Unnamed Occurrence (ARDF - MM179; southwest of Eldridge Glacier), Chulitna Mining District (Valdez Creek), Matanuska-Susitna Borough, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - MM179; southwest of Eldridge Glacier)	- not defined -
Chulitna Mining District (Valdez Creek)	Mining District
Matanuska-Susitna Borough	Borough
Alaska	State
USA	Country

This part of the Ruth pluton is in Denali Park and Preserve.
Location: The approximate location of this occurrence is on peak 8715 in section 12, T. 22 S., R. 15 W., Fairbanks Meridian.
Geology: This occurrence is in the northern part of the Ruth pluton, a late-stage granite differentiate of the lower Tertiary McKinley batholith (Reed and Lanphere, 1973). The pluton has not been studied in the Mt. McKinley quadrangle, but in the adjacent Talkeetna quadrangle it is locally enriched in fluorine, tin and uranium (Friedmann and Hinderman, 1979; Reed and Nelson, 1980). According to Reed and Nelson (1980), the north part of Ruth pluton is largely leucocratic, coarse-grained biotite or biotite-muscovite granite. Tin is anomalous in pan-concentrate samples collected below iron-stained, altered zones. Fluorite, tourmaline, and topaz, characteristic accessories of tin-granites, occur locally in the north part of the Ruth pluton, and are associated with zircon and apatite, which are typical accessory minerals in less-differentiated parts of the McKinley batholith. A rock sample (Reed and Nelson, number 122) collected about a quarter-mile south of the boundary of the Mt. McKinley quadrangle was dated at 55.7 Ma, a typical age for the McKinley batholith (Reed and Lanphere, 1973).
Workings: As of the date of this record, there is no record of any mineral exploration in the northern part of the Ruth pluton in the Mt. McKinley quadrangle. Reconnaissance exploration of the pluton in the adjacent Talkeetna quadrangle disclosed locally anomalous radioactivity (Friedmann and Hinderman, 1979). The granite is characterized by accessory fluorite, topaz, and tourmaline. Cassiterite or another tin mineral probably is present locally, as indicated by anomalous amounts of tin in pan-concentrate samples.
Age: Early Tertiary.
Alteration: Iron-staining; alteration of feldspar.

Commodities (Major) - F, Sn, U
Development Status: None
Deposit Model: Sn greisen (Cox and Singer, 1986; model number 15c).

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Link to USGS - Alaska:	MM179

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References