Monarch No. 1 and No. 2

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Pb; REE
Ore minerals allanite; arsenopyrite; chalcopyrite; galena; marcasite; native gold; pyrite; sphalerite
Gangue minerals calcite and quartz

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale D-3
Latitude 58.8668
Longitude -136.8484
Nearby scientific data Find additional scientific data near this location
Location and accuracy Monarch No. 1 is at an elevation ranging from 1850 to about 2100 feet about 0.2 mile east-northeast of triangulation station End, which has an elevation of 2480 feet. Monarch No. 1 is about one mile above the beach at the mouth of Reid Inlet. The Monarch No. 2 deposit is about 600 feet east of Monarch 1 at an elevation of about 1500 feet. Monarch No. 2's approximate latitude and longitude are, respectively, 58.8688 and 136. 8345. The locations of the prospects are known within 0.1 mile.

Geologic setting

Geologic description

The Monarch veins occur in granodiorite of Cretaceous age (Brew and others, 1978). Rossman (1959, B 1058-B) found two phases of granodiorite within the intrusion, but the differences were too subtle to be mapped.
The Monarch vein-bearing structures belong to a steep fault set of north to north-northwest strike; faults of this are relatively continuous. Another member of the same set is the Incas vein-fault (ARDF number MF023). A quartz-vein segment developed in the Monarch No. 1 crops out for 400 feet between 1875 and 2050 feet elevation. It is 1-5 feet thick and was explored for 225 feet in the Monarch No. 1 adit. The vein outcrop locally contained about 1 oz/ton gold (Reed, 1938, p. 63), but assays from underground mostly range from 0.01 to 0.03 ounce per ton gold. There has been little stoping in either Monarch No. 1 or No. 2 underground workings.
Quartz veins or lenses at the Monarch deposits locally contain pyrite, arsenopyrite, galena and minor free gold. The maximum arsenic detected in 11 vein samples was 7000 ppm (MacKevett and others, 1971, table 11; also Kimball and others, 1978, table C42). Arsenic is much less abundant than in the Le Roy mine (MF022) where the arsenic content is occasionally more than 10 percent. Allanite is apparently a characteristic mineral of the granodiorite near the Monarch.
Geologic map unit (-136.850268118924, 58.8663987687071)
Mineral deposit model Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Late Cretaceous or younger.
Alteration of deposit Oligoclase replaces original plagioclase; chlorite, epidote, and calcite are other alteration products (MacKevett and others, 1971, p. 61).

Production and reserves

Workings or exploration The Monarch lodes were discovered in 1924 by Joe Ibach, while the National Monument was closed to mining. After the Monument was opened to mining in 1936, Monarch claims were staked by Ibach and Rex Beach. The adit on Monarch No. 1 is 225 feet long, mostly as a drift. Monarch No. 2 was developed with a 140-foot adit with two short drifts. Minor production came from surface cuts and possibly from a small overhand stope at 70 feet in the No. 1 adit. Reed (1938) sampled a surface exposure in the original Monarch five-claim area located by Joseph Ibach and Rex Beach; an exposed vein contained 0.97 ounce per ton gold, 0.50 ounce per ton silver and 1.08 percent zinc. Rossman (1959, p. 50) reported rich veins near the Monarch No. 1; he thought they were too narrow to be significant.
Indication of production Yes; small
Reserve estimates None.
Production notes A small production of gold, probably from surface cuts.

Additional comments

The Monarch structures are weakly mineralized but relatively strong shear zones. Possibly ore might be found on short segments of northeast- striking veins exposed on the Monarch trend to the south. No prospecting is expected in the near future, because the veins are in Glacier Bay National Park and Preserve.