Section 21 Prospect, Goodpaster Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Section 21 Prospect	Prospect
Goodpaster Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

The Section 21 prospect is located within Doyon, Ltd. selected or conveyed land. For more information contact Doyon, Ltd., Fairbanks, Alaska.
Location: The Section 21 prospect is at an elevation of 4,700 feet on the southeast side of a ridge that extends south from Mount Harper. The prospect is about 2.5 miles southeast of Mount Harper in the headwaters of the Healy River. The coordinates are the approximate center of the prospect, in section 21, T. 8 S., R. 20 E, of the Fairbanks Meridian. The location is accurate. The Mount Harper area is locality 6 of Cobb (1972 [MF-393]). The Section 21 prospect is located within Doyon, Ltd. selected or conveyed land.
Geology: The Section 21 prospect is in the Mount Harper quartz-monzonite-granodiorite intrusive complex (WGM Inc., 1978). Biotite from the Mount Harper granite gave a 40Ar/39Ar plateau age of 105.8 +/- 0.4 Ma (Newberry and others, 1996). Mineralization and alteration at the Section 21 prospect is associated with a quartz porphyry-aplite plug about 800 meters in diameter (WGM Inc., 1978). A northeast-trending andesitic to dacitic dike complex intrudes both the quartz porphyry and granodiorite. The quartz porphyry-aplite plug contains quartz-molybdenite veining; the quartz veinlets are generally less than 1 millimeter wide. The molybdenite is fine grained, and pyrite is also present. In the quartz porphyry-aplite plug, silicification is the dominant alteration type, with lesser amounts of sericite and clay. Similar alteration is also present in the granodiorite near the quartz porphyry contact. Airborne magnetic surveys detected a magnetic high centered under the altered plug. Samples of vein material in the quartz-porphyry-aplite plug contain as much as 500 ppm molybdenum and 40 ppm tungsten. Samples of milky-quartz, vein material that contains bladed wolframite bordered by scheelite assays as much as 0.4 percent WO3 and 14 ppm silver. Samples collected by the U.S. Bureau of Mines (1995) include a wolframite-bearing quartz vein with 1.7 percent tungsten and 14 ppm silver and aplite and quartz-vein material with 180 ppm molybdenum. Muscovite from a quartz-wolframite vein at the Section 21 prospect gives a 40Ar/39Ar plateau age of 102 +/- 0.4 Ma (Newberry and others, 1998). There are several other molybdenum-tungsten prospects in the MtountHarper area, including VABM Good (EA092), Larsen Ridge (EA091), Quartz-Porphyry (EA094), and Airplane Ridge (EA093). Molybdenite in a quartz vein on the southern slope of Mount Harper was first reported by Chapin (1919). Anomalous tungsten, copper, and molybdenum values were found during stream-sediment reconnaissance in the Mount Harper area by WGM Inc. in 1975; this was followed by geologic mapping and rock sampling in 1976 (Dashevsky and others, 1986). Molybdenum mineralization was discovered at the Section 21 prospect in 1977 (WGM Inc., 1978). WGM Inc. concluded that low grades at surface could not be expected to improve with depth. In 1979, Union Carbide Corp. decided that the property showed features similar to large porphyry molybdenum deposits and that the property warranted drilling (WGM Inc., 1998 [DLR 98-10]). A drill hole by Union Carbide Corp. in 1981 was aborted early without penetrating mineralization (U.S. Bureau of Mines, 1995).
Workings: Molybdenite in a quartz vein on the southern slope of Mount Harper was first reported by Chapin (1919). Anomalous tungsten, copper, and molybdenum values were found during stream-sediment reconnaissance in the Mount Harper area by WGM Inc. in 1975; this was followed by geologic mapping and rock sampling in 1976 (Dashevsky and others, 1986). Molybdenum mineralization was discovered at the Section 21 prospect in 1977 (WGM Inc., 1978). WGM Inc. concluded that low grades at surface could not be expected to improve with depth. In 1979, Union Carbide Corp. decided that the property showed features similar to large porphyry molybdenum deposits and that the property warranted drilling (WGM Inc., 1998 [DLR 98-10]). A drill hole by Union Carbide Corp. in 1981 was aborted early without penetrating mineralization (U.S. Bureau of Mines, 1995).
Age: Muscovite from a quartz-wolframite vein at the Section 21 prospect gives a 40Ar/39Ar plateau age of 102 +/- 0.4 Ma (Newberry and others, 1996).
Alteration: In the quartz porphyry-aplite plug, silicification is the dominant alteration type; there are lesser amounts of sericite and clay. Similar alteration is also present in the granodiorite near the quartz porphyry contact.

Commodities (Major) - Mo, W; (Minor) - Ag
Development Status: None
Deposit Model: Porphyry Mo (Cox and Singer, 1986; model 21b).

Other Databases

Link to USGS - Alaska:	EA095

Other Regions, Features and Areas containing this locality

References