The manganese contained in the Plymouth deposit is predominantly in the form of a carbonate (rhodochrosite) whilst the iron exists in both oxide (hematite, magnetite and ilmenite) and carbonate minerals (predominantly siderite). The deposit type is sedimentary in origin and of the stratiform, BIF type. The host sequence consists of Silurian red and grey siliciclastic to calcareous siltstones and shales that have been metamorphosed under lower greenschist facies conditions. In addition to the main oxide, silicate and carbonate facies iron-manganese concentrations, host rocks contain minor magnetite and traces of pyrite in grey siltstone and black shale intervals. The manganese rich iron formation deposits occur in stratiform bodies and represent spatially distinct intervals that accumulated contemporaneously with surrounding sedimentary strata.

Iron and manganese are considered to have been deposited from seawater in an oxidizing environment and host strata have subsequently been structurally thickened through folding and faulting related to the Acadian Orogeny (middle to early Late Devonian in age). Some subsequent remobilization of manganese has occurred and resulted in re-deposition of manganese carbonate and oxides in fracture zones. Additional surficial weathering has also resulted in very limited oxidation at the overburden-bedrock interface, but is typically estimated to be limited to centimetres depth into bedrock.

Historical interpretation of th ........

The mining operation will use a conventional open pit mining method, off-highway haul trucks, and hydraulic excavator. The waste rock and mineral resource will be drilled and blasted using typical grade control methods and blasthole sampling.

Tetra Tech used an overall pit slope angle of 45°, as the required geotechnical data was not available to support the analysis required to assess the pit slope angles. Tetra Tech based this pit slope angle on estimates from previous projects and believes that this value is reasonable.

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