In the Tatsamenie Lake area, intensely folded and regionally metamorphosed Permian, Triassic and older strata are separated from less folded and less metamorphosed Mesozoic sedimentary and volcanic rocks by a pre-Upper Triassic unconformity. Foliated hornblende diorite of Juro-Triassic age intrudes the pre-Upper Triassic rocks. These are commonly altered to chlorite, hematite and epidote. The Mesozoic strata are overlain unconformably by flat-lying Upper Tertiary and Pleistocene plateau basalts of the Level Mountain Group.

The Permian strata consists of a 760 metre succession of limestone and dolomitic limestone, with local chert, shale and sandstone. The pre-Upper Triassic rocks consist of fine-grained crystal tuff to lapilli tuff with intercalated phyllite and greenstone, and minor chert, jasper greywacke and limestone. These are considered to be part of the Stikine Terrane Assemblage.

A major north to northwest trending fault, known as the Ophir Break Zone, extends through the area for over 10 kilometres, and is defined by areas of intense with abundant slickensiding; areas of carbonaceous and siliceous black siltstone and gouge; and linear quartz-iron carbonate-pyrite-fuchsite(?) (listwanites) and quartz-dolomite alteration zones. The listwanites occur in the tuffs.

Mineralization consists of pyrite, trace arsenopyrite and scorodite, native gold, pyrrhotite, chalcopyrite in amygdules in lapilli and altered fuchsite-bearing(?) tuff, stibnite, tetrahedrite and hessite. Pyrite occurs as late-stage veinlets and as earlier breccia matrix filling, fragments within breccias, wispy rims on silicified limestone fragments in breccia, and local laminations in fine bleached tuff.

Three major deposits, the Bear Main (see 104K 079), the Fleece Bowl and the Totem Silica (see 104K 088) zones, occur along the major north trending structure. The deposits are about 1.5 kilometres apart and exploration and development is progressing from the south to north deposit.

The Fleece Bowl Zone is bound by the West Wall and Black faults. The Black Fault, ranging from 6 to 20 metres wide, occurs in a graphitic, siliceous siltstone and dips to the east. Late-stage calcite veinlets cut the rock which is locally vuggy. The hanging wall zone consists of fuchsite-bearing(?) tuff with trace arsenopyrite in quartz veinlets.

The West Wall Fault, which dips steeply to the east cuts, silicified limestone and dolomite. A 12 metre slice, with strong north-striking foliation, consists of fuchsite-bearing(?) tuff (listwanite) with quartz-carbonate veining, and breccia. Pyrite occurs as disseminations and fracture fillings. Mineralization is also associated with a sericitized feldspar porphyry dyke.

Alteration minerals in the zone include quartz, dolomite and pyrite within the limestones and dolomite, kaolinite, sericite, illite, chlorite and pyrite in the metavolcanics. Age dating of sericite from the alteration zone, which gave an apparent age of 179 plus or minus 6 million years (Schroeter, 1987), suggests the main period of mineralization occurred in Early Jurassic.

Mineralization in the Fleece Bowl Zone occurs below surface, as indicated by drilling. Indicated resources are 110,666 tonnes grading 16.4 grams per tonne gold (George Cross News Letter No.84 (May 3), 1994).

The mineralization is primarily epigenetic, although supergene enrichment occurs locally. The deposits are characteristic of a low to medium temperature, low salinity, mesothermal system. Likely, mineralized solutions ascended the fault zone to an area of extensive tectonic brecciation and alteration. Intrusive activity, alteration and mineralization along the major regional fault is postulated to have occurred over a 50-million-year period, from 156 to 206 million years (Jurassic age). (Schroeter, 1987).

Production ceased in 2001 and the reported remaining reserve was in the Kodiak C zone. Wheaton River Minerals reported in their 1998 Annual Report a combined Measured, Indicated, and Inferred Resource of 276,000 tonnes grading 7.8 grams per tonne Au (www.sedar.com).