Mexican (ARDF #JU028) Au

Mexican

Prospect, Active

Commodities and mineralogy

Main commodities	Au
Other commodities	Ag; As; Cu; Pb; Sb; Te; Zn
Ore minerals	arsenopyrite; calaverite; chalcopyrite; galena; gold; hessite; petzite; pyrite; sphalerite; tetrahedrite
Gangue minerals	albite; ankerite; apatite; calcite; chlorite; ferroan dolomite; muscovite; quartz; rutile; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale	JU
Quadrangle map, 1:63,360-scale	D-4
Latitude	58.867
Longitude	-135.089
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	The Mexican prospect is at an elevation of about 2,050 feet, 2 miles northeast of Pt. Sherman on Lynn Canal and 1 mile west-southwest of Lions Head Mountain in the Kakuhan Range. It is 1/4 mile NW of the Kensington Mine (JU029) in the NW1/4 section 4, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description Note: Beginning in the 1990s, this and other old mines and prospects in the vicinity were consolidated by Coeur-Alaska into a single property (Birak, 2006). They have carried out major new drilling and underground exploration that better defines the mineralization, largely blurs the geologic distinction among the old deposits, and extends the ore bodies greatly. They have developed a coherent modern interpretation of the mineralization as a single deposit which Coeur-Alaska intends to mine as a unit. This deposit is described separately in ARDF as the Kensington (Coeur-Alaska) deposit (JU261). For geologic reference purposes and for their historic value, the pre-Coeur-Alaska data for this and the other old mines and prospects that Coeur-Alaska consolidated are retained in ARDF. The Mexican prospect was discovered in 1887 and developed by 2 adits, a 135-foot crosscut, and a 106-foot drift. The deposit consists of a 1- to 8-foot-thick quartz vein, and a quartz-vein stockwork along a shear zone in Jualin Diorite. The zone trends northerly and dips 60-84 degrees east. The vein is possibly the same as the main vein one at the Horrible Mine (JU027) (Redman and others, 1989).
Geologic map unit	(-135.090819405062, 58.8666699933436)
Mineral deposit model	Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number	36a
Age of mineralization	The age of mineralization in the Berners Bay district is about 55 Ma, the same as the other mesothermal gold-quartz-vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).
Alteration of deposit	Hydrothermal alteration adjacent to the veins is characterized by reddish-brown ferroan dolomite alteration (Miller and others, 1995). Other alteration includes sericitization of plagioclase, chloritization and sulfidization of mafic minerals, and albitization of feldspars (Leveille, 1991).

Production and reserves

Workings or exploration	In its early years, the Mexican prospect was developed by 2 adits, a 135-foot crosscut and a 106-foot drift.
Indication of production	None

References

References Birak, D.J., 2006, Kensington gold project: Unpublished Technical Report for Cour d'Alene Mines, 116 p. (posted on www/.sedar.com, April 20, 2006). Coeur d'Alene Mines Corporation, 2001, Corporate website: http://www.coeur.com; accessed August 2002 Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190. Knopf, Adolph, 1911, Geology of the Berners Bay region, Alaska: U.S. Geological Survey Bulletin 446, 58 p. Leveille, R.A., 1991, Geology and gold deposits of the Jualin mine area, Berners Bay district, southeastern Alaska: Fairbanks, University of Alaska, M.S. thesis, 200 p. Miller, L.D., Goldfarb, R.J., Gehrels, G,E., and Snee, L.W., 1994, Genetic links among fluid cycling, vein formation, regional deformation, and plutonism in the Juneau gold belt, southeastern Alaska: Geology, v. 22, p. 203-206 Miller, L.D., Goldfarb, R.J., Snee, L.W., Gent, C.A., and Kirkham, R.A., 1995, Structural geology, age, and mechanisms of gold vein formation at the Kensington and Jualin deposits, Berners Bay district, southeast Alaska: Economic Geology, v. 90, p. 343-368. Redman, E.C., Maas, K.M., Kurtak, J.M., and Miller, L.D., 1991, Section D: Juneau Gold Belt subarea, in U.S. Bureau of Mines, Mineral investigations in the Juneau Mining District, Alaska, 1984-1988: Volume 2 - Detailed mine, prospect, and mineral occurrence descriptions: U.S. Bureau of Mines Special Publication VOL. 2D, 424 p., 19 sheets. Swainbank, R.C., Bundtzen, T.K., and Wood, J.E., 1991, Alaska's mineral industry, 1990: Alaska Division of Geological and Geophysical Surveys Special Report 45, 78 p.
Reporters	J.C. Barnett and L.D. Miller (Juneau, Alaska ); D.J. Grybeck (Port Ludlow, WA)
Last report date	6/5/2008