Milena Project – Porphyry Cu, Mo, Au
Miocene Belt, Region IV, Chile
Located in región IV, Chile, 115 km east of La Serena (figure 1), a 7 DDH 2087m greenfield exploration program reveals mineralization consistent with major discoveries. Sericite mineralization from core was dated at 14.3 my, consistent with a nearby Infiernillo age intrusive diorite dated at 16 my. Assay spikes reach 0.65% Cu at the bottom of one DH only 175m below grade. Three other DH’s show a combined 680m estimated at @0.24% Au-Cu of continuous full depth lithocap mineralization. The Milena mineralizing system follows the timing and style of world-class Miocene porphyry systems such as the giants El Teniente, Los Bronces, Los Pelambres porphyry and new discoveries Los Azules, Valeriano and Encierro.
Offered for joint venture or lease is 15 square Km (1500 hectares) containing an Au-Cu mineralized rubble shell around a Miocene quartz diorite stock associated with rich chalcanthite bearing oxidized remnants of breccia pipes. The breccia pipes and the quartz diorite stock are exposed for hundreds of meters in drillroads and are ready for testing. Videos and photos available on YouTube and at the MilenaMining.com webpage show the outcrops and mineralization.
Following relatively new geological models incorporating groundwater, geomorphology and depth of erosion: depth to typical core mineralization can be reasonably modeled.
US$2.5-$3 million of exploratory work in 2008-2010 allows preliminary depth, volume and grade modelling. Four succesful DDH intercepts bound an irregular irregular prism 500m wide and 200 m deep containing roughly 25 million cubic meters of “prot-ore” @0.15-0.65% Cu. The prism-corner DDH’s all bottomed in mineralization, one @0.65% Cu only 175m below grade at TD (core bottom). One corner hole shows 232m @0.28 % Cu starting at the surface. Mineralization extends at least 750m along a dike/IP trend between prospective features: a 1 km-wide quartz diorite stock and chalcanthite-bearing breccia pipes.
Figure 2 shows drilling. Notable intercepts include 198m @0.21% Cu (MIL-01), 252m @0.24% Cu (MIL-02), and 232m @ 0.28% Cu (MIL-11). All four mineralized holes bottom in high mineral. Several show increasing grades at depth with highest grades of 0.5-0.65% Cu over 2-4m intervals near TD in one. One infill hole demonstrated mineralization is likely between drillholes 750m apart.
History and Surface exploration
There is no historical production but the area was explored and drilled in the 1980’s. In the 2000s it was explored for epithermal gold and for porphyry copper systems by Barrick and by Teck Lta.
Weak to moderate D-vein like structures and stockworks associated with sericite – limonite mineralization were found within a central zone on-strike with a quartz porphyry dike exiting from chalcanthite breccia pipes toward a mineralized quartz diorite stock/breccia. Surface sampling reveals strong enrichment of surficial material >1000ppm Cu, >100ppm Mo, >100ppb Au, >200ppm As. Results suggest ongoing leaching of gypsiferous lithocap and natural acidification of surface water. Talus and rock chip sampling, geophysical surveys (ground magnetic and IP-resistivity) show favorable undrilled areas. Mapping is available at 1:5000.
Alteration and Dating
Hydrothermal sericite at the system has been radiometrically Ar-Ar dated as 14.3 Ma, confirming a very favorable post Infirnillo-age Miocene mineralization event.
PIMA results show alteration reached potassic stage and that most core hosts clay-chlorite-sericite alteration that is accompanied by moderate to strong quartz-limonite stockwork, widespread propylitic alteration and irregular sericitic and potassic alteration.
Close examination reveals potassic altered-hornblende bearing dikes and clast-filled veins showing cemented quartz rimmed fine-grained pyritic clasts from deep parts of the system (see fig 2 core).
The cores are dominated by sericite-chlorite-quartz alteration with pyrite, chalcopyrite, leached-out gypsum and residual quartz consistent with an outcropping “steamed lithocap”. There are strong epidote halos around clasts and veins with indications the white/gray leached gypsum zone extends down about 75 meters.
Drilling tested the extent of an IP anomaly and tested the “outer” lithocap zones of the porphyry system that created the High Sulfidization mineral suite.
Copper mineral zonation: 1) surficial chalcanthite and covellite, 2) shallow covellite-cpy-chalcocite at 100+ meters, 3) indistinct blue-gray coppers and 4) chalcopyrite-pyrite in simple non-druzy “A-type” vein-like assemblages with little or no vein quartz.
Copper-bearing mineralization is hosted within breccia fragments, in veinlets and in matrix between fragments. Druzy open space quartz overgrowths are present around vein clasts (see Fig 2 core at 88m). Relatively fresh greenish propylitic rock is usually at found deeper than 50-100 meters. At depth, there are multiple meter intersections of primary mineralization consisting of chalcopyrite-bearing quartz granodiorite porphyry dikes showing biotite rimmed hornblende. The dikes extend from the potassic alteration zone of the underlying mineralizing intrusive and appear on the surface..
All seems above the “sulfate front” mineral zone (see fig. 3b).
Core and core photos can be made available and includes all 2,087 meters of core drilled.
The Concession covers flats at 4000m and steep slopes to 5200m (see Fig. 4). The offering includes several cirque basins and high ridges between two through-going features, a major NNW trending structural valley and a subparallel NNW trending ridge line that intersect at Cerro Desfilladero.
Country rock is mostly reported as Paleozoic granite and meta volcanic/sediments but published maps show Miocene hornblende diorite plugs and stocks in the área. One dated at 12-16 my by Sernageomin is visible adjacent to 5400 meter Cerro Desfilladero and appears leading toward the 1-km quartz diorite body
Google Earth images show a diorite plug emanates from branches off the NNW valley lineament and rests immediately adjacent to a felsic/mafic bimodal dike melange carapace making up Cerro Desfilladero.
Large parts of the target area including mineralized stockworks are concealed by red soil and moraine deposits.
Conclusions & Opportunity
Milena is a Miocene breccia-porphyry (Cu-Mo-Au) target with Deep and shallow targets tested by small number of relatively shallow holes that penétrate secondary mineral zonation and confirm primary copper mineralization, that increases at depth.
The latest discoveries such as the “Valeriano” and “El Encierro” projects, show on the surface, geological and geochemical evidence, which is less intense than what is seen at the Milena Concession.
Milena is currently one of the mining projects with the best evidence to become the next major porphyry discovery in Chile.
Figure 1: Regional Metallogenic belts, and Milena position.
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Figure 2: Local exceptional geology, GroungMag (Low), and geochemistry (Cu, Mo, Au, As).
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Figure 3: Porphyry Copper Discovery beneath the Valeriano Lithocap, Chile. (Sillitoe et al, 2016). Valeriano is completely concealed Miocene porphyry Cu-Au. See the low geochemical anomalies in outcrops vs high grade Cu-Au mineralization at Depth (>1.000m.)
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Figure 4: Milena Concession current land position.
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