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Title: Octahedral versus tetrahedral coordination of Al in synthetic micas determined by XANES

We used the JUMBO monochromator at SSRL to measure the Al K-edge X-ray absorption spectra of synthetic micas having variable Al content and occupancy, from 0 to 2/3 in the octahedral M positions, and 0 to 2/3 in the tetrahedral T positions. The measured Al K edges differ markedly, but the differences may have a common explanation: (1) Micas containing 1/3 Al in M or {1/4} Al in T have K edges that differ in the energy and intensity of the first two features, which are related to interaction of Al with its first-shell nearest neighbors (O and OH or F). They are nearly identical to the K edges of reference minerals such as albite (tetrahedral Al only) or grossular (octahedral Al only). (2) Micas containing Al in both M and T have K edges that can be interpreted as a weighed combination of the simple edges. 39 refs., 4 figs., 1 tab.
Authors:
;  [1] ;  [2]
  1. Universita di Roma Tre (Italy)
  2. Centre de Recherche sur la Synthese et la Chimie des Mineraux, Orleans (France) [and others
Publication Date:
OSTI Identifier:
543157
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Mineralogist; Journal Volume: 82; Journal Issue: 5-6; Other Information: PBD: May-Jun 1997
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; 58 GEOSCIENCES; MICA; STRUCTURAL CHEMICAL ANALYSIS; CRYSTAL STRUCTURE; ALUMINIUM; MINERALOGY