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Massachusetts

Prospect in Alaska, United States with commodities Gold, Lead, Zinc
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Economic information about the deposit and operations
  12. Mining district
  13. Links to other databases
  14. Bibliographic references
  15. General comments
  16. Reporter information

Geologic information

Identification information

Deposit ID 10094034
MRDS ID A012339
Record type Site
Current site name Massachusetts
Alternate or previous names Keystone
Related records 10282911

Geographic coordinates

Geographic coordinates: -131.17065, 55.38669 (WGS84)
Relative position This prospect is at an elevation of 500 feet in the south wall of the unnamed creek that flows west into Granite Lake . The site is about 0.3 mile east of Granite Lake, in section 8, T. 75 S., R. 94 E., of the Copper River Meridian. It corresponds to loc. 86 in Elliott and others (1978), and to loc. 298 in Maas and others (1995). The location is accurate within 0.1 mile.

Site location context

Political divisions (FIPS codes)

Ketchikan Gateway(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Ketchikan B-4(quadrangle 1:63,360 scale)

Ketchikan SW(quadrangle 1:100,000 scale)

Ketchikan(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Ketchikan(hydrologic unit)

Southern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Tongass National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Lead Secondary
Zinc Critical Secondary

Materials information

Materials Type of material
Galena Ore
Gold Ore
Pyrite Ore
Sphalerite Ore
Quartz Gangue

Alteration

  • (Local) 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).

Mineral occurrence model information

Model code 273
USGS model code 36a
Deposit model name Low-sulfide Au-quartz vein
Mark3 model number 27

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Schist > Greenschist

Nearby scientific data

(1) -131.17065, 55.38669
ListMap

Economic information

Comments on the geologic information

  • 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.
  • Age = Late Cretaceous or younger.

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Ketchikan

Comments on the workings information

  • 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.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Wright and Wright, 1908; Maas and others, 1995

General comments

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

Reporter information

Type Date Name Affiliation Comment
Reporter 03-JUL-99 H.C. Berg U.S. Geological Survey

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.