Jumbo

Prospect, Inactive

Alternative names

Marmot, lower basin

Commodities and mineralogy

Main commodities Ag; Mo; Pb; Zn
Other commodities Au; Cu; Zn
Ore minerals chalcopyrite; galena; molybdenite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale BC
Quadrangle map, 1:63,360-scale A-2
Latitude 56.019
Longitude -130.35
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The approximate location of the Jumbo prospect is in Section 36 on the southeast flank of Banded Mountain just above Through Glacier at an elevation of about 3400 feet (Elliott and Koch, 1981, p. 10, loc. 21). The location is probably accurate to within about a quarter of a mile.
Also see Additional Comments field, below.

Geologic setting

Geologic description

The country rocks in the area of this prospect are metamorphosed pelitic strata of the Jurassic or older Mesozoic Hazelton Group, which are underlain and locally intruded by the Triassic Texas Creek Granodiorite; and the Eocene Hyder Quartz Monzonite, which intrudes the Hazelton and Texas Creek rocks (Berg and others, 1977, p. 15-17; Koch, 1996).
The deposit (Buddington, 1929, p. 101) consists of quartz fissure veins up to about 2 feet thick that cut metagraywacke, argillite, and banded hornfels and contain pyrite, galena, molybdenite, and traces of chalcopyrite and sphalerite. A field investigation in 1972 by the U.S. Bureau of Mines did not locate the Jumbo prospect or find the Jumbo adit reportedly driven sometime after Buddington's work (1929). Samples of quartz veins, breccia zones, and iron-stained, locally sulfide-bearing country rocks collected in 1972 in the general area of the Jumbo prospect (Berg and others, 1977, p. 101-110) contained up to 200 ppm Ag, 6 percent Pb, 8 percent Zn, and more than 2000 ppm Mo, but the average values of these metals was much lower. The veins also contain minor Cu, Zn, and Au.
Lead-isotope studies of the galena at the Marmot lower basin prospect (Maas, 1995, p. 229-248) indicate that the deposit is Eocene in age, and contemporaneous with emplacement of the Hyder Quartz Monzonite.
Geologic map unit (-130.351705451066, 56.0186820738289)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Lead-isotope studies of the galena at the Marmot lower basin prospect (Maas, 1995, p. 229-248) indicate that the deposit is Eocene in age, and contemporaneous with emplacement of the Hyder Quartz Monzonite.
Alteration of deposit Local intense iron staining of veins and country rocks.

Production and reserves

Workings or exploration
An adit is said to have been driven sometime after 1929.
Samples collected in 1972 by U.S. Bureau of Mines contained up to 200 ppm Ag, 6 percent Pb, 8 percent Zn, and more than 2000 ppm Mo, but the average values of these metals was much lower.
Indication of production None

Additional comments

The Jumbo prospect on Banded Mountain (Buddington, 1929, p. 101) was originally staked in 1925 with 2 claims, restaked as a 6-claim group in 1933, 1935, and 1941, and covered in 1969 by the Marmot group of 51 claims (Berg and others, 1977, p. 40-41, 100-114). This record covers the area described as 'Marmot, lower basin (Jumbo area)' in Berg and others (1977, p. 101-106).
Site is in Misty Fiords National Monument.

References