Summary:
DEPOSIT TYPES
The deposit was more recently classified by Arce-Burgoa and Goldfarb (2009), as being a deformed example of the Iron Ore Copper Gold (IOCG) association.
The two main deposits types present on the Don Mario Property are exemplified by the copper-dominated UMZ deposit that shows direct association with a large calc-silicate zone, and the gold-dominated LMZ deposit that occurs beneath the UMZ and shows direct association with shear-focused silicification, calcsilicate, potassic, and iron oxide alteration. The Las Tojas and Cerro Felix deposits are similar in style and association with the LMZ, but no substantive additional examples of the UMZ style have been identified on the Property to date.
Tailings Storage Facility (TSF)
Tailings are not a “deposit type” in the conventional sense but in this case, for the purposes of considering Don Mario’s TSF content a Mineral Resource, they are described as an accumulation of loose material with grain size finer than sand, mainly composed by silt size material and less than 20% of clays. The tailings material humidity can vary from 20.8% to 51.4% (Sanchez et al., 2018).
The executed laboratory tests evidence that the tailings can be grouped into fine tailings and coarse tailings, classified respectively as silty sands and silts with low plasticity with the following characteristics:
- The coarse tailings, classified as silty sands, have a field density of 1.468 g/cm3 to 1.712 g/cm3,
a specific gravity of 2.81 to 2.93 and hydraulic conductivity of 2.81 E-04 cm/s to 4.03 E-05 cm/s.
- The fine tailings, classified as silt with low plasticity, have a field density of 1.157 g/cm3 to
1.649 g/cm3, a specific gravity of 2.45 to 2.91 and hydraulic conductivity of 2.28 E-04 cm/s to
1.10 E-06 cm/s.
Oxide Stockpiles
The oxide stockpiles provide for a rather unique and unconventional deposit type. Because the mineralized material that was used to build the stockpiles was well defined as to tonnes and grade, each of the stockpiles is in itself a “mineral deposit”. These oxide stockpiles form a rather unique deposit type because mines seldom stockpile mineralized material that has such high-grade mineralization. Consequently, these stockpiles cannot be evaluated using the traditional exploration techniques and tools utilized for in-situ mineral deposit.
Mineralization
Four principal mineral deposits on the Don Mario property have contributed to commercial mining operations to date. The most significant of these are the UMZ and LMZ. The CF deposit is located 500 meters northwest along strike from the LMZ and UMZ and supported a limited amount of open pit mining from 2009 to 2011. All occur within the Cristal Schist Belt and the Don Mario Shear Zone. Orvana also mined LMZ style mineralization from the Las Tojas (LT) deposit during the 2009 to 2011 period. This deposit i located about 12 km northwest of Don Mario mine and is associated with an un-named shear zone within the Eastern Schist Belt that is separate from, but parallels, the Cristal Schist Belt. Summary points relating to the main gold-copper-silver deposits of the Don Mario property are highlighted below:
Don Mario Shear Zone (Cristal Schist Belt):
- LMZ gold deposit: mined out predominantly by underground methods in 2009.
- UMZ copper-gold-silver deposit: overlies the LMZ.
- CF gold deposit: 0.5 km north of LMZ and UMZ; saw limited open pit production from 2009 to 2011; CF was a low copper grade and high gold grade deposit amenable for the CIL plant.
Unnamed Shear Zone (Eastern Schist Belt):
- LT gold deposit – mined out in 2011 & 2019.
- Oscar gold prospect northwest of LT has not been thoroughly tested by drilling and trenching to date.
- In addition to the known deposits, several geophysical and geochemically defined targets for exploration drilling have been identified along the 40 km length of this schist belt.
The UMZ forms a prominent, oval shaped, treeless hill that is oriented at approximately 315º, parallel to the regional shear fabric trend of the Cristal Schist Belt. The mineralized zone plunges northwest at approximately 15º. The UMZ has been divided into 9 main rock types, the most prevalent of which are calc-silicates such as diopside tremolite rock and massive tremolite rock plus dolomite/ophicalcite and talc schist.
The main UMZ calc silicate bearing zone is approximately 500 m long and forms the Cerro Don Mario, which is a ridge approximately 120 m high. This rock package has a maximum horizontal width of approximately 150 m and ranges from 5 m to 100 m thick. Part of the magnesio-silicate alteration and UMZ mineralization is weathered and is divided into four mineralization zones based on mineralogy:
- The Porous zone is characterized by vuggy cavities left by the dissolution of calcite and locally abundant masses of white and orange brown amorphous zinc carbonates and hydroxides, including smithsonite.
- The Oxide zone is characterized by abundant malachite with lesser chrysocolla, azurite, native copper, cuprite, pitch-imonite, and silver sulfosalts.
- The Transition zone features traces of pyrite, bornite, sphalerite, and galena withweathered limonite and chalcocite coatings, as well as minor copper oxides.
-The Sulphide zone consists of dark green tremolite with bornite, chalcopyrite, and sphalerite. Gold and silver grades are associated with chalcopyrite and bornite mineralization.
The LMZ mineralization is strata bound within a distinct package of metamorphic strata that consists of four mineralized subdivisions, that are readily distinguishable from hanging wall and footwall units.
The most important distinguishing feature of the LMZ units from the hanging wall and footwall schists is the complete absence of muscovite. The contacts are well defined over 1 m to 3 m widths with a drop in muscovite from 20% of the rock to only trace amounts. While the LMZ is characterized by the presence of Au, Ag, Cu, Pb, Zn Bi, W, and Mo, there is very little or no enrichment of these elements in the wall rocks.
Overall, unit, LMZ -quartz-amphibole-garnet-magnetite-cordierite ± biotite rock, is the main host of the mineralization, and has been termed. magic rock. by the project geologists. Assay results indicate that this unit hosts most of the economically significant mineralization below the 300 m level. Unit exhibits mineralogical and textural variability within individual drill holes and along strike. Gedrite-cordierite layers range in thickness from less than 0.10 m to more than 3.0 metres with the most common thickness ranging from 0.10 m to 0.80 metres. Due to metamorphism, recrystallization, accompanying potassic alteration, and later shearing of the quartz amphibole section, the protolith is indeterminate.
Unit LMZ quartz-garnet-amphibole-biotite is distinguished from unit LMZ quartz biotite ± sillimanite rock mainly on the basis of containing less than 5% almandine garnet, and the absence of sillimanite, which can comprise up to 20% of the latter unit. Sillimanite is regarded to have been a major component of the rock prior to potassic alteration.
The UMZ and LMZ are separated by sections of dark greenish-black, fine grained, well foliated chlorite schist ranging in thickness from less than one metre to greater than 10 metres. Similar schists are intercalated with LMZ lithologies with cross-cutting relationships, and all are grouped into Unit chlorite-serpentine-talc ± amphibole schist.