Geologic descriptionThe headwaters of Humbolt Creek are in an area southeast of the Oonatut Granite Complex (Hudson, 1979; Hudson and Arth, 1983). This area, consists of a Lower Paleozoic metasedimentary assemblage and a polydeformed, metapelitic schist of possible Precambrian age (Till and others, 1986); it is interpreted to be over buried extensions of the Oonatut Granite (Barnes and Hudson, 1977; Hudson, 1979). Cassiterite-rich mineralized zones have not been identified in the headwater bedrock but several high angle fault zones with polymetallic veins (BN048, BN 049, BN050, BN051, BN052) are probably part of tin metallizing systems. The alluvial gravels of Humbolt Creek carry significant gold, for which they have been placer mined, and abundant cassiterite. As early as 1908, gold-bearing concentrate with abundant pyrite and cassiterite was reported (Knopf, 1908). Hydraulic mining and dozer/sluice operations along 5,000 feet of the stream channel took place primarily before WW II (Cobb, 1975). The abundance of cassiterite was a handicap to gold mining; as much as 30 tons of tin concentrate (containing 36,000 pounds of metallic tin) were produced in 1919 (Brooks and Martin, 1921). Most of the cassiterite that was recovered by placer mining was not marketed; oil drums containing cassiterite-rich concentrate (60% tin) were still stored at this location in the 1960s (Sainsbury and others, 1968). The recovered cassiterite included nuggets up to 4 inches across, some show crystal faces, some are brecciated, and some are intergrown with quartz (Sainsbury and others, 1968). Gold and cassiterite can be panned from the surface down through several feet of unmined gravel near the headwater fork of the creek. The gravels here are not mined out (Cobb, 1975, OFR 75-429). The cassiterite-bearing placer deposits are the best indication that significant tin metallization has occurred in the headwaters of the drainage. |
