Heckman

Site Name

Primary: Heckman
Secondary: Unnamed (northwest of Heckman prospect)

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Commodity

Primary: Gold
Secondary: Zinc
Secondary: Lead

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Location

State: Alaska
District: Ketchikan

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Polymetallic veins
Model Name: Massive sulfide, Besshi (Japanese deposits)

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Orebody

Not available

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Structure

Not available

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Alterations

Not available

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Rocks

Name: Schist
Role: Host
Age Type: Host Rock
Age Young: Late Cretaceous

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Analytical Data

Not available

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Materials

Ore: Galena
Ore: Gold
Ore: Pyrite
Ore: Sphalerite
Gangue: Calcite
Gangue: Quartz

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Comments

Comment (Workings): Workings / Exploration = These prospects were discovered in the early 1900s (Brooks, 1902, p. 62; Wright and Wright, 1908, 179). The Heckman was explored at that time by a 60-foot shaft, and drifts totalling 32 feet. The other prospect was explored by a 50-foot shaft. Samples collected by Maas and others (1995) of the Heckman deposit indicated a zone up to about 10 feet wide containing 6.2 ppm Au and 1.6% Zn.

Comment (Geology): Geologic Description = The country rocks on southeastern Gravina Island are Upper Jurassic or Cretaceous marine andesitic or basaltic volcanic rocks that are gradationally interbedded with subordinate flyschlike sedimentary rocks (Berg, 1973; Berg and others, 1988). The strata were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The country rocks are cut by a high-angle fault along Tongass Narrows that displays about 4 miles of right-lateral offset.? Maas and others (1995, p. 194, 199, 201-202, and fig. 51) describe the Heckman prospect, and a similar unnamed lode about 0.3 mile to the northwest, as stratiform, sulfide-bearing, northwest-trending layers of greenschist or quartz-chlorite schist, locally cut by sulfide-bearing quartz fissure veins. At the Heckman prospect, pyrite, sphalerite, and galena occur as bands of massive sulfides, and as disseminations, in several layers of quartz-chlorite schist, separated by several layers of relatively barren schist.?The sulfides also occur in quartz stringers parallel to the foliation of the schist. The stratiform deposit, as exposed in old trenches, is at least 25 feet wide and 60 feet long. Samples of this deposit indicated a zone up to about 10 feet wide containing 6.2 ppm Au and 1.6% Zn. The other prospect, at sea level about 0.3 mile northwest of the Heckman prospect, consists of talc-chlorite schist that contains pyrite, sphalerite, and galena disseminated in quartz-rich layers parallel to the foliation of the schist. ? Brooks (1902, p. 62) interpreted the Heckman deposit as the southeast continuation of the deposit at the Goldstream (Bell) mine (KC072). Maas and others (1995, p. 194, 201) suggest that the stratiform deposits are of volcanogenic origin. If so, the Heckman probably can be classified as a metamorphosed Besshi massive sulfide deposit of Late Jurassic age. The sulfide-bearing quartz fissure veins that cut the foliation probably formed by remobilization, during or following Upper Cretaceous regional metamorphism.? These prospects were discovered in the early 1900s (Brooks, 1902, p. 62; Wright and Wright, 1908, 179). The Heckman was explored at that time by a 60-foot shaft, and drifts totalling 32 feet. The other prospect was explored by a 50-foot shaft.

Comment (Production): Production Notes = There is no public record of any production from the Heckman mine, but the extent of the underground workings suggests that at least a small amount of gold was recovered in the early 1900s.

Comment (Deposit): Model Name = Besshi massive sulfide?; Polymetallic veins (Cox and Singer, 1986; models 24b, 22c)

Comment (Deposit): Other Comments = Brooks (1902, p. 62), noting their similarity, interpreted the Heckman deposit as the southeast continuation of the deposit at the Goldstream (Bell) mine (KC072). ? Also see Production notes.

Comment (Geology): Age = Late Jurassic; Late Cretaceous or younger.

Comment (Reference): Primary Reference = Berg, 1973; Maas and others, 1995

Comment (Deposit): Model Number = 24b?, 22c

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References

Reference (Deposit): Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.

Reference (Deposit): Wright, F.E., and Wright, C.W., 1908, The Ketchikan and Wrangell mining districts, Alaska: U.S. Geological Survey Bulletin 347, 210 p.

Reference (Deposit): Berg, H.C., 1973, Geology of Gravina Island Alaska: U.S. Geological Survey Bulletin 1373, 41 p.

Reference (Deposit): Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 p., scale 1:250,000.

Reference (Deposit): Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

Reference (Deposit): Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.

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