Geologic descriptionThis prospect is in the west part of the Windy Creek stock, a mid-Cretaceous composite pluton of quartz monzonite, monzonite, syenite and some melanite-bearing nepheline syenite (Miller and others, 1971; 1972). Latite and greenish quartz porphyry, both commonly pyritiferous, and biotite granodiorite dikes locally crosscut the alkalic-related phases of the Windy Creek stock (Miller and others, 1971; 1972; Till and others, 1986). Roof pendants of metamorphic rocks are present. Miller and others (1971) collected five samples over a distance of about 2 miles. A sample of an oxidized quartz vein, their sample locality 8, contained 1,500 ppm Mo, 3,000 ppm Pb, 1,500 ppm Zn, 500 ppm Sn, 3 ppm Ag, and greater than 1,000 ppm La. The other four samples collected by Miller and others (1971) included quartz veins, quartz-veined monzonite, and oxidized aphanitic intrusive rock. Except for the aphanitic intrusive rock, these samples contained anomalous metal contents including up to 7 ppm Ag, greater than 5,000 ppm Ba, 15,000 ppm Pb, 700 ppm Mo, and 150 ppm Sn. In general, the west side of the Windy Creek stock is fractured and both quartz-sulfide and quartz-fluorite-sulfide veins are present (Till and others, 1986). Rare quartz veins up to 5 inches wide contain up to several percent fluorite, 1 to 2 percent molybdenite, galena, and sphalerite. Thin quartz veinlets containing pyrite, fluorite, molybdenite, scheelite, and minor galena and sphalerite are more common although stockwork vein systems have not been observed (Till and others, 1986). Alteration in the intrusive rocks includes limonite staining, weak to strong sericitization of plagioclase, and variable chloritization and sericitization of hornblende (Till and others, 1986). This area was staked in the 1970s as a potential porphyry molybdenum prospect. |
