Novodneprite (AuPb3), anyuiite [Au(Pb, Sb)2] and gold micro- and nano-inclusions within plastically deformed mantle-derived olivine from the Lherz peridotite (Pyrenees, France): a HRTEM–AEM–EELS study
- 280 Downloads
To contribute the problem of the missing (“invisible”) gold fraction in mantle rocks, olivine grains separated from orogenic lherzolite of the peridotite body of Lherz (Eastern Pyrenees, France) have been investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The results indicate the presence of micrometric inclusions of novodneprite, AuPb3, and anyuiite, Au(Pb,Sb)2, together with nanometric clusters of metallic gold. Both minerals have been recognised on TEM images as darker contrast inclusions and identified through selected area electron diffraction (SAED) and energy dispersive spectroscopy (EDS) analyses. Gold clusters have been indirectly identified in randomly distributed nano-sized rectangular areas that occur in TEM images obtained from the edges of olivine crystals. Within these volumes the EDS analyses reveal a constant presence of Au (0.1–0.2 wt %). High-resolution TEM (HRTEM) investigations evidence series of regularly alternating sigmoidal and ellipsoidal domains developed along . The EELS investigations revealed that the Au signal (M-series lines) arises from the ellipsoidal domains. It is proposed that novodneprite and anyuiite are the result of subsolidus recrystallization of the Pyrenean lherzolites accompanied by a secondary olivine grains growth that trapped inter-granular components. Likely, a process of plastic deformation favoured the formation of edge dislocations within olivine grains and thus, the circulation through them of Au-enriched fluids. A mass balance calculation of the missing gold percentage within this lherzolite points to olivine as one of the potential hosts for about the 80 % of the “invisible” gold in form of nano-inclusions, whereas only 20 % of the whole-rock Au-budget, would be hosted within assemblages of Cu–Fe–Ni sulphides.
KeywordsNovodneprite Anyuiite Gold nano-inclusions Olivine Lherz TEM–AEM EELS
The authors would like to thank the editor Milan Rieder for his expert handling of the paper and the two referees Nigel Cook and an anonymous one for their very fruitful criticism that helped improving the quality of the manuscript. CF is indebted to Prof. TJ White for the use of TEM and EELS instrumentation at the School of Materials Science & Engineering, NTU, Singapore.
- Alard O, Lorand J-P, Reisberg L, Bodinier J-L, Dautria J-M, O’Reilly SY (2011) Volatile-rich metasomatism in Montferrier xenoliths (Southern France): implications for the abundances of chalcophile and highly siderophile elements in the Sub continental Mantle. J Petrol 52:2009–2045CrossRefGoogle Scholar
- Conquéré F, Fabriès J (1984) Chemical disequilibrium and its thermal significance in spinel-peridotite from the Lherz and Freychinède ultramafic bodies (Ariège; French Pyrenees). In: Kornprobst J (ed) Kimberlites II: The mantle and crust-mantle relationships. Elsevier, Amsterdam, pp 319–332CrossRefGoogle Scholar
- Cook NJ, Chryssoulis SL (1990) Concentration of “invisible gold” in the common sulfides. Can Mineral 28:1–16Google Scholar
- Dusembaeva KS, Levin VL, Kotel’nikov PE, Bekenova GK (2006) Novodneprite, AuPb3, a new mineral from the Novodneprovskoe deposit (Northern Kazakhstan). Doklady Natsional’noy Akademii Nauk Respubliki Kazakhstan 5:46–50 (in Russian)Google Scholar
- Fabriès J, Lorand J-P, Bodinier JL, Dupuy C (1991) Evolution of the upper mantle beneath the Pyrenees: evidence from orogenic spinel lherzolite massifs. J Petrol (special Lherzolites issue), 55–76Google Scholar
- Ferraris C, Auchterloine G (2013) Inclusions and traces studied by TEM-AEM. In: Nieto F, Livi JJT (eds) Minerals at the nanoscale. European Mineralogical Union and the Mineralogical Society of Great Britain & Ireland, London, vol 14, pp 1–47Google Scholar
- Meisel T, Moser J (2004) Reference materials for geochemical PGE analysis: new analytical data for Ru, Rh, Pd, Os, It, Pt and Re by isotope dilution ICP-MS in 11 geological reference materials. In: Reisberg L, Lorand J-P, Alard O, Ohnenstetter M (eds) Highly siderophile elements and igneous processes. Chem Geol 208:319–338Google Scholar
- Osbahr I, Klem R, Oberthür Th, Brätz H, Schouwstra R (2013) Platinum-group element distribution in base-metal sulfides of the Merensky Reef from the eastern and western Bushveld Complex, South Africa. Contrib Mineral Petrol 48:211–232Google Scholar
- Peregoedova AV (1998) The experimental study of the Pt–Pd partitioning between monosulfide solid solution and Cu–Ni– sulfide melt at 900–840°C. In: 8th international platinum symposium abstracts. Geol Soc South Africa and South African Inst Min Metall Symposium Series S18:325–327Google Scholar
- Razin LV, Sidorenko GA (1989) Anyuiite AuPb2—a new intermetallic of gold and lead. Mineral Zhurnal 11(4):88–96 (In Russian)Google Scholar
- Walker RJ (2009) Highly siderophile elements in the Earth, Moon and Mars: update and implications for planetary accretion and differentiation. Geochemistry 69:101–125Google Scholar