Explained by William J. Pickthorn and Michael F. Diggles

On the choice of deposit models

The Northern Cascades contains belts of low- to moderate-grade regionally metamorphosed marine sedimentary and volcanic rocks which are penetratively deformed and cut by high-angle regional-scale faults and crosscutting serpentine bodies. Consideration of this tract as permissive for low-sulfide Au-quartz vein deposits (Berger, 1986) is supported by numerous small gold mines and occurrences in this area that are considered to belong to this model type.

On the delineation of permissive tracts

This tract was defined principally on the presence of belts of low- to moderate-grade regionally metamorphosed marine sedimentary and volcanic rocks depicted on the Washington State geologic map (Hunting and others, 1961) and the personal knowledge of the assessors. Although this tract contains no major low-sulfide Au-quartz vein deposits, several major mesothermal gold districts in similar or possibly equivalent rocks are found to the north in Canada.

Important examples of this type of deposit

No major low-sulfide Au-quartz deposits are recognized in this tract.

On the numerical estimates made

The team was unable to make an estimate because of lack of information on the nature of the gold occurrences in the tract.

References

Berger, B.R., 1986, Descriptive model of low-sulfide Au-quartz veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 239.