MARSTERS, PHYSIOGRAPHY OF THE PERUVIAN ANDES 357 



Passing over the lowland of Cerro de Pasco, we come to the noted 

 deposit of copper-silver ore now in part the property of the Cerro do 

 Pasco Mining Company. The ore-bod}' appears to be on or near the con- 

 tact of eruptives with a thick series of limestones. According to late 

 statistics, the amount of silver taken out of the surface portion of the 

 Cerro de Pasco deposit between the time of its discovery (1630) and the 

 end of the nineteenth century amounts to some 450,000,000 ounces. 



If we should return to the coast from Cerro de Pasco via the Cerro de 

 Pasco Eailway to Oroya, and thence via the Central Line to Lima and 

 Callao, we should pass through other mining localities such as Eio Blanca 

 and Morococha. Here again the respective ore-bodies are closely asso- 

 ciated with contact phenomena such as have already been described. In 

 the region of Matacana, a repetition of the same sort of occurrence may be 

 seen. In the region of Lima, there are copper-bearing ores associated 

 with eruptives in contact with limestones and shales. That is to say, the 

 occurrences of ores in each section can be correlated both geographically 

 and geologically. 



Let us look for a moment at a south section across the Cordillera, say 

 from Mollendo to Puno and the east. At Mollendo, we find that outliers 

 of the Cordillera, or Cadena de la Costa, are composed in part of gneissic 

 and granitoid masses, which are probably intrusive in sandstones and 

 shales. Within the gneissic zones occur small copper deposits. While 

 an attempt has been made to develop some of these, they have never 

 reached the productive stage. Passing into the edge of the foothills in 

 the region of Carabaya, just below Arequipa, we again find a band of 

 crystallines bordered on each side by sandstones and shales. Prospect- 

 ing on a small scale has brought to light small bodies of copper-silver 

 ore, mostly located in the crystallines, while the sandstones and shales 

 are reported to carry coal beds. It is not until we reach Lagunillas that 

 we again come to a region containing ore deposits. Here are silver- 

 gold-copper ores in a belt extending from Santa Lucia to Marivillas. 

 This is to be correlated with the Caylloma silver occurrence already re- 

 ferred to. Here, as noted in other sections, we have eruptives associated 

 with limestones and shales. These are probably to be correlated with the 

 Morrococha Belt on the Lima section. 



In the Titicaca basin to the south of Puno, ore deposits carrying silver 

 and lead have been prospected. I have not seen these, but I am informed 

 that the formations involved are the expected limestones associated with 

 eruptives. Geographically this should be correlated with the Cerro de 

 Pasco occurrence, as it lies in the Intercordilleran Belt and possesses 

 the same lithological relationships. 



