Unnamed Occurrence (ARDF - MF025; southwest of Mt. Parker), Hoonah-Angoon Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - MF025; southwest of Mt. Parker)	- not defined -
Hoonah-Angoon Census Area	Census Area
Alaska	State
USA	Country

The occurrence is of interest because of the strength and continuous nature of the vein-fault structure. Possibly, gold-bearing veins could occur in subsidiary tensional structures or at vein intersections. Rossman's main map (B 1058-B) suggests that the northeast vein-fault will intersect the projection of the northwest striking Ptarmigan Creek fault under cover in Ptarmigan Creek basin. (The Ptarmigan Creek fault appears to be the fundamental control of the Highland Chief prospect--MF030) No near term exploration is expected because the occurrence is in Glacier Bay National Park and Preserve.
Location: This occurrence consists of a locally mineralized fault or shear zone which can be traced for more than 4000-feet. The fault crosses the ridge about 0.2 mile southeast of Mt. Parker at an elevation of about 2900 feet. The coordinates, accurate within 0.1 mile, mark the point where the vein-fault crosses the ridge south of Mt. Parker. The fault continues southwesterly to Lamplugh Glacier and northeasterly into Ptarmigan Creek. Rossman (1959, B 1058-B, pl. 4, p. 55-56) reported two hydrothermally altered segments in the vein-fault, one to the northeast in Ptarmigan Creek; the second is about 2000 feet southwest of the ridge and 1000 feet east of Lamplugh Glacier.
Geology: A prominent locally mineralized fault cuts granodiorite of Cretaceous age on the ridge south of Mt. Parker, and enters the major cataclasite schist zone of the Ptarmigan basin to the northeast (Rossman, 1959, B 1058-B, pl. 4; Brew and others, 1978, pl. 1A). A 200-foot long quartz-bearing segment exposed on the west side of the Ptarmigan Creek basin is in schistose (cataclasite); a hydrothermally altered segment mapped by Rossman above Lamplugh Glacier is in granodiorite. The vein-fault is traceable for 4500 feet. It is one of the strongest mineralized structures in the Reid Inlet gold area (Kimball and others, 1978). In addition to quartz, mineralized segments contain arsenopyrite, pyrite and black sphalerite.
Workings: The vein-fault has only been traced on the surface. Prospectors who examined mineralized segments of the vein thought it contained ferberite, but Rossman identified the dark mineral as iron-rich sphalerite (Rossman, 1959, p. 55-56). No assays are given, probably owing to the absence of visible free gold in the vein-fault structure.
Age: Late Cretaceous or younger.
Alteration: Rossman (1959, B 1058-B, p. 56) reported alteration along the 4500-foot length of the structure. In general veins of the area are altered for as much as 10-15 feet on each side of the controlling fault structures; the alteration products include ankerite.

Commodities (Major) - Au; (Minor) - Ag, As, Zn
Development Status: No
Deposit Model: Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).

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Link to USGS - Alaska:	MF025

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References