Trace elements and mineral chemistry of silicified wood from Thailand: colours and elemental distribution |
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| Authors: | S Saminpanya |
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| Institution: | Department of General Science, Faculty of Science, Srinakharinwirot University, 114 Sukhumvit 23 Road, Khlong Toey Nua, Watthana, Bangkok 10110, Thailand |
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| Abstract: | Thai silicified woods were examined using electron probe microanalysis, yielding chemical data that characterised the samples into two groups: low and high silica contents (82—94 wt% and 94—98 wt%). The elements analysed in order of abundance include Si > Fe > Ca > Na > Al > Ti > K > Mg > Mn > Zr. Iron plays a major role in the colour range (red, orange, yellow, brown, grey and black) of the samples. Calcium is associated with Fe in the darker colours of the wood. Pseudo-crystallochemistry has been used for the substitution of trace elements for Si4+ in silica polymorphs. The atomic channels that run parallel to the c-axis of silica polymorphs or lattice defects, or even the charge balance for trivalent-ion substitution for Si4+, can accommodate monovalent ions (K+ and Na+). Vacant and atomic cavities, which are charged balanced by trivalent ions Al3+ or Fe3+ substituting for Si4+], are commonly occupied by divalent ions (Ca2+, Mg2+ and Mn2+). Quadrivalent ions, Ti4+ and Zr4+ are non-structurally incorporated but form clusters of mineral inclusions in the samples. Several other trace-element contents are also in the form of mineral/fluid inclusions hosted in the woods. |
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| Keywords: | Silicified wood trace elements EPMA geochemical characteristic colour Thailand |
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