Block Evaluation at Antamina Mine

Block Valuation at Antamina MineHarry Parker & Kim KirklandMintec Seminar April 2007

Antamina- Probably largest Polymetalic Mine in the World. Skarn hosted Cu-Zn-Mo-Ag deposit Deposit defined by 16 rock-types with varying mill throughput rates that can range from 50 ktpd to 100 ktpd.Nine major ore-types are demarcated and campaigned through concentrator with nominal annual capacity of 30 MtpyThe mine and processing facilities consist of an open pit, concentrator, slurry pipeline and port facility2005 payable metals production included 361,000 t of copper, 156,000 t of zinc, 6,720 t of moly, 409 t of lead, and 9.80 million oz silver

Since 1998 Feasibility Study of the Antamina Mine, block economics and ore typing have been based on Net Smelter Return (NSR). Blocks have been valued using Value.for which was written by MRDI/AMEC in 2000. Minor revisions have been made over the years.In May 2005, CMA and AMEC develop new system for ore typing and block valuation for use in long-range mine planning. In November 2005, Antamina asked AMEC to design and implement these features, as well as other enhancements to the Ore Control system. Background

Flowchart for options 1, 2, and 4

Advances in Block ValuationIntroduction of subtypes for each oretype to reflect constraints on arsenic, molybdenum, oxides, etc.Use of a complex series of metallurgical equations to partition tonnage and grade of 7 payable and penalty metals amongst five concentrate products.Use of ore value per concentrator hour as the main valuation metric. This enhances the value of materials such as M1 (copper-only, low bismuth) that can be processed at a greater rate, and penalizes the value of materials such as M4A (copper-zinc, high bismuth) that must be processed at a slower rate.

A. Components of Mill and G&A Fixed CostsAreaM$/yrMill General 23.1Other Fixed57.8Group Maintenance.25.3Total106.2

B. Allocation of Fixed Costs, Example for Caf Endoskarn OretypeThroughput Fixed Cost $/t Milledt/dkt/hrMt/yr Incremental to M1

M1995004.1536.32.920.00M2939003.9134.33.100.17M2A798003.3329.13.650.72M3845003.5230.83.440.52M4751003.1327.43.870.95M4A704002.9325.74.131.21M5704002.9325.74.131.21M6657002.7424.04.431.50MP516002.1518.85.642.71

C. Calculation of "Breakeven" NSR ($/t)OretypeFixed MillOtherTotalRequired NSR ($/t) G&A $/tCostsCostsIncremental to M1M1-2.92-5.00-7.927.920.00M2-3.10-5.00-8.108.100.17M2A-3.65-5.00-8.658.650.72M3-3.44-5.00-8.448.440.52M4-3.87-5.00-8.878.870.95M4A-4.13-5.00-9.139.131.21M5-4.13-5.00-9.139.131.21M6-4.43-5.00-9.439.431.50MP-5.64-5.00-10.6410.642.71

D. Calculation of Net Value/Concentrator HourOretypeNSR $/tFixed MillOtherNet Valuekt/hrNet ValueNet Value Rel. to M1G&A $/tCosts$/tk$/hr$/tk$/hrM120.00-2.92-5.0012.084.1550.06100%100%M220.00-3.10-5.0011.903.9146.5699%93%M2A20.00-3.65-5.0011.353.3337.7594%75%M320.00-3.44-5.0011.563.5240.6996%81%M420.00-3.87-5.0011.133.1334.8192%70%M4A20.00-4.13-5.0010.872.9331.8890%64%M520.00-4.13-5.0010.872.9331.8890%64%M620.00-4.43-5.0010.572.7428.9488%58%MP20.00-5.64-5.009.362.1520.1378%40%

E. Calculation of NSR Required to Produce Net Value of $14,000/Concentrator HourOretypeValue/hrThroughputNet ValueFixed MillOtherRequiredRel. to k$/hrkt/hr$/tG&A $/tCostsNSR $/tM1M114.004.153.382.925.0011.30100%M214.003.913.583.105.0011.68103%M2A14.003.334.213.655.0012.86114%M314.003.523.983.445.0012.42110%M414.003.134.473.875.0013.35118%M4A14.002.934.774.135.0013.91123%M514.002.934.774.135.0013.91123%M614.002.745.114.435.0014.54129%MP14.002.156.515.645.0017.15152%

Design CriteriaA feature of MineSight is its ability to link user-written Fortran subroutines. This permits the user to read from and write to the MineSight Project Database.Calculation speed was an essential design requirement. AMEC has prepared an approximately 9500 line MineSight user-subroutine module b612v14.for A single program that uses a modified main program to access the same set of subroutines to determine ore typing and make valuation calculations for four main options.

Functions of the User SubroutineOre and waste typingPartitioning of tonnage and grade to concentratesValuation of blast holes, Ore Control blocks, Ore Control polygons, and resource model blocks

Option 1: BLKVALBlock Valuation or BLKVAL, is the First Pass Valuation and assignment of optimal Metallurgical ore type MTYMSMTYMS is displayed to the computer screen to construct ore polygon diglinesCalculates all 9 possible ore value per hour OVPHR(9) variables and various other parameters for the metallurgical ore typeInvoked with IOP21=1 in the user runfile

Option 2: PROUTEPolygon Valuation or PROUTE, is the Second Pass Valuation for Ore Control which takes the nominated as routed ore type MTYFS for a group of blocks, and calculates concentrate tonnage and gradesCalculates applicable penalties and creditsThis option is necessary since Ore Control polygons often contain a minority of blocks that are included within an ore cut that have sub-optimal routingInvoked with IOP21=2 in the user runfile

4193 Bench Showing MTYMS in Ore Polygons

4193 Bench Showing MTYFS (as routed)

Option 3: BlastholesBlasthole option is for processing of blasthole assaysGrades and calculated values are extracted from, and stored back to AcQuire via ASCII filesStored values are ore/waste types and OVPHR(9) Invoked with IOP21=3 in the user runfile

Option 4: Resource ModelResource model option is for processing of 20 x 20 x 15 resource block models. No user interface, run only at command lineAssumes SMU block selectivity; thus blocks are assigned a metallurgical ore type, MTYMS. No need for two stepsCalculates a unique list of ore concentrate tonnages and grades for the five possible concentrate products. Calculates ore/waste values used for long-term mine planning Invoked with IOP21=4 in the user runfile

Arsenic Penalty Map

Moly Credit Bismuth Penalty

Input FilesOre and Waste Typing File OWTYPE01.CSVMetallurgical Parameters CONTAB04.CSVEconomic Parameters ECONLT01.CSVDrive File to specify run mode optionStandard MineSight Runfile

Ore Typing Parameter File

Metallurgical Parameter File

Economic Parameter FileOWTYPE01.CSVECONLT01.CSVCONTAB04.CSVInput Files

Drive FilesRun ModesLevels of Debug OutputInput and Output Files Names

Drive FileBt32_1k.csv

System Development (1)Parallel development:-MineSight Fortran User Subroutine (Kim Kirkland)-Other upgrades to ore-control system (Kim Kirkland)-Stand Alone Fortran Program (Harry Parker)-Spreadsheet Checker (Paul Gomez, Arndt Brettschneider)Except for main driver subroutine, all subroutines in MineSight User Subroutine same as in Stand Alone ProgramParallel development enabled checks of modules as developed in controlled environment

System Development (2)May 2005 block valuation used as foundation Detailed specification from July to November 2005Detailed interaction with Finance, Concentrator during November 2005, February 2006Test Version produced March 2006; precision problems in MineSightFurther tests and training in April and May 2006Final Installation May 30, 2006Documentation July - Sept 2006

System Checking14 versions of program using 39 testbedsSpecial dataset Master.dat built by Kim Kirkland and Paul Gomez to exercise all ore-types and metallurgical options440,000 Ore Control block data set built from nearly all blocks mined to end 2005.All 4 options checkedInserted small errors in input files to check error messages generatedSpreadsheet duplicates ore-typing, metallurgical equations, block valuation

Whats Next ?Valuation on a block-by-block basis can be a shortcoming. Individual blocks do not fairly represent campaign feed gradesMetallurgical recovery equations need a lot of work.Process costs per ore type need to be better understood.Rock recognition data from Aquila could greatly improve forecasts of mill throughputIntroduce iron as player in copper concentrate grade and recovery