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Geology
- Property Geology
- Mineralization
Four (4) distinct mineralization styles have been identified at the Rio Grande property:
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Near surface, fracture-controlled copper oxides ±sulphides (at depth) with gold (green targets on Figure 6), |
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Deeper porphyry copper-gold style mineralization (blue targets on Figure 6), |
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Structurally controlled gold (±copper) mineralization associated with pyrite (red targets on Figure 6), and |
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Gold-copper mineralization associated with quartz-magnetite stockworks in diorite intrusive rocks similar to the near by Linderos deposit (yellow targets on Figure 6). |
The main copper-gold mineralization at Rio Grande occurs as fracture-controlled copper oxides and sulphides, which form an annular ring around the main zone of alteration (Figure 5). Mineralization occurs as blue-green and black copper oxides in the near surface environment (i.e., upper ~100-150 metres) and mixed oxides and sulphides in the deeper environment (i.e., below ~150 metres); both with associated gold.
Mineralization covers a large area measuring at least 4 sq. km. and consists of disseminated and veinlet-controlled magnetite-chalcopyrite. Primary copper sulphides have been weathered to secondary, black and blue-green copper oxides to depths in excess of 200 m.
A thorough review of work previously completed by Teck Corporation (“Teck”) in 2000-2001, as well as new geological and structural mapping by Antares, has identified a series of target areas with potential for higher copper-gold grades within a distinct 2 km diameter ring of IP chargeability and anomalous surface and subsurface copper and gold geochemistry. The 200 m average estimated depth to the top of the IP anomalies suggests that there is potential for an extensive area of oxidized mineralization that may be amenable to SX-EW recovery of copper.
The principal copper oxide minerals are chrysocolla, malachite, and traces of azurite. The principal sulphide minerals are chalcopyrite and pyrite, which are typically associated with magnetite. Chalcopyrite (with gold) occurs as coarse-grained clots, disseminations, stringers, and fracture-fillings. In the near surface environment the chalcopyrite is commonly oxidized to a dark brown coloured, translucent “copper limonite”, as well as chrysocolla and other blue-green and black oxides (i.e., Cu-bearing Mn-oxides and neoticite).
A small diorite intrusion located near trenches T_6 and T_7 hosts’ minor quartz-magnetite sheeted veinlets which contain gold and copper; similar to the nearby Linderos deposit of Mansfield Minerals Inc. Mineralization of this style also occurs in the Northeast (NE) target (Figure 6), however little is known about this occurrence and is the subject on ongoing exploration. In addition to the mineralization described above, there are more classic, quartz-pyrite-magnetite veins and stockworks associated with K-feldspar alteration; which occur within the Crowded Feldspar Porphyry intrusive unit (CFPi) located in the sub-surface in drill-hole RGT_01_05.
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