Hoadley

Prospect, Undetermined

Alternative names

Hoadley Brothers

Commodities and mineralogy

Main commodities Au
Other commodities Bi
Ore minerals arsenopyrite; gold; pyrite; pyrrhotite; tetradymite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale B-6
Latitude 55.361
Longitude -131.684
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The Hoadley prospect is at an elevation of about 350 feet, approximately 0.3 mile northwest of Hoadley Creek, and about 0.5 mile southeast of the dam at the foot of Carlanna Lake. The site is in section 14, T. 75 S., R. 90 E., of the Copper River Meridian. It corresponds to loc. 62 in Elliott and others (1978), and to loc. 270 in Maas and others (1995). The location is accurate within about 0.1 mile.
Also see Additional comments.

Geologic setting

Geologic description

This part of Revillagigedo Island is underlain mainly by marine, pelitic sedimentary rocks and subordinate andesitic or basaltic volcanic rocks that are intruded by Cretaceous stocks, sills, and dikes of feldspar-porphyritic granodiorite, and by a stock and probably related plugs of Tertiary gabbro (Berg and others, 1988). The strata were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. They subsequently were contact metamorphosed to hornblende hornfels: locally, near some of the Cretaceous granodiorite contacts, and, more widely, peripheral to the Tertiary gabbro. The premetamorphic age range of the strata is uncertain. Berg and others (1988) note that they closely resemble Upper Jurassic to mid-Cretaceous flysch and volcanic rocks nearby on Gravina Island. The country rocks are cut by a high-angle fault along Tongass Narrows that displays about 4 miles of right-lateral offset.
The Hoadley deposit consists of sulfide-bearing quartz veins and argillaceous schists that strike northwest and are intruded by sills or dikes ranging in composition from syenite to gabbro (Wright and Wright, 1980, p. 151-152). The veins are mainly in the intrusive rocks, vary from 4-24 inches thick, and are up to a few hundred feet long. An older set of veins contains chiefly pyrite and pyrrhotite and strikes N and dips W. A younger set of thinner veins, characterized by arsenopyrite, free gold, and minor tetradymite, strikes NW and dips SW. According to Maas and others (1995, loc. 270: p. 194-200), the deposit, which in 1995 was covered by a condominium, is at a syenite-slate contact and consists of a quartz vein containing bands and disseminations of pyrite and arsenopyrite. A 1.5-foot-wide sample across vein rubble contained 88.25 ppm Au (Maas and others, 1995).
The Hoadley prospect was discovered around 1900 and developed in the early 1900s by opencuts, adits, and a 27-foot shaft. Other developments included an arrastre and a Gibson mill. A small amount of gold probably was recovered at that time, but there is no public record of any such production.
Geologic map unit (-131.685685753964, 55.3606527340011)
Mineral deposit model Polymetallic veins or low-sulfide, Au-quartz veins (Cox and Singer, 1986; models 22c or 36a)
Mineral deposit model number 22c or 36a
Age of mineralization Cretaceous or younger.
Alteration of deposit Greenschist-grade metasedimentary country rocks are contact metamorphosed to hornblende hornfels near contacts of Tertiary intrusive rocks.

Production and reserves

Workings or exploration The Hoadley prospect was discovered around 1900 and developed by opencuts, adits, and a 27-foot shaft. Other early developments included an arrastre and a Gibson mill. In 1995, the old workings were covered by a condominium. A 1.5-foot-wide sample across vein rubble contained 88.25 ppm Au (Maas and others, 1995).
Indication of production Yes; small
Production notes A small amount of gold probably was recovered in the early 1900s, but there is no public record of any such production.

Additional comments

The property has been covered by housing construction in the city of Ketchikan. In some early reports, the prospect was also referred to as Hoadley Brothers (Cobb and Elliott, 1980, p. 56).

References