450 EDSON S. BASTIN 
d) Frangitict foliates. 
Arkose-schists, graywacke-schists, and other metamorphic deriva- 
tives of sediments produced by disintegration of igneous rocks without 
much decomposition or mechanical sorting of the constituents. 
III. Foliates in which the parallel structure 1s in part primary and in part secondary. 
1) Injection foliales: 
Here belong the injection gneisses. 
The primary foliates whose foliated structure is due to differential 
movements within an igneous magma before complete solidification 
have the composition of massive igneous rocks and may therefore be 
excluded from this discussion. ‘The foliates of the third class, typified 
by the injection gneisses, are also excluded for obvious reasons. ‘The 
secondary foliates are therefore the only ones whose chemical char- 
acters we need discuss. The igneous and sedimentary types will be 
considered in order. 
THE META-IGNEOUS. FOLIATES 
The study of chemical characteristics by the method of averaging 
a large number of analyses, adopted for the meta-sedimentary foliates, 
is not applicable to the meta-igneous group because of the great 
variety of rocks represented and the relative scarcity of analytical data. 
It is necessary to restrict ourselves to the consideration of what appear 
to be representative cases and to comparisons between closely related 
rock groups. 
In Dr. Watson’s admirable report on The Granites and Gnetsses 
o/ Georgia? he gives a large number of analyses of the normal granites 
and the metamorphic granite-gneisses of the state. Many of the 
gneisses are highly contorted and thin-banded, and under the micro- 
scope show evidence of dynamic metamorphism in the presence of 
undulatory extinction, peripheral granulation of the mineral grains, 
fractures traversing the larger grains of quartz and feldspar, and 
frequent partial or complete recrystallization. Mineralogically they 
« The term “‘frangite” (from the Latin frango, ‘‘to break up”’) and its adjective 
“frangitic” is proposed as a comprehensive term for all sedimentary rocks formed from 
the disintegration of igneous rocks without extensive decomposition or mechanical 
sorting. It includes unconsolidated as well as cemented and dynamically metamor- 
phosed representatives. It includes arkoses, graywackes, grits, graywacke-schists, 
and gneisses, etc. 
2'Thos. L. Watson, Bull. gQ-A, Geological Survey of Georgia. 
