ECONOMIC GEOLOGY

It has now been a very long time since man first began to notice that certain mineral materials which he needed were to be found in certain places. Perhaps it was when he noticed that certain clays for pottery were to be found only in certain river banks, or that certain kinds of desirable rocks like flint or chert were found on some beaches but not on others. The next advance was to notice that these useful things occur with some kinds of rocks and not with others rather than in some places and not others. Thus the flints were to be found in chalk beds and limestone layers on the beaches where these rocks were being eroded.

Now, thousands of years later, a whole science of economic geology has been developed and a vast technology for the useful application and modification of natural mineral materials has been invented. In this book we need only look briefly at what economic geology is and at its basic principles. At the outset one would expect that an understanding of the origin of minerals and rocks would form the basis for any beginning of understanding of why useful materials occur where they do and where else we should look for them.

Limestone, salt and gypsum are very useful industrial materials. Each of them occurs as ordinary, bedded, sedimentary rocks with other bedded, sedimentary rocks. This means that we would look for these materials only in regions of sedimentary rocks and that we would expect them to occur like other sedimentary rocks.

Oil comes from the partial breakdown of organic materials in the bodies of living things after they die and after they have been buried under sand, mud and silt. Thus oil should be looked for only in regions of sedimentary rocks which are younger than the time of the beginning of life about five hundred million years ago. Oil occurs in many rocks of sedimentary origin but accumulates in quantities big enough to be useful only where it can gather in pores and openings in the rocks without breaking away. Thus porous rocks with a capping of non-porous rocks are required. Under the great plains of Western Canada favourable places for oil are the ancient, porous coral reefs, now buried hundreds or thousands of feet below the surface. Some of these reefs may actually be seen in the sides of some of the mountains in Banff National Park where erosion has exposed them. The oil in them has long since leaked away and been lost but they do show us what the old reefs were like.

Coal is formed when great thicknesses of forest debris or other vegetable material accumulates in swampy conditions which do not allow it to decay. After such an accumulation of plant material is buried beneath hundreds of feet of muds and clays, it turns gradually to coal by the loss of some of its substance in a sort of partial distillation, which is caused by the pressure of the overlying sediments, folding if there is any, and certain slow-moving chemical changes. Thus a lump of coal is no longer just a black lump of something to burn but a fossil fuel with a very long history going back to primitive forests of another era.

If we analyze all the rocks at the surface of the earth we find that metals are not very abundant. None, in fact, except iron and aluminum, are more than one percent of the total. This means that to find a deposit of copper or zinc or lead or gold we will be looking for a place where some natural process has concentrated it. This may happen in different ways.

If a tiny amount of gold is scattered through a rock, which is being weathered and carried off by one of the processes of erosion we examined earlier, it may become concentrated because it is so heavy. Thus along the sandbars and in the gravelly bottom of the Klondike River men found concentrations of fragments of gold eroded from the nearby hills. Some beaches show slightly darker and lighter areas where the waves are concentrating grains of particular minerals from the mass because they are heavier or lighter than the average.

Surface waters may concentrate certain materials as they percolate through the upper zones of rock and soil. This may be done either by addition or by subtraction or both. Suppose a weathering rock produces mixtures of several materials including iron. The iron may be concentrated by being dissolved in the ground waters, carried off somewhere else and redeposited in a more concentrated form. On the other hand, a similar concentration may be brought about by dissolving and removing everything but the iron. Many of the great iron deposits in Quebec and Labrador were probably low grade to begin with and were concentrated by one of these systems. Others may be in places where water concentrated iron-rich sands when the rocks were first being laid down as sediments in much the same way that iron sands are now accumulating on the north shore of the Gulf of St. Lawrence.

Other materials seem to be concentrated directly by igneous processes. When a great mass of rock is melted deep underground and starts to cool, several processes may tend to concentrate different compounds in different places. All the fluorine in the melt may collect in one pocket and millions of years after the rock has solidified, it may be found as a deposit of fluorite. Perhaps the lead and zinc will be carried off in hot waters, which seem to be part of all rock melts, and deposited in cracks and fissures in the rocks which surround the still molten body. Millions of years later erosion may lay these deposits open on the surface for man to discover.

Masses of molten rock which are cooling may crystallize very slowly so that some materials start crystallizing out while the remainder is still liquid. If these first crystals are heavier than the surrounding liquid they may sink to the bottom and accumulate there. This is another method of concentrating compounds which are in very small proportion to begin with in the large molten mass and may account for certain deposits of iron, chromium and nickel.

The old methods of prospecting for valuable mineral deposits were little more than hit-or-miss schemes whereby men went out and looked for something valuable. Nowadays some prospecting is still done that way by individuals hopeful of striking it rich, but for the most part it has become highly organized. Geologists pick out likely areas on the basis of a knowledge of the rocks and rock structures. Delicate instruments, often mounted in aircraft, measure the radioactivity, the magnetism and various electrical properties of the areas picked out. Then prospectors look at every available outcrop, geochemists measure to the millionth part the content of metals in soils and in the streams of the region. Drills are brought in to get samples in vital areas where no outcrops are to be found and which are thought to be promising. Small explosions may be set off a few feet under the surface and the echoes and reflections carefully measured to find out about the structures of the rocks below. These many tools are used to find mineral deposits but alas will fail to find what is not there.

Roadcuts east of Jasper townsite commonly reveal that the terraced hillsides there are cut in masses of bouldery gravel. These materials had their origin in glaciers which plucked them from the solid rock and carried them considerable distances before melting. Then the meltwaters carried the rock debris still further, rounding off the corners and washing out the finest clay particles before depositing them thus.

In review we can say that economic geology has to do with the finding of bodies of useful mineral material and their extraction, the understanding of how minerals originate and thus why they occur where they do and, eventually, prediction of where other such bodies may occur. We find that certain minerals occur with certain kinds of rocks so we look first for those rocks and then for the minerals which we expect to be associated with them. Limestone, gypsum, salt, coal and oil occur in sedimentary rocks because they originate by sedimentary processes. Copper, gold, nickel, lead, zinc, silver, and a host of other metallic minerals occur in igneous rocks and around the margins of igneous bodies because they originate during the igneous process. Man has come a long way since he first discovered the flints and clays are found in some places and not in others.

Conclusion

Every human seems to have born in him something which quickens in the presence of booming surf on a curving shore-line, the roar of a great waterfall or the colour of the sunset on mountains. Sparkling crystals and pretty stones have attracted man's eye since time began for him. Knowledge of how these things are made and what is happening to them enhances an appreciation of their beauty and deepens curiosity about them. The sparkling diamond, the deep green emerald, the starred sapphire are beautiful in anyone's gaze but for the man who understands what they are and how nature produced them there is an additional beauty in their symmetrical internal arrangement, and in their history. For the incurious traveller who stumbles across a fossil it may be just another irregular marking on a stone. But, for the man who is aware of what it means, there is an especial excitement as he sees the remains of a creature which lived and died, millions of years ago, when the earth was probably different from what it is now, and as he realizes that what he holds in his hand is a tiny fragment of a record of a billion years of living things which have changed gradually through the long passage of time.

A great wall of rock in the side of a mountain in Banff or Yoho is impressive to anyone, but is much more so when it is realized that the enormous thickness of layered rocks accumulated, inch by inch, as soft mud and sand and shells on the bottom of the sea, millions of years ago. It is beautiful at the shoreline at Terra Nova or in Cape Breton but it adds much to sense that what we are enjoying has resulted from a long history of erosion and deposition, of rising and falling of sea levels, of upthrusting and downwarping of parts of the earth's crust. What is just another rock cut in the parkway to one man may be, to another, the wondrous end result of seething igneous masses in the depths of the earth and their expulsion through a violent volcano, or of a gradual sedimentation in the lower end of a delta, which was thousands of miles from craggy mountains being slowly destroyed by weathering and erosion.

Perhaps the most intriguing thing of all is that, even as we are reading these lines and thinking about them, the whole complex of processes is steadily at work, scenery is slowly changing, life is slowly unfolding for each individual and for the whole living world. Nature is moving on in her cycle.

For further information, the following guides to the geology of specific National Parks may be purchased at National Park information bureaus or from the Queen's Printer, Ottawa. Money orders and cheques should be made payable to the Receiver-General of Canada.

The Story of the Mountains in Banff National Park by Dr. Helen R. Belyea, Ottawa, 1960. Geological Survey of Canada. 75 cents. This is a well-illustrated booklet on how geological forces have shaped the scenery of Banff National Park. Special detail is given on points of geological interest in the Park.

Rocks and Scenery of Fundy National Park by Dr. David M. Baird, Ottawa, 1961. Geological Survey of Canada. 75 cents. In 32 pages, this booklet describes the lessons of earth history that a visitor to Fundy National Park in New Brunswick can learn.

The Living Sands by Dr. David M. Baird, Ottawa, 1962. Geological Survey of Canada. 75 cents. A fascinating treatment of the sandy shoreline of Prince Edward Island National Park.

Yoho National Park—The Mountain, The Rocks, The Scenery, by Dr. David M. Baird, Ottawa, 1962. Geological Survey of Canada. $1.30. The geological features of this beautiful National Park are described in text and excellent photographs.

Behind the Mountains and Glaciers by Dr. David M. Baird, Ottawa, 1963. Geological Survey of Canada. $1.50. A detailed presentation of the geological features of Jasper National Park, with particular reference to the views of interest that can be seen along the Jasper-Banff Highway.

Guide to Geology of the Ontario National Parks by Dr. David M. Baird, Ottawa, 1963. Geological Survey of Canada. $1.00. In this fascinating guidebook, the geological features of the three National Parks in Ontario—Point Pelee, Georgian Bay Islands and St. Lawrence Islands—are explained in layman's language.

Questions on Canadian geology can be directed to The Director, Geological Survey of Canada, Ottawa.

Additional information on the National Parks of Canada is available from The Director, National Parks Branch, Department of Northern Affairs and National Resources, Ottawa.

The animals, plants and all other natural features of the Parks are protected and preserved for all who may come this way. Please do not harm, remove or damage them.