CHAPTER II 

 ORIGIN OF ORE DEPOSITS 



Meteoric Origin. In the light of the new planetesimal hypothe- 

 sis of the earth's origin which has been so admirably worked out 

 by Prof. T. C. Chamberlain there seems to be a continuous shower 

 of extraterrestial material falling upon the surface of the earth. 

 If this material strikes the land it mingles with the soil almost 

 unnoticed. If it falls into the sea its high specific gravity 

 carries the material to the ocean bottom where it is buried in 

 the muds of the sea floor. If it falls upon the Arctic snow 

 fields it enters into the ice and imparts the peculiar banded 

 appearance characteristic of so many glaciers. Wherever this 

 shower of meteoric dust may fall it becomes a possible source of 

 ore deposits through segregation by vadose waters. 



Number of Meteorites. According to Prof. C. A. Young 

 from 15,000,000 to 20,000,000 of meteorites enter the earth's 

 atmosphere every 24 hours. One of the most noted of modern 

 meteoric masses is that of the Canyon Diablo which fell in 

 eastern Arizona. C. R. Keyes says that 20 miles east of the 

 San Francisco mountains, in the midst of the vast level plain 

 forming the general surface of the high plateau, is a low mound 

 called Coon Butte. The center of this butte contains a crater- 

 like depression about 1000 ft. across. In the vicinity of this 

 hill such large amounts of meteoric iron have been found from 

 time to time as to give rise to the theory that the crater was 

 produced by an enormous meteorite striking the earth at this 

 point. The impact caused the fragments to scatter in all 

 directions. Meteorites are scattered over widespread areas 

 rather than of local occurrence. The reports of the Challenger 

 expedition cite a great abundance of chondrones of cosmic origin 

 in the abyssmal deposits of the ocean. Nordenskjold cites the 

 presence of minute, black, metallic particles in the Arctic snow 

 fields. C. R. Keyes calls attention to hailstones containing 

 fine metallic particles composed mainly of iron, nickel, cobalt 

 and copper. He also cites the constant occurrence of meteorites 



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