Glacier Creek Prospect, Haines, Alaska, USAi

Regional Level Types
Glacier Creek Prospect	Prospect
Haines	City Borough
Alaska	State
USA	Country

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Location: This prospect occurs within a prominent yellow-orange-red color anomaly on the north side of Glacier Creek between elevations of about 3,500 feet and 4,500 feet. It outcrops over a length of about 1/2 mile and its approximate center is given. It is in the NW1/4, section 6, T. 29 S., R. 54 E. of the Copper River Meridian. It is shown as location 12 by Cobb (1972 [MF 424]) and in figure 7 of Still (1984 [OF 118-84]).
Geology: According to MacKevett and others (1974), the prospect is a barite-rich lode that occurs within a large altered, fault zone that cuts greenschist and subordinate quartzite. The fault zone is up to several hundred feet wide and dips steeply to the north. Near its easternmost exposure, the fault zone strikes about N60W but at its western end it strikes about N85E. The main barite-rich lode outcrops discontinuously over a distance of about 1/2 mile and a vertical extent of more than 1,000 feet. The lode is variably sheared and consists mainly of barite with sparsely disseminated sulfides and, locally narrow, sulfide-rich bands. The sulfides include pyrite, galena, sphalerite, and chalcopyrite. Secondary minerals include gypsum, azurite, chrysocolla, limonite, and rare anglesite, cerussite, and smithsonite. Minor amounts of sericite, chlorite and quartz gangue occur within the barite lode (MacKevett and others, 1974). The deposit consists of two lenses. The western lens averages 15 feet thick over a length of 250 feet and the eastern lens averages 70 feet thick over a length of 800 feet. Samples contain up to 45% barite, 7.8% zinc, 1.8% copper, 0.52% lead, 147.43 ppm silver, and 0.607 ppm gold. Based on an average of 15 composite samples, the mineralization is estimated to average 60% barite, 1.73% zinc, and 60 ppm silver (Still, 1984 [OF 118-84]); Still and others, 1991). The greenschist that hosts the mineralization and its quartz-sericite-pyrite alteration envelope is a mafic volcanic that locally contains well preserved pillows. More recent interpretations (since MacKevett and others, 1974) regard the prospect as a stratiform, volcanogenic, massive sulfide (Still, 1984 [OF 118-84]; Still and others, 1991; Newberry and others, 1997). The quartz-sericite-pyrite alteration surrounding the mineralization is itself surrounded by a foliated zone of chloritic alteration. The sericitization in the alteration envelope and the mineralization itself are less competent units that were probably preferentially sheared and faulted relative to the surrounding metavolcanics. Drilling by various different companies, including Anaconda in 1979 and Rubicon Minerals in 1998, intersected extensive alteration and thin or weakly mineralized intervals that did not approach ore-gradethickness. (T. Crafford, personal observation; Rubicon Minerals, 1998). Rubicon Minerals (1998) interprets the Main Zone to be part of a nearly 5-mile-long, northwesterly striking mineral trend that extends from the Red Creek prospect (SK063) at the southeast end through this prospect to the unnamed occurrences (SK070) in the steep slopes immediately south of the Jarvis Glacier. They believe this trend to be at or near the apex of a shallowly plunging, northwest-trending antiform that is subparallel to another, similar trend that extends through the Nunatak (SK058), Cap (SK060), and Mount Henry Clay (SK068) prospects. The Main Zone/Palmer and other similar prospects in the Mt. Henry Clay area are probably correlative with the Windy Craggy deposit in Canada and the Greens Creek deposit on Admiralty Island and are therefore Late Triassic (Still, 1984 [OF 118-84]; Newberry and others, 1997).
Workings: The deposit was discovered in 1969 and 1971 by Merril Palmer and associates (MacKevett and others, 1974). A 3,000-pound bulk sample collected by ALYU Mining assayed 76.4% barite, 3.6% zinc, 0.98% copper, 0.12% lead, and 92 ppm silver (Still, 1984 [OF 118-84]). This prospect has been explored by numerous companies, including the Anaconda Minerals Company, Kennecott Alaska Exploration, Newmont Gold Company, Granges Inc., Cominco Alaska, Inc., Teck Corporation, and Rubicon Minerals-Atna Resources Ltd. Exploration expenditures in the area, including Mt. Henry Clay and other nearby volcanogenic massive sulfide occurrences through 1998 are estimated to be approximately US$2.2 million.
Age: Probably Late Triassic based on inferred relations to the Greens Creek Mine on Admiralty Island and the Windy Craggy deposit (Still, 1984 [OF 118-84]; Newberry and others, 1991).
Alteration: Quartz-sericite-pyrite (phyllic) alteration and chloritic alteration developed within mafic metavolcanics.
Reserves: A resource of 750,000 tons of ore was estimated based on projecting the barite lenses down dip for 1/2 of their strike length (Still, 1984 [OF 118-84]).

Commodities (Major) - Ag, Au, Ba, Cu, Pb, Zn
Development Status: None
Deposit Model: Probably a Kuroko-type volcanogenic massive sulfide (Cox and Singer)

Glacier Creek deposit consists of four tabular massive sulfide lenses with an inferred resource of 8.13 Mt, averaging 1.41% Cu, 5.25% Zn, 0.15% Pb, 0.32 g/t Au, and 31.7 g/t Ag

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

27 valid minerals.

Rock Types Recorded