GEOLOGIC SUMMARY. 25 
to have been most active in the Rampart region, and some of the rocks have been 
rendered somewhat schistose, and others have been brecciated by the forces which 
have been at work. The igneous rocks include both intrusives and extrusives, and 
are present in great variety and abundance in the Rampart region. 
Most of the gold-producing creeks tributary to Minook Creek from the cast head 
in areas composed of slates, quartzites, feldspathic quartzites, chert, and sheared 
chert derivatives, and flow in the lower parts of their valleys through areas of green- 
stone, which are largely tuffaceous. The schistose, fine-grained fragmentals, alter- 
nating with the slates and quartzites, form the greater part of the bed rock in the 
valleys of the streams tributary to Baker Creek. The same rocks strike off north- 
eastward and occupy large areas in the valleys of the headwaters of the Tolovana, 
which were traversed by the Brooks party in 1902, and still farther in the same 
direction are found in the White Mountain section. There is no essential difference 
in the bed rock of the northern and southern sides of the divide in the Rampart 
region, except that the greenstones are confined mostly to the northern side in the 
lower part of Minook Valley below Florida Creek. Victoria Creek, a tributary of 
Beaver Creek, where prospects were reported in the fall of 1904, heads in an area of 
chert, slates, and greenstones, like those of the Rampart region. 
The occurrence of gold has not been traced to a definite relation to any particular 
bed rock or to the quartz seams, which are rather common in the slates. Many of 
the dikes are more or less mineralized, and some of them are reported to carry values. 
The light-colored acid dikes of the Fortymile region, with their associated quartz 
veins, were not observed in the Rampart region. The slates contain generally a 
large amount of carbonaceous matter, and anthracitic material is common in some of 
the small quartz seams. Pyrite is often found in both the slates and the quartz seams. 
On creeks where the conditions are apparently least complex the only rocks observed 
are the carbonaceous slates with quartz seams, which occasionally are a foot or more 
in thickness, and the monzonitic intrusives in the ridge about the headwaters. The 
nuggets have frequently a considerable quantity of quartz attached, and it seems 
probable that the gold has been derived from the small quartz seams. The only gen- 
eral fact which seems to emphasize itself is that the occurrence of gold in quantities 
of economic importance is limited to an area where deformation of the rocks has 
been intense and where there has been much igneous activity. 
