Geology Reference
In-Depth Information
Table 5.1 Deposits in surficial settings
Type
Subtype
Commodity Process
Examples
Placer
Gold
Au
Accumulation of gold
particles in river or
beach gravels
California, Victoria,
Klondike,
Witwatersrand
Zr-Ti
minerals
Au
Accumulation of heavy
minerals in beach
sands
Western and Eastern
Australia, South
Africa, Florida
Diamond
Au
Accumulation of diamond
in near-shore gravels
South Africa,
Namibia
Sedimentary
Ironstones
(Algoman
type)
Fe
Reworking and
redeposition lateritic
oolites
Lorraine, France;
Minnesota, USA
Iron-
formation
(Superior
type)
Fe
Deposition of Mn
chemical sediments
Hammersley,
Australia; Brazil
Mn sediment Mn
Deposition of Fe-Si
chemical sediments
Groote Island,
Australia
Evaporite
Salt
(NaCl),
potash
(KCl)
Evaporation and
depositions of
chemical sediment
Various,
Saskatchewan,
Canada
Evaporite
Nitrates
Evaporation and
depositions of
chemical sediment
Atacama, Chile
Calcrete
Uranium
U
Deposition of uranium in
surfical deposits
Yeelerie, Australia
Laterite
Bauxite
Al
Lateritic soil on granite or
clay-rich sediment
Jamaica; Cuba;
Australia;
Salindres, France
Ni-laterite
Ni
Lateritic soil on ultramafic
rock
New Caledonia
Supergene
Various
Various
Upgrading of metal
concentrations in upper
parts of ore deposits
Various
3. The third type of ore body is made up of minerals that are stable in zones of
intense weathering at the surface of the Earth. Particularly in hot and humid
conditions, many rock-forming minerals break down to form secondary phases
that are soluble in surface waters. These compounds are removed by circulating
groundwater, leaving only the insoluble minerals that become increasingly
concentrated as the other minerals, which make up the bulk of the original
rock, are leached out. Bauxite (the ore of Al) and Ni lateritic deposits form in
this way. A similar type of process acts when other types of ore deposits are
exposed at the surface; the soluble components are leached out leaving a residual
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