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Multivariate statistical analysis of trace elements in pyrite: prediction, bias and artefacts in defining mineral signatures

Citation

Dmitrijeva, M and Cook, NJ and Ehrig, K and Ciobanu, CL and Metcalfe, AV and Kamenetsky, M and Kamenetsky, VS and Gilbert, S, Multivariate statistical analysis of trace elements in pyrite: prediction, bias and artefacts in defining mineral signatures, Minerals, 10, (1) Article 61. ISSN 2075-163X (2020) [Refereed Article]


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Copyright Statement

2020 by the authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) http://creativecommons.org/licenses/by/4.0/

Official URL: https://www.mdpi.com/2075-163X/10/1/61

DOI: doi:10.3390/min10010061

Abstract

Pyrite is the most common sulphide in a wide range of ore deposits and well known to host numerous trace elements, with implications for recovery of valuable metals and for generation of clean concentrates. Trace element signatures of pyrite are also widely used to understand ore-forming processes. Pyrite is an important component of the Olympic Dam CuUAuAg orebody, South Australia. Using a multivariate statistical approach applied to a large trace element dataset derived from analysis of random pyrite grains, trace element signatures in Olympic Dam pyrite are assessed. Pyrite is characterised by: (i) a AgBiPb signature predicting inclusions of tellurides (as PC1); and (ii) highly variable CoNi ratios likely representing an oscillatory zonation pattern in pyrite (as PC2). Pyrite is a major host for As, Co and probably also Ni. These three elements do not correlate well at the grain-scale, indicating high variability in zonation patterns. Arsenic is not, however, a good predictor for invisible Au at Olympic Dam. Most pyrites contain only negligible Au, suggesting that invisible gold in pyrite is not commonplace within the deposit. A minority of pyrite grains analysed do, however, contain Au which correlates with Ag, Bi and Te. The results are interpreted to reflect not only primary patterns but also the e ects of multi-stage overprinting, including cycles of partial replacement and recrystallisation. The latter may have caused element release from the pyrite lattice and entrapment as mineral inclusions, as widely observed for other ore and gangue minerals within the deposit. Results also show the critical impact on predictive interpretations made from statistical analysis of large datasets containing a large percentage of left-censored values (i.e., those falling below the minimum limits of detection). The treatment of such values in large datasets is critical as the number of these values impacts on the cluster results. Trimming of datasets to eliminate artefacts introduced by left-censored data should be performed with caution lest bias be unintentionally introduced. The practice may, however, reveal meaningful correlations that might be diluted using the complete dataset.

Item Details

Item Type:Refereed Article
Keywords:pyrite, trace elements, multivariate statistics, left-censored data, Olympic Dam
Research Division:Earth Sciences
Research Group:Geology
Research Field:Mineralogy and crystallography
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Mineral exploration
Objective Field:Copper ore exploration
UTAS Author:Kamenetsky, M (Dr Maya Kamenetsky)
UTAS Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
ID Code:137086
Year Published:2020
Funding Support:Australian Research Council (LP130100438)
Web of Science® Times Cited:3
Deposited By:CODES ARC
Deposited On:2020-01-30
Last Modified:2020-04-02
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