Summary:
Mineralization
Gold and silver mineralization at Cerro Caliche primarily occurs within a structural framework dominated by fractured Mesozoic quartzites and shale rock units, as well as in rhyolitic intrusive dikes and sills. The mineralization across the project area is closely associated with varying degrees of silicification, a process where silica-rich fluids permeate the rock, leading to the formation of quartz veins. This silicification ranges from moderate silica addition, forming weakly mineralized zones, to intense pervasive silica flooding, which is closely linked with higher-grade mineralization.
The mineralization style at Cerro Caliche is typical of low-sulphidation epithermal systems. These systems are characterized by the formation of quartz veins that display classic epithermal textures, such as open-space filling, irregular banding, and the presence of open vugs. These features suggest that the mineralization occurred at relatively shallow depths under conditions that allowed the formation of these open spaces, which were later filled by silica and precious metals.
The structural regime at Cerro Caliche is defined by broad listric faulting, which has created a somewhat en-echelon pattern of vein structures. These veins are spread across a corridor that covers approximately 25 square kilometers, illustrating the extensive nature of the mineralizing system. Individual vein structures observed on the project have a maximum strike length of up to three kilometers, although the exact displacements of these veins remain undetermined. The vertical extent of the mineralization, inferred from the topographic differences across the project area, is estimated to be around 600 meters. This significant vertical extent suggests that the mineralizing fluids were able to penetrate deep into the crust, leading to the formation of mineralized zones over a substantial depth range.
Mapping of the quartz veins has revealed a strong structural control on their orientation. Many of the rhyolite dikes that host the mineralization follow the same structural trends, indicating a close relationship between the emplacement of these dikes and the mineralizing events. This structural control is likely related to a broader rift extension zone, where tectonic forces created the fractures and faults that served as conduits for the mineralizing fluids. The continuity of these dikes and veins beyond the project area, extending into the nearby Cerro Prieto mine area and eastward towards the Mercedes Mine, further underscores the regional significance of this structural trend.
Significant Mineralized Zones
Exploration at Cerro Caliche has identified several main mineralized vein zones, each of which has been the focus of detailed exploration and drilling. These zones are named after historic mine sites and represent the primary targets for resource development at the project.
1. Los Japoneses Zone (including Cuervos, Boludito, and Buena Vista): The Los Japoneses mineralized zone is the largest and most extensively drill-defined vein zone on the property. This zone is characterized by its significant width, length, and volume, making it a primary target for future mining operations. The Cuervos vein zone is considered a southward extension of Los Japoneses, while the Boludito vein zone continues the trend to the north. The Buena Vista vein zone, which occupies a fault breccia zone, expands Los Japoneses to the northwest and merges with the Buena Suerte vein zone. Host rocks for these zones include rhyolite dikes and quartzite, which are typically associated with higher-grade mineralization.
2. Abejas Zone (including Veta de Oro and Rincon with Chinos NW and Chinos Altos): The Abejas zone, located north of Los Japoneses, is characterized by a combination of disseminated stockwork gold mineralization and more structurally controlled vein mineralization. The Veta de Oro vein zone, which extends southward into the Abejas zone, is a key feature of this area. As Veta de Oro continues southeast, it splays into four separate vein-like bodies, each approximately 500 meters long, with numerous quartz veinlets. These veins terminate in an arroyo area, where they are offset by a low-angle fault. The undrilled Chinos Altos zone lies to the south, while the northwest extension of Veta de Oro connects with the El Rincon vein zone, which has been extensively drilled, revealing significant gold mineralized intercepts.
3. Cabeza Blanca, Guadalupe, and El Colorado Zones: The Cabeza Blanca vein zone, trending north-south with a steep easterly dip, is one of the most significant mineralized zones on the property. The Guadalupe vein zone runs sub-parallel to Cabeza Blanca but with a lower dip angle, extending southward into the El Colorado zone. The El Colorado zone features typical quartz vein gold mineralization with sericitic alteration, indicating a strong hydrothermal influence. The presence of a flat, high-grade quartz vein, known as the El Colorado Vein, discovered in drill hole SRC-044, highlights the potential for high-grade mineralization within this zone.
4. La Española Zone: The La Española vein structure is a northwest-trending feature that continues across Cerro Caliche into the El Bellotoso zone. Although exploration in this area has been limited, drill results have indicated significant potential, with some areas displaying combined base metal levels exceeding 1%. The presence of base metals alongside gold and silver mineralization suggests that this zone may represent a more complex mineralizing system, potentially linked to deeper-seated hydrothermal processes.
Deposit Types
The Cerro Caliche Project, along with surrounding deposits, is classified as a low to intermediate sulphidation epithermal system, a deposit type that is well-represented in northeastern Sonora. Notable nearby deposits include the Santa Elena silver/gold mine, Las Chispas silver/gold mine, and the Mercedes mine. Similar deposits in the state of Chihuahua include the Dolores silver/gold mine and the Pinos Altos silver/gold mine.
At Cerro Caliche, the alteration intensity varies from weak to strong, with silicification being the most pervasive alteration type associated with mineralization. This silicification is often accompanied by sericite-illite-kaolinite assemblages, particularly in zones of intense fracturing and mineralization. Propylitic alteration, characterized by the presence of chlorite, epidote, and pyrite, forms broad haloes around the veins, especially in the more mafic rock types at depth.
The mineralization styles observed at Cerro Caliche are consistent with other low sulphidation epithermal deposits in the region, such as the nearby Mercedes and Cerro Prieto gold mines. The deposit model for Cerro Caliche includes various field-identifiable vein textures in quartz veins, such as lattice blading structures, which are indicative of boiling fluids and local acidic conditions during mineralization. Adularia, a potassium-rich mineral commonly associated with boiling in epithermal systems, is tentatively identified by its pink coloration within some vein material. The western side of the project, particularly near the Zorillo veins, contains white glassy quartz that, while only geochemically anomalous in gold, exhibits irregularly high levels of lead and zinc, suggesting a more complex mineralizing history in this part of the project.
The Cerro Caliche Project, with its diverse vein structures, extensive alteration, and significant gold and silver mineralization, represents a key exploration target within the broader context of epithermal gold-silver deposits in Sonora, Mexico.