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Geology
- Property Geology
- Lithology
The Rio Grande copper-gold prospect is located within a partially eroded, earliest Middle Miocene (16.5 Ma), andesite-dominated volcanic-intrusive complex of high-K, calc-alkaline affinity. The Rio Grande complex intrudes through granitic basement rocks into a continental back-arc basin filled with a thick (>1500m), oxidized sequence of continental red bed sandstones (Figure 1). Sections within this sequence contain sulphate evaporites and possible halite in the upper parts of the stratigraphy. Host rocks include a wide variety of dacite to andesite, sub-volcanic, hypabyssal intrusive rocks and dykes (Figures 2 and 3).
Geological remapping has shown that rocks within the Rio Grande volcano-intrusive complex are predominantly intrusive, and not extrusive as previously mapped. This suggests that the complex may be slightly more deeply eroded than previous workers suspected and hence, potential mineralization closer to the present day surface.
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