32 SIERRA DE UMANGO 
Rassmuss (1916) has investigated a granitic body of abyssal appea- — 
rance, penetrating a complex of precambrian schists, considered by him | 
to be of a lower palaeozoic age. The shape of the body is probably | 
that of a batholith with overhead stoping phenomena and a rem- 
nant of the roof still visible. 
It is necessary to carry on a detailed petrographical investi- 
gation of the different granitic types of the Famatina batholith 
and their exogene metamorphic products. The recent communica- 
tions by Bodenbender (1916) embrace principally stratigraphical 
observations, and as to myself I had but little occasion to collect 
specimens here. I have studied in some degree only the western 
foot of the Nevado, or the eastern border of the Vinchina valley. — 
In the following pages I will give a petrographical description of © 
the probably most important types, collected on the western side 
and also in some parts of the Sierra de Safiogasta. The plutonic 
metamorphism as concerning the Umango area has of course 
been studied with greater attention. 
a) GRANITE VARIETIES OF THE FAMATINA. 
During my excursions in the batholith area I got the impression, 
that the whole body has quite a uniform composition, at least con- 
cerning the Nevado de Famatina and its southern prolongation, the 
Sierra de Safiogasta. The most usual type seems to be a medium- — 
grained, reddish or grayish biotite granite. Amphibole bearing va- 
tities also occur. The structure lacks a parallel orientation, and 
porphyric development seems to be quite scarce. The reddish 
types are often acid or almost aplitic. In the last case a sharper © 
contact with other types may be observed. 
The biotite granite, which Bodenbender (1916) mentions from 
different localities, seems to be, according to my observations too, 
of a wide extension. The colour of the rock varies between reddish — 
and gray. 
A handspecimen of this type from the Quebrada de Tambillos, 
