25 Gold Prospect (Sill?), Bristol Bay Mining District, Lake and Peninsula Borough, Alaska, USAi

Regional Level Types
25 Gold Prospect (Sill?)	Prospect
Bristol Bay Mining District	Mining District
Lake and Peninsula Borough	Borough
Alaska	State
USA	Country

Location: The 25 Gold prospect is at an elevation of about 1,000 feet in the headwaters of the Koktuli River. It is about 1.2 miles west-southwest of locally-named Frying Pan Lake, in the NE1/4 sec. 8, T. 4 S., R. 35 W., Seward Meridian. The deposit could extend into the southern part of section 2, same township and range. The location is probably accurate within 0.5 mile (Northern Dynasty Minerals, 2003). The 25 Gold deposit probably is the same as the Sill deposit, discovered by Cominco in about 1987 (Bouley and others, 1995).
Geology: The 25 Gold deposit is a volcanic-rock-hosted, epithermal gold deposit (Northern Dynasty Minerals, 2003; Bouley and others, 1995). Gold accompanies relatively sparse pyrite and possibly other sulfide minerals in quartz veins which cut dacite (Bouley and others, 1995, analysis 13, table 2). The dacite analyzed by Bouley and others is fresh, contains phenocrysts of hornblende and zoned plagioclase, and plots in the high alkali field of a K20-Si02 diagram. The geology near the deposit is complex. In addition to Tertiary volcanic rocks, there are outcrops of biotite pyroxenite and mafic breccias similar to those at the Frying Pan Lake deposit (IL006). The prospect was drilled by Northern Dynasty Minerals in 2002. Several holes intersected substantial gold mineralization. Hole no. 58 intersected 350 feet averaging 0.3 gram of gold per tonne; hole TC-8 intersected 5 feet averaging 33.9 grams of gold per tonne (about 0.99 ounce); and hole 62 intersected 5.7 feet averaging 19.3 grams of gold per tonne (about 0.56 ounce) (Northern Dynasty Minerals, 2003). A soil survey conducted by Northern Dynasty Minerals showed local values of 500 or more parts per billion gold and delineated a lead-zinc anomaly.
Workings: The deposit, then called Sill, was discovered by Cominco geologists in 1987 and two shallow holes were drilled in 1988; the prospect was deemed worthy of future work. The deposit, subsequently called 25 Gold, was drilled by Northern Dynasty Minerals in 2002. Northern Dynasty also conducted a soil survey of the area; anomalous zones remain to be drilled (Northern Dynasty Minerals, 2003).
Age: Probably Early Tertiary, the age of the volcanic host rocks.
Alteration: Silicification.

Commodities (Major) - Ag, Au
Development Status: None
Deposit Model: Low-sulfide Au-quartz deposit (Cox and Singer, 1986; model 36a).

Other Databases

Link to USGS - Alaska:	IL005

Other Regions, Features and Areas containing this locality

References