| Basis for focus area |
Manganiferous iron-bearing Ordovician and Silurian slate or shale; see Miller (1947), especially figure 1. Focus areas are based on 3 districts; Northern, Central, and Southern. See Pavlides and Milton (1962) and Cannon and others (2017) for alternate names for the districts. Pavlides and Milton (1962) called the Central district the Maple and Hovey Mountains area. |
| Identified resources |
Identified manganese resources. |
| Production |
Unknown. |
| Status |
Unknown. |
| Estimated resources |
Reserves of 1,300,000 tons Mn from Miller (1947) updated to 323,000,000 tons Mn in Cannon and others (2017), citing work by Kilgore and Thomas (1982). |
| Geologic maps |
Pavlides (1971, 1972), scale 1:62,500; Pavlides and Milton (1962), scale 1:48,000. |
| Geophysical data |
Inadequate Rank 4 to 5 aeromagnetic and Rank 5 aeroradiometric coverage; Some 1950s coverage analyzed by Pavlides and Milton (1962). |
| Favorable rocks and structures |
Main units include Silurian Smyrna Mills Formation; Devonian-Silurian Bell Brook Formation, pelite member; Silurian Maple Mountain Formation; Silurian New Sweden Formation; Silurian-Ordovician Carys Mills Formation. "..sedimentary lenses interbedded with slate and calcareous shale. The manganese ores are partly in hematitic shale, and partly in siliceous, chloritic limestone. The manganese in the primary, unoxidized ore is combined--partly as oxide-silicate and partly as carbonate. The minerals braunite and bementite have been positively identified" (Miller, 1947, p. 1). Cannon and others (2017, p. L16), "The manganese-rich rocks occur in three beds of Silurian age and are of two lithologic types: (a) hematitic shale and slate and hematitic ironstone, and (b) siliceous carbonate rocks. |
| Deposits |
Gelot Hill (MRDS dep_id: 10145670), Capitol Hill, Dudley manganese deposit (MRDS dep_id: 10084656), Higgins manganese deposit (MRDS dep_id: 10306782), Henderson Hill manganese deposit (MRDS dep_id: 10084511), Maple-Hovey manganese deposit (MRDS dep_id: 10084515). |
| Evidence from mineral occurrences |
MRDS; Miller (1947). |
| Geochemical evidence |
Unknown. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Maple Mountain-Hovey Mountain area and North Aroostook district of Cannon and others (2017). |
| Comments |
The largest site is the Dudley deposit (Miller, 1947). Cannon and others (2017, p. L16) state that "Of these identified resources, those of Aroostook County, Maine (Maple Mountain-Hovey Mountain area and North Aroostook district) and the Cuyuna Range in Minnesota (fig. L3) are the only two that are of sufficient tonnage to be significant on a national scale of manganese demand. |
| Cover thickness and description |
1 to 3 m thick glacial drift that is thicker in the valleys (Miller, 1947). |
| Authors |
Gregory J. Walsh, Bernard E. Hubbard. |
| New data needs |
Geologic mapping at 1:24,000 scale. Airborne geophysics. Evaluate prospect locations on lidar. |
| Geologic mapping and modeling needs |
Modern 1:24,000 scale geologic mapping is needed. Some areas have 1:62,500 scale mapping (for example, Pavlides, 1971) and detailed site maps exist for some deposits (Miller, 1947). |
| Geophysical survey and modeling needs |
High resolution aeromagnetic data may image mafic rocks, associated structures, and possibly alteration zones. Radiometric data can help with geologic mapping in vegetated terrane. |
| Digital elevation data needs |
Lidar adequate. |
