CRYSTALLINE BASEMENT 30 
body, outcropping in a series of hilly ridges between Paiman and 
Chilecito (see the map by Bodenbender, 1916). ' This type may 
merely be regarded as an abyssal facies, where the consolidation 
proceeded in some other way.! The groundmass of the granite-por- 
phyry is viz. of a coarse grain (normal granitic structure). The pheno- 
crysts, measuring some cm in length, are orthoclase. They show a 
tendency to idiomorphic development. The other components are 
quartz, oligoclase-andesine, microcline, apatite, zircon, etc. (Boden- 
bender). There are seldom pegmatitic differentiates. According to 
Bodenbender this type dominates also in the region of La Agua- 
dita (between Los Angulos and Famatina). To the west the rock 
changes evidently into a more normal granite. 
As far as I have observed, the batholith generally seems to carry 
but few xenoliths except the large schist bodies in the upper parts 
of the Nevado. Only in some localities on the road between Puerto 
Alegre and Safiogasta I have noted the occurrence of a dark, 
quartzitic rock forming breccia floating in the homogeneous granite 
mass. But approaching the western border of the batholith, i. e., the 
eastern margin of the Sierra de Umango schist-area, there is, especially 
in the foothills of crystalline rocks, extending along a line between 
Villa Castelli and Villa Union, a marked zone of mingling and 
brecciation phenomena treated of in the following chapter. 
b) THE ZONE OF ABYSSAL MINGLING, BRECCIATION AND ASSIMILATION 
ON THE WESTERN BORDER OF THE FAMATINA BATHOLITH. 
Phenomena of plutonic metamorphism in a gigantic scale are 
well exposed in the foothills at the western slope of the Nevado 
and continue under the bottom sediments of the Vinchina valley 
until they appear again in the hills, belonging to the Sierra de 
Umango-mountains. The metamorphic products, occurring on the 
eastern side of the valley, are, however, of a special character, due 
= The phenocrysts may represent the exceeding part of an ,anchieutectic* gra- 
nitic-magma-mixture. 
