868 A TREATISE ON METAMORPHISM. 



Wisconsin, where there is a quartzite formation 130 kilometers long and 120 

 meters wide, the amount would be enormous. Supposing the induration 

 to have extended only to the depth of 2 kilometers along the dip, the 

 amount of water which must have passed through this formation in order 

 to have cemented it would be 4,056,000 cubic kilometers. Thus the 

 cementation of this single formation required the circulation of almost 

 incredible quantities of ground water; and the addition of the almost indefi- 

 nitely greater quantity of quartz cementing the quartzite formations now 

 existing would require a correspondingly greater amount of water. 



Even this point of view does not give a conception of the amount of 

 ground circulation required to cement the quartzites; for during geological 

 history probably a great many more quartzite formations than now exist 

 have been produced and destroyed by the processes of erosion. And in 

 the quartzites we have but a single phase of the work of ground water. 

 It therefore follows that the amount of ground water reqxiired to cement a 

 single formation is infinitesimal as compared with the amount which has 

 circulated through the rocks during geological ages. Indeed, it is probably 

 not too much to say that the same water has circulated through the 

 ground more than once, for it is doubtful whether the entire volume of the 

 water of the ocean is sufficient to have done the work of cementation and 

 metasomatism by use a single time. 



SCHIST-QUARTZITE OR QUAHTZITE-SCHIST. 



A schist-quartzite or quartzite-schist is a quartzose rock derived from a 

 sandstone or quartzite which has a more or less well-developed schistose 

 structure. These rocks are produced in the zone of anamorphism under 

 mass-mechanical conditions. Granulation. or recrystallization, or both, are 

 the dominant processes, but with these, welding and cementation are at 

 work. In order to produce a schist-quartzite it is not necessary to suppose 

 that cementation has filled the entire spaces between the sand grains; for 

 mashing, resulting in granulation, recrystallization, and welding may so 

 rearrange the material as to close the openings and lessen the volume of 

 the rock, with no added material from an outside source. Therefore it 

 can not be assumed that any considerable amount of material has been 

 added to schist-quartzites, unless evidence remains in the enlargements of 

 the quartz grains. Not infrequently in the schist-quartzites such evidence 

 may be seen. In the least mashed phases of schistose quartzites the quartz 



