CHEMICAL COMPOSITION IN SEDIMENTS A5I 
are almost identical with the normal granites. To quote Dr. Wat- 
son:t 
. the granite-gneisses differ from the more massive rock phases (granite) 
simply in the marked banded or foliated structure. These are secondary struc- 
tures induced by long-continued and profound dynamo-metamorphism, acting 
- on an originally massive rock, similar, in mineralogical and chemical compositions, 
to the existing massive granitic areas studied..... The granite-gneisses 
represent unquestionable foliated phases of the massive granite similar to the 
present areas but of an earlier intrusion. 
The granite-gneisses are entirely free from staurolite, andulusite, 
cordierite, kyanite, and similar minerals so characteristic of meta- 
sedimentary foliates. 
In order to compare the metamorphosed and unmetamorphosed 
granitic rocks, the writer computed their position in the quantitative 
system of classification.? The granites were so similar in composition 
that their analyses were averaged and only the systematic position of 
the average computed. The results may be tabulated as follows: 
GRANITES AND GRANITE-GNEISSES OF GEORGIA 
Class puke Order | Rang ae Name 
Normal granites | Average of I I 4 2 3 ‘Toscanose 
21 analyses 
Porphyritic gran- | Average of I il 4 2 3 Toscanose 
ites Io analyses 
4 analyses, il It 4 2) 3 ‘Toscanose 
separately 
computed 
Biante anite 2 analyses, I i 4 2 3-4 | Between 
cae separately Toscanose and 
gneiss 
computed Lassenose 
3 analyses, I IE 4 I 3 | Liparose 
separately 
computed 
It will be seen therefore that the granite-gneisses possess the 
composition of igneous rocks and are almost identical with the normal 
1 [bid., p. 263. 
2 Cross, Iddings, Pirsson, and Washington, Quantitative Classification of Igneous 
Rocks, 1903. 
