The amount and character of the tin resources in the Seward Peninsula tin granite belt in western Alaska are directly related to the depth of erosion of the plutonic system. Plutons that have little or no outcrop (little erosion), such as Kougarok or Lost River, are the site of lode tin deposits, whereas placer tin deposits are associated with somewhat eroded plutons (Cape Mountain, Ear Mountain) with a modest outcrop area. The largest pluton in the tin belt, the Oonatut Complex, is a deeply eroded pluton with little tin in either lode or placer deposits.

Textural units in the granite...