Natural Resources Canada > Earth Sciences Sector > Priorities > Geoscape Canada > Fort Fraser
Geoscape Fort Fraser Molybdenum in the Environment
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Figure 21a. Moybdenum dispersion with time.Figure 21b. Moybdenum concentrations in till and pine bark.
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Figure 21a. Moybdenum dispersion with time
Ancient origin of metal deposit
Molybdenum deposit forms 145 million years ago, 2 km below the Earth's surface.
Uplifting, faulting and erosion bring the deposit to the Earth's surface
The Ice Age: scattering the metal
Erosion by glaciers spreads molybdenum-rich fragments across the landscape.
Glaciers melt, forests and grasses become established
The last 12 000 years:metals on the move
Dispersion of molybdenum by ground water. Plants take up molybdenum, which is transferred to some animals
as they graze.
People arrive
Mining the riches
The molybdenum deposit is mined
Ranching / farming with metals in the environment
Cattle eat molybdenum-enriched forace, causing molybdenosis.
Figure 21b. Moybdenum concentrations in till and pine bark
MOLYBDENOSIS
Cattle that ingest too much molybdenum are unable to absorb sufficient copper from their food. Copper deficiency can cause growth and reproductive problems. This disorder is termed molybdenosis and can be treated by injecting the cow with a copper supplement.
Molybdenosis in cattle is linked to 1) soils with high molybdenum concentrations; 2) grazing on legumes (clover, pea-vine) rather than grass (grasses absorb less molybdenum than legumes); 3) alkaline soils, which increase the mobility of molybdenum (in limestone areas); and 4) high levels of sulphur in the soils or water.
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