Abstract

Electron diffraction, analytical electron microscopy, and high voltage, high resolution electron microscopy have been used to investigate crystal defects in calcium-rich saddle dolomites having pronounced curvature of the faces. Results show that branching, ribbon-like defects in these so-called 'saddle dolomites' are thin, coherent laths of calcitic material. The ribbons are profuse and explain the characteristic calcium excess found in most saddle dolomites. Because the lattice spacings of calcite are between 3.8% and 6.7% larger than the corresponding lattice spacings of dolomite, a calcitic ribbon causes local distortion of the host dolomite. The branching ribbons have a predominant {10-14} orientation and are generally present in high density. They may represent the source of crystal distortion that ultimately manifests itself on the macroscopic scale. The calcitic ribbons form during growth from aqueous solution, although they have features in common with similar defects found in carbonatite carbonates. This fine-scale intergrowth microstructure may be a variant of even finer-scale modulated structures found in other sedimentary calcian dolomites.

Original languageEnglish (US)
Pages (from-to)82-92
Number of pages11
JournalContributions to Mineralogy and Petrology
Volume91
Issue number1
DOIs
StatePublished - Sep 1985

Fingerprint

saddles
dolomite
ribbons
defect
electron microscopy
calcium
spacing
crystal
Calcium
Defects
Calcium Carbonate
Crystal defects
High resolution electron microscopy
carbonatite
Carbonates
defects
growth form
calcite
Electron diffraction
crystal defects

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

A tem microstructural study of dolomite with curved faces (saddle dolomite). / Barber, D. J.; Reeder, R. J.; Smith, David.

In: Contributions to Mineralogy and Petrology, Vol. 91, No. 1, 09.1985, p. 82-92.

Research output: Contribution to journalArticle

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