Lecture 29 Flashcards
Resource cycle
- Resources and raw materials
- Mining, cultivating, and harvesting
- Processing of raw materials
- Transport of materials
- Manufacturing of products
- Transportation of products
- Purchase and use by the consumer
- Final Disposal
Geochemically abundant elements comprise more than ___ of the crust
0.1%
Geochemically scarce elements comprise less than ___ of the crust
0.1%
Abundant metals
iron, aluminum, magnesium, manganese, titanium, silicon
Scarce and rare metals
copper, lead, zinc, nickel, chromium, gold, silver, tin, tungsten, mercury, molybdenum, uranium, platinum, etc
Non-metal resources are used for
chemicals, fertilizers, building, jewelry, and glass/ceramics
Types of minerals
metallics and non-metallics
Examples of metallic minerals
metals such as iron, aluminum, copper, gold, platinum, silver, etc
Metallic minerals
those mined for constituent metals
Nonmetallic minerals
those that we mine for their chemical or physical properties
Examples of non-metallic minerals
sodium, sodium chloride, calcium sulfate (gypsum), calcium carbonate (calcite, aragonite), diamonds and emeralds
Resource
a naturally occurring accumulation of material in concentrations and amounts that make extraction currently or potentially feasible
Reserve
resources that can be exploited economically under present conditions
mineral deposits
are localized concentrations of a resource
ore deposits
mineral deposits that can be exploited economically
Mineral deposits are derived from the following parts of the rock cycle:
- magmatic concentrations of elements
- hydrothermal concentration of elements
- weathering and concentration of the residual material in place
- by chemical sedimentary soncentration
As the magma chamber cools, minerals begin to crystalize as a function of temperature, a process called _________.
fractional crystalization
Crystals undergo gravitational ______ to the bottom of a magma chamber because they are ___ than surrounding magma
crystal settling
denser
Crystal flotation
Where crystalized minerals are less dense than the magma and begin to accumulate
Filter pressing
where much of the remaining magma moves through a fracture, leaving precipitated crystals behind
Cumulates form through:
- magma cools in fractional crystalization
- crystals precipitate
- crystals settle in a process called crystal settling
or
- crystal flotation where crystals float because they are less dense
- remaining magma moves through a fracture, leaving precipitated crystals behind
How pegmatites form
excluded elements and water are concentrated in the last portion of the magma to crystalize, which makes a coarse grained pegmatite
Pegmatite can be found in some _____
intrusions
Pegmatites often contain:
unusual minerals and high concentrations of rare elements (Be, Li, Nb, Cs)
Kimberlites
fragmented volcanic rocks from particularly explosive eruptions, where magma comes from the mantle beneath old/ stable continental lithosphere
Kimberlites contain:
Variety of high-pressure minerals such as diamond
Hydrothermal deposits:
A process where circulating groundwater is heated in volcanic areas and alters dissolved minerals. As the water moves away from the magma, it can cool, boil, or interact with oxygen and can reduce the solubility of dissolved metals causing them to precipitate. The heated water can also emerge from veins or fractures.
Types of hydrothermal deposits
veins, stratiform deposits, or disseminate ores
Vein hydrothermal deposit
fractures that have filled with mineral deposits
Stratiform hydrothermal deposits
formed when hydrothermal water escapes to the seafloor and deposits a layer of mineral particles, resulting in volcanogenic massive sulfides deposits near current and former tectonic boundaries
Disseminated ore hydrothermal deposits
Forms when hydrothermal water soaks through porosity in rocks and deposits mineral particles in pore spaces
Residual deposits
Chemical weathering dissolves some components of rock, leaving behind more resistant material.
Laterites
example of residual deposit (formed in tropical areas) and are rich in metals like nickel, aluminium, and iron
Placer deposits
flowing water concentrating dense material in sands
Black sands
rich in iron oxides are an example of placer deposits
minerals that concentrate in placers include:
gold, platinum, zircons, rutile (titanium), diamonds, and cassiterite (tine)
Aggregate
loose (exist as unconsolidated material) or can be crushed and sorted on site from a nearby rock
Cement
formation of limestone, heated clay, and other sulfates/silicates
Concrete
combining cement with sand and gravel
Evaporite deposits
Chemical sedimentary rocks are formed by the evaporation of sea water and the subsequent precipitation of minerals from the solution.
Important evaporites:
gypsum, halite (used on roads and human consumption), and potash (fertilizer/potassium)
Banded iron formations
Sedimentary rocks (2 Ga and older) contain iron-rich formations (common iron ore deposits). This is sought to have occurred from the precipitation of Fe by oxygen production by cyanobacteria.
Physical impacts of mining
volume of removed material may be difficult to replace, removal of plants can cause erosion, and erosion may contaminate streams
Mine tailings
byproducts that remain after resources are extracted from the deposit
Mine tailings and pyrite
Tailings piled on-site may be reactive when exposed to oxygen and water, when pyrite (FeS2) produce sulfuric acid (H2SO4) causing pH of surface and groundwater to be more acidic
Impacts of Acid mine drainage
Mine drainage often contains elevated concentrations of potentially toxic heavy metals and presents a major threat to surrounding groundwater and surface water resources, aquifers, aquatic systems, and human health
Smelting
a process used to extract target metal from the source ore which leads to a lot of greenhouse gases and acid rain.
