Shellhouse Prospects (Miller Prospects), Dall Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi

Regional Level Types
Shellhouse Prospects (Miller Prospects)	Group of Prospects
Dall Island	Island
Ketchikan Mining District	Mining District
Prince of Wales-Hyder Census Area	Census Area
Alaska	State
USA	Country

This prospect is on land that has been conveyed to the Sealaska Corporation, who hold the surface and subsurface rights, or the land is under application for transfer to them.

Location: The Shellhouse prospect is about 0.8 mile west-northwest of the northwest head of Coco Harbor, and about 0.4 mile northeast of the center of section 6, T. 79 S., R. 82 E. The location is accurate.

Geology: The Shellhouse and Miller prospects have been known since before 1909, but the early descriptions say little more than that the deposits consist of bodies of chalcopyrite and pyrrhotite in quartz-calcite gangue in limestone and siliceous schist (Wright, 1909; Chapin, 1918). Maas and others (1991) located several open cuts and an adit in dense vegetation. They describe the deposit as a 4-foot-thick sulfide lens with pyrite, pyrrhotite, and chalcopyrite in a contact zone between altered [Cretaceous?] diorite porphyry and metamorphosed, calcareous sedimentary rocks. They collected two samples that averaged 0.3 percent copper and 1.6 parts per million (ppm) silver. One sample contained 1.6 parts per billion (ppb) gold. Samples of massive pyrrhotite and pyrite collected by Hedderly-Smith (1999 [Inventory]) contained up to 1.17 percent copper, 403 ppm molybdenum, 6.5 ppm silver, and 121 ppb gold. He describes the deposit as a garnet-chlorite-actinolite-diopside skarn near the contact of weakly propylitized granodiorite. The sedimentary rocks in the area are part of Descon Formation of Silurian and Ordovician age (Eberlein and others, 1983; Brew, 1996).

Workings: The only workings on the property are several open cuts and an adit that probably date to before WW I.
Age: This skarn deposit is probably related to altered granodiorite. Its age is uncertain, but similar intrusions in the area have been variously dated as Mesozoic or Paleozoic, or Cretaceous (Eberlein and others, 1983; Brew, 1996).
Alteration: The deposit is mineralized garnet-chlorite-actinolite-diopside skarn associated with altered [Cretaceous?] diorite porphyry (Maas and others, 1991) or propylitized granodiorite (Hedderly-Smith, 1999 [Inventory]).

Commodities (Major) - Ag, Au, Cu, Mo
Development Status: None
Deposit Model: Cu-Mo skarn (Cox and Singer, 1986; model 18b).

Other Databases

Link to USGS - Alaska:	CR139

Other Regions, Features and Areas containing this locality

References