Geologic description
Note: As of 2008, this site and several others in the vicinity are being explored as a single entity by Freegold Ventures Inc. (Freeman, 2008) Considerable new mineralization has been discovered that indicates this is part of a larger mineralized system that is described as a separate ARDF site (LG207).
This antimony prospect was uncovered during placer mining operations and was described by Henry Joesting in a report to the Alaska Territorial Department of Mines in 1942. The antimony ore occurs as stibnite in a zone of white quartz and gouge that strikes east-west across the valley of Willow Creek (Joesting, 1942; ATDM PE 49-7). In the hydraulic cut where the overburden and gravel had been removed, high-grade ore could be traced continuously from the west side of the cut to the creek, a distance of about 75 feet. Ore is also found on the east side of the cut, about 100 feet from the creek. Between these two showings of ore, the zone consists mainly of quartz and gouge, with minor amounts of stibnite and pyrite, and occasionally arsenopyrite. Some pieces of high-grade stibnite found on the surface measured about a foot across. Most of the ore is fine-grained and massive with a minor portion made up of coarse-bladed crystals of stibnite. The higher grade portions contained 56 percent antimony. Small amounts of pyrite and arsenopyrite occur in the lower grade material. The bedrock is mainly a soft, badly weathered biotite schist, with considerable clay. The schist strikes east and dips steeply north. Several thin limestone beds were noted. A few of these beds about 100 feet upstream from the stibnite prospect contain sphalerite and pyrite. Numerous small veins and lenses of glassy quartz were also noted in the bedrock. Some contain small amounts of pyrite, arsenopyrite, and sphalerite. |