Lagunas Norte differs from many other large high- sulphidation epithermal gold deposits of the Andes in that a majority of the known resource is contained within Cretaceous siliciclastic sedimentary rocks, and a relatively small portion is within the Tertiary volcanic sequence that is the primary host elsewhere (e.g., Yanacocha, Pierina). The main host rock sequence at Lagunas Norte consists of quartz sandstones and subordinate interlayered mudstone, siltstone, and carbon-rich siltstone, correlated with the Lower Cretaceous Chimú Formation (Lewis, 2002).

The Lagunas Norte mineralization occurs in the southeast portion of the Alto Chicama property. The mineralization is finely disseminated and is hosted mostly by siliclastic sedimentary strata.

The mineralization within the present pit extends for approximately two kilometres in the north-northwest direction by approximately two kilometres in the east-northeast direction and for more than 200 m vertically.

Mineralization is the result of multiple volcanic and hydrothermal events. It is hosted in both the Tertiary volcanics of the Calipuy Group and the underlying Cretaceous sedimentary rocks of the Chimú Formation. The alteration associated with the mineralization is typical of a highsulphidation epithermal environment, characterized by silica (SiO 2 ), surrounded by alunite [KAl3(SO4)2(OH)6], dickite [Al2Si2O5(OH)4] and pyrophyllite [Al2Si4O10(OH)2]. Trace elements typically associated with these deposits include copper, arsenic, barium, bismuth, zinc, lead, and variable amounts of mercury (Silberman and Berger, 1985). The deposit has very low concentrations of carbonate minerals or other potentially acid neutralizing minerals.

There are both stratigraphic and structural controls on the mineralization. Mineralizing fluids ascended along the main fault systems and migrated laterally along stratigraphic contacts in both the sedimentary and volcanic rocks. At least two stages of sulphide mineralization are recognized. The sulphide assemblage comprises mainly pyrite (FeS2) with lesser amounts of enargite (Cu3AsS4) and occurs as replacement structures, veins, and disseminations in volcanic breccias and highly fractured and locally brecciated Chimú sandstones. Most of the mineralization (75%) occurs as oxide material, with approximately 25% occurring as sulphide material. Supergene oxidation has altered a large part of the sulphide assemblage to iron oxides and, to a lesser extent, sulphates. The extent of this oxidation ranges from a few metres to more than 300 m below surface. Approximately 90% of the mineralization is contained within the Chimú sediments and the balance is hosted in the Calipuy volcanic rocks.

The gold grade times thickness contours clearly show the Lagunas Norte deposit is approximately two kilometres by one kilometre wide.

The Lagunas Norte Mine is a traditional open pit truck/shovel heap leach operation that has been in continuous production since 2005.

Open pit mining operations are located on a mountain top with gentle to extreme terrain between elevations of 3,800 MASL and 4,200 MASL. Mining from a single pit will continue until 2023, at a rate of 4.8 Mtpa during 2016 and 1.3 Mtpa thereafter beginning in 2017. Heap leach placement will continue during mining, with mine operations concluding in 2023.

The Lagunas Norte ultimate pit measures approximately 2.5 km along strike, typically 0.8 km to 1.2 km across with a surface footprint of approximately 240 ha, and has a maximum depth of approximately 250 m. There are four main areas of development identified within the ultimate pit: Dafne, Josefa, Alexa, and the moraines furthest to the north. The open pit is overlooked by the Shulcahuanca Dome, a sacred feature, and there is an approximate 50 m standoff from the base of the Shulcahuanca Dome for mine planning and operations.

Final arrangement of the Lagunas Norte waste rock facilities is for the continued development of surface dumps surrounding the Lagunas Norte ultimate pit other than to the south-southeast where the HLF is located, resulting in a relatively compact overall footprint.

Under the current mine plan, the Refractory Project is expected to start operation in 2021, feeding sulphide ore from the stockpile until 2029. Mining will principally include deepening of the central and southern portions of the current open pit. Mining is expected to be carried out using the existing mine fleet, at a rate of approximately 25 Mtpa total material moved at a stripping ratio of 4.4:1 (waste: mineralization). Due to the higher stripping ratio, an expansion of the current waste rock storage facilities will be required.

The recovery process used at Lagunas Norte is a two-stage conventional crushing circuit, followed by heap leaching, and a Merrill Crowe zinc cementation plant and CIC for recovery of the precious metals. The major components of the process are:
• Primary crushing
• Secondary crushing
• Heap leaching
• Recovery plant
• Refinery
• Water discharge treatment plant.

CRUSHING CIRCUIT
The crushing circuit was originally designed to crush 42,000 tpd, but the capacity is permitted to 63,000 tpd. Historically, it was determined that the gold recovery from heap leaching at Lagunas Norte is not overly dependent on crush size so the size has been increased over time to allow more material to be processed through the crushing circuit. Haul trucks dump ore directly into the gyratory crusher. A rock breaker is available to break large rocks at the mouth of the primary crusher. The ore is discharged through an apron feeder onto belt conveyor number one whic ........