitrogen (N): - For leaf growth - Manufactured from the air Phosphorus (P): - Development of roots, flowers, seeds, fruit - From phosphate-bearing minerals/bones Potassium (K): - Strong stem growth, movement of water in plants, promotion of flowering and fruiting - From potash
Construction Minerals
- Aggregates: crushed stone, sand (for cement), gravel
- Clay: cement manufacture, industrial lubricant, beauty products
- Gypsum: drywall, cement manufacture
Metal Mineral Uses
- Tin: battery, brake pads, radiator, fuel tank, glass coatings, electronics, bearings
- Gold: electronic connectors, switch contacts, fuel cells, heat protection linings
- Tungsten: bearing linings, gear teeth coatings, integrated circuits, metallic films
- Tantalum: parking sensors, HID headlamps, airbag systems, traction control, dashboard, electric mirrors, window mechanisms, in car entertainment
Metallic Minerals
Abundant if: excess of 0.1% by weight in average continental crust
- Al, Fe, Mg, Mn, Ti
Scarce metals: less than 0.1% by weight in average continental crust
- often concentrated in sulfide deposits
- Copper, lead, zinc, nickel, gold, platinum
Reserve
The portion of an identified resource that can be recovered economically.
An ore is a reserve of metallic minerals
7 Major Classes of Minerals
- Silicates (most abundant in crust)
- Native elements (scarce metals)
- Oxides
- Sulfides (scarce metals)
- Sulfates
- Halides
- Carbonates
How do mineral deposits form?
All Earth resources have been generated by one or more geologic processes
- The distribution of resources globally is caused mainly by plate tectonics because it controls: the position of the continents and the geologic process responsible for forming, modifying, and destroying earth resources
The processes that can form and concentrate mineral resources include:
- Subsurface processes (igenous + metamorphic processes)
- Surface processes (weathering, physical and chemical sedimentation)
- Shallow subsurface and diagenetic (conversion of sediment to sedimentary rock) processes
- Meteor impact and mantle melt
Some mineral deposits are widely distributed because
They form from a range of igneous, sedimentary, and metamorphic processes
Other mineral deposits are very localized because
There is only one process that allows them to form
Which igneous processes create mineral resources?
- Continental bedrock: generally felsic/intermediate rocks (e.g granite)
- Seafloor: mafic rocks (basalt/gabbro)
Igenous rocks can be used in their raw form as:
building materials (dimension stone) or as crushed stone. These are non-metallic resources.
Basalts/gabbros form due to
partial melting in the subsurface (addition of volatiles/decompression)
Granites form from:
partial melting in subsurface (addition of volatiles/decompression) and differentiation processes (partial melting, magma migration, crystal settling, magma mixing)
Igneous rock formation details
- Felsic magmas contain several % water; mafic magmas contain less
- Quartz, K feldspar, plagioclase do not contain water
- Micas and amphibole contain small amount of water
- The rest of the water escapes along fractures and faults during and after emplacement
- The hot water contains dissolved elements that do not get incorporated into felsic minerals (Cu, Pb, Zn, Ag, S)
- Hydrothermal fluids move outwards from the magma and cool
- Pressure drops, mineral precipitate in cracked = veins
- Erosion may expose veins at the surface
Disseminated deposits
Widely distributed small particles or veinlets associated with emplacement of magma above a subduction zone, so occur in a zone parallel to a subduction zone
- Subduction in the past produced the porphyry copper deposits in the US
Disseminated deposit formation
- The main body of magma rejects water and incompatible elements
- Mineral-rich fluids migrate outward and crystallize in dikes, veins, and sills
- Fluids enhance rate of crystallization; very large (>3cm) form
- Rock has the same composition as granite, but with very large x-tals (pegmatite)
- Can also contain minerals made of fluorine, berylluim, lithium, rare earth elements, and gemstones i.e tourmaline, emerald, and aquamarine
Bowen’s reaction series:
Order of crystallization of mineral from a cooling melt
Discontinuous reaction (high T to low T): olivine, pyroxene, amphibole, biotite -> K feldspar, muscovite, quartz
Continuous reaction (high T to low T): Ca-rich plagioclase feldspar to Na-rich -> K feldspar, muscovite, quartz
Fractional crystallization
Produces progressively more felsic magmas as a result of crystal settling
- The first minerals to form are the densest and settle to the bottom of the magma chamber (mafic + others)
- Produces layered intrusions with some layers rich in useful minerals: chromium, nickel, and platinum
Which metamorphic processes create mineral resources?
Metamorphism occurs when a rock is subjected to increasing heat and pressure, resulting in recrystallization of minerals (NO MELTING)
- Regional
- Contact
Regional Metamorphism
Mountain building produces directed stress
- Turned shales to slate, schist, and gneiss with increasing metamorphic grade
- Foliated metamorphic split into slabs (good building material)
- Can also turn limestone in marble and sandstone into quartzite
Contact Metamorphism
Metamorphism around a hot intrusion
- Marble, quartzite used as building materials
- Also produces skarns: Ca-bearing silicate rocks that commonly contain valuble ores, form at the contact zone between a felsic igneous intrusion and carbonate rocks due to reactions with heated fluids given off by cooling intrusion or fluids within the country rock
- Metasomatism: fluids mix in contact zone, dissolve carbonate minerals and convert carbonate rocks into skarn deposits
Asbestos
- Fibrous and flexible so it can be spun
- Incombustible and resistant to biodegradation and has low electrical conductivity (thermal insulation, fire protection)
- Also causes lung cancer
Fluids squeezed out of rock during metamorphism may cause minerals to grow very large
- Garnet is a gemstone used as an abrasive
- Kyanite is a gemstone used in ceramics
- Regional metamorphism of ultramafic and mafic rocks in the presence of water can create asbestos (hydration of olivine)
- Talc: formed from metamorphism of Mg-rich minerals (olivine, pyroxene, amphibole, serpentine) in the presence of CO2 and water
Which sedimentary processes create mineral resources?
Sedimentation can produce valuable deposits: sand and gravel concentrated by rivers are sources of aggregate for concrete
Placer deposits
Moving water flushes less dense clay and sand away, concentrating dense minerals such as gold, platinum, and diamonds, at the bottom of river channels
Chemical sedimentation can produce mineral deposits through:
- Direct precipitation due to evaporation
- Volcanogenic deposits
- Chemical precipitates in marine waters
- Direct precipitation due to evaporation
- Evaporites
- Marine (halite, gypsum, etc.)
- Non-marine (calcium/sodium, carbonates, gypsum, etc.)
- Volcanogenic deposits
- Vents fluids to the surface
- Ocean-floor black smokers
- Massive sulfides
- Chemical precipitates in marine waters
- Banded-iron formation ores
- Formed before atmosphere has free oxygen
- Iron ejected into ocean from underwater hot springs reacted with oxygen produced by cyanobacteria and precipitated as a layer of iron oxides. Bands represent cyclic variation in available oxygen and formed until the ocean became fully oxygenated
Chemical weathering promotes mineral enrichment because it leaves behind a residue of less soluble minerals
- Oxisols/laterites are heavily weathered soils that form in hot/humid conditions
- “ironstones” rich in oxides of iron and aluminum and source of bauxite ore (mined for Al)
Secondary enrichment
- Disseminated minerals are often difficult to mine because the ore is so spread out
- Groundwater percolating downward to water table dissolves, transports and redeposits minerals at the water table, creating a secondary deposit of ore minerals
How do meteor impacts create mineral resources?
- The Sudbury Igneous Complex: 2nd largest impact crater in the world
- Formed 1.85bya by collision with meteor 10-15km in diameter, triggering melting
- One of the world’s principal sources of nickel and copper ores, with gold and platinum
- Deposits occur in veins and dikes and as contact-type deposits
Origins of Mineral Deposits: Mid-Ocean Ridge
Metals: copper and zinc as metallic oxides and sulfides
Deposit type: volcanogenic massive sulfide
Origins of Mineral Deposits: Volcanic Arc Basin
Metals: Copper, lead, zinc
Deposit Type: Stratabound
Origins of Mineral Deposits: Volcanic Island Arc
Metals: copper, molybdenum, gold, silver, lead, mercury, tin
Deposit Type: porphyry copper; hydrothermal veins
Origins of Mineral Deposits: Granitic Intrusions (Batholiths)
Metals: Copper, tungsten, tin, iron, gold, silver, molybdenum
Deposit Type: contact-metamorphic; hydrothermal veins
How are mineral resources mined?
- Dredging
- Hydraulic Mining
- Open-pit mining
- Dredging
Scooping up earth material under a body of water, for sand and gravel as well as placer deposits
- Increased erosion to channels and river banks
- Washes away soil
- Degrades water quality
- Damages aquatic and terrestrial ecosystems
- Hydraulic Mining
High-pressure water blasted through a nozzle at hillsides containing alluvial deposits, slurry is run over sluice boxes to remove gold
Processes large volumes of sediment quickly, but leads to major environmental damage:
- Flushes sediments to streams
- Promotes flood downstream
- Clogs irrigation, ruins cropland
- Addition of mercury aids gold recovery, but if not all mercury is recovered it accumulates in ecosystem
- Mostly blocked by 1900 by courts
- Open-pit mining
Practical way to extract low-grade, near-surface ore bodies, process enormous amounts of mineral
- Major disruption to landscape
- Increased erosion
- Leaching of toxic metals
- Acid mine drainage
