Optimisation grade control procedures at the open pit mines: GEOSTATISTICAL APPROACH

Transcription

1 Optmsaton grade control procedures at the open pt mnes: GEOSTATISTICAL APPROACH Dr. M.Abzalov Dr. M.Abzalov 1

2 Grade control

3 Grade control A large Copper open pt mne n Chle has lost US$134 mllon over a 10-year perod because of suboptmal grade control procedures based on the blast holes samplng. It was estmated by the dfference between actually used blast hole samplng protocol and ts optmzed verson. (P. Carrasco: WCSB1, Denmark 003)

4 Grade control at open pt mnes Grade control varable : Samplng grd : Sample qualty :

5 Grade control at open pt mnes Grade control varable : Samplng grd : Sample qualty :

6 Nugget Effect and Estmaton Error Nugget Effect h { Sll Varogram h

7 Nugget Effect and Estmaton Error Nugget Effect h Sll h Nugget effect s caused by: (a) poor samples repeatablty (.e. large precson error) and (b) geologcal factors (.e. geologcal varablty at the short dstances Nugget effect s a geostatstcal term defnng an apparent dscontnuty n the expermental varogram near the orgn caused by measurement errors or by nested structures that have ranges smaller than the samplng nterval, or both Olea, R.A., ed., 1991, Geostatstcal glossary and multlngual dctonary: Oxford Unversty Press, New York, Oxford, 177 p.

8 Nugget Effect and Estmaton Error CASE 1: Uranum ISL operaton

9 Nugget Effect and Estmaton Error CASE 1: Uranum ISL operaton Reference data r Case = r = 0.86 Case r = Case m Rel. Nug. 0% Rel. Nug. 11% Rel. Nug. 4% Rel. Nug. 40%

10 Nugget Effect and Estmaton Error CASE 1: Uranum ISL operaton Case 1 Case Case 3 Rel. Nug. 0% Rel. Nug. 11% Rel. Nug. 4% Rel. Nug. 40%

11 Nugget Effect and Estmaton Error CASE : Uranum project Avr. relatve error:

12 Nugget Effect and Estmaton Error h Varogram Nugget Effect Nugget effect s a geostatstcal term defnng an apparent dscontnuty n the expermental varogram near the orgn caused by measurement errors or by nested structures that have ranges smaller than the samplng nterval, or both Olea, R.A., ed., 1991, Geostatstcal glossary and multlngual dctonary: Oxford Unversty Press, New York, Oxford, 177 p. h

13 Grade control at open pt mnes Grade control varable : Samplng grd : Sample qualty :

14 Sample qualty CV N N 1 (a (a - b b ) ) N pars of Sample and Duplcate The average coeffcent of varaton (CV%) s suggested to be used as the unversal measure of relatve precson error Ptard, F. 004: Pers. Communcaton Stanley, C.R. and Lawe, D. 007: Average relatve error n geochemcal determnatons: clarfcaton, calculaton and a plea for consstency: Exploraton and Mnng Geology, 16(3-4): Abzalov, M.Z. 008: Qualty Control of Assay Data: A Revew of Procedures for Measurng and Montorng Precson and Accuracy, Exploraton and Mnng Geology, 17(3-4): 1-14 CV% can be calculated usng AMZ_QAQC.xls fle whch s explaned n (Abzalov, M.Z. 008, 011) and avalable on your request

15 Grade control at open pt mnes Grade control varable : Samplng grd : Sample qualty :

16 Samplng grd Par-wse Varogram PWR ( ) 1 N N 1 [Z(x ) - Z(x Z(x ) Z(x [ )] ) ] N N 1 [Z(x ) - Z(x Z(x ) Z(x ) )] N 1 PWR (Nugget Effect of ) PWR

17 Samplng grd vs. Sample qualty CV N N 1 (a (a - b ) b ) (Relatve Samplng Varance) PWR N 1 (Nugget Effect) Abzalov, M.Z. 011: Geostatstcal approach for estmaton samplng precson. n (eds.) Proceedngs of the 5 th World Internatonal Samplng Conference 011, p.43-50, Santago, Chle, 6-8 October, 011

18 Samplng grd vs. Sample qualty Contrbuton of the Samplng Errors and Geology to the Nugget Effect { { Abzalov, M.Z. 011: Geostatstcal approach for estmaton samplng precson. n (eds.) Proceedngs of the 5 th World Internatonal Samplng Conference 011, p.43-50, Santago, Chle, 6-8 October, 011

19 Samplng grd vs. Sample qualty Case : Bauxte project Contrbuton of the Samplng Errors and Geology to the Nugget Effect Abzalov, M.Z. 011: Geostatstcal approach for estmaton samplng precson. n (eds.) Proceedngs of the 5 th World Internatonal Samplng Conference 011, p.43-50, Santago, Chle, 6-8 October, 011

20 Samplng grd vs. Sample qualty Case : Bauxte project Contrbuton of the Samplng Errors and Geology to the Nugget Effect Geologcal Factor consttutes 13% of nugget effect of LOI Abzalov, M.Z. 011: Geostatstcal approach for estmaton samplng precson. n (eds.) Proceedngs of the 5 th World Internatonal Samplng Conference 011, p.43-50, Santago, Chle, 6-8 October, 011

21 Samplng grd vs. Sample qualty Case : Bauxte project Contrbuton of the Samplng Errors and Geology to the Nugget Effect Error decreased from 4% to 15% (1) by reducng drll spacng from 0x0m to 1.5 x 1.5m; () by optmsng samplng procedures and decreasng samplng error

22 Samplng grd vs. Sample qualty Case 3: Yand Open Pt Yand mne 7,480,000 S Yand 5 km Palaeochannel Ralway Creek Yand open pt Abzalov et al., 010: Optmsaton of the grade control procedures at the Yand ronore mne, Western Australa: geostatstcal approach, Appled Earth Scence Journal, v.119, No.3, p.13-14

23 Samplng grd vs. Sample qualty Case 3: Yand Open Pt Yand 7,48,000 S A B 7,480,000 S AlO 3 (wt%) < > 3.5 Abzalov et al., 010: Optmsaton of the grade control procedures at the Yand ron-ore mne, Western Australa: geostatstcal approach, Appled Earth Scence Journal, v.119, No.3, p.13-14

24 Samplng grd vs. Sample qualty Case 3: Yand Open Pt Yand Contrbuton of the Samplng Errors and Geology to the Nugget Effect Geologcal Factor consttutes 5% of nugget effect of Al O 3 Abzalov, M.Z. 011: Geostatstcal approach for estmaton samplng precson. n (eds.) Proceedngs of the 5 th World Internatonal Samplng Conference 011, p.43-50, Santago, Chle, 6-8 October, 011

25 Grade control at open pt mnes Grade control varable : Samplng grd : Sample qualty :

26 Economcs: OPEX vs. Cost of Lost/Ganed metal Cut off by VALUABLE component (e.g. Au, N, Fe)

27 Economcs: OPEX vs. Cost of Lost/Ganed metal Correlaton: 0.43 Ore to waste: 11% Waste to Ore: 11% Case 1 Mean 1 = 7.9 Mean = 7.9 CV% = 1% Correlaton: 0.95 Ore to waste: 3% Waste to Ore: 3% Case Estmated SMU grade Mean 1 = 7.9 Mean = 7.9 CV% = 6.7% Estmated SMU grade

28 Economcs: OPEX vs. Cost of Lost/Ganed metal ( Case 1 ) Nugget effect s caused by poor samples repeatablty (.e. large precson error)

29 Economcs: OPEX vs. Cost of Lost/Ganed metal h Nugget Effect h h Nugget Effect h ( Case ) Nugget effect s caused by geologcal factors (.e. geologcal varablty at the short dstances) G Geologcal Factors S Samplng Error

30 Economcs: OPEX vs. Cost of Lost/Ganed metal Condtonal Smulaton SO % In the current study Z was generated usng Condtonal Smulaton technque References can be found n: Abzalov, M.Z. and Bower, J. 009: Optmsaton of the drll grd at the Wepa bauxte depost usng condtonal smulaton. n (eds.ausimm) 7th Internatonal Mnng Geology Conference, p.47 51, Perth, Western Australa, August, 009

31 Economcs: OPEX vs. Cost of Lost/Ganed metal Case 3: Yand Open Pt Yand Explanaton (cut offs on Al O 3 %) 1 st opton (BH: 5 x 5m) nd opton (RC drllng: 5x5m).7% error: ORE blocks msclassfed as WASTE 4.1% error: ORE blocks msclassfed as WASTE 3 3.7% of SMU sze ORE blocks are msclassfed as WASTE 4.1% of SMU sze ORE blocks are msclassfed as WASTE Abzalov et al., 010: Optmsaton of the grade control procedures at the Yand ron -ore mne, Western Australa: geostatstcal approach, Appled Earth Scence Journal, v.119, No.3, p.13-14

32 Economcs: OPEX vs. Cost of Lost/Ganed metal CASE 4: Bauxte operaton Grd 0 x 0m Grd 50 x 50m Grd 100 x 100m X axs: 1 st Estmate - SO of the SMU blocks 1.3% msclassfed blocks.3% msclassfed blocks.7% msclassfed blocks Contan 80,775t bauxte Contan 139,75t bauxte Contan 161,145t Bauxte Whch cost $.8M Whch cost $4.9M Whch cost $5.6M 5318 drll holes 664 drll holes drll holes whch cost $3.03M whch cost $0.38M whch cost $0.13M

33 Summary and Conclusons Effcency of Grade control depends on samplng grd and samples qualty. Rght balance between -Wse Relatve Varogram [ PWR ] The proposed approach s as follows: CV Feld Duplcates Optmsaton of the grade control procedures requres estmaton costs of the lost/recovered metals whch are deduced from the Z vs. Z* dagrams.

34 MINING PROJECT DASHBOARD STANDARDISED SET of

35 Thank you Questons? Comments? Suggestons?

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37 CASE : Bauxte project South Amerca CV = 0.7% Feld (coarse) duplcates: No of sample duplcates = 1868 CV = 13.5% Pulp duplcates: No of sample duplcates = 47

38 CV m m x n a b a b a- a - b b- a - b (a - ) (b - ) ( ) ( ) (a - b) (b - a) (a - b) Standard Devaton a - b Mean (a b) CV m a - b (a b) a - b (a b)

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40 FSE ( ) Another errors ( ) 316 % It ncludes: Extracton Error P.Gy's Safety Lne cm cm 3 0.3cm 1 100% 3 % 10 % 3 % Preparaton Error Delmtaton Error etc. 1%