38 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
Geological structure. — The sediments in the immediate vicinity of 
the Park City area have a general northeast-southwest strike, and an 
average dip of about 40° NW. In general, then, the highest, or young- 
est beds occur in the northwest portion of the area, and the lowest or 
oldest in the southern and southeastern portions. But they have suf- 
fered strong deformation from two potent factors — Assuring with fault- 
ing, and intrusion. Although intense fracturing occurred in both 
north east- south west and northwest-southeast directions, the prevailing 
trend of the principal fissures thus far studied is northeast- southwest. 
The more common dip is steeply to the northwest, although some impor- 
tant fissures of this series dip to the southeast. The intrusions occur 
as regular laccolithic masses and as dikes. They extend northeast- 
ward through the district, in a direction accordant with the zone of 
weakness indicated by t lie fissures, from the great dioritic body of 
Clayton Peak on the sout Invest to extensive extrusive masses on 
the northeast. They sometimes disturb the prevailing dip of the 
sediments and cause local doming, as on the divides to the southeast 
and southwest of "Bald Mountain. Distinct southerly dips noted in 
the latter locality emphasize the general laccolithic character of this 
great northeast-soul invest, belt of intrusives. 
ECONOMIC GEOLOGY. 
General. — During the season of 1902 work was directed chiefly 
toward examining the areal geology with a view to establishing a firm 
foundation for later underground studies. Such information as was 
secured about economic questions was necessarily of a preliminary 
nature, so that only a few general characteristics will be given in this 
statement of progress. 
The Park City mining district stands very prominently among the 
great mining districts of this country as the home of large bodies of 
silver-lead ore carrying minor values of gold and copper. In 1901 
Park City mines supplied, roughly, seven -elevenths of the total out- 
put of silver from Utah and were the main factor in maintaining Utah's 
rank as third among the silver-producing States. 
Although relatively young, Park City is, in several ways, a great 
camp. Mining is conducted on an extensive scale, according to 
advanced methods, by able, experienced men. Ten shafts have 
reached a depth of at least 1,000 feet, 6 are down 1,300 feet or more, 
and 1 — that one, too, whose collar is lowest — has attained a depth of 
2,000 feet. There are four long drain or work tunnels, the longest of 
which extends out to the eastern slope, a distance of about 3 miles. 
Three large, highly efficient concentrating mills have been erected at 
individual properties for private work, and an enlarged sampler and 
a recently remodeled zinc plant are located below the town for custom 
work. An aerial tramway and a broad-gage railroad transport ores 
