The Camino Rojo property is 100% owned by Orla Mining Ltd. through its Mexican subsidiary Minera Camino Rojo S.A. de C.V.
Orla is the operator of the Camino Rojo Project and has full rights to explore, evaluate, and exploit the property. Pursuant to the option agreement dated November 7, 2017 between Newmont and the Company, if a sulphide project is defined through a positive Pre-Feasibility Study outlining one of the development scenarios A or B, Newmont may, at its option, enter into a joint venture for the purpose of future exploration, advancement, construction, and exploitation of the sulphide project.
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Summary:
The observed geological and geochemical characteristics of the gold-silver-lead-zinc deposit at Camino Rojo are consistent with an intermediate sulphidation-state (IS) epithermal and a distal oxidized gold skarn deposit.
Mineralization and Structure
The Camino Rojo property is in the eastern part of the Mexican Fold and Thrust Belt (MFTB). Bedrock mapping across the property has identified northeast vergent folds with moderate southwest dipping axial planes and gentle northwest-southeast plunging fold axes. Open pit mapping at Camino Rojo has identified folding within the Caracol Formation characterized by northeast vergent similar folds with thickening of mudstone layers in fold hinges. Sandstone layers tend to form similar folds with extensional features (e.g., fractures and tension gashes) on the outside of fold hinges. Short limbs are commonly steeply dipping or overturned and may be sheared out, commonly with centimetre-thick clay matrix cataclasite. Reverse faults with southwest side up sense of movement have also been identified within the open pit. Propertyscale reverse faults have not been identified.
The San Tiburcio Lineament (STL) is a major regional fault corridor that can be traced over a strike length of approximately 300 km. In the Camino Rojo area, there are second order lineaments striking northwest-southeast, e.g., the Guanamero, Los Lobos and Camino Rojo faults.
Historical workings around Camino Rojo are typically small, with strike lengths less than 30 m and depths less than 20 m. The historical workings exploited stratabound decimentre-scale veins with erratic Ag-Pb-Zn mineralization in carbonate stratigraphy.
Recent drilling at exploration targets on the Camino Rojo property have intercepted narrow high-grade gold mineralization at Guanamero, located approximately seven km northeast of the Camino Rojo open pit (Orla 2023).
Within the Sulphides Zone at Camino Rojo, the earliest phase of gold mineralization, Stage 1, is associated with pervasive potassic alteration and disseminated fine-grained pyrite. Disseminated pyrite formed preferentially in muddy sandstone to mudstone parts of graded beds. Gold grades are typically <0.4 g/t Au. No other metals are known to be associated with this phase of gold mineralization. Within Zone 22, Stage 1 gold mineralization is not well preserved, with few examples of potassic alteration and disseminated pyrite in siliciclastic intervals having been identified.
The main stage of gold mineralization, Stage 2, overprints Stage 1 pyrite mineralization. The Dike Zone, the steep northwest dipping, northeast-southwest striking structure intruded by dioritic dikes, and the Bx1 fault breccia, a moderate to steep northwest dipping, northeast-southwest striking brittle fault, have been identified as important deposit-scale structures that influenced the distribution of Stage 2 polymetallic sulphide veins. In the open pit, the Dike Zone and Bx1 intersect. Moving down plunge to the southwest, the Dike Zone and Bx1 diverge, with a separation of approximately 300 m at the base of the sulphides.
Within the sulphides, Stage 2 is controlled by mutually crosscutting moderate to steep northwest and shallow south-southwest dipping intermediate sulphidation veins. Where the Dike Zone and BX1 intersect, Stage 2 veins crosscut dioritic dikes. Moving down plunge, Stage 2 veins both crosscut and locally exploit the margins of dioritic dikes. Stage 2 veins consist of pyrite-arsenopyrite and pyrite-sphalerite-galena (Sanchez 2017). Where Stage 2 veins crosscut dioritic dikes, potassic alteration haloes with decreased Stage 1 pyrite content are evident. Within siliciclastic rocks, the potassic alteration halo is not visually obvious although a millimetre-scale halo of decreased Stage 1 pyrite content is common. Stage 2 veins crosscut northeast vergent folds in the Caracol Formation, locally exploiting structures associated with folding (e.g., hinge zones, extension gashes, etc.). No significant post-Stage 2 structures (e.g., offsetting of structural domains) associated with northeast vergent folding have been identified at this time.
Within Zone 22, Stage 2 mineralization consists of fine- to coarse-grained disseminated, patchy, and massive auriferous pyrrhotite-sphalerite-pyrite as carbonate bedding replacements and as steep veins or breccias along the margin of and within dioritic dikes. Zone 22 polymetallic sulphide mineralization occurring as bedding replacement appears to follow northeast vergent folding of carbonate stratigraphy. Crosscutting relationships in the sulphide minera lization indicates main stage gold mineralization is syn- to post-tectonic with respect to northeast.
The youngest metalliferous event identified at Camino Rojo are Stage 3 low sulphidation veins. Within the Sulphide Zone mineralization, Stage 3 mineralization consists of colloform banded quartz veins, drusy-coxcomb quartz veins and polymictic quartz cement hydrothermal breccia with pyrite-galena-sulphosalts with moderate to high gold and silver values (Longo 2017; Longo and Edwards, 2017). Within Zone 22, a younger phase of gold and silver mineralization, consisting of disseminated to patchy chalcopyrite-pyrrhotite associated with retrograde skarn alteration, has been identified. This younger phase of gold-silver mineralization is tentatively correlated with Phase 3 mineralization in the Sulphides based on crosscutting relationships. Stage 3 veins overprint and locally exploit Stage 2 structures.
Post-mineralization structures consist of unmineralized calcite veins in both the Sulphides and Zone 22 and brittle faults. The Bx1 Fault was reactivated as a normal fault. This interpretation is supported by the inclusion of Stage 2 vein fragments as clasts within Bx1 clay matrix cataclasite and slicken lines indicating northwest side down sense of movement. The youngest structures identified at the Camino Rojo Deposit are steep northwest and southeast striking fault breccias and crush breccias. These youngest structures are interpreted to be syn-tectonic with Miocene extension.
Oxidation
Oxidation ranges from complete oxidation in the uppermost parts of the deposit, to unoxidized in the sulphides and Zone 22. The transition between oxidized and unoxidized mineralization underlies or surrounds oxide mineralization. Oxidation within transition zones is controlled by faulting, fracturing and permeability of strata.
Oxidation is nearly complete in the uppermost parts of the deposit, generally extending from surface to depths of 150 to 200 m. The transitional zone of mixed oxide/sulphide extends as deep as 650 m below surface where oxidizing fluids penetrated along the Dike Zone and Bx1 structures.
Within the oxide open pit and Sulphides Zone, sandy layers of the Caracol Formation are preferentially oxidized, creating a stratigraphically interlayered sequence of oxide and sulphide material at the centimetre-scale, with oxidation along structures affecting all strata. Incomplete oxidation in the transition zone may result in nearly complete oxidation of the gold bearing parts of the rock, resulting in metallurgical characteristics more like oxide than sulphide hosted gold mineralization.
No oxidized material has been defined in Zone 22.
Conclusions
The distribution of auriferous mineralization at Camino Rojo is controlled by steep northwest and shallow south dipping polymetallic veins within the siliciclastic hosted oxide and sulphide zones. Within the carbonate hosted Zone 22, auriferous mineralization is controlled by disseminated, patchy and massive polymetallic sulphide replacement of carbonate strata and sulphide breccias along the margins and crosscutting dioritic dikes. Pervasive, near surface oxidation extends to approximately 150 to 200 m below surface and extends to greater depths along structurally controlled zones of fracturing and permeability.