Brownfield exploration implies the presence of former operating mines and therefore in all likelihood waste dumps and other surface residual materials resulting from historic operations.
Our licence portfolio host former producing mines and associated dumps.
Waste rock containing no economically recoverable metals that has been removed from above and around an orebody.
Waste rock dump material
Gold-bearing siliceous rocks with low copper content. This quartz-rich material was typically stripped from above the underlying copper ore. Former mines did not process the gold-rich ores as the Cypriot authorities in the 50’s to mid 70’s only paid a nominal price (ca. $35 per ounce) for gold in copper concentrates. The Caerus dump assessment programme seeks out these gold-rich oxides which are often found buried under other waste rock.
Siliceous gold oxide dump material
Low-grade ore stockpiles were created to segregate copper ore into different grade categories, <0.25% Cu, 0.25 to 0.5% Cu, >0.5% Cu and so on. Once segregated, the processing plant could blend different grade ores and deliver a feed to the processing plant at an optimum grade to maximise copper recovery.
Aerial view of typical low-grade ore stockpile found on a Caerus licence in Cyprus
Higher grade copper-bearing ore was typically stockpiled separately as this represented the rock of highest value on the mine. In addition, there were stockpiles created with ore that had a high silica content or contained a significant percentage of clay minerals, attributes that could impact on mineral processing efficiency and metal recovery where ore needed to be fed into the processing plant in a controlled manner to avoid disrupting production.
Aerial view of Troulli high-grade ore stockpile with trenching completed by Caerus
Evaluation involves establishing the origin of the material, its’ mineralogy, likely response to different metallurgical processes, tonnage, grade and accessibility.
Assessment typically begins with grab and channel sampling over surface materials to broadly determine whether the body of material under investigation contains copper and or gold.
Preliminary grad sampling programme on surface materials
Once the presence of residual metals has been established, Caerus typically undertakes a more comprehensive sampling programme that may involve trenching and drilling.
Percussion drilling of dumps
Trenching of dumps – Troulli ore stockpile
Trenching and drilling programmes assist in the collection of representative samples of dump material.
In the case of trenches, this allows Caerus to collect samples at regular intervals from trench sidewalls where a complete cross section of the dumped material can be found.
Dump cross section showing different generations of dumped material
Representative samples of different horizons in the trench profile are collected and dispatched for both independent laboratory analysis to determine metal content and for metallurgical test work.
Caerus also undertakes in-house pXRF analysis to provide an early indication of metal content.
The majority of dumps and other residual materials found on Caerus’s licences in Cyprus have typically been left untouched for a minimum of 45 years. During this time rainwater has reacted with sulphide minerals occurring in the waste rock, producing a natural acid that in turn has started the slow process of dissolving metals such as copper and transporting them down through the dump.
