•Theyhaveageneticrelationshipwiththetargetelements.Thismeansthatbothgroupsofelements(targetandpathfinder)originatefromthesamesourceorweredepositedatthesametimeandplace
•Inmostcases,pathfinderelementshavealargerhalo(duetohighermobility)thantargetelements.Thismeansthatpathfinderelementsoccurinalargerareathanthetargetelements,and,asaresult,thehaloofpathfinderelementsisusedasavectortowardthetargetelements’mineralizedzone(seeFigure1,nextpage).
Thetypeofpathfinderelementsdependsonthetargetelementanddeposittype/style.Preliminaryinvestigationshouldbecarriedoutineachareatofindsuitablepathfinderelements.Inpreciousmetalexploration,ahighcorrelationbetweenthetargetelementandagivenelement“X”(basedonthelaboratoryassays)mayshowthatelementXcanbeusedasapathfinderinfieldworkusingportablex-rayfluorescence(XRF).
ApplicationoftheThermoScientificPortableXRFAnalyzerinPGEExplorationExample from the Merensky Contact Reef, Bushveld Complex, South Africa
Introduction Miningandexplorationactivitiesforpreciousmetalshaverisenduetobothhighpricesandincreaseddemand.Preciousmetalsisacollectionofvaluablemetalsthatincludesgold,silver,andtheplatinumgroupelements(PGEs).Inmostinstances–suchasmining,oregradecontrol,andexplorationofrichzones–preciousmetalscanbedetecteddirectly.Inotheroccurrences–whereverylowconcentrationsofthesemetalsareunderexploration–pathfinderelements,whichcanbeenrichedwithpreciousmetals,areusedtolocatepotentialzones.Thesepathfinderelementshaveageneticrelationshipwiththepreciousmetals,and,therefore,cansuccessfullybeusedasexplorationtools.
Application Pathfinderelementsareveryimportantinfacilitatingtheexplorationofvarioustypesoforedepositsincludingpreciousmetalmineralization.Commonly,pathfinderelementshaveoneorafewofthefollowingcriteria:
•Theyaredetectedrelativelyeasilycomparedtothetargetelements.
•Theyarepresentathigherconcentrationsthantargetelements.
Benefits At-a-Glance
• Immediate geochemical analysis of ore, rock, drill core, chips, and rock face
• Help in confirming mineral deposit models
• Assistance with recognition of new or unexpected types of ore mineralization
• Drastic reduction of the number of samples sent for lab analysis
• Decision-making tools at your fingertips
“...it is possible to successfully locate zones of high
concentrations of precious metals (Pt, Pd, and Au, in this case) by using portable XRF on pathfinder elements.”
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ofchromite.ThePGEsarehostedindisseminatedsulphideswithtypicalgradesrangingfrom3to10g/t(ppm).Locally,PGEsarehostedinthefinelydisseminatedsulphidegrainsinthechromite-richlithologies.MiningisconductedintheBushveldComplexforallsixplatinumgroupelements(platinum,palladium,rhodium,ruthenium,iridium,andosmium)aswellasgold,nickel,andcopper.
ToinvestigatetheapplicationofportableXRFinPGEexplorationintheBushveldComplex,63sampleswerecollectedalongastratigraphicsection.Thesamplesthenwereanalyzedbyacommerciallab(SGS-Lakefield)usingICP.TwotypesofThermoScientificportableXRFanalyses(directshotonthesampleandpulverizedsample-pulp)werecarriedoutonthesesamples.
Results Usinglabassays,pathfinderelementswereselectedbasedontheircorrelationwiththetargetelements(Pt,Pd,andAu,inthiscase)asshowninFigure2.VisualexaminationofPt-AuandPt-PddiagramsindicatepositivecorrelationsbetweenPt,Pd,andAu,whichsuggeststhattheycanbefoundinthesameorclosestratigraphicunits.Also,positivecorrelationin
Portable XRF Analyzer Ouradvanced,handheld,ThermoScientificNitonXL3tSeriesXRFanalyzers,includingthehigh-performanceNiton®XL3tGOLDD+analyzer,deliveraccurateelementalanalysiswithunmatchedefficiencyforcompaniesacrossallstagesoftheexploration,mining,andrefiningprocesses.Theseinstrumentsmakeiteasytoperformtrendanalysisbyaveragingreadingsinreal-timeorbydownloadingresultslatertoaPC.
NitonXL3tSeriesanalyzersprovidethefollowingkeybenefits:
•Immediategeochemicalanalysisofore,rock,drillcore,chips,androckface
•Helpinconfirmingmineraldepositmodels
•Assistancewithrecognitionofneworunexpectedtypesoforemineralization
•Drasticreductionofthenumberofsamplessentforlabanalysis
•Decision-makingtoolsatyourfingertips
•Oreconcentrationtrackedinstantly
•LowlevelsofdetectionwithThermoScientificgeometricallyoptimizedlargeareadriftdetector(GOLDD)technologyformorethan25elements,includinglightelements(Mg-S)
Further,ouruniqueThermoScientificTestAllGeotechnologyprovidesapowerfulfeaturethatcanautomaticallydeterminethecorrectanalyticaltestmodeforthe rapidanalysisofmajor,minor,andtraceelementsingeologicalsamples.
Methodology ThetargetareaintheBushveldComplexinSouthAfricaistheMerenskyReef,alayerofigneousrock,which,togetherwithanunderlyinglayer,theUpperGroup2Reef(UG2),containsmostoftheworld’sknownreservesofPGEs.Inthestudiedarea,thestratigraphyincludespyroxenite,anorthosite,andharzburgite(pseudo/altered)withlocalstrings
Figure 1. Schematic showing the spatial relationship between target (ore zone) and two hypothetical pathfinder elements I and II. Note the larger size of the pathfinder elements’ halos.
Thermo Scientific portable XRF analyzers deliver fast and accurate analysis of pathfinder elements for precious metal exploration.
Analysis of PGE pathfinder elements (Ni and Cu from this case study) using the Thermo Scientific Niton XL3t GOLDD+ XRF analyzer.
Figure 2. Positive correlation between target elements (Pt, Pd, Au) and potential pathfinder elements (Ni, Cu) based on lab assay data.
savingtimeandmoneyinthefieldtolocatethesezones,andsubsequently,inanalyzingtherightsamples(notbarrenspecimens).Suchreal-timeaccesstoassaydatahelpsgeologistsmakeon-the-spotdecisionsandproficientlymanagetheirminingprojects.
Todiscussyourparticularapplicationsandperformancerequirements,ortoscheduleanon-sitedemonstration,pleasecontactyourlocalThermoScientificPortableXRFAnalyzerrepresentativeorcontactusdirectlybyemailatniton@thermofisher.com,orvisitourwebsiteatwww.thermoscientific.com/niton.
Note: Platinum and gold, two precious metals, are shown in the front page photo.
We would like to thank Boynton Platinum (Platmin Limited) for its technical and geological support.
Ni-PtandCu-PtdiagramsshowsthatNiandCucanbeusedaspathfinderelementsnotonlyforPt,butalsoforbothPdandAu.Notethatthisapproachisnecessarytodeterminepathfinderelements.
Inthenextstep,distributionofbothtargetandpathfinderelementsalongthesampledstratigraphicsectionisinvestigated(seeFigure3,nextpage).Bothtargetandpathfinderelementsclearlyshowthesameoraverysimilarstratigraphic-geochemicalpattern.Notethatevendirect-shotassaysofNiandCuusingThermoScientificportableXRFanalyzerscanbeusedtolocatezonesofhighPt,Pd,andAuconcentrations.
Conclusions Explorationofpreciousmetalsisverychallengingbecausethecut-offgradecontinuestodecreasewithtime,asthevalueofthemetalsincrease.Thisemphasizestheneedfornewandfasttechniquesforincreasingproductivityandefficiencyinthefield.
Thisstudyshowsthatitispossibletosuccessfullylocatezonesofhighconcentrationsofpreciousmetals(Pt,Pd,andAu,inthiscase)byusingportableXRFonpathfinderelements.Thesearethezonesthatshouldbesampledandassayedbylabmethodsforverylowconcentrations(sub-ppmlevels)ofpreciousmetals–
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Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details.
Copyrights in and to the platinum group elements (PGEs) photograph are owned by a third party and licensed for limited use only to Thermo Fisher Scientific by www.iRocks.com specimen, Joe Budd photo.
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Figure 3. Stratigraphic distribution of target (Pt, Pd, Au) and pathfinder elements (Cu, N
i) in the Bushveld Complex, South Africa, w
hich shows Cu and N
i assays using the Therm
o Scientific portable XRF analyzer can be used to locate Pt, Pd, and Au mineralized zones.
