ments in the stated proportions. 
THE METAMORPHIC CYCLE 305 
derived from the bases of the basic feldspars and ferromagnesian 
minerals. 
Physically, katamorphism of igneous rocks to average sediments 
means a slight increase in average volume of minerals of perhaps 3 
per cent., a figure derived by comparing the specific gravities of the 
ion Of Seg; 
anos Cime n 
Ss 
Shgles, sandstone % qua rtzite 
limestone &@ marble. 
a 
° 
3 
°o 
= 
3 
cis 
rT 
u 3 
2 2 
3 ° 
NG y Jogical S 
aj Kaolin, 20% Average mineralogic < 
> Feldspars 26% proportions not yet Anown 2 
S Mere se Quartz, 22% but approaching 7hose of A 
muds #clays , g Corer g 
a 80% Miscellaneous : The 1greous £ a - a 
= Minerals, 12% cfosely than de the sedi ments. = 
o a 
3 
: > 
= Py 
ag @ 
Feldspars 
Fic. 1.—Diagram showing mineralogical redistribution in metamorphism. 
minerals of the parent rock with those of the resultant average sedi- 
A similar result is obtained by cal- 
culating volume-changes from the chemical equations of the common 
alterations of the rock-making minerals to the minerals of the sedi- 
ments. Where altered to extreme end-products throughout, such as 
kaolin, quartz, and calcite, there is an average volume-increase of 
minerals in due proportions, of about 18 per cent. Katamorphism 
