Results reported earlier this year prompted a new interpretation of the Baritina targets highlighting the presence of a subvertical and subcircular “diatreme or phreatic” breccias that partially control the high-grade mineralization. The high-grade mineralization is concentrated in some sectors i.e., faults and/or feeder vents. Mineralization cuts across different lithologies with no stratigraphic further control.
Drill holes reported today targeted mainly the west mineralized halo of the high-grade core zone. Notable results included 14.62 m at 1.45 g./t Au starting at 33.25 m in hole PA-D21-86, and 10.77 m at 1.35 g./t Au starting at 35.00 m in hole PA-D21-90.
The new drilling results, reported in this press release, were integrated with the previous data into a new geological model that refined the high and low-grade domains. On the high-grade side, two distinct geometries have been modeled: a pipe shaped, possible feeder or vent, and a lateral structurally controlled subvertical tabular body. Both subdomains are being evaluated by the mine team as future feed for the CIL plant. On the low-grade side, an extended lateral halo domain will be evaluated as possible heap leach feed.
Figure 4. Baritina 3D view and of West - East slices showing high- and low-grade Domains
Araña mineralization is characterized by Fe-Mn oxides, barite, and cryptocrystalline quartz veinlets and stockworks and sectors with vuggy silica textures infilled by oxides). Trench results reported previously this year (see release July 7, 2021) including 4.80 m grading 4.09 g/t Au (PA-T21_029) and 9.40 m grading 5.06 g/t Au prompted this drill program that consisted in 5 holes, totalling 260.2 m. The Arana drill results resemble in a way the structures in Chulengo, with enriched shallow zones associated with hydrothermal breccias and faults. These discrete zones may reflect the upper segment of a possible central feeder zone, leaving the concept of a deeper target (coalescence of shallow structures) open for further exploration. Additionally, the NE-SW trend is open along strike in both directions. Notable a narrow structure with a true width of 0.32 m was intercepted in hole PA-D21-95 at 28.00 m carrying 21.2 g/t Au.
Figure 5. Araña drill hole and trench location
The area between two mined areas Armadillo and Mara was tested by several fence arrays of drill holes that intended to systematically investigate the occurrence of single or sheeted veins along the known West-East predominant trend. Both Mara and Armadillo are hosted by the Cerro Oro volcanics and are associated to West-east structures, that include high zones along strike length between 200 m and 350 meters.
The permissive trend between Armadillo and Mara is crosscut by late North South faults implying possible offsets. The zone that was drilled shares the same multispectral signature as both Armadillo and Mara, reflecting similar clay alteration mineralogy.
Several narrow hydrothermal breccia structures in the permissive rhyolitic rocks were intercepted in the holes reported in this release. Breccias and veins are composed by grey to black silica with varying sulphides content. Notably, hole MA-D21-043 intercepted 4.80 m at 1.21 g/t Au from 58.4 m in a brecciated interval that included semi massive sulphide mineralization. Given the proximity to the operation follow up for this and any additional relevant intercept in the holes yet to be reported will be carried out systematically by the Cerro Oro mine geological team.
Choique drillholes confirm the extension eastwards of the WNW-ESE structures, in the immediate adjacency of the current resource constraining pit. West extension drillholes show wide zone with strong silicification that links with silica ribs recognized at surface. There is a complex system of parallel and orthogonal faults to the mineralized structures that displaces them, however, they have been recognized in 200m in length.
Notable intercept in Choique includes 1.9 m (interval length, true width unknown as no relevant structural data was collected) grading 7.05 g/t Au in Hole CH-D21-049 and 2.7 m at 1 g/t Au in hole CH-D21-049, defining the East Trend that will be further tested by the mine team.
This trend has the potential of extending the east wall of the current operational pit adding shallow resources to Choique (see Figure 6)
The Gecko target is located immediately to the southeast of the Cerro Oro Pit. A 500 m West-East structure partially segmented by NS crossing Faults. Results reveal general low-grade mineralization along this strike length. The western zone, in the immediate vicinity to Cerro Oro, includes the same host rock of Cerro Oro-Coyote sheeted vein system, a quartz crystal-rich volcanoclastic unit. Mineralization in this segment (~ 100 m) is relatively more attractive than the rest of the trend with the occurrence of stockwork, veinlets and cement breccia. Two discrete structures were intercepted, the first corresponds to a quartz vein with lattice bladed texture and the second is a breccia with a pulse of grey silica as cement with wall clasts.
Figure 6. Choique LOM Pit and drill hole location
Figure 7. Gecko Trend and drill hole location
M11 target is located 300 m west of the western edge of the Cerro Oro Pit. A 5-drill hole program was completed with the double objective of sterilizing ground for a waste pile and targeting a magnetic anomaly.
Main host rock includes volcanoclastic and andesitic flows reflecting higher stratigraphy relative to Cerro Oro. A few discrete structures were intercepted by the M11 holes with varying degree of alteration and brecciation but failed to produce significant Au mineralization.