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University of California Publications in Geology 



[Vol. 8 



line and the waters escaped directly into fissures carrying both sulfids 

 and tourmaline, I should expect to find besides the veins some rather 

 remarkable tourmaliniferous dykes rich in sulfids following similar 

 fissures. I am free to admit, however, that the evidence adduced by 

 Knopf has more weight than most of that which is urged in favor of 

 the hypothesis of magmatic waters. 



LACCOLITHS AND BATHOLITHS IN EELATION TO OKE DEPOSITION 



Leaving now the more controversial side of this question I desire to 

 call attention to some general facts that must be taken into account 

 before it can be brought to a settlement. 



In my experience, contact deposits of ores are not characteristic of 

 the margins of those larger bodies of granitic rocks which have broad 

 contact zones of crystalline schists and which may be regarded as 

 batholiths. I am not as familiar as I should like to be with the smaller 

 laccolithic intrusions of the southwest and Mexico, which Mr. Lindgren 

 suggests I should study, but I have examined some of them and I have 

 spent the field seasons of several years on the great batholiths of the 

 Archean of Canada, and have been particularly interested in their 

 contact phenomena. I have also given some attention to the great 

 Sierran batholith. Those who have focused their attention upon the 

 intrusives of the southwest and Mexico doubtless come to regard them 

 as of the first order of magnitude. But this is far from being the case. 

 They are not in the same class with the vast intrusives of the Archean, 

 and it is very doubtful if any of them are real batholiths. Now if 

 granitic magmas should per se give off ore-bearing solutions and be in 

 that sense responsible for ore deposition on their contacts we might 

 reasonably expect that the larger manifestations of this process would 

 occur on the margins of the great batholiths. This expectation is not 

 realized in fact and I am, therefore, forced to believe that the develop- 

 ment of ore bodies in contact zones is not a characteristic of batholiths, 

 but only of those minor intrusions which are transgressively injected 

 into the earth's crust in the form of laccoliths, sills, etc., and which 

 are doubtless offshoots from the more profound magmas. When such 

 injection takes place sufficiently near the surface to be within the zone 

 of sedimentary rocks, charged as they are with water, there must of 

 necessity be a profound disturbance of the ground- water in the vicinity 

 of the intruded mass and it is thus easy to understand the immediate 

 and genetic connection of ore deposits with intrusive phenomena. 



