Multivariate outlier detection in exploration geochemistry

  • Authors:
  • Peter Filzmoser;Robert G. Garrett;Clemens Reimann

  • Affiliations:
  • Institute of Statistics and Probability Theory, Vienna University of Technology, Wiedner Hauptstr. 8-10, A-1040 Wien, Austria;Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, Ontario, Canada, K1A 0E8;Geological Survey of Norway, N-7491 Trondheim, Norway

  • Venue:
  • Computers & Geosciences
  • Year:
  • 2005

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Abstract

A new method for multivariate outlier detection able to distinguish between extreme values of a normal distribution and values originating from a different distribution (outliers) is presented. To facilitate visualising multivariate outliers spatially on a map, the multivariate outlier plot, is introduced. In this plot different symbols refer to a distance measure from the centre of the distribution, taking into account the shape of the distribution, and different colours are used to signify the magnitude of the values for each variable. The method is illustrated using a real geochemical data set from far-northern Europe. It is demonstrated that important processes such as the input of metals from contamination sources and the contribution of sea-salts via marine aerosols to the soil can be identified and separated.