Canadian Shield
The Canadian Shield forms the core of the continent and occupies
almost half of Canada's surface. The Canadian Shield is made up
of stable Precambrian rocks. The surface of the rocks is undulating
and marked by valleys. Over most of the Shield, average elevation
is approximately 300 metres above sea level. The Shield is comprised
of seven geological provinces: Bear, Churchill, Grenville, Nain,
Slave, Southern, and Superior. Each is distinguished by its unique
internal structural trends and style of folding.
The Canadian Shield is rich in metals and minerals of all kinds.
The Superior Province is one of the most important sources of metals
in Canada and is the location of copper, zinc, gold, iron and silver
deposits. The Sudbury mining district in the Southern Province,
known for its nickel and copper deposits, is one of the most important
mining areas in the world. Major gold deposits are mined in the
Slave Province, and copper, lead, zinc, uranium, nickel, cobalt
and tungsten have been discovered in the northwestern part of the
Churchill Province. The rocks of the Bear Province contain deposits
of uranium, copper, chalcocite, copper, bornite and chalcopyrite.
For its part, the Grenville Province has deposits of magnetite,
pegmatites containing mica, feldspar, apatite, uranium, titanium,
as well as zinc and lead sulphides. Few mineral discoveries have
been made in the Nain Province.
Platforms
The Canadian Shield is surrounded by the Interior, Arctic, Hudson
and St-Lawrence platforms. These platforms are comprised of a basement
of Precambrian rocks that are identical to those of the Shield,
overlain by beds of much younger, flat-lying rocks.
The Interior Platform, also referred to as the Interior Plains,
is located between the Shield and the Cordillera. It is in this
geological province that the majority of Canada’s oil and gas reserves
are located. While most of these are found in Alberta, others are
located in Manitoba, Saskatchewan and northeastern British Columbia
and all three territories. The Interior Platform is also a source
of coal, potash, salt, gypsum, limestone and other non-metallic
products.
The Arctic Platform extends under the islands of the Arctic archipelago,
between the Innuitian Orogen and the Shield. Some of its strata
may contain oil and natural gas.
The St. Lawrence Platform consists of two parts. The southwestern
part comprises the Great Lakes Lowlands, and the northeastern part
the St. Lawrence Lowlands. Oil and natural gas have also been found
and developed here, in the southwestern part of the St. Lawrence
Platform. The St. Lawrence Platform in general is a major source
of salt and building materials, but contains few metal resources.
This province is also the location of the Monteregian Hills, which
are the remains of small igneous rock intrusions that are more resistant
to erosion than the surrounding lithologies.
The fourth plateform, the Hudson Platform, lies beneath Hudson
Bay and its lowlands. Little drilling has been carried out in this
province and rock outcrops are rare. As a result, the resources
of the province are less well documented, although important deposits
of gypsum and lignite have been found here.
Orogenic Belts
The orogenic belts are areas that have undergone orogenic movement,
(mountain-building episodes), accompanied by volcanic eruptions
and metamorphism. The rocks in these belts have also undergone folding,
faulting and uplift. Canada has three orogenic belts the Appalachian,
Innuitian and Cordilleran which formed at different times.
The Appalachian orogenic belt extends south of the St. Lawrence,
east of an imaginary line between Quebec City and Lake Champlain.
This orogenic belt includes parts of Quebec and most or all of New
Brunswick, Nova Scotia, Prince Edward Island and Newfoundland. This
geological province is a source of industrial minerals that include
asbestos (Estrie region of Quebec), fluorite and iron (Newfoundland),
and copper, zinc, lead, gold and silver (Gaspé region of Quebec
and Newfoundland).
The Cordilleran orogenic belt (or Cordillera) is a province of
high mountains and plateaus extending along the west coast of Canada.
This geological province is part of the zone that borders the Americas,
extending as far northwest as the Aleutian Islands. In British Columbia,
this geologic province is divided into two regions by an extremely
long valley known as the Rocky Mountain Trench, which stretches
from the U.S. border to the Yukon. The area between the Pacific
Ocean and this valley is formed primarily of plutonic, volcanic
and metamorphic rocks. Between the valley and the Interior Platform
lie the Rocky Mountains and the Foothills, which are comprised of
folded and faulted sedimentary rocks. The western part of the Cordillera
is the location of numerous metal deposits as well as industrial
minerals and coal. The eastern part yields oil, natural gas and
industrial minerals.
The Innuitian orogenic belt extends from Ellesmere Island to Melville
Island. The basement of this province consists of highly deformed
sedimentary, metamorphic and volcanic rocks. Lead and zinc have
been found on Little Cornwallis Island, while magnetite has been
discovered on Axel Heiberg Island.
Continental Shelves
The continental shelves or platforms are areas that extend beneath the Atlantic, Pacific and Arctic oceans. Because of the difficulty of ocean drilling, relatively little is known about the composition of the rocks that make up these platforms. However, their approximate boundaries have been established, and it is these boundaries, rather than Canada’s shorelines, that are considered to represent the country’s continental boundaries. The mineral importance of the continental shelves lies in the presence of oil and gas deposits in the underlying rocks.
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