A Trace Element Study of the Circle Mining District, Alaska.
For Reference Only At Bureau Libraries :75 pages
Significant quantities of placer cassiterite and scheelite were found on Upper Boulder Creek in 1975. Although no lode source for these minerals could be found, unweathered pieces of cassiterite were seen with fragments of vein quartz and schist attached. The occurrence on Boulder Creek is located in the Birch Creek schist near the contact of the Circle Hot Spring intrusive. Examination of the sluice box concentrates indicated 63 percent cassiterite and 0.2 percent scheelite. Further Bureau of Mines work consisted of pan concentrate and limited stream sediment sampling of various creeks in the district and examination of numerous outcrops. Concentrate analyses plots were made of 10 elements occurring in heavy mineral samples and a zone of tin and tungsten mineralization was defined.
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