EASTERN ANDES: CORDILLERA VILCAPAMPA 



215 



THE VILCAPAMPA BATHOLITH AND ITS TOPOGEAPHIC EFFECTS 



The main axis of the Cordillera Vilcapampa consists of granite 

 in the form of a batholith between crystalline schists on the one 

 hand (southwest), and Carboniferous limestones and sandstones 

 and Silurian shales and slates on the other (northeast) . It is not 

 a domal uplift in the region in which it was observed in 1911, but 











CORDILLERA VILCAPAMPA 



PAMPACONAS 



^^^ — GRANITE 



'PORPHYRY 



S.by W. 



. --' "VALLEY 



~~-~^- •* -~-^-~ 





'O-^C^i' 







^^^-- : ^*<2^~~~~~~~ 



ZILSA H D S T N E 



IMbvE. ■ ^— — 





~ """ 



Fig. 141 — Composite geologic section on the northeastern border of the Cordillera 

 Vilcapampa, in the vicinity of Pampaconas. to show the deformative effects of the 

 granite intrusion. There is a limited amount of limestone near the border of the 

 Cordillera. Both limestone and sandstone are Carboniferous. See Appendix B. See 

 also Figs. 142 and 146. The section is about 15 miles long. 



an axial intrusion, in places restricted to a narrow belt not more 

 than a score of miles across. As we should expect from the 

 variable nature of the invaded material, the granite belt is not 

 uniform in width nor in the character of its marginal features. 

 In places the intrusion has produced strikingly little alteration 

 of the country rock; in other localities the granite has been 

 injected into the original material in so intimate a manner as 

 almost completely to alter it, and to give rise to a very broad 

 zone of highly metamorphosed rock. Furthermore, branches were 

 developed so that here and there tributary belts of granite 

 extend from the main mass to a distance of many miles. Out- 

 lying batholiths occur whose common petrographic character and 

 similar manner of occurrence leave little doubt that they are 

 related abyssally to a common plutonic mass. 



The Vilcapampa batholith has two highly contrasted borders, 

 whether Ave consider the degree of metamorphism of the country 

 rock, the definition of the border, or the resulting topographic 

 forms. On the northeastern ridge at Colpani the contact is so 

 sharp that the outstretched arms in some places embrace typical 



