Camino Rojo is an intrusive related, polymetallic gold-silver-zinc-lead deposit hosted in clastic sedimentary rocks along the boundary between the Mesa Central physiographic province and the Sierra Madre Oriental fold and thrust belt. The deposit is situated between splays of the regional northwest trending San Tiburcio fault zone, beneath a broad pediment of Tertiary and Quaternary alluvium. This pediment is surrounded by uplands of folded marine limestone of Late Jurassic through Cretaceous ages.
The most important host to gold mineralization is the Caracol Formation, a rhythmically interbedded sequence of weakly calcareous turbiditic sandstones, siltstones and shales. The underlying Indidura Formation, comprised of regularly bedded siltstones and shales, and the Cuesta del Cura limestone, recrystallized to fine-grained white marble, hosts a minor amount of polymetallic sulfides. Narrow igneous dikes intruded the sediments along linear NE-striking faults.
Mineralization is associated with a network of sheeted carbonate veins and breccia controlled by both primary bedding and discordant structures. Vein networks are enveloped by a zone of potassic alteration with low-grade disseminated gold in pyrite. The dikes are variably mineralized and display sericitic alteration.
Near-surface oxidation extends to depths more than 100m and extends to greater depths along structurally controlled zones of fracturing with high permeability. Oxidation of the deposit to depths of 100 to 150 m is approximately 100%. The underlying transitional zone of mixed oxide/sulphide extends to depths of 200 to >250m and is characterized by partial oxidation controlled along bedding and structures. Oxidation in the transitional zone is enhanced along structural zones and envelopes all strata, dependent on fracture intensity, with an oxide halo of several metres. Adjacent sandy layers are permeable and preferentially oxidized outward many tens of metres, creating a stratigraphically interlayered sequence of oxide and sulphide material at the cm scale. Such robust near-surface oxidation of the Camino Rojo type deposit will support a bulk-mineable open-pit scenario.