Goodluck Gulch

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; W
Ore minerals arsenopyrite; galena; gold; pyrite; scheelite
Gangue minerals albite; calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale C-1
Latitude 64.6447
Longitude -165.459
Nearby scientific data Find additional scientific data near this location
Location and accuracy Goodluck Gulch is on the low slopes along the east side of Snake River, 1,400 feet due west of the Snake River road and 1.8 miles northwest of Mount Byrnteson. The map location is in the SW1/4 section 3, T. 10 S., R. 34 W., Kateel River Meridian. This is locality 38 of Cobb (1972 [MF 467], 1978 [OFR 78-93]). It is also locality 4 of Hummel (1962 [MF 247]) but Hummel's location is approximate. The location in this record is accurate within 500 feet.

Geologic setting

Geologic description

A deposit at Goodluck Gulch, approximately located by Hummel (locality 4, 1962 [MF 247]) was relocated by Kennecott Exploration Company in 1995. It apparently was first reported by Moffit (1913, p. 131) who noted: 'A large amount of highly mineralized quartz is present in schist exposures south of Good Luck Gulch . . . Panning shows the presence of gold.' Bedrock was not visible when the prospect was visited by Cathcart (1922, p. 247-248), but he did find scheelite in thin-section examination of dump material. The location is important because Goodluck Gulch is the northernmost significant deposit in a belt of gold lodes east of Snake River that extends northerly from near Bonanza Hill (NM228) and the Anvil fault through Rock Creek (NM207). Surface expression of this deposit includes a large quartz-boulder felsenmeer on the Snake River plain adjacent to the deposit; white vein quartz boulders in the felsenmeer are as much as 3 feet across. Old prospect trenches are on the upland adjacent to the felsenmeer. The quartz vein system in bedrock probably also extends some distance into the Snake River flood plain because large blocks of quartz are visible in the Snake River gravels on a northwesterly projection of the deposit; these boulders are not present north of this projection. The deposit extends uphill nearly to the Snake River road (Hummel's 1962 location) but is best developed near Snake River.
Relocation of the prospect was followed in 1995 by soil geochemical sampling, trenching, and drilling. The deposit consists of schist extensively replaced by arsenopyrite, schist replaced by tabular albite impregnated by arsenopyrite, and veinlets and extensive masses of quartz as much as several feet across. Most of the deposit is crudely stratabound, and some is folded. Drill core in GLC95-2 at a depth of about 140 feet cuts nearly isoclinal folds with saddle-reef type quartz-feldspar veins in small-scale folds and as much as 5 percent arsenopyrite disseminated in the folded schist. Pyrite is less abundant than arsenopyrite, and galena is sparsely disseminated in quartz. Near the surface, the sulfidized schist is mainly weathered to a reddish iron oxide, probably hematite. Late-stage mineralized quartz occupies northeast-striking fissures, the common direction for late sheeted veins in the area. Bedrock in the area is graphitic schist probably of early Paleozoic protolith age (Hummel, 1962 [MF 247]; Sainsbury, Hummel, and Hudson, 1972 [OFR 72-326]; Till and Dumoulin, 1994; Bundtzen and others, 1994).
Geologic map unit (-165.461609257004, 64.6439339436289)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a); a residual gold placer is also developed on the lode.
Mineral deposit model number 36a
Age of mineralization Probably mid-Cretaceous or younger, the time of regional metamorphism of the enclosing schist. Fold-controlled mineralization at Goodluck Gulch is assumed to be somewhat older than sheeted veins developed at Rock Creek (NM207).
Alteration of deposit Albitization and sulfidization, including dissemination of arsenopyrite in schist prior to development of northeast-striking sheeted veins.

Production and reserves

Workings or exploration Cathcart (1922) reported that pits and short trenches were present on the property. In 1995, Kennecott Exploration Company explored the area with about 1,000 feet of backhoe trenches and diamond core holes; maximum gold grades were a few hundreths of an ounce per ton.
Indication of production None

Additional comments

There has probably been a very small amount of gold production from the residual placer. Cathcart (1922) reported sacked ore or concentrates on the property.

References

MRDS Number A012826

References

Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, v. G-1, p. 141-152.
Reporters C.C. Hawley and Travis L. Hudson
Last report date 7/10/2000