Trenching

Results

 - Trenching

During 2004-2005, Antares continued the utilization of trenching as a low-cost exploration tool at Rio Grande; cutting a total of 14 new trenches for 3,544 metres and the collection of 1,284 geochemical channel samples (Table 1; Figure 1). The principal objectives of the trenching program were to:

1. Test several areas with strong Au-Cu soil geochemical anomalies and little or no outcrop exposure,
2. Test for extensions of previously known mineralized zones (e.g., Discovery Zone),
3. Establish better controls on the geometry of the mineralized zones, and
4. Provide geological and structural information in areas of limited or no outcrop.

A Komatsu PC220-6 excavator was used for this work; which was found to be a highly versatile machine in comparison to a traditional backhoe. The excavator was also utilized for road construction, drill pad construction, and assisting in certain movements of drill equipment.

Trench locations were established first using all the available information within the Rio Grande GIS database. In order to avoid confusion in the numbering of the new trenches; the first new trench of the 2004-2005 campaign was designated T-23, with the last Teck trench from 2000-2001 being T-22. All proposed new trench locations were double-checked in the field before they were started; with corrections and/or adjustments in location, length, and depth made according to field conditions.

As a general rule and for safety reasons, all new trenches are no more than 2 metres deep. If bedrock was not encountered in the first 2 metres the trench was stopped. In the rare cases where the bedrock was not encountered within the first 2 metres, a series of shallow pits every 50 metres along the trace of the proposed trench were dug in attempt to locate shallower bedrock exposures.

Finally, where possible, the trenches were extended until areas of favourable alteration and/or mineralization passed into either fresh rock or at least areas of less altered non-mineralized rock. By doing this, a sufficient profile is established to provide geochemical contrasts and control in the mapping of the lithological units.

Table 1: Summary of 2004-2005 Antares Trenches.

Antares Trench Mapping

None of the previous 22 trenches completed by Teck appear to have been mapped in detail. As a result, a program of 1:500 scale trench mapping was initiated in 2004 using a consulting geologist, Daniel Bonafede from Salta Argentina, and a group of field assistants to help in cleaning the trenches and also measuring the advance of the mapping. Several of the original 22 Teck trenches were identified as being priorities for detailed geological mapping and 9 of these were completed in late 2004 by Daniel Bonafede.

In early 2005, a second phase of detailed, 1:500 scale trench mapping was envisaged for the 14 new trenches completed by Antares. Unfortunately, the onset of early cold weather and snow allowed for the completion of only 6 of the 14 trenches.

Both phases of trench mapping utilized the same mapping conventions, rock units, and coding systems as those used during the surface bedrock mapping program. To facilitate the integration of the trench mapping data with the drill-hole data; all trench data was converted into a “log format” similar to the logs used to record drill-hole information. Thus, each trench could be used as a “sub horizontal drill hole” for the purposes of plotting cross sections, etc.

Antares Trench Results

The principal result of the new trenching campaign has been the delineation of the new Sofia oxide-copper mineralized zone with trenches T-28, T-30, and T-31 (Figure 1). Additional trenches, T-32 and T-35, established the continuity of this new mineralization, and the connection with mineralization of the Discovery Zone (Figure 1).  Anomalous geochemical results from trenches to the NW of the Sofia Zone, T-27 and T-33, suggest that the mineralized zone may continue under the talus cover to the south of those trenches.

New trenching in the area of the Discovery Zone, T-23 and T-10 extension (Figure 1), has established the eastern limit of that mineralization. New trenching has also shown that the Discovery Zone mineralization remains open to the south and west where it disappears under rock talus cover; and as mentioned earlier, contiguous with the Sofia Zone to the north-northwest.

New trenches in the central area of the property, T-24, T-26, and T-29 (Figure 1), provide a good profile of geology, alteration, and geochemistry across the central portion of the Rio Grande system. The SW most portion of T-24 (Figure 1) encountered anomalous copper in bedrock, before it passed into thick rock talus cover. This may be the south-western extension to the Discovery Zone mineralization. Similar geochemical anomalies were encountered in the SW most part of T-25 (Figure1), before it too encountered thick rock talus cover.

In conclusion, trenching has proved to be positive, fast, cost effective method for testing soil geochemistry anomalies, delineating and extending known zones of mineralization, and for geological investigations in areas of talus cover or limited outcrop. Table 2 presents the geochemical results from the 2004-2005 Antares trenching program.

Table 2: Summary of the principal mineralized intervals cut by the 2004-2005 Antares trenches.

Previous Teck-Mansfield 2000-2001 Trenching Work

Previous trenching work at the Rio Grande project by Mansfield and Teck proved to be highly effective exploration technique. Within the area of mineralization there is only 10 to 15 percent outcrop: however, the surrounding colluvium cover is often less than 2 meters thick. Trenches were typically, 0.5 to 1.0 meters deep, with channel samples collected in areas where bedrock is exposed.

During 2000-2001, Teck constructed 22 trenches totalling approximately 2,650 metres (Figure 1). A total of 1,399 rock chip samples for Au, Ag, and Cu geochemical analyses were collected from these trenches. Trenches one (1) through five (5) were hand-dug; while all the others were completed using an excavator. Trenches were sampled in 2-meter intervals (4-meters in a few poorly exposed areas) by a portable diamond saw and hand channel sampling using a chisel and mallet. At the start of the program, all samples were analyzed for 32-elements using ICP and gold by fire assay; however in an apparent cost-cutting measure, the bulk of the remaining trenches were only sampled and analyzed for copper and silver by standard geochemical techniques, and gold by fire assay (Table 3).

Trench locations were surveyed using a Trimble differential GPS unit, while test pit locations were surveyed by using a Garmin 12XL GPS unit. Trench locations are shown schematically in Figure 150. Antares has subsequently found that the “surveyed” locations of these trenches does not match very well with their positions on recently acquired, high-resolution (i.e., 0.6 metre pixel size) Quick Bird images.

Table 3: Teck 2000-2001 trenching program highlights.