Download Lesson 1 - Economic Mineral deposits


Economic Minerals – minerals
that can be extracted,
processed, and marketed at a
profit.
Factors: -interest in the mineral,
-size of the deposit,
-mineral concentration,
-mineral depth below
the surface
-market value.

An ore is a natural material with
a high concentration of
economically valuable minerals
that can be mined for a profit

1) Magmatic Deposits
 accumulations of metals associated with
magma that forms igneous rocks
 Certain metals are enriched in certain
magmas and further concentrated during
cooling of the magma


Magmatic Deposits: A) Layered
Gravitational Settling
 heavy minerals that crystallize early, settle
and concentrate on the bottom of the
magma chamber this results in a layered
deposit.
High-density minerals sink to
the bottom of the magma
chamber.

Magmatic Deposits: B) Disseminated
 Deposits in which the metal is evenly
distributed in generally low concentrations
throughout large masses of igneous rock.
Ex: porphyry copper deposit
 (e.g. Sudbury, Ontario and Voisey’s Bay,
Newfoundland and Labrador)
A sample of nickel-bearing rock from
Sudbury.
 Diamonds
 Most diamonds are found in unique ultramafic
igneous rocks called kimberlites
 Magma generated by partial melting of
asthenosphere below 150 kilometres and then
rises quickly to the surface, picking up
diamonds from solid lithospheric mantle

2) Hydrothermal Deposits
 any concentration of metallic minerals
formed by the precipitation of solids
from hot mineral-rich water
(hydrothermal solution).
 hot water dissolves and transport
minerals, interconnected openings in the
rock allows the solutions to move, and
chemical reaction result in deposition.
Deposition can be caused by boiling, by
a drop in temperature, by mixing with a
cooler solution, or by chemical reactions
between the solution and a reactive rock.
 produce vein deposits.

Hydrothermal Deposits
 Can occur as disseminated deposits, which
are distributed throughout the rock body,
rather than concentrated in veins; called
porphyry deposits = (low grade; large volume)




3) Sedimentation
Secondary enrichment
A class of residual deposits formed by both
the removal of valueless material in solution
and the solution and redeposition of valuable
ore minerals.
Because solution and redeposition occurs
the process is known as a secondary
enrichment.

Weathering
 Secondary enrichment
 Bauxite
 Principal ore of aluminum
 Forms in rainy tropical climates from chemical
weathering and the removal of undesirable
elements by leaching
 Stratiform Deposits
 Copper-bearing brines moving through coarsegrained sedimentary rock are forced upward
through oxygen-poor, sulphide-rich mud,
which promotes precipitation of minerals

Sedimentary Deposits
 Banded Iron Formations
 Conditions during the early Precambrian
resulted in large quantities of ferrous iron in
solution
 At some point, photosynthesizing bacteria
generated sufficient oxygen to precipitate iron
oxide minerals. Ex: Bell Island Deposit

4) Placer deposits
 – formed when heavy metals are
mechanically concentrated by currents
 Examples:
 Gold, Platinum, Diamonds

5) Metamorphic Deposits
 Many of the most important
metamorphic ore deposits are
produced by contact metamorphism.
 Sphalerite (zinc)
 Galena (lead)
 Chalcopyrite (copper)