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Trench 7 - Divide Zone (Bonanza Hill)

Prospect, Undetermined

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Commodities and mineralogy

Main commodities Au
Ore minerals arsenopyrite; gold; pyrite
Gangue minerals albite; calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale C-1
Latitude 64.5833
Longitude -165.3941
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Trench 7--Divide deposit is at an elevation of 450 to 465 feet about 1,200 to 1,500 feet due east of the rounded top of Bonanza Hill. The map location is in the northwest corner of section 36, T. 10 S., R. 34 W., Kateel River Meridian, and it is accurate.

Geologic setting

Geologic description

The Trench 7 - Divide deposit was identified from exploration by BHP in 1990 and by Newmont Mining Company in 1992; there are some old trenches and cuts of uncertain age on the deposit. The area was mapped by Thomas Borovicka for Newmont in 1992; his map was modified for Kennecott Exploration Company by C.C. Hawley in 1993 and 1994.
The Trench 7 - Divide deposit appears to be bounded on the northwest by a steep fault that strikes N50E. The apparent displacement, evidenced by offset of a calcareous quartz-mica schist layer, is about 10 feet. Southeast of the fault, the deposit is about 200 feet across. Locally, there are sheeted veins of calcite and quartz; older sloughed trenches show accumulations of vein quartz boulders. The deposit is irregular; locally it contains 0.05 to 0.07 ounce of gold per ton. It is possible that the deposit continues to the northeast to Placer Dome trenches 88-3, -4 and -5 (NM223). Bonanza Hill is mainly underlain by nearly horizontal calcareous quartz-muscovite schist and marble probably of early Paleozoic protolith age (Hummel, 1962 [MF 247]; Sainsbury, Hummel, and Hudson, 1972 [OFR 72-326]; Till and Dumoulin, 1994; Bundtzen and others, 1994).
Geologic map unit (-165.39670467543, 64.5825347619276)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Mid-Cretaceous; veins cross cut regionally metamorphosed schist; see NM207.

Production and reserves

Workings or exploration This prospect has been explored by numerous trenches and shallow drill holes.
Indication of production None

References

MRDS Number 10308001

References

Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress report on the geology and mineral resources of the Nome mining district: Alaska Division of Geological and Geophysical Surveys, Public Data-File 94-39, 21 p., 2 sheets, scale 1:63,360.
Cobb, E.H., 1972, Metallic mineral resources map of the Nome quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-463, 2 sheets, scale 1:250,000.
Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Nome quadrangle, Alaska: U.S. Geological Survey Open-File report 78-93, 213 p.
Hummel, C.L., 1962, Preliminary geologic map of the Nome C-1 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-247, 1 sheet, scale 1:63,360.
Sainsbury, C.L., Hummel, C.L., and Hudson, Travis, 1972, Reconnaissance geologic map of the Nome quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 72-326, 28 p., 1 sheet, scale 1:250,000.
Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, v. G-1, p. 141-152.
Reporters C.C. Hawley and Travis L. Hudson
Last report date 7/10/2000