The ore body at El Porvenir 9 runs to the southern section of Atacocha, where further work will be done.

The ore bodies can be classified as replacenwnt bodies and veins. Both types are found at Machean and Atacocha, but replacen1ent has not been an important process at Milpo.

Bedding replacen1ents or ''mantos'' in Pucani linwstone are co1nmon at Machcan, where nearly half of the prospect pits and small adits explore manto-type deposits. The majority of the deposits are small, ranging from 50 centimeters to 1 meter in thickness and from 1 to 20 meters in lateral extent; only two ore bodies more than 50 meters long were observed. The bedding replacements are always assoeiated with veins and extend out from them. The veins probably served as feeders for the ore bodies. The walls of the mantos are often sharp and delineated by sinall bedding-plane faults.

Veins at Atacocha are found in all rock types but those in limestone and quartz sandstone are most important; only one vein in porphyry is being mined. Most veins strike from N. 50° W. to west and dip steeply. Veins in limestone are concentrated near the axis of a small cross fold near the Atacocha fault and have been found only in the upper mine workings. They may have filled tension fractures opened during the formation of the cross fold. Veins in quartz sandstone and chert breccia are found on all levels and are the principal source of ore in the deeper workings. Vein width is usually less than 1 meter but occasionally it increases to 3 or 4 meters The most persistent vein has been mined for a strike length of 150 meters and over a vertical extent of 300 meters.

The geologic features on a district-wide scale that may have been important in the localization of the Atacocha ore deposits are: the porphyry intrusives; the Atacocha fault; the contact of the :Nfitu and Pucara formations; and the series of northwesterly-striking faults.

El Porvenir is mined using overhand C&F and sublevel stoping (SLS) mining methods. The C&F mining method has the main following characteristics; access to stopes throughout ramp, sub-levels and rising crosscuts; horizontal drilling (Breasting); sub levels spaced vertically 20m and located at 60m distance from mineralized zone; cuts of 5m of height; use of raising crosscuts to access cuts in ascending direction; and use of detritic and hydraulic backfill. Following successful trials in 2018, El Porvenir will incorporate the SLS mining method into the LOM plan, representing 30% of ore production by tonnes. The SLS mining method has demonstrated increased productivities and reduced unit costs as compared to the C&F mining method. SLS stopes are located a minimum of 40 m from infrastructure, are 20 m high, 30 m long and have a minimum mining width of 4 m. Production is achieved by vertical blastholes, and backfilled using unconsolidated waste fill.

El Porvenir operates a conventional processing plant with 6,500 tonnes/day nominal capacity of ore feed that is currently operating at approximately 5,900 tonnes/day. El Porvenir uses a conventional multi stage crushing pant, grinding plant, and multistage differential flotation plant to produce three commercial quality concentrates: zinc concentrate, lead concentrate, and copper concentrate. Zinc concentrate accounts for the largest production from El Porvenir at approximately 77% of the total tonnage, lead concentrate accounts for approximately 21% of the tonnage, and copper concentrate for the remaining 2% approximately. Final flotation tails are subject to classification using hydrocyclone. The hydrocyclone’s coarse fraction represents approximately 40% to 60%, which is used for underground backfill. The hydrocyclone’s overflow is sent to a conventional tailing storage facility.