Feb 1 2016
Discovery Ventures Inc. is pleased to announce that it has received a technical report entitled Amended Preliminary Economic Assessment Technical Report on the Willa Property.
The report is an amendment of the Technical Report entitled "Preliminary Economic Assessment & Technical Report, Willa Max Project" dated May 26, 2014, which supported the original disclosure in a May 28, 2014 News Release entitled "WillaMAX PEA Highlights Low CAPEX and Robust Economics".
The amended report presents an updated Mineral Resource based on surface and underground drilling data collected between 1980 and 2004. The amended report also presents the results of a Preliminary Economic Assessment based on a mine plan focused on the Measured and Indicated Mineral Resources only of the west zone at Willa and processing the material at the MAX facility.
Mineral Resource Estimates
Updated Mineral Resources to form the basis of the PEA were estimated by Mr. Michael Waldegger, P.Geo., of MFW Geoscience Inc. Key assumptions and parameters considered during the preparation of the Mineral Resource estimate are described below.
Gold, copper, and silver grades from drillhole samples collected between 1980 and 2004 formed the basis of the Mineral Resource estimate. All drillholes were completed by historic operators and holes completed prior to 1980 were not considered for this estimate. All samples were of half diamond drill core at 2 m sample lengths and some at 1 m lengths. All missing intervals or blanks were replaced with half detection limits.
The estimate was prepared with commercial mining software packages employing 3D block modelling techniques.
A recoverable metal value per tonne ("RMV") was used to model the mineralized zones, which were used to constrain the grade estimate. The mineralized zones were modelled using geological modelling software Leapfrog Geo version 2.2.1 (Leapfrog) supplied by Aranz Geo. The RMV assumed metal prices guided by the three-year average metal prices ($US) of $1400/oz Au, $3.15/lb Cu and $20/oz Ag and milling recoveries based on metallurgical test work of 82% for Au, 90% for Cu, and 82% for Ag. The mineralized zones are represented by a RMV grade shell at a cut-off of $US 100/t.
A geology model based on lithological logs was completed using Leapfrog and was used to guide and validate the mineralized zone model.
Block model grade estimation was completed using mining software Geovia Gems version 6.7.1 supplied by Dassault Systems. Capped assays were composited to 2 m lengths and interrupted at the mineralized zone boundaries and the composites were used to estimate block grade by Ordinary Kriging within and outside of the mineralized zones. Blocks were sized to 4 m cubes and retained a percent rock type model. Assays were capped at 50 g/t for gold, 7% for copper, and at 100 g/t for silver.
Based on estimated block grades for gold copper and silver, a gold equivalent grade was computed by block based on the one-year average metal prices ($US) of $1200/oz Au, $2.75/lb Cu and $16.50/oz Ag and milling recoveries of 82% for Au, 90% for Cu, and 82% for Ag. The gold equivalent grade was used as the basis of the cut-off to report the Mineral Resources.
A trend of increasing density with increasing sample grade was observed within the mineralized zone and therefore a variable density model linked to grade was coded within the RMV shell. Outside of the mineralized zone the block model was coded with the mean density from samples grouped by the geological model rock type.
Mineral Resources were classified in accordance with CIM Definition Standards for Mineral Resources and Mineral Reserves (2014). Spacing of drillhole intersections was sufficient to reasonably assume continuity of mineralization and assign Indicated to most blocks within the RMV shell. Generally the Inferred category was assigned to the outer fringe of the RMV shell and where underground development intersected the RMV shell in the West Zone blocks were upgraded to Measured if they were within 10 m of an underground drillhole collar.
The updated Mineral Resources are estimated above a 3 g/t Au Equivalent cut-off to be:
- 198,000 t of Measured Resources at an average grade of 5.36 g/t Au, 0.83% Cu and 8.3 g/t Ag,
- 627,000 t of Indicated Resources at an average grade of 4.97 g/t Au, 0.86% Cu and 9.5 g/t Ag, and
- 151,000 t of Inferred Resources at an average grade of 4.21 g/t Au, 0.71% Cu and 9.8 g/t Ag.
Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.
Comparison of 2016 Mineral Resource Estimates to Previous Disclosed 2014 Estimate
The original PEA was based on Mineral Resources disclosed in a 2012 Technical Report and estimated above a 3.5 g/t Au cut off to be:
- 495,784 t of Measured Resources at an average grade of 7.18 g /t Au, 0.94% Cu and 12.16 g/t Ag,
- 262,415 t of Indicated Resources at an average grade of 5.71 g/t Au, 0.67% Cu, and 13.26 g/t Ag, and
- 73,591 t of Inferred Resources at an average grade of 3.39 g/t Au, 0.29% Cu, and 5.42 g/t Ag.
The only material technical information, pertinent to the mineral resource estimate, collected since the 2012 estimate was 96 samples of mineralized drill core tested for dry bulk density. The estimate presented in the Amended Technical Report has 21% more volume at a 3% lower density for 17% more tonnes. The reported tonnage is 23% lower in Au and Ag grades and 4% higher in Cu grade than the 2012 estimate. The updated resource contains 10% fewer ounces of gold, 21% more pounds of copper, and 8% fewer ounces of silver.
A detailed review of the previous model was not completed; however, the factors contributing to the largest changes are likely due to the following changes in methodology:
- The updated estimate used estimation constraints based on a grade shell model and applied hard boundaries during grade estimation. The previous estimate did not use estimation constraints other than the search radius extent.
- The updated estimate of grade used the Ordinary Kriging estimator. The previous estimate used Inverse Distance to the 3rd power.
- The updated estimate was reported above a 3 g/t gold equivalent cut-off grade, which considered recoverable contributions from gold, copper and silver. The previous resource was reported above a 3.5 g/t gold only cut-off grade.
- The updated estimate introduced a variable density model based on tests on samples of drill core and taking into account the observation of an increase in density with an increase in sample grade. The previous estimate applied a constant density of 2.9 t/m3.
- The current estimate applying different capping levels to raw assays.
- The current estimate was classified differently, with far less tonnage reporting to the measured category.