Cabri, L. J.

Fenoll Hach-Alí, P.

Gervilla, F.

Kojonen, K.

Papunen, H.

Sie, S. H.

Repositorio da Universidade da Coruña

Cadernos Lab. Xeolóxico de LaxeCoruña. 2000. Vol. 25, pp. 103-105Trace platinum group elements in arsenides and sulfarsenides from magmatic ores: Anelectron microprobe and proton microprobe(micro-pixe technique) studyElementos traza del grupo del platino enarseniatos y sulfoarseniatos de menasmagmáticas: estudio a la Microsonda electrónica y a la Microsonda de protones(técnica micro-pixe)GERVILLA, F.(1), CABRI, LJ.(2), KOJONEN, K.(3), SIE, S.H.(4), PAPUNEN, H.(5)& FENOLL HACH-ALÍ, P.(1).(1) Instituto Andaluz de Ciencias de la Tierra (Universidad de Granada-CSIC), Granada.(2) Consulting Mineralogist, Ottawa, Ontario (Canada)(3) Geological Survey of Finland, Espoo (Finland)(4) Department of Geology, University of Turku, Turku (Finland)(5) CSIRO, Perth, Western Australia (Australia)The usefulness of micro-PIXE techniqueto determine ppm quantities of platinum-group elements in sulfide minerals has beenwidely demonstrated in the past twentyyears (e.g., Cabri et al., 1984; Czamanske etal., 1992), although only few data arepublished on the distribution of suchelements in arsenides and sulfarsenides (e.g.Ryan et al., 1990). On the other hand, thedevelopment of the CSIRO-trace analysispackage at CSIRO, Perth, WesternAustralia (Robinson and Graham, 1992)has also made possible the determination ofnoble metals (at ppm levels) in ore mineralsby means of electron microprobe (e.g.,Gervilla et al., 1998; Kojonen andJohanson, 1999). In this note we present theresults obtained by these two techniques onarsenides and sulfarsenides from thefollowing localities: i) chromite-Ni arsenideores (Cr-Ni ores) and arsenide-bearingsulfide-graphite ores (S-G ores) of thebetico-rifean ultramafic massifs in Spainand Morocco (Gervilla and Leblanc, 1990),ii) arsenide-rich sulfide ores of the VammalaNi-Cu mine and iii) arsenide-sulfide andarsenide ore types from the Kylmäkoski Ni-Cu mine in the Vammala Nickel Belt,Finland (Gervilla et al., 1998).Though the analyses were not made onthe same points, a comparison of both setsof results provides an opportunity to makesome observations.The micro-PIXE analyses were done atCSIRO Exploration and MiningLaboratories, North Ryde, Australia.  Themeasurements were carried out with 10 x15µm beam spots.  Typical measurement timefor a 6 micro-Coulomb (µC) integratedcharge was 25 to 30 minutes. Count ratewas kept below 3000 counts per second.Under these conditions the detection limitfor Pd is of the order of 20 to 30 ppm.Detection limits for Ru and Rh are slightlylower, of the order of 10 to 15 ppm. Twoadditional runs were made at 32 and 58 µCfor about 3 and 5 hours, respectively, on onegrain of nickeline and one grain ofnickeliferous löllingite from betico-rifeanores, to reduce the detection limit down to≈ 2 ppm for Ru and Rh and 2.5 ppm for Pd.These two analyses will be called hereLDLA (low detection limit analysis). Thedetection limit for Pt is very high (≈ 400ppm) because of strong interferences withBi for the relatively weak PtLα line.The EMP analyses were performedwith a CAMECA SX50 instrument at theGeological Survey of Finland, Espoo, bymeans of the CSIRO-trace analysispackage. The calculated detection limit forPt (30-34 ppm) in the analyzed minerals ishigher than that for Rh (24-28 ppm), Ir(20-22 ppm) and Pd (18-20 ppm).With the micro-PIXE technique Ruwas detected in nickeline (4-23 ppm) andnickeliferous löllingite (9-19 ppm); Rhwas found in single LDLA in nickeliferouslöllingite (6 ppm) and in cobaltite (14ppm); Pt was not found above thedetection limit except for one analysis ofnickeliferous löllingite (756 ppm) andtwo of cobaltite (717 and 1031 ppm); Pdwas measured in nickeline (7-149 ppm),in nickeliferous löllingite (8-30 ppm), andprincipally in maucherite (18-265 ppm).Pd partitioning between coexistingnickeline and maucherite varies fromprimary ores crystallized at hightemperature (≈ 800ºC) to ore assemblages104 Gervilla, F., et al. CAD. LAB. XEOL. LAXE 25 (2000)XXas Jornadas S.E.M. Trace platinum group elements 105formed by remobilization at lowertemperatures (≈ 500ºC). Thus, in thearsenide globules occurring in S-G ores(Gervilla et al., 1996) nickeline contains70 ppm Pd and maucherite 58 ppm Pd.In the late magmatic, arsenide-rich Ni-Cusulfide ores of Vammala, nickelinecontains 44-149 ppm Pd and maucherite92-117 ppm Pd. In contrast, the Pdcontent in nickeline is close to or belowthe detection limit and ranges between 83and 265 ppm in maucherite in theremobilized sulfide-arsenide and arsenideores from Kylmäkoski By means of EMP only Pt and Pd wereboth found to be above the detection limit.Pt was detected in nickeliferous löllingite(52-162 ppm) and cobaltite (122-650 ppm).Pd was found in nickeline and maucheritefrom the arsenide-rich Ni-Cu sulfide ores ofVammala (28-63 ppm and 67-84 ppm,respectively) and maucherite from arsenideores of Kylmäkoski (76-120 ppm). Pdvalues close to the detection limit weremeasured too in nickeline (20-38 ppm),maucherite (21-38 ppm), nickeliferouslöllingite (22-38 ppm) and cobaltite (22-27ppm). As in the above set of results Pddistribution between coexisting nickelineand maucherite indicate a higher affinity ofPd for maucherite at relatively lowtemperatures (≈ 500ºC).Conclusions: i) The two techniques used give rise tocomparable analytical results for PGEabundances well above their respectivedetection limits.ii) In ore assemblages crystallized at hightemperature (≈ 800ºC) nickeline andmaucherite contain comparableamounts of Pd whereas at ≈ 500ºCmaucherite is the principal Pd carrier.This is in agreement with theexperimental results in the system Pd-Ni-As at 790º and 450ºC (Gervilla etal., 1994). iii) In spite of the high detection limits forPt by micro-PIXE, comparison of dataobtained with those from EMP suggestthat the principal carriers of Pt arenickeliferous löllingite and cobaltite.These minerals also carry some Ru andRh.REFERENCESCABRI, L.J., BLANK, H., EL GORESY, A.,LAFLAMME, J.H.G., NOBILING, R.,SIZGORIC, M.B. & TRAXEL, K. (1984). Can.Mineral., 22, 521-542.CZAMANSKE, G.K., KUNILOV, V.R.,ZIENTEK, M.L., CABRI, L.J., LIKHACHEV,A.P., CALK, L.C. & OSCARSON, R.L. (1992).Can. Mineral., 30, 249-287. GERVILLA, F. & LEBLANC, M. (1990). Econ.Geol., 85,112-132.GERVILLA, F., LEBLANC, M., TORRES-RUIZ,J. & FENOLL HACH-ALÍ, P. (1996). Can.Mineral., 34, 485-502.GERVILLA, F., MAKOVICKY, E., MAKOVICKY,M. & ROSE-HANSEN, J. (1994). Econ. Geol.,89, 1630-1639.GERVILLA, F., PAPUNEN, H., KOJONEN, K. &JOHANSON, B. (1998). Mineral. & Petrol. 64,163-185.KOJONEN, K. & JOHANSON, B. (1999).Mineral. & Petrol 67, 1-19.ROBINSON, B.W. & GRAHAM, J. (1992). J.Computer-Assisted Microscopy, 4 (3).RYAN, C.G., COUSENS, D.R., SIE, S.H.,GRIFFIN, W.L., SUTER G.F. & CLAYTON E.(1990). Nucl. Instr. and Meth. B47, 55-71.

Elementos traza del grupo del platino en arseniatos y sulfoarseniatos de menas magmáticas: estudio a la Microsonda electrónica y a la Microsonda de protones (técnica micro-pixe)

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Elementos traza del grupo del platino en arseniatos y sulfoarseniatos de menas magmáticas: estudio a la Microsonda electrónica y a la Microsonda de protones (técnica micro-pixe)

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