The geochemical background prior to mining must be determined by looking at premining sediments within the watershed. These seven metals are present in several different mineralogical sites in the rocks and mineralized zones in the watershed. Minor amounts of metals reside in carbonate phases. Strontium, for example resides almost entirely in the silicate phase. Vanadium resides in the iron oxides hematite and magnetite in volcanic and plutonic rocks.
Cobalt resides in both silicate phases and in pyrite.
Copper, lead, and zinc reside in silicate phases, but are greatly enriched in mineral deposits as are arsenic and antimony. Thus, a comparison between the two data sets will provide some measure of the distribution of the metals present in the different mineralogical phases present in the bed sediments. Steam flow discharge is on figure 9. Placer accumulation occurs when the carrying capacity of the stream is high and the silicate detrital rock fragments are carried away while leaving the heavy-mineral phases behind. Thus, the monitoring of magnetite distribution is an excellent measure of the placering process.