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Perth, Australia

Fisher L.,CSIRO | Fisher L.,Deep Exploration Technologies Cooperative Research Center | Gazley M.F.,Barrick Australia Pacific | Gazley M.F.,Victoria University of Wellington | And 5 more authors.
Geochemistry: Exploration, Environment, Analysis | Year: 2014

Portable X-ray fluorescence (pXRF) technology can be used to collect large amounts of multi-element data rapidly at relatively low cost and has been widely embraced within the minerals industry. However, to date, it has been difficult to compare data-sets collected by different users or at different times because there is no standardized approach to the collection of these data. The absence of information on standardization and calibration procedures raises concerns about a lack of internal consistency within these data-sets and precludes comparison of different data-sets. This paper seeks to address this issue by developing a workflow for the collection of pXRF data in an exploration or mining setting. Two case studies highlight the robustness and possible applications of pXRF data collected following QA/QC protocols. A good correlation between conventional laboratory analyses and pXRF data is demonstrated through comparison of analysis methods for a drill-hole at the Plutonic Gold Mine, Western Australia, and fine-scale lithostratigraphic variation is recognized in pXRF data collected on grade control pulps from a drill fan at the Agnew Gold Mine, Western Australia. The Agnew data precision is sufficient to distinguish alteration signals from background lithology, and to discern which alteration signals are associated with gold mineralization. © 2014 AAG/The Geological Society of London.

Gazley M.F.,CSIRO | Tutt C.M.,Barrick Australia Pacific | Brisbout L.I.,Geological Survey of Western Australia | Fisher L.A.,CSIRO | Duclaux G.,CSIRO
Geochemistry: Exploration, Environment, Analysis | Year: 2014

The amphibolite-facies, Au-mineralized mafic rocks at the Plutonic Gold Mine are intruded by a suite of dolerite dykes of unknown age. The zones between these intrusive units often host significant Au mineralization. It is unclear whether this enrichment in Au mineralization is a function of the intrusion of the dolerites themselves or the influence of pre-existing structures (e.g. faults or shears). Geochemical characterization of the different microcrystalline dolerite units is important to the understanding of the structural architecture of the deposit and to the possible relationship of the dolerites to Au mineralization. The collection of a large geochemical dataset (n = 497) from the dolerite dykes from across the deposit using portable X-ray fluorescence technology allows us to break them into four distinct geochemical groupings. Thus we can define their geometries with greater confidence than was possible using lithology alone. Traverses across individual dolerite dykes indicate that the chill margins are the most geochemically homogenous and most likely to represent the chemistry of the source magma. Plots of Ti v. Zr combined with principal component analysis (PCA) define four geochemically distinct suites of dolerites. By applying this understanding to dolerites in a small area of the deposit, a new interpretation was generated whereby significant amounts of rock that were previously modelled as being dolerite were reclassified as potential host-rock, thus increasing the potential for Au in this area. © 2014 AAG/The Geological Society of London.

Gazley M.F.,Barrick Australia Pacific | Gazley M.F.,CSIRO | Tutt C.M.,Barrick Australia Pacific | Fisher L.A.,CSIRO | And 4 more authors.
Journal of Geochemical Exploration | Year: 2014

Geological logging by mine and exploration geologists involves the application of a classification code that requires a geologist to make a subjective decision to classify a particular rock unit (e.g. rock type, alteration intensity, mineralisation content). Where multiple geologists carry out logging this approach will most likely result in inconsistencies that are difficult to monitor or assess over time. A potential solution to this problem is to have a method to determine the nature of a given sample based on a set of fixed and quantifiable parameters. Plutonic Gold Mine (Plutonic), in Western Australia, has a growing dataset of more than 150 000 portable X-ray fluorescence (pXRF) multi-element analyses from core and underground face samples, reconciled to Au fire-assay concentration, and logging codes. This study analyses and validates the consistency with which Plutonic's logging codes have been applied from 2009 to 2013. In doing so, we have developed a schema that allows objective logging by utilising elemental data from pXRF analyses to allocate a mineralisation code. A K/V ratio is used to determine the degree of alteration, while As. +. 12Cu concentrations are used to determine how sulphide-rich a sample is. Thresholds were defined to maintain consistency with pre-existing logged dataset. While far from replacing the geologist, this method is complementary that adds significant value to a dataset. © 2014.

Gazley M.F.,CSIRO | Duclaux G.,CSIRO | Fisher L.A.,CSIRO | Tutt C.M.,Barrick Australia Pacific | And 7 more authors.
Geochemistry: Exploration, Environment, Analysis | Year: 2015

Since 2009 all underground face samples and diamond-drill core samples at the Plutonic Gold Mine (Plutonic), Marymia Inlier, Western Australia have been analysed by portable X-ray fluorescence (pXRF) following a systematic approach. This method is rapid and cost-effective and provides analyses of a large suite of chemical elements which can be used to characterize lithology and alteration. The delivery of a comprehensive workflow for sample preparation, analysis, results correction, and rapid processing enabled a quantum leap in the way mine geologists use geochemistry in modeling the ore body. Interpretation of the mine-site dataset of over 200 000 multi-element analyses has resulted in significant improvements in the understanding of the Plutonic deposit. In this contribution, we review how our understanding of Plutonic has been significantly improved through the use of pXRF geochemical analyses. Incorporation of pXRF data into routine geological modelling at Plutonic has resulted in improved confidence in the models of the ore bodies themselves and late-stage dolerite intrusives. It has allowed better management of milling processes through the development of metallurgical proxies and for significant insights into the role of stratigraphy in controlling the location of gold mineralization. We highlight the potential that a systematic approach to collecting pXRF data can have in a mining environment. These same techniques could be adapted and used in other mine and/or exploration settings. © 2015

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