|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 approximate location of the Buck prospect, as described in early reports (Wright and Wright, 1908, fig. 10; Elliott and others, 1978, loc. 117), apparently coincides with the location of the North Paula prospect, as described by Maas and others (1995, loc. 310). The map site is for the North Paula prospect, at an elevation of about 150-175 feet on the NE flank of Punch Hill (sec 17, T. 77 S., R. 91 E., of the Copper River Meridian). The location of the North Paula prospect 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).
Wright and Wright (1908, p. 139) describe the Buck prospect only as a wide quartz vein, in altered quartzite and schist, that reportedly assayed well in Cu and Au. Maas and others (1995, p. 229) describe the North Paula deposit as seams and clasts of chalcopyrite and pyrite in silicified breccia in metavolcanic hostrock. Their best sample assayed 1.1% Cu across a 6-foot-wide section of the deposit. Workings, probably mainly dating to the early 1900s, included a 12.5-foot adit, a flooded shaft, and several trenches.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||(-131.734678623013, 55.1916529904721)|
|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, probably mainly dating to the early 1900s, included a 12.5-foot adit, a flooded shaft, and several trenches (Maas and others, 1995, p. 229). Maas and others' best sample assayed 1.1% Cu across a 6-foot-wide section of the deposit.|
|Indication of production||Undetermined|
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.
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.
Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.
|Reporters||H.C. Berg, USGS|
|Last report date||7/5/1999|