Improving Geological and Metallurgical Understanding of Plutonic Gold Mine, Western Australia, using Three-Dimensional Visualisation of Portable X-Ray Fluorescence Data

摘要

The amphibolite-facies metabasaltic rocks of the Mine Mafi c Package at Plutonic Gold Mine,rnMarymia Inlier, Western Australia, contain an estimated total endowment of 12.2 Moz of Au,rnwhich includes 4.71 Moz of past production and 2.77 Moz of reserves and resources; the remainderrncomprises lower-grade inventory. Over 65 000 multi-element analyses of whole-rock core and facernchannel samples from the underground workings of the deposit have been collected by portablernX-ray fl uorescence (pXRF) using a handheld Innov-X Omega pXRF unit. The analyses werernperformed on pulverised samples through paper bags, and were corrected using a pulverised,rnmatrix-matched, reference standard. This method of data correction compares favourably withrnconventional XRF analyses performed on the same samples.rnA preliminary study based on pXRF analyses from a small number of drill holes found thatrna geochemical stratigraphy was evident in the pXRF data, and that this stratigraphy stronglyrncontrolled the location of Au mineralisation. The present study incorporates a much larger pXRFrndata set that samples a greater volume of diamond drill core and face channel samples and presentsrnthe data in a three-dimensional (3D) framework.rnThis data set allows an investigation of the mineralogy of Au mineralisation with varying geochemicalrnassociations across the deposit. Historically, there has been a strong relationship identifi ed betweenrnAs and Au, which has caused issues with metallurgical performance, rendering some areas of therndeposit only marginally economic. Utilising seamless data integration of the pXRF data set allowsrnfor recognition of the different styles of Au mineralisation using elemental concentrations and ratiosrnfrom the multi-element analyses (Au:As, Au:As:Cu, As:Cu vs. K:V), and to visualise the distributionrnof these different mineralogical associations in 3D. The results of the 3D modelling and geochemicalrncharacterisation of the different styles of Au mineralisation are currently the focus of an extensivernmetallurgical testing program, the preliminary results of which are presented here.