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Title: Magmatic platinum nanoparticles in metasomatic silicate glasses and sulfides from Patagonian mantle xenoliths
Contributor(s): González-Jiménez, José María (author); Roqué-Rosell, Josep (author); Jiménez-Franco, Abigail (author); Tassara, Santiago (author); Nieto, Fernando (author); Gervilla, Fernando (author); Baurier, Sandra (author); Proenza, Joaquín A (author); Saunders, Edward  (author)orcid ; Deditius, Artur P (author); Schilling, Manuel (author); Corgne, Alexandre (author)
Publication Date: 2019-05-13
DOI: 10.1007/s00410-019-1583-5
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Abstract: Platinum-rich nanonuggets (s.l., nanoparticles) are commonly produced in experiments attempting to quantify the solubility or partitioning of noble metals in silicate and sulfide melts. However, it has been thought that these represent artifacts produced during quenching of the experimental runs. Here, we document nanoparticles (~ 20–80 nm) of Pt-rich alloys and arsenides dispersed in high-temperature metasomatic silicate glasses and in base-metal sulfides (BMS) entrained in them, found interstitially between minerals of mantle peridotite xenoliths from southern Patagonia. Pt-rich nanoparticles found in the interstitial silicate glasses are frequently attached to, or in the proximities of, oxides (ilmenite or Cr-spinel) suggesting a close link between the formation of the oxides and the Pt-rich nanoparticles. The interstitial glasses in the studied xenoliths correspond to quenched alkaline basaltic melts that infiltrated the subcontinental lithospheric mantle (SCLM) at > 1000 °C at an oxygen fugacity (fO2) near the fayalite–magnetite–quartz (FMQ) buffer. Experimental works indicate that at these conditions the crystallization of oxides such as ilmenite or Cr-spinel may lower fO2 to promote the precipitation of Pt-rich nanoparticles. The investigation of four Pt-rich nanoparticles hosted in two different pentlandite grains using a combination of focused ion beam and high-resolution transmission electron microscopy (FIB/HRTEM) show that these nanoparticles consists of polycrystalline aggregates < 10 nm that are randomly oriented relative to their sulfide host matrices. These observations suggest that these nanoparticles could be segregated either directly from the infiltrating alkaline basaltic melt prior to sulfur saturation in the silicate melt, or from droplets of immiscible sulfide melt once sulfur saturation was achieved. The formation of Pt-rich nanoparticles in high-temperature melts, either silicate or sulfide, provides new clues on the processes of fractionation, transport and concentration of Pt in the mantle.
Publication Type: Journal Article
Source of Publication: Contributions to Mineralogy and Petrology, 174(5), p. 1-18
Publisher: Springer
Place of Publication: Germany
ISSN: 1432-0967
Field of Research (FOR): 040306 Mineralogy and Crystallography
040307 Ore Deposit Petrology
040304 Igneous and Metamorphic Petrology
Socio-Economic Objective (SEO): 840205 Mining and Extraction of Precious (Noble) Metal Ores
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article
School of Environmental and Rural Science

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