METAMORPHISM 747 



place, but gaseous and liquid solutions * are agents everywhere 

 present and active, within the known crust of the earth. 



The Regions of Metamorpiiism. The regions where meta- 

 morphism of various kinds takes place are classified by Van Hise 

 (34:^5), according to depth, as follows: 



L The zone of katamorphism, or that zone in which simple 

 compounds are produced from more complex ones, comprising (a) 

 the belt of weathering, extending from the surface to the level of 

 ground water, and (b) the belt of cementation, extending from the 

 ground-water level to the next zone. 



11. The zone of anamorphism, or that zone in which complex 

 compounds are produced from simple ones. 



Characteristics of the Zones of Metamorphism. The belt of 

 weathering is the region of rock destruction; the belt of cementation 

 is the region of rock construction and the zone of anamorphism the 

 region of rock reconstruction. The zone of katamorphism is also the 

 zone of fracture of rocks, where openings may exist. Van Hise has 

 calculated that the maximum depth of this zone cannot be greater 

 than 12,000 meters, and in most cases is probably much less. The 

 zone of anamorphism also corresponds to the zone of rock flowage, 

 where the pressure is greater than the strength of the rocks, and 

 deformation will take place without fracture, but with rock flowage, 

 which will not permit the existence of empty pore spaces. 



Recent experiments on rock flowage made by Professors F. D. 

 Adams (2) and L. V. King (21) at McGill University, Montreal, 

 have shown that cavities can exist at much greater depths than 

 10,000 meters. They placed cylinders of granite, with holes bored 

 through them, in a testing machine, and subjected them for seventy 

 hours to a pressure of 96,000 pounds per square inch at a temper- 

 ature of 550° C. After the experiment it was found that the hole 

 was unchanged. The pressure obtained corresponded to that occur- 

 ring at a depth of about 15 miles, but the temperature was that esti- 

 mated to prevail in the earth's crust at a depth of only eleven miles. 



* Solutions have been defined as "homogeneous mixtures which cannot be 

 separated into their constituent parts by mechanical means" (Ostwald). They 

 may consist of gases mingled with other gases, with liquids or with solids, of 

 liquids mingled with liquids or with solids, and of solids mingled with solids. 

 "The solutions resulting from these various combinations may be gases, liquids, 

 or solids or partly two or all." (Van Hise-34:5p). The gases important in 

 rock alteration are oxygen (O2) sulphur (Ss to So) water vapor (H2O), ammonia 

 (NH3), carbon dioxide (CO2), sulphurous oxide (SO2), boric acid (H3BO3), hydro- 

 chloric acid (HCl) and hydrofluoric acid (HF). The liquid solutions are all 

 water solutions. 



