Two centers of gold mineralization in the Clearwater Mountains have been identified during a recent geochemical sampling program in the Healy A-1, B-1 quadrangles, Alaska. Both the Timberline Creek center and the Black Creek center are located near the same E-W trending fault system.
Sites of structural weakness along the zone have apparently guided the emplacement of small diorite and quartz diorite stocks that acted as hosts for later gold-quartz-carbonate veins. Recurrent movement along the faults has fractured and locally sheared the intrusives, providing discontinuous dilatant areas for subsequent vein deposition. Most of the auriferous veins are locallized within the fractured intrusives, although gold values in the range 0.02 to 20 ppm are found in much of the limonitic shear zone material in both intrusive and country rock. The coincidence of gold centers with intrusive bodies appears to be principally a tectonic association. Fractured dilatant intrusives along a generally impermeable fault zone have functioned as pipe-like avenues of ascent for mineralizing fluids.
A close association of gold and arsenic exists in both stream-sediment and bedrock geochemical samples. Mercury is concentrated along the major E-W trending shear system, but occurs between the gold centers, implying a crude hypogene zonation outward from the centers along the mineral belt.
The Denali Copper Prospect, discovered in 1963 (Kaufman, 1964, p. 6) and currently being explored is similarly located at a structural intersection along a major shear system trending N. 75° E. Additional minor occurrences of copper are located to the west along the same fault system on the south side of Windy Creek.
