Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

percent; highest copper value from quadrangle), gold (6.7 ppm; highest gold value from
quadrangle), and silver (112 ppm; second highest silver value from quadrangle). This
sample is has very low zinc (110 ppm) and lead (70 ppm). The sample suggests that the
pegmatites locally have disseminated chalcopyrite with relatively high gold and silver
values and explains the high interest in prospecting the pegmatites.
Another cluster of small to medium mines and prospects is present about 13,000 ft
west-southwest of Maysville, on the ridge between Como and McClure Creeks. The
mines and prospects are in biotite felsic gneiss (Xbfg) and muscovite felsic schist (Xmfs)
with abundant Berthoud-type pegmatites. The pegmatites have coarse magnetite crystals
and some muscovite. The main mines have sorted “ore” piles of quartz veins, vuggy
quartz veins and gossan material with some remnant chalcopyrite and galena. A
composite sample (05-237/237A/238, table 8) was collected from sorted piles from three
of the larger mines. The sample shows highly anomalous lead (1.96 percent), zinc (0.96
percent), copper (0.38 percent), and silver (27 ppm). The open-space, locally vuggy
character of the veins suggests they may be epithermal veins. A polished thin section
shows about 15 percent barite gangue and 5 percent carbonate gangue in the quartz veins.
Sulfides include chalcopyrite and galena, with much of the chalcopyrite replaced by
hematite.
The origin of the sulfide (-oxide) Zn-Cu-Pb-Ag mineralization is problematic.
The stratabound character and the meta-volcanic/metasedimentary protoliths are
supportive of a Proterozoic, stratabound and strataform massive sulfide origin. Although
the mineralized zones are relatively small in the Maysville quadrangle, the potential for
larger mineralized zones is suggested by nearby deposits like the Sedalia mine, where
grades were significantly improved by supergene enrichment. Overall, there is low to
moderate potential for the discovery of additional small, Cu-Zn-Pb-Ag-Au orebodies in
the Maysville quadrangle.
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