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concentrated in the cracks and fractures of the surrounding
andesites. These low-grade copper deposits contain from 0.2
to 2% copper and are extracted from large open-pit mines
(Figure 2.27b).
Divergent plate boundaries also yield valuable ore resources.
The island of Cyprus in the Mediterranean is rich in copper and
has been supplying all or part of the world's needs for the past
3000 years. The concentration of copper on Cyprus formed as
a result of precipitation adjacent to hydrothermal vents along a
divergent plate boundary. This deposit was brought to the sur-
face when the copper-rich seafl oor collided with the European
plate, warping the seafl oor and forming Cyprus.
Studies indicate that minerals of such metals as copper,
gold, iron, lead, silver, and zinc are currently forming in the
Red Sea. The Red Sea is opening as a result of plate diver-
gence and represents the earliest stage in the growth of an
ocean basin (Figures 2.16c and 2.17b).
You are part of a mining exploration team that is exploring
a promising and remote area of central Asia. You know that
former convergent and divergent plate boundaries frequently
are sites of ore deposits. What evidence would you look for
to determine whether the area you're exploring might be an
ancient convergent or divergent plate boundary? Is there any-
thing you can do before visiting the area that might help you
to determine the geology of the area?
eastern Mediterranean region to Pakistan. In addition, the
majority of the world's gold is associated with deposits lo-
cated at ancient convergent plate boundaries in such areas as
Canada, Alaska, California, Venezuela, Brazil, Russia, south-
ern India, and western Australia.
The copper deposits of western North and South America
are an excellent example of the relationship between conver-
gent plate boundaries and the distribution, concentration, and
exploitation of valuable metallic ores (
PLATE TECTONICS AND
Plate tectonic theory is as revolutionary and far-reaching in
its implications for geology as the theory of evolution was for
biology when it was proposed. Interestingly, it was the fossil
evidence that convinced Wegener, Suess, and du Toit, as well
as many other geologists, of the correctness of continental
drift. Together, the theories of plate tectonics and evolution
have changed the way we view our planet, and we should
Figure 2.27a). The
world's largest copper deposits are found along this belt. The
majority of the copper deposits in the Andes and the south-
western United States were formed less than 60 million years
ago when oceanic plates were subducted under the North and
South American plates. The rising magma and associated hy-
drothermal fl uids carried minute amounts of copper, which
were originally widely disseminated but eventually became
◗
◗
Figure 2.27
Copper Deposits and Convergent Plate Boundaries
North American
plate
Pacific
plate
Caribbean
plate
Cocos
plate
South
American
plate
Nazca
plate
Copper deposits
Subduction zone
Divergent boundary
a
Valuable copper deposits are located along the west coasts of North
and South America in association with convergent plate boundaries.
The rising magma and associated hydrothermal activity resulting from
subduction carried small amounts of copper, which became trapped and
concentrated in the surrounding rocks through time.
b
Bingham Copper Mine, near Salt Lake City, Utah, is a huge open-
pit copper mine with reserves estimated at 1.7 billion tons. More
than 400,000 tons of rock are removed for processing each day.
Note the small specks towards the middle of the photograph that
are the 12-feet high dump trucks!
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