Geology. Козлова Е.П. - 36 стр.

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                     How can gold ore concentrations be predicted?

       A reliable prediction of the gold content in gold-bearing ores could only be
made after a considerable body of knowledge about the reserves and projected
resources of gold in the depleted and prospected deposits had been built up. As soon
as we have figures we see a striking difference between the quantity of the noble
metal deposited in the rocks of specific geologo-genetic types. The largest deposits
(taking info account the extent of their erosion) serve as benchmarks helping estimate
the maximum gold concentration levels in the so-called ore-forming systems
associated with the formation of a particular deposit or a group of deposits. Thus, the
concept of “ore-forming system” is still construed differently in different situations.
In the case of hydrothermal gold ore deposits it normally implies a combination of
regions where ore-bearing solutions form and migrate, to eventually settle as ores.
The conditions in which such systems arise and their evolution have been studied but
very little so far. The overwhelming majority of hydrothermal deposits (at least, 1500
around the world) contain up to 100 tons of gold each. Actually, they contain at least
70 percent of the total known reserves of gold and some 80 percent of the projected
resources.
       To make projections, the manifestation of ore-forming systems of different
genetic types is related to the differentiated gold-bearing capacity of different
metallogenic provinces, zones and belts. Actually, some areas up to 1 000 km long
may have just a few deposits with total reserves of a few hundred tons, while others,
for example, the Abititi on the Canadian Shield (less then 300 km long) encompass
dozens of fields with a total content in excess of 10 000 tons of the noble metal. The
Canadian belt includes three clusters of very high concentration 12 000 to 3 000 tons.
Similar clusters of gold within ore regions have been established in some other
metallogenic provinces and belts as well.
       The ideas we have about the differentiated productivity of ore-forming systems
and its maximum levels, and also about the linear cluster disposition of highly
productive systems provide a basis for projections of new gold-bearing regions and
for a reassessment of the prospect in those already discovered in Russia.

                              Sources of vein gold in Russia
       Nearly all-Russian specialists share the view that the short-term prospects for
the gold-mining industry in this country are linked to primary deposits. To remind,
we have over 150 of them, only a few of them past the prospecting stage. The
majority of these deposits date from the Phanerozoic (the last 600 million years) and
are mostly gold-quartz and gold-carbonate veins. There are very slim hopes of any

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