The Yerba Project (Figure 1) occupies the southwest portion of the large Naltagua Copper System and comprises extensive outcropping copper mineralization and at least 10 historical workings that fall along a north-trending structure corridor 1.2km long and over 100m wide. The mineralization has also been mapped and sampled vertically in outcrop over 400m from RL800m to RL400m.
Figure 1: Location of the Yerba Project Area within the Naltagua Copper System.
Figure 2: Exploration Summary of the Yerba Project Area.
Copper mineralization has been mapped and sampled at several locations (where outcrop permits) along a 700m zone, which coincides with a much longer (1.2km long, 50m wide) Induced Polarisation (IP) resistivity anomaly. The resistivity anomaly is interpreted to be ‘mapping’ the hydrothermal alteration (silica-epidote) associated with the copper mineralization. Work continues in the search for new zones of mineralization along this trend.
Yerba Workings: The Yerba Workings lies at the northern end of the greater Yerba Project Area (refer to Figure 2 for location) and fall with the coherent IP resistivity anomaly.
Figure 3: Yerba Workings (mined early 1900’s).
A principal feature of the mullock left by the miners at Yerba is the pervasive disseminated copper sulphide mineralization (bornite) in the andesite and andesite breccia (Figure 4).
Figure 4: Disseminated copper sulphide (bornite) in andesite hydrothermal breccia from the Yerba Workings Mullock.
Equus has mapped and channel-sampled 541m of the underground Yerba Workings (the adits) and taken over 100 surface samples. Channel sampling across the back face of the Yerba pit returned 48m at 1.34% Cu and finished in copper mineralization at both ends of the channel.
Channel sampling of the adits returned a number of ore-grade intervals including 60m at 1.72% Cu, which remains open into the back-wall of the adit. At the time of mining (1905 to 1945), any mineralization grading less that 4% Cu could not be profitably treated at the near-by smelter.
The results of the sampling conducted by Equus is summarised below in long-section (Figure 5).
Figure 5: Results of underground and surface channel sampling of the Yerba Workings.