32 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
than any other, helps us to realize the force of the explosions that brecciated the 
rocks and the thorough mixing of the shattered material, whereby trees and pre¬ 
sumably weathered surface rocks could be so deeply entombed. Such mixing 
could scarcely take place unless the materials now filling the volcanic neck had been 
actually blown into the air, leaving a great pit into which they fell back in chaotic 
confusion. The position of this carbonaceous material affords material support to 
the view, presented in subsequent pages, that the Cripple Creek ores were deposited 
at a very moderate depth; or, in other words, that the post-volcanic erosion has 
effected little more than the reduction of a comparatively small volcanic cone. 
The presence of charred or carbonized wood is by no means uncommon in 
volcanic necks, and has been recorded by Archibald Geikie® in those of Scotland and 
by Cross b in the agglomerate of the Bassick neck in Custer County, Colo. 
INTRUSIVE MASSES WITHIN THE VOLCANIC NECK. 
The breccia, which constitutes the main filling of the volcanic funnel, incloses 
a number of masses of latite-phonolite and of syenite. These bodies are largest 
and most abundant in the part of the central breccia area lying between Victor and 
Cameron—that is, in the southeastern part of the volcanic neck. They are generally 
of very irregular shape and are undoubtedly in most cases intrusive into the breccia. 
Sharp contacts, however, seldom occur, as the adjacent breccia is often composed 
of fragments identical in petrographic character with the massive rock, and the 
massive rock itself is in many places greatly shattered. It is conceivable that 
some of these masses are remnants of larger intrusions solidified early in the volcanic 
period and partly shattered by later eruptions. 
The syenite occurs only within the main breccia area. The largest mass, 
which is inseparably involved with latite-phonolite, is at the south end of the town 
of Independence, and with other bodies exposed in the workings of the Vindicator 
mine. A smaller mass lies just west of the Vindicator body and is exposed under¬ 
ground in the Last Dollar mine. A third intrusion is mapped on the north slope of 
Battle Mountain and has been reached underground in the workings of the Portland 
mine. A fourth mass occurs at the Pointer mine, on the southwest slope of Gold 
Hill, and a fifth near the Logan mine, on Bull Hill. 
In Poverty Gulch are two dikes which were shown as andesite on the first 
geological map of the district. Though decomposed, they seem to be mainly 
syenite with perhaps some latite-phonolite facies. The longer dike is exposed in 
the workings of the Molly Kathleen mine, on the south slope of Tenderfoot Hill. 
The Vindicator syenite mass, which in -all probability consists really of several 
masses associated with latite-phonolite, gives place on the lower levels of that mine 
to latite-phonolite which is known to be continuous with the latite-phonolite of the 
Golden Cycle mine, north of Goldfield. The Last Dollar syenite body continues to 
at least 1,200 feet in depth, but shows many local gradual transitions to latite- 
phonolite. On the whole, latite-phonolite predominates underground in the Last 
Dollar and is probably connected with the syenite and latite-phonolite of the Vin- 
a On the Carboniferous volcanic rocks of the basin of the Firth of Forth—their structure in the field and under the 
microscope: Trans. Roy. Soc. Edinburgh, vol. 39, 1880, p. 471. 
b Geology of Silver Clifl and the Rosita Hills, Colorado: Seventeenth Ann. Rept. U. S. Geol. Survey, 1896, pt. 2, p. 311. 
