1. Mineral Resources
  2. Online Spatial Data
  3. Mineral Resource Data System (MRDS)

Road Cut

Prospect in Alaska, United States with commodities Gold, Copper, Silver
Map
XML
JSON
KML
B
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. Host and associated rocks
  9. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10308237
Record type Site
Current site name Road Cut

Geographic coordinates

Geographic coordinates: -135.45209, 59.19975 (WGS84)
Relative position This prospect is on the west side of the Chilkat Peninsula, 3.1 miles south of Haines on the Mud Bay Road as determined by mileposts.

Site location context

Political divisions (FIPS codes)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Skagway A-2 NE(quadrangle 1:24,000 scale)

Skagway SE(quadrangle 1:100,000 scale)

Skagway(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Chilkat-Skagway Rivers(hydrologic unit)

Northern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Copper Primary
Silver Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Pyrite Ore
Calcite Gangue
Quartz Gangue

Alteration

  • (Local) Calcification, pyritization, silicification.

Host and associated rocks

  • Host or associated Host
    Rock type
    Stratigraphic age (youngest) Late Triassic

Nearby scientific data

(1) -135.45209, 59.19975
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The following description is summarized from Still (1988). The prospect is in a thick metabasalt sequence within 1/4 mile of an ultramafic intrusive. Mineralization is fault-controlled and is in a fault zone, the Road Cut fault that is up to 40 feet thick, strikes N35-40W, and dips steeply to the northeast. The fault zone consists of silicified, brecciated, and sheared metabasalt and locally sheared and brecciated diorite. At the surface, a higher grade zone outcrops over a strike length of 227 feet. Its eastern (upper) margin includes an 0.2- to 3.5-foot-thick quartz-calcite zone with up to 75% combined pyrite and chalcopyrite. Samples from this quartz-calcite zone contained from 0.8 to 32.26 ppm gold. The remainder of the width of the better mineralized zone consists of a shear zone of silicified metabasalt with 0.06% to 3% chalcopyrite, up to 5% pyrite, and gold values of 0.07 to 0.14 ppm. The higher-grade zone at the surface occurs within a 590-foot-long section of lower grade mineralization that is defined by drill holes and extends to a depth of at least 125 feet. This lower grade zone, which is open along strike to the north and south and down dip, ranges in width from 12 to 40 feet and consists of silicified, locally pyritized, brecciated metabasalt and, locally, brecciated diorite. Gold and copper values average less than 0.48 ppm gold and 268 ppm copper. From the descriptions of Still (1988) it appears that mineralization at the Road Cut and Road Cut II (SK005) prospects occurs along fault and shear zones that are subsidiary shears and splits to the nearby Chilkat fault. If so, the age of the mineralization is probably Tertiary or younger since most movement along the Chilkat Fault has probably been post-Mesozoic (Lanphere, 1978). Plafker, Hudson and Silberling (1979) and Plafker and Hudson (1980) cite fossil evidence for a Late Triassic (Karnian) age for the metabasalts on the Chilkat Peninsula. The nearby ultramafic body is probably 108-109 m.y. old based on potassium-argon ages from a pyroxenite at Battery Point (MacKevett and others, 1974). A sample of a copper-stained zone in greenstone collected a short distance due west of the Road Cut Prospect on the western shore of the Chilkat Peninsula by Winkler and MacKevett (1970) contained more than 9,999 ppm copper.
  • Age = the age is not well established. It can be no older than the Late Triassic metabasalts that host the deposit (Plafker, Hudson and Silberling, 1979; Plafker and Hudson, 1980). If the structures that localize the mineralization are related to the Chilkat Fault, then the age of the mineralization is probably Tertiary or youner as most movement on the Chilkat Fault has been post-Mesozoic (Lanphere, 1978).

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Inactive

Mining district

District name Juneau (Skagway subdistrict)

Comments on the reserve resource information

  • Reserves = Still (1988) divides the mineralized area of the prospect into two zones, a higher grade gold-copper zone and a lower grade 'DDH' zone. He estimates a near-surface resource of 700 tons of material with 0.09 ounce of gold per ton, 0.17 ounce of silver per ton, and 0.8% copper in the gold-copper zone. A slightly deeper resource on this zone is estimated to consist of 4,729 tons of material with 0.02 ounces of gold per ton and 0.1% copper. He estimates a resource of 3 million tons of material with 0.008 ounces of gold per ton in the DDH zone.

Comments on the workings information

  • Workings / Exploration = Work by the U.S. Bureau of Mines in 1986 and 1987 included geologic mapping and sampling; 13 geophysical survey lines (magnetics, radiometrics and electromagnetics) totaling 7,600 feet in length; 7 diamond drill holes totaling 980 feet in length; and 6 trenches up to 6 feet deep and 20 feet long that were dug with mechanized equipment. Several geophysical anomalies that are subparallel to the deposit were drilled approximately 70 and 120 feet east of the surface mineralization but did not intersect significant mineralization (Still, 1988).

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Still, 1988

General comments

Subject category Comment text
Deposit Model Name = Copper sulfides with some precious metal values along a shear zone in metabasalt.
Deposit Other Comments = This prospect is within a mile of the Chilkat State Park.

Reporter information

Type Date Name Affiliation Comment
Reporter 04-FEB-01 T.C. Crafford T. Crafford & Associates

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.