Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)

Axinite crystals from the type locality (Oisans, French Alps) are considered among the more remarkable specimens known for their quality (lustre, colour, size, and purity) and crystalline forms. However, they have been the subject of only a few in-depth studies. This lack of knowledge provided the o...

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Main Authors: Michel Cathelineau, Olivier Gerbeaud, Chantal Peiffert
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Crystals
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Online Access:https://www.mdpi.com/2073-4352/15/5/402
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author Michel Cathelineau
Olivier Gerbeaud
Chantal Peiffert
author_facet Michel Cathelineau
Olivier Gerbeaud
Chantal Peiffert
author_sort Michel Cathelineau
collection DOAJ
description Axinite crystals from the type locality (Oisans, French Alps) are considered among the more remarkable specimens known for their quality (lustre, colour, size, and purity) and crystalline forms. However, they have been the subject of only a few in-depth studies. This lack of knowledge provided the opportunity for a systematic survey of axinites from Saint-Christophe-en-Oisans, where crystals appear to cover an extensive range of Fe-Mn substitution from an Fe-rich (axinite-Fe) to a Mn-rich field (axinite-Mn) in a same crystal, with compositional variations much more significant than initially described. An in-depth characterisation of the chemical zonation of the crystals using EPMA, Raman spectroscopy, X-ray micro-fluorescence, and LA-ICP-MS was carried out on the crystals showing the most significant variability. The micro-XRF method appeared extremely useful for describing spatial variations in chemical composition at the centimetre scale and preparing other in situ methods. Fe(Mg)-Mn substitution covers a large range but the Mn-enriched growth zones are relatively thin and localised at the periphery of crystals. In addition, chemical zonations highlighted in this study also reveal contrasted incorporation of trace elements as a function of the Fe/Mn ratio (in particular, Be, HREE, Sc, Ga, In, and Co), indicating changes in fluid chemistry during the crystal growth.
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spelling doaj-art-1a71e93885fe4e6088b4fd14d128048f2025-08-20T02:33:44ZengMDPI AGCrystals2073-43522025-04-0115540210.3390/cryst15050402Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)Michel Cathelineau0Olivier Gerbeaud1Chantal Peiffert2Université de Lorraine, CNRS, GeoRessources, 54500 Nancy, FranceIndependent Researcher, 73230 Les Déserts, FranceUniversité de Lorraine, CNRS, GeoRessources, 54500 Nancy, FranceAxinite crystals from the type locality (Oisans, French Alps) are considered among the more remarkable specimens known for their quality (lustre, colour, size, and purity) and crystalline forms. However, they have been the subject of only a few in-depth studies. This lack of knowledge provided the opportunity for a systematic survey of axinites from Saint-Christophe-en-Oisans, where crystals appear to cover an extensive range of Fe-Mn substitution from an Fe-rich (axinite-Fe) to a Mn-rich field (axinite-Mn) in a same crystal, with compositional variations much more significant than initially described. An in-depth characterisation of the chemical zonation of the crystals using EPMA, Raman spectroscopy, X-ray micro-fluorescence, and LA-ICP-MS was carried out on the crystals showing the most significant variability. The micro-XRF method appeared extremely useful for describing spatial variations in chemical composition at the centimetre scale and preparing other in situ methods. Fe(Mg)-Mn substitution covers a large range but the Mn-enriched growth zones are relatively thin and localised at the periphery of crystals. In addition, chemical zonations highlighted in this study also reveal contrasted incorporation of trace elements as a function of the Fe/Mn ratio (in particular, Be, HREE, Sc, Ga, In, and Co), indicating changes in fluid chemistry during the crystal growth.https://www.mdpi.com/2073-4352/15/5/402axiniteOisansmanganesemicro-X-ray fluorescence imagingLA-ICP-MS
spellingShingle Michel Cathelineau
Olivier Gerbeaud
Chantal Peiffert
Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)
Crystals
axinite
Oisans
manganese
micro-X-ray fluorescence imaging
LA-ICP-MS
title Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)
title_full Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)
title_fullStr Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)
title_full_unstemmed Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)
title_short Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)
title_sort axinite a borosilicate with extensive fe mn substitutions at the scale of monocrystal revealed by micro xrf imaging and in situ analysis an example from the type locality at oisans france
topic axinite
Oisans
manganese
micro-X-ray fluorescence imaging
LA-ICP-MS
url https://www.mdpi.com/2073-4352/15/5/402
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