- Positive Water Supply and Ore Hardness Results:
o Hydrology - High level Study indicates groundwater source with potential to supply water requirements for the conceptual Paris mining operation.
o Comminution (reduction in rock size) - Tests confirm silver is generally hosted in soft and low-abrasive rock.
- Preliminary Open-Pit Optimisation for the 2017 Upgraded Mineral Resource.
After the April 2017 release of the Paris Silver Mineral Resource estimate, upgraded to Indicated and Inferred categories of 9.3Mt @ 139g/t silver containing 42Moz of silver (at a 50g/t silver cut-off) (Investigator ASX Release: 19 April 2017), Investigator commenced a phased PFS study with an initial focus on potential water supplies and metallurgical performance. Test holes were drilled to aid the study of groundwater in local palaeochannels. A geometallurgical study enabled the selection of representative samples of the metallurgical domains within the Paris deposit. The PFS hydrological study and initial comminution phase of the metallurgical study are completed with on-going flotation and leach testwork progressing towards completion early in 2018.
Investigator Resources Managing Director John Anderson said "Test and modelling work by Investigator's consultants supports our prior perceptions of firstly, a substantial groundwater system of suitable salinity close to the Paris silver project, and secondly, that much of the silver ore at Paris can be considered soft with low abrasive properties.
These new results are a positive start for the PFS by showing potential for an adequate water supply, soft-dig open-pit mining scenarios and low-cost crushing and grinding costs at Paris.
Consultants have also remodelled a conceptual open-pit optimisation shell for the Paris Mineral Resource estimate. This will enable internal studies to proceed during the PFS, scheduled to be completed mid-2018.
In parallel with the PFS, planning for December drilling of the Paris silver extensions is near finalisation. A driller is also being sought to undertake testing of the Trojan IP target at the Nankivel copper-gold prospect as soon as possible. We will advise scheduled drill mobilisation dates when available." Mr Anderson added.
CORE Resources ("CORE") undertook the comminution testwork on the ore feed properties of the two dominant domains of breccia and dolomite hosts to the silver mineralisation.
Investigator supplied CORE with diamond drill core; 263Kg of Breccia, from five representative holes, and 146Kg of Dolomite, from four representative holes.
Various rock strength, hardness and abrasiveness tests were undertaken. These show the Paris silver ore can be considered to be 'soft' and have relative low abrasiveness properties compared to other ores the consultants usually evaluate. This indicates potentially lower capital and power costs with a likely smaller crushing and milling circuit and quicker throughput times than is usual for hard-rock operations.
The 'soft' ore is also beneficial for mining and could theoretically mean the limited need for drill and blasting within the open-pit, which will have the subsequent advantage of potentially lower mining costs.
Wallbridge Gilbert Aztec ("WGA") were appointed to undertake the preliminary assessment of the ground water potential for the Paris Silver Project. The hydrological study commenced with six hydrological investigation holes drilled in the June 2017 Quarter; four testing potential water sources in palaeochannels at Hector (12km east of Paris) and Alexander (3km west of Paris). Two holes were drilled within the Paris Mineral Resource outline to assess both the water source potential and groundwater conditions for mining.
Initial samples and data were provided to WGA, with water quality sampling to continue on three-monthly intervals to establish baseline data and variations. Within the Paris deposit, there is also the need to quantify the potential mine inflow and dewatering volumes which would form part of any future feasibility study.
The Hector palaeochannel was selected for the initial focus. The main paleochannel was geometrically modelled from the new hydrological drill holes (see Figure 1 in link below), prior exploration drill holes and gravity as extending approximately 13km (aquifer continuity was assumed in the model). The water is interpreted to flow from south to north with basic recharge tests to date indicating recharge potential is present, although at low rates. The 60 giga-litres of water estimated during the study in the Hector palaeochannel is in excess of that potentially required for the conceptual size and mine life of the Paris operation.
The study showed water-bearing sand intervals occur at 31m to 60m depth with average thicknesses of about 10m that were incorporated into the study.
The measured salinities are generally between 30,000mg/Lt and 45,000mg/Lt. These salinity levels are considered low enough for mineral processing water use. This is being further evaluated with a representative water sample obtained from PLAC139 (see Figure 1 in link below) being utilised by CORE as part of metallurgical flotation/leach tests.
The salinity measurements are greater than the National Water Quality Management Strategy (2000) recommended guidelines of 5,000mg/Lt for pastoral stock supply.
The nearest registered and used bore holes for pastoral purposes are located at least 4km from the Hector Paleochannel and target different water sources in fractured bedrock. It was concluded that water extraction from the paleochannel would be unlikely to have any effect on these water sources. IVR have started a monitoring program to record seasonal variations for future modelling work.
Conceptual Open-pit Optimisation Study
An independent Mining Consultancy completed a high-level open-pit optimisation study, utilising the April 2017 Paris Silver Mineral Resource estimate. The results cannot be reported at present since they are not considered to be categorised by JORC 2012 reporting standards as an Ore Reserve.
The open-pit model is conceptual and based on high-level assumptions. This along with preliminary mining schedules will be used for internal studies (see Figures 2 and 3 in link below).
The optimised open-pit shell figure is not a practical open-pit design incorporating berms, access ramps, etc. Both Indicated and Inferred Mineral Resources are included in the optimisation study and preliminary mining schedule.
To view figures, please visit:
About Investigator Resources Ltd
Investigator Resources Limited (ASX:IVR) is a metals explorer with a focus on the opportunities for greenfields silver-lead, copper-gold and nickel discoveries offered by the emerging minerals frontier of the southern Gawler Craton on South Australia’s northern Eyre Peninsula.
Investigator Resources Ltd