Crevice Creek

Prospect, Inactive

Alternative names

McNeil
Sargent (also Holly and others
Okchiak Creek
Reward-Ridgway
Cook & Bornland)

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Fe
Ore minerals azurite; chalcopyrite; chrysocolla; malachite; magnetite; pyrite
Gangue minerals actinolite; calcite; epidote; garnet; quartz

Geographic location

Quadrangle map, 1:250,000-scale IL
Quadrangle map, 1:63,360-scale A-5
Latitude 59.1369
Longitude -154.639
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The Crevice Creek prospect is at an elevation of about 1,250 feet on the northwest valley wall of Crevice Creek about 0.7 mile above the junction of Paint River. The coordinates are for the midpoint of the half-mile-long prospect area, near the center of SE1/4 sec. 15, T. 12 S., R. 32 W., Seward Meridian. The location is accurate within 500 feet. The site corresponds to number 8 of Richter and Herreid (1965), and approximately to locality 20 of Detterman and Cobb (1972).
Other creek names have been used in the area. Jasper (1953, plate 2) calls Crevice Creek Paint River, and calls locally-named Sargent Creek (IL039) Crevice Creek.

Geologic setting

Geologic description

The Crevice Creek prospect is a linear skarn deposit (tactite of Richter and Herreid, 1965) along the contact between intermediate and basic volcanic rocks of the Jurassic Talkeetna Formation and chert and limestone of the Triassic Kamishak(?) Formation (Richter and Herreid, 1965; Detterman and Reed, 1980). The Kamishak(?) Formation generally strikes northeast and dips steeply northwest (Richter and Herreid, 1965, p. 3). The deposit is about one mile south of a south-southwest-trending lobe of Jurassic granodiorite that possibly continues under the prospect area at shallow depth. The volcanic and sedimentary strata are cut by a few sills and hundreds of intermediate to basic dikes that generally strike N70W and dip 80N (Richter and Herreid, 1965, p. 6, fig. 3). A lesser number of diorite and granodiorite dikes and sills occur along Sargent Creek that strike west and dip north at a moderate angle (Richter and Herreid, 1965, fig. 6).
The Crevice Creek deposit consists chiefly of chalcopyrite and other metallic minerals in epidote-garnet skarn. Quartz-magnetite rock occurs locally. The deposit is irregular and lenticular, but can be traced generally northeast from Sargent Creek for about a half mile (Richter and Herreid, 1965, fig. 6). Actinolite is abundant and forms radiating crystals as much as 2 feet across; grossularite-andradite garnets are as much as 2 inches across. Calcite is common and locally massive (Richter and Herreid, 1965).
Chalcopyrite and pyrite are the main sulfide minerals; the chalcopyrite is locally oxidized to azurite, malachite, and chrysocolla. The sulfide-bearing skarn locally contains gold and silver, probably in, or associated with, chalcopyrite. Selected samples from the No. 3 adit at the Crevice Creek deposit assayed 0.04 to 0.08 ounce of gold per ton, 6.24 to 9.12 ounces of silver per ton, and 6.41 to 7.03 percent copper (Jasper, 1956). A selected sample from the No. 8 open cut south of Sargent Creek (IL039) contained 0.30 ounce of gold per ton and 3.66 percent copper (Jasper, 1953). In general, gold concentrations are low.
Claims were first staked in 1911 by C. H. McNeil, who prospected in the area until 1924. At least two test shipments of copper-rich ore were made. A one-ton shipment of hand-sorted ore graded 18.19 percent copper, 0.29 ounce of gold per ton, and 10.93 ounces of silver per ton. A 10.5-ton test shipment assayed 17.55 percent copper, 0.12 ounce of gold per ton, and 15 ounces of silver per ton (Mather, 1925; Jasper, 1953). It appears that most of the work on the property was done by McNeil between 1911 and 1924.
Geologic map unit (-154.641115698293, 59.1362098044073)
Mineral deposit model Fe skarn, Cu skarn (Cox and Singer, 1986; models 18d, 18b).
Mineral deposit model number 18d, 18b
Age of mineralization Probably Jurassic; the age of the nearby granodiorite pluton.
Alteration of deposit Alteration of cherty and calcareous sedimentary rocks and intermediate to basic volcanic rocks to garnet-epidote-actinolite-calcite skarn and subordinate quartz-magnetite rock (Richter and Herreid, 1965). Oxidation of copper.

Production and reserves

Workings or exploration
The area was located by C. H. McNeil in 1911 and prospected by him until 1924. The principal deposit was covered by four lode claims: McNeil and McNeil Nos. 1-3; and subsequently by McNeil Nos. 4-6 and Joker. The earlier McNeil claims were restaked as Reward and Reward Nos. 1-3
(Jasper, 1953, plate 2). At least two test shipments were made. One ton of ore shipped before 1925 graded $6.08 in gold (at $20.67 per ounce), 10.93 ounces of silver per ton, and 18.19 percent copper. Ten and a half tons shipped in 1914-1916 from scattered workings assayed $2.50 in gold, 15 ounces of silver per ton, and 17.55 percent copper (Mather, 1925, p. 173-174; Jasper, 1953). McNeil abandoned the claims around 1926 due in part to differences with his associates on the value of the claims (Jasper, 1953). The claims were relocated by E. Sargent and associates in 1953. The claims were examined for the Territory of Alaska by Jasper (1953, 1956) and for the State of Alaska by Richter and Herried (1965).
Indication of production Yes; small
Production notes One ton of ore shipped in the early part of 20th century graded $6.08 in gold (at $20.67 per ounce), 10.93 ounces of silver per ton, and 18.19 percent copper. Ten and a half tons shipped in 1914 to 1916 from scattered workings assayed $2.50 in gold, 15 ounces of silver per ton, and 17.55 percent copper (Mather, 1925). The shipments were probably from the Crevice Creek claims but possibly included some ore from claims in Sargent Creek (IL039).

References

MRDS Number A013050

References

Reporters C.C. Hawley, Hawley Resource Group, Anchorage, Alaska
Last report date 6/8/2003