Monte Cristo Creek; Marie Nabesna Prospect, Chisana Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
Monte Cristo Creek; Marie Nabesna Prospect	Prospect
Chisana Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

The prospect is in the Wrangell-St. Elias National Preserve.
Location: This prospect is at an elevation of about 3,600 feet on Monte Cristo Creek. It is about 3.6 miles upstream of the mouth of the creek and near the west boundary of the Nabesna A-4 quadrangle. The site is in the NE1/4 of section 16, T. 5 N., R. 13 E. of the Copper River Meridian. This is locality 1 of Richter (1973), locality 16 of Richter and others (1975), and National Park Service locality WRST-20 (unpublished data). Cobb and Richter (1980) included this prospect under the name 'Monte Cristo Cr.'. It is located to within a few hundred feet.
Geology: Disseminated molybdenite and quartz-pyrite-molybdenite veins occur in hydrothermally altered volcanic breccia of the Lower Cretaceous, Chisana Formation at its contact with a granodiorite pluton (Richter and others, 1975). A composite chip sample across 200 feet of the contact contained 5 parts per million molybdenum and 100 parts per million copper (Richter and Matson, 1970 [OFR 70-276]). The volcanic rocks of the Chisana Formation are extensively replaced by gypsum-quartz-pyrite assemblages in this part of Monte Cristo Creek (Richter and Matson, 1970 [OFR 70-276]; Richter, 1973, 1976). Richter and others (1975) and Richter, Lanphere, and Matson (1975) consider the granodiorite to be part of the mid-Cretaceous Nabesna pluton that has been dated by K/Ar methods as from 105 +/- 4.0 to 114 +/- 3.4 Ma.
Workings: The deposit has been prospected one or more times since 1967.
Age: Mid-Cretaceous. The deposit is at the contact of a granodiorite considered to be part of the mid-Cretaceous Nabesna pluton for which K/Ar dates range from 105 +/- 4.0 to 114 +/- 3.4 Ma (Richter and others, 1975; Richter, Lanphere, and Matson, 1975).
Alteration: Oxidation is indicated by abundant iron-oxide staining. This part of Monte Cristo Creek is marked by extensive gypsum-quartz-pyrite replacement of the volcanic rocks of the Chisana Formation (Richter, 1973; 1976).
Reserves: The porphyry molybdenum deposits in the Nabesna quadrangle are each estimated to contain 50 million tons grading 0.01 percent molybdenum (Richter and others, 1975).

Commodities (Major) - Mo
Development Status: No
Deposit Model: Porphyry Mo, Low-F (Cox and Singer, 1986; model 21b)

Other Databases

Link to USGS - Alaska:	NB037

Other Regions, Features and Areas containing this locality

References