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Paired rock and soil samples were collected at widely spaced locations in large segments of the porphyry-metal systems of the Montezuma district in central Colorado and of a northwestward extension of the Summitville district into Crater Creek in southern Colorado. The paired samples do not covary closely enough for one sample medium to proxy for the other. However, the areal distributions of elements in both rocks and soils in these two districts conform to alteration zoning as defined by mineralogy. Differing geochemical patterns of rocks and soils reflect species-dependent responses to weathering. Soils appear to be statistically enriched in ore elements and depleted in rock elements as compared to the matching rocks. These differences are largely artificial, owing to different methods of sample preparation and chemical analysis for rocks and for soils. The distributions of metals in soils delineate the occurrence of ore-metal minerals, mostly from vein deposits, whereas the distributions of metals in rocks conform to zones of pervasive hydrothermal alteration and to the distribution of varied mineral deposits among these zones. Rock and soil samples are equally useful, of comparable map resoluton, and complement one another as a basis for geochemically mapping these porphyry-metal systems.

Metals Score = Sum of the products: (workings size)X(mineral mode) where (workings size"), estimated from size of dump, is 1 for a prospect pit 2 for a small mine (3-15 m of adit and (or) shaft) A for a medium mine (15-60 m of workings) 8 for a large mine (more than '60 m of workings). and (mineral mode) is estimated from vein fragments on the dump as 1 for a trace to as much as 2 percent 2 for 2-15 percent 4 for 15-30 percent 8 for 30 per cent.or more.. The minerals whose modes are used in scoring are arsenopyrite,

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