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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

Online
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1945-3027
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Volume 92, Issue 10

Issues

Non-ideality and defectivity of the åkermanite-gehlenite solid solution: An X-ray diffraction and TEM study

Mauro Gemmi
  • Corresponding author
  • Dipartimento di Scienze della Terra “A. Desio,” Università degli Studi di Milano, via Botticelli, 23, I-20133 Milano, Italy
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/ Marco Merlini
  • Dipartimento di Scienze della Terra “A. Desio,” Università degli Studi di Milano, via Botticelli, 23, I-20133 Milano, Italy
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/ Giuseppe Cruciani
  • Dipartimento di Scienze della Terra, Università di Ferrara, via Saragat 1, I-44100 Ferrara, Italy
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/ Gilberto Artioli
  • Dipartimento di Scienze della Terra “A. Desio,” Università degli Studi di Milano, via Botticelli, 23, I-20133 Milano, Italy
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Published Online: 2015-04-01 | DOI: https://doi.org/10.2138/am.2007.2380

Abstract

This paper reports a structure analysis of the åkermanite-gehlenite solid solution. This solution is non-ideal with a negative excess volume in the entire compositional range. X-ray diffraction shows anomalous behavior of the cell parameters close to the gehlenite end-member (åk08ge92, åk35ge65). This behavior is correlated with an excess of Si and deficiency of Al with respect to the Mg content, which implies a defective, non-stoichiometric structure with Ca vacancies. Electron microscopy images have confirmed an increase in the defectivity on the atomic scale for Al-rich compositions, and single-crystal structure refinements show a correlated decrease of the tetrahedral volume preferentially occupied by Si. The incommensurate modulation, characteristic of åkermanite, has been observed also in åk95ge05, and it is still visible as diffuse scattering in åk75ge25. (210) twinning has been observed in the entire compositional range.

Keywords: Melilite; solid solution; X-ray diffraction; electron microscopy

About the article

Received: 2006-07-06

Accepted: 2007-05-31

Published Online: 2015-04-01

Published in Print: 2007-10-01


Citation Information: American Mineralogist, Volume 92, Issue 10, Pages 1685–1694, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2007.2380.

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