The mineralized zones in the Las Minas district are Au-Cu-bearing skarn deposits.

Copper and gold mineralization have been recognized in three settings within the Las Minas property: proximal skarn, distal skarn and quartz veins. Proximal-type skarn is the dominant skarn alteration observed within the Las Minas resource zones (El Dorado and Santa Cruz) while distal and gold-bearing quartz veins occur in the exploration targets to the east and north of the Las Minas resources.

Proximal skarn developed along marble-diorite contacts, both as exoskarn developed within the sedimentary rock, and as endoskarn developed within the intrusion. The skarn alteration has a typical zoning of marble-exoskarn-endoskarn-diorite. The distinction between exoskarn and endoskarn can be very difficult because the skarn alteration (especially garnet replacement) can be texturally destructive.

Proximal skarn alteration is dominantly garnet-rich with lesser amounts of pyroxene, and locally garnet appears to have replaced pyroxene. The skarn contains variable amounts of magnetite and lesser sulfide minerals.

Distal skarn is exposed within the canyon walls at elevations from ~1,700 m to 2,100 m. The distal skarn is highly variable in character. Distal skarn consists of massive sulphides and/or massive magnetite in stockworks, pipes, and replacement pods within the variably marbleized limestone.

Mineralization associated with various distal skarn mineral types is seen within the Changarro – La Perdida area at various locales such as Mina Changarro which appears to have exploited a near- vertical pipe of massive magnetite plus sulphides that has a width of 50 m. to 100 m.

Gold-bearing veins are found primarily at Pueblo Nuevo which is located about 4 km north of the Las Minas village. The veins are narrow, with widths ranging from 0.2 m to 0.8 m, strike generally within 10° of north-south, and have near-vertical dips. Veins with significant gold values persist over >1.5 km of strike and >650 m of elevation within a 600 m wide deformation zone, though the veining and deformation may be much more extensive. Vein gangue material is almost exclusively quartz, showing repeated or zoned open-space filling textures. Gold is associated with pyrite that forms < 5% of the vein fill, and with trace to locally 10% iron-rich sphalerite, galena and minor copper and silver minerals. These veins are prominent in both undeformed dioritic rocks which are believed to be the same intrusion that underlies the main skarn deposits at Las Minas, and in the overlying clastic meta sedimentary rocks and sheared limestone, as observed at the La Miqueta mine. The lower levels of the veins within the meta-clastics tend to show higher gold grades than in the higher level, limestone-hosted portions of the veins. Wallrock alteration is generally minimal in all country rock types.

El Dorado skarn occurs primarily at the contact between diorite and overlying marble. Being visually distinctive from the surrounding marble and intrusion, the skarn is seen in outcrop as dark-colored, with significant iron- and copper-staining. The occurrence of mineralized skarn was obvious to early explorers and was the locus of historical activity at the Juan Bran mine area on the west side of the canyon and El Dorado mine on the east side of the canyon. The El Dorado zone is broken into two horizons that are separated by a barren, north-northwest trending, 100 m to 150 m wide diorite dike that extends up from the lower diorite intrusion.

Modeling indicates that the El Dorado skarn mineral zone on the west side of the diorite dike has an 800 m northwest strike length, extends up to 450 m to the southwest away from the diorite dike, is on average 15 to 20 m thick, and can reach over 50 m in thickness along the northweststriking contact with the diorite dike. In contrast, the El Dorado zone on the east side of the dike has a strike length of 250 m northwest, extends up to 200 m to the northeast from the diorite dike, and is 5 to 10 m in thickness.

Highest metal grades within both zones are often within the skarn just below the marble-skarn contact. This contact can be very sharp with often a <0.1 m transition from weakly mineralized marble to high- grade skarn. The lower mineral contact is more gradational as the skarn alteration decreases into the weakly altered intrusive. The intrusive contact is sub-parallel to the observed remnant bedding in the overlying marble, which indicates that the intrusive contact might represent the upper contact of a thick sill.

The Santa Cruz zone lies about 0.5 km south of the Las Minas pueblo and is well exposed on a west-facing canyon wall just above a tributary of the Rio Las Minas. Skarn within the Santa Cruz zone lies along the west side of the dike, immediately to the south of and stratigraphically higher than the El Dorado and Juan Bran zones. The primarily east-dipping mineralization at Santa Cruz is more complex and discontinuous than observed at El Dorado due to the more variable intrusive-marble contact orientations (both near- vertical dike and east-dipping sills). In contrast to the El Dorado zone, magnesian skarn is common as indicated by the presence of olivine and serpentinite along the intrusive contacts. The increased magnesian skarn indicates a more dolomitic protolith.

Due to the steep west-dipping topography, drilling has been primarily east-directed, which is subparallel to the bedding/sill/mineralization orientation, making geologic interpretations somewhat uncertain. The Santa Cruz zone has a 200 m northwest strike length, extends up to 200 m downdip to the northeast from the topographic surface, and can be up to 50 m thick, though thickness is highly variable and often consists of stacked sequences of mineralized skarn. Occasional skarn intervals >100 m in thickness have been intersected, though this would include some intervals of dike and marble. In fact, quite commonly skarn (both exoskarn and endoskarn) are interlayered with thin (generally <5 m intervals of intrusion or marble.

The El Dorado deposit is separated into east and west mineralized zones by a roughly 150 m wide diorite dyke. The sub-horizontal skarn on the west side of the dyke has an 800 m northwest strike length, extends roughly 400 m in width and is 10 to 15 m in thickness on average. Towards the dyke, this zone forms an east-dipping keel extending up to 100 m with an average dip between 55 to 60 degrees. The portion of the El Dorado deposit on the east side of the dyke is sub-horizontal and has a strike length of 250 m, a width of 200 m, and is 5 to 10 in thickness.

The Santa Cruz deposit lies near surface, roughly 0.5 km south of the Las Minas pueblo. The deposit is near vertical, has a 200 m northwest strike length and extends up to 200 m down dip.

Mineralization consists of two deposits: El Dorado and Santa Cruz. Due to its proximity to surface, the El Dorado East Zone will be targeted early in mine life. This material will be mined via Room and Pillar (RPL) methods using three access points and will be hauled directly to the processing plant using underground haul trucks.

Prior to completion of Zone A, the Main Portal is developed to recover the deeper El Dorado West (Zones C, D, and E) material. Santa Cruz (Zone B) is developed using internal ramping, mined via longhole stoping methods, and hauled to the crusher. This deposit will be mined using a combination of Long-Hole Stoping (LHS) and room and pillar methods. All mineralized material will be hauled via truck to an underground crusher at 1367L, where it will be crushed and conveyed to the processing plant at surface. For LHS, levels will be located throughout the mine at 20 m vertical increments which will be connected by the main ramp sized at 5.0 m W x 5.0 m H. Where the deposit becomes shallow dipping, RPL is utilized to recover mineralized material. These areas will be accessed utilizing existing LHS development.

Longhole stopes will be backfilled utilizing a cemented paste backfill comprised of tailings which will be pumped from surface. Run of mine material will be backfilled where possible, particularly in empty room and pillar voids, to avoid additional haulage cost to place at surface.

Due to the deposit geometry, it will be developed using both longhole stoping and room and pillar mining. Long hole stopes account for 52% of production tonnes and will be utilized where the deposit is steeply dipping. Where the deposit becomes almost horizontal, room and pillar mining will be utilized as it allows for better extraction and lower backfill requirements. Room and pillar mining accounts for 41% of production tonnes. The remaining 7% of the mill feed tonnes is derived frommineralized development.

Room and Pillar
Room and pillar mining is applicable in the extraction of flat-bedded deposits of limited thickness. This method is used to recover resources in open stopes. Pillars are left behind to support the hanging wall and contain mineralized material which is non-recoverable. Rooms and pillars are arranged in regular patterns. The spans are 7 m and the pillars are 5 m x5 m. This makes for a mining extraction ratio of 83%.

Rooms do not typically require backfill, but where deposit thickness is greater than 6 m, mining will be completed in multiple passes working off mine rock fill, similar to post room an pillar mining. Rooms will be backfilled using a combination of waste development material and lightly cemented tailings. The tailings are cemented to prevent movement of material. The waste rock is stored underground to decrease the surface impact and decrease the size of the tailings storage facility.

Longhole Stoping
Longhole stoping is utilized in steeply dipping deposits. A top and bottom drift delineate the stope and blast holes are drilled between the two levels using a Longhole Drill. The stope is blasted, and material is extracted from the bottom drift by conventional remote mucking with LHDs.

Stopes are mined in a primary/secondary fashion where primary stopes are mined and backfilled with a cemented paste. Secondary stopes are also backfilled using lightly cemented paste and waste rock. Footwall access is driven parallel to the resource with cross-cut entries evenly spaced along strike. This allows for increased productivity and the ability to mine several stopes at a given time.

Mining begins with Zone A. This area is part of the El Dorado East deposit which is shallow dipping and outcrops at surface. Minimal work is required to access this area allowing mining to begin while the main ramp is developed to depth.

Zone B is developed using an access off the main ramp at the 1330L. While mining of Zone B progresses, the main ramp is extended to the 1200L where the mining of the remaining zones may begin. Here the deposit is steeply dipping, so LHS extraction is used. Mining proceeds sequentially by zone from the 1200L up. When the deposit becomes shallower, generally above the 1280L, Room and Pillar extraction methods are used.

When possible, waste rock will be trammed and placed in mined out areas as backfill. Waste rock which cannot be used as backfill will be mucked and hauled to surface.

The objective of the mine schedule is to develop the mine to maintain mill throughput of 1,400 t/d. Zone A is targeted initially due to its proximity near surface. This allows access to mineralized material immediately, while development to remaining zones is established at depth. This also minimizes initial development capital requirement. As LH stoping was sequenced from the bottom of the deposits upward, access to high-grade material is somewhat limited, however this was prioritized where possible.

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The processing plant at Las Minas is designed to treat 1,400 t/d of mineralized material and produce 2 concentrates: a copper/gold concentrate and a magnetite concentrate. The process plant will include:
• Crushing circuit;
• Primary grinding;
• Flotation circuit
• Rougher flotation;
• Regrind;
• Flotation cleaner;
• Magnetite recovery;
• Concentrate dewatering; and
• Tailings dewatering and paste plant.

A gravity circuit consisting of a single centrifugal concentrator, shaking table and associated tanks and pumps is included to recover coarse gold particles early in the circuit to a higher payable product. This circuit also acts to prevent mis-sized gold particles from escaping the grinding circuit to the flotation circuit. With only 1 gravity test conducted and because it is difficult to quantify the effect of gravity recovery on final recovery, the total recovery was maintained as the recovery found in the LCT but was split int ........