The Big Picture of Ore Deposits
Although there is definitely an elemnt of luck in the discovery of an orebody, locating such an orebody is usually more than just the result of circumstances which happen to be fortuitious. The formation of an orebody calls for special conditions which need to be understood by the person who is trying to find mines.
Taking a glance at the history of mining around the globe, it is the areas of Precambrian shield rock, together with the much younger orogenic (mountain) belts of western North and South America that have given most of the mines of the world.
The Canadian Shield, which occupies almost all of the central and northeastern portions of Canada, is considered one of the most prolific mning areas of the entire world – from the iron mines of Labrador to the gold and base metal mines of Val d’Or, Quebec, and Timmins in Ontario, all the way northwest to the gold mines of Yellowknife, N.W.T.
The Canadian Shield is composed of rocks formed during the Precambrian era (from 4.6 billion to 570 million years ago) and is one of the cooling Earth’s original land masses. Many of these rocks have since that time been highly metamorphosed. This region, as well as the Precambrian shields on every continent of the world, has proven to be rife with metal orebodies, mainly because the mountain-building and other tectonic activity that leads to the formation of orebodies was widespread and intense in these early days of the life of the planet.
Hundreds of millions of years of erosion have since then worn the old shield mountains down to their roots, moving the ore which the mountains have closer to the surface.
A band of relatively young and unstable rocks, which is known as the Cordillera, covers an extensive land area which stretches from Alaska to British Columbia and the Pacific states down into Mexico and Central America and the Andes mountains.the features it has are complex structures of rock which are favorable for deposits of metallic ore, it hosts soe of the largest base metal and richest gold deposits found in the past hundred years.
More than half a billion years after much of the tectonic activity in the Earth’s shields ceased, the Cordilleran region came to be as active as the shields were at one time, guiding to the formation of some of the world’s biggest ore deposits in areas like Chile, Nevada and British Columbia.