KEVETLLE RANGE, ECONOMIC GEOLOGY. 117 
The basalt is similar lit biologically to the later basalt and is prob- 
ably of Pliocene age, since the amount of erosion suffered render- it-. 
effusion in Pleistocene time improbable. 
STRUCTURE. 
The Paleozoic rocks are folded into a monocline striking north and 
south and dipping 15° to 30° W., but a corresponding eastward 
dipping arm of an anticline may be covered by the rhyolite of the 
eastern side of the range. Minor faults are present. Prior to the 
effusion of the rhyolite the rocks formed a rugged mountain range, 
(See fig. 10.) After the outflow of the rhyolite the range was sub- 
jected to orogenic movements, the compressive force acting from the 
east or the west, and the mountains were again uplilted, the rhyolite 
was slightly crumpled, and a north-south sheeting was produced. 
When the basalt flowed out the range was rugged and probably ap- 
proximately as high as at present. The small peak of rhyolite sur- 
rounded by basalt 6 miles w r est of norfh of Reveille Peak was prob- 
ably never complete^ covered by basalt. A decided thickening of 
the basalt occurs at the base of the mountains, but the dip of the flow 
Basalt F' 
.- i^^7^§^il^sss5B»££ri£r t grave! 
Rhyolite -porphyry Weber"- -~^j0<~' s "' ' "~'-' N < ' , ''~£^'Z\./J /N/ '-'iw'^-' 
Rhyolite 
3 miles 
Fig. 10. — East west section across Reveille Range at northern boundary of area surveyed. 
surface, in places 15° to 18°, is probably in part due to recent uplifts 
of the range. The vent from which the basalt was extruded was 
probably near the crest of the range 7 miles north of Reveille Peak. 
ECONOMIC GEOLOGY. 
The abandoned mining camp of Old Reveille lies H miles north of 
the area surveyed. The Gila mine, one of the best known of those 
extensively operated thirty years, ago, is situated in Paleozoic lime- 
stones and quartzites near the rhyolite contact. The ore occurs in 
quartz veins and stringers ramifying through brecciated zones in the 
Paleozoic rocks. The ores on the dump include malachite, azuritc, 
cerussite, and galena, with quartz and gypsum as gangues. Mala- 
chite here and there coats the surface of the dump and has doubtless 
been deposited since the mines were abandoned. Recently consider- 
able work has been done on similar deposits at New Reveille." The 
rhyolite of the Reveille Range, where examined, has not suffered the 
alterations which usually accompany ore deposits. 
" During the field work, New Reveille was believed by the topographers to be outside 
the boundary of the area mapped, but more accurate computations have placed it within. 
In the pressure of reconnaissance work the mines were not examined. 
