Unnamed Occurrence (ARDF - TL010), Yentna Mining District, Matanuska-Susitna Borough, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - TL010)	- not defined -
Yentna Mining District	Mining District
Matanuska-Susitna Borough	Borough
Alaska	State
USA	Country

Mineral occurrences in the Dall Trend are all within Denali National Park and Preserve.
Location: C.C. Hawley and Associates, Inc. (1978, sample site no. 234, Figure 4.0-B) show this occurrence between the Dall and the Yentna Glaciers in the northwest quarter of T. 30 N., R. 14 W., of the Seward Meridian in Denali National Park and Preserve.
Geology: This occurrence is described by C.C. Hawley and Associates, Inc. (1978) as a pod of massive sulfides, mainly pyrrhotite, with exposed dimensions of 4 feet by 20 feet. Assays from the massive sulfides contained as much as 0.14% copper, 0.17% nickel, 0.08% chrome. Soil samples from this part of the ultramafic belt contained values as high as 1500 ppm copper and 6000 ppm nickel. This is one of several chromite occurrences in a 25-mile long belt of alpine-type ultramafic bodies described by C.C. Hawley and Associates, Inc. (1978, Fig. 4.1-(C)3 and Fig. 4.0-B), as part of the Dall Trend, that are discontinuously exposed from the Dall Glacier northeast to the Lacuna Glacier. These chromite- and magnetite-bearing dunite and peridotite sills are shown by Reed and Nelson (1980) in a narrow belt of middle to upper Paleozoic sedimentary rocks that are exposed between the middle Tertiary (38 m.y.) Foraker pluton and the northwest-trending fault which places the Paleozoic rocks over the Mesozoic marine sedimentary rocks (KJs). Foley and others (1997, p. 431) suggest that these ultramafic bodies may be genetically related to the composite plutons (Tcp) of Reed and Nelson (1980) in the upper Yentna River. Other chromite occurrences in this trend are described in TL002, TL003, TL008 - 010, TL012, and TL055.
Workings: Reconnaissance mapping, stream silt and rock sampling are all that have been done here. Assays from the massive sulfides contained as much as 0.14% copper, 0.17% nickel, 0.08% chrome. Soil samples from this part of the ultramafic belt contained values as high as 1500 ppm copper and 6000 ppm nickel.
Age: Mesozoic and (or) Paleozoic (Reed and Nelson, 1980) or Late Cretaceous/early Tertiary (?) (Foley and others, 1997).

Commodities (Major) - Cr, Cu, Ni
Development Status: None
Deposit Model: Podiform chromite (Cox and Singer, 1986; model 8a).

Other Databases

Link to USGS - Alaska:	TL010

Other Regions, Features and Areas containing this locality

References