The concentration of tin deposits at the summits of small stocks, or cupolas, of granitic intrusives was recognized long ago by Steinman, Singewald, Ferguson and Bateman, and others.1 Butler2 showed that the chief ore deposits of Utah are concentrated in and near “apically truncated” stocks, and Billingsley and Grimes noted this relation for many of the deposits of Montana that are associated with satellitic stocks of the Boulder batholith.3 This relation is common in areas of cupolas intruded in the middle and lower depths and is conspicuously shown where erosion is deep enough to expose them. Stocks generally are elliptical in plan, and in the pre-Cambrian shields and in other deeply eroded metalliferous provinces the lodes that are concentrated in and near the intrusives generally strike nearly parallel to the long axes of the outcrops.4 This relation is so common that exploration at the ends of stocks nearly always . . .

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