Broken Shovel

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Hg; Sb
Ore minerals cinnabar; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale TA
Quadrangle map, 1:63,360-scale D-8
Latitude 60.806
Longitude -158.841
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Broken Shovel prospect is in the headwaters of an unnamed, north-flowing drainage, 0.5 mile northeast of upper Cinnabar Creek (TA001) and 3.5 miles southwest of USGS benchmark Prom (2,709 feet elevation). The map site is at an elevation of about 1,250 feet, in the NE1/4 of section 12, T 8 N, R 55 W, of the Seward Meridian. The deposit is exposed on the northwest flank of a small ridge separating headwater tributaries to the north-flowing creek; the westernmost of these tributaries is locally called Broken Shovel Gulch. It is accurately located (see Rutledge, 1950, fig. 6) and included in locality 1 of Cobb (1972 [MF 384]; 1976 [OF 76-606]).

Geologic setting

Geologic description

The Broken Shovel prospect is 0.5 mile northeast of the Cinnabar Creek lode mercury mine (TA001). It consists of a zone of discontinuous quartz-stibnite veins along the faulted contact of a vertical mafic dike in Triassic sedimentary rocks (Sainsbury and MacKevett, 1965). The dike, exposed in a few shallow dozer trenches, is 1- to 3-feet-thick and trends N 5-20 E for a distance of at least 320 feet (Sainsbury and MacKevett, p. 40). The quartz veins are narrow, discontinuous, and only locally contain small stibnite lenses and minor cinnabar. Cinnabar was reportedly panned in the gulch drainage downslope from the Broken Shovel prospect. Cady and others (1955) report that sills of silica-carbonate rock (inferred to be altered mafic intrusive rocks) are also present in the gulch.
Geologic map unit (-158.843276900807, 60.8052788833566)
Mineral deposit model Simple Sb deposits (Cox and Singer, 1986; model 27d)
Mineral deposit model number 27d
Age of mineralization Late Cretaceous or Tertiary (?). May be similar in age to other mercury deposits in southwest Alaska. Several of these postdate deposition and deformation of mid-Cretaceous clastic sedimentary rocks and emplacement of Upper Cretaceous or Tertiary intrusive rocks.
Alteration of deposit Quartz veining and silica-carbonate alteration of mafic rocks.

Production and reserves

Workings or exploration A few shallow dozer trenches have explored the prospect.
Indication of production None

References