Drilling and Resource Estimates
The first drill holes on the property were carried out by Placer Dome in 1993. They drilled six diamond drill holes with a total length of 1,953 m confirming the presences of the mineralised porphyry. General Minerals Corporation, between 1995 and 1998, drilled 61 diamond drill holes with a total length of 15,815 m. Drill hole spacing varied from 75 m in the center of the known mineralized zone to around 300 m on the periphery of the zone.
During 2007 and up to June 2008 the company completed 63 diamond drill holes for a total length of 17,487 m. AMEC International (Chile) SA was commissioned to prepare a resource estimate report compliant under NI 43-101. In August 2008 a resource estimate was published based on both historical and Los Andes Copper drilling totaling 35,255 metres in 130 drill holes.
The company carried out a further 16 diamond drill holes and a total length of 5,128 m during the remainder of 2008.
In 2013 Coffey and Alquimia Conceptos S.A. were commissioned to prepare an updated resource estimate and a Preliminary Economic Assessment compliant under NI 43-101. This was prepared using all 146 diamond drill holes with a total length of 40,383 m drilled by Placer Dome, General Minerals Corporation and Los Andes Copper Ltd.
The drill hole spacing varies from 75 m in the center of the project to around 200 m on the periphery, but is mainly a 100 m grid especially in the south of the project. The initial core diameter for the diamond drill holes was HQ (63.5 mm) but core size was reduced to NQ (47.6 mm) only when required by drilling conditions. The drill core is stored in covered racks at the camp site on the Vizcachitas property along with the pulp samples.
Table summarising the different drilling campaigns
Los Andes Copper published the first NI 43-101 compliant resource estimate in August 2008 based on drilling totaling 35,255 metres in 130 drill holes.
This resource estimate was updated as part of the Preliminary Economic Assessment on the Vizcachitas Property. The updated resource estimate includes the 16 diamond drill holes and a total length of 5,128 m that has been drilled since the cut-off for the 2008 resource estimate.
The lithology and mineral zone models have been interpreted from drill information through a series of vertical cross sections oriented at an azimuth of 110 degrees and spaced at 100 m intervals throughout the Property. This interpretation has been linked to a series of three-dimensional wireframe solids.
The Vizcachitas Mineral Resource estimate was completed using Minesight® software. The block model was constrained by the following: interpreted 3-D, solids, lithology and mineral zone. Copper and molybdenum were estimated for each block using Ordinary Kriging (OK).
A total of 24,254 assay intervals from 146 drill holes, were selected to define the Vizcachitas deposit Mineral Resource estimate. Samples were grouped according to their interpreted lithology and mineral zone. The exploration data analysis was conducted by creating probability and histogram plots of the data.
Variograms/Correlograms were calculated on capped composited data using Sage 2001© software. The estimation results are very sensitive to the variogram parameters, particularly the range and nugget effect. Care was taken to model the short-range structures and accurately fit the nugget effect.
The Vizcachitas resource estimation model interpolation was completed using Ordinary Kriging (OK) and Nearest Neighbor (NN) estimation methods for validation. The OK and NN estimations were completed in two iterations with the search parameters set by domain. The first iteration is designed to estimate a block grade where there is a minimum of two and up to a maximum of twenty five composites found with a limit of six composites per drill hole based on a 3D search radius equal to 400 metres. The second iteration overwrites the first and is dependent on the domains
Mineral resources have been classified according to the CIM Definition Standards on Mineral Resources and Mineral Reserves, as incorporated in the National Instrument NI 43-101.
Two criteria have been combined for mineral resource classification:
Tonnage and grade reliability can be defined as follows:
Coffey selected a drill hole spacing of 200 m x 200 m to meet the required reliability criteria accuracy within a range of 10-15 % at a 90 % confidence limit.
Complementing the drill hole spacing distance defined, a second criterion was introduced for resource class categorization:
The 400 metres maximum distance between drill hole collars is also in line with copper variogram ranges for the main domains.
In order to ensure that the reported resource has reasonable prospects for economic extraction, the resource estimated by ordinary Kriging method is limited within a pit shell generated about copper equivalent grades in blocks classified in the indicated and inferred categories at a copper price of 3.00 USD/lb.
Mineral resources are reported at 0.30 % copper equivalent cut-off under prevailing conditions1. At 0.3 % Cu Eq cut-off the Indicated Resources are 1,038 Mt @ 0.434 % Cu Eq, 0.373 % Cu and 0.012 % Mo; and Inferred Resources are 318 Mt @ 0.405 % Cu Eq, 0.345 % Cu and 0.013 % Mo.
1Copper equivalent grade (Cu Eq) has been calculated using the following expression: Cu Eq (%) = CuT (%) + 4.95 x Mo (%), where 4.95 reflects the Mo/Cu price ratio
The Vizcachitas Mineral Resource using multiple Cu Eq cut-off grades is presented below
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