Geologic descriptionPods of pyrrhotite-magnetite skarn occur in the Tushtena Pass unit at the contact with a gabbroic sill (S.S. Dashevsky, written communication, 2002). The Tushtena Pass unit consists mainly of medium- to coarse-grained calcareous quartz-sericite-chlorite schist with carbonate interbeds. The schist is typically green to gray and laminated to layered and contains quartz eyes. Discontinuous bands of siliceous limestone, dolomitic marble, and black pyritic metasiltstone are common. A poorly exposed graphitic member in its upper part is a stratigraphic marker that can be traced by electromagnetic surveys. Quartz-carbonate veins and bands are characteristic of the Tushtena Pass unit. It is intruded and thickened by gabbroic sills and dikes, many of which are associated with local hornfelsing in nearby rocks. |
Geologic map unit |
(-144.076951936642, 63.2748256413581) |
Mineral deposit model |
Iron skarn (Cox and Singer, 1986; model 18d). |
Mineral deposit model number |
18d |
Age of mineralization |
Mid-Triassic, on the basis of the U-Pb zircon age of gabbroic bodies that are related to this deposit (Dashevsky and others, 2003). |