|Quadrangle map, 1:250,000-scale||KC|
|Quadrangle map, 1:63,360-scale||A-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Bay View mine is at an elevation of less than 100 feet, about 300 feet west of the shoreline of Seal Cove, and about 0.3 mile south-southwest of the west head of the cove. The site is in section 17, T. 77 S., R. 91 E., of the Copper River Meridian. It corresponds to loc. 118 in Elliott and others (1978), and to loc. 311-12 in Maas and others (1995). The location is accurate within a hundred feet or so.|
Southern Gravina Island is underlain by an assemblage of undivided Silurian or Ordovician metamorphosed bedded and intrusive rocks; a stock and associated dikes of Silurian trondhjemite that cuts the metamorphic assemblage; and a sequence of Upper Triassic carbonate, clastic, rhyolitic, and basaltic strata that unconformably overlies the older rocks (Berg, 1973, 1982; Berg and others, 1988). The rocks are complexly folded and are cut by high-angle faults and by low-angle thrust faults. In many places, the Triassic rhyolite and the rocks beneath it are permeated by microscopic particles of hydrothermal hematite, giving them a pink, purple, or red hue (Berg, 1973, p. 14).
The Bay View deposit consists of a sulfide-bearing, quartz- and calcite-cemented, fault-breccia zone 30-40 feet wide that cuts metarhyolite, trondhjemite, and a prominent mafic dike (Brooks, 1902, p. 70; H.C. Berg, unpublished field data, 1968, 1969). The sulfide minerals include pyrite, chalcopyrite, and a little bornite and sphalerite. Brooks (1902, p. 70) describes two fault zones at this site. One strikes N30E; the other strikes about N60W and carries a foot-thick pyritic quartz vein that in the early 1900s had been explored by a 20-foot drift. Locally, quartz-calcite fissure veins in the mafic dike contain lenses of specular hematite up to several inches thick and several feet long.
Workings at the Bay View consist of a northwest-trending adit near sea level about 300 feet west of tidewater (Maas and others, 1995, p. 227). The adit, evidently an extension of the 20-foot drift described by Brooks, is accessible for about 200-250 feet, beyond which the roof has collapsed beneath a creek, and the workings are flooded. A small smelter shipment reportedly was made in the early 1900s (Cobb and Elliott, 1980, p. 13).
Samples of the breccia zone collected by the USGS in the 1960s contained up to 10 ppm Ag, 0.10 ppm Au, 200 ppm As, more than 2% Cu, and 150 ppm Sn (Koch and Elliott, 1978 [OFR 78-156A]).Maas and others (1995, p. 227) report that copper mineralization on southern Gravina Island generally is associated with faulting. The deposits are mainly in meta-andesite (greenschist) and trondhjemite, but also in the overlying Triassic strata. The deposits are chiefly chalcopyrite- and pyrite-bearing quartz fissure veins, but the sulfide minerals also occur as disseminations in the metavolcanic rocks, in silicified zones in the trondhjemite, and as clasts or pods in silicified or carbonatized breccia. The character and setting of the deposits suggest that they mainly are polymetallic veins of Late Triassic or younger age.
|Geologic map unit||(-131.730678571167, 55.1866531792642)|
|Mineral deposit model||Polymetallic veins (Cox and Singer, 1986; model 22c)|
|Mineral deposit model number||22c|
|Age of mineralization||Late Triassic or younger.|
|Alteration of deposit||Probably local silicification, carbonatization, pyritization, and introduction of hydrothermal hematite.|
|Workings or exploration||
Workings at the Bay View consist of a northwest-trending adit near sea level about 300 feet west of tidewater (Maas and others, 1995, p. 227). The adit, evidently an extension of a 20-foot drift described by Brooks (1902. p. 70), is accessible for about 200-250 feet, beyond which the roof has collapsed beneath a creek, and the workings are flooded.Samples of the breccia zone collected by the USGS in the 1960s contained up to 10 ppm Ag, 0.10 ppm Au, 200 ppm As, more than 2% Cu, and 150 ppm Sn (Koch and Elliott, 1978 [OFR 78-156A]).
|Indication of production||Yes; small|
|Production notes||A small smelter shipment reportedly was made in the early 1900s (Cobb and Elliott, 1980, p. 13).|
Berg, H.C., 1982, The Alaska Mineral Resource Assessment Program; guide to information about the geology and mineral resources of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Circular 855, 24 p.
Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map I-1807, 27 p., scale 1:250,000.
Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.
Cobb, E.H., and Elliott, R.L., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1053, 157 p.
Elliott, R.L., Berg, H.C., and Karl, S.M.,1978, Map and table describing metalliferous and selected non-metalliferous mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-73B, 17 p., 1 sheet, scale 1:250,000.
Koch, R.D., and Elliott, R.L., 1978, Analyses of rock samples from Ketchikan quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 78-156-A, 162 p., 1 sheet, scale l:250,000.
|Reporters||H.C. Berg, USGS|
|Last report date||7/5/1999|