Riverside Prospect, Valdez Creek Mining District, Matanuska-Susitna Borough, Alaska, USAi

Regional Level Types
Riverside Prospect	Prospect
Valdez Creek Mining District	Mining District
Matanuska-Susitna Borough	Borough
Alaska	State
USA	Country

Location: The prospect is on the south bank of the West Fork Chulitna River, just upstream from the mouth of Bryn Mawr Creek. It is located in sec. 26, T.19 S., R. 11 W., of the Fairbanks Meridian. Accuracy is within 0.5 miles. This is location 7 of Cobb (1978: OFR 78-1062).
Geology: The country rocks in the area of the Riverside prospect are Triassic, redbed sandstone, conglomerate and limestone that have been intruded by a hornblende-quartz diorite dike. The deposit is in hornfelsed bedded rocks and consists chiefly of quartz-sulfide veins, and stockworks, and of sulfide disseminations. 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 Small, sulfide-bearing skarn deposits are in marble adjacent to the dike (unpublished report by Addwest Minerals International Ltd., 1997).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 contain 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 satellitic to the Golden Zone deposit (HE043).
Workings: Mainly surface workings. 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. Samples contain 0.02 to 0.72 ounce of gold per ton and 0.3 to 2.10 ounces of silver per ton (Ross, 1933).
Age: Late Cretaceous (70 -65 Ma), assuming that the deposit is satellitic to the Golden Zone deposit (HE043).
Alteration: Narrow phyllic alteration haloes around and in porphyry dikes typically consists of sericite, quartz, and pyrite. In addition, skarn alteration minerals are garnet, pyroxene, and epidote.

Commodities (Major) - Ag, Au ; (Minor) - Cu, Pb, Zn
Development Status: None
Deposit Model: Cu skarn; Polymetallic veins (Cox and Singer, 1986; models 18b, 22c)

Other Databases

Link to USGS - Alaska:	HE033

Other Regions, Features and Areas containing this locality

References