Publications des scientifiques de l'IRD

Feneyrol J., Giuliani Gaston, Ohnenstetter D., Rondeau B., Fritsch E., Fallick A. E., Ichang'i D., Omito E., Rakotondrazafy M., Ranatsenho M., Lallier F. (2014). New typology and origin of tsavorite based on trace-element chemistry. European Journal of Mineralogy, 26 (2), p. 293-308. ISSN 0935-1221.

Titre du document
New typology and origin of tsavorite based on trace-element chemistry
Année de publication
2014
Type de document
Article référencé dans le Web of Science WOS:000334918100009
Auteurs
Feneyrol J., Giuliani Gaston, Ohnenstetter D., Rondeau B., Fritsch E., Fallick A. E., Ichang'i D., Omito E., Rakotondrazafy M., Ranatsenho M., Lallier F.
Source
European Journal of Mineralogy, 2014, 26 (2), p. 293-308 ISSN 0935-1221
New electron-microprobe analyses of 'tsavorites' from the Neoproterozoic Metamorphic Mozambique Belt deposits allow the characterization of green grossular according to its trace-element chemistry (V, Cr, Mn). Five chemical types are defined: type 1, vanadian grossular with V > Cr > Mn (in atoms per formula unit); type 2, vanadian grossular with V > Mn > Cr; type 3, Mn-bearing vanadian grossular with Mn > V > Cr; type 4, Mn-bearing chromian grossular with Mn > Cr > V; and type 5, Cr- and Mn-bearing grossular with Cr > Mn > V. These types are also characterized by different absorption spectra in the ultraviolet-visible-near infrared. Type 1 tsavorite spectra show a total absorption below 430 nm due to the high vanadium contents. Type 2 tsavorite spectra present the classical absorption bands of V. Types 3 and 4 tsavorite spectra display additional shoulders at 407 and 408 nm due to Mn2+, whereas spectra of Cr-bearing types 4 and 5 tsavorite show the two additional bands of Cr3+ at 697 and 701 nm. The different absorption spectra also indicate Fe2+-Ti4+ charge transfer. We measured OH equivalent to 0.08 to 0.38 wt% eq. H2O within the structure. Concentrations of vanadium, chromium and manganese are good chemical "fingerprints" for determining the geographic provenance of economic tsavorite from Kenya, Tanzania and Madagascar.
Plan de classement
Géologie et formations superficielles [064]
Description Géographique
AFRIQUE DE L'EST ; KENYA ; TANZANIE ; MADAGASCAR
Localisation
Fonds IRD [F B010062020]
Identifiant IRD
fdi:010062020
Contact