Unnamed (southwest of Hochandochtla Mountain)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Bi; Mo; W
Ore minerals azurite; chalcopyrite; malachite; pyrite
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale MZ
Quadrangle map, 1:63,360-scale C-4
Latitude 65.5124
Longitude -154.8432
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Alaska Division of Geological and Geophysical Surveys (ADGGS) reported 6 occurrences of sulfide-bearing and/or veined granodiorite in a 6-square-mile area that extends from Hochandochtla Mountain to south of Anotleneega Mountain. The site is located at the most mineralized site, ADGGS station 92DNS113 (Solie and others, 1993 [Public-Data File 93-18]). It is at an elevation of about 1,600 feet, 0.4 mile southwest of the center of section 2, T. 1 N., R. 19 E., Kateel River Meridian. The location is accurate.

Geologic setting

Geologic description

The rocks in the vicinity of these occurrences consist of Lower Cretaceous andesite, pillow basalt, andesitic tuff, volcanic conglomerate, volcanic breccia, chert, cherty tuff, and coquinoidal limestone (Patton and others, 1977). Younger Cretaceous rocks include graywacke and mudstone. Intrusive rocks include Upper Cretaceous dacite and rhyolite, porphyry plugs(?), and a stock of fine-to medium-grained, biotite-hornblende granodiorite. The granodiorite has extensively hornfelsed the bedded country rocks.
In the 1970s, the U.S. Geological Survey identified chalcopyrite and malachite in a fine-grained granitic dike in hornfelsed volcanic rock just south of Hochandochtla Mountain (T.P. Miller, 1978, written communication, in Chapman and Patton, 1978). The Alaska Division of Geological & Geophysical Surveys subsequently collected 8 rock samples at 3 sites on Hochandochtla Mountain (Solie and others, 1993 [Public-Data File 93-18]). The samples included quartz- or quartz-tourmaline-veined biotite granodiorite that contains variable amounts of chalcopyrite, pyrite, malachite, and azurite; andesite with trace chalcopyrite; and andesite agglomerate with chalcopyrite. The samples contained up to 1,179 parts per million (ppm) copper, 47 ppm bismuth, 18 ppm molybdenum, 38 ppm antimony, 350 ppm cerium, and 80 ppm tungsten.
Geologic map unit (-154.845791347583, 65.51183001458)
Mineral deposit model Porphyry Cu (Cox and Singer, 1986; model 17)
Mineral deposit model number 17
Age of mineralization Cretaceous or younger based on the age of the host rocks.
Alteration of deposit Widespread contact metamorphism (hornfelsing).

Production and reserves

Workings or exploration In the 1970s, the U.S. Geological Survey identified chalcopyrite and malachite in a fine-grained granitic dike in hornfelsed volcanic rock just south of Hochandochtla Mountain (T.P. Miller, 1978, written communication, in Chapman and Patton, 1978). The Alaska Division of Geological & Geophysical Surveys subsequently collected 8 rock samples at 3 sites on Hochandochtla Mountain (Solie and others, 1993 [Public-data file 93-18]). The samples included quartz- or quartz-tourmaline-veined biotite granodiorite containing variable amounts of chalcopyrite, pyrite, malachite, and azurite; andesite with trace chalcopyrite; and andesite agglomerate with chalcopyrite.
Indication of production None

References