The Santander Property hosts intrusion-related, carbonate-hosted, distal ‘passive’ replacement deposits, or carbon replacement deposits (“CRDs”). Controls on mineralization vary, however, with the majority of mineralization displaying very strong structural and lithological controls. The Santander CRD, in common with those in other districts, displays a strong mineralogic/metallic zonation: a ‘classic’ lateral or vertical zonation (from distal to proximal) would be Mn » Ag » Pb+Ag » Zn » Cu+Au. The 44-square-kilometre Santander Property is underlain by an approximately 2,600 m thick package of Cretaceous clastic and carbonate sedimentary rocks known as the Goyllarisquisga Group, within which an approximately 1,000 m thick sequence of massive limestones and limestoneshales of the Jumasha and Chulec Formations are the principal hosts identified to date. Pre-mineralization diabase dykes and sills are locally present within the section. The entire sequence is tightly folded into a series of orogenparallel, northwest-trending anticlines and synclines. The lower, predominantly clastic part of the section has been thrust over the mainly carbonate-rich upper portion (the favourable host rocks) along the regional northwest-trending Santander Fault Zone. Unconformably overlying the tightly folded Cretaceous sediments are moderately folded and faulted andesitic Tertiary volcanics of the Calipuy Formation. Syn-mineralization intrusive activity, considered to be the heat and fluid sources that produced base metal mineralization, has not been recognized on the Property to date. This absence is empirically considered indicative of a relatively large CRD system, and such bodies are inferred to be present at depth (>800 m) on the Property.

As part of the year-end tasks, Trevali has conducted aresource estimate for its Santander Property. The Santander Property includes four discrete deposit areas: the Magistral deposits, the Santander Pipe, the Puajanca Pipe, and the Tailings area.

The Magistral deposits consist of three main bodies: Magistral North, Magistral Central, and Magistral South; and six minor bodies: Rosa (depleted 2017), Bono, Fatima North, Fatima South, Magistral Central-North, and Oyon. Magistral mineralization is hosted in limestone of the Chulec formation, and the upper limits (or hanging wall) broadly correspond to a siliciclastic facies section of the Farat formation, often in fault contact. The lower limit (or footwall) of the mineralization is defined as the base of the last significant sulphide horizon and is occasionally gradational. Mineralized, narrow (generally less than 50 centimetres), but very high grade veins occur perpendicular to the main Magistral bodies and occasionally present massive sulphide replacement in between the veins, as in the cases of Rosa, Fatima South, and Fatima North. At depth, Oyon splits into two parallel (stacked) mantos: Oyon 1 and Oyon 2.

The Santander Pipe is located approximately 350 metres east of the Santander Mine’s processing plant. Sulphide mineralization is hosted within the Santander anticline and is associated with skarn and/or associated gangue (silicification, dolomitization, and calcic alteration) in various proportions largely dependent on the original character of the host rock and postulated distance from heat/mineral source or pathways. In detail, the skarn mineralization forms a circular, massive, plug-like body in the Jumasha and Pariatambo limestone formation to depths of approximately 250 metres below surface prior to forming more discrete skarn hosted replacements in the underlying interbedded Chulec limestone formation to 480-metre vertical depth, which is the vertical limit of historic mining operations. The average diameter of the skarn/sulphide body is approximately 120 metres. The mineralization remains open for expansion as underground exploration drilling indicates that the Santander Pipe extends a minimum of an additional 250 metres below the lowermost development levels for an approximate total vertical extent of 730 metres.

The Puajanca prospect is located approximately one km east-northeast of the Magistral North deposit. Mineralization is hosted within the Santander anticline, which also hosts the Santander Pipe approximately three km along strike and at a 700 metre lower elevation to the south-southeast. Mineralization occurs within the Pariatambo and uppermost portions of the underlying Chulec Formations. Within the preferred Chulec limestone, host replacement and vein mineralization is associated with weak skarn alteration. At Puajanca South, mineralization is exposed over an area approximately 120 metres long by 20 metres wide with variable thickness. Exploration drilling indicates that mineralization extends from surface to vertical depths of approximately 225 metres and remains open.

Underground mining commenced in 2013 and commercial production was declared effective January 31, 2014. All mining and mineral processing activities are performed by contractors.

The underground mine is accessed via three operational portals at Magistral North, Magistral Central, and Magistral South. Each portal has an associated ramp system, and the Magistral Central and Magistral South ramps are connected at the 4,510-metre and 4370-metre levels, with one ramp servicing both Magistral Central and Magistral South for the remainder of the depths of the currently defined mineralized lenses. By-passes connect the Magistral North ramp system to the Magistral Central and Magistral South system on the main levels on elevations of 4,510 metres, 4,580 metres, 4,370 metres, 4,300 metres and newly planned 4,230-metre level.

Avoca is the main mining method utilized at the Santander underground operations. It is supplemented by up-hole retreat for partial sill pillar recovery and by modified Avoca in some extremity stopes along strike of the mineralization. Underground mining is divided into 70-metre vertical height mining blocks, in which each mining block consists of three 18 metre high sublevel production stopes and a 10 to 12 metre thick sill pillar to be left in place for overall stability reasons.

Stope sequencing is retreated along strike from lens extremities. Ore is hauled to surface by 20-tonne capacity trucks loaded by Load-Haul-Dump vehicles (LHDs). Waste rock broken underground is hauled by LHDs to empty stopes as backfill, to underground temporary storage (remuck bays), or to surface temporary waste storage. Ore mucked from stopes is either loaded directly into trucks or stored in remuck bays along the ramps prior to truck haulage. LHDs fill empty stopes with waste rock from development, supplemented with waste rock back-hauled from existing surface waste rock stockpiles.

The concentrator is of conventional design based upon a three-stage crushing plant to prepare nominal 25 mm crushed material for a rod-ball milling circuit to prepare the mineralization for a differential flotation circuit for the recovery of the value metals.

Run-of-mine (ROM) material is delivered to the primary crusher pad where ROM is stored for blending to the plant. A grizzly above the coarse ore bin prevents oversized material entering the primary crusher. The grizzly aperture is nominally 12-16” with a rock breaker located above the grizzly to break oversized rocks.

The coarse material bin at 75 t nominal capacity is discharged by 2 apron feeders at 36” and 42” wide. The discharge from the bin is screened on a 4 ft by 12 ft double deck screen with 8? gaps on the top deck and 4? gaps on the bottom deck. Screen undersize passes to the collection conveyor while the oversize passes to the 24” by 36” primary jaw crusher.

Jaw crusher discharge combines with the by-pass fines for conveying to the secondary cone crusher. A 5ft by 14ft double deck screen ahead of the 4 ¼ ft standard Symons cone crusher is fitted with 3? aperture upper deck screen and a 1? lower deck aperture. Fines pass to the fine ore bin while the oversize passes to the secondary crusher operating in open circuit.

Secondary cone crusher discharge combines with the screen fines and is conveyed to the tertiary crushers, consisting of two circuits each with a fines product screen ahead of the 2 tertiary cones each being a 3 ft short head unit, operating in open circuit. Fines from each tertiary screen combines with the tertiary cone discharge as feed to the fine ore bin, at nominal 1? product.

The grinding circuit consists of two operating modules with each module consisting of a primary rod mill in open circuit followed by a secondary ball mill in closed circuit.

One module is a 7 ft by 12 ft rod mill, operating with an 8 ft by 12 ft ball mill. The second module consists of a 9 ft by 12 ft rod mill followed by a 10-1/2ft ball mill. Both circuits are identical in operation as described below:

Ore is withdrawn through belt feeders below the 1800 t fine ore bin. One feeder feeds each rod mill with the third feeder being reversible as a standby unit.

Ore is delivered to the rod mill over a weightometer to monitor the weight to each mill for metallurgical accounting.

The discharge from the rod mill combines with the discharge from the secondary ball mill and is pumped to a Skim-air (SK) cell for recovery of any high-grade lead in the circuit.

The SK unit cell tailing is pumped to a dedicated cyclone battery with 15? cyclones for classification of the mill products. Overflow as feed to the lead circuit gravitates to the flotation section of the plant.

Cyclone underflow as coarse oversize from the mills recycles to the ball mill feed chute for further grinding.

Overflow from both grinding modules combines as feed to flotation, at approximately 35 % solids and a P80 of 105 microns.

The concentrator is of conventional design based upon a three-stage crushing plant to prepare nominal 25 mm crushed material for a rod-ball milling circuit to prepare the mineralization for a differential flotation circuit for the recovery of the value metals. Concentrates are dewatered for road transportation to Callao.

The flotation circuit consists of a two-stage differential float in which the lead is floated ahead of the zinc, after which the zinc is activated and floated.

The lead rougher-scavenger cells consist of eight OK8 unit cells. The first four cells produce a rougher concentrate that passes to the primary cleaner, while the lead scavenger concentrate is pumped back to the head of the circuit. Scavenger tailings form the feed to the zinc circuit.

The primary cleaner consists of six DR24 cells, with primary cleaner tailings combining with the scavenger concentrate for recycle to the head of the circuit. Concentrate from the primary cleaner g ........