Riverside

Prospect, Active

Alternative names

Flaurier

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale HE
Quadrangle map, 1:63,360-scale A-6
Latitude 63.2388
Longitude -149.6121
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Riverside prospect is on the south bank of the West Fork Chulitna River, about 0.7 mile upstream from the mouth of Bryn Mawr Creek. It is about 0.3 mile west of the center of section 26, T.19 S., R. 11 W. The location is accurate. This is apparently the modern name for the old Flaurier prospect (HE036).

Geologic setting

Geologic description

Ross (1933) reported that the principal cuts he saw disclosed two nearly parallel lodes about 80 feet apart, both of which are replacement deposits that approximately follow the bedding of limestone lenses. The eastern lode strikes N 15 W and dips about 70 NE. Ore deposition has in part been controlled by poorly defined sheeting that trends N 25 W. The maximum observed width of mineralization is 5.5 feet, most of the ore is contained within a total width of 8 feet. This lode has been traced for about 60 feet along the strike. The second lode is similar, but its average strike is north and it stands nearly vertical. It has been traced for fully 80 feet on the strike, and the ore averages about 8 feet in width. Small cuts and outcrops in the general vicinity show that there are several other lenses of mineralized rock. One of these lenses parallels the bedding of banded limestone which dips vertical and trends N. 60 E., suggesting faulting or other structural disturbance.
The lode is composed irregular bunches and lenses of vein quartz and sulfides, in partly silicified and chloritized limestone. The principal sulfide is arsenopyrite, but pyrrhotite, pyrite, and chalcopyrite are also abundant, and sphalerite and galena are locally present. There is a very small amount of supergene chalcocite. Within a few inches of the surface the lode is thoroughly oxidized and in part clayey (Ross, 1933).
The rocks surrounding the Riverside prospect are Triassic, redbed sandstone, conglomerate, and limestone that have been intruded by a dike of hornblende, quartz diorite. The deposit is in hornfelsed bedded rocks and consists chiefly of quartz-sulfide veins, stockworks, and disseminated sulfides. The sulfide minerals are arsenopyrite, chalcopyrite, galena, pyrite, pyrrhotite, and sphalerite. Small, sulfide-bearing skarn deposits are in marble adjacent to the dike (unpublished report by Addwest Minerals International Ltd., 1997). Samples contained 0.02 to 0.72 ounce of gold per ton and 0.3 to 2.10 ounces of silver per ton (Ross, 1933). The relatively high gold and silver values may be due to supergene enrichment. A fault may truncate the deposit to the south. The Riverside deposit is similar in mineralogy and type to other deposits satellite to the Golden Zone Mine (HE043). The Riverside is the old Flaurier prospect that was briefly described by Capps (1919).
The 5-foot-wide Wells vein at the Riverside prospect was exposed and chip sampled by Hidefield Gold PLC in 2006 (Alix Resources Corp., 2011). Some notable intervals were 25.9 grams of gold per tonne across 0.79 meters; 34.6 grams of gold per tonne across 1.49 meters; and 30.9 grams of gold per tonne across 1.40 meters. The Riverside prospect was drilled in 2011 by Alix Resources Corp. (2012). The two holes successfully intercepted the Well vein. The vein in one hole was 1.50 meters thick and averaged 11.43 grams of gold per tonne, 24.57 grams of silver per ton, and 0.23 percent copper. In the other hole, the vein was 1.78 meters thick and contained 19.1 grams of gold per tonne, 48.63 grams of silver per tonne, and 0.77 percent copper.
Geologic map unit (-149.614391757454, 63.2383271737291)
Mineral deposit model Cu skarn; Polymetallic veins (Cox and Singer, 1986; models 18b, 22c).
Mineral deposit model number 18b, 22c
Age of mineralization Late Cretaceous (70-65 Ma), assuming that the deposit is a satellite to the Golden Zone Mine (HE043).
Alteration of deposit Narrow phyllic alteration haloes around and in porphyry dikes typically consists of sericite, quartz, and pyrite. In addition, skarn alteration is present as garnet, pyroxene, and epidote.

Production and reserves

Workings or exploration
Ross (1933) reported numerous cuts and pits on the property and several tunnels had been started, but none were carried far.
There are reports of a 10-foot tunnel and 15-foot shaft that are now caved. Recent geochemical exploration has identified a broad soil anomaly that outlines the deposit. The 5-foot-wide Wells vein at the Riverside prospect was exposed and chip sampled by Hidefield Gold Plc. in 2006 (Alix 2011). In 2011, two holes were drilled at the Riverside prospect and cut the Wells vein (Alix Resources Corp. (2012).
Indication of production None

References

MRDS Number A011332; AO11311

References

Reporters N. Van Wyck (Stevens Exploration Management Corporation); D.J. Grybeck (Contractor, USGS); F.H. Wilson (USGS)
Last report date 3/28/2016