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Natural Resources Research

, Volume 13, Issue 3, pp 173–187 | Cite as

Weights of Evidence Modeling of Mineral Potential: A Case Study Using Small Number of Prospects, Abra, Philippines

  • Emmanuel John M. Carranza
Article

Abstract

Weights of evidence (WofE) modeling usually is applied to map mineral potential in areas with large number of deposits/prospects. In this paper, WofE modeling is applied to a case study area measuring about 920 km2 with 12 known porphyry copper prospects. A pixel size of 100 m × 100 m was used in the spatial data analyses to represent in a raster-based GIS lateral extents of prospects and of geological features considered as spatial evidence. Predictor maps were created based on (a) estimates of studentized values of positive spatial association between prospects and spatial evidence; (b) proportion of number of prospects in zones where spatial evidence is present; and (c) geological interpretations of positive spatial association between prospects and spatial evidence. Uncertainty because of missing geochemical evidence is shown to have an influence on tests of assumption of conditional independence (CI) among predictor maps with respect to prospects. For the final predictive model, assumption of CI is rejected based on omnibus test but is accepted based on a new omnibus test. The final predictive model, which delineates 30% of study area as zones with potential for porphyry copper, has 83% success rate and 73% prediction rate. The results demonstrate plausibility of WofE modeling of mineral potential in large areas with small number of mineral prospects.

Spatial association uncertainty missing evidence conditional independence new omnibus test porphyry copper GIS 

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REFERENCES

  1. Agterberg, F. P., 1989, Systematic approach to dealing with uncertainty of geoscience information in mineral exploration: Proc.21st APCOM Symposium, Las Vegas, Chapter 18, p. 165–178.Google Scholar
  2. Agterberg F. P., 1992, Combining indicator patterns in weights of evidence modeling for resource evaluation: Nonrenewable Resources, v. 1, no. 1, p. 39–50.Google Scholar
  3. Agterberg, F. P., and Cheng, W., 2002, Conditional independence test of weights-of-evidence modeling: Natural Resources Research, v. 11, no. 4, p. 249–255.Google Scholar
  4. Agterberg, F. P., Bonham-Carter, G. F., and Wright, D. F., 1990, Statistical pattern integration for mineral exploration, in Gaál, G., and Merriam, D. F., eds., Computer Applications in Resource Estimation: Pergamon Press, Oxford, p. 1–21.Google Scholar
  5. Agterberg, F. P., Bonham-Carter, G. F., Cheng, Q., and Wright, D. F., 1993, Weights of evidence modeling and weighted logistic regression in mineral potential mapping, in Davis, J. C., and Herzfeld, U. C., eds., Computers in Geology: Oxford Univ. Press, New York, p. 13–32.Google Scholar
  6. Balce, G. R., Encina, R. Y., Momongan, A., and Lara, E., 1980, Geology of the Baguio district and its implications on the tectonic development of the Luzon Central Cordillera: Geology and Paleontology of Southeast Asia, v. 21, no. 3, p. 265–287.Google Scholar
  7. Berger, B. R., and Drew, L., 2002, Mineral-deposit models: new developments, in Fabbri, A.G., Gaál, G., and McCammon, R. B., eds., Deposit and Geoenvironmental Models for Resource Exploitation and Environmental Security: Kluwer Acad. Publishers, Dordrecht, p. 121–134.Google Scholar
  8. Bonham-Carter, G. F., 1991, Integration of geoscientific data using GIS, in Maguire, D. J., Goodchild, M. F., and Rhind, D. W., eds., Geographic Information Systems: Principles and Applications: Longman, London, v. 2, p. 171–184.Google Scholar
  9. Bonham-Carter, G. F., 1994, Geographic information systems for geoscientists, modeling with GIS: Pergamon, Press, Ontario, 398 p.Google Scholar
  10. Bonham-Carter, G. F., and Agterberg, F. P., 1990, Application of a microcomputer-based geographic information system to mineral potential mapping, in Hanley, T., and Merriam, D. F., eds., Microcomputers in Geology, v. 2, Pergamon Press, Oxford, p. 49–74.Google Scholar
  11. Bonham-Carter, G. F., Agterberg, F. P., and Wright, D. F., 1988, Integration of geological datasets for gold exploration in Nova Scotia: Photogrammetric Engineering and Remote Sensing, v. 54, no. 11, p. 1585–1592.Google Scholar
  12. Bonham-Carter, G. F., Agterberg, F. P., and Wright, D. F., 1989, Weights of evidence modelling: a new approach to mapping mineral potential, in Agterberg, F. P., and Bonham-Carter, G. F., eds., Statistical Applications in the Earth Sciences: Geol.Survey Canada Paper 89-9, p. 171–183.Google Scholar
  13. Bureau of Mines, 1976, Geology and mineral resources of Abra province: Bureau of Mines, Manila, Rept. Invest. No. 85, 14 p.Google Scholar
  14. BMG, 1982, Geology and mineral resources of the Philippines, Volume 1-Geology: Bur. Mines and Geosciences (BMG), Manila, 406 p.Google Scholar
  15. BMG, 1986, Geology and mineral resources of the Philippines, Volume 2-Mineral Resources: Bur. Mines and Geosciences (BMG), Manila, 446 p.Google Scholar
  16. Carranza, E. J. M., and Hale, M., 1997. A catchment basin approach to the analysis of geochemical-geological data from Albay province, Philippines, Jour. Geochemical Exploration, v. 60, no. 2, pp. 157–171.Google Scholar
  17. Carranza, E. J. M., and Hale, M., 2000, Geologically constrained probabilistic mapping of gold potential, Baguio district, Philippines: Natural Resources Research, v. 9, no. 3, p. 237–253.Google Scholar
  18. Carranza, E. J. M., and Hale, M., 2002, Where are porphyry copper deposits spatially localized? a case study in Benguet province, Philippines: Natural Resources Research, v. 11, no. 1, p. 45–59.Google Scholar
  19. JICA, 1980. Report on the Geological Survey of Northwestern Luzon, Phase II: Japan Intern. Cooperating Agency (JICA), Tokyo, unpaginated.Google Scholar
  20. Paganelli, F., Richards, J. P., and Grunsky, E. C., 2002, Integration of structural, gravity, and magnetic data using the weights of evidence method as a tool for kimberlite exploration in the Buffalo Head Hills, Northern Central Alberta, Canada: Natural Resources Research, v. 11, no. 3, p. 219–236.Google Scholar
  21. Porwal, A., Carranza, E. J. M., and Hale, M., 2003, Extended weights-of-evidence modelling for predictive mapping of base metal deposit potential in Aravalli province, western India: Exploration and Mining Geology, v. 10, no. 4, p. 155–163.Google Scholar
  22. Raines, G. L., and Mihalasky, M. J., 2002. Areconnaissance method for delineation of tracts for regional-scale mineral-resource assessment based on geologic-map data: Natural Resources Research, v. 11, no. 4, p. 241–248.Google Scholar
  23. Rangin, C., 1991, The Philippine mobile belt: a complex plate boundary: Jour. Southeast Asian Earth Sciences, v. 6, nos. 3 & 4,p.209–220.Google Scholar
  24. Ringenbach, J. C., Stephan, J. F., Maleterre, P., and Bellon, H., 1990, Structure and geologic history of the Lepanto-Cervantes releasing bend on the Abra River Fault, Luzon Central Cordillera, Philippines: Tectonophysics, v. 183, nos. 1-4, p. 225–241.Google Scholar
  25. Sillitoe, R. H., and Gappe, I. M., Jr., 1984, Philippine porphyry copper deposits: geological setting and characteristics: CCOP Tech. Publ. 14, Bangkok, 89 p.Google Scholar
  26. Snedecor, G. W., and Cochran, W. G., 1967. Statistical methods (6th edn.): Iowa State Univ. Press, Ames, Iowa, 593 p.Google Scholar
  27. Thiart, C., Bonham-Carter, G. F., and Agterberg, F. P., 2003, Conditional independence in weights-of-evidence: application of an improved test. Proc. IAMG 2003 Ann. Conf., Portsmouth, England, CD-ROMGoogle Scholar
  28. Thiart, C., Bonham-Carter, G. F., Agterberg, F. P., Cheng, Q., and Panahi, A., in press, An application of the new omnibus test for conditional independence in weights-of-evidence modeling, in Harris, J., ed., GAC Spec. Vol. GIS Applications to Geology.Google Scholar
  29. Wolfe, J. A., 1981, Philippines geochronology: Jour. Geol. Soc. Philippines, v. 35, no. 1, p. 1–30.Google Scholar
  30. Wright, D. F., and Bonham-Carter, G. F., 1996, VHMS favourability mapping with GIS-based integration models, Chisel Lake-Anderson Lake area, in Bonham-Carter, G. F., Galley, A. G., and Hall, G. E. M., eds., EXTECH I: A Multidisciplinary Approach to Massive Sulphide Research in the Rusty Lake-Snow Lake Greenstone Belts, Manitoba: Geol. Survey Canada Bull. 426, p. 339–376, 387-401.Google Scholar

Copyright information

© International Association for Mathematical Geology 2004

Authors and Affiliations

  • Emmanuel John M. Carranza
    • 1
  1. 1.Department of Earth Systems AnalysisInternational Institute for Geo-Information Science and Earth Observation (ITC)The Netherlands

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