Approximately one-half of the 270 samples from the Iron Canyon area, Nevada, analyzed for platinum-group metals, contain measurable amounts of palladium in the 0.001- to 0.02-part per million range with an average of 0.0034 ppm. The rocks include lower Paleozoic sedimentary and volcanic rocks, Tertiary granitic porphyries, and breccia, all of which exhibit various degrees of hydrothermal alteration. Fault-related iron oxides and vein quartz are also present. The area lies astride the outermost fringes of the zone of dispersed alteration visible in outcrops around the middle Tertiary porphyry-copper system at Copper Canyon, Nevada. At Iron Canyon, the palladium concentrations greater than 0.003 ppm seem to be spatially related to the Butte fault zone, a north-striking fault system active during the time of porphyry-type mineralization. Palladium contents vary directly with those of mercury, arsenic, strontium, silver, lanthanum, and boron, as well as with lead, gold, and copper in obviously metallized rocks. This relation probably reflects the mobility of palladium during porphyry-type mineralization. However, our study failed to document conclusively the overall introduction of palladium during mineralization. Among the likely sources of palladium are the lower Paleozoic volcanic rocks or fluids equilibrated with magma (s) associated with the middle Tertiary porphyries.
