Abstract

In many Canadian gold deposits the gold is one of the last minerals deposited. In some cases, considerable time has elapsed between its introduction and that of the other minerals; in others, a subordinate amount of gold was introduced with at least some of the other minerals, but the main gold enrichment was later.The tentative hypothesis is advanced that in such cases the bulk of the vein material left the magma before the gold. This early magmatic product left in the gaseous state but condensed to a liquid prior to its final deposition; the gold remained behind and was concentrated in the liquid end-product of the magma. The early gaseous phase when condensed to a liquid phase rich in super-heated water, could dissolve, transport and deposit much silica and account for much of the vein quartz. The cases in which both early and late gold are present are explainable on the basis of the partial intermingling of the two magmatic products.Distinctly late gold raises the question of the soundness of classifying many gold deposits on the basis of their associated vein minerals. The occurrence of gold-bearing ore shoots is often easily explainable, assuming gold to be late, by inferring late stresses resulting in suitable structures. Weak members, such as vein quartz, are loci for such favorable channels.

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