Page 284 - Geochemical Anomaly and Mineral Prospectivity Mapping in GIS

Data-Driven Modeling of Mineral Prospectivity 287

TABLE 8-IV

Properly calibrated classes of spatial data sets for evidential belief modeling of epithermal Au
prospectivity, Aroroy district (Philippines). Ranges of data values in bold are associated spatially
with the epithermal Au deposits in the case study area (see Chapter 6, Table 6-IX). The plots of
values of Bel versus the upper limits of classes of data are shown in Fig. 8-15.

2
1a
Classes of proximity to NNW Classes of proximity to NW
1b
Class code Range (km) Class code Range (km)
NNW1 0.00 NW1 0.00 – 0.33
NNW2 0.01 – 0.10 NW2 0.34 – 0.74
NNW3 0.11 – 0.19 NW3 0.75 – 1.26
NNW4 0.20 – 0.43 NW4 1.27 – 2.19
NNW5 0.44 – 3.47 NW5 2.20 – 5.23
4a
3
Classes of proximity to FI Classes of ANOMALY
4b
Class code Range (km) Class code Range
FI1 0.00 – 0.54 ANOM1 0.369 – 0.781
FI2 0.55 – 0.99 ANOM2 0.252 – 0.368
FI3 1.00 – 1.59 ANOM3 0.100 – 0.251
FI4 1.60 – 2.75 ANOM4 ≤0.099
FI5 2.76 – 5.87 ANOM5 ‘no data’
1a NNW-trending faults/fractures. Upper limits of proximity range are equivalent to the distances
1b
3
2
(m) in the first column of table in Fig. 8-13C. NW-trending faults/fractures. Intersections of
4a
NNW- and NW-trending faults/fractures. Integrated PC2 and PC3 scores obtained from the
4b
catchment basin analysis of stream sediment geochemical data (see Chapter 5, Fig. 5-12). Upper
limits of ANOMALY range are the same as values of anomaly in the first column of table in Fig.
8-11C, but in decreasing order.
applications of coherent deposit and proxy deposit locations result in better predictive
models of epithermal Au prospectivity in the study area.
The map of integrated values of Bel based on the training set of 13 known locations
of epithermal Au deposits (Fig. 8-16A) and the map of integrated values of Bel based on
the training set of 11 coherent locations of epithermal Au deposits (Fig. 8-17A) both
show circular patterns of intermediate and high values of integrated Bel reflecting the
spatial evidence of proximity to intersections of NNW- and NW-trending
faults/fractures. The values of integrated Bel are highest mostly where the circular
patterns intersect with the patterns reflecting the spatial evidence of proximity to NNW-
trending faults/fractures, which are more conspicuous in Fig. 8-16A than in Fig. 8-17A.
The pattern of intermediate and high integrated values of Bel in both maps (Figs. 8-16A
and 8-17A) seem odd but are consistent with the conceptual model of epithermal Au
mineralisation in dilational or extensional settings as depicted in Fig. 6-16.
The fitting-rates of the map of integrated values Bel based on the training set of 11
coherent locations of epithermal Au deposits (Fig. 8-17B) are better than the fitting-rates
of the map of integrated values Bel based on the training set of 13 known locations of