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Spatial Geochemistry: A Characterisation of Heterogeneity in Reference Materials
Author(s) -
Bédard L. Paul,
Néron Alexandre
Publication year - 2014
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2013.00255.x
Subject(s) - standard deviation , microbeam , geostatistics , range (aeronautics) , dispersion (optics) , geology , spatial analysis , relative standard deviation , sill , mineralogy , statistics , spatial variability , mathematics , materials science , physics , optics , geochemistry , detection limit , composite material
Geochemical reference materials ( RM s) for microbeam techniques are typically characterised by averages and dispersion statistics (e.g., standard deviation, variance) that are calculated for a number of measurements (beam shots). It is proposed that the mapping of RM s will add spatial information that better characterises the grouping and magnitudes of the heterogeneities and provides the information necessary to define a minimum analytical mass. A simple mathematical solution is proposed, which can be easily computed and understood. The analogous notions to sill and range from geostatistics are applied to the minimum analytical mass versus the relative standard deviation. To assess grouping and magnitudes of the heterogeneities, a ‘proximity number’ is computed for each average value ± ‘n’ standard deviations (magnitude). Different chemical anomalies have been simulated to demonstrate the behaviour of the proximity number. To further test the proposed spatial geochemistry concept, sulfide‐ and oxide‐bearing RM s have been selected because many are crippled with nugget effect. They have been mapped with a micro‐ XRF apparatus, and results are presented for CHR ‐ B kg, CHR ‐ P t+, MASS ‐1, MASS ‐3, WMS ‐1 and WMS ‐1a. MASS ‐1 and MASS ‐3 are the most suitable RM s for microbeam techniques. Spatial geochemistry offers a new approach to better characterise reference materials.