376 
BOLIVIAN COPPER DEPOSITS 
the two districts discloses, despite certain features of similarity, 
features of considerable difference, and renders it rather doubtful 
whether reasoning concerning the genesis of one has any direct 
applicability to that of the other. A close relationship is implied 
in an article by Alfred C. Lane on native copper deposits. After 
mentioning a number of occurrences of native copper ores, of 
which only the Lake Superior and Corocoro districts are of eco¬ 
nomic importance, he summarizes the following characteristics as 
common to them: 
1. All occur in connection with red sedimentaries. 
2. The deposition of the copper is attended by a blanching of 
the sandstones. 
3. The formation of the red sediments is associated with basal¬ 
tic dark-colored lavas containing a large amount of ferrous iron 
and a small percentage of copper. 
4. The native copper is associated with waters containing a 
high percentage of earthly chlorides. 
5. The native copper is characteristically irregular and in the 
nature of a replacement or infiltration of the country rock. 
6. Not absolutely universal is the occurrence of zeolites. 
It is obvious that these characteristics are more applicable to the 
North American native copper occurrences than to the Corocoro. 
Thoroughly applicable to the latter are points 1, 2, 4, and 5. 
Too little is known concerning the Corocoro mine waters to rule 
out the probability that their chemical character is merely a reflec¬ 
tion of the aridity of the climate and the character of the rocks 
through which they have flowed and that it has no genetic signifi¬ 
cance with regard to the ore deposition. The other three common 
characteristics, 1, 2, and 5, though probably significant are not of 
fundamental genetic import. Much of the Lake Superior ore is 
not in red sandstones, hence they were not essential agents in the 
precipitation of the native copper and they were not the source 
of the copper-bearing solutions. The Corocoro copper beds extend 
through a great thickness of strata and the mineralization is so 
closely related to the Corocoro fault that the ore deposition hardly 
took place pari passu with the deposition of the sediments. Con¬ 
sequently the conditions under which the red beds were formed 
were not essential to the precipitation of the ores. In other words, 
12 Types of Ore Deposits, 1911. 
