UTAH ACADEMY OF SCIENCES 123 
Above the smelter is about 700 feet of highly meta- 
morphosed strata consisting first of beds of limestones in 
which are crinoid stems, and a few Productus. The horizon 
is given as the Madera limestones of the Carboniferous, by. 
Waldamare Lingreen. Above the limestones are sandstones 
and shales, also of the carboniferous period. The whole 
series dips to the east 10 to 15 degrees. 
The greatest part of the igneous rocks is a granodiorite 
porphyry of a fairly uniform texture. Under a good lens 
crystals of andesite and hornblende are easily seen, imbed- 
ded in quartz and orthoclase. An analysis of this rock gave: 
SS Tee NR OSG 62.08 1 
ROBO awoke epckaitere aus 4.76 
1, 6 pe eee Ee 4.62 
1) OR Lele 2.84 
Besides the large laccolith there are several dykes in- 
truded into the limestones. One near the top of the moun- 
tain is a grayish-yellow porphyritic mass, without any dark 
crystals. The groundmass is orthoclase and quartz. 
Another dyke just below the one described has a fine grained 
white porphyritic texture with a groundmass of a micro- 
poikilitic intergrowth of quartz and orthoclase. 
‘T have not been able up to the present time to find any 
lamprophyric dykes. 
Contact metamorphism is extremely well shown, espe- 
cially in the roof of the laccolith. The whole sedimentary 
series that overlies the laccolith and forms the western sum- 
mit of the mountains is greatly altered. The limestone 
nearest the igneous rocks is irregularly crystallized and 
garnetized and contains calcopyrite. The shales above the 
limestones show less metamorphism, but they have a baked 
appearance (and have lost to a great degree, their fissility, 
and where they are calcareous hornfels containing diopsite 
and lime feldspars are formed). 
Considerable faulting has taken place subsequent to 
the igneous intrusion. All faults so far examined are of 
the normal type. The dip varies from 70 to 85 degrees and 
the throw from a few inches to 300 feet. 
1U. S. G. S. New Mex. No. 28. 
