42 SIERRA DE UMANGO 
plutonic, partly as ,neptunic".t All transitions between these two q 
have been; found as well. Keyes? in his paper on the Mary- 
land acid eruptive rocks distinguishes between intrusion- and 4 
separation-pegmatites. A similar division was also pointed by q 
Holmquist.® Regarding the Famatina granite-pegmatites above ~ 
described, they are all of a purely plutonic character, because 
they always form typical apophyses, crosscutting or following the 4 
schistosity planes of the older rocks. The circumstance, that the 
pegmatite dikes near the batholith show an extreme differentiation 
of the quartz and feldspar components, may be explained by 4 
assuming the assistance of katalytical gases, causing greater molecu- 
lar mobility at the beginning of the consolidation. 
d) PLUTONIC METAMORPHISM IN THE SIERRA DE UMANGO 
SCHIST-BODY. 
The western sector of the Famatina batholith injection aureole. 
It has been stated above, that the Famatina batholith is to a great 
extent exposed in the surface by a deeply cutting erosion. The 
consequence of this fact is, that also the cut through the aureole 
must be of a considerable breadth. A part of this aureole forms 
to the west the Sierra de Umango schist- area with its innumerable. 
granitic and pegmatitic dikes. In peripherical direction (to the 
west) it cannot be stated any decreasing intensity of the exogene con- 
tact influences, because the aureole is on this side cut off by a 
great fault. Also later intrusions have altered the succession of the 
contact zones referring to the batholith. Almost a similar intensity 
of plutonic metamorphism dominates thence the whole area, except 
1 C.R van Hise: A treatise on Metamorphism. U. S. Geol. Survey. Mono- 
graph 47. Wash. 1904. Page 720 and foll. 
2 C. R. Keyes: The origin and relations of the Central Maryland granites. U.S 
Geol. Survey. Ann. Rep. XV. Wash. 1893—94. 
3 P. J. Holmquist: The Archaean Geology of the Coast-regions of Stockholm. 
Geol. Foren. i Stockholm Förhandl. Band 32. Haft. 4. 1910. (Also Guide N:o 15 
of the Int. Geol. Congress, Stockholm 1910.) Page 801 and foll. 
POE eT eRe CE een YES 
