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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 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
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Online
ISSN
1945-3027
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Volume 97, Issue 10

Issues

Cation ordering in Pb2+-bearing, Mn3+-rich pargasite from Långban, Sweden

Ulf Hålenius
  • Corresponding author
  • Department of Mineralogy, Swedish Museum of Natural History, Box 50007, SE-10405 Stockholm, Sweden
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/ Ferdinando Bosi
  • Dipartimento di Scienze della Terra, Sapienza Università di Roma, P.le A. Moro, 5, I-00185 Rome, Italy
  • CNR-IGG Istituto di Geoscienze e Georisorse, Sede di Roma, P.le A. Moro, 5, I-00185 Roma, Italy
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Published Online: 2015-04-02 | DOI: https://doi.org/10.2138/am.2012.4137

Abstract

A multi-analytical approach using electron microprobe analysis, X-ray structural refinement, and polarized single-crystal Fourier transform infrared spectroscopy was used to characterize short-range and long-range structures of a Pb2+-bearing, Mn3+-rich pargasite. Site populations, derived from the results of site-scattering refinement and stereochemical analysis, demonstrate that Pb2+ is strongly ordered at the A-site in the monoclinic C2/m amphibole structure. This finding is in agreement with the observed ordering of Pb2+ in the rare Pb2+-bearing P2/a amphibole joesmithite, but is in contrast to a Pb2+ preference for the M4 site suggested by some studies on element partitioning between C2/m amphiboles and melts. Mn3+ is strongly ordered at the M2 site in structure of the present amphibole. Contrasting results obtained for mean M2-O bond lengths and reported local Mn3+-O bond lengths as well as between bond-length distortion of the mean M2 polyhedron and the local Mn3+-centered M2O6 octahedron in pargasite indicates that the structural relaxation of this polyhedron is complete or nearly so.

Keywords : Amphibole; pargasite; lead; manganese; structure refinement; IR spectroscopy

About the article

Received: 2012-02-22

Accepted: 2012-06-14

Published Online: 2015-04-02

Published in Print: 2012-10-01


Citation Information: American Mineralogist, Volume 97, Issue 10, Pages 1635–1640, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2012.4137.

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