Study of the copper-uranium deposits at Vilcabamba, Department of Cuzco, Peru

Uranium has been known in the Vilcabamba district of Cuzco, Peru since 1954. Copper ores of high silver content were worked by the Spaniards during the seventeenth and the early eighteenth centuries, At the beginning of the twentieth century these ores were worked intermittently; during the last fifty years no mining operation has been going on. The oldest rocks in the thesis area consist of Ordovician phyllites. The presence of Devonian in the area is questionable, but has been recognized 5 km. away from the thesis area. A conglomerate of limited lateral extent of Mississippian age overlies the Devonian (?) or Ordovician formation. Middle (?) and Upper Pennsylvanian and Dower Permian rocks are represented by about 2000 m, of Tarma and Copacabana limestone. Igneous rocks of Middle (?) Permian age appear to overlie the limestone formation. This is called the Mitu group and consists, in addition to the igneous rocks, of coarse red clastics overlying unconformably the Copacabana group. In the limestone area, two main dikes of grachyandesite composition appear to intersect the formation. Copper-nickel-uranium minerals of probable hydrothermal and contact mesosomatic origin occur as lenses or fissure fillings in the Permocaraboniferous limestone some associated with skarn. The ore minerals are tetrahedrite, bornite, chalcopyrite, covellite, niccolite, pitchblende, molybdenite and a variety of sulforarsenides of nickel and cobalt. Gangue is predominantly calcite and dolomite, with quartz in minor amounts. Skarn minerals are garnet epidote, apatite, hematite, and magnetite. The major amount of ore minerals seems to be structurally controlled, but chemical-physical conditions of the host rock may also play important roles. An economic evaluation can not be made at the present stage of exploration. More drilling and mapping is needed. Other factors which will affect this evaluation are the high cost of transportation and difficulty in evaluating tonnage due to the irregular distribution of the ore zones --Abstract, pages viii-ix