|Quadrangle map, 1:250,000-scale||PE|
|Quadrangle map, 1:63,360-scale||C-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is at the southeastern tip of Butterworth Island next to the south end of Whiskey Pass, which is the channel between Woewodski Island and Butterworth Island. The deposit extends out into the flat that uncovers at low tide between Butterworth Island and the small unnamed island off its south tip. It is near the northeast corner of section 3, T. 62 S, R. 79 E. The location is accurate.|
The Mad Dog prospect has been known since at least 1978 and has been examined and sampled by a succession of companies: Cominco Exploration, Colony Pacific, Amselco, Kennecott Exploration, and Westmin Resources. It currently (2008) is held by the Bravo Venture Group. Several holes have been drilled over the years; most recently Bravo drilled 4 holes in 2004. Some of the better mineralization is in the intertidal zone and only uncovers at low tide. The mineralization does not appear to extend onto Woewodski Island.
The host rocks on the southern tip of Butterworth Island are greenschist and greenstone of the Triassic Hyd Group (Brew, 1997; Karl and others, 1999). However, most of the island is Upper Cretaceous hornblende diorite.
The deposit consists of volcanogenic massive sulfide layers and lenses in Triassic Hyd Group rocks analogous to other similar deposits in the Duncan-Zarembo mineral belt (Berg and Grybeck, 1980; Berg, 1981). The massive sulfide layers and lenses are from about 0.1 to 1 foot thick , follow the layering in greenschist and phyllite, and consist mainly of pyrite, black sphalerite, and galena. The bands have an unusually high silver content relative to other massive sulfide deposits in the area. One of the better exposed zones of mineralization at the tip of Butterworth Island shows sulfide bands and lenses across 15 feet that extend for about 160 feet along strike. More mineralization was found near the tip of the small unnamed island south of Butterworth Island but it is exposed only at low tide. Still and others (2002) collected 15 samples of the richer portions of the mineralization. They contained from 58 to 3,927 parts per billion gold, 43 to 630.4 parts per million (ppm) silver, 341 to 9.76 percent lead, and 3,951 ppm to 20.1 percent zinc.In their 2004 drilling, Bravo Venture Group (2008) cut a 20-meter-thick mineralized zone. One intercept 3.8 meters long contained 16.4 ounces of silver per ton, 2.8 percent lead, and 22.4 percent zinc, and several other intercepts contained 131 to 437 grams of silver per ton, 0.59 to 5.03 percent lead, and 10.95 to 20.2 percent zinc.
|Geologic map unit||(-133.057223476775, 56.5317543194858)|
|Mineral deposit model||Barite facies of a Kuroko volcanogenic massive-sulfide model (Cox and Singer, 1986, model 28a). Alternatively a barite facies of a volcanogenic Sierran Kuroko model (Bliss, 1992, model 28a.1).|
|Mineral deposit model number||28a or 28a.1|
|Age of mineralization||Upper Triassic based on similarity to other volcanogenic massive sulfide deposits in the area.|
|Workings or exploration||The Mad Dog prospect has been known since at least 1978 and has been examined and sampled by a succession of companies: Cominco Exploration, Colony Pacific, Amselco, Kennecott Exploration, and Westmin Resources. It currently (2008) is held by the Bravo Venture Group. Several holes have been drilled over the years; most recently Bravo drilled 4 holes in 2004.|
|Indication of production||None|
Berg, H.C., 1981, Upper Triassic volcanogenic massive sulfide metallogenic province identified in southeastern Alaska, in Albert, N.R.D., and Hudson, Travis, eds., The United States Geological Survey in Alaska--Accomplishments during 1979: U.S. Geological Survey Circular 823-B, p. B104-B108.
Berg, H.C., and Grybeck, Donald, 1980, Upper Triassic volcanogenic Zn-Pb-Ag (-Cu-Au) mineral deposits near Petersburg, Alaska: U.S. Geological Survey Open-File Report 80-527, 11 p., 1 sheet.
Bravo Venture Group, 2008, http://www.bravoventuregroup.com/en/index.php?page=projects&projectid=14 (as of March 4, 2008).
Brew, D.A., 1997, Reconnaissance geologic map of the Petersburg C-4 quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-J, 21 p., 1 sheet, scale 1:63,360.
Karl, S.W., Haeussler, P.J., and McCafferty, A.E., 1999, Reconnaissance geologic map of the Duncan Canal-Zarembo Island area, southeastern Alaska: U.S. Geological Survey Open-File Report 99-0168, 30 p., 1 sheet, scale 1:150,000.
Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p.
|Reporters||H. C. Berg (Fullerton, California); D.J. Grybeck (Port Ludlow, WA)|
|Last report date||3/4/2008|