
ORE-FORMATIONS 241 
but here and there invading both overlying and underlying 
strata (see Fig. 91). 7 

FIG. 90.—TIRANSVERSE LODE. (After R. Beck.) 
Systems of Lodes.—While lodes often occur singly, it 
is more frequently the case that several or many are 
associated so as to form one or more systems. Their general 
disposition recalls that of the basalt-dykes described in 
Chapter XIV. Like these, they trend in certain definite 
directions, some appearing 
imeetnue faults, others in 
simple rents or fissures. 
In certain regions only one 
such system may be pre- 
sent; in other places two 
Of more systems may 
appear, one set crossing 
another. As the fissures 
and faults in which they 
@Geeur are the result of 
crustal movements, it is FIG. 91.—COINCIDENT LODE. (After 
not surprising that groups R. Beck.) 
of parallel lodes_ should 
often bear a definite relation to the principal folds and flexures 
of aregion. Some, therefore, coincide with the average strike 
of the country-rock, while others traverse the strike more or 
less at right angles. In mountain tracts lodes not infre- 
quently run parallel to the general axis of elevation. Hence, 
if the date of the elevation be known, the age of the faults 
Q 

