Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

y Sharp (1976) to be a fault slice of Paleozoic carbonate. The limestone is locally
silicified and contains minor disseminated to clotty pyrite and a trace of galena and
sphalerite. A select sample of mineralized limestone, silicified limestone, and silicified
fault-brecciated amphibolite gneiss (sample 05-280, table 8) from the shaft dump show
anomalous zinc (8,340 ppm) and lead (3,960 ppm), and weakly anomalous copper (220
ppm). Gold (0.011 ppm) and silver (3 ppm) are extremely low. A number of small mines
(caved adits) also are present in this area, most with silicified, fault-brecciated
Proterozoic rocks on the waste dumps.
Another area of very small mines and prospects is along the Shavano fault zone
north of Squaw Creek (Sections 3 and 4, T50N, R7E) and extends northeast across the
northern quadrangle boundary (Section 34, T51N, R7E). All of these mines and prospects
are all on silicified, fault-breccias along the Shavano fault. Some of the prospects occur in
the broken rock zone (BR/Xgdf) inboard of the main Shavano fault zone. Small mines are
on silicified, fault-brecciated Proterozoic foliated granodiorite (Xgdf) and prospects are
on silicified, fault-brecciated rhyolite porphyry (Trp) and aphyric rhyolite (Tr) dikes.
Minor quartz veins are locally associated with the silicified breccias. No sulfides were
observed. A sample of silicified, fault-brecciated Proterozoic granodiorite (05-335, table
8) was submitted for geochemistry and shows no anomalous values. The silicification and
quartz veins in the Tertiary rhyolite dikes indicate that some of the silicification in the
Shavano fault zone is younger than about 29 Ma.
A cluster of small mines occurs along the Shavano fault zone on the ridge
between Cree Creek and Lost Creek in the NW 1 / 4 , Section 30, T50N, R7E. The main
rock type is Berthoud-type granite and pegmatite dikes (YXgp) and minor hornblende
intermediated gneiss (Xhig). Silicified, fault-brecciated Proterozoic pegmatite is abundant
and some chalcedonic to vuggy quartz veins are present. One mine dump has minor
epidote-actinolite-chlorite calc-silicates. Minor Cu-oxides occur in the calc-silicates but
mostly occur in silicified pegmatite and gneiss. Some disseminated pyrite, chalcopyrite,
and galena occur in silicified rock and quartz veins. A select sample of mineralized
material from three caved adits (sample 05-854/855/857, table 8) has highly anomalous
copper (1.02 percent), lead (8,990 ppm), zinc (4,810 ppm), and silver (82 ppm). The
195