100 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
widened in outcrop, and the belts of quartzites which bound it on each 
side are thrust away to the right and to the left. There are also numerous 
minor complications in the structure of this hill, some of which are shown 
on the map. This is but one illustration of the complicated and puzzling 
structure found in this district. 
Many of the east-west faults are continuous across only one interval 
between neighboring north-south faults. Others traverse two or three such 
intervals, while some, as the Butte fault, cross the whole district. This 
Butte system, therefore, is less persistent than either of the north-south 
systems which have been described, and the faults belonging to it have 
usually much less throw than the faults belonging to those systems. Of 
the faults whose throw can be measured with a degree of- certainty, the 
Butte appears to be the largest, having a downthrow to the north of about 
400 feet. The Grand Duke fault, in Tourtelotte Park, near the Butte 
fault, is estimated to have a downthrow to the north of 200 feet; the Burro 
fault has a downthrow to the south of about 150 feet; but there are many 
faults in which the displacement averages less than 100 feet, which may 
be a downthrow either to the north or to the south. 
Age of east-west faults—he existence of ore in Tourtelotte Park along frac- 
tures and small faults belonging to the east-west systems shows that this 
set of fractures was originated before the ore deposition, probably about 
the same time as the West Aspen Mountain north-south faults and as the 
Castle Oreek fault itself. Ags examples of such mineralization, the Good 
Thunder fault, which carries an important ore shoot, and the “canyon” 
_ or shoot in the Justice mine, as well as similar shoots in neighboring mines, 
may be mentioned. But nearly all the faults of this system which have 
any important throw are barren, and apparently cut and dispose the ore 
bodies and the inclosing rocks in the same manner, showing that the chief 
movement was post mineral. This is also shown by the faulting of the 
premineral faults, such as the Saddle Rock and the Sarah Jane, as shown 
on the map; also by the faulting of the Castle Creek fault by the Butte 
fault. . . 
As to the relative age of the Justice system of north-south faults and 
the Butte system of east-west faults, it may be noted that the fact that the 
Butte system does not seem to fault the Justice system would indicate 
that they are of nearly the same age. It must be borne in mind, however, 
