1990 Volume 40 Issue 222 Pages 211-222
The Huanzala mine in Peruvian Andes is producing silver-lead-zinc ore. Its ore bodies are bedded or lenticular in shape, replacing a limestone formation of Cretaceous age.
Since 1964, systematic exploration and development for the Huanzala mine had been promoted intensively on the Huanzala north deposits located in the north side of the Torres river, some of whose ore bodies are exposed on the surface.
On the other hand, by the exploration in 1974 and 1975 in the Huanzala south district, located on the south side of the Torres river, neither outcrop of orebody nor well anomaly of IP survey has been found out except few outcrops of weak gossan. Consequently, the exploration on this district was suspended in 1976.
Through the development on the Huanzala North deposits, following facts were revealed by geological study.
(1) The mineralization is closely related to faults, and ore deposits are formed near to north-northeast faults with a steep dip and northwest thrust with a dip of 40°-60°.
(2) Also the mineralization is closely related to quartz porphyry sheets. Most of ore deposits are germinated near to these sheets. However, in a limestone formation some ore deposits appear about 500 m distant from the sheet intruded zone.
(3) Even weak anomaly of metal factor of IP survey indicates existence of ore deposit.
Applying these knowledge to the Huanzala south district, exploration was done again with core boring and tunnel excavation from 1981 to 1988. And in weak metal factor anomaly zones, the Huanzala south deposits were discovered, which are located near to the above mentioned faults in a limestone formation, maximum 300 m distant from quartz porphyry sheet. These are estimated a million tons of the ore reserves with ore grade of 0.01% Cu, 5.8% Pb, 12.2% Zn and 2.8 oz/st Ag.
