Unnamed Occurrence (ARDF - TL055; near Lacuna Glacier), Yentna Mining District, Matanuska-Susitna Borough, Alaska, USAi
Regional Level Types | |
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Unnamed Occurrence (ARDF - TL055; near Lacuna Glacier) | - not defined - |
Yentna Mining District | Mining District |
Matanuska-Susitna Borough | Borough |
Alaska | State |
USA | Country |
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Latitude & Longitude (WGS84):
62° 47' 24'' North , 151° 30' 36'' West
Latitude & Longitude (decimal):
Köppen climate type:
Mindat Locality ID:
201827
Long-form identifier:
mindat:1:2:201827:3
GUID (UUID V4):
76fa7619-64a3-493f-b3ba-c05096568b4f
Mineral occurrences in the Dall Trend are all within Denali National Park and Preserve.
Location: Reed and others (1978, locality 31) locate this occurrence west of the Lacuna Glacier at about 5400 feet elevation in the center of Section 10, T. 31 N., R. 12 N., of the Seward Meridian approximately 3500 feet northeast of TL003. The site is within Denali National Park and Preserve.
Geology: This locality is one of several chromite occurrences in a 25-mile-long belt of alpine-type ultramafic bodies that are discontinuously exposed from the Dall Glacier northeast to the Lacuna Glacier which is part of the Dall Trend, described by C.C. Hawley and Associates, Inc. (1978, Fig. 4.1-(C)3 and Fig. 4.0-B). These chromite- and magnetite-bearing dunite and peridotite sills are shown by Reed and Nelson (1980) within a narrow belt of middle to upper Paleozoic sedimentary rocks exposed between the middle Tertiary (38 m.y.) Foraker pluton and the northwest trending fault which places the Paleozoic strata 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. Reed and others (1978) describe these occurrences as magmatic segregations of podiform and disseminated chromite hosted in dunite sills. Chromite occurs as: (1) disseminated rounded grains 1-3 mm in diameter, (2) streaks and lenses, (3) irregular pods up to 6 feet long and (4) lens-like bodies up to 6 feet thick and 60 feet long throughout the dunite. Chromium content of 0.7 to 1% from typical dunite is given in Reed and others (1978). The average of 3 microprobe analyses of one sample: 58.4% Cr2O3 21.1% FeO, 8.9% MgO, and 9.7% Al2O3. Other chromite occurrences in this trend are described in TL002, TL003, and TL008 to TL012.
Workings: Reconnaissance mapping, stream silt and rock sampling are all that have been done here (C.C. Hawley and Associates, Inc., 1978). Chromium content of 0.7 to 1% from typical dunite is given in Reed and others (1978). The average of 3 microprobe analyses of one sample: 58.4% Cr2O3 21.1% FeO, 8.9% MgO, and 9.7% Al2O3.
Age: Mesozoic and (or) Paleozoic (Reed and Nelson, 1980) or Late Cretaceous/early Tertiary (?) (Foley and others, 1997).
Commodities (Major) - Cr, Fe
Development Status: None
Deposit Model: Podiform chromite (Cox and Singer, 1986; model 8a).
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsCommodity List
This is a list of exploitable or exploited mineral commodities recorded at this locality.Mineral List
3 valid minerals.
Detailed Mineral List:
ⓘ Chromite Formula: Fe2+Cr3+2O4 |
ⓘ Magnetite Formula: Fe2+Fe3+2O4 |
ⓘ Pyrrhotite Formula: Fe1-xS |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
Group 2 - Sulphides and Sulfosalts | |||
---|---|---|---|
ⓘ | Pyrrhotite | 2.CC.10 | Fe1-xS |
Group 4 - Oxides and Hydroxides | |||
ⓘ | Chromite | 4.BB.05 | Fe2+Cr3+2O4 |
ⓘ | Magnetite | 4.BB.05 | Fe2+Fe3+2O4 |
List of minerals for each chemical element
O | Oxygen | |
---|---|---|
O | ⓘ Chromite | Fe2+Cr23+O4 |
O | ⓘ Magnetite | Fe2+Fe23+O4 |
S | Sulfur | |
S | ⓘ Pyrrhotite | Fe1-xS |
Cr | Chromium | |
Cr | ⓘ Chromite | Fe2+Cr23+O4 |
Fe | Iron | |
Fe | ⓘ Chromite | Fe2+Cr23+O4 |
Fe | ⓘ Magnetite | Fe2+Fe23+O4 |
Fe | ⓘ Pyrrhotite | Fe1-xS |
Other Databases
Link to USGS - Alaska: | TL055 |
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Other Regions, Features and Areas containing this locality
North America PlateTectonic Plate
- Farewell-McGrath DomainDomain
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