Unnamed (on western Rootok Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Mo; Zn
Ore minerals chalcocite; chalcopyrite; malachite; pyrite
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale UM
Quadrangle map, 1:63,360-scale A-5
Latitude 54.042
Longitude -165.561
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site, anomaly 42 of Christie (1974), is located on the westernmost part of Rootok Island approximately 1/2 mile east of VABM Root. This location is accurate to within 500 feet.

Geologic setting

Geologic description

At this site the rocks consist of amygdaloidal and porphyritic andesites of probable Tertiary or later age. They are cut by diorite dikes or plugs (Christie, 1974). All of the intrusive rocks examined contained pyrite as disseminations and fracture fillings. This occurrence consists of a northern and a southern color anomaly separated by a covered area approximately 1000 feet wide.
In the northern area copper minerals occur along a north-facing sea cliff irregularly for 800 feet. The minerals are mainly malachite and minor chalcopyrite and chalcocite, and are sporadically distributed throughout the area. The minerals are mainly in breccia bodies, up to 60 feet in width, consisting of angular and rotated fragments of quartz-sericite-pyrite in a matrix of comminuted fragments and iron oxides. Malachite is present both in the fragments and matrix. One breccia contains 1 to 2 percent tourmaline. Wall rock around the breccias varies from pyritiferous volcanics to malachite-chalcopyrite-chalcocite-bearing diorite. The quartz-sericite-pyrite alteration grades outward to pervasive propylitization marked by epidote and pyrite.
The southern color anomaly exhibits pervasive propylitic alteration which grades southward to unaltered volcanics over distance of approximately 3000 feet.
Seventeen rock samples collected by the Aleut-Quintana-Duval JV contained up to 159 ppm copper, 0.46 ppm gold, 6 ppm molybdenum, 2.2 ppm silver, and 120 ppm zinc (Christie, 1974).
In 1975 Christie (1976) returned to this site and collected soils and silts and conducted a magnetometer survey of the covered area. This examination revealed strongly altered, biotite-bearing rock containing widely-spaced quartz veins. This material contained up to 790 ppm copper and 0.04 ppm gold.
Geologic map unit (-165.562973779746, 54.0411357466792)
Mineral deposit model Porphyry copper (Cox and Singer, 1986; model 17)
Mineral deposit model number 17
Age of mineralization Probably Tertiary.
Alteration of deposit The rocks exhibit pervasive propylitic alteration consisting of chlorite, epidote, and pyrite. The breccia bodies in the northern area are altered to quartz-sericite-pyrite. Wall rock adjoining the breccias varies from pyritized volcanics to malachite-chalcopyrite-chalcopyrite-bearing porphyritic diorite, whose feldspar phenocrysts are altered to clay.

Production and reserves

Workings or exploration
Christie (1974) conducted reconnaissance geologic mapping and limited sampling. That sampling generally indicated low values of copper and molybdenum and gold values as high as 0.46 ppm and silver values as high 2.2 ppm. Zinc values were moderately anomalous: a number of samples yielded values in the range of 90 to 120 ppm. Although Christie (1974) mentions copper values up to 0.25 percent, his sample data does not support this.
Christie (1976) did some additional work in the covered area in 1975, but concluded the area was not worth drilling.
Indication of production None

Additional comments

This site is on land patented by or conveyed to the Aleut Native Corporation.

References

MRDS Number 10308478

References

Christie, J.S., 1974, Aleut-Quintana-Duval 1974 joint venture, final report: Unpublished Quintana Minerals Corporation report, 24 p., 3 appendices, 2 maps. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Christie, J.S., 1976, Aleut-Quintana-Duval joint venture, final report, 1975, 20 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)
Reporters S.H. Pilcher (Anchorage)
Last report date 1/27/2000