226 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
DEPTH AT WHICH DEPOSITION TOOK PLACE. 
The ores were deposited in the fissures of a volcanic mountain. Near its present 
highest point, with an elevation of 10,800 feet above the sea, the ore has been proved 
from the surface to a depth of 1,600 feet, and near the southern base of the volcanic 
lulls, with an elevation of 9,700 feet, it has been followed to a depth of 1,200 feet—in 
each case without notable change in quality but with a distinct decrease in quantity 
(p. 214). From physiographic considerations (p. 38) it is probable that the volcanic 
mountain had an unsymmetrical conical shape and that near the highest points of 
the present time a minimum of 1,000 feet of rocks covered the present outcrops. 
It is further probable that near the southern base the vein croppings of to-day 
were buried at least 500 feet deep. It is concluded that the ores which we see now 
were deposited at moderate depths ranging from a few hundred feet below the old 
surface to a maximum of about 3,000 feet. The occurrence of carbonized tree 
trunks at many places in the breccia (p. 31) tends to confirm this conclusion. 
TEMPERATURE OF THE SOLUTIONS. 
As the solutions moved within a volcanic cone, shortly after the end of the erup¬ 
tions, and as, being heavily charged with silica, carbon dioxide, and hydrogen 
sulphide, they actively deposited material and energetically altered the country 
rock, it follows that they were in all probability hot solutions. The similarity of 
the deposits to those formed by many hot springs emerging at the surface lends 
additional support to this conclusion. The most direct proof is furnished by aqueous 
inclusions in the quartz deposited. In addition to a gas bubble these very often 
contain solid material forming transparent adhesions to the walls of the cavity, 
but evidently once dissolved in the water. No inclusions of carbon dioxide have 
been found. 
On the other hand, the temperature and pressure at which the veins were 
formed were not very high, as shown by the fact that carbonates crystallize freely 
in the rock by replacement and in the fissures by crustification and also by the 
general absence of minerals like biotite, garnet, and pyroxenes, which are apt to 
form during conditions of high temperature and pressure from aqueous solutions. 
The critical point of water ( + 364 C. and 200 atmospheres) was probably not reached. 
We are inclined to believe that the temperatures ranged from + 100° C. to +200° C. 
and the hydrostatic pressure up to 100 atmospheres—that is, for the portions of the 
veins now accessible. 
TIME OF DEPOSITION. 
The ores were formed later than the latest actual eruptions; that is, later 
than the basic dikes. These dikes had solidified and had cooled at least to such 
degree that carbonates could form in them. Although the basic dikes to some 
degree followed the prevailing directions of the fissure system, the latter was not 
formed until after their intrusion. As the paths were opened they were filled bv 
depositing solutions. The filling being in many cases only partial, we may infer 
that the solutions circulated for a limited time only. 
That the veins are not recent is indicated by the formation of considerable 
placer deposits and by the depth and extent of subsequent oxidation. If we assign 
