Christophosen

Prospect, Undetermined

Commodities and mineralogy

Main commodities Zn
Other commodities Ag; Au; Pb; Sb
Ore minerals chalcopyrite; galena; pyrite; sphalerite; stibnite
Gangue minerals ankerite; dolomite; quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale C-2
Latitude 64.6988
Longitude -165.5815
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Christophosen prospect is on the ridge between the headwaters of Oregon Creek and Penny River, just downslope and east of elevation 1620. It is about 0.4 mile north of the center of section 24, T. 9 S., R. 34 W. The location is accurate.

Geologic setting

Geologic description

The Christophosen prospect was discovered before 1916. When Mertie (1918) visited the prospect in 1916, he found one caved shaft and reported sphalerite and pyrite with quartz. The locality was visited by Herreid (1968), who reported dolomite with sparsely disseminated galena, chalcopyrite, and sphalerite in an old prospect area. Approximately 500 feet south-southeast of the Christophosen pits, a rubble crop of sphalerite-bearing schist is present that is similar to mineralization found about a mile to the north at the Aurora Creek prospect (NM140). The Christophosen prospect apparently lies stratigraphically above a graphitic quartz schist, as does the Aurora deposit. The zinc content of soils near the rubble crop exceeds 2,000 ppm; the soil also is strongly anomalous in lead and silver. The rubble crop is contained within a broader, north-northwest trending soil anomaly about 1,200 feet long and 400 feet wide notable for samples samples that contain 1,000 ppm or more zinc. A lens of fine-grained cherty rock, possibly an exhalite layer, with disseminated galena, sphalerite, and stibnite appears to be stratigraphically above the sphalerite-bearing schist (Cindy Buxton and C.C. Hawley, written communication 1992). Bundtzen and others (1994) interpret the rocks in the area as a tightly folded complex of felsic metavolcanic schist and mixed chloritic, calcareous, and felsic schist . Till and others (2011) map the host rocks as part of the Devonian Nome Complex that consists of pelitic, calcareous, and graphitic schist and see no evidence of volcanic rocks in the area (Slack and others, 2011).
More detailed work at the Aurora prospect (NM140) about 1.2 miles to the north-northwest indicates that this prospect is part of a north-northwest trending belt of zinc-barite mineralization that has been variously interpreted as a metamorphosed, volcanogenic massive sulfide deposit (Bundtzen and others, 1994) or a Devonian sedimentary exhalative (SEDEX) deposit, metamorphosed in the Cretaceous (Slack and others, 2011). Subsequently, the rocks in the area were subject to blueschist facies metamorphism, then retrograded to greenschist-facies metamorphic rocks in the Jurassic and early Cretaceous.
Geologic map unit (-165.584118586021, 64.6980344836816)
Mineral deposit model Metamorphosed Kuroko-type volcanogenic massive sulfide (Cox and Singer, 1986; model 28a) or sedimentary exhalative (SEDEX) deposit. (Cox and Singer, 1986, model 31a).
Mineral deposit model number 28a or 31a
Age of mineralization Either a syngenetic deposit or a volcanogenic massive-sulfide deposit in early Paleozoic (Devonian?) sedimentary and marine volcanic rocks.
Alteration of deposit Not noted.

Production and reserves

Workings or exploration Several prospect pits are present; a shallow shaft was caved by 1916. Surface examination and sampling by Kennecott Exploration Company in 1991 and 1992.
Indication of production None
Reserve estimates None.
Production notes None.

References

MRDS Number A012786

References

Slack, John, Till, A.B., Shanks, Wayne C., III, Ayuso, R.A., and Belkin, H.E., 2011, Stratabound Zn-Pb-Ag-Ba-F deposits and occurrences in the Nome Complex, Seward Peninsula: Characteristics, origin, and exploration application: Alaska Miners Assocation, 2011 Annual Convention, Abstracts, p. 24-25.
Reporters C.C. Hawley and Travis L. Hudson; D.J. Grybeck (Contractor, USGS)
Last report date 4/1/2012