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1 Namysłowska-Wilczyńska B.

1 2007

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Analizy przestrzenne z zastosowaniem metod geostatystycznych (Modelowanie 3D porfirowego złoża miedzi Rio Blanko w Peru)

Namysłowska-Wilczyńska B.

Roczniki Geomatyki

2007

T. 5, z. 1

91-103

Research methods for geostatistical spatial analyses are presented on the example of the results of 3D modelling of deposit data. The variation in the parameters of the Rio Blanco porphyritic copper deposit in Peru was investigated. Copper and molybdenum grades, deposit thickness and copper accumulation averages Z* were estimated and quantity of the copper deposit.s reserves was calculated. Geostatistical methods, i.e. variogram and covariance functions and the ordinary (block) kriging technique, were used to estimate averages Z*. Spatial analyses drew from a large database (n = 5121 samples), containing values of coordinates X, Y and Z (depth ordinate) and Cu and Mo content and deposit thickness determinations for 104 boreholes distributed over the deposit area. In addition, databases with assumed three cut-off values of Cu content, i.e. 0.7% Cu (n = 1903 samples), 0.5% Cu (n = 2905 samples) and 0.3% Cu (n = 4011 samples), were used in the geostatistical studies. The isotropic empirical variograms and covariograms of the deposit.s parameters were computed. Then a 3D analysis of the directional empirical variograms and covariograms, computed along 4 regular directions in the reference plane and perpendicularly to this plane, was carried out. These variograms and covariograms were calculated for a slicing height of 7.97 m. Then, averages Z* and standard estimation deviation ók of the above parameters were estimated in 3D for the considered deposit series and the cut-off values of Cu content, taking into account different spatial copper ore specific weight. The estimation was based on the results of modelling empirical covariograms by means of theoretical functions. The estimated averages Z* of the deposit parameters were presented in the form of raster maps for selected deposit (porphyritic rocks) layers at depth levels: of 10, 15, 25, 30, 40, 45, 50, 55, 65, 75 within the 1935-2685 m vertical profile interval. As a result of the spatial analyses, a 3D geostatistical model of the Rio Blanco porphyritic copper deposit.s parameter variation was obtained.