Geologic description
Maddren (1913) first identified quartz veins and veinlets along joint surfaces in bedrock on upper Right Fork, noted that at least one of the veins contained sulfides as well as specks and flakes of free gold. The best mineralization exposed at this site is just southwest of 'Friday the 13th Pup', a small tributary to Right Fork in the northeast quarter of section 13, T. 31 N., R 12 W. (Eden, 2000; Kurtak and others, 2002). Numerous thin quartz veins cut interbedded phyllite and schist of the Upper Devonian Beaucoup Formation (Dillon and others, 1986). Eighteen veins spaced at about 5 foot intervals, occur in one 100-foot-wide exposure of the phyllite near Friday the 13th Pup. The veins average about 0.5 inch thick; they generally strike about N60W and dip 75SW. The veins consist of coarse, white quartz, calcite, ankerite and dolomite, 1-2 percent pyrite, and sparse arsenopyrite, galena, hematite, marcasite, pyrrhotite, sphalerite, and stibnite. Visible gold occurs in some of these veins, mostly along their margins. A sample of a vein with visible gold contained 17.8 parts per million (ppm) gold Other veins contain 415 parts per billion (ppb) to 63.56 ppm gold, 126 to 3,802 ppm arsenic, and 7 to 748 ppm antimony. Samples of phyllite with minor pyrite in the vicinity of the veins contained 13 to 38 ppb gold. The phyllite along Right Fork from Friday the 13th Pup down to Vermont Creek is cut by similar veins that contained up to 815 ppb gold, 1,137 ppm copper, and 1,065 ppm arsenic. A cobble-size boulder of quartz with gold and 1 percent stibnite, presumably from a local source, was found by local placer miners in Right Fork (Dillon, 1982). |
