| Basis for focus area |
Stratabound manganese oxides occur within the Chapin Wash Formation, which is composed of interbedded conglomerates, sandstone, siltstone, minor tuff and basalts (early to middle Miocene). Numerous manganese veins are also documented in the region. Origin of primary manganese is suggested to be associated with hot-springs (Lasky and Webber, 1949; Spencer and Welty, 1986). Focus area outline from district map of Keith, Gest, DeWitt and others (1983) |
| Identified resources |
Historical production and identified resources of manganese. |
| Production |
Small historical manganese production. |
| Status |
Past mining. American Manganese Inc. has conducted drilling and mineral resource assessments within the last decade (Huang and others, 2012). |
| Estimated resources |
Maggie mine: 8,441,000 metric tons of 8.75% Mn (Kilgore and Thomas, 1982; Cannon and others, 2017). MacGregor open pit: at a base case cut-off of 1% Mn, estimated Indicated resource of 62,201,000 t at an average grade of 2.3% Mn, and an Inferred resource of 20,033,000 t at an average grade of 2.5% Mn (Huang and others, 2012). |
| Geologic maps |
Lasky and Webber (1949), scale 1:31,860; Lucchitta and Suneson (1985), scale 1:24,000; Spencer and others (2013), scale 1:24,000. |
| Geophysical data |
Inadequate Rank 5 aeromagnetic and Rank 3 aeroradiometric coverage. |
| Favorable rocks and structures |
Chapin Wash Formation (stratabound manganese); fissures and veins associated with younger extensional faulting. |
| Deposits |
Maggie mine (MRDS dep_id: 10102532), Alamo Queen mine (MRDS dep_id: 10027684), Black Diamond mine (MRDS dep_id: 10027608), Black Jack mine (MRDS dep_id: 10027635), Priceless mine (MRDS dep_id: 10027640), McGregor mine (MRDS dep_id: 10027643). |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
Manganese oxide mineralogy is hydrated manganese oxide (wad); ancillary minerals include psilomelane, pyrolusite, ramsdellite, coronadite, hollandite, and cryptomelane. Elevated Sr, Ba, and As are associated with Mn mineralization (Derby, 2012). |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
There are two distinct styles of Mn mineralization in the Artillery Peak district: 1) stratiform Mn deposits, and 2) vein Mn deposits. Stratiform Mn deposits in the Chapin Wash Formation are interpreted by Lasky and Webber (1949) to be syngenetic with the host sedimentary rocks, whereas Spencer, Grubensky and others (1989) suggest remobilization of Mn by secondary metasomatic fluids. Vein Mn occurs within or near the stratiform deposits, but are apparently younger than stratiform deposits. Although the two mineralization styles are not obviously related, the spatial association suggests some genetic link (Huang and others, 2012). |
| Cover thickness and description |
Additional resources may be present in stratiform units. |
| Authors |
Joshua M. Rosera. |
| New data needs |
Geochemistry, geophysics. |
| Geologic mapping and modeling needs |
Mapping in area is sufficient. |
| Geophysical survey and modeling needs |
High-resolution, Rank 1 aeromagnetic and radiometric surveys. |
| Digital elevation data needs |
Lidar complete only over part of the eastern third of the focus area; incomplete elsewhere. |
