|Quadrangle map, 1:250,000-scale||CR|
|Quadrangle map, 1:63,360-scale||A-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Boston prospects, which extend for several hundred feet, are centered about 0.5 mile east of Paul Lake and about 0.3 mile south-southeast of the northwest corner of section 5, T. 78 S., R. 89 E. The prospects, first called Boston by Herreid (1967), are a group of pits, adits, and shafts along the east shore of 'Amazon Lake.' (Amazon Lake is not shown on the USGS 1:63,360-scale topographic map, but it is frequently referred to by name in old reports on the area; it is the small lake about 0.4 mile east of Paul Lake and just southwest of Lake Williams). Maas and others (1991, 1995) also locate the Boston prospects there. However, the Boston prospects are in an area with numerous other claims and prospects, some of which cannot be precisely located or identified in the literature. One or more of the Boston prospects may previously have been described under other names (for example, see CR208-210).|
The Boston prospects east of Amazon Lake have been explored by trenches, open cuts, at least one adit, several shafts, and at least one drill hole. Herreid (1967) describes three prospects. One consists of slumped trenches and a caved adit in chlorite schist. It is a zone more than 30 feet wide of silicified marble and quartz veins that strike N60E and dip steeply. The central part of the zone is an irregular, brecciated quartz vein with less than 1 percent pyrite and tetrahedrite. The second prospect consists of an adit in banded silicified marble ('jasperoid') at least 50 feet wide that contains quartz veins. The dump of the adit is mainly quartz with minor tetrahedrite and copper staining. A sample contained 0.01 ounce of gold per ton. Two inclined shafts nearby are in banded quartzite cut by quartz veins with minor tetrahedrite. A sample contained 0.10 ounce of gold per ton. The third prospect consists of several quartz veins exposed in an adit and in surface pits. One 6-inch-thick quartz vein in marble contains about 10 percent tetrahedrite.
Maas and others (1991) sampled several quartz veins 2.2 to 3 feet thick. The samples contained 420 to 4,789 parts per billion gold; one sample contained 3.94 ounces of silver per ton and 636 parts per million (ppm) copper. Maas and others (1995) also sampled a quartz vein up to 12 feet thick that can be traced for about 530 feet; it averaged 2.7 ppm gold. Houston Oil and Minerals drilled at or near this site in the early 1980s (Oliver and Adams, 1984).The rocks in the Dolomi area are part of the Wales Group of Late Proterozoic and Cambrian age (Herreid, 1967). They are folded into a large dome centered over the eastern third of Paul Lake, and consist of several marble layers 200 to 1300 feet thick, interbedded with calcareous chlorite schist and marble.
|Geologic map unit||(-132.045901569098, 55.1402642002596)|
|Mineral deposit model||Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).|
|Mineral deposit model number||36a|
|Age of mineralization||Veins are younger than the Late Proterozoic or Cambrian host rocks.|
|Alteration of deposit||Silicification of marble.|
|Workings or exploration||Several prospects have been explored by trenches, open cuts, at least one adit, and several shafts. Houston Oil and Minerals drilled at or near this site in the early 1980s (Oliver and Adams, 1984).|
|Indication of production||None|
|Production notes||Apparently none.|
Herreid, Gordon, 1967, Geology and mineral deposits of the Dolomi area, Prince of Wales Island, Alaska: Alaska Division of Mines and Minerals Geologic Report 27, 17 p.
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.
Maas, K.M., Still, J.C., Clough, A.H., and Oliver, L.K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: southern Prince of Wales Island and vicinity: U.S. Bureau of Mines Open-File Report 33-91, 139 p., 12 sheets, scale 1:63,360.
Oliver, D.H., and Adams, J.B., 1984, Dolomi gold project, progress report: Houston Oil and Minerals Exploration Company, 41 p. (Unpublished report held by the Bureau of Land Management, Mineral Information Center, Juneau, Alaska.)
|Reporters||D.J. Grybeck (Applied Geology)|
|Last report date||5/1/2004|