Iron distribution in Fe-rich bustamite-type minerals

• Published in: Physics and chemistry of minerals 2019-02, Vol.46 (2), p.133-142
• Main Authors: Shchipalkina, Nadezhda V., Chukanov, Nikita V., Rusakov, Vyacheslav S., Pekov, Igor V., Koshlyakova, Natalya N., Scholz, Ricardo
• Format: Article
• Language: English
• Subjects: Aluminum; Crystal structure; Crystallography and Scattering Methods; Crystals; Earth and Environmental Science; Earth Sciences; Electron probes; Geochemistry; Iron; Magnesium; Manganese; Mineral Resources; Mineralogy; Minerals; Mossbauer spectroscopy; Organic chemistry; Original Paper; Zinc
• ISSN: 0342-1791; 1432-2021
• DOI: 10.1007/s00269-018-0992-8

The crystal chemical role of iron in Fe-rich pyroxenoids with bustamite-type structure was studied on five samples containing from 6.0 to 10.3 wt% FeO using electron microprobe, XRD crystal structure refinement and Mössbauer spectroscopy. The crystal chemical formulae are ( Z  = 1): M 1 (Mn 0.85 Fe 2+ 0.15 ) 2 M 2 (Ca 0.8 Mn 0.2 ) 2 M 3 (Fe 2 + 0.5 Mn 0.4 (Mg,Al,Zn) 0.1 ) M 4 Ca[Si 3 O 9 ] 2 (Broken Hill, New South Wales, Australia), M 1 (Mn 0.8 Fe 2+ 0.2 ) 2 M 2 (Mn 0.55 Са 0.45 ) 2 M 3 (Fe 2 + 0.60 Mn 0.40 ) M 4 Ca[Si 3 O 9 ] 2 (Olginskoe, Primorskiy Kray, Russia), M 1 (Mn 0.8 Fe 2+ 0.2 ) 2 M 2 (Ca 0.5 Mn 0.5 ) 2 M 3 (Mn 0.50 Fe 2+ 0.35 Mg 0.15 ) M 4 (Ca 0.7 Mn 0.3 )[Si 3 O 9 ] 2 (Broken Hill), M 1 Ca 2 M 2 Ca 2 M 3 Fe 2+ M 4 Ca[Si 3 O 9 ] 2 (Tyrnyauz, North Caucasus, Russia), M 1 Ca 2 M 2 Ca 2 M 3 (Fe 2 + 0.6 Mn 0.4 ) M 4 Ca[Si 3 O 9 ] 2 (Dalnegorsk, Primorskiy Kray, Russia). Iron in bustamite-type compounds concentrates at the M 1 and M 3 sites which are characterized by the shortest ⟨ M –O⟩ distances. In general, the distribution of Fe and Mn in bustamite-type minerals is rather similar. Iron only slightly prefer the smallest in volume M 3O 6 octahedron rather than M 1O 6 . Unlike related pyroxenoids of the rhodonite group, significant Mn:Fe ordering in bustamite-type minerals was not observed.