Double Glacier Occurrence, Redoubt Mining District, Kenai Peninsula Borough, Alaska, USAi

Regional Level Types
Double Glacier Occurrence	Occurrence
Redoubt Mining District	Mining District
Kenai Peninsula Borough	Borough
Alaska	State
USA	Country

This occurrence is owned by Cook Region Native Association.
Location: This occurrence is located near the mouth of Double Glacier in section 13, T. 1 S., R. 22 W., of the Seward Meridian. The occurrence is at an elevation of about 1,000 feet.
Geology: The Double Glacier occurrence is within the lower Jurassic Talkeetna Formation, an approximately 2,575 meter thick sequence of volcanic and volcaniclastic rocks (Determan and Hartsock, 1966). The volcanic section near the prospect is structurally bounded on the west by the Bruin Bay Fault, a major fault system traceable for over 500 kilometers. On the east, the volcanics are unconformably overlain by upper Jurassic marine sediments (Determan and Hartsock, 1965). The Talkeetna Formation is intruded by rocks of the Aleutian range -Talkeetna Mountain plutonic belt approximately 23 km. southwest of the prospect. These intrusives which consist dominantly of coarse-grained quartz diorites and quartz monzonites have been dated between 175 and 145 m.y. ( Steefel, 1987). At the Double Glacier occurrence, the Talkeetna Formation has been divided into three major groups (Steefel, 1987). The lowest group consist of purple and green andesite flows and breccia which locally show well-developed pillows. The middle group that host the mineralization, consists of coarse-grain felsic breccias, reworked volcaniclastic rocks, crystal tuff, and dacite flows. The upper group consist of polymitic andesitic breccias and conglomerates with andesitic flows. Informally, the middle group has been named the Johnson unit (Steefel, 1987). Numerous structures within the unit including turbidites and reverse graded bedding indicate a subaqueous origin. The mineralization consists of strataform massive sulfide layers and lens which contain pyrite, chalcopyrite, and sphalerite. There are no published assay results for this occurrence William Ellis (personal communcation, 1999) speculates that this occurrence is an upper portion of a Kuroko type massive sulfide deposit.
Workings: The occurence was discovered by Anaconda Minerals in 1982 as part of an exploration program at the Johnson River prospect. To date there has been detailed mapping, stream and soil geochemical surveys, and surface trenching and sampling. No assay results are avaible.
Age: Jurassic massive sulfide.
Alteration: The Double Glacier occurence has alteration characteristics of a Kuroko type massive sulfide deposit that include sulfate alteration and silification.

Commodities (Major) - Au, Cu, Zn
Development Status: None
Deposit Model: Kuroko massive sulfide (Cox and Singer, 1986; model 28a)

Other Databases

Link to USGS - Alaska:	KN007

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References