The Project covers an area of 161 square kilometres, of which 1) 46 km2 are covered by 19 exploitation concessions that are the subject of an option agreement between an indirect, wholly-owned subsidiary of World Copper, TriMetals Mining Chile SCM (“TMI Chile”), and a third- party vendor for a 100% interest in and to the concessions (the “Escalones Option”) and 2) 115 km2 are covered by 40 exploration concessions, owned by TMI Chile.
Summary:
The Escalones Property lies within the Miocene to Pliocene age Pelambres-El Teniente Porphyry copper belt, which hosts the world’s largest underground copper mine at El Teniente, as well as other large copper deposits at Los Bronces-Andina, Pelambres (Katsura, 2006) and Bajo La Alumbrera in Argentina. Copper mineralization at Escalones occurs in two forms: (1) as skarn and lithologically controlled mineralization hosted by altered sandstone/shale and intrusive dikes and sills and (2) as porphyry-style disseminated and stockwork mineralization hosted by an underlying intrusive granodiorite-diorite stock. Rock geochemistry from surface and drill core shows anomalous levels of gold, silver, and molybdenum that are spatially associated with the copper mineralization. This spatial relationship may also be due to separate pulses of mineralization or zoning within a much larger porphyry system.
Porphyry mineralization is associated with moderate to intense potassic alteration (as secondary biotite) in the granodiorite and adjacent hornfelsed sandstone. The metasomatic replacement or skarn-type mineralization is hosted by calcareous, feldspathic sediments, which form an open, upright, north-trending fold cored by the intrusive porphyry system. High-grade copper was historically mined (15 tonnes at 12% copper (Cu) (Katsura, 2006) at Escalones from exposures of magnetite-chalcopyrite skarn at Escalones Alto and prospects along Escalones Bajo. Previous drilling has demonstrated that high-grade magnetite skarn extends to the east and south from outcroppings at Escalones Alto and changes to calcsilicate dominated assemblages down-dip.
Skarn mineralization peripheral to the porphyry along the upper eastern margin (Escalones Alto) comprises mostly magnetite, garnet, and pyroxene skarn developed within sandstone, carbonate, and calcareous shale near contacts with intrusive rocks, with coarse copper oxides and carbonate near surface, transitioning to chalcopyrite-pyrite at depth. Finer disseminated and fracture-controlled mineralization occurs within biotite hornfels with quartz stockwork in steeply east-dipping hornfelsed calcareous shale and fine sandstone and, to a lesser extent, within altered andesite sills and dikes. Magnetite skarn generally hosts the better mineralization, especially in the upper oxidized portions. Grades are highest close to the contact of the reactive sedimentary rocks with the central intrusive complex.
Supergene weathering and mobilization of copper has developed a stratification subparallel to the current surface topography of enriched copper-gold-silver grades to roughly 300 metres below surface in both porphyry and skarn zones. The mineral zonation is clearly seen in core where upper portions are completely altered to clay with iron and copper oxides, transitioning down to mostly weakly altered rock with oxides primarily in fractures and faults, with the oxides diminishing with depth to where sulphides are preserved in fractures. The skarn is as deeply weathered and oxidized in places as the sedimentary and intrusive units with similar copper oxide minerals. However, the oxide-sulphide boundary is more complex within the skarn and controlled more by host lithology, with the coarse sulphides only partially converted to secondary minerals and extending closer to the surface, especially within calcareous units. Within thicker limestone beds, copper occurs mainly as fracture-controlled malachite or is confined to porphyry sills and dikes. The oxidation extends along sandstone and intrusive units well below the limestone on the east flank, indicating acidic oxidizing fluids migrated down and east from the ridge.
Copper and related gold-silver-molybdenum mineralization at Escalones occurs as skarn and porphyry types, as copper oxide (primarily chrysocolla), sulphate, and carbonate (malachite and azurite) down to approximately 3,400 metres elevation and along structures to 3,300 metres and transitioning at depth to chalcopyrite, chalcocite, bornite, and covellite. High-grade copper-oxide and copper-sulphide skarn mineralization forms the resistive high ridge at Escalones Alto and attracted the first exploration efforts and small-scale production from limited workings.
Porphyry mineralization is associated with moderate to intense potassic alteration (as secondary biotite) in the granodiorite. In general, potassic-altered hornfelsed shale/sandstone along both western and eastern flanks of the central intrusive complex hosts lower copper grades than the granodiorite and dacite porphyry hosts.
Enriched, oxidized porphyry mineralization is expected to continue under the southern extension of the lithocap, called the “Mancha Amarilla.” This area of gossanous argillic alteration extends over one kilometre to the south but has not been drill tested and only recently sampled at surface. Porphyry mineralization is also open to the west, between the western edge of the Meseta to the Escalones Bajo fault zone. Surface sampling indicates the fault zone is mineralized as well and may host higher-grade mineralization.
Skarn mineralization peripheral to the porphyry along the upper eastern margin (Escalones Alto) comprises mostly magnetite, garnet, and pyroxene skarn developed within sandstone, carbonate, and calcareous shale near contacts with intrusive rocks, with typical coarse copper oxides and carbonate near surface, transitioning to chalcopyrite-pyrite at depth. Finer disseminated and fracture-controlled mineralization occurs within biotite hornfels with quartz stockwork in steeply east-dipping hornfelsed calcareous shale and fine sandstone and, to a lesser extent, within altered andesite sills and dikes. Magnetite skarn generally hosts the better mineralization, especially in the upper oxidized portions. Grades are highest close to the contact of the reactive sedimentary rocks with the central intrusive complex.
The main skarn horizon forms the sharp ridge with the best mineralization at surface and dips steeply to depth under barren carbonate rocks to the east and north. The mineralization changes from garnet-magnetite-pyroxene skarn along the ridge crest to more of a calcsilicate assemblage within sandstone and shale and numerous feldspar porphyry sills. Extensive rock chip sampling of the outcrops returned wide intervals of significant copper oxide mineralization; the upper strata nearer the transition to overlying limestone were more reactive and are better mineralized.