The sedimentary-hosted copper-silver mineralisation found to date by Aurania is regional in nature and stratigraphically confined to key horizons of carbon-bearing sediments that have been verified in outcrop to extend for a minimum of 22km.
Few geological models could account for this very significant lateral extent. With company geologists bringing back samples containing copper-minerals hosted sediments the company is hypothesizing that the geological setting is perhaps like the red-bed mineralized zones in the Kupferschiefer (copper shale), currently mined by KGHM in Poland.
"Our geologists … started to bring an extraordinary array of copper-mineralised large boulders and slabs in from the jungle," said chairman and CEO Dr Keith Barron.
"Some of these samples were covered in vivid green chrysocolla and malachite, with azurite, cuprite and even native copper as well as more drab chalcocite and tenorite. At first, we treated these as a curiosity, and believed they were related to the supergene weathering of nearby porphyries.
"However, the copper minerals were hosted exclusively in well-bedded siltstone, mudstone, sandstone and shale, particularly in pieces showing abundant carbonaceous plant fragments and not in porphyry."
The boulders were traced back to outcrops over what is now a strike length of 22km and the copper mineralisation appeared to lie above a red-bed sequence of quartzose sediments in an overlying sequence of black shale with abundant carbonaceous plant trash.
The general model for mineralisation in the Kupferschiefer and the Central African Copperbelt of Zambia and the Democratic Republic of the Congo is that copper leached from the sedimentary basin remains in solution because of the oxidised state of the red sandstones (red-beds). Saline fluids from salt layers or domes within these sedimentary basins increase the solubility of copper, which forms stable, soluble copper-chloride complexes. Numerous salt domes are associated with the Jurassic red-beds in southeastern Ecuador.
When these basins are reactivated, the saline, copper-bearing fluids flow along the layering of the rock sequence to the faults, which constitute barriers to the fluids, and the fluids tend to rise along these permeability barriers. Where the fluids come into contact with reduced sedimentary layers, such as carbon-bearing black shale or limestone, the copper precipitates.
The Jurassic basin in southeastern Ecuador also has porphyry clusters, which could represent an additional significant source of copper potentially injected into the red-bed sequence.
No drilling has yet been performed in the area and Aurania does not intend to abandon its original exploration ideas in favour of sedimentary copper and silver exploration.
Shares in Aurania Resources (TSXV:ARU) are trading at C$3.62, valuing the company at $119 million. Its share price has increased almost 27% so far this year.