MASS DYNAMIC ACTION. 307 
similar conditions, but which contains water, might be adjusted by re- 
crystallization and form coarsely crystalline schists. This principle is 
believed to explain the difference of the character of the deformation of 
the different formations for many districts. Itis a well known fact that 
different rock masses of similar chemical composition in the same dis- 
trict vary greatly in the character of the deformation, some formations 
yielding by granulation, others by recrystallization. In general the sedi- 
taentary rocks contain a considerable percentage of water, and therefore 
when deformed are recrystallized. ‘The same is true of the porous igne- 
ous rocks, such as lavas and tuffs. In contrast with these are the massive 
igneous rocks, and especially the plutonic rocks which contain little water, 
and when deformed are apt to be granulated rather than recrystallized. 
One of the best districts to illustrate this principle is the Original Lau- 
rentian area described by Adams.* In this district are the anorthosites, 
the Grenville sedimentary series, and the Basement Gneiss of igneous 
origin. Adams’ careful descriptions show that the most fundamental 
point of difference between the three classes of rocks in their response 
to deformation is in reference to recrystallization and granulation. The 
sedimentary rocks of the Grenville series have been completely recrys- 
tallized and are typical crystalline schists.— ‘The igneous gneisses are 
largely deformed by granulation, but “‘ the granulation has perhaps been 
effected in part at least by recrystallization.”{ The anorthosites have been 
almost wholly deformed by granulation.§ Corresponding exactly with 
these facts are the contents of water. Analyses of three recrystallized 
Grenville gneisses give an average content of water of 1.46 per cent.]| 
An analysis of one partly granulated and partly recrystallized gneiss of 
igneous origin gives .70 per cent of water.4] An analysis of granulated 
anorthosites gives only .55 per cent of water.** 
As examples of recrystallized schists of igneous origin may be men- 
tioned the Kitchi schists, the mica-schists, and the Palmer gneisses of the 
Basement Complex of the Marquette district of Michigan. Two analyses 
of the Kitchi schists showed respectively 2.51 per cent and 2.70 per cent 
of water above 100° C.j+ A mica-schist gave off 2.04 per cent of water 
above 100° C.f{{ A Palmer gneiss gave off 2.33 per cent of water above 
100° C.S§_ Partial analyses of two other mica-schists from the same local- 
* Op. cit., p. 184. 
+ Loe. cit,, pp. 51, 61. 
{ Loe. cit., p. 45. 
2 Loe. cit., pp. 102, 105. 
|| Loe. cit., p. 58. 
4 Loe. cit., p. 43. 
** Loc. cit., p. 130. 
+7 Mon. xxviii, cit., p. 168. 
ti Ibid., p. 202, analysis no. 6. 
22 Ibid., p. 217. 
