NMR and EPR studies of the chemically intermediate plagioclase feldspars

✍ Scribed by C. M. Scala; D. R. Hutton; A. C. McLaren

• Publisher: Springer-Verlag
• Year: 1978
• Tongue: English
• Weight: 659 KB
• Volume: 3
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00357445

✦ Synopsis

The N M R spectra of 2VA1 and 23Na and the EPR spectra of Fe 3+ and Mn 2+ have been studied in a range of plagioclase feldspars, of intermediate composition. Many of these crystals have previously been investigated by TEM methods (McLaren and Marshall, 1974). The broad, central 27A1 signals observed in labradorites have been interpreted in terms of an overall order/disorder of the A1/Si distribution. Spin Hamiltonian parameters have been determined for the Fe 3 ÷ spectra observed in labradorites and bytownites; these spectra were similar and yielded evidence of disordering of the A1/Si distribution. The severe limitations imposed by the variety of sites, the complex microstructures and the disordering, limit the structural information available from the resonance methods.