Porphyry Copper/Gold Deposits

Porphyry copper/gold targets are becoming increasingly important in the global quest to replace declining copper and gold production. These kinds of deposits yield about two-thirds of the world’s copper and are therefore the world’s most important type of copper deposit.

Porphyry copper deposits are copper orebodies which are associated with porphyritic intrusive rocks and the fluids that accompany them. Porphyry orebodies typically contain between 0.4 and 1 % copper with smaller amounts of other metals such as molybdenum, silver and gold.

There are two factors that make these kinds of deposits so attractive to the world’s major mining companies – firstly by focusing on profitability and mine life instead of solely on grade your other inputs of scale/cost can offset the lower grade and this results in almost identical gross margins between high and low grade deposits. Low grade can mean big profits for mining companies – Copper/gold porphyries offer both size and profitability.

The second factor affecting profitability of these often immense deposits is the presence of more than one payable metal ie for gold miners using co-product (copper) accounting the cost of gold production is usually way below the industry average.

So not only are the traditional miners of these scarce and often immense ore bodies in competition for them but increasingly yesterdays gold only miners are becoming interested as well. These kinds of deposits are one of the few deposit types containing gold that have both the scale and the potential for decent economics that a major gold mining company can feel comfortable going after to replace and add to their gold reserves.

The Vancouver Sun newspaper said high copper demand combined with limited new supplies have made copper the new gold as far as profit margins are concerned.

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Rick Mills