Topic 3 Flashcards
(17 cards)
Minerals containing elements of economic value are generally present in all igneous rocks, but the elements may not be concentrated enough to make mining ______________
economical
minerals scattered throughout a host rock, but in sufficient amounts to mine profitably.
Disseminated deposits
If ore is distributed in many small
veins
Lode Deposit
As the magma cools, early forming dense mineral crystals begin to precipitate from the melt and sink due to their higher density
Crystal Settling
Eventually, significant deposits of sulfide minerals may accumulate on the bottom of a magma chamber. Layers are called
Cumulate
As a melt cools and crystallizes, hot, water-rich fluids may be released. These _________________ are rich in sulfur, sodium, potassium, copper, tin, tungsten, and other elements with relatively high solubilities
hydrothermal fluids
5 Categories of Hydrothermal Deposits
- Porphyry Deposits
- Skarn Deposits
- Volcanogenic Massive Sulfide Deposits
- Sedimentary Exhalative Deposits
- Epigenetic Deposits
are a special kind of hydrothermal deposit. They form when hydrothermal fluids, derived from magmas at depth, carry metals toward the surface and
deposit minerals to create disseminated ore deposits
Porphyry Deposit
Organic debris is buried in
sedimentary basins and
accumulates in oxygen-free
environments.
Heat and pressure increase with
burial, converting organic matter
into _____________
Kerogen
With further heating, kerogen
breaks down into
hydrocarbons (oil and gas).
Burial by sediments creates pressure
and heat, transforming plant material
into
Peat
With increasing pressure and heat,
peat becomes
lignite (brown coal)
Further burial leads to the formation of
bituminous coal (soft coal).
Under extreme conditions, bituminous
coal transforms into
anthracite (hard coal)
This process plant to coal, known as _______________, occurs over millions of years
coalification
