Effects of hydrous alteration on the distribution of base metals and platinum group elements within the Kevitsa magmatic nickel sulphide deposit

Vaillant, Margaux Le; Barnes, Stephen J.; Fiorentini, Marco L.; Santaguida, Frank; Törmänen, T.

doi:10.1016/j.oregeorev.2015.06.002

Cited by 41 publications

(13 citation statements)

References 38 publications

(45 reference statements)

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“…Le Vaillant et al (2014) investigated the direct use of pXRF as a lithogeochemical discrimination tool to distinguish potentially mineralised and barren komatiites, using geochemical criteria developed for laboratory analyses, and extended it to hydrothermal alteration mapping (Le Vaillant et al, 2016). More general applications of pXRF in geological reconnaissance and mapping were reviewed recently (Young et al, 2016).…”

Section: Lithogeochemistry and Hydrothermal Alterationmentioning

confidence: 99%

A review of pXRF (field portable X-ray fluorescence) applications for applied geochemistry

Lemière

2018

Journal of Geochemical Exploration

155

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In the last thirty years, portable X-ray fluorescence (pXRF) has grown from prototypes to being a key technique for field geochemical analyses, especially for mining and environmental applications. This technology provides real-time or near real-time decision support for operational field decisions (exploration, mining, site remediation or waste management), provides a cost-saving alternative to classical laboratory analysis programs, and deals efficiently with remote or harsh field conditions. The ability to rapidly collect a large number of samples and replicate analyses facilitates acquisition of higher data density compatible with geostatistics.pXRF can be used profitably for sample screening and selection tasks, dynamic sampling plans based on field observations and measurements, grid mapping of a site and determining relative element abundance. In waste management and remediation, pXRF is used to identify unknown waste composition, and verify waste loads before disposal or treatment.In all applications, having robust QA/QC plans and systematic laboratory controls on selected samples are essential for ensuring reliable measurements. The best overall results are usually achieved through a clever combination of field (pXRF) and lab data, with pXRF providing the bulk of the data at low cost, on larger data sets and potentially with better reliability than lab-based campaigns based on a limited number of samples.

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Section: Lithogeochemistry and Hydrothermal Alterationmentioning

confidence: 99%

A review of pXRF (field portable X-ray fluorescence) applications for applied geochemistry

Lemière

2018

Journal of Geochemical Exploration

155

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“…Disseminated sulfides in peridotitic and pyroxenitic cumulates have been studied in a number of deposits, with examples being given here from four: Kevitsa in arctic Finland (Yang et al, 2013;Santaguida et al, 2015;Le Vaillant et al, 2016), the Mirabela Intrusion (Santa Rita deposit) in north-eastern Brazil (Barnes et al, 2011c), the Merensky Reef of the Bushveld Complex in South Africa (Godel et al, 2010), and the JM Reef of the Stillwater Complex in the USA (Godel et al, 2006).…”

Section: Disseminated Sulfides In Layered Intrusion Cumulatesmentioning

confidence: 99%

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

Barnes

Mungall

Godel

et al. 2017

American Mineralogist

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122

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A large proportion of ores in magmatic sulfide deposits consist of mixtures of cumulus silicate minerals, sulfide liquid and silicate melt, with characteristic textural relationships that provide essential clues to their origin. Within silicate-sulfide cumulates, there is a range of sulfide abundance in magmatic-textured silicate-sulfide ores between ores with up to about five modal percent sulfides, called "disseminated ores", and "net-textured" (or "matrix") ores containing about 30 to 70 modal percent sulfide forming continuous networks enclosing cumulus silicates. Disseminated ores in cumulates have a variety of textural types relating to the presence or absence of trapped interstitial silicate melt and (rarely) vapour bubbles. Spherical or oblate spherical globules with smooth menisci, as in the Black Swan disseminated ores, are associated with silicate-filled cavities interpreted as amygdales or segregation vesicles. More irregular globules lacking internal differentiation and having partially facetted margins are interpreted as entrainment of previously segregated, partially solidified sulfide. There is a textural continuum between various types of disseminated and net-textured ores, intermediate types commonly taking the form of "patchy net-textured ores" containing sulfide-rich and sulfide-poor domains at cm to dm scale. These textures are ascribed primarily to the process of sulfide percolation, itself triggered by the process of competitive wetting whereby the silicate melt preferentially wets silicate crystal surfaces. The process is self-reinforcing as sulfide migration causes sulfide networks to grow by coalescence, with a larger rise height and hence a greater gravitational driving force for percolation and silicate melt displacement. Many of the textural variants catalogued here, including poikilitic or leopard-textured ores, can be explained in these terms. Additional complexity is added by factors such as the presence of oikocrysts and segregation of sulfide liquid during strain-rate dependent thixotropic behaviour of partially consolidated cumulates. Integrated textural and geochemical studies are critical to full understanding of ore-forming systems.

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“…The metaperidotite masks the identification of the primary lithology, and thus, the problems of identifying traceable magmatic layers were initially attributed to inconsistent logging practices. However, as recent geological works by [26,27] do not anymore support the idea of continuous smaller-scale magmatic layering within the resource area, it now seems that the evidence for obvious layering is lacking altogether. Individual horizons are inconsistent between boreholes based on lithology, whole-rock compositions, and ore grades [27].…”

Section: Geological Backgroundmentioning

confidence: 95%

Predicting Missing Seismic Velocity Values Using Self-Organizing Maps to Aid the Interpretation of Seismic Reflection Data from the Kevitsa Ni-Cu-PGE Deposit in Northern Finland

et al. 2019

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We use self-organizing map (SOM) analysis to predict missing seismic velocity values from other available borehole data. The site of this study is the Kevitsa Ni-Cu-PGE deposit within the mafic-ultramafic Kevitsa intrusion in northern Finland. The site has been the target of extensive seismic reflection surveys, which have revealed a series of reflections beneath the Kevitsa resource area. The interpretation of these reflections has been complicated by disparate borehole data, particularly because of the scarce amount of available sonic borehole logs and the varying practices in logging of borehole lithologies. SOM is an unsupervised data mining method based on vector quantization. In this study, SOM is used to predict missing seismic velocities from other geophysical, geochemical, geological, and geotechnical data. For test boreholes, for which measured seismic velocity logs are also available, the correlation between actual measured and predicted velocities is strong to moderate, depending on the parameters included in the SOM analysis. Predicted reflectivity logs, based on measured densities and predicted velocities, show that some contacts between olivine pyroxenite/olivine websterite-dominant host rocks of the Kevitsa disseminated sulfide mineralization-and metaperidotite-earlier extensively used "lithology" label that essentially describes various degrees of alteration of different olivine pyroxenite variants-are reflective, and thus, alteration can potentially cause reflectivity within the Kevitsa intrusion.Recently, data mining approaches, such as the self-organizing map (SOM; [1,2]) analysis employed in this study, have been increasingly used for analyses of the disparate and multivariate geoscientific datasets that are typical for mining and exploration environments (e.g., [3][4][5][6][7][8][9][10]). SOM is an artificial neural network that works on a vector quantization methodology allowing unsupervised analysis, i.e., no prior information is needed on the type or number of groupings within the data, to determine the underlying linear and non-linear relationships amongst different data. Typically 2D "maps" are used to visualize the underlying statistical relationships between the variables, which makes interpretation of the complex multidimensional data more effective (e.g., [11]). Major strengths of the methodology include the robust handling of sparse and disparate input data, labels, incomplete data, and the ability to predict missing data values for such data (e.g., [12][13][14]).Extensive seismic reflection data have been collected at the Kevitsa Ni-Cu-PGE deposit that is located in northern Finland (Figure 1). These data include four intersecting 2D seismic reflection profiles acquired in 2007 as a part of High-Resolution Reflection Seismics for Ore Exploration (HIRE) 2007-2010 project that aimed at testing the applicability of seismic exploration method in Kevitsa [16,17] and a 3D seismic reflection survey conducted in 2010 for mine planning and deep mineral exploration purposes [18,19]. Lateral...

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Effects of hydrous alteration on the distribution of base metals and platinum group elements within the Kevitsa magmatic nickel sulphide deposit

Cited by 41 publications

References 38 publications

A review of pXRF (field portable X-ray fluorescence) applications for applied geochemistry

A review of pXRF (field portable X-ray fluorescence) applications for applied geochemistry

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

Predicting Missing Seismic Velocity Values Using Self-Organizing Maps to Aid the Interpretation of Seismic Reflection Data from the Kevitsa Ni-Cu-PGE Deposit in Northern Finland

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