I found this This conclusion is best illustrated
by the Standby, Cochrane, Montana, and Montezuma mines. Thus,
structure, as well as lithology, controlled gold deposition in the
chert-silicate units. This combination, of course, is not unique
to the district. It applies equally as well to the Homestake mine
at Lead (Slaughter, 1968, p. 1450) and apparently to a number
of plunging folds of ferruginous chert in the Galena-Roubaix
district (Bayley, 1970). It therefore appears to be a regional
phenomenon which may have an important practical application,
particularly in the Rochford district where large plunging folds
of chert-silicate rocks are very numerous. Moreover, geochemical
sampling indicates that nearly all the major folds are at least
slightly mineralized in surface exposures. Whether this mineralization
increases with depth can only be determined by deep
exploration.