Massachusetts

The Massachusetts is a gold mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Massachusetts
Secondary: Keystone

Commodity

Primary: Gold
Secondary: Zinc
Secondary: Lead

Location

State: Alaska
District: Ketchikan

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

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

Physiography

Not available

Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: According to Maas and others (1995, p. 215), the wallrocks of the auriferous veins in the Sea Level mine area are hydrothermally altered to bluish-gray carbonate-sericite-pyrite rock, called 'blue porphyry' in some early reports (for example, Brooks, 1902; Wright and Wright, 1908) (also see KC095).

Rocks

Not available

Analytical Data

Not available

Materials

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

Comments

Comment (Reference): Primary Reference = Wright and Wright, 1908; Maas and others, 1995

Comment (Workings): Workings / Exploration = The prospect was explored in the early 1900s by several opencuts, an 80-foot adit, a 30-foot shaft, and a 50-foot drift off the shaft. Gold values of $12/ton (Au at $20.67/oz.) were reported by the operators at that time (Brooks, 1902, p. 68). Maas and others (1995, p. 217, 218) report a mean value of 2071 ppb Au in 12 samples of the Massachusetts deposit; their best assay showed 11.1 ppm Au and 134 ppm Ag in a 3-foot sample across the main vein.

Comment (Deposit): Other Comments = Wright and Wright (1908, p. 148) refer to this property as the Massachusetts claims nos. 1 and 2, and note that they were originally known as the Keystone claims (Brooks, 1902, p. 68).

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

Comment (Geology): Geologic Description = The country rocks in this part of Revillagigedo Island are marine, interbedded, andesitic and basaltic metavolcanic rocks and subordinate pelitic metasedimentary rocks that are intruded by stocks, sills, and dikes of Cretaceous feldspar-porphyritic granodiorite (Berg and others, 1988). The strata and some of the granodiorite were regionally metamorphosed to greenschist grade in Late Cretaceous time. These regionally metamorphosed rocks subsequently were locally remetamorphosed to hornblende hornfels near the contacts of Cretaceous granodiorite plutons that were emplaced after the regional metamorphism. The premetamorphic age of the strata is uncertain. Berg and others (1988) assign them a Mesozoic or (late) Paleozoic age. Berg (1982) and Crawford and others (in press) assign them to the Gravina belt, of Late Jurassic or Cretaceous age, or to the Taku terrane, of late Paleozoic to Late Triassic age. The metamorphic and intrusive rocks locally are overlain by basalt and andesite lava flows of Quaternary or Tertiary age.? the deposit consists of a sulfide-bearing quartz fissure vein in intercalated metapelitic and metavolcanic (greenstone) schists that are cut by a granodiorite dike (Wright and Wright, 1908, p. 148-9). The vein at the surface is five feet wide, but at depth it decreases to six inches and divides into stringers. The sulfides are pyrite, galena, and sphalerite, accompanied by favorable gold values near the surface. According to Maas and others (1995, p. 215), the Massachusetts auriferous veins strike NE and are hosted in hydrothermally altered mafic metavolcanic rocks that crop out on both sides of the granodiorite dike (see Alteration). The quartz in these veins is not recrystallized, so the veins are probably younger than most or all of the Late Cretaceous regional metamorphism.? the prospect was explored in the early 1900s by several opencuts, an 80-foot adit, a 30-foot shaft, and a 50-foot drift off the shaft. Gold values of $12/ton (Au at $20.67/oz.) were reported by the operators at that time (Brooks, 1902, p. 68). ? Maas and others (1995, p. 217, 218) report a mean value of 2071 ppb Au in 12 samples of the Massachusetts deposit; their best assay showed 11.1 ppm Au and 134 ppm Ag in a 3-foot sample across the main vein.

Comment (Deposit): Model Name = Low-sulfide gold-quartz veins (Cox and Singer, 1986; model 36a)

References

Reference (Deposit): Crawford, M.L., Crawford, W.A., and Gehrels, G.E., 2000, Terrane assembly and structural relationships in the eastern Prince Rupert quadrangle, British Columbia, in H.H. Stowell and W.C.McClelland, eds., Tectonics of the Coast Mountains, southeastern Alaska and British Columbia: Boulder, Colorado, Geological Society of America Special Paper 343, p. 1-21.?

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.

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): Berg, H.C., 1982, The Alaska Mineral Resource Assessment Program; guide to information about the geology and mineral resources of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Circular 855, 24 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): 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.

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