7. prospecting for ores

8/10/2019 7. Prospecting for Ores

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Prospecting for Ores

Chance has played a dominant role in the discovery ofmineral deposits. For example,

During the construction of the Canadian Pacific Railroad,the nickel deposits in Sudbury were discovered.

During drilling for water, the leadzinc deposits in

Oklahoma were discovered. Prior to the twentieth century, mineral deposits were found

by wandering prospectors who were looking for visibleevidence of mineralization. Valuable minerals wererecognized by their various distinctive physical properties.Gold is a heavy yellow metal; galena is dark grey, heavyand lustrous; magnetite is a black, heavy magneticmineral; etc.

This tedious method gave way as science progressed.


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Once an ore deposit has been located, its size and quality are

determined by sample drilling and studying the carrots obtained


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Geological Methods

As the science of geology progressed itwas discovered that certain types ofmineral deposits are associated with

certain types of rocks and structures. Athorough knowledge of geology becameimportant to locate an ore deposit

reasonably


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Geophysical Methods

As the science of physics progressed in methods of measuring the propertiesof matter, these methods were adopted by prospectors to help find deposits ofminerals that possess some detectable property not noticed by the naked eye:

The magnetometerwhich could detect very small forces of magnetism wasdeveloped to the point where it can be used effectively from an airplane. Oftenthe mineral possessing the magnetic property, magnetite, is associated withcopper, lead, and zinc minerals.

Some minerals are much heavier than others. The gravimeteris used tolocate deposits of chromite, etc.

Sulfide deposits act like giant batteries that cause the flow of electric current inthe nearby ground. These currents can be detected at the surface by sensitivemicroammeters.

Metallic ores are generally much better conductors of electricity than thebarren rock. A sensitive method of prospecting involves the injection of anelectric current into the ground by means of a generator and ground

electrodes. The flow of this manufactured electricity will be concentrated in thebest conductors. By means of a galvanometer, the path of this current can betraced, and if a metallic ore is present in the underground, it can be detected.

Radioactive minerals can be detected by eiger orscintillation counters


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Geochemical Methods

These methods involve chemical analysis fortraces of metals in soils, vegetation, and streamwater.

The weathering of metal-bearing ores at theEarths surface results in a residual soilcontaining a higher than normal amount of themetal.

Traces of this metal also find their way into thevegetation growing over the metal deposit andinto water and sediment of streams flowingaway from the deposit.


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Recent Developments

The latest radar Earth-observation satellite, Canadas -RADARSAT-1 delivers a large quantity of information to beused by exploration geologists. Linear structures, faults,and topographic features become clearly defined. It doesnot rely on solar illumination to collect images.RADARSAT-1 emits electromagnetic energy towards the

Earth and records the energy returned to the radar. Whenthe radar beam interacts with the surface, it scatters in alldirections.

An image is produced when the energy is reflected back tothe radar. This process is known as backscatter.RADARSAT-1 images also help identify hydrothermal

alternation zones associated with mineral deposits, areas ofsedimentation, flooded areas, old river systems, alluvialfans, rounded intrusions and other information useful formineral exploration.


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Now

Let us go mining the ore

deposits discovered

7. prospecting for ores

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