Suarez（aの頭に´）,S., Prichard,N.M., Velasco,F., Fisher,P.C. and McDonald,I.(2010): Alteration of platinum-group minerals and dispersion of platinum-group elements during progressive weathering of the Aguablanca Ni-Cu deposit, SW Spain. Miner. Deposita, 45, 331-350.

『南西スペインのアグアブランカ・ニッケル銅鉱床の累進風化の間の白金族鉱物の変質と白金族元素の分散』

『Abstract
　The distribution, mineralogy and mobility of the platinum-group elements (PGE) in the surface environment are poorly understood. This study of the lower, less altered and upper, more altered gossan, overlying the Aguablanca N-Cu-(PGE) magmatic deposit (Spain), has shown that the platinum-group minerals (PGM) are progressively oxidised and dispersed into iron oxides that from the gossan. A combination of the characterization of PGE in host PGM, using a scanning electron microscope, and measurement of PGE at lower concentrations in host iron oxides, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), has for the first time allowed the total distribution of the PGE within a gossan to be documented. This study has revealed a complete in situ alteration and dispersion sequence of the PGM including (1) breakdown of both the more stable Pt-arsenides, Pt/Pd-tellurides and the less stable bismuthotellurides, (2) formation of partially oxidised PGM, (3) development of a wide range of oxidised Pt- and Pd-bearing phases, (4) subsequent formation of Fe-PGE-oxides and PGE-hydroxides, (5) incorporation of PGE into ferruginous supergene products and lastly (6) concentration of PGE at the edges of veins and iron oxides. Dispersion of Pd is greater than for the other PGE with Pd being widely distributed throughout the iron oxides. This oxidising environment produced PGE-oxides rather than PGE-alloys, also commonly found in the surface environment, especially in placers. These results provide critical evidence for the stages of mineralogical change from PGE host mineralogy in magmatic ores to surface weathering producing PGE-oxides.

Keywords: Ni-Cu gossan; Platinum-group minerals; Platinum-group elements; LA-ICP-MS; Aguablanca; Sprain』

Introduction
The Aguablanca deposit
Sampling and analytical methods
The gossan
　Mineralogy
　Geochemistry
　Distribution of PGE
Platinum-group-element-bearing minerals
　Unweathered PGN: PGM-arsenides and tellurides
　　Arsenides: sperrylite (PtAs2)
　　Tellurides
　Secondary PGE-bearing phases
　　Partially oxidised PGM
　　Oxidised Pt- and Pd-bearing phases
　　Fe- or Cu-rich Pt-Pd-bearing oxides
LA-ICP-MS analysis
　Lower gossan
　Upper gossan
Discussion
　Least altered PGM at Aguablanca
　Oxidised PGM and dispersion of the PGE
　　Mobility of the PGE and copper
　PGE-oxide formation rather than alloys
Conclusions
Acknowledgements
References

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