Mineralization at Tahuehueto is classified as intrusion related epithermal low sulfidation polymetallic AgAu style (Corbett, 2007), with Au and Ag accompanied by Cu, Pb, and Zn mineralization. These types of deposits are interpreted to have been derived from porphyry intrusion source rocks at depth.

Mineralization at Tahuehueto occurs as polymetallic epithermal veins with multiple mineralizing events overprinted on one another in the same vein structure. The primary host rock is andesite of the lower volcanic series, but in at least one case, the hydrothermal system penetrated felsic ignimbrite of the upper volcanic series. Styles of mineralization identified by Corbett (2007) include:
-Initial pervasive propylitic-potassic alteration with local specular hematite develops as intrusion-related alteration.
-Early chalcopyrite-pyrite mineralization, locally with quartz-barite typically forms early and at deeper crustal levels in polymetallic Ag-Au vein systems.
-Polymetallic Ag-Au mineralization comprising pyrite-galena-sphalerite ± chalcopyrite ± chalcopyrite ±Ag sulfosalts ± barite represents the volumetrically most apparent mineralization and displays pronounced vertical variation discerned as changes in the sphalerite color from dark brown Fe-rich high temperature sphalerite formed early and at depth to red, yellow and less commonly white sphalerite as the Fe-poor low temperature end member that typically develops at higher crustal levels and as a later stage. Much of this mineralization occurs as sulfide lodes or as breccia infill. Bulk lower grade mineralization occurs as fine grained Au and Ag sulfosalts deposited within base metal sulfides as part of the main polymetallic mineralization, rising to higher grade Ag with increased base metal contents. These events evolve to mineralization with a more epithermal character and locally higher Au-Ag grades at later stages where base metal sulfides are overprinted by Ag-rich tetrahedrite (freibergite).
-Highest Ag-Au grades locally occur in the absence of Cu-Pb-Zn in ores described as the epithermal end member of polymetallic Ag-Au mineralization which is strongly structurally controlled. High grade Ag may occur as freibergite with celadonite in combination with white sphalerite and dark chlorite commonly with later stage opalchalcedony. Semi-massive to banded chlorite locally occurs with celadonite-pyrite-opal and displays elevated Au with significantly lower Ag: Au ratios. Hypogene hematite occurs with banded quartz as an epithermal assemblage which accounts for elevated Au grades overprinting earlier sulfiderich mineralization.

Breccias are an integral part of the Tahuehueto hydrothermal system and display several genetic styles. Corbett (2007) notes that many of the sulfide-mineralized zones display sulfide transport textures; typical of fluidized breccias. Milled breccias are those in which the clasts have undergone significant working while being transported from deeper to elevated crustal settings. These breccias typically contain rounded clasts in a matrix of milled rock flour which has undergone hydrothermal alteration. Expansion breccias, in which the fragments have been moved apart and filled in with carbonate or quartz in a jigsaw pattern, are typical in dilational structural settings. Magmatic hydrothermal breccias typically occur in near porphyry environments and contain clasts of porphyry intrusions and alteration in a milled matrix. Shingle breccias with elongate, parallel shingle-like fragments, are thought to have been formed by collapse following the explosive escape of volatiles from an underlying magma chamber.

The uppermost portions of the mineralized structures are oxidized. In the oxide zone, mineralization consists of malachite, azurite, chalcocite, covellite, limonite, and hematite. Malachite overprints tetrahedrite, and chalcocite and covellite form coatings on sphalerite. The depth of the oxide-sulfide interface varies considerably, but is generally less than 100m.

Sulfide mineralization lies below the oxidized zone and consists of sphalerite, galena, chalcopyrite, tennantite, tetrahedrite, and probably electrum. Gangue minerals are quartz, pyrite, chlorite, sericite, and calcite. Locally a light green phyllosilicate mineral interpreted to be celadonite (Loucks, et al 1988) forms as gangue and is closely associated with high-grade gold and silver mineralization.

The mining method used as the basis for PFS design was Overhand–Cut and–Fill mining with conventional drilling, blasting, mucking and hauling, scaling and ground support installation and backfilling with unconsolidated, mined waste materials. Full mechanization was assumed using diesel, rubber tired mining equipment and support vehicles.

GRINDING SECTION
This section of the plant works 12 hours per day and will receive ore from the mine in 20 t capacity dump trucks and discharge to the coarse ore bin with a capacity of 60 t. The coarse bin will have a 46 cm grizzly. The ore rocks greater than 46 cm will be reduced with the use of pneumatic hammer or by hand.

The ore from the coarse ore bin, will be fed to a primary jaw crusher by a 61 cm apron feeder, before passing through a fixed 5 cm screen, to send directly to the secondary crusher, using the 61 cm conveyor belt.

The ore fed to the primary crusher, is crushed to a size -5 cm and also passed to the 61 cm conveyor belt, which is fed along with the product -5 cm of the 5 cm screen to the secondary crusher.

The secondary crusher receives the -5 cm ore and reduces it to a -10 cm size, which is passed to a second 91 cm wide conveyor belt, which carries the ore to -10 cm vibrating screens, where the ore -10 cm is separated and passed to the fine ore bin with 500 t capacity. The ore +10 cm size, is transported by 61 cm belt conveyors and returned to the secondary crusher. The ore is then passed to the 91.4 cm conveyor belt which returns the ore to the -10 cm vibrating screens, thus creating a closed circuit to ensure having the fine ore bin ore with a size -10 cm for the next stage of the process.

MILL SECTION
The -10 mm crushed dry ore is fed to a 2.4 m x 2.4 m ball mill with a 300 HP motor, at an average of 20.83 tph. In this stage recycled and fresh water is added at a rate of 23 m3/h, (80% is recycled water (304 l/m) and 20% (76 l/m) is fresh water). Also at this point the first reagents for the flotation process is added, AF 404 and AF 242 promotors and 1,100 g/t of ZnSO4.

The download of the ore as pulp mill, is sent to a pair of cyclones, which return the ore with one size greater than 200 mesh to the mill to ensure that ore that will sent to the next stage in the gravimetric concentration and flotation section, reach a size to 80 % - 200 mesh.

The proposed processing plant is a conventional crushing/milling/flotation/filtering process designed to process 165,000 tonnes per year in 300 operating days, equivalent to 550 tonnes per day through the grinding and flotation circuits producing lead, copper, and zinc concentrates.

GRAVIMETRIC CONCENTRATION SECTION
The pulp from the cyclones at a size of 80% -200 mesh, is fed into a gravimetric concentrator Falcon or Nelson type, which by the use of centrifugal force and difference of specific gravity of the mineral components, concentrates free heavy metals such as gold, silver, and iron. This concentrate is sent to lead concentrate decanter to be mixed and filtered with it. The tailings of the gravimetric concentrator are then sent to the flotation section.

FLOTATION SECTION
The ore pulp is received into the conditioning tank for lead and copper, where the ore sits for a period of 30 minutes. Additional reagents will be added at this point, if requir ........