22 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1913, PART I. 
STRUCTURE. 
The structure of the district is relatively simple. When observed 
locally the sedimentary beds appear essentially horizontal. As one 
goes up the valley, however, the surface of the granite is seen to rise 
from the valley bottom to fully 350 feet above the bottom in a dis¬ 
tance of about 3 miles. The dip of the strata is therefore consid¬ 
erably greater than the grade of the stream. The granite surface 
apparently has a dip of 4°-5° NE. 
Some Assuring and faulting have occurred in the district. Many 
of the dikes, both the pegmatites and the basic dikes, strike about 
N. 70°-80° W. (magnetic) and dip very steeply. These dikes have 
evidently occupied fissures. There is also a prominent jointing in the 
granite having the same general direction. 
The fissures that have been occupied by the dikes were apparently 
formed prior to the deposition of the sedimentary rocks, soon after 
the granite was solidified, but along some of the prominent fissures 
there has been movement that has faulted the sedimentary rocks. 
Such faulting was noted near the McKinley mine, and a fault with 
GO to 70 feet throw crosses the canvon 1 to 14 miles east of Grant’s 
ranch. There has been considerable prospecting along this fault. 
It strikes in the same general direction as the others and is probably 
an old fissure which has been reopened. 
ORE DEPOSITS. 
Copper is the main valuable metal in the district, though the 
ores contain some gold and silver. It is reported that several car¬ 
loads of copper ore were shipped about 10 years ago. A matte 
smelter was erected in the district some years ago, and a few tons of 
ore treated. 
The ore deposits occur in fissures that cut both the igneous and 
sedimentary rocks. Several of the ore fissures are apparently due 
to later movements along the fissures in which the basic dikes were 
intruded,'and thus there is apparently a close relation between these 
dikes and the ore deposits, though basic dikes are not associated with 
all the deposits. 
In the ore deposits associated with basic dikes the vein usually 
lies along one wall of the dike, between the dike and the granite. 
The other deposits are distinct fissure veins with granite or shale 
walls, or where faulting has occurred granite may form one wall and 
shale the other for short distances. Most of the prospecting has been 
done in the igneous rocks, though on the Nancy claim ore occurs in 
the shale a short distance above the granite. Alteration of the mas¬ 
sive igneous rocks along fissures has usually been slight, but where 
the fault fissures have cut the sandstones there has been a marked 
