Phase transformation of Mg-calcite to aragonite in active-forming hot spring travertines
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A travertine specimen collected from the western part of Yunnan Province of China was subjected to microstructural analysis by powder X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. A new formation mechanism was proposed whereby polycrystalline rhombohedral particles of magnesium-containing calcite underwent a phase transformation into sheaf-like clusters of aragonite microrods. It is proposed that a high concentration of magnesium ions and embedded biological matter poisoned the growth of calcite and therefore instigated the phase transformation of the core of the rhombohedral calcite particles to an aragonite phase with a higher crystallinity. The single crystalline aragonite microrods with a higher density than the Mg-calcite nanocrystallites grew at the expense of the latter to generate sheaf-like clusters. This newly discovered formation mechanism is expected to enhance previous knowledge on this geologically important phase transformation from a morphology point of view.
Greer , H F , Zhou , W & Guo , L 2015 , ' Phase transformation of Mg-calcite to aragonite in active-forming hot spring travertines ' Mineralogy and Petrology , vol 109 , no. 4 , pp. 453-462 . DOI: 10.1007/s00710-015-0367-5
Mineralogy and Petrology
© Springer-Verlag Wien 2015. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final publication is available at Springer via http://dx.doi.org/10.1007/s00710-015-0367-5
HFG would like to thank the University of St Andrews for the studentship and Mr Ross Blackley for his help on using the SEM and TEM microscopes. WZZ thanks EPSRC for financial support on FEG-SEM equipment (EP/F019580/1) and a Platform (EP/K015540/1).
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