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Author |
Odin, G.P.; Vanmeert, F.; Janssens, K.; Lelièvre, H.; Mertz, J.-D.; Rouchon, V. |
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Title |
Accelerated ageing of shales of palaeontological interest : impact of temperature conditions |
Type |
A1 Journal article |
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Year  |
2014 |
Publication |
Annales de paléontologie |
Abbreviated Journal |
Ann Paleontol |
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Volume |
100 |
Issue |
2 |
Pages |
137-149 |
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Keywords |
A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation) |
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Abstract |
The palaeontological collections of the Muséum national dHistoire naturelle (MNHN, Paris, France) and the Muséum dHistoire naturelle dAutun (MHNA, Autun, France) include many fossil specimens originating from the argillaceous shales of the Autun basin (Saône-et-Loire, France). These fossils are preserved within sedimentary rocks containing unstable sulphide compounds, such as pyrite, which may deteriorate in contact with water and oxygen. This alteration provokes crystalline efflorescence and cracks, thus compromising the preservations of the fossils. This work constitutes the first step of a project that aims to understand the mechanisms of alteration of these materials in order to define conservation guidelines for palaeontological collections. For this purpose, eight damaged specimens originating from the Permian Autun basin (Saône-et-Loire, France) were selected and analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM/EDS) and X-ray absorption spectroscopy at the threshold of the sulphur Kα-edge (XANES). This methodology enabled the characterization of the matrices composition and the chemical nature of the alterations. Subsequently, we have sought to reproduce by artificial ageing the alteration phenomena encountered in the collections. New shale samples were collected on seven outcrops of the same Autun basin. They were analyzed and subjected to artificial ageing at 50% relative humidity (RH) and at temperatures ranging between 40 °C and 90 °C. Our work shows that damaged specimens and newly collected shale have a similar mineralogical composition. Yet the crystalline efflorescence material formed on the surface of damaged specimens belongs to the iron sulphate group whereas gypsum predominates on artificially aged shale samples. Reproducing the alterations observed on specimens by artificial ageing remains therefore problematic. Additionally, it appears that the temperature of ageing controls the nature of the damage: at 40 °C, many samples are mechanically damaged whereas no or minor crystalline efflorescence occurs. At 90 °C, it is the opposite tendency that is observed. Finally, mechanical damages do not seem to be correlated with the development of the efflorescence: samples with efflorescent crystals generally do not show clearly visible cracks; those that seem most fragmented do not show any visible efflorescence. |
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Wos |
000338607500006 |
Publication Date |
2014-01-24 |
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ISSN |
0753-3969 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
1.113 |
Times cited |
5 |
Open Access |
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Notes |
; This work is part of a PhD that is funded by the Museum national d'Histoire naturelle, Paris, France and was additionally supported via the S2-ART project (SDD programme of BELSPO, Brussels). The research was realized in partnership with the Palaeontological Collection Management Unit, Collection Department and with the Centre de Recherche sur la Paleodiversite et les Paleoenvironnements (CR2P, CNRS, UMR7207) of the Museum national d'Histoire naturelle, Paris, France. We are grateful to our colleagues MM. Jean Dejax and Dominique Chabard who provided palaeontological specimens and gave us access to shale deposits and Mrs Marie-Madeleine Blanc-Valleron who was of great help for the interpretation of the XRD data. ; |
Approved |
Most recent IF: 1.113; 2014 IF: 0.970 |
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Call Number |
UA @ admin @ c:irua:116594 |
Serial |
5456 |
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