STRUCTURE OF THE GOLf) DEPOSITS. 
165 
Productive fissure zones along basic dikes are in a general way similar to those 
along phonolite dikes. The basic dikes, like the phonolite dikes, readily develop 
platy parting parallel to their walls (PI. XVI, Ii). As a rule, however, the fissures in 
the “basalt” are smaller than those in phonolite, and in some cases, as in parts of 
the Conundrum lode, may form an exceedingly complicated network, as shown in 
PI. XIII (p. 160). 
Some sheeted zones, at the point where they cross a contact between two rocks, 
such as breccia and granite or breccia and phonolite, expand in one or both of the 
rocks into a network of irregular fractures. Such a mass of irregular fissures occurs 
in the granite of the El Paso mine, where the El Paso vein crosses from granite into 
a phonolite dike, and forms an important ore body described on page 354. Some of 
the ore bodies in the Prince Albert and Dead Pine mines are similarly related to the 
intersection of a fissure zone with a contact plane. 
INTERSECTIONS. 
The crossing of one fissure zone by another is a common occurrence in the 
Cripple Creek district, notwithstanding the general' radial arrangement of the most 
important lodes. Often the intersecting fissures have a strike nearly at right angles 
with the main fissure zone and are then usually known as cross veins. In other 
cases the strikes of the intersecting fissures are less than 45° apart and the shorter 
lode is often called a spur vein. In still other crossings the intersection is between 
a nearly vertical fissure zone and a so-called fiat vein. 
In most cases the fissures intersect without noticeable displacement of one by 
the other, a fact that is in full harmony with the usually very slight movement along 
the fissures indicated by their structural peculiarities. The rock near the inter¬ 
section, however, is often irregularly fissured and in many instances constitutes an 
ore body, so that the details of the crossing are not always clear. Intersections 
without visible fault displacement are so numerous that only a small number of the 
observed examples can be here given. Many additional occurrences are noted in 
the detailed descriptions of the mines. 
In the northern part of the Mary McKinney mine (see fig. 32, p. 323) the Mary 
McKinney, No. 1, No. 2, No. 4, No. 6, Black, No. 3 fiat, No. 5 flat, and other veins 
intersect at various points without faulting. Near many of the intersections the 
rocks are traversed by subsidiary fractures containing ore and forming with the 
main fissures some of the widest ore bodies in the mine. In Stratton’s Independence 
mine the flat vein, a nearly horizontal sheeted zone, is crossed by the fissures of the 
Independence lodei The conditions for detecting the occurrence of any displace¬ 
ment are here unusually favorable, but no faulting is apparent. In the northern 
part of the mine the Independence, Bobtail, Emerson, Grant, and other lodes all 
converge in a general way so as to meet the similarly converging Bobtail, Diamond, 
and No. 2 veins of the Portland mine. These lodes come together in a region of 
very complex Assuring, in which, however, there is no evidence of appreciable 
faulting. The Abe Lincoln, Anchork-Leland, Midget, and Anaconda mines all 
afford examples of fissure zones intersecting without faulting. 
There are a few cases, however, of one fissure faulting another. Some of the 
faulting fissures are productive. Others are barren and usually contain soft clay¬ 
like omime. In the Anchoria-Leland mine the fissure zone known as the Fault vein 
O o 
