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298                                                             Chapter 8

             TABLE 8-V

             Two models of discriminant functions for predictive mapping of epithermal Au prospectivity,
             Aroroy district (Philippines) based on training sets each with nearly balanced numbers of proxy
             deposit-type and non-deposit locations. Values in bold represent predictor variables, per set of
             spatial evidence, with strong positive spatial associations with the training deposit-type locations.

               Discriminant analysis using training set A 1   Discriminant analysis using training set B 2
                  (Wilks’ lambda = 0.192; α=0.0001)   (Wilks’ lambda = 0.172; α=0.0001)
                Predictor    Function coefficients   Predictor   Function coefficients
                                                          3
                      3
               variables    Standardised Unstandardised  variables    Standardised Unstandardised
                NNW1         0.239       0.092      NNW1         0.244       0.088
                NNW2         0.512       0.017      NNW2         0.727       0.024
                NNW3         0.554       0.021      NNW3         0.713       0.026
                NNW4         0.326       0.009      NNW4         0.537       0.014
                NW1          -0.229      -0.006     NW1         -0.221      -0.006
                NW2          0.094       0.003      NW2          0.069       0.002
                NW3          -0.071      -0.002     NW3         -0.069      -0.002
                NW4          -0.047      -0.001     NW4         -0.080      -0.002
                FI1          1.497       0.043      FI1          1.282       0.037
                FI2          1.006       0.028      FI2          0.939       0.025
                FI3          0.467       0.013      FI3          0.467       0.012
                FI4          -0.017      -0.001     FI4         -0.044      -0.001
                ANOM1        0.524       0.013      ANOM1        0.517       0.013
                ANOM2        0.163       0.004      ANOM2        0.233       0.006
                ANOM3        0.113       0.003      ANOM3        0.145       0.004
                Constant         -       -3.017     Constant        -       -3.323
             1 Consists of 79 randomly-selected proxy deposit-type locations (Fig. 8-8)  and 81 non-deposit
             locations with lowest predicted mineral occurrences (from set 2 non-deposit locations; Figs. 8-4
                     2
             and 8-7B).  Consists of 86 coherent proxy deposit-type locations (Fig. 8-8) and the same 81 non-
                                              3
             deposit locations in training data set A.  Statistically significant predictor  variables in the
             discriminant models (see ‘class code’ columns in Table 8-IV for explanations of variable names).

             variables in the discriminant model based on training set A are not so much higher than
             the standardised function coefficients of the same predictor variables in the discriminant
             model based  on training set B. These  results mean that, on the  one  hand, the
             contributions  of the ‘FI’ predictor  variables are more important to the discrimination
             between the randomly-selected proxy deposit-type locations and non-deposit locations in
             training set A than to the  discrimination between the coherent proxy deposit-type
             locations and non-deposit locations in training set B. This implies that any of the proxy
             deposit-type locations chosen randomly has stronger spatial association with
             intersections of NNW- and NW-trending faults/fractures than to either of these
             individual sets of faults/fractures. On the other hand, in addition to the contributions of
             the ‘FI’ predictor variables, the contributions of the ‘NNW’ variables are more important
             to the discrimination between the coherent proxy deposit-type locations and non-deposit
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