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Applicability of hand-held X-ray fluorescence spectrometry in the exploration and development of carbonatite-related niobium deposits; a case study of the Aley Carbonatite, British Columbia, Canada

G. J. Simandl, S. Paradis, R. S. Stone, R. Fajber, R. D. Kressall, K. Grattan, J. Crozier and L. J. Simandl
Applicability of hand-held X-ray fluorescence spectrometry in the exploration and development of carbonatite-related niobium deposits; a case study of the Aley Carbonatite, British Columbia, Canada
Geochemistry - Exploration, Environment, Analysis (August 2014) 14 (3): 211-221

Abstract

This study evaluates the suitability of portable (handheld) X-Ray fluorescence spectrometry (pXRF) in the exploration for Aley-type "hard-rock" (primary) carbonatite-hosted Nb deposits. The assessment consists of comparisons between: (1) results of pXRF analyses on selected pulp samples and results of analyses of the same pulps using traditional laboratory methods; (2) results of averaged, multiple pXRF spot field analyses performed directly on 10 to 15 cm long pieces of core (before pulverization) compared with those of traditional laboratory analyses of the same pieces of core after pulverization; and (3) results of a manual core scanning method compared with the results of conventional analytical methods of the pulps of the corresponding scanned sections. A strong correlation exists between pXRF measurements on pulps and laboratory methods for most specialty metals, such as Nb (r (super 2) = 0.99), La (r (super 2) = 0.97), Ce (r (super 2) = 0.67), Y (r (super 2) = 0.93), and P (r (super 2) = 0.89); however, the values of r (super 2) for Pr and Nd are 0.19 and 0.38, respectively. As expected, textural heterogeneities within sample intervals reduced the quality of pXRF results when multiple spot readings were taken directly on the core. Nevertheless, the data can still be used to identify carbonatite-related Nb (+ or - other specialty metal mineralization) and delimitate potentially economically significant zones within it. The core scanning reduced the degree of variation associated with spot analyses. Scanning is useful during the early exploration stages, but provides data limited by the inability of the operator to maintain constant scanning speed. The scanning results correlate with laboratory methods for Nb (r (super 2) = 0.88), Th (r (super 2) = 0.80), Fe (r (super 2) = 0.84), Sr (r (super 2) = 0.74), Ba (r (super 2) = 0.73), Y (r (super 2) = 0.59), and Zn (r (super 2) = 0.75). The values of r (super 2) for La, Ce, Pr, and Nd were only 0.31, 0.26, 0.01 and 0.03, respectively, suggesting that concentrations of these elements were too low, and/or that the light rare earth elements (LREEs) were present not only in the crystal structure of fersmite, pyrochlore and apatite, but also in minor or accessory minerals such as REE-bearing fluorocarbonates or zircon erratically distributed throughout the core. Portable XRF is a robust tool facilitating exploration-related decision-making in the field, assuming that elements of interest such as Nb are present in concentrations within the analytical range of the instrument. The pXRF core scanning reduces the need for sample preparation (no pulps) and can be done directly on the drill-site, but the precision and accuracy of the data are reduced relative to laboratory and pXRF pulp analyses. The multiple spot analyses (no pulps) approach is good for instant verification of unknown, potentially ore-bearing minerals and for analysing discrete homogeneous features, layers, veins, etc; however, under normal circumstances this method is inferior to pulp analyses in precision and accuracy, and to scanning for determining average grade of core intervals.


ISSN: 1467-7873
EISSN: 2041-4943
Serial Title: Geochemistry - Exploration, Environment, Analysis
Serial Volume: 14
Serial Issue: 3
Title: Applicability of hand-held X-ray fluorescence spectrometry in the exploration and development of carbonatite-related niobium deposits; a case study of the Aley Carbonatite, British Columbia, Canada
Affiliation: British Columbia Geological Survey, Victoria, BC, Canada
Pages: 211-221
Published: 201408
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
References: 23
Accession Number: 2014-099034
Categories: General geochemistryEconomic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, sketch map
N56°00'00" - N57°30'00", W124°30'00" - W123°00'00"
Secondary Affiliation: Geological Survey of Canada, CAN, CanadaDalhousie University, CAN, CanadaElemental Controls, CAN, CanadaHunter Dickinson, CAN, CanadaUniversity of Victoria, CAN, Canada
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201450
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